Isoforms of cytochrome P450 on organic nitrate-derived nitric oxide release in human heart vessels

Glutathione S-transferases and the cytochrome P450 system have been proposed for the vascular biotransformation systems in the metabolic activation of organic nitrates. The present study was designed to elucidate the role of human cytochrome P450 isoforms on nitric oxide formation from organic nitrates using lymphoblast microsomes transfected with human CYP isoforms cDNA. CYP3A4-transfected microsomes had the most effective potential of nitric oxide formation from isosorbide dinitrate. Anti-CYP3A2 antibody (which cross-reacts with CYP3A4) or ketoconazole (an inhibitor of the CYP3A superfamily) inhibited nitric oxide formation from isosorbide dinitrate in rat heart microsomes. Immunohistochemistry of human heart also showed intense bindings of CYP3A4 antibody in the endothelium of the endocardium and coronary vessels. These results suggest that the CYP3A4-NADPH-cytochrome P450 reductase system specifically participates in nitric oxide formation from isosorbide dinitrate.

Frameshift mutation of the STK11 gene in a sporadic gastrointestinal cancer with microsatellite instability

Germline mutations of the STK11 gene lead to emergence of hamartomas in the gastrointestinal tract of patients with Peutz-Jeghers syndrome, who bear an increased risk of malignancies of the gastrointestinal tract, genital tract, and other organs. We analyzed 80 sporadic colorectal cancers, six small-intestinal cancers, and 40 gastric cancers for somatic mutations of STK11 by SSCP methods. Among them only one colorectal cancer, which showed a phenotype of microsatellite instability, was found to possess a deleterious mutation in this gene, a frameshift involving deletion of one base at codons 279-281. This region of the gene contains a mononucleotide-repeat sequence, CCCCCC. The other allele of STK11 had been lost in this tumor. If the STK11 gene is one of the mutational targets of microsatellite instability, its inactivation may be associated with tumor development in a small proportion of colorectal cancers.

Hepatic cytochrome P450 is directly inactivated by nitric oxide, not by inflammatory cytokines, in the early phase of endotoxemia

BACKGROUND/AIMS

Although the activity of the liver in metabolizing and eliminating various drugs decreases in endotoxemia, the mechanism remains to be elucidated. The generation of nitric oxide by the inducible type of nitric oxide synthase increases in endotoxemia. Nitric oxide readily reacts with heme proteins such as cytochrome P450 that metabolize various compounds, including steroids and eicosanoids. The purpose of this study was to determine the effect of nitric oxide on the function of hepatic cytochrome P450 in endotoxemic rats.

METHODS

To determine the dynamic aspects of nitric oxide metabolism, hepatic levels of the inducible type of nitric oxide synthase and heme-iron nitrosyl complexes, and plasma levels of nitrite and nitrate were determined in rats before and after intravenous administration of lipopolysaccharide. Changes in the levels of P450 isoforms and testosterone hydroxylation activity in hepatic microsomes were also determined. To evaluate in vivo CYP3A2 activity, midazolam sleep time was measured.

RESULTS

When lipopolysaccharide increased the hepatic inducible type of nitric oxide synthase and plasma levels of nitric oxide metabolites, the intensity of low-spin signal of electron spin resonance responsible for the ferric form of P450 decreased with a concomitant increase in heme-iron nitrosyl complexes in the liver. Lipopolysaccharide-related nitric oxide generation is followed by an early decrease in the levels of cytochrome P450 and of testosterone hydroxylation activity in liver microsomes. Midazolam sleep time was prolonged by lipopolysaccharide. All these early changes were prevented by the inhibitor of nitric oxide synthase, N(G)-iminoethyl-L-ornithine. Moreover, lipopolysaccharide suppressed the gene expression of CYP2C11 and CYP3A2. Decreases in levels of cytochrome P450 and their mRNAs were more pronounced at 24 h after LPS administration, but apparently they are NO-independent.

CONCLUSIONS

These results suggest that lipopolysaccharide-induced modulation of cytochrome P450 may occur via the interplay of two different mechanisms and that, especially in the early phase, nitric oxide-dependent inhibition is more important.

Cytochrome P450 isoforms responsible for the N-deethylation and cyclohexane-hydroxylation of NS-21

1. Cytochrome P450 (P450) isoforms responsible for the N-deethylation and cyclohexane-hydroxylation of (+/-)-4-diethylamino-1,1-dimethylbut-2-yn-1-yl 2-cyclohexyl-2-hydroxy-2-phenylacetate monohydrochloride monohydrate (NS-21) have been identified in rat and man. 2. Anti-CYP2C11 antibody inhibited the N-deethylation of S- and R-NS-21 in rat hepatic microsomes by 84 and 66% respectively, indicating that CYP2C11 is mainly responsible for these activities in male rats. 3. Of several human recombinant P450 isoforms, CYP3A4 had the activities for the N-deethylation of S- and R-NS-21. In addition, triacetyloleandomycin (TAO), an inhibitor of the CYP3A subfamily, significantly inhibited the N-deethylation of S- and R-NS-21 in human hepatic microsomes by 67 and 69%, respectively. CYP3A4 therefore contributes to it in man. 4. Quinine, an inhibitor of the rat CYP2D subfamily, significantly inhibited the cyclohexane-4-cis-hydroxylation of S-NS-21 by 48% in rat hepatic microsomes. In contrast, this inhibitor had little effect on the cyclohexane-4-trans-hydroxylation of S-NS-21, and the cyclohexane-4-cis- and trans-hydroxylation of R-NS-21. 5. Human recombinant CYP3A4 catalysed the cyclohexane-4-trans-hydroxylation of S-NS-21, and CYP2D6 supported the cyclohexane-4-cis- and trans-hydroxylation of S-NS-21. Quinidine, an inhibitor of human CYP2D6, had little effect on these latter activities in human hepatic microsomes. TAO significantly inhibited the cyclohexane-4-trans-hydroxylation of S-NS-21 by 75%, indicating that CYP3A4 catalyses this reaction.

Phase II study of limited surgery for early gastric cancer: segmental gastric resection

BACKGROUND

Endoscopic resection for treatment of early gastric cancer (EGC) is widely performed. Recently, however, surgeons began performing a limited operation for EGC when endoscopic resection was not indicated. This report discusses the surgical technique and the results of the limited operation, which is generally referred to as "segmental resection" (SR).

METHODS

Since 1990, a total of 50 patients with intramucosal invasive EGC of the middle stomach underwent SR. The procedure included a limited gastrectomy, limited lymph node dissection, and preservation of the vagal nerve. We examined the surgical risk, postoperative complications, and patient survival rates and compared the results for the SR-treated patients (group A) with results for patients with EGC who underwent subtotal gastrectomy and systemic lymph node dissection (group B).

RESULTS

Blood loss was less in group A (239 +/- 180 ml) than in group B (342 +/- 176 ml) (P < .05). The incidence of postoperative complications was also lower in group A (2.0%) than in group B (14.0%) (P < .05). The incidence of postoperative cholelithiasis was lower in group A (4.0%) than in group B (18.0%) (P < .05). All patients in both groups are alive without recurrence.

CONCLUSIONS

Compared with distal gastrectomy, SR for EGC of the middle stomach decreased the surgical risk and postoperative complications without increasing the recurrence rate.

Developmental changes in the catalytic activity and expression of CYP2D isoforms in the rat liver

Developmental changes in bufuralol 1'-hydroxylation activity, which is known as a typical activity of cytochrome P-450 (CYP)2D isoforms, in the liver of rats were investigated. The catalytic activities of hepatic microsomes increased with development especially from 3 to 7 weeks. Eadie-Hofstee plots of bufuralol 1'-hydroxylation were obtained for monophasic kinetics (Km: 0.037 microM) at 1 week and for biphasic kinetics (Km: 0.051 and 6.4 microM) at 7 weeks of age. Quinine completely inhibited bufuralol 1'-hydroxylation activity of hepatic microsomes of 1- and 7-week-old rats. These results indicated that at least two kinds of CYP2D isoforms, which differ markedly in their affinity for bufuralol, were present at 7 weeks of age and that the CYP2D isoform that had low affinity for bufuralol was expressed with development. To assess the affinity of CYP2D isoforms for bufuralol, the kinetic properties of CYP2D1, 2D2, 2D3, and 2D4 expressed in yeast cells were investigated. The Km value of CYP2D2, 0.044 microM, was extremely small compared with that of the other rat CYP2D isoforms. We further investigated developmental changes of CYP2D isoform mRNA by reverse transcription-polymerase chain reaction. CYP2D3 mRNA increased with development although CYP2D1 and 2D2 mRNA were not changed. The CYP2D4 mRNA was not detected. These findings indicated that CYP2D2, which had high affinity for bufuralol, was expressed in immature and mature rats, but CYP2D3, which had low affinity for bufuralol, was expressed only in mature rats.

Increased blood proinsulin and decreased C-peptide levels in patients with pancreatic cancer

BACKGROUND/AIMS

Abnormal glucose tolerance during oral glucose tolerance test (OGTT) is frequently observed in patients with pancreatic cancer. The abnormality shown in previous studies, however, was characterized mainly by analyses based on immunoreactive insulin or C-peptide response during OGTT, despite their cross-reactivity with proinsulin. The mechanisms responsible for glucose intolerance in patients with pancreatic cancer remain controversial.

METHODOLOGY

Both proinsulin and C-peptide responses during 75 g of OGTT were determined without influence of immunologic cross-reactivity in 32 patients with pancreatic cancer and 32 control subjects of similar age, sex, fasting blood glucose levels, and OGTT pattern.

RESULTS

The pancreatic cancer patients had higher proinsulin and lower C-peptide levels than the control subjects both in the non-diabetic and diabetic groups. The ratio of the sum of five proinsulin values observed at 0, 30, 60, 120, and 180 min to that of the five C-peptide values (sigma proinsulin/sigma C-peptide ratio) was 6.1 +/- 3.2% in patients with pancreatic cancer and 2.5 +/- 1.0% in control subjects (p < 0.05), while it was not associated with the diabetic pattern in OGTT. The sigma proinsulin/sigma C-peptide ratio was not associated with tumor size, location or resectability but was associated with the number of islets left within or close to cancer stroma. The increased sigma proinsulin/sigma C-peptide ratio decreased after tumor removal.

CONCLUSIONS

Patients with pancreatic cancer are characterized by increased proinsulin secretion and decreased C-peptide production during OGTT probably due to impaired proinsulin conversion. Although further studies are required in a large scale of patients, measurement of proinsulin and C-peptide levels during OGTT should serve as an early marker to identify high risk groups of the disease.

Minute carcinoma of the pancreas measuring 1 cm or less in diameter--collective review of Japanese case reports

BACKGROUND/AIMS

According to Tsuchiya's collective review on small pancreatic cancer measuring 2 cm or less in diameter (5), more than half of them had obstructive jaundice and the 5-year survival rate was as low as 30%. Thus, a more aggressive diagnostic approach is needed to detect a smaller and more curable cancer of the pancreas.

METHODOLOGY

Thus, we collected 36 reported cases of "minute" pancreatic cancer measuring 1 cm or less in diameter, from Japanese medical literature, to analyze the relationships between the diagnostic processes and long-term results.

RESULTS

Excluding 3 patients with obstructive jaundice, the other 33 patients did not show any specific initial symptoms. However, 28 (78%) out of 36 patients showed an elevation in serum pancreatic enzyme levels and/or glucose intolerance. Among the 35 patients who had received ultrasonography (US) and/or computed tomography (CT), 20 (57%) patients showed duct dilation alone, whereas only 9 patients (26%) showed tumor mass. Among 35 patients who received an endoscopic retrograde pancreatography (ERP), all patients showed positive findings such as obstruction/stenosis, filling defect or duct dilation. All 36 patients underwent pancreatectomy and the 5-year survival rate was 57%. However, the 5-year survival rate was 34% in the 13 patients with jaundice and/or tumor mass depicted in US/CT, while it was 69% for the 22 patients without these two findings (p < 0.05).

CONCLUSIONS

These data lead us to conclude that an elevation of serum pancreatic enzyme levels, glucose intolerance, and duct dilation alone depicted by US/CT should not be overlooked. ERP should be more widely applied to such patients, instead of persisting in delineating the tumor mass by US/CT or follow-up by tumor marker.

Pancreatic invasion as the prognostic indicator of duodenal adenocarcinoma treated by pancreatoduodenectomy plus extended lymphadenectomy

Pancreatoduodenectomy has become the standard procedure in resection of the duodenal adenocarcinoma, and some adjuvant therapies can be added to obtain further improvement in postoperative outcome. However, for patient selection, it is necessary to have a predictive indicator showing, if possible before laparotomy, which instances are noncurable by surgery alone or need adjuvant therapies.

METHODS

A retrospective analysis was made for 24 consecutive patients whose duodenal adenocarcinoma were treated by pancreatoduodenectomy plus a wide range of lymphadenectomies without any adjuvant therapies at Osaka Medical Center for Cancer and Cardiovascular Diseases. Patient survival rates were related to macroscopic and microscopic findings and to findings obtained by preoperative imaging techniques.

RESULTS

The overall survival rate was 69% at 3 years and 57% at 5 years; locoregional recurrence was the primary cause of death. Although the 5-year survival rate was 44% in patients with nodal involvement and 76% in those without, this difference did not reach statistical significance (P = .079). Instead, invasion into the pancreatic parenchyma at a macroscopic level was the most significant prognostic factor; the 5-year survival rate was 78% in the 16 patients without and 16% in the 8 patients with pancreatic invasion (P = .0047). Invasion into the pancreas correlated well with the angiographic findings; the 5-year survival rate was 25% in patients whose angiograms delineated the pancreatic invasion and 83% in patients whose angiograms did not (P = .0084).

CONCLUSION

When duodenal adenocarcinoma was treated by pancreatoduodenectomy plus a wide range of lymphadenectomy, pancreatic invasion at a macroscopic level was most associated with patient survival. Pancreatic invasion was well delineated by the preoperative angiogram, which would be helpful in patient selection.

Dopamine formation from tyramine by CYP2D6

Dopamine is formed form L-tyrosine by tyrosine hydroxylase and aromatic L-amino acid decarboxylase. In addition to this pathway, however, the formation of catecholamines, including dopamine, from trace amines such as tyramine by hepatic microsomes has been demonstrated. In this study, we investigated the formation of dopamine from trace amines, using human hepatic microsomes and human cytochrome P450 (CYP) isoforms expressed in yeast. Among the 11 isoforms of human CYP expressed in yeast, CYP2D6 was the only isoform exhibiting strong ability to convert p-tyramine and m-tyramine to dopamine. In studies with human hepatic microsomes, the hydroxylation of tyramine to dopamine was inhibited by bufuralol, a typical substrate for CYP2D isoforms, and anti-CYP2D1 antiserum. This is the first report showing that CYP2D is capable of converting tyramine to dopamine. The Km values of CYP2D6, expressed in yeast, for p-tyramine and m-tyramine were 190.1 +/- 19.5 microM and 58.2 +/- 13.8 microM, respectively. Tyramine is an endogenous compound which exists in the brain as a trace amine but is also an exogenous compound which is found in foods such as cheese and wine. Our results suggest that dopamine is formed from endogenous and/or exogenous tyramine by this CYP2D isoform.

Presence of a threshold for promoting effects of phenobarbital on diethylnitrosamine-induced hepatic foci in the rat

The dose dependence of the hepatopromoting effects of phenobarbital (PB) was investigated in a rat liver medium-term bioassay (Ito test) to elucidate a practical threshold level. F344 rats were given a single i.p. injection of diethylnitrosamine (200 mg/kg body wt) and subjected to two-thirds partial hepatectomy at week 3. Commencing 2 weeks from the start, PB at doses of 0, 1, 2, 4, 7.5, 15 or 500 p.p.m. in experiment 1 and 0, 0.01, 0.1 or 0.5 p.p.m. in experiment 2 were fed to the rats for 6 weeks. Experiment 3 was conducted to confirm previous data using the same medium-term bioassay, with PB at doses of 0, 1, 2, 4, 7.5, 15, 30, 60, 125, 250 or 500 p.p.m. fed to the rats. All surviving animals were killed at week 8 in these experiments and their livers were immunohistochemically examined for expression of glutathione S-transferase placental form (GST-P). Quantitative values for GST-P-positive foci in the liver were increased dose dependently in rats given 60-500 p.p.m. PB. However, those for doses in the range 1-7.5 p.p.m. demonstrated a decrease as compared with the control group (0 p.p.m.), with significant differences observed for 1 and 2 p.p.m.. The results for 15-30 and 0.01-0.5 p.p.m. were comparable with the control values. Examination of transforming growth factor-alpha (TGF-alpha)-positive foci also produced similar results to those for GST-P in experiment 1. Immunohistochemical staining of TGF-alpha and GST-P using serial liver sections demonstrated that the TGF-alpha-positive foci comprised a sub-population of the GST-P-positive lesions, being approximately 1/8-1/10th as common in livers of animals treated with PB. TGF-alpha-positive foci were almost always negative on immunostaining for TGF-beta. Western blotting for proteins CYP2B1, 2C6 and 3A2 revealed a good correlation between changes in GST-P-positive foci and CYP3A2 protein expression. The finding of inhibition effects at low doses of PB confirms the presence of a threshold level for promoting effects by PB on liver carcinogenesis in rats.

Indications for hepatectomy for hepatocellular carcinoma - what stage of the disease is the best indication for surgery?

To determine the clinical and tumor stage of hepatocellular carcinoma (HCC) that is the best indication for surgery, the postoperative long-term outcomes of patients who underwent hepatic resection were examined retrospectively. Of 975 patients with HCC who underwent regional therapy, 384 patients (39%) received hepatic resection (HR), 534 (55%) had transcatheter arterial chemoembolization (TACE), and the remaining 57 (6%) received percutaneous ethanol injection (PEI) into the tumor. The criteria defined by liver Cancer Study Group of Japan was used for staging and liver functional reserve (i.e., clinical staging). In the 133 patients with stage I HCC, there were no significant differences among the survivals of the HR, TACE, and PEI groups. In the 314 patients with stage II HCC, the 5- and 7-year survival rates were 51% and 46% in the HR group, 23% and 10% in the TACE group, and 0% and 0% in the PEI group. The survival of the HR group was significantly better than the survivals of the TACE and PEI groups (P < 0.001). The 5- and 10-year survivals of the stage II HCC patients who had HR were 64% and 47% in the clinical stage I (i.e., good liver function) group, significantly better than the 5; and 10-year survivals (32% and 23%) in the clinical stage II (i.e., bad liver function) group (P < 0.0001). Patients with good liver function in stage II are expected to have better survival and are considered to be the most suitable for HR.

[The physiological role of P450-derived arachidonic acid metabolites]

Arachidonic acid is metabolized to biologically active substances by three major enzyme systems including cyclooxygenases, lipoxygenases and cytochrome P450s. The third pathway, P450-dependent pathway, includes allylic oxidation, omega-hydroxylation, and epoxidation of arachidonic acid. Of these metabolites, the physiological role of 20-hydroxyeicosatetraenoic acid (20-HETE) produced by CYP4A isoforms has been extensively studied. 20-HETE affects ion transport, constricts blood vessels and participates in tubuloglomerular feed back. Increased production of 20-HETE is a major factor in elevating blood pressure in spontaneously hypertensive rats (SHR). We have found that CYP4A2 level in SHR is much higher than that of normotensive rat. Recently, factors of endothelial origin other than nitric oxide and prostaglandins were reported. Inhibitors of P450-dependent arachidonic acid metabolism greatly reduce the vasodilator effect and this factor is speculated to be an epoxide of arachidonic acid. We have isolated CYP2C23 from rat kidney and have found that it produces arachidonic acid epoxides. We have investigated changes in the CYP2C23 levels in physiological and pathophysiological conditions. Multiple pathways of arachidonic acid metabolism by P450 have been reported and the diverse properties of these metabolites and the wide distribution of the P450 system make them prime candidates for participation in regulatory mechanisms of the circulation and transporting epithelia.

Isolation and characterization of a novel human pancreas-specific gene, pancpin, that is down-regulated in pancreatic cancer cells

By means of the differential display method, we isolated a novel human gene that is expressed specifically in pancreas. The cDNA, designated "pancpin," contained an open reading frame of 1,215 nucleotides encoding a 405 amino acid protein, showing a high degree of similarity to serine protease inhibitors belonging to the serpin superfamily. To investigate its possible role in pancreatic carcinogenesis, we looked for genetic alterations of this gene in pancreatic cancer cell lines and primary pancreatic cancer tissues. Expression of pancpin was barely detectable in any of the four pancreatic cancer cell lines examined, and very weak also in 10 of 13 pancreatic cancer tissues. A somatic missense mutation at codon 221 was found in two of 16 primary pancreatic cancers. These findings indicate that down-regulation of pancpin expression may play a significant role in development or progression of pancreatic cancer.

[A measure to continue intra-arterial infusion chemotherapy long-term for locally advanced pancreatic cancer]

For locally advanced non-resectable cancer of the pancreas, we have routinely performed intra-arterial chemotherapy: Each catheter is placed in the splenic artery and gastroduodenal artery during laparotomy, and a mixture of Methotrexate and Angiotensin-II is infused within 30 minutes. This treatment is repeated weekly at our outpatient clinic as long as possible. However, obstruction of the catheter or corresponding artery is the major cause of interruption of treatment. The present paper reports a case in which intra-arterial chemotherapy was possible by repeated catheterization for the catheter obstruction. A 54-year-old woman with non-resectable pancreatic cancer underwent catheter placement during laparotomy, but they became occluded one month later. Another catheter was placed into the common hepatic artery by the Seldinger method. After this catheter was occluded again, another catheter was placed into the inferior pancreaticoduodenal artery via the superior mesenteric artery by the Seldinger method. By repeating this catheter placement, we succeeded in continuing the intra-arterial chemotherapy, and the patient has remained alive (30 postoperative months) without losing her quality of life.

[Adjuvant intra-arterial chemotherapy with gastrin receptor antagonist after hepatic resection in colorectal cancer metastasis]

The aim of this study was to determine whether chemo-endocrine therapy after the resection of liver metastasis from colorectal cancer would prevent recurrence in the remnant liver and prolong survival. Eleven colorectal cancer patients underwent hepatic resection for liver metastasis. Subsequently, they were administered Proglumide gastrin antagonist 1,200 mg/day + 5'-DFUR 800 mg/day for 2 years. In seven of them, MMC 6-10 mg and ADM 20 mg were infused intra-arterially every two weeks alternately for one year. In four of them, 5-FU 250 mg/day was infused for seven days continuously intra-arterially every two weeks for one year. Recurrence in the remnant liver occurred in four of 11 patients. All of these patients underwent repeated hepatectomy. The mean disease-free survival in the remnant liver was 37 months and the five-year survival rate was 91%. These results indicate that intra-arterial chemotherapy with gastrin receptor antagonist might be effective for adjuvant therapy in patients with resectable liver metastasis from colorectal cancer.

[Report of case who survived more than five years after repeated intraperitoneal chemotherapy with cisplatin and 5-fluorouracil for treatment of macroscopically negative but microscopically positive peritoneal dissemination of gastric cancer]

Prognosis of patients with macroscopically negative but microscopically positive peritoneal dissemination is so poor that the two-year survival rate after the surgery was 0% during 1975-1981. It improved to 38% during 1982-1988 but the five year survival rate was 0%.

CASE REPORT

A 57-year-old male underwent distal gastrectomy and lymph node dissection on November 10, 1992 due to Borrmann type 3 gastric cancer measuring 5.4 cm in diameter and locating in the gastric antrum (H0 P0 t3 n3 stage IV a). Peritoneal lavage cytology revealed cancer cells, and, thus, this patient was treated with intraperitoneal chemotherapy using an intraperitoneal infuser port. Through the infuser port, cisplatin and 5-FU were given at a dose of 70 mg/m2 and 700 mg/m2, respectively. Because fluorouracil infusion caused abdominal pain after the second infusion, it was administered i.v. for 24 hours thereafter. The infuser port was removed after the four infusions because the patient developed appendicitis. Fluorouracil was given p.o. at a dose of 300 mg/day from one month after surgery (total dose of fluorouracil 54.6 g). Cytological examination of the ascites revealed no cancer cells after the second intraperitoneal chemotherapy, and the patient fared well five years and four months after the surgery. Therefore, it is suggested that intraperitoneal chemotherapy with cisplatin and fluorouracil is an effective treatment for microscopical peritoneal dissemination, though it may have an adverse effect such as chemical peritonitis.

Differential alterations in levels of hepatic microsomal cytochrome P450 isozymes following intracerebroventricular injection of bacterial lipopolysaccharide in rats

To investigate the effect of central inflammation due to bacterial infection, such as meningitis, on the activities of hepatic cytochromes P450 (CYPs), rats were injected intracerebroventricularly (i.c.v.) with 0.1 microg of bacterial lipopolysaccharide (LPS). The LPS i.c.v. injection significantly decreased the total P450 contents (by 30% of the levels of control rats treated with saline i.c.v.), the contents of CYP1A (48%), 2B (54%), 2C11 (37%) and 3A (40%) and related drug metabolizing activities, 7-ethoxycoumarin O-deethylation (36%), imipramine N-demethylation (41%) and erythromycin N-demethylation (33%) in liver microsomes 24 h after the treatment. In contrast, intraperitoneal (i.p.) injection of LPS at the same dose as i.c.v. (0.1 microg) did not significantly affect the hepatic microsomal contents of total P450 or the content of each individual CYP isozyme and its activity. CYP2D1 protein and the activity of imipramine 2-hydroxylase were not significantly decreased by LPS injection regardless of the route of administration. The inhibitory effects of 0.1 microg i.c.v. LPS on the activities of these CYPs were almost equal to those of 10 microg i.p. LPS, and 0.01 microg of i.c.v. LPS significantly decreased the activity of imipramine N-demethylase only. Therefore, the LPS i.c.v. injection resulted in CYP isozyme-selective inhibition at an ineffective dose when injected i.p.. It is suggested that a central inflammation, such as meningitis, differentially decreases the levels of hepatic CYP isozymes. A possible involvement is discussed of the central nervous system in this down-regulation.

[Inhibition of cytochrome P450 by nitric oxide]

Nitric oxide (NO) reacts with iron, superoxide, thiols and oxygen. Although NO reversibly interacts with the heme-iron of P450, the pathophysiological role of this interaction remains to be elucidated. We found that hepatic levels of P450 markedly decreased in endotoxemic rats, particularly when the rate of NO generation was increased. To determine the possible role of NO in the modulation of the structure and function of P450, changes in the levels and activities of P450 isozymes were determined in liver microsomes from normal and endotoxemic rats. Electron spin resonance analysis revealed that incubation of microsomes with the NO donor NOC-7 rapidly generated NO-P450 adducts. Microsomal levels of NO-P450 adducts increased and peaked at 10 min after incubation and decreased thereafter; it disappeared completely within 60 min. In contrast, microsomal levels of the low-spin ferric form and CO-differential spectrally detectable P450 rapidly decreased during the initial 10 min; the signal intensity for P450 recovered thereafter. Western blot analysis using specific antibodies against CYP3A2 and CYP2C11 isozymes revealed no detectable degradation of these isoforms. Effect of NO on the catalytic activity of the enzymes was also determined by using testosterone as the substrate. The hydroxylation activity in microsomes rapidly decreased during the initial 10 min and disappeared slowly thereafter. These results suggested that NO might form dissociable complexes with the heme moiety of P450 and irreversibly inactivate them. The mechanism for P450 inactivation by NO and the role of NO-P450 interaction in the pathogenesis of liver injury in endotoxemia are discussed.

Allelic imbalance of insulin-like growth factor II gene expression in cancerous and precancerous lesions of the liver

Allelic imbalance of the insulin-like growth factor II (IGF II) gene expression is often seen in hepatocellular carcinoma (HCC). To investigate the role of allelic imbalance in hepatocarcinogenesis, we have studied allelic expression status of the IGF II gene in dysplastic nodules, which are precancerous lesions of HCC, as well as in HCCs of different histological grade, and the influence of the allelic imbalance on IGF II gene expression has also been examined. Allelic imbalance was observed in 3 of 7 dysplastic nodules, in 7 of 9 well-differentiated HCCs, and in 8 of 9 moderately differentiated HCCs. IGF II gene expression level, which was studied by a semiquantitative reverse-transcriptase polymerase chain reaction (RT-PCR), was significantly higher (3.6-fold) in the dysplastic nodules than the control livers, but a significant increase in the IGF II gene expression was not observed in well- and moderately differentiated HCCs as compared with the control livers. These results demonstrate that the allelic imbalance of the IGF II gene expression is seen in the early stage (precancerous lesions) of hepatocarcinogenesis. Association of the allelic imbalance with an increased expression of the IGF II gene in the precancerous lesions might suggest a possible involvement of an IGF II autocrine loop in the pathogenesis of these lesions.

Activation of the beta-catenin gene in primary hepatocellular carcinomas by somatic alterations involving exon 3

We screened 75 primary hepatocellular carcinomas for somatic mutations in the entire coding region of the beta-catenin gene. We detected somatic mutations in 14 tumors; 12 were considered to cause amino acid substitutions and 2 were interstitial deletions of 51 or 195 nucleotides of genomic DNA, corresponding to exon 3. Among the 12 point mutations, 6 occurred at potential serine/threonine phosphorylation residues of codons 33, 41, or 45. The remaining six tumors contained a mutation at codon 32 (aspartic acid) or 34 (glycine), flanking to the serine residue at codon 33. By Western blot analysis, we confirmed accumulation of beta-catenin in five tumors for which frozen tissues were available; the five included tumors in which amino acid alterations had occurred at codons 32, 34, or 45, and one with a 17-amino acid deletion. Our results suggested that accumulation of beta-catenin due to amino acid substitutions at potential serine/threonine phosphorylation residues or at their neighboring codons or interstitial deletions involving exon 3 could contribute to hepatocellular carcinogenesis.

P450 isoforms in a murine macrophage cell line, RAW264.7, and changes in the levels of P450 isoforms by treatment of cells with lipopolysaccharide and interferon-gamma

The presence of P450 in a murine macrophage cell line, RAW264.7, was investigated to clarify the biological role and regulation of P450. Microsomes of RAW264.7 cells were isolated and subjected to immunoblotting with anti-rat CYP2A1, 2B1, and 4A2 antibodies. The microsomes gave staining bands with all these antibodies, suggesting the presence of mouse Cyp2a, 2b, and 4a isoforms in RAW264.7. RAW264. 7 cells were treated with typical inducers of P450 (phenobarbital, clofibrate, beta-naphthoflavone and 3-methylcholanthrene). None of these chemicals induced these P450s. Stimulation of RAW264.7 cells with lipopolysaccharide (LPS) and interferon-gamma (INF-gamma) which increase inducible nitric oxide synthase (iNOS) and cytokines in cells decreased Cyp4a protein but not Cyp2a and 2b proteins. To identify P450 isoforms in RAW264.7, we used polymerase chain reaction (PCR) primers for mouse Cyp2a4, 2a12, 2b9/10, 4a10, and 4a12. Total RNA was isolated from these cells and converted to cDNA by reverse transcriptase. PCR was done with these primers and the amplified nucleotides were analyzed by a DNA sequencer. Only Cyp2b9/10 and 4a12 primers gave clear bands, although all primers gave clear bands from liver total RNA. Nucleotide sequences of these products amplified by PCR were identical with Cyp2b9 and 4a12. These findings indicate that Cyp2b9 and 4a12 were present in a macrophage cell line, RAW264.7, and the regulation of P450 by inducers and cytokine differed from that in liver.

Limited surgery for early gastric cancer in cardia

BACKGROUND

Because there are some difficulties with the diagnosis of invasion or the endoscopic resection technique, almost all gastric tumors are resected surgically. Surgeons now are performing a limited operation for early gastric cancer of the upper stomach (EGCUS) without lymph node metastasis. This paper discusses and evaluates the surgical technique and the results of the limited operation for EGCUS.

PATIENTS AND METHODS

Since 1988, a total of 34 patients with EGCUS, diagnosed as intramucosal invasion, have undergone a limited operation--fundectomy--which includes a limited proximal gastrectomy, a limited lymph node dissection, and a procedure preserving the vagal nerve. The surgical risk, postoperative complications, and survival rates of the fundectomy patients (group A) were compared with those of patients undergoing a total gastrectomy for EGCUS (group B).

RESULTS

Blood loss was lower in group A (300+/-193 mL) than in group B (555+/-316 mL) (P <.05). The incidence of postoperative pancreatic fistula also was lower in group A (0%) than in group B (15.0%) (P <.05). All patients in both groups (except one who died of a cerebral infarction) are alive without recurrence.

CONCLUSION

Compared to the results of a total gastrectomy, performance of a limited fundectomy for EGCUS decreased surgical risk and postoperative complications without decreasing the survival rate.

Intraoperative cytodiagnosis for detecting a minute invasion of the portal vein during pancreatoduodenectomy for adenocarcinoma of the pancreatic head

During pancreatoduodenectomy for adenocarcinoma of the pancreatic head, we frequently encountered cases in which the superior mesenteric-portal venous confluence (SMPVC) was involved with cancer. With regard to the indication of the concomitant SMPVC resection, as suggested by recent papers, a better long-term outcome would be expected if the cancer invasions were limited to the tunica adventitia or media of the SMPVC wall. Since this raised fears whether such a small SMPVC invasion was always detectable by macroscopic inspection alone, we have performed an intraoperative cytology on the touch smear of the exposed SMPVC wall for 23 patients with pancreatic head cancer. All of their SMPVCs were separated from the pancreatic head and appeared to be intact at a macroscopic level. As a result of the cytologic examination, however, 7 patients (30%) were newly diagnosed as having cancer cells on the SMPVC wall, and they received an additional resection of the SMPVC. Postoperative histology indicated that cancer invasion into the SMPVC wall was present in 6 of the 7 patients, and that the cancer invasions were limited in the tunica adventitia in 5 patients and to the tunica media in 1 patient. Thus, in order not to miss the chance of cure by SMPVC resection, our intraoperative cytology on the touch smear of the SMPVC is worth performing more actively on the macroscopically intact-looking SMPVC during resection of pancreatic cancer.