Expressão de variantes transcricionais do gene homeoboxTGIF1 em carcinomas epidermóides de boca / Expression of transcript variants of the homeobox gene TGIF1 in oral squamous cell carcinoma

RESUMO

Genes da família homeobox têm sido alvo de intensas pesquisas científicasrelacionadas ao câncer. Recentemente, mostramos que o gene homeobox TGIF1está expresso no carcinoma epidermóide de boca na sua forma genérica. Porém,não foi feita uma discriminação entre quais variantes transcricionais, ou “subtipos”,do TGIF1 estariam expressas. Neste estudo, propusemo-nos a verificar diferençasna freqüência de expressão das variantes transcricionais do TGIF1 em carcinomasepidermóides de boca (CEB) em relação a tecidos morfologicamente não tumorais(TN), avaliar possíveis associações entre essas variantes nos pacientes portadoresde CEB e relacionar o grau de expressão dessas variantes com aspectos clínicos,histológicos e com a sobrevida dos pacientes. Adicionalmente, procuramos analisara expressão da proteína do TGIF1. Foram analisadas 48 amostras congeladas deCEB e 12 de TN. O RNA total de cada amostra foi extraído utilizando-se solução deTRizol®. Os transcritos do TGIF1 foram amplificados por RT-PCR para cada casode CEB e TN utilizando-se inicialmente um par de iniciadores genéricos para todasas suas variantes. Após essa triagem, os casos positivos foram amplificadosutilizando-se pares de iniciadores específicos para cada variante. Não houvediferença estatística entre a freqüência de expressão das variantes do TGIF1 nosgrupos CEB e TN, porém as variantes 4 e 8 foram as que apresentaram p-valoresmenores. Dentro do grupo de CEB, houve associação significativa entre algumas...

ABSTRACT

Genes of the homeobox family have been the subject of intense scientific researchrelated to cancer. Recently, we show that this gene is expressed in oral squamouscell carcinoma in its generic form. However, it was not made a discriminationbetween which transcript variants, or “subtypes", of TGIF1 were expressed. In thisstudy, we aim to verify differences in the expression of the eight transcript variantsdescribed for the homeobox gene TGIF1 in oral squamous cell carcinomas (OSCC)related with morphologically non-tumoral tissues (NT), evaluate possible associationsbetween these variants in patients with OSCC and relate the degree of expression ofthese variants with clinical, histological and survival aspects of patients. Additionally,we analyzed the expression of TGIF1 protein. It was analyzed 48 frozen samples ofOSCC and 12 of NT. The total RNA from each sample was extracted using TRizolsolution. TGIF1 transcripts were first amplified by RT-PCR for each case of OSCCand NT using a generic pair of primers. After these screening, the positive caseswere amplified using specific pair of primers for each variant. There was no statisticaldifference between the frequency of expression of TGIF1 transcript variants in OSSCand NT groups, but the variants 4 and 8 had the lowest p-values. Within the OSCCgroup, there was a significant association between some variants among themselves(seven of the twenty-one associations), in a way that the variants 1 and 4 were theones that had most association with other variants. Thus, we chose to continue thestudy using only variants 1, 4 and 8. There was no correlation between theexpression of the selected variants with the clinical and histological aspects.Regarding survival, the expression of variants 1 and 8 showed statistical correlationwith the outcome death, in a way that the group of patients that most expressed bothvariants was that one with the lower risk of death...