LEM4 confers tamoxifen resistance to breast cancer cells by activating cyclin D-CDK4/6-Rb and ERα pathway

PFKFB3 regulates breast cancer tumorigenesis and Fulvestrant sensitivity by affecting ERα stability

Estrogen receptor alpha (ERα) is expressed in approximately 70% of breast cancer cases and determines the sensitivity and effectiveness of endocrine therapy. 6-phosphofructo-2-kinase/fructose-2, 6-biphosphatase3 (PFKFB3) is a glycolytic enzyme that is highly expressed in a great many human tumors, and recent studies have shown that it plays a significant role in improving drug sensitivity. However, the role of PFKFB3 in regulating ERα expression and the underlying mechanism remains unclear. Here, we find by using immunohistochemistry (IHC) that PFKFB3 is elevated in ER-positive breast cancer and high expression of PFKFB3 resulted in a worse prognosis. In vitro and in vivo experiments verify that PFKFB3 promotes ER-positive breast cancer cell proliferation. The overexpression of PFKFB3 promotes the estrogen-independent ER-positive breast cancer growth. In an estrogen-free condition, RNA-sequencing data from MCF7 cells treated with siPFKFB3 showed enrichment of the estrogen signaling pathway, and a luciferase assay demonstrated that knockdown of PFKFB3 inhibited the ERα transcriptional activity. Mechanistically, down-regulation of PFKFB3 promotes STUB1 binding to ERα, which accelerates ERα degradation by K48-based ubiquitin linkage. Finally, growth of ER-positive breast cancer cells in vivo was more potently inhibited by fulvestrant combined with the PFKFB3 inhibitor PFK158 than for each drug alone. In conclusion, these data suggest that PFKFB3 is identified as an adverse prognosis factor for ER-positive breast cancer and plays a previously unrecognized role in the regulation of ERα stability and activity. Our results further explores an effective approach to improve fulvestrant sensitivity through the early combination with a PFKFB3 inhibitor.

Targeting LINC00152 activates cAMP/Ca2+/ferroptosis axis and overcomes tamoxifen resistance in ER+ breast cancer

Tamoxifen has been the mainstay therapy to treat early, locally advanced, and metastatic estrogen receptor-positive (ER + ) breast cancer, constituting around 75% of all cases. However, the emergence of resistance is common, necessitating the identification of novel therapeutic targets. Here, we demonstrated that long-noncoding RNA LINC00152 confers tamoxifen resistance by blocking tamoxifen-induced ferroptosis, an iron-mediated cell death. Mechanistically, inhibiting LINC00152 reduces the mRNA stability of phosphodiesterase 4D (PDE4D), leading to activation of the cAMP/PKA/CREB axis and increased expression of the TRPC1 Ca2+ channel. This causes cytosolic Ca2+ overload and generation of reactive oxygen species (ROS) that is, on the one hand, accompanied by downregulation of FTH1, a member of the iron sequestration unit, thus increasing intracellular Fe2+ levels; and on the other hand, inhibition of the peroxidase activity upon reduced GPX4 and xCT levels, in part by cAMP/CREB. These ultimately restore tamoxifen-dependent lipid peroxidation and ferroptotic cell death which are reversed upon chelating Ca2+ or overexpressing GPX4 or xCT. Overexpressing PDE4D reverses LINC00152 inhibition-mediated tamoxifen sensitization by de-activating the cAMP/Ca2+/ferroptosis axis. Importantly, high LINC00152 expression is significantly correlated with high PDE4D/low ferroptosis and worse survival in multiple cohorts of tamoxifen- or tamoxifen-containing endocrine therapy-treated ER+ breast cancer patients. Overall, we identified LINC00152 inhibition as a novel mechanism of tamoxifen sensitization via restoring tamoxifen-dependent ferroptosis upon destabilizing PDE4D, increasing cAMP and Ca2+ levels, thus leading to ROS generation and lipid peroxidation. Our findings reveal LINC00152 and its effectors as actionable therapeutic targets to improve clinical outcome in refractory ER+ breast cancer.

The expression and role of the Lem-D proteins Ankle2, Emerin, Lemd2, and TMPO in triple-negative breast cancer cell growth

Background

Triple-negative breast cancer (TNBC) is a sub-classification of breast carcinomas, which leads to poor survival outcomes for patients. TNBCs do not possess the hormone receptors that are frequently targeted as a therapeutic in other cancer subtypes and, therefore, chemotherapy remains the standard treatment for TNBC. Nuclear envelope proteins are frequently dysregulated in cancer cells, supporting their potential as novel cancer therapy targets. The Lem-domain (Lem-D) (LAP2, Emerin, MAN1 domain, and Lem-D) proteins are a family of inner nuclear membrane proteins, which share a ~45-residue Lem-D. The Lem-D proteins, including Ankle2, Lemd2, TMPO, and Emerin, have been shown to be associated with many of the hallmarks of cancer. This study aimed to define the association between the Lem-D proteins and TNBC and determine whether these proteins could be promising therapeutic targets.

Methods

GENT2, TCGA, and KM plotter were utilized to investigate the expression and prognostic implications of several Lem-D proteins: Ankle2, TMPO, Emerin, and Lemd2 in publicly available breast cancer patient data. Immunoblotting and immunofluorescent analysis of immortalized non-cancerous breast cells and a panel of TNBC cells were utilized to establish whether protein expression of the Lem-D proteins was significantly altered in TNBC. SiRNA was used to decrease individual Lem-D protein expression, and functional assays, including proliferation assays and apoptosis assays, were conducted.

Results

The Lem-D proteins were generally overexpressed in TNBC patient samples at the mRNA level and showed variable expression at the protein level in TNBC cell lysates. Similarly, protein levels were generally negatively correlated with patient survival outcomes. siRNA-mediated depletion of the individual Lem-D proteins in TNBC cells induced aberrant nuclear morphology, decreased proliferation, and induced cell death. However, minimal effects on nuclear morphology or cell viability were observed following Lem-D depletion in non-cancerous MCF10A cells.

Conclusion

There is evidence to suggest that Ankle2, TMPO, Emerin, and Lemd2 expressions are correlated with breast cancer patient outcomes, but larger patient sample numbers are required to confirm this. siRNA-mediated depletion of these proteins was shown to specifically impair TNBC cell growth, suggesting that the Lem-D proteins may be a specific anti-cancer target.

Molecular functions of ANKLE2 and its implications in human disease

Ankyrin repeat and LEM domain-containing 2 (ANKLE2) is a scaffolding protein with established roles in cell division and development, the dysfunction of which is increasingly implicated in human disease. ANKLE2 regulates nuclear envelope disassembly at the onset of mitosis and its reassembly after chromosome segregation. ANKLE2 dysfunction is associated with abnormal nuclear morphology and cell division. It regulates the nuclear envelope by mediating protein-protein interactions with barrier to autointegration factor (BANF1; also known as BAF) and with the kinase and phosphatase that modulate the phosphorylation state of BAF. In brain development, ANKLE2 is crucial for proper asymmetric division of neural progenitor cells. In humans, pathogenic loss-of-function mutations in ANKLE2 are associated with primary congenital microcephaly, a condition in which the brain is not properly developed at birth. ANKLE2 is also linked to other disease pathologies, including congenital Zika syndrome, cancer and tauopathy. Here, we review the molecular roles of ANKLE2 and the recent literature on human diseases caused by its dysfunction.

Targeted Therapies and Drug Resistance in Advanced Breast Cancer, Alternative Strategies and the Way beyond

"Targeted therapy" or "precision medicine" is a therapeutic strategy launched over two decades ago. It relies on drugs that inhibit key molecular mechanisms/pathways or genetic/epigenetic alterations that promote different cancer hallmarks. Many clinical trials, sponsored by multinational drug companies, have been carried out. During this time, research has increasingly uncovered the complexity of advanced breast cancer disease. Despite high expectations, patients have seen limited benefits from these clinical trials. Commonly, only a minority of trials are successful, and the few approved drugs are costly. The spread of this expensive therapeutic strategy has constrained the resources available for alternative research. Meanwhile, due to the high cost/benefit ratio, other therapeutic strategies have been proposed by researchers over time, though they are often not pursued due to a focus on precision medicine. Notable among these are drug repurposing and counteracting micrometastatic disease. The former provides an obvious answer to expensive targeted therapies, while the latter represents a new field to which efforts have recently been devoted, offering a "way beyond" the current research.

ASCC3 promotes the immunosuppression and progression of non-small cell lung cancer by impairing the type I interferon response via CAND1-mediated ubiquitination inhibition of STAT3

BACKGROUND

Activating signal cointegrator 3 (ASCC3) has been identified as an oncogenic factor that impairs host immune defense. However, the underlying mechanisms of carcinogenesis and its impact on the antitumor immune response remain unclear. In this study, we aimed to investigate the molecular mechanisms of ASCC3 in the progression of non-small cell lung cancer (NSCLC).

METHODS

Single-cell sequencing data from the Gene Expression Omnibus and gene expression profiles from The Cancer Genome Atlas database were analyzed. The expression, clinical relevance and biological functions of ASCC3 in NSCLC were explored. Then, RNA sequencing, immunoprecipitation, mass spectrometry, immunofluorescence, and flow cytometry analyses were conducted to explore the underlying molecular mechanisms. In addition, in vivo experiments in mouse models were conducted to explore the probability of ASCC3 knockdown to improve the efficacy of anti-Programmed Death-1 (PD-1) therapy in NSCLC.

RESULTS

ASCC3 was significantly upregulated in NSCLC and correlated with poor pathological characteristics and prognosis in patients with NSCLC. Overexpression of ASCC3 promoted malignant phenotypes of NSCLC cells and induced an immunosuppressive tumor microenvironment, which was characterized by a decrease in CD8+ T cells, natural killer cells and dendritic cells but an increase in regulatory T(Treg) cells. Mechanistically, ASCC3 stabilized signal transducer and activator of transcription (STAT)3 signaling by recruiting Cullin-associated and neddylation dissociated 1 (CAND1), which inhibited ubiquitin-mediated degradation of STAT3, thereby impairing the type I interferon response of tumor cells and promoting the immunosuppression and progression of NSCLC. Furthermore, high expression of ASCC3 impaired the efficacy of anti-PD-1 therapy, and an anti-PD-1 antibody combined with ASCC3 knockdown exerted promising synergistic efficacy in a preclinical mouse model.

CONCLUSION

ASCC3 could stabilize the STAT3 pathway via CAND1, reshaping the tumor microenvironment and inducing resistance to anti-PD-1 therapy, which promotes the progression of NSCLC. It is a reliable prognostic indicator and can be a target in combination therapy for NSCLC.

Small molecule inhibition of TFF3 overcomes tamoxifen resistance and enhances taxane efficacy in ER+ mammary carcinoma

Even though tamoxifen has significantly improved the survival of estrogen receptor positive (ER+) mammary carcinoma (MC) patients, the development of drug resistance with consequent disease recurrence has limited its therapeutic efficacy. Trefoil factor-3 (TFF3) has been previously reported to mediate anti-estrogen resistance in ER+MC. Herein, the efficacy of a small molecule inhibitor of TFF3 (AMPC) in enhancing sensitivity and mitigating acquired resistance to tamoxifen in ER+MC cells was investigated. AMPC induced apoptosis of tamoxifen-sensitive and resistant ER+MC cells and significantly reduced cell survival in 2D and 3D culture in vitro. In addition, AMPC reduced cancer stem cell (CSC)-like behavior in ER+MC cells in a BCL2-dependent manner. Synergistic effects of AMPC and tamoxifen were demonstrated in ER+MC cells and AMPC was observed to improve tamoxifen efficacy in tamoxifen-sensitive cells and to re-sensitize cells to tamoxifen in tamoxifen-resistant ER+MC in vitro and in vivo. Additionally, tamoxifen-resistant ER+MC cells were concomitantly resistant to anthracycline, platinum and fluoropyrimidine drugs, but not to Taxanes. Taxane treatment of tamoxifen-sensitive and resistant ER+MC cells increased TFF3 expression indicating a combination vulnerability for tamoxifen-resistant ER+MC cells. Taxanes increased CSC-like behavior of tamoxifen-sensitive and resistant ER+MC cells which was reduced by AMPC treatment. Taxanes synergized with AMPC to promote apoptosis and reduce CSC-like behavior in vitro and in vivo. Hence, AMPC restored the sensitivity of tamoxifen and enhanced the efficacy of Taxanes in tamoxifen-resistant ER+MC. In conclusion, pharmacological inhibition of TFF3 may serve as an effective combinatorial therapeutic strategy for the treatment of tamoxifen-resistant ER+MC.

Enhancing Tamoxifen Therapy with α-Mangostin: Synergistic Antiproliferative Effects on Breast Cancer Cells and Potential Reduced Endometrial Impact

Breast cancer is the most prevalent neoplasia among women worldwide. For the estrogen receptor-positive (ER+) phenotype, tamoxifen is the standard hormonal therapy; however, it carries the risk of promoting endometrial carcinoma. Hence, we aimed to evaluate the antiproliferative effect of the phytochemical α-mangostin (AM) as a co-adjuvant alongside tamoxifen on breast cancer cells to improve its efficacy while reducing its adverse effects on endometrium. For this, ER+ breast cancer cells (MCF-7 and T-47D) and endometrial cells (N30) were treated with AM, 4-hydroxytamoxifen (4-OH-TMX), and their combination. Cell proliferation was evaluated using sulforhodamine B assay, and the pharmacological interaction was determined through the combination index and the dose reduction index calculation. The genes KCNH1, CCDN1, MKI67, and BIRC5 were amplified by real-time PCR as indicators of oncogenesis, cell cycle progression, cell proliferation, and apoptosis, respectively. Additionally, genes involved in ER signaling were analyzed. In breast cancer cells, the combination of AM with 4-OH-TMX showed a synergistic antiproliferative effect and favorable dose reduction. AM and 4-OH-TMX decreased KCNH1, CCND1, and BIRC5 gene expression. In endometrial cells, AM decreased MKI-67 gene expression, while it reverted the 4-OH-TMX-dependent CCND1 upregulation. This study establishes the benefits of incorporating AM as a co-adjuvant for first-line ER+ breast cancer therapy.

Targeting LINC00152 activates cAMP/Ca2+/ferroptosis axis and overcomes tamoxifen resistance in ER+ breast cancer

Tamoxifen has been the mainstay therapy to treat early, locally advanced, and metastatic estrogen receptor-positive (ER+) breast cancer, constituting around 75% of all cases. However, emergence of resistance is common, necessitating the identification of novel therapeutic targets. Here, we demonstrated that long-noncoding RNA LINC00152 confers tamoxifen resistance via blocking tamoxifen-induced ferroptosis, an iron-mediated cell death. Mechanistically, inhibiting LINC00152 reduces the mRNA stability of phosphodiesterase 4D (PDE4D), leading to activation of cAMP/PKA/CREB axis and increased expression of TRPC1 Ca2+ channel. This causes cytosolic Ca2+ overload and generation of reactive oxygen species (ROS) that is, on one hand, accompanied by downregulation of FTH1, a member of the iron sequestration unit, thus increasing intracellular Fe2+ levels; and on the other hand, inhibition of the peroxidase activity upon reduced GPX4 and xCT levels. These ultimately induce lipid peroxidation and ferroptotic cell death in combination with tamoxifen. Overexpressing PDE4D rescues LINC00152 inhibition-mediated tamoxifen sensitization by de-activating the cAMP/Ca2+/ferroptosis axis. Importantly, high LINC00152 expression is significantly correlated with high PDE4D/low ferroptosis and worse survival in multiple cohorts of tamoxifen- or tamoxifen-containing endocrine therapy-treated ER+ breast cancer patients. Overall, we identified LINC00152 inhibition as a novel mechanism of ferroptosis induction and tamoxifen sensitization, thereby revealing LINC00152 and its effectors as actionable therapeutic targets to improve clinical outcome in refractory ER+ breast cancer.

Integration of scHi-C and scRNA-seq data defines distinct 3D-regulated and biological-context dependent cell subpopulations

An integration of 3D chromatin structure and gene expression at single-cell resolution has yet been demonstrated. Here, we develop a computational method, a multiomic data integration (MUDI) algorithm, which integrates scHi-C and scRNA-seq data to precisely define the 3D-regulated and biological-context dependent cell subpopulations or topologically integrated subpopulations (TISPs). We demonstrate its algorithmic utility on the publicly available and newly generated scHi-C and scRNA-seq data. We then test and apply MUDI in a breast cancer cell model system to demonstrate its biological-context dependent utility. We found the newly defined topologically conserved associating domain (CAD) is the characteristic single-cell 3D chromatin structure and better characterizes chromatin domains in single-cell resolution. We further identify 20 TISPs uniquely characterizing 3D-regulated breast cancer cellular states. We reveal two of TISPs are remarkably resemble to high cycling breast cancer persister cells and chromatin modifying enzymes might be functional regulators to drive the alteration of the 3D chromatin structures. Our comprehensive integration of scHi-C and scRNA-seq data in cancer cells at single-cell resolution provides mechanistic insights into 3D-regulated heterogeneity of developing drug-tolerant cancer cells.

High expression of autophagy-related gene EIF4EBP1 could promote tamoxifen resistance and predict poor prognosis in breast cancer

BACKGROUND

Breast cancer (BC) remains a public health problem. Tamoxifen (TAM) resistance has caused great difficulties for treatment of BC patients. Eukaryotic translation initiation factor 4E binding protein 1 (EIF4EBP1) plays critical roles in the tumorigenesis and progression of BC. However, the expression and mechanism of EIF4EBP1 in determining the efficacy of TAM therapy in BC patients are still unclear.

AIM

To investigate the expression and functions of EIF4EBP1 in determining the efficacy of TAM therapy in BC patients.

METHODS

High-throughput sequencing data of breast tumors were downloaded from the Gene Expression Omnibus database. Differential gene expression analysis identified EIF4EBP1 to be significantly upregulated in cancer tissues. Its prognostic value was analyzed. The biological function and related pathways of EIF4EBP1 was analyzed. Subsequently, the expression of EIF4EBP1 was determined by real-time reverse transcription polymerase chain reaction and western blotting. Cell Counting Kit-8 assays, colony formation assay and wound healing assay were used to understand the phenotypes of function of EIF4EBP1.

RESULTS

EIF4EBP1 was upregulated in the TAM-resistant cells, and EIF4EBP1 was related to the prognosis of BC patients. Gene Set Enrichment Analysis showed that EIF4EBP1 might be involved in Hedgehog signaling pathways. Decreasing the expression of EIF4EBP1 could reverse TAM resistance, whereas overexpression of EIF4EBP1 promoted TAM resistance.

CONCLUSION

This study indicated that EIF4EBP1 was overexpressed in the BC and TAM-resistant cell line, which increased cell proliferation, invasion, migration and TAM resistance in BC cells.

Emerging roles of Aurora-A kinase in cancer therapy resistance

Aurora kinase A (Aurora-A), a serine/threonine kinase, plays a pivotal role in various cellular processes, including mitotic entry, centrosome maturation and spindle formation. Overexpression or gene-amplification/mutation of Aurora-A kinase occurs in different types of cancer, including lung cancer, colorectal cancer, and breast cancer. Alteration of Aurora-A impacts multiple cancer hallmarks, especially, immortalization, energy metabolism, immune escape and cell death resistance which are involved in cancer progression and resistance. This review highlights the most recent advances in the oncogenic roles and related multiple cancer hallmarks of Aurora-A kinase-driving cancer therapy resistance, including chemoresistance (taxanes, cisplatin, cyclophosphamide), targeted therapy resistance (osimertinib, imatinib, sorafenib, etc.), endocrine therapy resistance (tamoxifen, fulvestrant) and radioresistance. Specifically, the mechanisms of Aurora-A kinase promote acquired resistance through modulating DNA damage repair, feedback activation bypass pathways, resistance to apoptosis, necroptosis and autophagy, metastasis, and stemness. Noticeably, our review also summarizes the promising synthetic lethality strategy for Aurora-A inhibitors in RB1, ARID1A and MYC gene mutation tumors, and potential synergistic strategy for mTOR, PAK1, MDM2, MEK inhibitors or PD-L1 antibodies combined with targeting Aurora-A kinase. In addition, we discuss the design and development of the novel class of Aurora-A inhibitors in precision medicine for cancer treatment.

Lysophosphatidic acid suppresses apoptosis of high-grade serous ovarian cancer cells by inducing autophagy activity and promotes cell-cycle progression via EGFR-PI3K/Aurora-AThr288-geminin dual signaling pathways

Lysophosphatidic acid (LPA) and geminin are overexpressed in ovarian cancer, and increasing evidence supports their contribution to ovarian tumor development. Here, we reveal that geminin depletion induces autophagy suppression and enhances reactive oxygen species (ROS) production and apoptosis of high-grade serous ovarian cancer (HGSOC) cells. Bioinformatics analysis and pharmacological inhibition studies confirm that LPA activates geminin expression in the early S phase in HGSOC cells via the LPAR_1/3/MMPs/EGFR/PI3K/mTOR pathway. Furthermore, LPA phosphorylates Aurora-A kinase on Thr288 through EGFR transactivation, and this event potentiates additional geminin stabilization. In turn, overexpressed and stabilized geminin regulates DNA replication, cell-cycle progression, and cell proliferation of HGSOC cells. Our data provide potential targets for enhancing the clinical benefit of HGSOC precision medicine.

Molecular Mechanisms of Anti-Estrogen Therapy Resistance and Novel Targeted Therapies

Breast cancer (BC) is the most commonly diagnosed cancer in women, constituting one-third of all cancers in women, and it is the second leading cause of cancer-related deaths in the United States. Anti-estrogen therapies, such as selective estrogen receptor modulators, significantly improve survival in estrogen receptor-positive (ER+) BC patients, which represents about 70% of cases. However, about 60% of patients inevitably experience intrinsic or acquired resistance to anti-estrogen therapies, representing a major clinical problem that leads to relapse, metastasis, and patient deaths. The resistance mechanisms involve mutations of the direct targets of anti-estrogen therapies, compensatory survival pathways, as well as alterations in the expression of non-coding RNAs (e.g., microRNA) that regulate the activity of survival and signaling pathways. Although cyclin-dependent kinase 4/6 and phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) inhibitors have significantly improved survival, the efficacy of these therapies alone and in combination with anti-estrogen therapy for advanced ER+ BC, are not curative in advanced and metastatic disease. Therefore, understanding the molecular mechanisms causing treatment resistance is critical for developing highly effective therapies and improving patient survival. This review focuses on the key mechanisms that contribute to anti-estrogen therapy resistance and potential new treatment strategies alone and in combination with anti-estrogen drugs to improve the survival of BC patients.

Targeted therapy for breast cancer: An overview of drug classes and outcomes

The last 25 years have seen significant growth in new therapeutic options for breast cancer, termed targeted therapies based on their ability to block specific pathways known to drive breast tumor growth and survival. Introduction of these drugs has been made possible through advances in the understanding of breast cancer biology. While the promise of targeted therapy for breast cancer has been clear for some time, the experience of the clinical use of multiple drugs and drug classes allows us to now present a summary and perspective as to the success and impact of this endeavor. Here we will review breast cancer targeted therapeutics in clinical use. We will provide the rationale for their indications and summarize clinical data in patients with different breast cancer subtypes, their impact on breast cancer progression and survival and their major adverse effects. The focus of this review will be on the development that has occurred within classes of targeted therapies and subsequent impact on breast cancer patient outcomes. We will conclude with a perspective on the role of targeted therapy in breast cancer treatment and highlight future areas of development.

DLGAP1-AS2 promotes estrogen receptor signalling and confers tamoxifen resistance in breast cancer

BACKGROUND

Tamoxifen is a first-line endocrine agent and is often used to treat estrogen receptor-positive (ER+) breast cancer. Unfortunately, approximately 30-40% of patients who received tamoxifen therapy experience recurrence or progression to a fatal advanced stage due to tamoxifen resistance. However, the mechanisms of tamoxifen resistance remain unclear.

METHODS

The expression of lncRNA DLGAP1 antisense RNA 2 (DLGAP1-AS2) was detected by qPCR. The effect of DLGAP1-AS2 on tamoxifen resistance was evaluated by MTT, colony formation, TUNEL and flow cytometric assays. The mechanisms by which DLGAP1-AS2 regulates tamoxifen resistance were investigated through qPCR, RNA pull-down assays and RNA immunoprecipitation (RIP) assays.

RESULTS

Our results showed that DLGAP1-AS2 is significantly upregulated in breast cancer and that tamoxifen can induce DLGAP1-AS2 expression. Further investigation suggested that upregulation of DLGAP1-AS2 can increase cell viability and inhibit apoptosis, while downregulation of DLGAP1-AS2 results in the opposite effects. Mechanistically, DLGAP1-AS2 can bind to the AFF3 protein to inhibit its degradation, which further promotes ER signalling.

CONCLUSIONS

Our research clarified that DLGAP1-AS2 promotes ER signalling to induce tamoxifen resistance and that targeting DLGAP1-AS2 might be a promising strategy to overcome tamoxifen resistance in breast cancer.

Circ_0001955 plays a carcinogenic role in breast cancer via positively regulating GLUT1 via decoying miR-1299

BACKGROUND

Breast cancer is widespread in females. The role of circular RNA (circRNA) in breast cancer has aroused much attention. However, the function of several circRNAs remain unclear. The aim of our study was to determine the role of circ_0001955 in breast cancer.

METHODS

Quantitative real-time PCR (qPCR) and western blot was employed for expression analysis of circ_0001955, miR-1299 and glucose transporter 1 (GLUT1). Cell functions including proliferation, apoptosis, migration, invasion and angiogenesis, were assessed using EdU, flow cytometry, transwell and tube formation assays. Glycolysis metabolism was assessed according to glucose consumption, lactate production and ATP content. Dual-luciferase reporter assay and RIP assay were utilized to validate the binding between miR-1299 and circ_0001955 or GLUT1. The effects of circ_0001955 in vivo were observed by animal study.

RESULTS

Upregulation of circ_0001955 was detected in breast cancer. Knockdown of circ_0001955 inhibited breast cancer cell proliferation, migration, invasion, angiogenesis and glycolysis. MiR-1299 was a target of circ_0001955, and its repression reversed the effects of circ_0001955 knockdown. Moreover, circ_0001955 targeted miR-1299 to positively regulate GLUT1 expression. GLUT1 overexpression reversed the effects of miR-1299 enrichment. GLUT1 knockdown was verified to block tumor growth in vivo.

CONCLUSIONS

Circ_0001955 was found to promote breast cancer malignant development via targeting of the miR-1299/GLUT1 pathway, which contributes to our understanding of the pathogenesis of breast cancer.

Identification of key genes involved in tamoxifen-resistant breast cancer using bioinformatics analysis

Background

The purpose of the present study was to investigate the molecular mechanisms of tamoxifen resistance in breast cancer and to identify potential targets for antitamoxifen resistance.

Methods

Differentially expressed genes (DEGs) in tamoxifen-resistant and tamoxifen-sensitive breast cancer cells were assessed using the GSE67916 dataset acquired from the Gene Expression Omnibus database. Gene ontology (GO) and pathway enrichment analyses were applied to investigate the functions and pathways of the DEGs. Subsequently, the protein-protein interaction (PPI) network was constructed using the Search Tool for the Retrieval of Interacting Genes (STRING), and subnetworks were further analyzed by Molecular Complex Detection (MCODE). The PPI network and subnetworks were visualized using Cytoscape software.

Results

In total, 438 DEGs were identified, of which 300 were upregulated and 138 were downregulated. The DEGs were significantly enriched in the protein binding, cellular response to estradiol stimulus, and immune response GO terms while the most significant pathways included the mitogen-activated protein kinase (MAPK) signaling pathway in cancer. The PPI network of DEGs was constructed with 288 nodes and 629 edges, and 2 subnetworks were screened out from the entire network.

Conclusions

A number of significant hub DEGs were identified based on their degree of connectivity in the PPI network, , included MAPK1 (node degree 36), ESR1 (node degree 27), SMARCA4 (node degree 27), RANBP2 (node degree 25), and PRKCA (node degree 21). These critical hub genes were found to be related to tamoxifen resistance in breast cancer. The results of this study further the understanding of tamoxifen resistance at the molecular level and identify potential therapeutic targets for tamoxifen-resistant breast cancer.

The efficacy of PI3Kγ and EGFR inhibitors on the suppression of the characteristics of cancer stem cells

Cancer stem cells (CSCs) are capable of continuous proliferation, self-renewal and are proposed to play significant roles in oncogenesis, tumor growth, metastasis and cancer recurrence. We have established a model of CSCs that was originally developed from mouse induced pluripotent stem cells (miPSCs) by proposing miPSCs to the conditioned medium (CM) of cancer derived cells, which is a mimic of carcinoma microenvironment. Further research found that not only PI3K-Akt but also EGFR signaling pathway was activated during converting miPSCs into CSCs. In this study, we tried to observe both of PI3Kγ inhibitor Eganelisib and EGFR inhibitor Gefitinib antitumor effects on the models of CSCs derived from miPSCs (miPS-CSC) in vitro and in vivo. As the results, targeting these two pathways exhibited significant inhibition of cell proliferation, self-renewal, migration and invasion abilities in vitro. Both Eganelisib and Gefitinib showed antitumor effects in vivo while Eganelisib displayed more significant therapeutic efficacy and less side effects than Gefitinib on all miPS-CSC models. Thus, these data suggest that the inhibitiors of PI3K and EGFR, especially PI3Kγ, might be a promising therapeutic strategy against CSCs defeating cancer in the near future.

The role of inner nuclear membrane proteins in tumourigenesis and as potential targets for cancer therapy

Despite significant advances in our understanding of tumourigenesis and cancer therapeutics, cancer continues to account for 30% of worldwide deaths. Therefore, there remains an unmet need for the development of cancer therapies to improve patient quality of life and survival outcomes. The inner nuclear membrane has an essential role in cell division, cell signalling, transcription, cell cycle progression, chromosome tethering, cell migration and mitosis. Furthermore, expression of several inner nuclear membrane proteins has been shown to be frequently altered in tumour cells, resulting in the dysregulation of cellular pathways to promote tumourigenesis. However, to date, minimal research has been conducted to investigate how targeting these dysregulated and variably expressed proteins may provide a novel avenue for cancer therapies. In this review, we present an overview of the involvement of the inner nuclear membrane proteins within the hallmarks of cancer and how they may be exploited as potent anti-cancer therapeutics.

p21 activated kinase-1 and tamoxifen - A deadly nexus impacting breast cancer outcomes

Tamoxifen is a commonly used drug in the treatment of ER + ve breast cancers since 1970. However, development of resistance towards tamoxifen limits its remarkable clinical success. In this review, we have attempted to provide a brief overview of multiple mechanism that may lead to tamoxifen resistance, with a special emphasis on the roles played by the oncogenic kinase- PAK1. Analysing the genomic data sets available in the cBioPortal, we found that PAK1 gene amplification significantly affects the Relapse Free Survival of the ER + ve breast cancer patients. While PAK1 is known to promote tamoxifen resistance by phosphorylating ERα at Ser305, existing literature suggests that PAK1 can fuel up tamoxifen resistance obliquely by phosphorylating other substrates. We have summarised some of the approaches in the mass spectrometry based proteomics, which would enable us to study the tamoxifen resistance specific phosphoproteomic landscape of PAK1. We also propose that elucidating the multiple mechanisms by which PAK1 promotes tamoxifen resistance might help us discover druggable targets and biomarkers.

Endocrine resistance in breast cancer: from molecular mechanisms to therapeutic strategies

Estrogen receptor-positive (ER +) breast cancer accounts for approximately 75% of all breast cancers. Endocrine therapies, including selective ER modulators (SERMs), aromatase inhibitors (AIs), and selective ER down-regulators (SERDs) provide substantial clinical benefit by reducing the risk of disease recurrence and mortality. However, resistance to endocrine therapies represents a major challenge, limiting the success of ER + breast cancer treatment. Mechanisms of endocrine resistance involve alterations in ER signaling via modulation of ER (e.g., ER downregulation, ESR1 mutations or fusions); alterations in ER coactivators/corepressors, transcription factors (TFs), nuclear receptors and epigenetic modulators; regulation of signaling pathways; modulation of cell cycle regulators; stress signaling; and alterations in tumor microenvironment, nutrient stress, and metabolic regulation. Current therapeutic strategies to improve outcome of endocrine-resistant patients in clinics include inhibitors against mechanistic target of rapamycin (mTOR), cyclin-dependent kinase (CDK) 4/6, and the phosphoinositide 3-kinase (PI3K) subunit, p110α. Preclinical studies reveal novel therapeutic targets, some of which are currently tested in clinical trials as single agents or in combination with endocrine therapies, such as ER partial agonists, ER proteolysis targeting chimeras (PROTACs), next-generation SERDs, AKT inhibitors, epidermal growth factor receptor 1 and 2 (EGFR/HER2) dual inhibitors, HER2 targeting antibody-drug conjugates (ADCs) and histone deacetylase (HDAC) inhibitors. In this review, we summarize the established and emerging mechanisms of endocrine resistance, alterations during metastatic recurrence, and discuss the approved therapies and ongoing clinical trials testing the combination of novel targeted therapies with endocrine therapy in endocrine-resistant ER + breast cancer patients.

Analysis of the estrogen receptor-associated lncRNA landscape identifies a role for ERLC1 in breast cancer progression

Estrogen receptor alpha (ERα) plays a vital role in the development of normal breast tissue and in breast cancer. By cross-analyzing The Cancer Genome Atlas (TCGA) database, ERα-regulated long noncoding RNA 1 (ERLC1) was identified as a long noncoding RNA exhibiting a strong association with ERα signaling and high specificity of expression in breast tissue. ERLC1 was transcriptionally activated by ERα, and ERLC1 stabilized the ESR1 transcript by sequestering miR-129 and tethering FXR1 to maintain a positive feedback loop that potentiated ERα signaling. ERLC1 was elevated in tamoxifen-resistant breast cancer cells, where ERLC1 depletion restored sensitivity to tamoxifen and increased the efficacy of palbociclib or fulvestrant therapy. Collectively, these data warrant further investigation of ERLC1 as a modulator of therapeutic response and potential therapeutic target in ER+ breast cancer.

Resistance to CDK4/6 Inhibitors in Estrogen Receptor-Positive Breast Cancer

Estrogen receptor-positive (ER+) breast cancer is the most common form of breast cancer. Antiestrogens were the first therapy aimed at treating this subtype, but resistance to these warranted the development of a new treatment option. CDK4/6 inhibitors address this problem by halting cell cycle progression in ER+ cells, and have proven to be successful in the clinic. Unfortunately, both intrinsic and acquired resistance to CDK4/6 inhibitors are common. Numerous mechanisms of how resistance occurs have been identified to date, including the activation of prominent growth signaling pathways, the loss of tumor-suppressive genes, and noncanonical cell cycle function. Many of these have been successfully targeted and demonstrate the ability to overcome resistance to CDK4/6 inhibitors in preclinical and clinical trials. Future studies should focus on the development of biomarkers so that patients likely to be resistant to CDK4/6 inhibition can initially be given alternative methods of treatment.

Nuclear Dynamics and Chromatin Structure: Implications for Pancreatic Cancer

Changes in nuclear shape have been extensively associated with the dynamics and functionality of cancer cells. In most normal cells, nuclei have a regular ellipsoid shape and minimal variation in nuclear size; however, an irregular nuclear contour and abnormal nuclear size is often observed in cancer, including pancreatic cancer. Furthermore, alterations in nuclear morphology have become the 'gold standard' for tumor staging and grading. Beyond the utility of altered nuclear morphology as a diagnostic tool in cancer, the implications of altered nuclear structure for the biology and behavior of cancer cells are profound as changes in nuclear morphology could impact cellular responses to physical strain, adaptation during migration, chromatin organization, and gene expression. Here, we aim to highlight and discuss the factors that regulate nuclear dynamics and their implications for pancreatic cancer biology.

Tripartite motif-containing 3 (TRIM3) enhances ER signaling and confers tamoxifen resistance in breast cancer

Tamoxifen resistance remains a clinical problem in estrogen receptor (ER)-positive breast cancer. SUMOylation of ERα enhances ERα-induced transcription activity. Tripartite motif-containing (TRIM) proteins are a new class of SUMO E3 ligases, which regulate the SUMOylation of proteins. However, the precise molecular mechanism and function of TRIM3 in SUMOylation and the response to tamoxifen remain unclear. In the present study, we observed that TRIM3 was dramatically overexpressed in breast cancer, which correlated with tamoxifen resistance. Furthermore, TRIM3 overexpression significantly correlated with poor survival of patients with ER⁺ breast cancer treated with tamoxifen. TRIM3 overexpression conferred cell survival and tumorigenesis, whereas knocking down of TRIM3 reduced these capabilities. Moreover, TRIM3, as a ubiquitin carrier protein 9 (UBC9) binding protein, promoted SUMO modification of estrogen receptor 1 (ESR1) and activated the ER pathway. Silencing UBC9 abolished the function of TRIM3 in regulating tamoxifen resistance. These results suggest TRIM3 as a novel biomarker for breast cancer therapy, indicating that inhibiting TRIM3 combined with tamoxifen might provide a potential treatment for breast cancer.

ELOVL2: a novel tumor suppressor attenuating tamoxifen resistance in breast cancer

Epigenetic events have successfully explained the cause of various cancer types, but little is known about tamoxifen resistance (TamR) that induces cancer recurrence. In this study, via genome-wide methylation analysis in MCF-7/TamR cells we show that elongation of very-long chain fatty acid protein 2 (ELOVL2) was hypermethylated and downregulated in the samples from TamR breast cancer patients (n = 28) compared with those from Tam-sensitive (TamS) patients (n = 33) (P < 0.001). Strikingly, in addition to having tumor suppressor activity, ELOVL2 was shown to recover Tam sensitivity up to 70% in the MCF-7/TamR cells and in a xenograft mouse model. A group of genes in the AKT and ERa signaling pathways, e.g., THEM4, which play crucial roles in drug resistance, were found to be regulated by ELOVL2. This study implies that the deregulation of a gene in fatty acid metabolism can lead to drug resistance, giving insight into the development of a new therapeutic strategy for drug-resistant breast cancer.

High expression of TRAF4 predicts poor prognosis in tamoxifen-treated breast cancer and promotes tamoxifen resistance

Tamoxifen is the main adjuvant endocrine therapeutic agent for patients with estrogen receptor positive breast cancer. However, the resistance to tamoxifen has become a serious clinical challenge and the underlying mechanisms are still poorly understood. TRAF4 is a member of tumor necrosis factor receptor-associated factor family and its role in tamoxifen resistance has not been found. In this study, we aimed to explore the roles of TRAF4 in tamoxifen-treated breast cancer and tamoxifen resistance. Through high-throughput sequencing and differential gene expression analyses, TRAF4 was identified as the research object in this study. The prognosis significance of TRAF4 was studied based on 155 tamoxifen-treated breast cancer patients obtained from Gene Expression Omnibus (GEO) database. We then investigated the TRAF4 expression level in tamoxifen-resistant and the tamoxifen-sensitive breast cancer cell lines with western blot and real-time quantitative PCR. The loss- and gain-of-function assay of TRAF4 in a tamoxifen-resistant cell line was evaluated using colony formation experiments and cell count kit-8 assay. We identified that TRAF4 was overexpressed in tamoxifen-resistant breast cancer cell line and TRAF4 overexpression was associated with worse overall survival (hazard ratio = 2.538, P = 0.017) and cancer-specific survival (hazard ratio = 2.713, P = 0.036) in tamoxifen-treated patients. Knockdown of TRAF4 reversed tamoxifen resistance, while overexpression of TRAF4 increased tamoxifen resistance, which confirmed the role of TRAF4 in tamoxifen resistance. Taken together, our study demonstrated that TRAF4 could be a novel prognostic biomarker for tamoxifen-treated breast cancer patients and a potential therapeutic target for tamoxifen resistance.

Estrogen Receptor Beta Prevents Signet Ring Cell Gastric Carcinoma Progression in Young Patients by Inhibiting Pseudopodia Formation via the mTOR-Arpc1b/EVL Signaling Pathway

Signet ring cell gastric carcinoma (SRCGC) is a poorly differentiated malignancy, and can be highly dangerous in the progression stage. There is a higher male to female ratio among patients with signet ring cell carcinoma as compared to patients with non-SRCGC. ERβ has been found to express in stomach adenocarcinoma, but how it affects tumor progression remains unclear. Here, we studied estrogen receptor beta (ERβ) to explore the role of sex-associated factors in SRCGC. We analyzed the clinicopathological statistics of patients with SRCGC, and conducted a series of in vitro experiments. Immunohistochemistry showed that patients with low ERβ expression were at risk of poor prognosis and higher T stage. In vitro assays indicated that ERβ might prevent SRCGC progression by inhibiting cell proliferation and invasiveness and by promoting anoikis. Western blotting and quantitative RT-PCR proved that the mTOR-Arpc1b/EVL signaling pathway might participate in the negative regulatory role of ERβ. In conclusion, our findings show that ERβ might inhibit the malignancy of signet ring cells in patients with SRCGC, indicating that ERβ might be a potential target in adjuvant treatment.

Progress in the Understanding of the Mechanism of Tamoxifen Resistance in Breast Cancer

Tamoxifen is a drug commonly used in the treatment of breast cancer, especially for postmenopausal patients. However, its efficacy is limited by the development of drug resistance. Downregulation of estrogen receptor alpha (ERα) is an important mechanism of tamoxifen resistance. In recent years, with progress in research into the protective autophagy of drug-resistant cells and cell cycle regulators, major breakthroughs have been made in research on tamoxifen resistance. For a better understanding of the mechanism of tamoxifen resistance, protective autophagy, cell cycle regulators, and some transcription factors and enzymes regulating the expression of the estrogen receptor are summarized in this review. In addition, recent progress in reducing resistance to tamoxifen is reviewed. Finally, we discuss the possible research directions into tamoxifen resistance in the future to provide assistance for the clinical treatment of breast cancer.

Identification and Characterization of the Copy Number Dosage-Sensitive Genes in Colorectal Cancer

Dosage effect is one of the common mechanisms of somatic copy number alteration in the development of colorectal cancer, yet the roles of dosage-sensitive genes (DSGs) in colorectal cancer (CRC) remain to be characterized more deeply. In this study, we developed a five-step pipeline to identify DSGs and analyzed their characterization in CRC. Results showed that our pipeline performed better than existing methods, and the result was significantly overlapped between solid tumor and cell line. We also found that the top five DSGs (PSMF1, RAF1, PTPRA, MKRN2, and ELP3) were associated with the progression of CRC. By analyzing the characterization, DSGs were enriched in driver genes and they drove sub-pathways of CRC. In addition, immune-related DSGs are associated with CRC progression. Our results also showed that the CRC samples affected by high microsatellites have fewer DSGs, but a higher overlap with DSGs in microsatellite low instability and microsatellite stable samples. In addition, we applied DSGs to identify potential drug targets, with the results showing that 22 amplified DSGs were more sensitive to four drugs. In conclusion, DSGs play an important role in CRC, and our pipeline is effective to identify them.

Autophagic Vacuole Secretion Triggered by Chidamide Participates in TRAIL Apoptosis Effect in Breast Cancer Cells

BACKGROUND

Breast cancer is one of the most prevalent diseases threatening women's health today. Indepth research on breast cancer (BC) pathogenesis and prevention and treatment methods are gradually receiving attention. Chidamide is a novel histone deacetylase inhibitor (HDACi) that depresses the function of histone deacetylase, consequently affecting the growth of BC cells through epigenetic modification. However, preclinical and clinical studies show that chidamide is ineffective in long-term treatment. We demonstrated in previous experiments that TNF-related apoptosis-inducing ligand (TRAIL) induces apoptosis in BC cells and is significantly less non-toxic to normal cells than chidamide. Therefore, in this study, we treated BC cells with chidamide and TRAIL to explore a novel option to reduce the clinical toxicity through augmenting the sensitivity for BC cells.

METHODS AND RESULTS

Results from the MTT and cell viability assays indicated that the combination of chidamide and TRAIL in MCF-7 and MDA-MB-231 cells induced BC cell death, while maintaining a reduced concentration of chidamide. Autophagy assay and annexin V analysis showed that the autophagosome microtubuleassociated protein1light chain3-II (LC3-II) was abnormally increased and much more early and late phase of apoptotic cells appeared during chidamide and TRAIL induction. Anti-tumor assays in a BC tumor xenograft model displayed that the mixture of chidamide and TRAIL exhibited stronger effects on inhibiting tumor growth. The data from real-time PCR and western blotting showed that the cytotoxic effect correlated with the expressions of related apoptosis and autophagy factors.

CONCLUSION

Our data are the first to demonstrate the synergistic effects of chidamide and TRAIL in BC cells, specifically, the pharmacological effects on cell death induction. These results lay a solid experimental and theoretical basis to solve the clinical resistance of chidamide.

A tetraprenylated benzophenone 7-epiclusianone induces cell cycle arrest at G1/S transition by modulating critical regulators of cell cycle in breast cancer cell lines

Breast cancer is a complex disease and encompassing different types of tumor. Although advances in understanding of the molecular bases of breast cancer biology, the therapeutic proposals available still are not effective. In this scenario, the present study aimed to evaluate the mechanisms associated to antitumor activity of 7-Epiclusianone (7-Epi), a tetraprenylated benzophenone, on luminal A (MCF-7) and claudin-low (Hs 578T) breast cancer cell lines. We found that 7-Epi efficiently inhibited cell proliferation and migration of these cells; however MCF-7 was slightly more responsive than Hs 578T. Cell cycle analysis showed accumulation of cells at G0/G1 phase with drastic reduction of S population in treated cultures. This effect was associated to downregulation of CDKN1A (p21) and cyclin E in both cell lines. In addition, 7-Epi reduced cyclin D1 and p-ERK expression levels in MCF-7 cell line. Cytotoxic effect of 7-Epi on breast cancer cell lines was associated to its ability to increase BAX/BCL-2 ratio. In conclusion, our findings showed that 7-Epi is a promising antitumor agent against breast cancer by modulating critical regulators of the cell cycle and apoptosis.

Molecular crosstalk between cancer and neurodegenerative diseases

The progression of cancers and neurodegenerative disorders is largely defined by a set of molecular determinants that are either complementarily deregulated, or share remarkably overlapping functional pathways. A large number of such molecules have been demonstrated to be involved in the progression of both diseases. In this review, we particularly discuss our current knowledge on p53, cyclin D, cyclin E, cyclin F, Pin1 and protein phosphatase 2A, and their implications in the shared or distinct pathways that lead to cancers or neurodegenerative diseases. In addition, we focus on the inter-dependent regulation of brain cancers and neurodegeneration, mediated by intercellular communication between tumor and neuronal cells in the brain through the extracellular microenvironment. Finally, we shed light on the therapeutic perspectives for the treatment of both cancer and neurodegenerative disorders.

SRC Promotes Tamoxifen Resistance in Breast Cancer via Up-Regulating SIRT1

Background

Endocrine therapy plays a key role in estrogen receptor-positive breast cancer patients; but, tamoxifen resistance could be a real difficulty for these patients. Several attempts have been made to explore the mechanism and new therapies for these patients. We intend to clarify the expression change of SRC and SIRT1 in tamoxifen-resistant breast cancer cells and explore their functions on tamoxifen resistance.

Methods

SRC and SIRT1 expressions were analyzed by RNA sequencing, qPCR and Western blotting. Loss and gain of function of SRC and SIRT1 were utilized to indicate their oncogenic roles in tamoxifen resistance in vitro and in vivo. Kaplan–Meier analysis and receiver operating characteristic curve were used to evaluate the survival and the predicted effects of SRC and SIRT1 on patients’ prognosis.

Results

High expressions of SRC and/or SIRT1 were found in tamoxifen-resistant cells and related to poor overall survival (p<0.05 for SRC, p<0.001 for SIRT1, p<0.001 for SRC and SIRT1) and cancer-specific survival (p<0.05 for SRC, p<0.01 for SIRT1, p<0.01 for SRC and SIRT1) of tamoxifen-treated breast cancer patients. Down-regulation of SRC (p<0.01) or SIRT1 (p<0.05) separately reversed the resistance to tamoxifen and the minimal concentration of SRC inhibitor KX-01 (p<0.05) or SIRT1 inhibitor EX527 (p<0.001) could also suppress cell proliferation. The expression level of SIRT1 was positively correlated with that of SRC. Overexpression of SRC significantly promotes the cell resistance to tamoxifen inhibited by SIRT1 (p<0.01). In vivo experiments confirmed the effects of SRC on tumor growth by over- or down-regulating SRC expression (p<0.001 and p<0.001, respectively).

Conclusion

SRC and SIRT1 are both up-regulated in tamoxifen-resistant breast cancer cells and related to a poor prognosis in tamoxifen-treated breast cancer. Moreover, SRC could promote tamoxifen resistance by up-regulating SIRT1. SRC and SIRT1 might be novel therapeutic targets in tamoxifen-resistant breast cancer and the interaction between SRC and SIRT1 needs to be further explored.

Screening Circular RNAs Related to Acquired Gefitinib Resistance in Non-small Cell Lung Cancer Cell Lines

Background: Gefitinib is a tyrosine kinase inhibitor (TKI) of epidermal growth factor receptor (EGFR) used to treat EGFR mutation-positive patients with non-small cell lung cancer (NSCLC). However, the efficacy of gefitinib is limited by the development of acquired resistance. Studies have shown that circular RNAs (circRNAs) are involved in the acquired resistance to many anticancer agents. However, the expression profiles and functions of circRNAs in gefitinib resistance in NSCLC are poorly understood so far. Methods: In this study, circRNA expression profiling was explored in two gefitinib-resistant NSCLC cell lines (HCC827/GR and PC9/GR) and their parental sensitive cells (HCC827 and PC9) using high-throughput RNA sequencing. Quantitative real-time PCR (qRT-PCR) was used to confirm the expression of selected differentially expressed circRNAs. Bioinformatic tools including gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), network analysis, and Kaplan-Meier plotter database were used to predict the functions and pathways of these differentially expressed circRNAs. Results: We identified 46 and 56 differentially expressed circRNAs in HCC827/GR and PC9/GR cell lines, respectively, compared with those in their parental cell lines. Gene ontology and KEGG pathway analysis identified that the host linear transcripts of these differentially expressed circRNAs were involved in many critical biological pathways and molecular functions. We found that hsa_circ_0000567 was consistently up-regulated, and hsa_circ_0006867 was consistently down-regulated in two resistant cell lines. We further used hsa_circ_0000567 and hsa_circ_0006867 as key circRNAs to construct circRNA-miRNA-mRNA networks. Several target mRNAs of these two circRNAs had been shown to significantly associate with the overall survival of patients with lung cancer. Conclusions: In this study, we generated the comprehensive expression and functional profiles of the differentially expressed circRNAs between gefitinib-resistant and -sensitive NSCLC cells, and showed that dysregulation of circRNAs might play an important role in the development of acquired resistance to gefitinib in NSCLC.

Although c‑MYC contributes to tamoxifen resistance, it improves cisplatin sensitivity in ER‑positive breast cancer

Tamoxifen (TAM) resistance is a major challenge in the treatment of estrogen receptor‑positive (ER+) breast cancer. To date, to the best of our knowledge, there are only a few studies available examining the response of patients with TAM‑resistant breast cancer to chemotherapy, and the guidelines do not specify recommended drugs for these patients. In the present study, TAM‑resistant cells were shown to exhibit increased proliferation and invasion compared with the parent cells, and the increased expression of c‑MYC was demonstrated to play an important role in TAM resistance. Furthermore, the TAM‑resistant cells were significantly more sensitive to cisplatin compared with the parent cells, and the silencing of c‑MYC expression desensitized the cells to cisplatin through the inhibition of the cell cycle. An increased c‑MYC expression was observed in 28 pairs of primary and metastatic tumors from patients treated with TAM, and the clinical remission rate of cisplatin‑based chemotherapy was significantly higher compared with other chemotherapy‑based regimens in 122 patients with TAM resistant breast cancer. Taken together, the data of the present study demonstrated that although c‑MYC was involved in TAM resistance, it increased the sensitivity of ER+ breast cancer to cisplatin. Thus, cisplatin may be a preferred chemotherapeutic agent for the treatment of patients with TAM‑resistant breast cancer, particularly in patients where the rapid control of disease progression is required.

Mechanisms of resistance to estrogen receptor modulators in ER+/HER2- advanced breast cancer

Endocrine therapy represents a mainstay adjuvant treatment of estrogen receptor-positive (ER+) breast cancer in clinical practice with an overall survival (OS) benefit. However, the emergence of resistance is inevitable over time and is present in one-third of the ER+ breast tumors. Several mechanisms of endocrine resistance in ER+/HER2- advanced breast cancers, through ERα itself, receptor tyrosine signaling, or cell cycle pathway, have been identified to be pivotal in endocrine therapy. The epigenetic alterations also contribute to ensuring tumor cells' escape from endocrine therapies. The strategy of combined hormone therapy with targeted pharmaceutical compounds has shown an improvement of progression-free survival or OS in clinical practice, including three different classes of drugs: CDK4/6 inhibitors, selective inhibitor of PI3Kα and mTOR inhibitors. Many therapeutic targets of cell cycle pathway and cell signaling and their combination strategies have recently entered clinical trials. This review focuses on Cyclin D-CDK4/6-RB axis, PI3K pathway and HDACs. Additionally, genomic evolution is complex in tumors exposed to hormonal therapy. We highlight the genomic alterations present in ESR1 and PIK3CA genes to elucidate adaptive mechanisms of endocrine resistance, and discuss how these mutations may inform novel combinations to improve clinical outcomes in the future.

lncRNA CYTOR promotes tamoxifen resistance in breast cancer cells via sponging miR‑125a‑5p

Development of resistance to endocrine therapy, such as tamoxifen, remains a tricky clinical problem during the treatment of breast cancer. Accumulating evidence suggested that dysregulation of long noncoding (lnc_RNAs contributes to the development of tamoxifen resistance. In the current study, via screening, cytoskeleton regulator RNA (CYTOR) was identified as the most significantly elevated lncRNA in the established tamoxifen resistant MCF7 cell lines (MCF7/TAM1 and MCF7/TAM2) compared with the parental MCF7 cells (MCF7-P). The CCK-8 assay indicated that silencing of CYTOR increased the sensitivity of MCF7/TAM1 and MCF7/TAM2 to tamoxifen treatment. Using bioinformatic analysis, it was predicted that microRNA (miR)-125a-5p might bind to CYTOR and the expression of miR-125a-5p was negatively correlated with CYTOR in the tumor tissues of breast cancer. In addition, RT-qPCR and dual luciferase assays validated that CYTOR directly repressed miR-125a-5p expression in breast cancer cells. Through regulation of miR-125a-5p, CYTOR elevated serum response factor (SRF) expression and activated Hippo and mitogen associated protein kinase signaling pathways to promote breast cancer cell survival upon tamoxifen treatment. In the collected tumor tissues of breast cancer in the present study, high expression of CYTOR was detected in tissues from patients with no response to tamoxifen compared with those from patients who were not treated with tamoxifen. A positive correlation between CYTOR and SRF mRNA expression was observed in tissues collected from patients with breast cancer. In conclusion, the results of the present study demonstrated a pivotal role of CYTOR in mediating tamoxifen resistance in breast cancer.

CDK4/6 inhibitor protects chemerin-induced human granulosa-lutein cells from apoptosis by inhibiting the p53/p21 waf pathway

Dysregulation of the cell cycle is common in human tumorigenesis. Therefore, CDK4/6 inhibitors targeting the cell cycle have been developed, and their antiapoptotic effects have been highly correlated with potential clinical therapies. The aim of this study was to identify the regulatory effect of the CDK4/6 inhibitor palbociclib on chemerin-induced apoptosis of immortalized human granulosa-lutein (hGL) cells and to elucidate its fundamental mechanism of action. Palbociclib enhanced antioxidative enzyme generation and diminished ROS generation in hGL cells. Furthermore, we found that palbociclib suppressed chemerin-induced apoptotic protein expression, reversing the Bcl-2/Bax ratio and inhibiting the p53/p21 ^waf pathway. Eventually, palbociclib decreased the level of cleaved caspase-3 and -9, hindering the apoptosis of hGL cells. In general, the antiapoptotic efficacy of palbociclib could be attributed in part to the modulation of the mitochondrial apoptotic pathway in hGL cells.

The Functions of DNA Damage Factor RNF8 in the Pathogenesis and Progression of Cancer

The really interesting new gene (RING) finger protein 8 (RNF8) is a central factor in DNA double strand break (DSB) signal transduction. DSB damage is the most toxic type of DNA damage to cells and is related to genomic instability. Multiple roles for RNF8 have been identified in DNA damage response as well as in other functions, such as telomere protection, cell cycle control and transcriptional regulation. These functions are closely correlated to tumorigenesis and cancer progression. Indeed, deficiency of RNF8 caused spontaneous tumorigenesis in a mouse model. Deciphering these mechanisms of RNF8 may shed light on strategies for cancer treatment. In this review, we summarize the current understanding of both classical and nonclassical functions of RNF8, and discuss its roles in the pathogenesis and progression of tumor.

Downregulation of RNF128 activates Wnt/β-catenin signaling to induce cellular EMT and stemness via CD44 and CTTN ubiquitination in melanoma

BACKGROUND

Ring finger proteins (RNFs) were involved in carcinogenesis. Here, we aimed to explore the detailed mechanism of RNF128 in the progression of melanoma.

METHODS

We reanalyzed several gene expression profiles from the Gene Expression Omnibus (GEO) database and obtained the overlapped differential expressed RNF genes. Among them, RNF128 was selected to further explore its expression, the biological significance, and the underlying molecular mechanism, as well as the clinical relevance in melanoma patients.

RESULTS

RNF128 was found to be significantly downregulated in the selected datasets, which was further verified in our melanoma tissues. Moreover, RNF128 downregulation was shown to correlate with the malignant phenotype of melanoma, and further functional assays demonstrated that low levels of RNF128 promoted melanoma progression via inducing cell epithelial-mesenchymal transition (EMT) and the acquisition of stemness. Mechanistically, RNF128 interference activated the Wnt pathway via simultaneously ubiquitinating CD44/cortactin (CTTN), resulting in CD44 and c-Myc transcription, thus revealed that RNF128 participated in a positive feedback of the Wnt pathway-CD44 loop. Clinically, we found that patients expressing low RNF128 and high CD44/CTTN levels had a poor prognosis.

CONCLUSION

Downregulated RNF128 activates Wnt signaling to induce cellular EMT and stemness by ubiquitinating and degrading CD44/CTTN, and RNF128 is a reliable diagnostic and prognostic biomarker, and a deeper understanding of RNF128 may contribute to the treatment of melanoma.

CDK4/6 inhibitor protects against myocardial cells apoptosis by inhibiting RB phosphorylation in H9c2 cells

Cell cycle dysregulation is typical in human cancers, and CDK4/6 inhibitors targeting cell cycle have potential antiapoptosis effect. The aim of this work is to identify the regulatory effect of Palbociclib on apoptosis of H9c2 cells induced by high glucose (HG) and to elucidate the fundamental mechanisms. It was observed that Palbociclib decreased intracellular ROS production, augmented mitochondrial membrane potential and hindered apoptosis of H9c2 cells. Palbociclib increased the Bcl-2/Bax ratio, diminished the expressions of Bax and cleaved-caspase-3, and affected the RB phosphorylation and p53 expression. Altogether, the anti-apoptotic efficacy of Palbociclib could be attributed in part to the modulation of the mitochondria apoptotic pathway.