A Fully Human IgE Specific for CD38 as a Potential Therapy for Multiple Myeloma

Multiple myeloma (MM) is an incurable malignancy of plasma cells and the second most common hematologic malignancy in the United States. Although antibodies in clinical cancer therapy are generally of the IgG class, antibodies of the IgE class have attractive properties as cancer therapeutics, such as their high affinity for Fc receptors (FcεRs), the low serum levels of endogenous IgE allowing for less competition for FcR occupancy, and the lack of inhibitory FcRs. Importantly, the FcεRs are expressed on immune cells that elicit antibody-dependent cell-mediated cytotoxicity (ADCC), antibody-dependent cell-mediated phagocytosis (ADCP), and/or antigen presentation such as mast cells, eosinophils, macrophages, and dendritic cells. We now report the development of a fully human IgE targeting human CD38 as a potential MM therapy. We targeted CD38 given its high and uniform expression on MM cells. The novel anti-CD38 IgE, expressed in mammalian cells, is properly assembled and secreted, exhibits the correct molecular weight, binds antigen and the high affinity FcεRI, and induces degranulation of FcεRI expressing cells in vitro and also in vivo in transgenic BALB/c mice expressing human FcεRIα. Moreover, the anti-CD38 IgE induces ADCC and ADCP mediated by monocytes/macrophages against human MM cells (MM.1S). Importantly, the anti-CD38 IgE also prolongs survival in a preclinical disseminated xenograft mouse model using SCID-Beige mice and human MM.1S cells when administered with human peripheral blood mononuclear cells (PBMCs) as a source of monocyte effector cells. Our results suggest that anti-CD38 IgE may be effective in humans bearing MM and other malignancies expressing CD38.

Efficacy of Antibodies Targeting TfR1 in Xenograft Mouse Models of AIDS-Related Non-Hodgkin Lymphoma

Transferrin receptor 1 (TfR1), also known as CD71, is a transmembrane protein involved in the cellular uptake of iron and the regulation of cell growth. This receptor is expressed at low levels on a variety of normal cells, but is upregulated on cells with a high rate of proliferation, including malignant cells and activated immune cells. Infection with the human immunodeficiency virus (HIV) leads to the chronic activation of B cells, resulting in high expression of TfR1, B-cell dysfunction, and ultimately the development of acquired immunodeficiency syndrome-related B-cell non-Hodgkin lymphoma (AIDS-NHL). Importantly, TfR1 expression is correlated with the stage and prognosis of NHL. Thus, it is a meaningful target for antibody-based NHL therapy. We previously developed a mouse/human chimeric IgG3 specific for TfR1 (ch128.1/IgG3) and showed that this antibody exhibits antitumor activity in an in vivo model of AIDS-NHL using NOD-SCID mice challenged intraperitoneally with 2F7 human Burkitt lymphoma (BL) cells that harbor the Epstein-Barr virus (EBV). We have also developed an IgG1 version of ch128.1 that shows significant antitumor activity in SCID-Beige mouse models of disseminated multiple myeloma, another B-cell malignancy. Here, we aim to explore the utility of ch128.1/IgG1 and its humanized version (hu128.1) in mouse models of AIDS-NHL. To accomplish this goal, we used the 2F7 cell line variant 2F7-BR44, which is more aggressive than the parental cell line and forms metastases in the brain of mice after systemic (intravenous) administration. We also used the human BL cell line JB, which in contrast to 2F7, is EBV-negative, allowing us to study both EBV-infected and non-infected NHL tumors. Treatment with ch128.1/IgG1 or hu128.1 of SCID-Beige mice challenged locally (subcutaneously) with 2F7-BR44 or JB cells results in significant antitumor activity against different stages of disease. Treatment of mice challenged systemically (intravenously) with either 2F7-BR44 or JB cells also showed significant antitumor activity, including long-term survival. Taken together, our results suggest that targeting TfR1 with antibodies, such as ch128.1/IgG1 or hu128.1, has potential as an effective therapy for AIDS-NHL.

Combination Therapy of an Antibody Specific for Transferrin Receptor 1 (ch128.1/IgG1) With Bortezomib or Lenalidomide Results in Increased Survival in an In Vivo Model of Human Multiple Myeloma: A Brief Communication

Transferrin receptor 1 (TfR1) is a universal cancer marker and a meaningful target for antibody-based immunotherapy. We previously developed a mouse/human chimeric antibody (ch128.1/IgG1) specific for the human TfR1 and reported that treatment of SCID-Beige mice bearing disseminated human multiple myeloma (MM) cells with ch128.1/IgG1 results in significant antitumor activity in early-stage and late-stage disease. Both bortezomib and lenalidomide are Food and Drug Administration (FDA) approved therapeutics used to treat MM in combination with other agents. Since combining treatments with different mechanisms of action is an effective antitumor strategy and given the relevance of bortezomib and lenalidomide in MM therapy, we decided to explore, for the first time, the combination of bortezomib or lenalidomide treatment with ch128.1/IgG1 within the context of late-stage MM disease. We found that treatment with a single dose of ch128.1/IgG1, or multiple doses of bortezomib or lenalidomide, used as single agents, results in significant antitumor activity in SCID-Beige mice bearing late-stage disseminated human MM.1S tumors. However, this antitumor activity is superior when ch128.1/IgG1 is combined with either bortezomib or lenalidomide, showing significantly longer survival compared with any therapy used alone. These novel results suggest that the combinations of ch128.1/IgG1 and bortezomib or lenalidomide are promising strategies against MM.

Host receptor-targeted therapeutic approach to counter pathogenic New World mammarenavirus infections

Five New World mammarenaviruses (NWMs) cause life-threatening hemorrhagic fever (HF). Cellular entry by these viruses is mediated by human transferrin receptor 1 (hTfR1). Here, we demonstrate that an antibody (ch128.1/IgG1) which binds the apical domain of hTfR1, potently inhibits infection of attenuated and pathogenic NWMs in vitro. Computational docking of the antibody Fab crystal structure onto the known structure of hTfR1 shows an overlapping receptor-binding region shared by the Fab and the viral envelope glycoprotein GP1 subunit that binds hTfR1, and we demonstrate competitive inhibition of NWM GP1 binding by ch128.1/IgG1 as the principal mechanism of action. Importantly, ch128.1/IgG1 protects hTfR1-expressing transgenic mice against lethal NWM challenge. Additionally, the antibody is well-tolerated and only partially reduces ferritin uptake. Our findings provide the basis for the development of a novel, host receptor-targeted antibody therapeutic broadly applicable to the treatment of HF of NWM etiology.

Targeting TfR1 with the ch128.1/IgG1 Antibody Inhibits EBV-driven Lymphomagenesis in Immunosuppressed Mice Bearing EBV+ Human Primary B-cells

Epstein-Barr virus (EBV) is a human gammaherpesvirus associated with the development of hematopoietic cancers of B-lymphocyte origin, including AIDS-related non-Hodgkin lymphoma (AIDS-NHL). Primary infection of B-cells with EBV results in their polyclonal activation and immortalization. The transferrin receptor 1 (TfR1), also known as CD71, is important for iron uptake and regulation of cellular proliferation. TfR1 is highly expressed in proliferating cells, including activated lymphocytes and malignant cells. We developed a mouse/human chimeric antibody targeting TfR1 (ch128.1/IgG1) that has previously shown significant antitumor activity in immunosuppressed mouse models bearing human malignant B-cells, including multiple myeloma and AIDS-NHL cells. In this article, we examined the effect of targeting TfR1 to inhibit EBV-driven activation and growth of human B-cells in vivo using an immunodeficient NOD.Cg-Prkdcscid Il2rgtm1Wjl /SzJ [NOD/SCID gamma (NSG)] mouse model. Mice were implanted with T-cell-depleted, human peripheral blood mononuclear cells (PBMCs), either without EBV (EBV-), or exposed to EBV in vitro (EBV+), intravenously via the tail vein. Mice implanted with EBV+ cells and treated with an IgG1 control antibody (400 μg/mouse) developed lymphoma-like growths of human B-cell origin that were EBV+, whereas mice implanted with EBV+ cells and treated with ch128.1/IgG1 (400 μg/mouse) showed increased survival and significantly reduced inflammation and B-cell activation. These results indicate that ch128.1/IgG1 is effective at preventing the growth of EBV+ human B-cell tumors in vivo, thus, indicating that there is significant potential for agents targeting TfR1 as therapeutic strategies to prevent the development of EBV-associated B-cell malignancies. SIGNIFICANCE: An anti-TfR1 antibody, ch128.1/IgG1, effectively inhibits the activation, growth, and immortalization of EBV+ human B-cells in vivo, as well as the development of these cells into lymphoma-like tumors in immunodeficient mice.

Antibodies Targeting the Transferrin Receptor 1 (TfR1) as Direct Anti-cancer Agents

The transferrin receptor 1 (TfR1), also known as cluster of differentiation 71 (CD71), is a type II transmembrane glycoprotein that binds transferrin (Tf) and performs a critical role in cellular iron uptake through the interaction with iron-bound Tf. Iron is required for multiple cellular processes and is essential for DNA synthesis and, thus, cellular proliferation. Due to its central role in cancer cell pathology, malignant cells often overexpress TfR1 and this increased expression can be associated with poor prognosis in different types of cancer. The elevated levels of TfR1 expression on malignant cells, together with its extracellular accessibility, ability to internalize, and central role in cancer cell pathology make this receptor an attractive target for antibody-mediated therapy. The TfR1 can be targeted by antibodies for cancer therapy in two distinct ways: (1) indirectly through the use of antibodies conjugated to anti-cancer agents that are internalized by receptor-mediated endocytosis or (2) directly through the use of antibodies that disrupt the function of the receptor and/or induce Fc effector functions, such as antibody-dependent cell-mediated cytotoxicity (ADCC), antibody-dependent cell-mediated phagocytosis (ADCP), or complement-dependent cytotoxicity (CDC). Although TfR1 has been used extensively as a target for antibody-mediated cancer therapy over the years, interest continues to increase for both targeting the receptor for delivery purposes and for its use as direct anti-cancer agents. This review focuses on the developments in the use of antibodies targeting TfR1 as direct anti-tumor agents.

Abstract LB-089: Targeting transferrin receptor 1 (TfR1) with the ch128.1/IgG1 antibody inhibits Epstein-Barr virus (EBV) driven lymphoproliferative growth and lymphomagenesis in immunosuppressed mice bearing human B cells

Epstein-Barr virus (EBV) is a human herpesvirus that is associated with malignancies of both B lymphocyte and epithelial cell origin. EBV is associated with the development of approximately 1.5% of all cancers worldwide, including AIDS-related non-Hodgkin lymphoma (AIDS-NHL), Hodgkin lymphoma (HL), and post-transplant lymphoproliferative disease (PTLD). Primary infection of B cells with EBV results in their polyclonal activation and immortalization. The transferrin receptor 1 (TfR1), also known as CD71, is important for iron uptake and regulation of cellular proliferation. The TfR1 is expressed at high levels in proliferating cells including activated lymphocytes and malignant cells. We have developed a mouse/human chimeric antibody targeting TfR1 (ch128.1/IgG1) that has shown significant anti-tumor activity in immunosuppressed mouse models bearing human malignant B cells, including multiple myeloma and AIDS-NHL cells. In this study, we examined the effect of targeting TfR1 to inhibit EBV driven transformation of human B cells in vivo using an immunodeficient NSG mouse model. T cell-depleted human peripheral blood mononuclear cells were infected by exposure to EBV-containing supernatants from a B-lymphoblastoid cell line (B95-8). Mice were inoculated with these cells immediately following infection with EBV (day 0), or after cells were cultured for 7 days post infection prior to injection (day 7), and treated with ch128.1/IgG1 or an IgG1 isotype control antibody at 2 and 28 days post-inoculation. We monitored survival, serum levels of human cytokines, and characterized tumor-like growths in spleen and liver by assessing expression of human CD19 (marker for human B cells), EBV latent membrane protein 1 (LMP1; a marker for EBV infection), and human immunoglobulin light chain kappa or lambda (markers for monoclonality) by immunohistochemistry. Treatment with ch128.1/IgG1 significantly enhanced survival, compared to mice treated with the isotype control IgG1. Lymphoma-like cells of human B cell origin that were EBV-LMP1-positive, and often monoclonal, developed in most mice injected with EBV-infected cells (day 0 and 7) treated with the IgG1 control antibody, but only rarely in ch128.1/IgG1 treated animals. In addition, serum levels of human IL-6, IL-8, IFN-γ, CXCL13, sCD25, and sCD27, indicators of human B cell activation and proliferation, were lower in animals treated with ch128.1/IgG1. Taken together, these results show that ch128.1/IgG1 inhibited EBV driven lymphomagenesis using the NSG mouse model newly adapted to study EBV infection/transformation, indicating that there is significant potential for agents targeting TfR1 as therapeutic strategies to prevent EBV-associated B cell malignancies, including AIDS-NHL, HL, and PTLD.

Citation Format: Laura E. Martinez, Tracy R. Daniels-Wells, Yu Guo, Larry I. Magpantay, Pierre V. Candelaria, Manuel L. Penichet, Otoniel Martinez-Maza, Marta Epeldegui. Targeting transferrin receptor 1 (TfR1) with the ch128.1/IgG1 antibody inhibits Epstein-Barr virus (EBV) driven lymphoproliferative growth and lymphomagenesis in immunosuppressed mice bearing human B cells [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr LB-089.

Abstract 5655: Efficacy of antibodies targeting TfR1 in xenograft mouse models of AIDS-related non-Hodgkin lymphoma

Infection with the human immunodeficiency virus (HIV) and the development of acquired immunodeficiency syndrome (AIDS) increases the risk of developing B-cell lymphomas. AIDS-related B-cell non-Hodgkin lymphoma (AIDS-NHL) remains a significant clinical problem in the era of effective combination anti-retroviral therapy. In fact, AIDS-NHL is currently the most common AIDS-related malignancy in developed countries, where NHL accounts for 23-30% of all AIDS-related deaths. Transferrin receptor 1 (TfR1), also known as CD71, is a type II transmembrane homodimeric protein involved in the cellular uptake of iron and the regulation of cell growth. It is expressed on normal B cells at low levels and is upregulated upon activation. HIV infection leads to the chronic activation of B cells, which results in high expression of TfR1 on these cells, B-cell dysfunction, and ultimately the development of AIDS-NHL. Importantly, TfR1 expression is correlated with stage and prognosis of NHL including AIDS-NHL. Thus, it is a meaningful target for antibody-based NHL therapy. We previously developed a mouse/human chimeric IgG3 specific for human TfR1 (ch128.1/IgG3) and have shown that this antibody administered intraperitoneally exhibits antitumor activity in an in vivo model of AIDS-NHL where NOD-SCID mice were challenged intraperitoneally with 2F7 human Burkitt lymphoma (BL) cells that are positive for the Epstein-Barr Virus (EBV). More recently, we have developed a mouse/human chimeric IgG1 version of ch128.1 that shows significant antitumor activity in various disseminated mouse models of human multiple myeloma (MM), another B-cell malignancy. In the present studies, we sought to further explore in two novel mouse models of human AIDS-NHL the utility of targeting the TfR1 with ch128.1/IgG1 and its recently developed humanized version (hu128.1). To accomplish this goal, we used the 2F7 cell line variant 2F7-BR44, which forms metastases in the brain of mice upon intravenous (i.v.) injection. We also used human JB cells, which are of particular relevance since they are human BL cells that are EBV negative. We found that systemic (i.v.) treatment with ch128.1/IgG1 or hu128.1 of SCID-Beige mice challenged locally (subcutaneously) with 2F7-BR44 or JB tumor cells results in significant antitumor activity against different stages of the disease. Treatment of mice challenged systemically (i.v.) with 2F7-BR44 or JB tumor cells also showed antitumor activity, including long-term survival in some cases. Taken together, our results suggest that targeting TfR1 with antibodies such as ch128.1/IgG1 and hu128.1 has potential as an effective therapy for B-cell malignancies, including MM and AIDS-NHL.

Citation Format: Tracy R. Daniels-Wells, Pierre V. Candelaria, Emiko Kranz, Jing Wen, Lan Weng, Masakazu Kamata, Juan Carlos Almagro, Otoniel Martinez-Maza, Manuel L. Penichet. Efficacy of antibodies targeting TfR1 in xenograft mouse models of AIDS-related non-Hodgkin lymphoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5655.

Amino acid residues involved in the heparin-binding activity of murine IL-12 in the context of an antibody-cytokine fusion protein

An antibody-cytokine fusion protein, composed of the murine single-chain cytokine interleukin-12 (IL-12) genetically fused to a human IgG3 specific for the human tumor-associated antigen HER2/neu maintains antigen binding, cytokine bioactivity, and IL-12 heparin-binding activity. This latter property is responsible for the binding of the cytokine to glycosaminoglycans (GAGs) on the cell surface and the extracellular matrix and has been implicated in modulating IL-12 bioactivity. Previous studies indicate that the p40 subunit of human and murine IL-12 is responsible for the heparin-binding activity of this heterodimeric cytokine. In the present study we used bioinformatic analysis and site-directed mutagenesis to develop a version of the antibody-(IL-12) fusion protein without heparin-binding activity. This was accomplished by replacing the basic arginine (R) and lysine (K) residues in the cluster of amino acids 254-260 (RKKEKMK) of the murine IL-12 p40 subunit by the neutral non-polar amino acid alanine (A), generating an AAAEAMA mutant fusion protein. ELISA and flow cytometry demonstrated that the antibody fusion protein lacks heparin-binding activity but retains antigen binding. A T-cell proliferation assay showed IL-12 bioactivity in this construct. However, the IL-12 bioactivity is decreased compared to its non-mutated counterpart, which is consistent with an ancillary role of the heparin-binding site of IL-12 in modulating its activity. Thus, we have defined a cluster of amino acid residues with a crucial role in the heparin-binding activity of murine IL-12 in the context of an antibody-cytokine fusion protein.

Abstract 5760: An IgG1 version of the anti-TfR1 antibody ch128.1 shows significant antitumor activity against different xenograft models of multiple myeloma

The transferrin receptor 1 (TfR1), also identified as CD71, is a type II transmembrane homodimeric protein involved in the cellular uptake of iron and in the regulation of cell growth. TfR1 is a meaningful target for antibody-based cancer immunotherapy due to its high expression levels on the surface of cancer cells and its central role in cancer pathology. We previously developed a mouse/human chimeric IgG3 specific for human TfR1 (ch128.1), which exhibits antitumor activity in SCID-Beige mice bearing disseminated multiple myeloma (MM) KMS-11 cells. Since human IgG1 has been the isotype of choice for therapeutic antibodies targeting malignant cells and has several advantages compared to IgG3, including a more established developability, we constructed an IgG1 version of ch128.1. This novel antibody, ch128.1/IgG1, expressed in murine cells (NS0/1), is properly assembled and secreted and binds antigen (TfR1) similar to its IgG3 counterpart, as demonstrated by ELISA and flow cytometry. Administration of a single dose of the IgG1 completely blocks subcutaneous KMS-11 tumor formation in SCID-Beige mice. Importantly, a single dose of the antibody also shows significant protection, including long-term survival, in this same strain of mice bearing disseminated human MM cells KMS-11 (Asian origin) or MM.1S (African American origin), at different stages of the disease. As expected, the protection was stronger when the mice were treated at an earlier disease stage. Studies using MM.1S cells are of particular relevance given the higher incidence and mortality of MM in African Americans compared to other racial groups. Importantly, we also found that ch128.1/IgG1 confers in vivo protection against MM.1R cells, the MM.1S variant that is dexamethasone resistant. We also developed a ch128.1/IgG1 triple mutant (L234A/L235A/P329S) antibody that does not bind to FcγRs and C1q (the initial protein of the complement pathway), but retains TfR1 binding, as well as binding to FcRn, the neonatal Fc receptor (also known as the Brambell receptor), which is critical in retaining antibody bioavailability in the blood. The triple mutant failed to confer protection in vivo against KMS-11 and MM.1S cells, suggesting a critical role of the antibody Fc fragment in ch128.1/IgG1-mediated antitumor activity, consistent with a potential role of functional effector cells present in this mouse model, such as macrophages. In fact, we found that ch128.1/IgG1 elicits antibody-dependent cell-mediated cytotoxicity (ADCC) and antibody-dependent cell-mediated phagocytosis (ADCP) in the presence of murine bone marrow derived macrophages as effectors and KMS-11 cells as targets, similar to its IgG3 counterpart. Taken together, our results suggest that ch128.1/IgG1 has great potential as an effective therapy for incurable human B-cell malignancies such as MM.

Citation Format: Tracy R. Daniels-Wells, Pierre V. Candelaria, Lai Sum Leoh, Otoniel Martinez-Maza, Manuel L. Penichet. An IgG1 version of the anti-TfR1 antibody ch128.1 shows significant antitumor activity against different xenograft models of multiple myeloma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5760.

Efficacy and Mechanism of Antitumor Activity of an Antibody Targeting Transferrin Receptor 1 in Mouse Models of Human Multiple Myeloma

The transferrin receptor 1 (TfR1) is an attractive target for Ab-mediated cancer therapy. We previously developed a mouse/human chimeric IgG3 Ab (ch128.1) targeting human TfR1, which exhibits direct in vitro cytotoxicity against certain human malignant B cells through TfR1 degradation and iron deprivation. ch128.1 also demonstrates exceptional antitumor activity against the B cell malignancy multiple myeloma (MM) in xenograft models of SCID-Beige mice bearing either disseminated ARH-77 or KMS-11 cells in an early disease setting. Interestingly, this activity is observed even against KMS-11 cells, which show no sensitivity to the direct cytotoxic activity of ch128.1 in vitro. To understand the contributions of the Fc fragment, we generated a ch128.1 mutant with impaired binding to FcγRs and to the complement component C1q, which retains binding to the neonatal Fc receptor. We now report that this mutant Ab does not show antitumor activity in these two MM models, indicating a crucial role of the Fc fragment in the antitumor activity of ch128.1, which can be attributed to effector functions (Ab-dependent cell-mediated cytotoxicity, Ab-dependent cell-mediated phagocytosis, and/or complement-dependent cytotoxicity). Interestingly, in the KMS-11 model, complement depletion does not affect protection, whereas macrophage depletion does. Consistent with this observation, we found that ch128.1 induces Ab-dependent cell-mediated cytotoxicity and Ab-dependent cell-mediated phagocytosis against KMS-11 cells in the presence of murine bone marrow-derived macrophages. Finally, we found that ch128.1 therapy effectively increases survival in a late MM disease setting. Our results suggest that macrophages play a major role in ch128.1-mediated antitumor protection in our models and that ch128.1 can be effective against human B cell malignancies such as MM.

Abstract 73: Role of macrophages in the antitumor activity of an anti-transferrin receptor 1 antibody ch128.1 in a xenograft model of multiple myeloma

The transferrin receptor 1 (TfR1), also known as CD71, is a membrane glycoprotein involved in cellular iron uptake and regulation of cell growth. The high level of TfR1 expression on malignant cells and its key role in cancer cell pathology make this receptor an attractive target for antibody cancer therapy. We previously developed a mouse/human chimeric IgG3 specific for human TfR1 (ch128.1). This antibody exhibits direct cytotoxicity against certain human malignant B cells in vitro through TfR1 degradation and iron deprivation. Importantly, ch128.1 shows remarkable anti-tumor activity in xenograft models of disseminated multiple myeloma (MM) in immunosuppressed mice (SCID-Beige). Interestingly, this anti-tumor protection was observed even against MM cells (KMS-11 cells) that show no sensitivity to this antibody in vitro, suggesting the in vivo contributions of antibody effector functions. This possibility was supported by the lack of anti-tumor protection observed using a ch128.1 Fc mutant with impaired binding to FcγRs and to the complement component C1q. To examine host effector functions involved in ch128.1-mediated protection in our mouse model bearing KMS-11 tumors, depletion studies of complement and macrophages were performed. Complement depletion using cobra venom factor (CVF) did not affect protection, suggesting that complement-mediated cytotoxicity (CDC) is not a relevant mechanism of action. Notably, we now report that macrophage depletion using clodronate liposomes (clodrolip) significantly reduced protection, suggesting that these effector cells play a relevant role in the anti-tumor activity. Consistent with this result, we also report that ch128.1 is capable of eliciting antibody-dependent cell-mediated cytotoxicity (ADCC) and antibody-dependent cell-mediated phagocytosis (ADCP) against KMS-11 cells in the presence of the murine macrophage cell line J774.2 or murine bone marrow-derived macrophages. To examine the role of iron deprivation in ch128.1-mediated tumor death in vivo, animals treated with ch128.1 were systemically supplemented with iron in a preliminary study. However, no difference in survival was observed, suggesting that iron deprivation is not a contributor to the effects of ch128.1 in our in vivo model or the iron dose tested was not optimal. Our results suggest that macrophages play a key role in ch128.1-mediated anti-tumor protection in our model and that ch128.1 can be an effective therapy of incurable human B-cell malignancies such as MM.

Citation Format: Lai Sum Leoh, Yoon Kyung Kim, Pierre V. Candelaria, Otoniel Martínez-Maza, Tracy R. Daniels-Wells, Manuel L. Penichet. Role of macrophages in the antitumor activity of an anti-transferrin receptor 1 antibody ch128.1 in a xenograft model of multiple myeloma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 73. doi:10.1158/1538-7445.AM2017-73

Leptin signaling and cancer chemoresistance: Perspectives

Obesity is a major health problem and currently is endemic around the world. Obesity is a risk factor for several different types of cancer, significantly promoting cancer incidence, progression, poor prognosis and resistance to anti-cancer therapies. The study of this resistance is critical as development of chemoresistance is a serious drawback for the successful and effective drug-based treatments of cancer. There is increasing evidence that augmented adiposity can impact on chemotherapeutic treatment of cancer and the development of resistance to these treatments, particularly through one of its signature mediators, the adipokine leptin. Leptin is a pro-inflammatory, pro-angiogenic and pro-tumorigenic adipokine that has been implicated in many cancers promoting processes such as angiogenesis, metastasis, tumorigenesis and survival/resistance to apoptosis. Several possible mechanisms that could potentially be developed by cancer cells to elicit drug resistance have been suggested in the literature. Here, we summarize and discuss the current state of the literature on the role of obesity and leptin on chemoresistance, particularly as it relates to breast and pancreatic cancers. We focus on the role of leptin and its significance in possibly driving these proposed chemoresistance mechanisms, and examine its effects on cancer cell survival signals and expansion of the cancer stem cell sub-populations.

Abstract P4-06-18: Targeting basal-like breast cancer through downstream effectors of oncogene cooperation

Basal-like breast cancer is a highly aggressive and lethal form of cancer, not amenable to treatment by molecularly targeted agents or conventional chemotherapy effective against other forms of breast cancer. Thus, discovery of novel intervention targets regulating tumorigenesis in basal-like breast cancer cells is critical. The success of molecularly targeted therapies against some forms of cancer has led to a search for additional cancer cell-specific targets that will permit effective tumor inhibition with minimal damage to normal cells. These efforts are largely focused on identification of novel oncogenes and tumor suppressors by genome sequencing or synthetic lethalities found via genome-wide RNAi screens. We employ a novel approach to identify cancer cell vulnerabilities among genes disregulated downstream of cooperating oncogenic mutations, which drive malignant transformation in large part through synergistic modulation of non-mutated downstream effector genes, the ‘cooperation response genes’ (CRGs) [McMurray et al., Nature, 19 June 2008]. After assessing how common was CRG disregulation in different epithelial cancers, via comparative genomic analysis of CRG expression patterns in tumor vs. normal tissue, we found that 34 CRGs (∼35%) were significantly disregulated in breast cancer. Because of the need for novel intervention targets in basal-like breast cancer, we focused our functional analysis there. We have tested a subset of CRGs disregulated in breast tumors for their contribution to malignancy in basal-like breast cancer cells, re-setting CRG levels toward normal cell levels by stable cDNA expression or shRNA-mediated knock-down and testing tumor formation capacity of perturbed cells. Our studies reveal that CRGs play an essential role in controlling tumor formation of basal-like breast cancer cells, with significant reductions in tumor volume, and in some cases reduced tumor incidence, upon CRG modulation. Disruption of cell behavior appears to be limited to cancer cells, as non-transformed mammary cells harboring analogous perturbations retain capacity to form acinar structures in 3D culture. Several FDA approved pharmacological agents, identified to reverse the CRG expression pattern, display inhibitory effects on basal-like breast cancer cell lines, with minimal effects on non-transformed cells. CRGs thus represent cancer cell-specific vulnerabilities in basal-like breast cancer, providing novel and unexpected opportunities for intervention against this difficult-to-target disease.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P4-06-18.

The importance of environment on respiratory genotype/phenotype relationships in the Inuit

BACKGROUND

Genetic and environmental influences and their interactions are central to asthma pathogenesis. This study aimed to investigate the effects of different macro-environments on asthma genotype-phenotype associations in two geographically separated populations with common ancestry.

METHODS

To accomplish this, two unselected populations of Inuit were recruited, one living in Greenland (n = 618) and the other in Denmark (n = 739). Subjects were genotyped for CD14 C-159T, SCGB1A1 A38G, ADRB2 Arg16Gly and Gln27Glu. The resulting genetic data were analysed for relationships with asthma-related parameters including lung function, ever asthma, atopy, rhinitis and dermatitis.

RESULTS

The results showed contrasting magnitude and direction of genetic associations between the two geographically separate Inuit populations. In Greenland, the ADRB2 16Arg allele was associated with male-specific lower lung function, but in Denmark the same allele was associated with male-specific higher lung function. This allele was also associated with higher incidence of ever asthma in Denmark but not in Greenland. The SCGB1A1 38A allele was associated with lower rhinitis prevalence in Greenland but not in Denmark.

CONCLUSIONS

These associations suggest that environment interacts with candidate asthma genes to modulate asthma pathogenesis in the Inuit.

Association between asthma-related phenotypes and the CC16 A38G polymorphism in an unselected population of young adult Danes

The gene for Clara cell 16-kDa (CC16) protein is a promising candidate for asthma susceptibility. The CC16 38A allele has been associated with decreased CC16 plasma levels and increased incidence of asthma in Australian children. To date these results have not been replicated in adults. Therefore, potential links between CC16 A38G, asthma and atopy were investigated in an unselected population of young adult Danes. Four hundred sixty-four Danes, aged 19-29 years, from Copenhagen participated in an asthma and allergy phenotype-genotype study. Genotyping was done by Sau96I restriction digestion of PCR products spanning the A38G polymorphism. Potential A38G genotype and asthma-related phenotype associations were investigated using regression analysis, adjusting for potential confounders where appropriate. Adults with the 38AA genotype had higher odds of current asthma (OR 3.2, P=0.013) and ever asthma (OR 2.2, P=0.045) compared with those with the 38GG genotype. Adjusting for atopy had minimal effect on this relationship. A positive linear trend was evident between the 38A allele and atopic dermatitis (OR 1.67, P=0.02). No associations were found between the A38G polymorphism and rhinitis, atopy, forced expiratory volume in 1 s (FEV(1)), forced vital capacity (FVC), airway responsiveness (AR) to histamine or peripheral blood eosinophil level (PBEL). An atopy-independent association between CC16 38AA and asthma prevalence was identified, suggesting the CC16 38A allele predisposes to adult asthma independent of Th1/Th2 processes. This finding is consistent with previous studies in children, but is the first reported association between CC16 A38G and asthma in adults. CC16 38A also displayed a positive linear trend with atopic dermatitis.

Growth in the presence of salicylate increases fluoroquinolone resistance in Staphylococcus aureus

Salicylate and acetylsalicylate slightly increased fluoroquinolone resistance in ciprofloxacin-susceptible and -resistant Staphylococcus aureus. Salicylate allowed a greater number of cells from ciprofloxacin-susceptible and -resistant strains to survive on high fluoroquinolone concentrations. Salicylate also increased the frequency with which a susceptible strain mutated to become more resistant to ciprofloxacin.