The expression of low molecular weight protein tyrosine phosphatase is up-regulated in 1,2-dimethylhydrazine-induced colon tumours in rats.

Recent studies have assessed the role of low molecular weight protein tyrosine phosphatase (LMW-PTP) in cell transformation and tumour onset and progression, observing a significant increase in the expression of LMW-PTP mRNA and protein in human breast, colon, bladder and kidney tumour samples. Moreover, its enhanced expression is generally prognostic of a more aggressive cancer. To better understand the role of this protein during colon carcinogenesis and to study whether its overexpression is also observed in earlier phases of carcinogenesis, we studied its expression in colon tumours, induced in rats by treatment with 1,2-dimethylhydrazine (DMH), an animal model that resemble the sequential formation of histopathological lesions of spontaneous carcinogenesis in humans. The results show a significant increase in LMW-PTP expression in adenocarcinomas, suggesting that this phenomenon is associated with the onset of malignancy. Moreover a significant overexpression of LMW-PTP transcript is associated with tumours originating in the proximal (right) part of the colon, confirming an observation already reported for human colon cancer.