Abstract 2954: Androgen deprivation therapy (ADT) and senescence-associated secretory phenotype (SASP) in vitro: Correlation with SASP in tumor specimens as well as in the serum of patients after ADT

Abstract Introduction: Androgen Deprivation Therapy (ADT) is a highly effective treatment for prostate cancer. However, resistance to ADT develops in most patients, leading to a lethal state of castration-resistant prostate cancer (CRPC). Senescent prostate cancer (SPC) cells can arise after ADT and contribute to therapy resistance. SPCs can restore replicative function and alter the tumor microenvironment through pro-tumorigenic senescence-associated secretory phenotype (SASP). We aimed to characterize changes in SASP in prostate cancer cell lines and serum samples from patients receiving ADT. Methods: SASP factors (Luminex 100/200 System, xMAP Instruments) were analyzed in patients undergoing ADT. To correlate SASP with the sensitivity to ADT, we sought to evaluate the regulation of SASP in vitro using PCa cell lines. The PC3 (AR resistant) and LNCaP (AR sensitive) cell lines were used in the experiments. We performed an analysis of archival tumor tissue (paired) from 18 patients with or without alterations in DNA repair genes (BRCA1, BRCA2, and CDK12). We performed immunohistochemical (IHC) staining of known SASP markers, such as P16, uPAR, gamma-H2AX, and Lamin B1. Results: In a cohort of patients (n=8) with pre and post-ADT matched status, we demonstrate increased levels of SASP factors such as IL-6 (pre-ADT: 1.54±0.24 pg/ml, post-ADT: 5.23±1.3 pg/ml p=0.001), IL-7 (pre-ADT: 3.11±0.6 pg/ml, post-ADT: 13.5±2.7 pg/ml p=0.01), IL-1 alpha (pre-ADT: 1.06±0.3 pg/ml, post-ADT: 15.3±3.5 pg/ml p=0.001), IL-15 (pre-ADT: 15.6±3.1 pg/ml, post-ADT: 37.1±4.8 pg/ml p=0.002), MIF (pre-ADT: 1036±67.6pg/ml, post-ADT: 2362±55.5 pg/ml p=0.003), and IL-15 (pre-ADT: 5±2.1 pg/ml, post-ADT: 37.5±5.1 pg/ml p=0.002). In vitro, the AR-responsive LNCaP cell line, exposed to AR blockade, showed similar findings in upregulating IL-6, IL-7, and IL-15 but not the PC3 cell line. We also demonstrate measurable differences between the expression of u-PAR, gamma-2AX, p16, and loss of Lamin B1 expression in tumor specimens from patients with advanced castration-resistant prostate cancer (n=18). The expression of p16 was significantly upregulated post-treatment irrespective of DDR status (p=0.0417). Other SASP factors showed a trend in upregulation but were insignificant (u-PAR p=0.056, gamma-H2AX p=0.62, Lamin B1 p=0.72) Conclusion: These results provide evidence of systemic increases in SASP-related cytokines following treatment with ADT. The in vitro results suggest that secretion of SASP is promoted by an AR-mediated mechanism. Preliminary results from tumor specimens suggest increased senescence marker p16 expression induced by therapy. Ongoing experiments are further characterizing the senescence markers in prostate tumor specimens and correlated to treatment effect. Citation Format: Maximilian Schwermann, Matthew Hadfield, Shaolei Lu, Praveen Srinivasan, Vida Tajiknia, William MacDonald, Andrew George, Shengliang Zhang, Leiqing Zhang, Kimberly Meza, Andre De Souza, Dragan Golijanin, Elias Hyams, Galina Lagos, Sheldon Holder, Anthony Mega, John Sedivy, Howard Safran, Wafik El-Deiry, Benedito Carneiro. Androgen deprivation therapy (ADT) and senescence-associated secretory phenotype (SASP) in vitro: Correlation with SASP in tumor specimens as well as in the serum of patients after ADT [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2954.