Augmented expression of endothelin-1, endothelin-3 and the endothelin-B receptor in breast carcinoma K Alanen, 1 D-X Deng 1 & S Chakrabarti 1,2 Departments of 1 Pathology and Microbiology and 2 Immunology, The University of Western Ontario, London Ontario, Canada Date of submission 19 October 1998 Accepted for publication 16 May 1999 Alanen K, Deng D-X & Chakrabarti S (2000) Histopathology 36, 161–167 Augmented expression of endothelin-1, endothelin-3 and the endothelin-B receptor in breast carcinoma Aims: Endothelins (ETs) are peptides expressed in many tumours which may stimulate angiogenesis and des- moplasia. Because ETs have not been extensively studied mammary neoplasia, we assessed ET protein and mRNA expression and receptor mRNA expression in normal and neoplastic breast tissues. Methods and results: Tissues from five normal breasts, six fibroadenomas, seven ductal carcinomas in situ (DCIS) and 25 invasive carcinomas were stained with anti-ET-1 and anti-ET-3 antibodies and analysed using a grading system. ET-1, ET-3, ET A and ET B mRNA expression was assessed by quantitative RT-PCR from eight carcinomas and five normals. Weak staining for ET-1 and ET-3 was detected in all normals. Moderate to strong staining was seen in 72% and 64% of carcinomas for ET-1 and ET-3, respectively. Most fibroadenomas showed weak positiv- ity for ET-1 (83%) and ET-3 (67%). ET-1 and ET-3 mRNA levels were upregulated in carcinomas compared with normal breast. No ET A mRNA was not detected in any tissue. ET B mRNA was detected in normal breast and was increased in carcinomas. Conclusion: These results suggest that the ET system is altered in breast carcinomas and this may be of importance in the progression from in-situ to invasive carcinoma. Keywords: breast, carcinoma, endothelin-1, endothelin-3, endothelin-B receptor Introduction In 1988, Yanagisawa and colleagues isolated an extremely potent vasoconstricting substance from porcine aortic endothelium which is now referred to as endothelin. 1 Endothelins (ETs) are a family of four short peptides, each of approximately 21 amino acids and are commonly referred to as ET-1, ET-2, ET-3 and ET-4. ET-1 may be critical in the pathophysiology of essential hypertension. 2 However, ET-1 is now known to have widespread tissue distribution and diverse physiological roles. For example, ET-1 promotes steroidogenesis in Leydig cells 3 and has neurotransmit- ter and neuromodulator activity in the retina. 4,5 Also, ET-1 stimulates melanogenesis in vivo and in vitro. 6 In addition, ETs appear to have critical roles in embryo- genesis. ET-1 gene knockout mice die very shortly after birth due to respiratory failure and have severe midline craniofacial abnormalities. 7 ET-2 is produced predomi- nantly in the kidneys and intestine and appears to have limited physiological function(s). ET-3 is produced by a variety of cell types and organs including kidneys, brain, and retina and is involved in the proliferation and development of several cell types. Increased ET-1 mediated expression of several oncogenes, such as c-fos and c-jun, has been demonstrated. 8–10 At least three ET receptors exist and are now referred to as ET A , ET B and ET C . 11 In the breast, ET receptors are located on stromal fibroblasts, not epithelial cells. 12 ET A shows selectivity for ET-1 whereas ET B binds both ET-1 Histopathology 2000, 36, 161–167  2000 Blackwell Science Limited. Presented at the US and Canadian Academy of Pathology Annual meeting, Boston, March 1998. Address for correspondence: Dr S Chakrabarti, Department of Pathology, Universityof Western Ontario, London Health Sciences Centre, London, Ontario, N6A 5A5, Canada. e-mail: schakrab@julian.uwo.ca