Downregulated ATP6V1B1 expression acidifies the intracellular environment of cancer cells leading to resistance to antib
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ORIGINAL ARTICLE
Downregulated ATP6V1B1 expression acidifies the intracellular environment of cancer cells leading to resistance to antibody‑dependent cellular cytotoxicity Mariko Nishie1 · Eiji Suzuki1,5 · Masakazu Hattori2 · Kosuke Kawaguch1 · Tatsuki R. Kataoka3 · Masahiro Hirata3 · Fengling Pu1 · Takeshi Kotake1 · Moe Tsuda1 · Ayane Yamaguchi1 · Tomoharu Sugie4 · Masakazu Toi1 Received: 6 August 2019 / Accepted: 20 September 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract 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 antibodydependent 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. Keywords Breast Cancer · V-ATPase · ADCC · Granzyme · Trastuzumab · HER2
Introduction Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00262-020-02732-3) contains supplementary material, which is available to authorized users. * Eiji Suzuki [email protected]‑u.ac.jp 1
Department of Breast Surgery, Graduate School of Medicine, Kyoto University, Kyoto, Japan
2
Department of Immunosenescence, Graduate School of Medicine, Kyoto University, Kyoto, Japan
3
Department of Diagnostic Pathology, Kyoto University Hospital, Kyoto, Japan
4
Department of Breast Surgery, Kansai Medical University, Osaka, Japan
5
Department of Breast Surgery, Kyoto University Hospital, 54 Shogoin‑kawaharacho, Sakyo‑ku, Kyoto 606‑8507, Japan
Human epidermal growth factor receptor 2-overexpressin
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