Insulin-like growth factor-I and -II in human benign prostatic hyperplasia: relationship with binding proteins 2 and 3 and androgens

Deciphering the Role of Insulin-Like Growth Factor 1 in Endometrial Cancer in Patients With Polycystic Ovary Syndrome: Protocol for a Methodological Approach Using Cell Culture Experiments

BACKGROUND

Endometrial cancer (EC) is the most common gynecological cancer in women globally. It is linked to increasing obesity rates and longer life spans. The molecular mechanisms leading to EC are unclear; however, women with polycystic ovary syndrome (PCOS) have a 3- to 5-fold increased EC risk. According to a pilot study conducted in the United Kingdom, insulin-like growth factor-1 (IGF-1) gene and protein were raised in the endometrium and blood of women with EC and PCOS, compared with those without PCOS (controls). Therefore, raised serum IGF-1 levels may contribute to an increased EC risk in women with PCOS, but it is necessary to test this hypothesis since not all studies have demonstrated this association.

OBJECTIVE

This study aims to investigate the role of IGF-1 in mediating EC risk in PCOS. This will be achieved by evaluating the proliferative effects of PCOS serum, IGF-1, and IGF-1 antagonist on human endometrial cancer 1-A and 1-B cell lines, with a comparison to controls (using serum from women without PCOS and cell culture media). The study will also identify differentially expressed genes and pathways activated by various treatments.

METHODS

We intend to recruit 20 women with PCOS and 20 women without PCOS for this cross-sectional study. All experiments will be carried out 4 times to ensure consistency. We will perform transcriptomic and phosphoproteomic profiling to identify differentially expressed genes and phosphoproteins between different treatments using RNA sequencing and phosphoproteomics. We will also perform bioinformatics pathway analysis to identify whether any unique collection of genes or phosphoproteins explains increased EC risk in PCOS. The primary outcome measure will be the cell proliferation (growth) difference measured by cell index values. Our protocol stands out due to its unique approach; no previous study has used this approach to investigate the oncogenic effect of serum from women with PCOS. Additionally, no previous study has considered the differential mutations of genes related to the insulin signaling pathway across various types of human EC cell lines and the potential impact of these variations on their experimental findings.

RESULTS

Participants are currently being recruited. It is expected that preliminary findings suitable for analysis and publication will be available by the summer of 2024.

CONCLUSIONS

Although we currently do not have any results to report, sharing our protocol at this stage will aid in research collaboration, provide an opportunity for early feedback, and help reduce duplication of effort by other research groups. The findings of our study will have broader implications. A deeper understanding of the mechanisms underlying the regulation of the IGF system in PCOS and EC will improve our ability to develop effective treatment modalities for EC and will be a vital step toward reducing EC in women globally.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/48127.

Emerging Roles for Browning of White Adipose Tissue in Prostate Cancer Malignant Behaviour

In addition to its well-known role as an energy repository, adipose tissue is one of the largest endocrine organs in the organism due to its ability to synthesize and release different bioactive molecules. Two main types of adipose tissue have been described, namely white adipose tissue (WAT) with a classical energy storage function, and brown adipose tissue (BAT) with thermogenic activity. The prostate, an exocrine gland present in the reproductive system of most mammals, is surrounded by periprostatic adipose tissue (PPAT) that contributes to maintaining glandular homeostasis in conjunction with other cell types of the microenvironment. In pathological conditions such as the development and progression of prostate cancer, adipose tissue plays a key role through paracrine and endocrine signaling. In this context, the role of WAT has been thoroughly studied. However, the influence of BAT on prostate tumor development and progression is unclear and has received much less attention. This review tries to bring an update on the role of different factors released by WAT which may participate in the initiation, progression and metastasis, as well as to compile the available information on BAT to discuss and open a new field of knowledge about the possible protective role of BAT in prostate cancer.

Linking pre-diabetes with benign prostate hyperplasia. IGFBP-3: a conductor of benign prostate hyperplasia development orchestra?

Benign prostatic hyperplasia (BPH) represents a pattern of non-malignant growth of prostatic fibromuscular stroma. Metabolic disturbances such us pre-diabetes and metabolic syndrome may have a role in BPH pathophysiology. A potential explanation for the above relationship involves the insulin-like growth factor (IGF) axis as well as IGF binding proteins, (IGFBPs) of which the most abundant form is IGFBP-3. Therefore, the aim of the present study was to investigate the association between intra-prostatic levels of IGF-1, IGF-2 as well as to evaluate the role of locally expressed IGFBP-3 in BPH development in pre-diabetes. A total of 49 patients admitted to the Urology department of a tertiary urban Greek hospital, for transurethral prostate resection, or prostatectomy and with pre-diabetes [impaired fasting glucose (IFG) and impaired glucose tolerance (IGT) or both] were finally included. The majority of the sample consisted of subjects with IGT (51.0%), followed by IFG and IGT (32.7%) and isolated IFG (16.3%). For all participants a clinical examination was performed and blood samples were collected. In addition, total prostate (TP) volume or transitional zone (TZ) volume were estimated by transrectal ultrasonography. The results of the multivariate analysis regarding TP volume showed that higher PSA (p<0.001), larger waist circumference (p=0.007) and higher IGFBP-3 expression levels (p<0.001) independently predicted higher TP volume. The results regarding the volume of the TZ showed that higher PSA (p<0.001), larger waist circumference (p<0.001) and higher IGFBP-3 expression levels (p=0.024) were independently associated with higher TZ volume. Our findings show that intra-prostatic levels of IGFBP-3, PSA and waist circumference, but not overall obesity, are positively associated with prostate volume. IGFBP-3 seems to be a multifunctional protein, which can potentiate or inhibit IGF activity.

Nutrition and benign prostatic hyperplasia

PURPOSE OF REVIEW

Nutrition seems to modify the pathogenesis of benign prostatic hyperplasia (BPH) effect symptomology in men suffering from lower urinary tract symptoms (LUTS). Although there are numerous pharmaceuticals and procedures for these conditions, nutrition may improve outcomes as a primary approach or in tandem with BPH medications or procedures. The purpose of this review is to highlight the benefits of nutrition and dietary supplements in men with BPH and LUTS.

RECENT FINDINGS

Dietary factors have an impact on metabolic disorders that lead to diabetes and obesity - both of which inversely effect BPH and LUTS. Dietary patterns associated with increased risks include starches and red meats, whereas moderate alcohol intake and polyunsaturated fat and vegetable consumption decrease risks. Dietary supplements of zinc, saw palmetto, and beta-sitosterol in relieving BPH symptoms have had mixed results. Randomized clinical trials of nutritional practices and other lifestyle alterations such as exercise for the prevention or treatment of BPH and LUTS have yet to be performed.

SUMMARY

Nutritional practices may provide for the prevention and treatment of BPH and LUTS while positively affecting other systemic parameters. Whereas there are a few clinical randomized trials for the prevention and treatment of BPH and LUTS, nutritional modifications may have a healthy lifestyle alternative with minimal to no adverse effects.

IGF2 increases de novo steroidogenesis in prostate cancer cells

IGF2 is a mitogenic foetal growth factor commonly over-expressed in cancers, including prostate cancer (PC). We recently demonstrated that insulin can activate de novo steroidogenesis in PC cells, a major pathway for reactivation of androgen pathways and PC progression. IGF2 can activate the IGF1 receptor (IGF1R) or insulin receptor (INSR) or hybrids of these two receptors. We therefore hypothesized that IGF2 may contribute to PC progression via de novo steroidogenesis. IGF2 mRNA but not IGF2 receptor mRNA expression was increased in patient samples during progression to castrate-resistant PC as was immunoreactivity to INSR and IGF1R antibodies. Treatment of androgen receptor (AR)-positive PC cell lines LNCaP and 22RV1 with IGF2 for 48 h resulted in increased expression of steroidogenic enzyme mRNA and protein, including steroid acute regulatory protein (StAR), cytochrome p450 family member (CYP)17A1, aldo-keto reductase family member (AKR)1C3 and hydroxysteroid dehydrogenase (HSD)17B3. IGF2 treatment resulted in increased steady state steroid levels and increased de novo steroidogenesis resulting in AR activation as demonstrated by PSA mRNA induction. Inhibition of the IGF1R/INSR signalling axis attenuated the effects of IGF2 on steroid hormone synthesis. We present a potential mechanism for prostatic IGF2 contributing to PC progression by inducing steroidogenesis and that IGF2 signalling and related pathways present attractive targets for PC therapy.

Prostate size correlates with fasting blood glucose in non-diabetic benign prostatic hyperplasia patients with normal testosterone levels

We evaluated the correlations between BMI, fasting glucose, insulin, testosterone level, insulin resistance, and prostate size in non-diabetic benign prostatic hyperplasia (BPH) patients with normal testosterone levels. Data from 212 non-diabetic BPH patients with normal testosterone levels, who underwent transurethral resection of the prostate (TURP) due to medical treatment failure, were evaluated retrospectively. Patients with prostate specific antigen (PSA) levels of ≥ 3 ng/mL underwent multicore transrectal prostate biopsy before TURP to rule out prostate cancer. Patients with diabetes mellitus (DM) or serum testosterone levels of < 3.50 ng/mL were excluded from analysis. Correlations between clinical and laboratory parameters were determined. Prostate size correlated positively with age (r = 0.227, P < 0.001), PSA (r = 0.510, P < 0.001), and fasting glucose level (r = 0.186, P = 0.007), but not with BMI, testosterone, insulin level, or insulin resistance (each P > 0.05). Testosterone level inversely correlated with BMI (r = -0.327, P < 0.001), insulin level (r = -0.207, P = 0.003), and insulin resistance (r = -0.221, P = 0.001), but not with age, prostate size, PSA, or fasting glucose level (each P > 0.05). Upon multiple adjusted linear regression analysis, prostate size correlated with elevated PSA (P < 0.001) and increased fasting glucose levels (P = 0.023). In non-DM BPH patients with normal testosterone levels, fasting glucose level is an independent risk factor for prostate hyperplasia.

Diabetes, growth hormone-insulin-like growth factor pathways and association to benign prostatic hyperplasia

Diabetes significantly increases the risk of benign prostatic hyperplasia (BPH) and low urinary tract symptoms (LUTS). The major endocrine aberration in connection with the metabolic syndrome is hyperinsulinemia. Insulin is an independent risk factor and a promoter of BPH. Insulin resistance may change the risk of BPH through several biological pathways. Hyperinsulinemia stimulates the liver to produce more insulin-like growth factor (IGF), another mitogen and an anti-apoptotic agent which binds insulin receptor/IGF receptor and stimulates prostate growth. The levels of IGFs and IGF binding proteins (IGFBPs) in prostate tissue and in blood are associated with BPH risk, with the regulation of circulating androgen and growth hormone. Stromal-epithelial interactions play a critical role in the development and growth of the prostate gland and BPH. Previously, we have shown that the expression of c-Jun in the fibroblastic stroma can promote secretion of IGF-I, which stimulates prostate epithelial cell proliferation through activating specific target genes. Here, we will review the epidemiologic, clinical, and molecular findings which have evaluated the relation between diabetes and development of BPH.

Macronutrients, fatty acids, cholesterol, and risk of benign prostatic hyperplasia

OBJECTIVES

To better understand the role of specific macronutrients on the risk of benign prostatic hyperplasia (BPH), we used data from an Italian case-control study. Although BPH is extremely common among the elderly, its etiology-and, particularly, the role of diet and specific macronutrients-is still unclear.

METHODS

A case-control study of 1369 patients with BPH and 1451 controls, admitted to the same hospitals for a wide spectrum of acute, non-neoplastic conditions, was conducted in Italy. The subjects' usual diet was investigated through a validated and reproducible food frequency questionnaire. Multivariate odds ratios (ORs) and 95% confidence intervals (CIs) were obtained after allowance for energy intake and other potential confounding factors.

RESULTS

A significant direct relation was observed between starch intake (OR 1.51, 95% CI 1.15 to 1.99 for highest quintile compared with lowest one), and an inverse relation was observed for polyunsaturated fatty acids (OR 0.72, 95% CI 0.55 to 0.93), linoleic acid (OR 0.73, 95% CI 0.56 to 0.94), and linolenic acid (OR 0.71, 95% CI 0.54 to 0.93).

CONCLUSIONS

The results of this study suggest a role for specific macronutrients in the risk of BPH, including, in particular, an unfavorable effect for starch and a beneficial one for polyunsaturated fatty acids.

Metabolic factors associated with benign prostatic hyperplasia

CONTEXT

Benign prostatic hyperplasia poses a significant public health problem, but its etiology remains unclear. Obesity and associated abnormalities in glucose homeostasis may play a role in benign prostatic hyperplasia development by influencing prostate growth.

OBJECTIVE

The objective of this study was to determine whether obesity, fasting plasma glucose concentration, and diabetes are associated with radiologically determined prostate enlargement, an objective measure of benign prostatic hyperplasia.

DESIGN

This study was a cross-sectional analysis with robust variance estimates to account for multiple measures over time in the same individuals.

SETTING

This prospective cohort study was composed of community volunteers.

PATIENTS

Patients studied were 422 adult men enrolled in The Baltimore Longitudinal Study of Aging.

MAIN OUTCOME MEASUREMENTS

Total prostate volume as determined by pelvic magnetic resonance imaging was measured.

RESULTS

Among 422 participants, 91 (21.6%) had prostate enlargement (defined as total prostate volume >/= 40 cc) at first visit. Compared with men of normal weight [body mass index (BMI) < 25 kg/m(2)], the age-adjusted odds ratio (OR) for prostate enlargement for overweight men (BMI, 25-29.9 kg/m(2)) was 1.41 (95% CI, 0.84-2.37), for obese men (BMI, 30-34 kg/m(2)) was 1.27 (95% CI, 0.68-2.39), and for severely obese men (BMI >/= 35 kg/m(2)) was 3.52 (95% CI, 1.45-8.56) (P = 0.01). Men with elevated fasting glucose (>110 mg/dl) were more likely to have an enlarged prostate than men with normal fasting glucose (

CONCLUSIONS

Obesity, elevated fasting plasma glucose, and diabetes are risk factors for benign prostatic hyperplasia.

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Key Words Collapse

MESH Headings

• Adult
• Aged
• Aged, 80 and over
• Black People
• Blood Glucose/analysis
• Body Mass Index
• Cohort Studies
• Cross-Sectional Studies
• Diabetes Complications
• Ethnicity
• Humans
• Longitudinal Studies
• Male
• Middle Aged
• Obesity/complications
• Odds Ratio
• Prospective Studies
• Prostate/pathology
• Prostatic Hyperplasia/etiology
• Prostatic Hyperplasia/metabolism
• Prostatic Hyperplasia/pathology
• Testosterone/blood
• Urologic Diseases/etiology
• Waist-Hip Ratio
• White People

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Grants

• Z01 AG000015-49 Intramural NIH HHS

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Affiliation(s)

J Kellogg Parsons Division of Urology, University of California San Diego, 200 West Arbor Drive, San Diego, California 21287, USA.
H Ballentine Carter
Alan W Partin
B Gwen Windham
E Jeffrey Metter
Luigi Ferrucci
Patricia Landis
Elizabeth A Platz

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Prostate carcinoma incidence in relation to prediagnostic circulating levels of insulin-like growth factor I, insulin-like growth factor binding protein 3, and insulin

BACKGROUND

There have been several epidemiologic studies investigating the association between circulating levels of insulin-like growth factor I (IGF-I), insulin-like growth factor binding protein 3 (IGFBP-3), and insulin in relation to the risk of prostate carcinoma, with conflicting results. To examine this issue further, the authors conducted a nested case-control study within the Cardiovascular Health Study cohort.

METHODS

In men who were diagnosed with prostate carcinoma (cases) between 1990 and 1999 (n=174), the levels of IGF-I, IGFBP-3, and insulin were measured on blood samples that were obtained 1-9 years prior to diagnosis (mean, 3.4 years). Similar measurements were made on 174 male participants without prostate carcinoma (controls) who were matched to cases based on the year blood was drawn, survival until the date of diagnosis, race, and age.

RESULTS

Relative to the men with IGF-I levels in the first (lowest) quartile of the distribution, the risk of prostate carcinoma for men in the second, third, and fourth (upper) quartiles were 0.77 (95% confidence interval [95% CI], 0.43-1.38), 0.73 (95% CI, 0.41-1.30), and 0.67 (95% CI, 0.37-1.25), respectively. The results were influenced little by adjustment for levels of IGFBP-3 or, instead, by evaluating the molar IGF-I/IGFBP-3 ratio. An analysis that was restricted to men who had plasma prostate-specific antigen levels <4 ng/mL at the time of the blood draw yielded similar results. The corresponding relative risks for IGFBP-3 were 0.91 (95% CI, 0.49-1.68), 0.47 (95% CI, 0.25-0.94), and 0.65 (95% CI, 0.35-1.20), respectively. The distribution of serum insulin levels in cases and controls were nearly identical.

CONCLUSIONS

The IGF-I level was not associated positively with the risk of prostate carcinoma; however, an increase in the IGFBP-3 level was associated with a modest decrease in risk.

Interleukin-8 expression is increased in senescent prostatic epithelial cells and promotes the development of benign prostatic hyperplasia

BACKGROUND

Benign prostatic hyperplasia (BPH) is an extremely common disease of older men characterized by increased growth of prostatic epithelial and stromal cells. Previously we showed that senescent epithelial cells accumulate in the prostate of aging men and secrete interleukin-1 alpha (IL-1 alpha). IL-8 is also present at increased levels in BPH tissues and induces expression of FGF2, a potent stromal growth factor. Therefore, we sought to determine if IL-8 is also expressed at increased levels by senescent epithelial cells and if this secreted IL-8 plays a role in the pathogenesis of BPH.

METHODS

Expression of IL-8 in human BPH tissue and primary cultures of prostatic epithelial cells was analyzed using an enzyme-linked immunoabsorption assay (ELISA). Tissue senescence was assessed by a quantitative assay for senescence-associated beta galactosidase (SA-beta gal). Proliferation of primary and immortalized prostatic epithelial cells in response to IL-8 was determined by counting of cells at intervals after addition of IL-8.

RESULTS

Expression of IL-8 is significantly increased in vitro when cultured prostatic epithelial cells undergo senescence. Quantitative assay of BPH tissue extracts revealed that tissue IL-8 levels are correlated with both SA-beta gal activity and prostate weight. IL-8 promotes proliferation of primary and immortalized prostatic epithelial cells in culture.

CONCLUSIONS

Senescence of prostatic epithelial cells results in increased expression of IL-8, which can promote proliferation of non-senescent epithelial and stromal cells by direct and indirect mechanisms, and in this manner contributes to the increased tissue growth seen in BPH.

Overexpression of IGBFB2 is a marker for malignant transformation in prostate epithelium

Insulin-like growth factor binding protein 2 (IGFBP2) has been shown to be overexpressed in prostatic intraepithelial neoplasia (PIN) and invasive cancer and the serum level to parallel that of prostate-specific antigen (PSA) in prostate cancer. A combination of cDNA and tissue microarray results recently demonstrated overexpression of IGFBP2 in hormone refractory prostate cancer, indicating that the IGF system may be part of a key growth regulatory pathway in prostate cancer. The present study reexamines the immunohistochemical expression of IGFBP2 and its relationship to grade in tissue from 193 radical prostatectomy specimens from patients with localized prostate adenocarcinoma. We found a significant overexpression of IGFBP2 in all instances of PIN and in more than 90% of cancers regardless of the grade. An intense overexpression was noted in the neuroendocrine cells in normal glands as well as in cancer. The IGFBP2 expression was also analyzed in 18 cases of biopsy diagnosed prostate cancer. In all these cases, the glands interpreted as invasive cancer in hematoxylin-eosin stained sections overexpressed IGFBP2, without a significant correlation to grade. We conclude that overexpression of IGFBP2 is a powerful marker for malignant transformation in the prostate epithelium and suggest that optimized immunohistochemical detection of IGFBP2 expression may be an adjunct tool in the diagnosis of prostate cancer.

Expression of the insulin-like growth factor (IGF) system and steroidogenic enzymes in canine testis tumors

Testis tumors occur frequently in dogs. The main types of tumors are Sertoli cell tumors, seminomas, and Leydig cell tumors. Mixed tumors and bilateral occurrence of tumors may be encountered frequently. To elucidate the possible relationship between the insulin-like growth factor (IGF) system and the development of different types of testis tumors in dogs, the expression of insulin-like growth factor-I and II (IGF-I and IGF-II), their type I receptor (IGF-IR), and their binding proteins (IGFBPs) was examined. In addition the expression of the steroidogenic enzymes p450-aromatase and 5alpha-reductase type I and type II, and the androgen receptor (AR) was investigated by a semiquantitative reverse-transcriptase PCR (RT-PCR). Both normal testes and testes with tumors were studied. In normal testes a clear expression of IGF-I, IGF-II, IGF-IR, IGFBP2, IGFBP4 and IGFBP5 was found. Expression of IGFBP1 and IGFBP3 was weak. There was also clear expression of the steroidogenic enzymes 5alpha-reductase, aromatase, and the AR. Quantification of RT-PCR products revealed significantly less expression of IGFBP1, IGF-I, and 5alpha-reductase type I in Sertoli cell tumors and seminomas. Leydig cell tumors and mixed tumors had a significantly higher expression of IGFBP4 and IGF-IR than normal testes. The expression of aromatase was lower in seminomas and in mixed tumors. The expression of AR, IGF-II and IGFBP2, IGFBP3, IGFBP5, and 5alpha-reductase type II did not differ among the different types of tumors. It was concluded that Sertoli cell tumors and seminomas have a comparable expression of the IGF system while Leydig cell tumors have a different pattern, suggesting difference in pathobiology among these types of tumors.

Relationship of serum sex-steroid hormones and prostate volume in African American men

BACKGROUND

Previous epidemiologic investigations of the associations of sex-steroid hormones and benign prostatic hyperplasia (BPH) have focused on predominately white populations. The objective of this study was to evaluate potential associations of body mass index (BMI), cigarette smoking, use of alcohol, and endogenous sex-steroid hormones with prostate volume in a population-based sample of African American (AA) men, ages 40-79 yr.

METHODS

A total of 369 AA men without clinical evidence of prostate cancer were identified in the Flint Men's Health Study by using a population-based sampling procedure. All subjects underwent a complete urologic evaluation that included prostate volume determination by transrectal ultrasonography and serum assays for androgens and estrogens.

RESULTS

After age adjustment, BMI (weight (kg)/height (m)2) was positively correlated with increasing levels of androstanediol glucuronide (AG), estradiol (E2), estrone sulfate (E1S), and the ratios of E2:total testosterone (TT) and E2:free testosterone (FT); however, increasing BMI was negatively correlated with androstenedione (AD), FT, TT, and sex hormone-binding globulin (SHBG). Multivariable regression models demonstrated that prostate volume increased with age (P < 0.001) and BMI (P = 0.02) and decreased with increasing levels of SHBG (P = 0.01). Larger prostatic volumes were also marginally associated with increasing levels of TT (P = 0.058).

CONCLUSION

Circulating serum levels of SHBG and endogenous sex-steroid hormones are correlated with prostate volume and potentially impact the natural history of BPH. However, longitudinal studies are needed to demonstrate the temporal relationships of hormones and growth factors in the pathogenesis of BPH in AA men.

Insulin-like growth factors and risk of benign prostatic hyperplasia

BACKGROUND

Insulin-like growth factors (IGFs) have potent growth mitogenic and anti-apoptotic effects on prostate tissue, whereas IGF binding proteins (IGFBPs) inhibit growth of prostatic tissue. The IGF axis has been implicated in prostate cancer risk, but its role in benign prostatic hyperplasia (BPH) is unclear.

METHODS

Plasma levels of IGF-I, IGF-II, IGFBP-1, and IGFBP-3 were determined from the fasting bloods of 206 BPH cases admitted for treatment and 306 randomly selected population controls in Shanghai, China.

RESULTS

Relative to the lowest tertile, men in the highest tertile of IGF-I levels had a significantly elevated risk of BPH (odds ratio [OR] = 2.80, 95% confidence interval [95% CI] = 1.60-4.92; P(trend) < 0.001). Results for IGF-I were more pronounced after adjustment for serum androgens. In contrast, men in the highest IGFBP-3 tertile had a significantly reduced risk (OR = 0.40; 95% CI = 0.23-0.69; P(trend) < 0.001). No associations of BPH with IGF-II and IGFBP-1 were observed.

CONCLUSION

As has been previously observed for prostate cancer, we found that IGF-I and IGFBP-3 are associated with BPH risk in China. Further investigation is needed to elucidate the role of the IGF axis in BPH etiology.

Gene expression signature of benign prostatic hyperplasia revealed by cDNA microarray analysis

BACKGROUND

Despite the high prevalence of benign prostatic hyperplasia (BPH) in the aging male, little is known regarding the etiology of this disease. A better understanding of the molecular etiology of BPH would be facilitated by a comprehensive analysis of gene expression patterns that are characteristic of benign growth in the prostate gland. Since genes differentially expressed between BPH and normal prostate tissues are likely to reflect underlying pathogenic mechanisms involved in the development of BPH, we performed comparative gene expression analysis using cDNA microarray technology to identify candidate genes associated with BPH.

METHODS

Total RNA was extracted from a set of 9 BPH specimens from men with extensive hyperplasia and a set of 12 histologically normal prostate tissues excised from radical prostatectomy specimens. Each of these 21 RNA samples was labeled with Cy3 in a reverse transcription reaction and cohybridized with a Cy5 labeled common reference sample to a cDNA microarray containing 6,500 human genes. Normalized fluorescent intensity ratios from each hybridization experiment were extracted to represent the relative mRNA abundance for each gene in each sample. Weighted gene and random permutation analyses were performed to generate a subset of genes with statistically significant differences in expression between BPH and normal prostate tissues. Semi-quantitative PCR analysis was performed to validate differential expression.

RESULTS

A subset of 76 genes involved in a wide range of cellular functions was identified to be differentially expressed between BPH and normal prostate tissues. Semi-quantitative PCR was performed on 10 genes and 8 were validated. Genes consistently upregulated in BPH when compared to normal prostate tissues included: a restricted set of growth factors and their binding proteins (e.g. IGF-1 and -2, TGF-beta3, BMP5, latent TGF-beta binding protein 1 and -2); hydrolases, proteases, and protease inhibitors (e.g. neuropathy target esterase, MMP2, alpha-2-macroglobulin); stress response enzymes (e.g. COX2, GSTM5); and extracellular matrix molecules (e.g. laminin alpha 4 and beta 1, chondroitin sulfate proteoglycan 2, lumican). Genes consistently expressing less mRNA in BPH than in normal prostate tissues were less commonly observed and included the transcription factor KLF4, thrombospondin 4, nitric oxide synthase 2A, transglutaminase 3, and gastrin releasing peptide.

CONCLUSIONS

We identified a diverse set of genes that are potentially related to benign prostatic hyperplasia, including genes both previously implicated in BPH pathogenesis as well as others not previously linked to this disease. Further targeted validation and investigations of these genes at the DNA, mRNA, and protein levels are warranted to determine the clinical relevance and possible therapeutic utility of these genes.

Insulin-like growth factor-1, insulin-like growth factor binding protein-3, and body mass index: clinical correlates of prostate volume among Black men

OBJECTIVES

To examine the relationship between insulin-like growth factor-1 (IGF-1), insulin-like growth factor binding protein-3 (IGFBP-3), and body mass index and prostate volume, as a surrogate marker for benign prostatic hyperplasia, in a community-based sample of black men. Epidemiologic studies examining the role of IGF-1 and IGFBP-3 suggest that increased levels of serum IGF-1 and decreased levels of serum IGFBP-3 are associated with an increased risk of prostate cancer. Few studies have examined these factors with respect to benign prostatic hyperplasia, and these have been limited to white men.

METHODS

The study population consisted of a sample of 364 black men, 40 to 79 years of age, residing in Genesee County, Michigan. Men with prostate cancer or prior prostate surgery were excluded. All subjects completed a clinical examination, which included a complete urologic examination with transrectal ultrasonography, anthropometric measurements, and serum assays for IGF-1 and IGFBP-3.

RESULTS

Multivariable regression models demonstrated that prostate volume increased with increasing age (P <0.0001) and body mass index (P = 0.03). IGFBP-3 rather than IGF-1 was positively associated with increasing prostate volume (P = 0.003).

CONCLUSIONS

This is the largest study describing the relationships between IGF-1, IGFBP-3, and body mass index and prostate volume, and the only study in black men. Although earlier studies demonstrated an association between IGF-1 and prostate cancer risk, our findings indicate that IGFBP-3 is more relevant for prostate enlargement, suggesting that IGF-1 and IGFBP-3 may play different pathophysiologic roles in benign and malignant prostatic conditions.

Up-regulation of hepatic IGFBP-1 production as a strategy for preventing benign prostatic hyperplasia

Many lines of evidence point to a prominent role for excess production and activity of stroma-derived, androgen-induced IGF-II in the stromal and epithelial hyperplasia characteristic of benign prostatic hyperplasia (BPH). Increased stromal expression of the type I IGF receptor, as well as altered local production of IGF binding proteins, appear to contribute to this increase in IGF activity. Systemic IGFBP-1, primarily of hepatic origin, is a functional antagonist of IGF-II; thus, boosting IGFBP-1 production might be expected to lessen risk for BPH. Minimizing diurnal insulin secretion, and possibly avoiding intake of animal proteins over-rich in essential amino acids, are practical strategies for increasing hepatic IGFBP-1 synthesis. This hypothesis may rationalize recent evidence that exercise and moderate alcohol consumption decrease risk for BPH, whereas heavy smoking increases this risk. A clinical impression that BPH is becoming more common in Japan, and evidence that Japanese making frequent use of meat and dairy products are at increased risk for this disorder, also appear consistent with this view.

Effects of androgens on the insulin-like growth factor system in an androgen-responsive human osteoblastic cell line

Although androgens have significant effects on bone metabolism, the mediators of their effects are still unclear. As the insulin-like growth factors (IGFs) and IGF-binding proteins (IGFBPs) have important effects on osteoblast proliferation and differentiation, we examined androgen effects on the IGF system in a conditionally immortalized human fetal osteoblastic cell line, hFOB/AR-6, which displays a mature osteoblastic phenotype and physiological levels of functional androgen receptors. The nonaromatizable androgen, 5alpha-dihydrotestosterone (5alphaDHT), and testosterone, but not dehydroepiandrosterone, increased IGF-I messenger RNA (mRNA) levels up to 4-fold in a dose (10(-12)-10(-6) M)- and time (2-72 h)-dependent fashion. These changes were prevented by the specific androgen receptor antagonist, hydroxyflutamide. In addition, 5alpha-DHT decreased IGFBP-4 mRNA and protein levels by 2- and 4-fold, respectively, and increased IGFBP-2 and -3 mRNA and protein levels by 6- and 7-fold (for mRNA) and 3- and 5-fold (for protein), respectively. hFOB/AR-6 cells expressed the type-I IGF receptor, but this was not regulated by 5alphaDHT. 5alphaDHT and IGFBP-3 specifically increased hFOB/AR-6 cell proliferation, and a monoclonal antibody specific for IGF-I blocked this effect. Thus, androgens increase the expression of IGF-I, IGFBP-2, and IGFBP-3, but decrease levels of the inhibitory IGFBP-4 in an androgen-responsive human osteoblastic cell line. Our data are consistent with the hypothesis that the effects of androgen on bone cells may be mediated at least in part by increases in IGF-I production and by differential regulation of IGFBPs.