A prospective validation pharmacogenomic study in the adjuvant setting of colorectal cancer patients treated with the 5-fluorouracil/leucovorin/oxaliplatin (FOLFOX4) regimen

The discovery of pharmacogenomic markers in colorectal cancer (CRC) could be setting-specific. FOLFOX4 is employed in the adjuvant and metastatic setting in CRC. This prospective study is aimed to validate in the adjuvant setting the pharmacogenomic markers of toxicity reported in the metastatic setting (that is, GSTP1-rs947894, and -rs1138272; GSTM1-null genotype; AGXT-rs4426527, -rs34116584 and del-74 bp), and to discover additional markers. CRC patients (n=144) treated with adjuvant FOLFOX4 were genotyped for 57 polymorphisms in 29 genes. Grade ≥ 2 neurotoxicity was associated (false discovery rate-adjusted q-value <0.1) with single-nucleotide polymorphisms in ABCC1 (rs2074087: odds ratio=0.43(0.22-0.86)), and ABCC2 (rs3740066: 2.99(1.16-7.70); rs1885301: 3.06(1.35-6.92); rs4148396: 4.69(1.60-13.74); rs717620: 14.39(1.63-127.02)). hMSH6-rs3136228 was associated with grade 3-4 neutropenia (3.23(1.38-7.57), q-value=0.0937). XRCC3-rs1799794 was associated with grade 3-4 non-hematological toxicity (8.90(2.48-31.97), q-value=0.0150). The markers previously identified in metastatic CRC were not validated. We have identified new markers of toxicity in genes of transport and DNA repair. If validated in other studies, they could help to identify patients at risk of toxicity.

Tumor response is predicted by patient genetic profile in rectal cancer patients treated with neo-adjuvant chemo-radiotherapy

The aim of the study was the identification of a pharmacogenetic profile predictive of the tumor regression grade (TRG), considered as tumor response parameter, after neo-adjuvant treatment in rectal cancer patients. A total of 238 rectal cancer patients treated in a neo-adjuvant setting by a fluoropyrimidines-based chemo-radiotherapy (RT) were genotyped for 25 genetic polymorphisms in 16 genes relevant for treatment-associated pathways. Two polymorphisms were associated with TRG in a multivariate analysis: hOGG1-1245C > G, which can affect radiosensitivity and MTHFR-677C > T, which is involved in fluoropyrimidines action. Patients bearing at least one variant allele had a lower chance to get TRG ≤ 2 (OR = 0.46 95% CI 0.23-0.90, P = 0.024; and OR = 0.48 95% CI 0.24-0.96, P = 0.034; respectively). An association trend was observed for ABCB1-3435C > T, which is responsible for the multi-drug resistance (odds ratio (OR) = 1.96, 95% confidence interval (CI) 0.98-3.95, P = 0.057). Exploratory classification and regression tree (CART) analysis highlighted high-order gene-gene and gene-environment interactions and a genetic signature associated with differential response, with hOGG1-1245C > G as the most predictive factor. Other significant variables were: ABCB1-3435C > T, MTHFR-677C > T, ERCC1-8092C > A, ABCC2-1249G > A, XRCC1-28152G > A, XRCC3-4541A > G and patients gender. On the basis of CART results, patients were categorized into three groups according to tumor response probability: intermediate and high profiles had a higher probability to get TRG ≤ 2 as compared with low profiles (OR = 4.12 95% CI 1.46-11.65, P < 0.001 and OR = 12.44, 95% CI 5.52-28.04, P < 0.0001, respectively). This study evidences a major role of hOGG1-1245C > G and MTHFR-677C > T polymorphisms in the tumor response of rectal cancer patients treated with chemo-RT in neo-adjuvant setting, and shows the relevance of gene-gene and gene-environment interactions for complex phenotypes as tumor response.

MTHFR polymorphisms in gastric cancer and in first-degree relatives of patients with gastric cancer

Two common mutations, 677 C→T and a1298 A→C, in the methylenetetrahydrofolate reductase gene (MTHFR) reduce the activity of MTHFR and folate metabolism. Familial aggregation in a variable but significant proportion of gastric cancer (GC) cases suggests the importance of genetic predisposition in determining risk. In this study, we evaluate MTHFR polymorphisms in 57 patients with a diagnosis of GC, in 37 with a history of GC in first-degree relatives (GC-relatives), and in 454 blood donors. Helicobacter pylori (HP) infection was also determined. An increased risk was found for 677TT in GC patients with respect to blood donors (odds ratio (OR) = 1.98), and statistical significance was sustained when we compared sex–age-matched GC patients and donors (OR = 2.37). The 677TT genotype association with GC was found in women (OR = 3.10), while a reduction in the 667C allele frequency was present in both the sex. No statistically significant association was detected when 677–1298 genotype was stratified by sex and age. Men of GC-relatives showed a higher 1298C allele frequency than donors (OR = 4.38). Between GC and GC-relatives, HP infection frequency was similar. In conclusion, overall findings support the hypothesis that folate plays a role in GC risk. GC-relatives evidence a similar 677TT frequency to that found in the general population.

Pharmacology of epidermal growth factor inhibitors

Research into the molecular bases of malignant diseases has yielded the development of many novel agents with potential antitumor activity. Evidence for a causative role for the epidermal growth factor receptor (EGFR), which is now regarded as an excellent target for cancer chemotherapy in human cancer, leads to the development of EGFR inhibitors. Two classes of anti-EGFR agents are currently in clinical use: monoclonal antibodies directed at the extracellular domain of the receptor, and the low-molecular-weight receptor tyrosine kinase inhibitors acting intracellularly by competing with adenosine triphosphate for binding to the tyrosine kinase portion of the EGFR. The effect on the receptor interferes with key biological functions including cell cycle arrest, potentiation of apoptosis, inhibition of angiogenesis and cell invasion and metastasis. Cetuximab, a monoclonal antibody, and the receptor tyrosine kinase inhibitors gefitinib and erlotinib are currently approved for the treatment of patients with cancer. New agents with clinical activity are entering the clinic, and new combinatorial approaches are being explored with the aim of improving the potency and pharmacokinetics of EGFR inhibition, to increase the synergistic activity in combination with chemotherapy and overcome resistance to the EGFR inhibitors.

Lack of association of CYP1 B1*3 polymorphism and ovarian cancer in a Caucasian population

CYP1B1 is the enzyme with the highest efficiency of conversion of estradiol to 4-hydroxyestradiol in humans. This metabolite has a well-known carcinogenic effect interacting with genomic DNA and has been hypothesized to be partly responsible for the role played by estrogens in ovarian cancer development. A polymorphism has been described for this enzyme causing a Leu to Val substitution in position 432 (CYP1B1*3). The Val432 allele has a higher efficiency of conversion of estradiol to 4-hydroxyestradiol and has been reported to increase the risk of ovarian cancer. A previous study reported a higher, significant prevalence of CYP1B1*3 polymorphism in ovarian cancer patients of mixed ethnicity. The aim of this study was to investigate the role of CYP1B1*3 polymorphism as a risk factor for ovarian cancer in a Caucasian population. The polymorphism frequency was determined in 223 cases of ovarian cancer and compared with that of 280 healthy female blood donors. Genetic analysis was performed on genomic DNA from PBMC and RFLP methods were used for mutation detection. No significant difference between cases and controls was found. These results do not support a favoring role of CYP1B1*3 in ovarian cancer development in our population.

Alcohol misuse and renal damage

Recent clinical and experimental studies have demonstrated that the habitual consumption of large amounts of ethanol has deleterious effects on the kidney. A variety of tubular defects have been described in patients with chronic alcoholism. Evidence is emerging that tubular dysfunction has an important pathophysiological role in a wide range of electrolyte and acid-base disturbances commonly observed in these patients, and possibly in alcohol-induced bone disease. These renal abnormalities are often reversible, disappearing with abstinence. However, since 1990 a few cases of a syndrome of acute tubular necrosis due to binge drinking of ethanol in the absence of other evident nephrotoxic mechanisms, or in association with the use of nonsteroidal anti-inflammatory drugs, have been reported. A link between glomerulonephritis and alcoholism has become evident. IgA nephropathy has been demonstrated at autopsy in 64% of chronic alcoholics and, more recently, the association between alcoholism and postinfectious glomerulonephritis has been described. Structural and functional abnormalities of the kidney are reported with increasing frequency in the fetal alcohol syndrome seen in children who have been prenatally exposed to ethanol. In addition, over the last few years experimental studies in vitro or in animal models have provided information about the biochemical and molecular basis of alcohol-induced injury to kidney. It is hoped that future experimental and clinical research will provide us with a more comprehensive knowledge of the mechanisms of renal damage in alcohol misuse.

Pharmacogenetics of irinotecan

Pharmacogenetics focuses on intersubjects variation in therapeutic drug effects and toxicity depending on genetic polymorphisms. This is particularly interesting in oncology since anticancer drugs usually have a narrow margin of safety. Irinotecan [7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin] is used in cancer chemotherapy as a topoisomerase I inhibitor and it is characterised by a sometimes unpredictable severe toxicity. It is mostly intestinal with nausea, vomit and diarrhoea or haematologic with leuko-thrombocytopenia. Its complex metabolism involves many proteins. Human carboxylesterase isoforms 1 and 2 (hCE1, hCE2) activate irinotecan to its metabolite SN-38 (7-ethyl-10-hydroxycamptothecin); cytochrome P450 isoforms 3A4 and 3A5 (CYP3A4, CYP3A5) mediate the oxidation of the parental compound to irinotecan; uridino-glucuronosil transferase isoform 1A1 (UGT1A1) catalyses glucuronidation of SN-38; the multi-resistance protein isoform 2 (MRP2) allows the cellular excretion of the SN-38 glucuronide (SN-38G) and the multi-drug resistance gene (MDR1), encoding for P-glycoprotein, is responsible for the excretion of irinotecan from the cell. Polymorphic structures in the genes encoding for all these proteins have been described. In particular, the UGT1A1*28 allele has been associated with an increased toxicity after irinotecan chemotherapy. Classical parameters used in the clinic, such as body-surface area, have no longer a meaningful correlation with clinical outcome. Hence it emerges the importance of studying the individual genotype to predict the toxicity and efficacy of irinotecan and to individualise therapy. In this review, we summarise the new developments on the study of the pharmacogenetics of irinotecan, stressing its importance in drug cytotoxic effect.

Long-term effects of erythropoietin therapy on fistula stenosis and plasma concentrations of PDGF and MCP-1 in hemodialysis patients

Among the adverse effects possibly associated with the use of erythropoietin (EPO) in hemodialysis patients is an increased incidence of thrombosis of the vascular access. However, little is known about the effect of EPO on the stenotic lesion in the venous outflow system, which is the leading cause of fistula thrombosis. This study was designed to explore the long-term effects of EPO treatment on progressive fistula stenosis and the plasma concentrations of some potential mediators of neointimal hyperplasia. A cross-sectional and 3-yr prospective, placebo-controlled, pilot study was performed in 30 hemodialysis patients with native arteriovenous fistula. Sixteen patients received EPO and 14 received a placebo. Venous dialysis pressure, urea recirculation, color Doppler sonography, and angiography were used to monitor vascular access patency. Compared with 60 healthy subjects, the hemodialysis patients had elevated plasma levels of platelet-derived growth factor, monocyte chemoattractant protein-1, and interleukin 6, three proteins that might be involved in the neointima formation regulating the proliferation of vascular smooth muscle cells. In addition, these patients had numerous endothelial and hemostatic abnormalities that indicated a thrombophilic state. Eleven patients, six (37.5%) receiving EPO and five (35.7%) taking placebo, developed a progressive stenosis in the venous circuit of the fistula. There was no significant difference in the vascular access, event-free survival over 36 mo between patients receiving EPO therapy and placebo. EPO induced a significant decrease in the plasma values of platelet-derived growth factor and vascular cell adhesion molecule-1 and an increase of monocyte chemoattractant protein-1 concentration. After EPO withdrawal, these parameters returned to pretreatment levels. In conclusion, long-term EPO therapy does not increase the risk of progressive stenosis of native arteriovenous fistula. The use of erythropoietin does not induce any prothrombotic change in hemostatic parameters, and further studies are required to elucidate the theoretically beneficial effects on the plasma concentration of some potential mediators of neointimal formation.

Risk factors for vascular disease and arteriovenous fistula dysfunction in hemodialysis patients

Vascular access dysfunction is an important cause of morbidity for dialysis patients and a major contributor to hemodialysis cost. Thrombosis is a leading cause of vascular access failure, and usually results from stenotic lesions in the venous outflow system. This study was designed to explore the impact of serum levels of various risk factors for thrombosis and accelerated fibrointimal hyperplasia on progressive stenosis, and the subsequent thrombosis of hemodialysis fistula. A cross-sectional and 2-yr prospective pilot study was performed in 30 nondiabetic hemodialysis patients with primary arteriovenous fistula. Venous dialysis pressure, urea recirculation, color Doppler sonography, and angiography were used to monitor vascular access patency. Eleven patients (37%) developed a progressive stenosis in the venous circuit, which was complicated by thrombosis in three patients. Compared with the patients without fistula dysfunction, these patients had higher serum levels of monocyte chemoattractant protein-1 and interleukin-6, two cytokines that regulate the proliferation of vascular smooth muscle cells, which is the key mechanism in the pathogenesis of fistula stenosis. In addition, they had hyperinsulinemia, hyperlipidemia, and increased plasma levels of two hemostasis-derived risk factors for thrombosis: plasminogen activator inhibitor type 1 and factor VII. Monocyte chemoattractant protein-1, interleukin-6, plasminogen activator inhibitor type 1, factor VII, triglycerides, and the ratios for cholesterol/HDL-cholesterol, apolipoprotein (apo) A-I/ apo C-III, apo A-I/apo B, and glucose/insulin were independent predictors of fistula dysfunction. This study demonstrates the influece of cytokines, hemostasis-derived vascular risk factor, hyperinsullnemia, and abnormallties of lipids and apolipoproteins on primary fistula survival. The assessment of these factors might be useful for the identification of the patients at risk of fistula stenosis and thrombosis.

Thrombocytopenia of chronic liver disease corrected by erythropoietin treatment

To investigate the possibility of correcting thrombocytopenia of chronic liver disease, 19 patients (6 male and 13 female) with long-term chronic liver disease and platelet count < or = 85,000/microliters were studied. Either a short-term course (7-20 days) of recombinant human erythropoietin, 4000 U daily SQ (12 patients) or placebo (7 patients) was administered. Treatment was interrupted if the platelets rose to > or = 100,000/microliters or if no significant increase was noted after 14 days. After treatment, platelets increased in the recombinant human erythropoietin group (from a baseline value of 70,000 +/- 11,184 to 101,250 +/- 37,625/microliters), while no difference was noted in the placebo group (70,714 +/- 9928 vs 70,000 +/- 10,231/microliters). The increase in the platelet count in the recombinant human erythropoietin group was significant, both compared to baseline values (paired Student's t-test, t = -3.80, p < 0.005) and to the results of treatment in the placebo group (unpaired Student's t-test, t = 2.71, p < 0.02). Eight out of 12 recombinant human erythropoietin-treated patients (66%) reached > or = 100,000/microliters platelets while four (33%) did not. In comparison to responders, non-responders had a significantly lower baseline platelet count (58,500 +/- 7937 vs 75,750 +/- 7498/microliters, t = -3.69, p = 0.004) and failed more frequently than responders to improve their haematocrit in response to recombinant human erythropoietin (Pearson chi 2 = 4.687, p = 0.03). When treatment was discontinued, the platelet count reverted to baseline in a few weeks. In conclusion, recombinant human erythropoietin treatment transiently corrected mild thrombocytopenia in patients with chronic liver disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Renal tubular dysfunction in chronic alcohol abuse--effects of abstinence

BACKGROUND

Alcohol abuse may be accompanied by a variety of disorders of electrolyte and acid-base metabolism. The role of the kidney in the pathogenesis of these disturbances is obscure. We sought to evaluate the alcohol-induced abnormalities of renal function and improvement during abstinence and to assess the relation between renal dysfunction and electrolyte and acid-base disorders.

METHODS

We measured biochemical constituents of blood and renal function before and after four weeks of abstinence in 61 patients with chronic alcoholism who had little or no liver disease.

RESULTS

On admission, 18 patients (30 percent) had hypophosphatemia and hypomagnesemia, 13 patients (21 percent) had hypocalcemia, and 8 patients (13 percent) had hypokalemia. Twenty-two patients (36 percent) had a variety of simple and mixed acid-base disorders. Twenty of these patients had metabolic acidosis, and among them, 80 percent had alcoholic acidosis. A wide range of defects in renal tubular function, with normal glomerular filtration rate, were detected in these patients. The defects included decreases in the threshold and maximal reabsorptive ability for glucose (38 percent of patients) and in the renal threshold for phosphate excretion (36 percent); increases in the fractional excretion of beta 2-microglobulin (38 percent), uric acid (12 percent), calcium (23 percent), and magnesium (21 percent); and aminoaciduria (38 percent). Seventeen patients (28 percent) had a defect in tubular acidification, and five an impairment in urinary concentrating ability. Urinary excretion of N-acetyl-beta-D-glucosaminidase and alanine aminopeptidase were increased in 41 and 34 percent of patients, respectively. The abnormalities of blood chemistry and renal tubular function disappeared after four weeks of abstinence.

CONCLUSIONS

Transient defects in renal tubular function are common in patients with chronic alcoholism and may contribute to their abnormalities of serum electrolyte and blood acid-base profiles.

Relief of pruritus and decreases in plasma histamine concentrations during erythropoietin therapy in patients with uremia

BACKGROUND

The pathophysiologic aspects of pruritus in patients with chronic renal insufficiency are poorly understood, and there is no universally effective treatment. The improvement of pruritus in several patients receiving erythropoietin therapy raised the possibility that erythropoietin affects uremic pruritus directly.

METHODS

We undertook a 10-week placebo-controlled, double-blind, crossover study in a group of patients receiving hemodialysis who had severe pruritus, to investigate the effects of recombinant human erythropoietin on their pruritus and plasma histamine levels. Twenty patients with uremia, of whom 10 had severe pruritus and 10 did not, received erythropoietin (36 units per kilogram of body weight three times weekly) and placebo in random order, each for five weeks. The severity of pruritus was scored weekly, and plasma histamine levels were measured at the beginning and end of each five-week period.

RESULTS

Eight of the 10 patients with pruritus had marked reductions in their pruritus scores during erythropoietin therapy. The mean (+/- SE) pruritus score decreased from 25 +/- 3 to 6 +/- 1 in these patients. The pruritus returned within one week after the discontinuation of therapy. The improvement was not related to the change in hemoglobin level. These eight patients were successfully treated again with low doses of erythropoietin (18 units per kilogram three times weekly), and the effect has persisted for six months. The patients with pruritus had elevated plasma histamine concentrations (20.7 +/- 2.7 nmol per liter), as compared with the patients without pruritus (4.2 +/- 0.6 nmol per liter; P less than 0.001) and normal subjects (2.1 +/- 0.2 nmol per liter; P less than 0.001). Therapy with erythropoietin induced a decrease in plasma histamine concentrations in both groups of patients with uremia, and recurrences of pruritus after the discontinuation of erythropoietin were accompanied by increases in plasma histamine concentrations.

CONCLUSIONS

Erythropoietin therapy lowers plasma histamine concentrations in patients with uremia and can result in marked improvement of pruritus.

Bardet-Biedl syndrome and cystinuria

An unusual association of Bardet-Biedl syndrome with cystinuria was described in one patient. A 21-year-old male was admitted to hospital because of renal failure, severe deterioration of visual acuity, polydactyly, brachydactyly, and mental retardation. Laboratory investigations revealed a serum creatinine of 292 mumol/L (3.3 mg/dL) and a GFR of 25 mL/min per 1.73 m2. Quantitative ion exchange chromatography demonstrated an increased urinary excretion rate of cystine, lysine, arginine, and ornithine. The ophthalmologic examination showed a severe atypical retinal dystrophy. Visual acuity was severely deteriorated and the patient could only count the examining physician's fingers. The patient had been previously evaluated at the age of 7 years for polyuria, polydipsia, and growth failure. His workup at that time demonstrated nephrogenic diabetes insipidus, normal GFR, and a urinary amino acid pattern consistent with the cystinuric phenotype. There was mental retardation notwithstanding the normal ophthalmologic examination. Intravenous pyelography showed calyceal clubbing, calyceal cysts, and lobulated renal outlines of the fetal type. The patient was evaluated again at the age of 13 years for deterioration of visual acuity and the ophthalmologic examination showed an atypical retinal dystrophy, with sparse pigmentation, central and peripheral atrophy, attenuated vessels, and marked optic disk pallor. To our knowledge the association of Bardet-Biedl syndrome with cystinuria has never been reported. It is unlikely that cystinuria may have contributed to the kidney damage. The possibility that mental retardation has been induced or aggravated by cystinuria cannot be excluded.

Hepatic computed tomography for monitoring the iron status of haemodialysis patients with haemosiderosis treated with recombinant human erythropoietin

1. A randomized, partial-crossover study was conducted in uraemic patients with dialysis-associated anaemia and transfusional iron overload to evaluate the effects of desferrioxamine chelation therapy and of recombinant human erythropoietin treatment on hepatic iron storage determined by computed tomography, as well as by serum ferritin concentration and transferrin saturation. 2. Twenty-one haemodialysis patients with moderate iron overload, confirmed by values of serum ferritin concentration, transferrin saturation and hepatic computed tomography density exceeding 1000 micrograms/l, 45% and 68 Hounsfield units respectively, were randomly allocated to three groups and were followed for 12 months. 3. During the first 6 months group 1 (n = 7) received desferrioxamine chelation therapy (30 mg/kg intravenously three times a week) and group 2 (n = 7) underwent recombinant human erythropoietin treatment (36 units/kg intravenously three times a week). Thereafter, in the second 6 months of observation patients in group 1 were switched to receive recombinant human erythropoietin. Because of a poor response in the desferrioxamine-treated group in the initial 6 months, patients in group 2 continued on the maintenance dose of recombinant human erythropoietin (18 units/kg three times a week) until the end of the trial. Patients in group 3 (n = 7) were maintained on placebo throughout the study. 4. In comparison with placebo, recombinant human erythropoietin treatment, but not desferrioxamine chelation therapy, reduced serum ferritin concentration, transferrin saturation and hepatic computed tomography density, and was associated with a rise in haemoglobin and packed cell volume. Hepatic computed tomography density, serum ferritin concentration and transferrin saturation decreased in 13 out of 14 patients (93%) during treatment with recombinant human erythropoietin.(ABSTRACT TRUNCATED AT 250 WORDS)