The loss of heterozygosity and mutation for nm23-H1 gene in colorectal carcinomas were studied by Southern blot and RT-PCR-SSCP/silver staining sequencing. The rate of loss of heterozygosity for nm23-H1 was 29.63%. The cases of Duke’s stage D and distant metastatsis had higher frequency of the loss of heterozygosity. No mutation for nm23-H1 was found in colorectal carcinomas. These reaults indicate that the loss of heterozygosity for nm23-H1 may play a significant role in the malignant progression and distant metastasis in colorectal carcinomas.
ObjectiveTo explore the presence of common genetic alterations in retinoblastoma and to localize the altered genomic regions.MethodsGenetic instability of chromosome 19, 20, 21, 22 and X of 15 microdissected retinoblastoma tumors were analyzed by the loss of heterozygosity (LOH) and microsatellite instability (MSI).ResultsAmong the 15 patients with retinoblastoma, genome instability ［LOH and(or) MSI］ at one or more loci on the 5 chromosomes in 10 (67%), in which the loss of a single allele was more frequent in chromosomes 19 (33%) and 20 (27%) than in the other 3 chromosomes. Highfrequency LOH between D19S902 and D19S571 suggested gene loci in the 19q13 region might be associated with tumor development in retina. According to the result of MSI, MSI occured at least in one subset of retinoblastoma.ConclusionsOur results provide first evidence of LOH in chromosomes 19 and 20 in retinoblastoma and further support the presence of genome instability in retinoblastoma that may play an important role in the tumorigenesis or progression of retinoblastoma.(Chin J Ocul Fundus Dis, 2005,21:28-31)
Objective To refine the loss of heterozygosity (LOH) on chromosome 7q21－22 and identify the new tumor suppressor gene(s) in colorectal tumorigenesis. Methods Fifteen polymorphic microsatellite markers were analyzed on chromosome 7 and another 5 markers were applied on chromosome 7q21-22 region in 83 cases of colorectal cancer and normal DNA by PCR. PCR products were electrophoresed on an ABI Prism 377 DNA sequencer. GeneScan 3.1 and Genotyper 2.1 software were used for LOH scanning and analysis. Results A distinct region of frequent allelic deletion was observed on chromosome, another 5 polymorphic microsatellite markers were applied to 7q21-22 and the minimal region of frequent LOH was established on 7q21-22 spanning the D7S657, D7S646 locus. Conclusion Through detailed deletion mapping studies, a critical and precise region spanning the D7S657, D7S646 locus is identified, which must contain one or more unknown tumor suppressor gene(s) on colorectal cancer.
A microsatellite is a short, repetitive sequence of DNA (usually 2 to 4 nucleotides in length). Multiple primary lung cancers (MPLC) are more than one primary lung cancer lesions arising synchronously in different locations of the same or different side of the lung. These neoplasms may have same or different histological types, but one lesion is not a metastasis from another, as each neoplasm arises independently in the lung. Abnormal microsatellite changes are closely related to the pathogenesis and development of MPLC. In this review, several aspects are discussed:①definition and origin of microsatellite; ②abnormal changes of microsatellite; ③definition and categories of MPLC; ④the influence of microsatellite on early diagnosis, treatment and prognosis of MPLC.