Proper protein folding in the endoplasmic reticulum (ER) is vital in all eukaryotes. When misfolded proteins accumulate in the ER lumen, the transmembrane kinase/endoribonuclease Ire1 initiates splicing of HAC1 mRNA to generate the bZIP transcription factor Hac1, which subsequently activates its target genes to increase the protein-folding capacity of the ER. This cellular machinery, called the unfolded protein response (UPR), is believed to be an evolutionarily conserved mechanism in eukaryotes. In this study, we comprehensively characterized mutant phenotypes of IRE1 and other related genes in the human fungal pathogen Candida glabrata. Unexpectedly, Ire1 was required for the ER stress response independently of Hac1 in this fungus. C. glabrata Ire1 did not cleave mRNAs encoding Hac1 and other bZIP transcription factors identified in the C. glabrata genome. Microarray analysis revealed that the transcriptional response to ER stress is not mediated by Ire1, but instead is dependent largely on calcineurin signaling and partially on the Slt2 MAPK pathway. The loss of Ire1 alone did not confer increased antifungal susceptibility in C. glabrata contrary to UPR-defective mutants in other fungi. Taken together, our results suggest that the canonical Ire1-Hac1 UPR is not conserved in C. glabrata. It is known in metazoans that active Ire1 nonspecifically cleaves and degrades a subset of ER-localized mRNAs to reduce the ER load. Intriguingly, this cellular response could occur in an Ire1 nuclease-dependent fashion in C. glabrata. We also uncovered the attenuated virulence of the C. glabrata Δire1 mutant in a mouse model of disseminated candidiasis. This study has unveiled the unique evolution of ER stress response mechanisms in C. glabrata.

A Candida glabrata calcineurin mutant exhibited increased susceptibility to both azole antifungal and cell wall-damaging agents and was also attenuated in virulence. Although a mutant lacking the downstream transcription factor Crz1 displayed a cell wall-associated phenotype intermediate to that of the calcineurin mutant and was modestly attenuated in virulence, it did not show increased azole susceptibility. These results suggest that calcineurin regulates both Crz1-dependent and -independent pathways depending on the type of stress.

The Slt2 mitogen-activated protein kinase pathway plays a major role in maintaining fungal cell wall integrity. In this study, we investigated the effects of SLT2 deletion and overexpression on drug susceptibility and virulence in the opportunistic fungal pathogen Candida glabrata. While the Deltaslt2 strain showed decreased tolerance to elevated temperature and cell wall-damaging agents, the SLT2-overexpressing strain exhibited increased tolerance to these stresses. A mutant lacking Rlm1, a transcription factor downstream of Slt2, displayed a cell wall-associated phenotype intermediate to that of the Deltaslt2 strain. When RLM1 was overexpressed, micafungin tolerance was increased in the wild-type strain and partial restoration of the drug tolerance was observed in the Deltaslt2 background. It was also demonstrated that echinocandin-class antifungals were more effective against C. glabrata under acidic conditions or when used concurrently with the chitin synthesis inhibitor nikkomycin Z. Finally, in a mouse model of disseminated candidiasis, the deletion and overexpression of C. glabrata SLT2 resulted in mild decreases and increases, respectively, in the CFUs from murine organs compared with the wild-type strain. These fundamental data will help in further understanding the mechanisms of cell wall stress response in C. glabrata and developing more effective treatments using echinocandin antifungals in clinical settings.

The prognosis of gallbladder cancer (GBC) remains poor despite recent advances in diagnostics and therapeutic strategies. Although the role of microRNAs (miRs) in GBC have not been well documented, miR-155 is known to be associated with inflammation-associated carcinogenesis in various types of cancers. The aim of this study was to investigate the clinical significance of miR-155 expression and the biological functions of miR-155 in GBC. The expression levels of miR-155 in surgically resected GBCs and gallbladders with pancreaticobiliary maljunction (PBM) were assessed by quantitative reverse transcription-polymerase chain reaction. The relationship between the expression levels of miR-155 and clinicopathological features of GBCs was analyzed. Human GBC cell lines were transfected with miR-155 inhibitors or mimics, and the effects on proliferation and invasion were assessed. miR-155 was significantly overexpressed in GBCs when compared with that in gallbladders with PBM (P=0.007) and normal gallbladders (P=0.04). The high expression level of miR-155 in GBCs was significantly associated with the presence of lymph node metastasis (P=0.01) and a poor prognosis (P=0.02). In vitro assays showed that aberrant expression of miR-155 significantly enhanced GBC cell proliferation and invasion. In conclusion, high miR-155 expression correlates with the aggressive behavior of GBCs, and miR-155 may become a prognostic marker and therapeutic target for GBC.

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Peroral pancreatoscopy using the SpyGlass system seems to be feasible and useful for assessment of IPMN with a dilated MPD.

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Patients with branch duct IPMNs who have 2 or more of the 4 predictive factors described above should undergo standard pancreatectomy with lymph node dissection, whereas patients who present with 0 or 1 predictive factor can be treated by minimal pancreatectomy without nodal dissection or by careful observation without resection. All patients with main duct IPMNs, therefore, should be treated with resection as suspected malignancies.