MED1 may explain the interaction between receptor tyrosine kinases and ERα66 in the complicated network of Tamoxifen resistance

Evaluating human epidermal growth factor receptor 2 roles in the efficacy of Tamoxifen treatment in breast cancer, a systematic review

PURPOSE

Hormone therapy with Tamoxifen is an effective treatment that can decrease recurrence rate and mortality. Numerous molecular mechanisms can modify the response to Tamoxifen. The objective of this study was to determine Tamoxifen efficacy on patients' recurrence and mortality rates, according to the human epidermal growth factor receptor 2 (HER2) status.

METHODS

In this meta-analysis of published studies, relapse and death rates were measured in both HER2 negative and positive patients treated with Tamoxifen. Besides, the relative risk of treatment with Tamoxifen compared to no Tamoxifen treatment was evaluated in both HER2 positive and negative patients.

RESULTS

There was an increased risk of recurrence in HER2 positive patients who received Tamoxifen compared with HER2 negative ones (RR = 1.63, p value < 0.001). Tamoxifen treatment is associated with decreased relapse rate (RR = 0.70, p value < 0.001); however, it did not effect on HER2 positive ones (RR = 1, p value = 0.99).

CONCLUSION

According to the analysis result, the relapse rate in breast cancer patients who were treated with Tamoxifen depends on the HER2 situation. Despite the limited sample size, it is revealed that Tamoxifen can decrease the relapse rate only in HER2 negative patients.

A novel tumor suppressor ZBTB1 regulates tamoxifen resistance and aerobic glycolysis through suppressing HER2 expression in breast cancer

Transcriptional repressor zinc finger and BTB domain containing 1 (ZBTB1) is required for DNA repair. Because DNA repair defects often underlie genome instability and tumorigenesis, we determined to study the role of ZBTB1 in cancer. In this study, we found that ZBTB1 is down-regulated in breast cancer and this down-regulation is associated with poor outcome of breast cancer patients. ZBTB1 suppresses breast cancer cell proliferation and tumor growth. The majority of breast cancers are estrogen receptor (ER) positive and selective estrogen receptor modulators such as tamoxifen have been widely used in the treatment of these patients. Unfortunately, many patients develop resistance to endocrine therapy. Tamoxifen-resistant cancer cells often exhibit higher HER2 expression and an increase of glycolysis. Our data revealed that ZBTB1 plays a critical role in tamoxifen resistance in vitro and in vivo To see if ZBTB1 regulates HER2 expression, we tested the recruitments of ZBTB1 on HER2 regulatory sequences. We observed that over-expressed ZBTB1 occupies the estrogen receptor α (ERα)-binding site of the HER2 intron in tamoxifen-resistant cells, suppressing tamoxifen-induced transcription. In an effort to identify potential microRNAs (miRNAs) regulating ZBTB1, we found that miR-23b-3p directly targets ZBTB1. MiR-23b-3p regulates HER2 expression and tamoxifen resistance via targeting ZBTB1. Finally, we found that miR-23b-3p/ZBTB1 regulates aerobic glycolysis in tamoxifen-resistant cells. Together, our data demonstrate that ZBTB1 is a tumor suppressor in breast cancer cells and that targeting the miR-23b-3p/ZBTB1 may serve as a potential therapeutic approach for the treatment of tamoxifen resistant breast cancer.

Dysregulation of DNA methylation patterns may identify patients with breast cancer resistant to endocrine therapy: A predictive classifier based on differentially methylated regions

Endocrine therapy (ET) is one of a number of targeted therapies for estrogen receptor-positive breast cancer (BRCA); however, resistance to ET has become the primary issue affecting treatment outcome. In the present study, a predictive classifier was created using a DNA methylation dataset to identify patients susceptible to endocrine resistance. DNA methylation and RNA sequencing data, and the clinicopathological features of BRCA, were obtained from The Cancer Genome Atlas. Stringent criteria were set to select and classify patients into two groups, namely those resistant to ET (n=11) and sensitive to ET (n=21) groups. Bump hunting analysis revealed that 502 out of 135,418 genomic regions were differentially methylated between these two groups; these regions were differentially methylated regions (DMRs). The majority of the CpG sites contained in the DMRs mapped to the promoter region. Functional enrichment analyses indicated that a total of 562 specific genes encompassing these DMRs were primarily associated with 'biological progress of organ morphogenesis and development' and 'cell-cell adhesion' gene ontologies. Logistic regression and Pearson's correlation analysis were conducted to construct a predictive classifier for distinguishing patients resistant or sensitive to ET. The highest areas under the curve and relatively low Akaike information criterion values were associated with a total of 60 DMRs; a risk score retained from this classifier was revealed to be an unfavorable predictor of survival in two additional independent datasets. Furthermore, the majority of genes (55/63) exhibited a statistically significant association between DNA methylation and mRNA expression (P<0.05). The association between the mRNA expression of a number of genes (namely calcium release activated channel regulator 2A, Schlafen family member 12, chromosome 3 open reading frame 18, zinc finger protein 880, dual oxidase 1, major histocompatibility complex, class II, DP β1, C-terminal binding protein 1, ALG13 UDP-N-acetylglucosaminyltransferase subunit and RAS protein activator like 2) and the prognosis of patients with estrogen receptor-positive BRCA and ET resistance was determined using Kaplan-Meier Plotter. In summary, the predictive classifier proposed in the present study may aid the identification of patients sensitive or resistant to ET, and numerous genes maybe potential therapeutic targets to delay the development of resistance to ET.

An estrogen receptor (ER)-related signature in predicting prognosis of ER-positive breast cancer following endocrine treatment

Quite a few estrogen receptor (ER)‐positive breast cancer patients receiving endocrine therapy are at risk of disease recurrence and death. ER‐related genes are involved in the progression and chemoresistance of breast cancer. In this study, we identified an ER‐related gene signature that can predict the prognosis of ER‐positive breast cancer patient receiving endocrine therapy. We collected RNA expression profiling from Gene Expression Omnibus database. An ER‐related signature was developed to separate patients into high‐risk and low‐risk groups. Patients in the low‐risk group had significantly better survival than those in the high‐risk group. ROC analysis indicated that this signature exhibited good diagnostic efficiency for the 1‐, 3‐ and 5‐year disease‐relapse events. Moreover, multivariate Cox regression analysis demonstrated that the ER‐related signature was an independent risk factor when adjusting for several clinical signatures. The prognostic value of this signature was validated in the validation sets. In addition, a nomogram was built and the calibration plots analysis indicated the good performance of this nomogram. In conclusion, combining with ER status, our results demonstrated that the ER‐related prognostic signature is a promising method for predicting the prognosis of ER‐positive breast cancer patients receiving endocrine therapy.

The knockdown of the Mediator complex subunit MED15 restrains urothelial bladder cancer cells' malignancy

The Mediator complex, a multi-subunit protein complex, plays an integral role in regulating transcription. Genetic alterations of the mediator subunit 15 (MED15) in separate tumor entities have been described previously. However, till now, not much is known about the role of MED15 in urothelial bladder cancer (BCa). Using cBioPortal, database analysis was executed for the mRNA expression and survival analysis of MED15 in BCa. Immunohistochemistry (IHC) analysis against MED15 was performed on tissue microarrays with 18 benign, 126 BCa, and 38 metastases samples. The intensity evaluation was performed using a staining intensity score from 0 to 3 and associated with clinicopathological data. The BCa cell lines T24 and TCCSUP were used for the functional investigation. After the MED15 knockdown by small interfering (si)RNA, cell proliferation, migration and invasion were investigated. On the mRNA level, only a low number of alterations (2%) was found for MED15 in BCa. Due to the small count of events, there were no significant differences or tendencies in survival. For IHC, MED15 was found to have a higher expression in non-muscle invasive BCa compared with benign and muscle invasive BCa. For survival analysis, no significant differences between samples with or without overexpression of MED15 were found. In the functional analysis, proliferation, migration, and invasion were significantly reduced in BCa-cells following the transient siRNA-mediated MED15 knockdown. In summary, MED15 appears to play a role in the tumor parameters proliferation, migration, and invasion in BCa, but further investigations are necessary.

The mediator complex in genomic and non-genomic signaling in cancer

Mediator is a conserved, multi-subunit macromolecular machine divided structurally into head, middle, and tail modules, along with a transiently associating kinase module. Mediator functions as an integrator of transcriptional regulatory activity by interacting with DNA-bound transcription factors and with RNA polymerase II (Pol II) to both activate and repress gene expression. Mediator has been shown to affect multiple steps in transcription, including chromatin looping between enhancers and promoters, pre-initiation complex formation, transcriptional elongation, and mRNA splicing. Individual Mediator subunits participate in regulation of gene expression by the estrogen and androgen receptors and are altered in a number of endocrine cancers, including breast and prostate cancer. In addition to its role in genomic signaling, MED12 has been implicated in non-genomic signaling by interacting with and activating TGF-beta receptor 2 in the cytoplasm. Recent structural studies have revealed extensive inter-domain interactions and complex architecture of the Mediator-Pol II complex, suggesting that Mediator is capable of reorganizing its conformation and composition to fit cellular needs. We propose that alterations in Mediator subunit expression that occur in various cancers could impact the organization and function of Mediator, resulting in changes in gene expression that promote malignancy. A better understanding of the role of Mediator in cancer could reveal new approaches to the diagnosis and treatment of Mediator-dependent endocrine cancers, especially in settings of therapy resistance.