(-)­Oleocanthal inhibits proliferation and migration by modulating Ca2+ entry through TRPC6 in breast cancer cells.

Triple negative breast cancer is an aggressive type of cancer that does not respond to hormonal therapy and current therapeutic strategies are accompanied by side effects due to cytotoxic actions on normal tissues. Therefore, there is a need for the identification of anti-cancer compounds with negligible effects on non-tumoral cells. Here we show that (-)­oleocanthal (OLCT), a phenolic compound isolated from olive oil, selectively impairs MDA-MB-231 cell proliferation and viability without affecting the ability of non-tumoral MCF10A cells to proliferate or their viability. Similarly, OLCT selectively impairs the ability of MDA-MB-231 cells to migrate while the ability of MCF10A to migrate was unaffected. The effect of OLCT was not exclusive for triple negative breast cancer cells as we found that OLCT also attenuate cell viability and proliferation of MCF7 cells. Our results indicate that OLCT is unable to induce Ca2+ mobilization in non-tumoral cells. By contrast, OLCT induces Ca2+ entry in MCF7 and MDA-MB-231 cells, which is impaired by TRPC6 expression silencing. We have found that MDA-MB-231 and MCF7 cells overexpress the channel TRPC6 as compared to non-tumoral MCF10A and treatment with OLCT for 24-72 h downregulates TRPC6 expression in MDA-MB-231 cells. These findings indicate that OLCT impairs the ability of breast cancer cells to proliferate and migrate via downregulation of TRPC6 channel expression while having no effect on the biology of non-tumoral breast cells.

Orai1 and Orai2 mediate store-operated calcium entry that regulates HL60 cell migration and FAK phosphorylation.

Store-operated Ca2+ entry (SOCE) is a major mechanism for the regulation of intracellular Ca2+ homeostasis and cellular function. Emerging evidence has revealed that altered expression and function of the molecular determinants of SOCE play a critical role in the development or maintenance of several cancer hallmarks, including enhanced proliferation and migration. Here we show that, in the acute myeloid leukemia cell line HL60, Orai2 is highly expressed at the transcript level, followed by the expression of Orai1. Using fluorescence Ca2+ imaging we found that Orai2 silencing significantly attenuated thapsigargin-induced SOCE, as well as knockdown of Orai1, while silencing the expression of both channels almost completely reduced SOCE, thus suggesting that SOCE in these cells is strongly dependent on Orai1 and Orai2. On the other hand, the expression of TRPC1, TRPC3 and TRPC6 is almost absent at the transcript and protein level. Bromodeoxyuridine cell proliferation assay revealed that Orai1 and Orai2 expression silencing significantly reduced HL60 cell proliferation. Furthermore, knockdown of Orai1 and Orai2 significantly attenuated the ability of HL60 to migrate in vitro as determined by transwell migration assay, probably due to the impairment of FAK tyrosine phosphorylation. These findings provide evidence for a role for Orai1 and Orai2, in SOCE and migration in the human HL60 promyeloblastic cell line. This article is part of a Special Issue entitled: ECS Meeting edited by Claus Heizmann, Joachim Krebs and Jacques Haiech.