Autophagy Is Required for Cell Growth and Protein Anabolism in Lung Cancer

Abstract

Background: Rampant and unregulated cell growth is a key hallmark of cancer pathology; however, much remains to be discovered about the process that allow for pathological growth in cancerous cells. Recently, we demonstrated that the autophagy-related cysteine protease ATG4B is required for protein anabolism in skeletal muscle, indicating a previously undescribed mechanism by which autophagy directly acts as a recycling/remodeling system for cellular anabolism. Purpose: To investigate if ATG4B is responsible for growth in cancer, and if inhibition of ATG4B is a successful strategy to target cancer growth. Hypothesis: We hypothesized that ATG4B would be higher in cancerous tissues versus healthy ones, and that inhibition of ATG4B by NSC185058 would inhibit cell growth and reduce protein anabolism. Methods: We used the UALCAN web tool to analyze the TCGA data set for differences in ATG4B gene expression in lung adenocarcinoma, comparing healthy to cancerous tissues as well as across cancer stages. Separately, we used the A549 lung cancer cell line as a model to study the effects of ATG4B inhibition, treating cells with 100 μM NSC185058 or equimolar DMSO as a vehicle control, and analyzing treated cells for proliferation and protein synthesis rates. Welch’s t-test was used to calculate differences in TCGA data, while a two-tailed student’s t-test was used to determine differences in proliferation at indicated time points, with an α-level of 0.05. Results: ATG4B expression is 22% higher in cancerous tissues vs healthy controls (p<0.05), and also higher in stages 1-4 of lung adenocarcinoma (Healthy vs Stage 1: +25%, Healthy vs Stage 2: +23%, Healthy vs Stage 3: +13%, Healthy vs Stage 4: +30%, p<0.05). Treatment with NSC185058 suppresses cell growth across 72 hours (24 hour VC vs NSC: -59%, 48 hour VC vs NSC: -83%, 72 Hour VC vs NSC: -90%), and reduces 24-hour rates of protein synthesis by 56% (p<0.05) in cancer cells. Conclusions: ATG4B expression is increased in lung adenocarcinoma, including in early-stage cancer, and inhibition by NSC185058 drastically reduces anabolism in cancerous cells. We posit that autophagy, mediated by ATG4B is required for protein anabolism in lung cancer, and that targeting this process represents a novel strategy to combat cancer pathology. This work was generously funded by the Huffnes Institute and School of Education and Human Development at Texas A&M University. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.