Novel Roles Of FoxM1in Metastasis And Targeted Therapy Resistance In Non-small-cell Lung Cancer

Part Ⅰ FoxM1contributes to poor prognosis of patients with non-small cell lung cancer through promoting tumor cell metastasisObjective:FoxMl was reported to be important in oncogenesis and progression. But whether FoxMl has the prognostic significance in non-small cell lung cancer remains unclear.Methods:FoxM1expression in tumor cells was studied immunohistochemically in175patients with NSCLC, and associations with clinicopathologic parameters were evaluated. Kaplan-Meier survival analysis and Cox proportional hazards models were used to estimate the effect of FoxMl expression on survival.Results:Clinicopathologically, FoxM1expression was found to be significantly associated with poorer differentiation (P=0.0052), higher TNM stage (P<0.001), lymph node metastasis (P<0.001), higher tumor stage (P<0.001), and poorer prognosis (P<0.001). Multivariable analysis confirmed that FoxM1expression increased the hazard of death after adjusting for other clinicopathologic parameters (hazard ratio,1.942;95%CI,1.051-3.589).Conclusions:These results suggested that FoxMl expression mediates prognosis through promoting metastasis in NSCLC patients. Part Ⅱ In vitro and vivo study of enhanced FoxM1facilitated invasion and metastasis potential in non-small cell lung cancer cell lineObjective:To test the role of FoxMl in the metastasis of non-small cell lung cancer.Methods:By lenti-virus transduction, the role of FoxM1in metastasis was also tested by in vivo and in vitro methods using different NSCLC cell lines.Results:In this study, we found that increased FoxM1expression could enhance the migratory and invasive abilities of lung cancer cells, while inhibition of FoxMl expression could reduce the migratory an invasive properties of lung cancer cells, which are the two important parameters of metastasis biology. Moreover, FoxMl was observed to promote the in vivo metastasis of lung cancer cells in mouse models. In addition, cells with high FoxMl expression were presented with phenotypic changes reminiscent of EMT, which was further proved by the results of immunoblotting with down-regulation of E-cadherin and ZO-1while up-regulation of N-cadherin and Vimentin.Conclusions:These results suggested that FoxM1plays an important role in lung cancer metastasis and elevated FoxMl expression could be used as an indicator of poor prognosis and high risk of metastasis of NSCLC patients. Part Ⅲ Study of FoxM1-mediated resistance of non-small-cell lung cancer cells to gefitinibObjective:Gefitinib is only effective in approximately20%of patients with non-small-cell lung cancer (NSCLC), and its underlying mechanisms remain unclear. FoxM1has been shown to be upregulated in NSCLC and has been associated with a poor prognosis in NSCLC patients. In this study, we examined whether the FoxMl gene has a specific role in gefitinib resistance, and if so, what the underlying mechanism might be.Methods:mRNA and protein expression levels of FoxM1were tested by quantitative real-time PCR and Western blot analysis. RNA interference was applied to suppress the expression of FoxMl in resistant SPC-A-1cells, and lentiviral infection was used to overexpress FoxMl in sensitive H292cells. An3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and flow cytometry were used to examine the proliferation and apoptosis of tumor cells.Results:The FoxM1expression pattern significantly differed between the resistant and sensitive lung cancer cell lines upon exposure to gefitinib. FoxM1was found to be upregulated in the resistant SPC-A-1cells and downregulated in the sensitive H292cells. Moreover, overexpression of FoxM1increased drug resistance in H292cells, while attenuated FoxM1expression in SPC-A-1cells restored gefitinib sensitivity by inhibiting proliferation and inducing apoptosis. Additionally, the expression levels of several downstream targets of FoxM1were found to be upregulated in SPC-A-1cells that were treated with gefitinib.Conclusions:These results suggest that FoxM1plays an important role in the resistance of NSCLC cells to gefitinib. FoxMl could be used as a therapeutic target to overcome resistance to gefitinib.