Novel Pharmacologic Targeting of Tight Junctions and Focal Adhesions in Prostate Cancer Cells

Abstract

Cancer cell resistance to anoikis driven by aberrant signaling sustained by the tumor microenvironment confers high invasive potential and therapeutic resistance. We recently generated a novel lead quinazoline-based Doxazosin® derivative, DZ-50, which impairs tumor growth and metastasis via anoikis. Genome-wide analysis in the human prostate cancer cell line DU-145 identified primary downregulated targets of DZ-50, including genes involved in focal adhesion integrity (fibronectin, integrin-α6 and talin), tight junction formation (claudin-11) as well as insulin growth factor binding protein 3 (IGFBP-3) and the angiogenesis modulator thrombospondin 1 (TSP-1). Confocal microscopy demonstrated structural disruption of both focal adhesions and tight junctions by the downregulation of these gene targets, resulting in decreased cell survival, migration and adhesion to extracellular matrix (ECM) components in two androgen-independent human prostate cancer cell lines, PC-3 and DU-145. Stabilization of cell-ECM interactions by overexpression of talin-1 and/or exposing cells to a fibronectin-rich environment mitigated the effect of DZ-50. Loss of expression of the intracellular focal adhesion signaling effectors talin-1 and integrin linked kinase (ILK) sensitized human prostate cancer to anoikis. Our findings suggest that DZ-50 exerts its antitumor effect by targeting the key functional intercellular interactions, focal adhesions and tight junctions, supporting the therapeutic significance of this agent for the treatment of advanced prostate cancer.

Anoikis and EMT: Lethal "Liaisons" during Cancer Progression

“…Genome-wide analysis of gene expression to identify primary targets of DZ-50 (an anticancer drug developed by our group 14 ) identified the downregulation of two EMT effector genes, Snail and insulin growth factor binding protein 3 ( IGFBP3 ), as well as integrin-α 6 , talin , and thrombospondin , all of which regulate cell-ECM adhesion and angiogenesis; and claudin-11 and -14, which are transmembrane proteins involved in tight junction (TJ) strands formation. 14 Selective targeting of claudin-11 during anoikis is significant as this TJ protein interacts with the actin cytoskeleton. 102–104 The focal adhesion effector, FAK, links AKT survival signaling to EMT via Snail activation.…”

“…105 IGFBP3, a secretory glycoprotein and IGF signaling regulator that promotes transforming growth factor beta– (TGFβ-) mediated EMT and confers antitumor resistance, is downregulated during anoikis induction by DZ-50. 14,102 A large body of evidence supports the functional coupling of phenotypic EMT-MET cycling to anoikis signaling via diverse mechanisms involving the following: (1) FAK regulation of Snail induction via AKT survival signaling; 105 (2) coordinated growth factor signaling network suppression of anoikis via proapoptotic proteins; 106 (3) recruitment of FAK and paxillin to β 1 integrin–promoting cancer cell migration via MAPK activation; 107 (4) combined activation of FAK and AKT survival signaling 101 ; and (5) regulators of fibronectin-ECM assembly through EMT transcription factors that dictate anoikis outcomes. 57,64,106,108,109 …”

“…11,12 The emergence of castration-resistant prostate cancer (CRPC) is due to the activation of survival pathways, including apoptosis suppression, anoikis (apoptosis upon detachment from the ECM) resistance, aberrant androgen signaling, and increased neovascularization. 6,13,14 The molecular exploitation of apoptotic signaling pathways has fueled the development of effective pharmacotherapies for the treatment of advanced metastatic CRPC. 15 This review discusses the current understanding of mechanisms underlying anoikis resistance in metastatic cancer, as well as efforts to overcome such resistance and enhance therapeutic response in patients with CRPC.…”

Clinical implications of leukocyte infiltration at the choroid plexus in (neuro)inflammatory disorders

“…Both the ECM and TJs have gained more interest as therapeutic targets in cancer and MS [110][111][112][113][114]. Targeting of the cell-ECM interface was successfully done in cancer because abnormal expression of integrins and their ECM ligands promotes cell proliferation, migration, and differentiation [113].…”

A selective alpha1D-adrenoreceptor antagonist inhibits human prostate cancer cell proliferation and motility “in vitro”

“…Quinazoline-based compounds significantly reduce cell motility [49] and adhesion [50,51] with an action mechanism independent of alpha1-AR activation [49]. Conversely, the lack of efficacy of A175 on DU145 migration is indicative of an alpha1D-AR mediated effect.…”