Is cyclin D2 a marker of B-cLL cell activation?

The most recent studies emphasize a link between B-cell proliferation in vivo and clinical outcome of B-cell chronic lymphocytic leukemia (B-CLL). The expression of cyclin D2 in B-CLL cells isolated from the peripheral blood of 27 untreated patients in relation to the apoptosis ratio both before and 72 h after culture in the absence of growth factors was analyzed by immunocytochemistry. The significant associations between cell death in culture and both cyclin D2 expression in freshly isolated cells and the rate of its decrement in culture found in this study confirm the special role of cyclin D2 in enhancing the longevity of these cells in vivo. As cyclin D2 is inducible in the early G1 phase, its increased expression might also reflect the activation of cells attempting to replicate in vivo. Furthermore, the finding that B-CLL progression positively correlates with the gradual increase in the proportion of apoptotic B lymphocytes in culture seems to support the notion of cells striving to undergo division in the absence of growth factors. All together, these results indicate the possibility that cyclin D2+ cells represent a pool of leukemic cells with the potential to enter the dividing compartment.