Clinical assessment of PTEN loss in endometrial carcinoma: immunohistochemistry outperforms gene sequencing

Abstract

PTEN is a tumor suppressor that negatively regulates the PI3K-AKT signaling pathway, which is implicated in the pathogenesis of endometrial carcinoma. Sanger sequencing has been considered to be the gold standard for detection of PTEN sequence abnormalities. However, this approach fails to address the epigenetic mechanisms that contribute to functional PTEN loss. Using a study cohort of 154 endometrioid and non-endometrioid endometrial carcinomas, we performed full-length PTEN sequencing and PTEN immunohistochemistry on each tumor. PTEN sequence abnormalities were detected in a significantly lower proportion of cases (43%) than PTEN protein loss (64%, p= 0.0004). Endometrioid tumors had a significantly higher proportion of PTEN sequence abnormalities and PTEN protein loss than non-endometrioid tumors. Within the latter group, PTEN sequence abnormalities and PTEN protein loss were most frequent in undifferentiated carcinomas, followed by mixed carcinomas; they were least frequent in carcinosarcomas. Overall, at least one PTEN sequence abnormality was detected in each exon, and the greatest number of sequence abnormalities was detected in exon 8. Pure endometrioid tumors had a significantly higher frequency of sequence abnormalities in exon 7 than did the non-endometrioid tumors (p=0.0199). Importantly, no mutational hotspots were identified. While PTEN protein loss by immunohistochemistry was identified in 89% of cases with a PTEN sequence abnormality, PTEN protein loss was detected by immunohistochemistry in 44% of cases classified as PTEN wildtype by sequencing. For the first time, we demonstrate that PTEN immunohistochemistry is able to identify the majority of cases with functional PTEN loss. However, PTEN immunohistochemistry also detects additional cases with PTEN protein loss that would otherwise be undetected by gene sequencing. Therefore, for clinical purposes, immunohistochemistry appears to be a preferable technique for identifying endometrial tumors with loss of PTEN function.

Reproducibility of histological cell type in high-grade endometrial carcinoma

“…The staining frequency of individual markers in our study is consistent with previous studies. [6][7][8]11,[16][17][18][19][20][21][22] By analyzing marker combinations using nominal logistic regression models and restricting the analysis to cases with an unambiguous morphological diagnosis (submitted consensus diagnosis), we identified a seven-marker panel (ER, CDKN2A (p16), TP53, VIM, PTEN, PGR, and IGF2BP3) that could differentiate endometrioid carcinoma FIGO grade 3 from serous carcinoma with 100% concordance compared with the morphological gold standard. Interestingly, a similar approach to the subclassification of high-grade endometrial carcinomas using mutational profiles did not generate a reliable multivariate logistic regression model.…”

“…It has also been shown that certain immunohistochemical markers such as PTEN 'outperform gene sequencing'. 22 Nevertheless, it is prudent to study how mutational status and immunohistochemical profiles overlap with each other and with morphology. Potentially, the best markers that arise from both techniques could be used as an ancillary technique to morphology to subclassify high-grade endometrial carcinomas in the future.…”

“…We chose a marker panel that is in routine diagnostic use in many laboratories and appended some experimental markers from the recent literature that might aid in the differential diagnosis of endometrioid, serous, or clear-cell types. [6][7][8]11,[16][17][18][19][20][21][22][23] …”

Expression of miRNAs and PTEN in endometrial specimens ranging from histologically normal to hyperplasia and endometrial adenocarcinoma

“…Immunohistochemical loss of PTEN included specimens scored as negative and heterogeneous according to previous reported methods. 38,39 Statistical Analysis Kruskal-Wallis test was used to compare the RQ of miRNA expression with respect to pathological findings of patients. Pathologic diagnosis was used as a standard reference.…”

Could S6K1 immunopositivity be used to distinguish early and advanced stages of endometrioid endometrial adenocarcinoma?

“…The deregulation of multiple elements of the mTOR pathway, such as amplification or mutation of PI3K, loss of PTEN function, and overexpression of AKT, S6K1, 4EBP1, and eIF4E, has been reported in numerous types of human diseases, including cancer, cardiac hypertrophy, type 2 diabetes, and obesity. (8,12,14). Aberrations of the mTOR signaling pathway are common in several types of human cancers, such as breast, ovarian, prostate, bladder, thyroid, colon, and head and neck cancers (8,(15)(16)(17)(18).…”