CCL2 is induced by chemotherapy and protects prostate cancer cells from docetaxel-induced cytotoxicity.

BACKGROUND: Metastatic prostate cancer is either inherently resistant to chemotherapy or rapidly acquires this phenotype after chemotherapy exposure. In this study, we identified a docetaxel-induced resistance mechanism centered on CCL2. METHODS: We compared the gene expression profiles in individual human prostate cancer specimens before and after exposure to chemotherapy collected from previously untreated patients who participated in a clinical trial of preoperative chemotherapy. Subsequently, we used the gain- and loss-of-function approach in vitro to identify a potential mechanism underlying chemotherapy resistance. RESULTS: Among the molecular signatures associated with treatment, several genes that regulate the inflammatory response and chemokine activity were upregulated including a significant increase in transcripts encoding the CC chemokine CCL2. Docetaxel increased CCL2 expression in prostate cancer cell lines in vitro. CCL2-specific siRNA inhibited LNCaP and LAPC4 cell proliferation and enhanced the growth inhibitory effect of low-dose docetaxel. In contrast, overexpression of CCL2 or recombinant CCL2 protein stimulated prostate cancer cell proliferation and rescued cells from docetaxel-induced cytotoxicity. This protective effect of CCL2 was associated with activation of the ERK/MAP kinase and PI3K/AKT, inhibition of docetaxel-induced Bcl2 phosphorylation at serine 70, phosphorylation of Bad, and activation of caspase-3. The addition of a PI3K/AKT inhibitor Ly294002 reversed the CCL2 protection and was additive to docetaxel-induced toxicity. CONCLUSION: These results support a mechanism of chemotherapy resistance mediated by cellular stress responses involving the induction of CCL2 expression and suggest that inhibiting CCL2 activity could enhance therapeutic responses to taxane-based therapy.

The iroquois homeobox gene 5 is regulated by 1,25-dihydroxyvitamin D3 in human prostate cancer and regulates apoptosis and the cell cycle in LNCaP prostate cancer cells.

1,25-Dihydroxyvitamin D3 [1,25(OH)2D3], the most active metabolite of vitamin D3, has significant antitumor activity in a broad range of preclinical models of cancer. In this study, we show that the Iroquois homeobox gene 5 (Irx5) is down-regulated by 1,25(OH)2D3 in human prostate cancer samples from patients randomly assigned to receive weekly high-dose 1,25(OH)2D3 or placebo before radical prostatectomy. Down-regulation of Irx5 by 1,25(OH)2D3 was also shown in the human androgen-sensitive prostate cancer cell line LNCaP and in estrogen-sensitive MCF-7 breast cancer cells. Knockdown of Irx5 by RNA interference showed a significant reduction in LNCaP cell viability, which was accompanied by an increase in p21 protein expression, G2-M arrest, and an increase in apoptosis. The induced apoptosis was partially mediated by p53, and p53 protein expression was increased as a result of Irx5 knockdown. Cell survival was similarly reduced by Irx5 knockdown in the colon cancer cell line HCT 116 and in MCF-7 breast cancer cells, each being derived from clinical tumor types that seem to be inhibited by 1,25(OH)2D3. Overexpression of Irx5 led to a reduction of p21 and p53 expression. This is the first report that Irx5 is regulated by 1,25(OH)2D3 in humans and the first report to show that Irx5 is involved in the regulation of both the cell cycle and apoptosis in human prostate cancer cells. Irx5 may be a promising new therapeutic target in cancer treatment.

Evaluation of the glutamate decarboxylase genes Gad1 and Gad2 as candidate genes for acute ethanol withdrawal severity in mice.

Previous studies in crosses between the C57BL/6J (B6) and the DBA/2J (D2) mice have implicated a role of the genes encoding for the 67- and 65-kDa isoforms of the glutamate decarboxylase (Gad1 and Gad2) in the manifestation and severity of multiple ethanol-related traits such as acute ethanol withdrawal severity [Buck, K.J., Metten, P., Belknap, J.K., Crabbe, J.C., 1997. Quantitative trait loci involved in genetic predisposition to acute alcohol withdrawal in mice. J. Neurosci. 17, 3946-3955], ethanol preference [Phillips, T.J., Belknap, J.K., Buck, K.J., Cunningham, C.L., 1998. Genes on mouse chromosomes 2 and 9 determine variation in ethanol consumption. Mamm. Genome 9, 936-941] and ethanol-induced locomotion [Demarest, K., McCaughran Jr., J., Mahjubi, E., Cipp, L., Hitzemann, R., 1999. Identification of an acute ethanol response quantitative trait locus on mouse chromosome 2. J. Neurosci. 19, 549-561]. Strain-specific sequencing experiments as well as gene expression studies in drug-naive and ethanol-treated D2 and B6 mice were carried out. The Gad1 sequence was similar, the Gad2 cDNA carried only a silent polymorphism (1017 G>C) between both strains. In addition, no significant GAD65 or GAD67 expression differences were detected in either drug-nai;ve or acute ethanol withdrawn animals by Western blot experiments. Therefore, these results do not support the hypothesis of an involvement of Gad1 or Gad2 in the pathophysiology of acute ethanol withdrawal severity and the other ethanol related traits.

Histologic changes associated with neoadjuvant chemotherapy are predictive of nodal metastases in patients with high-risk prostate cancer.

Clinical trials are evaluating the effect of neoadjuvant chemotherapy on men with high-risk prostate cancer. Little is known about the clinical significance of postchemotherapy tumor histopathologic features. We assessed the prognostic and predictive value of histologic features (intraductal carcinoma, vacuolated cell morphologic features, inconspicuous glands, cribriform architecture, and inconspicuous cancer cells) observed in 50 high-risk prostate cancers treated with preprostatectomy docetaxel and mitoxantrone. At a median follow-up of 65 months, the overall relapse-free survival (RFS) rates at 2 and 5 years were 65% and 49%, respectively. In univariate analyses (using the Kaplan-Meier method and log-rank tests), intraductal (P = .001) and cribriform (P = .014) histologic features were associated with shorter RFS. In multivariate analyses, using the Cox proportional hazards regression, baseline prostate-specific antigen (P = .004), lymph node metastases (P < .001), and cribriform histologic features (P = .007) were associated with shorter RFS. In multivariable logistic regression analysis, only intraductal pattern (P = .007) predicted lymph node metastases. Intraductal and cribriform histologic features apparently predict postchemotherapy outcome.

Phase 1/2 study of preoperative docetaxel and mitoxantrone for high-risk prostate cancer.

BACKGROUND: : A study was conducted to determine the 5-year recurrence-free survival in patients with high-risk prostate cancer after neoadjuvant combination chemotherapy followed by surgery. Secondary endpoints included safety, pathologic effects of chemotherapy, and predictors of disease recurrence. METHODS: : Fifty-seven patients were enrolled in a phase 1/2 study of weekly docetaxel 35 mg/m(2) and escalating mitoxantrone to 4 mg/m(2) before prostatectomy. Patients were treated with 16 weeks of chemotherapy administered weekly on a 3 of every 4 week schedule. A tissue microarray, constructed from the prostatectomy specimens, served to facilitate the exploratory evaluation of biomarkers. The primary endpoint was recurrence-free survival. Disease recurrence was defined as a confirmed serum prostate-specific antigen (PSA) >0.4 ng/mL. RESULTS: : Of the 57 patients, 54 received 4 cycles of docetaxel and mitoxantrone before radical prostatectomy. Grade 4 toxicities were limited to leukopenia, neutropenia, and hyperglycemia. Serum testosterone levels remained stable after chemotherapy. Negative surgical margins were attained in 67% of cases. Lymph node involvement was detected in 18.5% of cases. With a median follow-up of 63 months, 27 of 57 (47.4%) patients recurred. The Kaplan-Meier recurrence-free survival at 2 years was 65.5% (95% confidence interval [CI], 53.0%-78.0%) and was 49.8% at 5 years (95% CI, 35.5%-64.1%). Pretreatment serum PSA, lymph node involvement, and postchemotherapy tissue vascular endothelial growth factor expression were independent predictors of early recurrence. CONCLUSIONS: : Preoperative chemotherapy with docetaxel and mitoxantrone is feasible. Approximately half of the high-risk patients remain free of disease recurrence at 5 years, and clinical and molecular predictors of early recurrence were identified. Cancer 2010. (c) 2010 American Cancer Society.