In recent decades, despite the application of various treatment modalities for OSCC, the five‐year overall survival rate of OSCC remains at 50% [
35]. As a new, orally administered multi-target TKI, anlotinib exhibits excellent antitumor effects for several types of cancer [
12,
36‐
38]. Our previous study [
16] also confirmed that anlotinib exerted potent antiproliferation capability and induced apoptosis in OSCC cells, and favorable anticancer activity and manageable toxicities in patients with recurrent and metastatic OSCC. Until now tremendous studies have been performed to investigate the mechanism of anlotinib in the treatment of human cancers. Previous studies have found that PI3K/AKT/ mTOR signaling pathway and downstream apoptosis pathway were typical mechanism in anlotinib treatment [
13]. Song et al. [
13] found that anlotinib mainly inhibited the phosphorylation level of VEGFR2 and then affected PIK3/AKT signal activation in intrahepatic cholangiocarcinoma (ICC). Yang et al. [
39] suggested that anlotinib suppressed cell proliferation and angiogenesis via inhibition of VEGFR-2/AKT and FGFR, PDGFRβ and their downstream signaling ERK in colorectal cancer. In this study, we further confirmed that the antitumor effect of anlotinib was conducted by targeting FGFR3 and inhibiting the phosphorylation level of FGFR3, and subsequent inhibition of the AKT/mTOR and apoptosis signaling pathway in OSCC. Taken together, these results suggested that anlotinib may be involved in the FGFR3/AKT/mTOR signaling pathway in the therapeutics of OSCC.
As the most pervasive internal modification of mRNA, m
6A modification is installed by a methyltransferase complex (e.g., METTL3-METTL14), erased by demethylases (e.g., FTO and ALKBH5), and can be recognized by readers (e.g., YTHDF1-3, IGF2BP1-3) [
29]. Studies have proved that mRNA m
6A modification can affect RNA splicing, RNA stability, RNA translation efficiency, RNA secondary structure and RNA subcellular localization [
23]. Tremendous studies have shown that METTL3 promotes tumor growth, metastasis, and drug resistance in human cancers [
26‐
28,
40,
41]. Recently, Yan et al. [
42] identified the dynamic m
6A methylome as an additional epigenetic driver for reversible TKI tolerance. Ianniello et al. [
43] also revealed that downregulation of METTL3 and METTL14 overcame the resistance of chronic myeloid leukemia cells to the TKI imatinib mesylate (imatinib) through regulating ribosome levels and translation. Sa et al. [
44] demonstrated that insulin-like growth factor 2 mRNA-binding protein 2 (IGF2BP2)-dependent ERBB2 signaling activation contributes to acquired resistance to TKI of radioiodine-refractory papillary thyroid cancer. In the present study, we observed the function of m
6A methylation in regulating anlotinib sensitivity of OSCC, providing a mechanistic paradigm for drug sensitivity in cancer. Cell lost-of-functional assays revealed that FGFR3 act as the anlotinib target in OSCC cells. Our MeRIP-seq and MeRIP-qPCR results demonstrated that FGFR3 was selectively m
6A modified in OSCC. Depletion of METTL3 decreased FGFR3 m
6A methylation and mRNA stability, and promoted anlotinib sensitivity of OSCC cells. OSCC PDX models verified that METTL3 and FGFR3 levels were tightly correlated with the anlotinib efficacy in the treatment of OSCC, also the expression levels of METTL3 and FGFR were significantly negatively correlated in each PDX sample. Thus, METTL3-mediated m
6A modification played a critical function in the anlotinib sensitivity of OSCC.