Inhibition of constitutive and cxc-chemokine-induced NF-kappaB activity potentiates ansamycin-based HSP90-inhibitor cytotoxicity in castrate-resistant prostate cancer cells.
BACKGROUND
We determined how CXC-chemokine signalling and necrosis factor-kappaB (NF-kappaB) 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-kappaB 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-kappaB 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-kappaB activity in PC3 cells. AZ10397767 increased 17-AAG-induced apoptosis and necrosis and decreased NF-kappaB activity/CXCL8 expression in 17-AAG-treated PC3 cells.


CONCLUSIONS
Ansamycin cytotoxicity is enhanced by inhibiting NF-kappaB activity and/or CXC-chemokine signalling in CRPC cells. Detecting and/or inhibiting NF-kappaB activity may aid the selection and treatment response of CRPC patients to Hsp90 inhibitors.
Seaton
A
A
Centre for Cancer Research and Cell Biology, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7BL, Northern Ireland.
Maxwell
P J
PJ
Hill
A
A
Gallagher
R
R
Pettigrew
J
J
Wilson
R H
RH
Waugh
D J J
DJ
D017209:Apoptosis / Q000187:drug effects; D016227:Benzoquinones / Q000494:pharmacology*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics; D006801:Humans; D016209:Interleukin-8 / Q000235:genetics; D047029:Lactams, Macrocyclic / Q000494:pharmacology*; D008297:Male; D016328:NF-kappa B / Q000037:antagonists & inhibitors* / Q000502:physiology; D009336:Necrosis; D009570:Nitriles / Q000494:pharmacology; D009919:Orchiectomy; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000473:pathology; D023063:Receptors, Interleukin-8B / Q000037:antagonists & inhibitors* / Q000502:physiology; D017828:Rifabutin / Q000494:pharmacology*; D015398:Signal Transduction; D013450:Sulfones / Q000494:pharmacology
C434003:3-(4-methylphenylsulfonyl)-2-propenenitrile; D016227:Benzoquinones; D018841:HSP90 Heat-Shock Proteins; D016209:Interleukin-8; D047029:Lactams, Macrocyclic; D016328:NF-kappa B; D009570:Nitriles; D023063:Receptors, Interleukin-8B; D013450:Sulfones; D017828:Rifabutin; C112765:tanespimycin; C001277:geldanamycin