RESUMEN
Objective To refine the loss of heterozygosity(LOH) on chromosome 20q11-13 and identify the new tumor suppressor gene(s) in colorectal tumorigenesis. Methods From 1998 to 1999, 83 patients with colorectal cancer had been admitted to Shanghai First People's Hospital. Tumor tissues and adjacent normal mucosal tissues were collected. Ten polymorphic microsatellite markers were analyzed on chromosome 20 and another 10 markers were applied on chromosome 20q11-13 in 83 cases of colorectal and normal DNA by PCR. PCR products were eletrophoresed on an ABI 377 DNA sequencer. Genesean 3.1 and Genotyper 2.1 software were used for LOH scanning and analysis. Results We observed a distinct region of frequent allelic deletions on chromosome, another 10 polymorphric microsatellite markers were applied to 20q11-13 and 2 minimal regions of frequent LOH were established, that is to say 20q11.2, 20q12. Tumor suppressor genes E2F1, PMP24 and MAFB were found in the regions of 20q11.2 and 20q12. Conclusion Through our detailed deletion mapping studies, we have found 2 critical and precise regions, which must contain one or more unknown tumor suppressor gene (s) on colorectal cancer.