Prognostic impact of CXCL16 and CXCR6 in non-small cell lung cancer: combined high CXCL16 expression in tumor stroma and cancer cells yields improved survival

Background: The chemokine CXCL16 and its receptor CXCR6 are expressed by a variety of immune cells and have been shown to influence angiogenesis. The expression of CXCR6 and CXCL16 has been examined in numerous human cancers; however no studies have yet investigated their influence on prognosis in non-small cell lung cancer (NSCLC). We aimed to explore their prognostic significance in NSCLC, in addition to examining associations with previously investigated markers. Methods: Resected tumor tissue from 335 consecutive unselected stage I-IIIA NSCLC patients (1990-2005) were collected. Immunohistochemistry was used to evaluate the expression of CXCR6 and CXCL16 on tissue microarrays. In vitro, NSCLC cells (NCI-H460, A549 cells) were transfected with CXCL16 siRNA to examine effects on proliferation. Results: In univariate analysis,. stromal cell CXCL16 expression was a significant positive prognostic factor (P = 0.016). CXCR6 was expressed in cancer cells, but did not show any prognostic impact. In the multivariate analysis, combined. cancer, and. stromal cell CXCL16 expression was an independent positive prognostic factor when compared to. stromal and. cancer cell expression (HR: 0.42; 95 % CI: 0.20-0.88; P = 0.022). Knockdown of CXCL16 by siRNA resulted in accelerated proliferation of NSCLC cell lines. Conclusion: We have shown that combined. cancer and. stromal cell CXCL16 expression is an independent positive prognostic factor in NSCLC. Further studies are warranted to elucidate the biological mechanism underlying this finding.