Combination treatment of retinoic acid plus FAK inhibitor prevents tumor growth and breast cancer cells metastasis

Abstract

Background: All-trans retinoic acid (RA) and its natural and synthetic derivatives, known as retinoids, are promising agents in the treatment and chemoprevention of different neoplasias including breast cancer (BC). Focal adhesion kinase (FAK) is a key regulator of cell motility and its overexpression has been associated to a metastatic behavior of tumors. Thus, pharmaceutical FAK inhibitors (FAKi) have been developed to counter this action. In this work, we evaluated the effect of RA+FAKi combination in tumor progression.Methodology: the murine mammary adenocarcinoma cell line LM3 was used. MTT, pharmacological interaction analysis, western blot, immunofluorescence, adhesion, and migration assays were performed. The orthotopic tumor growth and lung metastasis assay were achieved. To bioinformatics analysis we used the publicly Gene Expression Omnibus database. Results: Bioinformatic data show that the expression of RARA, SRC, PTK2 (FAK) is high, meanwhile RARB and RARG are underexpressed in BC cells. We reveal that in metastatic BC cells, genes encoding proteins that are directly or indirectly modulated by FAK, are deregulated in comparison with normal cells. We showed a different pattern of genes up/down-regulated between RA-resistant and RA-sensitive BC cells. Additionally, we demonstrated that although RA and FAKi administered separately decrease cell viability, adhesion and migration in LM3 cells, their combination exerts a higher effect. In an orthotopic assay of LM3 tumor growth, RA and FAKi separately reduce tumor growth however the combined treatment induced the stronger inhibition. Furthermore, the combination increase mice survival. In an experimental metastatic assay, RA significantly reduced lung metastatic dissemination.Discussion: These results suggested that RA resistance would reflect a deregulation of most of the RA-target genes involved in cell adhesion, migration and invasion. RA+FAKi improves reducing tumor growth and metastasis increasing mice survival. This suggest that the sensibility to RA therapy could be exacerbated with FAKi coadministration in BC tumors.