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

AbstractAmong 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 g enes. The expression ofATP6V1B1, 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 generateATP6V1B1-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 theATP6V1B1-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 inATP6V1B1-knockout cells, but were not cytotoxic. These findings suggest that ...
Source: Cancer Immunology, Immunotherapy - Category: Cancer & Oncology Source Type: research