Project description:Tumor metastasis, the main cause of death in cancer patients, requires outgrowth of tumor cells after their dissemination and residence in microscopic niches. Nutrient sufficiency is a determinant of such outgrowth. Fatty acids (FA) can be metabolized by cancer cells for their energetic and anabolic needs, thereby supporting metastatic progression. The vascular endothelium serves as a barrier to access of molecules into tissues, but it is unclear how fatty acid delivery to early metastatic tumors is regulated. Using a mouse model of metastatic outgrowth in the lung, we show that tumor endothelium actively promotes tumor growth by transferring FA into developing metastatic tumors. Tumor burden was significantly reduced upon endothelial-specific targeted deletion of Raptor, a unique component of the mTORC1 complex (RptorECKO). The goal of this study was to investigate how endothelial mTORC1 alters metastatic tumor cells.
Project description:Metastatic breast cancer is an extremely complex disease with limited treatment options due to the lack of information about the major characteristics of metastatic disease. There is an urgent need, therefore, to understand the changes in cellular complexity and dynamics that occur during metastatic progression. In the current study, we analyzed the cellular and molecular differences between primary tumors and paired lung metastases using a syngeneic p53-null mammary tumor model of basal-like breast cancer. Distinct subpopulations driven by the Wnt- and/or STAT3 signaling pathways were detected in vivo using a lentiviral Wnt- and STAT3 signaling reporter system. A significant increase in the overlapping populations driven by both the Wnt- and STAT3 signaling pathways was observed in the lung metastases as compared to the primary tumors. Furthermore, STAT3 signaling activity was markedly enhanced in the metastatic lesions relative to the primary tumors with minimal changes observed in Wnt reporter activity. An analysis of the unique molecular features of the lung metastases revealed a significant association with immune response signatures. Specifically, Foxp3 gene expression was markedly increased and elevated levels of Foxp3+ Treg cells were detected in close proximity to lung metastases. Collectively, these studies illustrate the importance of analyzing intratumoral heterogeneity, changes in population dynamics and the immune microenvironment during metastatic progression.
Project description:Despite the high prevalence and poor outcome of patients with metastatic lung cancer, the mechanisms of tumour progression and metastasis remain largely uncharacterized. We modelled human lung adenocarcinoma, which frequently harbours activating point mutations in KRAS1 and inactivation of the p53-pathway2, using conditional alleles in mice3-5. Lentiviral-mediated somatic activation of oncogenic Kras and deletion of p53 in the lung epithelial cells of KrasLSL-G12D/+;p53flox/flox mice initiates lung adenocarcinoma development4. Although tumours are initiated synchronously by defined genetic alterations, only a subset become malignant, suggesting that disease progression requires additional alterations. Identification of the lentiviral integration sites allowed us to distinguish metastatic from non-metastatic tumours and determine the gene expression alterations that distinguish these tumour types. Cross-species analysis identified the NK-2 related homeobox transcription factor Nkx2-1 (Ttf-1/Titf1) as a candidate suppressor of malignant progression. In this mouse model, Nkx2-1-negativity is pathognomonic of high-grade poorly differentiated tumours. Gain- and loss-of-function experiments in cells derived from metastatic and non-metastatic tumours demonstrated that Nkx2-1 controls tumour differentiation and limits metastatic potential in vivo. Interrogation of Nkx2-1 regulated genes, analysis of tumours at defined developmental stages, and functional complementation experiments indicate that Nkx2-1 constrains tumours in part by repressing the embryonically-restricted chromatin regulator Hmga2. While focal amplification of NKX2-1 in a fraction of human lung adenocarcinomas has focused attention on its oncogenic function6-9, our data specifically link Nkx2-1 downregulation to loss of differentiation, enhanced tumour seeding ability, and increased metastatic proclivity. Thus, the oncogenic and suppressive functions of Nkx2-1 in the same tumour type substantiate its role as a dual function lineage factor. 23 cell lines derived from primary tumor or metastasis. 6 samples analyzed to determine the effect of Nkx2-1 knockdown on gene expression
Project description:In cancer progression to metastasis, disseminated cancer cells frequently lodge near vasculature in secondary organs. However, our understanding of the cellular crosstalk evoked at perivascular sites is still rudimentary. In this study, we identified an inter-cellular machinery governing formation of a pro-metastatic vascular niche during breast cancer colonization in lungs. Transcriptomic analysis of endothelial cells (ECs) isolated from mouse lungs with metastases revealed a marked upregulation of genes linked to proliferation, inflammation and numerous secreted proteins. We showed that four secreted factors, INHBB, SCGB3A1, OPG and LAMA1, induced in ECs form a supportive niche that promotes metastasis in mice, by enhancing stem cell properties and survival ability of cancer cells. Interestingly, the blocking vascular endothelial cell growth factor (VEGF), a major cytokine regulating EC behaviors, dramatically suppressed EC proliferation whereas no impact was observed on the expression of the four vascular niche factors in lung ECs. We found that the formation of a vascular niche is correlated with inflammation, and revealed that metastasis-associated macrophages are essential for production of all of four niche factors in lung ECs. Macrophages are activated via TNC-TLR4 at perivasculature and sequentially stimulate ECs to produce the four niche factors. Thus, our findings provide mechanistic insights into the formation of a perivascular niche and offer the possibility that targeting macrophages may synergize with existing anti-angiogenic drugs to effectively suppress vascular function in metastatic colonization. We used microarrays to analyze the global changes of gene expression in lung endothelial cells at different stages of lung colonization by MDA-MB-231-LM2 cells