Regulatory roles of endothelial cells in cancer

Thesis (Ph. D.)--Harvard-MIT Division of Health Sciences and Technology, June 2011."May 2011." Cataloged from PDF version of thesis.Includes bibliographical references (p. 109-121).This thesis describes the biochemical regulatory impact of endothelial cells, the cells that line all blood vessels, in cancer. Our work draws from concepts in vascular repair and tissue engineering and extends the view of tumor vessels from perfusing tubes to delivery platforms lined with potent paracrine regulatory cells. We focus on how the endothelial cells themselves regulate tumor biology in a state-dependent fashion. We found that healthy endothelial cells inhibit cancer cell proliferation, invasiveness, and inflammatory signaling and that a defined perturbation of the healthy endothelial cell state - silencing of the gene encoding perlecan - causes loss of the invasion-inhibitory capabilities of endothelial cells by transcriptional upregulation of IL-6. The use of matrixembedded endothelial implants enabled the effects in cell culture to be expanded and validated in animal models. Moreover, endothelial cells exposed to a pathologically activating and inflammatory culture environment, similar to endothelial cells exposed to the atherosclerotic milieu, were leaky and inflamed, with dysregulated proliferative and leukocyte binding properties. Unlike healthy endothelial cells, which suppress cancer cell proliferation and metastasis, these dysfunctional endothelial cells instead aggressively stimulated cancer cell inflammatory signaling and invasiveness, which correlated with stimulation of spontaneous metastasis when implanted as matrixembedded cell implants adjacent to tumors. Fascinatingly we were able to identify markers of endothelial dysfunction, including reduction of endothelial perlecan expression, in human non-small cell lung carcinoma specimens. The state-dependent impact of endothelial cells on cancer biology adds another element to stromal regulation of cancer and brings together a range of disciplines and disparate findings regarding vascular control of tumors. That healthy endothelial cells suppress and dysfunctional cells promote tumor aggression may help to explain undesired effects of therapies that target tumor blood vessels. The harnessing of tissue engineering to regulate vascular and cancer biology may motivate the development of innovative pharmacologic and cell-based therapies for cancer.by Joseph W. Franses.Ph.D

The Evolution of Endothelial Regulatory Paradigms in Cancer Biology and Vascular Repair

Although the roles of endothelial cells in cancer have primarily been considered to be related to tumor perfusion, the emerging appreciation of “angiocrine” regulation adds stromal regulatory capabilities to the expanding list of endothelial functions in tumors. We posit that an understanding of the state-dependent paracrine regulatory paradigms established in vascular disease and repair will be critical for a deep understanding of tumor biology, as endothelial cells regulate diverse processes in all vascularized tissues. Here, we outline the historical developments that led to the appreciation of the paracrine regulatory functions of endothelial cells, summarize classical views of blood vessels and stroma in cancer, and attempt to merge these ideas to include the stromal regulatory endothelial cell as a critical regulator of cancer. The notion of the endothelial cell as a biochemical regulator of cancer state in constant dynamic balance with its tumor could impact diagnosis, prognosis, and treatment of cancer. Such concepts might well explain the mixed results from antiangiogenic cancer therapeutics and how certain drugs that improve vascular health correlate with improved cancer prognosis.National Institutes of Health (U.S.) (R01 GM-49039)National Institutes of Health (U.S.). Medical Scientist Training Progra

Matrix-Embedded Endothelial Cells Attain a Progenitor-Like Phenotype

Culture of endothelial cells (ECs) embedded in 3D scaffolds of denatured collagen has shown tremendous therapeutic potential in clinical trials of tissue repair. It is postulated that these matrix-embedded ECs (MEECs) attain a differential phenotype similar to early progenitor forms, which cannot be attained in 2D culture. MEECs are compared to 2D-ECs and endothelial progenitor cells (EPCs) by secretome, phenotype, and genetic fingerprint, and are found to be altered from 2D-ECs on all levels, adopting an EPC-like phenotype. This manifests in elevation of CD34 expression—a progenitor cell marker—and protein secretion and gene expression profiles that are similar to EPCs. Even more striking is that EPCs in 2D lose their phenotype, evident by the loss of CD34 expression, but are able to regain expression over time when embedded in the same 3D matrices, suggesting that future in vitro EPC work should use ME-EPCs to recapitulate in vivo phenotype. These findings elucidate the relationship between EPCs and the substratum-dependent regulation imparted by ECs which is critical to understand in order to optimize MEEC therapy and propel it into the clinic.National Institutes of Health (Grant R01-GM49039

Mechanisms of Tissue Uptake and Retention in Zotarolimus-Coated Balloon Therapy

Background—Drug-coated balloons are increasingly used for peripheral vascular disease, and, yet, mechanisms of tissue uptake and retention remain poorly characterized. Most systems to date have used paclitaxel, touting its propensity to associate with various excipients that can optimize its transfer and retention. We examined zotarolimus pharmacokinetics. Methods and Results—Animal studies, bench-top experiments, and computational modeling were integrated to quantify arterial distribution after zotarolimus-coated balloon use. Drug diffusivity and binding parameters for use in computational modeling were estimated from the kinetics of zotarolimus uptake into excised porcine femoral artery specimens immersed in radiolabeled drug solutions. Like paclitaxel, zotarolimus exhibited high partitioning into the arterial wall. Exposure of intimal tissue to drug revealed differential distribution patterns, with zotarolimus concentration decreasing with transmural depth as opposed to the multiple peaks displayed by paclitaxel. Drug release kinetics was measured by inflating zotarolimus-coated balloons in whole blood. In vivo drug uptake in swine arteries increased with inflation time but not with balloon size. Simulations coupling transmural diffusion and reversible binding to tissue proteins predicted arterial distribution that correlated with in vivo uptake. Diffusion governed drug distribution soon after balloon expansion, but binding determined drug retention. Conclusions—A large bolus of zotarolimus releases during balloon inflation, some of which pervades the tissue, and a fraction of the remaining drug adheres to the tissue–lumen interface. As a result, the duration of delivery modulates tissue uptake where diffusion and reversible binding to tissue proteins determine drug transport and retention, respectively.National Institutes of Health (U.S.) (Grant R01 GM-49039)Abbott Vascula

Clinical Trial Perceptions Among Patients with Gastrointestinal Cancer in an Academic Cancer Center

Poster presented at GW Medical Student Research Day 2022