Use of signal-distinguishable probes in differential or sequential autoradiography in hybridization analysis

To avoid the time-consuming reprobing process in hybridization analysis, signal-distinguishable probes (32P, 35S or antigenic hapten-labeled DNA) can be added to the same hybridization mixture. After hybridization, an unambiguous result can be obtained by differential or sequential autoradiography.

Can cecal diverticulitis be differentiated from acute appendicitis?

Cecal diverticulitis is a rare disease entity, the diagnosis of which remains a difficult problem. The clinical picture of cecal diverticulitis is almost indistinguishable from acute appendicitis. We reviewed 11 cases of pathologically documented cecal diverticulitis who underwent treatment from May 1981 to April 1992. They were diagnosed incorrectly as acute appendicitis, ruptured appendicitis or appendiceal abscess prior to operative intervention. Thirty patients diagnosed correctly with acute appendicitis from March 1992 to April 1992 were included for a comparative study. We found that cecal diverticulitis presented with a longer duration of symptoms, initial pain over the right lower quadrant of the abdomen, older age, less migration of pain, nausea, vomiting, fever and leukocytosis, and an incidence of Alvarado's score > or = 7 than acute appendicitis.

Selective depression of T-lymphocyte subsets in gastric cancer patients: an implication of immunotherapy

The lymphocytes and their subsets were determined in the peripheral blood of 62 gastric cancer patients and 68 controls using fluorescent conjugated monoclonal antibodies and flow cytometry (FACScan method). A significant increase in the total number of white blood cells from gastric cancer patients was noted in comparison to controls, but the percentage of lymphocytes was the same. The percentage of suppressor (cytotoxic) T cells (CD8) showed no difference in all stages of gastric cancer patients evaluated, but the percentage of helper (inducer) T cells (CD4) and the CD4/CD8 ratio decreased significantly in the advanced stages III and IV. Depression of the CD4/CD8 ratio was well correlated with tumor invasion, lymph node metastasis, and tumor size but not with sex, age, tumor location, gross type, or histologic differentiation. It appeared that the immune defect of gastric cancer patients was associated with the afferent arm (CD4) and worsened as the disease advanced. These results suggest that immunotherapy to stimulate the deficient immune system may play an important part in the multimodality treatment of patients with advanced gastric cancer.

Endoscopic ultrasound-guided fine needle aspiration of pancreatic carcinoma

Endoscopic ultrasound (EUS) is reported to be the single best modality for visualizing small pancreatic carcinomas. Whereas tissue diagnosis by fine needle aspiration (FNA) can be performed with computed tomography (CT) or transabdominal ultrasound guidance, the diagnostic accuracy is limited by the ability of these modalities to visualize the lesion. Real time EUS-guided fine needle aspiration has recently been reported as a new diagnostic modality. The application of EUS-guided FNA in the diagnosis of small pancreatic carcinoma has not been reported. We present a case in which transduodenal EUS-guided FNA was successful in establishing a definitive tissue diagnosis of pancreatic carcinoma in a 1.6-cm lesion in the head of the pancreas. This case along with a review of the literature highlights the great potential of this new modality in the diagnosis of pancreatic carcinoma.

Opioid agonist binding affinity is increased by magnesium in the presence of guanosine diphosphate but decreased by magnesium in the presence of guanyl-5'-yl imidodiphosphate

Opioid receptors exist in multiple affinity states for agonists. Cations and guanine nucleotides affect mu-agonist affinity by modulating the interaction between receptor molecule and G-protein. In this study, we systematically examined the effects of cations and guanine nucleotides on the binding of mu-agonist [D-Ala2, N-Me-Phe4, Met-(O)5-ol]enkephalin in rat spinal cord and brain membranes. A homogeneous class of low-affinity receptors was obtained by conducting binding assays in the presence of Na+ (100 mM) + guanosine diphosphate (100 microM). The addition of Mg++ (5 mM) shifted a portion of the low-affinity receptors to the high-affinity state. In membranes preincubated with Na+ + guanosine diphosphate and with the binding assay performed in the presence of Mg++, a homogeneous class of high-affinity receptors was induced by the agonist. Further addition of Na+ + guanyl-5'-yl imidodiphosphate (30 microM) to the above Mg++-containing medium converted all receptors to a low-affinity state, whereas Na+ + guanyl-5'-yl imidodiphosphate produced a mixture of high- and low-affinity states. Our results suggest that, depending on which guanine nucleotide is bound with G-proteins, mg++induces opposite effects on the states of mu-receptor affinity: high affinity with GDP and low affinity with guanyl-5'-yl imidodiphosphate. Sodium ion promotes the low-affinity receptor conformation and increases total low-affinity binding sites. The affinity of the opiod antagonist naloxone is not sensitive to regulation by Mg++ and guanine nucleotides, except that the total receptor binding is increased by Na+.(ABSTRACT TRUNCATED AT 250 WORDS)

Five-drug combination chemotherapy (FAPEL) for advanced gastric cancer: a pilot study

To test if the incorporation of 5-fluorouracil (5-FU) and leucovorin in a modified etoposide, doxorubicin, cisplatin (EAP) regimen could diminish its toxicity and improve its efficacy, 18 patients with far-advanced, unresectable gastric cancer, diagnosed at National Taiwan University Hospital between January 1991 and December 1992, were treated with a FAPEL combination chemotherapy. The regimen consisted of doxorubicin 25 mg/m2 i.v. on day 1, cisplatin 60 mg/m2 i.v. infusion on day 1, etoposide 60 mg/m2/day i.v. infusion on days 1-3, 5-fluorouracil 500 mg/m2/day i.v. on days 1-3, and leucovorin 50 mg/day i.v. on days 1-3; repeated every three to four weeks. The patients included nine metastatic, six locally advanced and inoperable, and three post-gastrectomy recurrent cancer patients with median Karnofsky performance status of 60%. There were 11 men and seven women with a median age of 52.5 years. The patients tolerated the treatment toxicity relatively well and received an average of 4.3 courses of chemotherapy. Most patients completed the protocol therapy except one who refused and another who died of leucopenic sepsis. Myelosuppression was the limiting toxicity, with Eastern Cooperative Oncology Group (ECOG) grade 3-4 leucopenia developing in 35.9% and grade 3-4 thrombocytopenia developing in 11.5% of a total of 78 courses given. The overall objective response rate was 44.4% with 5.5% complete responses and 38.9% partial responses. The overall median survival was seven months (0.5-21 months). The median survival of responders and non-responders was 13 months (5-21 months) and three months (0.5-7 months), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Factors related to tumor size of breast cancer at treatment in Taiwan

METHODS. Personal information and clinical and pathological records were collected for 178 of 310 new cases of breast cancer in 1991 Cancer Registry of Taiwan. RESULTS. Among the subjects studied, 89.3% of the breast cancers were found incidentally. Delayed treatment, doctor shopping, and taking traditional medicine were common. Only 19.7% of the tumors were not more than 2 cm in diameter when the patients received treatment. The most important factors related to tumor size at treatment were occupation, family economic status, and action after detection. Those who were employed, had higher family economic status, and saw a doctor immediately after the tumor was detected were likely to have smaller (< or = 2 cm) tumors at treatment. The application of screening methods, however, did not show any significant relationship. The authors suggested implementing a breast self-examination health education program, evaluating cost-benefits of different screening methods, and setting up a breast cancer screening model that can meet the needs of Taiwanese women.

A novel, potent and selective nonpeptidic delta opioid receptor agonist BW373U86

Four different opioid receptor binding assays and three different isolated tissue studies were used to screen for delta receptor-selective nonpeptidic compounds. (+/-)-4-((alpha-R*)-alpha-((2S*,5R*)-4-Allyl-2,5- dimethyl-1-piperazinyl)-3-hydroxybenzyl)-N,N-diethylbenzamide (BW373U86) was a potent delta receptor-selective ligand in receptor binding assays. The Ki values were 1.8 +/- 0.4, 15 +/- 3, 85 +/- 4 and 34 +/- 3 nM for delta, mu, epsilon and kappa receptor binding sites, respectively. BW373U86 inhibited electrically evoked muscle contraction of mouse vas deferens with an ED50 value of 0.2 +/- 0.06 nM. This inhibitory effect of BW373U86 was antagonized by the delta receptor-selective antagonist naltrindole in a competitive manner: the Schild plot indicated a slope of 1 and a pA2 value of 9.43 (Ke = 3.7 x 10(-10) M), which is consistent with the high affinity of naltrindole in delta receptors. BW373U86 did not interact significantly with other receptors. BW373U86 inhibited the acoustic startle reflex after subcutaneous administration from 0.2- to 2-mg/kg doses in rats, and this inhibition was blocked by naltrindole. BW373U86 also induced a dose-dependent increase of locomotor activity in rats at similar doses. This effect was inhibited by naltrindole. These data suggest that BW373U86 is a potent and selective nonpeptidic delta agonist, and it elicits distinct in vivo pharmacological activities.

A nonpeptidic delta opioid receptor agonist, BW373U86, attenuates the development and expression of morphine abstinence precipitated by naloxone in rat

The effect of (+-)-4-((alpha-R*)-alpha-((2S*,5R*)-4-allyl-2,5-dimethyl-1- piperazinyl)-3-hydroxybenzyl)-N,N-diethylbenzamide (BW373U86), the first potent nonpeptidic, highly selective delta opioid receptor agonist, on morphine dependence was studied in rats. Continuous infusion of BW373U86 by a subcutaneously implanted osmotic minipump did not induce any abnormal behavior. After 6 days of BW373U86 infusion, intraperitoneal injection of a high dose of naloxone or naltrindole did not precipitate morphine-like abstinence syndromes. Furthermore, a single injection of BW373U86 did not induce abstinence syndromes or modulate morphine abstinence precipitated by naloxone in chronic morphine-treated rats. However, naloxone-precipitated abstinence syndromes in morphine-dependent rats were partially suppressed by BW373U86 in a dose-dependent manner when the compound was infused subcutaneously before and throughout morphine treatment. Abstinence signs such as wet-dog shake, forelimb tremor and teeth chattering were either suppressed or the intensity was significantly attenuated in these BW373U86-infused rats. This effect was antagonized by naltrindole. These data show that chronic infusion of BW373U86 does not produce physical dependence and that it attenuates some abstinence behaviors in morphine-dependent rats via delta opioid receptors.

A novel delta opioid agonist, BW373U86, in squirrel monkeys responding under a schedule of shock titration

The squirrel monkey titration procedure was used to assess the antinociceptive effects of the novel delta opioid agonist (+/-)-4-(a-R*)-a(2S*,5R*)-4-allyl-2,5-dimethyl-1-piperazinyl)-3-hydroxyb enzyl)- N,N-diethylbenzamide (BW373U86). Under this procedure shock increased every 15 sec from 0.01 to 2.0 mA in 30 steps. Five responses terminated the shock for 15 sec, after which the shock resumed at a lower intensity. The intensity at which the monkeys maintained the shock 50% of the time (median shock level, MSL) was determined. BW373U86 (1.0-30.0 mg/kg i.m.) increased MSL, but these increases were not dose-dependent and lasted only 15 min or less. Doses of BW373U86 that increased MSL often produced tremors and/or convulsions immediately after administration. When 1.0 mg/kg of naltrindole, a delta opioid antagonist, was given in combination with BW373U86, doses of BW373U86 up to 30 mg/kg no longer increased MSL nor did tremors and/or convulsions occur. Doses of BW373U86 (0.01-0.3 mg/kg i.m.) that did not increase MSL when administered alone shifted the dose-effect curve for the mu agonist l-methadone to the left. These shifts were antagonized dose-dependently by naltrindole. In monkeys that were tolerant to morphine, BW373U86 (0.03-0.1 mg/kg i.m.) shifted the morphine dose-effect curve leftward. In addition, BW373U86 altered the effects of the partial opioid agonists, buprenorphine, nalbuphine, butorphanol and levallorphan such that doses of these drugs that did not increase MSL when administered alone, often did so in the presence of BW373U86. Taken together, these findings indicate that BW373U86 has a delta agonist profile in the squirrel monkey; however, its antinociceptive effects in the shock titration procedure may be due to its toxic effects.

Convulsive effects of systemic administration of the delta opioid agonist BW373U86 in mice

A systemically active, nonpeptidic delta receptor-selective agonist, (+-)-4-((alpha-R*)-alpha-((2S*,5R*)-4-allyl-2,5-dimethyl-1-piperazinyl) -3- hydroxybenzyl)-N,N-diethylbenzamide (BW373U86), produced a brief, nonlethal convulsion in mice. The behavioral pattern of convulsion produced by pentylenetetrazol was similar to that produced by systemic administration of BW373U86. Although several episodes of convulsion occurred with pentylenetetrazol, BWB373U86 produced a single, brief episode. Naltrexone (10.0 and 100 mg/kg) and naltrindole (1.0, 3.2 and 10.0 mg/kg), but not midazolam (0.32 mg/kg), produced dose-dependent rightward shifts in the potency of BW373U86 to induce a convulsion. A dose of 3.2 mg/kg of midazolam completely eliminated convulsions induced by BW373U86. Midazolam (0.32 and 3.2 mg/kg), but not naltrindole (3.2 and 32.0 mg/kg), produced parallel rightward shifts in the pentylenetrazol dose-effect curve. Pretreatment with a single injection of BW373U86 (3.2, 10.0, 32.0 or 100 mg/kg) produced a dose-related reduction in the capacity of BW373U86 to induce a second convulsion. Recovery of sensitivity to BW373U86 did not return to control levels for up to 2 weeks after pretreatment with a single injection of 32.0 mg/kg of BW373U86. Naltrindole (3.2 mg/kg) administered within 1 hr, but not at 2 hr, after a pretreatment dose of 10.0 mg/kg of BW373U86 prevented the refractoriness (tolerance) induced by the single dose of BW373U86. These data suggest that the convulsions as well as the tolerance induced by BW373U86 were initiated through delta opioid receptors.

Discriminative stimulus effects of BW373U86: a nonpeptide ligand with selectivity for delta opioid receptors

Several opioid agonists were evaluated in pigeons trained to discriminate i.m. injections of sterile water from either the mu agonist morphine (5.6 mg/kg), the kappa agonist bremazocine (0.032mg/kg) or (+/-)-4-((alpha-R*)-alpha-((2S*,5R*)-4-allyl-2,5-dimethyl-1- piperazinyl)-3-hydroxybenzyl)-N,N-diethylbenzamide (BW373U86; 0.56 mg/kg). Pigeons were trained to peak one of two keys on a fixed-ratio 20 schedule for food reinforcement. The pattern of substitution of mu, kappa and delta selective agonists in the three groups of birds suggested that the discriminative stimulus effects of morphine, bremazocine and BW373U86 were different; however, a component of the discriminative stimulus effects of BW373U86 appeared to be shared with morphine. Apparent pA2 values for naltrexone with morphine, bremazocine and BW373U86 were 7.6, 6.8 and 6.3, respectively. The apparent pA2 value for naltrindole with BW373U86 was 8.3. Naltrindole (10.0 mg/kg) produced a 3-fold shift to the right in the dose-effect curve for morphine but did not antagonize bremazocine. Although results from the substitutions experiments suggested that a component of the BW373U86 discriminative stimulus was mediated through mu opioid receptors, the fact that naltrindole was 1000-fold more potent and naltrexone was 30-fold less potent in antagonizing BW373U86 than morphine indicated that the discriminative effects of BW373U86 were also mediated through delta opioid receptors.

Antinociceptive actions of BW373U86 in the mouse

This study explored the antinociceptive properties of (+-)-4-[(alpha- R*)-alpha-[(2S*,5R*)-4-allyl-2,5-dimethyl-1-piperazinol]-3-hydroxy benzyl] - N,N-diethyl-benzamide dihydrochloride (BW373U86) a nonpeptidic compound proposed to be a delta opioid agonist, using three models of nociception and four routes of administration in mice. BW373U86 produced dose- and time-dependent, naloxone-sensitive antinociception in both the tail-flick and tail-pinch assays when given intrathecally (i.t.). However, at doses up to 187 nmol/mouse, i.c.v. BW373U86 was inactive in the tail-flick or tail-pinch assays. Additionally, at doses up to 187 mumol/kg, BW373U86 was not active after i.p. or p.o. administration in these endpoints. Further, in the tail-flick test, i.c.v. BW373U86 did not antagonize the antinociceptive effects of i.c.v. [D-Pen2,D-Pen5]enkephalin or [D-Ala2,Glu4]deltorphin, but partially antagonized the effects of i.c.v. morphine. In the acetic-acid abdominal constriction assay, BW373U86 produced dose-dependent antinociceptive effects when given by the i.p., i.c.v. or i.t., but not by the p.o., routes. Intrathecal BW373U86 was 663-fold more potent in the abdominal constriction assay than when given by the same route in the tail-flick test. The effects of an A70 dose of i.p. or i.c.v. BW373U86 in the abdominal constriction assay were partially antagonized by i.c.v. naloxone, but not by i.c.v. N,N-diallyl-Tyr-Aib- Aib-Phe-Leu-OH, where Aib is alpha-aminoisobutyric acid (ICI-174,864) or naltrindole. In contrast, i.t. naloxone, ICI-174,864 or naltrindole antagonized the antinociceptive effect of i.p. or i.t. BW373U86 in the abdominal constriction assay.(ABSTRACT TRUNCATED AT 250 WORDS)

DNA methylation is not involved in growth regulation of gene expression of proliferating cell nuclear antigen

Expression of proliferating cell nuclear antigen (PCNA) gene is growth regulated. By Southern blot analysis with restriction enzymes such as HpaII and MspI, no change of DNA methylation state in this gene was detected during rat liver regeneration. There is only one HpaII site located in the promoter region of rat PCNA gene and this HpaII site was found to be demethylated in both normal and regenerating livers. Human hepatoma cell lines Hep G2 and Hep 3B were used to study the relation of PCNA gene expression and the DNA methylation. There are 16 HpaII sites in human PCNA gene, and according to the HpaII and MspI restriction patterns, many of the HpaII sites were methylated in vivo. Upon serum stimulation of quiescent cells, no change of DNA methylation state in the HpaII and HhaI sites was found. Demethylation by the methylation inhibitor, 5-azacytidine, did not affect the expression of PCNA gene in the hepatoma cells. With the human primary fibroblasts, Y2, the demethylation by 5-azacytidine did not seem to change the growth dependence of PCNA gene expression. This is consistent with the observation that the expression of PCNA gene of some cultured cell lines such as CHO.K1, in which the PCNA gene was unmethylated, showed growth dependence. Also, no variation in methylation pattern of PCNA gene was found among the different rat tissues in which the expression of PCNA varies. Therefore, we conclude that DNA methylation is not involved in growth regulation of the PCNA gene expression.

BW373U86: a nonpeptidic delta-opioid agonist with novel receptor-G protein-mediated actions in rat brain membranes and neuroblastoma cells

BW373U86 is a potent and highly selective nonpeptidic agonist for delta-opioid receptors. To determine its ability to couple with G protein-linked second messenger systems, this study examined the effects of BW373U86 on the inhibition of adenylyl cyclase and the stimulation of low-Km GTPase activity. In rat striatal membranes, BW373U86 inhibited basal adenylyl cyclase activity in a GTP-dependent manner, with maximal inhibition levels similar to those of the prototypic delta agonist [D-Ser2,Thr6]Leu-enkephalin (DSLET). However, BW373U86 was approximately 100 times more potent than DSLET in inhibiting adenylyl cyclase. Analysis of the inhibitory activity across 10 brain regions revealed that both low and high concentrations of BW373U86 inhibited adenylyl cyclase activity in a manner similar to that of DSLET. Inhibition of adenylyl cyclase by BW373U86 was delta receptor selective, because the delta receptor-selective antagonist naltrindole was significantly more potent than naloxone and the mu receptor-selective antagonist D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH2 was ineffective in blocking BW373U86 inhibition. BW373U86 also inhibited adenylyl cyclase activity in membranes prepared from NG108-15 cells, with an IC50 value 5 times lower than that of DSLET. This increased potency was not observed in concentration-effect curves for agonist-stimulated low-Km GTPase in NG108-15 membranes. BW373U86 is a competitive inhibitor of [3H]diprenorphine at delta receptors of NG108-15 cell membranes. However, unlike DSLET, BW373U86 displacement of [3H]diprenorphine binding to NG108-15 cell membranes was not affected by sodium and guanine nucleotides. This lack of GTP effect on binding apparently produced slow dissociation rates for this agonist, because naltrindole was less potent in blocking BW373U86 inhibition of adenylyl cyclase when membranes were preincubated with this agonist. These results demonstrate the novel finding that the binding of a full agonist to a G protein-coupled receptor is not regulated by GTP, and they also show how the lack of regulation in receptor binding affects agonist potency.

Alternative transcript of the nonselective-type endothelin receptor from rat brain

A novel cDNA encoding the nonselective type of endothelin (ET) receptor was isolated from a rat brain cDNA library. The cloned cDNA encoded a 442-amino acid protein with seven putative transmembrane domains. Nucleotide sequence analysis showed that the rat brain cDNA differed from the cloned rat lung nonselective ET receptor (ETB) cDNA by three extra nucleotides in its coding regions, which produced an encoded protein with four amino acid substitutions. In addition, both the 5' and 3' noncoding sequences of the rat brain cDNA were divergent from those of rat lung cDNA. Expression of the rat brain cDNA in COS-1 cells demonstrated that the encoded receptor displayed equal affinity toward the three ET isopeptides. However, Southern blot analysis indicated a single-copy gene for the rat ETB receptor. Further genomic cloning and sequence analysis demonstrated that rat brain cDNA encoded the authentic protein sequences of the rat ETB receptor. Moreover, the 5' noncoding sequences in rat brain cDNA that were divergent from those in rat lung cDNA were encoded by a distinct region, an upstream exon, in the rat ETB genome. All the findings suggest that rat brain cDNA represents an alternative transcript of the rat ETB gene. Preliminary Northern blot analysis indicated that the expression of this ETB cDNA sequence might be not only in the brain but also in other tissues, whereas its expression might be somehow tissue-specifically regulated.

Molecular cloning and sequence analysis of the cDNA for ancrod, a thrombin-like enzyme from the venom of Calloselasma rhodostoma

The 1.54 kb cDNA for ancrod, a thrombin-like enzyme, was cloned from a lambda ZAP cDNA library derived from the venom glands of Calloselasma (Agkistrodon) rhodostoma. The cDNA sequence reveals that ancrod is synthesized as a pre-zymogen of 258 amino acids, including a putative secretory peptide of 18 amino acids and a proposed zymogen peptide of 6 amino-acid residues. The amino-acid sequence of the predicted active form of the enzyme exhibits a high degree of sequence similarity to those of mammalian serine proteases (trypsin and pancreatic kallikrein) and other thrombin-like enzymes (batroxobin and flavoxobin). Key amino-acid residues (His43, Asp88, Ser182 and Asp176) that are thought to be involved in the substrate cleavage and in the substrate-binding reaction are conserved. Ancrod contains 13 cysteine residues. Based on alignment with the amino-acid sequences of trypsin and batroxobin, six disulphide bridges can be predicted to be present in the ancrod protein. The existence of a free cysteine, which changes the common sequence surrounding the Ser182 active site from Gly-Asp-Ser-Gly-Gly-Pro to Cys-Asp-Ser-Gly-Gly-Pro, is unusual for a serine protease.

Binding of BW 373U86, a non-peptidic delta opioid receptor agonist, is not regulated by guanine nucleotides and sodium

BW 373U86 is a novel, non-peptidic delta-opioid receptor ligand with agonist properties in mouse brain and in the mouse isolated vas deferens. The sensitivity of BW 373U86, and of the peptide delta-opioid agonists [D-Pen2,D-Pen5]enkephalin (DPDPE) and [D-Ala2,Glu4]deltorphin, to regulation by guanine nucleotides and sodium was evaluated in competition studies against the 5 selective radioligand [3H]naltrindole. The IC50 values for DPDPE and [D-Ala2,Glu4]deltorphin were significantly increased in brain and mouse vas deferens in the presence of Gpp(NH)p and NaCl. In contrast, the IC50 values for BW 373U86 were not altered in the presence of Gpp(NH)p and NaCl in either tissue. The data indicate that the agonist properties of BW 373U86 may not be affected by the supposed uncoupling of the alpha-subunit of the G-protein from a receptor thought to be G-protein linked.

DNA hypomethylation of proliferating cell nuclear antigen gene in human hepatocellular carcinoma is not due to cell proliferation

Proliferating cell nuclear antigen (PCNA) gene expresses preferentially in proliferative cells or tissues. The levels of PCNA mRNA are very low in livers of adult mammals. Expression of PCNA gene in hepatocellular carcinoma tissues was, however, elevated; and 5'-CCGG-3' sequences of the gene in neoplastic tissue were less methylated. Such DNA hypomethylation was concluded, on the basis of two observations, not to be due to the cell proliferation in hepatoma tissues. First, while the expression of PCNA was increased during serum-stimulation of quiescent Hep G2 cells, the DNA methylation pattern of PCNA gene remained unchanged. Second, in rat liver regeneration, the PCNA mRNA level rose and declined, but the DNA methylation status of PCNA gene was unaltered. Therefore, the DNA hypomethylation of the PCNA gene found in hepatocellular carcinoma was not due to cell proliferation, but a possible consequence of cell transformation.