Plasma levels of IGF-1, IGF-2, and IGFBP-3 in white and African-American men at increased risk of prostate cancer.

OBJECTIVES: To further investigate the relationship between the plasma levels of insulin-like growth factor-1 (IGF-1), insulin-like growth factor-2 (IGF-2), insulin-like growth factor binding protein-3 (IGFBP-3), growth hormone, testosterone, and demographic factors, particularly race, within a group of men at increased risk of prostate cancer development. METHODS: Enzyme-linked immunosorbent assays or an immunosorbent assay was used to quantitate the plasma levels of IGF-1, IGF-2, IGFBP-3, growth hormone, and testosterone. The study group consisted of 169 men (85 African-American, 84 white) aged 35 to 69 years, with no personal history of prostate cancer, but having at least one first-degree relative diagnosed with the disease, unless they were African-American. The relationships between the plasma levels and the categorical covariates were assessed using the nonparametric Wilcoxon test and between the continuous variables using Spearman's correlation coefficient. RESULTS: The mean plasma levels of IGFBP-3 were significantly lower in African-American (2657 ng/mL) than in white (2965 ng/mL) men (P = 0.0062). The plasma levels of IGF-2 were also lower in the African-American (503.5 ng/mL) than in the white (549.1 ng/mL) men (P = 0.0084). Overall, the IGF-1 plasma levels correlated positively with the IGF-2, IGFBP-3, and growth hormone levels and the IGF-2 plasma levels correlated negatively with the testosterone levels. CONCLUSIONS: Our results demonstrate that lower plasma levels of IGFBP-3 and IGF-2 are associated with race in a population of men at increased risk of developing prostate cancer. The ability of these markers to predict earlier disease onset is currently under investigation.

Racial differences in insulin-like growth factor binding protein-3 in men at increased risk of prostate cancer.

OBJECTIVES: To determine the overall plasma levels of insulin-like growth factor-1 (IGF-1) and insulin-like growth factor binding protein-3 (IGFBP-3) in a group of men at higher risk of prostate cancer development and to investigate the relationships between demographics and these levels, particularly with regard to race. METHODS: An enzyme-linked immunosorbant assay was used to quantitate plasma levels of IGF-1 and IGFBP-3. The study group consisted of 105 men (63 African American [AA], 42 white), aged 35 to 69 years, with no personal history of prostate cancer, but having at least one first-degree relative diagnosed with the disease, unless they were AA. Differences in plasma levels and categorical covariates were assessed using the nonparametric Wilcoxon test. Associations between plasma levels and the continuous variables were quantified using the nonparametric Spearman correlation coefficient. RESULTS: The mean plasma level of IGF-1 was not significantly different between AA (162.3 ng/mL) and white (172.1 ng/mL) men (P = 0.415). However, the mean plasma level of IGFBP-3 was lower in AA (2789 ng/mL) than in white (3216 ng/mL) men, and this decrease was highly significant (P = 0.0045). No correlation between IGFBP-3 plasma level and age was detected in the group as a whole, but an inverse relationship between IGF-1 plasma level and age was evident (P = 0.0079). CONCLUSIONS: Our results demonstrate that IGFBP-3 plasma levels are lower in AA men than in white men. Since IGFBP-3 can control IGF-1 bioavailability, the lowered IGFBP-3 could explain in part the increased risk of prostate cancer in AA men.

Prostate cancer risk assessment program. A model for the early detection of prostate cancer.

Prostate cancer is the most common form of cancer (except skin cancer) in men. Several factors have been associated with an increased risk for prostate cancer, including age, ethnicity, family history, lifestyle, and environmental exposures. Recognition of the importance of the interaction of these factors in prostate cancer has led to an interest in their evaluation as a model both for studying genetic susceptibility patterns and for studying and providing educational tools and preventive interventions. One such model has been developed at Fox Chase Cancer Center. Critical to the implementation of the model has been the establishment of the Prostate Cancer Risk Registry (PCRR) and Prostate Cancer Risk Assessment Program (PRAP). Together, they serve as a unique resource for investigating the interaction between environmental factors and genetic susceptibility patterns; exploring the early, premalignant biological markers of prostate cancer; and prospectively assessing the quality of life (QOL) of men at risk. In addition, PRAP facilitates the evaluation of models for prostate cancer risk counseling and screening in the community. This paper describes this model for early detection and risk reduction, along with preliminary data from its first two study aims. The program is particularly relevant in view of the wealth of genetic information emerging from the Human Genome Project.