Inhibition of constitutive and cxc-chemokine-induced NF-κB activity potentiates ansamycin-based HSP90-inhibitor cytotoxicity in castrate-resistant prostate cancer cells

Abstract

BACKGROUND: We determined how CXC-chemokine signalling and necrosis factor-kB (NF-kB) activity affected heat-shock protein 90 (Hsp90) inhibitor (geldanamycin (GA) and 17-allylamino-demethoxygeldanamycin (17-AAG)) cytotoxicity in castrate-resistant prostate cancer (CRPC). METHODS: Geldanamycin and 17-AAG toxicity, together with the CXCR2 antagonist AZ10397767 or NF-kB inhibitor BAY11-7082, was assessed by 3-(4, 5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assay in two CRPC lines, DU145 and PC3. Flow cytometry quantified apoptotic or necrosis profiles. Necrosis factor-kB activity was determined by luciferase readouts or indirectly by quantitative PCR and ELISA-based determination of CXCL8 expression. RESULTS: Geldanamycin and 17-AAG reduced PC3 and DU145 cell viability, although PC3 cells were less sensitive. Addition of AZ10397767 increased GA (e.g., PC3 IC 20 : from 1.67 ± 0.4 to 0.18 ± 0.2 nM) and 17-AAG (PC3 IC 20 : 43.7 ± 7.8 to 0.64 ± 1.8 nM) potency in PC3 but not DU145 cells. Similarly, BAY11-7082 increased the potency of 17-AAG in PC3 but not in DU145 cells, correlating with the elevated constitutive NF-kB activity in PC3 cells. AZ10397767 increased 17-AAG-induced apoptosis and necrosis and decreased NF-kB activity/CXCL8 expression in 17-AAG-treated PC3 cells. CONCLUSION: Ansamycin cytotoxicity is enhanced by inhibiting NF-kB activity and/or CXC-chemokine signalling in CRPC cells. Detecting and/or inhibiting NF-kB activity may aid the selection and treatment response of CRPC patients to Hsp90 inhibitors.

The Multiple Roles and Therapeutic Potential of Molecular Chaperones in Prostate Cancer

“…NF-κB is a transcription factor that has been involved in the transcription of many genes including CXCL8 and possibly HSP90 [145]. In PCa, high expression levels of the CXCR1/2 ligand CXCL8 (IL-8) and its receptors CXCR1 and two have been associated with the progression to CRPC.…”

“…In PCa, high expression levels of the CXCR1/2 ligand CXCL8 (IL-8) and its receptors CXCR1 and two have been associated with the progression to CRPC. Combination therapies including GA and AZ10397767, a CXCR2 antagonist, or GA and BAY11-7082, a NF-κB inhibitor, reduced the viability of PC3 cells [145]. Strikingly, the same therapeutic combination did not affect the viability of DU145 cells suggesting that metastatic PC3 cells, contrary to DU145 cells, are highly dependent on CXCL8 signaling [118].…”

Chemokine-Derived Peptides: Novel Antimicrobial and Antineoplasic Agents

“…Using the CXCR2 antagonist AZ10397767 indicates that it inhibited NF-κB mediated evasion of apoptosis in prostate cancer [ 152 ]. Finally, a chemokine chimeric molecule designated as ITIP, which was engineered by substituting the N-terminal and N-loop region of CXCL10 with those of CXCL11, led to stronger synergistic antitumor effects than the chemokines alone or in combination in vitro and in vivo [ 153 ] (Summarised in Table 2 ).…”

Redox-Mediated and Ionizing-Radiation-Induced Inflammatory Mediators in Prostate Cancer Development and Treatment

“…Therefore, inhibiting IL-8 signaling may be a promising strategy to sensitize advanced prostate cancer to chemotherapy. The reduction of intrinsic IL-8 potentiates ansamycin-based heat shock protein 90 cytotoxicity by several mechanisms, including inhibition of IL-8-induced NF-jB activity (158), cell cycle arrest at the G1/S boundary, and increased spontaneous apoptosis as well as enhancement of the efficacy of multiple chemotherapeutic drugs, such as Docetaxel, Staurosporine, and Rapamycin (168).…”