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

Effect of Ketogenic Diets on Cardio-Metabolic Outcomes in Cancer Patients: A Systematic Review and Meta-Analysis of Controlled Clinical Trials

In this systematic review and meta-analysis of clinical controlled trials (CCTs) we aimed to investigate the efficacy of KDs as an adjuvant therapy on cardiometabolic outcomes in patient with cancer compared to conventional non-ketogenic diets. Only CCTs involving cancer patients that were assigned to either a KD or a standard diet control group were selected. Two reviewers independently extracted the data, and a meta-analysis was performed using a random effects model to estimate weighted mean differences (WMDs) and confidence intervals (CIs) in body composition, metabolite, lipid profile, liver and kidney function parameters and quality of life. This meta-analysis showed a significant reduction in body weight (WMD= -2.99 kg; 95% CI: -4.67, -1.31; and P < 0.001), BMI (WMD= -1.08 kg/m²; 95% CI: -1.81, -0.34; P ≤ 0.002) and fat mass (WMD= -1.48 kg; 95% CI: -2.56, -0.40; and P = 0.007) by a KD. KDs significantly decreased glucose (WMD= -5.22 mg/dl; 95% CI: -9.0, -1.44; and P = 0.007), IGF-1 (WMD= -17.52 ng/ml; 95% CI: -20.24, -14.8; and P ˂0.001) and triglyceride (WMD= -24.46 mg/dl; 95% CI: -43.96, -4.95; and P = 0.014) levels. Furthermore, KDs induced ketosis by increasing β-hydroxybutyrate (WMD= 0.56 mmol/l; 95% CI: 0.37, 0.75; and P < 0.001). There were non-significant pooled effects of KDs on improving insulin, C-reactive protein and cholesterol levels and kidney and liver function. Emotional functioning was even increased significantly in the KD compared to the SD groups. In summary we found that KDs result in a greater reduction in glucose, IGF-1, triglycerides, body weight, BMI, and fat mass in cancer patients compared to traditional non-ketogenic diets and improved emotional functioning. The quality of evidence in the meta-analysis was moderate according to the Nutrigrade assessment.

Selective targeting of the androgen receptor-DNA binding domain by the novel antiandrogen SBF-1 and inhibition of the growth of prostate cancer cells

Prostate cancers are reliant on androgens for growth and survival. Clinicians and researchers are looking for potent treatments for the resistant forms of prostate cancer; however, a handful of small molecules used in the treatment of castration-resistant prostate cancer have not shown potent effects owing to the mutations in the AR (Androgen Receptor). We used SBF-1, a well-characterized antitumor agent with potent cytotoxic effects against different kinds of cancers and investigated its effect on human prostate cancer. SBF-1 substantially inhibited the proliferation, induced apoptosis, and caused cell cycle arrest in LNCaP and PC3/AR⁺ prostate cancer cell lines. SBF-1 inhibited the activation of the IGF-1-PNCA pathway, as demonstrated by decreased expression of IGF-1 (insulin-like growth factor 1), proliferating cell nuclear antigen (PCNA), and its downstream Bcl-2 protein. Using microscale thermophoresis (MST) and isothermal titration calorimetry (ITC) assays, we observed a direct binding of SBF-1 to the AR. SBF-1 binds to the AR-DBD (DNA-binding domain) and blocks the transcription of its target gene. SBF-1 demonstrated a potent antitumor effect in vivo; it inhibited AR signaling and suppressed tumor growth in animals. Our study suggests that SBF-1 is an inhibitor of the AR and might be used in the treatment of prostate cancer.

Role of αVβ3 in Prostate Cancer: Metastasis Initiator and Important Therapeutic Target

In prostate cancer, distant organ metastasis is the leading cause of patient death. Although the mechanism of malignant tumor metastasis is unclear, studies have confirmed that integrin αVβ3 plays an important role in this process. In prostate cancer, αVβ3 mediates adhesion, invasion, immune escape and neovascularization through interactions with different ligands. Among these ligands and in addition to proteins that are directly related to tumor invasion, other proteins that contain the RGD structure could also bind to αVβ3 and cause a number of biological effects. In this article, we summarized the ligand and downstream proteins related to αVβ3-mediated prostate cancer metastasis as well as some diagnostic and therapeutic measures targeting αVβ3.

Biochemical Characteristics and Recent Biological Knowledge on Prostate-Specific Antigen

Since its identification in seminal fluid in 1971, much new information has been obtained about the biology and expression of prostate-specific antigen (PSA). PSA is a glycoprotein composed of 93% amino acids and 7% carbohydrates, with a molecular weight of about 30,000 Da. Functionally and structurally PSA is a kallikrein-like serine protease, and its physiologic role is degradation of the major proteins of seminal coagulum (semenogelin I and II, fibronectin), which leads to semen liquefaction. The PSA gene is located on the 13q region of chromosome 19, and it has a high degree of homology (more than 80%) with genes of the human glandular kallikrein (hKGK1). PSA production and expression are preferentially but not exclusively associated to the normal, benign hyperplastic and cancerous tissues of the prostate. In fact, it has been demonstrated that PSA is also present in accessory male sex glands and breast cancer. It was recently reported that PSA was also present in milk of lactating women. Many factors may influence PSA synthesis and production, and among them the most important are androgen, retinoic acid and growth factor stimulation. Significant advances have been recently made as regards the molecular isoforms of PSA. In the seminal fluid PSA seems partially bound to a serpine (protein C inhibitor), whereas in serum it is predominantly associated to α-1-antichymotrypsin and in a small quantity to α-2-macroglobulin. These new findings will have implications for the clinical application of PSA as a tumor marker for prostate cancer.

Type I insulin-like growth factor receptor signaling in hematological malignancies

The insulin-like growth factor (IGF) signaling system plays key roles in the establishment and progression of different types of cancer. In agreement with this idea, substantial evidence has shown that the type I IGF receptor (IGF-IR) and its primary ligand IGF-I are important for maintaining the survival of malignant cells of hematopoietic origin. In this review, we discuss current understanding of the role of IGF-IR signaling in cancer with a focus on the hematological neoplasms. We also address the emergence of IGF-IR as a potential therapeutic target for the treatment of different types of cancer including plasma cell myeloma, leukemia, and lymphoma.

Fortifying the Treatment of Prostate Cancer with Physical Activity

Over the past decade, significant data have shown that obese men experience a survival detriment after treatment for prostate cancer. While methods to combat obesity are of utmost importance for the prostate cancer patient, newer data reveal the overall metabolic improvements that accompany increased activity levels and intense exercise beyond weight loss. Along these lines, a plethora of data have shown improvement in prostate cancer-specific outcomes after treatment accompanied with these activity levels. This review discusses the metabolic mechanisms in which increased activity levels and exercise can help improve both outcomes for men treated for prostate cancer while lowering the side effects of treatment.

Inhibition of IGF-1R diminishes transcriptional activity of the androgen receptor and its constitutively active, C-terminally truncated counterparts Q640X and AR-V7

PURPOSE

Failure of endocrine treatment in castration-resistant prostate cancer (CRPC) is often associated with the emergence of C-terminally truncated androgen receptor variants that function as constitutively active transcription factors (i.e., AR∆LBD). The mechanisms involved in the regulation of AR∆LBD signaling are largely unknown. Since the IGF-1 pathway was repeatedly shown to affect AR function, we studied whether an inhibition of IGF-1R could also affect AR∆LBD signaling.

METHODS

Regulation of androgen receptor (AR) and AR∆LBD signaling was analyzed by reporter gene assays, immunoblotting, ELISA and quantitative RT-PCR.

RESULTS

Inhibition of IGF-1R with the small-molecule inhibitor NVP-AEW541 reduced the transcriptional activity of the AR and its truncated counterparts Q640X and AR-V7. As shown in Q640X, the inhibition of transcriptional activity was paralleled by a decreased receptor phosphorylation.

CONCLUSIONS

Inhibition of IGF-1R leads to a down-regulation of AR∆LBD signaling and provides a rationale for CRPC therapies targeting growth factor receptors.

Dietary carbohydrate and prostate cancer risk: a meta-analysis

Carbohydrate intake has been inconsistently associated with risk of prostate cancer. We review and quantitatively summarize the evidence from observational studies in a meta-analysis. We searched the PubMed database for observational studies related to the association of carbohydrate intake and prostate cancer risk up to December 25, 2013. Summary relative risks (RRs) were estimated by the use of a random effects model. We included 13 case-control studies with 4,367 cases and 6,205 controls, and 5 cohort studies with 3,679 cases and 74,115 participants in this meta-analysis. The summary RR of prostate cancer for the highest vs. the lowest carbohydrate intake was 1.06 [95% confidence interval (CI): 0.93-1.20, I(2) = 46.8%] for all included studies. In the subgroup analyses stratified by study design, the summary RRs for the highest vs. the lowest carbohydrate intake were 1.04 (95% CI: 0.87-1.23) for case-control studies and 1.06 (95% CI: 0.88-1.28) for cohort studies. For the 5 studies that reported results for advanced prostate cancer, the summary RR was 0.92 (95% CI: 0.71-1.20). This meta-analysis of observational studies indicates that there is no association between carbohydrate intake and prostate cancer risk. Further studies are needed to confirm our findings.

Insulin-Like growth factor 1 related pathways and high-fat diet promotion of transgenic adenocarcinoma mouse prostate (TRAMP) cancer progression

INTRODUCTION

We aimed to investigate the role of IGF-1 related pathway in high-fat diet (HFD) promotion of TRAMP mouse PCa progression.

METHODS

TRAMP mice were randomly divided into two groups: HFD group and normal diet group. TRAMP mice of both groups were sacrificed and sampled on the 20th, 24th and 28th week respectively. Serum levels of insulin, IGF-1 and IGF-2 were tested by ELISA. Prostate tissue of TRAMP mice was used for both HE staining and immunohistochemical staining of IGF-1 related pathway proteins, including IGF-1Rα, IGF -1Rβ, IGFBPs and AKT.

RESULTS

The mortality of TRAMP mice from HFD group was significantly higher than that of normal diet group (23.81% and 7.14%, p=.035). The tumor incidence of HFD TRAMP mice at 20(th) week was significantly higher than normal diet group (78.57% and 35.71%, p=.022). Serum IGF-1 level of HFD TRAMP mice was significantly higher than that of normal diet TRAMP mice. Serum IGF-1 level tended to increase with HFD TRAMP mice's age. HFD TRAMP mice had higher positive staining rate of IGF-1Rα, IGF-1Rβ, IGFBP3 and Akt than normal diet TRAMP mice.

CONCLUSIONS

IGF-1 related pathway played an important role in high-fat diet promotion of TRAMP mouse PCa development and progression.

Targeting the IGF-1R: The Tale of the Tortoise and the Hare

The insulin-like growth factor type 1 receptor (IGF-1R) plays a key role in the development and maintenance of cancer. Since the first links between growth factor receptors and oncogenes were noted over three decades ago, targeting the IGF-1R has been of great interest. This review follows the progress from inception through intense pharmaceutical development, disappointing clinical trials and recent updates to the signaling paradigm. In light of major developments in signaling understanding and activation complexities, we examine reasons for failure of first line targeting approaches. Recent findings include the fact that the IGF-1R can signal in the absence of the ligand, in the absence of kinase activity, and utilizes components of the GPCR system. With recognition of the unappreciated complexities that this first wave of targeting approaches encountered, we advocate re-recognition of IGF-1R as a valid target for cancer treatment and look to future directions, where both research and pharmaceutical strengths can lend themselves to finally unearthing anti-IGF-1R potential.

Targeted prodrug approaches for hormone refractory prostate cancer

Due to the propensity of relapse and resistance with prolonged androgen deprivation therapy (ADT), there is a growing interest in developing non-hormonal therapeutic approaches as alternative treatment modalities for hormone refractory prostate cancer (HRPC). Although the standard treatment for HRPC consists of a combination of ADT with taxanes and anthracyclines, the clinical use of chemotherapeutics is limited by systemic toxicity stemming from nondiscriminatory drug exposure to normal tissues. In order to improve the tumor selectivity of chemotherapeutics, various targeted prodrug approaches have been explored. Antibody-directed enzyme prodrug therapy (ADEPT) and gene-directed enzyme prodrug therapy (GDEPT) strategies leverage tumor-specific antigens and transcription factors for the specific delivery of cytotoxic anticancer agents using various prodrug-activating enzymes. In prostate cancer, overexpression of tumor-specific proteases such as prostate-specific antigen (PSA) and prostate-specific membrane antigen (PSMA) is being exploited for selective activation of anticancer prodrugs designed to be activated through proteolysis by these prostate cancer-specific enzymes. PSMA- and PSA-activated prodrugs typically comprise an engineered high-specificity protease peptide substrate coupled to a potent cytotoxic agent via a linker for rapid release of cytotoxic species in the vicinity of prostate cancer cells following proteolytic cleavage. Over the past two decades, various such prodrugs have been developed and they were effective at inhibiting prostate tumor growth in rodent models; several of these prodrug approaches have been advanced to clinical trials and may be developed into effective therapies for HRPC.

SOCS2 mediates the cross talk between androgen and growth hormone signaling in prostate cancer

Anabolic signals such as androgens and the growth hormone/insulin-like growth factor 1 (GH/IGF-1) axis play an essential role in the normal development of the prostate but also in its malignant transformation. In this study, we investigated the role of suppressor of cytokine signaling 2 (SOCS2) as mediator of the cross talk between androgens and GH signals in the prostate and its potential role as tumor suppressor in prostate cancer (PCa). We observed that SOCS2 protein levels assayed by immunohistochemistry are elevated in hormone therapy-naive localized prostatic adenocarcinoma in comparison with benign tissue. In contrast, however, castration-resistant bone metastases exhibit reduced levels of SOCS2 in comparison with localized or hormone naive, untreated metastatic tumors. In PCa cells, SOCS2 expression is induced by androgens through a mechanism that requires signal transducer and activator of transcription 5 protein (STAT5) and androgen receptor-dependent transcription. Consequentially, SOCS2 inhibits GH activation of Janus kinase 2, Src and STAT5 as well as both cell invasion and cell proliferation in vitro. In vivo, SOCS2 limits proliferation and production of IGF-1 in the prostate in response to GH. Our results suggest that the use of GH-signaling inhibitors could be of value as a complementary treatment for castration-resistant PCa.

SUMMARY

Androgen induced SOCS2 ubiquitin ligase expression and inhibited GH signaling as well as cell proliferation and invasion in PCa, whereas reduced SOCS2 was present in castration-resistant cases. GH-signaling inhibitors might be a complementary therapeutic option for advanced PCa.

Diabetes mellitus and prostate cancer risk of different grade or stage: a systematic review and meta-analysis

AIM

Prior studies have reported that diabetes mellitus might reduce the overall prostate cancer risk. We examined this association by conducting a detailed meta-analysis of the studies published in peer-reviewed literature on the association between diabetes mellitus and prostate cancer risk of different stage or grade.

METHODS

A comprehensive search for articles of MEDLINE and EMBASE databases and bibliographies of retrieved articles published up to October 23, 2012 was performed. Methodological quality assessment of the trials was based on the Newcastle-Ottawa Scale. Meta-analysis was performed using STATA 12.0.

RESULTS

We included 9 studies in the meta-analysis (5 studies examining the relation of different stage only, 2 studies for grade only, and 2 studies for both grade and stage), and found an inverse association between diabetes mellitus and prostate cancer of different stage or grade. The relative risk (RRs) was moderately stronger for low grade (RR 0.74, 95% confidence interval (CI), 0.64-0.86) and localized disease (RR 0.72, 95% CI 0.67-0.76) compared with high grade (RR 0.78, 95% CI 0.67-0.90) and advanced disease (RR 0.85, 95% CI 0.75-0.97).

CONCLUSION

This study suggests an inverse relationship between diabetes mellitus and prostate cancer of different stage or grade. Possible biases underlying this association are discussed.

Dietary intakes of carbohydrates in relation to prostate cancer risk: a prospective study in the Malmö Diet and Cancer cohort

BACKGROUND

Dietary carbohydrates have been implicated in relation to prostate cancer.

OBJECTIVE

Our objective was to examine the associations between dietary intakes of carbohydrates, fiber, and their food sources and risk of prostate cancer, overall and by case severity, in the Malmö Diet and Cancer cohort.

DESIGN

The analysis included 8128 men aged 45-73 y without a history of cancer, cardiovascular disease, or diabetes and who were classified as adequate energy reporters. After a median follow-up time of 15 y, prostate cancer was diagnosed in 817 men. We used Cox proportional hazards regression to model associations between energy-adjusted nutrient and food intakes with risk of incident prostate cancer, with competing risk of death from non-prostate cancer causes taken into account.

RESULTS

After adjustment for age and other known or potential risk factors, we observed no associations between total carbohydrates or dietary fiber and prostate cancer. We observed positive associations between the intake of low-fiber cereals with overall and low-risk prostate cancer and between intakes of cake and biscuits and rice and pasta with low-risk prostate cancer (all P-trend < 0.05). A high intake compared with zero consumption of sugar-sweetened beverages was associated with increased risk of symptomatic prostate cancer (HR: 1.38; 95% CI: 1.04, 1.84).

CONCLUSIONS

Results from this large study with high-validity dietary data suggest that a high intake of refined carbohydrates may be associated with increased risk of prostate cancer. However we observed no significant associations with high-risk prostate cancer, and not all foods that are typically high in refined carbohydrates were associated with prostate cancer.

Effect of a low-fat diet combined with IGF-1 receptor blockade on 22Rv1 prostate cancer xenografts

In preclinical models, both dietary fat reduction and insulin-like growth factor I receptor (IGF-1R) blockade individually inhibit prostate cancer xenograft growth. We hypothesized that a low-fat diet combined with IGF-1R blockade would cause additive inhibition of prostate cancer growth and offset possible untoward metabolic effects of IGF-1R blockade antibody therapy. Fifty severe combined immunodeficient mice were injected with 22Rv1 cells subcutaneously. Ten days postinjection, the animals were randomized to four groups: (i) high-fat diet + saline (HF); (ii) high-fat diet + IGF-1R blocking antibody, ganitumab (HF/Ab); (iii) low-fat diet + saline (LF); and (iv) low-fat diet + ganitumab (LF/Ab). After 19 days of treatment, the animals were euthanized, serum was collected, and tumors were weighed. Tumor Ki67, Akt and extracellular signal-regulated kinase (ERK) activation, serum insulin, IGF-I and TNF-α were measured. In vitro, ganitumab treatment inhibited growth and induced apoptosis in several prostate cancer cell lines. In vivo, tumor weights and volumes were unaffected by the different treatments. The LF/Ab therapy significantly reduced proliferation (Ki67) and ERK activation in tumors. The HF/Ab group had significantly higher serum insulin levels than the HF group. However, LF/Ab combination significantly reduced serum insulin back to normal levels as well as normalizing serum TNF-α level. Whereas the combination of low-fat diet and IGF-1R blockade did not have additive inhibitory effects on tumor weight, it led to reduced tumor cell proliferation and a reduction in serum insulin and TNF-α levels.

Human periprostatic adipose tissue promotes prostate cancer aggressiveness in vitro

Background

Obesity is associated with prostate cancer aggressiveness and mortality. The contribution of periprostatic adipose tissue, which is often infiltrated by malignant cells, to cancer progression is largely unknown. Thus, this study aimed to determine if periprostatic adipose tissue is linked with aggressive tumor biology in prostate cancer.

Methods

Supernatants of whole adipose tissue (explants) or stromal vascular fraction (SVF) from paired fat samples of periprostatic (PP) and pre-peritoneal visceral (VIS) anatomic origin from different donors were prepared and analyzed for matrix metalloproteinases (MMPs) 2 and 9 activity. The effects of those conditioned media (CM) on growth and migration of hormone-refractory (PC-3) and hormone-sensitive (LNCaP) prostate cancer cells were measured.

Results

We show here that PP adipose tissue of overweight men has higher MMP9 activity in comparison with normal subjects. The observed increased activities of both MMP2 and MMP9 in PP whole adipose tissue explants, likely reveal the contribution of adipocytes plus stromal-vascular fraction (SVF) as opposed to SVF alone. MMP2 activity was higher for PP when compared to VIS adipose tissue. When PC-3 cells were stimulated with CM from PP adipose tissue explants, increased proliferative and migratory capacities were observed, but not in the presence of SVF. Conversely, when LNCaP cells were stimulated with PP explants CM, we found enhanced motility despite the inhibition of proliferation, whereas CM derived from SVF increased both cell proliferation and motility. Explants culture and using adipose tissue of PP origin are most effective in promoting proliferation and migration of PC-3 cells, as respectively compared with SVF culture and using adipose tissue of VIS origin. In LNCaP cells, while explants CM cause increased migration compared to SVF, the use of PP adipose tissue to generate CM result in the increase of both cellular proliferation and migration.

Conclusions

Our findings suggest that the PP depot has the potential to modulate extra-prostatic tumor cells' microenvironment through increased MMPs activity and to promote prostate cancer cell survival and migration. Adipocyte-derived factors likely have a relevant proliferative and motile role.

Risk factors for the onset of prostatic cancer: age, location, and behavioral correlates

At present, only three risk factors for prostate cancer have been firmly established; these are all nonmodifiable: age, race, and a positive family history of prostate cancer. However, numerous modifiable factors have also been implicated in the development of prostate cancer. In the current review, we summarize the epidemiologic data for age, location, and selected behavioral factors in relation to the onset of prostate cancer. Although the available data are not entirely consistent, possible preventative behavioral factors include increased physical activity, intakes of tomatoes, cruciferous vegetables, and soy. Factors that may enhance prostate cancer risk include frequent consumption of dairy products and, possibly, meat. By comparison, alcohol probably exerts no important influence on prostate cancer development. Similarly, dietary supplements are unlikely to protect against the onset of prostate cancer in healthy men. Several factors, such as smoking and obesity, show a weak association with prostate cancer incidence but a positive relation with prostate cancer mortality. Other factors, such as fish intake, also appear to be unassociated with incident prostate cancer but show an inverse relation with fatal prostate cancer. Such heterogeneity in the relationship between behavioral factors and nonadvanced, advanced, or fatal prostate cancers helps shed light on the carcinogenetic process because it discerns the impact of exposure on early and late stages of prostate cancer development. Inconsistent associations between behavioral factors and prostate cancer risk seen in previous studies may in part be due to uncontrolled detection bias because of current widespread use of prostate-specific antigen testing for prostate cancer, and the possibility that certain behavioral factors are systematically related to the likelihood of undergoing screening examinations. In addition, several genes may modify the study results, but data concerning specific gene-environment interactions are currently sparse. Despite large improvements in our understanding of prostate cancer risk factors in the past two decades, present knowledge does not allow definitive recommendations for specific preventative behavioral interventions.

Attenuation of IGF-I receptor signaling inhibits serum-induced proliferation of prostate cancer cells

OBJECTIVE

Several studies showed that high serum levels of insulin-like growth factor-I (IGF-I) correlate with an increased risk for prostate cancer, although the causal role of IGF-I remains to be established. In this study, we addressed the role of IGF-I as a serum factor on the growth of two androgen-independent cell lines (Du145 and PC3) and one androgen-dependent cell line (LNCaP).

DESIGN

We investigated the effects of a blocking antibody against the IGF-I receptor (αIR3) on DNA synthesis in prostate cancer cells cultured in the presence of recombinant human IGF-I or normal human serum (NHS).

RESULTS

We show that in all three prostate cancer cell lines, NHS exerts a markedly stronger stimulating effect on DNA synthesis than IGF-I, and that the effect of NHS can be completely abrogated by an antibody against the IGF-I receptor (αIR3). Using pharmacological inhibitors of the two canonical IGF-I receptor signaling pathways, we show that the phosphatidylinositol-3'-kinase (PI3K) and the Mek-Erk pathways are not required for the stimulating effect of NHS.

CONCLUSION

Our observations indicate that the stimulating effect of NHS is completely dependent on IGF-I receptor signaling transduction and that IGF-I stimulates DNA synthesis in prostate cancer cells in strong synergy with other serum factors. We speculate that the role of other serum factors could explain the discrepancy between the results observed in different animal models to study the function of IGF-I in prostate cancer.

Endoglin regulates cancer-stromal cell interactions in prostate tumors

Endoglin is an accessory receptor for TGF-β that has been implicated in prostate cancer cell detachment, migration, and invasiveness. However, the pathophysiologic significance of endoglin with respect to prostate tumorigenesis has yet to be fully established. In this study, we addressed this question by investigation of endoglin-dependent prostate cancer progression in a TRAMP (transgenic adenocarcinoma mouse prostate) mouse model where endoglin was genetically deleted. In this model, endoglin was haploinsufficient such that its allelic deletion slightly increased the frequency of tumorigenesis, yet produced smaller, less vascularized, and less metastatic tumors than TRAMP control tumors. Most strikingly, TRAMP:eng(+/-)-derived tumors lacked the pronounced infiltration of carcinoma-associated fibroblasts (CAF) that characterize TRAMP prostate tumors. Studies in human primary prostate-derived stromal cells (PrSC) confirmed that suppressing endoglin expression decreased cell proliferation, the ability to recruit endothelial cells, and the ability to migrate in response to tumor cell-conditioned medium. We found increased levels of secreted insulin-like growth factor-binding proteins (IGFBP) in the conditioned medium from endoglin-deficient PrSCs and that endoglin-dependent regulation of IGFBP-4 secretion was crucial for stromal cell-conditioned media to stimulate prostate tumor cell growth. Together, our results firmly establish the pathophysiologic involvement of endoglin in prostate cancer progression; furthermore, they show how endoglin acts to support the viability of tumor-infiltrating CAFs in the tumor microenvironment to promote neovascularization and growth.

Clinical outcomes after radical prostatectomy in diabetic patients treated with metformin

OBJECTIVES

To investigate the relationship between diabetes and metformin use with outcomes after radical prostatectomy (RP) for clinically localized cancer.

METHODS

A total of 112 diabetic metformin users and 98 diabetic non-metformin users treated with RP from 1990 to 2009 were identified. Nondiabetic controls were match using their 5-year risk of biochemical recurrence (BCR) as calculated by the preoperative Kattan nomogram.

RESULTS

A total of 616 patients were evaluated in this study. There was no significant difference between nondiabetic and diabetic patients, including metformin users, with respect to age, clinical stage, preoperative prostate-specific antigen (PSA) score, pathologic Gleason score, and pathologic stage. Diabetic patients, including metformin users, were more likely to be of African American or Hispanic background than were nondiabetic controls (P = .001). The estimated 5-year BCR-free survival was 75.0% for nondiabetic patients, compared with 66.1% for metformin users and 59.3% for diabetic non-metformin users (P = .004). In multivariate analysis, metformin use was not significantly associated with risk of BCR (HR = 0.94; 95% CI = 0.6-1.5, P = .817). However, being diabetic, regardless of metformin use, resulted in a 55% increase in risk of BCR (HR = 1.55; 95% CI = 1.03-2.33, P = .034).

CONCLUSIONS

Diabetes, regardless of metformin use, was significantly associated with an increased likelihood of BCR after RP. Metformin use did not prove to be of any benefit. These observations underscore the importance for further studies evaluating the metabolic pathways that affect prostate cancer biology.

Serial analysis of resected prostate cancer suggests up-regulation of type 1 IGF receptor with disease progression

OBJECTIVE

• To compare immunostaining protocols using different antibodies for the type 1 insulin-like growth factor receptor (IGF-1R) in channel transurethal resection of the prostate (chTURP) chips, and to investigate how IGF-1R expression varies with time in serial prostate cancer specimens from individual patients.

METHODS

• We studied IGF-1R expression in 44 prostate cancer specimens from 18 patients who had undergone serial chTURP at least 3 months apart. • Retrospective analysis of the hospital notes was undertaken to obtain clinical information, including age, Gleason score, prostate-specific antigen (PSA) level, hormone treatment and metastatic disease status at the time of each operation. • After an optimization process using three commercially-available IGF-1R antibodies, we used two antibodies for semiquantititve immunostaining of serial chTURP chips.

RESULTS

• Santa Cruz antibody sc713 gave positive staining in IGF-1R null R- cells, and was not used further. Antibodies from Cell Signaling Technology (Beverly, MA, USA) (CS) and NeoMarkers Inc. (Fremont, CA, USA) (NM) did not stain R- cells and, in prostate tissue, showed staining of the glandular epithelium, with negligible stromal staining. All 44 chTURP samples contained identifiable malignant tissue and, of these, 73% and 64% scored moderately or strongly (score 3 or 4) with the CS and NM antibodies respectively. • There was significant correlation of IGF-1R scores of malignant tissue between the two antibodies (P < 0.001). By contrast, staining of benign glands showed poor correlation between antibodies: CS gave significantly weaker staining than malignant epithelium in the same sections (P < 0.001), whereas NM showed poor discrimination between malignant and benign glands. IGF-1R staining scores generated by the CS antibody were used to analyze the clinical data. • Most patients (six of seven) with falling IGF-1R staining scores were responding to androgen deprivation therapy (confirmed by PSA response) between operations. Conversely, in seven of eight patients who had progression to androgen-independence between procedures, IGF-1R levels increased or remained high. Finally, seven of 11 patients who developed radiologically confirmed metastases between procedures showed stable or increasing IGF-1R staining scores.

CONCLUSION

• The present study is the first to assess changes in IGF-1R expression in serial prostate cancer samples. The results obtained indicate that IGF-1R expression usually remains high throughout the course of histologically-proven disease progression in serial specimens, suggesting that the IGF-1R remains a valid treatment target for advanced prostate cancer.

Prostate-specific antigen: an overlooked candidate for the targeted treatment and selective imaging of prostate cancer

The role of prostate-specific antigen (PSA) or kallikrein-related peptidase 3 (KLK3) as a biomarker for prostate cancer is well known; however, the precise physiological role of it's serine protease activity in prostate cancer remains a mystery. PSA is produced at high levels by both androgen-dependent and -independent prostate cancers. Studies have documented high levels of active PSA in the milieu surrounding osseous and soft tissue metastases. This evidence, coupled with growing experimental evidence, suggests that PSA plays an important role in the pathobiology of prostate cancer. These observations support the development of PSA-selective inhibitors as useful tools for the targeted treatment and imaging of prostate cancer. Here, we review the research that has been conducted to date on developing selective inhibitors for PSA. The different approaches used to determine PSA substrate specificity and for creating inhibitors are discussed. In addition, the unique active site characteristics of PSA and how these motifs aided our research in developing PSA targeted agents are highlighted.

Physical activity and genitourinary cancer prevention

The present review of epidemiologic studies of physical activity and genitourinary cancers (prostate, bladder, renal cell, and testicular cancers) suggests a weak inverse relation of physical activity to risk of prostate and renal cell cancer, with average risk decreases of less than 10% comparing high versus low levels of physical activity. For prostate cancer, studies that assessed activity intensity or those that considered fatal prostate cancer as a study endpoint produced the strongest inverse association. For renal cell cancer, the inverse relation with physical activity was more apparent among women than men, among normal weight than overweight or obese individuals, and among older than younger individuals. In contrast to prostate and renal cell cancer, available data show that physical activity is not associated with bladder or testicular cancer. Future research should include improvements in self-reported activity measures and incorporation of objective assessments of physical activity over the life course in order to more precisely characterize types, parameters, and timing of physical activity in relation to genitourinary cancers. Also, data are lacking regarding whether fitness potentially influences genitourinary cancer risk. The relation of physical activity and fitness to genitourinary cancer prognosis and survival requires specific attention. Mechanistic research should identify the underlying biologic pathways potentially linking physical activity to genitourinary cancers.

The protective effect of diabetes mellitus against prostate cancer: role of sex hormones

BACKGROUND

Diabetes mellitus (DM) has been associated with decreased risk of prostate cancer (PC) in several reports. Hormonal environment of diabetic patients is believed to be an important contributing factor in this regard.

METHODS

Using data from a multi-center case-control study in Iran, base line testosterone, sex hormone binding globulin (SHBG), estradiol, and albumin levels as well as thorough demographic and medical characteristics of 194 newly diagnosed prostate cancer patients were determined. There were 317 ethnicity-matched men with no cancer as controls as well. Data was analyzed for hormones of interest in DM patients regarding their cancer status.

RESULTS

Of 511 enrolled patients, twenty-one cases and 63 controls were diagnosed as DM. Patients with DM were significantly less likely to have PC (OR: 0.44, P = 0.003). Time since DM diagnosis was also inversely correlated with the risk of cancer (P trend < 0.0001). Control patients had significantly higher testosterone, estradiol, and testosterone/SHBG ratio (P < 0.05). As time since DM diagnosis increased by quartiles, testosterone significantly increased (P trend < 0.05). The risk of PC also significantly declined (P trend < 0.0001) following an initial remarkable increase early after DM diagnosis. After including the hormones in the logistic regression model, there was a weak, yet significant inverse association of testosterone/SHBG and DM duration with the risk of PC.

CONCLUSIONS

Based on our results DM duration is inversely correlated with the risk of prostate cancer. Our results do not support the hypothesis that sex hormones, including testosterone, play a major role in the protective effect of DM against PC.

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.

The effects of varying dietary carbohydrate and fat content on survival in a murine LNCaP prostate cancer xenograft model

PURPOSE

Numerous dietary factors elevate serum levels of insulin and insulin-like growth factor I (IGF-I), both potent prostate cancer mitogens. We tested whether varying dietary carbohydrate and fat, without energy restriction relative to comparison diets, would slow tumor growth and reduce serum insulin, IGF-I, and other molecular mediators of prostate cancer in a xenograft model.

EXPERIMENTAL DESIGN

Individually caged male severe combined immunodeficient mice (n = 130) were randomly assigned to one of three diets (described as percent total calories): very high-fat/no-carbohydrate ketogenic diet (NCKD: 83% fat, 0% carbohydrate, 17% protein), low-fat/high-carbohydrate diet (LFD: 12% fat, 71% carbohydrate, 17% protein), or high-fat/moderate-carbohydrate diet (MCD: 40% fat, 43% carbohydrate, 17% protein). Mice were fed to maintain similar average body weights among groups. Following a preliminary feeding period, mice were injected with 1 x 10(6) LNCaP cells (day 0) and sacrificed when tumors were >or=1,000 mm(3).

RESULTS

Two days before tumor injection, median NCKD body weight was 2.4 g (10%) and 2.1 g (8%) greater than the LFD and MCD groups, respectively (P < 0.0001). Diet was significantly associated with overall survival (log-rank P = 0.004). Relative to MCD, survival was significantly prolonged for the LFD (hazard ratio, 0.49; 95% confidence interval, 0.29-0.79; P = 0.004) and NCKD groups (hazard ratio, 0.59; 95% confidence interval, 0.37-0.93; P = 0.02). Median serum insulin, IGF-I, IGF-I/IGF binding protein-1 ratio, and IGF-I/IGF binding protein-3 ratio were significantly reduced in NCKD relative to MCD mice. Phospho-AKT/total AKT ratio and pathways associated with antiapoptosis, inflammation, insulin resistance, and obesity were also significantly reduced in NCKD relative to MCD tumors.

CONCLUSIONS

These results support further preclinical exploration of carbohydrate restriction in prostate cancer and possibly warrant pilot or feasibility testing in humans.

Diabetes mellitus and risk of prostate cancer in the health professionals follow-up study

History of diabetes may be associated with decreased prostate cancer (PCa) risk. Published studies have not always accounted for time since diabetes diagnosis or confounding and effect modification by lifestyle factors. The authors investigated the relationship between diabetes and PCa risk in men in the Health Professionals Follow-Up Study from 1986 to 2004. During that time, 4,511 new PCa cases were identified. Multivariate hazard ratios (HR) were estimated using Cox regression. The HR of PCa comparing men with vs. without diabetes was 0.83 and 95% confidence interval (CI): 0.74, 0.94. PCa risk was not reduced in the first year after diabetes diagnosis (HR: 1.30, CI: 0.97, 1.72), was lower for men diagnosed for 1-6 years (HR: 0.82, CI: 0.66, 1.02), and was even lower for men who had been diagnosed for 6-15 (HR: 0.75, CI: 0.61, 0.93) or >15 years (HR: 0.78, CI: 0.63, 0.96). Reduced PCa risk was stronger in men diagnosed before 1994 (pre-PSA era) vs. after 1994. The authors also demonstrated that obese and diabetic men had a lower HR for PCa than those who were either not obese and diabetic or obese and non-diabetic. Results are consistent with the hypothesis that diabetes is associated with reduced PCa risk. Potential biological mechanisms are discussed.

Distinct modes of activation of phosphatidylinositol 3-kinase in response to cyclic adenosine 3', 5'-monophosphate or insulin-like growth factor I play different roles in regulation of cyclin D1 and p27Kip1 in FRTL-5 cells

Bioactivities of IGFs in various cells are often potentiated in the presence of other hormones. In previous studies we showed that pretreatment of rat FRTL-5 thyroid cells with TSH or other cAMP-generating agents markedly potentiated DNA synthesis induced by IGF-I. Under these conditions we found that phosphatidylinositol (PI) 3-kinase was activated in response to either cAMP or IGF stimulus, and both activation modes were indispensable for the potentiation of DNA synthesis. The present studies were undertaken to elucidate how cAMP and/or IGF-I stimulus regulated the G1 cyclin-cyclin dependent kinase (CDK)-inhibitor system, and to determine the roles of PI 3-kinase activation by cAMP or IGF-I stimulus in this system. We found that cAMP pretreatment enhanced IGF-I-dependent increases in cyclin D1, due to synergistic increases in mRNA and elevation of translation rates. Furthermore, cAMP pretreatment enhanced IGF-I-induced protein degradation of the CDK inhibitor, p27(Kip1). These changes well explained an increase in cyclin E, leading to marked activation of G1 CDKs, followed by retinoblastoma protein phosphorylation. Our results using a PI 3-kinase inhibitor showed that cAMP-dependent PI 3-kinase activation plays an important role in the increase in cyclin D1 translation. In contrast, IGF-I-dependent PI 3-kinase activation was required for the increase in cyclin D1 mRNA levels and degradation of p27(Kip1). Together, the present study elucidates the role of cAMP and IGF-I in differentially activating PI 3-kinase as a mediator of multiple molecular events. These events converge in the regulation of cyclin D1 and p27(Kip1), leading to cAMP-dependent potentiation of IGF-I-dependent CDK activation and DNA synthesis.

Hormonal profile of diabetic men and the potential link to prostate cancer

OBJECTIVE

Previous studies suggest men with diabetes may be at reduced risk for prostate cancer as compared to men without diabetes. To investigate potential biological mechanisms, hormonal profiles of diabetic men and non-diabetic controls were compared.

METHODS

In the Health Professionals Follow-Up Study, plasma levels of C-peptide, testosterone, sex-hormone binding globulin, insulin-like growth factor-1, and insulin-like growth factor binding protein-3 were determined in 171 diabetic men and 3,001 non-diabetic controls. Multiple linear regression analysis was conducted and least square means were calculated for hormones of interest.

RESULTS

Plasma levels of several hormones either < or =1, 1.1-6, 6.1-14.9, or > or =15 years after diagnosis with diabetes were examined. As time since diabetes diagnosis increased, plasma levels of C-peptide and IGFBP-3 significantly decreased (p for trend: C-peptide =.05, IGFBP-3 =.03). While testosterone and SHBG levels both significantly increased with increasing time since diabetes diagnosis (p for trend: testosterone =.02, SHBG =.002), the ratio of testosterone to SHBG decreased, suggesting a reduction in bioavailable testosterone. Plasma IGF-1 levels were lower in diabetics than non-diabetics, but no significant time trend was noted.

CONCLUSION

This study of hormonal profiles of diabetic versus non-diabetic men identified changes in diabetic men that may be consistent with reduced prostate cancer risk.

Acromegaly: re-thinking the cancer risk

Acromegaly is characterized by sustained elevation of circulating growth hormone (GH) and insulin-like growth factor I (IGF-I), and is clearly associated with increased morbidity and overall mortality mainly due to cardiovascular, metabolic, and respiratory diseases. Although cancer-related mortality varies widely amongst retroperspective studies, it appears to be consistently elevated mainly in patients with uncontrolled disease. We review individual tumor types including neoplasms of the colon, breast, prostate, and thyroid where in vitro, animal studies, and studies in non-acromegalic cancer patients have established a role for the GH/IGF-I axis in tumor progression and possibly initiation. We highlight deficiencies in data in acromegalic patients where the evidence is less convincing. Instead, we explore the hypothesis that acromegaly, independent of hormone secretion, is a disease that heralds genetic and/or epigenetic alterations predisposing to cancer risk elsewhere.

Disruption of growth hormone signaling retards prostate carcinogenesis in the Probasin/TAg rat

We asked whether down-regulation of GH signaling could block carcinogenesis in the Probasin/TAg rat, a model of aggressive prostate cancer. The Spontaneous Dwarf rat, which lacks GH due to a mutation (dr) in its GH gene, was crossed with the Probasin/TAg rat, which develops prostate carcinomas at 100% incidence by 15 wk of age. Progeny were heterozygous for the TAg oncogene and homozygous for either the wild-type GH gene (TAg/Gh(+/+)) or the dr mutation (TAg/Gh(dr/dr)). Prostate tumor incidence and burden were significantly reduced, and tumor latency was delayed in TAg/Gh(dr/dr) rats relative to TAg/Gh(+/+) controls. At 25 wk of age, loss of GH resulted in a 20 and 80% decrease in the area of microinvasive carcinoma in the dorsal and lateral lobes, respectively. By 52 wk of age, invasive prostate adenocarcinomas were observed in all TAg/Gh(+/+) rats, whereas the majority of TAg/Gh(dr/dr) did not develop invasive tumors. Suppression of carcinogenesis could not be attributed to alterations in prostate expression of TAg or androgen receptor or changes in serum testosterone levels. As carcinogenesis progressed in TAg/Gh(+/+) rats, prostate GHR mRNA and protein expression increased significantly, but prostate IGF-I receptor mRNA and protein levels dropped. Furthermore, serum IGF-I and prostate IGF-I levels did not change significantly over the course of carcinogenesis. These findings suggest that GH plays a dominant role in progression from latent to malignant prostate cancer driven by the powerful probasin/TAg fusion gene in rats and suggest that GH antagonists may be effective at treating human prostate cancer.

Carbohydrate restriction, prostate cancer growth, and the insulin-like growth factor axis

BACKGROUND

Recent evidence suggests carbohydrate intake may influence prostate cancer biology. We tested whether a no-carbohydrate ketogenic diet (NCKD) would delay prostate cancer growth relative to Western and low-fat diets in a xenograft model.

METHODS

Seventy-five male SCID mice were fed a NCKD (84% fat-0% carbohydrate-16% protein kcal), low-fat (12% fat-72% carbohydrate-16% protein kcal), or Western diet (40% fat-44% carbohydrate-16% protein kcal). Low-fat mice were fed ad libitum and the other arms fed via a modified-paired feeding protocol. After 24 days, all mice were injected with LAPC-4 cells and sacrificed when tumors approached 1,000 mm(3).

RESULTS

Despite consuming equal calories, NCKD-fed mice lost weight (up to 15% body weight) relative to low-fat and Western diet-fed mice and required additional kcal to equalize body weight. Fifty-one days after injection, NCKD mice tumor volumes were 33% smaller than Western mice (rank-sum, P = 0.009). There were no differences in tumor volume between low-fat and NCKD mice. Dietary treatment was significantly associated with survival (log-rank, P = 0.006), with the longest survival among the NCKD mice, followed by the low-fat mice. Serum IGFBP-3 was highest and IGF-1:IGFBP-3 ratio was lowest among NCKD mice while serum insulin and IGF-1 levels were highest in Western mice. NCKD mice had significantly decreased hepatic fatty infiltration relative to the other arms.

CONCLUSIONS

In this xenograft model, despite consuming more calories, NCKD-fed mice had significantly reduced tumor growth and prolonged survival relative to Western mice and was associated with favorable changes in serum insulin and IGF axis hormones relative to low-fat or Western diet.

A meta-analysis of diabetes mellitus and the risk of prostate cancer

BACKGROUND

Studies investigating the association between diabetes mellitus and prostate cancer have reported inconsistent findings. We examined this association by conducting a detailed meta-analysis of the studies published on the subject.

METHODS

MEDLINE and EMBASE databases and bibliographies of retrieved articles were searched. Studies investigating the relationship between diabetes mellitus and prostate cancer were included in the meta-analysis. Potential sources of heterogeneity between studies were explored and publication bias was evaluated. Pooled relative risk (RR) was calculated using the random-effects model. Numerous relevant subgroup analyses were also done.

RESULTS

We included 19 studies, published between 1971 and 2005, in the meta-analysis and found an inverse association between diabetes mellitus and prostate cancer [RR, 0.84, 95% confidence interval (CI), 0.76-0.93, P for heterogeneity <or= 0.01]. For cohort studies alone, the RR was 0.81 (95% CI, 0.71-0.92, P for heterogeneity <or= 0.01) and for case-control studies alone, the RR was 0.89 (95% CI, 0.72-1.11, P for heterogeneity = 0.02). The significant heterogeneity was mitigated in some of the subgroup analyses. For studies conducted before prostate-specific antigen screening was introduced as a common procedure, the RR was 0.94 (95% CI, 0.85-1.03, P for heterogeneity = 0.15), and for studies conducted after this time, the RR was 0.73 (95% CI, 0.64-0.83, P for heterogeneity = 0.10). For studies that adjusted for three or more potential confounders, the RR was 0.74 (95% CI, 0.65-0.85, P for heterogeneity = 0.06) and for studies that adjusted for less than three potential confounders, the RR was 0.93 (95% CI, 0.86-1.02, P for heterogeneity = 0.18).

CONCLUSION

This study suggests an inverse relationship between diabetes and prostate cancer. Potential biological mechanisms underlying this association, as well as possible biases, are discussed.

Serum Insulin-like Growth Factor (IGF)-I and IGF-Binding Protein-3 Concentrations and Prostate Cancer Risk: Results from the European Prospective Investigation into Cancer and Nutrition

BACKGROUND

Some studies suggest that elevated serum insulin-like growth factor (IGF)-I concentrations are associated with an increased risk of prostate cancer and, in particular, with an increased risk of advanced-stage prostate cancer.

METHODS

We analyzed the association between prediagnostic serum concentrations of IGF-I and IGF-binding protein-3 (IGFBP-3) and prostate cancer risk in a case-control study nested in the European Prospective Investigation into Cancer and Nutrition. This study includes 630 incident prostate cancer cases and 630 matched control subjects. Odds ratios and their 95% confidence intervals (95% CI) were calculated for prostate cancer risk associated with increasing IGF-I and IGFBP-3 concentrations using conditional logistic regression.

RESULTS

The risk of total prostate cancer in the highest versus the lowest third of serum peptide concentration was 1.35 (95% CI, 0.99-1.82; Ptrend = 0.08) for IGF-I, 1.39 (95% CI, 1.02-1.89; Ptrend = 0.12) for the IGF-I residuals after adjusting for IGFBP-3, 1.22 (95% CI, 0.92-1.64; Ptrend = 0.38) for IGFBP-3, and 1.01 (95% CI, 0.74-1.37; Ptrend = 0.75) for the IGFBP-3 residuals after adjusting for IGF-I. There was no significant difference in the association of peptide hormones and prostate cancer by stage of disease, although the association of serum IGF-I concentration with risk was slightly stronger for advanced-stage disease; the odds ratio for the highest versus the lowest third was 1.65 (95% CI, 0.88-3.08; Ptrend = 0.21) for IGF-I and 1.76 (95% CI, 0.92-3.40; Ptrend = 0.11) for IGF-I adjusted for IGFBP-3.

CONCLUSIONS

In this large nested case-control study, serum IGF-I concentration is not strongly associated with prostate cancer risk, although the results are compatible with a small increase in risk, particularly for advanced-stage disease; no association for IGFBP-3 was observed.

Obesity and prostate cancer: epidemiology and clinical implications

OBJECTIVES

Both obesity and prostate cancer (PCa) are epidemic in Western society. Although initial epidemiological data appeared conflicting, recent studies have clarified the association between obesity and PCa. Therefore, we sought to review the epidemiological data linking obesity and PCa with an emphasis on the clinical implications and how to improve outcomes among obese men.

METHODS

A PubMed search using the keywords "prostate cancer" and "obesity" was performed. Relevant articles and references were reviewed for data on the association between obesity and PCa.

RESULTS

Recent data suggest obesity is associated with reduced risk of nonaggressive disease but increased risk of aggressive disease. This observation may be explained in part by an inherent bias in our ability to detect PCa in obese men (lower PSA values and larger sized prostates, making biopsy less accurate for finding an existent cancer), which ultimately leads to increased risk of cancer recurrence after primary therapy and increased PCa mortality. Despite this detection bias potentially contributing to more aggressive cancers, multiple biological links also exist between obesity and PCa including higher estradiol, insulin, free IGF-1, and leptin levels, and lower free testosterone and adiponectin levels, all of which may promote more aggressive cancers.

CONCLUSIONS

The association between obesity and PCa is complex. Emerging data suggest obesity increases the risk of aggressive cancer, while simultaneously decreasing the risk of more indolent disease. This is likely driven by both "biological" and "nonbiological" causes. Simple changes in clinical practice patterns can reduce the impact of nonbiological causes and may help improve PCa outcomes among obese men.

Interaction of factors related to the metabolic syndrome and vitamin D on risk of prostate cancer

BACKGROUND

Factors related to the metabolic syndrome and low levels of vitamin D have been implicated as risk factors for prostate cancer. Insofar, no studies have assessed their joint effects on prostate cancer risk.

METHODS

We studied (a) the associations of vitamin D with the metabolic syndrome factors body mass index, systolic and diastolic blood pressure, and high-density lipoprotein cholesterol (HDL-C) and (b) the prostate cancer risk associated with these factors and especially their joint effects with vitamin D on risk of prostate cancer. We did a longitudinal nested case-control study on 132 prostate cancer cases and 456 matched controls from a cohort of 18,939 Finnish middle-aged men from the Helsinki Heart Study. The odds ratios (OR) of prostate cancer were assessed via conditional logistic regression analysis.

RESULTS

Apart from HDL-C, there was no linear association between the metabolic syndrome factors and vitamin D levels. In univariate analysis, men in the highest quartiles of body mass index (>28 kg/m(2)) and systolic blood pressure (>150 mmHg) showed a modest increase in risks of prostate cancer, with ORs of 1.37 (P = 0.16) and 1.53 (P = 0.05) when compared with the three lower quartiles, but low HDL-C entailed no prostate cancer risk. However, with all three factors present, the OR was 3.36 (P = 0.02), and jointly with low vitamin D (<or=40 nmol/L), the OR was 8.03 (P = 0.005) compared with those with no metabolic syndrome factors and intermediate levels of vitamin D. There was an interaction between vitamin D and the metabolic syndrome factors so that a clustering of these factors entailed high risk of prostate cancer but only if vitamin D level was low (<or=40 nmol/L). If it was at intermediate levels, the metabolic syndrome factors entailed no prostate cancer risk.

CONCLUSIONS

We conclude that the prostate cancer risk associated with factors related to the metabolic syndrome is strongly conditioned by levels of vitamin D.

Effect of lycopene on insulin-like growth factor-I, IGF binding protein-3 and IGF type-I receptor in prostate cancer cells

PURPOSE

Prostate cancer is the second most common cancer that leads to death in elderly men. The risk of prostate cancer prevalence is often associated with the elevated level of insulin-like growth factor-I (IGF-I) and decreased level of IGF-binding protein 3 (IGFBP-3). Lycopene, a carotenoid, reduces the proliferation of cancer cells and induces apoptosis. Hence, higher intake of lycopene can be associated with the lower risk of prostate cancer. However, the mechanism of action of lycopene in the prevention of prostate cancer is still unclear. The present study was carried out to study the effects of lycopene on the components of IGF system and apoptosis in androgen-independent prostate cancer cells (PC-3 cells).

METHODS

PC-3 cells were treated with various concentrations of lycopene, (20, 40 and 60 microM) for 24, 48, 72 and 96 h. IGF-I, IGFBP-3 and IGF-I receptor (IGF-IR) levels in lycopene-treated cells were evaluated. Annexin V and propidium iodide (PI) binding studies were done to assess apoptosis.

RESULTS

PC-3 cells treated with lycopene showed a significant decrease in cell proliferation. Lycopene, at a dose of 40 microM, significantly increased the level of IGFBP-3. Lycopene-induced apoptosis was confirmed by annexin V and PI binding. Lycopene-induced DNA fragmentation was absent after 24 h treatment whereas the same was observed after 48 h treatment. There was a significant decrease in the IGF-IR expression after the cells were treated with lycopene and IGF-I.

CONCLUSION

The data obtained suggest that the components of the IGF system may act as a positive regulator of lycopene-induced apoptosis in PC-3 cells. Thus, the observed lycopene-induced biological effects and their associated mechanisms are encouraging and may lead to the development of a highly successful drug for the treatment of prostate cancer.

Birth weight and the risk of testicular cancer: A meta-analysis

The high incidence of testicular cancer in young males indicates a potential role of events during early life. Birth weight has been identified as a factor possibly associated with the risk of cancers later in life. To investigate the association between birth weight and testicular cancer, we conducted a Systematic Review and Meta-Analysis of published studies investigating the association between birth weight and testicular cancer. Data were combined using a fixed-effects model. Thirteen epidemiologic studies, published between 1983 and 2004, were included in the analysis, encompassing 5,663 patients with testicular cancer. Men weighing less than 2,500 grams at birth had a higher risk for developing testicular cancer later in life than those with normal birth weight (2,500-4,000 g) (OR = 1.18; 95% confidence interval (CI) 1.01-1.38). A similar trend was found for men with a birth weight above 4,000 g, (OR = 1.12; 95% CI 1.02-1.22). When seminoma and nonseminoma testicular cancer cases were considered separately, low birth weight was a risk factor specifically for seminomas (OR = 1.44; 95% CI 1.11-1.88). A U-shaped association was observed between birth weight and the risk for testicular cancer. The underlying biological mechanisms for this phenomenon remain to be elucidated.

Insulin-like growth factors and their binding proteins in prostate cancer: Cause or consequence?☆

Insulin-like growth factors (IGFs) promote growth and survival of many types of tumor cells. Epidemiologic studies have implicated carcinogenesis with high levels of IGFs in circulation or in tissues. The levels of IGF binding proteins (IGFBPs) have been associated with reduced risk for prostate and other cancers. Experimental studies have implicated high levels of IGF-I directly and IGFBP-3 inversely in prostate cancer growth, survival, and progression. However, recent evidence suggests a much weaker association of IGF-I with prostate cancer development and a stronger antagonistic association of IGFBP-3 with prostate cancer progression. Considering the clonal heterogeneity and unpredictable progression pattern of prostate cancer, the role of any single growth factor or its regulator (IGFBP) as a single determining factor is limited. This review is a critical appraisal of the role of IGFs, IGFBP, and IGF-I receptor (the IGF axis) in both experimental and clinical prostate cancer genesis and progression.

IGF-I secretion by prostate carcinoma cells does not alter tumor-bone cell interactions in vitro or in vivo

BACKGROUND

IGF-I is an important growth and differentiative factor for osteoblasts and may have a role in defining prostate cancer risk and skeletal metastases.

METHODS

Conditioned media (CM) from human prostate cancer (PC), C4-2 and C4-2B, which produce osteoblastic lesions, and PC-3, which causes osteolysis, was added to MC3T3-E1 bone cultures. SCID mice were injected intratibially with these engineered cells. Tumor bearing tibiae were analyzed by microCT and pQCT.

RESULTS

CM from PC cells increased osteoblast proliferation and differentiation and was unaltered by the type of PC cell, IGF-I antibodies, or exogenous IGF-I and IGFBP2. Study of intratibial PC tumors in SCID mice showed that C4-2 cells grew slowly preserving bone structure, while PC-3 tumors caused rapid osteolysis. Overexpression of IGF-I did not change either tumor progression or skeletal response.

CONCLUSIONS

IGF-I is neither necessary nor sufficient for the osteoblastic response to PC metastases.

RhoC GTPase is required for PC-3 prostate cancer cell invasion but not motility

It is projected that in 2005, approximately 220 900 men will be newly diagnosed with carcinoma of the prostate (CaP). Men who are diagnosed with locally advanced or metastatic disease undergo androgen ablation therapy and most will relapse and progress within 18 months. Metastasis to bone is the major clinical concern during CaP progression, as it is associated with intractable pain, bone fracture and paralysis resulting from spinal cord compression. Therefore, an understanding of the key mechanisms involved in CaP cell bone metastasis is vital to development of novel treatments. The Rho GTPases are molecular switches involved in cell survival, motility and invasion. Increased expression of RhoC GTPase is linked to enhanced metastatic potential in multiple cancers; however, the role of RhoC GTPase in CaP metastasis has not been addressed. In the current study, we demonstrate that RhoC GTPase is expressed and active in PC-3 CaP cells. RhoC inhibition, either pharmacologically with C3 exotransferase or molecularly through expression of a dominant-negative RhoC, promotes IGF-I stimulated random motility but decreases in vitro invasion and experimental metastases. Inhibition of RhoC activity results in drastic morphologic changes and alterations in the expression and distribution of focal adhesion-related proteins. These data suggest that RhoC inhibition leads to activation of other GTPases involved in nondirected motility and that expression of active RhoC is required for the invasive phenotype of PC-3 cells.

Inhibition of bone-derived insulin-like growth factors by a ligand-specific antibody suppresses the growth of human multiple myeloma in the human adult bone explanted in NOD/SCID mouse

Multiple myeloma (MM) is a fatal disease that affects plasma cells. Patients with MM have 1 or more osteolytic lesions in their bone tissues, where insulin-like growth factors (IGFs; IGF-I and IGF-II) are mainly stored. The role of bone-derived IGFs in the development of MM has not been extensively studied because reliable animal models are lacking. We established an animal model using a human MM cell line, RPMI8226, in nonobese diabetic/severe-combined immunodeficient (NOD/SCID) mice implanted with human adult bone (HAB) fragments. Treatment with an anti-human IGF-neutralizing monoclonal antibody, KM1468, inhibited the IGF-I-stimulated phosphorylation of type-I IGF receptors (IGF-IR) in RPMI8226 cells and the activation of the downstream PI3-K/Akt signaling pathway in vitro. KM1468 inhibited IGF-I-mediated RPMI8226 cell growth in a dose-dependent manner. In the NOD/SCID-HAB model, treatment with KM1468 significantly inhibited the growth of RPMI8226 cells (p<0.02). These results indicated that the growth of MM cells was predominantly stimulated not by serum-derived IGFs, but by bone-derived IGFs. Furthermore, the targeting of bone-derived IGFs, using a neutralizing antibody, may offer a new therapeutic strategy for MM.

Beneficial effects of tea and its polyphenols against prostate cancer

Tea, next to water, is the most widely consumed beverage in the world. Depending upon the level of fermentation, tea can be categorized into three types: green (unfermented), oolong (partially fermented), and black (highly to fully fermented). In general, green tea has been found to be superior to black and oolong tea in terms of antioxidant and health promoting benefits owing to the higher content of (-)-epigallocatechin-3-gallate. Tea polyphenols comprise about one-third of the weight of the dried leaf, and they exhibit biochemical and pharmacological activities including antioxidant activities, inhibition of cell proliferation, induction of apoptosis, cell cycle arrest and modulation of carcinogen metabolism. Several studies demonstrate that most tea polyphenols exert their effects by scavenging reactive oxygen species (ROS) since excessive production of ROS has been implicated in the development of a variety of ailments including cancer of the prostate gland (CaP). Using cell culture and animal model systems, molecular targets for these remarkable beneficial effects of green tea drinking on CaP prevention and therapy have been defined. Geographical and case-control studies are showing that green tea drinking could afford CaP chemopreventive effects in human population. In this review we attempt to summarize the experimental as well as the epidemiological basis for the possible role of tea and its polyphenols for chemoprevention and chemotherapy of CaP.

Insulin-like Growth Factor I Secreted from Prostate Stromal Cells Mediates Tumor-Stromal Cell Interactions of Prostate Cancer

Prostate cancer shows high expression of type I insulin-like growth factor (IGF-I) receptor (IGF-IR) and prostate stromal cells (PrSC) produce IGF-I. Although high plasma level of IGF-I is a risk factor of prostate cancer, the significance of the prostate stromal IGF-I in the regulation of prostate cancer remains elusive. Here we show that the stromal IGF-I certainly regulates the development of prostate cancer. Coinoculation of PrSC increased the growth of human prostate cancer LNCaP and DU-145 tumors in severe combined immunodeficient mice. The conditioned medium of PrSC, as well as IGF-I, induced phosphorylation of IGF-IR and increased the growth of LNCaP and DU-145 cells. PrSC, but not LNCaP and DU-145 cells, secreted significant amounts of IGF-I. Coculture with PrSC increased the growth of DU-145 cells in vitro but the pretreatment of PrSC with small interfering RNA of IGF-I did not enhance it. Furthermore, various chemical inhibitors consisting of 79 compounds with approximately 60 different targets led to the finding that only IGF-IR inhibitor suppressed the PrSC-induced growth enhancement of DU-145 cells. Thus, these results show that the prostate stromal IGF-I mediates tumor-stromal cell interactions of prostate cancer to accelerate tumor growth, supporting the idea that the IGF-I signaling is a valuable target for the treatment of prostate cancer.

Adiponectin as a growth inhibitor in prostate cancer cells

Prostate cancer is associated with obesity. However, the molecular basis of this association is not well known. Adiponectin is a major adipose cytokine that decreases in circulation in obesity and ameliorates obesity. Here, we identify adiponectin as a novel inhibitor in prostate cancer cell growth. Adiponectin occurs in non-proteolytic (full-length adiponectin: f-adiponectin) and proteolytic (globular adiponectin) forms in various oligomeric states (trimer, hexamer, and high molecular weight complex). The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay demonstrates that f-adiponectin inhibits prostate cancer cell growth drastically at subphysiological concentrations. Furthermore, velocity sedimentation analysis shows that the high molecular weight complex of f-adiponectin is the inhibitory form. Moreover, f-adiponectin suppresses leptin- and/or insulin-like growth factor-I (IGF-I)-stimulated, androgen-independent DU145 cell growth, and dihydrotestosterone-stimulated, androgen-dependent LNCaP-FGC cell growth. In addition, f-adiponectin enhances doxorubicin inhibition of prostate cancer cell growth. Therefore, f-adiponectin is a molecular mediator between prostate cancer and obesity, and may be therapeutic to prostate cancer.