Cellular and molecular responses of Salmonella Typhimurium to antimicrobial-induced stresses during the planktonic-to-biofilm transition

AIM

To characterize the cellular and molecular properties of Salmonella Typhimurium exposed to antimicrobials in association with physicochemical property, biofilm formation ability and gene expression patterns.

METHODS AND RESULTS

The antimicrobial susceptibilities against Salmonella Typhimurium were evaluated to determine the MICs of allyl isothiocyanate (AITC), thymol, eugenol and polyphenol. Cell surface hydrophobicity, aggregation and biofilm formation assays were conducted to assess the physicochemical properties of Salm. Typhimurium treated with sublethal concentrations (SLC(2D) ) of antimicrobials. The expression patterns of adhesion-related genes (adrA, csgD, fimA and lpfE), virulence-related genes (hilA and stn) and efflux-related genes (acrA, acrB, ompD and tolC) were evaluated by real-time RT-PCR. Thymol exhibited the highest antimicrobial activity against Salm. Typhimurium planktonic, biofilm and dispersed cells, showing 0·18, 0·96 and 0·42 mg ml(-1) of SLC(2D) values, respectively. The antimicrobial-treated Salm. Typhimurium showed low hydrophobicity. The highest auto-aggregation ability (67%) of polyphenol-treated Salm. Typhimurium was positively associated with the enhanced ability to form biofilms. The csgD, fimA, hilA and lpfE genes were up-regulated in the polyphenol-treated Salm. Typhimurium planktonic and biofilm cells.

CONCLUSION

The results suggest that the antimicrobial resistance and virulence potential varied depending on the physiological states of Salm. Typhimurium during the transition from planktonic to biofilm cell growth.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study can expand our understanding of cellular and molecular mechanisms of biofilm formation and also provide useful information for reducing biofilm-associated virulence potential.

Inhibition of the sole type I signal peptidase of Mycobacterium tuberculosis is bactericidal under replicating and nonreplicating conditions

Proteins secreted by bacteria perform functions vital for cell survival and play a role in virulence in Mycobacterium tuberculosis. M. tuberculosis lepB (Rv2903c) encodes the sole homolog of the type I signal peptidase (SPase). The lepB gene is essential in M. tuberculosis, since we could delete the chromosomal copy only when a second functional copy was provided elsewhere. By placing expression under the control of an anhydrotetracycline-inducible promoter, we confirmed that reduced lepB expression was detrimental to growth. Furthermore, we demonstrated that a serine-lysine catalytic dyad, characteristic for SPase function, is required for LepB function. We confirmed the involvement of LepB in the secretion of a reporter protein fused to an M. tuberculosis signal peptide. An inhibitor of LepB (MD3; a beta-aminoketone) was active against M. tuberculosis, exhibiting growth inhibition and bactericidal activity. Overexpression of lepB reduced the susceptibility of M. tuberculosis to MD3, and downregulation resulted in increased susceptibility, suggesting that LepB is the true target of MD3. MD3 lead to a rapid loss of viability and cell lysis. Interestingly, the compound had increased potency in nonreplicating cells, causing a reduction in viable cell numbers below the detection limit after 24 h. These data suggest that protein secretion is required to maintain viability under starvation conditions and that secreted proteins play a critical role in generating and surviving the persistent state. We conclude that LepB is a promising novel target for drug discovery in M. tuberculosis, since its inhibition results in rapid killing of persistent and replicating organisms.

CYP2D6 and ESR genotypes in adjuvant tamoxifen treatment for early breast cancer

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Background: The pharmacokinetics and pharmacodynamics of tamoxifen may influence the clinical outcome and tolerability of adjuvant treatment with tamoxifen in breast cancer. We investigated the effects of polymorphisms of CYP2D6, ESR1, and ESR2 for tamoxifen therapy in early stage breast cancer patients.

Methods: Tissue DNA from 187 patients who received tamoxifen only as an adjuvant systemic therapy between 1997 and 2002 were extracted and genotyped for polymorphisms of CYP2D6 (*2A, *10, *14, *41) and estrogen receptor (ESR1, ESR2). While CYP2D6*10, *14 and *41 have been reported to be associated with decreased activation of tamoxifen, CYP2D6*2A, ESR1 PvuII CC and ESR2-02 GG have been associated with enhanced activity of tamoxifen. Statistical analyses include Fisher exact test, Chi-square and Kaplan-Meier analyses.

Results: Median age was 43 years (range 25-49). Most of the patients (170/187) were stage I, while other patients were stage 0 (1/187) and stage II (17/187). None of the patients had nodal metastasis. Median follow-up was 100 months (7-166). Allele frequencies were as follows: CYP2D6*10, 0.69; *14, 0.02; *41, 0.01; *2A, 0.64; ESR1 PvuII C allele, 0.25; ESR2-02 G allele, 0.98. Each genotype group did not show significant differences in age, stage, pT, tumor size and follow up period. Twelve percent (24/187) had received tamoxifen therapy for less than 24 months. Of the 24 patients, 67% (16) discontinued tamoxifen therapy related to tolerability issues. Recurrence occurred in 12 patients (6.4%). There was no association between genotypes with either recurrence or tamoxifen duration < 2 years. Although statistically nonsignificant, patients with either CYP2D6*2A homozygote, ESR1 PvuII CC genotype, ESR2-02 GG genotype tended to have a longer DFS when compared concomitantly to wild-type (p=0.445).

Conclusions: Polymorphsims for CYP2D6*2A,*10, *14, *41, ESR1 PvuII, ESR2-02 did not show significant associations with either recurrence or tamoxifen duration > 2 years. However, grouped analysis for CYP2D6*2A, ESR1 PvuII, ESR2-0210 genotypes need further evaluation regarding with tamoxifen outcome.

A co-twin study of the relative effect of birth weight and gestational age on retinopathy of prematurity

PURPOSE

To determine the relative effect of birth weight and gestational age on retinopathy of prematurity (ROP) using preterm twin pairs discordant for birth weight.

METHODS

This study was a retrospective cohort study including 55 consecutive twin pairs of 110 preterm infants (gestational age ≤33 weeks). The outcomes of ROP including occurrence (any stage), severe ROP (stage 3 or more), and clinically significant ROP requiring laser treatment were compared between twins with the lower birth weight from each pair and their co-twins with the higher birth weight. Using twin pairs having different birth weight and identical gestational age, the independent effects of prematurity and intrauterine growth on ROP could be evaluated. Other perinatal morbidities related to prematurity were also compared between twin pairs.

RESULTS

No significant differences in ROP between larger and smaller infants were observed in the twin-paired analysis while analysis on individual infants showed strong association between small birth weight and ROP outcomes. However, in both the larger and smaller infant groups, gestational age of <28 weeks was significantly associated with ROP outcomes. No differences were found between twin pairs regarding other perinatal morbidities including bronchopulmonary dysplasia, respiratory distress syndrome, patent ductus arteriosus, intraventricular hemorrhage, and periventricular leukomalacia.

CONCLUSIONS

Birth weight is not associated with ROP, while gestational age is in the twin-paired study, suggesting that gestational age is a better predictor of ROP than birth weight. This indicates that maturity is more important in the pathogenesis of ROP than intrauterine growth.

Quantitative determination of mycotoxins in urine by LC-MS/MS

Naturally occurring mycotoxins are responsible for a wide array of adverse health effects. The measurement of urinary mycotoxin levels is a useful means of assessing an individual's exposure, but the development of sensitive and accurate analytical methods for detecting mycotoxins and their metabolites in urine samples is challenging. Urinary mycotoxins are present in low pg ml⁻¹ concentrations, and the chromatographic identification of their metabolites can be obscured by other endogenous metabolites. We developed an analytical method focused on the selection of two appropriate multiple-reaction monitoring transition for unambiguous identification and quantification of carcinogenic aflatoxin M₁ (AFM₁), ochratoxin A (OTA) and fumonisin B₁, B₂ (FB₁, FB₂) in urine samples from a small volunteer group in a pilot study. AFM₁, OTA, FB₁ and FB₂ were concentrated selectively, interfering substances were removed using an immunoaffinity column (IAC), and mycotoxins were measured using liquid chromatography-tandem mass spectrometry (LC-MS/MS) in combination with a stable-isotope standard-dilution assay (SIDA). The method was sensitive enough to measure mycotoxins and their metabolites at pg ml⁻¹ levels in urine. The combination of LC-MS/MS and SIDA was critical to distinguishing pseudo-OTα interference from genuine OTα. Twelve urine samples contained OTA ranging from 0.013 to 0.093 ng ml⁻¹ (mean = 0.031 ng ml⁻¹). AFM₁ were detected in one sample at a 0.002 ng ml⁻¹ level, while FB₁ and FB₂ were undetectable in all 12 samples. None of the samples in this pilot study contained a detectable level of OTα, despite the presence of OTA, and this may suggest the need for further epidemiological investigation of OTA exposure in the Korean population.

Prognostic factors and survial of advanced renal cell carcinoma with predominant sarcomatoid histology

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Background: Sarcomatoid renal cell carcinoma (SRCC) is known to have aggressive clinical course and poor response to treatment. Very limited data of clinical feature, prognostic factor, and survival are available for advanced disease with predominant sarcomatoid histology. We evaluated clinical features, response to treatment, and prognostic factors for survival.

Methods: Between 2001 and 2010, 30 patients with metastatic or recurrent RCC with predominant sarcomatoid histology (sarcomatoid component 30% or more for resected kidney or exclusive sarcomatoid carcinoma on needle biopsy) were treated at our institution. We reviewed these patients' records to identify clinical and pathologic features which could affect survival. The role of nephrectomy and systemic therapy on patient outcome was also investigated.

Results: There were 20 male and 10 female patients with a median age of 58 years (range, 43–83). Twenty patients had initially metastatic disease and 16 patients (53%) had ECOG performance status (PS) of 0–1. The most frequent metastatic site was lung (57%) followed by bone (43%) and distant lymph nodes (23%). Fourteen (70%) out of 20 patients with initially metastatic disease underwent primary nephrectomy and six patients also underwent metastasectomy. The median % of sarcomatoid component was 80% (range, 30–100%). All patients (N=10) who received immunotherapy had progressive disease as their best response and only one out of 5 patients treated with sunitinib or everolimus had a partial response. With a median follow-up duration of 22 months, the median survival was 3.6 months (95% CI, 0∼7.5) with 6-month survival rate of 43%. Only ECOG PS had impact on survival (P<0.001: ECOG=0, 14.1 months; ECOG=1, 7.4 months; ECOG=2, 3.2 months, and ECOG=3, 1.64 months). Survivals for initially metastatic disease were not significantly different whether patients underwent nephrectomy or not (2.0 months vs. 3.4 months, HR=0.62, 95% CI, 0.16–2.44 after correcting for potential prognostic factors).

Conclusions: Patients with SRCC have a fulminant clinical course and the majority of patients had disease progression irrespective of any treatment. Only performance status dose have impact on overall survival.

No significant financial relationships to disclose.

Phase II study of a polyethoxylated castor oil–free, polymeric micelle formulation of paclitaxel for patients with advanced urothelial cancer previously treated with gemcitabine and platinum

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Background: Paclitaxel-loaded polymeric micelle (Genexol-PM; G-PM) is a novel polyethoxylated castor oil (Cremophor EL [CrEL])-free formulation of paclitaxel. This multicenter phase II study was designed to evaluate the efficacy and safety of the G-PM monotherapy for the treatment of gemcitabine- and cisplatin-refractory advanced urothelial cancer.

Methods: Patients with advanced urothelial cancer received G-PM 240 mg/m2 intravenously over 3 hours every 3 weeks without premedication as salvage chemotherapy after failure to gemcitabine and cisplatin combination chemotherapy. Intrapatient dose escalation of G-PM to 300 mg/m2 was carried out from the second cycle if the prespecified toxicities were not observed after the first cycle.

Results: Thirty-seven patients were enrolled in this study. Platinum-free interval was less than 6 months in 72% of patients and 64% of patients were categorized into intermediate or poor prognostic group. Overall response rate was 19% including one complete response. When response occurs it is long lasting with a median response duration of 7.8 months (range 1.5∼19.3+). The median progression-free survival was 2.7 months (95% CI, 09-4.6) with a median overall survival of 5.7 months (95% CI, 3.1-8.3). The most common major grade 3-4 non-hematologic toxicity was peripheral neuropathy (sensory type 5.6% and motor type 8.3%) followed by infection (5.6%). Grade 3 or worse hematologic toxicities were observed in only one patient.

Conclusions: G-PM showed modest activity with favorable toxicity profiles when used as salvage therapy after gemcitabine-cisplatin failure in advanced urothelial cancer.

No significant financial relationships to disclose.

Multicenter prospective phase II study of sunitinib in non-clear cell type renal cell carcinoma

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Background: Sunitinib has been shown to produce a high response rate (RR), and improved progression-free survival (PFS) in patients (pts) with clear cell RCC. Retrospective data suggest sunitinib may be effective in papillary and chromophobe RCC. We conducted a multicenter phase II trial of sunitinib in non-clear cell RCC (nccRCC).

Methods: Eligibility criteria included PS 0-1, measurable disease, and adequate organ function. Pts with brain metastases were not excluded if controlled without steroid dependence. Response assessment was performed every 6 weeks. Primary endpoint was RR. Secondary endpoints were TTP, safety and OS.

Results: Between 6/2008 and 7/2010, 29 pts with nccRCC were enrolled (total accrual 35: P0=5%, P1=20%, alpha=0.05, beta=0.2, drop-out rate 15%). Median age was 52 (18–76). Twenty-four pts (84%) had prior nephrectomy. Seven pts (24%) had poor risk and 13 (45%) had intermediate risk disease by MSKCC criteria. Twenty-one pts had papillary RCC (type II in 11 and type not- specified in 10), and 4 patients had chromophobe RCC. Two pts discontinued protocol treatment due to toxicity prior to completion of cycle 1 (one pt had cardiogenic shock 27 days after start of therapy and the other refused further treatment 5 days after therapy). Eleven pts out of 29 had partial response with a RR of 38% (95% CI, 20.2%–55.6%) and additional 15 patients (52%) had SD with a disease control rate of 90%. Response rates were not significantly different according to the histologic type (43% in papillary type and 25% in chromophobe type). Median duration of response was 12.7 months (95% CI, 2.3∼23.1) and median TTP was 6.4 months (95% CI, 4.5∼8.3). With a median FU duration of 16 months (95% CI, 8.6∼23.4), 10 pts have been dead resulting in an estimated median OS of 17.9 months. Toxicity profiles were commensurate with prior reports on Korean patients (Yoo, et al. Jpn J Clin Oncol 2010). However, there was one treatment-related death caused by acute heart failure in patient without relevant risk factors for heart disease.

Conclusions: Although our study is ongoing, the primary endpoint has been met and these data suggest that suntinib has promising activity in patients with nccRCC.

No significant financial relationships to disclose.

Application of Western patients-based Adjuvant! Online (AOL) model on Korean colon cancer patients

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Background: Adjuvant! Online (AOL) is a web-accessible risk-assessment model that predicts the mortality and the benefits of adjuvant therapy ( www.adjuvantonline.org ). AOL has never been validated for Asian colon cancer patients.

Methods: Using the Yonsei Tumor Registry (YTR) database, we calculated the survival for the patients with T1-4, N0-2, M0 colon cancer who were treated at the Yonsei Cancer Center between 1990 and 2005. Observed and predicted 5-year survival was compared for each patient.

Results: The median age of the study population was 60 years (range, 15-87 years) and the median follow-up duration was 7.9 years (range, 0.06-19.8 years) for all 1,431 patients. While AOL underestimate overall survival (OS) (predicted-observed=-1.02%, P=0.008), it overestimate colon cancer-specific survival (CCSS) (predicted-observed=3.8%, P<0.001) in Korean patients. Especially, AOL underestimated OS and CCSS in younger patients than age 50 years (predicted-observed=-4.3%, P<0.001 and predicted-observed=-3.5%, P<0.001, respectively). We conducted an internal model validation by using a Korean version of AOL (KAOL), which was a new model for prognosis based on AOL's parameters. 5-year OS and CCSS between the observed and the KAOL predicted survival were not different (77.25 vs. 77.15, P=0.873 and 77.4% vs. 77.6%, P=0.78, respectively). The concordance indexes about OS and CCSS were 0.75 and 0.74, respectively.

Conclusions: KAOL model for Korean colon cancer patients is more suitable to predict 5-year outcomes compared to ALO model for Western patients.

No significant financial relationships to disclose.

Gene-expression profiles related to a synergistic effect of taxane and suberoylanilide hydroxamic acid combination treatment in gastric cancer cells

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Background: We evaluated the cytotoxic effects of combining of suberoylanilide hydroxamic acid (SAHA), a histone deacetylase inhibitor, with taxanes in human gastric cancer cell lines, and evaluated the pre-treatment difference of gene profile to identify genes that could potentially mediate the cytotoxic response.

Methods: Twenty-five gastric cancer cell lines with 22K gene expression data were treated with SAHA and paclitaxel or docetaxel, and the synergistic interaction between the drugs was evaluated in vitro using the combination index (CI) method. We performed significance analysis of microarray (SAM) to identify chemosensitivity-related genes in gastric cancer cell lines that were concomitantly treated with SAHA and taxane. We generated a correlation-matrix between gene expression and CI values to identify genes whose expression correlated with a combined effect of taxanes and SAHA.

Results: Taxane and SAHA combination had a synergistic cytotoxic effect against taxane-resistant gastric cancer cells. We selected 49 chemosensitivity-related genes, which were commonly identified in paclitaxel and docetaxel combined with SAHA, via SAM analysis. Among them, nine common genes (SLIT2, REEP2, EFEMP2, CDC42SE1, FSD1, POU1F1, ZNF79, ETNK1, and DOCK5) were extracted from the subsequent correlation-matrix analysis.

Conclusions: Taxane and SAHA combination could be efficacious for the treatment of gastric cancer. The genes which were related with the synergistic response to taxane and SAHA could serve as surrogate biomarkers to predict the therapeutic response in gastric cancer patients. We are researching to determine the expression of the nine genes in malignant human gastric cancer tissue and to correlate them with clinical information.

No significant financial relationships to disclose.

Use of class III beta tubulin to predict efficacy from paclitaxel- or docetaxel-based chemotherapy in patients with advanced gastric cancer

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Background: To predict clinical outcome in patients with advanced gastric cancer (AGC) received paclitaxel or docetaxel based chemotherapy, we evaluated expression of class III beta tubulin (bTubIII).

Methods: Expression of bTubIII was evaluated by immunohistochemistry (IHC) on formalin-fixed, paraffin-embedded tumors from the primary gastric cancer. Tumors were classified as bTubIII “low” and “high” according to median of IHC score [intensity (0-3) × portion (0-100)]. The expression of bTubIII was investigated for their association with clinical outcomes of efficacy and toxicity.

Results: One hundred twenty-four AGC pts who were treated with paclitaxel or docetaxel combined with an infusional 5-fluorouracil and low-dose leucovorin as first and second-line palliative chemotherapy were enrolled. Thirty-three patients (26.7%) were confirmed to have high expression of bTubIII. The patients with high expression of bTubIII showed higher disease control rate (DCR) and longer progression-free survival (PFS) than those with low expression in patients treated with paclitaxel (79.3 % vs. 57.3 %, p = 0.039, and 3.0 months vs. 1.5 months, p = 0.073). By contrast, there was no difference of DCR and PFS according to expression of bTubIII in patients treated with docetaxel. The expression of bTubIII was not associated with toxicity in both patients treated with paclitaxel or docetaxel.

Conclusions: The expression of bTubIII may be a predictive marker in AGC patients received paclitaxel based chemotherapy, but not docetaxel.

No significant financial relationships to disclose.