Nitric oxide sensitizes prostate carcinoma cell lines to TRAIL-mediated apoptosis via inactivation of NF-κB and inhibition of Bcl-xL expression

Abstract

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has been shown to be selective in the induction of apoptosis in cancer cells with minimal toxicity to normal tissues and this prompted its potential therapeutic application in cancer. However, not all cancers are sensitive to TRAIL-mediated apoptosis and, therefore, TRAIL-resistant cancer cells must be sensitized first to become sensitive to TRAIL. Treatment of prostate cancer (CaP) cell lines (DU145, PC-3, CL-1, and LNCaP) with nitric oxide donors (e.g.sensitized CaP cells to TRAIL-induced apoptosis and synergy was achieved. The mechanism by which DETANONOate mediated the sensitization was examined. DETANONOate inhibited the constitutive NF-jB activity as assessed by EMSA. Also, p50 was Snitrosylated by DETANONOate resulting in inhibition of NF-jB. Inhibition of NF-jB activity by the chemical inhibitor Bay 11-7085, like DETANONOate, sensitized CaP to TRAIL apoptosis. In addition, DETANONOate downregulated the expression of Bcl-2 related gene (Bcl-xL ) which is under the transcriptional regulation of NF-jB. The regulation of NF-jB and Bcl-xL by DETANONOate was corroborated by the use of Bcl-xL and Bcl-x jB reporter systems. DETANONOate inhibited luciferase activity in the wild type and had no effect on the mutant cells. Inhibition of NF-jB resulted in downregulation of Bcl-xL expression and sensitized CaP to TRAIL-induced apoptosis. The role of Bcl-xL in the regulation of TRAIL apoptosis was corroborated by inhibiting Bcl-xL function by the chemical inhibitor 2-methoxyantimycin A 3 and this resulted in sensitization of the cells to TRAIL apoptosis. Signaling by DETANONOate and TRAIL for apoptosis was examined. DETANONOate altered the mitochondria by inducing membrane depolarization and releasing modest amounts of cytochrome c and Smac/DIABLO in the absence of downstream activation of caspases 9 and 3. However, the combination of DETANONOate and TRAIL resulted in activation of the mitochondrial pathway and activation of caspases 9 and 3, and induction of apoptosis. These findings demonstrate that DETANONOate-mediated sensitization of CaP to TRAIL-induced apoptosis is via inhibition of constitutive NF-jB activity and Bcl-xL expression.

Mechanisms of nitric oxide-mediated inhibition of EMT in cancer

“…We have reported that treatment of prostate tumor and non-Hodgkin's B cell lymphoma (B-NHL) cell lines with DETANONOate reduced the NFκB DNA-binding activity attributed to S-nitrosylation of the NFκB p50 subunit by NO. 33,42,43 The above observations suggest that NO is a potent NFκB inhibitor and that DETANONOate mediates its anti-metastatic properties, in part, via suppression of NFκB signaling.…”

Constitutively Activated Nuclear Factor-κB, but not Induced NF-κB, Leads to TRAIL Resistance by Up-Regulation of X-Linked Inhibitor of Apoptosis Protein in Human Cancer Cells

“…Bcl-x L , another NF-nB antiapoptotic target gene, has been shown before to be involved in chemoresistance and TRAIL resistance in an NF-nB -dependent way (82)(83)(84)(85). Inhibition of constitutive NF-nB by overexpression of InB-SR inhibited expression of Bcl-x L (61,83,86,87), and down-regulation of Bcl-x L protein sensitized Panc-1 to TRAIL-mediated apoptosis (88). In addition, we found Bcl-x L to be elevated by TNF-a pretreatment.…”

NO-donating NSAIDs and cancer: An overview with a note on whether NO is required for their action

“…For example, Snitrosoglutathione inhibits the growth of various cancer cells [49] [50]. In addition, organic nitrates [51] diazeniumdiolates [52], syndominides [53], S-nitrosothiols [54] and even metal-NO complexes [55], all display anticancer properties in preclinical models of cancer, mostly cell lines. Since they differ structurally so broadly and their "common denominator" is that they are NO donors, it is fair to conclude that their anticancer properties are due or related to the NO that they release.…”