Background: We have mapped the human prostate-specific membrane antigen (PSM) gene to the chromosome 11p11.2 region at 62.5 cM, a region which also contains the prostatic cancer metastasis suppressor gene KAI-1. The genetic marker D11S1344 has been utilised for loss of heterozygosity (LOH) studies on the KAI-1 gene in a large series of prostate cancer specimens. The results were negative and it was concluded that deletions of the KAI-1 gene were not involved in the development of the metastatic phenotype in these tumours. One possible explanation for this result could be that D11S1344 is not sufficiently tightly linked to the KAI-1 gene to detect small deletions.
Objective: To attempt to identify a genetic marker more tightly linked to the KAI-1 gene than D11S1344.
Methods: Yeast artificial chromosome (YAC) clones containing the KAI-1 gene and the neighbouring marker D11S1344 were analysed by the fluorescent in situ hybridisation technique. The human genomic inserts in these novel clones were sized by pulsed field gel electrophoresis. For more accurate mapping of the KAI-1 gene, YACs containing it were screened for polymorphic markers (including D11S1344) from the 11p11.2 region.
Results: The novel YAC clones localised exclusively to the 11p11.2 region, with single hybridisation signals compared to the dual signals consistently obtained with nearby PSM-containing YACs. All the KAI-1 clones found had small inserts (<300 kb). The only known microsatellite which gave amplification products with these YACs was D11S986 which has been mapped at 61.3 cM on human chromosome 11.
Conclusions: We have precisely localised KAI-1 at 61.3 cM on human chromosome 11. This is some 1.2 cM away from the previously utilised LOH microsatellite marker, D11S1344. We suggest that the very tightly linked microsatellite D11S986 may be a more accurate marker to assess LOH of the KAI-1 gene and thus predict progression of prostate cancer. The region of genetic duplication around the PSM gene does not extend as far distally on 11p as KAI-1.