Overexpression of SPHK1 associated with targeted therapy resistance in predicting poor prognosis in renal cell carcinoma.

Background: Sphingosine kinase 1 (SPHK1) is a key enzyme that catalyzes the phosphorylation of sphingosine. Recent studies reported SPHK1 to be associated with renal cell carcinoma (RCC) progression by inducing targeted therapy resistance. However, the expression and the clinical significance of SPHK1 on RCC in those having received targeted therapy have not been elucidated. The present study explored the expression of SPHK1 in RCC tissues from targeted therapy recipients, the correlation of SPHK1 with clinicopathological parameters, and the effect of SPHK1 on RCC patient prognosis.

Methods: Differential gene expression analysis of RCC treated with and without targeted therapy was performed. The correlations of SPHK1 expression with clinical parameters of RCC were examined. Gene set enrichment analysis (GSEA) was performed to clarify the potential role of SPHK1 associated with targeted therapy resistance. The value of SPHK1 as a diagnostic marker for RCC was also evaluated. The Kaplan-Meier method was applied to analyze the correlation between SPHK1 expression and patient survival rate by using the clinical data from patients with RCC.

Results: Significant overexpression of SPHK1 was detected in RCC treated with targeted therapy. SPHK1 expression was closely correlated with RCC progression-related clinicopathological parameters. Therefore, elevated SPHK1 could effectively diagnose RCC and distinguish RCC with an advanced clinical stage and a high pathological grade. SPHK1 was associated with the stemness of RCC cells via the activation of the Wnt, Hedgehog, or Notch signaling pathways in targeted drug-treated or untreated RCC. Survival analysis of a large cohort of RCC samples indicated overexpression of SPHK1 to be inversely correlated with the overall and disease-free survival of patients with RCC.

Conclusions: Our study indicated that SPHK1 associated with targeted therapy resistance could serve as a potential prognostic marker and a valuable biomarker of response to angiogenic agents in RCC.