The effect of interleukin-6 on the proliferation of prostate cancer cells in vitro and the modulation of this procedure

Differential influence of normal and cancer-associated fibroblasts on the growth of human epithelial cells in an in vitro cocultivation model of prostate cancer

The prostate is composed of a number of different cell populations. The interaction between them is crucial for the development and proper function of the prostate. However, the effect of the molecular cross talk between these cells in the course of carcinogenesis is still unclear. Employing an approach wherein immortalized epithelial cells and immortalized human fibroblasts were cocultured, we show that normal associated fibroblasts (NAF) and cancer-associated fibroblasts (CAF) differentially influenced the growth and proliferation of immortalized human prostate epithelial cells. Whereas NAFs inhibited the growth of immortalized epithelial cells but promoted the growth of metastatic PC-3 cells, CAFs promoted the growth of immortalized epithelial cells but not of PC-3. Cytokine arrays revealed that NAFs secreted higher levels of tumor necrosis factor-alpha compared with CAFs whereas CAFs secreted higher levels of interleukin-6 (IL-6) compared with NAFs. The growth-inhibiting effects of NAFs were counteracted by the addition of IL-6, and the growth-promoting effects exerted by the CAFs were counteracted by tumor necrosis factor-alpha. Furthermore, CAFs induced the migration of endothelial cells in an IL-6-dependent manner. Here, we show that normal fibroblast cells have a protective function at very early stages of carcinogenesis by preventing immortalized epithelial cells from proliferating and forming new blood vessels whereas CAFs aid immortalized epithelial cells to further develop.

Ursolic acid, a naturally occurring triterpenoid, demonstrates anticancer activity on human prostate cancer cells

PURPOSE

Glucocorticoids are widely used as adjuvant therapy in hormonal refractory prostate cancer; their therapeutic role, however, remains unclear. Ursolic acid, a natural triterpene, structurally similar to dexamethasone, exhibits antitumor effects in various cell types. Our main objective was to investigate the effects of ursolic acid on cell viability, apoptosis and bcl-2 protein, in human hormone refractory and androgen-sensitive prostate cancer cells.

METHODS

The ursolic acid-induced changes in cell viability, apoptosis and bcl-2 protein were examined in human hormone refractory prostate cancer PC-3 cells and androgen-sensitive LNCaP cells, by MTT assay, flow cytometry and western blot analysis, respectively.

RESULTS

Ursolic acid inhibited significantly the cell viability and induced apoptosis in PC-3 cells at 55 microM and in LNCaP cells at 45 microM associated with a downregulation of bcl-2 protein.

CONCLUSIONS

The antiproliferative and apoptotic effects of ursolic acid in PC-3 and LNCaP cells implicate its potential therapeutic use for the treatment of hormone refractory and androgen-sensitive prostate cancer. The downregulation of bcl-2 may be one of the molecular mechanisms via which it induces apoptosis in PC-3 and LNCaP cells.

Aging-associated changes in gene expression in the ACI rat prostate: Implications for carcinogenesis

BACKGROUND

Prostate cancer is the most frequently diagnosed neoplasm and the second leading cause of cancer-related mortality in men. Although the incidence of prostate cancer increases with age, the link between aging and prostate cancer is poorly understood.

METHODS

Affymetrix oligonucleotide microarrays were used to analyze the mRNA expression levels in the dorsolateral prostates from 6- and 18-month-old ACI rats. Real-time RT-PCR and immunohistochemistry was performed to validate microarray data in a select set of genes.

RESULTS

Microarray analysis revealed changes in gene expression associated with inflammation, oxidative stress, tissue remodeling, and energy metabolism. Most of these changes have been related to increased proliferative status of the prostate, anti-apoptosis, activated stroma, and alteration of the energy metabolism.

CONCLUSIONS

Age-associated alterations in the gene expression profile may put the aging prostate in risk for the initiation, promotion, and progression of neoplastic transformation in both our animal model and humans.

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.