Secretion of epidermal growth factor and related polypeptides by the DU 145 human prostate cancer cell line

Peptides derived from growth factors: Exploring their diverse impact from antimicrobial properties to neuroprotection

Growth factor-derived peptides are bioactive molecules that play a crucial role in various physiological processes within the human body. Over the years, extensive research has revealed their diverse applications, ranging from antimicrobial properties to their potential in neuroprotection and treating various diseases. These peptides exhibit innate immune responses and have been found to possess potent antimicrobial properties against a wide range of pathogens. Growth factor-derived peptides have demonstrated the ability to promote neuronal survival, prevent cell death, and stimulate neural regeneration. As a result, they hold immense promise in the treatment of various neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, and multiple sclerosis, as well as in the management of traumatic brain injuries. Moreover, growth factor-derived peptides have shown potential for supporting tissue repair and wound healing processes. By enhancing cell proliferation and migration, these peptides contribute to the regeneration of damaged tissues and promote a more efficient healing response. The applications of growth factor-derived peptides extend beyond their therapeutic potential in health; they also have a role in various disease conditions. For example, researchers have explored their influence on cancer cells, where some peptides have demonstrated anti-cancer properties, inhibiting tumor growth and promoting apoptosis in cancer cells. Additionally, their immunomodulatory properties have been investigated for potential applications in autoimmune disorders. Despite the immense promise shown by growth factor-derived peptides, some challenges need to be addressed. Nevertheless, ongoing research and advancements in biotechnology offer promising avenues to overcome these obstacles. The review summarizes the foundational biology of growth factors and the intricate signaling pathways in various physiological processes as well as diseases such as cancer, neurodegenerative disorders, cardiovascular ailments, and metabolic syndromes.

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.

Vascular endothelial growth factor production in human prostate cancer cells is stimulated by overexpression of platelet 12-lipoxygenase

BACKGROUND

Elevated platelet 12-Lipoxygenase (P12-LOX) expression is associated with advanced stage and grade prostate cancer and overexpression in PC-3 cells promotes tumor growth and angiogenesis. The mechanisms underlying the role of P12-LOX in angiogenesis remain unclear.

METHODS

Enzyme linked immunosorbent assays were used to measure 12(S)-hydroxyeicosatetraenoic acid (12(S)-HETE) and vascular endothelial growth factor (VEGF) in conditioned media of PC-3 cells stably overexpressing human P12-LOX. Immunoblotting was used to observe stimulation of signal transduction in prostate cancer cell lines following exposure to 12(S)-HETE.

RESULTS

P12-LOX overexpression promotes increased accumulation of 12(S)-HETE and VEGF in culture media leading to constitutive ERK1/2 phosphorylation. 12(S)-HETE stimulates ERK1/2 phosphorylation via a pertussis toxin sensitive G-protein coupled receptor (GPCR) and MEK; the inhibition of which reduces VEGF accumulation by 36% and 70%, respectively.

CONCLUSIONS

Our data provide insight into a possible mechanism by which prostate cancer cells with elevated expression of P12-LOX stimulate VEGF production, thus increasing their angiogenic potential.

The antitumor and antiangiogenic activity of vascular endothelial growth factor receptor inhibition is potentiated by ErbB1 blockade

PURPOSE

Receptor tyrosine kinases of the ErbB family play important roles in the control of tumor growth. Vascular endothelial growth factor (VEGF) stimulates endothelial cell proliferation, enhances vascular permeability, and plays an important role in tumor vascularization. We evaluated the effects of selective VEGF receptor (VEGFR; PTK787/ZK222584) and ErbB (PKI166 and ZD1839) inhibitors on tumor growth and angiogenesis and asked whether additional therapeutic benefit was conferred by combination treatment.

EXPERIMENTAL DESIGN

The antitumor activity of each inhibitor alone or in combination was assessed in human cancer models in immunocompromised mice. ErbB receptor expression and activation of downstream signaling pathway was evaluated in both tumor and endothelial cells.

RESULTS

Both ErbB inhibitors significantly enhanced the antitumor activity of PTK787/ZK222584. In vitro, ErbB1 inhibition blocked VEGF release by tumor cells and proliferation of both tumor and endothelial cells. In an in vitro angiogenesis assay, epidermal growth factor (EGF) stimulated the release of VEGF by smooth muscle cells resulting in increased angiogenesis, a response blocked by administration of PTK787/ZK222584. Under basal condition, both ZD1839 and PTK787/ZK222584 blocked sprouting, likely via inhibition of an autocrine ErbB1 loop and VEGFR signaling, respectively, in endothelial cells. In conditions of limiting VEGF, EGF plays an important role in endothelial cell proliferation, survival, and sprouting.

CONCLUSION

We have shown that activation of ErbB1 triggers a plethora of effects, including direct effects on tumor and endothelial cells and indirect effects mediated via induction of VEGF release. Simultaneous blockade of ErbB1 and VEGFR pathways results in a cooperative antitumor effect, indicating that this combination may represent a valid therapeutic strategy.

Human prostate cancer risk factors

Prostate cancer has the highest prevalence of any nonskin cancer in the human body, with similar likelihood of neoplastic foci found within the prostates of men around the world regardless of diet, occupation, lifestyle, or other factors. Essentially all men with circulating androgens will develop microscopic prostate cancer if they live long enough. This review is a contemporary and comprehensive, literature-based analysis of the putative risk factors for human prostate cancer, and the results were presented at a multidisciplinary consensus conference held in Crystal City, Virginia, in the fall of 2002. The objectives were to evaluate known environmental factors and mechanisms of prostatic carcinogenesis and to identify existing data gaps and future research needs. The review is divided into four sections, including 1) epidemiology (endogenous factors [family history, hormones, race, aging and oxidative stress] and exogenous factors [diet, environmental agents, occupation and other factors, including lifestyle factors]); 2) animal and cell culture models for prediction of human risk (rodent models, transgenic models, mouse reconstitution models, severe combined immunodeficiency syndrome mouse models, canine models, xenograft models, and cell culture models); 3) biomarkers in prostate cancer, most of which have been tested only as predictive factors for patient outcome after treatment rather than as risk factors; and 4) genotoxic and nongenotoxic mechanisms of carcinogenesis. The authors conclude that most of the data regarding risk relies, of necessity, on epidemiologic studies, but animal and cell culture models offer promise in confirming some important findings. The current understanding of biomarkers of disease and risk factors is limited. An understanding of the risk factors for prostate cancer has practical importance for public health research and policy, genetic and nutritional education and chemoprevention, and prevention strategies.

Targeted inhibition of the epidermal growth factor receptor-tyrosine kinase by ZD1839 (?Iressa?) induces cell-cycle arrest and inhibits proliferation in prostate cancer cells

The epidermal growth factor (EGF) plays a role in the development of prostate cancer, which becomes essential after androgen resistance has emerged. The EGF receptor (EGFR) is therefore a potential target for anticancer therapy. We evaluated the effects of ZD1839 ('Iressa'), an orally active EGFR-tyrosine kinase inhibitor, on prostate cancer cell lines. The effects of ZD1839 were evaluated on the anchorage dependent and independent growth of androgen-responsive (LNCaP) and androgen-independent (DU145 and PC3) cells by a cell proliferation assay, cell counting, and soft agar analysis. Flow cytometric analysis and Western blotting were used to assess the effects on the cell-cycle and on protein expression levels, respectively. ZD1839 caused a dose- and time-dependent growth inhibition in all three cell lines. A dose-dependent supra-additive increase in growth inhibition was observed when ZD1839 was combined with the antiandrogen flutamide or ionizing radiation (IR). The antiproliferative effect of ZD1839 was mainly cytostatic and associated with a block in the G(0)/G(1) phase of the cell-cycle, evident after about 12 h of treatment. In the DU145 cells this block was associated with an increase in expression of the CDK inhibitor p27(Kip1), both in the cytoplasmic and nuclear fractions. The increase in p27(Kip1) was not evident in the LNCaP and PC3 cells. No changes were observed in the expression of cyclin D1 protein. These results demonstrate the antiproliferative effects of ZD1839 on the growth of prostate cancer cells and suggest that inhibition of EGFR-associated signal transduction pathway might represent a promising novel therapeutic strategy for the treatment of prostate cancer.

Grape seed extract inhibits EGF-induced and constitutively active mitogenic signaling but activates JNK in human prostate carcinoma DU145 cells: possible role in antiproliferation and apoptosis

A loss of functional androgen receptor and an enhanced expression of growth factor receptors and associated ligands are causal genetic events in prostate cancer (PCA) progression. These genetic alterations lead to an epigenetic mechanism where a feedback autocrine loop between membrane receptor and ligand (e.g. EGFR-TGFalpha) results in a constitutive activation of MAPK-Elk1-AP1-mediated mitogenic signaling in human PCA at an advanced and androgen-independent stage. We rationalized that inhibiting these epigenetic events could be useful in controlling advanced PCA growth. Recently, we found that grape seed extract (GSE), a dietary supplement rich in flavonoid procyanidins, inhibits advanced and androgen-independent human PCA DU145 cell growth in culture and nude mice. Here, we performed detailed mechanistic studies to define the effect of GSE on EGFR-Shc-MAPK-Elk1-AP1-mediated mitogenic signaling in DU145 cells. Pretreatment of serum-starved cells with GSE resulted in 70% to almost complete inhibition of EGF-induced EGFR activation and 50% to complete inhibition of Shc activation, which corroborated with a comparable decrease in EGF-induced Shc binding to EGFR. Conversely, EGF-induced ERK1/2 phosphorylation was inhibited only by lower doses of GSE; in fact, higher doses showed an increase. Additional studies showed that GSE alone causes a dose- and time-dependent increase in ERK1/2 phosphorylation in starved DU145 cells that is inhibited by an MEK1 inhibitor PD98059. Independent of this increase in ERK1/2 phosphorylation, GSE showed a strong inhibition of ERK1/2 kinase activity to Elk1 in both cellular and cell-free systems. GSE treatment of cells also inhibited both EGF-induced and constitutively active Elk1 phosphorylation and AP1 activation. GSE treatment also showed DNA synthesis inhibition in starved and EGF-stimulated cells as well as loss of cell viability and apoptotic death that was further increased by adding MEK1 inhibitor. Since GSE strongly induced apoptosis independent of its affect on an increase in phospho-ERK1/2, we hypothesized that apoptotic effect of GSE could be by other mechanism(s) including its effect on stress-associated MAPK, the JNK. Indeed, GSE-treated cells showed a strong and sustained increase in phospho-JNK1/JNK2 levels, JNK activity and phospho-cJun levels. An inhibition of GSE-induced JNK activation by a novel JNK inhibitor SP600125 resulted in a significant reversal of GSE-induced apoptotic death suggesting the involvement of JNK activation by GSE in its apoptosis response. Together, these results suggest that anticancer effects of GSE in PCA be mediated via impairment of EGFR-ERK1/2-Elk1-AP1-mediated mitogenic signaling and activation of JNK causing growth inhibition and apoptosis, respectively.

Nonandrogenic mediators of prostatic growth

Prostate growth and development are primarily under the control of androgens; however, other factors can also influence prostatic growth through alternative pathways. This article discusses some of the major nonandrogenic mediators of prostate growth. Information on the pathways by which these factors exert their effects is also reviewed.

Growth factors and epithelial-stromal interactions in prostate cancer development

Epithelial-stromal interactions are important not only in growth, development, and functional cytodifferentiation of the prostate but also in derangements of prostate gland such as BPH and prostate carcinoma. This chapter explores the roles of epithelium and stroma during this delicate process and highlights the role and mutual influence of each on the other. It also examines the importance of ECM in mediating the effects of androgens and drawn attention to estrogen and genetic factors in the process. During this process of epithelial-stromal interaction, growth factors play a central role in mediating the interactions. This chapter focuses on the role of several growth factors including epidermal growth factor, fibroblast growth factor, transforming growth factor alpha, transforming growth factor beta, insulin-like growth factor-1, vascular endothelial growth factor, nerve growth factor, platelet-derived growth factor, and hepatocyte growth factor. This chapter emphasizes the importance of epithelial-stromal interactions in tumorigenesis and highlights the switch of paracrine to autocrine mode during the process of carcinogenesis.

Production of epidermal growth factor in human prostatic cells cultured in vitro

The Epidermal Growth Factor (EGF) plays an important role in the regulation of in vitro growth of prostate cells inducing a strong mitogenic effect. Nevertheless in our previous study we observed that the treatment of human hypertrophic prostate cell line U285 with exogenous EGF produces a restricted effect on the cellular growth rate. This phenomenon could be due to the capacity of the cells to produce EGF. In this study we aimed to verify this hypothesis by evaluating the presence of mRNA of EGF and EGF receptor (EGF-R) and of their translation products in U285 cells, before and after the treatment with suramin and exogenous EGF. Moreover we studied the effects exerted by these substances on the proliferative rate of the cells U285 after different treatment protocols. The presence in the cells of mRNA for EGF and EGF-R and of their translation products was demonstrated by means of reverse transcription polymerase chain reaction (RT-PCR) and immunocytochemical methods respectively. The modification of growth rate induced by these drugs was studied by FRAME Cytotoxicity Test. The operative modalities adopted to carry out these growth assays tended to 1) focus the effects of suramin in relation to in vitro cellular growth phase; 2) verify the reversibility of its effects; 3) ascertain if it was possible to antagonize the action of suramin by adding exogenous EGF. The results obtained from the RT-PCR showed the presence, in the control cells and in the treated ones, of mRNA coding for EGF and EGF-R. The immunocytochemical analysis indicated that 20% of the control cells are EGF positive, and 83% are EGF-R positive, confirming the results obtained with RT-PCR. Moreover, these stainings showed that the treatment with EGF does not significantly modify the percentage of cells marked by the anti-EGF antibody, while treatments with suramin and suramin plus EGF double this percentage. None of the treatments modifies the percentage of EGF-R positive cells. The growth assays showed that the exposition to highest doses of suramin in the first 24 h of cultures causes a decrease (p < 0.05) of the cellular proliferation during the following 48 h and 72 h and that these effects are irreversible. Moreover, a contemporaneous exposition of the cells to EGF and suramin at seeding strengthens the cytotoxic action of the last drug. To sum up, the demonstration of the presence in the U285 cells of mRNA coding for EGF and EGF-R and of the corresponding proteins, confirms the hypothesis that these cells can produce EGF. Moreover, the cytotoxicity experiments allowed a focusing of the role of the endogenous EGF in the regulation of the U285 cells proliferation and confirmed the importance of biological events that take place in U285 cells during the first 24 h of culture.

Regulation of EGF-receptor expression by EGF and TGF alpha in epidermoid cancer cells is cell type-specific

The epidermal growth factor receptor (EGF-R) and its major ligands EGF and transforming growth factor alpha (TGF alpha) play an important role in the development of multiple human tumors. However, little is known of the comparative effects of each ligand on the regulation of EGF-R expression. To investigate this issue we used two similar human epidermoid cancer cell lines that overexpress EGF-Rs (KB and A431). In KB cells, EGF and TGF alpha increased EGF-R mRNA and protein levels by 2-3 fold over 8 h, associated with a greater than 4-fold stabilization of EGF-R mRNA half-life. EGF and TGF alpha also increased transcription of EGF-R mRNA 2-3-fold in KB cells. In contrast, EGF and TGF alpha only minimally increased EGF-R mRNA and protein in A431 cells, without changing EGF-R mRNA half-life. Basal EGF-R mRNA half-life was 2 fold greater in A431 cells than in KB cells (6-7 h versus 2-3 h), whilst the half-life of a mutant 2.6 kb EGF-R mRNA present in A431 cells, which lacks the 3-untranslated region (3'-UTR), was 2 fold greater than the full-length EGF-R mRNA. RNA gel-shift studies demonstrated that KB and A431 cells contain cytoplasmic proteins that bind specifically to an AU-rich sequence from the 3'-UTR of EGF-R mRNA. Taken together, these results demonstrate that in KB cells EGF and TGF alpha upregulate EGF-R expression at both transcriptional and post-transcriptional levels. The identification of AU-rich EGF-R mRNA-specific RNA-binding proteins from epidermoid cancer cells that overexpress EGF-Rs suggests that regulated RNA-protein interactions involving this region may play a central role in modulating EGF-R mRNA stability.

Molecular biology of prostate development and prostate cancer

The molecular mechanisms that control prostate development have been intensely studied in recent years due to the emergence of prostatic cancer as a major health concern. Several recent studies have led to the identification of numerous genes that are required for prostate organogenesis, many of which also contribute to prostate carcinogenesis. These genes fall into several categories, including proto-oncogenes, transcription factors, homeobox genes, growth factors and cell adhesion molecules. This review focuses on those genes which have been implicated in prostate growth and development, and which exhibit deregulated expression in prostate cancer.

Growth factor involvement in progression of prostate cancer

Understanding how the regulation of growth factor pathways alters during prostate cancer (PC) progression may enable researchers to develop targeted therapeutic strategies for advanced disease. PC progression involves the shifting of cells from androgen-dependent growth to an androgen-independent state, sometimes with the loss or mutation of the androgen receptors in PC cells. Both autocrine and paracrine pathways are up-regulated in androgen-independent tumors and may replace androgens as primary growth stimulatory factors in cancer progression. Our discussion focuses on growth factor families that maintain homeostasis between epithelial and stromal cells in the normal prostate and that undergo changes as PC progresses, often making stromal cells redundant. These growth factors include fibroblast growth factor, insulin-like growth factors, epidermal growth factor, transforming growth factor α, retinoic acid, vitamin D3, and the transforming growth factor β families. We review their role in normal prostate development and in cancer progression, using evidence from clinical specimens and models of PC cell growth.

NGF-beta, NE-cells and prostatic cancer cell lines. A study of neuroendocrine expression in the human prostatic cancer cell lines DU-145, PC-3, LNCaP, and TSU-pr1 following stimulation of the nerve growth factor-beta

Neuroendocrine (NE) cells are present in both benign and malignant human prostate. However, their function is poorly understood, mainly due to the lack of suitable experimental models. The nerve growth factor-beta (NGF-beta) promotes the rat pheochromocytoma cell line PC-12 to differentiate into neuronal like cells. We have studied the effect of NGF-beta on four human prostate cancer cell lines, LNCaP, DU-145, PC-3, and TSU-pr1. NGF-beta stimulates the growth rate in all these cell lines, but does not induce a neuronal phenotype. NE tumour markers (chromogranin A [CgA] and chromogranin B[CgB]) could not be demonstrated by immunocytochemistry (CgA and CgB), Northern blotting (CgA), or ELISA techniques (CgA), neither in control nor in NGF-beta stimulated cells. Consequently, other experimental models have to be sought in the study of NE cells in the human prostate.

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

BACKGROUND

Antiangiogenic therapy for prostatic cancer should offer additional ways of combating tumor progression. Knowledge of the possible angiogenic factors expressed by prostate cancer cell lines would therefore assist in the design and testing of such potential treatments.

METHODS

Changes in the proliferation and morphology of several endothelial cell lines (BAEC, HUVEC, and BACE) in response to either coculturing with human prostatic cell lines or culturing with conditioned medium derived from these lines were assessed.

RESULTS

Proliferation of BAEC cells was significantly stimulated by conditioned media from DU145, LNCaP, and DuPro-1, and also by coculture with LNCaP and DuPro-1. Growth of HUVEC cells was significantly increased with conditioned media from LNCaP, Ten12, and PC3, and by coculture with DU145 and DuPro-1. FGF2 supplementation is required for BACE growth in vitro, and only conditioned medium from Ten12 cells, which produce the highest levels of this growth factor, significantly increased cell numbers. BACE growth, however, was stimulated in coculture experiments with DU145, DuPro-1, PC3, and LNCaP. Morphological changes were only observed in the BAEC and BACE cells when cultured with conditioned media.

CONCLUSIONS

Prostatic carcinoma cell lines express a variety of angiogenic substances, including FGF2, which can stimulate endothelial cell proliferation in vitro, but this response may be modified by the prostatic-cell expression of other factors such as TGF alpha and TGF beta.

New EGF-R selective tyrosine kinase inhibitor reveals variable growth responses in prostate carcinoma cell lines PC-3 and DU-145

The effect of an EGF-R selective tyrosine kinase inhibitor ZM252868 was evaluated on the proliferation of PC-3 and DU-145 prostate cancer cell lines, which are purported to utilize an EGF-R-mediated autocrine pathway for regulation of cell growth. Basal growth of DU-145 cells was inhibited in a dose-dependent manner by the inhibitor, showing a 70% reduction at 1 microM, whilst the growth of PC-3 cells was not affected at this concentration. In the presence of 0.1 microM inhibitor, EGF and TGF alpha-stimulated DU-145 cell growth was decreased to below basal levels, while only TGF alpha-stimulated PC-3 cell growth was inhibited at a 1-microM concentration. Any growth responses to aFGF, bFGF, KGF, IGF1 and PDGF by DU-145 and PC-3 cells were unaffected by the inhibitor at concentrations of 1 microM or less. Additionally, the distribution of immunoreactive EGF-R varied between DU-145 and PC-3 cells, with EGF-R being predominately located on the cell membrane and in the cytoplasm, respectively.

Comparative studies of the mitogenic effects of epidermal growth factor and transforming growth factor-alpha and the expression of various growth factors in neoplastic and non-neoplastic prostatic cell lines

BACKGROUND

The role of growth factors in prostate cell growth has been investigated as these peptides may be involved in the autonomous growth of hormone-independent prostate cancer.

METHODS

Responses of neoplastic (PC-3 and CPA) and non-neoplastic (CAPE) prostatic cell lines to epidermal growth factor (EGF) and transforming growth factor-alpha (TGF-alpha) were determined using clonogenic and growth curve analysis. The constitutive expression of EGF, TGF-alpha, and TGF-beta 1-3 mRNA was examined using Northern blotting and EGF and TGF-alpha protein levels were determined immunohistochemically.

RESULTS

Growth curve and clonogenic analysis indicated that EGF and TGF-alpha were mitogenic in each cell line. The magnitude of the clonogenic response varied between the cell lines, with CPA cells showing the greatest growth increases. CPA cells also displayed the highest levels of EGF and TGF-alpha mRNA and protein. TGF-beta 1 mRNA was detected in the order of magnitude, PC-3 > CPA > CAPE. Furthermore, PC-3 and CPA cells expressed TGF-beta 3 and TGF-beta 2 transcripts respectively. In each cell line, the expression of any growth factor mRNA was not affected by exogenous EGF.

CONCLUSIONS

The growth responses of the cell lines to EGF and TGF-alpha did not correlate with their constitutive levels of EGF and TGF-alpha mRNA and protein, thus whilst growth factors may be important in malignant cell growth, other pathways may also be involved in the autocrine regulation of cell proliferation.

Differential gene expression of transforming growth factors alpha and beta, epidermal growth factor, keratinocyte growth factor, and their receptors in fetal and adult human prostatic tissues and cancer cell lines

OBJECTIVES

Recent studies have shown that growth factors may play a role in the etiology of benign prostatic hyperplasia (BPH) and prostatic carcinoma. Several growth factors have been reported to be expressed by prostatic tissues, but these growth factors have never been examined in human fetal prostate and compared with adult prostates and cancer cell lines. The present study was designed to investigate the messenger ribonucleic acid (mRNA) expression of transforming growth factor (TGF)-alpha, TGF-beta 1, TGF-beta 2, TGF- beta 3, keratinocyte growth factor (KGF), epidermal growth factor (EGF), EGF receptor (EGF-R), and KGF receptor (KGF-R) in human fetal and adult prostatic tissues and cancer cell lines by reverse-transcriptase-polymerase chain reaction-(RT-PCR) using specific oligonucleotide primers.

METHODS

Total RNA was extracted from human fetal and adult prostates (BPH tissues) and cancer cell lines. The gene expression of these growth factors and their receptors was determined by RT-PCR using specific oligonucleotide primers.

RESULTS

The results of these experiments suggest that: (1) human fetal prostate expressed mRNA transcripts for TGF-alpha, TGF-beta 1, TGF-beta 2, TGF-beta 3, and EGF. However, KGF, KGF-R, and EGF-R mRNA were not expressed by human fetal prostate; (2) human adult prostate (BPH tissues) showed mRNA transcripts for all growth factors and their receptors except KGF-R; (3) human BPH-1 cell lines expressed mRNA transcripts for TGF-alpha, TGF-beta 1, TGF-beta 2, TGF-beta 3, EGF, and KGF-R, but not for EGF-R and KGF growth factors; (4) human primary prostate cancer cell line (ND-1) showed mRNA transcripts for all growth factors except EGF and KGF; and (5) human prostate cancer cell lines (LNCaP, DU-145, PC-3) expressed mRNA transcripts for all growth factors except KGF, which was absent in all cell lines. However, KGF-R mRNA was absent in the PC-3 prostate cancer cell line.

CONCLUSIONS

These results suggest that the differential gene expression for various growth factors and their receptors in human fetal and adult prostatic tissues and cancer cell lines may be important in understanding the role of these factors in the pathophysiology of prostatic diseases.

EGF receptor signaling enhances in vivo invasiveness of DU-145 human prostate carcinoma cells

Carcinomas of the prostate and other lineages often present an autocrine stimulatory loop acting via the EGF receptor (EGFR). We have recently shown that EGFR-mediated signals enhance DU-145 prostate carcinoma cell transmigration of an extracellular matrix in vitro, and that this increased invasiveness was independent of proteolytic degradation of the matrix (Xie et al., 1995, Clin Exp Metastasis, 13, 407). To determine whether up-regulated EGFR signaling promotes tumor progression in vivo and to define the EGFR-induced cell property responsible, we inoculated athymic mice with genetically-engineered DU-145 cells. Parental DU-145 cells and those transduced to overexpress a full-length wild type (WT) EGFR formed tumors and metastasized to the lung when inoculated in the prostate and peritoneal cavity. The WT DU-145 tumors were more invasive. DU-145 cells expressing a mitogenically-active, but motility-deficient (c'973) EGFR formed small, non-invasive tumors without evidence of metastasis. All three sublines demonstrated identical, EGFR-dependent rates of cell growth in vitro, suggesting that the differential invasiveness was not due to altered growth rates. To determine whether cell motility may be, in part, responsible for tumor invasiveness, we treated WT DU-145 intraperitoneal tumors with a pharmacologic agent (U73122) which blocks EGFR-mediated cell motility but not mitogenesis. Under this treatment regimen, the WT DU-145 cells formed tumors of similar numbers and size to those formed without treatment; however, these tumors were much less invasive. These data suggest that EGFR-mediated cell motility is an important mechanism involved in tumor progression, and that this cell property may represent a novel target to limit the spread of tumors.

Regulation of prostatic growth and function by peptide growth factors

Polypeptide growth factors are positive and negative regulators of prostatic growth and function. Expression and biological effects of epidermal growth factor (EGF), transforming growth factors (TGFs) alpha and beta, fibroblast growth factors (FGFs), and insulin-like growth factors (IGFs) in the prostate have been extensively studied. EGF and TGF alpha, which share the same receptor, are strong mitogens for prostatic epithelial and stromal cells. Their paracrine mode of action in normal tissue and early-stage tumors is apparently altered towards an autocrine stimulation in hormone-independent tumors, which gain the ability to produce TGF alpha by themselves. TGF beta has a dual role in the regulation of prostatic growth. It inhibits growth of prostatic epithelial cells in culture and mediates programmed cell death after androgen withdrawal. However, advanced prostatic carcinomas become insensitive to the inhibitory effect of TGF beta. Several members of the FGF family have been identified in the prostate. They are mainly or exclusively expressed in the stromal cells, and stimulate the epithelial cells. In the rat Dunning tumor model, progression is accompanied by distinct changes in the expression of FGFs and their receptors. In the hyperplastic tissue, basic FGF (bFGF) is accumulated. This growth factor is also a potent angiogenic inducer, expression of which may determine the metastatic capability of a tumor. IGFs are paracrine growth stimulators in the normal and hyperplastic prostate. It is still under consideration whether prostatic cancer cells gain the ability to produce IGF-I by themselves and thus shift to an autocrine mode of IGF-I stimulation. Growth factors also interact with the androgen-signaling pathway. IGF-I in particular, other growth factors as well, can activate the androgen receptor.

Cloning and characterization of GRB14, a novel member of the GRB7 gene family

Screening of a human breast epithelial cell cDNA library with the tyrosine-phosphorylated C terminus of the epidermal growth factor receptor identified a novel member of the GRB7 gene family, designated GRB14. In addition to a pleckstrin homology domain-containing central region homologous to the Caenorhabditis elegans protein F10E9.6/mig 10 and a C-terminal Src homology 2 (SH2) domain, a conserved N-terminal motif, P(S/A)IPNPFPEL, can now be included as a hallmark of this family. GRB14 mRNA was expressed at high levels in the liver, kidney, pancreas, testis, ovary, heart, and skeletal muscle. Anti-Grb14 antibodies recognized a protein of approximately 58 kDa in a restricted range of human cell lines. Among those of breast cancer origin, GRB14 expression strongly correlated with estrogen receptor positivity, and differential expression was also observed among human prostate cancer cell lines. A GST-Grb14 SH2 domain fusion protein exhibited strong binding to activated platelet-derived growth factor (PDGF) receptors (PDGFRs) in vitro, but association between Grb14 and beta-PDGFRs could not be detected in vivo. In serum-starved cells, Grb14 was phosphorylated on serine residues, which increased with PDGF, but not EGF, treatment. Grb14 is therefore a target for a PDGF-regulated serine kinase, an interaction that does not require PDGFR-Grb14 association.

In vitro characterization of prolactin-induced effects on proliferation in the neoplastic LNCaP, DU145, and PC3 models of the human prostate

BACKGROUND

Proliferation of normal and tumoral prostate tissue is regulated by androgens and various growth factors. We characterized the in vitro proliferative influence of prolactin (PRL) in androgen-sensitive and androgen-insensitive human prostate cancers.

METHODS

The biologic models employed included the androgen-sensitive LNCaP and the androgen-insensitive DU145 and PC3 cell lines. PRL-induced influences (0.1-10 mIU/ml of medium) on proliferation were assessed using the colorimetric methylthiotetrazole assay. Androgen sensitivity in the three cell lines was determined by assessing the proliferative influence of dihydrotestosterone (DHT) (0.1-10 nM). PRL-induced modifications in PC3 cell kinetics were assessed using Feulgen-stained nuclear image cytometry.

RESULTS

Although DHT markedly stimulated LNCaP proliferation, it had no proliferative effect on the DU145 and PC3 cell lines. By contrast, PRL significantly modulated the proliferation of the DU145 and PC3 lines, but exerted weak, if any, effect on the proliferation of the LNCaP cell line. PRL increased the percentage of PC3 proliferating cells (i.e., cells in the S/G2 phases of the cell cycle) at low doses (0.1 mIU/mL) and decreased this percentage at high doses (10 mIU/ml).

CONCLUSIONS

Proliferation of androgen-insensitive human prostate cell lines can be significantly modulated by prolactin.

Epidermal growth factor (EGF) promotes chemomigration of a human prostate tumor cell line, and EGF immunoreactive proteins are present at sites of metastasis in the stroma of lymph nodes and medullary bone

Prostate tumor cells preferentially metastasize to bony sites and lymph nodes at a frequency in excess of that which would be predicted by random tumor cell dissemination. In order to determine whether chemoattractants in these organs promote organ-specific metastasis, we utilized human cell lines derived from and/or related to these organs as sources of potential chemoattractants. Secretory proteins derived from the cell lines MG-63 (osteosarcoma), SK-ES-1 (Ewing's sarcoma), and KG-1 (leukemia) stimulated chemomigration of the TSU-pr1 prostate tumor cells in a dose-dependent manner in Boyden chambers. In addition, secretory proteins from a human prostatic stromal cell line (hPS) and from the TSU-Pr1 prostate tumor cell line were also able to stimulate chemomigration of the TSU-pr1 cells through Boyden chambers. Since lymph nodes and bony sites represent organs of hematopoietic/lymphoid proliferation and activation, we undertook identification of specific cytokines present at these sites which may promote the chemomigration of prostate tumor cells. In this context, the cytokines interleukin-1 alpha, interleukin-2, interleukin-6, tumor necrosis factor-beta, transforming growth factor-beta, interferon alpha 2-a, and granulocyte-macrophage colony-stimulating factor did not stimulate chemomigration of the TSU-pr1 prostate tumor cell line. In contrast, the cytokine epidermal growth factor (EGF) stimulated chemomigration of the TSU-pr1 prostate tumor cells through the Boyden chambers in a dose-dependent manner. Western blot analysis of secretory proteins from the cell lines KG-1, SK-ES-1, MG-63, hPS, and TSU-pr1 identified EGF-immunoreactive proteins in all cases. In addition, EGF immunoreactivity was localized to the stroma of the human prostate, the osteogenic stroma of pelvic medullary bone, and the stroma within the capsule and trabeculae of pelvic lymph nodes. Hence, these results demonstrate that the cytokine EGF promotes the chemomigration of the TSU-pr1 prostate tumor cell line, and that EGF within the stroma of pelvic lymph nodes and medullary bone may act as a chemoattractant for prostate tumor cells, thereby facilitating the preferential formation of metastatic foci within these organs.

Influence of dihydrotestosterone, epidermal growth factor, and basic fibroblast growth factor on the cell kinetics of the PC3, DU145, and LNCaP prostatic cancer cell lines: relationship with DNA ploidy level

The cell kinetics (percentage of cells in the S+G2 phases of the cell cycle) and the DNA ploidy levels (nuclear DNA content) were determined in 108 samples each of the PC3, DU145, and LNCaP prostate cancer models. This was carried out by means of the digital cell image analysis of Feulgen-stained nuclei. Two to three hundred cell nuclei were analyzed for each of the 324 samples under study. The three cell lines were submitted to experimental conditions including the addition of dihydrotestosterone (DHT), epidermal growth factor (EGF), and basic fibroblast growth factor (bFGF), either alone or in combination, to the culture media. The results show that under the present culture conditions, the PC3 cell line was DHT-, EGF- and bFGF-insensitive. In contrast to what is generally reported in the literature, the DU145 cell line was DHT- and EGF-sensitive under the present culture conditions, but bFGF-insensitive. The LNCaP cell line was DHT-sensitive, but EGF- and bFGF-insensitive. While mainly tetraploid, the three cell lines nevertheless exhibited a significant level of heterogeneity in their nuclear DNA content distributions. Indeed, the proportions of non-tetraploid (diploid, hyperdiploid, triploid, hypertriploid, hypertetraploid, polymorphic) DNA histograms were 14% in the PC3, 16% in the DU145, and 29% in the LNCaP cell lines. These results suggest that the DNA ploidy level would not influence the hormone sensitivity level in the cell lines since they had significantly distinct hormone sensitivity profiles while remaining mainly tetraploid.

Stimulation of human prostate cancer cell lines by factors present in human osteoblast-like cells but not in bone marrow

Secondary deposits of prostate tumours are frequently found in the skeleton where they produce osteoblastic lesions. In this study both osteoblast-like cells and bone marrow from the proximal femur have been cultured to determine whether or not they can release factors which could support the growth of secondary prostate tumours. Media conditioned by both osteoblast-like cells (OBCM) and bone marrow were examined for their potential to stimulate prostate carcinoma cell lines. Whilst the results obtained demonstrated that OBCM could enhance the growth of both the hormone sensitive (LNCaP) and hormone unresponsive (PC-3 and DU-145) prostate carcinoma cell lines, no proliferative effect could be shown on cell lines derived from cancers of the breast, bladder, and liver. Significantly, media conditioned by either bone marrow or human skin fibroblasts also had no effect on the growth of prostate carcinoma cell lines. This study supports the possibility that the proliferation of prostate cancer cells at secondary skeletal sites, in vivo, may be due to osteoblast derived factors.

Enhancement of drug sensitivity of human malignancies by epidermal growth factor

We have previously shown that epidermal growth factor (EGF) enhances the in vitro and in vivo sensitivity of human ovarian carcinoma 2008 cells to cisplatin. EGF was found to enhance selectively the in vivo toxicity of cisplatin to 2008 cell xenografts without altering the toxicity of cisplatin to non-malignant target tissues such as the kidney or bone marrow. We now show that recombinant human EGF (rhEGF) enhances the cisplatin sensitivity of cell lines representative of many other types of malignancies in addition to ovarian carcinoma, including cancers of the head and neck, cervix, colon, pancreas and prostate, as well as non-small-cell carcinoma of the lung. In addition, rhEGF was found to sensitise cells to other platinum-containing drugs and several other classes of chemotherapeutic agents. rhEGF sensitised 2008 cells not only to cisplatin, but also to carboplatin and tetraplatin, as well as taxol, melphalan and 5-fluorouracil. We conclude that modulation of drug sensitivity by rhEGF is observed in cell lines representative of many human malignancies and for multiple classes of chemotherapeutic agents, indicating that it alters one or more components of the cellular damage response that are both common between cell lines and classes of drugs and fundamental to survival.

Epidermal growth factor receptor expression by northern analysis and immunohistochemistry in benign and malignant prostatic tumours

Epidermal growth factor receptor (EGFR) expression in 44 benign prostatic hyperplasia (BPH) and 55 prostatic carcinoma specimens has been investigated using Northern blot analysis and immunohistochemistry. The values obtained for the EGFR mRNA in the BPH and carcinoma specimens were not significantly different and in the latter there was no correlation with grade. In the immunohistochemical assays, two antibodies to the external and one to the internal domain of EGFR were used. The former ones stained the basal cell membranes intensely whilst cytoplasmic staining of secretory epithelium was seen in BPH specimens with the latter. In the carcinoma specimens, the intensity of membrane staining correlated with the two external domain antibodies, r = 0.640, P < 0.001, but neither of these correlated with the EGFR mRNA results. All three antibodies demonstrated a trend towards elevated expression of EGFR with dedifferentiation which reached significance only with the internal domain antibody results, P < 0.02. No correlation was observed with tumour EGFR mRNA values and the EGFR immunohistochemical results. The EGFR immunoreaction with the external domain antibody in 14 treated high-grade tumours was comparable to that obtained in 15 untreated anaplastic prostatic tumours. In 5 patients, both pre- and post-treatment samples were available and these exhibited little or no difference in EGFR expression with therapy.

Establishment and characterization of an immortalized but non-transformed human prostate epithelial cell line: BPH-1

This report describes the development and characterization of an epithelial cell line (BPH-1) from human prostate tissue obtained by transurethral resection. Primary epithelial cell cultures were immortalized with SV40 large T antigen. One of the isolated clones was designated BPH-1. These cells have a cobblestone appearance in monolayer culture and are non-tumorigenic in nude mice following subcutaneous injection or subrenal capsule grafting. They express the SV40 large T antigen and exhibit increased levels of p53, as determined by immunocytochemistry. Cytogenetic analysis by G-banding demonstrated an aneuploid karyotype with a modal chromosome number of 76 (range 71 to 79, n = 28) and 6 to 8 marker chromosomes. Some structurally rearranged chromosomes were observed, but the Y chromosome was normal. The expressed cytokeratin profile was consistent with a prostatic luminal epithelial cell. This profile was the same as that of primary prostatic epithelial cultures from which the BPH-1 cells were derived. In serum-free culture in plastic dishes epidermal growth factor (EGF), transforming growth factor (TGF)-alpha, fibroblast growth factor (FGF) 1 (aFGF), and FGF 7 (KGF) induced increased proliferation in these cells whereas FGF 2 (bFGF), TGF-beta 1, and TGF-beta 2 inhibited proliferative activity. Testosterone had no direct effect on the proliferative rate of BPH-1 cells. 5 alpha-Reductase, 3 alpha-hydroxysteroid oxidoreductase, and 17 beta-hydroxy-steroid oxidoreductase activities were detected in BPH-1 cells. Expression of androgen receptors and the secretory markers, prostate specific antigen and prostatic acid phosphatase, were not detectable by immunocytochemistry, biochemical assay, or RT-PCR analysis.

Tumorigenicity of SV40 T antigen immortalized human prostate epithelial cells: association with decreased epidermal growth factor receptor (EGFR) expression

Our primary objectives were to: 1) develop a system for the study of prostatic tumor evolution; and 2) examine the role of the epidermal growth factor/epidermal growth factor receptor (EGF/EGFR) pathway in prostate tumor progression. Adult human prostate epithelial cells previously immortalized by transfection with the SV40 T antigen gene (P69SV40T) produced tumors in only 2/18 mice with a 6 month latency period. Reinjection of cells recovered from these tumors after 1 or 2 cycles of growth in nude mice produced tumors in 2/4 and 2/3 mice with markedly decreased latent intervals of 12, 25, 25 and 25 days each. The chromosomal complement of each tumor was human, consistently pseudodiploid, and retained the Y chromosome. In both anchorage-independent and adherent cell growth assays, EGF stimulated proliferation by approximately 2-fold in both the parental P69SV40T line and the tumor sublines. The tumor sublines expressed less EGFR protein than the parental line, as assessed by Western immunoblotting and flow cytometric analysis. Immunoprecipitation revealed increased production of the 18 and 25 kDa TGF-alpha precursors parallel to decreases in detectable EGFR. The growth of both the parental P69SV40T line and the tumor sublines was inhibited by a neutralizing antibody to TGF-alpha under serum-free defined conditions. Inclusion of the TGF-alpha neutralizing antibody consistently inhibited the proliferation of the tumor sublines more than P69SV40T in both proliferation and [3H]thymidine incorporation assays. This finding suggests that the increased tumorigenicity and decreased latent interval observed among the human prostate tumor cells is partially due to activation of the TGF-alpha/EGFR autocrine network.

Characterization of high-affinity receptors for bombesin/gastrin releasing peptide on the human prostate cancer cell lines PC-3 and DU-145: internalization of receptor bound 125I-(Tyr4) bombesin by tumor cells

Specific receptors for bombesin/gastrin releasing peptide (GRP) on the androgen-independent human prostate cancer cell lines PC-3 and DU-145 were characterized. No specific binding of 125I-[Tyr4]-bombesin to the androgen-dependent human prostate cancer cell line LNCaP was detectable. The binding of 125I-[Tyr4]-bombesin to PC-3 and DU-145 cells was found to be time- and temperature-dependent, saturable, and reversible. Scatchard analysis revealed a single class of binding sites with high affinity (Kd 9.8 x 10(-11) M for PC-3, and 9.1 x 10(-11) M for DU-145 cells at 25 degrees C) and with a binding capacity of 44,000 binding sites/cell and 19,000 binding sites/cell, respectively. Bound 125I-[Tyr4]-bombesin was rapidly internalized by PC-3 cells. The nonhydrolyzable GTP analog GTP-gamma-S caused a dose-dependent inhibition of 125I-[Tyr4]-bombesin binding to PC-3 and DU-145 cells, indicating that a G-protein (guanine nucleotide-binding protein) couples the bombesin receptor to intracellular effector systems. Bombesin and GRP(14-27) inhibited the binding of 125I-[Tyr4]-bombesin to both cell lines in a dose-dependent manner with inhibition constants (Ki) of 0.5 nM and 0.4 nM, respectively. Both cell lines express the bombesin/GRP preferring bombesin receptor subtype, since, in displacement studies, neuromedin B was more than 200 times less potent than bombesin and GRP(14-27) in inhibiting the binding of 125I-[Tyr4]-bombesin. Two synthetic bombesin/GRP antagonists, RC-3095 and RC-3110, powerfully inhibited the specific binding of 125I-[Tyr4]-bombesin with Ki 0.92 nM and 0.26 nM on PC-3 cells, and 3.3 nM and 0.89 nM on DU-145 cells, respectively. These findings indicate that the PC-3 and DU-145 human prostate cancer cell lines possess specific high-affinity receptors for bombesin/GRP, and are suitable models for the evaluation of the antineoplastic activity of new bombesin/GRP antagonists in the treatment of androgen-independent prostate cancer.

Regulation of DU145 human prostate cancer cell proliferation by insulin-like growth factors and its interaction with the epidermal growth factor autocrine loop

The DU145 human prostate cancer cell line was shown to possess type I insulin-like growth factor receptors (IGFR). The addition of either IGF-I or IGF-II, but not insulin, to serum-free culture medium increases the rate of thymidine incorporation by the cells, a response which is suppressed by specific blockade of the previously described epidermal growth factor (EGF) autocrine growth regulatory loop. The DU145 cells secrete into conditional medium a specific IGF-binding protein (IGFBP) precipitated by an antibody to IGFBP-1, and whose secretion is also suppressed by interruption of the EGF autocrine loop. This IGFBP may modulate the bioactivity of IGFs arising from endocrine or paracrine sources in vivo. After removal of IGFBPs from the conditioned medium, no secretion of either IGF-I or IGF-II by this prostate cancer cell line is detected by radioimmunoassay and radioreceptor assay, respectively.

Epidermal growth factor receptor-dependent stimulation of amphiregulin expression in androgen-stimulated human prostate cancer cells

Amphiregulin is a heparin-binding epidermal growth factor (EGF)-related peptide that binds to the EGF receptor (EGF-R) with high affinity. In this study, we report a role for amphiregulin in androgen-stimulated regulation of prostate cancer cell growth. Androgen is known to enhance EGF-R expression in the androgen-sensitive LNCaP human prostate carcinoma cell line, and it has been suggested that androgenic stimuli may regulate proliferation, in part, through autocrine mechanisms involving the EGF-R. In this study, we demonstrate that LNCaP cells express amphiregulin mRNA and peptide and that this expression is elevated by androgenic stimulation. We also show that ligand-dependent EGF-R stimulation induces amphiregulin expression and that androgenic effects on amphiregulin synthesis are mediated through this EGF-R pathway. Parallel studies using the estrogen-responsive breast carcinoma cell line, MCF-7, suggest that regulation of amphiregulin by estrogen may also be mediated via an EGF-R pathway. In addition, heparin treatment of LNCaP cells inhibits androgen-stimulated cell growth further suggesting that amphiregulin can mediate androgen-stimulated LNCaP proliferation. Together, these results implicate an androgen-regulated autocrine loop composed of amphiregulin and its receptor in prostate cancer cell growth and suggest that the mechanism of steroid hormone regulation of amphiregulin synthesis may occur through androgen upregulation of the EGF-R and subsequent receptor-dependent pathways.

Effect of epidermal growth factor on prostate cancer cell line PC3 growth and invasion

Elevated levels of epidermal growth factor (EGF) and epidermal growth factor receptor (EGF-R) have been demonstrated in prostate cancer cell lines and clinical specimens suggesting a role for polypeptide growth factors in prostate tumor cell growth and invasion. To more clearly define the role of EGF in prostate cancer invasion, we undertook a series of studies utilizing the PC3 prostate cancer cell line, an aggressive, hormone-independent cell line derived from a metastatic lesion. No statistical differences were noted in the growth of PC3 cells under serum-free conditions when EGF (10(-10) M-10(-8) M) or monoclonal anti-EGF-R antibody (10(-11) M-10(-8) M) were added. Utilizing the Boyden chamber microinvasion assay, EGF supplemented cells demonstrated a statistically significant augmentation in invasion (P < 0.05) when compared to control cells at each time point in the study. With increasing length of exposure to EGF, the number of concentrations that produced significant invasion increased: day 1 (10(-8) M), day 3 (10(-8), 10(-9) M), and day 5 (10(-7), 10(-8), 10(-10) M). Northern blot analysis of EGF supplemented cells revealed an increase in expression of urokinase plasminogen activator (uPA) RNA, a serine protease involved in the regulation of pericellular proteolysis and membrane degradation. Protein analysis confirmed these findings. Statistically significant inhibition of invasion by anti-uPA antibodies was demonstrated for EGF-stimulated and PC3 control cells. Our results demonstrate that certain concentrations of EGF augment invasion in the PC3 cell line. This enhancement of invasion occurs in part by an overproduction of uPA, an extracellular protease. These findings suggest that the autocrine production of EGF may potentiate tumor cell invasion.

Effect of somatostatin analog RC-160 and bombesin/gastrin releasing peptide antagonist RC-3095 on growth of PC-3 human prostate-cancer xenografts in nude mice

Nude mice bearing xenografts of the androgen-independent human prostate-cancer cell line PC-3 were treated for 4 weeks with somatostatin analog RC-160, bombesin/gastrin-releasing peptide (GRP) antagonist (RC-3095), or the combination of both peptides. In the first experiment, treatment was started when the tumors measured approximately 10 mm3. Tumor volumes and weights were reduced by about 40% by RC-160 or RC-3095 administered by s.c. injections at doses of 100 micrograms/day/animal and 20 micrograms/day/animal respectively. The combination of RC-3095 with RC-160 did not further potentiate suppression of tumor growth, but histologically the ratio of apoptotic and mitotic indices was significantly higher in the groups treated with the combination than in the other groups. Serum gastrin levels were significantly reduced in all treated groups. Therapy with RC-160 or the combination also significantly decreased serum growth-hormone levels. Specific high-affinity binding sites for bombesin, somatostatin and epidermal growth factor (EGF) were found on the tumor membranes. Receptors for EGF were significantly down-regulated by treatment with RC-3095, RC-160 and a combination of both analogs. Tumors from mice treated with RC-160 showed a significant increase in maximal binding capacity for somatostatin as compared with control tumors, demonstrating the absence of down-regulation. In the second experiment, treatment was started when the tumors were well developed and measured approximately 90 mm3. No significant reduction in volume, weight and growth rate of tumors was found in the groups treated with RC-160 or RC-3095. Our results suggest that somatostatin analog RC-160 and bombesin/GRP antagonist RC-3095 can inhibit the growth of androgen-independent prostate cancer when the therapy is started at an early stage of tumor development.

Antagonists of bombesin/gastrin-releasing peptides as adjuncts to agonists of luteinizing hormone-releasing hormone in the treatment of experimental prostate cancer

BACKGROUND

Palliative methods for treatment of advanced prostatic carcinoma, including those based on luteinizing hormone-releasing hormone (LH-RH) agonists, cannot prevent the ultimate growth of hormone-independent cells, and the duration of disease remission in patients with prostate cancer is limited. New therapeutic approaches combining androgen ablation therapy with other compounds must be explored. Various studies suggest that bombesin or gastrin-releasing peptide (GRP) act as autocrine growth factors and may play a role in the initiation and progression of some cancers, including those of the prostate.

METHODS

The effects of treatment with bombesin/gastrin-releasing peptide (GRP) receptor antagonist [D-Tpi6, Leu13 psi(CH2NH)Leu14]BN(6-14)(RC-3095), an agonist of LH-RH [D-Lys6]-LH-RH and their combination were investigated in the androgen-dependent Dunning R-3327H rat prostate cancer model. Both analogs were administered by continuous subcutaneous infusion from osmotic minipumps for 7 weeks.

RESULTS

Tumor volumes and weights were significantly reduced by treatment with RC-3095, compared with those of controls. In rats that received [D-Lys6]-LH-RH, there was a greater decrease in tumor weight and volume than that produced by RC-3095, and the weights of testes, ventral prostate, and seminal vesicles also were reduced. The combination of RC-3095 and [D-Lys6]-LH-RH had the greatest inhibitory effect on tumor growth. Histologic parameters demonstrated a significant increase of the ratio of apoptotic to mitotic indices in the groups treated with [D-Lys6]-LH-RH or the combination. Serum LH and testosterone levels were greatly depressed by [D-Lys6]-LH-RH or the combination. Specific high-affinity binding sites for bombesin/GRP, epidermal growth factor (EGF), and insulin-like growth Factor I (IGF-I) were found on the tumor membranes. The concentration of receptors for EGF was significantly reduced by treatment with the bombesin/GRP antagonist RC-3095.

CONCLUSIONS

Combination therapy of LH-RH analogs with bombesin antagonists such as RC-3095 might be considered for improvement of hormonal therapy of prostate cancer.

Expression of mRNA for epidermal growth factor, transforming growth factor-alpha and their receptor in human prostate tissue and cell lines

Enhanced expression of the epidermal growth factor receptor (EGFR) or its ligands, epidermal growth factor (EGF) and transforming growth factor alpha (TGF-alpha) can increase signalling via receptor-mediated pathways which may lead to excessive proliferation and cellular transformation. Such autocrine regulation of growth has been demonstrated for prostate cancer cell lines in culture but its role in prostate cancer in vivo has not been established. To assess the potential of such a mechanism, we have examined the pathway components in prostate carcinomas (CaP) in comparison with non-malignant benign prostatic hyperplasias (BPH). In the present study, we investigate the dosage, structure and expression of EGF, TGF-alpha and EGFR genes in a series of 34 human prostate samples and 3 prostate cancer cell lines. All of the samples contained transcripts from each of the genes. The expression of pre-pro-TGF-alpha mRNA and pre-pro-EGF mRNA were significantly higher in CaP (n = 13) than BPH (n = 21) specimens (p < 0.05). The androgen-responsive prostatic carcinoma cell line, LNCaP, expressed high levels of EGF mRNA while the androgen-independent DU145 and PC-3 cell lines expressed high levels of TGF-alpha mRNA and EGFR mRNA. In general, overexpression of these mRNAs was not associated with amplification or detectable gene rearrangement; only DU145 cells demonstrated any alteration in these genes, with apparent amplification of the TGF-alpha gene. Relative to BPH, all prostate carcinomas and cell lines studied had elevated levels of mRNA for one or both mRNA coding for the ligands for EGFR.(ABSTRACT TRUNCATED AT 250 WORDS)

Growth factors and their receptors as determinants in the proliferation and metastasis of human prostate cancer

Prostate adenocarcinoma, the most common tumor occurring among North American men, preferentially metastasizes to bone, where it characteristically forms osteoblastic lesions. The following growth regulatory factors are expressed in some human prostate cancers and/or established cell lines: epidermal growth factor (EGF), transforming growth factor alpha, transforming growth factor beta, basic fibroblast growth factor (bFGF), and insulin-like growth factor. Some of these, especially EGF, bFGF, and TGF-beta, are also implicated in growth regulation in normal and benign hyperplastic prostates. Although evidence from in vitro study of the small number of prostate cell lines available demonstrates that these growth regulatory pathways are exploited by some of these cells, direct in vivo evidence is limited. The development of human prostate cancer cell lines which grow and metastasize in immune-deficient rodents is an advance which now permits experimental analysis of the role of these growth factors in prostatic metastasis, particularly to bone. The progression and metastasis of human prostate cancer results from the complex interactions of multiple growth factors, androgens, and cellular communication, which form a dynamic network. Continued progress in the study and treatment of this disease will require new conceptual frameworks as well as successful application of the techniques of molecular and cellular biology.

Immunohistochemical localization of epidermal growth factor and transforming growth factor alpha in the male rat accessory sex organs

We examined the presence of epidermal growth factor (EGF) and transforming growth factor alpha (TGF alpha) in the prostate (ventral, lateral, dorsal lobes), coagulating gland and seminal vesicle of Fisher 344 adult male rats by immunohistochemical and radioimmunoassay methods. Immunohistochemically demonstrable EGF was localized in the luminal secretion only of the dorsal lobe of the prostate. Reactive TGF alpha was localized in the lateral lobe (100% of epithelial cells), dorsal lobe (about 40% of the epithelial cells) and seminal vesicle (100% of epithelial cells), but not in the coagulating gland or ventral lobe of the prostate. Radioimmunoassay also demonstrated a measurable amount of TGF alpha in the lateral lobe (194 pg./gm. wet weight) and seminal vesicle (74 pg./gm.). Assayable EGF was demonstrated at much higher levels in all prostate lobes (ranging from 1.2 micrograms./gm. wet weight in the ventral lobe to 26.4 micrograms./gm. in the dorsal lobe) and wet weight in the ventral lobe to 26.4 micrograms./gm. in the dorsal lobe) and the seminal vesicle (0.9 micrograms./gm.). This is the first report describing the presence of immunoreactive TGF alpha and EGF in the male accessory sex organs.

Somatostatin analog RC-160 and bombesin/gastrin-releasing peptide antagonist RC-3095 inhibit the growth of androgen-independent DU-145 human prostate cancer line in nude mice

Nude mice bearing xenografts of the androgen-independent human prostate cancer DU-145 were treated for 4-5 weeks with somatostatin analog RC-160 or the bombesin/gastrin-releasing peptide (GRP) antagonist RC-3095. Tumor growth in animals treated with somatostatin analog RC-160 at a dose of 100 micrograms/day s.c. was significantly inhibited within 14 days of the start of the experiment. At necropsy, in mice given RC-160, tumor weight and volume were significantly decreased compared with control mice. Treatment with RC-3095 at a dose of 20 micrograms/day s.c. also suppressed tumor growth, the inhibition being significant after 2 weeks, but the reduction in tumor volume and weight was smaller than that produced by RC-160. Therapy with RC-160 significantly decreased serum growth hormone and gastrin levels. Specific binding sites for bombesin, somatostatin and epidermal growth factor (EGF) were found in the DU-145 tumor membranes. Receptors for EGF were significantly down-regulated after therapy with RC-3095 and RC-160. The finding that somatostatin analog RC-160 and bombesin/GRP antagonist RC-3095 inhibit the growth of androgen-independent prostate tumors in mice might be of practical importance for human prostate cancer therapy.

Epidermal growth factor in human breast cancer, endometrial carcinoma and lung cancer. Its relationship to epidermal growth factor receptor, estradiol receptor and tumor TNM

Epidermal growth factor (EGF) and its receptor (EGFR) were measured in 60 breast cancers (BC), 6 benign mammary tumors (BM), 8 samples of normal breast (NB), 6 endometrial carcinomas (EC) and 30 lung cancers (LC). EGF was measured in plasma, saliva and urine from 20 patients with BC, before and after tumor excision, and in 8 patients with metastatic disease. The median EGF in BM and BC was significantly higher (P < 0.05) than in NB. No significant correlation between EGF and EGFR was found in BC. Neither tumor excision nor the spreading of the disease significantly modified the EGF concentrations in biological fluids. In LC there was an inverse relationship between EGF and EGFR (rs = -0.36; P = 0.09), which disappeared in normal lung. It is concluded that EGF may play a role in malignant transformation; however, the weak correlation between EGF and EGFR lessens the importance of EGF in either autocrine or paracrine stimulation of tumor growth.

Effect of suramin on the mitogenic response of the human prostate carcinoma cell line PC-3

BACKGROUND

Suramin is an anthelmintic drug that recently has been shown to have clinical efficacy in the treatment of patients with some advanced malignancies, including prostate carcinoma. The current study was done to assess the effect of suramin at clinically relevant doses on the growth in culture of a human prostatic carcinoma cell line, PC-3.

METHODS

The antiproliferative effect of varying doses of suramin on PC-3 was assessed. Northern blot analysis was done to assess the potential changes in genetic expression at different times after the initiation of treatment.

RESULTS

Suramin inhibited the proliferation of PC-3 in a dose-related manner (concentration range, 30-300 microM). Compared with fetal calf serum 2%, when the cells were grown in fetal calf serum 10%, higher concentrations of suramin were required to inhibit tritiated thymidine incorporation. When grown in RPMI without supplement, the PC-3 cell number remained the same. When 100 microM suramin was included, the cell number decreased. By contrast, when RPMI was supplemented with insulin, transferrin, and selenium (ITS), PC-3 grew well. The inhibition of the proliferation of PC-3 cells by suramin was decreased when ITS were added to the cells grown under serum-free conditions.

CONCLUSIONS

These results were consistent with the hypothesis that in vitro inhibition of the growth of PC-3 cells by suramin may be caused, at least in part, by the growth factor antagonism of the drug. In fetal calf serum 2%, the suramin inhibition was reversible after 3 days. If the treatment was extended to 6 days, however, the PC-3 cells were unable to recover. Cell-cycle analysis revealed that, after 6 days of treatment, there was a decrease in the number of cells in G1 that corresponded with an increased number of cells in G2/M. This suggested that critical antineoplastic events were occurring during this time. Molecular analysis did not detect any altered expression of actin, transforming growth factors alpha or beta, or histone compared with untreated control samples.

Possible biological mechanisms for a relationship between vasectomy and prostatic cancer

Four hypotheses have been reviewed, each of which might serve as a hypothetical biological explanation for a relationship between vasectomy and prostate cancer. The endocrine hypothesis is the only one of these with any firm data to support it, although the majority of the available data does not lend credibility to that theory. The other hypotheses are purely speculative with no hard data to support them. In conclusion, it seems highly unlikely, but not impossible, that there is a biological mechanism supporting a relationship between vasectomy and prostate cancer.

Human primary prostate tumor cell line, ALVA-31: a new model for studying the hormonal regulation of prostate tumor cell growth

A new human prostate tumor cell line (ALVA-31) has been established from a biopsy specimen of primary tumor obtained during prostatectomy. The cell line has been maintained for more than 48 months in stable growth. The in vitro doubling time was determined to be approximately 26 hr. The chromosome number ranged from 24-112, with a modal number of 59 tested over several time points throughout continuous culture. Karyotypic analysis of late-passaged cells demonstrated approximately 70 human chromosomes, 8-14 markers, and two X chromosomes without a Y chromosome. Prostatic origin was confirmed by the expression of both prostate specific antigen and prostatic acid phosphatase, using specific antisera and immunoradiolabelling techniques. Prostate tumor xenografts were grown in intact male, castrate male, and female athymic mice; however, the rate of tumor growth was clearly dependent upon serum testosterone levels.

Genistein and biochanin A inhibit the growth of human prostate cancer cells but not epidermal growth factor receptor tyrosine autophosphorylation

The effect of the isoflavones, genistein, daidzein, and biochanin A on the growth of the LNCaP and DU-145 human prostate cancer cell lines has been examined. Genistein and biochanin A, but not daidzein, inhibit both serum and EGF-stimulated growth of LNCaP and DU-145 cells (IC50 values from 8.0 to 27 micrograms/ml for serum and 4.3 to 15 micrograms/ml for EGF), but have no significant effect of the EGF receptor tyrosine autophosphorylation. In contrast, tyrphostin 25, a specific EGF receptor tyrosine kinase inhibitor, inhibits EGF-stimulated growth and EGF receptor tyrosine autophosphorylation in these whole cells, but does not inhibit serum-stimulated growth. These data suggest that the mechanism of action of genistein and biochanin A does not depend on inhibition of EGF receptor tyrosine autophosphorylation, but on a more distal event in the EGF receptor-mediated signal transduction cascade.

Epidermal growth factor and transforming growth factor alpha concentrations in BPH and cancer of the prostate: their relationships with tissue androgen levels

We measured immunoreactive EGF and TGF alpha in prostate tissue extracts obtained from 19 patients with benign prostatic hyperplasia (BPH) and 19 with cancer of the prostate (CaP). Whilst both BPH and CaP expressed EGF (BPH = 195.61 +/- 19.94 ng g-1 protein; CaP = 235.60 +/- 24.45 ng g-1 protein) and TGF alpha (BPH = 92.57 +/- 7.60 ng g-1 protein; CaP = 100.73 +/- 15.47 ng g-1 protein) in equal concentrations, the levels of EGF in any tissue extract were on average twice those of TGF alpha. Furthermore analysis of the individual growth factor data revealed a direct correlation between EGF and TGF alpha in both BPH (r = 0.72, P < 0.001) and CaP (r = 0.69, P < 0.001). When the tumours were classified according to their Gleason score, a slight but significant increase in growth factor concentrations was noted as the tumour became less differentiated. We also measured the concentrations of testosterone and dihydrotestosterone (DHT) in prostate extracts with a view of elucidating the relationship between androgen and growth factors in this gland. There was a small positive correlation only between testosterone and EGF (r = 0.62, P < 0.05) and testosterone and TGF alpha (r = 0.61, P < 0.05) in CaP. The absence of any similar correlation in BPH where DHT becomes the predominant hormone may suggest an indirect role for testosterone in the regulation of growth factor production.

Dietary fat, fatty acids and prostate cancer

International comparisons suggest a relationship between prostate cancer incidence and dietary fat, an inference supported by migration studies, the changing incidence rates and levels of animal fat consumption in Japan and the results from some case-control studies. Overall, however, epidemiological studies have been inconclusive, and although prostate cancer is one of the hormone-dependent tumors, evidence of interactions between dietary fats and male endocrine function is incomplete. Laboratory experimentation has shown that n-6 fatty acids stimulate and n-3 fatty acids inhibit human prostate cancer cells in culture; also, feeding diets rich in marine oils suppresses growth of these cells as solid tumors in athymic nude mice. These growth effects of polyunsaturated fatty acids appear to involve both prostaglandins and leukotrienes and to interconnect with autocrine regulation by epidermal growth factor-related polypeptides.