Abstract. Carbapenemase-producing ʻsuper bacteriaʼ, particularly NDM-1 and its variants, have become a major public health concern worldwide. The present study aimed to explore the molecular mechanism for carbapenem resistance of clinical Enterobacteriaceae isolates. Seventy-eight non-repeated Enterobacteriaceae strains resistant to any carbapenem were screened at the First Affiliated Hospital of Zhengzhou University (Zhengzhou, China) between December 2011 and December 2015. Outer membrane porin (OMP) proteins were detected using SDS-PAGE. Carbapenemases, extended-spectrum β-lactamases (ESBLs) and plasmid AmpC enzyme genes were detected using polymerase chain reaction (PCR). PCR and SDS-PAGE demonstrated that 60.3% (47/78) of the strains produced carbapenemases, of which 33.3% (26/78) produced KPC-2 carbapenemase, suggesting that the strains resisted carbapenems primarily through carbapenemases. SDS-PAGE showed that the OMP proteins in the majority of carbapenem-resistant Enterobacteriaceae (CRE) strains were deleted or decreased compared with those in the sensitive strains. Of the 44 Klebsiella strains, 59.1% (26/44) did not express or expressed less OmpK35 or OmpK36. Among the 34 strains of other enterobacteria, 97.1% (33/34) did not express or expressed less OmpC or OmpF. Of all CRE strains, 35.9% (28/78) lost at least one OMP protein, indicating that the strains resisted carbapenems also by producing ESBLs and/or plasmid AmpC enzyme, as well as by losing OMP proteins. The resistance of clinically isolated CRE strains may primarily be attributed to the production of carbapenemases, and may also involve the deletion of OMP proteins or mutation of OMP genes.

Exosomes play a vital role in gastric cancer carcinogenesis and metastasis.

Long intergenic non-coding RNA Linc00472 has been considered as a tumor suppressor in some cancers. However, the function and mechanism of Linc00472 in colorectal cancer has not been well elucidated. In this study, we found that Linc00472 was down-regulated in colorectal cancer tissues and cells. Elevated Linc00472 expression suppressed proliferation and induced apoptosis in colorectal cancer cells. Moreover, Linc00472 acted as a competing endogenous RNA (ceRNA) of miR-196a to release programmed cell death 4 (PDCD4). Furthermore, miR-196a overexpression or PDCD4 knockdown reversed Linc00472-mediated proliferation inhibition and apoptosis induction in colorectal cancer cells. Ectopic Linc00472 expression hindered tumor growth in vivo. Our study demonstrated that Linc00472 suppressed proliferation and induced apoptosis through up-regulating PDCD4 by decoying miR-196a, which may be an effective therapeutic target for colorectal cancer.

Increasing evidence suggests that dysregulation of long non-coding RNAs (lncRNAs) is implicated in chemoresistance in cancers. However, the function and molecular mechanisms of lncRNAs in gastric cancer chemoresistance are still not well understood. In this study, we aimed to investigate the functional role and the underlying molecular mechanisms of lncRNA HOXD cluster antisense RNA 1 (HOXD-AS1) in cisplatin (DDP) resistance in gastric cancer. Our results revealed that HOXD-AS1 was upregulated in DDP-resistant gastric cancer tissues and cells. Patients with gastric cancer with high HOXD-AS1 expression levels had a poor prognosis. Knockdown of HOXD-AS1 facilitated the sensitivity of DDP-resistant gastric cancer cells to DDP. Additionally, HOXD-AS1 epigenetically silenced PDCD4 through binding to the histone methyltransferase enhancer of zeste homologue 2 (EZH2) on the promoter of PDCD4, thus increasing H3K27me3. More importantly, PDCD4 silencing counteracted HOXD-AS1 knockdown-mediated enhancement of DDP sensitivity in DDP-resistant gastric cancer cells. In summary, HOXD-AS1 led to DDP resistance in gastric cancer by epigenetically suppressing PDCD4 expression, providing a novel therapeutic strategy for patients with gastric cancer with chemoresistance.

No abstract