Synergistic Antitumor Activities of Docetaxel and Octreotide Associated with Apoptotic-Upregulation in Castration-Resistant Prostate Cancer

<div><p>Androgen deprivation therapy has become the fist-line treatment of metastatic prostate cancer; however, progression to castrate resistance disease occurs in the majority of patients. Thus, there is an urgent need for improvements in therapy for castration-resistant prostate cancer. The aims of the present study were to determine the efficacy somatostatin analogue octreotide (OCT) combined with a low dose of docetaxel (DTX) using castration resistant prostate cancer cells and to investigate the involved molecular mechanisms in vitro. The anti-proliferative and synergism potential effects were determined by MTT assay. Induction of apoptosis was analyzed employing annexing V and propidium iodide staining and flow cytometry. VEGFA, CASP9, CASP3 and ABCB1 gene expression was evaluated by RT-PCR and Q-RT-PCR analysis. OCT in combination with DTX treatments on DU145 cell migration was also evaluated. Investigation revealed that combined administration of DTX and OCT had significant, synergistically greater cytotoxicity than DTX or OCT treatment alone. The combination of the two drugs caused a more marked increase in apoptosis and resulted in greater suppression of invasive potential than either individual agent. There was obvious increase in caspase 3 expression in the OCT alone and two-drug combined treatment groups, however, VEGFA expression was markedly suppressed in them. These results support the conclusion that somatostatin analogues combined with docetaxel may enhance the chemotherapy efficacies through multiple mechanisms in castration-resistant PCa cell line. This work provides a preclinical rationale for the therapeutic strategies to improve the treatment in castrate resistance disease.</p></div

Effects of DTX, OCT alone and the combination of DTX/OCT on the mRNA expression of VEGFA, caspase 9, caspase 3 and ABCB1 in DU145 cells.

<p>M: Marker, The expression levels of objective genes were examined by RT-PCR (A, B, C and D) and quantitative real-time -PCR (B, D, F and H) respectively, using cells treated with the test drugs for 72 hours. The expression level of each mRNA was normalized to the level of β-actin mRNA. Values represent the means±SD of triplicate analyses (*<i>p</i><0.05, **<i>p</i><0.01).</p

Effect of DTX, OCT alone and two-drug combination treatment on DU145 cells apoptosis.

<p>Data are mean ± SEM of two independent experiments performed in triplicate. ***<i>p</i><0.000 vs. control.</p

Inhibition of cell growth by different concentrations of DTX (A), OCT (B) after 72 hours incubation and in a time- and dose-dependent manner both of them respectively (C and D) on DU145 proliferation.

<p>Cell viability was determined by MTT assay and expressed as a percentage of the control value (mean ± SEM of three experiments done in triplicate); error bars = SEM (n = 6).</p

Effect of DTX alone, synergistic effect of DTX in combination with 100(Fig. 3A) and various concentrations of two agents (Fig. 3B) on DU145 cells proliferation following 72 h of treatment.

<p>Results are the percentage of control value obtained with untreated cells (mean ± SEM of three experiments done in triplicate). (**) Proliferation was significantly decreased (<i>p</i><0.001); error bars = SEM.</p

Primers used for RT-qPCR analysis.

<p>Primers used for RT-qPCR analysis.</p