Two distinct regions of deletion on chromosome 13q in primary nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is rare in most parts of the world, but prevalent in Southern China. Although this disease poses a serious health problem in our population, the genetic alterations that lead to the development of NPC have yet to be defined. In a comparative genomic hybridization (CGH) study on NPC by our group, loss of the long arm of chromosome 13 has been identified as a frequent event. To investigate further the involvement of this genetic alteration in NPC tumorigenesis, we examined 31 primary NPC tumours by LOH analysis with a panel of 13 microsatellite polymorphic markers distributed along the long arm of chromosome 13. It was found that 19/31 tumours (60%) showed LOH for markers on chromosome 13q. The highest frequency of LOH was found at loci D13S133 (53.6%) on 13q14.3 and D13S796 (38.5%) on 13q32-34. Two distinct smallest deletion regions were delineated: the first region between D13S133 and D13S119 at 13q14.3-22, and the second region between D13S317 and D13S285 at 13q31-34. Our findings show that LOH of 13q is a common event in NPC and that at least 2 putative tumour-suppressor loci may be present on 13q. Mapping of the critical regions of these loci suggests that some candidate tumour-suppressor genes on 13q, other than Rb and BRCA2, may be involved in the development of NPC.