Insulin-like growth factor I is not a useful marker of prostate cancer in men with elevated levels of prostate-specific antigen

Connecting the Dots Between the Gut-IGF-1-Prostate Axis: A Role of IGF-1 in Prostate Carcinogenesis

Prostate cancer (PCa) is the most common malignancy in men worldwide, thus developing effective prevention strategies remain a critical challenge. Insulin-like growth factor 1 (IGF-1) is produced mainly in the liver by growth hormone signaling and is necessary for normal physical growth. However, several studies have shown an association between increased levels of circulating IGF-1 and the risk of developing solid malignancies, including PCa. Because the IGF-1 receptor is overexpressed in PCa, IGF-1 can accelerate PCa growth by activating phosphoinositide 3-kinase and mitogen-activated protein kinase, or increasing sex hormone sensitivity. Short-chain fatty acids (SCFAs) are beneficial gut microbial metabolites, mainly because of their anti-inflammatory effects. However, we have demonstrated that gut microbiota-derived SCFAs increase the production of IGF-1 in the liver and prostate. This promotes the progression of PCa by the activation of IGF-1 receptor downstream signaling. In addition, the relative abundance of SCFA-producing bacteria, such as Alistipes, are increased in gut microbiomes of patients with high-grade PCa. IGF-1 production is therefore affected by the gut microbiome, dietary habits, and genetic background, and may play a central role in prostate carcinogenesis. The pro-tumor effects of bacteria and diet-derived metabolites might be potentially countered through dietary regimens and supplements. The specific diets or supplements that are effective are unclear. Further research into the "Gut-IGF-1-Prostate Axis" may help discover optimal diets and nutritional supplements that could be implemented for prevention of PCa.

Increased Prevalence of Malignancies in Fibrous Dysplasia/McCune-Albright Syndrome (FD/MAS): Data from a National Referral Center and the Dutch National Pathology Registry (PALGA)

Malignant transformation of fibrous dysplasia lesions has been reported in patients with fibrous dysplasia/McCune-Albright syndrome (FD/MAS). Recently, we have observed an increased risk for breast cancer. In this study, the prevalence of skeletal and extraskeletal malignancies in patients with FD/MAS in the Netherlands was assessed by analyzing data from our cohort of FD/MAS patients, the Dutch Pathology Registry (PALGA), and the Netherlands Cancer Registry (NCR). We extracted data on sex, age at diagnosis of FD/MAS, type of FD/MAS, type of malignancy, and age at diagnosis of malignancy and histology of bone and malignant tissue when available, including GNAS-mutation analysis from patients' medical records. Standardized Morbidity Ratios (SMRs) with 95% confidence intervals were calculated. Twelve malignancies were identified in the LUMC FD/MAS cohort and 100 in the PALGA cohort. In this cohort, SMR was increased for osteosarcoma (19.7, 95% CI 3.5-48.9), cervical cancer (4.93, 95%CI 1.7-8.2), thyroid cancer (3.71, 95% CI 1.1-7.8), prostate cancer (3.08, 95% CI 1.8-4.6), and melanoma (2.01, 95%CI 1.2-3.1). SMRs for pancreatic cancer or hepatocellular carcinoma could not be calculated due to low numbers. The small number of malignancies identified in our FD/MAS cohort precluded the calculation of SMRs for our cohort specifically. Our findings show that patients with FD/MAS appear to have an increased risk for osteosarcoma, cervical, thyroid, and prostate cancer and melanoma. However, these data should be interpreted with caution, as true incidence rates of the identified malignancies may be influenced by the inclusion of only patients with histologically confirmed FD/MAS. The etiology of this increased risk for malignancies still needs to be elucidated.

Energy Restriction and Colorectal Cancer: A Call for Additional Research

: Colorectal cancer has the second highest cancer-related mortality rate, with an estimated 881,000 deaths worldwide in 2018. The urgent need to reduce the incidence and mortality rate requires innovative strategies to improve prevention, early diagnosis, prognostic biomarkers, and treatment effectiveness. Caloric restriction (CR) is known as the most robust nutritional intervention that extends lifespan and delays the progression of age-related diseases, with remarkable results for cancer protection. Other forms of energy restriction, such as periodic fasting, intermittent fasting, or fasting-mimicking diets, with or without reduction of total calorie intake, recapitulate the effects of chronic CR and confer a wide range of beneficial effects towards health and survival, including anti-cancer properties. In this review, the known molecular, cellular, and organismal effects of energy restriction in oncology will be discussed. Energy-restriction-based strategies implemented in colorectal models and clinical trials will be also revised. While energy restriction constitutes a promising intervention for the prevention and treatment of several malignant neoplasms, further investigations are essential to dissect the interplay between fundamental aspects of energy intake, such as feeding patterns, fasting length, or diet composition, with all of them influencing health and disease or cancer effects. Currently, effectiveness, safety, and practicability of different forms of fasting to fight cancer, particularly colorectal cancer, should still be contemplated with caution.

Does milk intake promote prostate cancer initiation or progression via effects on insulin-like growth factors (IGFs)? A systematic review and meta-analysis

PURPOSE

To establish whether the association between milk intake and prostate cancer operates via the insulin-like growth factor (IGF) pathway (including IGF-I, IGF-II, IGFBP-1, IGFBP-2, and IGFBP-3).

METHODS

Systematic review, collating data from all relevant studies examining associations of milk with IGF, and those examining associations of IGF with prostate cancer risk and progression. Data were extracted from experimental and observational studies conducted in either humans or animals, and analyzed using meta-analysis where possible, with summary data presented otherwise.

RESULTS

One hundred and seventy-two studies met the inclusion criteria: 31 examining the milk-IGF relationship; 132 examining the IGF-prostate cancer relationship in humans; and 10 animal studies examining the IGF-prostate cancer relationship. There was moderate evidence that circulating IGF-I and IGFBP-3 increase with milk (and dairy protein) intake (an estimated standardized effect size of 0.10 SD increase in IGF-I and 0.05 SD in IGFBP-3 per 1 SD increase in milk intake). There was moderate evidence that prostate cancer risk increased with IGF-I (Random effects meta-analysis OR per SD increase in IGF-I 1.09; 95% CI 1.03, 1.16; n = 51 studies) and decreased with IGFBP-3 (OR 0.90; 0.83, 0.98; n = 39 studies), but not with other growth factors. The IGFBP-3 -202A/C single nucleotide polymorphism was positively associated with prostate cancer (pooled OR for A/C vs. AA = 1.22; 95% CI 0.84, 1.79; OR for C/C vs. AA = 1.51; 1.03, 2.21, n = 8 studies). No strong associations were observed for IGF-II, IGFBP-1 or IGFBP-2 with either milk intake or prostate cancer risk. There was little consistency within the data extracted from the small number of animal studies. There was additional evidence to suggest that the suppression of IGF-II can reduce tumor size, and contradictory evidence with regards to the effect of IGFBP-3 suppression on tumor progression.

CONCLUSION

IGF-I is a potential mechanism underlying the observed associations between milk intake and prostate cancer risk.

The insulin-like growth factor system in cancer

Insulin-like growth factor (IGF) plays an important role in tissue growth and development. Several studies have demonstrated the association between circulating levels of IGF-1 and -2 and cancer risk, and the IGF system has been implicated in the oncogenesis of essentially all solid and hematologic malignancies. The optimal strategy for targeting IGF signaling in patients with cancer is not clear. The modest benefits reported thus far underscore the need for a better understanding of IGF signaling, which would enable clinicians to identify the subset of patients with the greatest likelihood of attaining benefit from this targeted approach.

Circulating insulin-like growth factors and IGF-binding proteins in PSA-detected prostate cancer: the large case-control study ProtecT

Circulating insulin-like growth factor-I (IGF-I) has been studied extensively in prostate cancer, but there is still little information about IGFs and IGF-binding proteins (IGFBP) in cancers detected by the prostate-specific antigen (PSA) test. Here, we report the findings of a U.K.-based case-control study to investigate circulating IGFs and IGFBPs in PSA-detected prostate cancer with regard to their potential associations with different cancer stages or grades. PSA testing was offered to 110,000 men aged 50 to 69 years from 2002 to 2009. Participants with an elevated level of PSA (≥3.0 ng/mL) underwent prostate biopsy and measurements of blood serum IGF-I, IGF-II, IGFBP-2, and IGFBP-3 obtained at recruitment. We found that serum levels of IGF-II (OR per SD increase: 1.16; 95% CI: 1.08-1.24; P(trend) < 0.001), IGFBP-2 (1.18; 1.06-1.31; P(trend) < 0.01) and IGFBP-3 (1.27; 1.19-1.36; P(trend) < 0.001), but not IGF-I (0.99; 0.93-1.04; P(trend) = 0.62), were associated with PSA-detected prostate cancer. After controlling for IGFBP-3, IGF-II was no longer associated (0.99; 0.91-1.08; P(trend) = 0.62) and IGF-I was inversely associated (0.85; 0.79-0.91; P(trend) < 0.001) with prostate cancer. In addition, no strong associations existed with cancer stage or grade. Overall, these findings suggest potentially important roles for circulating IGF-II, IGFBP-2, and IGFBP-3 in PSA-detected prostate cancer, in support of recent in vitro evidence. Although our findings for IGF-I agree with previous results from PSA screening trials, they contrast with positive associations in routinely detected disease, suggesting that reducing levels of circulating IGF-I might not prevent the initiation of prostate cancer but might, nonetheless, prevent its progression.

Circulating insulin-like growth factor peptides and prostate cancer risk: a systematic review and meta-analysis

Insulin-like growth factors (IGF-I, IGF-II) and their binding proteins (IGFBP-1-6) play a key role in cell proliferation, differentiation and apoptosis, suggesting possible involvement in carcinogenesis. Several epidemiological studies show associations of IGFs with prostate cancer. We searched the published literature for all studies relating levels of IGFs or IGFBPs with prostate cancer. We performed random effects meta-analysis to calculate summary odds ratios. The number of studies (prostate cancer cases) included in each meta-analysis were 42 (7,481) IGF-I; 10 (923) IGF-II; 3 (485) IGFBP-1; 5 (577) IGFBP-2; 29 (6,541) IGFBP-3 and 11 (3,545) IGF-1:IGFBP-3 ratio. The pooled odds ratios (95% confidence intervals) per standard deviation increase in peptide were: IGF-I, OR = 1.21 (1.07, 1.36); IGF-II, OR = 1.17 (0.93, 1.47); IGFBP-1, OR = 1.21 (0.62, 2.33); IGFBP-2, OR = 1.18 (0.90, 1.54); IGFBP-3, OR = 0.88 (0.79, 0.98); IGFI:IGFBP-3 ratio, OR = 1.10 (0.97, 1.24). For all exposures, there was substantial heterogeneity (all I(2) > 75%), partly explained by study design: the magnitude of associations was smaller in prospective vs. retrospective studies, and for IGFBP-3, the inverse association with prostate cancer risk was seen in retrospective but not prospective studies. There was weak evidence that associations of IGF-I and IGFBP-3 with prostate cancer were stronger for advanced disease. Our meta-analysis confirms that raised circulating lGF-I is positively associated with prostate cancer risk. Associations between IGFBP-3 and prostate cancer were inconsistent, and there was little evidence for a role of IGF-II, IGFBP-1 or IGFBP-2 in prostate cancer risk.

Effective prostate cancer chemopreventive intervention with green tea polyphenols in the TRAMP model depends on the stage of the disease

PURPOSE

We have shown previously that oral feeding of green tea polyphenols (GTP) to transgenic adenocarcinoma of the mouse prostate mice in a purely chemopreventive setting significantly inhibits prostate cancer development. To translate this to a human situation, the present study was designed to identify the stage of prostate cancer that is most vulnerable to chemopreventive intervention by GTP.

EXPERIMENTAL DESIGN

GTP infusion (0.1% in drinking water) to transgenic adenocarcinoma of the mouse prostate was initiated at ages representing different stage of the disease: (a) 6 weeks (group 1, normal prostate), (b) 12 weeks (group 2, prostatic intraepithelial neoplasia), (c) 18 weeks (group 3, well-differentiated adenocarcinoma), and (b) 28 weeks (group 4, moderately differentiated adenocarcinoma). At age 32 weeks, subsets of animals were evaluated by magnetic resonance imaging, ultrasound, and prostate weight and for serum insulin-like growth factor (IGF)-I/IGF binding protein-3 and IGF signaling.

RESULTS

Tumor-free survival was extended to 38 weeks (P < 0.001) in group 1, 31 weeks (P < 0.01) in group 2, and 24 weeks (P < 0.05) in group 3 compared with 19 weeks in water-fed controls. Median life expectancy was 68 weeks in group 1, 63 weeks in group 2, 56 weeks in group 3, and 51 weeks in group 4 compared with 42 weeks in the control mice. IGF-I and its downstream targets including phosphatidylinositol 3-kinase, pAkt, and phosphorylated extracellular signal-regulated kinase were significantly inhibited only when intervention was initiated early when prostatic intraepithelial neoplasia lesions were common.

CONCLUSIONS

Our studies indicate that chemopreventive potential of GTP decreases with advancing stage of the disease and underscore the need to design appropriate chemoprevention clinical trails.

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.

IGFs and IGFBPs: surrogate markers for diagnosis and surveillance of tumour growth?

Insulin-like growth factors (IGFs), IGF receptors, and IGF binding proteins (IGFBPs) constitute the IGF system. Comprehensive data indicate that these factors play a pivotal role in tumorigenesis. Epidemiological data indicate that cancer risk is associated with high serum IGF-I values. Because dysregulation of the IGF system is a frequent pattern in malignancy, IGFs/IGFBPs might represent novel tumour markers that could be useful both for diagnosis and surveillance.

Insulin-like growth factor-I and prostate cancer: a meta-analysis

Some, but not all, epidemiological found have shown that high circulating levels of insulin-like growth factor-I (IGF-I) are associated with an increased risk of prostate cancer. We performed a meta-analysis on all the studies reported so far to evaluate this association. In our Medline search, 14 case-control studies were identified. A standard protocol abstracted information for each study. Hedges' standardized mean difference (HSMD) and odds ratio (OR) were used to estimate the effect of IGF-I and IGF-binding proteins (IGFBP-3). The combined data showed that circulating levels of IGF-I were significantly higher in prostate cancer patients (HSMD = 0.194). The OR for prostate cancer was 1.47 (95% confidence interval (CI) 1.23-1.77) among men with high IGF-I compared to those with low IGF-I. The OR was 1.26 (95% CI 1.03-1.54) for IGFBP-3. Circulating levels of IGF-I and IGFBP-3 are likely to be higher in prostate cancer patients than in the controls. These findings support the suggestion that high IGF-I and IGFBP-3 are associated with an increased risk of prostate cancer.