Fat mass and obesity‐associated protein regulates arecoline‐exposed oral cancer immune response through programmed cell death‐ligand 1

Abstract

The high prevalence of oral squamous cell carcinoma (OSCC) in South Asia is associated with habitual areca nut chewing. Arecoline, a primary active carcinogen within areca nut extract, is known to promote OSCC pathological development. Dysregulation of N6‐methyladenosine (m6A) modification has begun to emerge as a significant contributor to cancer development and progression. However, the biological effects and molecular mechanisms of m6A modification in arecoline‐promoted OSCC malignance remain elusive. We reveal that chronic arecoline exposure substantially induces upregulation of fat mass and obesity‐associated protein (FTO), MYC, and programmed cell death‐ligand 1 (PD‐L1) in OSCC cells. Moreover, upregulation of PD‐L1 is observed in OSCC cell lines and tissues and is associated with areca nut chewing in OSCC patients. We also demonstrate that arecoline‐induced FTO promotes the stability and expression levels of PD ‐ L1 transcripts through mediating m6A modification and MYC activity, respectively. PD‐L1 upregulation confers superior cell proliferation, migration, and resistance to T‐cell killing to OSCC cells. Blockage of PD‐L1 by administration of anti‐PD‐L1 antibody shrinks tumor size and improves mouse survival by elevating T‐cell‐mediated tumor cell killing. Therefore, targeting PD‐L1 might be a potential therapeutic strategy for treating PD‐L1‐positive OSCC patients, especially those with habitual areca nut chewing.

RNA N6-Methyladenosine (m6A) Methyltransferase-like 3 Facilitates Tumorigenesis and Cisplatin Resistance of Arecoline-Exposed Oral Carcinoma

“…Our recent papers showed that OSCC cell lines that had undergone chronic low-dose arecoline transformation (designated as SCC25-A and CAL27-A) had greater tumorigenic effects than the parental OSCC cell lines (SCC25 and CAL27) [ 12 ]. The RNA-seq transcriptome results revealed that METTL3 gene was among the significantly (fold change > 2 and p < 0.05) elevated genes when comparing CAL27-A to CAL27 ( Figure S1 ) [ 15 ]. To further confirm this result, the protein and mRNA levels of METTL3 in CAL27, CAL27-A, SCC25, and SCC25-A were measured.…”

“…The m6A methyltransferase components primarily comprise three types of enzymes: “readers” (e.g., YT521-B homology (YTH) domain family proteins), “writers” (e.g., methyltransferase-like 3 (METTL3)), and “erasers” (e.g., alkB homologue 5 (ALKBH5)) [ 12 , 13 ]. Recent research has shown that several of these genes are implicated in the development of oral cancer [ 12 , 14 , 15 ]. The m6A modification gene’s role in arecoline-mediated oral cancer development and transformation, on the other hand, remains elusive.…”

The regulation of N6‐methyladenosine modification in PD‐L1‐induced anti‐tumor immunity

“…The knockdown of FTO causes a decrease in PD-L1 mRNA stability and reduces PD-L1 expression on the surface of the cellular membrane. 76,77 Additionally, FTO also manipulates the expression of MYC and promotes PD-L1 expression in a transcriptional manner. 76,78 Remarkably, the methylation level can also influence the expression level of FTO.…”

“…76,77 Additionally, FTO also manipulates the expression of MYC and promotes PD-L1 expression in a transcriptional manner. 76,78 Remarkably, the methylation level can also influence the expression level of FTO. The treatment of hypomethylating agents (HMA) promotes the m6A elimination, which also causes the up-regulation of FTO in a feedback pathway, rather than ALKBH5, METTL3 or METTL14, promoting the expression of PD-L1.…”

“…Further research found that FTO can directly bind with PD‐L1 mRNA and regulate m6A modification of PD‐L1 mainly in CDS and 3′‐UTR regions. The knockdown of FTO causes a decrease in PD‐L1 mRNA stability and reduces PD‐L1 expression on the surface of the cellular membrane 76,77 . Additionally, FTO also manipulates the expression of MYC and promotes PD‐L1 expression in a transcriptional manner 76,78 .…”