METTL3 safeguard cancer cells from programmed cell death during detachment from their surrounding extracellular matrix

Extracellular matrix (ECM) detachment is crucial for metastasis in cancer cells. During tumorigenesis, a programmed cell death (PCD) occurs to clear off the ECM detached cancer cells in the circulatory system; this phenomenon is referred to as anoikis. Metastatic cancer cells can evade anoikis by regulating mechanisms such as cell adhesion, cell growth, oxidative stress, cancer stemness, hypoxia and metabolic reprogramming. Studies have shown that RNA modifications regulate multiple cancer mechanisms; however, the role of RNA modifications in anoikis resistant is not established yet. Therefore, in this study, we assessed the role of N6-methyladenosine (m6A) modification of mRNAs in anoikis resistant conditions. First, we cultured cancer cells in low adhesive plates for six (6) days followed by quantitative real-time PCR (qRT-PCR) of major m6A regulators and quantification of the global m6A levels in detached vs attached cancer cells. We also assessed cell proliferation in detached cancer cells using STM2457, a potent and specific METTL3 inhibitor. Our results showed a significant (p < 0.05) increase in METTL3 expression and activity in anoikis resistant cancer cells. Furthermore, we observed an elevation in global m6A levels on mRNAs. Treatment of anoikis resistant cancer cells with STM2457 caused reduction in spheroid size, induction of apoptosis, and cell cycle arrest which were correlated with a decrease in global m6A levels. Conclusively, an increase in m6A levels is crucial for maintenance of cell survival and proliferation of anoikis resistant cancer cells.