The present study was to identify abnormal methylation genes implicated in esophageal squamous cell carcinoma (ESCC). Genomic methylation alterations in ESCC tissues were analyzed using laser-microdissection and whole-genome bisulfite sequencing. CXCL14 promoter was frequently hypermethylated in ESCC tissues. The correlation of CXCL14 hypermethylation status and the mRNA and protein expression levels were validated using nested methylation-specific PCR (nMS-PCR), RNAscope in situ hybridization (RISH) and Western blot. RISH results showed completely negative CXCL14 expression in 34.3% (34/99) ESCC, compared with those in the basal layer cells of normal epithelia. Low expression of CXCL14 was more present in patients with lower differentiation. The anticancer role of CXCL14 has been commonly associated with immune regulation in the literature. Here, we observed by functional analysis that CXCL14 can also act as a tumor suppressor in ESCC cells. 5-Aza-dC treatment suppressed CXCL14 methylation and up-regulated the expression of CXCL14. Ectopic expression of CXCL14 suppressed the proliferation, invasion, tumor growth, and lung metastasis of ESCC cells. Both ectopic expression and induction of CXCL14 with 5-Aza-dC inhibited the activity of SRC, MEK1/2 and STAT3 in ESCC cells, while activated EGFR. Importantly, a combination of CXCL14 expression and SRC or EGFR inhibitor dramatically repressed the proliferation of ESCC cells and the growth of xenografts. Our findings revealed a direct tumor suppressor role of CXCL14, but not through the immune system. The data suggest that for ESCC patients with low level CXCL14, increasing CXCL14 expression combined with inhibition of SRC or EGFR might be a promising therapeutic strategy.
Keywords: CXCL14; Hypermethylation; MEK; SRC; Tumor suppressor.
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