Castration-resistant prostate cancer: Androgen receptor inactivation induces telomere DNA damage, and damage response inhibition leads to cell death

Telomere stability is important for cell viability, as cells with telomere DNA damage that is not repaired do not survive. We reported previously that androgen receptor (AR) antagonist induces telomere DNA damage in androgen-sensitive LNCaP prostate cancer cells; this triggers a DNA damage response (DDR) at telomeres that includes activation of ATM, and blocking ATM activation prevents telomere DNA repair and leads to cell death. Remarkably, AR antagonist induces telomere DNA damage and triggers ATM activation at telomeres also in 22Rv1 castration-resistant prostate cancer (CRPC) cells that are not growth inhibited by AR antagonist. Treatment with AR antagonist enzalutamide (ENZ) or ATM inhibitor (ATMi) by itself had no effect on growth in vitro or in vivo, but combined treatment with ENZ plus ATMi significantly inhibited cell survival in vitro and tumor growth in vivo. By inducing telomere DNA damage and activating a telomere DDR, an opportunity to inhibit DNA repair and promote cell death was created, even in CRPC cells. 22Rv1 cells express both full-length AR and AR splice variant AR-V7, but full-length AR was found to be the predominant form of AR associated with telomeres and required for telomere stability. Although 22Rv1 growth of untreated 22Rv1 cells appears to be driven by AR-V7, it is, ironically, expression of full-length AR that makes them sensitive to growth inhibition by combined treatment with ENZ plus ATMi. Notably, this combined treatment approach to induce telomere DNA damage and inhibit the DDR was effective in inducing cell death also in other CRPC cell lines (LNCaP/AR and C4-2B). Thus, the use of ENZ in combination with a DDR inhibitor, such as ATMi, may be effective in prolonging disease-free survival of patients with AR-positive metastatic CRPC, even those that co-express AR splice variant

A Novel Role of Prostate-Specific Membrane Antigen in Telomere Stability in Prostate Cancer Cells

Prostate-specific membrane antigen (PSMA) expression increases with prostate cancer (PCa) grade and progression; however, the role of PSMA in PCa progression remains poorly understood. Telomere stability is essential for the survival and genome stability of cancer cells. We found massive telomere DNA damage in PSMA-negative PCa cells (PC-3 and DU145) compared to PSMA-positive PCa (LNCaP) cells. The ectopic expression of PSMA suppressed telomere DNA damage in PC3 cells. PSMA inhibitor, 2-PMPA, and PSMA knockdown induced telomere DNA damage in PSMA-positive LNCaP cells but not in PSMA-negative PC-3 cells, suggesting that PSMA plays a critical role in telomere stability in PCa cells. In addition, we observed that inhibition of PSMA or inhibition of glutamate receptor, which mediates PSMA-dependent activation of AKT, suppressed AKT phosphorylation and caused telomere DNA damage. Furthermore, 2-PMPA-induced telomere DNA damage in LNCaP cells was associated with telomere aberrations, such as telomere-telomere fusions, sister-chromatid telomere fusions, and telomere breakages. AKT is reported to promote cell growth by stabilizing telomere association with telomere-binding proteins TRF1 and TPP1. We observed that TRF1 and TPP1 transfection of LNCaP cells attenuated the inhibitory effect of 2-PMPA on cell growth and telomere DNA damage. Together, these observations indicate that PSMA role in maintaining telomere stability in PCa cells is mediated by AKT. Thus, these studies reveal an important role of PSMA in maintaining telomere stability that can promote cell survival and, thereby, PCa progression. Implications: the role of PSMA in telomere stability suggests a strong correlation between PSMA expression and prostate cancer progression

A ligand-free copper(II)-catalyzed three-component reaction in poly(ethylene glycol) medium: a versatile protocol for the preparation of selected 3-indole derivatives

International audienceAn efficient and eco-friendly method has been developed for the synthesis of selected 3-indole derivatives via a copper-catalyzed condensation between indole, aldehydes, and malononitrile in polyethylene glycol. The reagent system (PEG solvent plus catalyst) could be recycled up to 5 times for reaction with the same aldehyde and it was used also with at least three different aldehydes successively. This multi-component reaction (MCR) occurs first through Knoevenagel condensation followed by Michael addition of indole

Gracilis muscle flap for exposed prosthetic graft in the groin of a patient with previous sartorius myoplasty

Background: This video describes a technique for gracilis muscle flap for a patient with exposed prosthetic graft in the groin with prior failed sartorius myoplasty in the setting of multiple revascularization procedures

ATM Inhibition Potentiates Death of Androgen Receptor-inactivated Prostate Cancer Cells with Telomere Dysfunction.

Androgen receptor (AR) plays a role in maintaining telomere stability in prostate cancer cells, as AR inactivation induces telomere dysfunction within 3 h. Since telomere dysfunction in other systems is known to activate ATM (ataxia telangiectasia mutated)-mediated DNA damage response (DDR) signaling pathways, we investigated the role of ATM-mediated DDR signaling in AR-inactivated prostate cancer cells. Indeed, the induction of telomere dysfunction in cells treated with AR-antagonists (Casodex or MDV3100) or AR-siRNA was associated with a dramatic increase in phosphorylation (activation) of ATM and its downstream effector Chk2 and the presenceof phosphorylated ATM at telomeres, indicating activation of DDR signaling at telomeres. Moreover, Casodex washout led to the reversal of telomere dysfunction, indicating repair of damaged telomeres. ATM inhibitor blocked ATM phosphorylation, induced PARP cleavage, abrogated cell cycle checkpoint activation and attenuated the formation of γH2AX foci at telomeres in AR-inactivated cells, suggesting that ATM inhibitor induces apoptosis in AR-inactivated cells by blocking the repair of damaged DNA at telomeres. Finally, colony formation assay revealed a dramatic decrease in the survival of cells co-treated with Casodex and ATM inhibitor as compared with those treated with either Casodex or ATM inhibitor alone. These observations indicate that inhibitors of DDR signaling pathways may offer a unique opportunity to enhance the potency of AR-targeted therapies for the treatment of androgen-sensitive as well as castration-resistant prostate cancer

Thlaspi arvense L. (BR0000010532263)

Belgium Herbarium image of Meise Botanic Garden

A novel mutation (F71L) in αA-Crystallin with defective chaperone-like function associated with age-related cataract

AbstractAge-related cataract (ARC) is a multifactorial disease and the leading cause of blindness worldwide. Genetic predisposition in association with other etiological factors may contribute to ARC. However, gene mutation studies on ARC are scanty. In the present work, we identified a genetic variation (F71L) in the exon-2 of CRYAA (αA-crystallin) gene in three unrelated female sporadic cases among 711 ARC patients but not in 265 normal non-cataractous controls by SSCP and RFLP analysis. By comparing human recombinant wild-type and F71L-αA-crystallin, we characterized the functional significance of this missense mutation. Chromatography, fluorescence and far- and near-UV CD studies indicated that F71L missense mutation did not significantly affect the apparent molecular mass, secondary and tertiary structures and hydrophobicity of αA-crystallin. While the mutant αA-crystallin displayed significant (35–90%) loss of chaperone-like activity (CLA) in thermal aggregation of carbonic anhydrase, βL- and γ-crystallins, it showed moderate (10–50%) loss in CLA in DTT-induced aggregation of insulin and lysozyme. This is the first report of an αA-F71L mutation being associated with ARC and suggests that ARC in individuals carrying this mutation (F71L) might be due to the overall loss of in vivo chaperone activity due to interaction with other environmental factors