Decreased adhesiveness, resistance to anoikis and suppression of GRP94 are integral to the survival of circulating tumor cells in prostate cancer

Abstract

The presence of circulating tumor cells (CTC) is common in prostate cancer patients, however until recently their clinical significance was unknown. The CTC stage is essential for the formation of distant metastases, and their continuing presence after radical prostatectomy has been shown to predict recurrent or latent disease. Despite their mechanistic and prognostic importance, due both to their scarcity and difficulties in their isolation, little is known about the characteristics that enable their production and survival. The aim of this study was to investigate the molecular mechanisms underlying the survival of CTC cells. A novel CTC cell line from the bloodstream of an orthotopic mouse model of castration-resistant prostate cancer was established and compared with the primary tumor using attachment assays, detachment culture, Western blot, flow cytometry and 2D gel electrophoresis. Decreased adhesiveness and expression of adhesion molecules E-cadherin, beta4-integrin and gamma-catenin, together with resistance to detachment and drug-induced apoptosis and upregulation of Bcl-2 were integral to the development of CTC and their survival. Using proteomic studies, we observed that the GRP94 glycoprotein was suppressed in CTC. GRP94 was also shown to be suppressed in a tissue microarray study of 79 prostate cancer patients, indicating its possible role in prostate cancer progression. Overall, this study suggests molecular alterations accounting for the release and survival of CTC, which may be used as drug targets for either anti-metastatic therapy or the suppression of latent disease. We also indicate the novel involvement of GRP94 suppression in prostate cancer metastasis.

Circulating tumor cells: advances in detection methods, biological issues, and clinical relevance

“…This result conformed to the research conducted by Mao et al (2008). Howard et al (2008) investigated the molecular mechanism for the survival of CTCs, which was through downregulated adhesive molecules, resistance to anoikis, and low GPR94 expression.…”

Potentiated DNA Damage Response in Circulating Breast Tumor Cells Confers Resistance to Chemotherapy

“…Mouse CTCs were obtained from the blood specimens of the animals by cardiac puncturing as described previously (25). Nucleated cells from mouse blood were enriched in erythrocytes lysis buffer, and the epithelial cells were isolated by magnetic antibody cell separation (Miltenyi Biotec) and resuspended in 0.1 ml of PEB (1ϫ PBS, 0.1 mM EDTA, and 0.5% BSA fraction V) (Sigma) as described previously.…”

Lectin from Sambucus sieboldiana abrogates the anoikis resistance of colon cancer cells conferred by N-acetylglucosaminyltransferase V during hematogenous metastasis

“…Except for certain cell types such as blood cells, most cells are inter-connected via cell-cell and cell-extracellular matrix adhesions [2], and it is commonly observed that those cells develop apoptotic and necrotic signatures when placed under detached conditions [3, 4]. The deregulation of anoikis is emerging as a hallmark of cancer [5], and resistance to anoikis stress is one of the critical aspects for cancer stem cells [6] and circulating tumor cells (CTCs) [7]. Epithelial-mesenchymal transition was proposed as one of the mechanism underlying the acquisition of anoikis resistance of cancer cells [8].…”