Expression pattern of PAX2 in hyperplastic and malignant endometrium

Alteration in molecular properties during establishment and passaging of endometrial carcinoma patient-derived xenografts

Patient-derived xenograft (PDX) tumor models are known to maintain the genomic and phenotypic profiles, including the histopathological structures, of the parental tumors. On the other hand, unique enrichment of single-nucleotide variants or copy number aberrations has been reported in several types of tumors. However, an understanding of endometrial carcinoma PDXs is limited. The purpose of the present study was to clarify the presence or absence of the molecular properties of endometrial carcinomas in PDXs passaged up to eight times. Established PDXs of endometrioid carcinomas maintained their histopathological characteristics, but those of carcinosarcomas predominantly consisted of sarcomatous components when compared to the parental tumors. Alterations in the proportion of cells with positive/negative immunohistochemical staining for estrogen receptor, PTEN, PAX8, and PAX2 were observed, whereas the proportions of cells with AE1/AE3, TP53, ARID1A, PMS2, and MSH6 staining were unchanged. Variants of cancer-associated genes were compared between PDXs and parental tumors. Mutations in POLE and a frameshift deletion in BRCA1 were observed in the parental tumor tissue in each of the six cases, and additional genomic alterations, which were not apparently related to histopathological and immunohistochemical alterations, were found in the PDXs of these cases. The genomic and phenotypic alterations observed between endometrial carcinoma PDXs and parental tumors were partly associated with endometrial cancer-specific characteristics related to cellular differentiation and gene mutations.

ASH2L is involved in promotion of endometrial cancer progression via upregulation of PAX2 transcription

Absent, small or homeotic 2‐like protein (ASH2L) is a core component of a multimeric histone methyltransferase complex that is involved in the maintenance of active transcription, participating in several cancers, however the biological function and molecular mechanism of ASH2L in endometrial cancer (ECa) are largely unknown. Endometrial cancer is a common malignant tumor in women and the incidence of this cancer is on the rise. Estrogen‐ERα signaling, as an oncogenic pathway, plays a crucial role in endometrial carcinogenesis. Therefore, further exploration of the molecular mechanisms around ERα‐mediated gene transcription in ECa would be helpful to the understanding of tumor development and to finding a new therapeutic target for ECa. Here, our study demonstrated that ASH2L was highly expressed in ECa samples, and higher expression of ASH2L was positively correlated with a poor prognosis. Moreover, we identified that ASH2L associated with ERα and that knockdown of ASH2L resulted in decreased expression of a subset of the estrogen‐induced target genes, including paired box 2 (PAX2), an oncogenic gene in ECa. ASH2L was recruited to cis‐regulatory elements in PAX2, thereby altering histone H3K4me3 and H3K27me3 levels, to enhance ERα‐mediated transactivation. Finally, depletion of ASH2L suppressed endometrial cancer cell proliferation and migration. Our findings suggest that ASH2L participates in the promotion of ECa progression, if not totally at least partially, via upregulation of PAX2 transcription.

Benign and Premalignant Lesions of the Endometrium

In this review, we highlight the benign and premalignant lesions of the endometrium that the pathologist may encounter in daily practice. We begin by detailing our current understanding of excess estrogen in the progression of endometrial neoplasia. We outline the currently accepted terminology to be used when evaluating proliferative endometrial lesions, while highlighting their key features. Attention is then turned to the molecular underpinnings of neoplastic progression and how this can be exploited with immunohistochemical stains when appropriate. Finally, we discuss types of metaplasia and their associations, including so-called papillary proliferations of the endometrium.

Assessing the prognostic value of PAX2 and PTEN in endometrial carcinogenesis

In order to avoid the consequences of over- and under-treatment of endometrial hyperplasia, diagnostic accuracy and progression risk assessment must be improved. The aim of this study was to assess whether PAX2 or PTEN expression could predict progression-free survival in endometrial intraepithelial neoplasia (EIN) and endometrial endometrioid carcinoma (EEC). Immunohistochemistry for detection of PAX2 and PTEN was performed on 348 endometrial samples; 75 proliferative endometrium (PE), 36 EIN and 237 EEC. Cases classified as PTEN null (1 or more glands negatively stained) were more prevalent in EEC than in PE and EIN (64% EEC vs 11% PE/EIN). A progressive decrease in PAX2 expression was observed from PE to EIN to EEC. Long-term clinical follow-up (6-310 months, median: 126) was available for 62 PE cases, all 36 EIN cases and 178 EEC cases. No patients with PE demonstrated progression to EIN or EEC. Progression of disease was observed in 10 (28%) EIN patients. These patients had significantly lower PAX2 expression than those that regressed (P = 0.005). Progression-free survival analysis revealed that EIN patients with a high-risk PAX2 expression score (H-score ≤75) had a higher probability of progression of disease in comparison to those with a low-risk score (H-score >75). PAX2 expression was not prognostic in EEC nor was PTEN status of prognostic value in either EIN or EEC. PAX2 expression analysis by means of H-score has prognostic potential for the identification of high-risk progression cases in EIN but needs to be validated in a larger cohort.

Paired box 2 promotes progression of endometrial cancer via regulating cell cycle pathway

Background: Human paired box 2 (PAX2) plays a key role in cell fate, early patterning and organogenesis.

Methods: We investigated the function of PAX2 on the biological behavior of endometrial cancer in vitro and in vivo and to explore the regulation mechanism, stable knocking-down and over-expression PAX2 endometrial cancer cell lines were established. CCK-8 and transwell assays were applied to determine proliferation, invasion and migration ability. Cell cycle distribution was analyzed by flow cytometry. Affymetrix GeneChip® human Exon 1.0 ST arrays was used to screen the downstream target genes of PAX2.

Results: PAX2 significantly enhanced proliferation and invasiveness. In addition, PAX2 influenced the expression of cyclin-dependent kinase 1(CDK1), which play pivotal roles in cell cycle pathway. When CDK1 was knocked down, and the cell proliferation promotion role of PAX2 was attenuated dramatically to a level comparable with the control groups.

Conclusions: PAX2, though influencing the expression of CDK1, promotes the proliferation, enhances the mobility of endometrial cancer cells, thus exerts an important role in the carcinogenesis of endometrial cancer. PAX2 may be a potential therapeutic target for endometrial cancer.

DNA methylation promotes paired box 2 expression via myeloid zinc finger 1 in endometrial cancer

This work investigated the role of paired box 2 (PAX2) in endometrial cancer and its epigenetic regulation mechanism. Endometrial cancer tissues and cell lines exhibited increased PAX2 expression compared with hyperplasia, normal endometrium and endometrial epithelial cells. Knock-down of PAX2 resulted in reduced cell viability, invasion and migration, and PAX2 overexpression caused the opposite effects. Increased methylation of the PAX2 promoter was observed in both cancer tissues and cell lines and was positively correlated with PAX2 expression. After 5-Aza-CdR treatment, PAX2 mRNA and protein were down-regulated, and PAX2 methylation was decreased. Deletion analysis confirmed that a repressive transcriptional regulatory region of the PAX2 promoter coincided with the hypermethylated region identified in MassARRAY analysis. Binding sites of myeloid zinc finger 1 (MZF1) are predicted in the defined region. Knock-down of MZF1 up-regulated the transcriptional activity and protein level of PAX2 after 5-Aza-CdR treatment, which indicated that MZF1 may act as a repressive transcription factor when the PAX2 promoter is unmethylated. In conclusion, PAX2 is involved in the carcinogenesis of endometrial cancer by stimulating cell growth and promoting cell motility. The overexpression of PAX2 in endometrial cancer is regulated by promoter hypermethylation and the transcription factor MZF1.

New concepts for an old problem: the diagnosis of endometrial hyperplasia

BACKGROUND

Endometrial hyperplasia (EH) is a uterine pathology representing a spectrum of morphological endometrial alterations. It is predominantly characterized by an increase in the endometrial gland-to-stroma ratio when compared to normal proliferative endometrium. The clinical significance of EH lies in the associated risk of progression to endometrioid endometrial cancer (EC) and 'atypical' forms of EH are regarded as premalignant lesions. Traditional histopathological classification systems for EH exhibit wide and varying degrees of diagnostic reproducibility and, as a consequence, standardized patient management can be challenging.

OBJECTIVE AND RATIONALE

EC is the most common gynaecological malignancy in developed countries. The incidence of EC is rising, with alarming increases described in the 40-44-year-old age group. This review appraises the current EH classification systems used to stratify women at risk of malignant progression to EC. In addition, we summarize the evidence base regarding the use of immunohistochemical biomarkers for EH and discuss an emerging role for genomic analysis.

SEARCH METHODS

PubMed, Medline and the Cochrane Database were searched for original peer-reviewed primary and review articles, from January 2000 to January 2016. The following search terms were used: 'endometrial hyperplasia', 'endometrial intraepithelial neoplasia', 'atypical hyperplasia', 'complex atypical hyperplasia', 'biomarker', 'immunohistochemistry', 'progression', 'genomic', 'classification' and 'stratification'.

OUTCOMES

Recent changes to EH classification reflect our current understanding of the genesis of endometrioid ECs. The concept of endometrial intraepithelial neoplasia (EIN) as a mutationally activated, monoclonal pre-malignancy represents a fundamental shift from the previously held notion that unopposed oestrogenic stimulation causes ever-increasing hyperplastic proliferation, with accumulating cytological atypia that imperceptibly leads to the development of endometrioid EC. Our review highlights several key biomarker candidates that have been described as both diagnostic tools for EH and markers of progression to EC. We propose that, moving forwards, a 'panel' approach of combinations of the immunohistochemical biomarkers described in this review may be more informative since no single candidate can currently fill the entire role.

WIDER IMPLICATIONS

EC has historically been considered a predominantly postmenopausal disease. Owing in part to the current unprecedented rates of obesity, we are starting to see signs of a shift towards a rising incidence of EC amongst pre- and peri-menopausal woman. This creates unique challenges both diagnostically and therapeutically. Furthering our understanding of the premalignant stages of EC development will allow us to pursue earlier diagnosis and facilitate appropriate stratification of women at risk of developing EC, permitting timely and appropriate therapeutic interventions.