Anie Monast

Regulation of the Met Receptor-tyrosine Kinase by the Protein-tyrosine Phosphatase 1B and T-cell Phosphatase

The non-receptor protein-tyrosine phosphatases (PTPs) 1B and T-cell phosphatase (TCPTP) have been implicated as negative regulators of multiple signaling pathways including receptor-tyrosine kinases. We have identified PTP1B and TCPTP as negative regulators of the hepatocyte growth factor receptor, the Met receptor-tyrosine kinase. In vivo, loss of PTP1B or TCPTP enhances hepatocyte growth factor-mediated phosphorylation of Met. Using substrate trapping mutants of PTP1B or TCPTP, we have demonstrated that both phosphatases interact with Met and that these interactions require phosphorylation of twin tyrosines (Tyr-1234/1235) in the activation loop of the Met kinase domain. Using confocal microscopy, we show that trapping mutants of both PTP1B and the endoplasmic reticulum-targeted TCPTP isoform, TC48, colocalize with Met and that activation of Met enables the nuclear-localized isoform of TCPTP, TC45, to exit the nucleus. Using small interfering RNA against PTP1B and TCPTP, we demonstrate that phosphorylation of Tyr-1234/1235 in the activation loop of the Met receptor is elevated in the absence of either PTP1B or TCPTP and further elevated upon loss of both phosphatases. This enhanced phosphorylation of Met corresponds to enhanced biological activity and cellular invasion. Our data demonstrate that PTP1B and TCPTP play distinct and non-redundant roles in the regulation of the Met receptor-tyrosine kinase.

Claudin-2 Promotes Breast Cancer Liver Metastasis by Facilitating Tumor Cell Interactions with Hepatocytes

ABSTRACT We previously identified claudin-2 as a functional mediator of breast cancer liver metastasis. We now confirm that claudin-2 levels are elevated in liver metastases, but not in skin metastases, compared to levels in their matched primary tumors in patients with breast cancer. Moreover, claudin-2 is specifically expressed in liver-metastatic breast cancer cells compared to populations derived from bone or lung metastases. The increased liver tropism exhibited by claudin-2-expressing breast cancer cells requires claudin-2-mediated interactions between breast cancer cells and primary hepatocytes. Furthermore, the reduction of the claudin-2 expression level, either in cancer cells or in primary hepatocytes, diminishes these heterotypic cell-cell interactions. Finally, we demonstrate that the first claudin-2 extracellular loop is essential for mediating tumor cell-hepatocyte interactions and the ability of breast cancer cells to form liver metastases in vivo. Thus, during breast cancer liver metastasis, claudin-2 shifts from acting within tight-junctional complexes to functioning as an adhesion molecule between breast cancer cells and hepatocytes.

Crk adaptor proteins act as key signaling integrators for breast tumorigenesis

IntroductionCT10 regulator of kinase (Crk) adaptor proteins (CrkI, CrkII and CrkL) play a role in integrating signals for migration and invasion of highly malignant breast cancer cell lines. This has important implications, as elevated CrkI/II protein levels were observed in a small cohort of breast cancer patients, which identified a potential role for Crk proteins in breast cancer progression. Numerous in vitro studies identified a role for Crk proteins in cell motility, but little is known about how Crk proteins contribute to breast cancer progression in vivo.MethodsThe clinical significance of Crk proteins in human breast cancer was assessed by analyzing published breast cancer datasets using a gene expression signature that was generated following CrkII over-expression and by examining Crk protein expression in tissue microarrays of breast tumors (n = 254). Stable knockdown of Crk (CrkI/CrkII/CrkL) proteins was accomplished using a short hairpin RNA (shRNA)-mediated approach in two basal breast cancer cell lines, MDA-231 1833TR and SUM1315, where the former have a high affinity to form bone metastases. Both in vitro assays (cell migration, invasion, soft agar growth) and in vivo experiments (intra-cardiac, tibial and mammary fat pad injections) were performed to assess the functional significance of Crk proteins in breast cancer.ResultsA gene signature derived following CrkII over-expression correlated significantly with basal breast cancers and with high grade and poor outcome in general. Moreover, elevated Crk immunostaining on tissue microarrays revealed a significant association with highly proliferative tumors within the basal subtype. RNAi-mediated knockdown of all three Crk proteins in metastatic basal breast cancer cells established a continued requirement for Crk in cell migration and invasion in vitro and metastatic growth in vivo. Furthermore, Crk ablation suppressed anchorage independent growth and in vivo orthotopic tumor growth. This was associated with diminished cell proliferation and was rescued by expression of non-shRNA targeted CrkI/II. Perturbations in tumor progression correlated with altered integrin signaling, including decreased cell spreading, diminished p130Cas phosphorylation, and Cdc42 activation.ConclusionsThese data highlight the physiological importance of Crk proteins in regulating growth of aggressive basal breast cancer cells and identify Crk-dependent signaling networks as promising therapeutic targets.

Dynamic Reprogramming of Signaling Upon Met Inhibition Reveals a Mechanism of Drug Resistance in Gastric Cancer

Understanding how inhibitors rewire the Met receptor pathway points to a strategy for more effective gastric cancer treatment. Met with Resistance in Gastric Cancer The hepatocyte growth factor receptor Met is associated with poor prognosis in various cancers, but the efficacy of Met inhibitors is often impeded by resistance. By comparing transcriptional changes at multiple time points after stimulation or inhibition of Met, Lai et al. identified critical mediators of Met-induced proliferation and Met inhibitor resistance in gastric cancer cell lines. Cancer cells or tumors exposed to Met inhibitors had decreased abundance of phosphatases, and this correlated with reactivation of the pro-proliferative MEK-ERK pathway and the emergence of drug resistance. Combining Met and MEK inhibitors was more cytotoxic to gastric cancer cells in culture than was either inhibitor alone, suggesting that this combination strategy may be effective in gastric cancer. The Met receptor tyrosine kinase is activated or genetically amplified in some gastric cancers, but resistance to small-molecule inhibitors of Met often emerges in patients. We found that Met abundance correlated with a proliferation marker in patient gastric tumor sections, and gastric cancer cell lines that have MET amplifications depended on Met for proliferation and anchorage-independent growth in culture. Inhibition of Met induced temporal changes in gene expression in the cell lines, initiated by a rapid decrease in the expression of genes encoding transcription factors, followed by those encoding proteins involved in epithelial-mesenchymal transition, and finally those encoding cell cycle–related proteins. In the gastric cancer cell lines, microarray and chromatin immunoprecipitation analysis revealed considerable overlap between genes regulated in response to Met stimulation and those regulated by signal transducer and activator of transcription 3 (STAT3). The activity of STAT3, extracellular signal–regulated kinase (ERK), and the kinase Akt was decreased by Met inhibition, but only inhibitors of STAT3 were as effective as the Met inhibitor in decreasing tumor cell proliferation in culture and in xenografts, suggesting that STAT3 mediates the pro-proliferative program induced by Met. However, the phosphorylation of ERK increased after prolonged Met inhibition in culture, correlating with decreased abundance of the phosphatases DUSP4 and DUSP6, which inhibit ERK. Combined inhibition of Met and the mitogen-activated protein kinase kinase (MEK)–ERK pathway induced greater cell death in cultured gastric cancer cells than did either inhibitor alone. These findings indicate combination therapies that may counteract resistance to Met inhibitors.

5′-Inositol phosphatase SHIP2 recruits Mena to stabilize invadopodia for cancer cell invasion

Invadopodia are membrane protrusions used by cancer cells to remodel and invade the extracellular matrix. Here, Rajadurai et al. show that the lipid phosphatase SHIP2 recruits the Ena/VASP-family actin regulatory protein Mena to stabilize invadopodia membrane protrusions and promote cell invasion.

Abstract 1135: DRD2 is critical for pancreatic cancer and promises pharmacological therapy by already established antagonists

Introduction and aims: Although the overall five-year survival of all patients with cancer stands at 63%, for pancreatic cancer patients, it is a disheartening 8% - a number that remains largely unchanged for three decades. Of the patients diagnosed with pancreatic cancer, about 85% exhibit pancreatic ductal adenocarcinoma (PDAC). Most of these patients die within 4 to 6 months after diagnosis. The poor prognosis is caused by the detection at only late stages, and lack of effective options for chemotherapy. The widely used chemotherapeutic agent gemcitabine, confers a median survival advantage of only 6 months, and resistance to therapy develops in the vast majority of patients. Given this poor prognosis of patients with PDAC, there is an urgent need to find more effective therapies. Experimental procedures: Microarrays were used to perform global gene expression profiling in 195 PDAC and 41 normal pancreatic tissue samples. Using these profiling data, we undertook an extensive analysis of PDAC transcriptome by superimposing the pathway context and interaction networks of aberrantly expressed genes to identify factors with central roles in PDAC pathways. Next, tissue microarray analysis (TMA) were used to verify the expression of the candidate target in independent set of 152 samples comprising 40 normal pancreatic tissues, 49 chronic pancreatitis sections (CP) and 63 PDAC samples. We further validated the functional relevance of the candidate molecule through RNA interference (RNAi) and pharmacological inhibition in vitro and in vivo. Results: We identified dopamine receptor D2 (DRD2) as a key modulator of cancer pathways in PDAC. DRD2 up-regulation at the protein level was validated in a large independent sample cohort. Most importantly, we found that blockade of DRD2, through RNAi or pharmacological inhibition using FDA-approved antagonists hampers the proliferative and invasive capacities of pancreatic cancer cells while modulating cAMP and endoplasmic reticulum stress pathways. Also, we observed a potent effect of DRD2 antagonists on inhibition of cancer cell proliferation using different model of primary and metastatic tumor cells derived from spontaneous pancreatic cancer mouse models and patient-derived pancreatic adenocarcinoma mouse xenograft (PDX) models. Conclusions: Our findings demonstrate that inhibiting DRD2 represents a novel therapeutic approach for PDAC. Since DRD2 inhibitors are already in the clinic for the management of schizophrenia, our results from this study could support a drug repurposing strategy to expedite clinical evaluation of these agents as novel therapy against pancreatic cancer. Citation Format: Pouria Jandaghi, Hamed S. Najafabadi, Andrea Bauer, Andreas I. Papadakis, Matteo Fassan, Anita Hall, Anie Monast, Maryam Safisamghabadi, Magnus von Knebel Doeberitz, John P. Neoptolemos, Eithne Costello, William Greenhalf, Aldo Scarpa, Bence Sipos, Daniel Auld, Mark Lathrop, Morag Park, Markus W. Buchler, Oliver Strobel, Thilo Hackert, Nathalia Giese, George Zogopoulos, Veena Sangwan, Sidong Huang, Jorg D. Hoheisel, Yaser Riazalhosseini. DRD2 is critical for pancreatic cancer and promises pharmacological therapy by already established antagonists [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1135. doi:10.1158/1538-7445.AM2017-1135

Abstract 2386: Microfluidic single cell exome-seq and RNA-seq analysis of tumor composition

Human breast tumors have been shown to exhibit extensive inter- and intra-tumor heterogeneity. While recent advances in genomic technologies have allowed us to deconvolute this heterogeneity, few studies have addressed the functional consequences of diversity within tumor populations. Here, we identified an index case for which we have derived a patient-derived xenograft (PDX) as a renewable tissue source to identify subpopulations and perform functional assays. On pathology, the tumor was an invasive ductal carcinoma which was hormone receptor-negative, HER2-positive (IHC 2+, FISH average HER2/CEP17 2.4), though the FISH signal was noted to be heterogeneous. On gene expression profiling of bulk samples, the primary tumor and PDX were classified as basal-like. We performed single cell RNA and exome sequencing of the PDX to identify population structure. Using a single sample predictor of breast cancer subtype, we have identified single basal-like, HER2-enriched and normal-like cells co-existing within the PDX tumor, a finding replicated in several independent experiments. Genes differentially expressed between these subpopulations are involved in proliferation and differentiation. One population was characterized by high MYC and the other high EGFR/KRT14. These findings were validated using immunohistochemistry on PDX and primary tumor material. Further functional experiments showed that that EGFR subpopulation has stem cell character istics and forms metastasis in the animal model. Microfluidic whole genome amplification followed by whole exome capture of 81 single cells, along with exome sequencing of the germline, primary and post treatment tumor and whole PDX showed that BRCA1 and TP53 are mutated in all single cells, as well as a number of sub-clonal mutations that are being investigated further. Loss of heterozygocity was observed in 16 TCGA cancer driver genes and novel mutations in 7 known cancer driver genes. Careful comparison of the exome sequencing data allowed the association of driver gene mutation prevalence with tumor progression. These findings are important in our understanding the functional consequences of intra-tumor heterogeneity with respect to clinically important phenotypes such as invasion, metastasis and drug-resistance. Citation Format: Ioannis Ragoussis, Paul Savage, Yu-Chang Wang, Timothee Revil, Dunarel Badescu, Sadiq Saleh, Ernesto Iacucci, Nicolas Bertos, Anie Monast, Attila Omeroglou, Dongmei Zuo, Morag Park. Microfluidic single cell exome-seq and RNA-seq analysis of tumor composition. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2386.

Abstract LB-129: Identifying tumor subpopulations and the functional consequences of intratumor heterogeneity using single-cell profiling of breast cancer patient-derived xenografts

Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PA Human breast tumors have been shown to exhibit extensive inter- and intra-tumor heterogeneity. While recent advances in genomic technologies have allowed us to deconvolute this heterogeneity, few studies have addressed the functional consequences of diversity within tumor populations. Here, we identified an index case for which we have derived a patient-derived xenograft (PDX) as a renewable tissue source to identify subpopulations and perform functional assays. On pathology, the tumor was an invasive ductal carcinoma which was hormone receptor-negative, HER2-positive (IHC 2+, FISH average HER2/CEP17 2.4), though the FISH signal was noted to be heterogeneous. On gene expression profiling of bulk samples, the primary tumor and PDX were classified as basal-like. We performed single cell RNA and exome sequencing of the PDX to identify population structure. Using a single sample predictor of breast cancer subtype, we have identified single basal-like, HER2-enriched and normal-like cells co-existing within the PDX tumor. Genes differentially expressed between these subpopulations are involved in proliferation and differentiation. Functional studies distinguishing these subpopulations are ongoing. Microfluidic whole genome amplification followed by whole exome capture of 81 single cells showed high and homogeneous target enrichment with >75% of reads mapping uniquely on target. Variant calling using GATK and Samtools revealed founder mutations in key genes as BRCA1 and TP53, as well as subclonal mutations that are being investigated further. Loss of heterozygocity was observed in 16 TCGA cancer driver genes and novel mutations in 7 cancer driver genes. These findings may be important in understanding the functional consequences of intra-tumor heterogeneity with respect to clinically important phenotypes such as invasion, metastasis and drug-resistance. Citation Format: Paul Savage, Sadiq M. Saleh, Ernesto Iacucci, Timothe Revil, Yu-Chang Wang, Nicholas Bertos, Anie Monast, Hong Zhao, Margarita Souleimanova, Keith Szulwach, Chandana Batchu, Atilla Omeroglu, Morag Park, Ioannis Ragoussis. Identifying tumor subpopulations and the functional consequences of intratumor heterogeneity using single-cell profiling of breast cancer patient-derived xenografts. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr LB-129. doi:10.1158/1538-7445.AM2015-LB-129

Abstract 918: A key role for Crk adaptor proteins in basal breast cancer tumor growth in vivo

Elevated levels of Crk proteins are observed in human cancers, including breast cancer, identifying a potential role for Crk in tumor progression. However, little is known about how Crk contributes to breast cancer progression in vivo. Crk proteins (CrkI, CrkII, CrkL) can regulate cell signaling downstream of integrins and various receptor tyrosine kinases through the formation of protein-protein complexes. We tested the hypothesis that Crk proteins are key signaling nodes for breast cancer tumorigenesis using shRNA-mediated knockdown of all 3 Crk proteins in highly aggressive human basal breast cancer cell lines. Crk knockdown cells show no differences in cell proliferation under 2D culture conditions, but show significantly decreased growth in soft agar under low serum conditions. This demonstrates that Crk loss imparts a renewed dependence on adhesion and growth factor signaling in highly aggressive breast tumor cell lines and highlights a requirement for Crk dependent signals for anchorage independent growth in vitro. Consistent with this, loss of Crk in basal breast cancer cells inhibited in vivo orthotopic tumor growth in nude mice. Using immunohistochemical staining of cells 3 days post-injection, Crk knockdown diminished proliferation in vivo, but did not alter cell apoptosis when compared to controls. This difference was reflected in the formation of smaller lesions by Crk knockdown cells by 8 days post-injection. Importantly, rescue of Crk protein expression restored in vivo tumor growth, demonstrating a specific requirement for Crk proteins in this process. To evaluate the significance of Crk in human breast cancer, immunohistochemistry was performed on two independent tissue microarrays of human breast tumors (n=209, n=234). Crk protein levels and the proliferative index were assessed by staining with antibodies to Crk and Ki67. Both Crk and Ki67 antigen positivity correlated strongly with high tumor grade (p=0.001, p=2.27e-10). Within both TMA datasets, CrkI/II (R 2 =0.3855, p=0.0004) and CrkL (R 2 =0.3845, p=0.0002) protein levels showed a strong positive correlation with cell proliferation within basal tumors, demonstrating a strong link between elevated Crk protein and an aggressive tumor phenotype. In addition to assessing Crk protein levels, a gene expression signature consisting of 151 genes was derived following Crk overexpression in a breast cancer cell line that initially had low levels of Crk. Notably, when this signature was applied to 5 breast cancer gene expression datasets (n=1469 breast cancers) there was a strong correlation with both the basal molecular subtype (p These findings demonstrate that Crk proteins are unexpectedly essential for growth of aggressive human breast cancer cell lines in vivo, and suggest a key role for Crk proteins in basal breast cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 918. doi:10.1158/1538-7445.AM2011-918