Growth factor receptors and oncogene expression in prostate cells

Evaluating the effect of secretome of human amniotic mesenchymal stromal cells on apoptosis induction and epithelial-mesenchymal transition inhibition in LNCaP prostate cancer cells based on 2D and 3D cell culture models

Prostate cancer (PCa) is the second most prevalent cancer in men worldwide. Most cases of death from PCa are due to metastasis. Early stages of metastasis are mediated by epithelial-mesenchymal transition (EMT) process through which cancer cells acquire motility and invasive characteristics. Thus, more potent and novel therapeutic strategies must be designed based on the inhibition of EMT or metastasis. Herein, we employ a co-culture system to evaluate the anti-EMT effects of human amniotic mesenchymal stromal cells (hAMSCs) on LNCaP PCa cells. The RNA of treated (sample) and untreated cancer cells (control) and whole-cell lysates of related cells were prepared and analysed through quantitative real-time polymerase chain reaction (qRT-PCR) and western blot, respectively. Based on the results, the expression of vimentin, Snail and Zeb1 in LNCaP cells decreased and the expression of E-cadherin increased after treatment with hAMSCs. Furthermore, induction of the cellular apoptosis in LNCaP cells was detected. The anti-cancer activity of conditioned medium from hAMSCs was shown using hanging drop technique (a 3D cell culture model). Our findings support the idea that stem cells can be considered as a novel therapeutic approach to inhibit prostate cancer cells. SIGNIFICANCE OF THE STUDY: The anti-tumour activity of hAMSCs on LNCaP prostate cancer cells using 2D and 3D cell culture models via induction of apoptosis, suppression of EMT process and down-regulation of EGFR was shown. The results of the present study support this idea that hAMSCs may be a potent therapeutic tool to suppress tumour growth in LNCaP prostate cancer cells.

Association Study of Polymorphisms of Epidermal Growth Factor and Epidermal Growth Factor Receptor With Benign Prostatic Hyperplasia in a Korean Population

Purpose

Recent studies have suggested that specific single-nucleotide polymorphisms (SNPs) contribute to the clinical features of benign prostatic hyperplasia (BPH). In this study, we investigated the relationships of genetic polymorphisms of the epidermal growth factor (EGF) gene and the epidermal growth factor receptor (EGFR) gene with BPH.

Methods

A total of 218 patients with BPH were enrolled in this study. We evaluated the relationship between eight SNPs in the EGF and EGFR genes and prostate volume, prostate-specific antigen (PSA), and International Prostate Symptom Score of BPH patients. Each SNP was genotyped by direct sequencing. Statistical analysis applying codominant, dominant, recessive, and log-additive models was performed via logistic regression.

Results

The rs11568943 and rs11569017 SNPs in the EGF gene showed significant associations with prostate volume (rs11568943: P=0.038 in the log-additive model, P=0.024 in the allele distribution; rs11569017, P=0.031 in the dominant model, P=0.028 in the log-additive model, P=0.020 in the allele distribution). Additionally, the rs3756261, rs11568943, and rs11569017 SNPs of the EGF gene and the rs2293347 SNP of the EGFR gene were associated with PSA levels (P<0.05 in each model, respectively).

Conclusions

These results suggest that the EGF gene may affect prostate volume. In addition, the EGF and EGFR genes may be associated with PSA levels in patients with BPH.

Expression and clinical significance of epidermal growth factor receptor and insulin-like growth factor receptor 1 in patients with ampullary adenocarcinoma

Epidermal growth factor receptor (EGFR) and insulin-like growth factor receptor 1 (IGF-1R) play important roles in cell proliferation, antiapoptosis, angiogenesis, and metastasis and have been used for targeted therapies for patients with advanced colorectal and lung cancers. However, the expression and function of EGFR and IGF-1R in ampullary adenocarcinoma (AA) have not been examined in detail. We examined the expression of EGFR and IGF-1R in 106 AA patients at our institution using tissue microarrays and immunohistochemistry. The results were correlated with the clinicopathological parameters and survival. Overexpression of EGFR and IGF-1R was detected in 18 (17%) and 26 (25%) of AAs, respectively. Patients with EGFR-high tumors had shorter overall survival (mean, 109.8 ± 22.3 months) than those patients whose tumors were EGFR-low in overall study population (mean, 164.2 ± 10.6 months; P = .04). Overexpression of EGFR correlated with poor overall survival in patients with intestinal-type AA (P = .01) but not in those with pancreaticobiliary-type AAs (P = .47). In multivariate analysis, EGFR overexpression was an independent prognostic factor for overall survival (P = .02). In addition, we found that overexpression of IGF-1R correlated with AAs of pancreaticobiliary histology. No additional correlation between the expression of EGFR or IGF-1R and other clinicopathological factors was observed in our patient population. Our study demonstrates that EGFR and IGF-1R appear to be overexpressed in a subset of AAs and that strong membranous expression of EGFR is an independent predictor for overall survival in patients with AA. EGFR and IGF-1R represent potential therapeutic targets for treatment of patient with AAs.

Exogenous p27KIP1 expression induces anti-tumour effects and inhibits the EGFR/PI3K/Akt signalling pathway in PC3 cells

p27 is a cyclin-dependent kinase inhibitor that regulates the progression of cells from G(1) to S phase of the cell cycle. Loss of p27 has been associated with disease progression and with an unfavourable outcome in prostate cancer. In this study, we investigated whether exogenous p27 expression in the human androgen-independent prostate cancer PC3 cell line had any effect on cell growth, and we studied the molecular mechanisms involved. p27 expression was restored in PC3 cells by plasmid delivery. Cell proliferation and apoptosis were assessed in PC3 cells transfected with p27. We also investigated the effects of p27 on the epidermal growth factor receptor (EGFR)/phosphatidylinositol 3-kinase (PI3K)/Akt signalling pathway in PC3 cells. By restoring p27 expression in PC3 cells, we observed that p27 reduced proliferation and induced arrest in G(0)/G(1) phase. Moreover, p27-transfected PC3 cells underwent apoptosis, as shown by flow cytometric analysis and western blotting analysis of Bcl-2, Bax, Bad, caspase-3 and poly(ADP-ribose)polymerase expression. Furthermore, the p27-induced anti-tumour action correlated with inhibition of the EGFR/PI3K/Akt signalling pathway, as confirmed by western blotting analysis and densitometry of EGFR, PI3K (p85), Akt and p-Akt(S473) expression. Our results suggest that exogenous expression of p27 inhibits the proliferation of PC3 cells through induction of G(1) arrest and apoptosis, and this process correlates with inhibition of the EGFR/PI3K/Akt signalling pathway.

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.

Inhibition of EGFR signaling in human prostate cancer PC-3 cells by combination treatment with β-phenylethyl isothiocyanate and curcumin

Many naturally occurring compounds, including beta-phenylethyl isothiocyanate (PEITC) and curcumin, exhibit significant anti-cancer chemopreventive effects. In this study, we investigated the combined effects of PEITC and curcumin in PC-3 human prostate cancer cells and in PC-3 cells that were stably transfected with an NF-kappaB luciferase plasmid (PC-3 C4). We found an additive effect of PEITC and curcumin for the induction of apoptosis. To elucidate the potential mechanisms of this effect, we studied several critical cellular signaling pathways, including the critical NF-kappaB cell survival signal that is hyper-activated in PC-3 cells and many other cancers. PEITC and curcumin additively inhibited NF-kappaB luciferase activity. Furthermore, the combined treatment significantly increased the activity of poly(ADP-Ribose) polymerase and cleavage of caspase-3 in correlation with apoptotic cell death. Studying upstream signaling events, we found that the phosphorylations of IkappaBalpha and Akt (Ser473, Thr308) were significantly attenuated by the combination of PEITC and curcumin. As these events can be downstream of the activation of epidermal growth factor receptor (EGFR), we pretreated PC-3 cells with PEITC and curcumin and then stimulated them with EGF. EGFR phosphorylations (Y845 and Y1068) were dramatically suppressed by PEITC or curcumin, and more so by the combination. Importantly, the degree of Akt and PI3K phosphorylations induced by EGF were also significantly suppressed. We conclude that the simultaneous targeting of EGFR, Akt and NF-kappaB signaling pathways by PEITC and curcumin could be the molecular targets by which PEITC and curcumin exert their additive inhibitory effects on cell proliferation and ultimately lead to programmed cell death of tumor cells.

Epidermal growth factor receptor–related peptide inhibits growth of PC-3 prostate cancer cells

Interference with the activation of growth factor receptors, specifically epidermal growth factor receptor (EGFR), represents a promising strategy for the development of novel and selective anticancer therapies. We reported that EGFR-related peptide (ERRP), a recently isolated negative regulator of EGFR, could be a potential therapeutic agent for colorectal cancer. To determine whether ERRP could potentially be a therapeutic agent for prostate carcinoma, we examined the effect of recombinant ERRP on the growth of the prostate cancer cell line PC-3 in vitro. Events of the EGFR signal transduction pathways were also examined. ERRP caused a marked inhibition of cell growth in a dose- and time-dependent manner and also induced apoptosis. The latter was evidenced by increased number of apoptotic cells, activation of caspase-3, and cleavage of poly(ADP-ribose)polymerase. The transforming growth factor-α–induced stimulation of cell growth and activation of EGFR was also inhibited by ERRP. These changes were accompanied by a concomitant attenuation of activation of Akt and mitogen-activated protein kinases as well as basal and transforming growth factor-α–induced activation of nuclear factor-κB. Inhibition of EGFR activation by ERRP could be partly attributed to increased sequestration of EGFR ligands. In summary, our data show that ERRP inhibits the growth of prostate cancer cells by attenuating EGFR signaling processes. ERRP could potentially be an effective therapeutic agent for prostate cancer.

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.

Molecular and genetic mechanisms of prostate cancer

Prostate cancer is the most commonly diagnosed malignancy in American men and is the second leading cause of cancer death in males in the United States. Despite its high incidence, the molecular and genetic events involved in progression of prostate cancer remain poorly understood. In vitro models of human prostate epithelial (HPE) cells provide a practical approach to the analysis of the molecular and genetic mechanisms underlying prostate carcinogenesis. We reported the immortalization of normal adult HPE cells by transfection of the HPV-18 DNA and the subsequent conversion of such nontumorigenic but immortalized cells (HPV-18 C-1) into tumorigenic cells by the introduction of an activated Kras oncogene. Recently, we have demonstrated the malignant transformation of HPV-18 C-1 cells after multiple exposures to the chemical carcinogen N-nitroso-N-methylurea (NMU). Such transformants showed morphological alterations and anchorage-independent growth in soft agar and induced carcinomas when transplanted into nude mice. No TP53 or RAS mutations were observed. Stepwise chromosomal changes in the progression to tumorigenicity were observed. Loss of the p arms of chromosome 8 (p10>pter) and chromosome 10(p10>pter) and gain of the q arm of chromosome 8 (p10>ptr) (the most frequent cytogenetic changes observed directly in prostate cancer patients) were observed only in the tumor outgrowths. These findings provide the first evidence of malignant transformation of HPE cells exposed to a chemical carcinogen.

Evidence for the differential expression of a variant EGF receptor protein in human prostate cancer

Earlier studies have demonstrated an unexplained depletion of the epidermal growth factor receptor (EGFR) protein expression in prostatic cancer. We now attribute this phenomenon to the presence of a variant EGFR (EGFRvIII) that is highly expressed in malignant prostatic neoplasms. In a retrospective study, normal, benign hyperplastic and malignant prostatic tissues were examined at the mRNA and protein levels for the presence of this mutant receptor. The results demonstrated that whilst EGFRvIII was not present in normal prostatic glands, the level of expression of this variant protein increased progressively with the gradual transformation of the tissues to the malignant phenotype. The selective association of high EGFRvIII levels with the cancer phenotype underlines the role that this mutant receptor may maintain in the initiation and progression of malignant prostatic growth, and opens the way for new approaches in the management of this disease including gene therapy.

Androgenic and antiandrogenic control on epidermal growth factor, epidermal growth factor receptor, and androgen receptor expression in human prostate cancer cell line LNCaP

Both androgen and antiandrogen treatments enhance the proliferation rate of the hormone-dependent prostate cancer cell line LNCaP, expressing a mutated androgen receptor (AR). We studied the modification of the expression of epidermal growth factor (EGF), of its receptor (EGF-R), and of androgen receptor (AR) in the LNCaP cell line, under basal conditions and during androgen (R1881) and antiandrogen hydroxy-flutamide (OH-FLU) treatment. After prolonged R1881 administration, a marked increase of EGF release was observed, completely blocked by the addition of OH-FLU. The Scatchard plot analysis of EGF-R binding revealed two classes of binding sites with high and low affinity. The administration of OH-FLU alone or combined with R1881 did not modify the affinity constants, while the low-affinity component disappeared after androgen administration. Both androgen and antiandrogen administration led to a significant increase of the EGF-R high-affinity component. AR mRNA and protein levels were downregulated by R1881 treatment. Following OH-FLU administration, AR mRNA was slightly downregulated, and there was not a strict parallelism between AR mRNA levels and AR binding capacity. When combined with R1881, OH-FLU partially counteracted the androgen-induced AR downregulation. Our data show that EGF-R binding capacity is the only parameter constantly raised in cell proliferation with respect to quiescent cells, and highlights the nonunivocal action of OH-FLU on androgen-induced effects.

A phase I study of the somatostatin analogue somatuline in patients with metastatic hormone-refractory prostate cancer

BACKGROUND

Somatuline, a somatostatin analogue, has proven to be effective in several animal models of prostate cancer. Preliminary clinical studies also have suggested antitumor activity in patients with prostate cancer. The authors conducted a dose-escalation trial of 25 patients with metastatic hormone-refractory prostate cancer.

METHODS

Dosages of 4, 7, 10, 13, 18, and 24 mg/day were administered by continuous intravenous infusion for at least 28 days.

RESULTS

Plasma levels of insulin-like growth factor-I (IGF-I), but not those of IGF-II, declined modestly during therapy. Toxicities included grade I diarrhea, bloating, infection, nausea, and flatus. The gastrointestinal side effects were typically self-limiting and occurred during the initial portion of treatment cycles. In addition, three patients experienced grade II catheter-related infections. No clinical response was noted by either radiographic or tumor marker criteria. The maximally tolerated dose of somatuline was not determined.

CONCLUSION

A continuous intravenous infusion of 24 mg/day of somatuline is well tolerated and could be evaluated in other types of cancer or possibly in less advanced prostate cancer, but no clinical activity was noted at this dose in patients with advanced metastatic hormone-refractory prostate cancer.

Differential immunoreactivity of epidermal growth factor receptor in benign, dysplastic and malignant prostatic tissues

To investigate epidermal growth factor receptor (EGFr) presence in the prostate, monoclonal antibody (clone EGFR1) immunohistochemical examination of radical prostatectomy specimens was performed (n = 37). All prostatic specimens contained benign prostatic hyperplasia (BPH) and/or dysplasia (prostatic intraepithelial neoplasia or PIN), as well as prostatic carcinoma (CaP). Areas of dysplasia were further categorized as to the basal cell layer and the luminal cell area. BPH, PIN, and CaP tissues in each specimen were analyzed by a single observer and graded on a scale from 0-4+. Fifteen samples were also analyzed for EGFr content utilizing a Cell Analysis Systems (CAS 200) image cytometer. EGFr immunoreactivity of BPH basal cells was significantly higher than EGFr immunoreactivity in areas of CaP (p < 0.001). EGFr staining of BPH basal cells was also significantly higher than that seen in PIN luminal cells (p < 0.001). Immunoreactivity of EGFr in PIN basal cells was significantly higher than in PIN luminal cells (p < 0.001). EGFr staining of basal cells in BPH tissues was higher than that seen in the PIN basal cell layer but the difference was not statistically significant (p = 0.06). The amount of staining present in PIN luminal cells was also significantly greater than in CaP tissues (p = 0.002). Quantitative image analysis utilizing the CAS 200 image cytometer was performed on BPH and CaP areas exclusively. EGFr immunoreactivity in basal cells of the BPH tissues was significantly greater than that seen in CaP tissues (p < 0.001). The decreased EGFr immunoreactivity in CaP may reflect a differentiating role for EGFr in normal tissues. Loss of EGFr influence may be associated with an increased proliferative state in PIN and CaP. Destruction or alteration of the epidermal grwoth factor receptor by a protease, such as prostatic specific antigen, may also explain our findings. At the present time the meaning of the different amounts of EGFr in the various types of prostate tissues is unknown.

Insulin-like growth factor I: action and receptor characterization in human prostate cancer cell lines

The role of insulin-like growth factor I (IGF-I) in the growth and development of prostate cancer was studied using established human prostate cancer cell lines. Under steroid and growth factor-free culture conditions, IGF-I significantly stimulated the androgen-independent cell lines PC-3 and DU-145 to incorporate [3H]thymidine into DNA, while the androgen-dependent cell line, LNCaP, was not affected. However, in the presence of dihydrotestosterone (DHT), DNA synthesis of LNCaP cells was stimulated by IGF-I in a dose-dependent manner. None of the cell lines tested secreted an immunoreactive level of IGF-I into their conditioned medium. Characterization of receptors by ligand binding assays revealed that all prostate cancer cell lines tested express specific binding sites for IGF-I with similar dissociation constants (0.23-0.39 nM). Crosslinking studies supported the suggestion that 125I-IGF-I was bound to a receptor on these cells. The IGF-I receptor concentrations of androgen-independent cell lines were significantly higher than those of the androgen-dependent cell line. Androgen appeared to affect neither the expression of IGF-I receptors nor the secretion of IGF-I. The results suggest that IGF-I may play an important role in stimulating the growth and progression of prostate cancer.

The role of endocrine therapy in prostatic cancer

When judged by randomized clinical trial, current endocrine therapies offer symptomatic relief to prostatic cancer patients for an average period of 1-2 years following initiation of therapy. Medical castration with LHRH analogues is a safe and effective way of achieving 'castrate' levels of circulating androgens without the undesirable aspects of surgery. While there is some evidence for the value of combined therapies using these agents in combination with anti-androgens for 'total androgen blockade' in some patients, overall this approach has not been shown to offer advantages over castration, either surgical or medical, alone in controlled trials. Secondary endocrine therapy does not offer convincing objective response rates, suggesting that disease progression is independent of androgens.