Maxwell P J, Gallagher R, Seaton A, Wilson C, Scullin P, Pettigrew J, Stratford I J, Williams K J, Johnston P G, Waugh D J J
Centre for Cancer Research and Cell Biology, Queens University Belfast, Belfast, Northern Ireland.
Oncogene. 2007 Nov 15;26(52):7333-45. doi: 10.1038/sj.onc.1210536. Epub 2007 May 28.
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.
缺氧癌细胞对治疗具有抗性，从而导致具有更恶性表型的细胞被选择出来。白细胞介素-8（IL-8）的表达在包括前列腺癌在内的实体瘤的肿瘤发生和转移中起重要作用。最近，我们在人前列腺癌组织中检测到IL-8及其受体的表达升高。本研究的目的是确定缺氧是否会增加前列腺癌细胞中IL-8及其受体的表达，以及这是否有助于缺氧细胞的生存优势。PC3细胞中IL-8、CXCR1和CXCR2信使核糖核酸（mRNA）的表达随缺氧呈时间依赖性上调。通过酶联免疫吸附测定法检测到缺氧后IL-8分泌增加，而免疫印迹法证实受体表达升高。使用小干扰RNA（siRNA）、HIF-1显性阴性和药理抑制剂减弱缺氧诱导因子（HIF-1）和核因子-κB（NF-κB）的转录活性，可消除PC3细胞中缺氧诱导的CXCR1和CXCR2转录。此外，染色质免疫沉淀分析表明HIF-1和NF-κB与CXCR1结合。最后，抑制IL-8信号通路可增强依托泊苷诱导的缺氧PC3细胞死亡。这些结果表明，IL-8信号通路赋予缺氧前列腺癌细胞生存优势，因此，抑制IL-8信号通路的策略可能使缺氧肿瘤细胞对传统治疗敏感。
