Abstract 942: Novel CDK2/9 inhibitor has antineoplastic activity in lung cancer by inducing anaphase catastrophe
Authors: Kawakami Masanori , Mustachio Lisa Maria , Liu Xi , Hu Shanhu , Lu Yun , Sekula David , Freemantle Sarah , Dmitrovsky Ethan 
Published: August 2015

Our prior work revealed the first generation CDK2/9/7 inhibitor seliciclib (R-roscovitine, CYC202) significantly inhibited lung cancer growth and tumorigenicity by increasing apoptosis via induced anaphase catastrophe. In anaphase catastrophe, cells with aneuploidy (a hallmark of cancer), cannot cluster supernumerary centrosomes. This triggers abnormal anaphase and apoptosis. This study explored lung cancer antineoplastic effects of a next generation CDK2 inhibitor: CCT68127 (Cyclacel Ltd). This is a more potent and selective CDK2/9 inhibitor than seliciclib (IC50 for CDK2 and CDK9 are 30nM and 110nM, respectively). We compared antineoplastic activities of CCT68127 versus seliciclib in murine (transgenic mouse model-derived) versus human lung cancer cells. In murine lung cancer cell lines (ED1, LKR13, and 393P), IC50 of CCT68127 at 48 hours was &lt;1μM; while the IC50 of seliciclib was &gt;25μM. Lung cancer cell lines with mutant KRAS (LKR13 and 393P) were more responsive to CCT68127 than ED1 cells with wild-type expression. Minimal growth-inhibition occurred in C10 murine pulmonary epithelial cells. In human lung cancer cell lines (Hop62, A549, H2122, H522, and H1703), CCT68127 IC50s were comparable to the studied murine lung cancer cells. Notably, lung cancer cells with mutant KRAS (Hop62, A549, and H2122) were more sensitive than lines with wild-type KRAS expression (H522 and H1703). Human BEAS-2B immortalized bronchial epithelial cells were relatively resistant to CCT68127 treatment. CCT68127 induced apoptosis in a dose-dependent manner in murine lung cancer cell lines (ED1 and LKR13). CCT68127 induced apoptosis at the 1μM concentration to levels seen with seliciclib 20μM concentrations in these cancer cells. Apoptosis was induced in Hop62, A549, H522, and H1703 human lung cancer cell lines. A mechanism responsible for these effects was uncovered. CCT68127 treatment triggered anaphase catastrophe in both murine and human lung cancer cell lines independently of KRAS mutation status. To identify other mechanisms engaged by CDK2/9 antagonism, RPPA (Reverse Phase Protein Assay) analyses were performed in CCT68127-treated lung cancer cells. Expression levels were studied in nearly 200 critical growth-regulatory proteins. Analyses were examined before and after 6, 24, and 48 hours of CCT68127 or vehicle treatments in murine (LKR13 or ED1) and human (Hop62 or H522) lung cancer cells having or not KRAS mutations. A distinct profile was identified and included DNA repair, Hippo pathway and Rab GTPase pathways that were markedly down-regulated by CDK2/9 antagonism. Taken together, both anaphase catastrophe and specific growth regulatory proteins are engaged to elicit antineoplastic effects of a highly selective and specific CDK2/9 inhibitor.

Citation Format: Masanori Kawakami, Lisa Maria Mustachio, Xi Liu, Shanhu Hu, Yun Lu, David Sekula, Sarah Freemantle, Ethan Dmitrovsky. Novel CDK2/9 inhibitor has antineoplastic activity in lung cancer by inducing anaphase catastrophe. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 942. doi:10.1158/1538-7445.AM2015-942