Colin Purcell

Chemotherapy-Induced CXC-Chemokine/CXC-Chemokine Receptor Signaling in Metastatic Prostate Cancer Cells Confers Resistance to Oxaliplatin through Potentiation of Nuclear Factor-κB Transcription and Evasion of Apoptosis

Constitutive activation of nuclear factor (NF)-κB is linked with the intrinsic resistance of androgen-independent prostate cancer (AIPC) to cytotoxic chemotherapy. Interleukin-8 (CXCL8) is a transcriptional target of NF-κB whose expression is elevated in AIPC. This study sought to determine the significance of CXCL8 signaling in regulating the response of AIPC cells to oxaliplatin, a drug whose activity is reportedly sensitive to NF-κB activity. Administration of oxaliplatin to PC3 and DU145 cells increased NF-κB activity, promoting antiapoptotic gene transcription. In addition, oxaliplatin increased the transcription and secretion of CXCL8 and the related CXC-chemokine CXCL1 and increased the transcription and expression of CXC-chemokine receptors, especially CXC-chemokine receptor (CXCR) 2, which transduces the biological effects of CXCL8 and CXCL1. Stimulation of AIPC cells with CXCL8 potentiated NF-κB activation in AIPC cells, increasing the transcription and expression of NF-κB-regulated antiapoptotic genes of the Bcl-2 and IAP families. Coadministration of a CXCR2-selective antagonist, AZ10397767 (Bioorg Med Chem Lett 18:798–803, 2008), attenuated oxaliplatin-induced NF-κB activation, increased oxaliplatin cytotoxicity, and potentiated oxaliplatin-induced apoptosis in AIPC cells. Pharmacological inhibition of NF-κBorRNA interference-mediated suppression of Bcl-2 and survivin was also shown to sensitize AIPC cells to oxaliplatin. Our results further support NF-κB activity as an important determinant of cancer cell sensitivity to oxaliplatin and identify the induction of autocrine CXCR2 signaling as a novel mode of resistance to this drug.

Interleukin-8 Signaling Promotes Translational Regulation of Cyclin D in Androgen-Independent Prostate Cancer Cells

We have shown previously that interleukin-8 (IL-8) and IL-8 receptor expression is elevated in tumor cells of human prostate biopsy tissue and correlates with increased cyclin D1 expression. Using PC3 and DU145 cell lines, we sought to determine whether IL-8 signaling regulated cyclin D1 expression in androgen-independent prostate cancer (AIPC) cells and to characterize the signaling pathways underpinning this response and that of IL-8–promoted proliferation. Administration of recombinant human IL-8 induced a rapid, time-dependent increase in cyclin D1 expression in AIPC cells, a response attenuated by the translation inhibitor cycloheximide but not by the RNA synthesis inhibitor, actinomycin D. Suppression of endogenous IL-8 signaling using neutralizing antibodies to IL-8 or its receptors also attenuated basal cyclin D1 expression in AIPC cells. Immunoblotting using phospho-specific antibodies confirmed that recombinant human IL-8 induced rapid time-dependent phosphorylation of Akt and the mammalian target of rapamycin substrate proteins, 4E-BP1 and ribosomal S6 kinase, resulting in a downstream phosphorylation of the ribosomal S6 protein (rS6). LY294002 and rapamycin each abrogated the IL-8–promoted phosphorylation of rS6 and attenuated the rate of AIPC cell proliferation. Our results indicate that IL-8 signaling (a) regulates cyclin D1 expression at the level of translation, (b) regulates the activation of proteins associated with the translation of capped and 5′-oligopyrimidine tract transcripts, and (c) activates signal transduction pathways underpinning AIPC cell proliferation. This study provides a molecular basis to support the correlation of IL-8 expression with that of cyclin D1 in human prostate cancer and suggests a mechanism by which this chemokine promotes cell proliferation. (Mol Cancer Res 2007;5(7):737–48)

CHEMOTHERAPY-INDUCED CXC-CHEMOKINE/CXCR2 SIGNALING IN METASTATIC PROSTATE CANCER CELLS CONFERS RESISTANCE TO OXALIPLATIN THROUGH POTENTIATION OF NF-κB TRANSCRIPTION AND EVASION OF APOPTOSIS

Constitutive activation of nuclear factor (NF)-κB is linked with the intrinsic resistance of androgen-independent prostate cancer (AIPC) to cytotoxic chemotherapy. Interleukin-8 (CXCL8) is a transcriptional target of NF-κB whose expression is elevated in AIPC. This study sought to determine the significance of CXCL8 signaling in regulating the response of AIPC cells to oxaliplatin, a drug whose activity is reportedly sensitive to NF-κB activity. Administration of oxaliplatin to PC3 and DU145 cells increased NF-κB activity, promoting antiapoptotic gene transcription. In addition, oxaliplatin increased the transcription and secretion of CXCL8 and the related CXC-chemokine CXCL1 and increased the transcription and expression of CXC-chemokine receptors, especially CXC-chemokine receptor (CXCR) 2, which transduces the biological effects of CXCL8 and CXCL1. Stimulation of AIPC cells with CXCL8 potentiated NF-κB activation in AIPC cells, increasing the transcription and expression of NF-κB-regulated antiapoptotic genes of the Bcl-2 and IAP families. Coadministration of a CXCR2-selective antagonist, AZ10397767 (Bioorg Med Chem Lett 18:798–803, 2008), attenuated oxaliplatin-induced NF-κB activation, increased oxaliplatin cytotoxicity, and potentiated oxaliplatin-induced apoptosis in AIPC cells. Pharmacological inhibition of NF-κBorRNA interference-mediated suppression of Bcl-2 and survivin was also shown to sensitize AIPC cells to oxaliplatin. Our results further support NF-κB activity as an important determinant of cancer cell sensitivity to oxaliplatin and identify the induction of autocrine CXCR2 signaling as a novel mode of resistance to this drug.

The expression and prognostic impact of CXC-chemokines in stage II and III colorectal cancer epithelial and stromal tissue

Background:The CXC-chemokine expression is linked with colorectal cancer (CRC) progression but their significance in resected CRC is unclear. We explored the prognostic impact of such expression in stage II and III CRC.Methods:Tissue microarrays were constructed from stage II and III CRC biopsies (n=254), and the expression of CXCL1 and CXCL8, and their receptors CXCR1 and CXCR2, in malignant and adjacent normal tissue was graded by immunohistochemistry and was correlated with prognostic factors.Results:Expression of CXCL1, CXCR1 and CXCR2 was elevated in tumour epithelium relative to normal adjacent tissue (P<0.001). CXCL8 expression was detectable in the peritumoural inflammatory infiltrate. There was no overall association between CXCL1, CXCR1 or CXCR2 expression and prognostic endpoints; however, univariate subgroup survival analysis demonstrated an inverse association between CXCL1 and recurrence-free survival (RFS) in stage III patients (P=0.041). The CXCL8 positivity in the tumour infiltrate, however, correlated with earlier disease stage (P<0.001) and improved relapse-free survival across the cohort (P<0.001). Disease stage (P<0.001) and tumour infiltrate CXCL8 positivity (P=0.007) were associated with enhanced RFS in multivariate Cox regression analysis.Conclusion:Autocrine CXC-chemokine signalling may have adverse prognostic effects in early CRC. Conversely, CXCL8 positivity within the immune infiltrate may have good prognostic significance.

Clinical Tumor Staging of Adenocarcinoma of the Esophagus and Esophagogastric Junction

TO THEEDITOR: We congratulate Davies et al 1 on the retrospective analysis of 400 patients treated with neoadjuvant chemotherapy followed by surgery at two high-volume London centers over the course of a decade. Rather than examining the prognostic effect of tumor regression, the authors focused on the downstaging effect of neoadjuvant chemotherapy as a predictor of recurrence-free and overall survival. Following adjustment for known clinicopathologic variables, tumor downstaging was associated with a reduction in the risk of recurrence and death, suggesting that major clinical decisions should be based on postchemotherapy staging. As mentioned by the authors, advanced diagnostic staging procedures, such as positron emission tomography-computed tomography (PET-CT),areimportantfordetectingnodaldiseaseanddistantmetastases.Toclassifyatumorasdownstaged,itisessentialtonotonlyaccurately define the pathologic stage following surgical resection but also to define the clinical stage before chemotherapy. Although much work has been carried out to standardize the reporting of pathologic stage, the use of clinical staging methodologies has varied over time and between centers. 2,3 StagingthatusesPET-CTcandetectoccultmetastaticdiseaseinup

The prognostic relevance of CXC-chemokines in stage II and III colorectal cancer (CRC) tissue and inflammatory infiltrate.

10588 Background: Studies have linked CXC chemokines with CRC progression but their role in resected CRC is unclear. We explored the prognostic impact of CXC chemokine/receptor expression by immunohistochemistry (IHC) in stage II and III CRC tissue and stroma. Methods: Tissue microarrays were constructed from stage II and III CRC biopsies (n = 254) from a phase III study comparing 5FU/folinic acid chemotherapy with observation alone after surgery. Expression of CXCL1 and CXCL8, and their receptors CXCR1 and CXCR2 in CRC cells and adjacent normal tissue was graded by IHC, using a combined score of the proportion of cells with staining and the intensity of the staining. CXCL8 expression in the inflammatory infiltrate was scored as positive or negative. Data was correlated with clinicopathological factors and survival endpoints. Results: Expression of CXCL1, CXCR1 and CXCR2 was elevated in tumour epithelium relative to patient-matched normal tissue (Wilcoxon signed ranks test; p < 0.01). CXCL1 expression cor...