Efeito do tratamento TKI-258 sobre a expressão gênica de seus receptores-alvo e ativação de suas efetoras GTPases Rho em carcinoma epidermoide oral in vitro.

Abstract

Oral squamous cell carcinoma represents the majority of malignant lesions of the head and neck region. The behavior of their cells is regulated by the binding of extracellular molecules to cell membrane receptors, which initiate signal transduction pathways. TKI-258 is a tyrosine kinase inhibitor that blocks the receptors of growth factors: fibroblasts (FGFRs), platelet derivatives (PDGFRs) and vascular endothelials (VEGFRs), which makes it attractive for the treatment of this neoplasm. This study aimed to evaluate the effect of TKI-258 treatment on the gene expression of its target receptors, the activation of its Rho GTPases effectors and the organization of cytokeratin and vimentin in oral squamous cell carcinoma in vitro. SCC-4 cells controlled and treated with TKI-258 at 5 μM were cultured for 24 hours for the following assays: gene expression of FGFR3b, VEGFR1, PDGFRα and PDGFRβ; immunofluorescence for RhoA, RhoB, Rac1 and Cdc42 in three-dimensional cultures; immunofluorescence to cytokeratin and vimentin. The differences were considered significant when p<0.05. The cells treated with TKI-258 showed a tendency to decrease gene expression of FGFR3b, VEGFR-1, PDGFRα and PDGFRβ. The RhoA and RhoB GTPases were seen externally to the actin cortex (active form) in control cells and treated with TKI-258. Rac1 was seen externally to the actin cortex (active form) in cells treated with TKI-258, but not in control cells. Cdc42 was not seen in control cells and treated with TKI-258. The percentage of positive treated cells decreased to cytokeratin and was similar for vimentin. The results showed that inhibition of signal transduction pathways with treatment with TKI-258 in oral squamous cell cells in vitro leads to a trend of decreased gene expression of FGFR3b, VEGFR-1, PDGFRα, and PDGFRβ. However, it keeps the RhoA, RhoB and Rac1 GTPases in their active form. Also, it reduces the amount of cells positive for cytokeratin, while vimentin is not affected.