Anna Durrans

Epithelial-to-mesenchymal transition is not required for lung metastasis but contributes to chemoresistance.

The role of epithelial-to-mesenchymal transition (EMT) in metastasis is a longstanding source of debate, largely owing to an inability to monitor transient and reversible EMT phenotypes in vivo. Here we establish an EMT lineage-tracing system to monitor this process in mice, using a mesenchymal-specific Cre-mediated fluorescent marker switch system in spontaneous breast-to-lung metastasis models. We show that within a predominantly epithelial primary tumour, a small proportion of tumour cells undergo EMT. Notably, lung metastases mainly consist of non-EMT tumour cells that maintain their epithelial phenotype. Inhibiting EMT by overexpressing the microRNA miR-200 does not affect lung metastasis development. However, EMT cells significantly contribute to recurrent lung metastasis formation after chemotherapy. These cells survived cyclophosphamide treatment owing to reduced proliferation, apoptotic tolerance and increased expression of chemoresistance-related genes. Overexpression of miR-200 abrogated this resistance. This study suggests the potential of an EMT-targeting strategy, in conjunction with conventional chemotherapies, for breast cancer treatment.The role of epithelial to mesenchymal transition (EMT) in metastasis is a longstanding source of controversy, largely due to an inability to monitor transient and reversible EMT phenotypes in vivo. We established an EMT lineage tracing system to monitor this process, using a mesenchymal-specific Cre-mediated fluorescent marker switch system in spontaneous breast-to-lung metastasis models. We confirmed that within a predominantly epithelial primary tumor, a small portion of tumor cells undergo EMT. Strikingly, lung metastases mainly consisted of non-EMT tumor cells maintaining their epithelial phenotype. Inhibiting EMT by overexpressing miR-200 did not impact lung metastasis development. However, EMT cells significantly contribute to recurrent lung metastasis formation after chemotherapy. These cells survived cyclophosphamide treatment due to reduced proliferation, apoptotic tolerance, and elevated expression of chemoresistance-related genes. Overexpression of miR-200 abrogated this resistance. This study suggests the potential of an EMT-targeting strategy, in conjunction with conventional chemotherapies, for breast cancer treatment.

A role for Egfl7 during endothelial organization in the embryoid body model system

Epidermal growth factor-like domain 7, Egfl7, is a largely endothelial restricted gene which is thought to have a role during the differentiation of embryonic stem cells (ESCs) along the endothelial lineage. While it has been shown that Egfl7 knock-down in zebrafish impairs endothelial cord formation, the role of the gene in mammals has been unresolved. Interpretation of mouse knockout studies has been complicated by the fact that deletion of miR-126, an intronic microRNA located within Egfl7, results in vascular defects. Here we use an siRNA knock-down approach to target specific regions of Egfl7 without affecting miR-126 expression. Egfl7 was knocked down in mouse ESCs and the effect on vascular development was assessed using the in vitro embryoid body (EB) model after either 7 or 14 days of differentiation. Knock-down of Egfl7 resulted in the formation of abnormal sheet-like CD31+ structures that were abundant within EBs after 7 days of differentiation. Only up to 60% of these sheets co-expressed basement membrane and endothelial cell junction markers. Similar CD31+ sheets were also seen as outgrowths from 7 day EBs into collagen gels. A partial remodelling occurred by 14 days of differentiation when fewer CD31+ sheets were seen both within EBs, and as outgrowths from EBs. Formation of these sheets was due, at least in part, to increased proliferation specifically of CD31+ cells. Cell death within EBs was unaffected by Egfl7 knock-down. In conclusion, our work shows that knock-down of Egfl7 causes defects in early vascular cord formation, and results in the development of CD31+ sheet-like structures. This suggests that Egfl7 is vital for the formation of endothelial cell cords, and that the gene has an important role during both vasculogenesis and angiogenesis in mammalian cells.

Matrix Metalloproteinase 14 promotes lung cancer by cleavage of Heparin-Binding EGF-like Growth Factor

Molecularly targeted therapies benefit approximately 15–20% of non-small cell lung cancer (NSCLC) patients carrying specific drug-sensitive mutations. Thus, there is a clinically unmet need for the identification of novel targets for drug development. Here, we performed RNA-deep sequencing to identify altered gene expression between malignant and non-malignant lung tissue. Matrix Metalloproteinase 14 (MMP14), a membrane-bound proteinase, was significantly up-regulated in the tumor epithelial cells and intratumoral myeloid compartments in both mouse and human NSCLC. Overexpression of a soluble dominant negative MMP14 (DN-MMP14) or pharmacological inhibition of MMP14 blocked invasion of lung cancer cells through a collagen I matrix in vitro and reduced tumor incidence in an orthotopic K-RasG12D/+p53−/− mouse model of lung cancer. Additionally, MMP14 activity mediated proteolytic processing and activation of Heparin-Binding EGF-like Growth Factor (HB-EGF), stimulating the EGFR signaling pathway to increase proliferation and tumor growth. This study highlights the potential for development of therapeutic strategies that target MMP14 in NSCLC with particular focus on MMP14-HB-EGF axis.

Identification of Reprogrammed Myeloid Cell Transcriptomes in NSCLC

Lung cancer is the leading cause of cancer related mortality worldwide, with non-small cell lung cancer (NSCLC) as the most prevalent form. Despite advances in treatment options including minimally invasive surgery, CT-guided radiation, novel chemotherapeutic regimens, and targeted therapeutics, prognosis remains dismal. Therefore, further molecular analysis of NSCLC is necessary to identify novel molecular targets that impact prognosis and the design of new-targeted therapies. In recent years, tumor “activated/reprogrammed” stromal cells that promote carcinogenesis have emerged as potential therapeutic targets. However, the contribution of stromal cells to NSCLC is poorly understood. Here, we show increased numbers of bone marrow (BM)-derived hematopoietic cells in the tumor parenchyma of NSCLC patients compared with matched adjacent non-neoplastic lung tissue. By sorting specific cellular fractions from lung cancer patients, we compared the transcriptomes of intratumoral myeloid compartments within the tumor bed with their counterparts within adjacent non-neoplastic tissue from NSCLC patients. The RNA sequencing of specific myeloid compartments (immature monocytic myeloid cells and polymorphonuclear neutrophils) identified differentially regulated genes and mRNA isoforms, which were inconspicuous in whole tumor analysis. Genes encoding secreted factors, including osteopontin (OPN), chemokine (C-C motif) ligand 7 (CCL7) and thrombospondin 1 (TSP1) were identified, which enhanced tumorigenic properties of lung cancer cells indicative of their potential as targets for therapy. This study demonstrates that analysis of homogeneous stromal populations isolated directly from fresh clinical specimens can detect important stromal genes of therapeutic value.

Abstract 4721: Epithelial to mesenchymal transition is not required for breast to lung metastasis but contributes to chemoresistance

The role of epithelial to mesenchymal transition (EMT) in metastasis is a longstanding source of controversy, largely due to an inability to monitor transient and reversible EMT phenotypes in vivo. We have established a novel and unique EMT lineage tracing system in spontaneous breast to lung metastasis models. In these models, mesenchymal-specific Cre-mediated recombination initiates permanent switch of fluorescent markers in tumor cells undergoing EMT. This allows us to track EMT tumor cells in the primary tumor, circulation and distant organs following the trail of breast to lung metastasis in vivo. We confirmed that within a predominantly epithelial primary tumor, a small portion of tumor cells undergo EMT. Strikingly, lung metastases were mainly comprised of non-EMT tumor cells maintaining their epithelial phenotype. Inhibiting EMT by overexpressing miR-200 did not impact lung metastasis development. However, EMT cells significantly contribute to recurrent lung metastasis formation after chemotherapy. These cells survived cyclophosphamide treatment due to reduced proliferation, apoptotic tolerance, and elevated expression of chemoresistance-related genes. This study suggests the potential of an EMT-targeting strategy, in conjunction with conventional chemotherapies, in the treatment of breast cancer patients. Citation Format: Kari R. Fischer, Anna Durrans, Sharrell Lee, Jianting Sheng, Hyejin Choi, Fuhai Li, Stephen Wong, Nasser K. Altorki, Vivek Mittal, Dingcheng Gao. Epithelial to mesenchymal transition is not required for breast to lung metastasis but contributes to chemoresistance. [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 4721. doi:10.1158/1538-7445.AM2015-4721

Abstract 1159: A novel HGF-MET paracrine signaling pathway promotes growth and resistance to chemotherapy in lung cancer

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Lung cancer is a leading cause of deaths from cancer among men and women worldwide with an estimated 1.5 million deaths each year. Available molecularly targeted therapies benefit a limited number of patients and even in these patients acquired resistance is a major impediment to effective therapeutic response. To address the need for additional therapeutic targets, we used a unique approach to identify and target tumor-stroma paracrine crosstalk pathways in non-small cell lung cancer (NSCLC). To explore paracrine crosstalk in NSCLC, we analyzed transcriptomes of specific stromal and epithelial compartments that were sorted from Kras driven mouse model of NSCLC. Transcriptome analysis and computational modeling of multi-cellular network identified potential tumor-stroma crosstalk signaling pathways. We have selected the hepatocyte growth factor (HGF)-MET tyrosine kinase receptor signaling pathway because both HGF and MET are associated with poor survival in many cancer types including lung cancer. Notably, we identified reprogrammed intratumoral macrophages as unique source of HGF, while the expression of MET receptor was confined to tumor epithelial compartment. Importantly, we have observed elevated HGF in chemoresistant tumors both in mouse and human. Previous studies have implicated MET receptor amplification or mutations as the main mechanism of acquired resistance to EGFR TKIs, but little is known about the contribution of HGF ligand-dependent activation of MET signaling in NSCLC growth and resistance to chemotherapeutic regimens that are widely used. We have used a combination of culture experiments and in vivo genetic approaches to show that macrophage-derived HGF interacts with the MET receptor on tumor epithelial cells in a paracrine fashion, to activate downstream signaling pathways that promote tumor progression and mediate resistance to standard chemotherapies. Our investigations on this relatively unexplored HGF-MET paracrine interaction as a key mechanism of resistance to standard-of-care chemotherapeutic regimens-and not just EGFR targeted therapies-have the potential to benefit the NSCLC population as whole rather than a small subset of patients. Citation Format: Hyejin Choi, Ding Cheng Gao, Sharrell B. Lee, Anna Durrans, Seongho Ryu, Olivier Elemento, Stephen Wong, Nasser K. Altorki, Vivek Mittal. A novel HGF-MET paracrine signaling pathway promotes growth and resistance to chemotherapy in lung cancer. [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 1159. doi:10.1158/1538-7445.AM2014-1159

Abstract 1420: Mechanisms of stroma-derived CCL7 in promoting lung cancer.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC Lung cancer is a leading cause of cancer related deaths worldwide, with non-small cell lung cancer (NSCLC) being the most prevalent form. Considerable attention has been directed to cancer cell intrinsic abnormalities (K-ras, p53, EGFR, AML-ALK4 fusions etc.), but little is known about the contribution of stromal cells to NSCLC progression. We have undertaken a comprehensive analysis to determine the contribution and biological function of the stromal cells in NSCLC. We show increased recruitment of BM hematopoietic cells in the tumor beds compared to matched adjacent non-neoplastic lung tissue in NSCLC patients. Genome-wide transcriptome analysis on specific cell populations from fresh samples of NSCLC patients identified differentially regulated genes and mRNA isoforms in NSCLC stromal cells. Genes that were successfully validated by independent RT-PCR on sorted stromal cells and tumor cells were used for further analysis. Many genes encoded secreted proteins, suggesting the activation of aberrant autocrine and paracrine regulatory loops likely to support stroma-mediated tumor progression. Among these genes, CCL7 was upregulated in myeloid progenitor cells and was selected for further investigation. Immunostaining of lung tumor and adjacent non-neoplastic tissue of patients shows highest expression of CCL7 in BM-derived cells (CD45+ cells) in the tumor. Cross species analysis showed that, consistent with the observation in human tissue, CCL7 was differentially regulated in BM derived cells in a mouse model of NSCLC generated in KrasG12D and p53-/- transgenic mice. We have genetically ablated CCL7 in the BM cells using lentiviral shRNA and BMT approaches and will discuss consequences of this ablation in CCL7-mediated crosstalk between tumor cells and stromal cells that regulate NSCLC progression. Citation Format: Hyejin Choi, Anna Durrans, Dingcheng Gao, Seongho Ryu, Nasser Altorki, Vivek Mittal. Mechanisms of stroma-derived CCL7 in promoting lung cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1420. doi:10.1158/1538-7445.AM2013-1420