BRAF Mutation in Endometrial Carcinoma and Hyperplasia: Correlation with KRAS and p53 Mutations and Mismatch Repair Protein Expression

Abstract

Purpose: Although several gene abnormalities have been reported in endometrial carcinoma, the genetic alterations have not fully been elucidated. Recent studies have revealed frequent activating mutations of the gene for BRAF, an effector of Ras protein in the mitogen-activated protein kinase pathway, in several malignancies. However, the prevalence and significance of BRAF mutations in endometrial carcinoma remain unclear. Experimental Design:We examined BRAF mutations in exons11and15 in 97 cases of endometrial carcinoma (endometrioid type, 78; nonendometrioid type,19), 9 cases of atypical endometrial hyperplasia, and 20 cases of normal endometrium by direct sequencing. In addition, mutations of KRAS and p53 and the immunohistochemical expression of hMLH1 and hMSH2 were also examined. Results: Of the 97 carcinomas and 9 hyperplasias, 20 (21%) and 1 (11%) had BRAF mutations, most of them at previously unreported sites. Twenty samples of normal endometrium and 21 samples of normal endometrium obtained from sites adjacent to neoplastic lesions had no BRAF mutations. There was no apparent difference in the prevalence of BRAF mutation among stages, histologic subtypes, or grades. Mutations of KRAS and p53 were found in 18 (19%) and 22 (23%) cases, and 65 (67%) and 92 (95%) cases showed positive immunostaining for hMLH1 and hMSH2, respectively. BRAF mutation was more frequently found in hMLH1-negative cases (12 of 32, 41%) than in hMLH1-positive cases (7 of 65, 11%; P = 0.008), suggesting that it is associated with an abnormal mismatch repair function. Conclusions: These findings suggest that mutations of the BRAF gene are partly involved in the malignant transformation of the endometrium.Endometrial carcinomas are now classified into two histologic subtypes: endometrioid type and nonendometrioid type (1); and the molecular genetic changes involved differ between the two (2 -4). In endometrioid-type carcinomas, mutations of PTEN, KRAS, b-catenin, and p53 genes and microsatellite instability have been reported in f5% to 50% of cases. By contrast, in nonendometrioid-type carcinomas, as exemplified by serous papillary adenocarcinoma, the p53 gene is reportedly mutated in f90% of cases. However, the genetic changes in endometrial carcinoma have not fully been elucidated.Raf proteins are cytoplasmic serine-threonine kinases and play central roles in the conserved Ras/Raf/mitogen-activated protein/extracellular signal-regulated kinase kinase/extracellular signal-regulated kinase pathway, acting to relay signals from activated Ras proteins via mitogen-activated protein kinase/extracellular signal-regulated kinase kinase 1/2 to p42/ 44 mitogen-activated protein kinase or extracellular signalregulated kinase 1/2, the key effector of the pathway (5, 6). A recent report has shown the presence of an activating mutation in one of three Raf protein subtypes, B-Raf, in human melanomas and colon cancers, and that the mutation of BRAF transforms NIH 3T3 cells independent of KRAS gene mutation (7). In addition, mutual exclusi...

PIK3CA mutations in the kinase domain (exon 20) of uterine endometrial adenocarcinomas are associated with adverse prognostic parameters

“…Mutational analysis was performed using previously reported PCR conditions and primers for exons 9 and 20 of PIK3CA, 31 exons 1-9 of PTEN, 8 exon 3 of CTNNB1, 13 exon 1 of K-RAS, 11 and exons 11 and 15 of B-RAF genes. 32 The thermal cycling conditions included an initial 12 min at 941C, followed by 40 cycles of 45 s at 941C, 45 s at specific annealing primer temperature of 52-621C, 1 min at 721C, and a final extension of 10 min at 721C. The PCR conditions for exon 9 of PIK3CA were optimized to avoid mispriming with the PIK3CA pseudogene spanning exons 9-13 on chromosome 22.…”

Regulation of Uptake of18F-FDG by a Follicular Human Thyroid Cancer Cell Line with Mutation-Activated K-Ras

“…This view is supported by the observation that radioiodine-negative metastases exhibit increased glucose uptake more frequently than radioiodine-positive neoplasms (1). Furthermore, the survival of patients harboring 18 F-FDG-positive tumor deposits is significantly shorter than that of subjects with 18 F-FDGnegative metastases (2).…”

“…Asi gnificant proportion of metastases of well-differentiated thyroid carcinomas have increased glucose metabolism (1) and may thus be localized using PET with 18 F-FDG. It is generally believed that an increase in 18 F-FDG uptake reflects dedifferentiation of these tumors.…”

“…It is generally believed that an increase in 18 F-FDG uptake reflects dedifferentiation of these tumors. This view is supported by the observation that radioiodine-negative metastases exhibit increased glucose uptake more frequently than radioiodine-positive neoplasms (1).…”

“…Consequently, analogs of cAMP such as (Bu) 2 cAMP that are able to cross the cell membrane have also been shown to stimulate glucose metabolism in the well-differentiated rat cell line FRTL-5 (4). However, in contrast to iodine transport, the TSH-induced increase of 18 F-FDG accumulation does not depend on protein kinase A (PKA) but on phosphatidylinositol-3-kinase (PI3-kinase) in FRTL-5 cells (7,8).…”