Smooth Muscle Endothelin B Receptors Regulate Blood Pressure but Not Vascular Function or Neointimal Remodeling

The role of smooth muscle endothelin$_{B}$ (ET$_{B}$) receptors in regulating vascular function, blood pressure (BP), and neointimal remodeling has not been established. Selective knockout mice were generated to address the hypothesis that loss of smooth muscle ET$_{B}$ receptors would reduce BP, alter vascular contractility, and inhibit neointimal remodeling. ET$_{B}$ receptors were selectively deleted from smooth muscle by crossing floxed ET$_{B}$ mice with those expressing cre-recombinase controlled by the transgelin promoter. Functional consequences of ET$_{B}$ deletion were assessed using myography. BP was measured by telemetry, and neointimal lesion formation induced by femoral artery injury. Lesion size and composition (day 28) were analyzed using optical projection tomography, histology, and immunohistochemistry. Selective deletion of ET$_{B}$ was confirmed by genotyping, autoradiography, polymerase chain reaction, and immunohistochemistry. ET$_{B}$-mediated contraction was reduced in trachea, but abolished from mesenteric veins, of knockout mice. Induction of ET$_{B}$-mediated contraction in mesenteric arteries was also abolished in these mice. Femoral artery function was unaltered, and baseline BP modestly elevated in smooth muscle ET$_{B}$ knockout compared with controls (+4.2±0.2 mm Hg; $\textit{P}$<0.0001), but salt-induced and ET$_{B}$ blockade-mediated hypertension were unaltered. Circulating endothelin-1 was not altered in knockout mice. ET$_{B}$-mediated contraction was not induced in femoral arteries by incubation in culture medium or lesion formation, and lesion size was not altered in smooth muscle ET$_{B}$ knockout mice. In the absence of other pathology, ET$_{B}$ receptors in vascular smooth muscle make a small but significant contribution to ET$_{B}$-dependent regulation of BP. These ET$_{B}$ receptors have no effect on vascular contraction or neointimal remodeling.This work was funded by the British Heart Foundation (Project Grant PG/08/068/25461, P.W.F. Hadoke and D.J. Webb; Intermediate Clinical Research Fellowship FS/13/30/29994, N. Dhaun; and Centre of Research Excellence Award) and the Wellcome Trust (107715/Z/15/Z, A.P. Davenport and R.E. Kuc)

Improving systemic breast cancer therapy : time to look beyond the primary tumour?

Aim: Intra and inter tumour heterogeneity is a known feature in cancer because tumour cells undergo changes at genetic and epigenetic level as they spread from their primary tumour site. Adjuvant treatment protocols in breast cancer are currently based on the biological characteristics of the primary tumour, which in most cases has been removed surgically. Considering tumour heterogeneity in metastases we examined the present status of knowledge regarding measurable differences in tumour profiling between the primary breast tumour and its synchronous axillary lymph node metastases (ALNM) and if so whether adjuvant therapy directed towards the tumour characteristics of the ALNM instead of those of the primary tumour is more effective. Methods: We performed a literature search in Pubmed with the following MeSH headings: HUMAN and BREAST NEOPLASMS and RECEPTORS and ErbB-2. Results: A significant change in tumour features was seen in metachronous metastases. In contrast, a high concordance of biomarker expression was reported between a primary breast tumour and its synchronous ALNM. Conclusion: Tumour heterogeneity is a challenge for targeted therapy. A poor response can be explained by the diversity of tumour cells. The biological profile of synchronous ALNM measured by oestrogen (ER), progesterone (PR) and her-2-neu receptor status does not differ from the primary breast tumour and is not predictive of the tumour profile in metachronous metastasis. New techniques, such as profiling of circulating tumour cells or tumour behaviour in xenografts, are promising in directing more effective adjuvant therapy