Abstract 1226: Polyphenol rich extract from <i>Caesalpinia spinosa</i> plant delays cell death through autophagy induction to enhance immunogenic signals in melanoma cells
Authors: Karol M. Prieto, Claudia Urueña, Susana Fiorentino, Alfonso Barreto
Journal: Cancer Research (2020)

Abstract Globally cancer is the second leading cause of death, for that reason, there is emerging research of new substances with potential anticancer activity or in combination with existing therapies to enhance their antitumoral activity. In this sense, therapies based on natural compounds derived from plants have shown antitumor efficacy with reduced side effects and more tolerable toxicity profiles than conventional chemotherapeutic drugs. Plant extracts contain a diverse range of compounds including polyphenols, which may exert their therapeutic functions by inducing oxidative stress, ER stress, autophagy or apoptosis of tumor cells. Traditionally, natural compounds purified have been used in cancer therapies. However, researchers have described more efficacy in antitumor therapy with plant extracts by synergism between several compounds with multiple molecular targets. We obtained the polyphenol-rich extract P2Et derived from Caesalpinia spinosa plant, which leads to immunogenic cell death (ICD) in murine melanoma and breast cancer models. Recently, using mechanistic analysis we published that P2Et induce apoptosis and immunogenic signals (DAMPs) in an ER stress and PERK depending form. Here, we aim to elucidate the mechanism through autophagy-mediated by a plant extract and its associated compounds induce apoptosis and DAMPs in the B16-F10 melanoma model. First, we treated B16-F10 melanoma cells with P2Et, Gallic Acid (GA) or Ethyl Gallate (EG) (most abundant polyphenols in P2Et extract) and we evaluated autophagy induction. In addition, we used chemical inhibitors of autophagy and CRISPR/Cas9 system to generate knock-out in beclin-1 gene, which is involved in autophagy initiation, to evaluate the role of autophagy in cell death and DAMPs generation. B16-F10 treatment showed that P2Et, GA, and EG increase autophagy in a similar proportion. However, P2ET and EG promote a complete autophagy flux, while GA block it. On the other hand, autophagy inhibition decreased apoptosis in cells treated with GA, showing that GA induces cytotoxic autophagy. In contrast, autophagy inhibition increases cell death in P2Et and EG treated cells with decrease in DAMPs generation. Additionally, three DAMPs were evaluated (calreticulin cell surface exposure and ATP and HMGB-1 release) finding a greater induction by P2Et than EG, meanwhile GA did not induce any of them. Take all together our results suggest that autophagy induced by P2Et delays cell death allowing an increase in DAMPs generation. These results could explain the mechanisms used by natural plant extracts to induce ICD, and we propose a synergism between the plant extract compounds, each one with a different action mechanism could be advantageous in cancer treatment using whole extracts compared to use of isolated compounds. Citation Format: Karol M. Prieto, Claudia Urueña, Susana Fiorentino, Alfonso Barreto, Immunobiology and Cellular Biology Group. Polyphenol rich extract from Caesalpinia spinosa plant delays cell death through autophagy induction to enhance immunogenic signals in melanoma cells [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1226.