Abstract 4162: Development of low-toxic targeted therapies for KRAS-mutant tumors: Harnessing synergistic effects of fasting-mimicking diet (FMD) and ascorbate

Abstract Pharmacological doses of vitamin C (ascorbate) have been proposed as a potential anticancer therapy, according to several preclinical and clinical studies. However, the exact mechanisms of its function in cancer cells remains controversial. Our laboratory demonstrated that fasting and fasting-mimicking diet (FMD) delay tumor progression and sensitize a wide range of tumors to various types of treatment, such as chemotherapy, immunotherapy and tyrosine kinase inhibitors (TKIs). In addition, FMD can enhance the therapeutic effects of pharmacological doses of vitamin C across different cancer cell lines bearing mutations in KRAS oncogene. Namely, combination of pharmacological doses of ascorbate and FMD in preclinical models has displayed a significant anticancer activity on KRAS-positive colorectal carcinomas, delaying tumor progression, but not achieving cancer free survival because of cellular resistance mechanisms. According to our latest findings FMD has been shown to activate specific starvation-induced escape pathways (SEPs) in triple-negative breast cancer (TNBC) cells that can be identified and targeted by specific targeted treatments. For this reason, this study not only investigates the synergistic effects of short-term starvation (STS) and high-dose ascorbate on cancer cell viability, but aims as well at disentangling the resistance mechanisms of the cells not responsive to the proposed treatment. To unravel these resistance mechanisms, we performed bulk RNA-sequencing analysis on vitamin C and STS/FMD resistant cancer cells. Results unveiled a significant upregulation of different signaling pathways in pancreatic, colorectal and non-small cell lung cancer cell lines non responding to vitamin C and STS. Namely, targeting these pathways by specific inhibitors reactivated sensitivity to ascorbate and STS causing cell death in the resistant cell population. In this study we also highlighted the mechanism through which STS and ascorbate, if combined with inhibitors, induces cancer cell death. Reactive oxygen species (ROS) mediated the cytotoxicity of the combinatorial treatment, as antioxidants were able to reverse the cell death. Next, we also assessed the impact of FMD and ascorbate treatment on the tumor microenvironment: we observed a reshaping of collagen deposition and a normalization of vasculature inside the tumor stroma, which could improve drug delivery and immune cell infiltration. To conclude, this project provides evidence that FMD and ascorbate synergize to cause toxicity in different cancer cell lines. Furthermore, we identified a common escape mechanism toward the abovementioned treatment. All these data together suggest so far that a combinatorial low-toxicity treatment can be developed, thus possibly improving clinical outcomes for cancer patients. Citation Format: Anastasiya Shmahala, Valter D. Longo. Development of low-toxic targeted therapies for KRAS-mutant tumors: Harnessing synergistic effects of fasting-mimicking diet (FMD) and ascorbate [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 4162.