Cell cycle regulators p27 and pRb in lymphomas - correlation with histology and proliferative activity

The cell cycle is a complex event in which multiple regulator-proteins part icipate. The G(1)/S checkpoint of the cell cycle is controlled by pRb prote in, which functions in its hypophosphorylated form as a negative regulator of growth, p27 (Kip1), a member of CIP/KIP family of cyclin inhibitory prot eins, participates in inhibition of forming complexes that allow pRb to pho sphorylate and lead the cell into mitosis. The expression of these importan t cell cycle regulator proteins was studied in a total of 96 non-Hodgkin's lymphoma (NHL) samples, which were classified according to the REAL classif ication. The expression of p27, pRb and the cell proliferation marker Ki-67 (MIB-1) was evaluated in lymphomas using immunohistochemistry. This study showed that there were coordinate changes in the expression of p27 and pRb in NHL. When compared to low-grade lymphomas, high-grade lymphomas showed s ignificantly reduced expression of p27 and inversely pRb expression was inc reased (P < 0.001), increase in expression of Ki-67 was parallel with pRb e xpression, and was mainly seen in cells that lacked p27 expression (P < 0.0 007). This study suggests that changes in the control of the cell cycle clo sely relate to the pathobiology of NHL. (C) 2000 Cancer Research Campaign.