Angiogenic factors expressed by human prostatic cell lines: effect on endothelial cell growth in vitro

PTRF/Cavin-1 decreases prostate cancer angiogenesis and lymphangiogenesis

Caveolae are specialized plasma membrane subdomains implicated in cellular functions such as migration, signalling and trafficking. Caveolin-1 and polymerase I and transcript release factor (PTRF)/cavin-1 are essential for caveola formation. Caveolin-1 is overexpressed and secreted in prostate tumors and promotes aggressiveness and angiogenesis. In contrast, a lack of PTRF expression is reported in prostate cancer, and ectopic PTRF expression in prostate cancer cells inhibits tumor growth and metastasis. We experimentally manipulated PTRF expression in three prostate cancer cell lines, namely the caveolin-1 positive cells PC3 and DU145 and the caveolin-1-negative LNCaP cells, to evaluate angiogenesis- and lymphangiogenesis-regulating functions of PTRF. We show that the conditioned medium of PTRF-expressing prostate cancer cells decreases ECs proliferation, migration and differentiation in vitro and ex vivo. This can occur independently from caveolin-1 expression and secretion or caveola formation, since the anti-angiogenic effects of PTRF were detected in caveolin-1-negative LNCaP cells. Additionally, PTRF expression in PC3 cells significantly decreased blood and lymphatic vessel densities in orthotopic tumors in mice. Our results suggest that the absence of PTRF in prostate cancer cells contributes significantly to tumour progression and metastasis by promoting the angiogenesis and lymphangiogenesis potential of the cancer cells, and this could be exploited for therapy.

The Ron receptor tyrosine kinase positively regulates angiogenic chemokine production in prostate cancer cells

Overexpression of the Ron receptor tyrosine kinase has recently been shown in a wide variety of human cancers. However, no studies have examined Ron receptor expression or function during prostate tumorigenesis. We report here that Ron is highly expressed in human prostate adenocarcinoma and metastatic lymph nodes compared to normal prostate or benign prostate hyperplasia. Furthermore, we show that Ron is overexpressed in PC-3 and DU145 prostate cancer cell lines, and that levels of angiogenic chemokines produced by prostate cancer cells positively correlates with Ron expression. Knockdown of Ron in PC-3 or DU145 cells results in a significant decrease in angiogenic chemokine production and is associated with decreased activation of the transcription factor NF-kappaB. Moreover, exogenous overexpression of Ron in LNCaP cells is sufficient to induce a significant increase in angiogenic chemokines that can be abrogated by inhibition of NF-kappaB signaling. Given that the function of angiogenic chemokines is important in the development of new blood vessels, we also examined the ability of Ron to modulate endothelial cell migration. Our data show that knockdown of Ron in prostate cancer cells results both in significantly less endothelial cell chemotaxis compared to Ron-expressing cells in vitro as well as in reduced tumor growth and decreased microvessel density following orthotopic transplantation into the prostate in vivo. In total, our data suggest that the Ron receptor is important in modulating prostate tumor growth by modulating angiogenic chemokine production and subsequent endothelial cell recruitment.

Influence of neuroendocrine tumor cells on proliferation in prostatic carcinoma

Neuroendocrine (NE) tumor cells in prostatic carcinoma (PCa) may influence tumor proliferation by a paracrine stimulus. The role of NE tumor cells is discussed controversially. This study investigates the influence of NE tumor differentiation on proliferation in PCa. Neuroendocrine differentiation, Ki-67, and Polo-like kinase 1 were studied immunohistochemically in 73 consecutive prostatectomies. Polo-like kinase 1 (PLK1) expression was also studied by Western and Northern blot analysis. Tumors were classified as high NE (HNE) and low NE differentiated (LNE), and depending on the growth pattern, with solitary and clusters of NE tumor cells. Low NE differentiated tumors were defined as less than 30 and HNE as 30 or more NE tumor cells per hot spot. Patients were followed by serum prostate-specific antigen (PSA) analysis. Neuroendocrine differentiation was present at least focally in 70% of tumors; 57% were HNE and 43% LNE. Solitary NE tumor cells were more often found in low-grade PCa, whereas clusters of NE tumor cells were more frequent in high-grade PCa. PLK1 messenger RNA and protein as well as Ki-67 were overexpressed in tumor tissue compared with tumor-free tissue. A stronger proliferation as determined by Ki-67 and PLK1 expression was present in HNE tumors compared with LNE tumors and in tumors with clusters in contrast to tumors with solitary NE tumor cells. Analysis for PSA relapse-free survival showed an earlier progression in HNE than in LNE tumors and in PCa with clusters of NE tumor cells. A significant and clustered NE differentiation in PCa may lead to an increased proliferation and earlier tumor progression, whereas few and solitary NE tumor cells have no prognostic impact.

Leptin induces cell migration and the expression of growth factors in human prostate cancer cells

BACKGROUND

The adipocyte hormone leptin has been shown to increase migration and angiogenesis in epithelial cells. Therefore, we hypothesized that leptin would induce prostate cancer cell migration and growth factor expression in vitro.

METHODS

Prostate cancer cell lines DU145 and PC-3 (androgen-resistant) were treated with leptin over time. Supernatants were assayed for growth factor expression via enzyme-linked immunosorbent assay (ELISA). Becton Dickinson-Falcon Transwell systems were used to assay leptin-induced migration.

RESULTS

Leptin significantly induced expression of vascular endothelial growth factor (VEGF), transforming growth factor-beta1 (TGF-beta1), and basic fibroblast growth factor (bFGF) in DU145 and PC-3 cells. Prostate cancer cell migration was enhanced by leptin and inhibited 50% to 70% with the addition of mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3K) inhibitors.

CONCLUSIONS

The mitogenic effects of leptin on cancer cells, in combination with the increased migration and expression of growth factors, overall likely contributes to the progression of prostate cancer. Therefore, obesity associated with high leptin levels should be considered a risk factor in prostate cancer patients.

Angiogenesis and prostate cancer tumor growth

The initiation of new blood vessels through angiogenesis is critical to tumor growth. Tumor cells release soluble angiogenic factors that induce neovascularization, without which nutrients and oxygen would not be available to allow tumors to grow more than 2-3 mm in diameter. This "angiogenic switch" or angiogenic phenotype requires an imbalance between proangiogenic and antiangiogenic factors since the formation of new blood vessels is highly regulated. This review discusses angiogenesis mediators, and the potential for manipulation of angiogenic factors as a practical cancer therapy, particularly in prostate cancer.

Characterization of a transplantable hormone-responsive human prostatic cancer xenograft TEN12 and its androgen-resistant sublines

BACKGROUND

Models for human prostate cancer can facilitate the study of resistance to endocrine therapy, aid drug discovery, and pre-clinical assessment.

METHODS

Characteristics thought relevant to the growth in athymic nude mice of TEN12, an androgen-dependent transplantable prostatic cell line derived from a primary prostate carcinoma, and its two androgen-independent sublines, TEN12F and TEN12C, have been assessed immunocytochemically.

RESULTS

The xenografts of the parental TEN12 line are moderately differentiated with both papillary and glandular regions, pleomorphic nuclei and abundant mitotic figures and are extremely vascular. The cells express androgen receptor (AR), PSA, VEGF, EGFR, c-erbB2, and TGFalpha. Both TEN12F and TEN12C xenografts possessed a more anaplastic morphology and displayed significantly lower growth rates, reduced blood vessel density (BVD), decreased MIB-1 antigen and E-cadherin expression and increased cytoplasmic AR and HSP90 staining. Elevated EGFR (membrane) but not c-erbB2 expression was demonstrated in the TEN12F line only. Castration of mice bearing TEN12 xenografts rapidly induced the appearance of cytoplasmic AR in the cells, PSA levels decreased initially but recovered to below pre-castration levels whilst reduced TGFalpha and loss of VEGF expression was seen in the long-term castrates.

CONCLUSIONS

TEN12 and its sublines offer additional in vivo models to study the factors involved in the progression of prostatic cancer to androgen-independence.

Reinsertion of stimulated nucleus pulposus cells retards intervertebral disc degeneration: an in vitro and in vivo experimental study

Reinsertion of autogenous nucleus pulposus, an innovative method to delay further disc degeneration, has been proved with an experimental animal model. This study examined whether coculture of nucleus pulposus cells with annulus fibrosus cells (a) activates annulus fibrosus cells and (b) retards disc degeneration when reinserted into the disc in a rabbit model of disc degeneration. Coculture of the two cell types stimulated proliferation of each, as indicated by increased DNA synthesis measured by increases in DNA polymerase alpha expression and uptake of 5-bromo-2'deoxy-uridine assessed by an enzyme-linked immunosorbent assay. In a model of disc degeneration in rabbits, reinsertion of activated nucleus pulposus cells delayed the formation of clusters of chondrocyte-like cells, the destruction of disc architecture, and the elaboration of type-II collagen as measured immunohistochemically compared with no treatment. The direct reinsertion of activated nucleus pulposus cells into the disc offers a promising line of investigation for delaying intervertebral disc degeneration, although these results obtained with notochordal cells may not necessarily apply when mature central nucleus pulposus cells are used.

Correlation between neovascularisation and neuroendocrine differentiation in prostatic carcinoma

Neuroendocrine (NE) differentiated tumor cells are found in almost all prostatic carcinomas. Prostatic carcinomas with a high NE differentiation have a poor prognosis and increased metastatic potential. A relationship between the neovascularisation density in the tumor and the metastatic potential in prostatic carcinoma is well known. NE cells and microvessels were demonstrated immunohistochemically on 102 radical prostatectomy specimens using antibodies against Chromogranin A and CD34. Standard areas (7.9 mm2) of maximal Chromogranin A expression and highest vascularisation were determined and topographically related by light microscopy. Area density of microvessels was evaluated morphometrically. NE tumor cells were present in all prostatic carcinomas studied. High grade prostatic carcinomas expressed significantly more NE tumor cells and exhibited a higher neovascularisation than low grade carcinomas. There was significantly higher neovascularisation in high grade tumors with many, as compared to high grade tumors with few, NE tumor cells. Poorer pathological staging correlated with increased neovascularisation and stronger NE differentiation. A topographical relationship between the area of maximal NE tumor cells and the area of highest neovascularisation was found in 80.4% of all cases. An analysis of variance revealed a large number of NE tumor cells as the only predictor of an increased neovascularisation (p = 0.0006). These observations support the concept that increased neovascularisation is influenced not only by poor pathological grading but also by a high NE differentiation.