Abstract 956: NCX 4040 and napabucasin synergistically inhibits stemness in human prostate cancer (PCa) cellular models and potently targets transgenic murine PCa cells via inducing oxidative stress

Abstract Prostate cancer (PCa) continues to have a substantial impact on men’s wellbeing and quality of life regardless of recent progress in diagnosis and treatments and it continues to have the second highest occurrence rate following lung cancer. The strategy of combination drug therapy has gradually become a valuable choice for treating various cancer types, addressing the heterogeneity within tumors, and surpassing the constraints of existing treatment methods. In our previous work, when we combined two drugs NCX 4040 (an oxidative stress inducer) and napabucasin (a STAT3 signaling inhibitor), we discovered that the combination treatment synergistically works to inhibit the malignant characteristics of human PCa cells. Also, the combination upregulated the cGAS-STING immunogenic pathway in PCa cells which could potentially activate the cancer-targeting cytotoxic T-cells. In the current study, we aimed at investigating the anti-stemness properties of the drug duo which can not only inhibit cancer cell differentiation but also can be effective in preventing cancer relapse. We used two cell lines i. e. , BPH-Cd which served as a model of cadmium induced PCa and DU145 as a model of advanced PCa to examine the anti-stemness properties of the drug combination. Based on western-blot analysis, we found the downregulation of transcription factors such as Oct4, Sox2, Nanog, β-catenin and cell surface markers like CD44, CD133 and ALDHA1, which are responsible for stem-cell like properties. In addition, we have tested the combinatory anticancer effects in transgenic mouse derived PCa cell line (Myc-Cap) as a prelude to conduct future studies in FVB mouse syngeneic model to evaluate the tumor suppressive and the antitumor immunogenic responses of combination treatment as it activated cGAS-STING pathway. By performing the cell viability assay, we found that the IC50 value of NCX 4040 is ~10µM and that of napabucasin is ~1μM, however when used in combination, ~90% inhibition is seen at 10µM of NCX and 250nM of napabucasin dual treatment. The drug combination also showed synergy in inhibiting tumorigenicity in clonogenic assay and migratory potential in wound-healing assay. By investigating the ROS production, cell death and cell cycle mechanism using flow cytometric analysis, it was observed that the combination therapy synergistically induces cellular oxidative stress which causes cancer cells to undergo late apoptosis and halts the growth of Myc-Cap cells in G2M phase of cell cycle. In conclusion, our data suggests that combination therapy of NCX 4040 and napabucasin can be potential treatment strategy for PCa warranting further evaluation in in vivo models. Citation Format: Shrushti Shah, Gnanasekar Munirathinam. NCX 4040 and napabucasin synergistically inhibits stemness in human prostate cancer (PCa) cellular models and potently targets transgenic murine PCa cells via inducing oxidative stress 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 (6Suppl): Abstract nr 956.