[show abstract][hide abstract] ABSTRACT: Despite significant advances in biology and medicine, the incidence and mortality due to breast cancer world-wide is still unacceptably high. Thus, there is an urgent need to discover new molecular targets. In this paper, we show evidence for a novel target in human breast cancer, the tetraspan protein epithelial membrane protein-2 (EMP2). Using tissue tumor arrays, protein expression of EMP2 was measured and found to be minimal in normal mammary tissue, but it was upregulated in 63% of invasive breast cancer tumors and in 73% of triple negative tumors tested. To test the hypothesis that EMP2 may be a suitable target for therapy, we constructed a fully human IgG1 antibody specific for a conserved domain of human and murine EMP2. Treatment of breast cancer cells with the anti-EMP2 IgG1 significantly inhibited EMP2 mediated signaling, blocked FAK/Src signaling, inhibited invasion, and promoted apoptosis in vitro. In both human xenograft and syngeneic metastatic tumor monotherapy models, anti-EMP2 IgG1 retarded tumor growth without detectable systemic toxicity. This anti-tumor effect was in part attributable to a potent ADCC response as well as direct cytotoxicity induced by the monoclonal antibody. Together, these results identify EMP2 as a novel therapeutic target for invasive breast cancer.
Molecular Cancer Therapeutics 01/2014; · 5.60 Impact Factor
[show abstract][hide abstract] ABSTRACT: We previously developed an antibody-avidin fusion protein (ch128.1Av) specific for the human transferrin receptor 1 (TfR1; CD71) to be used as a delivery vector for cancer therapy and showed that ch128.1Av delivers the biotinylated plant toxin saporin-6 into malignant B cells. However, due to widespread expression of TfR1, delivery of the toxin to normal cells is a concern. Therefore, we explored the potential of dual targeted lentiviral-mediated gene therapy approaches to restrict gene expression to malignant B cells. Targeting occurs through the use of ch128.1Av or its parental antibody without avidin (ch128.1) and through transcriptional regulation using an immunoglobulin promoter.
Flow cytometry was used to detect the expression of enhanced green fluorescent protein (EGFP) in a panel of cell lines. Cell viability after specific delivery of the therapeutic gene FCU1, a chimeric enzyme consisting of cytosine deaminase genetically fused to uracil phosphoribosyltransferse that converts the 5-fluorocytosine (5-FC) prodrug into toxic metabolites, was monitored by an MTS assay.
We found that EGFP was specifically expressed in a panel of human malignant B cells, but not in human T cell lines. EGFP expression was observed in all cell lines when a ubiquitous promoter was used. Furthermore, we show the decrease of cell viability in malignant plasma cells in the presence of 5-FC.
These studies demonstrate that gene expression can be restricted to malignant B cells and suggest that this dual targeted gene therapy strategy may help to circumvent the potential side effects of certain TfR1-targeted protein delivery approaches. This article is protected by copyright. All rights reserved.
The Journal of Gene Medicine 01/2014; · 2.16 Impact Factor
[show abstract][hide abstract] ABSTRACT: Breast cancer remains the second leading cause of cancer death among women in the United States. The breast cancer prognosis is particularly poor in case of tumors overexpressing the oncoprotein HER2/neu. A new nanobioconjugate of the Polycefin(TM) family of anti-cancer drugs based on biodegradable and non-toxic polymalic acid (PMLA) was engineered for a multi-pronged attack on HER2/neu-positive breast cancer cells. An antibody cytokine fusion protein consisting of the immunostimulatory cytokine interleukin-2 (IL-2) genetically fused to an antibody specific for human HER2/neu [anti-HER2/neu IgG3-(IL-2)] was covalently attached to the PMLA backbone to target HER2/neu expressing tumors and ensuring the delivery of IL-2 to the tumor microenvironment. Antisense oligonucleotides (AON) were conjugated to the nanodrug to inhibit the expression of vascular tumor protein laminin-411 in order to block tumor angiogenesis. It is shown that the nanobioconjugate was capable of specifically binding human HER2/neu and retaining the biological activity of IL-2. We also showed the uptake of the nanobioconjugate by HER2/neu-positive breast cancer cells and enhanced tumor targeting in vivo. In addition, the nanobioconjugate was capable of eliciting anti-tumor activity in immunocompetent mice bearing D2F2/E2 murine mammary tumors that express human HER2/neu. Both IgG1 and IgG2a levels were significantly increased in animals treated with the PMLA-fusion nanobioconjugate compared to animals treated with the antibody-cytokine fusion protein alone or control animals, indicative of the induction of a humoral (TH2) and cell-mediated (TH1) immune responses. Animal survival in vivo was significantly longer after treatment with leading nanobioconjugate with fusion [anti-HER2/neu IgG3-(IL-2)] antibody, p<0.05. The combination of these molecules on a single polymeric platform is expected to act through direct elimination of cancer cells, inhibition of tumor angiogenesis, and orchestration of a potent immune response against tumor.
Journal of Controlled Release 06/2013; · 7.63 Impact Factor
[show abstract][hide abstract] ABSTRACT: BACKGROUND: Prostate cancer (PCa) is the second leading cause of cancer deaths in men in the United States. The prostate-specific antigen (PSA), often found at high levels in the serum of PCa patients, has been used as a marker for PCa detection and as a target of immunotherapy. The murine IgG1 monoclonal antibody AR47.47, specific for human PSA, has been shown to enhance antigen presentation by human dendritic cells and induce both CD4 and CD8 T-cell activation when complexed with PSA. In this study, we explored the properties of a novel mouse/human chimeric anti-PSA IgE containing the variable regions of AR47.47 as a potential therapy for PCa. Our goal was to take advantage of the unique properties of IgE in order to trigger immune activation against PCa. METHODS: Binding characteristics of the antibody were determined by ELISA and flow cytometry. In vitro degranulation was determined by the release of beta-hexosaminidase from effector cells. In vivo degranulation was monitored in human FcepsilonRIalpha transgenic mice using the passive cutaneous anaphylaxis assay. These mice were also used for a vaccination study to determine the in vivo anti-cancer effects of this antibody. Significant differences in survival were determined using the Log Rank test. In vitro T-cell activation was studied using human dendritic cells and autologous T cells. RESULTS: The anti-PSA IgE, expressed in murine myeloma cells, is properly assembled and secreted, and binds the antigen and FcepsilonRI. In addition, this antibody is capable of triggering effector cell degranulation in vitro and in vivo when artificially cross-linked, but not in the presence of the natural soluble antigen, suggesting that such an interaction will not trigger systemic anaphylaxis. Importantly, the anti-PSA IgE combined with PSA also triggers immune activation in vitro and in vivo and significantly prolongs the survival of human FcepsilonRIalpha transgenic mice challenged with PSA-expressing tumors in a prophylactic vaccination setting. CONCLUSIONS: The anti-PSA IgE exhibits the expected biological properties and is capable of triggering immune activation and anti-tumor protection. Further studies on this antibody as a potential PCa therapy are warranted.
BMC Cancer 04/2013; 13(1):195. · 3.33 Impact Factor
[show abstract][hide abstract] ABSTRACT: Currently, few rodent models of AIDS-associated non-Hodgkin's lymphoma (AIDS-NHL) exist. In these studies, a novel mouse/human xenograft model of AIDS-associated Burkitt lymphoma (AIDS-BL) was created by injecting cells of the human AIDS-BL cell line, 2F7, intraperitoneally into NOD-SCID mice. Mice developed tumors in the peritoneal cavity, with metastases to the spleen, thymus, and mesenteric lymph nodes. Expression of the chemokine receptor, CXCR5, was greatly elevated in vivo on BL tumor cells in this model, as shown by flow cytometry. CXCL13 is the ligand for CXCR5, and serum and ascites levels of murine, but not human, CXCL13 showed a striking elevation in tumor-bearing mice, with levels as high as 200,000 pg/ml in ascites, as measured by ELISA. As shown by immunohistochemistry, murine CXCL13 was associated with macrophage-like tumor-infiltrating cells that appeared to be histiocytes. Blocking CXCR5 on 2F7 cells with neutralizing antibodies prior to injection into the mice substantially delayed tumor formation. The marked elevations in tumor cell CXCR5 expression and in murine CXCL13 levels seen in the model may potentially identify an important link between tumor-interacting histiocytes and tumor cells in AIDS-BL. These results also identify CXCL13 as a potential biomarker for this disease, which is consistent with previous studies showing that serum levels of CXCL13 were elevated in human subjects who developed AIDS-lymphoma. This mouse model may be useful for future studies on the interactions of the innate immune system and AIDS-BL tumor cells, as well as for the assessment of potential tumor biomarkers for this disease.
PLoS ONE 01/2013; 8(8):e72414. · 3.73 Impact Factor
[show abstract][hide abstract] ABSTRACT: Multiple myeloma is a non-curable B-cell malignancy in which iron metabolism plays an important role. Patients with this disorder almost universally suffer from clinically significant anemia, which is often symptomatic, and which is due to impaired iron utilization. Recent studies have indicated that the proximal cause of dysregulated iron metabolism and anemia in these patients is cytokine-induced upregulation of hepcidin expression. Malignant myeloma cells are dependent on an increased influx of iron, and therapeutic efforts are being made to target this requirement. The studies detailing the characteristics and biochemical abnormalities in iron metabolism causing anemia and the initial attempts to target iron therapeutically are described in this review.
Critical reviews in oncogenesis 01/2013; 18(5):449-61.
[show abstract][hide abstract] ABSTRACT: We previously developed an antibody-avidin fusion protein (ch128.1Av) that targets the human transferrin receptor 1 (TfR1) and exhibits direct cytotoxicity against malignant B cells in an iron-dependent manner. ch128.1Av is also a delivery system and its conjugation with biotinylated saporin (b-SO6), a plant ribosome-inactivating toxin, results in a dramatic iron-independent cytotoxicity, both in malignant cells that are sensitive or resistant to ch128.1Av alone, in which the toxin effectively inhibits protein synthesis and triggers caspase activation. We have now found that the ch128.1Av/b-SO6 complex induces a transcriptional response consistent with oxidative stress and DNA damage, a response that is not observed with ch128.1Av alone. Furthermore, we show that the antioxidant N-acetylcysteine partially blocks saporin-induced apoptosis suggesting that oxidative stress contributes to DNA damage and ultimately saporin-induced cell death. Interestingly, the toxin was detected in nuclear extracts by immunoblotting, suggesting the possibility that saporin might induce direct DNA damage. However, confocal microscopy did not show a clear and consistent pattern of intranuclear localization. Finally, using the long-term culture-initiating cell assay we found that ch128.1Av/b-SO6 is not toxic to normal human hematopoietic stem cells suggesting that this critical cell population would be preserved in therapeutic interventions using this immunotoxin.
[show abstract][hide abstract] ABSTRACT: Multiple myeloma (MM) is an incurable B-lymphocyte malignancy. New therapeutic options have become available during the past several years; however nearly all patients acquire resistance to currently available therapeutic agents. Mechanisms contributing to the pathogenesis and chemoresistance of MM include genetic abnormalities, chromosomal translocations, gene mutations, the interaction between MM cells and the bone marrow microenvironment, and defects in the apoptotic signaling pathways. Survival signaling pathways associated with the pathogenesis of MM and bone marrow stromal cells play crucial roles in promoting growth, survival, adhesion, immortalization, angiogenesis, and drug resistance. The receptor activator of nuclear factor-kappa B/receptor activator of nuclear factor-kappa B ligand/tumor necrosis factor receptor-associated factor (RANK/RANKL-TRAF6) signal pathway mediates osteolytic bone lesions through the activation of the NF-κB and Janus kinase/signal transducer and activator of transcription (JNK) pathways in osteoclast precursor cells and thus contributes to the main clinical manifestations of bone disease. TRAF6 has also been identified as a ligase for Akt ubiquitination and membrane recruitment and its phosphorylation on growth factor stimulation. The inhibition of TRAF6 by silencing RNA or by decoy peptides decreases MM tumor cell proliferation and increases apoptosis as well as bone resorption. Some proteasome inhibitors and benzoxadiazole derivatives showed inhibitory effects on the activity and function of TRAF6. Overall, we propose that TRAF6 may be considered as a potential therapeutic target for the treatment of MM.
[show abstract][hide abstract] ABSTRACT: Five New World (NW) arenaviruses cause human hemorrhagic fevers. Four of these arenaviruses are known to enter cells by binding human transferrin receptor 1 (hTfR1). Here we show that the fifth arenavirus, Chapare virus, similarly uses hTfR1. We also identify an anti-hTfR1 antibody, ch128.1, which efficiently inhibits entry mediated by the glycoproteins of all five viruses, as well as replication of infectious Junín virus. Our data indicate that all NW hemorrhagic fever arenaviruses utilize a common hTfR1 apical-domain epitope and suggest that therapeutic agents targeting this epitope, including ch128.1 itself, can be broadly effective in treating South American hemorrhagic fevers.
Journal of Virology 01/2012; 86(7):4024-8. · 5.08 Impact Factor
[show abstract][hide abstract] ABSTRACT: Although most monoclonal antibodies developed for cancer therapy are of the IgG class, antibodies of the IgE class have certain properties that make them attractive as cancer therapeutics. These properties include the superior affinity for the Fc epsilon receptors (FcεRs), the low serum level of IgE that minimizes competition of endogenous IgE for FcεR occupancy, and the ability to induce a broad and vigorous immune response through the interaction with multiple cells including mast cells, basophils, monocytes, macrophages, dendritic cells, and eosinophils. Tumor-targeted IgE antibodies are expected to harness the allergic response against tumors and activate a secondary, T-cell-mediated immune response. Importantly, the IgE antibody can be used for passive immunotherapy and as an adjuvant of cancer vaccines. However, there are important limitations in the use of animal models including the fact that human IgE does not interact with rodent FcεRs and that there is a different cellular distribution of FcεRs in humans and rodents. Despite these limitations, different murine models have been used with success to evaluate the in vivo anti-cancer activity of several IgE antibodies. These models include wild-type immunocompetent animals bearing syngeneic tumors, xenograft models using immunocompromised mice bearing human tumors and reconstituted with human effector cells, and human FcεRIα transgenic mice bearing syngeneic tumors. In addition, non-human primates such as cynomolgus monkeys can be potentially used for toxicological and pharmacokinetic studies. This article describes the advantages and disadvantages of these models and their use in evaluating the in vivo properties of IgE antibodies for cancer therapy.
Cancer Immunology and Immunotherapy 12/2011; 61(9):1535-46. · 3.64 Impact Factor
[show abstract][hide abstract] ABSTRACT: Breast and ovarian cancer are two of the leading causes of cancer deaths among women in the United States. Overexpression of the HER2/neu oncoprotein has been reported in patients affected with breast and ovarian cancers, and is associated with poor prognosis. To develop a novel targeted therapy for HER2/neu expressing tumors, we have constructed a fully human IgE with the variable regions of the scFv C6MH3-B1 specific for HER2/neu. This antibody was expressed in murine myeloma cells and was properly assembled and secreted. The Fc region of this antibody triggers in vitro degranulation of rat basophilic cells expressing human FcεRI (RBL SX-38) in the presence of murine mammary carcinoma cells that express human HER2/neu (D2F2/E2), but not the shed (soluble) antigen (ECD(HER2)) alone. This IgE is also capable of inducing passive cutaneous anaphylaxis in a human FcεRIα transgenic mouse model, in the presence of a cross-linking antibody, but not in the presence of soluble ECD(HER2). Additionally, IgE enhances antigen presentation in human dendritic cells and facilitates cross-priming, suggesting that the antibody is able to stimulate a secondary T-cell anti-tumor response. Furthermore, we show that this IgE significantly prolongs survival of human FcεRIα transgenic mice bearing D2F2/E2 tumors. We also report that the anti-HER2/neu IgE is well tolerated in a preliminary study conducted in Macaca fascicularis (cynomolgus) monkeys. In summary, our results suggest that this IgE should be further explored as a potential therapeutic against HER2/neu overexpressing tumors, such as breast and ovarian cancers.
Cancer Immunology and Immunotherapy 11/2011; 61(7):991-1003. · 3.64 Impact Factor
[show abstract][hide abstract] ABSTRACT: HER2/neu is an oncogene that facilitates neoplastic transformation due to its ability to transduce growth signals in a ligand-independent manner, is over-expressed in 20-30% of human breast cancers correlating with aggressive disease and has been successfully targeted with trastuzumab (Herceptin®). Because trastuzumab alone achieves only a 15-30% response rate, it is now commonly combined with conventional chemotherapeutic drugs. While the combination of trastuzumab plus chemotherapy has greatly improved response rates and increased survival, these conventional chemotherapy drugs are frequently associated with gastrointestinal and cardiac toxicity, bone marrow and immune suppression. These drawbacks necessitate the development of new, less toxic drugs that can be combined with trastuzumab. Recently, we reported that orally administered alpha-tocopheryloxyacetic acid (α-TEA), a novel ether derivative of alpha-tocopherol, dramatically suppressed primary tumor growth and reduced the incidence of lung metastases both in a transplanted and a spontaneous mouse model of breast cancer without discernable toxicity.
In this study we examined the effect of α-TEA plus HER2/neu-specific antibody treatment on HER2/neu-expressing breast cancer cells in vitro and in a HER2/neu positive human xenograft tumor model in vivo.
We show in vitro that α-TEA plus anti-HER2/neu antibody has an increased cytotoxic effect against murine mammary tumor cells and human breast cancer cells and that the anti-tumor effect of α-TEA is independent of HER2/neu status. More importantly, in a human breast cancer xenograft model, the combination of α-TEA plus trastuzumab resulted in faster tumor regression and more tumor-free animals than trastuzumab alone.
Due to the cancer cell selectivity of α-TEA, and because α-TEA kills both HER2/neu positive and HER2/neu negative breast cancer cells, it has the potential to be effective and less toxic than existing chemotherapeutic drugs when used in combination with HER2/neu antibody.
[show abstract][hide abstract] ABSTRACT: A number of antibodies have been developed that induce lethal iron deprivation (LID) by targeting the transferrin receptor 1 (TfR1/CD71) and either neutralizing transferrin (Tf) binding, blocking internalization of the receptor and/or inducing its degradation. We have developed recombinant antibodies targeting human TfR1 (ch128.1 and ch128.1Av), which induce receptor degradation and are cytotoxic to certain malignant B-cells. We now show that internalization of TfR1 bound to these antibodies can lead to its sequestration and degradation, as well as reduced Tf uptake, and the induction of a transcriptional response consistent with iron deprivation, which is mediated in part by downstream targets of p53. Cells resistant to these antibodies do not sequester and degrade TfR1 after internalization of the antibody/receptor complex, and accordingly maintain their ability to internalize Tf. These findings are expected to facilitate the rational design and clinical use of therapeutic agents targeting iron import via TfR1 in hematopoietic malignancies.
[show abstract][hide abstract] ABSTRACT: Traditional cancer therapy can be successful in destroying tumors, but can also cause dangerous side effects. Therefore, many targeted therapies are in development. The transferrin receptor (TfR) functions in cellular iron uptake through its interaction with transferrin. This receptor is an attractive molecule for the targeted therapy of cancer since it is upregulated on the surface of many cancer types and is efficiently internalized. This receptor can be targeted in two ways: 1) for the delivery of therapeutic molecules into malignant cells or 2) to block the natural function of the receptor leading directly to cancer cell death.
In the present article we discuss the strategies used to target the TfR for the delivery of therapeutic agents into cancer cells. We provide a summary of the vast types of anti-cancer drugs that have been delivered into cancer cells employing a variety of receptor binding molecules including Tf, anti-TfR antibodies, or TfR-binding peptides alone or in combination with carrier molecules including nanoparticles and viruses.
Targeting the TfR has been shown to be effective in delivering many different therapeutic agents and causing cytotoxic effects in cancer cells in vitro and in vivo.
The extensive use of TfR for targeted therapy attests to the versatility of targeting this receptor for therapeutic purposes against malignant cells. More advances in this area are expected to further improve the therapeutic potential of targeting the TfR for cancer therapy leading to an increase in the number of clinical trials of molecules targeting this receptor. This article is part of a Special Issue entitled Transferrins: molecular mechanisms of iron transport and disorders.
Biochimica et Biophysica Acta 08/2011; 1820(3):291-317. · 4.66 Impact Factor
[show abstract][hide abstract] ABSTRACT: Multiple myeloma (MM) is the second most common hematological and incurable malignancy of plasma cells with low proliferative activity in the bone marrow. MM patients initially respond to conventional therapy, however, many develop resistance and recurrences occur. We have identified RKIP as a novel gene product that is differentially overexpressed in MM cell lines and MM tissues compared to other studied tumors and normal bone marrow. This overexpression consisted, in large part, of a phosphorylated inactive form of RKIP at Ser153 (p-Ser153 RKIP). In contrast to RKIP, p-Ser153 RKIP lacks its ability to inhibit the MAPK signaling pathway. The overexpression of p-Ser153 RKIP in MM cell lines and MM tissues was further validated in a mouse model carrying a human MM xenograft, namely, LAGλ-1B. Bioinformatic analyses from databases support the presence of increased RKIP mRNA expression in MM compared to normal plasma cells. In these databases, high RKIP levels in MM are also correlated with the nonhyperdiploid status and the presence of IgH translocations, parameters that generally display more aggressive clinical features and shorter patients' survival irrespective of the treatment. Since RKIP expression regulates both the NF-κB and MAPK survival pathways, the overexpression of "inactive" p-Ser153 RKIP in MM might contribute positively to the overall cell survival/antiapoptotic phenotype and drug resistance of MM through the constitutive activation of survival pathways and downstream the transcription of anti-apoptotic gene products. The overexpression of RKIP and p-Ser153 RKIP in MM is the first demonstration in the literature, since in most tumor tissues the expression of RKIP is very low and the expression of p-Ser153 RKIP is much lower. The relationship between the levels of active RKIP and inactive p-Ser153 RKIP in MM may be of prognostic significance, and the regulation of RKIP activity may be a target for therapeutic intervention.
Forum on immunopathological diseases and therapeutics 04/2011; 2(2).
[show abstract][hide abstract] ABSTRACT: Conventional approaches for the detection of antibody dependent cell-mediated cytotoxicity (ADCC) activity rely on quantification of the release of traceable compounds from target cells or flow cytometry analysis of population-wide phenomena. We report a new method for the direct imaging and quantification of ADCC of cancer cells. The proposed method using imaging flow cytometry combines the statistical power of flow cytometry with the analytical advantages of cell imaging, providing a novel and more comprehensive perspective of effector/target cell interactions during ADCC events. With this method we can quantify and show in detail the morphological changes in target and effector cells, their apoptotic index, the physical interaction between effector and target cells, and a directional transfer of cytosolic contents from effector to target cells. As a model system we used the therapeutic anti-CD20 antibody rituximab to target CFSE labeled Ramos human Burkitt's lymphoma cells, to CMTPX-labeled human monocytic U-937 effector cells. We expect that similar studies using different effector and target cell populations may contribute to the pre-clinical evaluation of therapeutic antibodies and help to identify mechanisms that could be beneficial in the immunotherapy of cancer.
Journal of immunological methods 03/2011; 368(1-2):54-63. · 2.35 Impact Factor
[show abstract][hide abstract] ABSTRACT: Biodegradable nanopolymers are believed to offer great potential in cancer therapy. Here, we report the characterization of a novel, targeted, nanobiopolymeric conjugate based on biodegradable, nontoxic, and nonimmunogenic PMLA [poly(β-l-malic acid)]. The PMLA nanoplatform was synthesized for repetitive systemic treatments of HER2/neu-positive human breast tumors in a xenogeneic mouse model. Various moieties were covalently attached to PMLA, including a combination of morpholino antisense oligonucleotides (AON) directed against HER2/neu mRNA, to block new HER2/neu receptor synthesis; anti-HER2/neu antibody trastuzumab (Herceptin), to target breast cancer cells and inhibit receptor activity simultaneously; and transferrin receptor antibody, to target the tumor vasculature and mediate delivery of the nanobiopolymer through the host endothelial system. The results of the study showed that the lead drug tested significantly inhibited the growth of HER2/neu-positive breast cancer cells in vitro and in vivo by enhanced apoptosis and inhibition of HER2/neu receptor signaling with suppression of Akt phosphorylation. In vivo imaging analysis and confocal microscopy demonstrated selective accumulation of the nanodrug in tumor cells via an active delivery mechanism. Systemic treatment of human breast tumor-bearing nude mice resulted in more than 90% inhibition of tumor growth and tumor regression, as compared with partial (50%) tumor growth inhibition in mice treated with trastuzumab or AON, either free or attached to PMLA. Our findings offer a preclinical proof of concept for use of the PMLA nanoplatform for combination cancer therapy.
Cancer Research 02/2011; 71(4):1454-64. · 8.65 Impact Factor
[show abstract][hide abstract] ABSTRACT: We previously developed an antibody-avidin fusion protein (ch128.1Av) targeting the human transferrin receptor 1 (TfR1, also known as CD71), which demonstrates direct in vitro cytotoxicity against malignant hematopoietic cells. This cytotoxicity is attributed to its ability to decrease the level of TfR1 leading to lethal iron deprivation. We now report that ch128.1Av shows the ability to bind the Fcγ receptors and the complement component C1q, suggesting that it is capable of eliciting Fc-mediated effector functions such as antibody-dependent cell-mediated cytotoxicity and complement-mediated cytotoxicity. In addition, in 2 disseminated multiple myeloma xenograft mouse models, we show that a single dose of ch128.1Av results in significant antitumor activity, including long-term survival. It is interesting to note that the parental antibody without avidin (ch128.1) also shows remarkable in vivo anticancer activity despite its limited in vitro cytotoxicity. Finally, we demonstrate that ch128.1Av is not toxic to pluripotent hematopoietic progenitor cells using the long-term cell-initiating culture assay suggesting that these important progenitors would be preserved in different therapeutic approaches, including the in vitro purging of cancer cells for autologous transplantation and in vivo passive immunotherapy. Our results suggest that ch128.1Av and ch128.1 may be effective in the therapy of human multiple myeloma and potentially other hematopoietic malignancies.
[show abstract][hide abstract] ABSTRACT: The HOX genes encode a family of transcription factors that are dysregulated in several malignancies and have been implicated in oncogenesis and cancer cell survival. Disruption of HOX protein function using the peptide HXR9 has shown anti-tumor effects against melanoma, lung cancer and renal cancer. In this report, we evaluated the expression of all 39 HOX genes in a panel of six malignant B-cell lines, including multiple myeloma cells and found different levels of expression of HOX family members suggesting that they also have a role in malignant B-cell survival. We show that disrupting HOX function using the peptide HXR9 induces significant cytotoxicity in the entire panel of cell lines. Importantly, we found that the cytotoxic effects of HXR9 can be enhanced by combining it with ch128.1Av, an antibody-avidin fusion protein specific for the human transferrin receptor 1 (CD71). Iron starvation induced by the fusion protein contributes to the enhanced effect and involves, at least in part, the induction of a caspase-independent pathway. These results show the relevance of HOX proteins in malignant B-cell survival and suggest that our therapeutic strategy may be effective in the treatment of incurable B-cell malignancies such as multiple myeloma.
Leukemia: official journal of the Leukemia Society of America, Leukemia Research Fund, U.K 09/2010; 24(9):1555-65. · 10.16 Impact Factor