Functional characterization of OPN in human laryngeal squamous cell carcinoma and its xenograft model in nude mice

Background: Osteopontin (OPN) is involved in promotion of cancer cells by regulating various facets of tumor progression such as cell proliferation, angiogenesis and metastasis. To understand the role of OPN in laryngeal squamous cell carcinoma (LSCC), we thus explored the biological function of OPN in LSCC after silencing OPN expression by RNA interference (RNAi). Method: The OPN expression in tumor tissues of LSCC was determined immunohistochemically in both LSCC and adjacent normal tissues. Lentivirus vector with RNAi small hairpin gene sequence of OPN (named LV-shOPN) was transfected into Hep-2 cells and transplanted into BALB/c-nu mice. After siRNA transfection, the viability of Hep-2 cells was examined by MTS, OPN expression was detected by Western blotting, and tumor angiogenesis was assessed by microvessel densities (MVD). Results: The difference of positive rate of OPN in 72 cases LSCC (54 cases, 75.0%) and adjacent normal tissues (15 cases, 20.8%) was statistically significant (P<0.001) and the OPN expression was also significantly correlated with tumor stage, grade and the presence of lymph node. Hep-2 cells infected with LV-shOPN significantly decreased OPN expression, in comparison to cells with LV-shNon transfection (as the control) (P<0.05). The constructed LV-shOPN effectively inhibited the viability of Hep-2 cell and growth of xenograft tumors in nude mice (all P<0.050). The expression of OPN and MVD was significantly decreased in xenograft tumors (all P<0.05). Conclusion: RNAi silencing of OPN expression can significantly inhibit tumor growth and angiogenesis of Hep-2 cells, and OPN may be considered as one of gene targeting therapy for LSCC.