Clinical Focus

  • Hematology

Honors & Awards

  • Trainee Research Award, American Society of Hematology (2005)
  • MacKenzie Foundation Award, MacKenzie Foundation (2006-2009)
  • Medical Student Research Training Fellowship, Howard Hughes Medical Institute (2007-2009)
  • First Place Award, Medical Student Research Symposium, Stanford University (2008)
  • Keystone Symposia Scholarship, Keystone Symposia (2008)
  • Medical Student Summer Fellowship, American Brain Tumor Association (2009)
  • Graduate Student Scholar, Genentech Scholars Program (2009)
  • Merck Scholar-in-Training Award, American Association for Cancer Research (2010)

Education & Certifications

  • Residency:Stanford University Internal Medicine Residency Training (2013) CA
  • Fellowship:Stanford University Hematology and Oncology Program (2016) CA
  • Medical Education:Stanford University School of Medicine Registrar (2011) CA
  • Board Certification: Hematology, American Board of Internal Medicine (2016)
  • Board Certification: Internal Medicine, American Board of Internal Medicine (2014)
  • M.D., Stanford University School of Medicine, Medicine (2011)
  • Ph.D., Stanford University, Cancer Biology (2010)

Research & Scholarship

Current Research and Scholarly Interests

I am interested in the characterization and therapeutic targeting of cancer stem cells in human malignancies. Specifically I have been investigating antibody-specific approaches to therapeutically target leukemic stem cells in acute myeloid leukemia as well as targeting of cancer cells in other hematologic malignancies. This work has led to the identification and development of a monoclonal antibody targeting the anti-phagocytic signal CD47 for the treatment of human malignancies.


All Publications

  • CD47 Blockade by Hu5F9-G4 and Rituximab in Non-Hodgkin's Lymphoma. The New England journal of medicine Advani, R., Flinn, I., Popplewell, L., Forero, A., Bartlett, N. L., Ghosh, N., Kline, J., Roschewski, M., LaCasce, A., Collins, G. P., Tran, T., Lynn, J., Chen, J. Y., Volkmer, J., Agoram, B., Huang, J., Majeti, R., Weissman, I. L., Takimoto, C. H., Chao, M. P., Smith, S. M. 2018; 379 (18): 1711–21


    BACKGROUND: The Hu5F9-G4 (hereafter, 5F9) antibody is a macrophage immune checkpoint inhibitor blocking CD47 that induces tumor-cell phagocytosis. 5F9 synergizes with rituximab to eliminate B-cell non-Hodgkin's lymphoma cells by enhancing macrophage-mediated antibody-dependent cellular phagocytosis. This combination was evaluated clinically.METHODS: We conducted a phase 1b study involving patients with relapsed or refractory non-Hodgkin's lymphoma. Patients may have had diffuse large B-cell lymphoma (DLBCL) or follicular lymphoma. 5F9 (at a priming dose of 1 mg per kilogram of body weight, administered intravenously, with weekly maintenance doses of 10 to 30 mg per kilogram) was given with rituximab to determine safety and efficacy and to suggest a phase 2 dose.RESULTS: A total of 22 patients (15 with DLBCL and 7 with follicular lymphoma) were enrolled. Patients had received a median of 4 (range, 2 to 10) previous therapies, and 95% of the patients had disease that was refractory to rituximab. Adverse events were predominantly of grade 1 or 2. The most common adverse events were anemia and infusion-related reactions. Anemia (an expected on-target effect) was mitigated by the strategy of 5F9 prime and maintenance dosing. Dose-limiting side effects were rare. A selected phase 2 dose of 30 mg of 5F9 per kilogram led to an approximate 100% CD47-receptor occupancy on circulating white and red cells. A total of 50% of the patients had an objective (i.e., complete or partial) response, with 36% having a complete response. The rates of objective response and complete response were 40% and 33%, respectively, among patients with DLBCL and 71% and 43%, respectively, among those with follicular lymphoma. At a median follow-up of 6.2 months among patients with DLBCL and 8.1 months among those with follicular lymphoma, 91% of the responses were ongoing.CONCLUSIONS: The macrophage checkpoint inhibitor 5F9 combined with rituximab showed promising activity in patients with aggressive and indolent lymphoma. No clinically significant safety events were observed in this initial study. (Funded by Forty Seven and the Leukemia and Lymphoma Society; number, NCT02953509 .).

    View details for DOI 10.1056/NEJMoa1807315

    View details for PubMedID 30380386

  • Human AML-iPSCs Reacquire Leukemic Properties after Differentiation and Model Clonal Variation of Disease. Cell stem cell Chao, M. P., Gentles, A. J., Chatterjee, S., Lan, F., Reinisch, A., Corces, M. R., Xavy, S., Shen, J., Haag, D., Chanda, S., Sinha, R., Morganti, R. M., Nishimura, T., Ameen, M., Wu, H., Wernig, M., Wu, J. C., Majeti, R. 2017; 20 (3): 329-344 e7


    Understanding the relative contributions of genetic and epigenetic abnormalities to acute myeloid leukemia (AML) should assist integrated design of targeted therapies. In this study, we generated induced pluripotent stem cells (iPSCs) from AML patient samples harboring MLL rearrangements and found that they retained leukemic mutations but reset leukemic DNA methylation/gene expression patterns. AML-iPSCs lacked leukemic potential, but when differentiated into hematopoietic cells, they reacquired the ability to give rise to leukemia in vivo and reestablished leukemic DNA methylation/gene expression patterns, including an aberrant MLL signature. Epigenetic reprogramming was therefore not sufficient to eliminate leukemic behavior. This approach also allowed us to study the properties of distinct AML subclones, including differential drug susceptibilities of KRAS mutant and wild-type cells, and predict relapse based on increased cytarabine resistance of a KRAS wild-type subclone. Overall, our findings illustrate the value of AML-iPSCs for investigating the mechanistic basis and clonal properties of human AML.

    View details for DOI 10.1016/j.stem.2016.11.018

    View details for PubMedID 28089908

  • Refractory warm IgM-mediated autoimmune hemolytic anemia associated with Churg-Strauss syndrome responsive to eculizumab and rituximab AMERICAN JOURNAL OF HEMATOLOGY Chao, M. P., Hong, J., Kunder, C., Lester, L., Schrier, S. L., Majeti, R. 2015; 90 (1): 78-81

    View details for DOI 10.1002/ajh.23791

    View details for Web of Science ID 000346771400022

    View details for PubMedID 24942207

  • A Two-Step Pretargeted Nanotherapy for CD20 Crosslinking May Achieve Superior Anti-Lymphoma Efficacy to Rituximab THERANOSTICS Chu, T., Zhang, R., Yang, J., Chao, M. P., Shami, P. J., Kopecek, J. 2015; 5 (8): 834-846


    The use of rituximab, an anti-CD20 mAb, in combination with chemotherapy is the current standard for the treatment of B-cell lymphomas. However, because of a significant number of treatment failures, there is a demand for new, improved therapeutics. Here, we designed a nanomedicine that crosslinks CD20 and directly induces apoptosis of B-cells without the need for toxins or immune effector functions. The therapeutic system comprises a pretargeting component (anti-CD20 Fab' conjugated with an oligonucleotide1) and a crosslinking component (N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer grafted with multiple complementary oligonucleotide2). Consecutive treatment with the two components resulted in CD20 clustering on the cell surface and effectively killed malignant B-cells in vivo. To enhance therapeutic efficacy, a two-step pretargeting approach was employed. We showed that the time lag between the two doses can be optimized based on pharmacokinetics and biodistribution of the Fab'-oligonucleotide1 conjugate. In a mouse model of human non-Hodgkin lymphoma (NHL), increasing the time lag from 1 h to 5 h resulted in dramatically improved tumor growth inhibition and animal survival. When the 5 h interval was used, the nanotherapy was more efficacious than rituximab and led to complete eradication of lymphoma cells with no signs of metastasis or disease recurrence. We further evaluated the nanomedicine using patient mantle cell lymphoma cells; the treatment demonstrated more potent apoptosis-inducing activity than rituximab hyper-crosslinked with secondary antibodies. In summary, our approach may constitute a novel treatment for NHL and other B-cell malignancies with significant advantages over conventional chemo-immunotherapy.

    View details for DOI 10.7150/thno.12040

    View details for Web of Science ID 000354959900005

    View details for PubMedID 26000056

    View details for PubMedCentralID PMC4440441

  • Pre-Clinical Development of a Humanized Anti-CD47 Antibody with Anti-Cancer Therapeutic Potential. PloS one Liu, J., Wang, L., Zhao, F., Tseng, S., Narayanan, C., Shura, L., Willingham, S., Howard, M., Prohaska, S., Volkmer, J., Chao, M., Weissman, I. L., Majeti, R. 2015; 10 (9)

    View details for DOI 10.1371/journal.pone.0137345

    View details for PubMedID 26390038

  • Inhibition of lymphoma vascularization and dissemination by estrogen receptor beta agonists BLOOD Yakimchuk, K., Hasni, M. S., Guan, J., Chao, M. P., Sander, B., Okret, S. 2014; 123 (13): 2054-2061


    Most lymphomas show an increased incidence and poorer prognosis in males vs females, suggesting endocrine regulation. We have previously shown that tumor growth in vivo of a murine T-cell-derived lymphoma is repressed following activation of estrogen receptor β (ERβ, ESR2). By using ERβ-deficient mice, we now demonstrate that this inhibition is mediated via a direct effect on the tumor cells and not on the microenvironment. Furthermore, we show that the growth-suppressing effects of ERβ agonist are also valid for human B-cell lymphomas as demonstrated in tumors derived from Granta-519 mantle cell lymphoma (MCL) and Raji Burkitt lymphoma (BL) cells. In Granta-519 MCL tumors, activation of ERβ reduced expression of BAFF and GRB7, 2 important molecules involved in B-cell proliferation and survival. Importantly, activation of ERβ inhibited angiogenesis and lymphangiogenesis, possibly mediated by impaired vascular endothelial growth factor C expression. Furthermore, using disseminating Raji BL cells, we show that ERβ activation reduces dissemination of grafted Raji BL tumors. We also show by immunohistochemistry that ERβ is expressed in primary MCL tissue. These results suggest that targeting ERβ with agonists may be valuable in the treatment of some lymphomas, affecting several aspects of the malignant process, including proliferation, vascularization, and dissemination.

    View details for DOI 10.1182/blood-2013-07-517292

    View details for Web of Science ID 000335852200017

    View details for PubMedID 24470591

  • Treatment challenges in the management of relapsed or refractory non-Hodgkin's lymphoma - novel and emerging therapies. Cancer management and research Chao, M. P. 2013; 5: 251-269


    Over the last few decades, advances in immunochemotherapy have led to dramatic improvement in the prognosis of non-Hodgkin's lymphoma (NHL). Despite these advances, relapsed and refractory disease represents a major treatment challenge. For both aggressive and indolent subtypes of NHL, there is no standard of care for salvage regimens, with prognosis after relapse remaining relatively poor. Nevertheless, there are multiple emerging classes of targeted therapies for relapsed/refractory disease, including monoclonal antibodies, antibody- drug conjugates, radioimmunotherapy, small-molecule inhibitors of cell-growth pathways, and novel chemotherapy agents. This review will discuss treatment challenges of NHL, current available salvage regimens for relapsed/refractory NHL, and the safety and efficacy of novel emerging therapies.

    View details for DOI 10.2147/CMAR.S34273

    View details for PubMedID 24049458

    View details for PubMedCentralID PMC3775637

  • Janus-like opposing roles of CD47 in autoimmune brain inflammation in humans and mice JOURNAL OF EXPERIMENTAL MEDICINE Han, M. H., Lundgren, D. H., Jaiswal, S., Chao, M., Graham, K. L., Garris, C. S., Axtell, R. C., Ho, P. P., Lock, C. B., Woodard, J. I., Brownell, S. E., Zoudilova, M., Hunt, J. F., Baranzini, S. E., Butcher, E. C., Raine, C. S., Sobel, R. A., Han, D. K., Weissman, I., Steinman, L. 2012; 209 (7): 1325-1334


    Comparison of transcriptomic and proteomic data from pathologically similar multiple sclerosis (MS) lesions reveals down-regulation of CD47 at the messenger RNA level and low abundance at the protein level. Immunohistochemical studies demonstrate that CD47 is expressed in normal myelin and in foamy macrophages and reactive astrocytes within active MS lesions. We demonstrate that CD47(-/-) mice are refractory to experimental autoimmune encephalomyelitis (EAE), primarily as the result of failure of immune cell activation after immunization with myelin antigen. In contrast, blocking with a monoclonal antibody against CD47 in mice at the peak of paralysis worsens EAE severity and enhances immune activation in the peripheral immune system. In vitro assays demonstrate that blocking CD47 also promotes phagocytosis of myelin and that this effect is dependent on signal regulatory protein α (SIRP-α). Immune regulation and phagocytosis are mechanisms for CD47 signaling in autoimmune neuroinflammation. Depending on the cell type, location, and disease stage, CD47 has Janus-like roles, with opposing effects on EAE pathogenesis.

    View details for DOI 10.1084/jem.20101974

    View details for Web of Science ID 000306174300008

    View details for PubMedID 22734047

    View details for PubMedCentralID PMC3405500

  • The CD47-signal regulatory protein alpha (SIRPa) interaction is a therapeutic target for human solid tumors PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Willingham, S. B., Volkmer, J., Gentles, A. J., Sahoo, D., Dalerba, P., Mitra, S. S., Wang, J., Contreras-Trujillo, H., Martin, R., Cohen, J. D., Lovelace, P., Scheeren, F. A., Chao, M. P., Weiskopf, K., Tang, C., Volkmer, A. K., Naik, T. J., Storm, T. A., Mosley, A. R., Edris, B., Schmid, S. M., Sun, C. K., Chua, M., Murillo, O., Rajendran, P., Cha, A. C., Chin, R. K., Kim, D., Adorno, M., Raveh, T., Tseng, D., Jaiswal, S., Enger, P. O., Steinberg, G. K., Li, G., So, S. K., Majeti, R., Harsh, G. R., van de Rijn, M., Teng, N. N., Sunwoo, J. B., Alizadeh, A. A., Clarke, M. F., Weissman, I. L. 2012; 109 (17): 6662-6667


    CD47, a "don't eat me" signal for phagocytic cells, is expressed on the surface of all human solid tumor cells. Analysis of patient tumor and matched adjacent normal (nontumor) tissue revealed that CD47 is overexpressed on cancer cells. CD47 mRNA expression levels correlated with a decreased probability of survival for multiple types of cancer. CD47 is a ligand for SIRPα, a protein expressed on macrophages and dendritic cells. In vitro, blockade of CD47 signaling using targeted monoclonal antibodies enabled macrophage phagocytosis of tumor cells that were otherwise protected. Administration of anti-CD47 antibodies inhibited tumor growth in orthotopic immunodeficient mouse xenotransplantation models established with patient tumor cells and increased the survival of the mice over time. Anti-CD47 antibody therapy initiated on larger tumors inhibited tumor growth and prevented or treated metastasis, but initiation of the therapy on smaller tumors was potentially curative. The safety and efficacy of targeting CD47 was further tested and validated in immune competent hosts using an orthotopic mouse breast cancer model. These results suggest all human solid tumor cells require CD47 expression to suppress phagocytic innate immune surveillance and elimination. These data, taken together with similar findings with other human neoplasms, show that CD47 is a commonly expressed molecule on all cancers, its function to block phagocytosis is known, and blockade of its function leads to tumor cell phagocytosis and elimination. CD47 is therefore a validated target for cancer therapies.

    View details for DOI 10.1073/pnas.1121623109

    View details for Web of Science ID 000303249100065

    View details for PubMedID 22451913

    View details for PubMedCentralID PMC3340046

  • The CD47-SIRP alpha pathway in cancer immune evasion and potential therapeutic implications CURRENT OPINION IN IMMUNOLOGY Chao, M. P., Weissman, I. L., Majeti, R. 2012; 24 (2): 225-232


    Multiple lines of investigation have demonstrated that the immune system plays an important role in preventing tumor initiation and controlling tumor growth. Accordingly, many cancers have evolved diverse mechanisms to evade such monitoring. While multiple immune cell types mediate tumor surveillance, recent evidence demonstrates that macrophages, and other phagocytic cells, play a key role in regulating tumor growth through phagocytic clearance. In this review we highlight the role of tumor immune evasion through the inhibition of phagocytosis, specifically through the CD47-signal-regulatory protein-α pathway, and discuss how targeting this pathway might lead to more effective cancer immunotherapies.

    View details for DOI 10.1016/j.coi.2012.01.010

    View details for Web of Science ID 000303187600017

    View details for PubMedID 22310103

    View details for PubMedCentralID PMC3319521

  • Programmed cell removal: a new obstacle in the road to developing cancer. Nature reviews. Cancer Chao, M. P., Majeti, R., Weissman, I. L. 2012; 12 (1): 58-67


    The development of cancer involves mechanisms by which aberrant cells overcome normal regulatory pathways that limit their numbers and their migration. The evasion of programmed cell death is one of several key early events that need to be overcome in the progression from normal cellular homeostasis to malignant transformation. Recently, we provided evidence in mouse and human cancers that successful cancer clones must also overcome programmed cell removal. In this Opinion article, we explore the role of programmed cell removal in both normal and neoplastic cells, and we place this pathway in the context of the initiation of programmed cell death.

    View details for DOI 10.1038/nrc3171

    View details for PubMedID 22158022

  • Programmed cell removal: a new obstacle in the road to developing cancer NATURE REVIEWS CANCER Chao, M. P., Majeti, R., Weissman, I. L. 2012; 12 (1): 58-67


    The development of cancer involves mechanisms by which aberrant cells overcome normal regulatory pathways that limit their numbers and their migration. The evasion of programmed cell death is one of several key early events that need to be overcome in the progression from normal cellular homeostasis to malignant transformation. Recently, we provided evidence in mouse and human cancers that successful cancer clones must also overcome programmed cell removal. In this Opinion article, we explore the role of programmed cell removal in both normal and neoplastic cells, and we place this pathway in the context of the initiation of programmed cell death.

    View details for DOI 10.1038/nrc3171

    View details for Web of Science ID 000298369300014

  • Extranodal dissemination of non-Hodgkin lymphoma requires CD47 and is inhibited by anti-CD47 antibody therapy BLOOD Chao, M. P., Tang, C., Pachynski, R. K., Chin, R., Majeti, R., Weissman, I. L. 2011; 118 (18): 4890-4901


    Non-Hodgkin lymphoma (NHL) presents as both localized and disseminated disease with spread to secondary sites carrying a worse prognosis. Although pathways driving NHL dissemination have been identified, there are few therapies capable of inhibiting them. Here, we report a novel role for the immunomodulatory protein CD47 in NHL dissemination, and we demonstrate that therapeutic targeting of CD47 can prevent such spread. We developed 2 in vivo lymphoma metastasis models using Raji cells, a human NHL cell line, and primary cells from a lymphoma patient. CD47 expression was required for Raji cell dissemination to the liver in mouse xenotransplants. Targeting of CD47 with a blocking antibody inhibited Raji cell dissemination to major organs, including the central nervous system, and inhibited hematogenous dissemination of primary lymphoma cells. We hypothesized that anti-CD47 antibody-mediated elimination of circulating tumor cells occurred through phagocytosis, a previously described mechanism for blocking anti-CD47 antibodies. As predicted, inhibition of dissemination by anti-CD47 antibodies was dependent on blockade of phagocyte SIRPα and required macrophage effector cells. These results demonstrate that CD47 is required for NHL dissemination, which can be therapeutically targeted with a blocking anti-CD47 antibody. Ultimately, these findings are potentially applicable to the dissemination and metastasis of other solid tumors.

    View details for DOI 10.1182/blood-2011-02-338020

    View details for Web of Science ID 000296714500018

    View details for PubMedID 21828138

    View details for PubMedCentralID PMC3208297

  • Prospective separation of normal and leukemic stem cells based on differential expression of TIM3, a human acute myeloid leukemia stem cell marker PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Jan, M., Chao, M. P., Cha, A. C., Alizadeh, A. A., Gentles, A. J., Weissman, I. L., Majeti, R. 2011; 108 (12): 5009-5014


    Hematopoietic tissues in acute myeloid leukemia (AML) patients contain both leukemia stem cells (LSC) and residual normal hematopoietic stem cells (HSC). The ability to prospectively separate residual HSC from LSC would enable important scientific and clinical investigation including the possibility of purged autologous hematopoietic cell transplants. We report here the identification of TIM3 as an AML stem cell surface marker more highly expressed on multiple specimens of AML LSC than on normal bone marrow HSC. TIM3 expression was detected in all cytogenetic subgroups of AML, but was significantly higher in AML-associated with core binding factor translocations or mutations in CEBPA. By assessing engraftment in NOD/SCID/IL2Rγ-null mice, we determined that HSC function resides predominantly in the TIM3-negative fraction of normal bone marrow, whereas LSC function from multiple AML specimens resides predominantly in the TIM3-positive compartment. Significantly, differential TIM3 expression enabled the prospective separation of HSC from LSC in the majority of AML specimens with detectable residual HSC function.

    View details for DOI 10.1073/pnas.1100551108

    View details for Web of Science ID 000288712200061

    View details for PubMedID 21383193

    View details for PubMedCentralID PMC3064328

  • CD137 stimulation enhances the antilymphoma activity of anti-CD20 antibodies BLOOD Kohrt, H. E., Houot, R., Goldstein, M. J., Weiskopf, K., Alizadeh, A. A., Brody, J., Mueller, A., Pachynski, R., Czerwinski, D., Coutre, S., Chao, M. P., Chen, L., Tedder, T. F., Levy, R. 2011; 117 (8): 2423-2432


    Antibody-dependent cell-mediated cytotoxicity (ADCC), which is largely mediated by natural killer (NK) cells, is thought to play an important role in the efficacy of rituximab, an anti-CD20 monoclonal antibody (mAb) used to treat patients with B-cell lymphomas. CD137 is a costimulatory molecule expressed on a variety of immune cells after activation, including NK cells. In the present study, we show that an anti-CD137 agonistic mAb enhances the antilymphoma activity of rituximab by enhancing ADCC. Human NK cells up-regulate CD137 after encountering rituximab-coated tumor B cells, and subsequent stimulation of these NK cells with anti-CD137 mAb enhances rituximab-dependent cytotoxicity against the lymphoma cells. In a syngeneic murine lymphoma model and in a xenotransplanted human lymphoma model, sequential administration of anti-CD20 mAb followed by anti-CD137 mAb had potent antilymphoma activity in vivo. These results support a novel, sequential antibody approach against B-cell malignancies by targeting first the tumor and then the host immune system.

    View details for DOI 10.1182/blood-2010-08-301945

    View details for Web of Science ID 000287698800023

    View details for PubMedID 21193697

    View details for PubMedCentralID PMC3062409

  • Therapeutic Antibody Targeting of CD47 Eliminates Human Acute Lymphoblastic Leukemia CANCER RESEARCH Chao, M. P., Alizadeh, A. A., Tang, C., Jan, M., Weissman-Tsukamoto, R., Zhao, F., Park, C. Y., Weissman, I. L., Majeti, R. 2011; 71 (4): 1374-1384


    Acute lymphoblastic leukemia (ALL) is the most common pediatric malignancy and constitutes 15% of adult leukemias. Although overall prognosis for pediatric ALL is favorable, high-risk pediatric patients and most adult patients have significantly worse outcomes. Multiagent chemotherapy is standard of care for both pediatric and adult ALL, but is associated with systemic toxicity and long-term side effects and is relatively ineffective against certain ALL subtypes. Recent efforts have focused on the development of targeted therapies for ALL including monoclonal antibodies. Here, we report the identification of CD47, a protein that inhibits phagocytosis, as an antibody target in standard and high-risk ALL. CD47 was found to be more highly expressed on a subset of human ALL patient samples compared with normal cell counterparts and to be an independent predictor of survival and disease refractoriness in several ALL patient cohorts. In addition, a blocking monoclonal antibody against CD47 enabled phagocytosis of ALL cells by macrophages in vitro and inhibited tumor engraftment in vivo. Significantly, anti-CD47 antibody eliminated ALL in the peripheral blood, bone marrow, spleen, and liver of mice engrafted with primary human ALL. These data provide preclinical support for the development of an anti-CD47 antibody therapy for treatment of human ALL.

    View details for DOI 10.1158/0008-5472.CAN-10-2238

    View details for Web of Science ID 000287352600020

    View details for PubMedID 21177380

    View details for PubMedCentralID PMC3041855

  • Calreticulin Is the Dominant Pro-Phagocytic Signal on Multiple Human Cancers and Is Counterbalanced by CD47 SCIENCE TRANSLATIONAL MEDICINE Chao, M. P., Jaiswal, S., Weissman-Tsukamoto, R., Alizadeh, A. A., Gentles, A. J., Volkmer, J., Weiskopf, K., Willingham, S. B., Raveh, T., Park, C. Y., Majeti, R., Weissman, I. L. 2010; 2 (63)


    Under normal physiological conditions, cellular homeostasis is partly regulated by a balance of pro- and anti-phagocytic signals. CD47, which prevents cancer cell phagocytosis by the innate immune system, is highly expressed on several human cancers including acute myeloid leukemia, non-Hodgkin's lymphoma, and bladder cancer. Blocking CD47 with a monoclonal antibody results in phagocytosis of cancer cells and leads to in vivo tumor elimination, yet normal cells remain mostly unaffected. Thus, we postulated that cancer cells must also display a potent pro-phagocytic signal. Here, we identified calreticulin as a pro-phagocytic signal that was highly expressed on the surface of several human cancers, but was minimally expressed on most normal cells. Increased CD47 expression correlated with high amounts of calreticulin on cancer cells and was necessary for protection from calreticulin-mediated phagocytosis. Blocking the interaction of target cell calreticulin with its receptor, low-density lipoprotein receptor-related protein, on phagocytic cells prevented anti-CD47 antibody-mediated phagocytosis. Furthermore, increased calreticulin expression was an adverse prognostic factor in diverse tumors including neuroblastoma, bladder cancer, and non-Hodgkin's lymphoma. These findings identify calreticulin as the dominant pro-phagocytic signal on several human cancers, provide an explanation for the selective targeting of tumor cells by anti-CD47 antibody, and highlight the balance between pro- and anti-phagocytic signals in the immune evasion of cancer.

    View details for DOI 10.1126/scitranslmed.3001375

    View details for Web of Science ID 000288444900003

    View details for PubMedID 21178137

  • Anti-CD47 Antibody Synergizes with Rituximab to Promote Phagocytosis and Eradicate Non-Hodgkin Lymphoma CELL Chao, M. P., Alizadeh, A. A., Tang, C., Myklebust, J. H., Varghese, B., Gill, S., Jan, M., Cha, A. C., Chan, C. K., Tan, B. T., Park, C. Y., Zhao, F., Kohrt, H. E., Malumbres, R., Briones, J., Gascoyne, R. D., Lossos, I. S., Levy, R., Weissman, I. L., Majeti, R. 2010; 142 (5): 699-713


    Monoclonal antibodies are standard therapeutics for several cancers including the anti-CD20 antibody rituximab for B cell non-Hodgkin lymphoma (NHL). Rituximab and other antibodies are not curative and must be combined with cytotoxic chemotherapy for clinical benefit. Here we report the eradication of human NHL solely with a monoclonal antibody therapy combining rituximab with a blocking anti-CD47 antibody. We identified increased expression of CD47 on human NHL cells and determined that higher CD47 expression independently predicted adverse clinical outcomes in multiple NHL subtypes. Blocking anti-CD47 antibodies preferentially enabled phagocytosis of NHL cells and synergized with rituximab. Treatment of human NHL-engrafted mice with anti-CD47 antibody reduced lymphoma burden and improved survival, while combination treatment with rituximab led to elimination of lymphoma and cure. These antibodies synergized through a mechanism combining Fc receptor (FcR)-dependent and FcR-independent stimulation of phagocytosis that might be applicable to many other cancers.

    View details for DOI 10.1016/j.cell.2010.07.044

    View details for Web of Science ID 000281523200014

    View details for PubMedID 20813259

    View details for PubMedCentralID PMC2943345

  • Macrophages as mediators of tumor immunosurveillance TRENDS IN IMMUNOLOGY Jaiswal, S., Chao, M. P., Majeti, R., Weissman, I. L. 2010; 31 (6): 212-219


    Tumor immunosurveillance is a well-established mechanism for regulation of tumor growth. In this regard, most studies have focused on the role of T- and NK-cells as the critical immune effector cells. However, macrophages play a major role in the recognition and clearance of foreign, aged, and damaged cells. Macrophage phagocytosis is negatively regulated via the receptor SIRPalpha upon binding to CD47, a ubiquitously expressed protein. We recently showed that CD47 is up-regulated in myeloid leukemia and migrating hematopoietic progenitors, and that the level of protein expression correlates with the ability to evade phagocytosis. These results implicate macrophages in the immunosurveillance of hematopoietic cells and leukemias. The ability of macrophages to phagocytose tumor cells might be exploited therapeutically by blocking the CD47-SIRPalpha interaction.

    View details for DOI 10.1016/

    View details for Web of Science ID 000279427000002

    View details for PubMedID 20452821

    View details for PubMedCentralID PMC3646798

  • Identification, molecular characterization, clinical prognosis, and therapeutic targeting of human bladder tumor-initiating cells PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Chan, K. S., Espinosa, I., Chao, M., Wong, D., Ailles, L., Diehn, M., Gill, H., Presti, J., Chang, H. Y., van de Rijn, M., Shortliffe, L., Weissman, I. L. 2009; 106 (33): 14016-14021


    Major clinical issues in bladder cancer include the identification of prediction markers and novel therapeutic targets for invasive bladder cancer. In the current study, we describe the isolation and characterization of a tumor-initiating cell (T-IC) subpopulation in primary human bladder cancer, based on the expression of markers similar to that of normal bladder basal cells (Lineage-CD44(+)CK5(+)CK20(-)). The bladder T-IC subpopulation was defined functionally by its enriched ability to induce xenograft tumors in vivo that recapitulated the heterogeneity of the original tumor. Further, molecular analysis of more than 300 bladder cancer specimens revealed heterogeneity among activated oncogenic pathways in T-IC (e.g., 80% Gli1, 45% Stat3, 10% Bmi-1, and 5% beta-catenin). Despite this molecular heterogeneity, we identified a unique bladder T-IC gene signature by gene chip analysis. This T-IC gene signature, which effectively distinguishes muscle-invasive bladder cancer with worse clinical prognosis from non-muscle-invasive (superficial) cancer, has significant clinical value. It also can predict the progression of a subset of recurring non-muscle-invasive cancers. Finally, we found that CD47, a protein that provides an inhibitory signal for macrophage phagocytosis, is highly expressed in bladder T-ICs compared with the rest of the tumor. Blockade of CD47 by a mAb resulted in macrophage engulfment of bladder cancer cells in vitro. In summary, we have identified a T-IC subpopulation with potential prognostic and therapeutic value for invasive bladder cancer.

    View details for DOI 10.1073/pnas.0906549106

    View details for Web of Science ID 000269078700071

    View details for PubMedID 19666525

    View details for PubMedCentralID PMC2720852

  • CD47 Is an Adverse Prognostic Factor and Therapeutic Antibody Target on Human Acute Myeloid Leukemia Stem Cells CELL Majeti, R., Chao, M. P., Alizadeh, A. A., Pang, W. W., Jaiswal, S., Gibbs, K. D., van Rooijen, N., Weissman, I. L. 2009; 138 (2): 286-299


    Acute myeloid leukemia (AML) is organized as a cellular hierarchy initiated and maintained by a subset of self-renewing leukemia stem cells (LSC). We hypothesized that increased CD47 expression on human AML LSC contributes to pathogenesis by inhibiting their phagocytosis through the interaction of CD47 with an inhibitory receptor on phagocytes. We found that CD47 was more highly expressed on AML LSC than their normal counterparts, and that increased CD47 expression predicted worse overall survival in three independent cohorts of adult AML patients. Furthermore, blocking monoclonal antibodies directed against CD47 preferentially enabled phagocytosis of AML LSC and inhibited their engraftment in vivo. Finally, treatment of human AML LSC-engrafted mice with anti-CD47 antibody depleted AML and targeted AML LSC. In summary, increased CD47 expression is an independent, poor prognostic factor that can be targeted on human AML stem cells with blocking monoclonal antibodies capable of enabling phagocytosis of LSC.

    View details for DOI 10.1016/j.cell.2009.05.045

    View details for Web of Science ID 000268277000011

    View details for PubMedID 19632179

    View details for PubMedCentralID PMC2726837

  • CD47 Is Upregulated on Circulating Hematopoietic Stem Cells and Leukemia Cells to Avoid Phagocytosis CELL Jaiswal, S., Jamieson, C. H., Pang, W. W., Park, C. Y., Chao, M. P., Majeti, R., Traver, D., van Rooijen, N., Weissman, I. L. 2009; 138 (2): 271-285


    Macrophages clear pathogens and damaged or aged cells from the blood stream via phagocytosis. Cell-surface CD47 interacts with its receptor on macrophages, SIRPalpha, to inhibit phagocytosis of normal, healthy cells. We find that mobilizing cytokines and inflammatory stimuli cause CD47 to be transiently upregulated on mouse hematopoietic stem cells (HSCs) and progenitors just prior to and during their migratory phase, and that the level of CD47 on these cells determines the probability that they are engulfed in vivo. CD47 is also constitutively upregulated on mouse and human myeloid leukemias, and overexpression of CD47 on a myeloid leukemia line increases its pathogenicity by allowing it to evade phagocytosis. We conclude that CD47 upregulation is an important mechanism that provides protection to normal HSCs during inflammation-mediated mobilization, and that leukemic progenitors co-opt this ability in order to evade macrophage killing.

    View details for DOI 10.1016/j.cell.2009.05.046

    View details for Web of Science ID 000268277000010

    View details for PubMedID 19632178

    View details for PubMedCentralID PMC2775564

  • Cancer Stem Cells: On the Verge of Clinical Translation LABMEDICINE Chao, M. P., Weissman, I. L., Park, C. Y. 2008; 39 (11): 679-686
  • Establishment of a Normal Hematopoietic and Leukemia Stem Cell Hierarchy 73rd Cold Spring Harbor Symposium on Quantitative Biology Chao, M. P., Seita, J., Weissman, I. L. COLD SPRING HARBOR LABORATORY PRESS. 2008: 439–449


    Many types of adult tissues, especially for high turnover tissues such as the blood and intestinal system, stand on a hierarchical tissue-specific stem cell system. Tissue-specific stem cells concurrently have self-renewal capacity and potential to give rise to all types of mature cells in their tissue. The differentiation process of the tissue-specific stem cell is successive restriction of these capacities. The first progeny of tissue-specific stem cells are multipotent progenitors (MPPs) that lose long-term self-renewal capacity yet have full lineage potential. MPPs in turn give rise to oligopotent progenitors, which then commit into lineage-restricted progenitors. This hierarchical system enables a lifelong supply of matured functional cells that generally have a short life span and a relatively high turnover rate. In this chapter, we review our findings and other key experiments that have led to the establishment of the current cellular stem and progenitor hierarchy in the blood-forming systems of mice and humans for both normal and leukemic hematopoiesis. We also review select signaling pathways intrinsic to normal hematopoietic and leukemic stem cell populations as well our recent findings elucidating the possible origin of the leukemia stem cell.

    View details for Web of Science ID 000267135700050

    View details for PubMedID 19022770

  • Distribution, levels and phosphorylation of Raf-1 in Alzheimer's disease JOURNAL OF NEUROCHEMISTRY Mei, M., Su, B., Harrison, K., Chao, M., Siedlak, S. L., Previll, L. A., Jackson, L., Cai, D. X., Zhu, X. 2006; 99 (5): 1377-1388


    Extracellular signal-regulated kinase (ERK), a member of the mitogen-activated protein kinase pathway, has been increasingly implicated in the pathogenesis of Alzheimer's disease due to its critical role in brain function. While we previously demonstrated that ERK is activated in Alzheimer's disease, the upstream cascade leading to its activation had not been fully examined. In this study, we focused on Raf-1, one of the physiological activators of the ERK pathway. Raf-1 is activated by phosphorylation at Ser338 and Tyr340/341 and inhibited by phosphorylation at Ser259. Interestingly, phosphorylation at all three sites on Raf-1 was increased as evidenced by both immunocytochemistry and immunoblot analysis in Alzheimer's disease brains compared to age-matched controls. Both phospho-Raf-1 (Ser259) and phospho-Raf-1 (Ser338) were localized to intracytoplasmic granular structures, whereas phospho-Raf-1 (Tyr340/341) was localized to neurofibrillary tangles and granules in pyramidal neurons in Alzheimer's disease hippocampus. There is extensive overlap between phospho-Raf-1 (Ser338) and phospho-Mek1/2, the downstream effector of Raf-1, suggestive of a mechanistic link. Additionally, increased levels of Raf-1 are associated with Ras and MEK1 in Alzheimer's disease as evidenced by its coimmunoprecipitation with Ras and Mek1, respectively. Based on these findings, we speculate that Raf-1 is activated to effectively mediate Ras-dependent signals in Alzheimer's disease.

    View details for DOI 10.1111/j.1471-4159.2006.04174.x

    View details for Web of Science ID 000241951300006

    View details for PubMedID 17064357

  • The JAK2 V617F mutation occurs in hematopoietic stem cells in polycythemia vera and predisposes toward erythroid differentiation PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Jamieson, C. H., Gotlib, J., Durocher, J. A., Chao, M. P., Mariappan, M. R., Lay, M., Jones, C., Zehnder, J. L., Lilleberg, S. L., Weissman, I. L. 2006; 103 (16): 6224-6229


    Although a large proportion of patients with polycythemia vera (PV) harbor a valine-to-phenylalanine mutation at amino acid 617 (V617F) in the JAK2 signaling molecule, the stage of hematopoiesis at which the mutation arises is unknown. Here we isolated and characterized hematopoietic stem cells (HSC) and myeloid progenitors from 16 PV patient samples and 14 normal individuals, testing whether the JAK2 mutation could be found at the level of stem or progenitor cells and whether the JAK2 V617F-positive cells had altered differentiation potential. In all PV samples analyzed, there were increased numbers of cells with a HSC phenotype (CD34+CD38-CD90+Lin-) compared with normal samples. Hematopoietic progenitor assays demonstrated that the differentiation potential of PV was already skewed toward the erythroid lineage at the HSC level. The JAK2 V617F mutation was detectable within HSC and their progeny in PV. Moreover, the aberrant erythroid potential of PV HSC was potently inhibited with a JAK2 inhibitor, AG490.

    View details for DOI 10.1073/pnas.0601462103

    View details for Web of Science ID 000236999000031

    View details for PubMedID 16603627

    View details for PubMedCentralID PMC1434515

  • Heme oxygenase in Candida albicans is regulated by hemoglobin and is necessary for metabolism of exogenous heme and hemoglobin to alpha-biliverdin JOURNAL OF BIOLOGICAL CHEMISTRY Pendrak, M. L., Chao, M. P., Yan, S. S., Roberts, D. D. 2004; 279 (5): 3426-3433


    Candida albicans is an opportunistic pathogen that has adapted uniquely to life in mammalian hosts. One of the host factors recognized by this yeast is hemoglobin, which binds to a specific cell surface receptor. In addition to its regulating the expression of adhesion receptors on the yeast, we have found that hemoglobin induces the expression of a C. albicans heme oxygenase (CaHmx1p). Hemoglobin transcriptionally induces the CaHMX1 gene independent of the presence of inorganic iron in the medium. A Renilla luciferase reporter driven by the CaHMX1 promoter demonstrated rapid activation of transcription by hemoglobin and (cobalt protoporphyrin IX) globin but not by apoglobin or other proteins. In contrast, iron deficiency or exogenous hemin did not activate the reporter until after 3 h, suggesting that induction of the promoter by hemoglobin is mediated by receptor signaling rather than heme or iron flux into the cell. As observed following disruption of the Saccharomyces cerevisiae ortholog, HMX1, a CaHMX1 null mutant was unable to grow under iron restriction. This suggests a role for CaHmx1p in inorganic iron acquisition. CaHMX1 encodes a functional heme oxygenase. Exogenous heme or hemoglobin is exclusively metabolized to alpha-biliverdin. CaHMX1 is required for utilization of these exogenous substrates, indicating that C. albicans heme oxygenase confers a nutritional advantage for growth in mammalian hosts.

    View details for DOI 10.1074/jbc.M311550200

    View details for Web of Science ID 000188379600037

    View details for PubMedID 14615478

  • Oxidative stress and neuronal adaptation in Alzheimer disease: The role of SAPK pathways ANTIOXIDANTS & REDOX SIGNALING Zhu, X. W., Raina, A. K., Lee, H. G., Chao, M., Nunomura, A., Tabaton, M., Petersen, R. B., Perry, G., Smith, M. A. 2003; 5 (5): 571-576


    Recent evidence indicates that oxidative stress occurs early in the progression of Alzheimer disease, significantly before the development of the hallmark pathologies, namely neurofibrillary tangles and senile plaques. The interaction of abnormal mitochondria, redox transition metals, and oxidative stress response elements contributes to the generation of reactive oxygen species in diseased neurons. Oxidative damage to major cellular molecules is seen in a number of disease states that are either acute or chronic and it is apparent that without eliciting compensations that restore redox balance, cells will rapidly succumb to death. Indeed, although oxidative stress is a prominent feature in Alzheimer disease, few vulnerable neurons show clear signs of apoptosis, suggesting that the level of oxidative stress does not significantly exceed neuronal oxidative defenses. In light of this observation, we propose that neurons in Alzheimer disease are exposed to low, but chronic, levels of oxidative stress that lead neurons to elicit adaptive responses such as the activation of stress-activated protein kinase pathways.

    View details for Web of Science ID 000186101200009

    View details for PubMedID 14580312