Identification of key genes and long non-coding RNA associated ceRNA networks in hepatocellular carcinoma

Clinical Implication of E2F Transcription Factor 1 in Hepatocellular Carcinoma Tissues

Background: To date, the clinical management of advanced hepatocellular carcinoma (HCC) patients remains challenging and the mechanisms of E2F transcription factor 1 (E2F1) underlying HCC are obscure. Materials and Methods: Our study integrated datasets mined from several public databases to comprehensively understand the deregulated expression status of E2F1. Tissue microarrays and immunohistochemistry staining was used to validate E2F1 expression level. The prognostic value of E2F1 was assessed. In-depth subgroup analyses were implemented to compare the differentially expressed levels of E2F1 in HCC patients with various tumor stages. Functional enrichments were used to address the predominant targets of E2F1 and shedding light on their potential roles in HCC. Results: We confirmed the elevated expression of E2F1 in HCC. Subgroup analyses indicated that elevated E2F1 level was independent of various stages in HCC. E2F1 possessed moderate discriminatory capability in differentiating HCC patients from non-HCC controls. Elevated E2F1 correlated with Asian race, tumor classification, neoplasm histologic grade, eastern cancer oncology group, and plasma AFP levels. Furthermore, high E2F1 correlated with poor survival condition and pooled HR signified E2F1 as a risk factor for HCC. Enrichment analysis of differentially expressed genes, coexpressed genes, and putative targets of E2F1 emphasized the importance of cell cycle pathway, where CCNE1 and CCNA2 served as hub genes. Conclusions: We confirmed the upregulation of E2F1 and explored the prognostic value of E2F1 in HCC patients. Two putative targeted genes (CCNE1 and CCNA2) of E2F1 were identified for their potential roles in regulating cell cycle and promote antiapoptotic activity in HCC patients.

Long Noncoding RNA Cytoskeleton Regulator RNA Suppresses Apoptosis in Hepatoma Cells by Modulating the miR-125a-5p/HS1-Associated Protein X-1 Axis to Induce Caspase-9 Inactivation

Background/Aims

The involvement of long noncoding RNAs in the carcinogenesis of hepatocellular carcinoma (HCC) has been well documented by substantial evidence. However, whether cytoskeleton regulator RNA (CYTOR) could affect the progression of HCC remains unclear.

Methods

The relative expression of CYTOR, miR-125a-5p and HS1-associated protein X-1 (HAX-1) mRNA in HCC cells were determined via quantitative real-time polymerase chain reaction. The viability of treated HCC cells was measured by Cell Counting Kit-8 assay. Cell apoptosis was estimated by flow cytometry analysis, assessment of caspase-9 activity and terminal deoxynucleotidyl transferase dUTP nick-end labeling staining, and Western blot of apoptosis-related proteins. The interplay between CYTOR or HAX-1 and miR-125a-5p was validated by dual-luciferase reporter assay.

Results

CYTOR was upregulated and miR-125a-5p was downregulated in HCC cells. CYTOR silencing inhibited cell proliferation and promoted cell apoptosis in HepG2 and SMMC-7721 cells. miR-125a-5p was sponged and negatively regulated by CYTOR, and HAX-1 was directly targeted and negatively modulated by miR-125a-5p. Overexpression of miR-125a-5p enhanced the repressive effects of CYTOR knockdown on HCC cells, and knockdown of HAX-1 enhanced the inhibitory effects of miR-125a-5p mimics on HCC cells.

Conclusions

CYTOR silencing facilitates HCC cell apoptosis in vitro via the miR-125a-5p/HAX-1 axis.

In silico analysis of the association between long non-coding RNA family with sequence similarity 99 member A (FAM99A) and hepatic cancer

The link between family with sequence similarity 99 member A (FAM99A), a type of long non-coding RNA, and tumourigenesis remains ambiguous. Therefore, in this study, the authors conducted an expression profile analysis of FAM99A based on 33 types of cancer within The Cancer Genome Atlas project. The expression profile data revealed low expression levels of FAM99A in hepatocellular carcinoma, cholangiocarcinoma, and testicular germ cell tumour tissues than in the normal control tissues. Survival analysis indicated a correlation between low FAM99A expression and worse survival outcome in patients with hepatic cancer. Further investigation revealed the possible implication of DNA methylation, but not copy number variation, in FAM99A-associated hepatic tumourigenesis. The authors also identified a set of differentially expressed genes between patients with hepatic cancer and negative controls, which were found to be related to biochemical metabolism or the cell cycle. Additionally, FAM99A expression may be associated with the infiltration status of several immune cells, such as dendritic cells, natural killer cells, and neutrophils. Overall, FAM99A may function as a prognostic marker that is potentially associated with DNA methylation, immune cell infiltration, and biochemical metabolism in hepatic cancer.

Long Non-Coding RNA ZEB2-AS1 Promotes Hepatocellular Carcinoma Progression by Regulating The miR-582-5p/FOXC1 Axis

OBJECTIVE

Long non-coding RNAs (lncRNAs) feature prominently in tumors. Reportedly, lncRNA zinc finger E-box-binding homeobox 2 antisense RNA 1 (ZEB2-AS1) is aberrantly expressed in a variety of tumors. The present study was aimed to explore ZEB2-AS1 functions and determine mechanism in hepatocellular carcinoma (HCC) progression.

MATERIALS AND METHODS

In this experimental study, expressions of ZEB2-AS1, microRNA (miR)-582-5p and forkhead box C1 (FOXC1) mRNA in HCC tissues and cell lines were detected via quantitative reveres transcription polymerase chain reaction (qRT-PCR). After establishing gain- and loss-of-functions models, cell counting kit-8, 5-bromo-2'-deoxyuridine (BrdU), Transwell assays and flow cytometry analysis were conducted to examine HCC cell multiplication, migration, invasion and apoptosis, respectively. The targeted relationship between miR-582- 5p and ZEB2-AS1 was verified via dual-luciferase reporter gene assay. Western blot was utilized for detecting FOXC1 expression in HCC cells after selectively regulating ZEB2-AS1 and miR-582-5p.

RESULTS

In HCC tissues and cells, ZEB2-AS1 expression was increased. High ZEB2-AS1 expression was related to relatively large tumor volume, increased tumor-node-metastasis (TNM) stage and positive lymph node metastasis of the patients. ZEB2-AS1 overexpression facilitated HCC cell multiplication, migration, invasion and suppressed apoptosis, while ZEB2-AS1 knock-down caused the opposite effects. It was also confirmed that ZEB2-AS1 could competitively bind with miR-582-5p to repress its expression, and indirectly up-regulate FOXC1 expression level in HCC cells.

CONCLUSION

The current study revealed that ZEB2-AS1 was over-expressed in HCC tissues and cells. It also upregulated (FOXC1), through sponging miR-582-5p, to promote HCC progression. This provides new perspectives for elucidating the pathogenesis of HCC.

lncRNA–mRNA Expression Patterns in Invasive Pituitary Adenomas: A Microarray Analysis

Background. Long noncoding RNAs (lncRNAs) play important roles in the tumorigenesis and progression of various cancer types; however, their roles in the development of invasive pituitary adenomas (PAs) remain to be investigated. Methods. lncRNA microarray analysis was performed for three invasive and three noninvasive PAs. Gene Ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis were performed, and coexpression networks between lncRNA and mRNA were constructed. Furthermore, three differentially expressed lncRNAs were selected for validation in PA samples by real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR). The diagnostic values of these three lncRNAs were further evaluated by a receiver operating characteristic (ROC) curve analysis. Results. A total of 8872 lncRNAs were identified in invasive and paired noninvasive PAs via lncRNA microarray analysis. Among these, the differentially expressed lncRNAs included 81 that were upregulated and 165 that were downregulated. GO enrichment and KEGG pathway analysis showed that these differentially expressed lncRNAs were associated with the posttranslational modifications of proteins. Furthermore, we performed target gene prediction and coexpression analysis. The interrelationships between the significantly differentially expressed lncRNAs and mRNAs were identified. Additionally, three differentially expressed lncRNAs were selected for validation in 41 PA samples by qRT-PCR. The expression levels of FAM182B, LOC105371531, and LOC105375785 were significantly lower in the invasive PAs than in the noninvasive PAs ( $P<0.05$ ). These results were consistent with the microarray data. ROC curve analysis suggested that the expression levels of FAM182B and LOC105375785 could be used to distinguish invasive PAs from noninvasive PAs. Conclusion. Our findings demonstrated the expression patterns of lncRNAs in invasive PAs. FAM182B and LOC105375785 may be involved in the invasiveness of PAs and serve as new candidate biomarkers for the diagnosis of invasive PAs.

Reconstruction and analysis of the aberrant lncRNA-miRNA-mRNA network based on competitive endogenous RNA in adenoid cystic carcinoma of the salivary gland

Background

The aim of this work was to investigate the competing endogenous RNA (ceRNA) network in adenoid cystic carcinoma of the salivary gland (SACC).

Methods

Differentially expressed lncRNAs (DElncRNAs), miRNAs (DEmiRNAs), and mRNAs (DEmRNAs) between cancer tissues and normal salivary gland (NSG) in ACC were identified using data from the Gene Expression Omnibus (GEO) database. Functional annotation and pathway enrichment analysis of DEmRNAs were performed using the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases. The miRNAs that are targeted by lncRNAs were predicted using miRanda and PITA, while the target mRNAs of miRNAs were retrieved from miRanda, miRWalk, and TargetScan. A protein-protein interaction (PPI) network was constructed using the Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) database, and then we constructed the lncRNA-miRNA-mRNA networks of ACC.

Results

Differentially expressed RNAs were identified in SACC. Upon comparing cancer tissues and NSG tissues, 103 upregulated and 52 downregulated lncRNAs and 745 upregulated and 866 downregulated mRNAs were identified in GSE88804; in addition, 39 upregulated and 43 downregulated miRNAs were identified in GSE117275. GO enrichment analyses revealed that the most relevant GO terms were regulation of transcription DNA-templated, transcription DNA-templated, and cell division. KEGG pathway enrichment analysis showed that differentially expressed genes (DEGs) were mainly enriched in the cell cycle, pathways in cancer, PI3K-Akt signaling pathway, breast cancer, and microRNAs in cancer. The PPI network consisted of 27 upregulated and 54 downregulated mRNAs. By constructing ceRNA network, NONHSAT251752.1-hsa-miR-6817-5p-NOTCH1, NONHSAT251752.1-hsa-miR-204-5p/hsa-miR-138-5p-CDK6 regulatory axises were identified and all genes in the network were verified by qRT-PCR.

Conclusions

The present study constructed ceRNA networks in SACC and provided a novel perspective of the molecular mechanisms for SACC.

Procollagen-lysine, 2-oxoglutarate 5-dioxygenase 1 increases cellular proliferation and colony formation capacity in lung cancer via activation of E2F transcription factor 1

Procollagen-lysine, 2-oxoglutarate 5-dioxygenase 1 (PLOD1) is an enzyme that catalyzes the hydroxylation of lysyl residues in collagen-like peptides, and is responsible for the stability of intermolecular crosslinks. High PLOD1 mRNA levels have been determined to be prognostically significant in numerous human malignancies. The objective of the present study was to elucidate the pathological mechanism of PLOD1 in lung cancer. The expression status and prognostic value of PLOD1 in lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSA) were investigated using Gene Expression Profiling Interactive Analysis (GEPIA). Cell Counting Kit 8 and colony formation assays were performed to assess the impact of PLOD1 depletion and overexpression on the proliferation and colony formation abilities of the A549 lung cancer cell line. Luciferase reporter assays were used to clarify whether E2F transcription factor 1 (E2F1) was a downstream target of PLOD1 in lung cancer. Finally, the correlations between PLOD1 expression and a typical central downstream effector molecule of E2F1 signaling were determined using cBioportal. The GEPIA datasets revealed that PLOD1 mRNA levels were upregulated in LUAD and LUSC samples. Furthermore, the overexpression of PLOD1 promoted cancer cell proliferation and colony formation in vitro, while PLOD1-knockout produced the opposite effect. Notably, PLOD1 markedly induced the transcriptional activity of E2F1. Additionally, the expression of PLOD1 was significantly correlated with that of H2A histone family member X. In conclusion, the findings of the present study indicate that PLOD1 promoted lung cancer through E2F1 activation, and proposed a rationale for targeting the PLOD1/E2F1 axis to treat lung cancer.

Identification of Prognostic Biomarkers and Correlation With Immune Infiltrates in Hepatocellular Carcinoma Based on a Competing Endogenous RNA Network

Background

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors worldwide. Recently, competing endogenous RNAs (ceRNA) have revealed a significant role in the progression of HCC. Herein, we aimed to construct a ceRNA network to identify potential biomarkers and illustrate its correlation with immune infiltration in HCC.

Methods

RNA sequencing data and clinical traits of HCC patients were downloaded from TCGA. The limma R package was used to identify differentially expressed (DE) RNAs. The predicted prognostic model was established using univariate and multivariate Cox regression. A K-M curve, TISIDB and GEPIA website were utilized for survival analysis. Functional annotation was determined using Enrichr and Reactome. Protein-to-protein network analysis was implemented using SRTNG and Cytoscape. Hub gene expression was validated by quantitative polymerase chain reaction, Oncomine and the Hunan Protein Atlas database. Immune infiltration was analyzed by TIMMER, and Drugbank was exploited to identify bioactive compounds.

Results

The predicted model that was established revealed significant efficacy with 3- and 5-years of the area under ROC at 0.804 and 0.744, respectively. Eleven DEmiRNAs were screened out by a K-M survival analysis. Then, we constructed a ceRNA network, including 56 DElncRNAs, 6 DEmiRNAs, and 28 DEmRNAs. The 28 DEmRNAs were enriched in cancer-related pathways, for example, the TNF signaling pathway. Moreover, six hub genes, CEP55, DEPDC1, KIF23, CLSPN, MYBL2, and RACGAP1, were all overexpressed in HCC tissues and independently correlated with survival rate. Furthermore, expression of hub genes was related to immune cell infiltration in HCC, including B cells, CD8⁺ T cells, CD4⁺ T cells, monocytes, macrophages, neutrophils, and dendritic cells.

Conclusion

The findings from this study demonstrate that CEP55, DEPDC1, KIF23, CLSPN, MYBL2, and RACGAP1 are closely associated with prognosis and immune infiltration, representing potential therapeutic targets or prognostic biomarkers in HCC.

LncRNA SNHG6 promotes G1/S-phase transition in hepatocellular carcinoma by impairing miR-204-5p-mediated inhibition of E2F1

Emerging evidence suggests that long noncoding RNAs (lncRNAs) function as competitive endogenous RNA (ceRNA) targeting proteins and genes; however, the role of lncRNAs in hepatocellular carcinoma (HCC) is not well understood. We investigated the mechanism by which lncRNA SNHG6 promotes the development of HCC. RT-qPCR revealed upregulated lncRNA SNHG6 in the HCC setting. Elevated SNHG6 expression was indicative of poor prognosis in patients with HCC. SNHG6 overexpression resulted in increased cyclin D1, cyclin E1, and E2F1 expression both in vitro and in vivo. SNHG6 also promoted HCC cell proliferation by enhancing G1-S phase transition in vitro. Dual luciferase reporter assays, RIP, and RNA pull-down assays demonstrated SNHG6 competitively bound to miR-204-5p and inhibited its expression preventing miR-204-5p from targeting E2F1. Overexpression of miR-204-5p abolished the effect of SNHG6. Our data suggest that SNHG6 functions as a ceRNA that targets miR-204-5p resulting in an increased E2F1 expression and enhanced G1-S phase transition, thereby promoting the tumorigenesis of HCC.

SNHG1 knockdown upregulates miR-376a and downregulates FOXK1/Snail axis to prevent tumor growth and metastasis in HCC

Long non-coding RNAs (lncRNAs), microRNAs (miRNAs or miRs), and genes are emerging players in cancer progression. In the present study, we explored the roles and interactions of oncogenic lncRNA small nucleolar RNA host gene 1 (SNHG1), miR-376, forkhead box protein K1 (FOXK1), and Snail in hepatocellular carcinoma (HCC). Expression of SNHG1, miR-376, and FOXK1 in HCC was characterized in clinical HCC tissues of 75 patients with HCC. The interactions between SNHG1 and miR-376 and between miR-376 and FOXK1 were predicted and confirmed by dual-luciferase reporter gene and RNA immunoprecipitation assays. Overexpression and knockdown experiments were performed in HCC cells to examine the effects of the SNHG1/miR-376/FOXK1/Snail axis on viability, apoptosis, invasiveness, and migrating abilities. Their effects on tumor growth and metastasis were validated in nude mouse models. SNHG1 and FOXK1 were upregulated, and miR-376a was downregulated in HCC. SNHG1 knockdown contributed to suppression of HCC cell viability, invasion, and migration properties and promotion of apoptosis. SNHG1 could competitively bind to miR-376a to upregulate its target gene FOXK1, which upregulated Snail. SNHG1 knockdown delayed cancer progression both in vitro and in vivo by upregulating miR-376a and downregulating FOXK1 and Snail. SNHG1 knockdown exerts anti-tumor activity in HCC, suggesting a therapeutic target.

LncRNA SNHG3, a potential oncogene in human cancers

Long noncoding RNAs (lncRNAs) are composed of > 200 nucleotides; they lack the ability to encode proteins but play important roles in a variety of human tumors. A large number of studies have shown that dysregulated expression of lncRNAs is related to tumor oncogenesis and progression. Emerging evidence shows that SNHG3 is a novel oncogenic lncRNA that is abnormally expressed in various tumors, including osteosarcoma, liver cancer, lung cancer, etc. SNHG3 primarily competes as a competitive endogenous RNA (ceRNA) that targets tumor suppressor microRNAs (miRNAs) and ceRNA mechanisms that regulate biological processes of tumors. In addition, abnormal expression of SNHG3 is significantly correlated with patient clinical features. Upregulation of SNHG3 contributes to biological functions, including tumor cell proliferation, migration, invasion and EMT. Therefore, SNHG3 may represent a potential diagnostic and prognostic biomarker, as well as a novel therapeutic target.

KPNA2-Associated Immune Analyses Highlight the Dysregulation and Prognostic Effects of GRB2, NRAS, and Their RNA-Binding Proteins in Hepatocellular Carcinoma

Karyopherin α2 (KPNA2) was reported to be overexpressed and have unfavorable prognostic effects in many malignancies including hepatocellular carcinoma (HCC). Although its contributions to inflammatory response were reported in many studies, its specific associations with immune infiltrations and immune pathways during cancer progression were unclear. Here, we aimed to identify new markers for HCC diagnosis and prognosis through KPNA2-associated immune analyses. RNA-seq expression data of HCC datasets were downloaded from The Cancer Genome Atlas and International Cancer Genome Consortium. The gene expressions were counts per million normalized. The infiltrations of 24 kinds of immune cells in the samples were evaluated with ImmuCellAI (Immune Cell Abundance Identifier). The Spearman correlations of the immune infiltrations with KPNA2 expression were investigated, and the specific positive correlation of B-cell infiltration with KPNA2 expression in HCC tumors was identified. Fifteen genes in KEGG (Kyoto Encyclopedia of Genes and Genomes) B-cell receptor signaling pathway presented significant correlations with KPNA2 expression in HCC. Among them, GRB2 and NRAS were indicated to be independent unfavorable prognostic factors for HCC overall survival. Clinical Proteomic Tumor Analysis Consortium HCC dataset was investigated to validate the results at protein level. The upregulation and unfavorable prognostic effects of KPNA2 and GRB2 were confirmed, whereas, unlike its mRNA form, NRAS protein was presented to be downregulated and have favorable prognostic effects. Through receiver operating characteristic curve analysis, the diagnostic potential of the three proteins was shown. The RNA-binding proteins (RBPs) of KPNA2, NRAS, and GRB2, downloaded via The Encyclopedia of RNA Interactomes, were investigated for their clinical significance in HCC at protein level. An eight-RBP signature with independent prognostic value and dysregulations in HCC was identified. All the RBPs were significantly correlated with MKI67 expression and at least one of KPNA2, GRB2, and NRAS at protein level in HCC, indicating their roles in HCC progression and the regulation of the three proteins. We concluded that KPNA2, GRB2, NRAS, and their RBPs might have coordinating roles in HCC immunoregulation and progression. They might be new markers for HCC diagnosis and prognosis predication and new targets for HCC immunotherapy.

Long Intergenic Non-Protein Coding RNA 1094 Promotes Initiation and Progression of Glioblastoma by Promoting microRNA-577-Regulated Stabilization of Brain-Derived Neurotrophic Factor

Purpose

The long intergenic non-protein coding RNA 1094 (LINC01094) plays a vital role in the oncogenicity of clear cell renal cell carcinoma. However, its expression profile and detailed roles in glioblastoma (GBM) remain unknown. In this study, we mainly investigated the expression and roles of LINC01094 in GBM and focused on the mechanism by which LINC01094 regulates the malignant characteristics of GBM.

Patients and Methods

LINC01094 expression in GBM was determined with quantitative reverse transcription polymerase chain reaction. The proliferation, apoptosis, migration, invasion in vitro, and tumor growth in vivo of GBM cells were evaluated using Cell Counting Kit-8 assay, flow cytometry analysis, migration assay, invasion assay, and tumor xenograft models, respectively.

Results

LINC01094 was overexpressed in GBM tissues and cell lines. Moreover, increased LINC01094 expression was associated with adverse clinicopathological parameters in patients with GBM. Loss of LINC01094 inhibited GBM cell proliferation, migration, and invasion; promoted cell apoptosis; and suppressed tumor growth in vivo. Mechanically, LINC01094 functioned as a molecular sponge for microRNA-577 (miR-577) and consequently enhanced the expression of brain-derived neurotrophic factor (BDNF) in GBM cells. Both miR-577 inhibition and BDNF expression enhancement reversed LINC01094 deficiency-mediated inhibition of malignant processes in GBM cells.

Conclusion

Our results verified the involvement of the LINC01094/miR-577/BDNF pathway in GBM cells and its enhancing effects on the aggressive behaviors of GBM cells in vitro and in vivo. This pathway may be a novel and promising focus for the future development of targeted therapies for GBM.

Circular RNA hsa_circ_0003141 promotes tumorigenesis of hepatocellular carcinoma via a miR-1827/UBAP2 axis

Circular RNAs (circRNAs) play an important role in the tumorigenesis of hepatocellular carcinoma (HCC), but their specific functions in HCC remain largely unknown. Using bioinformatics analysis, we have found that the expression of circRNA hsa_circ_0003141 is significantly increased in HCC tissues. Ubiquitin-associated protein 2 (UBAP2) is the parent gene for hsa_circ_0003141, and its high expression correlates with poor overall survival rates in HCC patients. In addition, our results show that miR-1827 is a binding target of hsa_circ_0003141, and indicate that hsa_circ_0003141 regulates UBAP2 expression by sponging miR-1827 in HCC cells. Downregulation of hsa_circ_0003141 suppresses UBAP2 expression, induces apoptosis, and inhibits proliferation and invasion by HCC Huh-7 cells. Importantly, downregulation of hsa_circ_0003141 inhibits tumorigenesis in a xenograft mouse model of HCC. Together, our results indicate that hsa_circ_0003141 functions as an oncogene in HCC cells, and suggest that the hsa_circ_0003141/miR-1827/UBAP2 axis might represent a novel therapeutic option for the treatment of HCC.

A Novel Polysaccharide Depolymerase Encoded by the Phage SH-KP152226 Confers Specific Activity Against Multidrug-Resistant Klebsiella pneumoniae via Biofilm Degradation

The increasing prevalence of infections caused by multidrug-resistant Klebsiella pneumoniae necessitates the development of alternative therapies. Here, we isolated, characterized, and sequenced a K. pneumoniae bacteriophage (SH-KP152226) that specifically infects and lyses K. pneumoniae capsular type K47. The phage SH-KP152226 contains a genome of 41,420 bp that encodes 48 predicted proteins. Among these proteins, Dep42, the gene product of ORF42, is a putative tail fiber protein and hypothetically possesses depolymerase activity. We demonstrated that recombinant Dep42 showed specific enzymatic activities in the depolymerization of the K47 capsule of K. pneumoniae and was able to significantly inhibit biofilm formation and/or degrade formed biofilms. We also showed that Dep42 could enhance polymyxin activity against K. pneumoniae biofilms when used in combination with antibiotics. These results suggest that combination of the identified novel depolymerase Dep42, encoded by the phage SH-KP152226, with antibiotics may represent a promising strategy to combat infections caused by drug-resistant and biofilm-forming K. pneumoniae.