Caveolin-1 inhibits the growth of human laryngeal squamous cell carcinoma and down regulates EGFR-MAPKs signaling pathway

Objective: To investigate the effects of caveolin-1 on the growth of laryngeal squamous cell cancer HEp2 cell line in vitro and in vivo. Methods: The caveolin-1 gene was introduced into HEp2 cells and stable over-expressing caveolin-1 clones were obtained. In vitro and anchorage-independent growth rates were measured by methyl thiazolyl tetrazolium (MTT) and colony formation in soft agar assay, respectively. Flow cytometry was used to analyze the cell cycle and apoptosis. Activities of extracellular signal-regulated kinase 1/2 (Erk1/2) and epidermal growth factor receptor (EGFR) were determined by Western blot analysis, and the interaction between EGFR and caveolin-1 was determined by coinummoprecipitation assay. The effect of caveolin-1 on the tumor growth in vivo was tested by tumorigenicity assay in nude mice. Results: Stable over-expressing caveolin-1 clones, namely HEp2-CAV1-2 and HEp2-CAV1-3, exhibited a slower rate of growth in vitro and reduced capacity of anchorage-independent growth. In addition, overexpression of caveolin-1 resulted in a cell cycle arrest in the G(0)/G(1) phase and increased the apoptotic cell fraction by 3.86-fold and 3.71-fold in HEp2-CAV1-2 and HEp2CAV1-3 cells. Compared with the parental HEp2 cells, the phosphorylation. of EGFR and Erk1/2 was reduced by 66% and 83% in HEp2-CAV1-2 cells and by 58% and 78% in HEp2-CAV1-3 cells, respectively; an interaction between EGFR and caveolin-1 was observed. Moreover, over-expression of caveolin-1 in HEp2 cells significantly reduced the probability of tumor formation in vivo. Conclusion: Caveolin-1 inhibits the growth of human laryngeal squamous cell carcinoma HEp2 cell line in vitro and in vivo. Downregulation of EGFR-mitogen-activated protein kinase signaling pathway may be critical for understanding its mechanism of tumor suppression.