Genetic aspects of cancer

Allelic loss of 10q23.3, the PTEN gene locus in cervical carcinoma from Northern Indian population

Cervical cancer is one of the most common malignant diseases affecting women worldwide. Studies on loss of heterozygosity have been made for PTEN gene specific microsatellite markers in malignancies like breast, ovary and lungs and the results have shown a significant association. However the role of this gene is not clearly understood in cervical cancer from Indian population. A total of 135 cervical carcinoma tissues samples were analyzed for loss of heterozygosity. DNA was isolated from the samples and their matched control specimens. Polymerase chain reaction was performed using primer specific for two intragenic markers (D10S198 & D10S192) and one marker (D10S541) in flanking region and further electrophoresed on 8% denaturing polyacrylamide gel. Overall, 31 out of 133(23%) informative cases showed loss of heterozygosity in at least one locus in the region examined. The percentage of loss of heterozygosity for these markers ranged from 8% (D10S192) to 13% (D10S198). Loss of heterozygosity was more frequently detected in intragenic region (D10S198 & D10S192) than in flanking region, D10S541 (21% versus 9%). These data argue that PTEN is a tumor suppressor gene whose inactivation may play an important role in the carcinoma of uterine cervix.

Allelotype analysis of the myelodysplastic syndrome

Myelodysplastic syndromes (MDS) are a group of clonal hematologic disorders found predominantly in the elderly. The molecular mechanisms underlying the development of MDS remain obscure. In order to begin to identify tumor suppressor genes involved in these disorders, we performed a detailed microsatellite allelotype of chromosomal deletions associated with MDS. DNAs from both bone marrow and peripheral blood of 32 MDS patients were studied using 84 highly informative microsatellite markers on all autosomal arms, excluding the short arms of the acrocentric chromosomes. A high percentage of loss of heterozygosity (LOH) was identified on chromosome 5q (40% of informative cases), 7q (45%), 17p (23%) and 20q (20%), which corresponds to the most common cytogenetic abnormalities reported in MDS. In addition, a high incidence of LOH (> or =20%) was observed on chromosomal arms which had not been previously reported including 1p (36%), 1q (35%), and 18q (23%). This extensive allelotype analysis focuses attention on several novel genomic regions that probably contain novel tumor suppressor genes whose loss of function contributes to the development of MDS.

Analysis of FHIT transcripts in cervical and endometrial cancers

Carcinoma of the uterine cervix is a common malignancy, and many affected women, have been found to exhibit loss of heterozygosity (LOH) in the chromosome 3p region. Recent studies have localized the FHIT (fragile histidine triad) gene in this region and also demonstrated a high frequency of abnormalities of this gene in various cancers. To determine the role of the FHIT gene in cervical and uterine carcinomas, 16 cases of cervical carcinoma and 7 cases of endometrial carcinoma, as well as nearby non-cancerous tissues in these patients, were analyzed by reverse transcription of the FHIT mRNA followed by polymerase chain reaction amplification and sequencing of the products. In this study, 13 of 16 cervical cancers and 4 of 7 endometrial cancers displayed abnormal FHIT transcripts, including a lack of 2 or more exons of the FHIT gene, the insertion of several bases in the deletion junctions, and a 282 bp deletion from cDNA 171 to 452, resulting in a frameshift. Moreover, 5 of 16 matched non-cancerous tissues from the cervical cancer patients and 4 of 7 non-cancerous tissues from endometrial cancer patients also showed the presence of abnormal transcripts lacking 3 or more exons of the FHIT gene. Only 1 of 23 paired samples exhibited LOH. Our results suggest that the abnormal transcript of the FHIT gene is common in both normal and tumor tissues of the uterus and cervix. We also checked for HPV infection in these samples and found no definite relationship between the abnormal transcript and human papillomavirus infection.