Trastuzumab-mediated Antibody-dependent Cellular Cytotoxicity Research Articles

Downregulated ATP6V1B1 expression acidifies the intracellular environment of cancer cells leading to resistance to antibody-dependent cellular cytotoxicity.

Among several mechanisms for the resistance of human epidermal growth factor receptor 2-overexpressing (HER2 +) cancer cells to trastuzumab, little is known regarding the mechanism underlying the resistance to trastuzumab-mediated antibody-dependent cellular cytotoxicity (ADCC). Cell death due to ADCC is caused by apoptosis of target cells induced by granzymes released from natural killer cells. Because optimal granzyme physiological activity occurs at neutral pH, we assumed that the pH of the intracellular environment influences the cytotoxic effects of granzymes. We established ADCC-resistant cells and compared them with wild-type cells in terms of the expression of intracellular pH-regulating genes. The expression of ATP6V1B1, which encodes a component of vacuolar ATPases, was downregulated in the ADCC-resistant cells. Thus, to functionally characterize ATP6V1B1, we used a CRISPR/Cas9 system to generate ATP6V1B1-knockout SKBR3 and JIMT-1 cells (both HER2 + human breast cancer cell line). The resulting cells exhibited significantly less ADCC than the control SKBR3 and JIMT-1 cells. The intracellular pH of the ATP6V1B1-knockout SKBR3 and JIMT-1 cells was significantly lower than control SKBR3 and JIMT-1cells. An analysis of granzyme dynamics during the ADCC reaction in cancer cells revealed that granzymes degraded intracellularly in the control SKBR3 and JIMT-1 cells and accumulated in ATP6V1B1-knockout cells, but were not cytotoxic. These findings suggest that decreased vacuolar ATPase activity alters the cytoplasmic pH of cancer cells to create an environment that is less suitable for granzyme bioactivity, which adversely affects the induction of apoptosis of cancer cells by NK cells.

Abstract 2218: High affinity and cleavage resistant CD16 enhances Trastuzumab mediated killing of gastric cancer targets by human placental CD34+-derived natural killer cells

Abstract Introduction: When targeting tumors with monoclonal antibodies, natural killer (NK) cells are key effectors of antibody dependent cellular cytotoxicity (ADCC) following recognition of antibody Fc by CD16. Celularity has developed a novel proprietary technology platform that enables production of an allogeneic, off-the-shelf, placental CD34+-derived NK cell therapy for the treatment of hematologic and solid tumor malignancies. Here we report the genetic modification of CD16 in NK cells for high binding affinity to IgG and resistance to protease cleavage, together with functional evaluation of anti-tumor ADCC activity against epidermal growth factor receptor 2 (HER2) positive gastric cancer cells in combination with Trastuzumab (anti-Her2). Methods: Human placental CD34+ cells were transduced with lentivirus expressing a high binding affinity (158Val) and protease resistant (197Pro) CD16 variant (CD16VP) and cultured for 35 days in the presence of cytokines, including thrombopoietin, SCF, Flt3 ligand, IL-7, IL-15 and IL-2, to generate CD16VP cells. The tumorigenic activity of CD16VP cells against HER2-positive gastric cancer cell lines NCI-N87 and OE19 was assessed in combination with Trastuzumab. ADCC activity was measured by real-time xCELLigence, and cytokine secretion by Luminex. The kinase inhibitors PD98059 (MEK/ERK), SB203580 (p38 MAPK), SP600125 (JNK), and Wortmannin (PI3K) were used to study the molecular mechanisms underlying cytotoxicity of CD16VP cells against gastric cancer. Results and conclusion: High transduction efficiency was achieved in multiple placental CD34+ donors with an average of 64.6 ± 10.3% (n=8) CD16 expression on NK cells compared to 12.1 ± 3.3% (n=8) on non-transduced cells. These cells expanded [7095 ± 2998-fold (n=8)] and differentiated into NK cells with >90% purity (CD56+CD3-). While treatment of PMA/ionomycin for 4 hours resulted in >89% CD16 cleavage on non-transduced cells, <11% cleavage was observed on CD16VP cells, demonstrating shedding resistance. CD16VP cells in the presence of Trastuzumab compared to IgG control, showed enhanced lysis of NCI-N87 and OE19 targets (97 ± 7% and 95 ± 2% vs. 55 ± 19% and 42 ± 14% respectively, p<0.01), secreted higher levels of GM-CSF, IFN-γ, and TNF-α, and demonstrated increased degranulation against OE19. The ADCC mediated cytotoxicity and degranulation were PI3K and JNK pathway-dependent as Wortmannin decreased ADCC by 82.2 ± 17.7% and degranulation by 43.9 ± 1.9%, and SP600125 decreased degranulation by 72.3 ± 1.2%. Our results demonstrate that CD16VP cells have enhanced Trastuzumab-mediated ADCC activity against gastric cancer tumor cell lines with resistance to CD16 cleavage. Development of CD16VP cells provides a combination therapeutic option by harnessing the anti-tumor activities of both targeted biologics and innate cytotoxicity of NK cells. Citation Format: Irene Raitman, Salvatore Rotondo, Tanel Mahlakõiv, Xuan Guo, Andrea DiFiglia, Hemlata Rana, Qian Ye, Srinivas Somanchi, William van der Touw, Lin Kang, Robert Hariri, Xiaokui Zhang. High affinity and cleavage resistant CD16 enhances Trastuzumab mediated killing of gastric cancer targets by human placental CD34+-derived natural killer 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 2218.

Canine non-B, non-T NK lymphocytes have a potential antibody-dependent cellular cytotoxicity function against antibody-coated tumor cells

BackgroundThe antibody-dependent cellular cytotoxicity (ADCC) is a cell-mediated immune defense mechanism in which effector immune cells actively lyse antibody-coated target cells. The ADCC of tumor cells is employed in the treatment of various cancers overexpressing unique antigens, and only natural killer (NK) cells are known to be major effectors of antibody mediated ADCC activity. Canine NK cells are still defined as non-B, non-T large granular lymphocytes because of the lack of information regarding the NK cell-restricted specific marker in dogs, and it has never been demonstrated that canine NK cells have ADCC ability against tumor cells. In the present study, we investigated whether canine non-B, non-T NK cells have ADCC ability against target antibody-coated tumor cells, using cetuximab and trastuzumab, the only human antibodies reported binding to canine cancer cells.ResultsActivated canine non-B, non-T NK cells (CD3−CD21−CD5−TCRαβ−TCRγδ−) for 13~17 days ex vivo showed ADCC ability against trastuzumab- or cetuximab-coated target tumor cells expressing various levels of human epidermal growth factor receptor 2 (HER-2) and epidermal growth factor receptor (EGFR). Trastuzumab and cetuximab induced significant ADCC responses of canine NK cells even in CMT-U334 and CF41.Mg cells expressing low levels of HER-2 and/or EGFR, as well as in SKBR3 and DU145 cells overexpressing HER-2 and/or EGFR. The trastuzumab-mediated ADCC activity of NK cells was significantly enhanced by treatment with rcIL-21.ConclusionsThe results of this study suggest that canine non-B, non-T NK lymphocytes have a potential ADCC function and that combinational strategies of monoclonal antibodies with either cytokines, which activate NK cells in vivo, or adoptive transfer of NK cells may be a feasible method for amplifying the efficacy of immunotherapy against malignant cancers even with very low expression of target molecules in dogs.

Augmentation of antibody-dependent cellular cytotoxicity with defucosylated monoclonal antibodies in patients with GI-tract cancer.

Enhancement of antibody-dependent cellular cytotoxicity (ADCC) with some modalities may be a promising approach to enhance the efficacy of therapeutic monoclonal antibodies (mAbs). It has previously been demonstrated that the removal of fucose from antibody oligosaccharides (defucosylation) leads to augmentation of ADCC activity. To establish clinically relevant evidence of this procedure, the present study evaluated trastuzumab- and cetuximab-mediated ADCC by comparing defucosylated mAbs with conventional mAbs using peripheral blood mononuclear cells (PBMCs). PBMCs were isolated from 20 patients with gastrointestinal tract cancer and 10 healthy volunteers. ADCCs were measured using PBMCs as effector cells and two gastric cancer cell lines as target cells. ADCCs were significantly enhanced with defucosylated mAbs compared with conventional mAbs using PBMC from the healthy donors and patients with cancer. The results confirmed that the cetuximab- and trastuzumab-mediated ADCCs in advanced disease were impaired in comparison to those in early disease or healthy individuals. However, when the defucosylated mAbs were used instead of the conventional mAbs, the ADCC activities in the advanced cases were almost comparable with those in early disease or healthy individuals. Furthermore, the expression of ADCC associated molecules were modified toward immunosuppressive status with a mitogen-activated protein kinase inhibitor in vitro, the conventional cetuximab- and trastuzumab-mediated ADCC was downregulated, and the defucosylated mAbs overcome the downregulation of ADCC. In conclusion, defucosylated therapeutic mAbs may enhance ADCC activities in patients with cancer, which may lead to more effective anti-cancer treatments.

Lapatinib enhances trastuzumab-mediated antibody-dependent cellular cytotoxicity via upregulation of HER2 in malignant mesothelioma cells.

EGFR/HER2 are frequently expressed in MPM tissues, however, no studies have shown the clinical benefit of using EGFR/HER2-targeting drugs in patients with malignant pleural mesothelioma (MPM). It was reported that the tyrosine kinase inhibitor (TKI) lapatinib enhanced trastuzumab-mediated antibody-dependent cellular cytotoxicity (ADCC) in HER2-positive breast cancer, suggesting that this combination is a promising strategy for MPM treatment. The aim of the present study was to explore the possibility of a TKI combined with trastuzumab to enhance ADCC in MPM cells. Five MPM cell lines were used to test the effects of TKIs targeting EGFR (gefitinib, afatinib and lapatinib) on cell proliferation and the expression of the HER family receptor. The combined effects of TKI with trastuzumab on ADCC were evaluated using the LDH release assay. Additionally, MPM cells were isolated from patients and evaluated for lapatinib-induced upregulation of HER family receptors and trastuzumab- or cetuximab-mediated ADCC. In MPM cell lines, HER2 expression was upregulated by lapatinib, downregulated by afatinib and unaffected by gefitinib. As expected, more trastuzumab bound to MPM cells pretreated with lapatinib than untreated cells, resulting in the enhancement of trastuzumab-mediated ADCC in MPM cells. In patient-derived MPM cells, both HER2 and EGFR were upregulated by lapatinib, resulting in the enhancement of both trastuzumab- and cetuximab-mediated ADCC. Of the three TKIs, only lapatinib enhanced trastuzumab-mediated ADCC via the upregulation of HER2 expression in MPM cells, suggesting that sequential combination of lapatinib and trastuzumab may be a promising strategy for MPM treatment.

200 Lapatinib enhances trastuzumab-mediated antibody-dependent cellular cytotoxicity by upregulating HER2 in malignant pleural mesothelioma cells

200 Lapatinib enhances trastuzumab-mediated antibody-dependent cellular cytotoxicity by upregulating HER2 in malignant pleural mesothelioma cells

Abstract 720: Downregulation of ATP6V1B1 in HER2-overexpressing human breast cancer cell line leads resistance against trastuzumab-mediated antibody-dependent cellular cytotoxicity

Abstract Introduction: PIK3CA mutation has been becoming widely recognized as a resistant mechanism or therapeutic biomarker for trastuzumab based anti HER2 targeting therapy, however little is clear on resistant mechanism of trastuzumab mediated antibody dependent cellular cytotoxicity (ADCC) in HER2 overexpressing (HER2+) breast cancer patients. In the current study, we investigated the role of Vacuolar-ATPase subunit ATP6V1B1 on the resistant mechanism of trastuzumab mediated ADCC in HER2+ human breast cancer cell line SK-BR-3. Methods and Results:To establish the trastuzumab mediated ADCC resistant SK-BR-3, isolated healthy PBMCs are co-cultured with 1-10 μg/ml of trastuzumab and SK-BR-3 for 4-9 hours. The cell mixture was incubated with CD45 magnetic beads and CD45 positive PBMCs were removed from the mixture using MACS cell separation system (Miltenyi Biotec, Germany). The survived SK-BR-3 thereafter co-cultured with 1-10 μg/ml of trastuzumab and PBMCs for several times. After 7 passages of the resistant cell making procedure (approximately for 6 months), cytotoxicity was measured by conventional ADCC assay (E/T ratio = 10/1) with various concentration of trastuzumab. The cytotoxicity of ADCC resistant SK-BR-3 was significantly reduced as compared with normal SK-BR-3 cytotoxicity in 10μg/ml of trastuzumab (15.9% and 42.8%, respectively). Then, we analyzed the gene expression profile of ADCC resistant SK-BR-3 by using DNA microarray to sort candidate genes for the resistance. Several genes were up- or down-regulated in ADCC resistant SK-BR-3 and we focused on ATP6V1B1 gene that was significantly reduced on the resistant cells. To clarify the result of comprehensive gene expression analysis, we investigated ATP6V1B1 mRNA level of SK-BR-3 and resistant cell by using real time PCR and found the 50% reduction of ATP6V1B1 mRNA level in ADCC resistant cells. Thus, to evaluate the role of ATP6V1B1 on the trastuzumab mediated ADCC resistant mechanism, ATP6V1B1-knocked down SK-BR-3 (sh-RNA knockdown method) were tested in trastuzumab mediated ADCC assay and found that ATP6V1B1-knocked down SK-BR-3 were significantly less ADCC activity with LDH assay as compared to control SK-BR-3 (19.1% and 40.0%, respectively).Conclusions: ATP6V1B1 might be one factor for trastuzumab mediated ADCC resistance in HER2+ breast cancer cells. Citation Format: Mariko Nishie, Eiji Suzuki, Kosuke Kawaguchi, Keiko Sakamoto, Yuji Fukushima, Masakazu Hattori, Tomoharu Sugie, Masakazu Toi. Downregulation of ATP6V1B1 in HER2-overexpressing human breast cancer cell line leads resistance against trastuzumab-mediated antibody-dependent cellular cytotoxicity. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 720. doi:10.1158/1538-7445.AM2015-720

Abstract 2466: Sequential tumor and immune targeted immunotherapy: Anti-tumor activity of antibody drug conjugate Trastuzumab Emtansine (T-DM1) with CD137 stimulation in HER-2+ breast cancer therapy

Abstract The mainstay of HER2+ breast cancer treatment has been monoclonal antibody therapy with Trastuzumab, a humanized antibody that targets HER-2. However, the efficacy of Trastuzumab monotherapy is only 10-15%. Therefore, strategies are being developed to enhance its therapeutic efficacy. Our previous study demonstrated that stimulation of NK cells with an anti-CD137 agonistic mAb enhanced Trastuzumab-mediated Antibody Dependent Cellular Cytotoxicity (ADCC). Anti-CD137 agonistic mAb enhanced anti-breast cancer activity of Trastuzumab in vivo in a xenotransplanted human breast cancer model (Kohrt et al. J Clin. Invest, 2012, 22:3). We have developed a treatment regimen consisting of sequential administration of Trastuzumab followed by CD137 antibody as three weekly injections. This regimen demonstrated more potent antitumor activity than administration of anti-CD137 mAb followed by Trastuzumab. Our combination therapy was superior to Traztuzumab alone in a primary HER2-overexpressing-breast tumor xenotransplant model but was ineffective in low HER-2 expressing breast cancer model. Next, we evaluated the therapeutic efficacy of FDA approved antibody drug conjugate Trastuzumab Emtansine (T-DM1) in combination with CD137 antibody. We used HER2 over-expressing HER18 xenograft model and an SU-258 primary breast cancer model in our studies. Following tumor inoculation, mice received either T-DM1 on day 3 (for HER18 xenograft), or day 30 (for SU-258) and anti-CD137 antibody on day 4(or HER18) or day 31(for SU-258) with each treatment repeated weekly for a total of three weeks. Sequential antibody strategy with T-DM1 and CD137 significantly improved survival compared to T-DM1 alone or with Trastuzumab and CD137 antibody. Our results demonstrate that T-DM1 retains its potency and demonstrates synergistic activity with anti-CD137 mAb therapy against HER2-overexpressing breast cancer models. Our results support a novel, sequential antibody approach against HER-2+breast cancer, by targeting first the tumor with an antibody drug conjugate and then the host immune system. Clinical investigations are now planned to determine the clinical outcome of our immunotherapy strategy. Citation Format: Suparna Dutt, Narendiran Rajasekaran, Aurelien Marabelle, Roch Houot, Mohith Sadaram, Jonathan Hebb, Idit Sagiv-Barfi, Sid Ambulkar, Amanda Rajapaksa, Cariad Chester, Erin Waller, Holbrook Kohrt. Sequential tumor and immune targeted immunotherapy: Anti-tumor activity of antibody drug conjugate Trastuzumab Emtansine (T-DM1) with CD137 stimulation in HER-2+ breast cancer therapy. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2466. doi:10.1158/1538-7445.AM2015-2466

Adipose cells promote resistance of breast cancer cells to trastuzumab-mediated antibody-dependent cellular cytotoxicity.

IntroductionTrastuzumab has been used in the treatment of human epidermal growth factor receptor 2 (HER2)-expressing breast cancer, but its efficacy is limited by de novo or acquired resistance. Although many mechanisms have been proposed to explain resistance to trastuzumab, little is known concerning the role of the tumor microenvironment. Given the importance of antibody-dependent cellular cytotoxicity (ADCC) in the antitumor effect of trastuzumab and the abundance of adipose tissue in the breast, we investigated the impact of adipocytes on ADCC.MethodsWe set up a coculture system to study the effect of adipocytes on ADCC in vitro. The results were validated in vivo in a mouse xenograft model.ResultsWe found that adipocytes, as well as preadipocytes, inhibited trastuzumab-mediated ADCC in HER2-expressing breast cancer cells via the secretion of soluble factors. The inhibition of ADCC was not due to titration or degradation of the antibody. We found that adipose cells decreased the secretion of interferon-γ by natural killer cells, but did not alter natural killer cells’ cytotoxicity. Preincubation of breast cancer cells with the conditioned medium derived from adipocytes reduced the sensitivity of cancer cells to ADCC. Using a transcriptomic approach, we found that cancer cells undergo major modifications when exposed to adipocyte-conditioned medium. Importantly, breast tumors grafted next to lipomas displayed resistance to trastuzumab in mouse xenograft models.ConclusionsCollectively, our findings underline the importance of adipose tissue in the resistance to trastuzumab and suggest that approaches targeting the adipocyte–cancer cell crosstalk may help sensitize cancer cells to trastuzumab-based therapy.Electronic supplementary materialThe online version of this article (doi:10.1186/s13058-015-0569-0) contains supplementary material, which is available to authorized users.

Abstract 153: High neuropilin-1 expression on monocytes is positively associated with trastuzumab-mediated antibody-dependent cellular cytotoxicity of the HER2-overexpressing breast cancer cell line

Abstract Purpose Neuropilin-1 (Nrp1) was initially characterized as a guide for migrating cells and axons in developing nervous systems and is essential for the precise formation of neurons and vasculature. However, it was recently reported to also play an important role in the immune system. This study aimed to investigate the role of Nrp1 on monocytes in trastuzumab-mediated antibody-dependent cellular cytotoxicity (ADCC) targeting the HER2-positive human breast cancer cell line SKBR3. In addition, we evaluated the gene expression profile of monocytes expressing high and low levels of Nrp1. Methods Peripheral blood mononuclear cells from healthy volunteers were prepared using BD Vacutainer CPT Cell Preparation Tubes. The cells were stained with fluorescein isothiocyanate-conjugated anti-CD14 and allophycocyanin-conjugated anti-Nrp1 antibodies, and Nrp1high and Nrp1low monocyte subsets were sorted using FACSAria. These cells were used as effector cells in a conventional ADCC assay with SKBR3 as target cells and trastuzumab as the antibody. Target cell cytotoxicity was measured using the LDH cytotoxic test kit. The effector cell to target cell ratios of 20:1 and 10:1 were used. Gene expression analysis was performed by Affymetrix GeneChip microarrays. All study protocols were approved by the Ethics Committee for Clinical Research, Kyoto University Hospital, Kyoto, Japan (authorization number G424). Results The LDH cytotoxic test revealed significantly higher target cancer cell cytotoxicity in sorted Nrp1high monocytes than in Nrp1low monocytes (75% vs. 45%, p<0.01). Trastuzumab-mediated ADCC was significantly suppressed by Nrp1 neutralization antibodies in a dose-dependent manner (Control arm 14.3%, Treatment arm 6%; p<0.01). Gene expression analysis revealed that 308 genes were up-regulated in the Nrp1high population, including monocyte-specific chemokine receptor and hematopoietic transcriptional factor. Conclusion These results suggest that determination of Nrp1 expression can be used to classify monocytes as populations with and without cellular cytotoxic activity. Analysis of Nrp1 expression levels in monocytes can therefore be used to identify HER2-positive breast cancer patients for whom trastuzumab therapy will be less effective. Citation Format: Kosuke Kawaguchi, Eiji Suzuki, Masao Kawashima, Masakazu Toi. High neuropilin-1 expression on monocytes is positively associated with trastuzumab-mediated antibody-dependent cellular cytotoxicity of the HER2-overexpressing breast cancer cell line. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 153. doi:10.1158/1538-7445.AM2014-153

Abstract 3783: Adipocytes inhibit trastuzumab-mediated ADCC via induction of GDF15

Abstract Background : Trastuzumab is a monoclonal antibody that has been approved in the treatment of HER2-expressing breast cancer. Despite its efficacy, resistance often occurs. Little is known about the role of the tumor microenvironment in resistance to trastuzumab. Recent studies have shown rising role of adipose tissue in promoting cancer progression and inducing resistance to chemotherapy. Given the abundance of adipose tissue in breast and its proximity to cancer cells, we investigated the impact of adipocytes on antibody-dependent cellular cytotoxicity (ADCC), one of the main mechanisms of action of trastuzumab. Methods: We set up a co-culture system in the presence of undifferentiated or differentiated human multi-potent adipose-derived stem (hMADS) cells, HER2-expressing human breast cancer cell lines (BT474, MDA-453, SKBR3, MDA-MB-361), and human natural killer NK-92 expressing the Fc receptor CD16. Trastuzumab-mediated cytotoxicity was assessed by calcein-release assay. Morphological changes on cancer cells and NK-92-CD16 cells were investigated by microscopy and flow cytometry. Results: We found that adipocytes, as well as pre-adipocytes, inhibited trastuzumab-mediated ADCC by approximately 30%. Notably, this inhibition was enhanced in hypoxic conditions with 1% O2 (up to 60% inhibition). The inhibition of ADCC by adipose cells was not due to a titration or degradation of the antibody, but via factors that are secreted by adipose cells into the conditioned media. Analysis of cell phenotype did not reveal any modification of NK cell receptors (CD16, NKG2D, NKG2A, NKp30, NKp44) or NK cell activation markers (CD25, CD69, CD107a), nor of HER2 levels in the presence of adipocytes. Pre-incubation of NK cells with the conditioned medium from adipocytes did not alter NK cytotoxicity. Conversely, pre-incubation of cancer cells with adipocyte-conditioned medium reduced sensitivity of cancer cells to ADCC. Using transcriptomic approach, we found GDF15 to be rapidly up-regulated in cancer cells exposed to adipocyte-conditioned medium. Down-regulation of GDF15 by siRNA reversed the adipocyte-induced inhibition of ADCC. Conclusion: Adipocytes inhibit antitumor activity of trastuzumab in HER2-expressing breast cancer cells via secretion of factors that reduce cancer cell sensitivity to ADCC. Our findings underline the importance of adipose tissue in the resistance to trastuzumab, and suggest that development of approaches targeting GDF15 may sensitize cancer cells to trastuzumab-based therapy. Citation Format: Minh Ngoc Duong, Aurore Cleret, Eva-Laure Matera, Kamel Chettab, Doriane Poloni, Sandrine Valsesia-Wittmann, Béatrice Clémenceau, Charles Dumontet. Adipocytes inhibit trastuzumab-mediated ADCC via induction of GDF15. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3783. doi:10.1158/1538-7445.AM2014-3783

Abstract 1077: Loss of HER2 via trogocytosis by CD14+ cells in HER2-overexpressing breast cancer cells is associated with diminishing of trastuzumab-mediated antibody-dependent cellular cytotoxicity

Abstract The transfer of cell-surface membrane proteins and membrane patches from one cell to another at the time of contact, known as trogocytosis, was reported in chronic lymphocytic leukemia and multiple myeloma patients and was associated with clinical outcome. However, in solid malignant tumors, such as breast cancer, there is no evidence that trogocytosis occurs clinically thus its clinical importance has not been evaluated yet. In the current study, we found significantly high HER2 expression on tumor-infiltrated CD14+ cells as compared to control CD14+ cells of PBMCs in HER2 overexpressing breast cancer patient who had been treated with trastuzmab. Digested tumor cell suspension and its autologous PBMCs were co-cultured at 1:10 ratio with 0 and 1 μg/ml of trastuzumab as trogocytosis assay. Percentage of HER2 positive CD14+ cells was higher in the treatment of 1 μg/ml of trastuzumab as compared to that of 0 μg/ml of trastuzumab (17% and 12%, respectively) while HER2 expression of digested tumor cells was lower in 1 μg/ml of trastuzumab treatment as compared to that of 0 μg/ml of trastuzumab (18% and 25%, respectively). These findings suggested that HER2 might be transferred from HER2 overexpressing breast tumor cells to CD14+ cells, which was possibility of evidence of trogocytosis in the HER2+ breast cancer patient, and suggested that CD14+ cell might have an important role in the trogocytosis. We next define the role of CD14+ cells and CD56+ cells in the process of both trogocytosis and antibody dependent cellular cytotoxicity (ADCC) in experimental setting using SK-BR-3 and BT-474, both HER2 overexpressing human breast cancer cell lines, and MCF-7 and MDA-MB-231, both HER2 negative human breast cancer cell lines. We found that trogocytosis was observed specifically on HER2 overexpressing breast cancer cell lines in in vitro torogocytosis assay and CD14+ cells have a role for trogocytosis dominantly as compared to CD56+ cells. HER2 loss was increased as Effector / Target ratio or concentration of trastuzumab was increased. HER2 loss on target cancer cells caused by trogocytosis of CD14+ cells inhibits CD56+ cell-mediated ADCC, however when CD14+ cells are depleted, such inhibitory effects are recovered and CD56+ cells show better cytotoxicity. Currently analyzed preliminary clinical sample data and experimental data of HER2 loss via trogocytosis might explain different level of treatment response of trastuzumab in individual patients. Citation Format: Eiji Suzuki, Mariko Nishie, Kosuke Kawaguchi, Sunao Tanaka, Masakazu Toi. Loss of HER2 via trogocytosis by CD14+ cells in HER2-overexpressing breast cancer cells is associated with diminishing of trastuzumab-mediated antibody-dependent cellular cytotoxicity. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1077. doi:10.1158/1538-7445.AM2014-1077

Abstract P5-08-03: In vitro resistance to ERBB2-targeted therapies does not bestow cross-resistance to antibody dependent cellular cytotoxicity

Abstract Background: The advent of ERBB2-directed therapies, including trastuzumab and lapatinib, has changed the clinical management of ERBB2+ breast cancer and improved patient outcomes. However, both de novo and acquired resistance to ERBB2-targeting agents remain significant clinical problems; thus, it is important to understand the mechanisms that tumor cells use to resist and/ or escape ERBB2-directed therapeutic agents. A growing body of evidence supports the role of immune effector cells in trastuzumab-induced tumor cell lysis in vivo, which is hypothesized to occur through antibody dependent cellular cytotoxicity (ADCC) mediated by natural killer cells bearing FC gamma receptors. Existing in vitro models of trastuzumab and lapatinib resistance are limited in that they are most often generated by incubating tumor cells with drug alone, outside the context of the host immune system. Consequently, the impact of in vitro generated drug resistance on ADCC susceptibility has not been defined. In this study, we tested existing trastuzumab and lapatinib resistant breast cancer cell lines for ADCC sensitivity. Materials and Methods: The ERBB2 amplified breast cancer cell lines BT474 and SKBR3, which are sensitive to trastuzumab-mediated ADCC, were selected for trastuzumab and lapatinib resistance. Drug resistant cells were generated by serial culture in the presence of escalating doses of trastuzumab and/or lapatinib until complete tolerance was acquired at clinically achievable concentrations (100μg/ml trastuzumab and 2.6μM lapatinib). Drug sensitivity was assessed by Alamar Blue assay. Cell resistance to trastuzumab-mediated ADCC was measured by Calcein-AM release assay, using 1μg/ml antibody concentration and four different effector target ratios (20:1, 10:1, 5:1, and 1:1), with a minimum of five replicates. Human peripheral blood lymphocytes freshly isolated from buffy coat were used as effector cells. Results and Discussion: Neither BT474 nor SKBR3 cells with acquired resistance to single agent trastuzumab (HerR), lapatinib (LapR), or both in combination (DualR) demonstrated cross-resistance to effector cell-mediated ADCC at any of the E:T ratios tested. At the highest E:T ratio tested (20:1), trastuzumab-induced ADCC of control BT474 cells resulted in 61.92% cell lysis (95% CI = 3.97), compared to 64.97% lysis for BT-HerR cells (95% CI = 2.87, Student's t-test p > 0.1). Similarly, BT-LapR and DualR cell lysis was 58.13% and 63.66%, respectively (95% CI = 2.62 and 6.57, Student's t-test p > 0.1). Additionally, trastuzumab-induced ADCC of control SKBR3 cells resulted in 89.98% cell lysis (95% CI = 4.29), compared to 93.53% lysis for SK-HerR cells (95% CI = 0.81, Student's t-test p > 0.1). SK-LapR and DualR cell lysis was 94.81% and 92.09%, respectively (95% CI = 0.6 and 2.66, Student's t-test p > 0.1). Our results indicate the importance of incorporating immune effector cells to in vitro models of trastuzumab resistance. Accordingly, we have begun modeling ADCC resistance in vitro to further investigate the relationship between targeted antibody therapies, effector cell-mediated cytolysis, and mechanisms of tumor immune escape. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-08-03.

Abstract 1536: Neurropilin-1 high monocytes play an important role in trastuzumab mediated antibody-dependent cellular cytotoxicity in HER2 positive breast cancer cell lines.

Abstract Purpose Neuropilin-1 (NRP-1) was initially characterized as a neuronal receptor for specific secreted members of the semaphorin family involved in axon repulsion. However, it was recently reported to play an important role in the immune system. This study aimed to investigate the role of NRP-1 expression on monocytes in trastuzumab-mediated antibody-dependent cellular cytotoxicity (ADCC) targeting the HER2-positive human breast cell line SKBR3. Methods Peripheral blood mononuclear cells (PBMCs) from healthy volunteers were prepared using Lymphoprep. The cells were stained with fluorescein isothiocyanate (FITC)-conjugated anti-CD14 and allophycocyanin (APC)-conjugated anti-NRP-1 antibodies, and an NRP-1high and NRP-1low monocyte subset was sorted using FACSAria. These cells were used as effector cells in a conventional ADCC assay using SKBR3 as target cells and trastuzumab as an antibody. Target cell cytotoxicity was measured using the LDH cytotoxic test kit. A CD107a degranulation assay was also used to determine the role of NRP-1 expression on monocytes in ADCC. PBMCs were co-cultured with target SKBR3 cells and trastuzumab for 2 h, stained with APC-conjugated anti-NRP-1 and PE-Cy5-conjugated anti-CD107a antibodies, and analyzed by flow cytometry. Results The LDH cytotoxic test revealed significantly higher target cancer cell cytotoxicity in sorted NRP-1 high monocytes (12%) than in NRP-1 low monocytes (4%). Interestingly, microscopic findings showed that most NRP-1 high monocytes covered trastuzumab-treated target cancer cells (showing higher cellular cytotoxicity) while NRP-1 low monocytes did not cover the target cells but changed their morphology from a round to a dendritic shape (showing less cellular cytotoxicity) during ADCC. Moreover, the degranulation assay showed a higher expression of CD107a in NRP-1 high monocytes (17.4%) than in NRP-1 low monocytes (1.16%). Mean fluorescence intensity of CD107a in NRP-1 high and NRP-1 low monocytes was 92.6 and 26.3, respectively. Conclusions These data suggest that NRP-1 high monocytes exhibit higher trastuzumab-mediated ADCC than NRP-1 low monocytes in HER2-positive breast cancer cell lines. It may therefore be possible to differentiate HER2-positive breast cancer patients for whom trastuzumab will be less effective by testing for monocyte NRP-1 expression levels. Citation Format: Kosuke Kawaguchi, Eiji Suzuki, Tomoharu Sugie, Fumiaki Sato, Masakazu Toi. Neurropilin-1 high monocytes play an important role in trastuzumab mediated antibody-dependent cellular cytotoxicity in HER2 positive breast cancer cell lines. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1536. doi:10.1158/1538-7445.AM2013-1536

Lapatinib acts on gastric cancer through both antiproliferative function and augmentation of trastuzumab-mediated antibody-dependent cellular cytotoxicity

Trastuzumab has been recently approved for clinical use to treat HER2-expressing advanced gastric cancer, and anti-HER2-targeting therapy has become a promising option for gastric cancer. Lapatinib is a dual tyrosine kinase inhibitor targeting EGFR and HER2. The aim of the present study was to explore the utility of lapatinib for gastric cancer, with a particular focus on trastuzumab-mediated antibody-dependent cellular cytotoxicity (ADCC). Nine gastric cancer cell lines were evaluated for the effects of lapatinib on the cell-surface accumulation of HER2 and analyzed for their additional effects on trastuzumab-mediated ADCC. Also, HER2 signaling with Western blot, proliferative function with the MTT assay, and apoptosis-inducing activity with 7ADD/Annexin-V were investigated when a panel of gastric cancer cell lines was treated with lapatinib. Lapatinib inhibited HER2 signaling and cell proliferation in the panel of gastric cancer cell lines. Lapatinib also induced the accumulation of HER2 on the cell surface, resulting in the enhancement of trastuzumab-mediated ADCC of gastric cancer. Lapatinib exhibits inhibitory activity in gastric cancer cells, and the combination of lapatinib with trastuzumab may be a promising treatment strategy for gastric cancer patients.

Mechanism of resistance to trastuzumab and molecular sensitization via ADCC activation by exogenous expression of HER2-extracellular domain in human cancer cells.

Trastuzumab, a humanized antibody targeting HER2, exhibits remarkable therapeutic efficacy against HER2-positive breast and gastric cancers; however, acquired resistance presents a formidable obstacle to long-term tumor responses in the majority of patients. Here, we show the mechanism of resistance to trastuzumab in HER2-positive human cancer cells and explore the molecular sensitization by exogenous expression of HER2-extracellular domain (ECD) in HER2-negative or trastuzumab-resistant human cancer cells. We found that long-term exposure to trastuzumab induced resistance in HER2-positive cancer cells; HER2 expression was downregulated, and antibody-dependent cellular cytotoxicity (ADCC) activity was impaired. We next examined the hypothesis that trastuzumab-resistant cells could be re-sensitized by the transfer of non-functional HER2-ECD. Exogenous HER2-ECD expression induced by the stable transfection of a plasmid vector or infection with a replication-deficient adenovirus vector had no apparent effect on the signaling pathway, but strongly enhanced ADCC activity in low HER2-expressing or trastuzumab-resistant human cancer cells. Our data indicate that restoration of HER2-ECD expression sensitizes HER2-negative or HER2-downregulated human cancer cells to trastuzumab-mediated ADCC, an outcome that has important implications for the treatment of human cancers.

E‐cadherin expression on human carcinoma cell affects trastuzumab‐mediated antibody‐dependent cellular cytotoxicity through killer cell lectin‐like receptor G1 on natural killer cells

Trastuzumab is a recombinant antibody drug that is widely used for the treatment of HER2-overexpressing breast carcinoma. Despite encouraging clinical results, many HER2-overexpressing carcinomas are primarily resistant to trastuzumab. We attempted to explain trastuzumab resistance and search for solutions. Since the killer cell lectin-like receptor G1 (KLRG1), an inhibitory receptor expressed on subsets of natural killer (NK) cells recognizes E-cadherin as ligands and may inhibit immune responses by regulating the effector function of NK cells, we used HER2-overexpressing carcinoma cells which were expressing E-cadherin to investigate the role of antibody-dependent cellular cytotoxicity (ADCC) through KLRG1 on NK cells in vitro and vivo. The results indicated that HER2-overexpressing carcinoma cells were killed by trastuzumab-mediated ADCC and the ADCC activity was reflected the degree of E-cadherin expression on carcinoma cells. We found that expression of E-cadherin was shown to be a predictor of response to trastuzumab-based treatment for HER2-overexpressing carcinomas, furthermore, trastuzumab-mediated ADCC was markedly enhanced by KLRG1-negative peripheral blood mononuclear cells (PBMCs(KLRG1(-))).

Multiple molecular mechanisms underlying trastuzumab and lapatinib resistance in JIMT-1 breast cancer cells

Trastuzumab plays an important role in breast cancer therapy. However, a significant fraction of patients do not respond to therapy or they tend to develop resistance shortly after beginning therapy. Although some resistance mechanisms have been described, it is unclear whether these mechanisms can coexist. In this study, we analyzed the resistance mechanisms in the breast cancer cell line JIMT-1, a model of intrinsic trastuzumab resistance. We compared the JIMT-1 cell line with a panel of eight HER-2 positive breast cancer cell lines. All cell lines were characterized for the phosphatidylinositol 3-kinase ( PIK3CA) mutation status, expression levels of the phosphatase and tensin homolog on chromosome 10 (PTEN) and neuregulin-1 (NRG1) mRNA, HER-2 gene copy number, and protein expression. The results were correlated to the sensitivity to trastuzumab and lapatinib as well as the potency of trastuzumab-mediated antibody-dependent cellular cytotoxicity (ADCC) evoked by trastuzumab. JIMT-1 cells showed several co-existing drug resistance mechanisms, including an activating mutation of the PIK3CA gene, low expression of PTEN, high expression of NRG1, and relatively low expression of HER-2 receptor protein (despite gene amplification). All these features were present at variable levels in other cell lines, whereas JIMT-1 was unique in displaying all these factors at the same time. Unexpectedly, ADCC reaction by normal lymphocytes was equally strong in all HER-2 positive cell lines, without any correlation to molecular markers or direct sensitivity to the drugs. Resistance to trastuzumab and lapatinib is probably caused by several co-existing molecular mechanisms. Direct sensitivity to trastuzumab and lapatinib was not correlated with ADCC.

Effect of lapatinib on accumulation of inactive HER2 at the cell membrane and on antibody-dependent cellular cytotoxicity (ADCC) mediated by trastuzumab: A novel mechanism for the enhanced effects of combined anti-HER2 therapy

3594 Background: Lapatinib is a HER2 tyrosine kinase inhibitor that has clinical activity in HER2 overexpressing (HER2+) breast cancer. In vitro and clinical studies have shown that lapatinib enhances the effects of the monoclonal antibody trastuzumab suggesting partially non-overlapping mechanisms of action. In order to dissect the differential mechanims of these agents, we have studied the effects of lapatinib and trastuzumab on receptor expression and signaling and have explored a new potential mechanism underlying the profound antitumor activity of the combination. Methods: HER2+ breast cancer cells SKBR3 and MCF7-HER2 were treated with lapatinib, trastuzumab or both. Assays of receptor expression, phosphorylation, signalling and tumor growth were performed. Trastuzumab-dependent cellular cytotoxicity was measured with different levels of HER2 expression and doses of lapatinib. Results: Lapatinib treatment of HER2+ breast cancer cells inhibited HER2 phosphorylation, prevented ubiquitination and resulted in a marked accumulation of inactive receptors at the cell surface. By contrast, trastuzumab caused enhanced HER2 phosphorylation, ubiquitination and degradation of the receptor. By immunoprecipitation and computational protein modelling techniques we further demonstrated that the lapatinib-induced accumulation of HER2 lead to stabilization of inactive HER2 homo- and hetero-dimers. Accumulation of HER2 induced by lapatinib and downregulation of HER2 mediated by trastuzumab were also observed in vivo, where the combination of the two agents triggered complete tumor remission in all cases after 10 days of treatment. Lapatinib-induced accumulation of HER2 at the cell surface markedly enhanced trastuzumab-mediated ADCC. Conclusions: Lapatinib results in a marked accumulation of inactive HER2 receptors at the cell surface both in vitro and in vivo. This increase in receptors number at the cell surface enhances ADCC by trastuzumab. We propose that this is a novel mechanism that may be clinically relevant and exploitable in the therapy of patients with HER2+ tumors. Author Disclosure Employment or Leadership Consultant or Advisory Role Stock Ownership Honoraria Research Expert Testimony Other Remuneration Genentech

Trastuzumab decreases the number of circulating and disseminated tumor cells despite trastuzumab resistance of the primary tumor

We have recently shown that despite of the fact that the ErbB2-positive JIMT-1 human breast cancer cells intrinsically resistant to trastuzumab in vitro, trastuzumab inhibited the outgrowth of early phase JIMT-1 xenografts in SCID mice via antibody-dependent cellular cytotoxicity (ADCC). Here we show that trastuzumab significantly reduces the number of circulating and disseminated tumor cells (CTCs and DTCs) in this xenograft model system at a time when the primary tumor is already unresponsive to trastuzumab. This observation suggests that ErbB2 positive CTCs and DTCs might be sensitive to trastuzumab-mediated ADCC even if when the primary tumor is already non-responsive. Thus, trastuzumab treatment might also be beneficial in the case of patients with breast cancer that is already trastuzumab resistant.