Clinical significance of STAT3 and MAPK phosphorylation, and the protein expression of cyclin D1 in skin squamous cell carcinoma tissues.

The present study aimed to investigate the significance of the phosphorylation of signal transducer and activator of transcription 3 (STAT3) and mitogen‑activated protein kinase (MAPK), and the protein expression of cyclin D1, in skin squamous cell carcinoma (SCC) tissues. SCC specimens from the skin were collected from 30 patients, and normal skin tissues were collected from 10 individuals as a control. Immunohistochemistry was used to assess the protein expression levels of phosphorylated (p‑)STAT3, p‑MAPK and cyclin D1 in the SCC tissues. The levels of p‑STAT3 protein were abnormally increased in SCC (P<0.05); however, no significant differences in the protein expression of p‑MAPK were identified between the normal skin and the SCC specimens. The extent of the upregulation of the expression of p‑STAT3 and cyclin D1 correlated with the depth of tumor invasion (P<0.05). A positive correlation existed between the expression of p‑STAT3 and cyclin D1 in SCC. However, no association between the expression intensity of p‑MAPK and cyclin D1 was identified in SCC. It is postulated that the activation of STAT3 may induce the overexpression of cyclin D1, which results in the persistent proliferation of these tumor cells in SCC.