Expression of p-STAT3 in human colorectal adenocarcinoma and adenoma; correlation with clinicopathological factors

Background: The signal transducer and activator of transcription 3 ( STAT3) is a key signalling molecule implicated in the regulation of growth and malignant transformation. Constitutive activation of STAT3 is seen in several tumour derived cell lines, and in a wide variety of human malignancies. Aims: To examine the relation between p- STAT3 ( activated form of STAT3) expression and clinicopathological factors in human colorectal adenocarcinoma and adenoma. Methods: Immunohistochemical analyses were carried out on tissues from 44 colorectal adenomas and 95 colorectal adenocarcinomas, comprising 18 intramucosal carcinomas and 77 invasive carcinomas. Results: Seventy seven of these 139 samples ( 55.4%) showed immunoreactivity for p- STAT3. Positive staining for p- STAT3 was seen in 69 of the 95 carcinomas. Only eight of the 44 adenomas showed immunopositivity for p- STAT3, resulting in a significant difference between total adenocarcinomas and adenomas ( p < 0.001). Among the 95 cases of colorectal adenocarcinoma, p- STAT3 immunoreactivity was significantly correlated with the depth of tumour invasion ( p < 0.05), venous invasion ( p < 0.05), lymph node metastasis ( p < 0.05), and increasing stages of the Dukes' classification ( p < 0.01). Expression of p- STAT3 was detected by Western blot analysis in two different cultured human colorectal carcinoma cell lines and six colon carcinoma tissue samples obtained at surgery. Conclusion: This is the first study to report a significant correlation of p- STAT3 expression with the depth of tumour invasion. These findings suggest that p- STAT3 expression is an important factor related to carcinogenesis and/ or tumour invasion of colorectal adenocarcinoma.