Role of estrogen receptor coregulators in endocrine resistant breast cancer

KMT2C and KMT2D aberrations in breast cancer

KMT2C and KMT2D are histone lysine methyltransferases responsible for the monomethylation of histone 3 lysine 4 (H3K4) residues at gene enhancer sites. KMT2C/D are the most frequently mutated histone methyltransferases (HMTs) in breast cancer, occurring at frequencies of 10-20% collectively. Frequent damaging and truncating somatic mutations indicate a tumour-suppressive role of KMT2C/D in breast oncogenesis. Recent studies using cell lines and mouse models to replicate KMT2C/D loss show that these genes contribute to oestrogen receptor (ER)-driven transcription in ER+ breast cancers through the priming of gene enhancer regions. This review provides an overview of the functions of KMT2C/D and outlines the recent clinical and experimental evidence of the roles of KMT2C and KMT2D in breast cancer development.

Therapeutic significance of long noncoding RNAs in estrogen receptor-positive breast cancer

About 70% of cases of breast cancer are compromised by Estrogen-positive breast cancer. Through its regulation of several processes, including cell proliferation, cell cycle progression, and apoptosis, Estrogen signaling plays a pivotal role in the genesis and progression of this particular kind of breast cancer. One of the best treatment strategies for treating Estrogen-positive breast cancer is blocking Estrogen signaling. However, patients' treatment failure is mainly caused by the emergence of resistance and metastases, necessitating the development of novel therapeutic targets. Numerous studies have shown long noncoding RNAs (lncRNAs) to play a role in Estrogen-mediated carcinogenesis. These lncRNAs interact with co-regulators and the Estrogen signaling cascade components, primarily due to Estrogen activation. Vimentin and E-cadherin are examples of epithelial-to-mesenchymal transition markers, and they regulate genes involved in cell cycle progression, such as Cyclins, to affect the growth, proliferation, and metastasis of Estrogen-positive breast cancer. Furthermore, a few of these lncRNAs contribute to developing resistance to chemotherapy, making them more desirable targets for enhancing results. Thus, to shed light on the creation of fresh approaches for treating this cancer, this review attempts to compile recently conducted studies on the relationship between lncRNAs and the advancement of Estrogen-positive breast cancer.

Determination of the anticancer activity of standardized extract of Centella asiatica (ECa 233) on cell growth and metastatic behavior in oral cancer cells

Background and purpose

The anticancer drugs used for oral cancer treatment present many disadvantages, such as low solubility, low permeability, and poor bioavailability. However, the anticancer activity of ECa 233 has not been widely studied. Therefore, the anticancer activity of ECa 233 was investigated in this study.

Experimental approach

MTT assay was carried out to determine cell viability. Characterizations of cell apoptosis were monitored using DAPI and FDA staining and Hoechst 33258 and AO staining. Confirmation of the apoptosis-induced KON cells was done using annexin V-FITC staining, and ROS generation was determined by DCFDA staining. Cell death and the cell cycle arrest activity of ECa 233 were demonstrated by a flow cytometer. The anti-migration and anti-invasion properties of ECa 233 were examined. The anti-proliferative of ECa 233 was investigated. Cellular uptake of ECa 233 was measured by TEER values. The pharmacokinetics of ECa 233 were estimated using the pkCSM web server.

Findings/Results

ECa 233 decreased the KON cell viability. Morphological analysis showed the KON cells' loss of cell stability and structure, disorganized nucleus and cytoplasm, and induced cell death. ECa 233 acted as a cell cycle arrest in the G0/G1 phase and reduced the migration and invasion ability in KON cells. TEER values significantly increased in KON cells, which decreased cell colony and multicellular spheroid formations. The pharmacokinetic profiles of the main components are of interest for future usage.

Conclusion and implication

ECa 233 can be used as an alternative therapy as well as a medicinal plant selected for sensitizing oral cancer cells to chemotherapy.

Significant Association of Estrogen Receptor-β Isoforms and Coactivators in Breast Cancer Subtypes

Nuclear receptor coregulators are the principal regulators of Estrogen Receptor (ER)-mediated transcription. ERβ, an ER subtype first identified in 1996, is associated with poor outcomes in breast cancer (BCa) subtypes, and the coexpression of the ERβ1 isoform and AIB-1 and TIF-2 coactivators in BCa-associated myofibroblasts is associated with high-grade BCa. We aimed to identify the specific coactivators that are involved in the progression of ERβ-expressing BCa. ERβ isoforms, coactivators, and prognostic markers were tested using standard immunohistochemistry. AIB-1, TIF-2, NF-kB, p-c-Jun, and/or cyclin D1 were differentially correlated with ERβ isoform expression in the BCa subtypes and subgroups. The coexpression of the ERβ5 and/or ERβ1 isoforms and the coactivators were found to be correlated with a high expression of P53, Ki-67, and Her2/neu and large-sized and/or high-grade tumors in BCa. Our study supports the notion that ERβ isoforms and coactivators seemingly coregulate the proliferation and progression of BCa and may provide insight into the potential therapeutic uses of the coactivators in BCa.

Non-Coding RNAs Modulating Estrogen Signaling and Response to Endocrine Therapy in Breast Cancer

The largest part of human DNA is transcribed into RNA that does not code for proteins. These non-coding RNAs (ncRNAs) are key regulators of protein-coding gene expression and have been shown to play important roles in health, disease and therapy response. Today, endocrine therapy of ERα-positive breast cancer (BC) is a successful treatment approach, but resistance to this therapy is a major clinical problem. Therefore, a deeper understanding of resistance mechanisms is important to overcome this resistance. An increasing amount of evidence demonstrate that ncRNAs affect the response to endocrine therapy. Thus, ncRNAs are considered versatile biomarkers to predict or monitor therapy response. In this review article, we intend to give a summary and update on the effects of microRNAs (miRNAs), long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs) on estrogen signaling in BC cells, this pathway being the target of endocrine therapy, and their role in therapy resistance. For this purpose, we reviewed articles on these topics listed in the PubMed database. Finally, we provide an assessment regarding the clinical use of these ncRNA types, particularly their circulating forms, as predictive BC biomarkers and their potential role as therapy targets to overcome endocrine resistance.

Codon adaptation by synonymous mutations impacts the functional properties of the estrogen receptor-alpha protein in breast cancer cells

Oestrogen receptor-alpha (ERα) positivity is intimately associated with the development of hormone-dependent breast cancers. A major challenge in the treatment of these cancers is to understand and overcome the mechanisms of endocrine resistance. Recently, two distinct translation programmes using specific transfer RNA (tRNA) repertoires and codon usage frequencies were evidenced during cell proliferation and differentiation. Considering the phenotype switch of cancer cells to more proliferating and less-differentiated states, we can speculate that the changes in the tRNA pool and codon usage that likely occur make the ERα coding sequence no longer adapted, impacting translational rate, co-translational folding and the resulting functional properties of the protein. To verify this hypothesis, we generated an ERα synonymous coding sequence whose codon usage was optimized to the frequencies observed in genes expressed specifically in proliferating cells and then investigated the functional properties of the encoded receptor. We demonstrate that such a codon adaptation restores ERα activities to levels observed in differentiated cells, including: (a) an enhanced contribution exerted by transactivation function 1 (AF1) in ERα transcriptional activity; (b) enhanced interactions with nuclear receptor corepressor 1 and 2 [NCoR1 and NCoR2 (also known as SMRT) respectively], promoting repressive capability; and (c) reduced interactions with SRC proto-oncogene, non-receptor tyrosine kinase (Src) and phosphoinositide 3-kinase (PI3K) p85 kinases, inhibiting MAPK and AKT signalling pathway.

Nuclear Receptor Coregulators in Hormone-Dependent Cancers

Nuclear receptors (NRs) function collectively as a transcriptional signaling network that mediates gene regulatory actions to either maintain cellular homeostasis in response to hormonal, dietary and other environmental factors, or act as orphan receptors with no known ligand. NR complexes are large and interact with multiple protein partners, collectively termed coregulators. Coregulators are essential for regulating NR activity and can dictate whether a target gene is activated or repressed by a variety of mechanisms including the regulation of chromatin accessibility. Altered expression of coregulators contributes to a variety of hormone-dependent cancers including breast and prostate cancers. Therefore, understanding the mechanisms by which coregulators interact with and modulate the activity of NRs provides opportunities to develop better prognostic and diagnostic approaches, as well as novel therapeutic targets. This review aims to gather and summarize recent studies, techniques and bioinformatics methods used to identify distorted NR coregulator interactions that contribute as cancer drivers in hormone-dependent cancers.