[Research on the mechanisms of PTEN gene inactivation in ovarian cancer].
OBJECTIVE
To investigate the mechanisms of PTEN gene inactivation starting from DNA, mRNA and protein levels in ovarian cancers.


METHODS
Tumor tissue samples were obtained from 48 patients with epithelial ovarian cancers. Using four polymorphic markers (D10s541, D10s583, D10s1687 and D10s2491) within and flanking the PTEN gene located in chromosome 10q 23.3, polymerase chain reaction (PCR) and loss of heterozygosity (LOH) were introduced to examine LOH of PTEN gene; PCR-single strand conformation polymorphism (PCR-SSCP) was introduced to examine mutations of the fifth, sixth, seventh, and eighth exons of PTEN. Reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemistry (SP method) were applied to detect PTEN mRNA and PTEN protein expressions, respectively.


RESULTS
LOH of PTEN gene was observed in 19 of 48 (39.6%) ovarian cancers. PTEN mutations were found only in 2 (4.2%) of the cases. Absence of PTEN mRNA expression was 18.8% (9 of 48). Immunostaining of 48 cancer samples revealed that 13 (27.1%) were PTEN immunostain negative. Of these 13 samples, only 2 (15.4%) had structural, biallelic inactivation by intragenic PTEN mutations and loss of the remaining wild-type allele; 7 (53.8%) showed evidence of LOH, 5 of these 7 samples showed deletion of PTEN mRNA expression, another 2 samples showed positive expression of PTEN mRNA; 4 (30.8%) tumors had neither PTEN gene mutation nor LOH but exhibited no PTEN protein expression, 2 of these 4 cases showed deletion of PTEN mRNA expression, another 2 showed positive expression of PTEN mRNA. For the cases of PTEN protein absent staining, the rate of LOH was 69.2% (9 of 13), higher than 28.6% (10 of 35) for the positive staining (P < 0.05).


CONCLUSIONS
PTEN gene inactivation may contribute to epithelial ovarian carcinogenesis. There may be several mechanisms of PTEN gene inactivation in ovarian cancers. Protein expression deletions may be a significant mechanism.
Lü
Qing-jie
QJ
Department of Pathology, The Second Clinical College, China Medical University, Shenyang 110004, China. lvqjie@163.com
Zhao
Xiao-dong
XD
Song
Ji-ye
JY
Li
Xiao-han
XH
Ma
Ying
Y
Meng
Hui
H
Jiang
Wei-guo
WG
D000328:Adult; D000368:Aged; D002879:Chromosomes, Human, Pair 10; D005091:Exons; D005260:Female; D017353:Gene Deletion; D015972:Gene Expression Regulation, Neoplastic; D016147:Genes, Tumor Suppressor; D006801:Humans; D019656:Loss of Heterozygosity; D008875:Middle Aged; D009154:Mutation; D010051:Ovarian Neoplasms / Q000235:genetics* / Q000378:metabolism; D051059:PTEN Phosphohydrolase / Q000096:biosynthesis / Q000235:genetics*; D016133:Polymerase Chain Reaction; D018807:Polymorphism, Single-Stranded Conformational; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics
D012333:RNA, Messenger; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human