Preinvasive Stage in the Endometrium: Relation and Role of Clonal Expansion and PTEN.
Huseyin Baloglu. GATA Haydarpasa Training Hospital, Istanbul, Turkey
Background: Physiologic endometrium may undergo proliferation under unopposed estrogenic stimulation that progress to hyperplasia. Some of the hyperplastic glands gain capacity to generate monoclonal proliferation and stromal invasion. The role of PTEN gene in this process still remains uncertain, although there are many theories. In this study, we investigated a neoplastic transition spectrum in 80 cases model to understand the place of clonal expansion and its relation to PTEN functional loss (mutation or promoter methylation) in the way of progression to invasive carcinoma process.
Design: Endometrial samples of 80 hysterectomy specimens diagnosed as benign (n=20), hyperplasia (30 with atypia, 10 without atypia) and endometrioid carcinoma were studied. Due to the performance of applied techniques like laser micro dissection, DNA extraction, PCR, clonality analysis, DNA sequencing and methylation analysis, 25 cases were excluded from the study and replaced by new cases. All hyperplasia cases were selected on the basis of the absence of concomitant carcinoma. Epithelial components were collected by laser micro-dissection. After DNA extraction, clonality was determined by human androgen receptor gene assays based on methylation- specific PCR (HUMAR-MPS). PTEN gene exons were amplified by PCR and sequenced. According to the clonality and PTEN mutation results, cases of only monoclonal and PTEN wild type hyperplasia were submitted to methylation detection procedure.
Results: All benign endometria were polyclonal (PC) and all carcinoma were monoclonal (MC). Glandular proliferation was MC in 31 and PC in 9 cases of 40 hyperplasia. Five of 10 cases of hyperplasia without atypia were PC and remaining 5 were MC. In 30 atypical hyperplasia cases, 26 were MC whereas only 4 were PC. None of the benign endometrial samples – which represented atrophy, secretion, proliferation and polyp – revealed PNEN mutation. In atypical group, only one of 10 hyperplasia cases without atypia revealed PNET mutation whereas PTEN mutations were seen in 8 cases. Four of each low and high grade carcinomas were PTEN-mutated. None of the PC samples were consistent with PTEN mutations. In all 51 MC lesions, 17 were PTEN-mutated and most of the PTEN mutations were in exon 5 and 7. In all 22 monoclonal hyperplasia cases with wild type PTEN, 13 revealed PTEN promoter methylation.
Conclusions: Our findings suggest that there is strong evidence that functional loss of PTEN, either because of mutations or promoter methylation, occurs following monoclonal expansion in the endometrial glandular neoplastic transformation.
Category: Gynecologic & Obstetrics
Wednesday, March 2, 2011 1:00 PM
Poster Session VI # 146, Wednesday Afternoon