The emergence of targeted drugs in breast cancer to prevent resistance to endocrine treatment and chemotherapy

Synthesis and biological evaluation of novel isatin-phenol hybrids as potential antitumor agents

Chemotherapy was one of indispensable methods for treating cancer, and the development of novel antitumor drugs was necessary due to the emergent drug resistance and undesirable side effects. In the current study, we successfully constructed a novel library of isatin-phenol hybrids by chemical coupling of isatin (1) with a series of active phenols including honokiol (2), magnolol (3), bis(4-hydroxy-3-methylphenyl) sulfide (4), bisphenol A (5), carvacrol (6), and hydroxyqunioline (7) respectively. The target molecules were screened for anticancer activity, and we further investigate the anti-cancer mechanism of the most potent compound IPH10 in vitro and in vivo. Animal experiments demonstrated that IPH10 possessed strong anti-tumor effects in vivo without hepatic and renal toxicity. Moreover, the effects of IPH10 on mitochondrial membrane potential (JC-1) and reactive oxygen species (ROS) in tumor cells were investigated, and the results showed that IPH10 could significantly increase the content of ROS and dramatically decrease the mitochondrial membrane potential in tumor cells. Furthermore, the effect of IPH10 on apoptotic proteins in tumor cells was also explored by Western blotting analysis, which revealed that IPH10 could significantly increase the protein content of cleaved caspase-9/cleaved caspase-3/cleaved caspase-7/cleaved PARP. Taken together, the current study reported a promising novel chemotherapeutic drug candidate IPH10 that could inhibit the growth and induce the apoptosis of tumor cells.

Multimodal diagnostic models and subtype analysis for neoadjuvant therapy in breast cancer

Background

Breast cancer, a heterogeneous malignancy, comprises multiple subtypes and poses a substantial threat to women's health globally. Neoadjuvant therapy (NAT), administered prior to surgery, is integral to breast cancer treatment strategies. It aims to downsize tumors, optimize surgical outcomes, and evaluate tumor responsiveness to treatment. However, accurately predicting NAT efficacy remains challenging due to the disease's complexity and the diverse responses across different molecular subtypes.

Methods

In this study, we harnessed multimodal data, including proteomic, genomic, MRI imaging, and clinical information, sourced from multiple cohorts such as I-SPY2, TCGA-BRCA, GSE161529, and METABRIC. Post data preprocessing, Lasso regression was utilized for feature extraction and selection. Five machine learning algorithms were employed to construct diagnostic models, with pathological complete response (pCR) as the predictive endpoint.

Results

Our results revealed that the multi-omics Ridge regression model achieved the optimal performance in predicting pCR, with an AUC of 0.917. Through unsupervised clustering using the R package MOVICS and nine clustering algorithms, we identified four distinct multimodal breast cancer subtypes associated with NAT. These subtypes exhibited significant differences in proteomic profiles, hallmark cancer gene sets, pathway activities, tumor immune microenvironments, transcription factor activities, and clinical characteristics. For instance, CS1 subtype, predominantly ER-positive, had a low pCR rate and poor response to chemotherapy drugs, while CS4 subtype, characterized by high immune infiltration, showed a better response to immunotherapy. At the single-cell level, we detected significant heterogeneity in the tumor microenvironment among the four subtypes. Malignant cells in different subtypes displayed distinct copy number variations, differentiation levels, and evolutionary trajectories. Cell-cell communication analysis further highlighted differential interaction patterns among the subtypes, with implications for tumor progression and treatment response.

Conclusion

Our multimodal diagnostic model and subtype analysis provide novel insights into predicting NAT efficacy in breast cancer. These findings hold promise for guiding personalized treatment strategies. Future research should focus on experimental validation, in-depth exploration of the underlying mechanisms, and extension of these methods to other cancers and treatment modalities.

Upregulation of miR-99b-5p Modulates ESR1 Expression as an Adaptive Mechanism to Circumvent Drug Response via Facilitating ER/HER2 Crosstalk

Background

Endocrine resistance remains a significant therapeutic challenge in estrogen receptor-positive (ER+) breast cancer, the most common subtype, contributing to increased morbidity and mortality. The interaction between ER and HER family receptors, particularly HER2 and epidermal growth factor receptor (EGFR), drives resistance to standard therapies such as tamoxifen and trastuzumab by activating key signaling pathways, including PI3K/AKT and RAS/MAPK. Dysregulated miRNAs, which are non-coding gene expression regulators, have been linked to therapy response.

Aims

To investigate the role of miR-99b-5p in ER-HER2/EGFR crosstalk in BT-474 cells.

Study Design

Experimental study.

Methods

The expression profile and prognostic significance of miR- 99b-5p in breast cancer were analyzed using The Cancer Genome Atlas (TCGA) database. BT-474 cells were transfected with miR-99b-5p mimics and inhibitors, followed by treatment with tamoxifen and trastuzumab to assess their impact on cell proliferation and ER-HER2/EGFR crosstalk. Western blotting was performed to quantify EGFR, HER2, and ESR1 protein levels. Real-time proliferation analysis evaluated changes in cell growth following miRNA transfection and drug treatment.

Results

The study revealed that miR-99b-5p is significantly overexpressed in tumors compared to normal tissues and is associated with poor patient survival and enhanced ER signaling. Transfection with miR-99b-5p mimics increased ESR1 expression and cell proliferation, even in the presence of tamoxifen or trastuzumab, indicating that miR-99b-5p contributes to therapy resistance through receptor crosstalk. Conversely, miR-99b-5p inhibition significantly restored drug sensitivity, reducing proliferation and enhancing the effectiveness of tamoxifen and trastuzumab.

Conclusion

These findings establish miR-99b-5p as a key regulator of endocrine and HER2-targeted therapy resistance. Targeting miR-99b-5p could represent a potential therapeutic strategy to improve treatment outcomes in ER+/HER2+ breast cancer. Further research is needed to clarify the underlying molecular mechanisms and validate the therapeutic potential of miR-99b-5p inhibition in clinical applications.

Unveiling the anti-cancer potentiality of phthalimide-based Analogues targeting tubulin polymerization in MCF-7 cancerous Cells: Rational design, chemical Synthesis, and Biological-coupled Computational investigation

The present study deals with an anti-cancer investigation of an array of phthalimide-1,2,3-triazole molecular conjugates with various sulfonamide fragments against human breast MCF-7 and prostate PC3 cancer cell lines. The targeted 1,2,3-triazole derivatives 4a-l and 6a-c were synthesized from focused phthalimide-based alkyne precursors using a facile click synthesis approach and were thoroughly characterized using several spectroscopic techniques (IR, 1H, 13C NMR, and elemental analysis). The hybrid click adducts 4b, 4 h, and 6c displayed cytotoxic potency (IC50 values of 1.49, 1.07, and 0.56 μM, respectively) against MCF-7 cells. On the contrary, none of the synthesized compounds showed apparent cytotoxic efficacy for PC3 cells (IC50 ranging from 9.87- >100 μM). As a part of the mechanism analysis, compound 6c demonstrated a potent inhibitory effect (78.3 % inhibition) of tubulin polymerization in vitro with an IC50 value of 6.53 µM. In addition, biological assays showed that compound 6c could prompt apoptotic cell death and induce G2/M cell cycle arrest in MCF-7 cells. Accordingly, compound 6c can be further developed as an anti-breast cancer agent through apoptosis-induction.

Relative efficacy of antibody-drug conjugates and other anti-HER2 treatments on survival in HER2-positive advanced breast cancer: a systematic review and meta-analysis

BACKGROUND

Novel antibody-drug conjugates (ADCs) drugs present a promising anti-cancer treatment, although survival benefits for HER2-positive advanced breast cancer (BC) remain controversial. The aim of this meta-analysis was to evaluate the comparative effect of ADCs and other anti-HER2 therapy on progression-free survival (PFS) and overall survival (OS) for treatment of HER2-positive locally advanced or metastatic BC.

METHODS

Relevant randomized controlled trials (RCTs) were retrieved from five databases. The risk of bias was assessed with the Cochrane Collaboration's tool for RCTs by RevMan5.4 software. The hazard ratio (HR) and 95% confidence intervals (CIs) were extracted to evaluate the benefit of ADCs on PFS and OS in HER2-positive advanced BC by meta-analysis.

RESULTS

Meta-analysis of six RCTs with 3870 patients revealed that ADCs significantly improved PFS (HR: 0.63, 95% CI: 0.49-0.80, P = 0.0002) and OS (HR: 0.79, 95% CI: 0.72-0.86, P < 0.0001) of patients with HER2-positive locally advanced or metastatic BC. Subgroup analysis showed that PFS and OS were obviously prolonged for patients who previously received HER2-targeted therapy. Sensitivity analysis and publication bias suggested that the results were stable and reliable.

CONCLUSION

Statistically significant benefits for PFS and OS were observed with ADCs in HER2-positive locally advanced or metastatic BC, especially for those who received prior anti-HER2 treatment.

The Function of Autophagy in the Initiation, and Development of Breast Cancer

Autophagy is a significant catabolic procedure that increases in stressful conditions. This mechanism is mostly triggered after damage to the organelles, the presence of unnatural proteins, and nutrient recycling in reaction to these stresses. One of the key points in this article is that cleaning and preserving damaged organelles and accumulated molecules through autophagy in normal cells helps prevent cancer. Since dysfunction of autophagy is associated with various diseases, including cancer, it has a dual function in tumor suppression and expansion. It has newly become clear that the regulation of autophagy can be used for the treatment of breast cancer, which has a promising effect of increasing the efficiency of anticancer treatment in a tissue- and cell-type-specific manner by affecting the fundamental molecular mechanisms. Regulation of autophagy and its function in tumorigenesis is a vital part of modern anticancer techniques. This study discusses the current advances related to the mechanisms that describe essential modulators of autophagy involved in the metastasis of cancers and the development of new breast cancer treatments.

Influence of cyclin D1 splicing variants expression on breast cancer chemoresistance via CDK4/CyclinD1-pRB-E2F1 pathway

Cyclin D1 (CCND1), a mediator of cell cycle control, has a G870A polymorphism which results in the formation of two splicing variants: full-length CCND1 (CCND1a) and C-terminally truncated CCND1 species (CCND1b). However, the role of CCND1a and CCND1b variants in cancer chemoresistance remains unknown. Therefore, this study aimed to explore the molecular mechanism of alternative splicing of CCND1 in breast cancer (BC) chemoresistance. To address the contribution of G870A polymorphism to the production of CCND1 variants in BC chemoresistance, we sequenced the G870A polymorphism and analysed the expressions of CCND1a and CCND1b in MCF-7 and MCF-7/ADM cells. In comparison with MCF-7 cells, MCF-7/ADM cells with the A allele could enhance alternative splicing with the increase of SC-35, upregulate the ratio of CCND1b/a at both mRNA and protein levels, and activate the CDK4/CyclinD1-pRB-E2F1 pathway. Furthermore, CCND1b expression and the downstream signalling pathway were analysed through Western blotting and cell cycle in MCF-7/ADM cells with knockdown of CCND1b. Knockdown of CCND1b downregulated the ratio of CCND1b/a, demoted cell proliferation, decelerated cell cycle progression, inhibited the CDK4/CyclinD1-pRB-E2F1 pathway and thereby decreased the chemoresistance of MCF-7/ADM cells. Finally, CCND1 G870A polymorphism, the alternative splicing of CCDN1 was detected through Sequenom Mass ARRAY platform, Sanger sequencing, semi-quantitative RT-PCR, Western blotting and immunohistochemistry in clinical BC specimens. The increase of the ratio of CCND1b/a caused by G870A polymorphism was involved in BC chemoresistance. Thus, these findings revealed that CCND1b/a ratio caused by the polymorphism is involved in BC chemoresistance via CDK4/CyclinD1-pRB-E2F1 pathway.

Mechanism of inflammasomes in cancer and targeted therapies

Inflammasomes, composed of the nucleotide-binding oligomerization domain(NOD)-like receptors (NLRs), are immune-functional protein multimers that are closely linked to the host defense mechanism. When NLRs sense pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs), they assemble into inflammasomes. Inflammasomes can activate various inflammatory signaling pathways, including nuclear factor kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways, and produce a large number of proinflammatory cytokines, which are closely associated with multiple cancers. They can also accelerate the occurrence and development of cancer by providing suitable tumor microenvironments, promoting tumor cell proliferation, and inhibiting tumor cell apoptosis. Therefore, the exploitation of novel targeted drugs against various inflammasomes and proinflammatory cytokines is a new idea for the treatment of cancer. In recent years, more than 50 natural extracts and synthetic small molecule targeted drugs have been reported to be in the research stage or have been applied to the clinic. Herein, we will overview the mechanisms of inflammasomes in common cancers and discuss the therapeutic prospects of natural extracts and synthetic targeted agents.

Co-delivery of doxorubicin and SIS3 by folate-targeted polymeric micelles for overcoming tumor multidrug resistance

Multidrug resistance (MDR) is considered as a critical limiting factor for the successful chemotherapy, which is mainly characterized by the overexpression of ATP-binding cassette (ABC) transporter ABCB1 or ABCG2. In this study, folate-targeted polymeric micellar carrier was successfully constructed to co-delivery of doxorubicin (DOX) and SIS3 (FA/DOX/SIS3 micelles), a specific Smad3 inhibitor which sensitizes ABCB1- and ABCG2-overexpressing cancer cells to chemotherapeutic agents. The ratio of DOX to SIS3 in polymeric micelles was determined based on the anti-tumor activity against resistant breast cells. In addition, FA/DOX/SIS3 micelles exhibited a much longer circulation time in blood and were preferentially accumulated in resistant tumor tissue. Pharmacodynamic studies showed that FA/DOX/SIS3 micelles possessed superior anti-tumor activity than other DOX-based treatments. Overall, FA/DOX/SIS3 micelles are a promising formulation for the synergistic treatment of drug-resistant tumor.

Long non-coding RNAs as the critical regulators of doxorubicin resistance in tumor cells

Resistance against conventional chemotherapeutic agents is one of the main reasons for tumor relapse and poor clinical outcomes in cancer patients. Various mechanisms are associated with drug resistance, including drug efflux, cell cycle, DNA repair and apoptosis. Doxorubicin (DOX) is a widely used first-line anti-cancer drug that functions as a DNA topoisomerase II inhibitor. However, DOX resistance has emerged as a large hurdle in efficient tumor therapy. Furthermore, despite its wide clinical application, DOX is a double-edged sword: it can damage normal tissues and affect the quality of patients’ lives during and after treatment. It is essential to clarify the molecular basis of DOX resistance to support the development of novel therapeutic modalities with fewer and/or lower-impact side effects in cancer patients. Long non-coding RNAs (lncRNAs) have critical roles in the drug resistance of various tumors. In this review, we summarize the state of knowledge on all the lncRNAs associated with DOX resistance. The majority are involved in promoting DOX resistance. This review paves the way to introducing an lncRNA panel marker for the prediction of the DOX response and clinical outcomes for cancer patients.

LncRNA as a multifunctional regulator in cancer multi-drug resistance

BACKGROUND

Malignant tumors have become the most dangerous disease in recent years. Chemotherapy is the most effective treatment for this disease; however, the problem of drug resistance has become even more common, which leads to the poor prognosis of patients suffering from cancers. Thus, necessary measures should be taken to address these problems at the earliest. Many studies have demonstrated that drug resistance is closely related to the abnormal expressions of long non-coding RNAs (lncRNAs).

METHODS AND RESULTS

This review aimed to summarize the molecular mechanisms underlying the association of lncRNAs and the development of drug resistance and to find potential strategies for the clinical diagnosis and treatment of cancer drug resistance. Studies showed that lncRNAs can regulate the expression of genes through chromatin remodeling, transcriptional regulation, and post-transcriptional processing. Furthermore, lncRNAs have been reported to be closely related to the occurrence of malignant tumors. In summary, lncRNAs have gained attention in related fields during recent years. According to previous studies, lncRNAs have a vital role in several different types of cancers owing to their multiple mechanisms of action. Different mechanisms have different functions that could result in different consequences in the same disease.

CONCLUSIONS

LncRNAs closely participated in cancer drug resistance by regulating miRNA, signaling pathways, proteins, cancer stem cells, pro- and ant-apoptosis, and autophagy. lncRNAs can be used as biomarkers of the possible treatment target in chemotherapy, which could provide solutions to the problem of drug resistance in chemotherapy in the future.

MicroRNAs as the critical regulators of Doxorubicin resistance in breast tumor cells

BACKGROUND

Chemotherapy is one of the most common treatment options for breast cancer (BC) patients. However, about half of the BC patients are chemotherapeutic resistant. Doxorubicin (DOX) is considered as one of the first line drugs in the treatment of BC patients whose function is negatively affected by multi drug resistance. Due to the severe side effects of DOX, it is very important to diagnose the DOX resistant BC patients. Therefore, assessment of molecular mechanisms involved in DOX resistance can improve the clinical outcomes in BC patients by introducing the novel therapeutic and diagnostic molecular markers. MicroRNAs (miRNAs) as members of the non-coding RNAs family have pivotal roles in various cellular processes including cell proliferation and apoptosis. Therefore, aberrant miRNAs functions and expressions can be associated with tumor progression, metastasis, and drug resistance. Moreover, due to miRNAs stability in body fluids, they can be considered as non-invasive diagnostic markers for the DOX response in BC patients.

MAIN BODY

In the present review, we have summarized all of the miRNAs that have been reported to be associated with DOX resistance in BC for the first time in the world.

CONCLUSIONS

Since, DOX has severe side effects; it is required to distinguish the non DOX-responders from responders to improve the clinical outcomes of BC patients. This review highlights the miRNAs as pivotal regulators of DOX resistance in breast tumor cells. Moreover, the present review paves the way of introducing a non-invasive panel of prediction markers for DOX response among BC patients.

Fecal Metabolic Profiling of Breast Cancer Patients during Neoadjuvant Chemotherapy Reveals Potential Biomarkers

Breast cancer (BC) is the most common form of cancer among women worldwide. Despite the huge advancements in its treatment, the exact etiology of breast cancer still remains unresolved. There is an increasing interest in the role of the gut microbiome in modulating the anti-cancer therapeutic response. It seems that alteration of the microbiome-derived metabolome potentially promotes carcinogenesis. Taken together, metabolomics has arisen as a fascinating new omics field to screen promising metabolic biomarkers. In this study, fecal metabolite profiling was performed using NMR spectroscopy, to identify potential biomarker candidates that can predict response to neoadjuvant chemotherapy (NAC) for breast cancer. Metabolic profiles of feces from patients (n = 8) following chemotherapy treatment cycles were studied. Interestingly, amino acids were found to be upregulated, while lactate and fumaric acid were downregulated in patients under the second and third cycles compared with patients before treatment. Furthermore, short-chain fatty acids (SCFAs) were significantly differentiated between the studied groups. These results strongly suggest that chemotherapy treatment plays a key role in modulating the fecal metabolomic profile of BC patients. In conclusion, we demonstrate the feasibility of identifying specific fecal metabolic profiles reflecting biochemical changes that occur during the chemotherapy treatment. These data give an interesting insight that may complement and improve clinical tools for BC monitoring.

CT1-3, a novel magnolol-sulforaphane hybrid suppresses tumorigenesis through inducing mitochondria-mediated apoptosis and inhibiting epithelial mesenchymal transition

Chemotherapy is recognized as one of the indispensable treatment for solid tumors. However, the emergent drug resistance and undesirable side effects have become a substantial challenge and the bottleneck of cancer chemotherapy. Magnolol (MAG) is a natural polyphenol with various bioactivities. Sulforaphane (SFN) is identified as one of the most effective naturally occurring anticancer agents. In this study, we successfully synthesized the magnolol-sulforaphane (MAG-SFN) hybrid CT1-3, showcasing more efficient anticancer activity than its lead compounds MAG and SFN with IC₅₀ values ranging from 5.10 to 14.06 μM in multiple cancer cells. We also demonstrated that CT1-3 elicited a strong antitumor effect in vivo but has no hepatic and renal toxicity. Furthermore, we found out CT1-3 treatment resulted in reduction of Bcl-2 and XIAP levels, in addition to increase of phospho-JNK and Bax levels, leading to mitochondria-mediated apoptosis in human cancer cells. Moreover, we revealed that CT1-3 could reduce the capacity of migration and invasion of human cancer cells via regulating the E-cadherin/Snail axis. Taken together, we provided strong evidences that the first example of MAG-SFN hybrid CT1-3 is a promising anticancer drug candidate without apparent adverse effects, which suppresses tumorigenesis partly through inducing mitochondria-mediated apoptosis and inhibiting epithelial mesenchymal transition (EMT).

Research Progress on Long Non-coding RNAs and Drug Resistance of Breast Cancer

Breast cancer, as the foremost cause of women's death in the world, is highly metastatic and mutable. Resistance to drugs for chemotherapies, endocrine therapies, and targeted therapies is an important factor that impacts the prognosis of breast cancer. Long non-coding ribonucleic acids (LncRNAs) are crucial regulators of intracellular gene expressions. Some researchers have suggested that expression level of several types of LncRNAs were closely related to the prognosis of patients with breast cancer. LncRNAs significantly impact biological processes such as drug transport, detoxication, apoptosis, epithelial to mesenchymal transition (EMT), and autophagy by regulating intracellular signaling pathways such as multi-drug resistance gene 1 (MDR1), nuclear factor erythroid 2-related factor 2 (NRF2), phosphoinositide 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR), transforming growth factor-β (TGF-β), BRCA1/2, and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). This paper will summarize research progress on correlations between LncRNA and drug resistance of breast cancer. It will particularly expound molecular mechanisms through which LncRNAs regulate drug resistance of breast cancer. It will further discuss the feasibility as molecular markers for forecasting drug resistance of breast cancer and may be becoming new targets for treating breast cancer in the future.

A Randomized, Open-label, Presurgical, Window-of-Opportunity Study Comparing the Pharmacodynamic Effects of the Novel Oral SERD AZD9496 with Fulvestrant in Patients with Newly Diagnosed ER+ HER2- Primary Breast Cancer

PURPOSE

Fulvestrant, the first-in-class selective estrogen receptor (ER) degrader (SERD), is clinically effective in patients with ER⁺ breast cancer, but it has administration and pharmacokinetic limitations. Pharmacodynamic data suggest complete ER degradation is not achieved at fulvestrant's clinically feasible dose. This presurgical study (NCT03236974) compared the pharmacodynamic effects of fulvestrant with AZD9496, a novel, orally bioavailable, nonsteroidal, potent SERD, in treatment-naïve patients with ER⁺ HER2^- primary breast cancer awaiting curative intent surgery.

PATIENTS AND METHODS

Patients were randomized 1:1 to receive AZD9496 250 mg twice daily from day 1 for 5-14 days, or fulvestrant 500 mg on day 1. On-treatment imaging-guided core tumor biopsies were taken between day 5 and 14 and compared with pretreatment diagnostic biopsies. The primary objective was to compare the effects of AZD9496 and fulvestrant on ER expression. Secondary objectives included changes in progesterone receptor (PR) and Ki-67 pharmacokinetic/pharmacodynamic relationships and safety.

RESULTS

Forty-six women received treatment (AZD9496 n = 22; fulvestrant n = 24); 35 paired biopsies were evaluable (AZD9496 n = 15; fulvestrant n = 20). The least square mean estimate for ER H-score reduction was 24% after AZD9496 versus 36% after fulvestrant treatment (P = 0.86). AZD9496 also reduced PR H-scores (-33.3%) and Ki-67 levels (-39.9%) from baseline, but was also not superior to fulvestrant (PR: -68.7%, P = 0.97; Ki-67: -75.4%, P = 0.98). No new safety findings were identified.

CONCLUSIONS

This was the first presurgical study to demonstrate that an oral SERD affects its key biological targets. However, AZD9496 was not superior to fulvestrant at the dose tested.

Clinical Relevance of Immune Checkpoints on Circulating Tumor Cells in Breast Cancer

The role of CD47 and PD-L1 expression on circulating tumor cells (CTCs) remains unclear, and it is currently unknown whether their distribution varies between the blood and tumor tissue in breast cancer (BC). In this study, CD47 and PD-L1 expression was investigated a) on peripheral blood mononuclear cell (PBMC) cytospins from early (n = 100) and metastatic (n = 98) BC patients, by triple immunofluorescence for CD47/PD-L1/Cytokeratins, and b) on matched primary and/or metastatic tumor tissue from CTC-positive patients using immunohistochemistry. CD47+and/orPD-L1+ CTCs were detected in 11%, 16.9%, and 29.6% of early, recurrent, and de novo metastatic patients (p = 0.016). In metastatic disease, CD47^highand/orPD-L1^high CTCs were associated with disease progression (p = 0.005) and shorter progression-free survival (PFS) (p = 0.010), and independently predicted for an increased risk of relapse (HR: 2.719; p = 0.008) and death (HR: 2.398; p = 0.034). PD-L1 expression rates differed between CTCs and tissue tumor cells and between peripheral blood mononuclear cells (PBMCs) and tumor-infiltrating lymphocytes (TILs) (positive concordance of 3.8% and 4%, respectively). CD47 expression also differed between CTCs and tumor cells (positive concordance of 11.5%). In conclusion, CTCs expressing CD47 and PD-L1 have independent poor prognostic implications in metastatic BC, indicating a potential role of innate and adaptive immune evasion mechanisms in their metastatic potential. The clinical value of the parallel assessment of the peripheral and local immune response merits further evaluation in BC.

CDK4/6 inhibitors in breast cancer - from in vitro models to clinical trials

Background: Breast cancer (BC) is one of the leading causes of cancer-related deaths worldwide. Standard therapies aim to disrupt pathways that regulate the growth and survival of BC cells. Therapeutic agents such as endocrine therapy target hormone dependent cancer cells and have shown to be suitable approaches in BC treatment. However, in the case of metastatic BC, curative options are limited, thus strategies have been explored to improve survival and clinical benefit. In this review we provide an up to date overview of the development of anti-cancer agents, particularly the newly developed CDK4/6 inhibitors.Material and methods: A search of PubMed was conducted to identify preclinical data surrounding the development of endocrine therapy and CDK4/6 inhibitors in early and metastatic BC. Clinical data were also sought using PubMed and clinicaltrials.gov.Results: Agents targeting oestrogen and its receptor have demonstrated positive outcomes in clinical trial with improvements in objective responses and overall survival. However, patients do exhibit adverse effects and some will eventually fail to respond to endocrine therapy. Subsequently, the development and success of 3rd generation CDK4/6 inhibitors in preclinical studies has allowed their introduction in clinical studies. In patients with ER + BC, CDK4/6 have demonstrated dramatic improvements in progression free survival when used in combination with endocrine therapies. Similar findings were also observed in metastatic disease. Adverse effects were limited in CDK4/6 treated patients, demonstrating the safety of these agents.Conclusion: CDK4/6 inhibitors are highly specific making them a safe and viable therapeutic for BC and there is increasing evidence of their potential to improve survival, even in the metastatic setting. Although a number of trials have demonstrated this, as a lone therapy or in combination, optimisation of treatment scheduling are still required in further clinical investigations.

Intrinsic adriamycin resistance in p53-mutated breast cancer is related to the miR-30c/FANCF/REV1-mediated DNA damage response

Adriamycin(ADR) is still considered to be one of the most effective agents in the treatment of breast cancer (BrCa), its efficacy is compromised by intrinsic resistance or acquire characteristics of multidrug resistance. At present, there are few genetic alterations that can be exploited as biomarkers to guide targeted use of ADR in clinical. Therefore, exploring the determinants of ADR sensitivity is pertinent for their optimal clinical application. TP53 is the most frequently mutated gene in human BrCa, p53 mutation has been reported to be closely related to ADR resistance, whereas the underlying mechanisms that cause endogenous ADR resistance in p53-mutant BrCa cells are not completely understood. The aim of the present study was to investigate the potential roles of miRNA in the response to ADR in p53-mutated breast cancer. Here, we report that BrCa cells expressing mutp53 are more resistant to ADR than cells with wild-type p53 (wtp53). The DNA repair protein- Fanconi anemia complementation group F protein (FANCF) and the translesion synthesis DNA polymerase REV1 protein is frequently abundant in the context of mutant p53 of BrCa. By targeting two key factors, miR-30c increases the sensitivity of BrCa cells to ADR. Furthermore, p53 directly activates the transcription of miR-30c by binding to its promoter. Subsequent analyses revealed that p53 regulates REV1 and FANCF by modulating miR-30c expression. Mutation of the p53 abolished this response. Consistently, reduced miR-30c expression is highly correlated with human BrCa with p53 mutational status and is associated with poor survival. We propose that one of the pathways affected by mutant p53 to increase intrinsic resistance to ADR involves miR-30c downregulation and the consequent upregulation of FANCF and REV1. The novel miRNA-mediated pathway that regulates chemoresistance in breast cancer will facilitate the development of novel therapeutic strategies.

Knockdown of lncRNA-HOTAIR downregulates the drug-resistance of breast cancer cells to doxorubicin via the PI3K/AKT/mTOR signaling pathway

The resistance to chemotherapeutic drugs is a critical feature of breast cancer recurrence and metastasis. Long non-coding RNAs (LncRNAs) serve key roles in tumor drug resistance. LncRNA-HOX transcript antisense RNA (HOTAIR) has been reported to be overexpressed in certain types of cancer and may be closely associated with tumor resistance. The current study aimed to investigate the role of lncRNA-HOTAIR in the regulation of breast cancer resistance to doxorubicin (DOX). A breast cancer cell line (MCF-7) and DOX-resistant breast cancer cell line (DOXR-MCF-7) were utilized in the current study. DOXR-MCF-7 cells were transfected with lncRNA-HOTAIR small interfering RNA (siRNA) and control siRNA. Subsequently, MTT and colony formation assays were performed to assess cell proliferation. Cell apoptosis was also evaluated via flow cytometry. In addition, western blotting and reverse transcription-quantitative polymerase chain reaction were performed to detect the expression of caspase-3, B-cell lymphoma 2, Bcl-2-associated X protein, phosphoinositide 3-kinase (PI3K), protein kinase B (AKT) and mechanistic target of rapamycin (mTOR), and the phosphorylation of PI3K, AKT, and mTOR. The data indicated that lncRNA-HOTAIR silencing decreased cell proliferation and increased apoptosis in MCF-7 and DOXR MCF-7 cells. Furthermore, lncRNA-HOTAIR silencing significantly decreased the phosphorylation of PI3K, AKT and mTOR, indicating that the knockdown of lncRNA-HOTAIR effectively attenuates the resistance of breast cancer cells to DOX by inhibiting the PI3K/AKT/mTOR pathway. In summary, the present study indicated that the knockdown of lncRNA-HOTAIR weakened the resistance of breast cancer cells to DOX via PI3K/AKT/mTOR signaling, suggesting that lncRNA-HOTAIR may be a novel intervention target to reverse DOX-resistance in breast cancer.

Atorvastatin Inhibits Breast Cancer Cells by Downregulating PTEN/AKT Pathway via Promoting Ras Homolog Family Member B (RhoB)

Background

Breast cancer (BC) is one of the most common malignant tumors in women around the world. Atorvastatin (ATO) was found to be associated with a decreased risk of recurrence and mortality in cancer. But the exact mechanism of its carcinostatic effects is unclear. The expression level of Ras homolog family member B (RhoB) in breast cancer cells was found to be upregulated after being treated with ATO. Thus, we conjecture that altered expression of RhoB induced by ATO may be decisive for the migration and progression of breast cancer.

Methods

The effects of ATO on breast tumor cells in vivo and in vitro were detected by clone formation assay, CCK-8 assay, flow cytometry, wound healing, transwell assays, tumor xenograft model, and immunohistochemistry. Distribution of RhoB in different breast cancer tissues and its influence on prognosis were analyzed using the data from TCGA or GEO databases. The relationship between RhoB and PTEN/AKT pathway was detected by Western blotting and RT-qPCR.

Results

ATO inhibits proliferation, invasion, EMT, and PTEN/AKT pathway and promotes apoptosis in breast tumor cells. In addition, ATO inhibits the volume and weight of breast tumor in tumor-bearing mice and upregulated RhoB in tumor tissues. The expression of RhoB in mRNA and protein level was upregulated in statin-treated breast cancer cells and downregulated in cancer tissues. Low expression of RhoB links with poor prognosis in patients with breast cancer (HR = 0.74[0.66-0.83], p =7e^-8, log-rank test). Further research found that RhoB inhibits the proliferation, invasion, EMT, and PTEN/AKT signal pathway in breast tumor cells.

Conclusions

The exact mechanism of ATO's carcinostatic effects in breast cancer is related to downregulating PTEN/AKT pathway via promoting RhoB. Our study also demonstrates the potential applicability of RhoB as a therapeutic target for breast cancer.

Strategies to degrade estrogen receptor α in primary and ESR1 mutant-expressing metastatic breast cancer

With the advent of omic technologies, our understanding of the molecular mechanisms underlying estrogen receptor α (ERα)-expressing breast cancer (BC) progression has grown exponentially. Nevertheless, the most widely used therapy for inhibiting this disease is endocrine therapy (ET) (i.e., aromatase inhibitors, tamoxifen - Tam, faslodex/fulvestrant - FUL). However, in a considerable number of cases, prolonged patient treatment with ET generates the development of resistant tumor cells and, consequently, tumor relapse, which manifests as metastatic disease that is extremely difficult to manage, especially because such metastatic BCs (MBCs) often express ERα mutations (e.g., Y537S, D538G) that confer pronounced growth advantages to tumor cells. Interestingly, ET continues to be the therapy of choice for this neoplasia, which underscores the need to identify novel drugs that could work in primary and MBCs. In this study, we review the approaches that have been undertaken to discover these new anti-ERα compounds, especially considering those focused on evaluating ERα degradation. A literature analysis demonstrated that current strategies for discovering new anti-BC drugs are focusing on the identification either of novel ERα inhibitors, of compounds that inhibit ERα-related pathways or of drugs that influence ERα-unrelated cellular pathways. Several lines of evidence suggest that all of these molecules alter the ERα content and block the proliferation of both primary and MBCs. In turn, we propose to rationalize all these discoveries into the definition of e.m.eral.d.s (i.e., selective modulators of ERα levels and degradation) as a novel supercategory of anti-ERα drugs that function both as modulators of ERα levels and inhibitors of BC cell proliferation.

The transcriptional coactivator WBP2 primes triple-negative breast cancer cells for responses to Wnt signaling via the JNK/Jun kinase pathway

The transcriptional coactivator WW domain-binding protein 2 (WBP2) is an emerging oncogene and serves as a node between the signaling protein Wnt and other signaling molecules and pathways, including epidermal growth factor receptor, estrogen receptor/progesterone receptor, and the Hippo pathway. The upstream regulation of WBP2 is well-studied, but its downstream activity remains unclear. Here, we elucidated WBP2's role in triple-negative breast cancer (TNBC), in which Wnt signaling is predominantly activated. Using RNAi coupled with RNA-Seq and MS analyses to identify Wnt/WBP2- and WBP2-dependent targets in MDA-MB-231 TNBC cells, we found that WBP2 is required for the expression of a core set of genes in Wnt signaling. These included AXIN2, which was essential for Wnt/WBP2-mediated breast cancer growth and migration. WBP2 also regulated a much larger set of genes and proteins independently of Wnt, revealing that WBP2 primes cells to Wnt activity by up-regulating G protein pathway suppressor 1 (GPS1) and TRAF2- and NCK-interacting kinase (TNIK). GPS1 activated the c-Jun N-terminal kinase (JNK)/Jun pathway, resulting in a positive feedback loop with TNIK that mediated Wnt-induced AXIN2 expression. WBP2 promoted TNBC growth by integrating JNK with Wnt signaling, and its expression profoundly influenced the sensitivity of TNBC to JNK/TNIK inhibitors. In conclusion, WBP2 links JNK to Wnt signaling in TNBC. GPS1 and TNIK are constituents of a WBP2-initiated cascade that primes responses to Wnt ligands and are also important for TNBC biology. We propose that WBP2 is a potential drug target for JNK/TNIK-based precision medicine for managing TNBC.

Three dimensional primary cultures for selecting human breast cancers that are sensitive to the anti-tumor activity of ipatasertib or taselisib in combination with anti-microtubule cytotoxic drugs

Two inhibitors of phosphatidylinositol 3-kinase (PI3K) pathway taselisib, targeting the mutant PI3K-subunit-alpha (PI3KA) and ipatasertib, AKT-inhibitor, are currently under clinical investigation in breast cancer (BC) patients. We have previously demonstrated the anti-tumor efficacy of these anti-PI3K/AKT-inibitors in combination with anti-microtubule drugs in human BC cell lines, through a complete cytoskeleton disorganization. In this work, we generated ex-vivo three-dimensional (3D) cultures from human BC as a model to test drug efficacy and to identify new molecular biomarkers for selection of BC patients suitable for anti-PI3K/AKT-inibitors treatment. We have established 3D cultures from 25/27 human BC samples, in which the ability of growth in vitro replicates the clinical and biological aggressiveness of the original tumors. According to the results of next generation sequencing analysis, a direct correlation was found between PI3KA mutations and the sensitivity in 3D models in vitro to taselisib and ipatasertib alone and combined with anti-microtubule agents. Moreover, mutations in HER and MAPK families related genes, including EGFR, KRAS and BRAF, were found in resistant samples, suggesting their potential role as negative predictive factors of response to these agents. Thus, we demonstrated that ex vivo 3D cultures from human BC patients allow a rapid and efficient drug screening for chemotherapies and targeted agents in genetically selected patients and represent an innovative model to identify new biomarkers of drug resistance.

Effect of resveratrol on doxorubicin resistance in breast neoplasm cells by modulating PI3K/Akt signaling pathway

In the study, we probed into the effect of Resveratrol (RES) on Doxorubicin (DOX)-resistant breast neoplasm cell line MCF-7/DOX as well as the mechanism of RES underlying the DOX-resistant breast cancer. CCK-8 assay was utilized to assess the survival rates and sensitivity of breast neoplasm cell lines MCF-7 or MDA-MB-231 to DOX and RES. DOX-resistant MCF-7 cell line was successfully cultivated with DOX dose increasing and was named MCF-7/DOX. Afterwards, wound healing and Transwell assays were performed to measure the migration and invasion capabilities of MCF-7/DOX cells, while cell propagation and apoptosis were determined by colony formation assay and flow cytometry analysis. Both western blotting and immunohistochemistry were conducted to examine the expression of proteins involved in PI3K/Akt signaling pathway. Nude mice xenograft model was constructed to further verify the effects of DOX and RES on breast neoplasm in vivo. RES restored DOX sensitivity in MCF-7/DOX cells, inhibiting biological functions of MCF-7/DOX cells and promoting cell apoptosis in vitro and impeding tumor growth in vivo. It was revealed by the mechanistic studies that MCF-7/DOX cells could regain the drug sensibility with RES treatment through inactivating the PI3K/Akt signal transduction pathway. RES could reverse DOX resistance in breast neoplasm cells and inhibited DOX-resistant breast cancer cell propagation and metastasis and facilitated cell apoptosis by modulating PI3K/Akt signaling pathway. © 2018 IUBMB Life, 70(6):491-500, 2018.

Evaluation of the Cytotoxic and Autophagic Effects of Atorvastatin on MCF-7 Breast Cancer Cells

Background:

Recently, cytotoxic effects of statins on breast cancer cells have been reported. However, the mechanism of anti-proliferative effects is currently unknown. Autophagy is non-apoptotic programmed cell death, which is characterized by degradation of cytoplasmic components and as having a role in cancer pathogenesis.

Aims:

To investigate the anti-proliferative effects of atorvastatin on MCF-7 human breast adenocarcinoma cells with respect to both autophagy and apoptosis.

Study Design:

Cell culture study.

Methods:

Cell viability was analyzed using WST-1 cell proliferation assay. Apoptosis was determined by the TUNEL method, whereas autophagy was assessed by Beclin-1 and LC3B immunofluorescence staining. Ultrastructural analysis of cells was performed by electron microscopy.

Results:

Atorvastatin reduced MCF-7 cell proliferation in a dose- and time-dependent manner inducing TUNEL-, Beclin-1-, and LC3B-positive cells. Moreover, ultrastructural analysis showed apoptotic, autophagic, and necrotic morphological changes in treatment groups. A statistically significant increase in the apoptotic index was detected with higher concentrations of atorvastatin at 24 h and 48 h (p<0.05).

Conclusion:

The anti-proliferative effects of atorvastatin on breast cancer cells is mediated by the induction of both apoptosis and autophagy which shows statins as a potential treatment option for breast cancer.

Autophagy is essential for flavopiridol‑induced cytotoxicity against MCF‑7 breast cancer cells

Flavopiridol (FP) exerts antitumoral effects by triggering tumor cell cycle arrest and cytotoxicity in human breast cancer cell lines. The potent antitumor activity of FP is through its inhibition of cyclin‑dependent kinases; however, this may not be the only mechanism of action. The present study aimed to investigate whether FP is able to induce autophagy and to examine the effects of autophagy on cell death in FP‑treated MCF‑7 human breast cancer cells. MCF‑7 cells were treated with either FP alone or FP in combination with chloroquine (CQ). Expression levels of autophagy‑related protein LC3B‑II and p62/sequestosome 1 (SQSTM1) were used to monitor autophagic flux. MCF‑7 cells were transfected with autophagy‑related 5 (ATG5) small interfering (si)RNA to block autophagy. Cell viability and cell cycle status were determined. Following incubation with FP, MCF‑7 cells exhibited significantly higher autophagy compared with untreated control cells, and the level of autophagy is comparable with cells under rapamycin induction, which was verified by immunodetection of LC3B‑II and p62/SQSTM1 expression and inhibition by CQ. The addition of CQ treatment or ATG5‑siRNA transfection against autophagy components attenuated the cytotoxic effects of FP treatment of MCF‑7 cells. Furthermore, this autophagy inhibition did not impair the FP‑induced cell cycle arrest. These results revealed that autophagy may be involved in FP‑induced MCF‑7 cell death and autophagy inhibition enhanced the tumor cell pro‑survival ability. It is possibly that potential autophagy regulatory drugs may be used as a chemotherapy adjuvant.

Phosphatidylinositol 3-kinase (PI3Kα)/AKT axis blockade with taselisib or ipatasertib enhances the efficacy of anti-microtubule drugs in human breast cancer cells

Purpose

The Phosphatidylinositol 3-kinase (PI3Ks) pathway is commonly altereted in breast cancer patients, but its role is still unclear. Taselisib, a mutant PI3Kα selective inhibitor, and ipatasertib, an AKT inhibitor, are currently under investigation in clinical trials in combination with paclitaxel or hormonal therapies in breast cancer. The aim of this study was to evaluate if PI3K or AKT inhibition can prevent resistance to chemotherapy and potentiate its efficacy.

Experimental design

The efficacy of combined treatment of ipatasertib and taselisib plus vinorelbine or paclitaxel or eribulin was evaluated in vitro on human breast cancer cells (with different expression profile of hormonal receptors, HER2, and of PI3Ka mutation) on cell survival by using MTT (3,(4,5-dimethylthiazol-2)2,5 difeniltetrazolium bromide) and colony forming assays on cell apoptosis by flow-cytometry analysis. We also investigated the effect of combined treatment on downstream intracellular signaling, by western blot analysis, and on metastatic properties, by migration assays. Finally, we analyzed changes in cell cytoskeleton by immunofluorescence.

Results

A significant synergism of ipatasertib or taselisib plus anti-microtubule chemotherapy in terms of anti-proliferative, pro-apoptotic and anti-metastatic effect was observed. The combined treatment completely inhibited the activation of proteins downstream of PI3K and MAPK pathways and affected the expression of survivin. Combined treatments completely disorganized the cytoskeleton in human breast cancer cells, with contemporary delocalization of survivin from cytoplasm to nucleus, thus suggesting a potential mechanism for this combination.

Conclusions

Targeting PI3K may enhance the efficacy of anti-microtubule drugs in human breast cancer cells.

A current and comprehensive review of cyclin-dependent kinase inhibitors for the treatment of metastatic breast cancer

BACKGROUND

Resistance to endocrine treatment generally occurs over time, especially in the metastatic stage. In this paper, we aimed to review the mechanisms of cyclin-dependent kinase (CDK) 4/6 inhibition and clinical usage of new agents in the light of recent literature updates.

SCOPE

A literature search was carried out using PubMed, Medline and ASCO and ESMO annual-meeting abstracts by using the following search keywords; "palbociclib", "abemaciclib", "ribociclib", "cyclin-dependent kinase inhibitors" and "CDK 4/6" in metastatic breast cancer (MBC). The last search was on 10 June 2017.

FINDINGS

CDKs and cyclins are two molecules that have a key role in cell cycle progression. Today, there are three highly selective CDK4/6 inhibitors in clinical development - palbociclib, ribociclib and abemaciclib. Palbociclib and ribociclib were recently approved by the US FDA in combination with letrozole for the treatment of MBC in a first-line setting, as well as palbociclib in combination with fulvestrant for hormone-receptor (HR)-positive MBC that had progressed while on previous endocrine therapy according to the PALOMA-1, MONALEESA-2 and PALOMA-3 trials, respectively. In the recently published randomized phase III MONARCH 2 trial, abemaciclib plus letrozole had longer progression-free survival and higher objective response rates with less serious adverse events in advanced HR-positive breast cancer previously treated with hormonal treatment.

CONCLUSION

CDK4/6 inhibition is a new and promising target for patients with hormone-receptor-positive MBC. Both palbociclib and ribociclib showed significant additive benefit for patients receiving first-line treatment for HR-positive, epidermal growth factor receptor-2-negative advanced breast cancer. Palbociclib and abemaciclib also had significant activity in combination with fulvestrant for patients with MBC that progressed on previous endocrine therapy.

Synthesis of Saccharumoside-B analogue with potential of antiproliferative and pro-apoptotic activities

A new series of phenolic glycoside esters, saccharumoside-B and its analogs (9b-9n, 10) have been synthesized by the Koenigs-Knorr reaction. Antiproliferative activities of the compounds (9b-9n, 10) were evaluated on various cancer cell lines including, MCF-7 breast, HL-60 leukemia, MIA PaCa-2 pancreatic, DU145 prostate, HeLa cervical and CaCo-2 colon, as well as normal human MCF10A mammary epithelial and human peripheral blood mononuclear cells (PBMC) by MTT assay. Compounds (9b-9n, 10) exhibited considerable antiproliferative effects against cancer cells with IC₅₀ range of 4.43 ± 0.35 to 49.63 ± 3.59 µM, but they are less cytotoxic on normal cells (IC₅₀ > 100 µM). Among all the compounds, 9f showed substantial antiproliferative activity against MCF-7 and HL-60 cells with IC₅₀ of 6.13 ± 0.64 and 4.43 ± 0.35, respectively. Further mechanistic studies of 9f were carried out on MCF-7 and HL-60 cell lines. 9f caused arrest of cell cycle of MCF-7 and HL-60 cells at G0/G1 phase. Apoptotic population elevation, mitochondrial membrane potential loss, increase of cytosolic cytochrome c and Bax levels, decrease of Bcl-2 levels and enhanced caspases-9 and -3 activities were observed in 9f-treated MCF-7 and HL-60 cells. These results demonstrate anticancer and apoptosis-inducing potentials of 9f in MCF-7 and HL-60 cells via intrinsic pathway.

DMXL2 drives epithelial to mesenchymal transition in hormonal therapy resistant breast cancer through Notch hyper-activation

The acquisition of endocrine therapy resistance in estrogen receptor α (ERα) breast cancer patients represents a major clinical problem. Notch signalling has been extensively linked to breast cancer especially in patients who fail to respond to endocrine therapy. Following activation, Notch intracellular domain is released and enters the nucleus where activates transcription of target genes. The numerous steps that cascade after activation of the receptor complicate using Notch as biomarker. Hence, this warrants the development of reliable indicators of Notch activity. DMXL2 is a novel regulator of Notch signalling not yet investigated in breast cancer. Here, we demonstrate that DMXL2 is overexpressed in a subset of endocrine therapy resistant breast cancer cell lines where it promotes epithelial to mesenchymal transition through hyper-activation of Notch signalling via V-ATPase dependent acidification. Following DMXL2 depletion or treatment with Bafilomycin A1, both EMT targets and Notch signalling pathway significantly decrease. We show for the first time that DMXL2 protein levels are significantly increased in ERα positive breast cancer patients that progress after endocrine therapy. Finally, we demonstrate that DMXL2 is a transmembrane protein with a potential extra-cellular domain. These findings identify DMXL2 as a novel, functional biomarker for ERα positive breast cancer.

Cyclin-Dependent Kinase Inhibitors for the Treatment of Breast Cancer: Past, Present, and Future

Treatment of metastatic breast cancer (MBC) that is resistant to endocrine therapy presents a significant clinical challenge. The well-known role of cell cycle dysregulation in these patients is partly mediated by cyclin-dependent kinase (CDK) activity. Specific cyclin and CDK complexes regulate cell cycle progression by managing the transition through the cell cycle, and inhibition of CDKs represents an important target for novel agents. First-generation CDK inhibitors (e.g., flavopiridol) were relatively nonselective and had an unacceptable toxicity profile in early trials. Second-generation CDK inhibitors were designed to target the CDK4 and CDK6 (CDK4/6) pathway and have shown promising clinical activity with an acceptable toxicity profile in patients with MBC. Palbociclib is a first-in-class CDK4/6 inhibitor that was granted accelerated U.S. Food and Drug Administration approval in combination with letrozole for the treatment of MBC in the first-line setting (February 2015) as well as in combination with fulvestrant for MBC that had progressed on previous endocrine therapy (February 2016). Other CDK4/6 inhibitors, including ribociclib and abemaciclib, are under investigation as monotherapy and in combination with endocrine or anti-human epidermal growth receptor 2 therapy for the treatment of MBC. Ongoing clinical trials should provide additional information to guide the appropriate use of these agents and identify patient populations that could derive the most benefit.

MDM2 turnover and expression of ATRX determine the choice between quiescence and senescence in response to CDK4 inhibition

CDK4 inhibitors (CDK4i) earned Breakthrough Therapy Designation from the FDA last year and are entering phase III clinical trials in several cancers. However, not all tumors respond favorably to these drugs. CDK4 activity is critical for progression through G1 phase and into the mitotic cell cycle. Inhibiting this kinase induces Rb-positive cells to exit the cell cycle into either a quiescent or senescent state. In this report, using well-differentiated and dedifferentiated liposarcoma (WD/DDLS) cell lines, we show that the proteolytic turnover of MDM2 is required for CDK4i-induced senescence. Failure to reduce MDM2 does not prevent CDK4i-induced withdrawal from the cell cycle but the cells remain in a reversible quiescent state. Reducing MDM2 in these cells drives them into the more stable senescent state. CDK4i-induced senescence associated with loss of MDM2 is also observed in some breast cancer, lung cancer and glioma cell lines indicating that this is not limited to WD/DDLS cells in which MDM2 is overexpressed or in cells that contain wild type p53. MDM2 turnover depends on its E3 ligase activity and expression of ATRX. Interestingly, in seven patients the changes in MDM2 expression were correlated with outcome. These insights identify MDM2 and ATRX as new regulators controlling geroconversion, the process by which quiescent cells become senescent, and this insight may be exploited to improve the activity of CDK4i in cancer therapy.

AZD9496: An Oral Estrogen Receptor Inhibitor That Blocks the Growth of ER-Positive and ESR1-Mutant Breast Tumors in Preclinical Models

Fulvestrant is an estrogen receptor (ER) antagonist administered to breast cancer patients by monthly intramuscular injection. Given its present limitations of dosing and route of administration, a more flexible orally available compound has been sought to pursue the potential benefits of this drug in patients with advanced metastatic disease. Here we report the identification and characterization of AZD9496, a nonsteroidal small-molecule inhibitor of ERα, which is a potent and selective antagonist and downregulator of ERα in vitro and in vivo in ER-positive models of breast cancer. Significant tumor growth inhibition was observed as low as 0.5 mg/kg dose in the estrogen-dependent MCF-7 xenograft model, where this effect was accompanied by a dose-dependent decrease in PR protein levels, demonstrating potent antagonist activity. Combining AZD9496 with PI3K pathway and CDK4/6 inhibitors led to further growth-inhibitory effects compared with monotherapy alone. Tumor regressions were also seen in a long-term estrogen-deprived breast model, where significant downregulation of ERα protein was observed. AZD9496 bound and downregulated clinically relevant ESR1 mutants in vitro and inhibited tumor growth in an ESR1-mutant patient-derived xenograft model that included a D538G mutation. Collectively, the pharmacologic evidence showed that AZD9496 is an oral, nonsteroidal, selective estrogen receptor antagonist and downregulator in ER(+) breast cells that could provide meaningful benefit to ER(+) breast cancer patients. AZD9496 is currently being evaluated in a phase I clinical trial. Cancer Res; 76(11); 3307-18. ©2016 AACR.

Overcoming Resistance to Endocrine Therapy in Breast Cancer: New Approaches to a Nagging Problem

In the majority of women, breast cancer progresses through increased transcriptional activity due to over-expressed oestrogen receptors (ER). Therapeutic strategies include: (i) reduction of circulating ovarian oestrogens or of peripherally produced oestrogen (in postmenopausal women) with aromatase inhibitors and (ii) application of selective ER modulators for receptor blockade. The success of these interventions is limited by the variable but persistent onset of acquired resistance and by an intrinsic refractiveness which manifests despite adequate levels of ER in about 50% of patients with advanced metastatic disease. Loss of functional ER leads to endocrine insensitivity, loss of cellular adhesion and polarity, and increased migratory potential due to trans-differentiation of the epithelial cancer cells into a mesenchymal-like phenotype (epithelial-mesenchymal transition; EMT). Multiple mechanisms contributing to therapeutic failure have been proposed: (i) loss or modification of ER expression including epigenetic mechanisms, (ii) agonistic actions of selective ER modulators that may be enhanced through an increased expression of co-activators, (iii) attenuation of the tamoxifen metabolism through expression of genetic variants of P450 cytochromes which leads to more or less active metabolites and (iv) increased growth factor signalling particularly through epidermal growth factor receptor activation of pathways involving keratinocyte growth factor, platelet-derived growth factor, and nuclear factor x03BA;B. In addition, the small non-coding microRNAs, recently recognized as critical gene regulators, exhibit differential expression in tamoxifen-sensitive versus resistant cell lines. Several studies suggest the potential of using these either as targets or as therapeutic agents to modulate EMT regulators as a means of reversing the aggressive metastatic phenotype by reversal of the EMT, with the added benefit of re-sensitization to anti-oestrogens.

The Src non-receptor tyrosine kinase paradigm: New insights into mammalian Sertoli cell biology

Src kinases are non-receptor tyrosine kinases that phosphorylate diverse substrates, which control processes such as cell proliferation, differentiation and survival; cell adhesion; and cell motility. c-Src, the prototypical member of this protein family, is widely expressed by several organs that include the testis. In the seminiferous epithelium of the adult rat testis, c-Src is highest at the tubule lumen during the release of mature spermatids. Other studies show that testosterone regulates spermatid adhesion to Sertoli cells via c-Src, indicating Src phosphorylates key substrates that prompt the disassembly of Sertoli cell-spermatid junctions. A more recent in vitro study reveals that c-Src participates in the internalization of proteins that constitute the blood-testis barrier, which is present between Sertoli cells, suggesting a similar mechanism of junction disassembly is at play during spermiation. In this review, we discuss recent findings on c-Src, with an emphasis on its role in spermatogenesis in the mammalian testis.

High Bak Expression Is Associated with a Favorable Prognosis in Breast Cancer and Sensitizes Breast Cancer Cells to Paclitaxel

Breast cancer has become the leading cause of cancer-related death among women. A large number of patients become resistant to drug chemotherapy. Paclitaxel (Taxol) is an effective chemotherapeutic agent used to treat cancer patients. Taxol has been widely used in human malignancies including breast cancer because it can stabilize microtubules resulting in cell death by causing an arrest during the G2/M phase of the cell cycle. Pro-apoptotic Bcl-2 antagonist killer 1 (Bak) plays an important role in Taxol-induced apoptosis in breast cancer. In our present study, we investigated the expression of the Bak protein and clinicopathological correlations in a large sample of breast cancer tissues by immunohistochemistry. We found that the percentage of high scores of Bak expression in breast cancer was significantly lower than that of the non-cancerous breast control tissue. In addition, lower Bak expression was positively associated with the clinical TNM stage of breast cancer with a significant decrease in overall survival compared with those with higher Bak expression especially in the Luminal and HER2 subtypes. Importantly, higher Bak expression predicted a favorable clinical outcome in the cases treated with Taxol indicated by a higher overall survival than that of patients with lower Bak expression especially in Luminal and HER2 subtypes. Furthermore, these results were confirmed in vitro since overexpression of Bak sensitized breast cancer cells to Taxol by inhibiting proliferation and promoting apoptosis; in contrast, downregulation of Bak through siRNA transfection inhibited Taxol induced-apoptosis. Therefore, our results demonstrate that Bak acts as a sensitive biomarker and favorable prognostic factor for Taxol treatment in breast cancer. The restoration of Bak expression would be therapeutically beneficial for Taxol resistant breast cancer patients.

Doxorubicin resistance in breast cancer is driven by light at night-induced disruption of the circadian melatonin signal

Chemotherapeutic resistance, particularly to doxorubicin (Dox), represents a major impediment to successfully treating breast cancer and is linked to elevated tumor metabolism and tumor over-expression and/or activation of various families of receptor- and non-receptor-associated tyrosine kinases. Disruption of circadian time structure and suppression of nocturnal melatonin production by dim light exposure at night (dLEN), as occurs with shift work, and/or disturbed sleep-wake cycles, is associated with a significantly increased risk of an array of diseases, including breast cancer. Melatonin inhibits human breast cancer growth via mechanisms that include the suppression of tumor metabolism and inhibition of expression or phospho-activation of the receptor kinases AKT and ERK1/2 and various other kinases and transcription factors. We demonstrate in tissue-isolated estrogen receptor alpha-positive (ERα+) MCF-7 human breast cancer xenografts, grown in nude rats maintained on a light/dark cycle of LD 12:12 in which dLEN is present during the dark phase (suppressed endogenous nocturnal melatonin), a significant shortening of tumor latency-to-onset, increased tumor metabolism and growth, and complete intrinsic resistance to Dox therapy. Conversely, a LD 12:12 dLEN environment incorporating nocturnal melatonin replacement resulted in significantly lengthened tumor latency-to-onset, tumor regression, suppression of nighttime tumor metabolism, and kinase and transcription factor phosphorylation, while Dox sensitivity was completely restored. Melatonin acts as both a tumor metabolic inhibitor and circadian-regulated kinase inhibitor to reestablish the sensitivity of breast tumors to Dox and drive tumor regression, indicating that dLEN-induced circadian disruption of nocturnal melatonin production contributes to a complete loss of tumor sensitivity to Dox chemotherapy.

Melatonin: an inhibitor of breast cancer

The present review discusses recent work on melatonin-mediated circadian regulation, the metabolic and molecular signaling mechanisms that are involved in human breast cancer growth, and the associated consequences of circadian disruption by exposure to light at night (LEN). The anti-cancer actions of the circadian melatonin signal in human breast cancer cell lines and xenografts heavily involve MT1 receptor-mediated mechanisms. In estrogen receptor alpha (ERα)-positive human breast cancer, melatonin suppresses ERα mRNA expression and ERα transcriptional activity via the MT1 receptor. Melatonin also regulates the transactivation of other members of the nuclear receptor superfamily, estrogen-metabolizing enzymes, and the expression of core clock and clock-related genes. Furthermore, melatonin also suppresses tumor aerobic metabolism (the Warburg effect) and, subsequently, cell-signaling pathways critical to cell proliferation, cell survival, metastasis, and drug resistance. Melatonin demonstrates both cytostatic and cytotoxic activity in breast cancer cells that appears to be cell type-specific. Melatonin also possesses anti-invasive/anti-metastatic actions that involve multiple pathways, including inhibition of p38 MAPK and repression of epithelial-mesenchymal transition (EMT). Studies have demonstrated that melatonin promotes genomic stability by inhibiting the expression of LINE-1 retrotransposons. Finally, research in animal and human models has indicated that LEN-induced disruption of the circadian nocturnal melatonin signal promotes the growth, metabolism, and signaling of human breast cancer and drives breast tumors to endocrine and chemotherapeutic resistance. These data provide the strongest understanding and support of the mechanisms that underpin the epidemiologic demonstration of elevated breast cancer risk in night-shift workers and other individuals who are increasingly exposed to LEN.

Targeting autophagy in breast cancer

Macroautophagy (referred to as autophagy here) is an intracellular degradation pathway enhanced in response to a variety of stresses and in response to nutrient deprivation. This process provides the cell with nutrients and energy by degrading aggregated and damaged proteins as well as compromised organelles. Since autophagy has been linked to diverse diseases including cancer, it has recently become a very interesting target in breast cancer treatment. Indeed, current clinical trials are trying to use chloroquine or hydroxychloroquine, alone or in combination with other drugs to inhibit autophagy during breast cancer therapy since chemotherapy and radiation, regimens that are used to treat breast cancer, are known to induce autophagy in cancer cells. Importantly, in breast cancer, autophagy has been involved in the development of resistance to chemotherapy and to anti-estrogens. Moreover, a close relationship has recently been described between autophagy and the HER2 receptor. Here, we discuss some of the recent findings relating autophagy and cancer with a particular focus on breast cancer therapy.

MEK inhibitor effective against proliferation in breast cancer cell

The targeted small-molecule drug AZD6244 is an allosteric, ATP-noncompetitive inhibitor of MEK1/2 that has shown activity against several malignant tumors. Here, we report that AZD6244 repressed cell growth and induced apoptosis and G1-phase arrest in the breast cancer cell lines MDA-MB-231 and HCC1937. Using microRNA (miRNA) arrays and quantitative RT-PCR, we found that miR-203 was up-regulated after AZD6244 treatment. In accordance with bioinformatics and luciferase activity analyses, CUL1 was found to be the direct target of miR-203. Furthermore, miR-203 inhibition and CUL1 overexpression reversed the cytotoxicity of AZD6244 on the MDA-MB-231 and HCC1937 cells. Collectively, our data indicate that miR-203 mediates the AZD6244-induced cytotoxicity of breast cancer cells and that the MEK/ERK/miR-203/CUL1 signaling pathway may participate in this process.