Tumor ENPP1 (CD203a)/Haptoglobin Axis Exploits Myeloid-Derived Suppressor Cells to Promote Post-Radiotherapy Local Recurrence in Breast Cancer.

ABSTRACT: Locoregional failure (LRF) in patients with breast cancer post-surgery and post-irradiation is linked to a dismal prognosis. In a refined new model, we identified ectonucleotide pyrophosphatase/phosphodiesterase 1/CD203a (ENPP1) to be closely associated with LRF. ENPP1hi circulating tumor cells (CTC) contribute to relapse by a self-seeding mechanism. This process requires the infiltration of polymorphonuclear myeloid-derived suppressor cells and neutrophil extracellular trap (NET) formation. Genetic and pharmacologic ENPP1 inhibition or NET blockade extends relapse-free survival. Furthermore, in combination with fractionated irradiation, ENPP1 abrogation obliterates LRF. Mechanistically, ENPP1-generated adenosinergic metabolites enhance haptoglobin (HP) expression. This inflammatory mediator elicits myeloid invasiveness and promotes NET formation. Accordingly, a significant increase in ENPP1 and NET formation is detected in relapsed human breast cancer tumors. Moreover, high ENPP1 or HP levels are associated with poor prognosis. These findings unveil the ENPP1/HP axis as an unanticipated mechanism exploited by tumor cells linking inflammation to immune remodeling favoring local relapse. SIGNIFICANCE: CTC exploit the ENPP1/HP axis to promote local recurrence post-surgery and post-irradiation by subduing myeloid suppressor cells in breast tumors. Blocking this axis impairs tumor engraftment, impedes immunosuppression, and obliterates NET formation, unveiling new opportunities for therapeutic intervention to eradicate local relapse and ameliorate patient survival. This article is highlighted in the In This Issue feature, p. 1171.

An integrative approach unveils FOSL1 as an oncogene vulnerability in KRAS-driven lung and pancreatic cancer.

KRAS mutated tumours represent a large fraction of human cancers, but the vast majority remains refractory to current clinical therapies. Thus, a deeper understanding of the molecular mechanisms triggered by KRAS oncogene may yield alternative therapeutic strategies. Here we report the identification of a common transcriptional signature across mutant KRAS cancers of distinct tissue origin that includes the transcription factor FOSL1. High FOSL1 expression identifies mutant KRAS lung and pancreatic cancer patients with the worst survival outcome. Furthermore, FOSL1 genetic inhibition is detrimental to both KRAS-driven tumour types. Mechanistically, FOSL1 links the KRAS oncogene to components of the mitotic machinery, a pathway previously postulated to function orthogonally to oncogenic KRAS. FOSL1 targets include AURKA, whose inhibition impairs viability of mutant KRAS cells. Lastly, combination of AURKA and MEK inhibitors induces a deleterious effect on mutant KRAS cells. Our findings unveil KRAS downstream effectors that provide opportunities to treat KRAS-driven cancers.

The Usefulness of Bone Biomarkers for Monitoring Treatment Disease: A Comparative Study in Osteolytic and Osteosclerotic Bone Metastasis Models.

BACKGROUND: The skeleton is the most common site of colonization by metastatic cancers. Zoledronic acid (ZA) has been shown to be effective for the treatment of bone metastases regardless of whether the bone lesions are osteolytic or osteoblastic. Biochemical markers of bone turnover may be useful tools to quantify the degree of bone remodeling in the presence of bone metastases. The aim of this work was to establish the correlation between tumor dispersion (bioluminescence) and biochemical markers of bone turnover in two osteolytic and osteoblastic metastasis models in mice. METHODS: The A549M1 cell line that produces osteolytic metastases and the LADOB cell line extracted from a patient with a lung carcinoma and osteoblastic metastases cells were retrovirally transduced with a luciferase reporter gene for in vivo image analysis. Forty-four-week-old mice were inoculated in the left cardiac ventricle with A549M1 or LADOB cells. Twenty mouse of each group were treated with a single dose of ZA (70 µg/kg) 5 days after i.c. Ten animals of each group were sacrificed at 21 and 28 days postinoculation in A549M1 and 60 and 75 days in the LADOB assay. Bioluminescence analysis was quantified 7, 14, 21 ,and 28 days postinoculation in A549M1 mice and 33, 45, 60, and 75 days after inoculation in LADOB mice. Osteocalcin (BGP), aminoterminal propeptide of procollagen I (PINP), carboxiterminal telopeptide of type I collagen (CTX), and 5b isoenzyme of tartrate-resistant acid phosphatase were measured by ELISA (IDS, UK). RESULTS: Bioluminescence imaging revealed a significant increase of tumor burden on time in both osteolytic and osteoblastic mice models. ZA administration resulted in a significant decrease in tumor burden at 21 and 28 days in the A549M1 animals and 60 and 70 days postinoculation in the LADOB line. Biomarkers levels were significantly increased in the untreated group at every point in the osteolytic model. In the osteoblastic model, 2 months after inoculation, all biomarkers were significantly increased. However, 2.5 months postinoculation, only PINP and CTX were significantly increased. Serum bone remodeling markers decreased in ZA-treated mice as compared with tumor groups in both models. With respect to the correlation between bone turnover markers and tumor burden, in the osteolytic model, PINP and BGP demonstrate a strong correlation with bioluminescence in both tumoral and ZA animals, and only CTX was significantly associated with bioluminescence in the group of animals that were not treated with ZA. CONCLUSIONS: We found that the best biomarkers for the diagnosis of both osteolytic and osteoblastic metastasis are formation markers, especially BGP. Moreover, these markers can be useful in the follow-up of the treatment with ZA in both types of metastasis.

EPCR promotes breast cancer progression by altering SPOCK1/testican 1-mediated 3D growth.

BACKGROUND: Activated protein C/endothelial protein C receptor (APC/EPCR) axis is physiologically involved in anticoagulant and cytoprotective activities in endothelial cells. Emerging evidence indicates that EPCR also plays a role in breast stemness and human tumorigenesis. Yet, its contribution to breast cancer progression and metastasis has not been elucidated. METHODS: Transcriptomic status of EPCR was examined in a cohort of 286 breast cancer patients. Cell growth kinetics was evaluated in control and EPCR and SPARC/osteonectin, Cwcv, and kazal-like domains proteoglycan (SPOCK1/testican 1) silenced breast cancer cells in 2D, 3D, and in co-culture conditions. Orthotopic tumor growth and lung and osseous metastases were evaluated in several human and murine xenograft breast cancer models. Tumor-stroma interactions were further studied in vivo by immunohistochemistry and flow cytometry. An EPCR-induced gene signature was identified by microarray analysis. RESULTS: Analysis of a cohort of breast cancer patients revealed an association of high EPCR levels with adverse clinical outcome. Interestingly, EPCR knockdown did not affect cell growth kinetics in 2D but significantly reduced cell growth in 3D cultures. Using several human and murine xenograft breast cancer models, we showed that EPCR silencing reduced primary tumor growth and secondary outgrowths at metastatic sites, including the skeleton and the lungs. Interestingly, these effects were independent of APC ligand stimulation in vitro and in vivo. Transcriptomic analysis of EPCR-silenced tumors unveiled an effect mediated by matricellular secreted proteoglycan SPOCK1/testican 1. Interestingly, SPOCK1 silencing suppressed in vitro 3D growth. Moreover, SPOCK1 ablation severely decreased orthotopic tumor growth and reduced bone metastatic osteolytic tumors. High SPOCK1 levels were also associated with poor clinical outcome in a subset breast cancer patients. Our results suggest that EPCR through SPOCK1 confers a cell growth advantage in 3D promoting breast tumorigenesis and metastasis. CONCLUSIONS: EPCR represents a clinically relevant factor associated with poor outcome and a novel vulnerability to develop combination therapies for breast cancer patients.

Matrix-Gla protein promotes osteosarcoma lung metastasis and associates with poor prognosis.

Osteosarcoma (OS) is the most prevalent osseous tumour in children and adolescents and, within this, lung metastases remain one of the factors associated with a dismal prognosis. At present, the genetic determinants driving pulmonary metastasis are poorly understood. We adopted a novel strategy using robust filtering analysis of transcriptomic profiling in tumour osteoblastic cell populations derived from human chemo-naive primary tumours displaying extreme phenotypes (indolent versus metastatic) to uncover predictors associated with metastasis and poor survival. We identified MGP, encoding matrix-Gla protein (MGP), a non-collagenous matrix protein previously associated with the inhibition of arterial calcification. Using different orthotopic models, we found that ectopic expression of Mgp in murine and human OS cells led to a marked increase in lung metastasis. This effect was independent of the carboxylation of glutamic acid residues required for its physiological role. Abrogation of Mgp prevented lung metastatic activity, an effect that was rescued by forced expression. Mgp levels dramatically altered endothelial adhesion, trans-endothelial migration in vitro and tumour cell extravasation ability in vivo. Furthermore, Mgp modulated metalloproteinase activities and TGFß-induced Smad2/3 phosphorylation. In the clinical setting, OS patients who developed lung metastases had high serum levels of MGP at diagnosis. Thus, MGP represents a novel adverse prognostic factor and a potential therapeutic target in OS. Microarray datasets may be found at: http://bioinfow.dep.usal.es/osteosarcoma/ Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Sphere-derived tumor cells exhibit impaired metastasis by a host-mediated quiescent phenotype.

The spread of lung cancer cells to distant sites represents a common event associated with poor prognosis. A fraction of tumor cells named cancer stem cells (CSCs) have the ability to overcome therapeutic stress and remain quiescent. However, whether these CSCs have also the capacity to initiate and sustain metastasis remains unclear. Here, we used tumor sphere cultures (TSC) isolated from mouse and human lung cancer models to enrich for CSCs, and assessed their metastatic potential as compared to non-CSCs. As expected, TSC overexpressed a variety of stem cell markers and displayed chemoresistance. The CSC phenotype of TSC was confirmed by their higher growth ability in soft agar and tumorigenic potential in vivo, despite their reduced in vitro cell growth kinetics. Surprisingly, the appearance of spontaneous lung metastases was strongly delayed in mice injected with TSC as compared to non-TSC cells. Similarly, this finding was confirmed in several other models of metastasis, an effect associated with a retarded colonization activity. Interestingly, such delay correlated with a quiescent phenotype whose underlined mechanisms included an increase in p27 protein and lower phospho-ERK1/2 levels. Thus, these data suggest that cells enriched for CSC properties display an impaired metastatic activity, a finding with potential clinical implications.

miRNA cargo within exosome-like vesicle transfer influences metastatic bone colonization.

Bone metastasis represents one of the most deleterious clinical consequences arising in the context of many solid tumors. Severe osteolysis results from tumor cell colonization of the bone compartment, a process which entails reciprocal exchange of soluble signals between tumor cells and their osseous microenvironment. Recent evidence indicates that tumor-intrinsic miRNAs are pleiotropic regulators of gene expression. But they are also frequently released in exosome-like vesicles (ELV). Yet the functional relevance of the transference of tumor-derived ELV and their miRNA cargo to the extracellular milieu during osseous colonization is unknown. Comparative transcriptomic profiling using an in vivo murine model of bone metastasis identified a repressed miRNA signature associated with high prometastatic activity. Forced expression of single miRNAs identified miR-192 that markedly appeased osseous metastasis in vivo, as shown by X-ray, bioluminescence imaging and microCT scans. Histological examination of metastatic lesions revealed impaired tumor-induced angiogenesis in vivo, an effect that was associated in vitro with decreased hallmarks of angiogenesis. Isolation and characterization of ELV by flow cytometry, Western blot analysis, transmission electron microscopy and nanoparticle tracking analysis revealed the ELV cargo enrichment in miR-192. Consistent with these findings, fluorescent labeled miR-192-enriched-ELV showed the in vitro transfer and release of miR-192 in target endothelial cells and abrogation of the angiogenic program by repression of proangiogenic IL-8, ICAM and CXCL1. Moreover, in vivo infusion of fluorescent labeled ELV efficiently targeted cells of the osseous compartment. Furthermore, treatment with miR-192 enriched ELV in a model of in vivo bone metastasis pre-conditioned osseous milieu and impaired tumor-induced angiogenesis, thereby reducing the metastatic burden and tumor colonization. Changes in the miRNA-cargo content within ELV represent a novel mechanism heavily influencing bone metastatic colonization, which is most likely relevant in other target organs. Mechanistic mimicry of this phenomenon by synthetic nanoparticles could eventually emerge as a novel therapeutic approach.

miR-326 associates with biochemical markers of bone turnover in lung cancer bone metastasis.

Recent evidence suggests that miRNAs could be used as serum markers in a variety of normal and pathological conditions. In this study, we aimed to identify novel miRNAs associated with skeletal metastatic disease in a preclinical model of lung cancer bone metastasis. We assessed the validity of these miRNAs as reliable serum biochemical markers to monitor the extent of disease and response to treatment in comparison to imaging techniques and standard biochemical markers of bone turnover. Using a murine model of human lung cancer bone metastasis after zoledronic acid (ZA) treatment, PINP (procollagen I amino-terminal propeptide) was the only marker that exhibited a strong correlation with osteolytic lesions and tumor burden at early and late stages of bone colonization. In contrast, BGP (osteocalcin) and CTX (carboxyterminal telopeptide) demonstrated a strong correlation only at late stages. We performed qPCR based screening of a panel of 380 human miRNAs and quantified bone metastatic burden using micro-CT scans, X-rays and bioluminescence imaging. Interestingly, levels of miR-326 strongly associated with tumor burden and PINP in vehicle-treated animals, whereas no association was found in ZA-treated animals. Only miR-193 was associated with biochemical markers PINP, BGP and CTX in ZA-treated animals. Consistently, miR-326 and PINP demonstrated a strong correlation with tumor burden. Our findings, taken together, indicate that miR-326 could potentially serve as a novel biochemical marker for monitoring bone metastatic progression.

Receptor of activated protein C promotes metastasis and correlates with clinical outcome in lung adenocarcinoma.

RATIONALE: Efficient metastasis requires survival and adaptation of tumor cells to stringent conditions imposed by the extracellular milieu. Identification of critical survival signaling pathways in tumor cells might unveil novel targets relevant in disease progression. OBJECTIVES: To investigate the contribution of activated protein C (APC) and its receptor (endothelial protein C receptor [EPCR]) in animal models of lung cancer metastasis and in patients with lung adenocarcinoma. METHODS: Signaling pathway triggered by APC/EPCR and its relevance in apoptosis was studied in vitro. Functional significance was assessed by silencing and blocking antibodies in several in vivo models of lung cancer metastasis in athymic nude Foxn1(nu) mice. We examined EPCR levels using a microarray dataset of 107 patients. Immunohistochemical analysis was performed in an independent cohort of 295 patients with lung adenocarcinoma. MEASUREMENTS AND MAIN RESULTS: The effects of APC binding to EPCR rapidly triggered Akt and extracellular signal-regulated kinase signaling pathways, leading to attenuated in vitro apoptosis. In vivo, silencing of EPCR expression or blocking APC/EPCR interaction reduced infiltration in the target organ, resulting in impaired prometastatic activity. Moreover, overexpression of EPCR induced an increased metastatic activity to target organs. Analysis of clinical samples showed a robust association between high EPCR levels and poor prognosis, particularly in stage I patients. CONCLUSIONS: EPCR and its ligand APC promote cell survival that contributes to tumor cell endurance to stress favoring prometastatic activity of lung adenocarcinoma. EPCR/APC is a novel target of relevance in the clinical outcome of early-stage lung cancer.

Inhibition of collagen receptor discoidin domain receptor-1 (DDR1) reduces cell survival, homing, and colonization in lung cancer bone metastasis.

PURPOSE: We investigated the role of the collagen-binding receptor discoidin domain receptor-1 (DDR1) in the initiation and development of bone metastasis. EXPERIMENTAL DESIGN: We conducted immunohistochemical analyses in a cohort of 83 lung cancer specimens and examined phosphorylation status in a panel of human lung cancer cell lines. Adhesion, chemotaxis, invasiveness, metalloproteolytic, osteoclastogenic, and apoptotic assays were conducted in DDR1-silenced cells. In vivo, metastatic osseous homing and colonization were assessed in a murine model of metastasis. RESULTS: DDR1 was expressed in a panel of human lung cancer cell lines, and high DDR1 levels in human lung tumors were associated with poor survival. Knockdown (shDDR1) cells displayed unaltered growth kinetics in vitro and in vivo. In contrast, shDDR1 cells showed reduced invasiveness in collagen matrices and increased apoptosis in basal conditions and induced apoptosis in vitro. More importantly, conditioned media of DDR1-knockdown cells decreased osteoclastogenic activity in vitro. Consequently, in a model of tumor metastasis to bone, lack of DDR1 showed decreased metastatic activity associated with reduced tumor burden and osteolytic lesions. These effects were consistent with a substantial reduction in the number of cells reaching the bone compartment. Moreover, intratibial injection of shDDR1 cells significantly decreased bone tumor burden, suggesting impaired colonization ability that was highly dependent on the bone microenvironment. CONCLUSIONS: Disruption of DDR1 hampers tumor cell survival, leading to impaired early tumor-bone engagement during skeletal homing. Furthermore, inhibition of DDR1 crucially alters bone colonization. We suggest that DDR1 represents a novel therapeutic target involved in bone metastasis.

Tumor-stromal interactions of the bone microenvironment: in vitro findings and potential in vivo relevance in metastatic lung cancer models.

Lung cancer comprises a large variety of histological subtypes with a frequent proclivity to form bone metastasis; a condition associated with dismal prognosis. To identify common mechanisms in the development of osteolytic metastasis, we systematically screened a battery of lung cancer cell lines and developed three models of non-small cell lung cancer (NSCLC) with a common proclivity to form osseous lesions, which represented different histological subtypes. Comparative analysis revealed different incidences and latency times. These differences were correlated with cell-type-specific secretion of osteoclastogenic factors, including macrophage inflammatory protein-1α, interleukin-8 and parathyroid hormone-related protein, some of which were exacerbated in conditions that mimicked tumor-stroma interactions. In addition, a distinct signature of matrix metalloproteinase (MMP) activity derived from reciprocal tumor-stroma interactions was detected for each tumor cell line. Thus, these results suggest subtle differences in the mechanisms of bone colonization for each lung cancer subtype, but share, although each to a different degree, dual MMP and osteoclastogenic activities that are differentially enhanced upon tumor-stromal interactions.