HIF-1 and NF-kappaB-mediated upregulation of CXCR1 and CXCR2 expression promotes cell survival in hypoxic prostate cancer cells.
Hypoxic cancer cells are resistant to treatment, leading to the selection of cells with a more malignant phenotype. The expression of interleukin-8 (IL-8) plays an important role in the tumorigenesis and metastasis of solid tumors including prostate cancer. Recently, we detected elevated expression of IL-8 and IL-8 receptors in human prostate cancer tissue. The objective of the current study was to determine whether hypoxia increases IL-8 and IL-8 receptor expression in prostate cancer cells and whether this contributes to a survival advantage in hypoxic cells. IL-8, CXCR1 and CXCR2 messenger RNA (mRNA) expression in PC3 cells was upregulated in response to hypoxia in a time-dependent manner. Elevated IL-8 secretion following hypoxia was detected by enzyme-linked immunosorbent assay, while immunoblotting confirmed elevated receptor expression. Attenuation of hypoxia-inducible factor (HIF-1) and nuclear factor-kappaB (NF-kappaB) transcriptional activity using small interfering RNA (siRNA), a HIF-1 dominant-negative and pharmacological inhibitors, abrogated hypoxia-induced transcription of CXCR1 and CXCR2 in PC3 cells. Furthermore, chromatin-IP analysis demonstrated binding of HIF-1 and NF-kappaB to CXCR1. Finally, inhibition of IL-8 signaling potentiated etoposide-induced cell death in hypoxic PC3 cells. These results suggest that IL-8 signaling confers a survival advantage to hypoxic prostate cancer cells, and therefore, strategies to inhibit IL-8 signaling may sensitize hypoxic tumor cells to conventional treatments.
Maxwell
P J
PJ
Centre for Cancer Research and Cell Biology, Queens University Belfast, Belfast, Northern Ireland.
Gallagher
R
R
Seaton
A
A
Wilson
C
C
Scullin
P
P
Pettigrew
J
J
Stratford
I J
IJ
Williams
K J
KJ
Johnston
P G
PG
Waugh
D J J
DJ
D002470:Cell Survival; D047369:Chromatin Immunoprecipitation; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D006801:Humans; D000860:Hypoxia; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D015151:Immunoblotting; D047468:Immunoprecipitation; D016209:Interleukin-8 / Q000378:metabolism; D008297:Male; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011471:Prostatic Neoplasms / Q000378:metabolism* / Q000473:pathology; D023062:Receptors, Interleukin-8A / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D023063:Receptors, Interleukin-8B / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D014158:Transcription, Genetic; D015854:Up-Regulation
C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D016209:Interleukin-8; D016328:NF-kappa B; D023062:Receptors, Interleukin-8A; D023063:Receptors, Interleukin-8B