LINC00973 is involved in cancer immune suppression through positive regulation of Siglec-15 in clear-cell renal cell carcinoma.

The pioneering work from Lieping Chen's laboratory identified Siglec-15 as a novel tumor immune suppressor, while the regulatory mechanisms underlying the broad upregulation of Siglec-15 in human cancers remain obscure. Here we found that long non-coding RNA (lncRNA) LINC00973 was higher in Siglec-15-positive clear-cell renal cell carcinoma (ccRCC), and LINC00973 positively regulated Siglec-15 expression at transcriptional level. This effect was evidently dependent on miR-7109-3p (designated as miR-7109 hereafter), and we provided evidence that Siglec-15 is a direct target of miR-7109. Through sponging miR-7109, LINC00973 functioned as competing endogenous RNA (ceRNA) to control cell surface abundance of Siglec-15, and, consequently, was involved in cancer immune suppression. We further demonstrated that LINC00973 and miR-7109 expression in ccRCC antagonistically influenced immune activation of co-cultured Jurkat cells. Our study highlighted the importance of LINC00973-miR-7109-Siglec-15 in immune evasion in ccRCC, which offers significant opportunity for both therapeutic intervention and diagnostic/prognostic exploitations.