細胞の密集が癌の進行に与える影響

タイトル: Cell crowding induces TRPV4 inhibition and its relocation to plasma membranes, implicating pro-invasive cell volume reduction mechanotransduction pathway

概要: Cell crowding is a common microenvironmental factor that affects various disease processes, but its impact on cell invasiveness into surrounding tissues is not well understood. This study investigates the biomechanical changes induced by cell crowding, focusing on pro-invasive cell volume reduction in ductal carcinoma in situ (DCIS) cells. DCIS is a non-invasive form of breast cancer characterized by abnormal cell growth confined within the breast duct. While DCIS can undergo invasive transition, it is unclear which DCIS cells are predisposed to this transition. We discovered that cell crowding enhanced the invasiveness of high-grade DCIS cells, which experienced significant cell volume reduction compared to hyperplasia-mimicking or normal cells. Mass spectrometry analyses revealed that cell crowding relocated ion channels, including TRPV4, a calcium-permeant ion channel, to the plasma membrane selectively in high-grade DCIS cells but not in less aggressive or normal cells. Cell crowding inhibited TRPV4 activity in high-grade DCIS cells, decreasing intracellular calcium levels and reducing cell volume. This inhibition also triggered the relocation of TRPV4 to the plasma membrane, effectively priming the inactive channel for activation and mitigating the calcium loss caused by crowding-induced inhibition. Analyses of patient-derived breast cancer tissues validated that TRPV4 is selectively associated with the plasma membrane in high-grade DCIS but not in lower-grade DCIS or less aggressive pathologies. The extent of plasma membrane TRPV4 association scaled with cell volume reduction and increased cell invasiveness and motility, suggesting its utility as an active pro-invasive mechanotransduction pathway indicator. Additionally, hyperosmotic conditions and pharmacologic TRPV4 inhibition mimicked the pro-invasive volume reduction observed under cell crowding, while TRPV4 activation reversed this effect by inducing cell volume increase. Silencing the TRPV4 gene via shRNA diminished the mechanotransduction capability of high-grade DCIS cells, as demonstrated by reduced intracellular calcium depletion, attenuated cell volume reduction, and decreased motility. In summary, this study uncovers a previously unrecognized pro-invasive mechanotransduction pathway initiated by cell crowding, which is specific to high-grade DCIS cells, revealing a potential biomarker for identifying DCIS patients at high risk of invasive transition.