ABSTRACT
OBJECTIVES: We sought to assess loss of heterozygosity (LOH) profiles of 3p, 6q, 8q, 10q, 12q, 13q, and 17p and to identify the tumor suppressor genes involved in salivary gland neoplasms. STUDY DESIGN: LOH analysis was performed using 26 microsatellite markers by polymerase chain reaction-polyacrylamide gel electrophoresis method in 20 benign and 6 malignant salivary gland tumors. RESULTS: Overall, LOH was detected in at least one informative locus in 18 of 20 (90%) of benign tumors and in all of 6 cases of malignant tumors. High LOH frequencies were revealed at the loci D3S1307 (22%, 3p26), D3S966 (41%, 3p21), D6S255 (27%, 6q25), D8S166 (25%, 8q12), D8S199 (21%, 8q24), and D10S1765 (28%, 10q23) in benign tumors, defining the hotspot regions for putative tumor suppressor genes. CONCLUSIONS AND SIGNIFICANCE: The hotspot regions defined by the present study suggest that new tumor suppressor genes related to the development of salivary gland tumors may reside at several chromosomal loci, including loci at 3p, 6q, 8q and 10q.
Subject(s)
Chromosomes, Human, Pair 3/genetics , Loss of Heterozygosity/genetics , Parotid Neoplasms/genetics , Submandibular Gland Neoplasms/genetics , Adenolymphoma/genetics , Adenoma, Pleomorphic/genetics , Adult , Aged , Carcinoma/genetics , Carcinoma, Squamous Cell/genetics , Chromosome Mapping , Chromosomes, Human, Pair 10/genetics , Chromosomes, Human, Pair 12/genetics , Chromosomes, Human, Pair 13/genetics , Chromosomes, Human, Pair 17/genetics , Chromosomes, Human, Pair 6/genetics , Chromosomes, Human, Pair 8/genetics , Female , Genes, Tumor Suppressor , Humans , Male , Microsatellite Repeats/genetics , Middle AgedABSTRACT
PURPOSE: Aims of the study are to narrow-down the hotspot region on 10q21 defined by previous genome-wide loss of heterozygosity (LOH) analysis in head and neck squamous cell carcinomas (HNSCC) and to define candidate tumor suppressor genes (TSG) concerned with 10q21. MATERIALS AND METHODS: LOH analysis was carried out with ten polymorphic microsatellite markers. Expression analysis was performed by semi-quantitative RT-PCR, and mutation analysis by PCR and direct sequencing. RESULTS: LOH analysis on 10q21 in 52 HNSCC indicated distinctive and frequent allelic loss at D10S589 (42%). Among flanking genes, we found the RHOBTB1 gene as a candidate TSG, since an intragenic marker demonstrated the highest LOH (44%). Expression analysis revealed down-regulation of RHOBTB1 mRNA in 37% of tumors. Interestingly, all the five tumors that showed decreased expression of RHOBTB1 were accompanied with LOH, supporting the haploinsufficiency and class 2 TSG characteristics of RHOBTB1. No pathogenic mutation of RHOBTB1 was found. Furthermore, another gene within the region, EGR2, was also taken under scope. LOH frequencies around the EGR2 gene were relatively low (23 and 33%). Albeit semi-quantitative expression analysis of EGR2 demonstrated downregulation in 45% of tumor samples, no relation was found between the expression levels and LOH status. CONCLUSION: Frequent allelic loss and decreased expression of RHOBTB1 suggested that this gene has a role in tumorigenesis of a subset of HNSCC.
