Mutations and differential expression of the ras family genes in human nasal polyposis

Abstract

Although it is well established that ras genes contribute to tumourigenesis either through the accumulation of mutations or by aberrant expression in a wide range of human cancers, little is known regarding their involvement in human nasal polyps (NPs). In the present study, the occurrence of mutations in codons 11 and 12 of the ras family genes was examined by PCR/RFLP and direct sequencing in 23 human NPs and their adjacent turbinates, as well as in turbinates from 13 control subjects. Moreover, the expression pattern of ras mRNA levels was assessed in NP specimens and compared to adjacent and control tissues. K-ras codon 11 and 12 mutations were detected in 17 and 35% of NPs, respectively, and were found in the adjacent inferior turbinate (AIT) (22 and 16%, respectively) and adjacent middle turbinates (AMT) (16 and 26%, respectively). K- and H-ras expression levels were elevated, whereas N-ras mRNA levels were lower in NPs and adjacent turbinates as compared to the control tissues. K-ras mRNA levels were up-regulated in advanced-stage polyps (P=0.037), while N-ras levels were found elevated in small polyps (P=0.046). Statistically significant negative correlations between K- and N-ras expression profiles arose in NPs and AITs (P=0.009 and 0.003, respectively). This, to our knowledge, is the first report on ras mutations and expression analysis in NPs. Our findings suggest a potential key role for activated members of ras family genes in terms of their contribution to the development of NPs as well as to the hypertrophy of adjacent turbinates.