Overexpression of phosphorylated-STAT3 correlated with the invasion and metastasis of cutaneous squamous cell carcinoma

In order to evaluate the possible effects of STAT3 phosphorylation and expression of E-cadherin on metastasis of some human epidermal non-melanoma cutaneous tumors, the expression of phosphorylated STAT3 (p-STAT3) and E-cadherin were analyzed by immunohistochemistry staining in formalin-fixed, paraffin-embedded tissue sections of human cutaneous squamous cell carcinoma (SCC), basal cell carcinoma (BCC) and seborrhoeic keratosis (SK). An immunohistochemistry staining technique was employed to measure the expression of p-STAT3 and E-cadherin protein in 30 cases of cutaneous SCC, 20 cases of BCC, 20 cases of SK, and 20 specimens of normal skin. The results were as follows: 1) p-STAT3 protein was abnormally increased in SCC as compared to normal skin and SK (p < 0.001). Expression of p-STAT3 in SCC was also significantly higher than in BCC (p < 0.05). 2) Expression of p-STAT3 was higher in poorly-differentiated SCC than in well-differentiated ones (p < 0.05). The positive rate of the expression of p-STAT3 correlated well with the depth of tumor invasion and with metastasis (p < 0.05), but there was no correlation between the positive rate and tumor size. 3) E-cadherin was strongly expressed on the cell membranes of normal skin and SK, especially on basal cells. E-cadherin was weakly expressed on cell membranes of SCC and BCC (p < 0.001), whereas its expression was significantly lower in SCC than in BCC (p < 0.05). In SCC, the intensity of E-cadherin expression was correlated with the extent of tumor differentiation, but there was no correlation between the expression intensity and the depth of tumor invasion or tumor size. 4) There was a negative correlation between the expression intensity of p-STAT3 and E-cadherin in SCC (r(x) = -0.372, p < 0.05). We concluded that the overexpression of p-STAT3 may have an important role in the development of epidermal tumors. Abnormal activation of STAT3 may be related to metastasis potential in SCC and the simultaneous detection of p-STAT3 and E-cadherin may contribute to predicating the prognosis in SCC.