Overexpressed FOXM1 collaborates with MMB to increase WEE1 inhibitor sensitivity in NSCLC

BACKGROUND: Non-small cell lung cancer (NSCLC) is a common lung tumor with high mortality. The complex formed by MYB-MuvB complex (MMB) and forkhead box M1 (FOXM1) (MMB-FOXM1) plays a vital role in cell cycle progression to affect the progression of diseases. The role of the FOXM1-MMB complex in Wee1-like protein kinase (WEE1) inhibitor sensitivity in NSCLC keeps unclear. METHODS: The reverse transcription quantitative polymerase chain reaction (RT-qPCR) was performed to measure the mRNA levels of FOXM1, LIN54, Replication Protein A (RPA), gammaH2AX (γH2AX) and Cyclin B (CCNB). The western blot was performed to examine the corresponding protein expressions. The Cell Counting Kit-8 (CCK-8) assay was performed to test cell survival. RESULT: It was demonstrated that after AZD-1775 treatment, the decrease in cell survival mediated by FOXM1 overexpression (P<0.001) could be reversed by LIN54 knockdown (P<0.01) and that cell survival in the control group did not differ obviously from that in the pcDNA3.1-FOXM1+siLIN54 group, indicating that the FOXM1-MMB complex was necessary for WEE1 inhibitor sensitivity. Moreover, the mRNA and protein expression levels of RPA and γH2AX were increased after AZD-1775 treatment and FOXM1 overexpression (P<0.01), suggesting that FOXM1 upregulation enhanced DNA replication stress and DNA damage. Finally, we found that the increases in the mRNA and protein expression levels of CCNB mediated by FOXM1 (P<0.01) could be rescued by silencing LIN54 (P<0.001) and that CCNB expression in the control group did not differ obviously from that in the pcDNA3.1-FOXM1+siLIN54 group. These findings revealed that the FOXM1-MMB complex activated G2/M checkpoints. In our work, it was discovered that FOXM1 overexpression increased DNA replication stress, which increased DNA replication and pressure on the WEE1 checkpoint. On the other hand, FOXM1 can enhance CCNB expression, increase the threshold content of the CCNB/CDK1 complex, facilitate mitosis, and promote WEE1 dephosphorylation. Under these two conditions, sensitivity to the WEE1 inhibitor AZD-1775 is increased, which leads to the accumulation of DNA damage and drives the activation of apoptosis. CONCLUSIONS: Overexpressed FOXM1 collaborates with MMB to increase WEE1 inhibitor sensitivity in NSCLC. This discovery might highlight the regulatory function of FOXM1/MMB in the treatment of NSCLC patients.