Punicalagin Regulates Apoptosis-Autophagy Switch via Modulation of Annexin A1 in Colorectal Cancer

Abstract

Punicalagin (PU), a polyphenol extracted from pomegranate (Punica granatum) husk is proven to have anti-cancer effects on different types of cancer including colorectal cancer (CRC). Its role in modulating endogenous protein as a means of eliciting its anti-cancer effects, however, has not been explored to date. Hence, this study aimed to investigate the role of PU in modulating the interplay between apoptosis and autophagy by regulating Annexin A1 (Anx-A1) expression in HCT 116 colorectal adenocarcinoma cells. In the study, selective cytotoxicity, pro-apoptotic, autophagic and Anx-A1 downregulating properties of PU were shown which indicate therapeutic potential that this polyphenol has against CRC. Autophagy flux analysis via flow cytometry showed significant autophagosomes degradation in treated cells, proving the involvement of autophagy. Proteome profiling of 35 different proteins in the presence and absence of Anx-A1 antagonists in PU-treated cells demonstrated a complex interplay that happens between apoptosis and autophagy that suggests the possible simultaneous induction and inhibition of these two cell death mechanisms by PU. Overall, this study suggests that PU induces autophagy while maintaining basal level of apoptosis as the main mechanisms of cytotoxicity via the modulation of Anx-A1 expression in HCT 116 cells, and thus has a promising translational potential.

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“…At the same time, punicalagin also exhibited pro-apoptotic and autophagic properties, as confirmed by the entry of treated cells into early apoptosis and the degradation of the autophagosome. Finally, in order to better understand the punicalagin mechanisms of action, Ganesan et al (100) detected the expression levels of Annexin A1 (Anx-A1), a protein generally upregulated in colorectal cancer. Specifically, they observed that Anx-A1 was significantly downregulated in the treated cells compared to control, suggesting that punicalagin exerted a selective cytotoxic effect on tumor cells.…”

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“…Ganesan et al [ 31 ] observed proapoptotic impact of Pug on human colorectal cancer cell line HCT116, reflected by the increase in early apoptotic cells (assessed by Annexin V/PI flow cytometry) and cytochrome C release from the mitochondrium. This finding is in accordance with the results obtained by Seeram et al [ 18 ] showing an antiapoptotic Pug effect in HCT116 as well as HT-29 (human colon adenocarcinoma) cell lines.…”

“…This finding is in accordance with the results obtained by Seeram et al [ 18 ] showing an antiapoptotic Pug effect in HCT116 as well as HT-29 (human colon adenocarcinoma) cell lines. However, Ganesan et al [ 31 ] observed that 72-h Pug treatment of HCT116 cells downregulated caspases 3/7, 8, and 9. Hence, the authors checked for the features indicative of autophagy stimulation by Pug, and with the application of autophagy flux assay via flow cytometry, noted autophagosomes degradation (reflecting autophagy involvement).…”

“…Therefore, in colorectal cancer, this protein seems to favor neoplastic development, hence its suppressing by Pug is favorable. Further, Ganesan et al [ 31 ] performed a proteome profiling analysis testing the impact of Pug (with annexin A1-route involvement) on 35 different proteins associated with apoptosis and autophagy processes. They observed four significantly altered proteins in HCT116 cells treated both with punicalagin and formyl peptide receptors (FPR) inhibitors (applied to block annexin A1 signaling).…”

“…Both apoptosis and autophagy seem to have been responsible for the aforementioned punicalagin induction of human colorectal [ 31 ] and glioma [ 37 ] cancer cells’ death. Additionally, in the first case, the authors demonstrated the involvement of annexin A1 signaling suppressed by Pug, whereas in glioma cancer cells Pug treatment led to cell death through the activation of AMPK route.…”