INTRODUCTION

Previous studies by us and others demonstrated tumor suppressive effects of adiponectin, an adipocyte derived hormone. Adiponectin signaling occurs through two distinct membrane receptors; AdipoR1 and AdipoR2. There is paucity of data how their activation leads to tumor suppression. Here we present data indicating localization of AdipoR1 to the mitochondria and its role in apoptosis of cancer cells.

MATERIALS AND METHODS

Human kidney (RCC1932) and cervical (HeLa CCL-2) cancer cells as well as human embryonic kidney cells (HEK 293) were used as models. Full length AdipoR1 and its N-terminal (ligand binding) and C-terminal (intracellular moiety) truncated mutants (mutAdipoR1) ORFs were subcloned into YFP expressing vectors (pEYFP- AdipoR1, pEYFPmutAdipoR1). Cells were seeded onto glass cover slips in multi-well culture plates and transfected with vectors through Lipofectamine-2000 (Invitrogen) method 24 h after seeding. The effect of adiponectin (BioVendor) supplementation was also tested. Immunocytochemistry staining were with MitoTracker labeling or anti-MnSOD (mitochondria), anti-Stearoyl-CoA desaturase (SCD-1, ER), anti-Reb5, anti-manose-6-phosphatase receptor (M6P, endosome); or anti-Catalase (peroxisome). Images of the cells were collected with DM IRB Deconvolution Microscope (Leica) or Confocal microscope LSM510 (Carl Zeiss). Apoptosis was determined by sub-diploid population detection and or annexin binding using flow cytometry.

RESULTS

Over-expression of AdipoR1 in the cells induced apoptosis which was further augmented by adiponectin treatment. This was evident only in cells expressing full length AdipoR1. Furthermore, cells expressing mutAdipoR1 had different intracellular distributions with loss of mitochondrial localization of the receptor and pro-apoptotic activity.

CONCLUSIONS

This is the first report showing that AdipoR1 can be localized in the mitochondria. Adiponectin induce apoptosis in cancer cells through mitochondrial localization related mechanism that requires both ligand and signaling domains of AdipoR1.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 70.