Combined deletion of Pten and p53 in mammary epithelium accelerates triple-negative breast cancer with dependency on eEF2K

eEF2K as an important kinase associated with cancer survival and prognosis

Eukaryotic Elongation Factor 2 Kinase (eEF2K), a member of the α-kinase family, services as a crucial negative regulator of protein synthesis, particularly under conditions of cellular stress. A pan-cancer analysis of eEF2K expression, genetic variants, and clinical relevance across multiple tumor types was performed using data from the Cancer Genome Atlas (TCGA) and GEO. Our findings suggest that eEF2K has dual roles in cancer progression, with its expression correlating with patient prognosis. Significant phosphorylation of eEF2 at T57, Y434, and T59 was observed, which may regulate protein synthesis during stress. The elevated T59 phosphorylation in COAD, despite the low eEF2K expression, indicates that this may be regulated by alternative kinases, such as AMPK or mTOR. This suggests that compensatory mechanisms may be involved. In addition to modulating eEF2 phosphorylation, eEF2K is involved in a number of other processes, including peptidyl-serine phosphorylation, the G2/M transition, and the MAPK cascade. The protein products of eEF2K are capable of localizing to the nucleus, cytoplasm, and cytosol, where they bind to a range of proteins, including ATP and calcium ions. These findings provide novel insights into the role of eEF2K in cancer biology and suggest that the targeting of eEF2K and eEF2 phosphorylation may offer promising therapeutic strategies.

DNA methylation profiling deciphers three EMT subtypes with distinct prognoses and therapeutic vulnerabilities in breast cancer

Background: Epithelial-mesenchymal transition (EMT), deemed a pivotal hallmark of tumours, is intricately regulated by DNA methylation and encompasses multiple states along tumour progression. The potential mechanisms that drive the intrinsic heterogeneity of breast cancer (BC) via EMT transformation have not been identified, presenting a significant obstacle in clinical diagnosis and treatment. Methods: A total of 7,602 patients have been included in this study. We leveraged integrated multiomics data (epigenomic, genomic, and transcriptomic data) to delineate the comprehensive landscape of EMT in BC. Subsequently, a subtyping classifier was developed through a machine learning framework proposed by us. Results: We classified the BC samples into three methylation-driven EMT subtypes with distinct features, namely, C1 (the mammary duct development subtype with TP53 activation), C2 (the immune infiltration subtype with high TP53 mutation), and C3 (the ERBB2 amplification subtype with an unfavorable prognosis). Specifically, patients with the C1 subtype might respond to endocrine therapy or the p53-MDM2 antagonist nutlin-3. Patients with the C2 subtype might benefit from combined therapeutic regimens involving radiotherapy, PARP inhibitors, and immune checkpoint blockade therapy. Patients with the C3 subtype might benefit from anti-HER2 agents such as lapatinib. Notably, to increase the clinical applicability of the EMT subtypes, we devised a 96-gene panel-based classifier via a machine learning framework. Conclusions: Our study identified three methylation-driven EMT subtypes with distinct prognoses and biological traits to capture heterogeneity in BC and provided a rationale for the use of this classification as a powerful tool for developing new strategies for clinical trials.

PTEN deficiency induces an extrahepatic cholangitis-cholangiocarcinoma continuum via aurora kinase A in mice

BACKGROUND & AIMS

The PTEN-AKT pathway is frequently altered in extrahepatic cholangiocarcinoma (eCCA). We aimed to evaluate the role of PTEN in the pathogenesis of eCCA and identify novel therapeutic targets for this disease.

METHODS

The Pten gene was genetically deleted using the Cre-loxp system in biliary epithelial cells. The pathologies were evaluated both macroscopically and histologically. The characteristics were further analyzed by immunohistochemistry, reverse-transcription PCR, cell culture, and RNA sequencing. Some features were compared to those in human eCCA samples. Further mechanistic studies utilized the conditional knockout of Trp53 and Aurora kinase A (Aurka) genes. We also tested the effectiveness of an Aurka inhibitor.

RESULTS

We observed that genetic deletion of the Pten gene in the extrahepatic biliary epithelium and peri-ductal glands initiated sclerosing cholangitis-like lesions in mice, resulting in enlarged and distorted extrahepatic bile ducts in mice as early as 1 month after birth. Histologically, these lesions exhibited increased epithelial proliferation, inflammatory cell infiltration, and fibrosis. With aging, the lesions progressed from low-grade dysplasia to invasive carcinoma. Trp53 inactivation further accelerated disease progression, potentially by downregulating senescence. Further mechanistic studies showed that both human and mouse eCCA showed high expression of AURKA. Notably, the genetic deletion of Aurka completely eliminated Pten deficiency-induced extrahepatic bile duct lesions. Furthermore, pharmacological inhibition of Aurka alleviated disease progression.

CONCLUSIONS

Pten deficiency in extrahepatic cholangiocytes and peribiliary glands led to a cholangitis-to-cholangiocarcinoma continuum that was dependent on Aurka. These findings offer new insights into preventive and therapeutic interventions for extrahepatic CCA.

IMPACT AND IMPLICATIONS

The aberrant PTEN-PI3K-AKT signaling pathway is commonly observed in human extrahepatic cholangiocarcinoma (eCCA), a disease with a poor prognosis. In our study, we developed a mouse model mimicking cholangitis to eCCA progression by conditionally deleting the Pten gene via Pdx1-Cre in epithelial cells and peribiliary glands of the extrahepatic biliary duct. The conditional Pten deletion in these cells led to cholangitis, which gradually advanced to dysplasia, ultimately resulting in eCCA. The loss of Pten heightened Akt signaling, cell proliferation, inflammation, fibrosis, DNA damage, epigenetic signaling, epithelial-mesenchymal transition, cell dysplasia, and cellular senescence. Genetic deletion or pharmacological inhibition of Aurka successfully halted disease progression. This model will be valuable for testing novel therapies and unraveling the mechanisms of eCCA tumorigenesis.

Investigation the apoptotic effect of silver nanoparticles (Ag-NPs) on MDA-MB 231 breast cancer epithelial cells via signaling pathways

Background

The discovery of novel cancer therapeutic strategies leads to the development of nanotechnology-based methods for cancer treatment. Silver nanoparticles (Ag-NPs) have garnered considerable interest owing to their size, shape, and capacity to modify chemical, optical, and photonic properties. This study aimed to investigate the impact of Ag-NPs on inducing of apoptosis in MDA-MB 231 cells by examining specific signaling pathways.

Materials and methods

The cytotoxicity of Ag-NPs was determined using an MTT assay in MDA-MB 231 cells. The apoptotic effects were assessed using the Annexin-V/PI assay. Real-time PCR and western blotting were conducted to analyze the expression of apoptosis-related genes and proteins, respectively. Levels of ERK1/2 and cyclin D1 were measured using ELISA. Cell cycle assay was determined by flow cytometry. Cell migration was evaluated by scratch assay.

Results

The results revealed that Ag-NPs triggered apoptosis and cell cycle arrest in MDA-MB 231 cells. The expression level of Bax (pro-apoptotic gene) was increased, while Bcl-2 (anti-apoptotic gene) expression was decreased. Increased apoptosis was correlated with increased levels of p53 and PTEN. Additionally, notable alterations were observed in protein expression related to the Janus kinase/Signal transducers (JAK/STAT) pathway, including p-AKT. Additionally, reduced expression of h-TERT was observed following exposure to Ag-NPs. ELISA results demonstrated a significant reduction in p-ERK/Total ERK and cyclin D1 levels in Ag-NPs-exposed MDA-MB 231 cells. Western blotting analysis also confirmed the reduction of p-ERK/Total ERK and cyclin D1. Decreased level of cyclin D is associated with suppression of cell cycle progression. The migratory ability of MDA-MB-231 cells was reduced upon treatment with Ag-NPs.

Conclusions

Our findings revealed that Ag-NPs influenced the proliferation, apoptosis, cell cycle, and migration in MDA-MB 231 cells, possibly by modulating protein expression of the AKT/ERK/Cyclin D1 axis.

Distinct shared and compartment-enriched oncogenic networks drive primary versus metastatic breast cancer

Metastatic breast-cancer is a major cause of death in women worldwide, yet the relationship between oncogenic drivers that promote metastatic versus primary cancer is still contentious. To elucidate this relationship in treatment-naive animals, we hereby describe mammary-specific transposon-mutagenesis screens in female mice together with loss-of-function Rb, which is frequently inactivated in breast-cancer. We report gene-centric common insertion-sites (gCIS) that are enriched in primary-tumors, in metastases or shared by both compartments. Shared-gCIS comprise a major MET-RAS network, whereas metastasis-gCIS form three additional hubs: Rho-signaling, Ubiquitination and RNA-processing. Pathway analysis of four clinical cohorts with paired primary-tumors and metastases reveals similar organization in human breast-cancer with subtype-specific shared-drivers (e.g. RB1-loss, TP53-loss, high MET, RAS, ER), primary-enriched (EGFR, TGFβ and STAT3) and metastasis-enriched (RHO, PI3K) oncogenic signaling. Inhibitors of RB1-deficiency or MET plus RHO-signaling cooperate to block cell migration and drive tumor cell-death. Thus, targeting shared- and metastasis- but not primary-enriched derivers offers a rational avenue to prevent metastatic breast-cancer.

The role of MEOX1 in non-neoplastic and neoplastic diseases

Targeted gene therapy has shown durable efficacy in non-neoplastic and neoplastic patients. Therefore, finding a suitable target has become a key area of research. Mesenchyme homeobox 1 (MEOX1) is a transcriptional factor that plays a significant role in regulation of somite development. Evidence indicates that abnormalities in MEOX1 expression and function are associated with a variety of pathologies, including non-neoplastic and neoplastic diseases. MEOX1 expression is upregulated during progression of most diseases and plays a critical role in maintenance of the cellular phenotypes such as cell differentiation, cell cycle arrest and senescence, migration, and proliferation. Therefore, MEOX1 may become an important molecular target and therapeutic target. This review will discuss the current state of knowledge on the role of MEOX1 in different diseases.

Loss of Epigenetic Regulation Disrupts Lineage Integrity, Induces Aberrant Alveogenesis, and Promotes Breast Cancer

Systematically investigating the scores of genes mutated in cancer and discerning disease drivers from inconsequential bystanders is a prerequisite for precision medicine but remains challenging. Here, we developed a somatic CRISPR/Cas9 mutagenesis screen to study 215 recurrent "long-tail" breast cancer genes, which revealed epigenetic regulation as a major tumor-suppressive mechanism. We report that components of the BAP1 and COMPASS-like complexes, including KMT2C/D, KDM6A, BAP1, and ASXL1/2 ("EpiDrivers"), cooperate with PIK3CAH1047R to transform mouse and human breast epithelial cells. Mechanistically, we find that activation of PIK3CAH1047R and concomitant EpiDriver loss triggered an alveolar-like lineage conversion of basal mammary epithelial cells and accelerated formation of luminal-like tumors, suggesting a basal origin for luminal tumors. EpiDriver mutations are found in ∼39% of human breast cancers, and ∼50% of ductal carcinoma in situ express casein, suggesting that lineage infidelity and alveogenic mimicry may significantly contribute to early steps of breast cancer etiology.

SIGNIFICANCE

Infrequently mutated genes comprise most of the mutational burden in breast tumors but are poorly understood. In vivo CRISPR screening identified functional tumor suppressors that converged on epigenetic regulation. Loss of epigenetic regulators accelerated tumorigenesis and revealed lineage infidelity and aberrant expression of alveogenesis genes as potential early events in tumorigenesis. This article is highlighted in the In This Issue feature, p. 2711.

Pten and p53 Loss in the Mouse Lung Causes Adenocarcinoma and Sarcomatoid Carcinoma

Simple Summary

Lung cancer is the world leading cause of cancer death. Therefore, a better understanding of the disease is needed to improve patient survival. In this work, we have deleted the tumor suppressor genes Pten and Trp53 in adult mouse lungs to analyze its impact on tumor formation. Double mutant mice develop Adenocarcinoma and Pulmonary Sarcomatoid Carcinoma, two different types of Non-Small Cell Carcinoma whose biological relationships are a matter of debate. The former is very common, with various models described and some therapeutic options. The latter is very rare with very poor prognosis, no effective treatment and lack of models reported so far. Interestingly, this study reports the first mouse model of pulmonary sarcomatoid carcinoma available for preclinical research.

Abstract

Lung cancer remains the leading cause of cancer deaths worldwide. Among the Non-Small Cell Carcinoma (NSCLC) category, Adenocarcinoma (ADC) represents the most common type, with different reported driver mutations, a bunch of models described and therapeutic options. Meanwhile, Pulmonary Sarcomatoid Carcinoma (PSC) is one of the rarest, with very poor outcomes, scarce availability of patient material, no effective therapies and no models available for preclinical research. Here, we describe that the combined deletion of Pten and Trp53 in the lungs of adult conditional mice leads to the development of both ADC and PSC irrespective of the lung targeted cell type after naphthalene induced airway epithelial regeneration. Although this model shows long latency periods and incomplete penetrance for tumor development, it is the first PSC mouse model reported so far, and sheds light on the relationships between ADC and PSC and their cells of origin. Moreover, human ADC show strong transcriptomic similarities to the mouse PSC, providing a link between both tumor types and the human ADC.

Eukaryotic Extension Factor 2 Kinase may Affect the Occurrence and Development of Glioblastoma Through Immune Cell Infiltration

Glioblastoma (GBM) is one of the most common malignancies among primary brain tumors in adults, featuring a poor prognosis and a high recurrence rate. Eukaryotic elongation factor 2 kinase (eEF2K) is a calcium/calmodulin-dependent protein kinase that is involved in promoting tumor cell proliferation, migration, invasion, and survival. However, its expression level in GBM, its prognostic impact and correlation with immune infiltration are not yet known. In this study, we used The Cancer Genome Atlas (TCGA) database to explore the potential molecular mechanisms of eEF2K in GBM development and clinical prognosis in terms of gene expression, survival status, immune infiltration, and associated cellular pathways. We found that eEF2K expression levels were elevated in GBM, but eEF2K was not associated with the prognosis of GBM patients; eEF2K expression in GBM was associated with multiple immune cell infiltrations. These results show a statistical correlation between eEF2K expression and the development of GBM and immune cell infiltration, which helps us to understand the roles of eEF2K in GBM from different perspectives.

In silico, synthesis and anticancer evaluation of benzamide tryptamine derivatives as novel eEF2K inhibitors

Eukaryotic elongation factor 2 kinase (eEF2K), a member of the atypical α-kinase family, is highly expressed in a variety of tumor tissues. Inhibition of eEF2K function can effectively kill cancer cells without affecting the function of normal cells. Therefore, eEF2K is a promising new target for cancer therapy. In this study, a series of benzamide tryptamine derivatives were designed and synthesized as novel eEF2K inhibitors. The druggability properties of the synthesized compounds were predicted in silico and performed well. The MTT assay indicated that most of these compounds displayed good antiproliferative activity against human leukemia CCRF-CEM and K562 cell lines. The structure-activity relationship (SAR) revealed that substituents with different electronic effects on the C5 position of indole ring or C2', C4' positions of benzene ring have a great influence on the anti-proliferative activity. Among them, 5j demonstrated the highest anti-proliferative activity with IC₅₀ value of 1.63-3.54 μM. this compound displayed an effective eEF2K inhibition by down-regulated the level of phosphorylated eEF2 in CCRF-CEM cells. Additionally, the western blot analysis further revealed that 5j also significantly affected eEF2K-related signaling pathways. Anticancer mechanism studies have shown that 5j arrested the cell cycle in G0/G1 and induced CCRF-CEM cells apoptosis. Furthermore, 5j activated cleaved caspase-9, 8, 3 and cleaved PARP in a time-dependent manner, which suggesting that 5j induced cancer cells apoptosis through both intrinsic and extrinsic pathways. In summary, benzamide tryptamine derivative 5j represents a novel and promising lead structure for the development of eEF2K inhibitors in cancer therapy.

The AKT1E17K Allele Promotes Breast Cancer in Mice

Simple Summary

The main finding reported in this manuscript is that the gain-of-function mutation AKT1E17K is a bona fide oncogene for mammary epithelium, being able to efficiently initiate breast cancer in mice. On the basis of high-molecular-weight cytokeratins expressed by AKT1E17K-derived tumors supported by additional integrative gene expression analysis these tumors resulted similar to human basal-like cancer, phenotypically and molecularly. These results indicate that the AKTE17K strain may represent an appropriate model of human basal-like breast cancer for the identification of novel therapies specific for this type of tumor.

Abstract

The gain-of-function mutation in the pleckstrin homology domain of AKT1 (AKT1E17K) occurs in lung and breast cancer. Through the use of human cellular models and of a AKT1E17K transgenic Cre-inducible murine strain (R26-AKT1E17K mice), we have demonstrated that AKT1E17K is a bona fide oncogene for lung epithelial cells. However, the role of AKT1E17K in breast cancer remains to be determined. Here, we report the generation and the characterization of a MMTV-CRE; R26-AKT1E17K mouse strain that expresses the mutant AKT1E17K allele in the mammary epithelium. We observed that AKT1E17K stimulates the development of mammary tumors classified as ductal adenocarcinoma of medium–high grade and presented a variety of proliferative alterations classified as adenosis with low-to-high grade dysplasia in the mammary epithelium. A subsequent immunohistochemical characterization suggested they were PR⁻/HER2⁻/ER⁺, basal-like and CK8⁻/CK10⁻/CK5⁺/CK14⁺. We also observed that, in parallel with an increased proliferation rate, tumors expressing mutant AKT1E17K presented an activation of the GSK3/cyclin D1 pathway in the mammary epithelium and cluster significantly with the human basal-like tumors. In conclusion, we demonstrate AKT1E17K is a bona fide oncogene that can initiate tumors at high efficiency in murine mammary epithelium in vivo.

eEF2K promotes PD-L1 stabilization through inactivating GSK3β in melanoma

Background

Immune checkpoint blockade (ICB) targeting programmed death ligand-1 (PD-L1)/programmed cell death protein-1 (PD-1) pathway has become an attractive strategy for cancer treatment; however, unsatisfactory efficacy has limited its clinical benefits. Therefore, a more comprehensive understanding of the regulation of PD-L1 expression is essential for developing more effective cancer immunotherapy. Recent studies have revealed the important roles of eukaryotic elongation factor 2 kinase (eEF2K) in promoting epithelial-mesenchymal transition (EMT), angiogenesis, tumor cell migration and invasion; nevertheless, the exact role of eEF2K in the regulation of tumor immune microenvironment (TIME) remains largely unknown.

Methods

In this study, we used a cohort of 38 patients with melanoma who received anti-PD-1 treatment to explore the association between eEF2K expression and immunotherapy efficacy against melanoma. Immunoprecipitation-mass spectrometry analysis and in vitro assays were used to examine the role and molecular mechanism of eEF2K in regulating PD-L1 expression. We also determined the effects of eEF2K on tumor growth and cytotoxicity of CD8⁺ T cells in TIME in a mouse melanoma model. We further investigated the efficacy of the eEF2K inhibition in combination with anti-PD-1 treatment in vivo.

Results

High eEF2K expression is correlated with better therapeutic response and longer survival in patients with melanoma treated with PD-1 monoclonal antibody (mAb). Moreover, eEF2K protein expression is positively correlated with PD-L1 protein expression. Mechanistically, eEF2K directly bound to and inactivated glycogen synthase kinase 3 beta (GSK3β) by phosphorylating it at serine 9 (S9), leading to PD-L1 protein stabilization and upregulation, and subsequently tumor immune evasion. Knockdown of eEF2K decreased PD-L1 expression and enhanced CD8⁺ T cell activity, thus dramatically attenuating murine B16F10 melanoma growth in vivo. Clinically, p-GSK3β/S9 expression is positively correlated with the expressions of eEF2K and PD-L1, and the response to anti-PD-1 immunotherapy. Furthermore, eEF2K inhibitor, NH125 treatment or eEF2K knockdown enhanced the efficacy of PD-1 mAb therapy in a melanoma mouse model.

Conclusions

Our results suggest that eEF2K may serve as a biomarker for predicting therapeutic response and prognosis in patients receiving anti-PD-1 therapy, reveal a vital role of eEF2K in regulating TIME by controlling PD-L1 expression and provide a potential combination therapeutic strategy of eEF2K inhibition with ICB therapy.

Functions and Regulation of Translation Elongation Factors

Translation elongation is a key step of protein synthesis, during which the nascent polypeptide chain extends by one amino acid residue during one elongation cycle. More and more data revealed that the elongation is a key regulatory node for translational control in health and disease. During elongation, elongation factor Tu (EF-Tu, eEF1A in eukaryotes) is used to deliver aminoacyl-tRNA (aa-tRNA) to the A-site of the ribosome, and elongation factor G (EF-G, EF2 in eukaryotes and archaea) is used to facilitate the translocation of the tRNA₂-mRNA complex on the ribosome. Other elongation factors, such as EF-Ts/eEF1B, EF-P/eIF5A, EF4, eEF3, SelB/EFsec, TetO/Tet(M), RelA and BipA, have been found to affect the overall rate of elongation. Here, we made a systematic review on the canonical and non-canonical functions and regulation of these elongation factors. In particular, we discussed the close link between translational factors and human diseases, and clarified how post-translational modifications control the activity of translational factors in tumors.

Common Genomic Aberrations in Mouse and Human Breast Cancers with Concurrent P53 Deficiency and Activated PTEN-PI3K-AKT Pathway

Simultaneous P53 loss and activation of the PTEN-restricted PI3K-AKT pathway frequently occur in aggressive breast cancers. P53 loss causes genome instability, while PTEN loss and/or activating mutations of PIK3CA and AKT promote cancer cell proliferation that also increases incidences of genomic aberrations. However, the genomic alterations associated with P53 loss and activated PTEN-PI3K-AKT signaling in breast cancer have not been defined. Spatiotemporally controlled breast cancer models with inactivation of both P53 and Pten in adult mice have not been established for studying genomic alterations. Herein, we deleted both floxed Pten and Tp53 genes in the mammary gland epithelial cells in adult mice using a RCAS virus-mediated Cre-expressing system. These mice developed small tumors in 21 weeks, and poorly differentiated larger tumors in 26 weeks. In these tumors, we identified 360 genes mutated by nonsynonymous point mutations and small insertions and deletions (NSPMs/InDels), 435 genes altered by copy number amplifications (CNAs), and 450 genes inactivated by copy number deletions (CNDs). Importantly, 22.2%, 75.9% and 27.3% of these genes were also altered in human breast tumors with P53 and PTEN losses or P53 loss and activated PI3K-AKT signaling by NSPMs/InDels, CNAs and CNDs, respectively. Therefore, inactivation of P53 and Pten in adult mice causes rapid-growing breast tumors, and these tumors recapitulate a significant number of genetic aberrations in human breast tumors with inactivated P53 and activated PTEN-PI3K-AKT signaling. Further characterization of these commonly altered genes in breast cancer should help to identify novel cancer-driving genes and molecular targets for developing therapeutics.

Therapeutic Potential of Thymoquinone in Triple-Negative Breast Cancer Prevention and Progression through the Modulation of the Tumor Microenvironment

To date, the tumor microenvironment (TME) has gained considerable attention in various areas of cancer research due to its role in driving a loss of immune surveillance and enabling rapid advanced tumor development and progression. The TME plays an integral role in driving advanced aggressive breast cancers, including triple-negative breast cancer (TNBC), a pivotal mediator for tumor cells to communicate with the surrounding cells via lymphatic and circulatory systems. Furthermore, the TME plays a significant role in all steps and stages of carcinogenesis by promoting and stimulating uncontrolled cell proliferation and protecting tumor cells from the immune system. Various cellular components of the TME work together to drive cancer processes, some of which include tumor-associated adipocytes, fibroblasts, macrophages, and neutrophils which sustain perpetual amplification and release of pro-inflammatory molecules such as cytokines. Thymoquinone (TQ), a natural chemical component from black cumin seed, is widely used traditionally and now in clinical trials for the treatment/prevention of multiple types of cancer, showing a potential to mitigate components of TME at various stages by various pathways. In this review, we focus on the role of TME in TNBC cancer progression and the effect of TQ on the TME, emphasizing their anticipated role in the prevention and treatment of TNBC. It was concluded from this review that the multiple components of the TME serve as a critical part of TNBC tumor promotion and stimulation of uncontrolled cell proliferation. Meanwhile, TQ could be a crucial compound in the prevention and progression of TNBC therapy through the modulation of the TME.

Targeting microRNAs with thymoquinone: a new approach for cancer therapy

Cancer is a global disease involving transformation of normal cells into tumor types via numerous mechanisms, with mortality among all generations, in spite of the breakthroughs in chemotherapy, radiotherapy and/or surgery for cancer treatment. Since one in six deaths is due to cancer, it is one of the overriding priorities of world health. Recently, bioactive natural compounds have been widely recognized due to their therapeutic effects for treatment of various chronic disorders, notably cancer. Thymoquinone (TQ), the most valuable constituent of black cumin seeds, has shown anti-cancer characteristics in a wide range of animal models. The revolutionary findings have revealed TQ's ability to regulate microRNA (miRNA) expression, offering a promising approach for cancer therapy. MiRNAs are small noncoding RNAs that modulate gene expression by means of variation in features of mRNA. MiRNAs manage several biological processes including gene expression and cellular signaling pathways. Accordingly, miRNAs can be considered as hallmarks for cancer diagnosis, prognosis and therapy. The purpose of this study was to review the various molecular mechanisms by which TQ exerts its potential as an anti-cancer agent through modulating miRNAs.

Small Molecules Targeting Programmed Cell Death in Breast Cancer Cells

Targeted chemotherapy has become the forefront for cancer treatment in recent years. The selective and specific features allow more effective treatment with reduced side effects. Most targeted therapies, which include small molecules, act on specific molecular targets that are altered in tumour cells, mainly in cancers such as breast, lung, colorectal, lymphoma and leukaemia. With the recent exponential progress in drug development, programmed cell death, which includes apoptosis and autophagy, has become a promising therapeutic target. The research in identifying effective small molecules that target compensatory mechanisms in tumour cells alleviates the emergence of drug resistance. Due to the heterogenous nature of breast cancer, various attempts were made to overcome chemoresistance. Amongst breast cancers, triple negative breast cancer (TNBC) is of particular interest due to its heterogeneous nature in response to chemotherapy. TNBC represents approximately 15% of all breast tumours, however, and still has a poor prognosis. Unlike other breast tumours, signature targets lack for TNBCs, causing high morbidity and mortality. This review highlights several small molecules with promising preclinical data that target autophagy and apoptosis to induce cell death in TNBC cells.

Transgenic mouse models of breast cancer

Transgenic breast cancer mouse models are critical tools for preclinical studies of human breast cancer. Genetic editing of the murine mammary gland allows for modeling of abnormal genetic events frequently found in human breast cancers. Genetically engineered mouse models (GEMMs) of breast cancer employ tissue-specific genetic manipulation for tumorigenic induction within the mammary tissue. Under the transcriptional control of mammary-specific promoters, transgenic mouse models can simulate spontaneous mammary tumorigenesis by expressing one or more putative oncogenes, such as MYC, HRAS, and PIK3CA. Alternatively, the Cre-Lox system allows for tissue-specific deletion of tumor suppressors, such as p53, Rb1, and Brca1, or specific knock-in of putative oncogenes. Thus, GEMMs can be designed to implement one or more genetic events to induce mammary tumorigenesis. Features of GEMMs, such as age of transgene expression, breeding quality, tumor latency, histopathological characteristics, and propensity for local and distant metastasis, are variable and strain-dependent. This review aims to summarize currently available transgenic breast cancer mouse models that undergo spontaneous mammary tumorigenesis upon genetic manipulation, their varying characteristics, and their individual genetic manipulations that model aberrant signaling events observed in human breast cancers.

Multifaceted control of mRNA translation machinery in cancer

The mRNA translation machinery is tightly regulated through several, at times overlapping, mechanisms that modulate its efficiency and accuracy. Due to their fast rate of growth and metabolism, cancer cells require an excessive amount of mRNA translation and protein synthesis. However, unfavorable conditions, such as hypoxia, amino acid starvation, and oxidative stress, which are abundant in cancer, as well as many anti-cancer treatments inhibit mRNA translation. Cancer cells adapt to the various internal and environmental stresses by employing specialised transcript-specific translation to survive and gain a proliferative advantage. We will highlight the major signaling pathways and mechanisms of translation that regulate the global or mRNA-specific translation in response to the intra- or extra-cellular signals and stresses that are key components in the process of tumourigenesis.

Inhibition of eEF2K synergizes with glutaminase inhibitors or 4EBP1 depletion to suppress growth of triple-negative breast cancer cells

The eukaryotic elongation factor-2 kinase, eEF2K, which restricts protein translation elongation, has been identified as a potential therapeutic target for diverse types of malignancies including triple negative breast cancer (TNBC). However, the contexts in which eEF2K inhibition is essential in TNBC and its consequences on the proteome are largely unknown. Here we show that genetic or pharmacological inhibition of eEF2K cooperated with glutamine (Gln) starvation, and synergized with glutaminase (GLS1) inhibitors to suppress growth of diverse TNBC cell lines. eEF2K inhibition also synergized with depletion of eukaryotic translation initiation factor 4E-binding protein 1 (eIF4EBP1; 4EBP1), a suppressor of eukaryotic protein translation initiation factor 4E (eIF4E), to induce c-MYC and Cyclin D1 expression, yet attenuate growth of TNBC cells. Proteomic analysis revealed that whereas eEF2K depletion alone uniquely induced Cyclin Dependent Kinase 1 (CDK1) and 6 (CDK6), combined depletion of eEF2K and 4EBP1 resulted in overlapping effects on the proteome, with the highest impact on the 'Collagen containing extracellular matrix' pathway (e.g. COL1A1), as well as the amino-acid transporter, SLC7A5/LAT1, suggesting a regulatory loop via mTORC1. In addition, combined depletion of eEF2K and 4EBP1 indirectly reduced the levels of IFN-dependent innate immune response-related factors. Thus, eEF2K inhibition triggers cell cycle arrest/death under unfavourable metabolic conditions such as Gln-starvation/GLS1 inhibition or 4EBP1 depletion, uncovering new therapeutic avenues for TNBC and underscoring a pressing need for clinically relevant eEF2K inhibitors.

Elongation factor eEF2 kinase and autophagy jointly promote survival of cancer cells

Cells within solid tumours can become deprived of nutrients; in order to survive, they need to invoke mechanisms to conserve these resources. Using cancer cells in culture in the absence of key nutrients, we have explored the roles of two potential survival mechanisms, autophagy and elongation factor 2 kinase (eEF2K), which, when activated, inhibits the resource-intensive elongation stage of protein synthesis. Both processes are regulated through the nutrient-sensitive AMP-activated protein kinase and mechanistic target of rapamycin complex 1 signalling pathways. We find that disabling both autophagy and eEF2K strongly compromises the survival of nutrient-deprived lung and breast cancer cells, whereas, for example, knocking out eEF2K alone has little effect. Contrary to some earlier reports, we find no evidence that eEF2K regulates autophagy. Unexpectedly, eEF2K does not facilitate survival of prostate cancer PC3 cells. Thus, eEF2K and autophagy enable survival of certain cell-types in a mutually complementary manner. To explore this further, we generated, by selection, cells which were able to survive nutrient starvation even when autophagy and eEF2K were disabled. Proteome profiling using mass spectrometry revealed that these 'resistant' cells showed lower levels of diverse proteins which are required for energy-consuming processes such as protein and fatty acid synthesis, although different clones of 'resistant cells' appear to adapt in dissimilar ways. Our data provide further information of the ways that human cells cope with nutrient limitation and to understanding of the utility of eEF2K as a potential target in oncology.

Small-Molecule Drug Discovery in Triple Negative Breast Cancer: Current Situation and Future Directions

Triple negative breast cancer (TNBC) is the most aggressive subtype of breast cancer, but an effective targeted therapy has not been well-established so far. Considering the lack of effective targets, where do we go next in the current TNBC drug development? A promising intervention for TNBC might lie in de novo small-molecule drugs that precisely target different molecular characteristics of TNBC. However, an ideal single-target drug discovery still faces a huge challenge. Alternatively, other new emerging strategies, such as dual-target drug, drug repurposing, and combination strategies, may provide new insight into the improvement of TNBC therapeutics. In this review, we focus on summarizing the current situation of a series of candidate small-molecule drugs in TNBC therapy, including single-target drugs, dual-target drugs, as well as drug repurposing and combination strategies that will together shed new light on the future directions targeting TNBC vulnerabilities with small-molecule drugs for future therapeutic purposes.

Progress in the Development of Eukaryotic Elongation Factor 2 Kinase (eEF2K) Natural Product and Synthetic Small Molecule Inhibitors for Cancer Chemotherapy

Eukaryotic elongation factor 2 kinase (eEF2K or Ca2+/calmodulin-dependent protein kinase, CAMKIII) is a new member of an atypical α-kinase family different from conventional protein kinases that is now considered as a potential target for the treatment of cancer. This protein regulates the phosphorylation of eukaryotic elongation factor 2 (eEF2) to restrain activity and inhibit the elongation stage of protein synthesis. Mounting evidence shows that eEF2K regulates the cell cycle, autophagy, apoptosis, angiogenesis, invasion, and metastasis in several types of cancers. The expression of eEF2K promotes survival of cancer cells, and the level of this protein is increased in many cancer cells to adapt them to the microenvironment conditions including hypoxia, nutrient depletion, and acidosis. The physiological function of eEF2K and its role in the development and progression of cancer are here reviewed in detail. In addition, a summary of progress for in vitro eEF2K inhibitors from anti-cancer drug discovery research in recent years, along with their structure-activity relationships (SARs) and synthetic routes or natural sources, is also described. Special attention is given to those inhibitors that have been already validated in vivo, with the overall aim to provide reference context for the further development of new first-in-class anti-cancer drugs that target eEF2K.

Carboxypeptidase A4 negatively correlates with p53 expression and regulates the stemness of breast cancer cells

Background: Triple-negative breast cancer (TNBC) is an aggressive cancer subtype lacking effective treatment options, and p53 is the most frequently mutated or deleted gene. Carboxypeptidase A4 (CPA4) is an extracellular metallocarboxypeptidase, which was closely associated with aggressiveness. Although a recent study indicated that CPA4 could induce epithelial‑mesenchymal transition in breast cancer cells, no studies investigated its stemness-related function and the correlation between CPA4 and p53 in TNBC. In this study, we aimed to investigate the CPA4 levels in breast cancer tissues and analyze its association with p53, and study its roles in cancer stemness maintenance. Methods: CPA4 mRNA level and its prognostic value were analyzed by using online database UALCAN (http://ualcan.path.uab.edu) and Kaplan-Meier plotter (www.kmplot.com), respectively. The expression of CPA4, p53 and ALDH1A1 in breast cancer and adjacent normal tissues were evaluated by IHC using the corresponding primary antibodies on a commercial tissue array (Shanghai Biochip Co., Ltd., Shanghai, China). siRNA knockdown was used to study the function of proliferation, colony formation assay and sphere formation in serum-free medium. Results: Analysis of the UALCAN datasets identified that CPA4 mRNA levels were elevated in TNBC, especially in the TP53-mutant subgroup. Furthermore, high levels of CPA4 mRNA were significantly associated with unfavourable overall survival OS in breast cancer patients. Immunohistochemistical analysis demonstrated that CPA4 levels were elevated in 32.1% of breast cancer samples (45/140), and the positive rates of ALDH1A1 and p53 in the breast cancer tissues were 25% (35/140) and 50% (70/140), respectively. Statistical analysis revealed high levels of CPA4 was significantly associated with TNBC phenotype. Correlation analysis indicated that CPA4 over-expression was positively associated with ALDH1A1 (P<0.01) and negatively correlated with p53 (P<0.05). In Kaplan-Meier survival analysis, either high CPA4 or ALDH1A1 levels was significantly correlated with poor survival in breast cancer patients. Functional studies demonstrated that down-regulation of CPA4 significantly inhibited TNBC cell proliferation, colony-formation assays in soft agar and sphere formation in serum-free medium. Conclusion: This study demonstrated for the first time that CPA4 was negatively correlates with p53 expression and inhibition of CPA4 could reduce the number of breast cancer cells with stemness property. It might be a potential target for the TNBC treatment.

YY1-mediated long non-coding RNA Kcnq1ot1 promotes the tumor progression by regulating PTEN via DNMT1 in triple negative breast cancer

Triple-negative breast cancer (TNBC) is an aggressive cancer, and rapidly progresses following relapse in advanced stage. This cancer is usually associated with worse overall survival, so the carcinogenesis of TNBC needs to be further explored to find more effective therapies. In this study, we intended to identify the roles of YY1-mediated long non-coding RNA Kcnq1ot1 in TNBC. First, the paired samples of tumor tissues and adjacent tissues were collected to determine YY1, lncRNA Kcnq1ot1, and PTEN expression using RT-qPCR and Western blot analysis followed by analysis of the relationship between them and patient survival. The results revealed that YY1 and lncRNA Kcnq1ot1 were upregulated in TNBC tissues, and high expression of YY1 and lncRNA Kcnq1ot1 was associated with poor patient survival. Then, ChIP and MSP assays were employed to explore interactions between YY1, lncRNA Kcnq1ot1, and PTEN gene. We obtained that YY1 upregulated lncRNA Kcnq1ot1, which mediated PTEN methylation via DNMT1, thus decreasing PTEN expression. Afterward, TNBC cells were examined for their viability using functional assays with the results displaying that overexpression of YY1 facilitated TNBC cell proliferation, invasion, and migration. Mechanistically, upregulated YY1 repressed tumor growth by inhibiting PTEN via upregulation of lncRNA Kcnq1ot1. Mouse models were also constructed, and the above effects of YY1, lncRNA Kcnq1ot1, and PTEN on TNBC were also established in vivo. Taken together, this study demonstrates that the silencing of YY1 exerted tumor-suppressive effects on TNBC by modulating lncRNA Kcnq1ot1/DNMT1/PTEN pathway, in support of further investigation into anti-tumor therapy for TNBC.

Core-Shell Nanosystems for Self-Activated Drug-Gene Combinations against Triple-Negative Breast Cancer

The combination of gene therapy with chemotherapeutics provides an efficacious strategy for enhanced tumor therapy. RNA-cleaving DNAzyme has been recognized as a promising gene-silencing tool, while its combination with chemotherapeutic drugs has been limited by the lack of an effective codelivery system to allow sufficient intracellular DNAzyme activation, which requires specific metal ions as a cofactor. Here, a self-activatable DNAzyme/drug core-shell codelivery system is fabricated to combat triple-negative breast cancer (TNBC). The hydrophobic chemotherapeutic, rapamycin (RAP), is self-assembled into the pure drug nanocore, and the metal-organic framework (MOF) shell based on coordination between Mn²⁺ and tannic acid (TA) is coated on the surface to coload an autophagy-inhibiting DNAzyme. The nanosystem efficiently delivers the payloads into tumor cells, and upon endocytosis, the MOF shell is disintegrated to release the therapeutics in response to an acidic endo/lysosome environment and intracellular glutathione (GSH). Notably, the coreleased Mn²⁺ serves as the cofactor of DNAzyme for effective self-activation, which suppresses the expression of Beclin 1 protein, the key initiator of autophagy, resulting in a significantly strengthened antitumor effect of RAP. Using tumor-bearing mouse models, the nanosystem could passively accumulate into the tumor tissue, impose potent gene-silencing efficacy, and thus sensitize chemotherapy to inhibit tumor growth upon intravenous administration, providing opportunities for combined gene-drug TNBC therapy.

AKT isoforms have discrete expression in triple negative breast cancers and roles in cisplatin sensitivity

AKT, a serine threonine kinase, exists in three different isoforms and is known for regulating several biological processes including tumorigenesis. In this study, we investigated the expression and net effect of the individual isoforms in triple negative breast cancers and response to cisplatin treatment using cellular, mice models and clinical samples. Interestingly, analysis of the expressions of AKT isoforms in clinical samples showed relatively higher expression of AKT1 in primary tissues; whereas lung and liver metastatic samples showed elevated expression of AKT2. Similarly, triple-negative breast cancer cell lines, BT-549 and MDA-MB-231, with high proliferative and invasive properties, displayed higher expression levels of AKT1/2. By modulating AKT isoform expression in MCF-10A and BT-549 cell lines, we found that presence of AKT2 was associated with invasiveness, stemness and sensitivity to drug treatment. It was observed that the silencing of AKT2 suppressed the cancer stem cell populations (CD44^high CD24^low, ALDH1), mammosphere formation, invasive and migratory potential in MCF-10A and BT-549 cells. It was further demonstrated that loss of function of AKT1 isoform is associated with reduced sensitivity towards cisplatin treatment in triple-negative breast cancers cellular and syngeneic mice models. The decrease in cisplatin treatment response in shAKT1 cells was allied with the upregulation in the expression of transporter protein ABCG2, whereas silencing of ABCG2 restored cisplatin sensitivity in these cells through AKT/SNAIL/ABCG2 axis. In conclusion, our study demonstrated the varied expression of AKT isoforms in triple-negative breast cancers and also confirmed differential role of isoforms in stemness, invasiveness and response towards the cisplatin treatment.

FBI-1 enhanced the resistance of triple-negative breast cancer cells to chemotherapeutic agents via the miR-30c/PXR axis

The factor that binds to the inducer of short transcripts-1 (FBI-1) is a transcription suppressor and an important proto-oncogene that plays multiple roles in carcinogenesis and therapeutic resistance. In the present work, our results indicated that FBI-1 enhanced the resistance of triple-negative breast cancer (TNBC) cells to chemotherapeutic agents by repressing the expression of micoRNA-30c targeting the pregnane X receptor (PXR). The expression of FBI-1 was positively related to PXR and its downstream drug resistance-related genes in TNBC tissues. FBI-1 enhanced the expression of PXR and enhanced the activation of the PXR pathway. The miR-30c decreased the expression of PXR by targeting the 3'-UTR of PXR, and FBI-1 increased the expression of PXR by repressing miR-30c's expression. Through the miR-30c/PXR axis, FBI-1 accelerated the clearance or elimination of antitumor agents in TNBC cells (the TNBC cell lines or the patients derived cells [PDCs]) and induced the resistance of cells to antitumor agents. Therefore, the results indicated that the miR-30c/PXR axis participates in the FBI-1-mediated drug-resistance of TNBC cells.

Combined p53- and PTEN-deficiency activates expression of mesenchyme homeobox 1 (MEOX1) required for growth of triple-negative breast cancer

Triple-negative breast cancer (TNBC) is an aggressive cancer subtype for which effective therapies are unavailable. TNBC has a high frequency of tumor protein p53 (Tp53/p53)- and phosphatase and tensin homolog (PTEN) deficiencies, and combined p53- and PTEN-deficiency is associated with poor prognosis and poor response to anticancer therapies. In this study, we discovered that combined p53- and PTEN-deficiency in TNBC activates expression of the transcription factor mesenchyme homeobox 1 (MEOX1). We found that MEOX1 is expressed only in TNBC cells with frequent deficiencies in p53 and PTEN, and that its expression is undetectable in luminal A, luminal B, and HER2+ subtypes, as well as in normal breast cells with wild-type (WT) p53 and PTEN. Notably, siRNA knockdown of both p53 and PTEN activated MEOX1 expression in breast cancer cells, whereas individual knockdowns of either p53 or PTEN had only minimal effects on MEOX1 expression. MEOX1 knockdown abolished cell proliferation of p53- and PTEN-deficient TNBC in vitro and inhibited tumor growth in vivo, but had no effect on the proliferation of luminal and HER2+ cancer cells and normal breast cells. RNA-Seq and immunoblotting analyses showed that MEOX1 knockdown decreased expression of tyrosine kinase 2 (TYK2), signal transducer and activator of transcription 5B (STAT5B), and STAT6 in p53- and PTEN-deficient TNBC cells. These results reveal the effects of combined p53- and PTEN-deficiency on MEOX1 expression and TNBC cell proliferation, suggesting that MEOX1 may serve as a potential therapeutic target for managing p53- and PTEN-deficient TNBC.

Combined targeting of G protein-coupled receptor and EGF receptor signaling overcomes resistance to PI3K pathway inhibitors in PTEN-null triple negative breast cancer

Triple-negative breast cancer (TNBC) has poorer prognosis compared to other types of breast cancers due to the lack of effective therapies and markers for patient stratification. Loss of PTEN tumor suppressor gene expression is a frequent event in TNBC, resulting in over-activation of the PI 3-kinase (PI3K) pathway and sensitivity to its inhibition. However, PI3K pathway inhibitors show limited efficacy as monotherapies on these tumors. We report a whole-genome screen to identify targets whose inhibition enhanced the effects of different PI3K pathway inhibitors on PTEN-null TNBC. This identified a signaling network that relies on both the G protein-coupled receptor for thrombin (PAR1/F2R) and downstream G protein βγ subunits and also epidermal growth factor receptor (EGFR) for the activation of the PI3K isoform p110β and AKT. Compensation mechanisms involving these two branches of the pathway could bypass PI3K blockade, but combination targeting of both EGFR and PI3Kβ suppressed ribosomal protein S6 phosphorylation and exerted anti-tumor activity both in vitro and in vivo, suggesting a new potential therapeutic strategy for PTEN-null TNBC.

Targeting kinases with thymoquinone: a molecular approach to cancer therapeutics

Kinases are enzymes that are important for cellular functions, but their overexpression has strong connections with carcinogenesis, rendering them important targets for anticancer drugs. Thymoquinone (TQ) is a natural compound with proven anticancer activities, at least in preclinical studies. TQ can target several kinases, including phosphoinositide 3-kinase (PI3K), mitogen-activated protein kinase (MAPK), Janus kinase/signal transducers and activators of transcription (JAK/STAT), polo-like kinase 1 (PLK1), and tyrosine kinase in different cancer cells and animal models. Inhibiting the activity of kinases or suppressing their expression might be among the mechanisms of TQ anticancer activity. In this review, we discuss the role of TQ in kinase regulation in different cancer models.

Modeling germline mutations in pineoblastoma uncovers lysosome disruption-based therapy

Pineoblastoma is a rare pediatric cancer induced by germline mutations in the tumor suppressors RB1 or DICER1. Presence of leptomeningeal metastases is indicative of poor prognosis. Here we report that inactivation of Rb plus p53 via a WAP-Cre transgene, commonly used to target the mammary gland during pregnancy, induces metastatic pineoblastoma resembling the human disease with 100% penetrance. A stabilizing mutation rather than deletion of p53 accelerates metastatic dissemination. Deletion of Dicer1 plus p53 via WAP-Cre also predisposes to pineoblastoma, albeit with lower penetrance. In silico analysis predicts tricyclic antidepressants such as nortriptyline as potential therapeutics for both pineoblastoma models. Nortriptyline disrupts the lysosome, leading to accumulation of non-functional autophagosome, cathepsin B release and pineoblastoma cell death. Nortriptyline further synergizes with the antineoplastic drug gemcitabine to effectively suppress pineoblastoma in our preclinical models, offering new modality for this lethal childhood malignancy.

Using Phosphatidylinositol Phosphorylation as Markers for Hyperglycemic Related Breast Cancer

Studies have suggested that type 2 diabetes (T2D) is associated with a higher incidence of breast cancer and related mortality rates. T2D postmenopausal women have an ~20% increased chance of developing breast cancer, and women with T2D and breast cancer have a 50% increase in mortality compared to breast cancer patients without diabetes. This correlation has been attributed to the general activation of insulin receptor signaling, glucose metabolism, phosphatidylinositol (PI) kinases, and growth pathways. Furthermore, the presence of breast cancer specific PI kinase and/or phosphatase mutations enhance metastatic breast cancer phenotypes. We hypothesized that each of the breast cancer subtypes may have characteristic PI phosphorylation profiles that are changed in T2D conditions. Therefore, we sought to characterize the PI phosphorylation when equilibrated in normal glycemic versus hyperglycemic serum conditions. Our results suggest that hyperglycemia leads to: 1) A reduction in PI3P and PIP3, with increased PI4P that is later converted to PI(3,4)P2 at the cell surface in hormone receptor positive breast cancer; 2) a reduction in PI3P and PI4P with increased PIP3 surface expression in human epidermal growth factor receptor 2-positive (HER2+) breast cancer; and 3) an increase in di- and tri-phosphorylated PIs due to turnover of PI3P in triple negative breast cancer. This study begins to describe some of the crucial changes in PIs that play a role in T2D related breast cancer incidence and metastasis.

Control of translation elongation in health and disease

Regulation of protein synthesis makes a major contribution to post-transcriptional control pathways. During disease, or under stress, cells initiate processes to reprogramme protein synthesis and thus orchestrate the appropriate cellular response. Recent data show that the elongation stage of protein synthesis is a key regulatory node for translational control in health and disease. There is a complex set of factors that individually affect the overall rate of elongation and, for the most part, these influence either transfer RNA (tRNA)- and eukaryotic elongation factor 1A (eEF1A)-dependent codon decoding, and/or elongation factor 2 (eEF2)-dependent ribosome translocation along the mRNA. Decoding speeds depend on the relative abundance of each tRNA, the cognate:near-cognate tRNA ratios and the degree of tRNA modification, whereas eEF2-dependent ribosome translocation is negatively regulated by phosphorylation on threonine-56 by eEF2 kinase. Additional factors that contribute to the control of the elongation rate include epigenetic modification of the mRNA, coding sequence variation and the expression of eIF5A, which stimulates peptide bond formation between proline residues. Importantly, dysregulation of elongation control is central to disease mechanisms in both tumorigenesis and neurodegeneration, making the individual key steps in this process attractive therapeutic targets. Here, we discuss the relative contribution of individual components of the translational apparatus (e.g. tRNAs, elongation factors and their modifiers) to the overall control of translation elongation and how their dysregulation contributes towards disease processes.

Breast Cancer: A Molecularly Heterogenous Disease Needing Subtype-Specific Treatments

Breast cancer is the most commonly occurring cancer in women. There were over two-million new cases in world in 2018. It is the second leading cause of death from cancer in western countries. At the molecular level, breast cancer is a heterogeneous disease, which is characterized by high genomic instability evidenced by somatic gene mutations, copy number alterations, and chromosome structural rearrangements. The genomic instability is caused by defects in DNA damage repair, transcription, DNA replication, telomere maintenance and mitotic chromosome segregation. According to molecular features, breast cancers are subdivided in subtypes, according to activation of hormone receptors (estrogen receptor and progesterone receptor), of human epidermal growth factors receptor 2 (HER2), and or BRCA mutations. In-depth analyses of the molecular features of primary and metastatic breast cancer have shown the great heterogeneity of genetic alterations and their clonal evolution during disease development. These studies have contributed to identify a repertoire of numerous disease-causing genes that are altered through different mutational processes. While early-stage breast cancer is a curable disease in about 70% of patients, advanced breast cancer is largely incurable. However, molecular studies have contributed to develop new therapeutic approaches targeting HER2, CDK4/6, PI3K, or involving poly(ADP-ribose) polymerase inhibitors for BRCA mutation carriers and immunotherapy.

Molecular stratification within triple-negative breast cancer subtypes

Triple-negative breast cancer (TNBC) has been subdivided into six distinct subgroups: basal-like 1 (BL1), basal-like 2 (BL2), mesenchymal (M), mesenchymal stem-like (MSL), immunomodulatory (IM), and luminal androgen receptor (LAR). We recently identified a subgroup of TNBC with loss of the tumor suppressor PTEN and five specific microRNAs that exhibits exceedingly poor clinical outcome and contains TP53 mutation, RB1 loss and high MYC and WNT signalling. Here, show that these PTEN-low/miRNA-low lesions cluster with BL1 TNBC. These tumors exhibited high RhoA signalling and were significantly stratified on the basis of PTEN-low/RhoA-signalling-high with hazard ratios (HRs) of 8.2 (P = 0.0009) and 4.87 (P = 0.033) in training and test cohorts, respectively. For BL2 TNBC, we identified AKT1 copy gain/high mRNA expression as surrogate for poor prognosis (HR = 3.9; P = 0.02 and HR = 6.1; P = 0.0032). In IM, programmed cell death 1 (PD1) was elevated and predictive of poor prognosis (HR = 5.3; P = 0.01 and HR = 3.5; P < 0.004). Additional alterations, albeit without prognostic power, characterized each subtype including high E2F2 and TGFβ signalling and CXCL8 expression in BL2, high IFNα and IFNγ signalling and CTLA4 expression in IM, and high EGFR signalling in MSL, and may be targeted for therapy. This study identified PTEN-low/RhoA-signalling-high, and high AKT1 and PD1 expression as potent prognostications for BL1, BL2 and IM subtypes with survival differences of over 14, 2.75 and 10.5 years, respectively. This intrinsic heterogeneity could be exploited to prioritize patients for precision medicine.

eEF2 kinase mediated autophagy as a potential therapeutic target for paclitaxel-resistant triple-negative breast cancer

Background

Triple-negative breast cancers (TNBCs) are initially responsive to chemotherapy, but most recurrent TNBCs develop resistance. Autophagy is believed to play dual roles in cancer and might contribute to chemoresistance. In this study, we aimed to investigate the role of autophagy and its regulator, eukaryotic elongation factor 2 kinase (eEF2K), in determining the biological nature of TNBC.

Methods

We used in vitro models of TNBC, namely, paclitaxel-resistant cell lines derived from sensitive cell lines. Various approaches to measuring autophagy flux were applied. We assessed the effects of inhibiting autophagy and silencing eEF2K on cell viability, tumor formation and invasion. We also collected residual tumor samples from 222 breast cancer patients who underwent neoadjuvant chemotherapy and measured eEF2K and LC3 expression levels by immunohistochemistry (IHC). Multivariate survival analysis was used to determine prognostic variables.

Results

Compared to the parental lines, the chemoresistant lines exhibited enhanced starvation-stimulated autophagy and showed significant decreases in cell viability, growth and invasion upon treatment with autophagy inhibitors. eEF2K silencing also resulted in the suppression of autophagic activity and in aggressive biological behavior. In the survival analysis, residual tumor LC3 (P=0.001) and eEF2K (P=0.027) expression levels were independent prognostic factors for patients who underwent neoadjuvant chemotherapy, especially in those with TNBC.

Conclusions

Our study indicated that eEF2K and autophagy play key roles in the maintenance of aggressive tumor behavior and chemoresistance in resistant TNBC. eEF2K silencing may be a novel strategy for the treatment of TNBC.

Loss of heterozygosity and immunoexpression of PTEN in oral epithelial dysplasia and squamous cell carcinoma

INTRODUCTION

Oral epithelial dysplasia (OED) is a risk factor for developing subsequent oral squamous cell carcinoma (OSCC). Loss of heterozygosity (LOH) profiles have been validated as risk predictors of malignant transformation of OED. It is still unclear if Phosphatase and tensin homologue deleted on chromosome 10 (PTEN) allelic loss also occurs in initial stage malignant lesions and if the allelic loss is involved as one of the mechanisms of oral carcinogenesis. Thus, this study objective investigate LOH of PTEN gene and the immunohistochemical expression of the protein in OED and OSCC samples.

MATERIAL AND METHODS

Formalin-fixed paraffin-embedded samples of 19 OEDs and 16 OSCCs were included to immunohistochemistry and LOH analysis. Two polymorphic microsatellite markers (AFMA086WG9 and D10S1765) located in chromosome 10 were used in this study for LOH analysis. For immunohistochemical analysis, 5 random fields with 400× magnification were evaluated quantitatively and qualitatively in epithelial and neoplastic cells.

RESULTS

AFMA086WG9 marker only demonstrated LOH in OEDs cases (10.5%). D10S1765 marker demonstrated LOH in 57.2% of OEDs and 50% of OSCCs. Higher nuclear immunostaining was detected in cases of OSCCs when compared to OEDs (p < .001) and there was strong cytoplasmic immunoexpression in OSCCs (p < .045).

CONCLUSIONS

We provide evidence that the allelic loss of PTEN is present in premalignant oral lesions and OSCCs, however the LOH of PTEN does not seems to influence its protein expression.

Autophagy-related Proteins as a Prognostic Factor of Patients With Colorectal Cancer

OBJECTIVES

Autophagy plays a dual role in tumorigenesis. In the initial stages, it promotes cell survival and suppresses carcinogenesis, whereas in cancer development, it induces cancer cell survival. In this study, we investigate the role of autophagy as a protective or tumor suppressor mechanism in colorectal cancer (CRC) cell lines and evaluate its role as a potential biomarker in human tumor samples.

MATERIALS AND METHODS

The data of 68 patients with CRC treated at our Department from January 1 to December 31, 2016 were analyzed. Immunohistochemistry evaluation of p62, LC3B, Beclin-1, and Rab-7 in formalin-fixed paraffin-embedded tissue samples was performed and their expression was correlated with clinicopathologic characteristics, mutation status, and therapeutic approach. The χ was used to test an association among categorical variables. Survival curves were estimated using the Kaplan-Meier method and differences were assessed using the log-rank test. Colo-205, HT29, SW-480, and Caco-2 cell lines were also used so as to test the autophagy markers with oxaliplatin, irinotecan, hydroxychloroquine, and 3-methyladenine.

RESULTS

Overexpression of Beclin-1 is associated with poor survival (P=0.001) in patients with CRC treated with chemotherapy, irrespective of the stage and mutational status. Rab-7 is also correlated with progression-free survival (PFS) (P=0.088). Oxaliplatin (10 and 20 μΜ) and irinotecan (10 and 20 μΜ) inhibit autophagy in microsatellite stable (MSS) CRC cell lines. The inhibition of autophagy in MSS CRC cell lines after treatment with oxaliplatin and irinotecan is further identified through monodancylcadaverine staining. Moreover, inhibition of autophagy with molecules such as hydroxychloroquine (20 μΜ) and 3-methyladenine (5 mM) was identified by the accumulation of p62 and LC3B.

CONCLUSIONS

Beclin-1 is an independent prognostic factor of overall survival and PFS. Also, Rab-7 is identified as an independent prognostic factor of PFS. Besides, several chemotherapeutic drugs such as oxaliplatin and irinotecan inhibit autophagy in MSS CRC cell lines in a similar way like hydroxychloroquine and 3-methyladenine. Thus, in MSS patients who develop chemoresistance, a combination of other therapies that include an autophagy inhibitor could be more beneficial. Further clinical trials are needed to investigate these therapeutic strategies.

Stem Cells and the Differentiation Hierarchy in Mammary Gland Development

The mammary gland is a highly dynamic organ that undergoes profound changes within its epithelium during puberty and the reproductive cycle. These changes are fueled by dedicated stem and progenitor cells. Both short- and long-lived lineage-restricted progenitors have been identified in adult tissue as well as a small pool of multipotent mammary stem cells (MaSCs), reflecting intrinsic complexity within the epithelial hierarchy. While unipotent progenitor cells predominantly execute day-to-day homeostasis and postnatal morphogenesis during puberty and pregnancy, multipotent MaSCs have been implicated in coordinating alveologenesis and long-term ductal maintenance. Nonetheless, the multipotency of stem cells in the adult remains controversial. The advent of large-scale single-cell molecular profiling has revealed striking changes in the gene expression landscape through ontogeny and the presence of transient intermediate populations. An increasing number of lineage cell-fate determination factors and potential niche regulators have now been mapped along the hierarchy, with many implicated in breast carcinogenesis. The emerging diversity among stem and progenitor populations of the mammary epithelium is likely to underpin the heterogeneity that characterizes breast cancer.

Identification of CDC25 as a Common Therapeutic Target for Triple-Negative Breast Cancer

CDK4/6 inhibitors are effective against cancer cells expressing the tumor suppressor RB1, but not RB1-deficient cells, posing the challenge of how to target RB1 loss. In triple-negative breast cancer (TNBC), RB1 and PTEN are frequently inactivated together with TP53. We performed kinome/phosphatase inhibitor screens on primary mouse Rb/p53-, Pten/p53-, and human RB1/PTEN/TP53-deficient TNBC cell lines and identified CDC25 phosphatase as a common target. Pharmacological or genetic inhibition of CDC25 suppressed growth of RB1-deficient TNBC cells that are resistant to combined CDK4/6 plus CDK2 inhibition. Minimal cooperation was observed in vitro between CDC25 antagonists and CDK1, CDK2, or CDK4/6 inhibitors, but strong synergy with WEE1 inhibition was apparent. In accordance with increased PI3K signaling following long-term CDC25 inhibition, CDC25 and PI3K inhibitors effectively synergized to suppress TNBC growth both in vitro and in xenotransplantation models. These results provide a rationale for the development of CDC25-based therapies for diverse RB1/PTEN/TP53-deficient and -proficient TNBCs.

Liu et al. report that inhibition of the protein phosphatase CDC25 kills diverse triple-negative breast cancer (TNBC) cells. Moreover, CDC25 antagonists cooperate with other drugs, such as PI3K inhibitors, to efficiently suppress growth of human TNBC engrafted into mice.

Intraclonal Plasticity in Mammary Tumors Revealed through Large-Scale Single-Cell Resolution 3D Imaging

Breast tumors are inherently heterogeneous, but the evolving cellular organization through neoplastic progression is poorly understood. Here we report a rapid, large-scale single-cell resolution 3D imaging protocol based on a one-step clearing agent that allows visualization of normal tissue architecture and entire tumors at cellular resolution. Imaging of multicolor lineage-tracing models of breast cancer targeted to either basal or luminal progenitor cells revealed profound clonal restriction during progression. Expression profiling of clones arising in Pten/Trp53-deficient tumors identified distinct molecular signatures. Strikingly, most clones harbored cells that had undergone an epithelial-to-mesenchymal transition, indicating widespread, inherent plasticity. Hence, an integrative pipeline that combines lineage tracing, 3D imaging, and clonal RNA sequencing technologies offers a comprehensive path for studying mechanisms underlying heterogeneity in whole tumors.

Estrogen receptor beta increases sensitivity to enzalutamide in androgen receptor-positive triple-negative breast cancer

PURPOSE

Androgen receptor (AR) is playing an important role in the progression of a subset of TNBC. We evaluated the impact of ERβ expression along with anti-AR drugs in AR-positive TNBC.

METHODS

ERβ expression was examined in AR-positive TNBC cell line using MTT assay, scratch and Annexin V-FITC assay in the presence or absence of anti-androgens. Protein levels of involved molecules were assessed using Western blot. Receptors' localization was detected by immunofluorescence and their physical association was examined using proximity ligation assay (PLA), which enables the visualization of interacting proteins in fixed cells and tissues.

RESULTS

Transient transfection of ERβ in MDA-MB 453 AR-positive TNBC cell line significantly inhibited cell proliferation, metastatic potential and induced apoptosis. ERβ expression reversed the aggravating role of AR in both indirect and direct ways. Indirectly, ERβ decreased AR activation through the inhibition of PI3K/AKT signaling pathway. Directly, ERβ formed heterodimers with AR in MDA-MB 453 cells and in human tissue samples impeding AR from forming homodimers. Enzalutamide is a more potent anti-androgen in AR + TNBC compared to bicalutamide. ERβ expression increased the sensitivity of MDA-MB 453 cells to anti-androgens and especially to enzalutamide. The administration of enzalutamide enhanced AR:ERβ heterodimers formation increasing the anti-tumor capacity of ERβ.

CONCLUSIONS

Collectively, our results provide evidence for a novel mechanism by which ERβ exerts oncosuppressive effect in AR-positive TBNC through direct and indirect interactions with AR. Moreover, ERβ expression may identify a new subset of TNBC that would respond more favorable to anti-androgens.

Alleles of Insm1 determine whether RIP1-Tag2 mice produce insulinomas or nonfunctioning pancreatic neuroendocrine tumors

The two most common types of pancreatic neuroendocrine tumors (PanNETs) are insulinomas and nonfunctioning PanNETs (NF-PanNETs). Insulinomas are small, rarely metastatic tumors that secrete high amounts of insulin, and nonfunctioning PanNETs are larger tumors that are frequently metastatic but that do not secrete hormones. Insulinomas are modeled by the highly studied RIP1-Tag2 (RT2) transgenic mice when bred into a C57Bl/6 (B6) genetic background (also known as RT2 B6 mice). But there has been a need for an animal model of nonfunctioning PanNETs, which in the clinic are a more common and severe disease. Here we show that when bred into a hybrid AB6F1 genetic background, RT2 mice make nonfunctioning PanNETs. Compared to insulinomas produced by RT2 B6 mice, the tumors produced by RT2 AB6F1 mice were larger and more metastatic, and the animals did not suffer from hypoglycemia or hyperinsulinemia. Genetic crosses revealed that a locus in mouse chromosome 2qG1 was linked to liver metastasis and to lack of insulin production. This locus was tightly linked to the gene encoding Insm1, a beta cell transcription factor that was highly expressed in human insulinomas but unexpressed in other types of PanNETs due to promoter hypermethylation. Insm1-deficient human cell lines expressed stem cell markers, were more invasive in vitro, and metastasized at higher rates in vivo when compared to isogenic Insm1-expressing cell lines. These data demonstrate that expression of Insm1 can determine whether a PanNET is a localized insulinoma or a metastatic nonfunctioning tumor.

A subgroup of microRNAs defines PTEN-deficient, triple-negative breast cancer patients with poorest prognosis and alterations in RB1, MYC, and Wnt signaling

BACKGROUND

Triple-negative breast cancer (TNBC) represents a heterogeneous group of ER- and HER2-negative tumors with poor clinical outcome. We recently reported that Pten-loss cooperates with low expression of microRNA-145 to induce aggressive TNBC-like lesions in mice. To systematically identify microRNAs that cooperate with PTEN-loss to induce aggressive human BC, we screened for miRNAs whose expression correlated with PTEN mRNA levels and determined the prognostic power of each PTEN-miRNA pair alone and in combination with other miRs.

METHODS

Publically available data sets with mRNA, microRNA, genomics, and clinical outcome were interrogated to identify miRs that correlate with PTEN expression and predict poor clinical outcome. Alterations in genomic landscape and signaling pathways were identified in most aggressive TNBC subgroups. Connectivity mapping was used to predict response to therapy.

RESULTS

In TNBC, PTEN loss cooperated with reduced expression of hsa-miR-4324, hsa-miR-125b, hsa-miR-381, hsa-miR-145, and has-miR136, all previously implicated in metastasis, to predict poor prognosis. A subgroup of TNBC patients with PTEN-low and reduced expression of four or five of these miRs exhibited the worst clinical outcome relative to other TNBCs (hazard ratio (HR) = 3.91; P < 0.0001), and this was validated on an independent cohort (HR = 4.42; P = 0.0003). The PTEN-low/miR-low subgroup showed distinct oncogenic alterations as well as TP53 mutation, high RB1-loss signature and high MYC, PI3K, and β-catenin signaling. This lethal subgroup almost completely overlapped with TNBC patients selected on the basis of Pten-low and RB1 signature loss or β-catenin signaling-high. Connectivity mapping predicted response to inhibitors of the PI3K pathway.

CONCLUSIONS

This analysis identified microRNAs that define a subclass of highly lethal TNBCs that should be prioritized for aggressive therapy.

Thymoquinone inhibits cell proliferation, migration, and invasion by regulating the elongation factor 2 kinase (eEF-2K) signaling axis in triple-negative breast cancer

BACKGROUND/PURPOSE

Triple-negative breast cancer (TNBC) is the most aggressive and chemoresistant subtype of breast cancer. Therefore, new molecular targets and treatments need to be developed to improve poor patient prognosis and survival. We have previously shown that eukaryotic elongation factor 2 kinase (eEF-2K) is highly expressed in TNBC cells, is associated with poor patient survival and prognosis, and promotes cell proliferation, migration, and invasion. In vivo targeting of eEF-2K significantly reduces the tumor growth of orthotopic TNBC xenograft mouse models, suggesting that eEF-2K may serve as a potential novel therapeutic target.

METHODS/RESULTS

In the current study, we identified thymoquinone (TQ), an active ingredient of Nigella sativa, as a potential safe and effective eEF-2K inhibitor in TNBC. We demonstrated for the first time that TQ inhibits the protein and mRNA expression of eEF-2K, as well as the clinically relevant downstream targets, including Src/FAK and Akt, and induces the tumor suppressor miR-603, in response to NF-kB inhibition. This effect was associated with a significant decrease in the proliferation, colony formation, migration, and invasion of TNBC cells. Furthermore, systemic in vivo injection of TQ (20 and 100 mg/kg) significantly reduced the growth of MDA-MB-231 tumors and inhibited the eEF-2K expression in an orthotopic tumor model in mice.

CONCLUSION

Our study provides first evidence that TQ treatment inhibits cell proliferation, migration/invasion, and tumor growth, in part through the inhibition of eEF-2K signaling in TNBC. Thus, our findings suggest that systemic TQ treatment may be used as a targeted therapeutic strategy for the inhibition of eEF-2K in TNBC tumor growth and progression.

Identifying and Targeting Sporadic Oncogenic Genetic Aberrations in Mouse Models of Triple-Negative Breast Cancer

Triple-negative breast cancers (TNBC) are genetically characterized by aberrations in TP53 and a low rate of activating point mutations in common oncogenes, rendering it challenging in applying targeted therapies. We performed whole-exome sequencing (WES) and RNA sequencing (RNA-seq) to identify somatic genetic alterations in mouse models of TNBCs driven by loss of Trp53 alone or in combination with Brca1 Amplifications or translocations that resulted in elevated oncoprotein expression or oncoprotein-containing fusions, respectively, as well as frameshift mutations of tumor suppressors were identified in approximately 50% of the tumors evaluated. Although the spectrum of sporadic genetic alterations was diverse, the majority had in common the ability to activate the MAPK/PI3K pathways. Importantly, we demonstrated that approved or experimental drugs efficiently induce tumor regression specifically in tumors harboring somatic aberrations of the drug target. Our study suggests that the combination of WES and RNA-seq on human TNBC will lead to the identification of actionable therapeutic targets for precision medicine-guided TNBC treatment.Significance: Using combined WES and RNA-seq analyses, we identified sporadic oncogenic events in TNBC mouse models that share the capacity to activate the MAPK and/or PI3K pathways. Our data support a treatment tailored to the genetics of individual tumors that parallels the approaches being investigated in the ongoing NCI-MATCH, My Pathway Trial, and ESMART clinical trials. Cancer Discov; 8(3); 354-69. ©2017 AACR.See related commentary by Natrajan et al., p. 272See related article by Matissek et al., p. 336This article is highlighted in the In This Issue feature, p. 253.

Eukaryotic elongation factor 2 kinase upregulates the expression of proteins implicated in cell migration and cancer cell metastasis

Eukaryotic elongation factor 2 kinase (eEF2K) negatively regulates the elongation phase of mRNA translation and hence protein synthesis. Increasing evidence indicates that eEF2K plays an important role in the survival and migration of cancer cells and in tumor progression. As demonstrated by two-dimensional wound-healing and three-dimensional transwell invasion assays, knocking down or inhibiting eEF2K in cancer cells impairs migration and invasion of cancer cells. Conversely, exogenous expression of eEF2K or knocking down eEF2 (the substrate of eEF2K) accelerates wound healing and invasion. Importantly, using LC-HDMS^E analysis, we identify 150 proteins whose expression is decreased and 73 proteins which are increased upon knocking down eEF2K in human lung carcinoma cells. Of interest, 34 downregulated proteins are integrins and other proteins implicated in cell migration, suggesting that inhibiting eEF2K may help prevent cancer cell mobility and metastasis. Interestingly, eEF2K promotes the association of integrin mRNAs with polysomes, providing a mechanism by which eEF2K may enhance their cellular levels. Consistent with this, genetic knock down or pharmacological inhibition of eEF2K reduces the protein expression levels of integrins. Notably, pharmacological or genetic inhibition of eEF2K almost completely blocked tumor growth and effectively prevented the spread of tumor cells in vivo. High levels of eEF2K expression were associated with invasive carcinoma and metastatic tumors. These data provide the evidence that eEF2K is a new potential therapeutic target for preventing tumor metastasis.

Translational opportunities for broad-spectrum natural phytochemicals and targeted agent combinations in breast cancer

Breast cancer (BC) prevention and therapy in the context of life-style risk factors and biological drivers is a major focus of developmental therapeutics in oncology. Obesity, alcohol, chronic estrogen signaling and smoking have distinct BC precipitating and facilitating effects that may act alone or in combination. A spectrum of signaling events including enhanced oxidative stress and changes in estrogen-receptor (ER)-dependent and -independent signaling drive the progression of BC. Breast tumors modulate ERα/ERβ ratio, upregulate proliferative pathways driven by ERα and HER2 with a parallel loss and/or downregulation of tumor suppressors such as TP53 and PTEN which together impact the efficacy of therapeutic strategies and frequently lead to emergence of drug resistance. Natural phytochemicals modulate oxidative stress, leptin, integrin, HER2, MAPK, ERK, Wnt/β-catenin and NFκB signaling along with regulating ERα and ERβ, thereby presenting unique opportunities for both primary and combinatorial interventions in BC. In this regard, this article focuses on critical analyses of the evidence from multiple studies on the efficacy of natural phytochemicals in BC. In addition, areas in which the combinations of such effective natural phytochemicals with approved and/or developing anticancer agents can be translationally beneficial are discussed to derive evidence-based inference for addressing challenges in BC control and therapy.