Blockade of CaV3 calcium channels and induction of G0/G1 cell cycle arrest in colon cancer cells by gossypol

Abstract

Background and purpose: Gastrointestinal tumours overexpress voltage-gated calcium (Ca_V3) channels (Ca_V3.1, 3.2 and 3.3). Ca_V3 channels regulate cell growth and apoptosis colorectal cancer. Gossypol, a polyphenolic aldehyde found in the cotton plant, has anti-tumour properties and inhibits Ca_V3 currents. A systematic study was performed on gossypol blocking mechanism on Ca_V3 channels and its potential anticancer effects in colon cancer cells, which express Ca_V3 isoforms.

Experimental approach: Transcripts for Ca_V3 proteins were analysed in gastrointestinal cancers using public repositories and in human colorectal cancer cell lines HCT116, SW480 and SW620. The gossypol blocking mechanism on Ca_V3 channels was investigated by combining heterologous expression systems and patch-clamp experiments. The anti-tumoural properties of gossypol were estimated by cell proliferation, viability and cell cycle assays. Ca²⁺ dynamics were evaluated with cytosolic and endoplasmic reticulum (ER) Ca²⁺ indicators.

Key results: High levels of Ca_V3 transcripts correlate with poor prognosis in gastrointestinal cancers. Gossypol blockade of Ca_V3 isoforms is concentration- and use-dependent interacting with the closed, activated and inactivated conformations of Ca_V3 channels. Gossypol and Ca_V3 channels down-regulation inhibit colorectal cancer cell proliferation by arresting cell cycles at the G₀/G₁ and G₂/M phases, respectively. Ca_V3 channels underlie the vectorial Ca²⁺ uptake by endoplasmic reticulum in colorectal cancer cells.

Conclusion and implications: Gossypol differentially blocked Ca_V3 channel and its anticancer activity was correlated with high levels of Ca_V3.1 and Ca_V3.2 in colorectal cancer cells. The Ca_V3 regulates cell proliferation and Ca²⁺ dynamics in colorectal cancer cells. Understanding this blocking mechanism maybe improve cancer therapies.

Keywords: CaV3 calcium channels; TTA‐P2; blocking mechanism; gastrointestinal cancers; gossypol; ion channel blockers.