A molecular view of the role of chirality in charge-driven polypeptide complexation.

Polyelectrolyte molecules of opposite charge are known to form stable complexes in solution. Depending on the system conditions, such complexes can be solid or liquid. The latter are known as complex coacervates, and they appear as a second liquid phase in equilibrium with a polymer-dilute aqueous phase. This work considers the complexation between poly(glutamic acid) and poly(lysine), which is of particular interest because it enables examination of the role of chirality in ionic complexation, without changes to the overall chemical composition. Systematic atomic-level simulations are carried out for chains of poly(glutamic acid) and poly(lysine) with varying combinations of chirality along the backbone. Achiral chains form unstructured complexes. In contrast, homochiral chains lead to formation of stable ß-sheets between molecules of opposite charge, and experiments indicate that ß-sheet formation is correlated with the formation of solid precipitates. Changes in chirality along the peptide backbone are found to cause "kinks" in the ß-sheets. These are energetically unfavorable and result in irregular structures that are more difficult to pack together. Taken together, these results provide new insights that may be of use for the development of simple yet strong bioinspired materials consisting of ß-rich domains and amorphous regions.

Using macromolecular-crystallography beamline and microfluidic platform for small-angle diffraction studies of lipidic matrices for membrane-protein crystallization.

Macromolecular-crystallography (MX) beamlines routinely provide a possibility to change X-ray beam energy, focus the beam to a size of tens of microns, align a sample on a microdiffractometer using on-axis video microscope, and collect data with an area-detector positioned in three dimensions. These capabilities allow for running complementary measurements of small-angle X-ray scattering and diffraction (SAXS) at the same beamline with such additions to the standard MX setup as a vacuum path between the sample and the detector, a modified beam stop, and a custom sample cell. On the 21-ID-D MX beamline at the Advanced Photon Source we attach a vacuum flight tube to the area detector support and use the support motion for aligning a beam stop built into the rear end of the flight tube. At 8 KeV energy and 1 m sample-to-detector distance we can achieve a small-angle resolution of 0.01A-1 in the reciprocal space. Measuring SAXS with this setup, we have studied phase diagrams of lipidic mesophases used as matrices for membrane-protein crystallization. The outcome of crystallization trials is significantly affected by the structure of the lipidic mesophases, which is determined by the composition of the crystallization mixture. We use a microfluidic chip for the mesophase formulation and in situ SAXS data collection. Using the MX beamline and the microfluidic platform we have demonstrated the viability of the high-throughput SAXS studies facilitating screening of lipidic matrices for membrane-protein crystallization.

Lymphangiogenesis in abdominal aortic aneurysm.

BACKGROUND: Ongoing angiogenesis is implicated in the inflammatory environment that characterizes abdominal aortic aneurysm (AAA). Although lymphangiogenesis has been associated with chronic inflammatory conditions, it has yet to be demonstrated in AAA. The aim was to determine the presence of lymphangiogenesis and to delineate the relationship between inflammation and neovascularization in AAA tissue. METHODS: AAA samples and preoperative computed tomography images were obtained from patients undergoing elective AAA repair. Control samples were age-matched abdominal aortic tissue. Specific immunostains for blood vessels (CD31, CD105), lymphatic vessels (D2-40), vascular endothelial growth factor (VEGF) A and VEGF receptor (VEGFR) 3 allowed characterization and quantitation of vasculature. RESULTS: The AAA wall contained high levels of inflammatory infiltrate; microvascular densities of blood (P < 0·001) and lymphatic (P = 0·003) vessels were significantly increased in AAA samples compared with controls. Maximal AAA vascularity was observed in inflammatory areas, with vessels that stained positively for CD31 (ρ = 0·625, P = 0·017), CD105 (ρ = 0·692, P = 0·009) and D2-40 (ρ = 0·675, P = 0·008) correlating positively with the extent of inflammation. Increased VEGFR-3 and VEGF-A expression was also evident within inflammatory AAA areas. CONCLUSION: These findings demonstrated lymphatic vessel involvement in end-stage AAA disease, which was associated with the degree of inflammation, and confirmed the involvement of neovascularization.

Carcinoembryonic antigen is the preferred biomarker for in vivo colorectal cancer targeting.

BACKGROUND: Colorectal cancer-specific biomarkers have been used as molecular targets for fluorescent intra-operative imaging, targeted PET/MRI, and selective cytotoxic drug delivery yet the selection of biomarkers used is rarely evidence-based. We evaluated sensitivities and specificites of four of the most commonly used markers: carcinoembryonic antigen (CEA), tumour-associated glycoprotein-72 (TAG-72), folate receptor-α (FRα) and Epithelial growth factor receptor (EGFR). METHODS: Marker expression was evaluated semi-quantitatively in matched mucosal and colorectal cancer tissues from 280 patients using immunohistochemistry (scores of 0-15). Matched positive and negative lymph nodes from 18 patients were also examined. RESULTS: Markers were more highly expressed in tumour tissue than in matched normal tissue in 98.8%, 79.0%, 37.1% and 32.8% of cases for CEA, TAG-72, FRα and EGFR, respectively. Carcinoembryonic antigen showed the greatest differential expression, with tumours scoring a mean of 10.8 points higher than normal tissues (95% CI 10.31-11.21, P<0.001). Similarly, CEA showed the greatest differential expression between positive and negative lymph nodes. Receiver operating characteristic analyses showed CEA to have the best sensitivity (93.7%) and specificity (96.1%) for colorectal cancer detection. CONCLUSION: Carcinoembryonic antigen has the greatest potential to allow highly specific tumour imaging and drug delivery; future translational research should aim to exploit this.

The omega-3 polyunsaturated fatty acid eicosapentaenoic acid inhibits mouse MC-26 colorectal cancer cell liver metastasis via inhibition of PGE2-dependent cell motility.

BACKGROUND AND PURPOSE: The omega-3 polyunsaturated fatty acid (PUFA) eicosapentaenoic acid (EPA) has antineoplastic activity at early stages of colorectal carcinogenesis, relevant to chemoprevention of colorectal cancer (CRC). We tested the hypothesis that EPA also has anti-CRC activity at later stages of colorectal carcinogenesis, relevant to treatment of metastatic CRC, via modulation of E-type PG synthesis. EXPERIMENTAL APPROACH: A BALB/c mouse model, in which intrasplenic injection of syngeneic MC-26 mouse CRC cells leads to development of liver metastases, was used. Dietary EPA was administered in the free fatty acid (FFA) form for 2 weeks before and after ultrasound-guided intrasplenic injection of 1 × 10(6) MC-26 cells (n= 16 each group). KEY RESULTS: Treatment with 5% (w w(-1)) EPA-FFA was associated with a reduced MC-26 mouse CRC cell liver tumour burden compared with control animals (median liver weight 1.03 g vs. 1.62 g; P < 0.034). Administration of 5% EPA-FFA was also linked to a significant increase in tumour EPA incorporation and lower intratumoural PGE(2) levels (with concomitant increased production of PGE(3)). Liver tumours from 5% EPA-FFA- treated mice demonstrated decreased 5-bromo-2-deoxyuridine-positive CRC cell proliferation and reduced phosphorylated ERK 1/2 expression at the invasive edge of tumours. A concentration-dependent reduction in MC-26 CRC cell Transwell® migration following EPA-FFA treatment (50-200 µM) in vitro was rescued by exogenous PGE(2) (10 µM) and PGE(1)-alcohol (1 µM). CONCLUSIONS AND IMPLICATIONS: EPA-FFA inhibits MC-26 CRC cell liver metastasis. EPA incorporation is associated with a 'PGE(2) to PGE(3) switch' in liver tumours. Inhibition of PGE(2)-EP(4) receptor-dependent CRC cell motility probably contributes to the antineoplastic activity of EPA.

Dichloroacetate induces apoptosis and cell-cycle arrest in colorectal cancer cells.

BACKGROUND: Cancer cells are highly dependent on glycolysis. Our aim was to determine if switching metabolism from glycolysis towards mitochondrial respiration would reduce growth preferentially in colorectal cancer cells over normal cells, and to examine the underlying mechanisms. METHODS: Representative colorectal cancer and non-cancerous cell lines were treated with dichloroacetate (DCA), an inhibitor of pyruvate dehydrogenase kinase. RESULTS: Dichloroacetate (20 mM) did not reduce growth of non-cancerous cells but caused significant decrease in cancer cell proliferation (P=0.009), which was associated with apoptosis and G(2) phase cell-cycle arrest. The largest apoptotic effect was evident in metastatic LoVo cells, in which DCA induced up to a ten-fold increase in apoptotic cell counts after 48 h. The most striking G(2) arrest was evident in well-differentiated HT29 cells, in which DCA caused an eight-fold increase in cells in G(2) phase after 48 h. Dichloroacetate reduced lactate levels in growth media and induced dephosphorylation of E1alpha subunit of pyruvate dehydrogenase complex in all cell lines, but the intrinsic mitochondrial membrane potential was reduced in only cancer cells (P=0.04). CONCLUSIONS: Pyruvate dehydrogenase kinase inhibition attenuates glycolysis and facilitates mitochondrial oxidative phosphorylation, leading to reduced growth of colorectal cancer cells but not of non-cancerous cells.

Expression of cyclin D2 is an independent predictor of the development of hepatic metastasis in colorectal cancer.

INTRODUCTION: Cyclin D1 has been implicated in the progression of several cancers by virtue of its influence on progression of the G1/S phase of the cell cycle. However, little is known about the possible roles of cyclin D2 and D3 in colorectal cancers (CRCs). METHOD: We investigated the expression levels of cyclin D2 and D3 in 84 CRC specimens. Antigen expression was determined by immunohistochemical analysis of cyclin D1, D2, D3, p16INK4A and Ki67 on tissue microarrays constructed using core samples from tumour centres and margins. RESULTS: For the whole cohort, expression of cyclin D2 at the margin was associated with vascular invasion (P = 0.039), lymph node metastasis (P = 0.020) and liver metastasis (P < 0.001). In patients with stage I and II tumours (n = 84), elevated cyclin D2 and D3 were associated with vascular invasion (P = 0.014 and 0.028 respectively), liver metastasis (P = 0.001 and 0.007 respectively) and reduced disease specific survival (Cyclin D2, P < 0.022). No association was noted between the proliferative marker Ki-67 and the D-type cyclins. CONCLUSION: These findings suggest that cyclin D2 expression at the invasive margin of CRCs is associated with liver metastasis and may serve as a useful prognostic marker and indicator of the need for adjuvant therapy.

Heparin-dependent platelet factor 4 antibodies and the impact of renal function on clinical outcomes: a retrospective study in hospitalized patients.

Patients who develop thrombocytopenia and heparin-dependent platelet factor 4 antibodies while on or shortly after receiving a heparin product are often considered for alternative anticoagulation to minimize the occurrence of life and limb-threatening events. We retrospectively reviewed the hospital records of 97 patients with heparin-dependent platelet factor 4 antibodies (at least 65 of whom were felt by the primary team to have HIT) to determine the influence of renal performance on alternative anticoagulant selection and associated clinical events. For GFR > 30, approximately 30% of patients who did not receive alternative anticoagulation had documentation of concern for HIT versus 60% of patients in the GFR < 30 group. We found that a smaller proportion of patients with severe renal insufficiency, GFRs < 30 ml/min/1.73 m(2) were treated with an alternative anticoagulant-this despite their high incidence of thromboembolic events and comparable rates of HIT. Overall, rates of hemorrhage did not differ between patients when compared to those without renal insufficiency. However, there was a higher percentage of hemorrhagic events for patients with GFR < 30 ml/min/1.73 m(2) on alternative anticoagulants. This study demonstrates that patient's with GFRs < 30 ml/min/1.73 m(2) need to be assessed for overall hemorrhagic risk at the time of starting an alternative anticoagulant and need to be monitored closely to avoid hemorrhagic events.

Lack of interleukin-4 receptor alpha chain-dependent signalling promotes azoxymethane-induced colorectal aberrant crypt focus formation in Balb/c mice.

Interleukin (IL)-4 receptor (IL-4R) alpha chain-dependent signalling by IL-4 and IL-13 promotes tumour growth and metastasis in mouse models of colorectal cancer. However, the role of IL-4R alpha-dependent signalling during the early, pre-malignant stages of colorectal carcinogenesis has not been investigated. Therefore, we investigated the effect of deletion of the IL-4R alpha gene on azoxymethane-induced colorectal aberrant crypt focus (ACF) multiplicity and size in Balb/c mice. IL-4R alpha(-/-) mice developed significantly more ACFs [median 8, inter-quartile range (IQR) 4-11.5; n = 9] than wild-type (WT) animals (median 4, IQR 1-6; n = 9; p = 0.04, Mann-Whitney U-test). There were significantly higher levels of IL-4 in serum from azoxymethane- and sham-treated IL-4R alpha(-/-) mice than WT animals, but no difference in serum IL-13 levels. In the absence of functional IL-4Rs, IL-13 can also signal via the IL-13R alpha2 receptor, leading to induction of transforming growth factor (TGF) beta, which has pro-tumourigenic activity at early stages of intestinal tumourigenesis. We found that mucosal TGFbeta mRNA levels and intestinal epithelial cell TGFbeta immunoreactivity were significantly higher in IL-4R alpha(-/-) mice than in WT animals. In summary, IL-4R alpha-dependent signalling has a protective, anti-neoplastic role during the post-initiation phase of azoxymethane-induced colorectal carcinogenesis in Balb/c mice. Our data should prompt thorough investigation of the role of IL-4R alpha-dependent signalling during human colorectal carcinogenesis, particularly as antagonism of IL-4R signalling represents a therapeutic strategy for asthma and other allergic diseases.

Interleukin 13 and inflammatory markers in human sepsis.

BACKGROUND: Interleukin (IL) 13 is an anti-inflammatory cytokine that reduces inflammatory cytokine production, and enhances monocyte survival and MHC class II and CD23 expression. The only report of IL-13 in human sepsis noted no increase in IL-13 concentration, in contrast to animal data. This study further examined the expression of IL-13 in relation to human sepsis. METHODS: In a prospective observational study of 31 patients (24 men) with sepsis or septic shock, high-sensitivity enzyme-linked immunoabsorbent assay (ELISA) was used to quantify levels of tumour necrosis factor (TNF) alpha on admission, and on days 1, 3, 5 and 7 thereafter. IL-13 and IL-2 were assayed by standard ELISA, and HLA-DR on CD14-positive monocytes was measured by flow cytometry. RESULTS: Twenty-three patients developed septic shock. Monocyte HLA-DR levels showed greater depression and a slower recovery in shocked than non-shocked patients. The serum IL-13 concentration was significantly higher in the shocked group from admission to day 3, but subsequently decreased to levels similar to those in the non-shocked group. IL-13 concentrations were higher in non-survivors. The TNF-alpha concentration was higher in those with septic shock than in those without. The TNF-alpha level correlated with IL-13 concentration (r(S) = 0.61, P = 0.002). The IL-13/TNF-alpha ratio was greater in patients with shock than those with sepsis only (P = 0.017). IL-2 was undetectable. CONCLUSION: In human sepsis and septic shock, IL-13 correlated with TNF-alpha expression, but its effect on HLA-DR class II molecules remains unclear.

Immediate IL-10 expression following major orthopaedic trauma: relationship to anti-inflammatory response and subsequent development of sepsis.

OBJECTIVE: To assess the relationship between IL-10 release and anti-inflammatory response following blunt trauma. DESIGN: Prospective longitudinal clinical study. SETTING: Departments of trauma and anaesthetics in a university teaching hospital. PATIENTS: Forty-eight adult patients with a mean injury severity score of 14.5 (range 9-57) were prospectively studied following blunt trauma. MEASUREMENTS AND RESULTS: Venous blood samples were collected on arrival and at 16 and 24 h, and at 3, 5, and 7 days. Peripheral blood mononuclear cell (HLA-DR) expression on CD14 + monocytes was quantified by flow cytometry and serum IL-10 was assayed by ELISA. Anti-inflammatory response was defined as monocyte HLA-DR expression of less than 30% of that seen in healthy controls. Serum IL-10 levels in trauma patients on arrival was significantly elevated, 70.0 [48.0-92.1, 95% confidence interval, (CI)] compared to the control group, 3 (0-5) (P < 0.0001), and monocyte HLA-DR expression was significantly lower, 14.2 (12.1-16.3, 95% CI), in patients versus 25.2 (22.4-28.1) in controls (P < 0.001). Patients with low HLA-DR expression (n = 14) had significantly higher serum IL-10 levels than those whose HLA-DR expression remained above 30% of the control value (n = 34), (P < 0.038). In patients who developed sepsis (n = 11), serum IL-10 levels were greater on admission, [143.7 (80.2-207.2) pg/ml(-1)], and remained elevated during the study period compared with non-complicated patients, [50.16 (33.5-66.8) pg/ml(-1)]. Immediate IL-10 (2 h following trauma) was negatively correlated with simultaneous HLA-DR expression, (r = -0.49, P = 0.0005). CONCLUSION: These findings support the view that IL-10 release regulates monocyte HLA-DR expression and may be related to an anti-inflammatory response and development of sepsis following trauma.

Interleukin-10 release and monocyte human leukocyte antigen-DR expression during femoral nailing.

This study determined the effect of femoral nailing on the expression of monocyte Class II antigens and interleukin-10 release and sought to differentiate any differences in the release of these elements of immune reactivity in patients undergoing reamed and unreamed nailing. Thirty-two patients presenting with an acute femoral fracture were studied. In 15 patients, the femoral fracture was stabilized with a reamed technique and in 17 patients with an unreamed technique. Venous blood samples were taken at presentation, at anesthetic induction, immediately after nail insertion, and subsequently at 1, 4, and 24 hours and at 3, 5, and 7 days after surgery. Serum interleukin-10 was measured by an enzyme-linked immunosorbent assay, and monocyte human leukocyte antigen-DR expression was quantified by flow cytometry. Serum interleukin-10 release and human leukocyte antigen-DR expression on monocytes showed a clear response to the nailing procedure. The group of patients undergoing a reamed femoral nailing procedure showed significantly higher interleukin-10 release and a significant depression in the expression of human leukocyte antigen-DR on monocytes compared with those whose nail had been inserted unreamed. One patient in the reamed femoral nailing group died of adult respiratory distress syndrome 3 days after injury. Reamed intramedullary nailing appears to be associated with greater impairment of immune reactivity than is the unreamed nailing technique.

Activated mesothelial cells produce heparin-binding growth factors: implications for tumour metastases.

Curative surgery for gastrointestinal malignancy is commonly thwarted by local tumour recurrence. The heparin-binding growth factors, basic fibroblast growth factor (bFGF), heparin-binding epidermal growth factor-like growth factor (HB-EGF) and vascular epidermal growth factor (VEGF) are all implicated in the metastatic process, but whether or not these essential growth factors are produced by the activated peritoneum is unknown. This study reveals that peritoneal mesothelial cells constitutively express mRNA for bFGF, HB-EGF and two VEGF spliced variants, VEGF121 and VEGF165. Mesothelial activation with interleukin (IL)-1b or tumour necrosis factor (TNF)-a produced an up-regulation of mRNA for HB-EGF and VEGF, but not bFGF expression. IL-6 failed to stimulate growth factor expression, whereas IL-2 produced a marked suppression in HB-EGF and bFGF, but not VEGF expression. Mesothelial cells were shown to predominantly express mRNA for the intermediate affinity (bg(c)) IL-2 receptor. Cytokine-induced growth factor up-regulation was confirmed at the protein level using Western blotting of mesothelial cell lysates for HB-EGF and culture supernatant enzyme-linked immunosorbent assay for VEGF. The production of these growth factors by human mesothelial cells may play a significant role in post-operative peritoneal tumour recurrence. Their common heparin-binding property offers a potential therapeutic target for manipulating the growth factor environment of the human peritoneum.

Effects of prostaglandins and indomethacin on the cellular inflammatory response following surgical trauma in fetal rabbits.

This study has examined the effects of prostaglandins E2 and F2a (PGE2 and PGF2a) and indomethacin on cellular inflammation in fetal rabbits. Fetuses heal differently from adults: incisions heal with no scar or inflammation; excisional wounds exposed to amniotic fluid (AF) do not heal or become inflamed, and have high tissue levels of PGE2 and PGF2a; excisional wounds protected from AF do heal and become inflamed, and have low tissue PG levels. The authors inserted slow-release pellets [control, PGE2 (10 micrograms), PGF2a (10 micrograms), indomethacin (10 micrograms)] into subcutaneous pockets in fetal rabbits on day 25 of gestation (one per fetus). Pellets were also placed in subcutaneous pockets in the does. Fetuses and doe tissues were recovered 72 h after surgery. Control pellets in fetuses had a slight inflammatory response, with some cells present. Fetal PGE2 pellets had a layer 5-10 cells thick surrounding the pellet, and fetal PGF2a pellets had a 10-15-cell layer. Fetal indomethacin pellets had no response, with no inflammatory cells present. All pellets placed in does elicited a slight cellular inflammatory response, equal to that seen with control pellet in fetuses. These results show that PGE2 and PGF2a are potent in-vivo promoters of cellular inflammation in fetal rabbits, but not in adult rabbits. Indomethacin suppresses the foreign-body response in fetal rabbits, but not in adult rabbits.

Improved porcine renal preservation with a simple extracellular solution--PBS140.

In this prospective randomized trial a porcine model of renal autotransplantation was used to compare quality of preservation, as reflected by detailed analysis of posttransplant renal function, following 24-hr cold storage in phosphate-buffered sucrose (PBS140), hyperosmolar citrate (HOC), and University of Wisconsin (UW) preservation solutions. There were 6 deaths with primary nonfunction: 3 of 5 HOC, 2 of 5 UW, but only 1 of 5 PBS140. Analysis of the whole group and separate analysis of the survivors demonstrated significantly better renal function following preservation with PBS140 when compared with both HOC and UW, with a lower peak serum creatinine (P = 0.02) and improved loop of Henle function (P = 0.02). The animals in the PBS140 group also demonstrated a more rapid return to normal creatinine, higher GFR, improved tubular function, and higher effective renal plasma flow, with figures approaching statistical significance (P = 0.06-0.07). The proposal of UW as a universal storage medium prompted this study, and its results suggest the need for a clinical comparison of renal preservation using UW and PBS140 in a prospective randomized trial.

Ranolazine--a new drug with beneficial effects on renal preservation.

Ranolazine is a new drug with a novel mode of action as a metabolic modulator and membrane stabilizer. In this prospective randomized double-blind trial, a porcine model of renal autotransplantation was used to assess the effects of this drug during preservation and reperfusion of kidneys cold-stored for 24 hr in phosphate-buffered sucrose (PBS140). Three groups of 10 animals were compared: a Placebo group (placebo given intravenously to the animal before nephrectomy, added to the preservation solution, and given again to the animal during reperfusion); a Storage group (Ranolazine before and during storage, placebo during reperfusion); and a Reperfusion group (placebo before and during storage, Ranolazine during reperfusion). Detailed analysis of posttransplant renal function was carried out over a 14-day follow-up period. There were 7 deaths with primary nonfunction: 2 Placebo, 1 Storage, 4 Reperfusion. Analysis of the whole group and separate analysis of the survivors demonstrated significantly improved glomerular (P less than 0.05), tubular (P less than 0.05), and loop of Henle (P less than 0.05) function in the Storage group. The results of this study clearly demonstrate the beneficial effects of Ranolazine during the storage phase of porcine renal preservation, and further investigation of this drug is warranted.

The role of diet in prostate cancer.

This is a one-to-one, age- and race-matched case-control study involving 55 histologically confirmed black prostate cancer patients and 55 controls who were seen at three major hospitals in Washington, DC from 1982 to 1984. Personal interviews were conducted to obtain the number of times food items of specified serving size were consumed per week by cases and controls; the subjects were grouped according to the age periods 30-49 and 50 years and older. We then calculated the average daily consumption of each of 18 nutrients per 1,000 calories. There was a significant negative association between linoleic acid (p less than 0.04) for the 50 years and older group, thiamin (p less than 0.05) for those 30-49 years old, riboflavin (p less than 0.03) for the 50 and older group, and iron (p less than 0.05) for those 30-49 years old. The results of this study suggest that the intake of thiamin and iron (in subjects 30-49 years old), linoleic acid and riboflavin (in subjects 50 years and over) could be protective because control subjects consumed more of these nutrients than did the cases.

Nutrition and prostate cancer: a case-control study.

This one-to-one, age- and race-matched case-control study involved 181 histologically confirmed black prostate cancer patients and 181 controls seen at three major hospitals in Washington, DC, during the period 1979-1982. Personal interviews were conducted to obtain the number of times food items of specified serving size were consumed per week by cases and controls during the age periods 30-49 and 50 years and older. Then the average daily consumption of each of 18 nutrients per 1,000 calories was calculated. There was risk enhancement associated with increased intake of proteins, total fat, saturated fat, oleic acid, and vitamin A during the age period 30-49 years. The association was highly significant for vitamin A and approached statistical significance for the other four nutrients. A hypothesis based on disturbance of the zinc-retinol binding protein-vitamin A axis was put forward to explain the relative risk enhancement effect of vitamin A on prostate cancer.