C-erbB2, p27 and G1/S aberrations in human primary breast cancer.

BACKGROUND

C-erbB2 is overexpressed in approximately one-fourth of human breast cancers. In spite of numerous reports suggesting a connection of c-erbB2 overexpression with cell cycle regulation through p27, D cyclins and c-myc, the relationship between c-erbB2 and proliferation through de-regulation of the pRb pathway in primary breast cancer has not been fully clarified.

MATERIALS AND METHODS

For this purpose we compared the expression of c-erbB2 in a total of 105 primary breast tumours with a variety of cell cycle proteins and clinical parameters.

RESULTS

C-erbB2 was strongly correlated with down-regulation of p27 and overexpression of c-erbB2 was, as expected, associated with poor survival. However, there was no correlation with proliferation. There was, nevertheless, an association between c-erbB2 and proliferation in certain subtypes of breast cancer, as in oestrogen-receptor-positive tumours, tumours with high cyclin D1, and in tumours with an overall linear pRb pathway, i.e. tumours with a preserved linearity between cyclin D1, pRb phosphorylation and proliferation.

CONCLUSION

Our results suggest that c-erbB2 may have alternative functions in different subtypes of breast cancer, and further stress that c-erbB2, in addition to promoting proliferation, also functions through other mechanisms in breast cancer.