Targeting KIFC1 induces anaphase catastrophe in small cell lung cancer

Cancer cells often possess more than two centrosomes, which is one of the hallmarks of cancer. By clustering these supernumerary centrosomes during mitosis, cancer cells can achieve bipolar division. We previously reported that in non-small cell lung cancer, CDK2 inhibition suppresses centrosome clustering, leading to multipolar cell division and apoptotic cell death-a phenomenon termed anaphase catastrophe. Because normal cells have only two centrosomes, anaphase catastrophe does not appreciably affect them, making it a promising therapeutic strategy for selectively eliminating cancer cells. However, as CDK2 inhibition also interferes with normal cell cycle progression, identifying therapeutic targets that can induce anaphase catastrophe preferentially is desirable. Motor protein KIFC1 has been implicated in centrosome clustering. Here, we investigated its potential as a novel therapeutic target to induce anaphase catastrophe in small cell lung cancer (SCLC). Owing to p53 inactivation, SCLC is expected to frequently harbor supernumerary centrosomes and be vulnerable to mitotic abnormalities, including anaphase catastrophe. First, in vitro experiments using multiple SCLC cell lines were conducted. Immunofluorescence staining for pericentrin confirmed that centrosome amplification occurs more frequently in SCLC cells than in normal human bronchial epithelial (NHBE) cells. Western blotting revealed that KIFC1 was overexpressed in SCLC cells as compared with NHBE cells. Functional analyses, both pharmacologic (using a specific inhibitor) and genetic (using siRNAs and the CRISPR-Cas9 system), demonstrated that inhibition of KIFC1 induced apoptosis and suppressed proliferation in SCLC cell lines, whereas these effects were largely absent in NHBE cells. Furthermore, immunostaining for alpha-tubulin, pericentrin, and DAPI showed a statistically significant increase in multipolar mitotic cells and a decrease in cells with clustered supernumerary centrosomes among dividing cells, implicating KIFC1 inhibition in conferring anaphase catastrophe in SCLC. These findings were validated and extended in the in vivo setting. In human SCLC cell-derived xenograft models, administration of KIFC1 inhibitor statistically significantly suppressed tumor growth. Staining of excised tumors for pericentrin revealed reduced numbers of cells with clustered supernumerary centrosomes and increased numbers undergoing multipolar mitosis, consistent with in vitro findings and indicative of anaphase catastrophe induction. Finally, potential combination therapies with other pharmacologic targets were explored and will be presented. In conclusion, inhibition of KIFC1 disrupts the clustering of supernumerary centrosomes and caused anaphase catastrophe, indicating its promise as a novel therapeutic target for SCLC.