Although the role of TGF-β in tumor progression has been studied extensively, its impact on drug delivery in tumors remains far from understood. In this study, we examined the effect of TGF-β blockade on the delivery and efficacy of conventional therapeutics and nanotherapeutics in orthotopic mammary carcinoma mouse models. We used both genetic (overexpression of sTβRII, a soluble TGF-β type II receptor) and pharmacologic (1D11, a TGF-β neutralizing antibody) approaches to block TGF-β signaling. In two orthotopic mammary carcinoma models (human MDA-MB-231 and murine 4T1 cell lines), TGF-β blockade significantly decreased tumor growth and metastasis. TGF-β blockade also increased the recruitment and incorporation of perivascular cells into tumor blood vessels and increased the fraction of perfused vessels. Moreover, TGF-β blockade normalized the tumor interstitial matrix by decreasing collagen I content. As a result of this vessel and interstitial matrix normalization, TGF-β blockade improved the intratumoral penetration of both a low-molecular-weight conventional chemotherapeutic drug and a nanotherapeutic agent, leading to better control of tumor growth.breast cancer | vessel normalization | drug delivery B reast cancer is the second leading cause of cancer death in women, with most fatalities resulting from a failure to control metastatic disease with systemically administered therapies. In addition to the induction of cellular resistance mechanisms (decreased apoptosis, increased drug efflux, etc.), impaired intratumoral drug delivery is an important physiological factor contributing toward chemoresistance (1, 2). TGF-β is an important regulator of normal mammary gland development and function, as well as of the progression of mammary carcinomas (3-8). Although the role of TGF-β in tumor progression and metastasis has been studied extensively, little is known about its impact on drug delivery.Transport of a therapeutic agent from the circulation to cancer cells is a three-step process. Systemically administered drugs must (i) travel to different regions within a tumor via the vascular network; (ii) cross the vessel wall; and finally (iii) diffuse through the interstitial space to reach the tumor cells, with each step being hindered by the presence of an abnormal vasculature and/or matrix (1, 2, 9, 10). Tumor blood vessels are structurally and functionally abnormal, characterized by increased permeability and heterogeneous perfusion. Poor vascular perfusion decreases drug delivery and, as a result, impairs the efficacy of blood-borne antitumor agents (1, 11). In addition, the dense collagen-rich interstitial matrix further hinders drug transport to tumor cells-a feature especially relevant to larger therapeutics, such as nanoparticles (1-100 nm) (1, 10, 12, 13). The dense collagen matrix also contributes to solid stress, which compresses tumor vessels (14). Hence, depleting collagen will reduce stress and open up compressed vessels. TGF-β is a negative regulator of pericyte recruitment during blood vessel stab...

The relationship between physicians and nurses in the delivery of anesthesia care is politically and financially charged, and hotly debated. Against this backdrop, federal regulators have proposed dropping a Medicare requirement that nurse anesthetists be supervised by a physician. Proponents note that the new regulations would resolve inconsistencies between Medicare supervisory requirements and state law, while opponents voice concerns for patient safety. This Issue Brief describes the current controversy, and summarizes a newly published study that suggests differences in patient outcomes depending on the nature and level of anesthesiologist involvement in surgical care. License This work is licensed under a Creative Commons Attribution-No Derivative Works 4.0 License.