FOXK2 MODULATION AND CLINICAL IMPLICATIONS IN CANCER

INTRODUCTION AND OBJECTIVE: FOXK2 is a transcription factor that plays a dual role in cancer, acting either as a tumor suppressor or an oncogene, depending on the tissue type. In breast cancer, a highly heterogeneous disease, FOXK2 acts as a tumor suppressor. Also, resistance to therapy is the main cause of therapeutic failure. Therefore, we aimed to investigate how FOXK2 modulates chemosensitivity in breast cancer and evaluate FOXK2 gene expression as a potential biomarker in different tumor types. MATERIAL AND METHODS: The role of FOXK2 modulation in breast cancer was assessed by shRNA viral transductions in MCF-7 (chemosensitive) and MDA-MB-231 (chemoresistant) cell lines. The validation of shRNA FOXK2 cell lines was assessed by western blotting and RT-qPCR real time assays. These cells were treated with docetaxel and doxorubicin to evaluate drug-induced cytotoxicity by MTT assays and colony formation ability by clonogenic assays. Then, an in silico analysis has been performed to evaluate patient’s pathological complete response to therapy and relapse-free survival at 5 years using FOXK2 transcriptome-level data of breast cancer patients extracted from the ROCplotter platform. To compare FOXK2 gene expression between normal adjacent and tumor patient’s samples in different tumor types we analyzed transcriptome-level data extracted from the TNMplotter platform. The impact of FOXK2 on patient’s overall survival was evaluated by Kaplan-Meier curves extracted from KMplotter platform. Information on FOXK2 promoter methylation was assessed at OncoDB platform. RESULTS AND CONCLUSION: Our results show that FOXK2 shRNA stable cells lines seem to be more resistant to docetaxel and doxorubicin, an effect that was more prominent in MCF-7 than MDA-MB-231 cells. Interestingly, low FOXK2 gene expression has been found in grade II patients who received chemotherapy and relapsed before 5 years. Similarly, reduced FOXK2 expression has also been found in non-responders compared to responders, particularly in luminal B patients treated with the FEC chemotherapeutic combination (fluorouracil, epirubicin and cyclophosphamide). Therefore, FOXK2 low expression was related to poor responses to treatment in breast cancer. Notably, we found differences in FOXK2 expression, with high transcript levels observed in different tumor types, compared to normal tissues. Also, we found no direct association of FOXK2 gene expression with FOXK2 methylation status, which points to additional transcriptional or post-translational mechanisms governing FOXK2 regulation. From all tumors analyzed, patients diagnosed with kidney renal clear cell carcinoma and liver hepatocellular carcinoma with low FOXK2 levels showed up a remarkable improve on overall survival. Altogether, our findings suggest that analyzing FOXK2 gene expression might be a good predictor of response to therapy, diagnosis and prognosis in some tumor types.