Antiproliferative effect of a prostatic cell-derived activity on the human androgen-dependent prostatic carcinoma cell line LNCaP

Action, localization and structure-function relationship of growth factors and their receptors in the prostate

Whereas the direct action of sex steroids, namely of androgens, on prostate cell division was questioned as early as in the 1970s, and remains so, the interest in prostatic growth factors (GFs) is rather recent but has expanded tremendously in the last five years. This lag period can be partly explained by the fact that, at the time, androgen receptors had just been discovered, and newly developed hormonal regimens or strategies to treat patients with prostate carcinoma (PCa) or epithelioma had generated great enthusiasm and hopes in the medical and scientific community. Another point to consider was the difficulty in maintaining prostate tissues in organ cultures and the relative novelty of culturing prostate epithelial cells in monolayers. Failures of sex steroids to elicit a direct positive response on prostate cell divisionin vitro, as seenin vivo, were interpreted as resulting from inappropriate models or culture conditions. However, the increasing number of reports confirming the lack of mitogenic activity of sex steroidsin vitro, coupled with the powerful mitogenic activity of GFs displayed in other systems, the discovery of GF receptors (GF-Rs), and the elucidation of their signalling pathways showing sex steroid receptors as potential substrates of GF-activated protein kinases gradually led to an increased interest in the putative role of GFs in prostate physiopathology. Of utmost importance was the recognition that hormone refractiveness was responsible for PCa progression, and for the poor outcome of patients with advanced disease under endocrine therapies. This problem remains a major issue and it raises several key questions that need to be solved at the fundamental and clinical levels.

Anti-proliferative effects of evodiamine on human prostate cancer cell lines DU145 and PC3

Prostate carcinoma is one of the most common malignant tumors and has become a more common cancer in men. Previous studies demonstrated that evodiamine (EVO) exhibited anti-tumor activities on several cancers, but its effects on androgen-independent prostate cancer are unclear. In the present study, the action mechanisms of EVO on the growth of androgen-independent prostate cancer cells (DU145 and PC3 cells) were explored. EVO dramatically inhibited the growth and elevated cytotoxicity of DU145 and PC3 cells. The flow cytometric analysis of EVO-treated cells indicated a block of G2/M phase and an elevated level of DNA fragmentation. The G2/M arrest was accompanied by elevated Cdc2 kinase activity, an increase in expression of cyclin B1 and phosphorylated Cdc2 (Thr 161), and a decrease in expression of phosphorylated Cdc2 (Tyr 15), Myt-1, and interphase Cdc25C. TUNEL examination showed that EVO-induced apoptosis was observed at 72 h. EVO elevated the activities of caspase 3, 8, and 9 in DU145 cells, while in PC3 cells only the activities of caspase 3 and 9 were elevated. EVO also triggered the processing of caspase 3 and 9 in both DU145 and PC3 cells. We demonstrate that roscovitine treatment result in the reversion of G2/M arrest in response to EVO in both DU145 and PC3. However, inhibitory effect of roscovitine on EVO-induced apoptosis could only be observed in DU145 rather than PC3. In DU145, G2/M arrest might be a signal for initiation of EVO-triggered apoptosis. Whereas EVO-triggered PC3 apoptosis might be independent of G2/M arrest. These results suggested that EVO inhibited the growth of prostate cancer cell lines, DU145 and PC3, through an accumulation at G2/M phase and an induction of apoptosis.

Co-operative functions between nuclear factors NFkappaB and CCAT/enhancer-binding protein-beta (C/EBP-beta) regulate the IL-6 promoter in autocrine human prostate cancer cells

BACKGROUND

IL-6 is a growth and survival factor for prostate cancer cells through autocrine pathways. Here, we have systematically examined the transcriptional regulation mechanisms of IL-6 in autocrine prostate cancer cells.

METHODS

RT-PCR and immunohistochemical staining were used to determine IL-6 production in the cells. Serial mutant IL-6 promoter luciferase reporters were generated and their transcriptional activities were examined. The transcription factors involved in IL-6 regulation were identified with super-shift EMSA. Overexpression of NFkappaB p65 and C/EBP-beta, and blockade of NFkappaB with IkappaBalpha or CAPE were performed to demonstrate the cooperation between NFkappaB p65 and C/EBP-beta in activation of IL-6.

RESULTS

Transcription factor regulatory sites IL6-NFkappaB, IL6-C/EBP, IL6-CREB, and IL6-AP1, are responsive to constitutively activated IL-6 production in autocrine prostate cancer cell lines. Among these sites, IL6-AP1 and IL6-C/EBP appear most important, while IL6-NFkappaB shows the least effect for IL-6 promoter activity as determined by mutant IL-6 promoter luciferase reporter assay. Nevertheless, nuclear factor NFkappaB is activated and required. Such activation is minimally dependent upon the IL6-NFkappaB site, occurring through cooperation with other transcription factors that bind the IL-6 promoter. Cooperation between NFkappaB p65 and C/EBP-beta did not require a functional IL6-NFkappaB binding site.

CONCLUSIONS

These data support a unique role for NFkappaB p65 as the primary trigger in autocrine production of IL-6 in prostate cancer cells. Furthermore, we describe a novel transcriptional activation mechanism for NFkappaB that is independent of its regulatory binding site, occurring through cooperation with other transcription factors that facilitate the neighboring regulatory site.

Expression of the matrix metalloproteinase promatrilysin in coculture of prostate carcinoma cell lines

BACKGROUND

Matrix metalloproteinases (MMPs) are involved in tumor progression. Matrilysin (MMP-7) has been shown to be upregulated in prostatic carcinomas and can increase the invasive capacity of DU-145 cells. Because of the heterogenous nature of prostatic tumors, we examined promatrilysin expression in cocultures containing two different prostatic carcinoma cell lines, DU-145 and LNCaP.

METHODS

Using enzyme linked immunosorbent assay (ELISA) analyses, promatrilysin expression was measured in DU-145/LNCaP cocultures and conditioned media cross-cultures. The effects of blocking IL-6 on promatrilysin expression were examined by pretreating conditioned media with IL-6 neutralizing antibody.

RESULTS

A significant induction of promatrilysin expression was observed in DU-145/LNCaP cocultures compared to LNCaP cells alone. In addition, DU-145 conditioned medium induced the same fold induction of promatrilysin as was observed in the cocultures. LNCaP cell conditioned medium did not induce promatrilysin expression in DU-145 cells. Neutralization of IL-6 with neutralizing antibody abrogated DU-145 conditioned media induced promatrilysin expression to baseline levels.

CONCLUSIONS

IL-6 secreted by DU-145 cells can induce promatrilysin expression in LNCaP cells. IL-6, in vivo, may act as a paracrine signaling factor that regulates matrix metalloproteinase expression. Therefore, IL-6 may play a role in invasive metastatic processes of a prostate carcinoma.

Endothelin-1 from prostate cancer cells is enhanced by bone contact which blocks osteoclastic bone resorption

The causes for the propensity of metastasized prostate cancer cells to grow in bone and to induce osteoblastic lesions remain unresolved. Co-culture of human prostate cancer cell lines with bone slices was determined to increase the level of endothelin-1 (ET-1) mRNA and its production. ET-1 is an ejaculate protein that also stimulates osteoblasts. Osteoclastic bone resorption was significantly blocked by the presence of androgen-independent prostate cancer cells in a dose-dependent manner as that of synthetic ET-1. The inhibition could be neutralized by specific ET-1 antibody, indicating the association of prostate cancer-derived ET-1 with inhibition of bone resorption. The combined ET-1 activity on osteoclasts and osteoblasts disrupts bone remodelling. ET-1 production is also elevated in the presence of prostate-specific antigen (PSA). ET-1 in turn enhances DNA synthesis of prostate cancer cells. Interactions among cancer cells, bone, ET-1 and PSA may be critical in cancer growth and lesions in bone.