[Cyclin-dependent kinase inhibitory proteins in normal and transformed choroidal melanocytes].

PURPOSE

Recent studies have demonstrated the close link between oncogenesis and cell cycle machinery. Cyclin dependent kinase inhibitory proteins (Ckis) have been shown to be implicated in cancer progression. We investigated the levels of the different regulatory inhibitory proteins involved in the G1 progression and G1/S in choroidal melanomas.

METHODS

Immunoblotting, immunoprecipitation and immunohistochemistry were performed on human choroidal cell lines and human choroïdal tumors.

RESULTS

Our findings suggested a lack of expression of Cdk inhibitor p21 in two of three melanoma cell lines and a striking underexpression of p27 in the three transformed cell lines. The p16 level was found to be almost the same in both normal and transformed cells, a loss of p16-Cdk4 interaction was observed in two of the three melanoma cell lines. In immunohistochemistry, nuclear positivity for p16 was observed in six tumors. Nuclear positivity for p21 was observed in five tumors. All of theses tumors had scleral invasion (p = 0.003). Nuclear positivity for p27 was observed in only two tumors.

CONCLUSION

Our results demonstrate that immunoreactivity for p16, p21 and p27 could be implicated in progression of melanoma tumors. More cases are required to further clarify this issue.