A study of caloric restriction versus standard diet in overweight men with newly diagnosed prostate cancer: a randomized controlled trial.

INTRODUCTION: Obese men have an increased risk of prostate cancer (PCa)-specific mortality. Potential mechanisms include insulin and related proteins. We investigate whether a short-term caloric restriction diet in overweight/obese men with newly diagnosed PCa can lead to measurable changes in patient anthropometrics and insulin-related proteins. METHODS: Overweight and obese PCa patients choosing active surveillance or radical prostatectomy were randomized to a 6-week, caloric-restricted diet or to continue their current diet. Changes from baseline to end of study in anthropometrics, dietary constituents and serum proteins (insulin, c-peptide, IGF-1, adiponectin, IGF-BP3) were compared between the intervention and control groups using a Generalized Estimating Equation model. RESULTS: Nineteen patients were randomized to the intervention (N = 10) or control (N = 9) group. Men in the intervention group had a 1.7% (3.7 lbs) mean decline in weight versus 1.0% (2.0 lbs) in controls (P < 0.05), and a reduced intake of calories, total and saturated fat, protein and starch (all P < 0.1 compared to controls). There was a significant difference (P = 0.002) in mean serum IGFBP-3 between the intervention (+2.8%) and control group (-6.9%). Other biomarkers changed with the diet intervention to a degree similar to previous weight loss studies but were not statistically significant compared with controls. CONCLUSION: In this small pilot study, a 6-week caloric restricted diet in men with newly diagnosed PCa produced changes in weight, diet and serum proteins possibly related to prognosis. These results support larger-scale trials testing longer-term weight loss effects on potential PCa progression biomarkers.

Tumor suppressor BRCA1 is expressed in prostate cancer and controls insulin-like growth factor I receptor (IGF-IR) gene transcription in an androgen receptor-dependent manner.

PURPOSE: The insulin-like growth factor (IGF) system plays an important role in prostate cancer. The BRCA1 gene encodes a transcription factor with tumor suppressor activity. The involvement of BRCA1 in prostate cancer, however, has not yet been elucidated. The purpose of the present study was to examine the functional correlations between BRCA1 and the IGF system in prostate cancer. EXPERIMENTAL DESIGN: An immunohistochemical analysis of BRCA1 was done on tissue microarrays comprising 203 primary prostate cancer specimens. In addition, BRCA1 levels were measured in prostate cancer xenografts and in cell lines representing early stages (P69 cells) and advanced stages (M12 cells) of the disease. The ability of BRCA1 to regulate IGF-I receptor (IGF-IR) expression was studied by coexpression experiments using a BRCA1 expression vector along with an IGF-IR promoter-luciferase reporter. RESULTS: We found significantly elevated BRCA1 levels in prostate cancer in comparison with histologically normal prostate tissue (P<0.001). In addition, an inverse correlation between BRCA1 and IGF-IR levels was observed in the androgen receptor (AR)-negative prostate cancer-derived P69 and M12 cell lines. Coexpression experiments in M12 cells revealed that BRCA1 was able to suppress IGF-IR promoter activity and endogenous IGF-IR levels. On the other hand, BRCA1 enhanced IGF-IR levels in LNCaP C4-2 cells expressing an endogenous AR. CONCLUSIONS: We provide evidence that BRCA1 differentially regulates IGF-IR expression in AR-positive and AR-negative prostate cancer cells. The mechanism of action of BRCA1 involves modulation of IGF-IR gene transcription. In addition, immunohistochemical data are consistent with a potential survival role of BRCA1 in prostate cancer.

Insulin-like growth factor-I receptor blockade improves outcome in mouse model of lung injury.

RATIONALE: The insulin-like growth factor-I (IGF-I) pathway is an important determinant of survival and proliferation in many cells. However, little is known about the role of the IGF-I pathway in lung injury. We previously showed elevated levels of IGF-I in bronchoalveolar lavage fluid from patients with acute respiratory distress syndrome. Furthermore, immunodepletion of IGF from acute respiratory distress syndrome bronchoalveolar lavage increased fibroblast apoptosis. OBJECTIVES: We examined the effect of blockade of type 1 IGF tyrosine kinase receptor (IGF-IR) in a murine model of bleomycin-induced lung injury and fibrosis. METHODS: Mice were treated with a monoclonal antibody against the IGF-I receptor (A12) or vehicle after intratracheal bleomycin instillation. MEASUREMENTS AND MAIN RESULTS: Mice treated with A12 antibody had significantly improved survival after bleomycin injury compared with control mice. Both groups of mice had a similar degree of fibrosis on days 7 and 14, but by Day 28 the A12-treated group had significantly less fibrosis. Delayed treatment with A12 also resulted in decreased fibrosis. A12-treated mice had significantly decreased apoptotic cells on Day 28 compared with control mice. We confirmed that A12 treatment induced mouse lung fibroblast apoptosis in vitro. In addition, IGF-I increased lung fibroblast migration. The primary pathway activated by IGF-I in lung fibroblasts was the insulin receptor substrate-2/phosphatidylinositol 3-kinase/Akt axis. CONCLUSIONS: IGF-I regulated survival and migration of fibrogenic cells in the lung. Blockade of the IGF pathway increased fibroblast apoptosis and subsequent resolution of pulmonary fibrosis. Thus, IGF-IR may be a potential target for treatment of lung injury and fibrosis.

An antibody targeting the type I insulin-like growth factor receptor enhances the castration-induced response in androgen-dependent prostate cancer.

PURPOSE: To determine the effect of inhibition of insulin-like growth factor-IR (IGF-IR) signaling with an antibody to the IGF-IR, A12, in conjunction with androgen withdrawal on prostate cancer progression in a human prostate xenograft model, LuCaP 35. EXPERIMENTAL DESIGN: LuCaP 35 was implanted s.c. in severe combined immunodeficient mice. At the time of castration, mice were randomized to one of three groups. Group 1 was castrate only; group 2 received A12 40 mg/kg i.p. for 2 weeks beginning 1 week after castration; and group 3 received A12 40 mg/kg i.p. for 2 weeks beginning 2 weeks after castration. RESULTS: In group 1, tumor volume decreased to 60% of the starting volume 4 weeks post-castration. In groups 2 and 3, tumor volumes nadired 6 weeks after castration at <10% of the volume at time of castration (P < 0.01). Tumor regrowth was not seen in groups 2 or 3 until 15 weeks after castration. Androgen receptor (AR) localization in tumors showed a decrease in nuclear staining in groups 2 and 3 compared with group 1 (P < 0.001). Tumor volume correlated with nuclear AR intensity. AR-regulated genes increased early in group 1, but did not increase in groups 2 and 3. Thus, tumor-specific survival was prolonged by the addition of A12 to castration. CONCLUSIONS: This study shows that the inhibition of IGF-IR enhances the effects of castration in prostate cancer. These effects are associated with a decrease in AR signaling and nuclear AR localization, and recurrence is associated with an increase in AR-regulated gene expression.

Combined in vivo effect of A12, a type 1 insulin-like growth factor receptor antibody, and docetaxel against prostate cancer tumors.

PURPOSE: A human type 1 insulin-like growth factor receptor antibody (A12) has been shown to effectively inhibit human xenograft tumor growth, including androgen-dependent and androgen-independent prostate tumors. Docetaxel, either as a single agent or combined with others, has shown a survival benefit in prostate cancer patients. Based on these data, we investigated the combined in vivo effect of A12 and docetaxel on human androgen-independent and osseous prostate tumor growth. EXPERIMENTAL DESIGN: To study human androgen-independent prostate cancer model, LuCaP35V tumors were implanted s.c. into castrated severe combined immunodeficient mice. When tumors reached about 100 mm3, animals were treated with vehicle control docetaxel (10 or 20 mg/kg) and docetaxel in combination with A12 (40 microg/kg) for 4 weeks. To study human osseous prostate cancer model, LuCaP 23.1 tumors were implanted intratibiae. When serum prostate-specific antigen reached 5 to 10 ng/mL, treatments were initiated. RESULTS: A12 markedly augmented the inhibition of docetaxel on tumor growth. When docetaxel is combined with A12, the inhibition of tumor growth continued after treatment cessation, which was associated with continued apoptosis and decreased proliferation of tumor cells. Gene expression profiles indicated that the posttreatment suppression of tumor growth may be due to enhanced negative regulation of cell cycle progression- and/or cell survival-associated genes, some of which have been shown to induce resistance to docetaxel. CONCLUSIONS: Our findings suggest that targeting type 1 insulin-like growth factor receptor can enhance the therapeutic effect of docetaxel on advanced prostate cancer. Our findings also suggest a potential mechanism to improve the treatment efficacy of docetaxel in prostate cancer.

Interaction of IGF signaling and the androgen receptor in prostate cancer progression.

The insulin-like growth factor type I receptor (IGF-IR) has been suggested to play an important role in prostate cancer progression and possibly in the progression to androgen-independent (AI) disease. The term AI may not be entirely correct, in that recent data suggest that expression of androgen receptor (AR) and androgen-regulated genes is the primary association with prostate cancer progression after hormone ablation. Therefore, signaling through other growth factors has been thought to play a role in AR-mediated prostate cancer progression to AI disease in the absence of androgen ligand. However, existing data on how IGF-IR signaling interacts with AR activation in prostate cancer are conflicting. In this Prospect article, we review some of the published data on the mechanisms of IGF-IR/AR interaction and present new evidence that IGF-IR signaling may modulate AR compartmentation and thus alter AR activity in prostate cancer cells. Inhibition of IGF-IR signaling can result in cytoplasmic AR retention and a significant change in androgen-regulated gene expression. Translocation of AR from the cytoplasm to the nucleus may be associated with IGF-induced dephosphorylation. Since fully humanized antibodies targeting the IGF-IR are now in clinical trials, the current review is intended to reveal the mechanisms of potential therapeutic effects of these antibodies on AI prostate cancers.

In vivo effects of the human type I insulin-like growth factor receptor antibody A12 on androgen-dependent and androgen-independent xenograft human prostate tumors.

PURPOSE: The type I insulin-like growth factor receptor (IGF-IR) and its ligands have been shown to play a critical role in prostate carcinoma development, growth, and metastasis. Targeting the IGF-IR may be a potential treatment for prostate cancer. A fully human monoclonal antibody, A12, specific to IGF-IR, has shown potent antitumor effects in breast, colon, and pancreatic cancers in vitro and in vivo. In this study, we tested the in vivo effects of A12 on androgen-dependent and androgen-independent prostate tumor growth. EXPERIMENTAL DESIGN: Androgen-dependent LuCaP 35 and androgen-independent LuCaP 35V prostate tumors were implanted s.c. into intact and castrated severe combined immunodeficient mice, respectively. When tumor volume reached about 150 to 200 mm(3), A12 was injected at 40 mg/kg body weight thrice a week for up to 5 weeks. RESULTS: We find that A12 significantly inhibits growth of androgen-dependent LuCaP 35 and androgen-independent LuCaP 35V prostate xenografts, however, by different mechanisms. In LuCaP 35 xenografts, A12 treatment induces tumor cell apoptosis or G(1) cycle arrest. In LuCaP 35V xenografts, A12 treatment induces tumor cell G(2)-M cycle arrest. Moreover, we find that blocking the function of IGF-IR down-regulates androgen-regulated gene expression in androgen-independent LuCaP 35V tumor cells. CONCLUSIONS: Our findings suggest that A12 is a therapeutic candidate for both androgen-dependent and androgen-independent prostate cancer. Our findings also suggest an IGF-IR-dependent activity of the androgen receptor in androgen-independent prostate cancer cells.

Prevalent expression of the immunostimulatory MHC class I chain-related molecule is counteracted by shedding in prostate cancer.

The MHC class I chain-related molecules (MICs) have previously been shown to be induced on most epithelial tumor cells. Engagement of MIC by the activating immune receptor NKG2D triggers NK cells and augments antigen-specific CTL anti-tumor immunity. The MIC-NKG2D system was proposed to participate in epithelial tumor immune surveillance. Paradoxically, studies suggest that tumors may evade MIC-NKG2D-mediated immunity by MIC shedding-induced impairment of effector cell function. Here we demonstrate the first evidence to our knowledge of a significant correlation of MIC shedding and deficiency in NK cell function with the grade of disease in prostate cancer. MIC is widely expressed in prostate carcinoma. The presence of surface target MIC, however, is counteracted by shedding. A significant increase in serum levels of soluble MIC (sMIC) and deficiency in NK cell function was shown in patients with advanced cancer. Finally, the deficiency in NK cell function can be overcome by treatment with IL-2 or IL-15 in vitro. Our results suggest that (a) deficiency in MIC-NKG2D immune surveillance may contribute to prostate cancer progression, (b) sMIC may be a novel biomarker for prostate cancer, and (c) using cytokines to restore MIC-NKG2D-mediated immunity may have clinical significance for prostate cancer in cell-based adaptive immunotherapy.

Suppression of growth and tumorigenicity in the prostate tumor cell line M12 by overexpression of the transcription factor SOX9.

Overexpression of mac25 in the prostate cancer cell line M12 effects a dramatic reversal of the transformed phenotype. cDNA array analysis of RNA from cells overproducing the mac25 protein (M12/mac25) indicated upregulation of the sex determining transcription factor SOX9. In this study, we have confirmed increased expression of SOX9 in M12/mac25 cells and have further investigated the physiological effects of increased SOX9 production. Greatly increased levels of SOX9 RNA and mature protein were demonstrated in cells transfected with a SOX9 cDNA (M12/SOX9), and gel mobility shift assays confirmed binding of nuclear protein from these cells to an oligonucleotide containing the SOX9 consensus binding sequence. M12/SOX9 cells assumed the spindle-shaped morphology characteristic of M12/mac25 cells, suggesting that SOX9 mediates some effects of mac25. Elevated expression of SOX9 resulted in a decreased rate of cellular proliferation, cell cycle arrest in G0/G1, and increased sensitivity to apoptosis. Tumor development in athymic nude mice was inhibited by 80%. Finally, prostate-specific antigen and the androgen receptor, two genes whose expression is characteristic of differentiated cells, were both upregulated in M12/SOX9 cells. These data indicate that SOX9 contributes to growth regulation by mac25 via inhibition of cell growth and promotion of differentiation.

Increased manganese superoxide dismutase (SOD-2) is part of the mechanism for prostate tumor suppression by Mac25/insulin-like growth factor binding-protein-related protein-1.

Increased expression of mac25/insulin-like growth factor binding-protein related protein-1 (IGFBP-rP1) in human breast and prostate epithelial cell lines results in the suppression of tumor growth. CDNA expression array analysis revealed increased manganese superoxide dismutase (SOD-2) expression in the mac25/IGFBP-rP1-transfected M12 human prostate cancer cell line compared to M12 control cells. SOD-2 has been postulated to be a tumor suppressor. SOD-2 was also increased in LNCaP cells stably transfected with mac25/IGFBP-rP1, but not in mac25/IGFBP-rP1-transfected PC-3 cells. Mac25 LNCaP cells had a marked decrease in tumor growth in nude mice compared to controls, but there was no difference in tumor growth in mac25 PC-3 cells compared to control. Phosphorylated Erk and Akt were increased in the M12 and LNCaP transfected mac25/IGFBP-rP1 cells but not PC-3 mac25. Inhibition of PI-3 kinase results in a marked decrease in viability of the M12-mac25 cells compared to M12 controls. Cells treated with H(2)O(2) result in an increase in phospho-ERK. Transfection of SOD-2 in M12 cells markedly decreased tumor growth, apoptosis, G1 delay in the cell cycle, and expression of senescence associated beta-galactosidase. These results suggest that one of the downstream mediators of the senescence-associated tumor suppression effect of mac25/IGFBP-rP1 is SOD-2.