FOXF1 belongs to a multigene family of FOX that is abnormal expression in various malignant tumors and is involved in various biological processes, such as proliferation, differentiation, metabolic balance of tumor cells. However, the role of FOXF1 in malignant tumors, especially ovarian cancer, have rarely been studied. In this study, we first investigated the expression of FOXF1 in all kinds of cancer including ovarian cancer. The sub-group analysis of multiple clinic pathological features also showed a close connection between FOXF1 and ovarian cancer in the present study. The correlation between FOXF1 and immune infiltrates has also been analyzed to gain more detailed insights into the underlying functions of FOXF1 in tumor immune. In addition, genes co-expressed and potential targeted drugs with FOXF1 in ovarian cancer were analyzed to explore the regulatory effect and targeted therapeutic values of FOXF1 in ovarian cancer.
Early screening methods and biomarkers were lacking in the early diagnosis of ovarian cancer. Hence, it is urgent to find more biomarkers to improve early diagnosis. Numerous reports have shown that FOXF1 was abnormal expression in several kind of tumor which were consistent with the results in our study[13, 18]. FOXF1 expression is also significantly associated with the malignant phenotypes of CRC and papillary thyroid cancer (PTC)[13, 18]. These results suggest FOXF1 exists potential diagnosis values in these cancers. The expression of FOXF1 in ovarian cancer has been found notably reduced compared with that in adjacent tissue in our study. The sub-group analysis also showed the expression of FOXF1 decreased conspicuously with the grade progression of tumor. We suggest that FOXF1 deserves further clinical validation as prognostic factor.
In addition to early diagnosis, effective treatment is also essential to improve the prognosis of cancer patients. Immune-related mechanisms have been reported to be involved in occurrence and development of ovarian cancer[19, 20]. Therefore, immunotherapy strategy is also considered to be a promising direction in the clinical treatment of ovarian cancer. Therefore, this study also illustrates a significant association between FOXF1 expression and multiple tumor-infiltrating immune cells in ovarian cancer. The expression of FOXF1 had a notable negative correlation with infiltration of B cells, CD8 + T cells, monocyte cells, Tregs, macrophage M1, macrophage M2, neutrophils, and NK cells in our study. Overexpression of FOXF1 could change the level of monocyte chemoattractant protein 1 (MCP-1) in FOXF1 + mice[21]. MCP-1 has specific chemokine activation to monocytes and macrophages. FOXF1 has also been proved that it was correlated with high macrophage infiltration in glioma microenvironment[22]. In ovariectomised (OVX) mice, FOXF1 was expressed in bone marrow-derived macrophages (BMMs)[23]. Therefore, FOXF1 expression had a significant impact on the regulation of immune infiltration levels and tumor-immune interaction in ovarian cancer. Gene copy number alterations are common in cancer and are closely associated with recurrence and death of cancer. Amplification, deletion and mutation are common ways in which genes change[24]. Our results showed most genetic variations in FOXF1 were deep deletion. The deep deletion of FOXF1 was also associated with immune cell infiltration of B cells, CD8 + T cells and Tregs. Therefore, deep deletion of FOXF1 may also be associated with immune cell infiltration in ovarian cancer.
In order to explore biological function and signaling pathways which were related to FOXF1 in ovarian cancer, the genes co-expressed with FXOF1 has been identified. After that, functional enrichment analyses showed FOXF1 mainly involved in cell adhesion, NADH dehydrogenase complex, MHC protein complex, cytokine binding and rRNA binding. KEGG pathway analysis denoted that FOXF1 was mainly enriched in the pathways involved in DNA replication and ECM-receptor interaction. Overexpression of FOXF1 correlated with decreased expression of vascular cell adhesion molecule-1 (VCAM-1) in mice[25]. The expression of some cytokine factors could also be regulated by FOXF1[26]. In addition, depletion of FOXF1 in breast cancer cells led to increased DNA re-replication[27]. These results suggest that FOXF1 affects the malignant progression of ovarian cancer through a variety of modulatory mechanisms.
To further study the molecular mechanism of FOXF1 in ovarian cancer, kinase, miRNA or transcription factor targets which were related to FOXF1 have also been shown in the present research. PRKG1, miR-151 and SRF have been regarded as hub targets of FOXF1 in the study. These hub targets mainly participated in the regulation of calcium ion transport, cell division, homotypic cell-cell adhesion and pri-miRNA transcription by RNA polymerase II. PRKG1 has been reported as a diagnosis and prognostic factor in ovarian cancer[28, 29]. In ovarian cancer, miR-151 could also inhibit proliferation and migration of cancer cell through regulate MEX3C level[30]. As a transcription factor, SRF has been shown to regulate cell proliferation and motility of ovarian cancer[31]. Therefore, our analyses suggest that PRKG1, miR-151 and SRF are key targets of FOXF1. FOXF1 is likely to affect the development of ovarian cancer through regulate the expression of these genes.
Besides, we used CMap to screen out several potential small molecules for ovarian cancer treatment, like veliparib, PD-0325901 and prazosin. Veliparib with first-line chemotherapy could enhance progression-free survival rate in ovarian cancer patients[32]. Veliparib with carboplatin and paclitaxel could also improve progression-free survival rate in patients with germline BRCA mutation-associated advanced breast cancer[33]. MEK inhibitor PD-0325901 may also be used in advanced ovarian cancer[34]. Prazosin, a non-selective α1-adrenoceptor and a selective α2B-adrenoceptor antagonist, is reported to possess anti-cancer activity in some types of cancer[35, 36]. However, the therapeutic potential of prazosin in ovarian cancer has not been studied. In conclusion, the small molecular compounds screened in this study, such as veliparib, PD-0325901 and prazosin, may play important roles in inhibiting the progression of ovarian cancer.