Mutation and downregulation of the transforming growth factor β type II receptor gene in primary squamous cell carcinomas of the head and neck

Abstract

In the present study, we analyzed 28 squamous cell carcinomas of the head and neck (SCCHN) for mutations in the coding region of TβR-II using 'Cold' SSCP and automatic DNA sequencing analyses. Twenty-one percent (6/28) of the SCCHN examined contained TβR-II mutations compared with patient-matched normal tissues. These alterations included five missense mutations (A:T→G:C transitions in codons 250, 401, 448 and 488, and a G:C→T:A transversion in codon 373), and a 38-bp deletion between nucleotides 1825 to 1862. In addition to these code-altering mutations, one case exhibited a silent mutation (A:T→G:C transition in codon 451) and three cases contained one of two potential population polymorphisms (codons 354 and 389). In contrast to colon and gastric cancers exhibiting microsatellite instability (MI) or replication errors (RER +), no 'indirect' frameshift mutations were identified within a 10-bp polyadenine repeat present in the TβR-II coding sequence. All of the mutations in the present study occurred within the highly conserved serine/threonine kinase domain and represent the first report of such 'direct' TβR-II mutations in primary human tumors. In addition, we analyzed a subset of SCCHN and corresponding normal samples for TβR-II mRNA expression using semi-quantitative multiplex RT-PCR. Expression of TβR-II was decreased by 24% to 74% in 20 of 23 SCCHN (87%) compared with patient-matched normal tissues. Taken together, the results from this study suggest that alterations in the nucleic acid sequence and mRNA expression of TβR-II are prevalent events in the development of SCCHN, which may deregulate cell cycle control.