Monzosertib, a selective CDC7 inhibitor, induces cell death via premature mitosis promoted by the FOXM1-cyclinB1 axis

Introduction: Cell division cycle 7 (CDC7) is a highly conserved serine/threonine kinase that plays a critical role in initiation of DNA replication and in replication stress checkpoint. Aberrant CDC7 expression has been implicated in various malignancies, highlighting its potential as a therapeutic target in cancer treatment. Consequently, CDC7 inhibitors are being explored as a novel class of anticancer agents. However, the mechanisms underlying cancer cell death induced by CDC7 inhibition are not fully elucidated. Monzosertib (AS-0141) is a potent, selective, and orally bioavailable CDC7 inhibitor, currently undergoing Phase I clinical trials in patients with solid and hematologic malignancies. In this study, we investigated the mechanisms of cell death induced by monzosertib in human cervical cancer cell lines by comparing cell lines with differential sensitivity to CDC7 inhibition. Method: Six human cervical cancer cell lines (HeLa, CaSki, ME-180, SKG-I, SKG-IIIa, and C33-A) were used to evaluate their sensitivity to CDC7 inhibitors including monzosertib and simurosertib (TAK-931). Cell viability was assessed by the resazurin assay. Cell cycle distribution and apoptosis were analyzed by flow cytometry. Protein and gene expression levels related to CDC7 and cell cycle regulation were analyzed by Western blotting and real-time PCR, respectively. FOXM1 knockdown was performed by introducing shRNA via lentiviral transduction. Result: We evaluated the antiproliferative activity of CDC7 inhibitors in six human cervical cancer cell lines. Among tested cell lines, HeLa cells were the most sensitive to CDC7 inhibition, whereas SKG-I cells exhibited the highest resistance. Treatment with monzosertib led to an increase in the sub-G1 population in these cell lines, depending on their sensitivity. Monzosertib increased the expression of the G2 and M-phase marker, cyclin B1 and phospho-CDK1 in HeLa cells in a dose-dependent manner, but not in SKG-I cells. Cell cycle analysis revealed that monzosertib induced cyclin B1 expression during the S-phase, which is characteristic of premature mitosis. These findings indicate that monzosertib-induced cell death appears to result from impaired mitotic progression. Since cyclin B1 expression was found to be elevated, we next examined the role of FOXM1, a transcription factor which regulates cyclin B1 gene expression. Treatment with monzosertib significantly increased FOXM1 expression in HeLa cells, whereas only a mild increase was observed in SKG-I cells. Knockdown of FOXM1 in HeLa cells resulted in reduced cyclin B1 expression and decreased sensitivity to CDC7 inhibition. Conclusion: We found that the FOXM1- cyclin B1 axis contributes to cell death in cervical cancer cells induced by the selective CDC7 inhibitor, monzosertib.