Constitutive and Treatment-Induced CXCL8-Signalling Selectively Modulates the Efficacy of Anti-Metabolite Therapeutics in Metastatic Prostate Cancer

BackgroundThe current study was undertaken to characterize the effect of anti-metabolites on inducing CXCL8 signaling and determining whether the constitutive and/or drug-induced CXCL8 signaling in metastatic prostate cancer (CaP) cells modulates their sensitivity to this class of agent.
MethodsThe response of metastatic CaP cells to 5-Fluorouracil (5-FU), Pemetrexed or Tomudex was determined using cell count assays, flow cytometry and PARP cleavage analysis. Quantitative-PCR, ELISA and immunoblots were employed to determine effects of drugs or CXCL8 administration on target gene/protein expression.
ResultsAdministration of 5-FU but not pemetrexed potentiated CXCL8 secretion and increased CXCR1 and CXCR2 gene expression in metastatic PC3 cells. Consistent with this, the inhibition of CXCL8 signaling using a CXCR2 antagonist, AZ10397767, increased the cytotoxicity of 5-FU by 4-fold (P<0.001), and increased 5-FU-induced apoptosis in PC3 cells (P<0.01). In contrast, while administration of AZ10397767 had no effect on the sensitivity of pemetrexed, the CXCR2 antagonist exerted the greatest effect in increasing the sensitivity of PC3 cells to Tomudex, a directed thymidylate synthase (TS) inhibitor. Subsequent experiments confirmed that administration of recombinant human CXCL8 increased TS expression, a response mediated in part by the CXCR2 receptor. Moreover, siRNA-mediated knockdown of the CXCL8-target gene Bcl-2 increased the sensitivity of PC3 cells to 5-FU.
ConclusionsCXCL8 signaling provides a selective resistance of metastatic prostate cancer cells to specific anti-metabolites by promoting a target-associated resistance, in addition to underpinning an evasion of treatment-induced apoptosis.

背景 本研究旨在阐明抗代谢物对诱导CXCL8信号通路的作用，并明确转移性前列腺癌（CaP）细胞中组成型和/或药物诱导的CXCL8信号通路是否会调节其对该类药物的敏感性。
方法 本研究通过细胞计数实验、流式细胞术及聚ADP核糖聚合酶（PARP）裂解分析，检测转移性CaP细胞对氟尿嘧啶（5-Fluorouracil, 5-FU）、培美曲塞（Pemetrexed）或雷替曲塞（Tomudex）的应答反应。同时采用定量聚合酶链式反应（Quantitative-PCR）、酶联免疫吸附测定（ELISA）及免疫印迹（immunoblots），探究药物或CXCL8处理对靶基因/蛋白表达的影响。
结果 在转移性PC3细胞中，氟尿嘧啶（5-FU）处理可增强CXCL8的分泌并上调CXCR1与CXCR2的基因表达，而培美曲塞无此效应。与此一致的是，采用CXCR2拮抗剂AZ10397767抑制CXCL8信号通路后，氟尿嘧啶（5-FU）的细胞毒性提升了4倍（P<0.001），同时增强了氟尿嘧啶诱导的PC3细胞凋亡（P<0.01）。与之相反，CXCR2拮抗剂AZ10397767对培美曲塞的细胞敏感性无显著影响，但可最大程度提升PC3细胞对雷替曲塞——一种特异性胸苷酸合成酶（TS）抑制剂——的敏感性。后续实验证实，重组人CXCL8处理可上调TS的表达，该效应部分由CXCR2受体介导。此外，通过小干扰RNA（siRNA）介导沉默CXCL8的靶基因Bcl-2，可提升PC3细胞对氟尿嘧啶（5-FU）的敏感性。
结论 CXCL8信号通路不仅可介导转移性前列腺癌（CaP）细胞逃避治疗诱导的细胞凋亡，还通过靶标相关耐药机制，使这类细胞对特定抗代谢物产生选择性耐药。