[Detailed mapping and clinical significance of loss of heterozygosity on 9p13-23 in laryngeal squamous cell carcinoma by microsatellite analysis].

BACKGROUND & OBJECTIVE: Microsatellites are the repeated DNA sequences scattered widely within the biological genomes and closely linked with many important genes. In carcinogenesis, microsatellites often display loss of heterozygosity(LOH) as tumor suppressor genes. Some microsatellite loci often exist in the hot spots of LOH at high frequency in some specific maligances. The tumor suppressor genes, which are associated with the development and progression of the tumor, possibly harbor in the vicinity of these hot spots. Therefore, the study of LOH by microsatellite analysis is an important way to detect the putative tumor suppressor genes. This study was designed to refine the hot spots of LOH on 9p13-23 in laryngeal squamous cell carcinoma and compare the correlation between the incidence of microsatellite LOH and the clinicopathological parameters.

METHODS

Tumor tissues were obtained from paraffin embedded sections with microdissection. Genomic DNA was extracted from tumor tissues and peripheral blood lymphocytes with the phenol-chloroform. Polymerase chain reaction(PCR) amplification and denaturing gel electrophoresis were performed on a set of 42 laryngeal squamous cell carcinoma and corresponding peripheral blood lymphocytes using 13 highly polymorphic microsatellite markers on 9p13-23. The correlation was analyzed between microsatellite LOH at the high frequency on 9p13-23 and clinicopathological characteristics in the patients with squamous cell carcinoma of larynx.

RESULTS

(1)Of the 42 laryngeal cancers, 41(97.6%) showed LOH in at least one of the microsatellite markers tested on 9p13-23. The most frequently deleted marker was D9S162 in 17 of the 19 (89.5%) informative samples. The marker D9S171, which is located on 9p21, had LOH detected in 12 of the 15 informative cases (80.0%). LOH at the D9S1748 marker (closest to the p16 gene locus) was detected in 18 of the 36 informative cases (50.0%). (2)Allelic deletion mapping revealed two minimal regions of LOH encompassing markers D9S161-D9S171 on 9p21 and IFNA-D9S162 on 9p22-23. (3) Multiple LOH (>or= 4) on 9p21-23 was found more frequently in the patients under 60 years, with supraglottic squamous cell carcinoma or cervical lymph node metastasis than those over 60 years, with glottic squamous cell carcinoma or without cervical lymph node metastasis (P< 0.01,P< 0.01,P< 0.05, respectively). On the contrary, there was no correlation between T stages or pathologic classification and the frequency of LOH on 9p21-23 in 42 squamous cell carcinoma of larynx.

CONCLUSION

These findings imply the presence of at least two putative tumor suppressor genes on 9p13-23 in laryngeal squamous cell carcinoma. Multiple genetic alterations are probably implicated in supraglottic squamous cell carcinoma with cervical lymph node metastasis in younger patients.