High expression of leucine‑rich repeat‑containing�8A is indicative of a worse outcome of colon cancer patients by enhancing cancer cell growth and metastasis

Abstract

To survive, cells need to avoid excessive volume change that jeopardizes structural integrity and stability of the intracellular milieu. Searching for the molecular identity of volume-regulated anion channel (VRAC) has yielded multiple potential candidates, but none has been confirmed. Recently, it is reported that leucine-rich repeat-containing 8A (LRRC8A) is a main molecular determinant of VRAC current. The biological functions of LRRC8 family proteins are poorly understood, particularly in cancer. In the present study, we investigated LRRC8A in the most common cancers of the digestive system. LRRC8A proteins were found to be abundantly expressed in the esophagus, stomach, duodenum, colon, rectum, liver and pancreas. LRRC8A was elevated in 60% of colorectal cancer patient tissues, which was higher than that in patients with cancer of the esophagus, stomach, duodenum, liver and pancreas. Colon cancer patients with high- expressed LRRC8A had a survival time of 54.9±5.5 months, shorter than that of patients with low-expressed LRRC8A (77.1±3.7). Moreover, survival time (52.6±7.3 months) of patients with metastases in the lymph nodes was shorter than that of patients without positive lymph nodes (72.2±3.6); patients with positive lymph nodes and an elevated LRRC8A expression had the highest mortality rate (~80%). These rates were not observed in rectal cancer. After LRRC8A protein was knocked down in colon cancer HCT116 cells, VRAC currents, migration and tumorigenesis in nude mice were significantly inhibited. In conclusion, we propose that LRRC8A could be a novel prognostic biomarker for colon cancer patient survival, and that the elevated expression of LRRC8A may enhance cancer cell growth and metastasis, and worsen the outcome of patients.

The Volume-Regulated Anion Channel LRRC8/VRAC Is Dispensable for Cell Proliferation and Migration

“…The identification of LRRC8 proteins as essential VRAC components [4,5] enabled investigating physiological functions of VRAC by molecular biological tools. Using this approach, siRNA-mediated downregulation of the essential VRAC subunit LRRC8A reduced proliferation of primary glioblastoma and U251 GBM cells [40], and knockdown of LRRC8A in the colorectal cancer cell line HCT116 was shown to impair cell migration in a wound healing assay [41].…”

“…More recently, the VRAC inhibitor 4-[(2-Butyl-6,7-dichloro-2-cyclopentyl-2,3-dihydro-1-oxo-1H-inden-5-yl)oxy]butanoic acid (DCPIB) was shown to reduce the migration of glioblastoma cell lines [28]. The siRNA-mediated knockdown of the obligate VRAC subunit LRRC8A was reported to limit the proliferation of glioblastoma cells [40] and reduce the migration of human colon cancer HCT116 cells [41].…”

Contribution of Anoctamins to Cell Survival and Cell Death

“…Apart from ANO1 and ANO6, also VRAC is blocked by niclosamide [95]. Because VRAC induces resistance towards cisplatin and other anticancer drugs and leads to metastasis and bad patient outcome, inhibition of VRAC may be another mechanism how niclosamide inhibits growth of cancer [215,234,235].…”

“…Taken together, a functional relationship exists between VRAC and ANO1, possibly because activation of both channels involves release of Ca 2+ from the ER-store [200,236]. As VRAC controls survival of cells, the functional crosstalk with ANO1 is highly relevant for tumor biology [215,234,236].…”

TMEM16F/Anoctamin 6 in Ferroptotic Cell Death

“…Along this line, membrane exposure of LRRC8A, the essential subunit of the volume regulated anion channel (VRAC), depends on activation of TMEM16A [55]. VRAC controls cell death and chemoresistance of cancer cells, and is therefore of relevance for tumor biology [56,57]. As shown in Figure 4, activation of TMEM16A supports phospholipid scrambling by activating TMEM16F and therefore supports activation of VRAC [58].…”