Crosstalk between Bradykinin and Retinoic Acid Receptors signaling pathways in colorectal cancer cells

Abstract

Colorectal cancer is a main cause of morbidity and mortality worldwide and chronic inflammation is key in its development and progression. Bradykinin (BK), a vasoactive peptide, is implicated in inflammation-induced tumor progression of many types of cancer where it exerts its action through specific G-protein coupled receptor. On the other hand, all-trans retinoic acid (ATRA), the active metabolite of vitamin A, mediates essential cellular functions including an anti-inflammatory role in various cell types; and abnormalities in the retinoid receptors signaling are commonly observed in tumorigenesis. Hence, we investigated the potential crosstalk between BK and retinoic acid receptors (RARs) signaling pathways and how it is translated in various cellular functions related to colorectal cancer formation and progression. In the present study, we tested the effect of BK and-or ATRA on cell proliferation and anchorage-independent growth of colorectal cells, and on the modulation of bradykinin receptor B2 (B2R) and RARγ protein profile and their subcellular localization. We also evaluated the effect of BK and ATRA on the modulation of inflammatory, differentiation, and mesenchymal markers, and on downstream signaling transduction proteins. We showed that BK increased growth of colorectal cancer cell lines (HCT116 and HCT116 p53---), while having an opposite effect on the normal-like colon cell line (NCM460) using the MTT assay. In addition, BK induced colony growth of the tested cancer cells, through B2R, while sparing the normal-like counterparts, while ATRA abrogated BK effect in soft agar colony formation assay. We observed by western blot analysis differential protein profile of B2R, RARγ, E-cadherin, and fibronectin upon treatment with BK, ATRA, and their combination. Interestingly, BK treatment resulted in an activation of ERK1-2 in NCM460 and HCT116 and activation of AKT in NCM460 cells only. These findings might be of considerable significance in uncovering novel mechanism, biomarkers and th