Antibody-mediated targeting of Claudins in cancer

Tight junctions (TJs) are large intercellular adhesion complexes that maintain cell polarity in normal epithelia and endothelia. Claudins are critical components of TJs, forming homo- and heteromeric interaction between adjacent cells, which have emerged as key functional modulators of carcinogenesis and metastasis. Numerous epithelial-derived cancers display altered claudin expression patterns, and these aberrantly expressed claudins have been shown to regulate cancer cell proliferation/growth, metabolism, metastasis and cell stemness. Certain claudins can now be used as biomarkers to predict patient prognosis in a variety of solid cancers. Our understanding of the distinct roles played by claudins during the cancer progression has progressed significantly over the last decade and claudins are now being investigated as possible diagnostic markers and therapeutic targets. In this review, we will summarize recent progress in the use of antibody-based or related strategies for targeting claudins in cancer treatment. We first describe pre-clinical studies that have facilitated the development of neutralizing antibodies and antibody-drug-conjugates targeting Claudins (Claudins-1, -3, -4, -6 and 18.2). Next, we summarize clinical trials assessing the efficacy of antibodies targeting Claudin-6 or Claudin-18.2. Finally, emerging strategies for targeting Claudins, including Chimeric Antigen Receptor (CAR)-T cell therapy and Bi-specific T cell engagers (BiTEs), are also discussed.

Abstract 2466: Detection of extracellular vesicle-associated DNA in mouse metastatic breast cancer cells

Background: Breast cancer is the second most common type of cancer worldwide, and while primary disease is often well controlled, metastatic breast cancer (MBC) is responsible for the majority of deaths. MBC cells can metastasize to distant sites including the liver, lung, brain and bone, and the mechanisms underlying this organotropism remain largely unknown. MBC has high genetic heterogeneity, and studies have reported mutations in oncogenic pathways such as TP53, PIK3CA and ESR1. Liquid biopsy has been used to detect extracellular vesicle-associated DNA (EV-DNA), bypassing the limits of tissue biopsies often invasive and difficult to obtain. EVs are nanoparticles of diverse sizes released in the extracellular environment by all types of cells and are known to carry cargos including EV associated proteins, lipids, RNA and DNA with the potential to interact with surrounding cells and be explored as markers of disease progression. The goal of our study was to detect EV associated oncogenes derived from MBC cell lines. EV-DNA can potentially be incorporated into cancer diagnosis and prognosis in the clinical setting.

Methods: In this study, we isolated EVs from 4T1 mouse mammary tumor model with primary cells and 4T1 induced liver-metastatic variants (2776, 2792 cells). We isolated and characterized the EVs using nanoparticle tracking analysis (NTA) and dynamic light scattering (DLS) for particle size and concentration, as well as western blot (WB) for EV markers. EV-DNA was isolated using the Gentra puregene blood kit (Qiagen) and quantified using a Qubit fluorometer, and oncogenic mutations assessed using droplet digital polymerase chain reaction (ddPCR) to detect mutant PIK3CA H1047R, TP53 P31T, and ESR1 D538G.

Results: EVs isolated from primary and liver metastatic MBC cell lines were positive for EV markers synthenin-1 and CD63. NTA showed higher concentrations of EVs from liver-metastatic variants cell lines (2776: 1.11x1011 particles/ml, mean size 109.2 nm; 2792: 1.37x1011 particles/ml, mean size 122.7 nm) compared to primary tumor cells (4T1: 5.83x1010 particles/ml; mean size: 120.3 nm). These results suggest an increased EV emission from metastatic variants cell lines compared to parental cells. Interestingly, significantly higher EV-DNA concentration was found in liver-metastatic cells (2776: 2.85 ng/μl; 2792: 1.48 ng/μl) than in parental cells (0.23 ng/μl).

Conclusions: These findings suggest circulating oncogenic EV-DNA may be a useful biomarker to monitor MBC patients throughout disease progression. For future investigation of EV enriched material, we will assess the mutant copies of oncogenes TP53 P31T, PIK3CA H1047R and ESR1 D538G associated with the EVs of parental cells and metastatic variants. Extensive studies in vitro and in vivo are required to validate and clarify definitive roles of EVs in tumor invasion and to further our understanding of the role of EV cargo in spreading malignancies.

Citation Format: Amélie Nadeau, Kyle Dickinson, Thupten Tsering, Emilie Solymoss, Sébastien Tabariès, Peter Siegel, Julia Burnier. Detection of extracellular vesicle-associated DNA in mouse metastatic breast cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2466.

Histopathological growth patterns of liver metastasis: updated consensus guidelines for pattern scoring, perspectives and recent mechanistic insights

The first consensus guidelines for scoring the histopathological growth patterns (HGPs) of liver metastases were established in 2017. Since then, numerous studies have applied these guidelines, have further substantiated the potential clinical value of the HGPs in patients with liver metastases from various tumour types and are starting to shed light on the biology of the distinct HGPs. In the present guidelines, we give an overview of these studies, discuss novel strategies for predicting the HGPs of liver metastases, such as deep-learning algorithms for whole-slide histopathology images and medical imaging, and highlight liver metastasis animal models that exhibit features of the different HGPs. Based on a pooled analysis of large cohorts of patients with liver-metastatic colorectal cancer, we propose a new cut-off to categorise patients according to the HGPs. An up-to-date standard method for HGP assessment within liver metastases is also presented with the aim of incorporating HGPs into the decision-making processes surrounding the treatment of patients with liver-metastatic cancer. Finally, we propose hypotheses on the cellular and molecular mechanisms that drive the biology of the different HGPs, opening some exciting preclinical and clinical research perspectives.

Runt related transcription factor-1 plays a central role in vessel co-option of colorectal cancer liver metastases

Colorectal cancer liver metastasis (CRCLM) has two major histopathological growth patterns: angiogenic desmoplastic and non-angiogenic replacement. The replacement lesions obtain their blood supply through vessel co-option, wherein the cancer cells hijack pre-existing blood vessels of the surrounding liver tissue. Consequentially, anti-angiogenic therapies are less efficacious in CRCLM patients with replacement lesions. However, the mechanisms which drive vessel co-option in the replacement lesions are unknown. Here, we show that Runt Related Transcription Factor-1 (RUNX1) overexpression in the cancer cells of the replacement lesions drives cancer cell motility via ARP2/3 to achieve vessel co-option. Furthermore, overexpression of RUNX1 in the cancer cells is mediated by Transforming Growth Factor Beta-1 (TGFβ1) and thrombospondin 1 (TSP1). Importantly, RUNX1 knockdown impaired the metastatic capability of colorectal cancer cells in vivo and induced the development of angiogenic lesions in liver. Our results confirm that RUNX1 may be a potential target to overcome vessel co-option in CRCLM.

Abstract 1927: Cancer cells induce apoptosis in hepatocytes as one of the mechanisms to displace hepatocytes in vessel co-opted colorectal cancer liver metastases

Vessel co-option in colorectal cancer liver metastases (CRCLM) has been recognized as one of the mechanistic pathways of resistance against anti-angiogenic therapy. The cancer cells are highly motile in co-opted lesions, which move toward and along the pre-existing sinusoidal vessels and hijack them to gain access to nutrient. The movement of cancer cells is accompanied by displacement of the hepatocytes. However, the molecular mechanisms underlying this displacement are unclear yet. To examine whether apoptosis involved in hepatocytes displacement by cancer cells in co-opted lesions, we performed immunohistochemical staining for pro-apoptotic markers, such as cleaved caspase-3 and cleaved PARP-1. We observed overexpression of pro-apoptotic markers in liver parenchyma of co-opted lesions compared to angiogenic lesions, specifically the hepatocytes that are in close proximity to the cancer cells. In vitro, we found that culturing hepatocytes with either colorectal cancer cells or conditioned media of co-opted CRCLM organoids induces apoptosis. Importantly, our results also suggested proprotein convertase subtilisin/kexin type 9 (PCSK-9 or PC-9) as a potential mediator of cancer cells-driven hepatocytes apoptosis. Altogether, these results confirm that cancer cells exploit apoptosis to establish vessel co-option in CRCLM.

Citation Format: Miran Rada, Migmar Tsamchoe, Audrey Kapelanski-Lamoureux, Jessica Bloom, Stephanie Petrillo, Sébastien Tabariès, Diane H. Kim, Peter Younan, Alex Gregorieff, Peter Siegel, Anthoula Lazaris, Peter Metrakos. Cancer cells induce apoptosis in hepatocytes as one of the mechanisms to displace hepatocytes in vessel co-opted colorectal cancer liver metastases [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1927.

Claudin-2 promotes colorectal cancer liver metastasis and is a biomarker of the replacement type growth pattern

Claudin-2 promotes breast cancer liver metastasis by enabling seeding and early cancer cell survival. We now demonstrate that Claudin-2 is functionally required for colorectal cancer liver metastasis and that Claudin-2 expression in primary colorectal cancers is associated with poor overall and liver metastasis-free survival. We have examined the role of Claudin-2, and other claudin family members, as potential prognostic biomarkers of the desmoplastic and replacement histopathological growth pattern associated with colorectal cancer liver metastases. Immunohistochemical analysis revealed higher Claudin-2 levels in replacement type metastases when compared to those with desmoplastic features. In contrast, Claudin-8 was highly expressed in desmoplastic colorectal cancer liver metastases. Similar observations were made following immunohistochemical staining of patient-derived xenografts (PDXs) that we have established, which faithfully retain the histopathology of desmoplastic or replacement type colorectal cancer liver metastases. We provide evidence that Claudin-2 status in patient-derived extracellular vesicles may serve as a relevant prognostic biomarker to predict whether colorectal cancer patients have developed replacement type liver metastases. Such a biomarker will be a valuable tool in designing optimal treatment strategies to better manage patients with colorectal cancer liver metastases.

Tabariès et al. describe that claudin 2 is a promoter of colorectal cancer liver metastasis. Furthermore, high Claudin-2 expression is associated with shorter time to liver-specific recurrence and is a biomarker of replacement type CRC liver metastases.

Afadin (AF6) in cancer progression: A multidomain scaffold protein with complex and contradictory roles

Adherens (AJ) and tight junctions (TJ) maintain cell-cell adhesions and cellular polarity in normal tissues. Afadin, a multi-domain scaffold protein, is commonly found in both adherens and tight junctions, where it plays both structural and signal-modulating roles. Afadin is a complex modulator of cellular processes implicated in cancer progression, including signal transduction, migration, invasion, and apoptosis. In keeping with the complexities associated with the roles of adherens and tight junctions in cancer, afadin exhibits both tumor suppressive and pro-metastatic functions. In this review, we will explore the dichotomous roles that afadin plays during cancer progression.

Abstract 3935: Runt related transcription factor-1 (runx1) plays a central role in vessel co-option of colorectal cancer liver metastases

Colorectal cancer liver metastasis (CRCLM) has two major morphological growth pattern subtypes including desmoplastic (DHGP) and replacement (RHGP). The DHGP tumors depend on angiogenesis for their growth. Conversely, RHGP tumors are non-angiogenic and obtain their blood supply through vessel co-option, which the cancer cells hijacking pre-existing blood vessels of the surrounding liver tissue. Therefore, anti-angiogenic therapies have shown modest efficacy in CRCLM patients with RHGP lesions. In this study, we found overexpression of Runt Related Transcription Factor-1 (RUNX1) in the cancer cells of RHGP lesions. Upregulation of RUNX1 is positively correlated with cancer cell motility and epithelial mesenchymal transition (EMT) in vitro. Our results also showed that RUNX1 regulated by Transforming Growth Factor Beta-1 (TGFβ1) through TGFβ Receptor II (TGFβRII). Significantly, RUNX1 knockdown induced conversion RHGP lesions to DHGP in vivo. Collectively, this study suggests RUNX1 as a potential target therapy to overcome resistance to anti-angiogenic therapy in CRCLM.

Citation Format: Miran Rada, Audrey Kapelanski-Lamoureux, Stephanie Petrillo, Sébastien Tabariès, Peter Siegel, Anthoula Lazaris, Peter Metrakos. Runt related transcription factor-1 (runx1) plays a central role in vessel co-option of colorectal cancer liver metastases [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3935.

Immature Low-Density Neutrophils Exhibit Metabolic Flexibility that Facilitates Breast Cancer Liver Metastasis

Neutrophils are phenotypically heterogeneous and exert either anti- or pro-metastatic functions. We show that cancer-cell-derived G-CSF is necessary, but not sufficient, to mobilize immature low-density neutrophils (iLDNs) that promote liver metastasis. In contrast, mature high-density neutrophils inhibit the formation of liver metastases. Transcriptomic and metabolomic analyses of high- and low-density neutrophils reveal engagement of numerous metabolic pathways specifically in low-density neutrophils. iLDNs exhibit enhanced global bioenergetic capacity, through their ability to engage mitochondrial-dependent ATP production, and remain capable of executing pro-metastatic neutrophil functions, including NETosis, under nutrient-deprived conditions. We demonstrate that NETosis is an important neutrophil function that promotes breast cancer liver metastasis. iLDNs rely on the catabolism of glutamate and proline to support mitochondrial-dependent metabolism in the absence of glucose, which enables sustained NETosis. These data reveal that distinct pro-metastatic neutrophil populations exhibit a high degree of metabolic flexibility, which facilitates the formation of liver metastases.

Dipeptidase-1 Is an Adhesion Receptor for Neutrophil Recruitment in Lungs and Liver

A hallmark feature of inflammation is the orchestrated recruitment of neutrophils from the bloodstream into inflamed tissue. Although selectins and integrins mediate recruitment in many tissues, they have a minimal role in the lungs and liver. Exploiting an unbiased in vivo functional screen, we identified a lung and liver homing peptide that functionally abrogates neutrophil recruitment to these organs. Using biochemical, genetic, and confocal intravital imaging approaches, we identified dipeptidase-1 (DPEP1) as the target and established its role as a physical adhesion receptor for neutrophil sequestration independent of its enzymatic activity. Importantly, genetic ablation or functional peptide blocking of DPEP1 significantly reduced neutrophil recruitment to the lungs and liver and provided improved survival in models of endotoxemia. Our data establish DPEP1 as a major adhesion receptor on the lung and liver endothelium and identify a therapeutic target for neutrophil-driven inflammatory diseases of the lungs.

Abstract A26: Immune profiling and organoids generation of a rare case of prostate cancer liver metastasis

Introduction: Prostate cancer (PCa) is the second most frequent cancer in men and a leading cause of cancer-related mortality. Despite major advances in immunotherapy, PCa remains a poor responder. Metastatic PCa is responsible for the majority of PCa-associated mortality. Most PCa metastases are multifocal and display a strong bones tropism (91.1% of cases), but PCa metastases can also spread to the lymph nodes (8.7%), lungs (5.7%), liver (4.5%) and brain (1.8%). Liver metastases are associated with worse prognosis but due to their multifocal nature and frequent spreading to other sites, PCa metastases are rarely resected. Therefore, immunologic characterization of these lesions concomitant with generation of research tools derived from these lesions are urgently needed to understand how to intercept disease progression.

Methods: A 62-year-old male who previously underwent radical prostatectomy in 2016 was diagnosed in July 2018 with a single liver metastasis (5.3 cm) by MRI. The tumor was surgically resected and tumor tissue along with peripheral blood was collected and processed for in-depth immunologic/molecular characterization and generation of tumor models. The study was done in accordance with the guidelines approved by MUHC IRB. Prior written informed consent was obtained from the subject to participate in the study (protocol: SDR-11-066).

Results: The prostatic origin of the tumor mass was confirmed by positivity for PSMA and NKX3.1 expression. Patient-derived xenografts, 2D cell and organoid cultures were generated and immunophenotyping of the innate and adaptive peripheral and tumor-infiltrating immune cells subsets was performed. Genomic alterations are currently being characterized by multiplex ligation-dependent probe amplification (MLPA). Additionally, chromatin accessibility-based characterization of the gene regulatory network of tumor luminal cells (CD49-CD26+) using the assay for transposase-accessible chromatin using sequencing (ATAC-seq) together with RNA-seq is presently under way.

Conclusions: Our collaborative effort will provide the much-needed research tools required to model and understand the processes leading to the rare, but lethal, progression from a localized PCa lesion to liver metastases. Combined with other ongoing research efforts, we believe this case will help us understand the molecular basis to the liver tropism of a subset of PCa metastases and ultimately provide biomarkers for early identification of patients with increased metastatic potential as well as a basis to determine the appropriate immunotherapy modality for metastatic patients.

Citation Format: Aurélie Y. Le Page, Anna de Polo, K-P Guérard, A. Lazaris, S.K. Petrillo, W. Ebrahimizadeh, S. Tabariès, S. Shinde-Jadhav, A. Feldiorean, N. Boufaeid, W. Kassouf, C. Piccirillo, P.M. Siegel, A. Aprikian, A. Gregorieff, J. Lapointe, P. Metrakos, D.P. Labbé. Immune profiling and organoids generation of a rare case of prostate cancer liver metastasis [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr A26.

p66ShcA functions as a contextual promoter of breast cancer metastasis

Background

The p66ShcA redox protein is the longest isoform of the Shc1 gene and is variably expressed in breast cancers. In response to a variety of stress stimuli, p66ShcA becomes phosphorylated on serine 36, which allows it to translocate from the cytoplasm to the mitochondria where it stimulates the formation of reactive oxygen species (ROS). Conflicting studies suggest both pro- and anti-tumorigenic functions for p66ShcA, which prompted us to examine the contribution of tumor cell-intrinsic functions of p66ShcA during breast cancer metastasis.

Methods

We tested whether p66ShcA impacts the lung-metastatic ability of breast cancer cells. Breast cancer cells characteristic of the ErbB2+/luminal (NIC) or basal (4T1) subtypes were engineered to overexpress p66ShcA. In addition, lung-metastatic 4T1 variants (4T1-537) were engineered to lack endogenous p66ShcA via Crispr/Cas9 genomic editing. p66ShcA null cells were then reconstituted with wild-type p66ShcA or a mutant (S36A) that cannot translocate to the mitochondria, thereby lacking the ability to stimulate mitochondrial-dependent ROS production. These cells were tested for their ability to form spontaneous metastases from the primary site or seed and colonize the lung in experimental (tail vein) metastasis assays. These cells were further characterized with respect to their migration rates, focal adhesion dynamics, and resistance to anoikis in vitro. Finally, their ability to survive in circulation and seed the lungs of mice was assessed in vivo.

Results

We show that p66ShcA increases the lung-metastatic potential of breast cancer cells by augmenting their ability to navigate each stage of the metastatic cascade. A non-phosphorylatable p66ShcA-S36A mutant, which cannot translocate to the mitochondria, still potentiated breast cancer cell migration, lung colonization, and growth of secondary lung metastases. However, breast cancer cell survival in the circulation uniquely required an intact p66ShcA S36 phosphorylation site.

Conclusion

This study provides the first evidence that both mitochondrial and non-mitochondrial p66ShcA pools collaborate in breast cancer cells to promote their maximal metastatic fitness.

Afadin cooperates with Claudin-2 to promote breast cancer metastasis

Tabariès et al. show that signaling downstream from a Claudin-2/Afadin complex enables the efficient formation of breast cancer metastases.

Claudin-2 promotes breast cancer liver metastasis by enabling seeding and early cancer cell survival. We now demonstrate that the PDZ-binding motif of Claudin-2 is necessary for anchorage-independent growth of cancer cells and is required for liver metastasis. Several PDZ domain-containing proteins were identified that interact with the PDZ-binding motif of Claudin-2 in liver metastatic breast cancer cells, including Afadin, Arhgap21, Pdlim2, Pdlim7, Rims2, Scrib, and ZO-1. We specifically examined the role of Afadin as a potential Claudin-2-interacting partner that promotes breast cancer liver metastasis. Afadin associates with Claudin-2, an interaction that requires the PDZ-binding motif of Claudin-2. Loss of Afadin also impairs the ability of breast cancer cells to form colonies in soft agar and metastasize to the lungs or liver. Immunohistochemical analysis of Claudin-2 and/or Afadin expression in 206 metastatic breast cancer tumors revealed that high levels of both Claudin-2 and Afadin in primary tumors were associated with poor disease-specific survival, relapse-free survival, lung-specific relapse, and liver-specific relapse. Our findings indicate that signaling downstream from a Claudin-2/Afadin complex enables the efficient formation of breast cancer metastases. Moreover, combining Claudin-2 and Afadin as prognostic markers better predicts the potential of breast cancer to metastasize to soft tissues.

Exosomal Release of L-Plastin by Breast Cancer Cells Facilitates Metastatic Bone Osteolysis

Bone metastasis from breast and prostate carcinomas is facilitated by activation of bone-resorbing osteoclasts. Using proteomics approaches, we have identified peroxiredoxin-4 (PRDX4) as a cancer-secreted mediator of osteoclastogenesis. We now report characterization of L-plastin in the conditioned media (CM) of MDA-MB-231 human breast cancer cells using immunoblotting and mass spectrometry. The osteoclastogenic potential of MDA-MB-231 CM with siRNA-silenced L-plastin was significantly reduced. L-plastin was detected in cancer-derived exosomes, and inhibition of exosomal release significantly decreased the osteoclastogenic capacity of MDA-MB-231 CM. When added to osteoclast precursors primed with RANKL for 2 days, recombinant L-plastin induced calcium/NFATc1-mediated osteoclastogenesis to the levels similar to continuous treatment with RANKL. Using shRNA, we generated MDA-MB-231 cells lacking L-plastin, PRDX4, or both and injected these cell populations intratibially in CD-1 immunodeficient mice. Micro-CT and histomorphometric analysis demonstrated a complete loss of osteolysis when MDA-MB-231 cells lacking both L-plastin and PRDX4 were injected. A meta-analysis established an increase in L-plastin and PRDX4 mRNA expression in numerous human cancers, including breast and prostate carcinomas. This study demonstrates that secreted L-plastin and PRDX4 mediate osteoclast activation by human breast cancer cells.

Abstract 21: p66ShcA is a contextual breast cancer metastasis promoter or suppressor depending on the tumor microenvironment

Introduction: Src homology and collagen A (ShcA) adaptor proteins are essential during breast cancer progression. However, the role of the largest isoform, p66ShcA, is conflicting and still poorly understood. Under high levels of stress p66ShcA is phosphorylated on serine36, within its CH2 domain, allowing it to translocate to the mitochondria and induce the formation of reactive oxygen species (ROS) to promote apoptosis. Previously, we provided the first in vivo evidence that p66ShcA can influence both pro and anti-tumorigenic functions in ErbB2+ luminal breast cancer. Stable overexpression of p66ShcA reduced tumor outgrowth while simultaneously elevating the expression of mesenchymal genes to promote tumor plasticity. In this study, we evaluated the role of p66ShcA in metastatic dissemination to the lung in a model of basal breast cancer, which typically is associated with poor outcome. Hypothesis: p66ShcA regulates basal breast cancer metastasis to the lung. Methods: Screening a panel of basal breast cancer cells in vivo selected to the lung, liver and bone, we found p66ShcA enriched in lung and liver metastatic variant cell lines relative to parental breast cancer cells and those in vivo selected through the mammary fatpad. Using CRISPR/Cas technology we genetically deleted p66ShcA and rescued with p66ShcA-WT or a p66ShcA-S36A mutant. Lung metastatic basal breast cancer cells were injected into the fourth gland of the mammary fatpad. Tumors were measured using calipers 3 times/week following first palpation (>50mm3) followed by surgical resection to monitor the lung metastatic burden. In addition, we performed tail vein injections to monitor lung metastatic burden following direct entry into the circulation. Results: Loss of p66ShcA significantly reduced the metastatic burden to the lung following surgical tumor resection and this reduction was partially rescued by stable overexpression of wild type (WT), but not S36A mutated p66ShcA from the primary site. These effects were not due to altered anti-oxidant expression levels, changes in oxidative DNA Damage or microvessel density. Intriguingly, we found that WT-rescue of p66ShcA significantly elevated the migratory speed of breast cancer cells in vitro and corroborates our in vivo metastatic burden data. However, this is in stark contrast to our tail vein data, where WT-rescue of p66ShcA significantly inhibited lung metastasis. Conclusion: p66ShcA is required for efficient metastasis to the lung in a mitrochondrial-ROS-dependent fashion from the primary site. Our data suggest that cues from the tumor microenvironement of the mammary fatpad are essential for successful colonization and outgrowth at oxygen rich sites, such as the lung, as breast cancer cells with elevated expression of p66ShcA directly entering the circulation suppressed lung metastatic burden.

Citation Format: Jesse Hudson, Kyle Lewis, Julien Senécal, Alexander Kiepas, Sébastien Tabariès, Valérie Sabourin, Ryuhjin Ahn, Rachel La Selva, Peter Siegel, Giuseppina Ursini-Siegel. p66ShcA is a contextual breast cancer metastasis promoter or suppressor depending on the tumor microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 21.

PGC-1α Promotes Breast Cancer Metastasis and Confers Bioenergetic Flexibility against Metabolic Drugs

Metabolic adaptations play a key role in fueling tumor growth. However, less is known regarding the metabolic changes that promote cancer progression to metastatic disease. Herein, we reveal that breast cancer cells that preferentially metastasize to the lung or bone display relatively high expression of PGC-1α compared with those that metastasize to the liver. PGC-1α promotes breast cancer cell migration and invasion in vitro and augments lung metastasis in vivo. Pro-metastatic capabilities of PGC-1α are linked to enhanced global bioenergetic capacity, facilitating the ability to cope with bioenergetic disruptors like biguanides. Indeed, biguanides fail to mitigate the PGC-1α-dependent lung metastatic phenotype and PGC-1α confers resistance to stepwise increases in metformin concentration. Overall, our results reveal that PGC-1α stimulates bioenergetic potential, which promotes breast cancer metastasis and facilitates adaptation to metabolic drugs.

Intra-tumor delivery of zoledronate mitigates metastasis-induced osteolysis superior to systemic administration

Bisphosphonates (BPs) have recently been shown to have direct anti-tumor properties. Systemic treatment with BPs can have multiple adverse effects such as osteonecrosis of the jaw and BP induced bone fracturing and spine instability. While benefits of systemic BP treatments may outweigh risks, local treatment with BPs has been explored as an alternate strategy to reduce unwarranted risk. In the present study, we examined whether local delivery of BPs inhibits tumor-induced osteolysis and tumor growth more effectively than systemic treatment in an animal model of tumor-induced bone disease. Following establishment of an intra-tibial model of bone metastases in athymic mice, the experimental group was treated by local administration of zoledronate into the tibial lesion. A comparison of the effect of local versus systemic delivery of zoledronate on the formation of tumor-induced osteolysis was also carried out. A significant increase in mean bone volume/tissue volume % (BV/TV) of the locally treated group (12.30±2.80%) compared to the control group (7.13±1.22%) (P<0.001). Additionally, there was a significant increase in the BV/TV (10.90±1.25%) in the locally treated group compared to the systemically treated group (7.53±0.75%) (P=0.005). These preliminary results suggest that local delivery of BPs outperforms both systemic and control treatments to inhibit tumor-induced osteolysis.

The histone H3K9 demethylase KDM3A promotes anoikis by transcriptionally activating pro-apoptotic genes BNIP3 and BNIP3L

Epithelial cells that lose attachment to the extracellular matrix undergo a specialized form of apoptosis called anoikis. Here, using large-scale RNA interference (RNAi) screening, we find that KDM3A, a histone H3 lysine 9 (H3K9) mono- and di-demethylase, plays a pivotal role in anoikis induction. In attached breast epithelial cells, KDM3A expression is maintained at low levels by integrin signaling. Following detachment, integrin signaling is decreased resulting in increased KDM3A expression. RNAi-mediated knockdown of KDM3A substantially reduces apoptosis following detachment and, conversely, ectopic expression of KDM3A induces cell death in attached cells. We find that KDM3A promotes anoikis through transcriptional activation of BNIP3 and BNIP3L, which encode pro-apoptotic proteins. Using mouse models of breast cancer metastasis we show that knockdown of Kdm3a enhances metastatic potential. Finally, we find defective KDM3A expression in human breast cancer cell lines and tumors. Collectively, our results reveal a novel transcriptional regulatory program that mediates anoikis.

DOI:http://dx.doi.org/10.7554/eLife.16844.001

Epithelial cells line the inside of blood vessels, intestines and other organs throughout the body. Any epithelial cells that become detached from their natural surroundings die by a process called anoikis (a Greek word meaning “being without a home”). This process has an important role in preventing cancer from spreading around the body because it eliminates cells that are not in their proper environment. However, some cancers that start from epithelial cells, such as breast cancer, develop resistance to anoikis. Gaining a better understanding of the cellular factors that regulate anoikis, and how resistance develops, may reveal new drug targets for the treatment of breast cancer.

Previous studies found proteins called BIM and BMF promote anoikis by inducing cell suicide. However, it is possible that other factors can also promote this process in different ways. Pedanou et al. performed a large-scale genetic screen in human breast epithelial cells and identified several new factors that promote anoikis.

Inside our cells, DNA is packaged around proteins called histones, which can influence whether a gene is switched on or off. One of the factors Pedanou et al. identified is a protein called KDM3A that can remove small chemical groups (known as methyl groups) from histones – a process that is known to switch on genes. Further experiments show that epithelial cells in their natural surroundings only produce low levels of KDM3A, but that the levels of this protein increase if these cells become detached. This promotes anoikis by activating two genes called BNIP3 and BNIP3L that induce cell suicide. However, KDM3A levels are low in human breast cancers, which suggests that these cancers become resistant to anoikis by preventing increases in KDM3A production.

Using a mouse model of breast cancer, Pedanou et al. found that switching off KDM3A in cancer cells increases their ability to move around the body. Collectively, these findings reveal a new mechanism that triggers anoikis in normal breast epithelial cells and is disabled during breast cancer development. Future challenges are to identify factors that directly regulate the production of KDM3A, and to understand how these factors are manipulated in breast cancer cells to cause anoikis resistance.

DOI:http://dx.doi.org/10.7554/eLife.16844.002

Lyn modulates Claudin-2 expression and is a therapeutic target for breast cancer liver metastasis

Claudin-2 enhances breast cancer liver metastasis and promotes the development of colorectal cancers. The objective of our current study is to define the regulatory mechanisms controlling Claudin-2 expression in breast cancer cells. We evaluated the effect of several Src Family Kinase (SFK) inhibitors or knockdown of individual SFK members on Claudin-2 expression in breast cancer cells. We also assessed the potential effects of pan-SFK and SFK-selective inhibitors on the formation of breast cancer liver metastases. This study reveals that pan inhibition of SFK signaling pathways significantly elevated Claudin-2 expression levels in breast cancer cells. In addition, our data demonstrate that pan-SFK inhibitors can enhance breast cancer metastasis to the liver. Knockdown of individual SFK members reveals that loss of Yes or Fyn induces Claudin-2 expression; whereas, diminished Lyn levels impairs Claudin-2 expression in breast cancer cells. The Lyn-selective kinase inhibitor, Bafetinib (INNO-406), acts to reduce Claudin-2 expression and suppress breast cancer liver metastasis. Our findings may have major clinical implications and advise against the treatment of breast cancer patients with broad-acting SFK inhibitors and support the use of Lyn-specific inhibitors.

Granulocytic immune infiltrates are essential for the efficient formation of breast cancer liver metastases

Introduction

Breast cancer cells display preferences for specific metastatic sites including the bone, lung and liver. Metastasis is a complex process that relies, in part, on interactions between disseminated cancer cells and resident/infiltrating stromal cells that constitute the metastatic microenvironment. Distinct immune infiltrates can either impair the metastatic process or conversely, assist in the seeding, colonization and growth of disseminated cancer cells.

Methods

Using in vivo selection approaches, we previously isolated 4T1-derived breast cancer cells that preferentially metastasize to these organs and tissues. In this study, we examined whether the propensity of breast cancer cells to metastasize to the lung, liver or bone is associated with and dependent on distinct patterns of immune cell infiltration. Immunohistocytochemistry and immunohistofluorescence approaches were used to quantify innate immune cell infiltrates within distinct metastases and depletion of Gr1⁺ (Ly-6C and Ly-6G) or specifically Ly-6G⁺ cells was performed to functionally interrogate the role of Ly-6G⁺ infiltrates in promoting metastasis to these organs.

Results

We show that T lymphocytes (CD3⁺), myeloid-derived (Gr-1⁺) cells and neutrophils (Ly-6G⁺ or NE⁺) exhibit the most pronounced recruitment in lung and liver metastases, with markedly less recruitment within bone metastatic lesions. Interestingly, these infiltrating cell populations display different patterns of localization within soft tissue metastases. T lymphocytes and granulocytic immune infiltrates are localized around the periphery of liver metastases whereas they were dispersed throughout the lung metastases. Furthermore, Gr-1⁺ cell-depletion studies demonstrate that infiltrating myeloid-derived cells are essential for the formation of breast cancer liver metastases but dispensable for metastasis to the lung and bone. A specific role for the granulocytic component of the innate immune infiltrate was revealed through Ly-6G⁺ cell-depletion experiments, which resulted in significantly impaired formation of liver metastases. Finally, we demonstrate that the CD11b⁺/Ly-6G⁺ neutrophils that infiltrate and surround the liver metastases are polarized toward an N2 phenotype, which have previously been shown to enhance tumor growth and metastasis.

Conclusions

Our results demonstrate that the liver-metastatic potential of breast cancer cells is heavily reliant on interactions with infiltrating Ly-6G⁺ cells within the liver microenvironment.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-015-0558-3) contains supplementary material, which is available to authorized users.

Peroxiredoxin 4: a novel secreted mediator of cancer induced osteoclastogenesis

Bone is a common site of metastasis from breast and prostate carcinoma, where activation of bone resorbing osteoclasts is important for cancer progression. A large body of evidence indicates that soluble factors produced by the cancer cells act to promote osteoclast formation. Using mass spectrometry, we identified peroxiredoxin (PRDX) as a secreted mediator of cancer-induced osteoclastogenesis. Both breast (MCF7 and MDA-MB-231) and prostate (PC3 and LNCaP) carcinoma cells secreted PRDX4. PRDX4 knockdown using shRNA (shPRDX4) diminished PRDX4 secretion from MDA-MB-231 and PC3 cells and significantly decreased the ability of cancer-derived factors to induce osteoclast formation from late precursors in vitro. Tibial injection of shPRDX4 PC3 cells led to the development of significantly smaller osteolytic lesions characterized by significantly reduced osteoclast numbers compared to control PC3 cells. A meta-analysis demonstrated an increase in PRDX4 mRNA expression in carcinoma and metastatic breast and prostate tissues. Moreover, high expression of PRDX4 in the primary breast tumor was consistently associated with metastasis at 5 years. These data identify a novel function of secreted PRDX4 in mediating osteoclast activation by cancer cells.

The IGF-Trap: Novel Inhibitor of Carcinoma Growth and Metastasis

The IGFI receptor promotes malignant progression and has been recognized as a target for cancer therapy. Clinical trials with anti-IGFIR antibodies provided evidence of therapeutic efficacy but exposed limitations due in part to effects on, and the compensatory function of, the insulin receptor system. Here, we report on the production, characterization, and biologic activity of a novel, IGF-targeting protein (the IGF-Trap) comprising a soluble form of hIGFIR and the Fc portion of hIgG1. The IGF-Trap has a high affinity for hIGFI and hIGFII but low affinity for insulin, as revealed by surface plasmon resonance. It efficiently blocked IGFIR signaling in several carcinoma cell types and inhibited tumor cell proliferation, migration, and invasion in vitro. In vivo, the IGF-Trap showed favorable pharmacokinetic properties and could suppress the growth of established breast carcinoma tumors when administered therapeutically into tumor-bearing mice, improving disease-free survival. Moreover, IGF-Trap treatment markedly reduced experimental liver metastasis of colon and lung carcinoma cells, increasing tumor cell apoptosis and reducing angiogenesis. Finally, when compared with an anti-IGFIR antibody or IGF-binding protein-1 that were used at similar or higher concentrations, the IGF-Trap showed superior therapeutic efficacy to both inhibitors. Taken together, we have developed a targeted therapeutic molecule with highly potent anticancer effects that could address limitations of current IGFIR-targeting agents.

Abstract 3367: Understanding the role of metabolic reprogramming in breast cancer progression and metastasis

Background: The emergence of metastatic breast cancer is the most deadly aspect of the disease and once it has spread from the primary site, it is largely incurable. Important metabolic changes have been correlated with breast cancer progression and acquisition of the metastatic phenotype. One prominent example includes the well-established Warburg effect, which stipulates that cancer cells preferentially utilize rapid glycolytic metabolism over mitochondrial respiration to produce energy. Such a metabolic shift ensures that cancer cells can meet the bioenergetics and biosynthetic demands associated with increased proliferation.

Objectives: The energetic requirements of individual cancer cells will greatly vary as the tumor grows and acquires malignant characteristics. The metabolic demands during tumor initiation will differ from those that occur during tumor growth at the primary site and dissemination to distant metastatic sites. Therefore, we hypothesize that distinct metabolic signatures are associated with each one of these steps and that a better characterization of these transitions, as well as the key regulators governing this process, will help identifying potential therapeutic targets.

Results: Using a series of mouse mammary cancer cells derived from a spontaneous mammary tumor, which includes 67NR (tumorigenic/non-metastatic), 66cl4 (tumorigenic/lung metastatic) and 4T1 (tumorigenic/metastatic to multiple sites), we examined changes in several parameters of cellular metabolism that could be associated with different stages of tumor progression. Using mass spectrometry, we assessed the uptake and metabolic flux of labeled glucose through the cellular metabolic pathways. Our results suggest that there is a further shift towards a “Warburg-like” phenotype as tumor cells acquire aggressive characteristics. Using an in vivo selection approach on the 4T1 breast cancer cells, we have established subpopulations that aggressively form liver metastases. Glucose tracing experiments reveal an accumulation of lactate at the expense of reduced allocation of glucose towards citrate production suggesting that these cells have a further increased glycolytic phenotypes compared to the 4T1 parental cells. These results raise the possibility that unique metabolic processes and checkpoints are engaged in metastatic populations that contribute to their metastatic ability. PDK1 is an enzyme that prevents the uptake of pyruvate into the TCA cycle. We show that PDK1 is upregulated with the increase in metastatic potential. This has led us to hypothesize that the “Warburg-like” phenotype observed is mediated by a PDK1-induced switch favouring glycolysis. We demonstrate that PDK1 is required to form liver metastases in vivo following splenic injections. Ongoing experiments are being pursued to uncover the mechanism by which PDK1 is regulated and how it influences the metastatic process.

Citation Format: Fanny Dupuy, Julianna Blagih, Sébastien Tabariès, Julie St-Pierre, Russell G. Jones, Peter M. Siegel. Understanding the role of metabolic reprogramming in breast cancer progression and metastasis. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3367. doi:10.1158/1538-7445.AM2014-3367

Multiple promoters and alternative splicing: Hoxa5 transcriptional complexity in the mouse embryo

Background

The genomic organization of Hox clusters is fundamental for the precise spatio-temporal regulation and the function of each Hox gene, and hence for correct embryo patterning. Multiple overlapping transcriptional units exist at the Hoxa5 locus reflecting the complexity of Hox clustering: a major form of 1.8 kb corresponding to the two characterized exons of the gene and polyadenylated RNA species of 5.0, 9.5 and 11.0 kb. This transcriptional intricacy raises the question of the involvement of the larger transcripts in Hox function and regulation.

Methodology/Principal Findings

We have undertaken the molecular characterization of the Hoxa5 larger transcripts. They initiate from two highly conserved distal promoters, one corresponding to the putative Hoxa6 promoter, and a second located nearby Hoxa7. Alternative splicing is also involved in the generation of the different transcripts. No functional polyadenylation sequence was found at the Hoxa6 locus and all larger transcripts use the polyadenylation site of the Hoxa5 gene. Some larger transcripts are potential Hoxa6/Hoxa5 bicistronic units. However, even though all transcripts could produce the genuine 270 a.a. HOXA5 protein, only the 1.8 kb form is translated into the protein, indicative of its essential role in Hoxa5 gene function. The Hoxa6 mutation disrupts the larger transcripts without major phenotypic impact on axial specification in their expression domain. However, Hoxa5-like skeletal anomalies are observed in Hoxa6 mutants and these defects can be explained by the loss of expression of the 1.8 kb transcript. Our data raise the possibility that the larger transcripts may be involved in Hoxa5 gene regulation.

Significance

Our observation that the Hoxa5 larger transcripts possess a developmentally-regulated expression combined to the increasing sum of data on the role of long noncoding RNAs in transcriptional regulation suggest that the Hoxa5 larger transcripts may participate in the control of Hox gene expression.

Comparative analysis of Hoxa5 allelic series

Analysis of the Hoxa5(-/-) mutants has revealed the critical role of Hoxa5 in survival, specification of axial identity, and ontogeny of organs, including the respiratory tract. The presence of the selection cassette in the original Hoxa5(-/-) mutation may interfere with the interpretation of the phenotypes. To circumvent this aspect and to bypass the lethality of the Hoxa5 mutation, we have designed a conditional approach and generated Hoxa5 allelic variants. The conditional allele (Hoxa5(floxed)) behaves as a wild-type allele. In contrast, both the Hoxa5(Delta) and the Hoxa5(floxneo) alleles are characterized by the loss of the functional transcript and protein, the lethality due to lung defects and the skeletal homeotic transformations similar to those of the Hoxa5(-/-) mutants. Analysis of neighboring Hox gene expression patterns in the Hoxa5 mutants produced further confirmed that the Hoxa5 allelic variants are true null alleles.

Cdx protein interaction with Hoxa5 regulatory sequences contributes to Hoxa5 regional expression along the axial skeleton

Hox gene functions are intimately linked to correct developmental expression of the genes. The identification of cis-acting regulatory sequences and their associated trans-acting factors constitutes a key step in deciphering the mechanisms underlying the correct positioning of the functional domain of Hox genes along the anterior-posterior axis. We have identified DNA elements driving Hoxa5 regionalized expression in mice, using the 2.1-kb mesodermal enhancer (MES) localized in Hoxa5 3' flanking sequences as a starting point. The MES sequence comprises regulatory elements targeting Hoxa5 expression in the limbs, the urogenital and gastrointestinal tracts, and the cervical-upper thoracic region of the prevertebral column. A 164-bp DNA fragment within the MES caudally restricts Hoxa5 expression at the level of prevertebra 10, corresponding to the posterior limit of its functional domain. Cdx proteins directly bind to this element in vitro via two conserved sites. Preventing Cdx binding by mutating the sites causes caudal expansion of the transgene expression domain. Of all three murine Cdx proteins that bind this element in vitro, Cdx4 has emerged as a potential regional posterior repressor of Hoxa5 expression. The restrictive control provided by Cdx interactions with Hoxa5 regulatory sequences may be one of the critical events in cervicothoracic axial specification.