Caracterização molecular de EGFR, KRAS, BRAF, PTEN E NTH1 em pacientes brasileiros com carcinoma de não-pequenas células de pulmão (NSCLC)

Abstract

Lung cancer is the leading global cause of cancer -related mortality and the patients have poor prognosis . To improve the survival rate of lung cancer patients, a better understanding of tumor biology is required as well as the subsequent development of new therapeutic strategies. EGFR, KRAS, BRAF and PTEN genes play important role in the regulation of cell growth, proliferation, migration, survival and inhibition of apoptosis, while NTH1 function as a DNA glycosylase in DNA repair pathway. Somatic alterations in these genes may be associated with the development of lung cancer. To investigate these molecular alterations, we analyzed the targeted regions of NTH1 (exons 1-6), PTEN (exons 1-9), KRAS (exons 2 and 3), BRAF (exon 15) and EGFR (exons 18-21) in eighty-two Brazilian patients with non-small cell lung cancer (NSCLC). PTEN protein expression was evaluated in twenty -one samples by immunohistochemistry. We analyzed the genomic ancestry of our patients through 40 biallelic indels. No mutations or polymorphisms were detected in PTEN and BRAF. The nuclear PTEN expression was higher in neoplastic cells compared to benign cells. The analysis detected the presence of KRAS mutation G228A in codon 12 in one patient (1.2%) and two patients (2.4%) showed polymorphism at codon 61 (rs17851045). In EGFR sequences we found 746_750 deletion (domain LREA) in exon 19 in 3.6% patients and no alterations in exons 18 and 21. In exon 20, two polymorphisms were identified: a silent substitution ( CAG> CAA) at position c.2538 (rs1050171) was detected in 54.9% of cases and a substitution 2284-60T> C upstream of exon 20 (rs10241451) was found in 13.4% of cases. The substitution 2284 -60T> C was significantly associated with the disease for both, allele and genotype frequency (p = 0.03 and p = 0.02, respectively). Ancestry analysis showed a greater African component in our sample. Analysis of NTH1, showed the G99T polymorphism (rs2302102), 140-17C> T (rs2233518) and 131 (C> A) in only two patients (4%), wich may be related to the disease. As shown, our data show a low frequency of mutations in EGFR, KRAS, BRAF and PTEN, which can be explained by the high African component of our patients. Our data highlight that the genetic heterogeneity of the EGFR pathw ay in NSCLC may differ between populations. Therefore, it underscores the need to reassess the use of therapeutic agents for the inhibition of this pathway in different populations. Futhermore, these results should be expanded and validated in studies of larger scope, focusing on Brazilian patients in general.