Osteoprotegerin secreted by inflammatory and invasive breast cancer cells induces aneuploidy, cell proliferation and angiogenesis

Abstract

BackgroundOsteoprotegerin (OPG) is a glycoprotein that has multifaceted role and is associated with several cancer malignancies like that of bladder carcinoma, gastric carcinoma, prostate cancer, multiple myeloma and breast cancer. Also OPG has been associated with several organ pathologies. The widespread expression of OPG suggests that OPG may have multiple biological activities that are yet to be explored.MethodsThe anchorage-independent sphere cultures of the adherent cells were instrumental in our study as it provided a deeper insight into the complexity of a 3D tumor. Cytokine profiling was performed for OPG’s detection in the microenvironment. ELISA and western blotting were performed to quantify the OPG secretion and measure the protein levels respectively. OPG expression was detected in human breast cancer tissue samples by IHC. To decipher OPG’s role in tumor aggressiveness both recombinant human OPG as well as OPG rich and depleted breast cancer cell conditioned media were tested. Western blotting and MTT assay were performed to detect changes in signaling pathways and proliferation that were induced in presence of OPG. Onset of aneuploidy, in presence of OPG, was measured by cell cycle analysis and western blotting. Finally, human Breast Cancer qBiomarker Copy Number PCR Array was used to detect how OPG remarkably induced gene copy numbers for oncogenic pathway regulators.ResultsSUM149PT and SUM1315M02 cells secrete high levels of the cytokine OPG compared to primary human mammary epithelial cells (HMEC). High expression of OPG was also detected in human breast cancer tissue samples compared to the uninvolved tissue from the same patient. OPG induced proliferation of control HMEC spheres and triggered the onset of aneuploidy in HMEC sphere cultures. OPG induced the expression of aneuploidy related kinases Aurora-A Kinase (IAK-1), Bub1 and BubR1 probably through the receptor activator of nuclear factor kappa-B ligand (RANKL) and syndecan-1 receptors via the Erk, AKT and GSK3(3 signaling pathway. Gene copy numbers for oncogenic pathway regulators such AKT1, Aurora-A Kinase (AURKA or IAK-1), epidermal growth factor receptor (EGFR) and MYC with a reduction in the copy numbers of cyclin dependent kinase inhibitor 2A (CDKN2A), PTEN and DNA topoisomerase 2 alpha (TOP2A) were induced in presence of OPG.ConclusionsThese results highlight the role of OPG in reprogramming normal mammary epithelial cells to a tumorigenic state and suggest promising avenues for treating inflammatory breast cancer as well as highly invasive breast cancer with new therapeutic targets.Electronic supplementary materialThe online version of this article (doi:10.1186/s12885-015-1837-1) contains supplementary material, which is available to authorized users.

Osteoprotegerin rich tumor microenvironment: implications in breast cancer

“…Proteomic landscape of the breast cancer TME includes diverse factors involved in tumor growth, proliferation, metastasis, vascularity, evading cell death pathways and host immune system. In our previous study we demonstrated that inflammatory and invasive breast cancer TME is rich in OPG, chemokines such as urokinase-type plasminogen activator receptor (uPAR), Oncostatin M (OSM), IL-6 and GRO-α [6]. Here, we focus only on osteoprotegerin (OPG) as one of the factors present in the TME of inflammatory and invasive breast cancer cell lines, and discuss how it multitasks various functions to drive tumorigenesis.…”

“…Our study [6] for the first time, revealed that OPG is secreted and expressed at very high levels from the SUM1315MO2 invasive breast cancer cell line, as well as the SUM149PT and SUM190PT inflammatory breast cancer cell lines. OPG was secreted at a concentration of 500 pg/ml and 1100 pg/ml from SUM1315MO2 and SUM149PT, respectively [6].…”

Screening for Multiple Autoantibodies in Plasma of Patients with Breast Cancer

“…OPG plays a range of functional roles in cancer cell survival and progression, including tumor cell survival (56,65), TRAILinduced apoptosis resistance (66), cell phenotype, proliferation, and angiogenesis (67). Results from a study performed by Goswami and Sharma-Waila showed a consistently high OPG expression in infiltrating ductal carcinoma breast tissue samples when compared to control, uninvolved tissue samples (62). Moreover, when these results are taken together with other observations, it is proposed that OPG plays a major role in the angiogenic signature of aggressive breast tumor microenvironments (62).…”

“…Results from a study performed by Goswami and Sharma-Waila showed a consistently high OPG expression in infiltrating ductal carcinoma breast tissue samples when compared to control, uninvolved tissue samples (62). Moreover, when these results are taken together with other observations, it is proposed that OPG plays a major role in the angiogenic signature of aggressive breast tumor microenvironments (62). A study performed by Lane et al showed that OPG acts as a survival factor by protecting TRAIL-induced apoptosis of ovarian cancer cells (68).…”

“…It is expressed in other tissues such as the skin, heart, stomach, lung, kidney, liver, intestines, and breast (59,60). Recent data shows OPG production in breast tumor cells and its ability to promote both tumor growth and metastasis (61,62). In vitro studies propose that acting as a decoy receptor, OPG binds to tumor necrosis factor (TNF-related apoptosisinducing ligand (TRAIL), thus inhibiting apoptosis of cancer cells (63,64).…”