Isolation of tumor endothelial cells from murine cancer

Rebuilding the microenvironment of primary tumors in humans: a focus on stroma

Conventional tumor models have critical shortcomings in that they lack the complexity of the human stroma. The heterogeneous stroma is a central compartment of the tumor microenvironment (TME) that must be addressed in cancer research and precision medicine. To fully model the human tumor stroma, the deconstruction and reconstruction of tumor tissues have been suggested as new approaches for in vitro tumor modeling. In this review, we summarize the heterogeneity of tumor-associated stromal cells and general deconstruction approaches used to isolate patient-specific stromal cells from tumor tissue; we also address the effect of the deconstruction procedure on the characteristics of primary cells. Finally, perspectives on the future of reconstructed tumor models are discussed, with an emphasis on the essential prerequisites for developing authentic humanized tumor models.

Endothelial cells metabolically regulate breast cancer invasion toward a microvessel

Breast cancer metastasis is initiated by invasion of tumor cells into the collagen type I-rich stroma to reach adjacent blood vessels. Prior work has identified that metabolic plasticity is a key requirement of tumor cell invasion into collagen. However, it remains largely unclear how blood vessels affect this relationship. Here, we developed a microfluidic platform to analyze how tumor cells invade collagen in the presence and absence of a microvascular channel. We demonstrate that endothelial cells secrete pro-migratory factors that direct tumor cell invasion toward the microvessel. Analysis of tumor cell metabolism using metabolic imaging, metabolomics, and computational flux balance analysis revealed that these changes are accompanied by increased rates of glycolysis and oxygen consumption caused by broad alterations of glucose metabolism. Indeed, restricting glucose availability decreased endothelial cell-induced tumor cell invasion. Our results suggest that endothelial cells promote tumor invasion into the stroma due, in part, to reprogramming tumor cell metabolism.

Human breast tumor derived endothelial cells exhibit distinct biological properties

BACKGROUND INFORMATION

Excessive angiogenesis characterized by leaky, tortuous, and chaotic vasculature is one of the hallmarks of cancers and is significantly correlated to poor prognosis. Disorganized angiogenesis leads to poor perfusion of anti-cancer drugs and limits access to immune cells. Hence, impeding angiogenesis is one of the attractive therapeutic targets to inhibit progression and metastasis in several solid tumors including breast.

RESULTS

We have developed a robust and reproducible method for isolating and ex vivo culture of endothelial cells (EC) derived from non-malignant (Endo-N) and malignant (Endo-T) part from clinically characterized human breast tumors. RT-PCR and immunoblotting analysis indicated that these cells exhibited expression of endothelial specific genes such as PECAM-1 (CD31), Endoglin (CD105), eNOS, VE-cadherin, VCAM1, and MCAM. Vasculogenic mimicry and contamination of progenitor EC recruited in tumors was ruled out by absence of CD133 expression and normal karyotype. Both the cell types showed stable expression of CD31 and CD105 up to seven passages. Furthermore, compared to Endo-N cells, Endo-T cells showed (a) constitutively increased proliferation marked by nearly 36% of cells in mitotic phase, (b) requirement of glutamine for cell survival, (c) pro-migratory phenotype, (d) produced increased number of sprouts in 3D cultures, and (e) resistance to sorafenib.

CONCLUSION

Tumor derived EC showed distinct biological properties compared to normal breast EC.

SIGNIFICANCE

Our method for isolating endothelial cell types from human breast tumors may be explored to (a) understand cellular and molecular mechanisms, (b) screen anti-angiogenic molecules, and (c) formulate organoid cultures to develop personalized medicine facilitating better clinical management of breast cancers.

BMP9 signaling promotes the normalization of tumor blood vessels

The presence of an immature tumor vascular network contributes to cancer dissemination and the development of resistance to therapies. Strategies to normalize the tumor vasculature are therefore of significant therapeutic interest for cancer treatments. VEGF inhibitors are used clinically to normalize tumor blood vessels. However, the time frame and dosage of these inhibitors required to achieve normalization is rather narrow, and there is a need to identify additional signaling targets to attain vascular normalization. In addition to VEGF, the endothelial-specific receptor Alk1 plays a critical role in vascular development and promotes vascular remodeling and maturation. Therefore, we sought to evaluate the effects of the Alk1 ligand BMP9 on tumor vascular formation. BMP9 overexpression in Lewis Lung Carcinoma (LLC) tumors significantly delayed tumor growth. Blood vessels in BMP9-overexpressing LLC tumors displayed markers of vascular maturation and were characterized by increased perivascular cell coverage. Tumor vasculature normalization was associated with decreased permeability and increased perfusion. These changes in vascular function in BMP9-overexpressing LLC tumors resulted in significant alterations of the tumor microenvironment, characterized by a decrease in hypoxia and an increase in immune infiltration. In conclusion, we show that BMP9 promotes vascular normalization in LLC tumors that leads to changes in the microenvironment.