Evaluation of factors affecting epidermal growth factor receptor tyrosine kinase inhibitor-induced hepatotoxicity in Japanese patients with non-small cell lung cancer: a two-center retrospective study.

BACKGROUND: Gefitinib and erlotinib, are epidermal growth factor receptor tyrosine kinase inhibitors, and are currently recommended for non-small cell lung cancer stage IV in the elderly and in patients with decreased performance status in the Japanese Lung Cancer Society Guideline, but they occasionally caused severe hepatotoxicity requiring postponement or modification of treatment. However, little is known about the risk factors for hepatotoxicity in patients receiving gefitinib and erlotinib. In this study, we investigated the factors influencing hepatotoxicity in Japanese non-small cell lung cancer (NSCLC) patients treated with gefitinib or erlotinib monotherapy. METHODS: Japanese patients with NSCLC who started gefitinib or erlotinib monotherapy from January 2005 to December 2017 at Kanazawa University Hospital or Kanazawa Medical University Hospital were included in this study. Factors affecting hepatotoxicity were retrospectively investigated by multiple logistic regression analysis. RESULTS: A total of 102 patients who received gefitinib and 95 patients who received erlotinib were included in the analysis. In the gefitinib group, a body mass index (BMI) ≥ 25 was associated with an increased risk of hepatotoxicity (OR = 4.571, 95% CI = 1.486-14.056, P = 0.008). In the erlotinib group, concomitant use of acid-suppressing medications (AS), namely proton pump inhibitors or histamine-2 receptor antagonists, was associated with a reduced risk of hepatotoxicity (OR = 0.341, 95% CI = 0.129-0.900, P = 0.030). CONCLUSIONS: BMI ≥ 25 in patients treated with gefitinib increased the risk of hepatotoxicity. In contrast, AS combination with erlotinib reduced the risk of hepatotoxicity. Thus, because different factors influence the risk of hepatotoxicity, monitoring for adverse events should take into account patient background factors and concomitant medications.

Oxidation of 3'-methoxyflavone, 4'-methoxyflavone, and 3',4'-dimethoxyflavone and their derivatives having 5,7-dihydroxyl moieties by human cytochromes P450 1B1 and 2A13.

Oxidation of 3'-methoxyflavone, 4'-methoxyflavone, and 3',4'-dimethoxyflavone and their derivatives containing 5,7-dihydroxyl groups by human cytochrome P450 (P450 or CYP) 1B1 and 2A13 was determined using LC-MS/MS systems.3'-Methoxyflavone and 4'-methoxyflavone were mainly O-demethylated to form 3'-hydroxyflavone and 4'-hydroxyflavone, respectively, and then 3',4'-dihydroxyflavone at higher rates with CYP1B1 than with CYP2A13. 4'-Methoxy-5,7-dihydroxyflavone (acacetin) was found to be demethylated by CYP1B1 and 2A13 to form 4',5,7-trihydroxyflavone (apigenin) at rates of 0.098-1 and 0.42 min-1, respectively. 3'-Methoxy-5,7-dihydroxyflavone was also demethylated by both P450s, with CYP2A13 being more active.3',4'-Dimethoxyflavone was a good substrate for CYP1B1 but not for CYP2A13 and was found to be mainly O-demethylated to form 3',4'-dihydroxyflavone (at a rate of 4.2 min-1) and also several ring-oxygenated products having m/z 299 fragments. Molecular docking analysis supported the proper orientation for formation of these products by CYP1B1.Our present results showed that 3'- and 4'-methoxyflavone can be oxidised to their O-demethylated products and, to a lesser extent, to ring oxidation products by both P450s 1B1 and 2A13 and that 3',4'-dimethoxyflavone is a good substrate for CYP1B1 in forming both O-demethylated and ring-oxidation products. Introduction of a 57diOHF moiety into these methoxylated flavonoids caused decreased in oxidation by CYP1B1 and 2A13.

Risk factors for interstitial lung disease induced by gemcitabine plus albumin-bound paclitaxel therapy in pancreatic ductal adenocarcinoma patients.

BACKGROUND: Gemcitabine plus nab-paclitaxel (GnP) therapy is used for unresectable pancreatic ductal adenocarcinoma, but may cause interstitial lung disease (ILD) as a serious side effect. However, the risk factors for ILD in patients receiving GnP therapy are not well established. Here, we retrospectively investigated the incidence of GnP-induced ILD in pancreatic ductal adenocarcinoma patients, and the risk factors. METHODS: We investigated the patients' background, laboratory data, previous treatment history, concomitant medications, number of doses of GnP, cumulative dosage and administration period, and occurrence of side effects. RESULTS: Of the 105 patients included in this study, ILD occurred in 10 (9.5%). Patients with ILD had a significantly higher frequency of concomitant treatment with Kampo medicines, especially goshajinkigan, which is considered to help prevent chemotherapy-induced peripheral neuropathy (CIPN) (odds ratio: 11.5, 95% confidence interval: 2.67-49.38). No significant differences were observed in other clinical characteristics. Notably, the severity of CIPN in patients who used goshajinkigan for prevention was not significantly different from that in patients who did not use goshajinkigan in this study. CONCLUSIONS: These results suggest that administration of goshajinkigan to patients receiving GnP therapy for prevention of CIPN may need to be reconsidered.

Roles of cytochrome P450 2A6 in the oxidation of flavone, 4'-hydroxyflavone, and 4'-, 3'-, and 2'-methoxyflavones by human liver microsomes.

Nine forms of recombinant cytochrome P450 (P450 or CYP) enzymes were used to study roles of individual P450 enzymes in the oxidation of flavone and some other flavonoids, 4'-hydroxyflavone and 4'-, 3'-, and 2'-methoxyflavones, by human liver microsomes using LC-MS/MS analysis.As has been reported previously , 4'-, 3'-, and 2'-methoxyflavones were preferentially O-demethylated by human liver P450 enzymes to form 4'-, 3'-, and 2'-hydroxylated flavones and also 3',4'-dihydroxyflavone from the former two substrates.In comparisons of product formation by oxidation of these methoxylated flavones, CYP2A6 was found to be a major enzyme catalysing flavone 4'- and 3'-hydroxylations by human liver microsomes but did not play significant roles in 2'-hydroxylation of flavone, O-demethylations of three methoxylated flavones, and the oxidation of 4'-hydroxyflavone to 3',4'-dihydroxyflavone.The effects of anti-CYP2A6 IgG and chemical P450 inhibitors suggested that different P450 enzymes, as well as CYP2A6, catalysed oxidation of these flavonoids at different positions by liver microsomes.These studies suggest that CYP2A6 catalyses flavone 4'- and 3'-hydroxylations in human liver microsomes and that other P450 enzymes have different roles in oxidizing these flavonoids.

Liquid chromatography-tandem mass spectrometry analysis of oxidation of 2'-, 3'-, 4'- and 6-hydroxyflavanones by human cytochrome P450 enzymes.

2'-Hydroxyflavanone (2'OHFva), 3'OHFva, 4'OHFva, and 6OHFva, the major oxidative products of flavanone by human cytochrome P450 (P450, CYP) enzymes, were studied in regard to further oxidation by human CYP1A1, 1A2, 1B1.1, 1B1.3, and 2A6. The products formed were analyzed with LC-MS/MS and characterized by their positive ion fragmentations on mass spectrometry. Several di-hydroxylated flavanone (diOHFva) and di-hydroxylated flavone (diOHFvo) products, detected by analyzing parent ions at m/z 257 and 255, respectively, were found following incubation of these four hydroxylated flavanones with P450s. The m/z 257 products were produced at higher levels than the latter with four substrates examined. The structures of the m/z 257 products were characterized by LC-MS/MS product ion spectra, and the results suggest that 3'OHFva and 4'OHFva are further oxidized mainly at B-ring by P450s while 6OHFva oxidation was at A-ring. Different diOHFvo products (m/z 255) were also characterized by LC-MS/MS, and the results suggested that most of these diOHFvo products were formed through oxidation or desaturation of the diOHFva products (m/z 257) by P450s. Only when 4'OHFva (m/z 241) was used as a substrate, formation of 4'OHFvo (m/z 239) was detected, indicating that diOHFvo might also be formed through oxidation of 4'OHFvo by P450s. Finally, our results indicated that CYP1 family enzymes were more active than CYP2A6 in catalyzing the oxidation of these four hydroxylated flavanones, and these findings were supported by molecular docking studies of these chemicals with active sites of P450 enzymes.

Risk Factors for Delayed Elimination of Methotrexate in Children, Adolescents and Young Adults With Osteosarcoma.

BACKGROUND/AIM: High-dose methotrexate (HD-MTX) is pivotal chemotherapy in the treatment of patients with osteosarcoma. Blood concentrations of MTX are associated with several side effects, but there are large individual differences in the elimination of MTX. The aim of this study was to explore risk factors for delayed elimination of MTX in children, adolescents and young adults with osteosarcoma. PATIENTS AND METHODS: We conducted a retrospective study on Japanese patients with osteosarcoma who were treated with HD-MTX at Kanazawa University Hospital from April 2006 to March 2015. Risk factors for delayed elimination of methotrexate were identified by multiple logistic regression analysis. RESULTS: A total of 92 cycles of HD-MTX therapy were analyzed. Female and lower creatinine clearance (CCr) were identified as independent risk factors for delayed elimination of MTX. CONCLUSION: Knowing the factors associated with delayed elimination of MTX could lead to safer and optimized chemotherapy for patients with osteosarcoma.

Administration of erlotinib in apple juice overcomes decreased absorption in a rat model of gastric acid suppression.

Erlotinib shows pH-dependent solubility and its absorption is decreased in patients receiving gastric acid suppression therapy. Here, we examined whether administration of erlotinib in acidic solutions would improve its solubility and absorption characteristics. In vitro, the solubility of erlotinib in HCl solution increased with decreasing pH, and was far higher than that in tap water. The solubility in apple juice (pH 3.7) was higher than that in HCl solution of the same pH. In vivo, the absorption of erlotinib administered in tap water was decreased in omeprazole-treated (OP) rats, used as a model of gastric acid suppression, compared to control rats. In the OP rats, the plasma concentrations in the groups given erlotinib in apple juice and in HCl (pH 3.7) were significantly higher than in the tap water group in the initial phase of absorption. AUC in OP rats given erlotinib in apple juice was 1.69-fold larger than that of control rats given erlotinib in tap water, and 2.49-fold larger than that of OP rats given erlotinib in tap water. Thus, administration of erlotinib in an acidic beverage to patients receiving gastric acid suppression therapy might be effective to increase solubility and absorption.

Comparison of Tolerability Between 2-Weekly and 3-Weekly Docetaxel Regimen in Castration-resistant Prostate Cancer.

BACKGROUND: The tolerability of 2-weekly docetaxel at 25-35 mg/m2 for castration-resistant prostate cancer (CRPC) has not been fully evaluated. The aim of this study was to evaluate its tolerability compared to 3-weekly docetaxel at 60-75 mg/m2 in patients with CRPC. PATIENTS AND METHODS: In this retrospective study, data were compared with respect to efficacy and safety between 2-weekly and 3-weekly docetaxel regimens in patients with CRPC. RESULTS: Time to treatment failure and prostate-specific antigen (PSA) response rate did not differ significantly between the two regimens. Compared to 3-weekly administration, incidence of severe leukopenia and febrile neutropenia was significantly lower (p<0.05), and relative dose intensity was significantly higher (p<0.05) for the 2-weekly schedule. Docetaxel dosage and PSA response were identified as independent risk factors for severe leukopenia. CONCLUSION: Two-weekly treatment seems better tolerated than three-weekly treatment in Japanese patients with CRPC.

Preference for O-demethylation reactions in the oxidation of 2'-, 3'-, and 4'-methoxyflavones by human cytochrome P450 enzymes.

2'-, 3'-, and 4'-Methoxyflavones (MeFs) were incubated with nine forms of recombinant human cytochrome P450 (P450 or CYP) enzymes in the presence of an NADPH-generating system and the products formed were analyzed with LC-MS/MS methods.CYP1B1.1 and 1B1.3 were highly active in demethylating 4'MeF to form 4'-hydroxyflavone (rate of 5.0 nmol/min/nmol P450) and further to 3',4'-dihydroxyflavone (rates of 2.1 and 0.66 nmol/min/nmol P450, respectively). 3'MeF was found to be oxidized by P450s to m/z 239 (M-14) products (presumably 3'-hydroxyflavone) and then to 3',4'-dihydroxyflavone. P450s also catalyzed oxidation of 2'MeF to m/z 239 (M-14) and m/z 255 (M-14, M-14 + 16) products, presumably mono- and di-hydroxylated products, respectively.At least two types of ring oxidation products having m/z 269 fragments were formed, although at slower rates than the formation of mono- and di-hydroxylated products, on incubation of these MeFs with P450s; one type was products oxidized at the C-ring, having m/z 121 fragments, and the other one was the products oxidized at the A-ring (having m/z 137 fragments).Molecular docking analysis indicated the preference of interaction of O-methoxy moiety of methoxyflavones in the active site of CYP1A2.These results suggest that 2'-, 3'-, and 4'-methoxyflavones are principally demethylated by human P450s to form mono- and di-hydroxyflavones and that direct oxidation occurs in these MeFs to form mono-hydroxylated products, oxidized at the A- or B-ring of MeF.

Detailed assessment and risk factor analysis of corticosteroid-induced psychiatric disorders in pediatric, adolescent, and young adult patients undergoing induction or consolidation therapy for hematologic malignancy.

BACKGROUND: Corticosteroid-induced psychiatric disorders (CIPDs) represent an adverse effect that can cause severe emotional and behavioral problems. The aim of the present study was to assess the incidence and risk factors of CIPDs. METHODS: A retrospective analysis of 92 pediatric and young adult patients with hematologic malignancies was conducted. RESULTS: The incidence of CIPDs in patients receiving a treatment regimen with prednisolone or dexamethasone was 64.9% and 77.5%, respectively, both of which were significantly higher than that in patients not receiving corticosteroids. Independent risk factors and adjusted odds ratios (95% confidence intervals) related to severe CIPD were 2.15 (1.11-4.18) for dexamethasone (using prednisolone as the reference) and 0.81 (0.75-0.87) for age, suggesting that the odds increase with decreasing age. Frequently observed symptoms, respectively in terms of behavioral and emotional problems were defiance, crying, psychomotor excitement, dysphoria, irritability, and depression. To our knowledge, this is the first report to mention the risk factors and characteristics for clinical symptoms of CIPDs during the developmental process. CONCLUSIONS: Healthcare professionals should predict and prepare for psychiatric adverse events prior to chemotherapy in the clinical settings, especially in patients in younger age and receiving a treatment regimen with dexamethasone.

Oxidation of Flavone, 5-Hydroxyflavone, and 5,7-Dihydroxyflavone to Mono-, Di-, and Tri-Hydroxyflavones by Human Cytochrome P450 Enzymes.

Biologically active plant flavonoids, including 5,7-dihydroxyflavone (57diOHF, chrysin), 4',5,7-trihydroxyflavone (4'57triOHF, apigenin), and 5,6,7-trihydroxyflavone (567triOHF, baicalein), have important pharmacological and toxicological significance, e.g., antiallergic, anti-inflammatory, antioxidative, antimicrobial, and antitumorgenic properties. In order to better understand the metabolism of these flavonoids in humans, we examined the oxidation of flavone, 5-hydroxyflavone (5OHF), and 57diOHF to various products by human cytochrome P450 (P450 or CYP) and liver microsomal enzymes. Individual human P450s and liver microsomes oxidized flavone to 6-hydroxyflavone, small amounts of 5OHF, and 11 other monohydroxylated products at different rates and also produced several dihydroxylated products (including 57diOHF and 7,8-dihydroxyflavone) from flavone. We also found that 5OHF was oxidized by several P450 enzymes and human liver microsomes to 57diOHF and further to 567triOHF, but the turnover rates in these reactions were low. Interestingly, both CYP1B1.1 and 1B1.3 converted 57diOHF to 567triOHF at turnover rates (on the basis of P450 contents) of >3.0 min-1, and CYP1A1 and 1A2 produced 567triOHF at rates of 0.51 and 0.72 min-1, respectively. CYP2A13 and 2A6 catalyzed the oxidation of 57diOHF to 4'57triOHF at rates of 0.7 and 0.1 min-1, respectively. Our present results show that different P450s have individual roles in oxidizing these phytochemical flavonoids and that these reactions may cause changes in their biological and toxicological properties in mammals.

Multiday corticosteroids in cancer chemotherapy delay the diagnosis of and antimicrobial administration for febrile neutropenia: a double-center retrospective study.

BACKGROUND: Medical staff should promptly administer antimicrobials to patients with febrile neutropenia (FN) to decrease the mortality related to cancer chemotherapy. Corticosteroids, which are used in cancer chemotherapy, have a fever-suppressive effect. This effect could lead to a blunt fever response and any local signs of infection, especially in patients receiving multiday corticosteroid administration. The aim of this study was to determine whether multiday corticosteroid administration in cancer chemotherapy delays the diagnosis of and antimicrobial treatment for FN. METHODS: We conducted a double-center retrospective study in Japanese patients with FN. The patients were divided into two groups based on the corticosteroid administration method, i.e., whether administration was multiday or not. To evaluate the degree of masking on FN by corticosteroids, we assessed the correlation between body temperature variation and time of antimicrobial administration after the initiation of chemotherapy. Risk factors for delayed antimicrobial administration were identified by multiple logistic regression analysis. RESULTS: Two hundred thirteen patients were analyzed. The median time required to body temperature reaching 37.5 °C and for antimicrobial administration was longer in the multiday group than in the non-multiday group, with 0.64 and 0.60 days (P = 0.002 and P < 0.001), respectively. Multiday corticosteroid use was identified as an independent risk factor for delayed antimicrobial administration (odds ratio = 3.94; 95% confidence interval = 1.80-8.62; P < 0.001). CONCLUSIONS: Multiday corticosteroid administration in cancer chemotherapy delayed the diagnosis of and antimicrobial administration for FN. Furthermore, it was the only risk factor for delayed antimicrobial administration. We could thus provide evidence that the diagnosis of and antimicrobial administration for FN in patients receiving multiday corticosteroid administration should not be based on body temperature variation alone.

Palonosetron on Days 1 and 5 Versus Granisetron Daily (Days 1-5) in Germ Cell Tumour Therapy.

BACKGROUND/AIM: The control of chemotherapy-induced nausea and vomiting during bleomycin, etoposide, and cisplatin (BEP) treatment is important for maintaining treatment intensity. The effects of palonosetron and granisetron were compared in BEP chemotherapy. PATIENTS AND METHODS: The administration of palonosetron on days 1 and 5 (Pal method) and granisetron daily (days 1-5, Gra method) were compared in terms of their efficacy and cost-effectiveness. RESULTS: Additional rescue antiemetic agents were used in 15 of 32 and 30 of 30 cycles in the Pal and Gra method groups, respectively (p<0.05). The complete response rate, defined as no vomiting and no rescue agent usage, in each cycle, was 50% and 0% in the Pal and Gra method groups, respectively (p<0.05). The average cost of antiemetic agents in a cycle was 50,759 and 54,555 yen in the Pal and Gra method groups, respectively (p<0.05). CONCLUSION: The Pal method may be the standard method in BEP.

Cytochrome P450 2A6 and other human P450 enzymes in the oxidation of flavone and flavanone.

1. We previously reported that flavone and flavanone interact spectrally with cytochrome P450 (P450 or CYP) 2A6 and 2A13 and other human P450s and inhibit catalytic activities of these P450 enzymes. In this study, we studied abilities of CYP1A1, 1A2, 1B1, 2A6, 2A13, 2C9 and 3A4 to oxidize flavone and flavanone. 2. Human P450s oxidized flavone to 6- and 5-hydroxylated flavones, seven uncharacterized mono-hydroxylated flavones, and five di-hydroxylated flavones. CYP2A6 was most active in forming 6-hydroxy- and 5-hydroxyflavones and several mono- and di-hydroxylated products. 3. CYP2A6 was also very active in catalyzing flavanone to form 2'- and 6-hydroxyflavanones, the major products, at turnover rates of 4.8 min-1 and 1.3 min-1, respectively. Other flavanone metabolites were 4'-, 3'- and 7-hydroxyflavanone, three uncharacterized mono-hydroxylated flavanones and five mono-hydroxylated flavones, including 6-hydroxyflavone. CYP2A6 catalyzed flavanone to produce flavone at a turnover rate of 0.72 min-1 that was ∼3-fold higher than that catalyzed by CYP2A13 (0.29 min-1). 4. These results indicate that CYP2A6 and other human P450s have important roles in metabolizing flavone and flavanone, two unsubstituted flavonoids, present in dietary foods. Chemical mechanisms of P450-catalyzed desaturation of flavanone to form flavone are discussed.

Site-specific oxidation of flavanone and flavone by cytochrome P450 2A6 in human liver microsomes.

The roles of human cytochrome P450 (P450 or CYP) 2A6 in the oxidation of flavanone [(2R)- and (2S)-enantiomers] and flavone were studied in human liver microsomes and recombinant human P450 enzymes. CYP2A6 was highly active in oxidizing flavanone to form flavone, 2'-hydroxy-, 4'-, and 6-hydroxyflavanones and in oxidizing flavone to form mono- and di-hydroxylated products, such as mono-hydroxy flavones M6, M7, and M11 and di-hydroxy flavones M3, M4, and M5. Liver microsomes prepared from human sample HH2, defective in coumarin 7-hydroxylation activity, were very inefficient in forming 2'-hydroxyflavanone from flavanone and a mono-hydroxylated product, M6, from flavone. Coumarin and anti-CYP2A6 antibodies strongly inhibited the formation of these metabolites in microsomes prepared from liver samples HH47 and 54, which were active in coumarin oxidation activities. Molecular docking analysis showed that the C2'-position of (2R)-flavanone (3.8 Å) was closer to the iron center of CYP2A6 than the C6-position (10 Å), while distances from C2' and C6 of (2S)-flavanone to the CYP2A6 were 6.91 Å and 5.42 Å, respectively. These results suggest that CYP2A6 catalyzes site-specific oxidation of (racemic) flavanone and also flavone in human liver microsomes. CYP1A2 and CYP2B6 were also found to play significant roles in some of the oxidations of these flavonoids by human liver microsomes.

Risk factors for oxaliplatin-induced vascular pain in patients with colorectal cancer and comparison of the efficacy of preventive methods.

BACKGROUND: Vascular pain is a common adverse drug reaction in colorectal cancer patients receiving peripheral venous administration of oxaliplatin. The aim of this work was to identify risk factors for vascular pain, and to examine whether currently used treatments reduce its incidence. METHODS: We conducted a multicenter retrospective study in Japanese colorectal cancer patients receiving peripheral venous administration of oxaliplatin. The effects of various treatments (administration of analgesics, addition of dexamethasone to the infusion solution for pH adjustment, dilution of the infusion solution, or use of hot gel for warming the injection site) on the incidence of vascular pain were assessed. Risk factors for vascular pain were identified by multiple logistic regression analysis. RESULTS: One hundred and ninety patients who had received an oxaliplatin-containing regimen via a peripheral venous route were analyzed. None of the preventive methods examined significantly reduced the incidence of vascular pain. BMI (BMI < 22), clinical stage (I-III) and oxaliplatin dosage (130 mg/m2 versus dose reduction) were identified as independent risk factors for development of vascular pain. The incidence of oxaliplatin-induced vascular pain was significantly higher in patients who had two or more risk factors. CONCLUSIONS: BMI, clinical stage and oxaliplatin dosage were identified as independent predictive markers for oxaliplatin-induced vascular pain. Existing treatments for vascular pain are not effective in reducing its incidence.

Contribution of equilibrative nucleoside transporters 1 and 2 to gemcitabine uptake in pancreatic cancer cells.

Hepatic arterial infusion (HAI) chemotherapy is expected to be a more effective and safer method to treat the hepatic metastasis of pancreatic cancer than intravenous (iv) administration because of higher tumor exposure and lower systemic exposure. To clarify the uptake mechanism of nucleoside anticancer drugs, including gemcitabine (GEM), in pancreatic cancer, we investigated the uptakes of radiolabeled uridine (a general substrate of nucleoside transporters) and GEM in pancreatic cancer cell lines MIA-PaCa2 and As-PC1. Uridine uptake was inhibited by non-labeled GEM and also by S-(4-nitrobenzyl)-6-thioinosine (NBMPR; an inhibitor of equilibrative nucleoside transporters, ENTs) in a concentration-dependent manner, suggesting that ENTs contribute to uridine uptake in pancreatic cancer cells. As for GEM, saturable uptake was mediated by high- and low-affinity components with Km values of micromolar and millimolar orders, respectively. Uptake was inhibited in a concentration-dependent manner by NBMPR and was sodium ion-independent. Moreover, the concentration dependence of uptake in the presence of 0.1 µM NBMPR showed a single low-affinity site. These results indicated that the high- and low-affinity sites correspond to hENT1 and hENT2, respectively. The results indicated that at clinically relevant hepatic concentrations of GEM in GEM-HAI therapy, the metastatic tumor exposure of GEM is predominantly determined by hENT2 under unsaturated conditions, suggesting that hENT2 expression in metastatic tumor would be a candidate biomarker for indicating anticancer therapy with GEM-HAI.

Oxidation of 1-chloropyrene by human CYP1 family and CYP2A subfamily cytochrome P450 enzymes: catalytic roles of two CYP1B1 and five CYP2A13 allelic variants.

1. 1-Chloropyrene, one of the major chlorinated polycyclic aromatic hydrocarbon contaminants, was incubated with human cytochrome P450 (P450 or CYP) enzymes including CYP1A1, 1A2, 1B1, 2A6, 2A13, 2B6, 2C9, 2D6, 2E1, 3A4 and 3A5. Catalytic differences in 1-chloropyrene oxidation by polymorphic two CYP1B1 and five CYP2A13 allelic variants were also examined. 2. CYP1A1 oxidized 1-chloropyrene at the 6- and 8-positions more actively than at the 3-position, while both CYP1B1.1 and 1B1.3 preferentially catalyzed 6-hydroxylation. 3. Five CYP2A13 allelic variants oxidized 8-hydroxylation much more than 6- and 3-hydroxylation, and the variant CYP2A13.3 was found to slowly catalyze these reactions with a lower kcat value than other CYP2A13.1 variants. 4. CYP2A6 catalyzed 1-chloropyrene 6-hydroxylation at a higher rate than the CYP2A13 enzymes, but the rate was lower than the CYP1A1 and 1B1 variants. Other human P450 enzymes had low activities towards 1-chloropyrene. 5. Molecular docking analysis suggested differences in the interaction of 1-chloropyrene with active sites of CYP1 and 2 A enzymes. In addition, a naturally occurring Thr134 insertion in CYP2A13.3 was found to affect the orientation of Asn297 in the I-helix in interacting with 1-chloropyrene (and also 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, NNK) and caused changes in the active site of CYP2A13.3 as compared with CYP2A13.1.

Inhibition of Carcinogen-Activating Cytochrome P450 Enzymes by Xenobiotic Chemicals in Relation to Antimutagenicity and Anticarcinogenicity.

A variety of xenobiotic chemicals, such as polycyclic aromatic hydrocarbons (PAHs), aryl- and heterocyclic amines and tobacco related nitrosamines, are ubiquitous environmental carcinogens and are required to be activated to chemically reactive metabolites by xenobiotic-metabolizing enzymes, including cytochrome P450 (P450 or CYP), in order to initiate cell transformation. Of various human P450 enzymes determined to date, CYP1A1, 1A2, 1B1, 2A13, 2A6, 2E1, and 3A4 are reported to play critical roles in the bioactivation of these carcinogenic chemicals. In vivo studies have shown that disruption of Cyp1b1 and Cyp2a5 genes in mice resulted in suppression of tumor formation caused by 7,12-dimethylbenz[a]anthracene and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, respectively. In addition, specific inhibitors for CYP1 and 2A enzymes are able to suppress tumor formation caused by several carcinogens in experimental animals in vivo, when these inhibitors are applied before or just after the administration of carcinogens. In this review, we describe recent progress, including our own studies done during past decade, on the nature of inhibitors of human CYP1 and CYP2A enzymes that have been shown to activate carcinogenic PAHs and tobacco-related nitrosamines, respectively, in humans. The inhibitors considered here include a variety of carcinogenic and/or non-carcinogenic PAHs and acethylenic PAHs, many flavonoid derivatives, derivatives of naphthalene, phenanthrene, biphenyl, and pyrene and chemopreventive organoselenium compounds, such as benzyl selenocyanate and benzyl selenocyanate; o-XSC, 1,2-, 1,3-, and 1,4-phenylenebis( methylene)selenocyanate.

Drug interaction between methotrexate and salazosulfapyridine in Japanese patients with rheumatoid arthritis.

BACKGROUND: Methotrexate (MTX) and salazosulfapyridine (SASP) are disease-modifying drugs that are commonly used in the treatment of rheumatoid arthritis (RA), and combination therapy with MTX and SASP is recommended for RA patients who show an inadequate response to monotherapy with either drug. This study was designed to examine the interaction between the two drugs from the viewpoint of serum MTX concentration in Japanese RA patients, who were receiving combination therapy with relatively low doses of MTX and SASP. METHODS: This is a 24-week open-label intervention study of stable RA patients (n = 10) with low disease activity. In these patients, who had received SASP/MTX combination therapy for at least 12 weeks, SASP was discontinued, and the patients received MTX monotherapy for the next 24 weeks. The primary outcome was change of serum MTX concentration at 12 weeks after discontinuation of SASP. Two disease activity markers, simplified disease activity index (SDAI) and disease activity score-C reactive protein (DAS28-CRP), were assessed as secondary outcomes at 24 weeks after discontinuation of SASP. We also monitored levels of matrix metalloproteinase-3 (MMP-3) and inflammatory cytokines. Patients were asked to complete a questionnaire after the study. RESULTS: Serum MTX concentration in RA patients who discontinued SASP increased more than 2-fold within 4 weeks, and the higher level was maintained thereafter. No significant differences were detected in SDAI, DAS28-CRP, MMP-3 or inflammatory cytokines. Most participants reported no change in physical condition after withdrawal of SASP, and most preferred MTX monotherapy for future treatment. CONCLUSIONS: Withdrawal of SASP from patients receiving SASP/MTX caused a rapid, marked increase of serum MTX concentration, without any apparent change in disease parameters or side effects. Our results suggest that SASP can be discontinued without adverse effects in stable RA patients receiving combination therapy, at least among Japanese patients receiving relatively low doses of the two drugs. TRIAL REGISTRATION: UMIN000024507. October 21, 2016 retrospectively registered.