Evaluation of endoscopic hemostasis in upper gastrointestinal bleeding related to Mallory-Weiss syndrome.

BACKGROUND AND STUDY AIMS: The endoscopic hemostatic method has been introduced as a safe and effective mechanical approach to hemostasis for upper gastrointestinal bleeding related to Mallory-Weiss syndrome (MWS). However, the indications for when to use endoscopic treatment are debatable because many patients need only medical observation. The study was designed to evaluate the necessity and efficacy of endoscopic hemostasis in upper gastrointestinal bleeding related to MWS. PATIENTS AND METHODS: From July 1994 to May 2000, we conducted a clinical trial in 76 patients who were found by endoscopy to have active bleeding (I, spurting; II, oozing), protruding visible vessels (III), and/or adherent clots (IV). Two study periods can be differentiated: in the first 3 years endoscopic treatment (n = 30) was prospectively analyzed and in the final 3 years medical treatment (n = 46) was analyzed in both cases to compare the outcome in MWS bleeding II-IV. In the first study period, in addition, endoscopic treatment was randomised to an injection method, using a mixture of hypertonic saline and epinephrine (HSE) (n = 14) and a hemoclipping or band ligation method (n = 16). RESULTS: Rebleeding was observed in four of 14 patients who had received endoscopic hemostasis with HSE injection and one of 46 patients who had been managed with medical treatment. No rebleeding was found following hemoclipping or band ligation. While all rebleeding was in bleeding stigmata of the I (1) and II (4) grades, there was no rebleeding in protruding visible vessels (III) or in adherent clots (IV), regardless of treatment methods. CONCLUSIONS: Our results suggested that endoscopic hemostasis is not necessary in patients without active bleeding stigmata, and the mechanical hemostatic method is more effective than HSE injection in patients with active bleeding stigmata.

Temporospatial sequence of cellular events associated with etoposide-induced neuronal cell death: role of antiapoptotic protein Bcl-X(L).

Etoposide-induced death comprises such nuclear events as the formation of topoisomerase II-DNA cleavable complex and cytosolic events including caspase activation. By first establishing the temporospatial death sequence triggered by etoposide in a neuronal cell line, MN9D overexpressing Bcl-X(L) (MN9D/Bcl-X(L)) or control vector (MN9D/Neo), we examined whether formation of this complex is primarily responsible for cell death and at which strategic points and how Bcl-X(L) blocks etoposide-induced neuronal death. Etoposide induced death that was dependent on caspase, cycloheximide, and calpain in MN9D/Neo cells. Etoposide also induced death in enucleated MN9D/Neo cells, although this was less severe. The level of topoisomerase II-DNA cleavable complex reached at a maximum of 2 hr after etoposide treatment was identical in MN9D/Neo and MN9D/Bcl-X(L) cells. In MN9D/Neo cells, cytochrome c release into the cytosol and caspase activation occurred as early as 2 hr and 3-6 hr after etoposide treatment, respectively. Etoposide-induced DNA laddering potentially via caspase appeared as early as 12 hr after drug treatment, followed by nuclear swelling in MN9D/Neo cells (>18-20 hr). Subsequently, nuclear condensation started by 24-28 hr and became apparent thereafter. All of these events except for nuclear swelling were substantially blocked in MN9D/Bcl-X(L). At the later stage of cell death (<32-36 hr), a specific cleavage of Bax and fodrin appeared that was completely blocked by calpain inhibitor or by Bcl-X(L). Taken together, our data suggest that Bcl-X(L) prevents etoposide-induced neuronal death by exerting its anticaspase and anticalpain effect on cellular events after the formation of topoisomerase II-DNA cleavable complex that may not be a major contributor to cell death.

Endoscopic factors predisposing to rebleeding following endoscopic hemostasis in bleeding peptic ulcers.

BACKGROUND AND STUDY AIMS: Various clinical and endoscopic factors have been proposed and used as predictors of endoscopic treatment failure in bleeding peptic ulcers. Recently, several endoscopic factors have been considered to be more significant than various clinical factors, except for shock. Detailed knowledge of which endoscopic factors can be classified as predictors of rebleeding following endoscopic hemostasis is needed. This study describes newly defined endoscopic variables and evaluates their usefulness as predictors of endoscopic treatment failure. PATIENTS AND METHODS: Between January 1996 and April 1999, diagnostic and therapeutic endoscopies were carried out in 143 patients with active bleeding peptic ulcers. Nine clinical and eight endoscopic variables were studied. Endoscopic factors were classified by three types of stigmata bleeding, 14 locations, two ulcer sizes, three ulcer bases, three visible vessel colors, two ulcer depths, two margin shapes, and three endoscopic treatment methods (injection, hemoclipping, and combination). RESULTS: 36 patients experienced rebleeding (25.2 %), 11 patients needed operations (7.7 %) and five deaths occurred (3.5 %). In univariate analysis, rebleeding was significantly related to: i) presence of spurting activity (odds ratio [OR] = 4.91, P = 0.006), ii) ulcer size larger than 2 cm (OR = 2.78, P = 0.017); and iii) location in stomach (OR = 2.81, P = 0.026). Clinical variables including age, shock, and initial hemoglobin levels were not significantly related to rebleeding. In multiple logistic regression using selected significant variables, presence of spurting activity remained a significant independent predictor of rebleeding (adjusted OR = 6.48, P = 0.003). CONCLUSION: Our data support the hypothesis that endoscopic factors are more important than clinical ones when predicting rebleeding of peptic ulcers. Based on statistical analysis of risk factors, the ulcers most likely to rebleed after endoscopic therapy are those which are located in the stomach, are greater than 2 cm in diameter and exhibit oozing or spurting of blood.

Cell type-dependent regulation of human DNA topoisomerase III alpha gene expression by upstream stimulatory factor 2.

Here, we report that an E-box element located within the human topoisomerase III alpha (hTOP3 alpha) gene promoter acts as a cell type-specific enhancer. The upstream stimulatory factor (USF) was shown to specifically recognize the mutationally sensitive E-box element. When assayed by transient transfection with hTOP3 alpha promoter-dependent reporter genes, USF is transcriptionally active in HeLa cells but lacks transcriptional activity in Saos-2 cells. The hTOP3 alpha mRNA level in Saos-2 cells was reduced to about 30% of the level observed for HeLa cells, suggesting that the inactivity of USF in hTOP3 alpha promoter activity may be the cause of the marked reduction of hTOP3 alpha mRNA levels in Saos-2 cells. Using transient transfection assays in HeLa cells, we demonstrated that ectopically expressed USF2, but not USF1, was capable of activating hTOP3 alpha transcription through the E-box element. However, USF2 did not stimulate hTOP3 alpha promoter activity in Saos-2 cells. This cell type-specific regulation of promoter activity by USF2 may provide a mechanism for the differential expression of hTOP3 alpha in various tissues and during developmental stages.

A single-stranded telomere binding protein in the nematode Caenorhabditis elegans.

We identified and characterized a protein (STB-1) from the nuclear extract of Caenorhabditis elegans that specifically binds single-stranded telomere DNA sequences, but not the corresponding RNA sequences. STB-1 binding activity is specific to the nematode telomere, but not to the human or plant telomere. STB-1 requires the core nucleotides of GCTTAGG and three spacer nucleotides in front of them for binding. While any single nucleotide change in the core sequence abolishes binding, the spacer nucleotides tolerate substitution. STB-1 was determined to be a basic protein of 45 kDa by Southwestern analyses. STB-1 forms a stable complex with DNA once bound to the telomere.

Sequence-specific binding property of Arabidopsis thaliana telomeric DNA binding protein 1 (AtTBP1).

We have identified an Arabidopsis thaliana cDNA, designated as AtTBP1, encoding a protein with a predicted size of 70.6 kDa that specifically binds to the plant telomeric repeat sequence TTTAGGG. AtTBP1 is present as a single-copy gene in Arabidopsis genome and is expressed ubiquitously in various organs. AtTBP1 has a single Myb telomeric DNA binding domain at the C-terminus and an extensive homology with other known telomere-binding proteins. The isolated C-terminus of AtTBP1 is capable of sequence-specific DNA binding to plant duplex telomeric DNA. These results suggest that AtTBP1 may play important roles in plant telomere function in vivo.

Regulation of mouse DNA topoisomerase IIIalpha gene expression by YY1 and USF transcription factors.

To investigate the mechanisms responsible for the regulation of DNA topoisomerase IIIalpha (TOP3alpha) gene expression, the promoter region of the mouse gene has been cloned and analyzed. The promoter region is moderately high in GC content and lacks a canonical TATA box, typical for promoters of a number of housekeeping genes. Transient expression of a luciferase reporter gene under the control of serially deleted 5'-flanking sequences demonstrated that the 34-bp region from -137 to -170 upstream of the transcription initiation site contains a positive regulatory element(s) for the efficient expression of mouse TOP3alpha gene. Combined analyses by gel mobility shift and supershift assays revealed that both YY1 and USF transcription factors were capable of binding to the 34-bp region. When YY1 and USF-binding elements were selectively mutated, the luciferase activity of the resulted constructs was greatly reduced, indicating that both YY1 and USF function as transcriptional activators. Interestingly, YY1 and USF-binding elements are conserved in both human and mouse TOP3alpha promoters. This suggests that mammalian TOP3alpha genes may possess a common mechanism of transcription regulation through these elements.

In vitro function of S rnases in Lycopersicon peruvianum.

S RNases are products of the S locus that are expressed in the stylar tissue of Lycopersicon peruvianum with the gametophytic self-incompatibility (SI) system. Two S RNases (S12 and Sa) with RNase activity from the S12Sa genotype of L. peruvianum were purified using gel filtration and cation-exchange chromatography. The molecular masses of the two RNases, S12 and Sa, were 21 and 23.1 kDa, respectively. The specific activities of S12 and Sa for torula yeast rRNA as a substrate were 8,500 and 6,000 units/ml, respectively. Of various reagents tested for RNase activities, ZnSO4 and CuSO4 were found to remarkably reduce its activity. The growth of S12Sa pollen was inhibited when it was cultured in a pollen germination medium that contained the purified S12 RNase. The result suggested that the S RNase was either a probable inhibitor of pollen growth or controlled pollen growth. Additionally, 512Sa pollens germinated well in vitro in a germination medium that contained S12 RNase in the presence of ZnSO4 and CuSO4. Our finding suggests that the treatment of S RNase with its inhibitor destroys the SI ability on an in vitro self-pollen growth test.

What is the best method to diagnose Helicobacter infection in bleeding peptic ulcers?: a prospective trial.

BACKGROUND: It has been debated which diagnostic test should be preferred for the diagnosis of Helicobacter pylori (HP) in patients with peptic ulcer diseases. Several limitations are reported in bleeding peptic ulcers because of intragastric blood and possibility of changed numbers of organisms by medication. This study was designed to find out the best method for diagnosis of HP infection, in aspect of deciding the times of detection and the specific tests in bleeding peptic ulcers. METHODS: We prospectively examined histology, rapid urease test (CLO test), urea breath test (13C-UBT) and serology in HP diagnostics in 32 patients with bleeding peptic ulcers to detect HP infection. Each test was performed two times (four methods at first 24 hours and former three methods at 7th day after initial therapeutic endoscopy). We evaluated the sensitivity of each test, compared the two-times results and evaluated the effect of these tests to an outcome of endoscopic hemostasis. RESULTS: Diagnostic sensitivities of histology, CLO test, 13C-UBT and serology are 75%, 67.8%, 100% and 100% at first endoscopy, and 71.4%, 78.5%, 89.3% at 7th day endoscopy, respectively. Histologic study and CLO test had diagnostic limitation at emergent first endoscopy contrary to UBT (p < 0.01). Histologic study, CLO test and UBT have limitations at 7th day endoscopy. Only 3 patients (9.4%) rebled with subsequent complete endoscopic hemostasis and all diagnostic tests at initial endoscopy did not influence the outcome of hemostasis. CONCLUSION: First day histologic and CLO tests are inadequate methods in detecting HP infection in patients with bleeding peptic ulcers. 7-day histologic, CLO test and UBT have a low sensitivity. First-day UBT can be a standard test to diagnose HP infection in patients with bleeding peptic ulcers.

Bleeding Dieulafoy's lesions and the choice of endoscopic method: comparing the hemostatic efficacy of mechanical and injection methods.

BACKGROUND: Dieulafoy's lesion has unique endoscopic and histopathologic characteristics. This is a clinical trial of endoscopic therapy in 24 patients with Dieulafoy's lesions. METHODS: Patients were divided into 2 groups according to initial endoscopic treatment method. Data were analyzed with respect to clinical and endoscopic characteristics as well as outcomes. The 24 patients were evenly divided into mechanical (9 hemoclipping, 3 band ligation) and injection groups (12). RESULTS: The average number of therapeutic endoscopic sessions needed to achieve permanent hemostasis for the mechanical and injection groups were 1.17 and 1.67, respectively. Initial hemostasis was achieved in 91.7% of patients undergoing mechanical therapy and 75% of those undergoing injection therapy, with none in the former group needing subsequent surgery in comparison to 17% of the latter group. The rate of recurrent bleeding in the mechanical therapy group was significantly lower in comparison to the injection therapy group (8.3% versus 33.3%, p < 0. 05). CONCLUSIONS: Higher efficacy in terms of initial hemostasis and less recurrent bleeding was achieved by mechanical hemostatic therapy with hemoclip and band ligation compared with injection therapy. Endoscopic mechanical therapy is recommended as effective for bleeding Dieulafoy's lesions.

Analysis of OPT8511 RAPD fragments closely linked with cold sensitivity at seedling stage in rice (Oryza sativa L.).

OPT8(511) was confirmed to be strongly associated with cold sensitivity of rice by random amplified polymorphic DNA (RAPD) analysis for the cold tolerance with 94 F2 population crossed with 'Dular' (cold sensitive cultivar) and 'Toyohatamochi' (cold resistant cultivar). A DNA marker from the RAPD fragment, OPT8(511), has been cloned with genomic DNA from rice cultivar ('Dular') and the nucleotide sequence has been determined. The nucleotide sequence revealed that the putative open reading frame was 511 base pairs and contained 169 amino acid residues. It is 79% and 57% identical to the rice cDNA (C26347) in DataBank at the nucleotide and amino acid sequence levels, respectively. The clone OPT8(511) specifically amplified a 511 bp band from the DNA of cold sensitive cultivars. Use of this marker could facilitate early selection of character associated with cold tolerance in rice.

Characterization and developmental expression of single-stranded telomeric DNA-binding proteins from mung bean (Vigna radiata).

We have identified and characterized protein factors from mung bean (Vigna radiata) nuclear extracts that specifically bind the single-stranded G-rich telomeric DNA repeats. Nuclear extracts were prepared from three different types of plant tissue, radicle, hypocotyl, and root, in order to examine changes in the expression patterns of telomere-binding proteins during the development of mung bean. At least three types of specific complexes (A, B, and C) were detected by gel retardation assays with synthetic telomere and nuclear extract from radicle tissue, whereas the two major faster-migrating complexes (A and B) were formed with nuclear extracts from hypocotyl and root tissues. Gel retardation assays also revealed differences in relative amount of each complex forming activity in radicle, hypocotyl, and root nuclear extracts. These data suggest that the expression of telomere-binding proteins is developmentally regulated in plants, and that the factor involved in the formation of complex C may be required during the early stages of development. The binding factors have properties of proteins and are hence designated as mung bean G-rich telomere-binding proteins (MGBP). MGBPs bind DNA substrates with three or more single-stranded TTTAGGG repeats, while none of them show binding affinity to either double-stranded or single-stranded C-rich telomeric DNA. These proteins have a lower affinity to human telomeric sequences than to plant telomeric sequences and do not exhibit a significant binding activity to Tetrahymena telomeric sequence or mutated plant telomeric sequences, indicating that their binding activities are specific to plant telomere. Furthermore, RNase treatment of the nuclear extracts did not affect the complex formation activities. This result indicates that the single-stranded telomere-binding activities may be attributed to a simple protein but not a ribonucleoprotein. The ability of MGBPs to bind specifically the single-stranded TTTAGGG repeats may suggest their in vivo functions in the chromosome ends of plants.

Sequence-specific DNA recognition by the Myb-like domain of plant telomeric protein RTBP1.

We have identified a rice gene encoding a DNA-binding protein that specifically recognizes the telomeric repeat sequence TTTAGGG found in plants. This gene, which we refer to as RTBP1 (rice telomere-binding protein 1), encodes a polypeptide with a predicted molecular mass of 70 kDa. RTBP1 is ubiquitously expressed in various organs and binds DNA with two or more duplex TTTAGGG repeats. The predicted protein sequence includes a single domain at the C terminus with extensive homology to Myb-like DNA binding motif. The Myb-like domain of RTBP1 is very closely related to that of other telomere-binding proteins, including TRF1, TRF2, Taz1p, and Tbf1p, indicating that DNA-binding domains of telomere-binding proteins are well conserved among evolutionarily distant species. To obtain precise information on the sequence of the DNA binding site recognized by RTBP1, we analyzed the sequence-specific binding properties of the isolated Myb-like domain of RTBP1. The isolated Myb-like domain was capable of sequence-specific DNA binding as a homodimer. Gel retardation analysis with a series of mutated telomere probes revealed that the internal GGGTTT sequence in the two-telomere repeats is critical for binding of Myb-like domain of RTBP1, which is consistent with the model of the TRF1.DNA complex showing that base-specific contacts are made within the sequence GGGTTA. To the best of our knowledge, RTBP1 is the first cloned gene in which the product is able to bind double-stranded telomeric DNA in plants. Because the Myb-like domain appears to be a significant motif for a large class of proteins that bind the duplex telomeric DNA, RTBP1 may play important roles in plant telomere function in vivo.

The p53 tumor suppressor stimulates the catalytic activity of human topoisomerase IIalpha by enhancing the rate of ATP hydrolysis.

DNA topoisomerase II is an essential nuclear enzyme for proliferation of eukaryotic cells and plays important roles in many aspects of DNA processes. In this report, we have demonstrated that the catalytic activity of topoisomerase IIalpha, as measured by decatenation of kinetoplast DNA and by relaxation of negatively supercoiled DNA, was stimulated approximately 2-3-fold by the tumor suppressor p53 protein. In order to determine the mechanism by which p53 activates the enzyme, the effects of p53 on the topoisomerase IIalpha-mediated DNA cleavage/religation equilibrium were assessed using the prototypical topoisomerase II poison, etoposide. p53 had no effect on the ability of the enzyme to make double-stranded DNA break and religate linear DNA, indicating that the stimulation of the enzyme catalytic activity by p53 was not due to alteration in the formation of covalent cleavable complexes formed between topoisomerase IIalpha and DNA. The effects of p53 on the catalytic inhibition of topoisomerase IIalpha were examined using a specific catalytic inhibitor, ICRF-193, which blocks the ATP hydrolysis step of the enzyme catalytic cycle. Clearly manifested in decatenation and relaxation assays, p53 reduced the catalytic inhibition of topoisomerase IIalpha by ICRF-193. ATP hydrolysis assays revealed that the ATPase activity of topoisomerase IIalpha was specifically enhanced by p53. Immunoprecipitation experiments revealed that p53 physically interacts with topoisomerase IIalpha to form molecular complexes without a double-stranded DNA intermediary in vitro. To investigate whether p53 stimulates the catalytic activity of topoisomerase II in vivo, we expressed wild-type and mutant p53 in Saos-2 osteosarcoma cells lacking functional p53. Wild-type, but not mutant, p53 stimulated topoisomerase II activity in nuclear extract from these transfected cells. Our data propose a new role for p53 to modulate the catalytic activity of topoisomerase IIalpha. Taken together, we suggest that the p53-mediated response of the cell cycle to DNA damage may involve activation of topoisomerase IIalpha.

The clinical significance of upper gastrointestinal endoscopy in gastrointestinal vasculitis related to scrub typhus.

BACKGROUND AND STUDY AIMS: Scrub typhus is an acute febrile illness caused by Rickettsia tsutsugamushi-induced vasculitis, which is common in Asia and the Pacific islands and is sometimes encountered in Western countries because of increased travel and economic changes spurred by world globalization. Skin rash and eschar are typical physical findings on the trunk and extremities, but endoscopic mucosal changes have not been described in the gastrointestinal tract until now. We aimed to describe different endoscopic characteristics of the gastrointestinal manifestation of scrub typhus, to ascertain the necessity for endoscopy, and to determine correlations between the degrees of endoscopic lesion and clinical severity, including cutaneous manifestation. PATIENTS AND METHODS: Between January 1993 and October 1998, out of 256 scrub typhus patients, we applied esophagogastroduodenoscopy to 58 patients who complained of gastrointestinal symptoms but had no past history of these symptoms. We categorized clinical severity into four grades according to the degree of six clinical indicators of systemic complications, and endoscopic findings were graded from I to IV (I, normal, nonspecific hyperemia; II, distinct hyperemia, petechiae, purpura; II, superficial hemorrhage, erosion; IV, ulcer, active bleeding). RESULTS: Endoscopic findings of scrub typhus were characterized by petechiae, superficial hemorrhage, erosion, ulcers, and vascular bleeding (grade I, 14 patients; grade II, 11 patients; grade III, 16 patients; grade IV, 17 patients). In 83.3% of patients there was multiple occurrence of lesions without any predilection sites. Clinical severity was graded (grade I, 7 patients; grade II, 23 patients; grade III, 22 patients; grade IV, 6 patients). There was a correlation between clinical severity and endoscopic findings (P < 0.01). The grade of lesion was high in patients with cutaneous lesions (r(s) 0.359, P < 0.01). In two cases of gastric vascular bleeding, complete hemostasis was achieved by endoscopic hemoclipping. CONCLUSIONS: The major endoscopic features that can develop in scrub typhus are superficial mucosal hemorrhage, multiple erosions and ulcers without any predilection sites, and unusual vascular bleeding. The endoscopic features are related to cutaneous lesions and severity of the disease. Endoscopy is useful for diagnosis and management of gastrointestinal vasculitis related to scrub typhus.

Comparison of the hemostatic efficacy of the endoscopic hemoclip method with hypertonic saline-epinephrine injection and a combination of the two for the management of bleeding peptic ulcers.

BACKGROUND: The endoscopic hemoclip method is a safe and effective hemostatic method for managing bleeding peptic ulcers. We compared the hemostatic efficacy of the endoscopic hemoclip method with that of hypertonic saline-epinephrine (HSE) injection and a combined method in the management of bleeding peptic ulcers. METHODS: From July 1994 to July 1997, we conducted a randomized clinical trial of endoscopic hemostasis involving 124 patients with actively bleeding or visible vessels at endoscopic inspection. RESULTS: Patients were randomly assigned to hemoclip (41 patients), HSE (41 patients), and combined treatment groups (42 patients). Initial hemostasis was achieved in 97.6%, 95.1%, and 97.6% of cases, respectively. Recurrent bleeding developed in 2.4%, 14.6%, and 9.5% of cases. Emergency operations were performed in 4.9%, 14.6%, and 2.3% of cases. The hemostasis rate was 71.4%, 50%, and 66.7% for spurting hemorrhage in each group. Permanent hemostasis was achieved in 95.1%, 85.4%, and 95.2% of cases. Three patients had complications, all in the HSE group. CONCLUSIONS: The hemoclip method is an effective hemostatic procedure and is safer than HSE injection. The combined method does not provide substantial advantage over use of the hemoclip method alone in the hemostatic management of bleeding peptic ulcers.

Induction of topoisomerase II-mediated DNA cleavage by a protoberberine alkaloid, berberrubine.

Topoisomerase II is the cytotoxic target for a number of clinically relevant antitumor drugs. Berberrubine, a protoberberine alkaloid which exhibits antitumor activity in animal models, has been identified as a specific poison of topoisomerase II in vitro. Topoisomerase II-mediated DNA cleavage assays showed that berberrubine poisons the enzyme by stabilizing topoisomerase II-DNA cleavable complexes. Subsequent proteinase K treatments revealed that berberrubine-induced DNA cleavage was generated solely by topoisomerase II. Topoisomerase II-mediated DNA religation with elevated temperature revealed a substantial reduction in DNA cleavage induced by berberrubine, to the extent comparable to that of other prototypical topoisomerase II poison, etoposide, suggesting that DNA cleavage involves stabilization of the reversible enzyme-DNA cleavable complex. However, the step at which berberrubine induces cleavable complex may differ from that of etoposide as revealed by the difference in the formation of the intermediate product, nicked DNA. This suggests that berberrubine's primary mode of linear formation may involve trapping nicked molecules, formed at transition from linear to covalently closed circular DNA. Unwinding of the duplex DNA by berberrubine is consistent with an intercalative binding mode for this compound. In addition to the ability to induce the cleavable complex mediated with topoisomerase II, berberrubine at high concentrations was shown to specifically inhibit topoisomerase II catalytic activity. Berberrubine, however, did not inhibit topoisomerase I at concentrations up to 240 microM. Cleavage sites induced by topoisomerase II in the presence of berberrubine and etoposide were mapped in DNA. Berberrubine induces DNA cleavage in a site-specific and concentration-dependent manner. Comparison of the cleavage pattern of berberrubine with that of etoposide revealed that they share many common sites of cleavage. Taken together, these results indicate that berberrubine represents a new class of antitumor agent which exhibits the topoisomerase II poison activity as well as catalytic inhibition activity and may have a potential clinical value in cancer treatment.