RB status as a determinant of response to UCN-01 in non-small cell lung carcinoma

7-Hydroxystaurosporine (UCN-01), a protein kinase inhibitor in clinical dev elopment, demonstrates potent anti-neoplastic activity. To determine whethe r specific genetic abnormalities would modulate the response to UCN-01, a m odel of human non-small cell lung carcinoma (NSCLC) cell lines with differe ntial abnormalities of p16(CDKN2), RB, and p53 was used for these studies, Cell growth was measured by the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenylte tra-zolium bromide assay, and cell cycling was studied using flow cytometri c analysis of DNA content, Changes in protein levels and phosphorylation we re assessed by Western blotting, In cell lines expressing wild-type RB (A54 9 and Calul), UCN-01 treatment resulted in dose-dependent growth inhibition , arrest of cells in G(1), and a reduction of cells in S phase. p16(CDKN2)- null cells showed similar growth inhibition to normal fetal lung fibroblast s, UCN-01-induced growth arrest was accompanied by induction of p21(CDKN1) and shift of Rb to the hypophosphorylated state in both p53 wild-type and m utant cell lines. In contrast, UCN-01 treatment of the RB-null cell line H5 96 resulted in less growth inhibition, To test the role of RE in response t o UCN-01, effects of treatment were examined in two human isogenic models o f RB expression: the bladder cancer cell line 5637 (RB-null) and the prosta te cancer cell line DU-145 (RB-mutant). In the Rb-expressing 5637 subline ( RB5), UCN-01 treatment resulted in Rb hypophosphorylation and an accumulati on in G(1) in contrast to the parent line. Similarly, the wild-type Rb-expr essing DU-145 sublines (DU1.1 and B5) show ed increased G(1) arrest compare d a with the parent cells. We conclude that UCN-01-induced G(1) arrest can occur in cells null for p53 and p16(CDKN2), and that RB status influences t he ability of UCN-01 to induce a G(1) arrest. These data suggest that the m olecular profile of cell cycle regulating genes in individual tumors may pr edict responsiveness and provide insight into optimal therapeutic applicati on of this new antineoplastic agent.