Type 3 IP3 receptors: The chameleon in cancer.

Inositol 1,4,5-trisphosphate (IP3) receptors (IP3Rs), intracellular calcium (Ca2+) release channels, fulfill key functions in cell death and survival processes, whose dysregulation contributes to oncogenesis. This is essentially due to the presence of IP3Rs in microdomains of the endoplasmic reticulum (ER) in close proximity to the mitochondria. As such, IP3Rs enable efficient Ca2+ transfers from the ER to the mitochondria, thus regulating metabolism and cell fate. This review focuses on one of the three IP3R isoforms, the type 3 IP3R (IP3R3), which is linked to proapoptotic ER-mitochondrial Ca2+ transfers. Alterations in IP3R3 expression have been highlighted in numerous cancer types, leading to dysregulations of Ca2+ signaling and cellular functions. However, the outcome of IP3R3-mediated Ca2+ transfers for mitochondrial function is complex with opposing effects on oncogenesis. IP3R3 can either suppress cancer by promoting cell death and cellular senescence or support cancer by driving metabolism, anabolic processes, cell cycle progression, proliferation and invasion. The aim of this review is to provide an overview of IP3R3 dysregulations in cancer and describe how such dysregulations alter critical cellular processes such as proliferation or cell death and survival. Here, we pose that the IP3R3 isoform is not only linked to proapoptotic ER-mitochondrial Ca2+ transfers but might also be involved in prosurvival signaling.