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The angiotensin receptor blocker, Losartan, inhibits mammary tumor development and progression to invasive carcinoma
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Abstract
Rhiannon Coulson1,8, Seng H. Liew2, Angela A. Connelly3, Nicholas S. Yee4, Siddhartha Deb5, Beena Kumar6, Ana C. Vargas7, Sandra A. O’Toole7,8,9, Adam C. Parslow10,16, Ashleigh Poh11, Tracy Putoczki11, Riley J. Morrow4, Mariah Alorro4, Kyren A. Lazarus1,12, Evie F.W. Yeap1, Kelly L. Walton13, Craig A. Harrison13, Natalie J. Hannan14, Amee J. George15, Colin D. Clyne1, Matthias Ernst4,16, Andrew M. Allen3 and Ashwini L. Chand1,4,16
1 Cancer Drug Discovery, Hudson’s Institute of Medical Research, Clayton, VIC, Australia
2 Department of Anatomy and Developmental Biology, Monash University, Clayton, VIC, Australia
3 Department of Physiology, University of Melbourne, VIC, Australia
4 Cancer and Inflammation Laboratory, Olivia Newton-John Cancer Research Institute, Heidelberg, VIC, Australia
5 Anatomical Pathology, Olivia Newton-John Cancer Research Institute, Heidelberg, VIC, Australia
6 Anatomical Pathology, Monash Health, Clayton, VIC, Australia
7 Department of Tissue Pathology and Diagnostic Oncology, Royal Prince Alfred Hospital, NSW, Australia
8 Translational Breast Cancer Research, Garvan Institute, Darlinghurst, Sydney, NSW, Australia
9 Sydney Medical School, Sydney University, NSW, Australia
10 Tumor Targeting Laboratory, Olivia Newton-John Cancer Research Institute, Heidelberg, VIC, Australia
11 Inflammation Division, WEHI, VIC, Australia
12 Department of Pharmacology, University of Cambridge, Cambridge, UK
13 Department of Physiology, Monash University, Clayton, VIC, Australia
14 Translational Obstetrics Group, Department of Obstetrics and Gynaecology, University of Melbourne, Mercy Hospital, Heidelberg, VIC, Australia
15 The ACRF Department of Cancer Biology and Therapeutics, John Curtin School of Medical Research, Australian National University, Canberra, ACT, Australia
16 School of Cancer Medicine, La Trobe University, Heidelberg, VIC, Australia
Correspondence to:
Ashwini L. Chand, email:
Keywords: invasive ductal carcinoma, luminal breast cancer, angiotensin receptor, interleukin 6, tumor necrosis factor
Received: November 21, 2016 Accepted: February 07, 2017 Published: February 20, 2017
Abstract
Drugs that target the Renin-Angiotensin System (RAS) have recently come into focus for their potential utility as cancer treatments. The use of Angiotensin Receptor Blockers (ARBs) and Angiotensin-Converting Enzyme (ACE) Inhibitors (ACEIs) to manage hypertension in cancer patients is correlated with improved survival outcomes for renal, prostate, breast and small cell lung cancer. Previous studies demonstrate that the Angiotensin Receptor Type I (AT1R) is linked to breast cancer pathogenesis, with unbiased analysis of gene-expression studies identifying significant up-regulation of AGTR1, the gene encoding AT1R in ER+ve/HER2-ve tumors correlating with poor prognosis. However, there is no evidence, so far, of the functional contribution of AT1R to breast tumorigenesis. We explored the potential therapeutic benefit of ARB in a carcinogen-induced mouse model of breast cancer and clarified the mechanisms associated with its success.
Mammary tumors were induced with 7,12-dimethylbenz[α]antracene (DMBA) and medroxyprogesterone acetate (MPA) in female wild type mice and the effects of the ARB, Losartan treatment assessed in a preventative setting (n = 15 per group). Tumor histopathology was characterised by immunohistochemistry, real-time qPCR to detect gene expression signatures, and tumor cytokine levels measured with quantitative bioplex assays. AT1R was detected with radiolabelled ligand binding assays in fresh frozen tumor samples.
We showed that therapeutic inhibition of AT1R, with Losartan, resulted in a significant reduction in tumor burden; and no mammary tumor incidence in 20% of animals. We observed a significant reduction in tumor progression from DCIS to invasive cancer with Losartan treatment. This was associated with reduced tumor cell proliferation and a significant reduction in IL-6, pSTAT3 and TNFα levels. Analysis of tumor immune cell infiltrates, however, demonstrated no significant differences in the recruitment of lymphocytes or tumour-associated macrophages in Losartan or vehicle-treated mammary tumors.
Analysis of AT1R expression with radiolabelled ligand binding assays in human breast cancer biopsies showed high AT1R levels in 30% of invasive ductal carcinomas analysed. Furthermore, analysis of the TCGA database identified that high AT1R expression to be associated with luminal breast cancer subtype.
Our in vivo data and analysis of human invasive ductal carcinoma samples identify the AT1R is a potential therapeutic target in breast cancer, with the availability of a range of well-tolerated inhibitors currently used in clinics. We describe a novel signalling pathway critical in breast tumorigenesis, that may provide new therapeutic avenues to complement current treatments.
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