Robotic versus laparoscopic distal pancreatectomy for pancreatic adenocarcinoma in obese patients

BACKGROUND

Robotic distal pancreatectomy (RDP) is associated with a lower conversion rate and less blood loss than laparoscopic distal pancreatectomy (LDP). LDP has similar oncological outcomes as open surgery in PDAC. The aim of this study was to compare perioperative and oncological outcomes in obese patients with RDP versus LDP for PDAC.

MATERIALS AND METHODS

Retrospectively, all obese patients who underwent RDP or LDP for PDAC between 2012 and 2022 at 12 international expert centres were included.

RESULTS

out of 372, 81 patients were included. All baseline features were comparable between the two groups. RDP was associated with decreased blood loss (495mlLDP vs. 188mlRDP; p = 0.003), lower conversion rate (13.5%RDP vs. 36.4%LDP; p = 0.019) and lower rate of Clavien-Dindo ≥3 complications (13.5%RDP vs. 36.4%LDP; p = 0.019). Overall and disease-free survival were comparable.

CONCLUSIONS

In obese patients with left-sided PDAC, the robotic approach was associated with improved intraoperative outcomes and fewer severe complications.

Robotic versus laparoscopic distal pancreatectomy in obese patients

BACKGROUND

Although robotic distal pancreatectomy (RDP) has a lower conversion rate to open surgery and causes less blood loss than laparoscopic distal pancreatectomy (LDP), clear evidence on the impact of the surgical approach on morbidity is lacking. Prior studies have shown a higher rate of complications among obese patients undergoing pancreatectomy. The primary aim of this study is to compare short-term outcomes of RDP vs. LDP in patients with a BMI ≥ 30.

METHODS

In this multicenter study, all obese patients who underwent RDP or LDP for any indication between 2012 and 2022 at 18 international expert centers were included. The baseline characteristics underwent inverse probability treatment weighting to minimize allocation bias.

RESULTS

Of 446 patients, 219 (50.2%) patients underwent RDP. The median age was 60 years, the median BMI was 33 (31-36), and the preoperative diagnosis was ductal adenocarcinoma in 21% of cases. The conversion rate was 19.9%, the overall complication rate was 57.8%, and the 90-day mortality rate was 0.7% (3 patients). RDP was associated with a lower complication rate (OR 0.68, 95% CI 0.52-0.89; p = 0.005), less blood loss (150 vs. 200 ml; p < 0.001), fewer blood transfusion requirements (OR 0.28, 95% CI 0.15-0.50; p < 0.001) and a lower Comprehensive Complications Index (8.7 vs. 8.9, p < 0.001) than LPD. RPD had a lower conversion rate (OR 0.27, 95% CI 0.19-0.39; p < 0.001) and achieved better spleen preservation rate (OR 1.96, 95% CI 1.13-3.39; p = 0.016) than LPD.

CONCLUSIONS

In obese patients, RDP is associated with a lower conversion rate, fewer complications and better short-term outcomes than LPD.

circEPS15 Overexpression in Hepatocellular Carcinoma Modulates Tumor Invasion and Migration

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related deaths worldwide. Recent evidence has shown that circular RNAs (circRNAs) play important roles in tissue development, gene transcription, signal regulation and tumorigenesis. However, whether circRNAs are involved in HCC progression and encode functional proteins remains largely unknown. In the present study, we aimed to explore the function and molecular mechanism of circRNAs in HCC. First, many circRNAs were found to be differentially expressed in HCC samples and paired adjacent normal liver tissues. The validation of dysregulated circRNAs by qRT-PCR revealed that circEPS15 expression was downregulated in HCC tissues, and the survival curves showed that low circEPS15 levels were associated with poor overall survival in HCC patients. Then, the overexpression of circEPS15 suppressed tumor cell invasion and migration by inhibiting the TJP1/CDH2/VIM signaling pathway and retarded cell cycle progression, which was confirmed by the Transwell culture system, wound healing assays, flow cytometry and western blot assays. After that, the spanning junction open reading frame in circEPS15 driven by IRES was shown to encode a novel protein, which was verified by western blotting with full-length, mutated, and truncated sequences of circEPS15 with a FLAG tag. Moreover, ceRNA analysis and qRT-PCR results suggest a possible circRNA (circEPS15)-miRNA-mRNA network in HCC. Collectively, our study reveals that endogenous circEPS15 plays a novel role in repressing HCC through the ceRNA network and encodes a functional protein.

O-242 Metabolic coupling and spermatogenesis

Abstract text

The microenvironment of spermatogenesis mainly consists of Sertoli cells, Leydig cells, and peritubular cells. The traditional theory considers that spermatogenesis is regulated by hypothalamus-pituitary gland- gonadal axis. In the hypothalamus-pituitary gland- gonadal axis, the microenvironmental cells are mainly regulated by the hormones, which are secreted by the hypothalamus or/and pituitary gland. Meanwhile, Sertoli cells and Leydig cells also secrete related factors to feedback the functions of the hypothalamus and pituitary gland. With the development of research, it has found that metabolic disorders are closely related to the spermatogenesis. Some components involving in lipid metabolism pathways, including saturated fatty acids, cholesterol, and triglycerides, etc. affect the functions of Sertoli and Leydig cells through metabolic coupling pathway. The disorder function of Sertoli and Leydig impairs the microenvironment of spermatogenesis, which finally leads to spermatogenic failure. Current studies have found that the imbalance of lipid metabolism can affect the intestinal flora, which induces the changes of related metabolites, and finally leads to the occurrence of male infertility. Based on the current research, we regulated the lipid metabolism by Omega-3 and metformin in clinic, the activity of spermatogenesis can be remolded.

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Laparoscopic middle segment splenectomy for central splenic hemangioma: A case report

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Laparoscopic middle segment splenectomy for central splenic hemangioma is a new technique.

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Laparoscopic middle segment splenectomy for central splenic hemangioma is very useful for some selected patients.

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In patients with splenic artery bifurcation point far from the splenic hilus parenchyma and in those cases where the blood supply of the upper and lower pole splenic segments can be ensured, when the splenic tumor is resected, performing LPS and retaining some upper and lower splenic segments is possible to ensure sufficient residual spleen.

Introduction

Laparoscopic surgery plays an important role in the treatment of splenichematologic pathologies and solid lesions. Splenic hemangioma is the most common benign tumor of the spleen. In patients with benign splenic space-occupying lesions, laparoscopic partial splenectomy (LPS) has a lower incidence of postoperative complications than laparoscopic total splenectomy (LTS). Currently, no uniform standard for the indication of LPS is available.

Presentation of case

Herein, we report a case of hemangioma in a 23-year-old woman treated with LPS. After multidisciplinary evaluation, laparoscopic splenectomy was indicated in this case; upon evaluating the age of the patient and the affected spleen portion, a middle segment splenectomy was proposed, with preservation of the upper and lower pole. The intraoperative frozen section of the specimen was negative for malignancies.

Discussion

Surgery remains the first choice in the treatment of solid lesions of the spleen. In this case, the volume of splenic hemangioma was large and accumulated in the upper and lower segments of the spleen. After the middle branch of splenic artery was cut off, the tumor was completely contained in the middle of upper and lower ischemic lines splenic segment. We think that the central type of benign splenic space occupying is not an absolute contraindication of LPS. For the patients whose splenic artery bifurcation point is far from the splenic hilus parenchyma and in those cases where the blood supply of the upper and lower poles of the splenic segments can be ensured, when the splenic tumor is resected, performing LPS and retaining some parts of the upper and lower splenic segments is possible to ensure sufficient residual spleen.

Down-regulated of PCDH10 predicts poor prognosis in hepatocellular carcinoma patients

Protocadherin10 (PCDH10), a member of the nonclustered protocadherin family, functions as a tumor suppressor in many cancers. The aim of this study was to evaluate the expression level and prognostic value of PCDH10 in hepatocellular carcinoma (HCC) patients.Quantitative real-time polymerase chain reaction was used to analyze the expression level of PCDH10 in HCC tissues and adjacent nontumor tissues. The association of PCDH10 expression with clinicopathological features of patients was evaluated by chi-squared test. Overall survival was estimated using the Kaplan-Meier method. Besides, the patient prognosis was also evaluated by Cox regression analysis.PCDH10 expression was significantly lower in HCC tissues than that in adjacent nontumor tissues (P = .000). Kaplan-Meier curves showed that patients with lower PCDH10 expression had a worse overall survival. Moreover, PCDH10 expression level was associated tumor size (P = .005), tumor node metastasis stage (P = .002), smoking status (P = .000), and drinking status (P = .005). Multivariate analysis showed that the expression of PCDH10 (P = .000; hazard ratio = 4.784; 95% confidence interval: 2.550-8.977) was an independently associated with poor overall survival rates, as well as smoking status and drinking status.Our findings indicated that the decreased expression of PCDH10 was closely associated with poor prognosis of HCC patients. It might be considered as a valuable biomarker for HCC.

Diet-Induced Hyperhomocysteinaemia Increases Intestinal Inflammation in an Animal Model of Colitis

BACKGROUND

Hyperhomocysteinaemia [HHcy] is a common phenomenon observed in patients with inflammatory bowel disease [IBD]. Homocysteine is a pro-inflammatory molecule and has been identified as a risk factor for cardiovascular and cerebral diseases. Whether HHcy contributes to the chronic inflammation of the colon in IBD has rarely been explored. The aim of this study was to investigate the effect of HHcy on dextran sulphate sodium [DSS]-induced colitis.

METHODS

Wistar rats were randomly divided into eight groups: [1] Control; [2] HHcy; [3] p38 inhibitor; [4] DSS; [5] HHcy + DSS; [6] HHcy + DSS+p38 inhibitor; [7] HHcy + DSS [21 days]; and [8] HHcy + DSS + folate [21 days]. Colitis was induced by 5% DSS. HHcy was induced by the normal rodent diet containing 1.7% methionine. The mRNA expression of interleukin 17 [IL-17] was detected by qRT-PCR. The protein expressions of IL-17, retinoid-related orphan nuclear receptor-γt [RORγt], p38 MAPK, phosphorylated-p38 MAPK, cytosolic phospolipaseA2 [cPLA2], phosphorylated-cPLA2, and cyclooxygenase 2 [COX2] were detected by immunoblot analysis.

RESULTS

The rats of the HHcy + DSS group had significantly higher myeloperoxidase [MPO] activity, DAI score, and histological score. HHcy significantly increased the plasma concentration, the colonic mRNA, and the protein levels of IL-17. HHcy also activated p38 MAPK and cPLA2, and increased the protein levels of COX2 and RORγt as well as the plasma level of prostaglandin E2 [PGE2]. Folate supplementation down-regulated homocysteine-induced IL-17 and RORγt expressions.

CONCLUSIONS

HHcy aggravated DSS-induced colitis by stimulating IL-17 expression via the p38/cPLA2/COX2/PGE2 signalling pathway. The folate supplementation may represent a novel approach to treating the chronic intestinal inflammation of IBD exacerbated by HHcy.

Activation of the interleukin-34 inflammatory pathway in response to influenza A virus infection

Interleukin 34 (IL-34) is a newly recognized cytokine that functions similarly to macrophage colony-stimulating factor. This study investigated the mechanism by which IL-34 is produced in response to exogenous pathogen infections in humans. The results showed that the IL-34 levels were higher in the serum and peripheral blood mononuclear cells (PBMCs) from 155 influenza A virus (IAV)-infected patients than in those from 145 healthy individuals. The expression level of IL-34 in IAV-infected PBMCs was blocked by IL-22-specific siRNA. This result indicated that IL-34 was induced by IL-22 in the inflammatory cascade. The mRNA and protein expression levels of IL-22 activated by IAV infection were significantly inhibited by IL-34 overexpression but induced by IL-34-specific siRNA. Thus, a feedback system most likely exists between IL-34 and IL-22. The IL-22 expression in T helper type 17 (Th17) cells of PBMCs was higher than IL-34 expression in Th17 cells of PBMCs, and there was IL-34 expression in IL-22+ Th17 cells. This result showed that the production of IL-22 and IL-34 is both from the same and different subset of cells, which indicated that the regulatory mechanism of IL-22/IL-34 is through the autocrine or paracrine systems. In conclusion, IL-34 is induced by IL-22 in the inflammatory cascade in response to IAV infection. Therefore, IL-34 is a promising target for the screening of anti-inflammatory medicines.

The plasma S-adenosylmethionine level is associated with the severity of hepatitis B-related liver disease

Alterations in methionine metabolism that involve changes in the plasma S-adenosylmethionine (SAMe) level occur in chronic liver diseases. However, no evidence is available on whether circulating SAMe is involved in the development of liver cirrhosis and liver cancer. Cross-sectional data on clinical characteristics and plasma SAMe were collected for 130 cases of chronic hepatitis B (CHB) and HCC as well as for normal volunteers. Univariate and multivariate linear regression and receiver operating characteristic curves were introduced to determine their correlations. Serum ALB and PT levels were independent clinical factors that were correlated with the plasma SAMe levels in CHB and HCC patients. A higher SAMe concentration was observed in the HCC than in the normal and CHB. By exploring the association of the Child-Pugh score with the plasma SAMe level, we found a higher SAMe level at advanced Stage C than at stage A in CHB and HCC patients. We further assessed the diagnostic performance of SAMe with respect to the stages of liver fibrosis and Child-Pugh stage. The AUROC of SAMe for the prediction of cirrhosis was 0.721, and the sensitivity and specificity was 0.707 and 0.769, respectively. The AUROC of plasma SAMe to predict Child-Pugh stage C was 0.706 in patients with CHB and 0.825 in HCC patients. The sensitivity was 0.467 and 0.800, respectively; the specificity was 0.904 and 0.781, respectively. The plasma SAMe level was positively correlated with the severity of liver disease and might be a potential noninvasive biomarker.

Gene expression of the p16(INK4a)-Rb and p19(Arf)-p53-p21(Cip/Waf1) signaling pathways in the regulation of hematopoietic stem cell aging by ginsenoside Rg1

The elucidation of the molecular mechanisms underlying the effects of traditional Chinese medicines in clinical practice is a key step toward their worldwide application, and this topic is currently a subject of intense research interest. Rg1, a component of ginsenoside, has recently been shown to perform several pharmacological functions; however, the underlying mechanisms of these effects remain unclear. In the present study, we investigated whether Rg1 has an anti-senescence effect on hematopoietic stem cells (HSCs) and the possible molecular mechanisms driving any effects. The results showed that Rg1 could effectively delay tert-butyl hydroperoxide (t-BHP)-induced senescence and inhibit gene expression in the p16(INK4a)-Rb and p19(Arf)-p53-p21(Cip/Waf1) signaling pathways in HSCs. Our study suggested that these two signaling pathways might be potential targets for elucidating the molecular mechanisms of the Rg1 anti-senescence effect.

Glucocorticoid-induced S-adenosylmethionine enhances the interferon signaling pathway by restoring STAT1 protein methylation in hepatitis B virus-infected cells

Patients with chronic hepatitis B usually exhibit a low response to treatment with interferon α (IFN-α). An alternative approach to increase the response rate of IFN-α might be to immunologically stimulate the host with glucocorticoids (GCs) before treatment with IFN-α, but the underlying mechanism remains unclear. We hypothesized that the GCs enhance IFN signaling by inducing S-adenosylmethionine (AdoMet) when hepatitis B virus (HBV) replication was effectively suppressed by IFN-α. Here, we investigated the effect of GCs and IFN-α on AdoMet production and methionine adenosyltransferase 1A (MAT1A) expression in vitro. Furthermore, we determined whether post-transcriptional regulation is involved in HBV-repressed MAT1A expression and AdoMet production induced by dexamethasone (Dex). We found that AdoMet homeostasis was disrupted by Dex and that Dex directly regulated MAT1A expression by enhancing the binding of the glucocorticoid receptor (GR) to the glucocorticoid-response element (GRE) of the MAT1A promoter. HBV reduced AdoMet production by increasing methylation at GRE sites within the MAT1A promoter. The X protein of hepatitis B virus led to hypermethylation in the MAT1A promoter by recruiting DNA methyltransferase 1, and it inhibited GR binding to the GRE in the MAT1A promoter. Dex could increase an antiviral effect by inducing AdoMet production via a positive feedback loop when HBV is effectively suppressed by IFN-α, and the mechanism that involves Dex-induced AdoMet could increase STAT1 methylation rather than STAT1 phosphorylation. These findings provide a possible mechanism by which GC-induced AdoMet enhances the antiviral activity of IFN-α by restoring STAT1 methylation in HBV-infected cells.

Hepatitis B virus inhibits the expression of CD82 through hypermethylation of its promoter in hepatoma cells

The tumor suppressor gene CD82, also known as KAI1, may act as a general suppressor of metastasis in numerous types of cancer. It is hypothesized that downregulation of CD82 gene expression may be an important factor in the induction of hepatocellular carcinoma (HCC), however the mechanism for this requires further study. In the present study, the relative mRNA and protein expression levels of the CD82 gene were determined in HCC and adjacent non‑tumor tissues. The association between the CD82 gene and the hepatitis B virus (HBV) was also investigated, by quantitative polymerase chain reaction, western blotting, luciferase reporter assays and mass spectrometry with matrix‑assisted laser desorption/ionization time‑of‑flight mass array. CD82 expression was shown to be suppressed in response to HCC promoter methylation. Relative CD82 mRNA and protein expression levels were downregulated in HCC tissues (P<0.05). HBx protein inhibited CD82 promoter activity and subsequently the mRNA and protein expression levels. Furthermore, it was demonstrated that HBV could inhibit the expression of CD82 at the transcriptional level, and repress the activity of the CD82 promoter through hypermethylation. In addition, the methyl enzyme inhibitor 5‑aza‑CdR could induce the CD82 promoter activity and the relative expression level of CD82 mRNA, as observed by an increase in luciferase activity driven by the CD82 promoter. The observations of the present study suggest that hypermethylation of the CD82 promoter may be an event leading to the development of HCC. Low expression of CD82 is likely to be involved in tumor progression. HBV may inhibit the expression of CD82 through hypermethylation of the promoter in hepatoma cells.

CCL25/CCR9 interactions regulate the function of iNKT cells in oxazolone-induced colitis in mice

BACKGROUND

Natural killer T (NKT) cells share phenotypic and functional properties with both conventional natural killer cells and T cells. These cells might have an important role in the pathogenesis of ulcerative colitis (UC). The interaction of chemokine ligand 25 (CCL25) with chemokine receptor 9 (CCR9) is involved in gut-specific migration of leukocytes and induces regulatory T cells (Tregs) to migrate to the intestine in chronic ileitis.

METHODOLOGY/FINDINGS

In UC patients, NKT receptor CD161, CCL25, and CCR9 expression levels were evaluated by qRT-PCR. A murine model of oxazolone-induced colitis was induced in BALB/c mice. The mRNA levels of NK1.1, CCL25 and CCR9, and pro-inflammatory cytokines in mice were evaluated. The CCR9 expression on Type I or invariant NKT (iNKT) cells, and the iNKT cells chemotaxis are observed according to flow cytometry. NKT receptor CD161, CCL25 and CCR9 expression levels were significantly increased in UC patients. And, the mRNA expression levels of NK1.1, CCL25 and CCR9 were increased in oxazolone-induced colitis in mice. The production of pro-inflammatory cytokines was significantly increased, especially interleukin 4 (IL-4), IL-10 and IL-13. We observed significantly increased CCR9 expression on iNKT cells. Furthermore, we found an increased iNKT population and enhanced chemotaxis during oxazolone-induced colitis.

CONCLUSIONS/SIGNIFICANCE

Our study suggests that CCL25/CCR9 interactions may promote the induction and function of iNKT cells during oxazolone-induced colitis. These findings may have important implications for UC treatment and suggest a role for CCR9 inhibitors.

Effects of sinomenine on the expression of microRNA-155 in 2,4,6-trinitrobenzenesulfonic acid-induced colitis in mice

Background

Sinomenine, a pure alkaloid isolated in Chinese medicine from the root of Sinomenium acutum, has been demonstrated to have anti-inflammatory and immunosuppressive effects. MicroRNAs (miRNAs) are gradually being recognized as critical mediators of disease pathogenesis via coordinated regulation of molecular effector pathways.

Methodology/Findings

After colitis was induced in mice by instillation of 5% (w/v) 2,4,6-trinitrobenzenesulfonic acid (TNBS), sinomenine at a dose of 100 or 200 mg/kg was orally administered once daily for 7 days. We evaluated body weight, survival rate, diarrhea score, histological score and myeloperoxidase (MPO) activity. The mRNA and protein expression levels of miR-155, c-Maf, TNF-α and IFN-γ were determined by quantitative RT-PCR and immunohistochemistry, respectively. Sinomenine (100 or 200 mg/kg)-treated mice with TNBS-induced colitis were significantly improved in terms of body weight, survival rate, diarrhea score, histological score and MPO activity compared with untreated mice. Both dosages of sinomenine significantly decreased the mRNA and protein expression levels of c-Maf, TNF-α and IFN-γ, which elevated in TNBS-induced colitis. Furthermore, sinomenine at a dose of 200 mg/kg significantly decreased the level of miR-155 expression by 71% (p = 0.025) compared with untreated TNBS-induced colitis in mice.

Conclusions/Significance

Our study evaluated the effects and potential mechanisms of sinomenine in the anti-inflammatory response via miRNA-155 in mice with TNBS-induced colitis. Our findings suggest that sinomenine has anti-inflammatory effects on TNBS-induced colitis by down-regulating the levels of miR-155 and several related inflammatory cytokines.

Hypermethylation-repressed methionine adenosyltransferase 1A as a potential biomarker for hepatocellular carcinoma

AIM

Methionine adenosyltransferase 1A (MAT1A) is inactivated in HCC and may be stimulated by an epigenetic change involving promoter hypermethylation in hepatocarcinogenesis. However, the possible clinical impact and prognosis of this inactivation have not been investigated.

METHODS

We studied the methylation status of the CpG sites in the promoter region and the mRNA and protein expression of MAT1A in HCC and corresponding adjacent non-tumor tissues using methylation-specific polymerase chain reaction, reverse transcription polymerase chain reaction and immunohistochemistry techniques.

RESULTS

MAT1A promoter methylation was significantly higher in HCC than that in adjacent non-tumor tissues (P < 0.0001). Bisulfite sequencing showed that the four CpG sites were hypermethylated in HCC while hypomethylation was found in the corresponding adjacent non-tumor tissues. Furthermore, MAT1A methylation was significantly associated with protein expression (P = 0.022). Low expression of MAT1A was correlated with larger tumor size, higher tumor-node-metastasis stage, positive hepatitis B surface antigen status and high α-fetoprotein (AFP) serum levels (P < 0.05). MAT1A promoter methylation was also correlated with high AFP serum level (P < 0.05). In univariate survival analysis, low expression of MAT1A was significantly associated with shortened patient survival (P < 0.001). Furthermore, in multivariate analysis, MAT1A expression was found as an independent prognostic factor (P = 0.016).

CONCLUSION

Our observations suggest that hypermethylation of the MAT1A promoter may be one of the events in the development of HCC. Low expression of MAT1A is likely involved in the progression of the tumor and was found to be an independent factor for poor prognosis of patients with HCC.

Electric-field-induced redistribution of polar nano-regions in a relaxor ferroelectric

Relaxor ferroelectrics, with their strong dependence of polarization on the applied electric field, are of considerable technological importance. On a microscopic scale, however, there exists competition as well as coexistence between short-range and long-range polar order. The conventional picture is that the polar nano-regions (PNRs) that appear at high temperatures beyond the Curie transition, form nuclei for the field-induced long-range order at low temperatures. Here, we report high-energy X-ray diffuse-scattering measurements on the relaxor Pb(Zn(1/3)Nb(2/3))O(3) (PZN) to study the short-range polar order under an electric field applied along the [111] direction. In contrast to conventional expectations, the overall diffuse-scattering intensity is not suppressed. On the other hand, the field induces a marked change on the shape of the three-dimensional diffuse-scattering intensity pattern, corresponding to a redistribution of PNRs in real space. We show that these surprising results are consistent with a model in which the PNRs with [110]-type polarizations, orthogonal to that of the surrounding environment, are embedded and persist in the [111]-polarized ferroelectric order of the bulk.

[Genetic evaluation for rifampicin-susceptibility of Mycobacterium tuberculosis]

We evaluated the relationship between rifampicin (RFP)-susceptibility and genetic alterations in rpoB gene of clinically isolated Mycobacterium tuberculosis strains, collected from different geographic locations within Japan. Alterations in rpoB gene were detected by PCR-direct sequencing analysis, and the minimum inhibitory concentrations (MICs) of RFP were determined by broth microdilution method using Middlebrook 7H9 broth. One hundred and sixty six epidemiologically unrelated M. tuberculosis strains were examined. A total of 99 genetic alterations in the 69 bp core region of rpoB gene were detected in 95 out of 166 strains. Among them, 96 out of 166 strains showed RFP-resistant phenotypes with MICs > or = 2 micrograms/ml. Examination of the correlation between the MICs of RFP and amino acid substitutions in 69 bp core region of rpoB gene revealed that 58 out of 59 strains containing amino acid substitution in codon 531 showed highly RFP-resistant phenotypes with MICs > or = 64 micrograms/ml. In contrast, a variable level of RFP-susceptibility was observed among strains containing amino acid substitutions in either codon 516 or 526. On the other hand, the MICs of three strains with a point mutation in either codon 515 or 533 were all < or = 1 microgram/ml. Our results suggest that rpoB gene sequencing is useful for not only the detection of RFP-resistant M. tuberculosis strains, but also the prediction of RFP-susceptibility of the strains.