Pesticin-Like Effector VgrG3cp Targeting Peptidoglycan Delivered by the Type VI Secretion System Contributes to Vibrio cholerae Interbacterial Competition.

Vibrio cholerae can utilize a type VI secretion system (T6SS) to increase its intra- and interspecies competition. However, much still remains to be understood about the underlying mechanism of this intraspecies competition. In this study, we isolated an environmental V. cholerae strain E1 that lacked the typical virulence factors toxin-coregulated pilus and cholera toxin and that encoded a functional T6SS. We identified an evolved VgrG3 variant with a predicted C-terminal pesticin-like domain in V. cholerae E1, designated VgrG3cp. Using heterologous expression, protein secretion, and peptidoglycan-degrading assays, we demonstrated that VgrG3cp is a T6SS-dependent effector harboring cell wall muramidase activity and that its toxicity can be neutralized by cognate immunity protein TsiV3cp. Site-directed mutagenesis proved that the aspartic acid residue at position 867 is crucial for VgrG3cp-mediated antibacterial activity. Bioinformatic analysis showed that genes encoding VgrG3cp-like homologs are distributed in Vibrio species, are linked with T6SS structural genes and auxiliary genes, and the vgrG3cp-tsiV3cp gene pair of V. cholerae probably evolved from Vibrio anguillarum and Vibrio fluvialis via homologous recombination. Through a time-lapse microscopy assay, we directly determined that cells accumulating VgrG3cp disrupted bacterial division, while the cells continued to increase in size until the loss of membrane potential and cell wall breakage and finally burst. The results of the competitive killing assay showed that VgrG3cp contributes to V. cholerae interspecies competition. Collectively, our study revealed a novel T6SS E-I pair representing a new T6SS toxin family which allows V. cholerae to gain dominance within polymicrobial communities by T6SS. IMPORTANCE The type VI secretion system used by a broad range of Gram-negative bacteria delivers toxic proteins to target adjacent eukaryotic and prokaryotic cells. Diversification of effector proteins determines the complex bacterium-bacterium interactions and impacts the health of hosts and environmental ecosystems in which bacteria reside. This work uncovered an evolved valine-glycine repeat protein G3, carrying a C-terminal pesticin-like domain (VgrG3cp), which has been suggested to harbor cell wall hydrolase activity and is able to affect cell division and the integrity of cell wall structure. Pesticin-like homologs constitute a family of T6SS-associated effectors targeting bacterial peptidoglycan which are distributed in Vibrio species, and genetic loci of them are linked with T6SS structural genes and auxiliary genes. T6SS-delivered VgrG3cp mediated broad-spectrum antibacterial activity for several microorganisms tested, indicating that VgrG3cp-mediated antimicrobial activity is capable of conferring bacteria a competitive advantage over competitors in the same niches.

Interleukin-18 promotes the antitumor ability of natural killer cells in colorectal cancer via the miR-574-3p/TGF-ß1 axis.

Interleukin (IL)-18 has a clear antitumor effect; however, its mechanisms of action are not understood in patients with colorectal cancer (CRC). Here, we investigated the potential mechanism of IL-18 in CRC. The results showed that IL-18 treatment alone had no effect on HCT116 cells apoptosis, whereas IL-18 in the presence of natural killer (NK) cells resulted in apoptosis and inhibition of cells proliferation in vitro. Profiling of miRNA expression following coculture with NK cells and treatment with IL-18 resulted in significant downregulation of miR-574-3p expression and upregulated expression of the target gene transforming growth factor beta 1 (TGF-ß1). miR-574-3p binds to TGF-ß1, and miR-574-3p overexpression increased the proliferation and decreased the apoptotic rate of HCT116 cells in NK cells coculture with IL-18 treatment; overexpression of TGF-ß1 restored the effect of miR-574-3p overexpression. The miRNA profile of HCT116 undergoes significant alteration before and after coculturing with NK cells and treatment with IL-18. IL-18 alone did not affect HCT116 cells apoptosis but did promote the antitumor ability of NK cells in coculture with HCT116 cells via the miR-574-3p/TGF-ß1 axis. Our study suggested that IL-18 can be a new potential target for cancer immunotherapy for CRC.

The expressions and significance of B7-H3 and CTLA-4 in the clinical stages of non-small-cell lung cancer.

The aim of this study was to analyze the expressions and significance of B7-H3 and CTLA-4 in the clinical stages of non-small-cell lung cancer (NSCLC). Seventy patients with NSCLC who underwent surgical resection or biopsy between January 2016 and February 2018 were enrolled. Among them, 30 were cases of paracancerous tissues and were assigned to the control group (CON). These cases were analyzed using immunochemical methods. Of the 70 cases, 48 were of adenocarcinoma, 19 were of squamous cell carcinoma, and 3 were of adenosquamous carcinoma. The expression rates of B7-H3 and CTLA-4 in the observation group (OBS) were 64.2% and 57.1% respectively, and those in the CON group were 6.7% and 0%, respectively (χ2=27.988, 28.571, P<0.001). The expression levels of B7-H3 and CTLA-4 in patients with poor differentiation, in stages III-IV, or with lymph node metastasis were significantly higher than those in patients with good-to-moderate differentiation, in stages I-II, and without lymph node metastasis (P<0.05). There was a positive correlation between the expressions of B7-H3 and CTLA-4 in the OBS group (r=0.74, P<0.05). B7-H3 and CTLA-4 are highly expressed and positively correlated with each other in NSCLC patients and are also closely related to clinical stages.

Clinical relevance of using autofluorescence bronchoscopy and white light bronchoscopy in different types of airway lesions.

OBJECTIVES: The aim of this study was to evaluate the sensitivity and specificity of autofluorescence bronchoscopy (AFB) according to the macroscopic appearance of airway lesions under white light bronchoscopy (WLB). MATERIALS AND METHODS: The bronchoscopic findings of 708 patients, who were pathologically and clinically diagnosed with airway lesions and underwent both WLB and AFB, were analyzed. RESULTS: We recruited 708 patients for this study, of which 336 (47.5%) had benign lesions; 300 and 254 benign lesions were detected by AFB (specificity, 89.3%) and WLB (specificity, 75.6%), respectively. In 372 (52.5%) patients with bronchiogenic carcinoma, 356 and 235 lesions were identified by AFB (sensitivity, 95.7%) and WLB (sensitivity, 63.2%), respectively. The sensitivity and specificity of AFB for diagnosing lung cancer were higher than those of WLB (P < 0.05). Moreover, AFB showed high sensitivity for detecting lung cancer in cases in which WLB revealed hyperplasia, infiltration, and stenosis (P < 0.05). CONCLUSIONS: AFB combined with WLB could effectively improve the diagnosis of airway lesions.

[Value of peritoneoscopy via natural orifice transluminal endoscopic surgery in the diagnosis of peritoneal carcinomatosis].

OBJECTIVE: To evaluate the value of peritoneoscopy via natural orifice transluminal endoscopic surgery (NOTES) in the diagnosis of patients with peritoneal carcinomatosis. METHODS: A total of 32 patients with peritoneal carcinomatosis were diagnosed by histological examination of biopsies at our hospital from April 2007 to October 2010. Their data of clinical manifestations, gastroscopy, colonoscopy, abdominal ultrasonography, abdominal computed tomography, magnetic resonance imaging, ascitic cytology and transgastric peritoneoscopy via NOTES were analyzed retrospectively. RESULTS: Among them, gastrointestinal cancers were diagnosed by digestive endoscopy in 9 cases (28.1%). And ovarian lesions in 8 cases (25.0%), pancreatic cancer in 2 cases (6.3%), primary liver cancer in 2 cases (6.3%) and bile duct carcinoma in 1 case (3.1%) were suspected according to imaging examinations. No peritoneal carcinomatosis was found by digestive endoscopy or imaging examinations. Ascitic cytology was positive in 6 cases (18.8%). Peritoneal carcinomatosis was diagnosed by transgastric peritoneoscopy via NOTES with histological examination of biopsies in all patients. Their findings of transgastric peritoneoscopy via NOTES were divided into 5 types, i.e., mass type (n = 3, 9.4%), nodular type (n = 5, 15.6%), ulcerative type (n = 1, 3.1%), omentum-embracing type (n = 1, 3.1%) and mixture type (n = 22, 68.8%). CONCLUSION: Transgastric peritoneoscopy via NOTES with histological examination of biopsies has important value in the pathologic diagnosis and the endoscopic typing of peritoneal carcinomatosis.