Abstract 5983: The secretome produced by senescent gastric cancer cells can lead to different paracrine effects depending on the status of autophagy
Authors: Valenzuela Claudio A. , Rebolledo Danitza , Cayo Angel , Venturini Whitney , Segovia Raúl , Moore-Carrasco Rodrigo , Brown Nelson 
Published: April 2023

Introduction: The initial transition from a proliferative to a senescent state is accompanied by a reduction in the activity of the cyclin-cyclin-dependent kinase (CDK) complexes, which in turn could be explained by the activation of the p53-p21CIP1/WAF1 and/or p16INK4a-pRB signaling pathways. As overexpression of D-type cyclins is commonly observed in gastric cancer cells, the use of CDK4/6 inhibitors could represent a viable alternative for gastric cancer treatment. Nonetheless, senescent cell can synthesize and secrete a plethora of bioactive molecules (a feature known as the senescence-associated secretory phenotype, SASP) with the potential of modifying the tumor microenvironment in ways that could be therapeutically deleterious. Among processes that are upregulated in most senescent cells, autophagy has received great attention during the last years. So far, however, the role of autophagy in the modulation of SASPs has yet to be clarified. Previous work from our lab has revealed an increased autophagic flux in gastric cancer cell lines undergoing drug-induced senescence, suggesting a regulatory role in the implementation of this modality of cellular senescence. More specifically, the secretory phenotype of senescent gastric cancer cells seems to depend on the autophagy status.

Materials and Methods: In order to determine the role of autophagy in the modulation of the SASP, cellular senescence was pharmacologically triggered in gastric cancer cell lines (AGS, MKN-45) through inhibition of CDK4/6 activity (0.5-1.0 μM of Palbociclib for 48 and 96 hours), with or without the concomitant inhibition of autophagy by either genetic (knocking down ATG5) or pharmacologic (treatment with 0.5 μM of Spautin-1) approaches. The expression of factors secreted by senescent cells under different experimental conditions was analyzed from conditioned media; and the same conditioned media were used in assays aimed to assess migration, invasion, and cell proliferation of non-senescent cells.

Results and Discussion: Inhibition of autophagy in senescent cells led to a downregulation in the expression of proinflammatory molecules that were overexpressed in autophagy-proficient senescent cells (MIF, IL-8, IL1β). Unlike conditioned media derived from AGS cells, conditioned media derived from senescent MKN-45 cells that were rendered deficient in autophagy enhanced the invasive capabilities of non-senescent cells. Our results suggest that autophagy modulates the expression of SASP components and, by so doing, affects the behavior of neighboring non-senescent cells. Interestingly, these effects were also influenced by the genetic status of gastric cancer cells. This work was supported by Fondecyt ANID 11201182

Citation Format: Claudio A. Valenzuela, Danitza Rebolledo, Angel Cayo, Whitney Venturini, Raúl Segovia, Rodrigo Moore-Carrasco, Nelson Brown. The secretome produced by senescent gastric cancer cells can lead to different paracrine effects depending on the status of autophagy. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5983.