Abstract 5717: Novel evidence for FTO as an oncogenic player and mediator of chemoresistance in colorectal cancer
Authors: Garg Rachana , Melstorm Laleh , Chen Jianjun , He Chuan , Goel Ajay 
Published: June 2022

Abstract
Background: Colorectal cancer (CRC) is the second leading cause of cancer-related deaths worldwide. Although, 5-flurouracil (5FU) based chemotherapy and surgical resection are considered most effective treatments for CRC patients, the 5-year survival rates remain poor primarily due to distant metastasis, local recurrence and acquired drug resistance. Fat mass and obesity-associated protein (FTO), an RNA N6-methyladenosine demethylase, has recently been reported to be upregulated in various cancers, including CRC. However, thus far, the molecular mechanism underlying the role of FTO in CRC and/or acquisition of 5FU resistance remains unclear.
Methods: To study the relevance of FTO overexpression in CRC, we adopted various approaches: a) lentiviral-mediated stable depletion of FTO or (b) CS1-mediated pharmacological inhibition in CRC cells, c) lentiviral-mediated FTO overexpression in normal colonic epithelial cells (NCM460), and thereafter analyzed the effect on cell viability, cell cycle, wound healing, invasion, epithelial-mesenchymal transition (EMT), cancer stemness, 5FU drug response and tumor forming capability in nude mice. Expression of markers of cell proliferation and apoptosis in the tumor extracts were analyzed by western blotting. To augment the clinical relevance, we evaluated the effect of CS1 on the growth and response to 5FU in patient-derived organoids (PDOs). Kaplan Meier analysis was performed to correlate the significance of FTO overexpression with survival in CRC patient cohorts.
Results: A significant upregulation of both mRNA and protein expression of FTO was found in various CRC cells compared to NCM460 cells. Notably, FTO inhibition hampered the proliferative, migratory and invasive capabilities of CRC cells whilst, ectopic overexpression of FTO in the NCM460 cells promoted oncogenic phenotype. Furthermore, FTO depletion in CRC cells led to EMT reversal, impaired tumor-sphere formation and stemness traits, which in turn was reflected in the sensitization towards 5FU in otherwise resistant cells. Moreover, xenograft tumor forming capabilities of CRC cells was severely hindered in FTO depleted cells. Besides, FTO-depleted xenografts displayed a significant decrease in the expression of markers of cell survival and proliferation (p-AKT and PCNA), while there was an increment in the apoptotic marker, Caspase 9. The relevance of our in vitro and in vivo findings was further strengthened as CS1-mediated inhibition not only decrease the number and size of PDO, but also sensitized them towards 5FU. In addition, we unambiguously demonstrate a significant correlation between FTO upregulation and poor overall and recurrence-free-survival of CRC patients.
Conclusions: Our study establishes the functional importance of FTO in CRC and provides novel evidence for the potential use of FTO inhibitor as an adjunctive treatment to 5FU based chemotherapy for CRC patients.
Citation Format: Rachana Garg, Laleh Melstorm, Jianjun Chen, Chuan He, Ajay Goel. Novel evidence for FTO as an oncogenic player and mediator of chemoresistance in colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5717.