STAT3 and apoptosis regulators: Bak and Bcl-xL in endometrioid adenocarcinomas of different estrogen receptor-α immunoprofile

Roles of estrogen receptor α in endometrial carcinoma (Review)

Endometrial carcinoma (EC) is a group of endometrial epithelial malignancies, most of which are adenocarcinomas and occur in perimenopausal and postmenopausal women. It is one of the most common carcinomas of the female reproductive system. It has been shown that the occurrence and development of EC is closely associated with the interaction between estrogen (estradiol, E2) and estrogen receptors (ERs), particularly ERα. As a key nuclear transcription factor, ERα is a carcinogenic factor in EC. Its interactions with upstream and downstream effectors and co-regulators have important implications for the proliferation, metastasis, invasion and inhibition of apoptosis of EC. In the present review, the structure of ERα and the regulation of ERα in multiple dimensions are described. In addition, the classical E2/ERα signaling pathway and the crosstalk between ERα and other EC regulators are elucidated, as well as the therapeutic targeting of ERα, which may provide a new direction for clinical applications of ERα in the future.

Activated STAT3 Could Reduce Survival in Patients with Esophageal Squamous Cell Carcinoma by Up-regulating VEGF and Cyclin D1 Expression

Signal transduction and activators of transcription factor (STAT) 3 is associated with a poor prognosis in certain types of cancer. The purpose of the present study was to investigate the clinical and prognostic significance of STAT3/p-STAT3 expression in esophageal squamous cell cancer (ESCC) patients. A total of 71 patients were enrolled in the study. STAT3 and p-STAT3 expression were detected by Western Blot and immunohistochemistry assays. Stattic, the STAT3 inhibitor, was used to block the activation of STAT3 in ESCC cell lines Eca-109 and Kyse-30, and the CCK8 assay was performed to detect the effect of Stattic on the viability of ESCC cells. The expression of associated genes was assessed by RT-PCR and Western blot at RNA and protein levels, respectively. STAT3 expression was correlated with infiltration degree (pT) and pTNM. And p-STAT3 expression was correlated with pT, lymphatic metastasis (pN) and pTNM. The expression of VEGF, Bcl-xl and Cyclin D1 was up-regulated in ESCC tissues and positively correlated with p-STAT3 level, besides Bcl-xl. In vitro, Stattic inhibited the viability of Eca-109 and Kyse-30 cells in a dose- and time- dependent manner, and significantly inhibited the expression of VEGF, Bcl-xl and CyclinD1 at mRNA and protein level. The 5-year survival rate of the 71 patients was significantly associated with pT, pN, pTNM stage, p-STAT3 level, VEGF expression and Cyclin D1 expression. pN and p-STAT3 expression were independent relevant factors. Our results showed that p-STAT3 might serve as an essential biomarker for tumor invasion and metastasis in ESCC.

Comparison of E-cadherin with STAT3 and apoptosis regulators: Bak and Bcl-xL in endometrioid adenocarcinomas of different ER-alpha immunoprofile

E-cadherin is a factor of good prognosis in endometrioid adenocarcinomas, while STAT3 is an oncogenic driver of carcinogenesis. E-cadherin, Bak, Bcl-xL and STAT3 were immunohistochemically detected in 78 human endometrioid adenocarcinomas. E-cadherin correlated with STAT3 (p <. 001, r = 0.537) as well as Bak (p = .005, r = 0.314) and Bcl-xL (p = .002, r = 0.340) in the whole study group. In G2 tumors, E-cadherin associated with Bak (p = .021, r = 0.319), Bcl-xL (p = .026, r = 0.309) and STAT3 (p <.001, r = 0.513) but not in G3 adenocarcinomas. E-cadherin correlated with Bak and Bcl-xL in both G1- and estrogen receptor (ER)-negative tumors with significant relation of E-cadherin and STAT3 in G1- and ER-negative tumors. Antigrowth synergy of expression was preserved for antiapoptotic Bak and proliferation-suppressing E-cadherin in IA adenocarcinomas (p = .031, r = 0.342) with no significance between Bak and E-cadherin or STAT3 and emerging correlation between E-cadherin and Bcl-xL in IB + II tumors instead (p = .003, r = 0.472). E-cadherin correlated with Bak and Bcl-xL in ER-positive adenocarcinomas (p =  .002, r = 0.382 and p <.001, r = 0.439, respectively) but not in ER-negative tumors. In conclusion, expression deregulation of studied proteins is reflected in selective loss of correlation between suppressors of tumor growth (E-cadherin and Bak) presumably due to progressing impairment of growth-inhibitory properties of clone of neoplastic cells within higher staging and poorer differentiation.

Association of STAT3 with Cx26 and Cx43 in human uterine endometrioid adenocarcinoma

Signal transducer and activator of transcription-3 (STAT3) drives endometrial carcinogenesis, while signaling via gap junctions gets weakened during cancer progression. Connexin 26 (Cx26), Cx43 and STAT3 were immunohistochemically evaluated in 78 endometrioid adenocarcinomas: Nuclear expression of STAT3 positively correlated with cytoplasmic immunoreactivity to Cx43 (P=0.004, r=0.318) and Cx26 (P=0.006, r=0.309). STAT3 correlated with Cx43 (P=0.022, r=0.411) and Cx26 (P=0.008 r=0.466) in G1 tumors. A statistically significant linkage remained in G2 cancers between STAT3 and Cx43 (P=0.061, r=0.262) and Cx26 (P=0.016, r=0.331); however, no correlations were observed in G3 tumors. STAT3 was significantly associated with Cx 43 (p=0.003, r=0.684) and Cx26 (p=0.049, r=0.500) in estrogen receptor (ER) negative adenocarcinomas. STAT3 did not correlate with Cx43 in ER positive adenocarcinomas; however, STAT3 expression remained correlated with Cx26 expression (P=0.035, r=0.268). In progesterone receptor negative tumors STAT3 was significantly associated with Cx43 (P=0.035, r=0.451) and Cx26 (P<0.0001, r=0.707). However, in PgR positive adenocarcinomas STAT3 correlated with Cx43 (P=0.03, r=0.290) but not with Cx26. Thus, it appears that hormone dependent acceleration of cancer growth breaks the association between STAT3 and Cx expression. These associations become weaker as the tumors dedifferentiate from G1 to G3 endometrioid adenocarcinomas. The present study provides evidence that the loss of correlation between STAT3 and selected Cx proteins occurs in tumors with more aggressive behavior.

MicroRNAs in endometrial cancers from black and white patients

OBJECTIVE

Previous studies have identified differences in gene mutations among endometrial cancers from whites and blacks suggesting that differences in tumor biology may explain racial disparities in patient outcome. Micro RNAs (miRNAs) have emerged as regulators of transcript expression and their aberrant expression has been discovered in many diseases, including endometrial cancer. We performed quantitative polymerase chain reaction-based analysis in a set of endometrial cancers to identify whether there are racial differences in miRNA expression.

STUDY DESIGN

Tumor cells from 50 stage-I endometrioid endometrial cancer specimens from 41 white and 9 black patients were prepared by laser microdissection and miRNA extracts were analyzed using TaqMan (Life Technologies, Carlsbad, CA) low-density arrays. Statistically significant, differentially expressed miRNAs between blacks and whites were identified using multidimensional scaling, Wilcoxon testing, and analysis of variance.

RESULTS

There were no global differences in miRNA expression between endometrial cancers from 41 white and 9 black patients. To minimize potential bias introduced by unbalanced sample size, we performed a subset analysis with stage- and histology-matched specimens from 9 whites and 9 blacks that identified 18 differentially abundant miRNAs (>2-fold at P < .005). Quantitative polymerase chain reaction validated miRNA-337-3p in an independent set of endometrial cancer specimens from 23 white and 24 black women. There were no racial differences in hsa-miR-337-3p expression in normal endometrium.

CONCLUSION

These data indicate that hsa-mir-337-3p is more frequently down-regulated in endometrial cancers from whites compared to blacks. Future studies are focused on determining the phenotypic impact of miR-337-3p and whether its differential expression is associated with clinical outcome.

Eventual proapoptotic or anti-apoptotic impact of aberrantly expressed Cx43 and Cx26 can depend on ER-alpha overexpression in human endometrioid adenocarcinoma

Estrogen receptor (ER) and progesterone receptor (PgR) accumulations lead to impairment of gap junctional intercellular communication in endometrial cancer. The task of this study was to explore relationships of Cx26 and Cx43 with anti-apoptotic protein Bcl-xL and proapoptotic agent Bak in ER-alpha and PgR negative or variably positive endometrioid adenocarcinomas. Cx26, Cx43, Bak, Bcl-xL, PgR and ER-alpha were detected in 78 endometrioid adenocarcinomas with immunohistochemistry. There was a remarkable cellular re-distribution of Cx26 and Cx43 from normally membranous location in normal endometrium to aberrantly cytoplasmic expression in endometrioid adenocarcinomas, thus suggesting the decrease of functional membranous gap junctions in the malignancy. Bak failed to correlate with Cx43 regardless of either PgR or ER-alpha status of tumors, while Bcl-xL positively correlated with Cx43 in ER-alpha positive tumors (p = 0.001, r = 0.427) and both PgR positive (p = 0.019, r = 0.312) and negative (p = 0.015, r = 0.509) cancers. Similarly, Bcl-xL significantly associated with Cx26 in ER-alpha positive tumors (p = 0.036, r = 0.267) and both PgR positive (p = 0.026, r = 0.297) and negative (p = 0.046, r = 0.429) cancers. On the contrary, Bak exclusively correlated with Cx26 only in ER-alpha negative tumors (p = 0.027, r = 0.551). ER-alpha status of endometrioid adenocarcinomas could restrict eventual proapoptotic or anti-apoptotic impact of aberrantly expressed Cx43 and Cx26 in these tumors.