The oncogene HER2/neu (ERBB2) requires the hypoxia-inducible factor HIF-1 for mammary tumor growth and anoikis resistance

Targeting anoikis resistance as a strategy for cancer therapy

Anoikis, known as matrix detachment-induced apoptosis or detachment-induced cell death, is crucial for tissue development and homeostasis. Cancer cells develop means to evade anoikis, e.g. anoikis resistance, thereby allowing for cells to survive under anchorage-independent conditions. Uncovering the mechanisms of anoikis resistance will provide details about cancer metastasis, and potential strategies against cancer cell dissemination and metastasis. Here, we summarize the principal elements and core molecular mechanisms of anoikis and anoikis resistance. We discuss the latest progress of how anoikis and anoikis resistance are regulated in cancers. Furthermore, we summarize emerging data on selective compounds and nanomedicines, explaining how inhibiting anoikis resistance can serve as a meaningful treatment modality against cancers. Finally, we discuss the key limitations of this therapeutic paradigm and possible strategies to overcome them. In this review, we suggest that pharmacological modulation of anoikis and anoikis resistance by bioactive compounds could surmount anoikis resistance, highlighting a promising therapeutic regimen that could be used to overcome anoikis resistance in cancers.

EDI3 knockdown in ER-HER2+ breast cancer cells reduces tumor burden and improves survival in two mouse models of experimental metastasis

BACKGROUND

Despite progress understanding the mechanisms underlying tumor spread, metastasis remains a clinical challenge. We identified the choline-producing glycerophosphodiesterase, EDI3 and reported its association with metastasis-free survival in endometrial cancer. We also observed that silencing EDI3 slowed cell migration and other cancer-relevant phenotypes in vitro. Recent work demonstrated high EDI3 expression in ER-HER2+ breast cancer compared to the other molecular subtypes. Silencing EDI3 in ER-HER2+ cells significantly reduced cell survival in vitro and decreased tumor growth in vivo. However, a role for EDI3 in tumor metastasis in this breast cancer subtype was not explored. Therefore, in the present work we investigate whether silencing EDI3 in ER-HER2+ breast cancer cell lines alters phenotypes linked to metastasis in vitro, and metastasis formation in vivo using mouse models of experimental metastasis.

METHODS

To inducibly silence EDI3, luciferase-expressing HCC1954 cells were transduced with lentiviral particles containing shRNA oligos targeting EDI3 under the control of doxycycline. The effect on cell migration, adhesion, colony formation and anoikis was determined in vitro, and significant findings were confirmed in a second ER-HER2+ cell line, SUM190PT. Doxycycline-induced HCC1954-luc shEDI3 cells were injected into the tail vein or peritoneum of immunodeficient mice to generate lung and peritoneal metastases, respectively and monitored using non-invasive bioluminescence imaging. Metabolite levels in cells and tumor tissue were analyzed using targeted mass spectrometry and MALDI mass spectrometry imaging (MALDI-MSI), respectively.

RESULTS

Inducibly silencing EDI3 reduced cell adhesion and colony formation, as well as increased susceptibility to anoikis in HCC1954-luc cells, which was confirmed in SUM190PT cells. No influence on cell migration was observed. Reduced luminescence was seen in lungs and peritoneum of mice injected with cells expressing less EDI3 after tail vein and intraperitoneal injection, respectively, indicative of reduced metastasis. Importantly, mice injected with EDI3-silenced cells survived longer. Closer analysis of the peritoneal organs revealed that silencing EDI3 had no effect on metastatic organotropism but instead reduced metastatic burden. Finally, metabolic analyses revealed significant changes in choline and glycerophospholipid metabolites in cells and in pancreatic metastases in vivo.

CONCLUSIONS

Reduced metastasis upon silencing supports EDI3's potential as a treatment target in metastasizing ER-HER2+ breast cancer.

SARS-CoV-2 Infection to Premature Neuronal Aging and Neurodegenerative Diseases: Is there any Connection with Hypoxia?

The pandemic of coronavirus disease-2019 (COVID-19), caused by SARS-CoV-2, has become a global concern as it leads to a spectrum of mild to severe symptoms and increases death tolls around the world. Severe COVID-19 results in acute respiratory distress syndrome, hypoxia, and multi- organ dysfunction. However, the long-term effects of post-COVID-19 infection are still unknown. Based on the emerging evidence, there is a high possibility that COVID-19 infection accelerates premature neuronal aging and increases the risk of age-related neurodegenerative diseases in mild to severely infected patients during the post-COVID period. Several studies correlate COVID-19 infection with neuronal effects, though the mechanism through which they contribute to the aggravation of neuroinflammation and neurodegeneration is still under investigation. SARS-CoV-2 predominantly targets pulmonary tissues and interferes with gas exchange, leading to systemic hypoxia. The neurons in the brain require a constant supply of oxygen for their proper functioning, suggesting that they are more vulnerable to any alteration in oxygen saturation level that results in neuronal injury with or without neuroinflammation. We hypothesize that hypoxia is one of the major clinical manifestations of severe SARS-CoV-2 infection; it directly or indirectly contributes to premature neuronal aging, neuroinflammation, and neurodegeneration by altering the expression of various genes responsible for the survival of the cells. This review focuses on the interplay between COVID-19 infection, hypoxia, premature neuronal aging, and neurodegenerative diseases and provides a novel insight into the molecular mechanisms of neurodegeneration.

HER2 Alterations in Non-Small Cell Lung Cancer: Biologico-Clinical Consequences and Interest in Therapeutic Strategies

Lung cancer stands as the first cause of death by cancer in the world. Despite the improvement in patients' outcomes in the past decades through the development of personalized medicine approaches, a substantial portion of patients remains ineligible for targeted therapies due to the lack of a "druggable" molecular target. HER2, a receptor tyrosine kinase member of the EGFR/ErbB family, is known to show oncogenic properties. In this review, we focus on the different HER2 dysregulation mechanisms that have been observed in non-small cell lung cancer (NSCLC): gene mutation, gene amplification, protein overexpression and protein hyper-phosphorylation, the latter suggesting that HER2 dysregulation can occur independently of any molecular aberration. These HER2 alterations inevitably have consequences on tumor biology. Here, we discuss how they are not only involved in abnormal proliferation and survival of cancer cells but also potentially in increased angiogenic properties, mesenchymal features and tumor immune escape. Finally, we review the impact of these HER2 alterations in various therapeutic approaches. While standard chemotherapy and groundbreaking immunotherapy seem rather ineffective for HER2-altered NSCLCs, the development of HER2-targeted therapies such as tyrosine kinase inhibitors, anti-HER2 antibodies and especially antibody-drug conjugates could provide new hopes for patients.

Hypoxia signaling and metastatic progression

Disruption of oxygen homeostasis, resulting from an imbalance between O2 supply and demand during malignant proliferation, leads to the development of hypoxic tumor microenvironments that promote the acquisition of aggressive cancer cell phenotypes linked to metastasis and patient mortality. In this review, the mechanistic links between tumor hypoxia and metastatic progression are presented. Current status and perspectives of targeting hypoxia signaling pathways as a strategy to halt cancer cell metastatic activities are emphasized.

Anoikis resistance--protagonists of breast cancer cells survive and metastasize after ECM detachment

Breast cancer exhibits the highest global incidence among all tumor types. Regardless of the type of breast cancer, metastasis is a crucial cause of poor prognosis. Anoikis, a form of apoptosis initiated by cell detachment from the native environment, is an outside-in process commencing with the disruption of cytosolic connectors such as integrin-ECM and cadherin-cell. This disruption subsequently leads to intracellular cytoskeletal and signaling pathway alterations, ultimately activating caspases and initiating programmed cell death. Development of an anoikis-resistant phenotype is a critical initial step in tumor metastasis. Breast cancer employs a series of stromal alterations to suppress anoikis in cancer cells. Comprehensive investigation of anoikis resistance mechanisms can inform strategies for preventing and regressing metastatic breast cancer. The present review first outlines the physiological mechanisms of anoikis, elucidating the alterations in signaling pathways, cytoskeleton, and protein targets that transpire from the outside in upon adhesion loss in normal breast cells. The specific anoikis resistance mechanisms induced by pathological changes in various spatial structures during breast cancer development are also discussed. Additionally, the genetic loci of targets altered in the development of anoikis resistance in breast cancer, are summarized. Finally, the micro-RNAs and targeted drugs reported in the literature concerning anoikis are compiled, with keratocin being the most functionally comprehensive. Video Abstract.

Mammalian orthoreovirus infection in human epidermal growth factor receptor 2 positive (HER2+) breast cancer cells

Mammalian orthoreovirus (MRV) is a clinically benign oncolytic virus which has been investigated for use in multiple cancer types, including breast cancer (BC). In human clinical trials, MRV has been shown to be safe, and multiple BC patients have shown partial responses to intratumoral and intravenous virus delivery. Combination therapies inclusive of MRV and current FDA approved BC chemotherapies are being investigated to target metastatic, early BC, and triple negative BC. Though MRV is being tested clinically, we still do not fully understand the highly variable patient responses to MRV therapy. One of the most aggressive BC subtypes is HER2+ BC, in which human epidermal growth factor receptor 2 (HER2) is dysregulated, resulting in increased growth, survival, and metastasis of cancer cells. FDA approved therapies, trastuzumab and pertuzumab, target HER2 to prevent signaling of the phosphoinositide 3-kinase (PI3K) pathway. However, recent findings show that accumulation of hypoxia inducible factor-1 alpha (HIF-1α) in HER2+ BC cells contributes to trastuzumab resistance. In this work, we provide evidence that MRV infects, replicates in, and kills HER2 overexpressing cells. MRV infection is also found to have variable effects on signaling pathways that activate or are activated by HER2 expression. Finally, we show that MRV reduces HIF-1α accumulation in all the cell lines tested, including a HER2+ BC cell line. These studies provide further evidence that MRV holds promise for use in conjunction with trastuzumab to treat HER2+ BC patients.

Anoikis resistance in diffuse glioma: The potential therapeutic targets in the future

Glioma is the most common malignant intracranial tumor and exhibits diffuse metastasis and a high recurrence rate. The invasive property of glioma results from cell detachment. Anoikis is a special form of apoptosis that is activated upon cell detachment. Resistance to anoikis has proven to be a protumor factor. Therefore, it is suggested that anoikis resistance commonly occurs in glioma and promotes diffuse invasion. Several factors, such as integrin, E-cadherin, EGFR, IGFR, Trk, TGF-β, the Hippo pathway, NF-κB, eEF-2 kinase, MOB2, hypoxia, acidosis, ROS, Hsp and protective autophagy, have been shown to induce anoikis resistance in glioma. In our present review, we aim to summarize the underlying mechanism of resistance and the therapeutic potential of these molecules.

The prognostic outcome of 'type 2 diabetes mellitus and breast cancer' association pivots on hypoxia-hyperglycemia axis

Type 2 diabetes mellitus and breast cancer are complex, chronic, heterogeneous, and multi-factorial diseases; with common risk factors including but not limited to diet, obesity, and age. They also share mutually inclusive phenotypic features such as the metabolic deregulations resulting from hyperglycemia, hypoxic conditions and hormonal imbalances. Although, the association between diabetes and cancer has long been speculated; however, the exact molecular nature of this link remains to be fully elucidated. Both the diseases are leading causes of death worldwide and a causal relationship between the two if not addressed, may translate into a major global health concern. Previous studies have hypothesized hyperglycemia, hyperinsulinemia, hormonal imbalances and chronic inflammation, as some of the possible grounds for explaining how diabetes may lead to cancer initiation, yet further research still needs to be done to validate these proposed mechanisms. At the crux of this dilemma, hyperglycemia and hypoxia are two intimately related states involving an intricate level of crosstalk and hypoxia inducible factor 1, at the center of this, plays a key role in mediating an aggressive disease state, particularly in solid tumors such as breast cancer. Subsequently, elucidating the role of HIF1 in establishing the diabetes-breast cancer link on hypoxia-hyperglycemia axis may not only provide an insight into the molecular mechanisms underlying the association but also, illuminate on the prognostic outcome of the therapeutic targeting of HIF1 signaling in diabetic patients with breast cancer or vice versa. Hence, this review highlights the critical role of HIF1 signaling in patients with both T2DM and breast cancer, potentiates its significance as a prognostic marker in comorbid patients, and further discusses the potential prognostic outcome of targeting HIF1, subsequently establishing the pressing need for HIF1 molecular profiling-based patient selection leading to more effective therapeutic strategies emerging from personalized medicine.

Fibronectin assembly regulates lumen formation in breast acini

Fibronectin (FN) is an extracellular matrix (ECM) glycoprotein that self-assembles into FN fibrils, forming a FN matrix contributing to the stiffness of the ECM. Stromal FN stiffness in cancer has been shown to impact epithelial functions such as migration, cancer metastasis, and epithelial-to-mesenchymal transition. The role of the FN matrix of epithelial cells in driving such processes remains less well understood and is the focus of this study. Hypoxia, defined by low oxygen tension (<5%) is one of the hallmarks of tumor microenvironments impacting fibril reorganization in stromal and epithelial cells. Here, using the MCF10 breast epithelial progression series of cell lines encompassing normal, preinvasive, and invasive states, we show that FN fibril formation decreases during hypoxia, coinciding with a decrease in migratory potential of these cells. Conversely, we find that FN fibril disruption during three-dimensional acinar growth of normal breast cells resulted in acinar luminal filling. Our data also demonstrates that the luminal filling upon fibril disruption in untransformed MCF10A cells results in a loss of apicobasal polarity, characteristic of pre-invasive and invasive breast cell lines MCF10AT and MCF10 DCIS.com. Overall this is the first study that relates fibril-mediated changes in epithelial cells as critical players in lumen clearing of breast acini and maintenance of the untransformed growth characteristic.

Mechanisms for Modulating Anoikis Resistance in Cancer and the Relevance of Metabolic Reprogramming

The attachment of cells to the extracellular matrix (ECM) is the hallmark of structure–function stability and well-being. ECM detachment in localized tumors precedes abnormal dissemination of tumor cells culminating in metastasis. Programmed cell death (PCD) is activated during tumorigenesis to clear off ECM-detached cells through “anoikis.” However, cancer cells develop several mechanisms for abrogating anoikis, thus promoting their invasiveness and metastasis. Specific factors, such as growth proteins, pH, transcriptional signaling pathways, and oxidative stress, have been reported as drivers of anoikis resistance, thus enhancing cancer proliferation and metastasis. Recent studies highlighted the key contributions of metabolic pathways, enabling the cells to bypass anoikis. Therefore, understanding the mechanisms driving anoikis resistance could help to counteract tumor progression and prevent metastasis. This review elucidates the dynamics employed by cancer cells to impede anoikis, thus promoting proliferation, invasion, and metastasis. In addition, the authors have discussed other metabolic intermediates (especially amino acids and nucleotides) that are less explored, which could be crucial for anoikis resistance and metastasis.

Novel Small Molecule Hsp90/Cdc37 Interface Inhibitors Indirectly Target K-Ras-Signaling

The ATP-competitive inhibitors of Hsp90 have been tested predominantly in kinase addicted cancers; however, they have had limited success. A mechanistic connection between Hsp90 and oncogenic K-Ras is not known. Here, we show that K-Ras selectivity is enabled by the loss of the K-Ras membrane nanocluster modulator galectin-3 downstream of the Hsp90 client HIF-1α. This mechanism suggests a higher drug sensitivity in the context of KRAS mutant, HIF-1α-high and/or Gal3-high cancer cells, such as those found, in particular, in pancreatic adenocarcinoma. The low toxicity of conglobatin further indicates a beneficial on-target toxicity profile for Hsp90/Cdc37 interface inhibitors. We therefore computationally screened >7 M compounds, and identified four novel small molecules with activities of 4 μM-44 μM in vitro. All of the compounds were K-Ras selective, and potently decreased the Hsp90 client protein levels without inducing the heat shock response. Moreover, they all inhibited the 2D proliferation of breast, pancreatic, and lung cancer cell lines. The most active compounds from each scaffold, furthermore, significantly blocked 3D spheroids and the growth of K-Ras-dependent microtumors. We foresee new opportunities for improved Hsp90/Cdc37 interface inhibitors in cancer and other aging-associated diseases.

Using sufficient direction factor model to analyze latent activities associated with breast cancer survival

High-dimensional gene expression data often exhibit intricate correlation patterns as the result of coordinated genetic regulation. In practice, however, it is difficult to directly measure these coordinated underlying activities. Analysis of breast cancer survival data with gene expressions motivates us to use a two-stage latent factor approach to estimate these unobserved coordinated biological processes. Compared to existing approaches, our proposed procedure has several unique characteristics. In the first stage, an important distinction is that our procedure incorporates prior biological knowledge about gene-pathway membership into the analysis and explicitly model the effects of genetic pathways on the latent factors. Second, to characterize the molecular heterogeneity of breast cancer, our approach provides estimates specific to each cancer subtype. Finally, our proposed framework incorporates sparsity condition due to the fact that genetic networks are often sparse. In the second stage, we investigate the relationship between latent factor activity levels and survival time with censoring using a general dimension reduction model in the survival analysis context. Combining the factor model and sufficient direction model provides an efficient way of analyzing high-dimensional data and reveals some interesting relations in the breast cancer gene expression data.

Upregulation of HIF1-α via an NF-κB/COX2 pathway confers proliferative dominance of HER2-negative ductal carcinoma in situ cells in response to inflammatory stimuli

There are data to suggest that some ductal carcinoma in situ (DCIS) may evolve through an evolutionary bottleneck, where minor clones susceptible to the imposed selective pressure drive disease progression. Here, we tested the hypothesis that an impact of the inflammatory environment on DCIS evolution is HER2-dependent, conferring proliferative dominance of HER2-negative cells. In tissue samples, density of tumour-infiltrating immune cells (TIICs) was associated only with high tumour nuclear grade, but in 9% of predominantly HER2-negative cases, the presence of tumoral foci ('hot-spots') of basal-like cells with HIF1-α activity adjacent to the areas of dense stromal infiltration was noted. Results of in vitro analyses further demonstrated that IL-1β and TNF-α as well as macrophage-conditioned medium triggered phosphorylation of NF-κB and subsequent upregulation of COX2 and HIF1-α, exclusively in HER2-negative cells. Treatment with both IL-1β and TNF-α resulted in growth stimulation and inhibition of HER2-negative and HER2-positive cells, respectively. Moreover, ectopic overexpression of HIF1-α rescued HER2-positive cells from the negative effect of IL-1β and TNF-α on cell growth. Our data provide novel insight into the molecular basis of HER2-dependent proliferation of DCIS cells and indicate the NF-κB/COX2 → HIF1-α signalling axis as a dominant mechanism of DCIS evolution induced by inflammatory microenvironment. Presented findings also highlight the clinical significance of heterogeneity of DCIS tumours and suggest that HIF1-α might be considered as a predictive marker of disease progression.

Integrative In Vivo Drug Testing Using Gene Expression Signature and Patient-Derived Xenografts from Treatment-Refractory HER2 Positive and Triple-Negative Subtypes of Breast Cancer

Patient-derived xenografts (PDXs) are powerful tools for translational cancer research. Here, we established PDX models from different molecular subtypes of breast cancer for in vivo drug tests and compared the histopathologic features of PDX model tumors with those of patient tumors. Predictive biomarkers were identified by gene expression analysis of PDX samples using Nanostring nCount cancer panels. Validation of predictive biomarkers for treatment response was conducted in established PDX models by in vivo drug testing. Twenty breast cancer PDX models were generated from different molecular subtypes (overall success rate, 17.5%; 3.6% for HR⁺/HER2^-, 21.4% for HR⁺/HER2⁺, 21.9% for HR^-/HER2⁺ and 22.5% for triple-negative breast cancer (TNBC)). The histopathologic features of original tumors were retained in the PDX models. We detected upregulated HIF1A, RAF1, AKT2 and VEGFA in TNBC cases and demonstrated the efficacy of combined treatment with sorafenib and everolimus or docetaxel and bevacizumab in each TNBC model. Additionally, we identified upregulated HIF1A in two cases of trastuzumab-exposed HR^-/HER2⁺ PDX models and validated the efficacy of the HIF1A inhibitor, PX-478, alone or in combination with neratinib. Our results demonstrate that PDX models can be used as effective tools for predicting therapeutic markers and evaluating personalized treatment strategies in breast cancer patients with resistance to standard chemotherapy regimens.

Overexpression of HIF-1α contributes to melphalan resistance in multiple myeloma cells by activation of ERK1/2, Akt, and NF-κB

Multiple myeloma (MM) commonly displays multidrug resistance and is associated with poor prognosis. Therefore, it is important to identify the mechanisms by which MM cells develop multidrug resistance. Our previous study showed that multidrug resistance is correlated with overexpression of multidrug resistance protein 1 (MDR1) and Survivin, and downregulation of Bim expression in melphalan-resistant RPMI8226/L-PAM cells; however, the underlying mechanism of multidrug resistance remains unclear. In the present study, we investigated the mechanism of multidrug resistance in melphalan-resistant cells. We found that RPMI8226/L-PAM and ARH-77/L-PAM cells showed increased phosphorylation of extracellular signal-regulated protein kinase 1/2 (ERK1/2) and Akt, and nuclear localization of nuclear factor κB (NF-κB). The combination of ERK1/2, Akt, and NF-κB inhibitors with melphalan reversed melphalan resistance via suppression of Survivin expression and enhanced Bim expression in melphalan-resistant cells. In addition, RPMI8226/L-PAM and ARH-77/L-PAM cells overexpressed hypoxia-inducible factor 1α (HIF-1α) via activation of ERK1/2, Akt, and NF-κB. Moreover, suppression of HIF-1α by echinomycin or HIF-1α siRNA resensitized RPMI8226/L-PAM cells to melphalan through downregulation of Survivin expression and upregulation of Bim expression. These results indicate that enhanced Survivin expression and decreased Bim expression by HIF-1α via activation of ERK1/2, Akt, and NF-κB play a critical role in melphalan resistance. Our findings suggest that HIF-1α, ERK1/2, Akt, and NF-κB inhibitors are potentially useful as anti-MDR agents for the treatment of melphalan-resistant MM.

Translational and HIF-1α-Dependent Metabolic Reprogramming Underpin Metabolic Plasticity and Responses to Kinase Inhibitors and Biguanides

There is increasing interest in therapeutically exploiting metabolic differences between normal and cancer cells. We show that kinase inhibitors (KIs) and biguanides synergistically and selectively target a variety of cancer cells. Synthesis of non-essential amino acids (NEAAs) aspartate, asparagine, and serine, as well as glutamine metabolism, are major determinants of the efficacy of KI/biguanide combinations. The mTORC1/4E-BP axis regulates aspartate, asparagine, and serine synthesis by modulating mRNA translation, while ablation of 4E-BP1/2 substantially decreases sensitivity of breast cancer and melanoma cells to KI/biguanide combinations. Efficacy of the KI/biguanide combinations is also determined by HIF-1α-dependent perturbations in glutamine metabolism, which were observed in VHL-deficient renal cancer cells. This suggests that cancer cells display metabolic plasticity by engaging non-redundant adaptive mechanisms, which allows them to survive therapeutic insults that target cancer metabolism.

HER2-mediated GLI2 stabilization promotes anoikis resistance and metastasis of breast cancer cells

Breast cancer metastasis is a multi-step process and requires cells to overcome anoikis. Anoikis is defined as cell-death that occurs due to loss of cell adhesion. During the course of cancer progression, tumor cells acquire resistance to anoikis. However, mechanisms of anoikis resistance are not clear. Human epidermal growth receptor 2 (HER2) overexpressing breast tumors are known to be highly aggressive and metastatic. The mechanisms correlating HER2 with metastasis are poorly understood. We observed increased anoikis resistance in HER2 overexpressing breast cancer cells. In addition, we identified that HER2 overexpression was also associated with increased sonic hedgehog (SHH) signaling especially GLI2, and that inhibition of SHH pathway suppressed anoikis resistance. GSK3β is known to facilitate proteasome-mediated degradation of GLI2. Moreover, we observed that silencing of GLI2 resulted in reduced migration and invasion of HER2 overexpressing cells. Anoikis resistant HER2 overexpressing cells also showed increased rate and extent of metastasis in vivo, as compared to wild type anoikis resistant cells. Taken together, this study indicates a novel role of HER2/GSK3β/GLI2 axis in anoikis resistance and metastasis, and that GLI2 could be a potential target for anti-cancer therapies.

BHLHE40 confers a pro-survival and pro-metastatic phenotype to breast cancer cells by modulating HBEGF secretion

Background

Metastasis is responsible for a significant number of breast cancer-related deaths. Hypoxia, a primary driving force of cancer metastasis, induces the expression of BHLHE40, a transcription regulator. This study aimed to elucidate the function of BHLHE40 in the metastatic process of breast cancer cells.

Methods

To define the role of BHLHE40 in breast cancer, BHLHE40 expression was knocked down by a lentiviral construct expressing a short hairpin RNA against BHLHE40 or knocked out by the CRISPR/Cas9 editing system. Orthotopic xenograft and experimental metastasis (tail vein injection) mouse models were used to analyze the role of BHLHE40 in lung metastasis of breast cancer. Global gene expression analysis and public database mining were performed to identify signaling pathways regulated by BHLHE40 in breast cancer. The action mechanism of BHLHE40 was examined by chromatin immunoprecipitation (ChIP), co-immunoprecipitation (CoIP), exosome analysis, and cell-based assays for metastatic potential.

Results

BHLHE40 knockdown significantly reduced primary tumor growth and lung metastasis in orthotopic xenograft and experimental metastasis models of breast cancer. Gene expression analysis implicated a role of BHLHE40 in transcriptional activation of heparin-binding epidermal growth factor (HBEGF). ChIP and CoIP assays revealed that BHLHE40 induces HBEGF transcription by blocking DNA binding of histone deacetylases (HDAC)1 and HDAC2. Cell-based assays showed that HBEGF is secreted through exosomes and acts to promote cell survival and migration. Public databases provided evidence linking high expression of BHLHE40 and HBEGF to poor prognosis of triple-negative breast cancer.

Conclusion

This study reveals a novel role of BHLHE40 in promoting tumor cell survival and migration by regulating HBEGF secretion.

Unconventional Ways to Live and Die: Cell Death and Survival in Development, Homeostasis, and Disease

Balancing cell death and survival is essential for normal development and homeostasis and for preventing diseases, especially cancer. Conventional cell death pathways include apoptosis, a form of programmed cell death controlled by a well-defined biochemical pathway, and necrosis, the lysis of acutely injured cells. New types of regulated cell death include necroptosis, pyroptosis, ferroptosis, phagoptosis, and entosis. Autophagy can promote survival or can cause death. Newly described processes of anastasis and resuscitation show that, remarkably, cells can recover from the brink of apoptosis or necroptosis. Important new work shows that epithelia achieve homeostasis by extruding excess cells, which then die by anoikis due to loss of survival signals. This mechanically regulated process both maintains barrier function as cells die and matches rates of proliferation and death. In this review, we describe these unconventional ways in which cells have evolved to die or survive, as well as the contributions that these processes make to homeostasis and cancer.

CAIX furthers tumour progression in the hypoxic tumour microenvironment of esophageal carcinoma and is a possible therapeutic target

The hypoxic tumour microenvironment of solid tumours represents an important starting point for modulating progression and metastatic spread. Carbonic anhydrase IX (CAIX) is a known HIF-1α-dependent key player in maintaining cell pH conditions under hypoxia. We show that CAIX is strongly expressed in esophageal carcinoma tissues. We hypothesize that a moderate CAIX expression facilitates metastases and thereby worsens prognosis. Selective inhibition of CAIX by specific CAIX inhibitors and a CAIX knockdown effectively inhibit proliferation and migration in vitro. In the orthotopic esophageal carcinoma model, the humanized HER2 antibody trastuzumab down-regulates CAIX, possibly through CAIX’s linkage with HER2 in the hypoxic microenvironment. Our results show CAIX to be an essential part of the tumour microenvironment and a possible master regulator of tumour progression. This makes CAIX a highly effective and feasible therapeutic target for selective cancer treatment.

Investigation of hypoxia networks in ovarian cancer via bioinformatics analysis

Background

Ovarian cancer is a leading cause of the death from gynecologic malignancies. Hypoxia is closely related to the malignant growth of cells. However, the molecular mechanism of hypoxia-regulated ovarian cancer cells remains unclear. Thus, this study was conducted to identify the key genes and pathways implicated in the regulation of hypoxia by bioinformatics analysis.

Methods

Using the datasets of GSE53012 downloaded from the Gene Expression Omnibus (GEO), the differentially expressed genes (DEGs) were screened by comparing the RNA expression from cycling hypoxia group, chronic hypoxia group, and control group. Subsequently, cluster analysis was performed followed by the construction of the protein-protein interaction (PPI) network of the overlapping DEGs between the cycling hypoxia and chronic hypoxia using ClusterONE. In addition, gene ontology (GO) functional and pathway enrichment analyses of the DEGs in the most remarkable module were performed using Database for Annotation, Visualization and Integrated Discovery (DAVID) software. Ultimately, the signaling pathways associated with hypoxia were verified by RT-PCR, WB, and MTT assays.

Results

A total of 931 overlapping DEGs were identified. Nine hub genes and seven node genes were screened by analyzing the PPI and pathway integration networks, including ESR1, MMP2, ErbB2, MYC, VIM, CYBB, EDN1, SERPINE1, and PDK. Additionally, 11 key pathways closely associated with hypoxia were identified, including focal adhesion, ErbB signaling, and proteoglycans in cancer, among which the ErbB signaling pathway was verified by RT-PCR, WB, and MTT assays. Furthermore, functional enrichment analysis revealed that these genes were mainly involved in the proliferation of ovarian cancer cells, such as regulation of cell proliferation, cell adhesion, positive regulation of cell migration, focal adhesion, and extracellular matrix binding.

Conclusion

The results show that hypoxia can promote the proliferation of ovarian cancer cells by affecting the invasion and adhesion functions through the dysregulation of ErbB signaling, which may be governed by the HIF-1α-TGFA-EGFR-ErbB2-MYC axis. These findings will contribute to the identification of new targets for the diagnosis and treatment of ovarian cancer.

Electronic supplementary material

The online version of this article (10.1186/s13048-018-0388-x) contains supplementary material, which is available to authorized users.

A hypoxic signature marks tumors formed by disseminated tumor cells in the BALB-neuT mammary cancer model

Metastasis is the final stage of cancer progression. Some evidence indicates that tumor cell dissemination occurs early in the natural history of cancer progression. Disseminated tumor cells (DTC) have been described in the bone marrow (BM) of cancer patients as well as in experimental models, where they correlate with later development of metastasis. However, little is known about the tumorigenic features of DTC obtained at different time points along tumor progression. Here, we found that early DTC isolated from BM of 15-17 week-old Her2/neu transgenic (BALB-neuT) mice were not tumorigenic in immunodeficient mice. In contrast, DTC-derived tumors were easily detectable when late DTC obtained from 19-22 week-old BALB-neuT mice were injected. Angiogenesis, which contributes to regulate tumor dormancy, appeared dispensable to reactivate late DTC, although it accelerated growth of secondary DTC tumors. Compared with parental mammary tumors, gene expression profiling disclosed a distinctive transcriptional signature of late DTC tumors which was enriched for hypoxia-related transcripts and was maintained in ex-vivo cell culture. Altogether, these findings highlight a different tumorigenic potential of early and late DTC in the BALB-neuT model and describe a HIF-1α-related transcriptional signature in DTC tumors, which may render DTC angiogenesis-competent, when placed in a favourable environment.

NRF2 Regulates HER1 Signaling Pathway to Modulate the Sensitivity of Ovarian Cancer Cells to Lapatinib and Erlotinib

NF-E2-related factor 2 (NRF2) regulates the transcription of a battery of metabolic and cytoprotective genes. NRF2 and epidermal growth factor receptors (EGFRs/HERs) are regulators of cellular proliferation and determinants of cancer initiation and progression. NRF2 and HERs confer cancers with resistance to several therapeutic agents. Nevertheless, there is limited understanding of the regulation of HER expression and activation and the link between NRF2 and HER signalling pathways. We show that NRF2 regulates both basal and inducible expression of HER1, as treatment of ovarian cancer cells (PEO1, OVCAR3, and SKOV3) with NRF2 activator tBHQ inducing HER1, while inhibition of NRF2 by siRNA knockdown or with retinoid represses HER1. Furthermore, treatment of cells with tBHQ increased total and phosphorylated NRF2, HER1, and AKT levels and compromised the cytotoxic effect of lapatinib or erlotinib. Treatment with siRNA or retinoid antagonised the effect of tBHQ on NRF2 and HER1 levels and enhanced the sensitivity of ovarian cancer cells to lapatinib or erlotinib. Pharmacological or genetic inhibition of NRF2 and/or treatment with lapatinib or erlotinib elevated cellular ROS and depleted glutathione. This extends the understanding of NRF2 and its regulation of HER family receptors and opens a strategic target for improving cancer therapy.

Deciphering metabolic rewiring in breast cancer subtypes

Metabolic reprogramming, an emerging hallmark of cancer, is observed in breast cancer. Breast cancer cells rewire their cellular metabolism to meet the demands of survival, proliferation, and invasion. However, breast cancer is a heterogeneous disease, and metabolic rewiring is not uniform. Each subtype of breast cancer displays distinct metabolic alterations. Here, we focus on unique metabolic reprogramming associated with subtypes of breast cancer, as well as common features. Therapeutic opportunities based on subtype-specific metabolic alterations are also discussed. Through this discussion, we aim to provide insight into subtype-specific metabolic rewiring and vulnerabilities that have the potential to better guide therapy and improve outcomes for patients.

BH3-only protein BIM: An emerging target in chemotherapy

BH3-only proteins constitute major proportion of pro-apoptotic members of B-cell lymphoma 2 (Bcl-2) family of apoptotic regulatory proteins and participate in embryonic development, tissue homeostasis and immunity. Absence of BH3-only proteins contributes to autoimmune disorders and tumorigenesis. Bim (Bcl-2 Interacting Mediator of cell death), most important member of BH3-only proteins, shares a BH3-only domain (9-16 aa) among 4 domains (BH1-BH4) of Bcl-2 family proteins and highly pro-apoptotic in nature. Bim initiates the intrinsic apoptotic pathway under both physiological and patho-physiological conditions. Reduction in Bim expression was found to be associated with tumor promotion and autoimmunity, while overexpression inhibited tumor growth and drug resistance as cancer cells suppress Bim expression and stability. Apart from its role in normal homeostasis, Bim has emerged as a central player in regulation of tumorigenesis, therefore gaining attention as a plausible target for chemotherapy. Regulation of Bim expression and stability is complicated and regulated at multiple levels viz. transcriptional, post-transcriptional, post-translational (preferably by phosphorylation and ubiquitination), epigenetic (by promoter acetylation or methylation) including miRNAs. Furthermore, control over Bim expression and stability may be exploited to enhance chemotherapeutic efficacy, overcome drug resistance and select anticancer drug regimen as various chemotherapeutic agents exploit Bim as an executioner of cell death. Owing to its potent anti-tumorigenic activity many BH3 mimetics e.g. ABT-737, ABT-263, obatoclax, AT-101and A-1210477 have been developed and entered in clinical trials. It is more likely that in near future strategies commanding Bim expression and stability ultimately lead to Bim based therapeutic regimen for cancer treatment.

Hypoxic pathobiology of breast cancer metastasis

Dissemination of breast cancer cells (BCCs) to distant sites (metastasis) is the ultimate cause of mortality in patients with breast cancer. Hypoxia (low O₂) is a microenvironmental hallmark of most solid cancers arising as a mismatch between cellular O₂ consumption and supply. Hypoxic selection of BCCs triggers molecular and cellular adaptations dependent upon hypoxia-inducible factors (HIFs), a family of evolutionarily conserved transcriptional activators that coordinate the expression of numerous genes controlling each step of the metastatic process. In this review, we summarize current advances in the understanding of HIF-driven molecular mechanisms that promote BCC metastatic dissemination and patient mortality. In addition, we discuss the clinical and therapeutic implications of HIF targeting in breast cancers.

Comparative expression analysis of hypoxia-inducible factor-alpha and its natural occurring antisense in breast cancer tissues and adjacent noncancerous tissues

Hypoxia-inducible factors (HIFs) have been shown to be upregulated in tumor tissues and linked with tumor progression and metastasis in breast cancer. Among regulatory mechanisms for HIF expression is a natural occurring antisense named aHIF, which has been shown to be overexpressed in breast cancer and influence the level of the HIF-1α transcript. In the present study, we analyzed the expression of HIF-1α and aHIF in breast cancer tissues versus adjacent noncancer tissues (ANCTs) in relation with the clinical and biological behavior of the tumors. aHIF has been shown to be expressed in 67.4% of invasive ductal carcinoma samples, while none of ANCTs showed its expression. HIF-1α has been expressed in all of tumors and 90% of ANCTs. Comparison of HIF-1α expression level between tumor and ANCT tissues showed a total upregulation in tumor samples. No statistically significant association has been found between the level of HIF-1α expression in tumor samples and clinicopathologic and demographic characteristics such as age, tumor size, estrogen receptor status, progesterone receptor status, HER2/neu expression level, lymph node status, histological grade, and stage except for a weak correlation between HIF-1α expression and Ki-67 status. Besides, we could not detect any significant correlation between relative expression of HIF-1α and aHIF in tumor samples. Collectively, these data suggest that aHIF overexpression can be used as a potential biomarker in breast cancer. However, further studies are needed for the evaluation of its mechanism of action in regulation of HIF-1α expression in different pathological conditions. HIF-1α overexpression results in the upregulation of several genes that participated in cancer-associated pathways such as proliferation, angiogenesis, and glucose metabolism. We showed that HIF-1α is upregulated in breast tumor samples compared with adjacent noncancerous tissues. Its expression has been associated with Ki-67 status. Its natural occurring antisense is only expressed in tumor tissues. Thus, it can be used as a potential biomarker in breast cancer.

SMARCE1 regulates metastatic potential of breast cancer cells through the HIF1A/PTK2 pathway

Background

While aberrant activation of the chromatin-remodeling SWI/SNF complexes has been associated with cancer development and progression, the role of each subunit in tumor cells is poorly defined. This study is aimed to characterize the role of SMARCE1/BAF57 in regulating metastasis of breast cancer cells.

Methods

Genetic approaches and chemical inhibitors were used to manipulate the activities of SMARCE1 and its downstream targets in multiple breast cancer cell lines. Xenograft mouse models were used to analyze the role of SMARCE1 in lung metastasis in vivo. Nonadherent culture conditions were used to elucidate the role of SMARCE1 in regulating anoikis. Chromatin immunoprecipitation (ChIP), immunoprecipitation, and immunoblotting assays were designed to dissect the mechanism of action of SMARCE1. Public databases were used to investigate the relationship between SMARCE1 deregulation and breast cancer prognosis.

Results

SMARCE1 knockdown reduced lung metastasis of breast cancer cells and sensitized tumor cells to anoikis. In response to loss of attachment, SMARCE1 interacted with and potentiated transcriptional activity of HIF1A, resulting in rapid PTK2 activation. Both HIF1A and PTK2 were indispensable for SMARCE1-mediated protection against anoikis by promoting activation of ERK and AKT pathways while suppressing the expression of pro-apoptotic BIM protein. Expression data analysis of a large cohort of human breast tumors revealed that high expression of SMARCE1 or PTK2 is associated with poor prognosis and tumor relapse, and PTK2 expression is positively correlated with SMARCE1 expression in basal-like and luminal B subtypes of breast tumors.

Conclusions

SMARCE1 plays an essential role in breast cancer metastasis by protecting cells against anoikis through the HIF1A/PTK2 pathway. SMARCE1-mediated PTK2 activation likely plays a key role in promoting metastasis of basal-like and luminal B subtype of breast tumors.

Protein disulfide isomerases in the endoplasmic reticulum promote anchorage-independent growth of breast cancer cells

Metastatic breast cancer cells are exposed to stress of detachment from the extracellular matrix (ECM). Cultured breast cancer cells that survive this stress and are capable of anchorage-independent proliferation form mammospheres. The purpose of this study was to explore a link between mammosphere growth, ECM gene expression, and the protein quality control system in the endoplasmic reticulum (ER). We compared the mRNA and protein levels of ER folding factors in SUM159PT and MCF10DCIS.com breast cancer cells grown as mammospheres versus adherent conditions. Publicly available gene expression data for mammospheres formed by primary breast cancer cells and for circulating tumor cells (CTCs) were analyzed to assess the status of ECM/ER folding factor genes in clinically relevant samples. Knock-down of selected protein disulfide isomerase (PDI) family members was performed to examine their roles in SUM159PT mammosphere growth. We found that cells grown as mammospheres had elevated expression of ECM genes and ER folding quality control genes. CTC gene expression data for an index patient indicated that upregulation of ECM and ER folding factor genes occurred at the time of acquired therapy resistance and disease progression. Knock-down of PDI, ERp44, or ERp57, three members of the PDI family with elevated protein levels in mammospheres, in SUM159PT cells partially inhibited the mammosphere growth. Thus, breast cancer cell survival and growth under detachment conditions require enhanced assistance of the ER protein folding machinery. Targeting ER folding factors, in particular members of the PDI family, may improve the therapeutic outcomes in metastatic breast cancer.

Involvement of Numb-mediated HIF-1α inhibition in anti-proliferative effect of PNA-antimiR-182 in trastuzumab-sensitive and -resistant SKBR3 cells

Trastuzumab is a humanized monoclonal antibody against the human epidermal growth factor receptor 2 (HER2) that is overexpressed in about 25 % of breast cancer patients. However, primary and/or acquired resistance to trastuzumab develops in most affected persons. In this study, we explored the functional role of miR-182 inhibition with aiming the sensitization of SKBR3 cells to trastuzumab. Cell viability, apoptosis, colony formation, and migration capacities of SKBR3(S) (sensitive) and SKBR3(R) (resistant) cells were assessed to determine the anti-proliferative effects of PNA-antimiR-182. In addition, the expression levels of miR-182, mRNA of FOXO1, and Bim as well as the protein levels of HER2 and Notch1 signaling factors were evaluated by stem-loop RT-qPCR, RT-qPCR, and Western blot, respectively. The results indicated that miR-182 might play a causal role in the mechanism of trastuzumab. In line with that, PNA-antimiR-182 inhibited synergistically the viability of both the sensitive and resistant cell groups. Furthermore, the inhibitory effect of PNA-anitmiR-182 on migration in SKBR3 cells was more than the induction of apoptosis. In addition, PNA-antimiR-182 reduced the levels of NICD, Hes1, HIF-1α, and p-Akt in both cell groups, while it augmented the intracellular content of FOXO1 and Numb suppressor proteins. In other words, PNA-antimiR-182-mediated upregulation of Numb was associated with downregulation of HIF-1α and Hes1. Consequently, downregulation of miR-182 might find therapeutical value for overcoming trastuzumab resistance. Graphical Abstract The crosstalk between HER2 and Notch1 signaling pathway is mediated by miR-182.

Anti-tumor efficacy of BEZ235 is complemented by its anti-angiogenic effects via downregulation of PI3K-mTOR-HIF1alpha signaling in HER2-defined breast cancers

Activation of the PI3K-mTOR pathway via HER2: HER3-mediated signaling in HER2+ breast cancers pose one of the major threats towards the success of trastuzumab. First, trastuzumab cannot perturb survival/proliferative signals following HER2: HER3 heterodimerization in HER2+ tumor cells. Second, trastuzumab treatment has been reported to cause drug-mediated resistance in over 50% of HER2+ breast cancers. We have reported that treatment with an anti-angiogenic drug imparted a significant anti-tumor advantage when combined with trastuzumab plus pertuzumab in the trastuzumab-resistant model of HER2+ breast cancers (PMID: 23959459). The very fact as revealed by our study that an inclusion of anti-angiogenic drug conferred a significant anti-tumor advantage when combined with dual anti-HER2 therapy clearly indicated a critical and indispensable role of angiogenesis in these tumors. Hence, we hypothesized that BEZ235 a dual PI3K/mTOR inhibitor will have an effect on the tumor as well as the angiogenic stromal compartments. In vitro and in vivo efficacy of BEZ235 was determined in HER2+ trastuzumab-sensitive, trastuzumab-resistant and HER2 amplified/PIK3CA mutated cell lines. BEZ235 alone and in combination with trastuzumab was tested on the tumor as well as stromal compartments. AKT-mTOR signal was suppressed following BEZ235 treatment in a concentration and time-dependent manner. AnnexinV, cl-CASPASE3, SURVIVIN and p-FOXO1 indicated that BEZ235-induced cell death occurred predominantly via an apoptotic pathway. Heregulin-induced HIF1α synthesis was also significantly decreased. Oncoprint data (cBioPortal) representing PAM50 Her2 enriched tumors (TCGA, Nature 2012) and Her2-positive breast tumors (TCGA, cell 2015) showed 91.4% genetic alterations and 79.2% genetic alterations in a set of four genes comprised of PIK3CA, ERBB2, VEGFA and HIF1alpha. The co-occurrence of HIF1alpha with VEGFA in PAM50 Her2 enriched tumors (TCGA, Nature 2012) and the co-occurrence of HIF1alpha with VEGFA pair as well as HIF1alpha with PIK3CA pair in Her2-positive breast tumors (TCGA, cell 2015) were found statistically significant. In xenograft models, BEZ235 blocked tumor growth and decreased Ki67, CD31, p-AKT, p-S6RP, p-4EBP1 IHC-expressions. These decreases were more pronounced when BEZ235 was combined with trastuzumab in HER2+/trastuzumab-sensitive, trastuzumab-resistant and HER2+/PIK3CA mutated models. We demonstrated that combined targeting of HER2 and the PI3K-AKT-mTOR pathway is superior to HER2-directed therapy alone. Mechanistically the inhibition of tumor-induced angiogenesis by BEZ235 caused by the down-regulation of PI3K-mTOR-HIF1alpha signaling irrespective of the trastuzumab-sensitivity status of HER2+ breast cancers proving evidence for the first time that the inhibition of angiogenesis is an important component of the anti-tumor efficacy of BEZ235 in HER2 defined breast cancers.

Heat Shock Proteins Promote Cancer: It's a Protection Racket

Heat shock proteins (HSP) are expressed at high levels in cancer and form a fostering environment that is essential for tumor development. Here, we review the recent data in this area, concentrating mainly on Hsp27, Hsp70, and Hsp90. The overriding role of HSPs in cancer is to stabilize the active functions of overexpressed and mutated cancer genes. Thus, elevated HSPs are required for many of the traits that underlie the morbidity of cancer, including increased growth, survival, and formation of secondary cancers. In addition, HSPs participate in the evolution of cancer treatment resistance. HSPs are also released from cancer cells and influence malignant properties by receptor-mediated signaling. Current data strongly support efforts to target HSPs in cancer treatment.

Expression and mechanism of microRNA-181A on incidence and survival in late liver metastases of colorectal cancer

The emerging role of microRNA-181A (miR-181A) in CRC patients with late liver metastases was studied. In the present study we investigated the association between expression and mechanism of miRNA-181A, liver metastasis and prognosis of colorectal cancer (CRC). The expression of miR-181A and PTEN in CRC patients with late liver metastases was higher than that of the normal (control) group, whereas the expression of miR-181A and PTEN was lower in all pathological groups (TNM I-TNM IV). Overall survival (OS) of lower expression miR-181A CRC patients with late liver metastases was higher than that of higher expression miR-181A CRC patients with late liver metastases. The expression of miR-181A and PTEN in the colon cell line NCM460 was lower than that of the colon cancer SW620 cell line. Upregulation of miR-181A promoted cell viability and inhibited apoptosis of SW620 cells, suppressed PTEN expression and activated phosphorylation of AKT (p-AKT) in SW620 cells. Additionally, downregulation of miR-181A inhibited cell viability of SW620 cells through promotion of PTEN and inhibition of p-AKT. Together, our results indicate that miR-181A expression is associated with CRC patients with late liver metastases through PTEN/AKT signaling.

Hypoxia/HIF1α induces lapatinib resistance in ERBB2-positive breast cancer cells via regulation of DUSP2

ERBB2/HER2 belongs to the EGFR-family of receptor tyrosine kinases and its overexpression can promote tumor progression. Breast cancer patients with ERBB2 amplifications are currently treated with lapatinib, a small-molecule kinase inhibitor that specifically blocks EGFR/ERBB2 signaling. Here, we show that hypoxia, via HIF-1, induces resistance to lapatinib-mediated effects in ERBB2-expressing mammary epithelial and ERBB2-positive breast cancer cells. Lapatinib-mediated growth inhibition and apoptosis in three-dimensional (3D) cultures are decreased under hypoxic conditions. Hypoxia can maintain activation of signaling pathways downstream from ERBB2 including AKT and ERK in the presence of lapatinib. HIF-1 is both required and sufficient to induce lapatinib resistance as overexpression of stable HIF-1 in ERBB2-expressing cells blocks lapatinib-mediated effects and maintains ERBB2-downstream signaling under normoxic conditions. Under hypoxia, activation of ERK signaling is required for lapatinib resistance as treatment with MEK inhibitor trametinib reverses hypoxia-mediated lapatinib resistance. HIF-1 can bypass the lapatinib-treated inhibition of the ERK pathway via inhibition of the dual-specificity phosphatase 2 (DUSP2). Indeed, overexpression of DUSP2 in ErbB2-positve breast cancer cells reverses hypoxia-mediated lapatinib resistance. Thus, our results provide rationale for therapeutic evaluation of the treatment of hypoxic ERBB2 expressing breast tumors with a combination of lapatinib and MEK inhibitors.

Regulation of Bim in Health and Disease

The BH3-only Bim protein is a major determinant for initiating the intrinsic apoptotic pathway under both physiological and pathophysiological conditions. Tight regulation of its expression and activity at the transcriptional, translational and post-translational levels together with the induction of alternatively spliced isoforms with different pro-apoptotic potential, ensure timely activation of Bim. Under physiological conditions, Bim is essential for shaping immune responses where its absence promotes autoimmunity, while too early Bim induction eliminates cytotoxic T cells prematurely, resulting in chronic inflammation and tumor progression. Enhanced Bim induction in neurons causes neurodegenerative disorders including Alzheimer's, Parkinson's and Huntington's diseases. Moreover, type I diabetes is promoted by genetically predisposed elevation of Bim in β-cells. On the contrary, cancer cells have developed mechanisms that suppress Bim expression necessary for tumor progression and metastasis. This review focuses on the intricate network regulating Bim activity and its involvement in physiological and pathophysiological processes.

Progress toward overcoming hypoxia-induced resistance to solid tumor therapy

Hypoxic tumors are associated with poor clinical outcome for multiple types of human cancer. This may be due, in part, to hypoxic cancer cells being resistant to anticancer therapy, including radiation therapy, chemotherapy, and targeted therapy. Hypoxia inducible factor 1, a major regulator of cellular response to hypoxia, regulates the expression of genes that are involved in multiple aspects of cancer biology, including cell survival, proliferation, metabolism, invasion, and angiogenesis. Here, we review multiple pathways regulated by hypoxia/hypoxia inducible factor 1 in cancer cells and discuss the latest advancements in overcoming hypoxia-mediated tumor resistance.

Protein tyrosine kinase 6 promotes ERBB2-induced mammary gland tumorigenesis in the mouse

Protein tyrosine kinase 6 (PTK6) expression, activation, and amplification of the PTK6 gene have been reported in ERBB2/HER2-positive mammary gland cancers. To explore contributions of PTK6 to mammary gland tumorigenesis promoted by activated ERBB2, we crossed Ptk6^−/− mice with the mouse mammary tumor virus-ERBB2 transgenic mouse line expressing activated ERBB2 and characterized tumor development and progression. ERBB2-induced tumorigenesis was significantly delayed and diminished in mice lacking PTK6. PTK6 expression was induced in the mammary glands of ERBB2 transgenic mice before tumor development and correlated with activation of signal transducer and activator of transcription 3 (STAT3) and increased proliferation. Disruption of PTK6 impaired STAT3 activation and proliferation. Phosphorylation of the PTK6 substrates focal adhesion kinase (FAK) and breast cancer anti-estrogen resistance 1 (BCAR1; p130CAS) was decreased in Ptk6^−/− mammary gland tumors. Reduced numbers of metastases were detected in the lungs of Ptk6^−/− mice expressing activated ERBB2, compared with wild-type ERBB2 transgenic mice. PTK6 activation was detected at the edges of ERBB2-positive tumors. These data support roles for PTK6 in both ERBB2-induced mammary gland tumor initiation and metastasis, and identify STAT3, FAK, and BCAR1 as physiologically relevant PTK6 substrates in breast cancer. Including PTK6 inhibitors as part of a treatment regimen could have distinct benefits in ERBB2/HER2-positive breast cancers.

Analysis of Hypoxia-Inducible Factor-1α Expression Relative to Other Key Factors in Malignant Canine Mammary Tumours

Hypoxia-inducible factor (HIF)-1α plays important physiological roles, but is also of significance in carcinogenesis in man and animals. This study aimed to identify HIF-1α expression in malignant canine mammary tumours (CMTs) and to find correlations with other key factors by using immunohistochemistry (IHC). The histological classification, grading and evaluation of lymphatic invasion were achieved by examining sections stained by haematoxylin and eosin. Determination of molecular subtype, expression of HIF-1α, oestrogen receptor (OR), progesterone receptor (PR), human epidermal growth factor receptor (HER)-2, Ki67, vascular endothelial growth factor (VEGF) and E-cadherin was evaluated by IHC in 87 samples of malignant CMTs. HIF-1α expression correlated significantly with histological type, grade of cancer, negativity for OR and expression of Ki67 and VEGF. Lymphatic invasion, molecular subtype, PR, HER-2 and E-cadherin levels did not significantly correlate with HIF-1α expression. The results of this study imply that HIF-1α may potentially play a role in increased malignancy of CMTs, as it does in human breast cancer.

Expression of HIF-1α and Markers of Angiogenesis Are Not Significantly Different in Triple Negative Breast Cancer Compared to Other Breast Cancer Molecular Subtypes: Implications for Future Therapy

INTRODUCTION

Triple negative breast cancer lacks estrogen, progesterone and epidermal growth factor receptors rendering it refractory to available targetedtherapies. TNBC is associated with central fibrosis and necrosis, both indicators of tumor hypoxia. Hypoxia inducible factor 1α is up-regulated under hypoxia and its expression is associated with induction of angiogenesis resulting in proliferation, aggressive tumor phenotype and metastasis. In this study we evaluate the potential use of HIF-1α as aTNBC-specific marker.

METHODS

62 TNBC, 64 HER2+, and 64 hormone-receptors positive breast cancer cases were evaluated for central fibrosis and necrosis, HIF-1α, HIF-1β, VEGFR3, CD31 expression and microvessel density. RNA extraction from paraffin-embedded samples, followed by quantitative real-time polymerase chain reaction (qRT-PCR) evaluation of HIF-1α and VEGF transcripts was performed on 54 cases (18 from each subtype).

RESULTS

HIF-1α protein was expressed in 35.5% TNBC, 45.3% HER2+and 25.0% ER+/PR+ (p = 0.055; χ2 test). PCRanalysis of subgroup of breast cancers, 84.2% expressed HIF-1α protein and its transcripts, while only 66.7% expressed VEGF transcripts simultaneously with the HIF-1α protein and its transcripts. Central fibrosis and necrosis was highest in TNBC (p = 0.015; χ2 test), while MVD was comparable among all groups (p = 0.928; χ2 test). VEGFR3 was highest in TNBC expressing HIF-1α. HIF-1β protein was expressed in 32.0% of HIF-1α(+), and in (44.3%) of HIF-1α(-) breast cancer cases (p = 0.033; χ2 test). Moreover, HIF-1α expression in cases with central fibrosis and necrosis was highest in the HER2+ followed by the TNBC (p = 0.156; χ2 test).

CONCLUSIONS

A proportion of TNBC express HIF-1α but not in a significantly different manner from other breast cancer subtypes. The potential of anti-HIF-1α targeted therapy is therefore not a candidate for exclusive use in TNBC, but should be considered in all breast cancers, especially in the setting of clinically aggressive or refractory disease.

Role of hypoxia-inducible factor-1α and CD146 in epidermal growth factor receptor-mediated angiogenesis in salivary gland adenoid cystic carcinoma

Adenoid cystic carcinoma (AdCC) of the salivary gland in the head and neck is characterized by indolent yet persistent growth, multiple local recurrences and early hematogenous metastasis. Considering the possible association between the epidermal growth factor receptor (EGFR) signaling pathway and angiogenesis in various types of cancer and the overexpression of EGFR in AdCC, it is reasonable to examine the correlation between angiogenesis and the EGFR signaling pathway in this carcinoma. In the present study, the expression of EGFR, CD31, CD146 and hypoxia-inducible factor-1α (HIF-1α) were evaluated by immunohistochemical staining with tissue microarray containing normal salivary gland (NSG), pleomorphic adenoma (PMA) and AdCC tissues. Pearson's correlation coefficient was conducted to demonstrate the correlation between EGFR, CD31, CD146 and HIF-1α. To determine their similarity and intimacy, hierarchical analysis was performed with Cluster 3.0 and then visualized using TreeView software. Immunohistochemical results of tissue microarrays were quantified, revealing that the expression of EGFR, CD146 and HIF-1α increased in AdCC compared with in PMA and NSG tissues. The association between the expression of EGFR and CD31 was significant and positive. The expression of CD146 and HIF-1α was positively correlated with EGFR and CD31, respectively. These findings suggest that the EGFR signaling pathway has a vital role in AdCC progression and may be associated with HIF-1α-mediated angiogenesis. These results may enhance our understanding of the mechanism underlying AdCC progression and provide potential clinical therapeutic strategies based on the inhibition of EGFR.

Metabolism and its sequelae in cancer evolution and therapy

Cancers progress through a series of events that can be characterized as "somatic evolution." A central premise of Darwinian evolutionary theory is that the environment imparts pressure to select for species that are most fit within that particular microenvironmental context. Furthermore, the rate of evolution is proportional to both (1) the strength of the environmental selection and (2) the phenotypic variance of the selected population. It is notable that, during the progression of cancers from carcinogenesis to local invasion to metastasis, the selective landscape continuously changes, and throughout this process, there is increased selection for cells that have altered metabolic phenotypes: implying that these phenotypes impart a selective advantage during the process of environmental selection. One of the most prevalent selected phenotypes is that of aerobic glycolysis, that is, the continued fermentation of glucose even in the presence of adequate oxygen. The mechanisms of this so-called "Warburg effect" have been well studied, and there are multiple models to explain how this occurs at the molecular level. Herein, we propose that unifying insights can be gained by evaluating the environmental context within which this phenotype arises. In other words, we focus not on the "how" but the "why" do cancer cells exhibit high aerobic glycolysis. This is best approached by examining the sequelae of aerobic glycolysis that may impart a selective advantage. Many of these have been considered, including generation of anabolic substrates, response rates of glycolysis vis-à-vis respiration, and generation of antioxidants. A further sequeala considered here is that aerobic glycolysis results in a high rate of lactic acid production; resulting in acidification of the extracellular space. Indeed, it has been shown that a low extracellular pH promotes local invasion, promotes metastasis, and inhibits antitumor immunity. In naturally occurring cancers, low extracellular pH is a strong negative prognostic indicator of metastasis-free survival. Furthermore, it has been shown that inhibition of extracellular acidosis can inhibit metastasis and promote antitumor immunity. Hence, we propose that excess acid production confers a selective advantage for cells during the somatic evolution of cancers.

The role of multicellular aggregation in the survival of ErbB2-positive breast cancer cells during extracellular matrix detachment

The metastasis of cancer cells from the site of the primary tumor to distant sites in the body represents the most deadly manifestation of cancer. In order for metastasis to occur, cancer cells need to evade anoikis, which is defined as apoptosis caused by loss of attachment to extracellular matrix (ECM). Signaling from ErbB2 has previously been linked to the evasion of anoikis in breast cancer cells but the precise molecular mechanisms by which ErbB2 blocks anoikis have yet to be unveiled. In this study, we have identified a novel mechanism by which anoikis is inhibited in ErbB2-expressing cells: multicellular aggregation during ECM-detachment. Our data demonstrate that disruption of aggregation in ErbB2-positive cells is sufficient to induce anoikis and that this anoikis inhibition is a result of aggregation-induced stabilization of EGFR and consequent ERK/MAPK survival signaling. Furthermore, these data suggest that ECM-detached ErbB2-expressing cells may be uniquely susceptible to targeted therapy against EGFR and that this sensitivity could be exploited for specific elimination of ECM-detached cancer cells.

Anoikis evasion in inflammatory breast cancer cells is mediated by Bim-EL sequestration

Inflammatory breast cancer (IBC) is a rare and highly invasive type of breast cancer, and patients diagnosed with IBC often face a very poor prognosis. IBC is characterized by the lack of primary tumor formation and the rapid accumulation of cancerous epithelial cells in the dermal lymphatic vessels. Given that normal epithelial cells require attachment to the extracellular matrix (ECM) for survival, a comprehensive examination of the molecular mechanisms underlying IBC cell survival in the lymphatic vessels is of paramount importance to our understanding of IBC pathogenesis. Here we demonstrate that, in contrast to normal mammary epithelial cells, IBC cells evade ECM-detachment-induced apoptosis (anoikis). ErbB2 and EGFR knockdown in KPL-4 and SUM149 cells, respectively, causes decreased colony growth in soft agar and increased caspase activation following ECM detachment. ERK/MAPK signaling was found to operate downstream of ErbB2 and EGFR to protect cells from anoikis by facilitating the formation of a protein complex containing Bim-EL, LC8, and Beclin-1. This complex forms as a result of Bim-EL phosphorylation on serine 59, and thus Bim-EL cannot localize to the mitochondria and cause anoikis. These results reveal a novel mechanism that could be targeted with innovative therapeutics to induce anoikis in IBC cells.

Cancer cell survival during detachment from the ECM: multiple barriers to tumour progression

Epithelial cells require attachment to the extracellular matrix (ECM) for survival. However, during tumour progression and metastasis, cancerous epithelial cells must adapt to and survive in the absence of ECM. During the past 20 years, several cellular changes, including anoikis, have been shown to regulate cell viability when cells become detached from the ECM. In this Opinion article, we review in detail how cancer cells can overcome or take advantage of these specific processes. Gaining a better understanding of how cancer cells survive during detachment from the ECM will be instrumental in designing chemotherapeutic strategies that aim to eliminate ECM-detached metastatic cells.

Deconstructing breast cancer cell biology and the mechanisms of multidrug resistance

Cancer complexity constantly challenges the way that clinicians manage breast cancer therapy. Tumor heterogeneity and intratumoral stroma characteristics allow cells with different phenotypes and deregulated apoptotic, proliferative and migration abilities to co-exist contributing to a disappointing therapeutic response. While new approaches are being associated with conventional chemotherapy, such as hormonal therapy or target monoclonal antibodies, recurrence and metastasization are still observed. Membrane transporters are the cell's first line of contact with anticancer drugs having a major role in multidrug resistance events. This structural-based activity enables the cell to be drug-resistant by decreasing drug intracellular concentration through an efflux-transport mechanism, mainly associated with overexpression of ATP-binding cassette (ABC) proteins. This review focuses on some of the important structural and biological properties of the malignant cell and tumor microenvironment, addressing the role of the membrane ABC transporters in therapeutic outcomes, and highlighting related molecular pathways that may represent meaningful target therapies.