PTEN mutations in uterine sarcomas.

OBJECTIVE: Uterinesarcomas comprise three main types: carcinosarcomas, leiomyosarcomas, and endometrial stromal sarcomas. Carcinosarcomas are highly aggressive neoplasms with a biphasic histology of carcinomatous and sarcomatous elements. It is now generally accepted that carcinosarcomas are biphasic tumors that have to be regarded as endometrial carcinomas where metaplasia occurs. Mutations of the PTEN tumor suppressor gene, located on 10q23, play a significant role in the pathogenesis of the endometrioid type of endometrial carcinoma. Loss of heterozygosity of chromosome 10q has been reported in uterine leiomyosarcoma. Since little is known about the molecular pathobiology, our goal was to investigate the potential role of the PTEN gene in the carcinogenesis of uterine sarcomas. METHODS: We examined 21 carcinosarcomas, 21 leiomyosarcomas, and 5 endometrial stromal sarcomas using exon-by-exon polymerase chain reaction-single-strand conformation polymorphism analysis. RESULTS: Overall 8.5% (4/47) of uterine sarcomas were found to harbor somatic PTEN mutations. Of these, approximately 17% (3/18) were carcinosarcomas with endometrioid-type carcinoma components and approximately 5% (1/21) were leiomyosarcomas. No mutations were detected in carcinosarcomas with nonendometrioid carcinoma components (0/3) and in endometrial stromal sarcomas (0/5). CONCLUSIONS: These data suggest that intragenic PTEN mutations are involved in the genesis of uterine carcinosarcomas with endometrioid-type carcinoma components but rarely contribute to the pathobiology of uterine leiomyosarcomas.

Ehrlichia ruminantium major antigenic protein gene (map1) variants are not geographically constrained and show no evidence of having evolved under positive selection pressure.

In a search for tools to distinguish antigenic variants of Ehrlichia ruminantium, we sequenced the major antigenic protein genes (map1 genes) of 21 different isolates and found that the sequence polymorphisms were too great to permit the design of probes which could be used as markers for immunogenicity. Phylogenetic comparison of the 21 deduced MAP1 sequences plus another 9 sequences which had been previously published did not reveal any geographic clustering among the isolates. Maximum likelihood analysis of codon and amino acid changes over the phylogeny provided no statistical evidence that the gene is under positive selection pressure, suggesting that it may not be important for the evasion of host immune responses.

Microsatellite instability in uterine sarcomas.

Studies have shown a 15-30% frequency of microsatellite instability in endometrial cancer. In addition, we found a 21% frequency of microsatellite instability in endometrial cancer. Our aim was to investigate the presence of microsatellite instability and loss of heterozygosity in uterine sarcomas. The records of 69 women referred to Kalafong Academic and Pretoria Academic Hospital with a primary diagnosis of uterine sarcoma were reviewed. At histological review of 43 cases with a primary diagnosis of leiomyosarcoma, diagnosis of mitotically active leiomyoma was made in 21. Diagnosis of carcinosarcoma was made in 21 cases and endometrial stromal sarcoma in five. In all cases, genomic DNA was extracted from normal myometrium and tumor and analyzed for microsatellite instability and loss of heterozygosity. High-frequency microsatellite instability was absent in leiomyosarcoma, endometrial stromal sarcoma, and mitotically active leiomyomas and was observed in 1 (5%) carcinosarcoma. Loss of heterozygosity for chromosome 11 was present in 8/48 (17%) of uterine sarcomas, equally distributed between leiomyosarcomas (4/22 = 18%) and carcinosarcomas (4/21 = 19%). There was no loss of alleles in endometrial stromal sarcoma nor mitotically active leiomyomas. In conclusion, it is suggested that tumor suppressor genes may play a role in the tumorigenesis of uterine mesenchymal cells, whereas mismatch repair genes contribute to the carcinogenesis of endometrial cancer.