Regulation of death receptor signaling by the autophagy protein TP53INP2.

TP53INP2 positively regulates autophagy by binding to Atg8 proteins. Here, we uncover a novel role of TP53INP2 in death-receptor signaling. TP53INP2 sensitizes cells to apoptosis induced by death receptor ligands. In keeping with this, TP53INP2 deficiency in cultured cells or mouse livers protects against death receptor-induced apoptosis. TP53INP2 binds caspase-8 and the ubiquitin ligase TRAF6, thereby promoting the ubiquitination and activation of caspase-8 by TRAF6. We have defined a TRAF6-interacting motif (TIM) and a ubiquitin-interacting motif in TP53INP2, enabling it to function as a scaffold bridging already ubiquitinated caspase-8 to TRAF6 for further polyubiquitination of caspase-8. Mutations of key TIM residues in TP53INP2 abrogate its interaction with TRAF6 and caspase-8, and subsequently reduce levels of death receptor-induced apoptosis. A screen of cancer cell lines showed that those with higher protein levels of TP53INP2 are more prone to TRAIL-induced apoptosis, making TP53INP2 a potential predictive marker of cancer cell responsiveness to TRAIL treatment. These findings uncover a novel mechanism for the regulation of caspase-8 ubiquitination and reveal TP53INP2 as an important regulator of the death receptor pathway.

TGFbeta primes breast tumors for lung metastasis seeding through angiopoietin-like 4.

Cells released from primary tumors seed metastases to specific organs by a nonrandom process, implying the involvement of biologically selective mechanisms. Based on clinical, functional, and molecular evidence, we show that the cytokine TGFbeta in the breast tumor microenvironment primes cancer cells for metastasis to the lungs. Central to this process is the induction of angiopoietin-like 4 (ANGPTL4) by TGFbeta via the Smad signaling pathway. TGFbeta induction of Angptl4 in cancer cells that are about to enter the circulation enhances their subsequent retention in the lungs, but not in the bone. Tumor cell-derived Angptl4 disrupts vascular endothelial cell-cell junctions, increases the permeability of lung capillaries, and facilitates the trans-endothelial passage of tumor cells. These results suggest a mechanism for metastasis whereby a cytokine in the primary tumor microenvironment induces the expression of another cytokine in departing tumor cells, empowering these cells to disrupt lung capillary walls and seed pulmonary metastases.

From latency to overt bone metastasis in breast cancer: potential for treatment and prevention.

Bone metastasis is present in a high percentage of breast cancer (BCa) patients with distant disease, especially in those with the estrogen receptor-positive (ER+ ) subtype. Most cells that escape primary tumors are unable to establish metastatic lesions, which suggests that target organ microenvironments are hostile for tumor cells. This implies that BCa cells must achieve a process of speciation to adapt to the new conditions imposed in the new organ. Bone has unique characteristics that can be exploited by cancer cells: it undergoes constant remodeling and comprises diverse environments (including osteogenic, perivascular, and hematopoietic stem cell niches). This allows colonizing cells to take advantage of numerous adhesion molecules, matrix proteins, and soluble factors that facilitate homing, survival, and, eventually, metastatic outgrowth. However, in most cases, metastatic lesions enter into a latency state that can last months, years, or even decades, before forming a clinically detectable macrometastasis. This dormant state challenges the effectiveness of adjuvant chemotherapy. Detecting which tumors are more prone to metastasize to bone and developing new specific therapies that target bone metastasis represent urgent clinical needs. Here, we review the biological mechanisms of BCa bone metastasis and provide the latest options of treatments and predictive markers that are currently in clinical use or are being tested in clinical assays. © 2019 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Effect of MAF amplification on treatment outcomes with adjuvant zoledronic acid in early breast cancer: a secondary analysis of the international, open-label, randomised, controlled, phase 3 AZURE (BIG 01/04) trial.

BACKGROUND: Adjuvant use of bisphosphonates can reduce the incidence of bone metastases in early breast cancer. Recurrence and survival seem to be improved only in postmenopausal patients, but the underlying mechanisms remain unclear. We investigated whether MAF amplification (a biomarker for bone metastasis) in primary tumours could predict the treatment outcomes of adjuvant zoledronic acid. METHODS: The study population included patients enrolled in the international, open-label, randomised, controlled, phase 3 AZURE trial at eligible UK sites who had stage II or III breast cancer and who gave consent for use of their primary tumour samples. Patients were randomly assigned (1:1) to receive standard adjuvant systemic therapy alone (control group) or with zoledronic acid every 3-4 weeks for six doses, then every 3-6 months until the end of 5 years. Minimisation took into account the number of involved axillary lymph nodes, clinical tumour stage, oestrogen-receptor status, type and timing of systemic therapy, menopausal status, statin use, and treating centre. The primary endpoint was disease-free survival; the secondary endpoint, invasive-disease-free survival, was the primary disease endpoint for the analysis in this report. MAF amplification was assessed by fluorescence in-situ hybridisation of two cores of breast tumour tissue in a microarray, done in a central laboratory by technicians unaware of treatment assignment. We used multivariate analyses to assess disease outcomes by intention to treat. We also assessed interactions between MAF-positive status and menopausal status on efficacy of zoledronic acid. The AZURE trial is registered with the International Standard Randomised Controlled Trial Registry, number ISRCTN79831382. FINDINGS: 1739 AZURE patients contributed primary tumour samples, of whom 865 (50%) had two assessable cores (445 in the control groups and 420 in the zoledronic acid group). 184 (21%) tumours were MAF positive (85 in the control groups and 99 in the zoledronic acid group) and the remaining tumours were MAF negative. At a median follow-up of 84·6 months (IQR 72·0-95·8), MAF status was not prognostic for invasive-disease-free survival in the control group (MAF-positive vs MAF-negative: hazard ratio [HR] 0·92, 95% CI 0·59-1·41), but was in the zoledronic acid group (0·52, 0·36-0·75). In patients with MAF-negative tumours, zoledronic acid was associated with higher invasive-disease-free survival than was control treatment (HR 0·74, 95% CI 0·56-0·98), but not in patients who had MAF-positive tumours. Additionally, among 121 patients not postmenopausal at randomisation with MAF-positive tumours, zoledronic acid was associated with lower invasive-disease-free survival (HR 2·47, 95% CI 1·23-4·97) and overall survival (2·27, 95% CI 1·04-4·93) than control treatment. INTERPRETATION: MAF status can predict likelihood of benefit from adjuvant zoledronic acid and merits further investigation as a potential companion diagnostic. FUNDING: Novartis Global and Inbiomotion.

Tumour stroma-derived lipocalin-2 promotes breast cancer metastasis.

Tumour cell-secreted factors skew infiltrating immune cells towards a tumour-supporting phenotype, expressing pro-tumourigenic mediators. However, the influence of lipocalin-2 (Lcn2) on the metastatic cascade in the tumour micro-environment is still not clearly defined. Here, we explored the role of stroma-derived, especially macrophage-released, Lcn2 in breast cancer progression. Knockdown studies and neutralizing antibody approaches showed that Lcn2 contributes to the early events of metastasis in vitro. The release of Lcn2 from macrophages induced an epithelial-mesenchymal transition programme in MCF-7 breast cancer cells and enhanced local migration as well as invasion into the extracellular matrix, using a three-dimensioanl (3D) spheroid model. Moreover, a global Lcn2 deficiency attenuated breast cancer metastasis in both the MMTV-PyMT breast cancer model and a xenograft model inoculating MCF-7 cells pretreated with supernatants from wild-type and Lcn2-knockdown macrophages. To dissect the role of stroma-derived Lcn2, we employed an orthotopic mammary tumour mouse model. Implantation of wild-type PyMT tumour cells into Lcn2-deficient mice left primary mammary tumour formation unaltered, but specifically reduced tumour cell dissemination into the lung. We conclude that stroma-secreted Lcn2 promotes metastasis in vitro and in vivo, thereby contributing to tumour progression. Our study highlights the tumourigenic potential of stroma-released Lcn2 and suggests Lcn2 as a putative therapeutic target. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

MiniAp-4: A Venom-Inspired Peptidomimetic for Brain Delivery.

Drug delivery across the blood-brain barrier (BBB) is a formidable challenge for therapies targeting the central nervous system. Although BBB shuttle peptides enhance transport into the brain non-invasively, their application is partly limited by lability to proteases. The present study proposes the use of cyclic peptides derived from venoms as an affordable way to circumvent this drawback. Apamin, a neurotoxin from bee venom, was minimized by reducing its complexity, toxicity, and immunogenicity, while preserving brain targeting, active transport, and protease resistance. Among the analogues designed, the monocyclic lactam-bridged peptidomimetic MiniAp-4 was the most permeable. This molecule is capable of translocating proteins and nanoparticles in a human-cell-based BBB model. Furthermore, MiniAp-4 can efficiently deliver a cargo across the BBB into the brain parenchyma of mice.

Genes that mediate breast cancer metastasis to the brain.

The molecular basis for breast cancer metastasis to the brain is largely unknown. Brain relapse typically occurs years after the removal of a breast tumour, suggesting that disseminated cancer cells must acquire specialized functions to take over this organ. Here we show that breast cancer metastasis to the brain involves mediators of extravasation through non-fenestrated capillaries, complemented by specific enhancers of blood-brain barrier crossing and brain colonization. We isolated cells that preferentially infiltrate the brain from patients with advanced disease. Gene expression analysis of these cells and of clinical samples, coupled with functional analysis, identified the cyclooxygenase COX2 (also known as PTGS2), the epidermal growth factor receptor (EGFR) ligand HBEGF, and the alpha2,6-sialyltransferase ST6GALNAC5 as mediators of cancer cell passage through the blood-brain barrier. EGFR ligands and COX2 were previously linked to breast cancer infiltration of the lungs, but not the bones or liver, suggesting a sharing of these mediators in cerebral and pulmonary metastases. In contrast, ST6GALNAC5 specifically mediates brain metastasis. Normally restricted to the brain, the expression of ST6GALNAC5 in breast cancer cells enhances their adhesion to brain endothelial cells and their passage through the blood-brain barrier. This co-option of a brain sialyltransferase highlights the role of cell-surface glycosylation in organ-specific metastatic interactions.

Cyclooxygenase-2 inhibitor suppresses tumour progression of prostate cancer bone metastases in nude mice.

OBJECTIVE: To assess whether celecoxib, a selective cyclooxygenase-2 (COX-2) inhibitor with anti-cancer properties, has an inhibitory effect on tumour establishment and progression of prostate cancer (PCa) bone metastases. MATERIALS AND METHODS: PC-3 stable luciferase-expressing cells were injected into male nude mice by intracardiac (i.c.) and intratibial (i.t.) injections, and the effect of celecoxib on bone metastases was then recorded using bioluminescence image analysis. In cases of chemoprevention, mice received 3 mg/kg celecoxib from 1 week before cell implantation until the end of the study, and to test the therapeutic effect, mice received celecoxib 1 week after cell implantation until the end of the study. Tumour tissue samples were histologically examined and COX-2 expression was quantified at the protein level. RESULTS: Celecoxib significantly decreased cell viability and the proliferation of human PCa cells in vitro in a dose-dependent manner. Bone metastases were detected after i.c. injection in nude mice. Celecoxib (15 ppm) administered before i.c. injection did not inhibit the cellular metastatic potential, as the numbers of bone metastases were similar in both groups. However, celecoxib did decrease metastatic progression in the osseous environment when cells were injected directly into the tibia (P < 0.05). At the protein level, COX-2 expression was significantly decreased in the celecoxib treatment group (P < 0.01). CONCLUSION: In a preclinical mice model, celecoxib administered orally at the standard human dose inhibits the progression of established PCa bone metastases.

C/EBPbeta at the core of the TGFbeta cytostatic response and its evasion in metastatic breast cancer cells.

Breast cancers may evade the growth-inhibitory action of TGFbeta by accumulating defects of unknown nature that selectively eliminate cytostatic gene responses. We found the transcription factor C/EBPbeta to be essential for TGFbeta induction of the cell cycle inhibitor p15INK4b by a FoxO-Smad complex and repression of c-MYC by an E2F4/5-Smad complex in human epithelial cells. These cytostatic responses are selectively missing in metastatic breast cancer cells from half of the patients that we tested. The basis for this loss was traced to an excess of the C/EBPbeta inhibitory isoform LIP. We suggest that C/EBPbeta plays a key role in the coordination of TGFbeta cytostatic gene responses, and its malfunction may trigger evasion of these responses in breast cancer.

Identification of NOG as a specific breast cancer bone metastasis-supporting gene.

Metastasis requires numerous biological functions that jointly provide tumor cells from a primary site to seed and colonize a distant organ. Some of these activities are selected for in the primary site, whereas others are acquired at the metastatic niche. We provide molecular evidence showing that the BMP inhibitor, NOG, provides metastatic breast cancer cells with the ability to colonize the bone. NOG expression is acquired during the late events of metastasis, once cells have departed from the primary site, because it is not enriched in primary tumors with high risk of bone relapse. On the contrary, breast cancer bone metastatic lesions do select for high levels of NOG expression when compared with metastasis to the lung, liver, and brain. Pivotal to the bone colonization functions is the contribution of NOG to metastatic autonomous and nonautonomous cell functions. Using genetic approaches, we show that when NOG is expressed in human breast cancer cells, it facilitates bone colonization by fostering osteoclast differentiation and bone degradation and also contributes to metastatic lesions reinitiation. These findings reveal how aggressive cancer cell autonomous and nonautonomous functions can be mechanistically coupled to greater bone metastatic potential.

Mediators of vascular remodelling co-opted for sequential steps in lung metastasis.

Metastasis entails numerous biological functions that collectively enable cancerous cells from a primary site to disseminate and overtake distant organs. Using genetic and pharmacological approaches, we show that the epidermal growth factor receptor ligand epiregulin, the cyclooxygenase COX2, and the matrix metalloproteinases 1 and 2, when expressed in human breast cancer cells, collectively facilitate the assembly of new tumour blood vessels, the release of tumour cells into the circulation, and the breaching of lung capillaries by circulating tumour cells to seed pulmonary metastasis. These findings reveal how aggressive primary tumorigenic functions can be mechanistically coupled to greater lung metastatic potential, and how such biological activities may be therapeutically targeted with specific drug combinations.

Long-term platinum-based drug accumulation in cancer-associated fibroblasts promotes colorectal cancer progression and resistance to therapy.

A substantial proportion of cancer patients do not benefit from platinum-based chemotherapy (CT) due to the emergence of drug resistance. Here, we apply elemental imaging to the mapping of CT biodistribution after therapy in residual colorectal cancer and achieve a comprehensive analysis of the genetic program induced by oxaliplatin-based CT in the tumor microenvironment. We show that oxaliplatin is largely retained by cancer-associated fibroblasts (CAFs) long time after the treatment ceased. We determine that CT accumulation in CAFs intensifies TGF-beta activity, leading to the production of multiple factors enhancing cancer aggressiveness. We establish periostin as a stromal marker of chemotherapeutic activity intrinsically upregulated in consensus molecular subtype 4 (CMS4) tumors and highly expressed before and/or after treatment in patients unresponsive to therapy. Collectively, our study underscores the ability of CT-retaining CAFs to support cancer progression and resistance to treatment.

MAF amplification licenses ERα through epigenetic remodelling to drive breast cancer metastasis.

MAF amplification increases the risk of breast cancer (BCa) metastasis through mechanisms that are still poorly understood yet have important clinical implications. Oestrogen-receptor-positive (ER+) BCa requires oestrogen for both growth and metastasis, albeit by ill-known mechanisms. Here we integrate proteomics, transcriptomics, epigenomics, chromatin accessibility and functional assays from human and syngeneic mouse BCa models to show that MAF directly interacts with oestrogen receptor alpha (ERα), thereby promoting a unique chromatin landscape that favours metastatic spread. We identify metastasis-promoting genes that are de novo licensed following oestrogen exposure in a MAF-dependent manner. The histone demethylase KDM1A is key to the epigenomic remodelling that facilitates the expression of the pro-metastatic MAF/oestrogen-driven gene expression program, and loss of KDM1A activity prevents this metastasis. We have thus determined that the molecular basis underlying MAF/oestrogen-mediated metastasis requires genetic, epigenetic and hormone signals from the systemic environment, which influence the ability of BCa cells to metastasize.

Ecology and evolution of dormant metastasis.

Genetic studies suggest that sequential dissemination from a primary metastasis, usually at the bone, is a major route of metastatic progression in early, radically resected cancer. Disseminated tumor cells (DTCs) can likely infiltrate but not grow, and may remain dormant once disseminated for extended intervals (from months to decades). The stationary nature of DTCs prevents them from being successfully treated as an asymptomatic residual disease in the adjuvant setting; critically, they can eventually relapse, adapt, and develop therapy resistance, causing incurable overt metastasis. Metastatic lesions usually first appear in one tissue, which invigorates metastatic cells for further dissemination to other organs, with a fatal outcome. Clinical and genetic data now indicate that metastatic lesions in one organ can seed secondary metastases in other organs: in other words, metastasis arising from metastasis. Herein we discuss recent insight into metastasis cell dormancy mechanisms, survival, communication with the local microenvironment, and eventual changes that endow DTCs with the capacity to expand and colonize to other metastatic sites.

Design and optimization of oestrogen receptor PROTACs based on 4-hydroxytamoxifen.

In the last four decades, treatment of oestrogen receptor positive (ER+) breast cancer (BCa), has focused on targeting the estrogenic receptor signaling pathway. This signaling function is pivotal to sustain cell proliferation. Tamoxifen, a competitive inhibitor of oestrogen, has played a major role in therapeutics. However, primary and acquired resistance to hormone blockade occurs in a large subset of these cancers, and new approaches are urgently needed. Aromatase inhibitors and receptor degraders were approved and alternatively used. Yet, resistance appears in the metastatic setting. Here we report the design and synthesis of a series of proteolysis targeting chimeras (PROTACs) that induce the degradation of estrogen receptor alpha in breast cancer MCF-7 (ER+) cells at nanomolar concentration. Using a warhead based on 4-hydroxytamoxifen, bifunctional degraders recruiting either cereblon or the Von Hippel Lindau E3 ligases were synthesized. Our efforts resulted in the discovery of TVHL-1, a potent ERα degrader (DC50: 4.5 nM) that we envisage as a useful tool for biological study and a platform for potential therapeutics.

Targeted immunotherapy against distinct cancer-associated fibroblasts overcomes treatment resistance in refractory HER2+ breast tumors.

About 50% of human epidermal growth factor receptor 2 (HER2)+ breast cancer patients do not benefit from HER2-targeted therapy and almost 20% of them relapse after treatment. Here, we conduct a detailed analysis of two independent cohorts of HER2+ breast cancer patients treated with trastuzumab to elucidate the mechanisms of resistance to anti-HER2 monoclonal antibodies. In addition, we develop a fully humanized immunocompetent model of HER2+ breast cancer recapitulating ex vivo the biological processes that associate with patients' response to treatment. Thanks to these two approaches, we uncover a population of TGF-beta-activated cancer-associated fibroblasts (CAF) specific from tumors resistant to therapy. The presence of this cellular subset related to previously described myofibroblastic (CAF-S1) and podoplanin+ CAF subtypes in breast cancer associates with low IL2 activity. Correspondingly, we find that stroma-targeted stimulation of IL2 pathway in unresponsive tumors restores trastuzumab anti-cancer efficiency. Overall, our study underscores the therapeutic potential of exploiting the tumor microenvironment to identify and overcome mechanisms of resistance to anti-cancer treatment.

LCOR mediates interferon-independent tumor immunogenicity and responsiveness to immune-checkpoint blockade in triple-negative breast cancer.

Ligand-dependent corepressor (LCOR) mediates normal and malignant breast stem cell differentiation. Cancer stem cells (CSCs) generate phenotypic heterogeneity and drive therapy resistance, yet their role in immunotherapy is poorly understood. Here we show that immune-checkpoint blockade (ICB) therapy selects for LCORlow CSCs with reduced antigen processing/presentation machinery (APM) driving immune escape and ICB resistance in triple-negative breast cancer (TNBC). We unveil an unexpected function of LCOR as a master transcriptional activator of APM genes binding to IFN-stimulated response elements (ISREs) in an IFN signaling-independent manner. Through genetic modification of LCOR expression, we demonstrate its central role in modulation of tumor immunogenicity and ICB responsiveness. In TNBC, LCOR associates with ICB clinical response. Importantly, extracellular vesicle (EV) Lcor-messenger RNA therapy in combination with anti-PD-L1 overcame resistance and eradicated breast cancer metastasis in preclinical models. Collectively, these data support LCOR as a promising target for enhancement of ICB efficacy in TNBC, by boosting of tumor APM independently of IFN.

In Vivo Assessment of Metastatic Cell Potential in Prostate Cancer.

Metastasis is the main cause of death for cancer patients, but our ability to improve clinical outcome first requires a better understanding of the dynamics, cellular mechanisms, and kinetics of metastasis. In prostate cancer (PCa), metastatic tumor cells preferentially colonize to bone. However, a lack of applicable mouse models has limited our ability to study this process accurately. Here, we describe a strategy to bypass this limitation: human PCa cells are injected into immunodeficient mice (at tibia, the left ventricle of heart and the iliac artery). Using this novel technique, the metastatic capabilities of these human PCa cells (e.g., colonization and proliferation potential) can be analyzed in bone with an in vivo imaging system.

Cysteine and Folate Metabolism Are Targetable Vulnerabilities of Metastatic Colorectal Cancer.

With most cancer-related deaths resulting from metastasis, the development of new therapeutic approaches against metastatic colorectal cancer (mCRC) is essential to increasing patient survival. The metabolic adaptations that support mCRC remain undefined and their elucidation is crucial to identify potential therapeutic targets. Here, we employed a strategy for the rational identification of targetable metabolic vulnerabilities. This strategy involved first a thorough metabolic characterisation of same-patient-derived cell lines from primary colon adenocarcinoma (SW480), its lymph node metastasis (SW620) and a liver metastatic derivative (SW620-LiM2), and second, using a novel multi-omics integration workflow, identification of metabolic vulnerabilities specific to the metastatic cell lines. We discovered that the metastatic cell lines are selectively vulnerable to the inhibition of cystine import and folate metabolism, two key pathways in redox homeostasis. Specifically, we identified the system xCT and MTHFD1 genes as potential therapeutic targets, both individually and combined, for combating mCRC.