LAUSR

Simple Summary FOXP3 is a critical transcription factor that works as a master regulator of the lymphoid lineage. The expression of FOXP3 was also observed in tumor cells; in cervical cancer, FOXP3 increases as the tumor progresses. However, the biological role of FOXP3 in cervical pathology is not well understood. In addition, FOXP3 has isoforms that could have different biological properties. In this work, the expression of FOXP3 and its isoforms were evaluated. It was found that the isoform FOXP3Δ2Δ7 is expressed in the cervical cancer-derived cell line SiHa. The transduction of this isoform in nontumorigenic keratinocytes induces proliferation, cell division, and migration. RNAseq analysis indicated that the FOXP3Δ2Δ7 isoform induces the expression of different protooncogenes and modulates essential pathways related to the immune response and the tumorigenic process. Abstract Cervical cancer (CC) is the fourth most common type of cancer among women; the main predisposing factor is persistent infection by high-risk human papillomavirus (hr-HPV), mainly the 16 or 18 genotypes. Both hr-HPVs are known to manipulate the cellular machinery and the immune system to favor cell transformation. FOXP3, a critical transcription factor involved in the biology of regulatory T cells, has been detected as highly expressed in the tumor cells of CC patients. However, its biological role in CC, particularly in the keratinocytes, remained unclarified. Therefore, this work aimed to uncover the effect of FOXP3 on the biology of the tumoral cells. First, public databases were analyzed to identify the FOXP3 expression levels and the transcribed isoforms in CC and normal tissue samples. The study’s findings demonstrated an increased expression of FOXP3 in HPV16+ CC samples. Additionally, the FOXP3Δ2 variant was detected as the most frequent splicing isoform in tumoral cells, with a high differential expression level in metastatic samples. However, the analysis of FOXP3 expression in different CC cell lines, HPV+ and HPV-, suggests no relationship between the presence of HPV and FOXP3 expression. Since the variant FOXP3Δ2Δ7 was found highly expressed in the HPV16+ SiHa cell line, a model with constitutive expression of FOXP3Δ2Δ7 was established to evaluate its role in proliferation, migration, and cell division. Finally, RNAseq was performed to identify differentially expressed genes and enriched pathways modulated by FOXP3Δ2Δ7. The exogenous expression of FOXP3Δ2Δ7 promotes cell division, proliferation, and migration. The transcriptomic analyses highlight the upregulation of multiple genes with protumor activities. Moreover, immunological and oncogenic pathways were detected as highly enriched. These data support the hypothesis that FOXP3Δ2Δ7 in epithelial cells induces cancer-related hallmarks and provides information about the molecular events triggered by this isoform, which could be important for developing CC.