Avaliação da função do receptor do fator de ativação plaquetária na carcinogênese bucal experimental

Abstract

The oral squamous cell carcinoma (OSCC) is the cancer most common of the oral cavity. The OSCC has a high rate of local invasiveness and to regional lymph nodes, which contributes to poor prognosis. The lipid mediator platelet activating factor (PAF) has angiogenic and oncogenic properties and thus could affect tumor invasiveness. The aim of this study was to evaluate the role of PAF in experimental oral carcinogenesis induced by 4NQO (4-nitroquinoline-1-oxide). Male WT (wild type) and PAFRKO (PAF receptor deficient) mice of C57BL/6 and BALB / c strains were used. Treated group mice received chemical carcinogen (4NQO) diluted in drinking water (50 µg/ ml) during 28 weeks. After this period, the mice were euthanized and their tongues collected for macroscopic, histolopathological, immunohistochemical, inflammatory infiltrate and molecular analysis. Serum was collected for analysis of systemic cytokines and chemokines by ELISA. PAF receptor antagonist (UK-74,505) was used to investigate the effect of inhibiting PAF activity in cell invasiveness of metastatic (HN12) and non-metastatic (HN13) OSCC cell lines in vitro. OSCC tongue lesions incidence was similar between treated WT C57BL/6 and PAFRKO mice. The same is pattern was observed when evaluate epithelial dysplasia and PCNA immunostaining. BALB/c WT and PAFRKO mice treated 4NQO showed no incidence of tongue lesions and similar PCNA immunostaining. However, epithelial dysplasia was higher in WT BALB/c treated mice when compared to PAFRKO from the same group. The histochemical analysis showed 4NQO increase eosinophil infiltrate in WT treated mice of both strains. Regarding transgenic mice, carcinogen treatment reduced eosinophils infiltrate in PAFRKO BALB/c mice. Systemic level of CCL4 and CCL5 was significantly increased after treatment with 4NQO in WT C57BL/6 mice when compared to WT control ones, but remained unchanged in WT BALB/c treated mice. Regarding PAFRKO mice, treatment with 4NQO reduced levels of CCL4 and CCL5 in C57BL/6 strain mice but no changes happened in treated PAFRKO BALB/c strain mice. Treatment with 4NQO increased molecular levels of cytokines, inflammatory mediators, growth factors and extracellular matrix components in WT C57BL/6 and PAFRKO mice. Use of PAF receptor antagonist inhibited in vitro cell invasion of OSCC lineages HN12 and HN13, but this inhibition was significantly only for metastatic lineage (HN12). In conclusion, PAF precursor (lyso-PAF) production was increased during oral carcinogenesis induced in mice; PAF receptor antagonism results in inhibition of in vitro invasion of OSCC lineage; absence of PAF signaling in transgenic C57BL/6 strain mice does not alter the progression of carcinogenesis, however BALB/c PAFRKO strain mice had lower epithelial dysplasia score; tumor progression is different for WT BALB/c and C57BL/6 strains mice and BALB/c strain mice are more resistant OSCC induced tongue lesions.