The proinflammatory chemokine interleukin-8 (IL-8) is undetectable in androgen-responsive prostate cancer cells (e.g., LNCaP and LAPC-4), but it is highly expressed in androgen-independent metastatic cells, such as PC-3. In this report, we show IL-8 functions in androgen independence, chemoresistance, tumor growth, and angiogenesis. We stably transfected LNCaP and LAPC-4 cells with IL-8 cDNA and selected IL-8-secreting (IL8-S) transfectants. The IL8-S trans-
Silencing of androgen receptor (AR) signaling is a specific and effective mechanism to cure cancer of the prostate (CaP). In this study, the isolation and characterization of a compound from the aromatic berries of Pimenta dioica (allspice) that silences AR is presented. Potential antitumor activities of an aqueous allspice extract (AAE) and a compound purified from the extract were
The CXC receptor-1 (CXCR1) is a coreceptor for interleukin-8 (IL-8) and is expressed on both normal and tumor cells. The function of CXCR1 in prostate cancer was investigated by silencing its expression, using RNA interference. We established stable cell colonies of PC-3 cells, depleted of CXCR1, using lentiviral plasmids (pLK0.1puro) generating small hairpin RNA (shRNA) against CXCR1 mRNA. Stable shRNA transfectants (PLK1-PLK5) that express significantly reduced CXCR1 mRNA (≥90% down) and protein (≥43% down) or vector-only transfectants (PC-3V) were characterized. PLK cells showed reduced cell proliferation (down, ≥66%), due to cell cycle arrest at G 1 -S phase, decreases in Cyclin D1, CDK4, phosphorylated Rb, and extracellular signal-regulated kinase 1/2 levels compared with those in PC-3V cells. CXCR1 depletion lead to increases in spontaneous apoptosis by mitochondria-mediated intrinsic mechanism and increases in proapoptotic proteins (BAD, 40%; BAX, 12%), but decreases in antiapoptotic proteins (BCL2, down 38%; BCL xL , 20%). PLK2 cells grew as slowgrowing tumors (decrease of 54%), compared with that of PC3V tumors in athymic mice. Ex vivo analyses of PLK2 tumor tissues showed reduced expression of Cyclin D1 and vascular endothelial growth factor, and increased apoptosis activity. Other IL-8-expressing prostate cancer cell lines also exhibited similar phenotypes when CXCR1 was depleted by CXCR1 shRNA transfection. In contrast to these cells, CXCR1 depletion had little effect on IL-8 ligand-deficient LNCaP cells. RNA interference rescue using mutated CXCR1 plasmids reversed the silencing effect of PLK2, thus demonstrating the specificity of phenotypic alteration by CXCR1 shRNA. These studies establish that CXCR1 promotes IL-8-mediated tumor growth. [Cancer Res 2009;69(21):8265-74]
BIRM is an anticancer herbal formulation from Ecuador. Previous study established its antitumor and antimetastatic activity against prostate cancer models. The activity of BIRM against human prostate cancer (PCa) cells was investigated to uncover its mechanism of antitumor activity. In androgen receptor (AR)-expressing PCa cells BIRM was 2.5-fold (250%) more cytotoxic in presence of androgen (DHT) compared to cells grown in the absence of DHT. In AR-positive cells (LAPC-4 and LNCaP) BIRM caused a dose and time-dependent down-regulation of AR and increased apoptosis. Exposing cells to BIRM did not affect the synthesis of AR and AR promoter activity but increased degradation of AR via proteasome-pathway. BIRM caused destabilization of HSP90-AR association in LAPC-4 cells. It induced apoptosis in PCa cells by activation of caspase-8 via death receptor and FADD-mediated pathways. A synthetic inhibitor of Caspase-8 cleavage (IETD-CHO) aborted BIRM–induced apoptosis. The effect of BIRM on AKT-mediated survival pathway in both AR+ and AR- negative (PC-3 and DU145) showed decreased levels of p-AKTser 473 in all PCa cell lines. BIRM dosed by oral gavage in mice bearing PC-3ML tumors showed selective efficacy on tumor growth; before tumors are established but limited efficacy when treated on existing tumors. Moreover, BIRM inhibited the LNCaP tumor generated by orthotropic implantation into dorsal prostate of nude mice. Partial purification of BIRM by liquid-liquid extraction and further fractionation by HPLC showed 4-fold increased specific activity on PCa cells. These results demonstrate a mechanistic basis of anti-tumor activity of the herbal extract BIRM.
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