Ethics statement
This study was approved by the Academic Committee of Tongji University. All of the datasets were retrieved from the online databases and published literature, so it was confirmed that all written informed consent had been obtained.
ONCOMINE database
The mRNA expression of PCK1 in HCC was analyzed within the Oncomine database (www.oncomine.org), an integrated online cancer microarray database [22-24]. This analysis included these studies of Chen Liver [14], Roessler Liver 2, Roessler Liver [15] and Wurmbach Liver [16]using a Student’s t test. The cutoff of p value and fold change were defined as 0.05 and 2, respectively.
UALCAN
The relative expression of PCK1 between HCC tumors and normal liver tissues, with individual cancer stages, tumor grade or other clinicopathological features was analyzed by UALCAN [25] (http://ualcan.path.uab.edu), which was an interactive web-portal covering level 3 RNA-seq and clinical data from 31 cancer types via TCGA.
Human Protein Atlas
The expression of PCK1 at protein level between human HCC tumors and normal tissues was shown as immunohistochemistry image, which derived from the Human Protein Atlas (https://www.proteinatlas.org). The Human Protein Atlas was a website focusing on a particular aspect of the genome-wide analysis of the human proteins covering common kinds of cancers and normal tissues [26].
Western blot
Tissues were lysed with lysis buffer and harvested. The loading samples were quantified with BCA protein quantification kit (Yeasen). The equal tissue lysates were prepared for sodiumdodecyl sulfate-polyacrylamide gel (SDS-PAGE) electrophoresis and then transferred to nitrocellulose (NC) membranes (Millipore, Billerica, MA, USA). The NC membranes were blocked with 5% non-fat milk then incubated with the primary antibodies at 4°C overnight. Next, the membranes incubated with horseradish peroxidase-labelled secondary antibody (Abcam). The protein bands were detected with the enhanced chemiluminescence kit (Beyotime).
Kaplan-Meier Plotter
The prognostic value of PCK1 expression at mRNA level in HCC was analyzed by using Kaplan Meier plotter (http://kmplot.com/analysis/), which is capable to assess the effects of 54k genes on survival in 21 cancer types [27-30]. The largest datasets include breast cancer, ovarian cancer, lung cancer, and gastric cancer. The Information including the number-at-risk cases, median values of mRNA expression levels, HRs, 95% CIs and p-values was shown on the K-M plotter chart. Statically significant difference was considered when a p value < 0.05.
Xenograft tumor mice
The male nude mice (5~6 weeks old) were used for the subcutaneous xenograft model. Hepatoma cells were injected subcutaneously into the flanks of nude mice (1×105cells/inoculation). For tumor weight analysis, mice were sacrificed and tumors tissues were obtained for assessment. Tumor volumes were measured every seven days after inoculation. All animal experimental procedures were approved by the Institutional Animal Care and Use Committee of Tongji University School of Medicine.
cBioPortal
The cBio Cancer Genomics Portal (http://cbioportal.org) is an open-access website including data sets of multidimensional cancer genomics [31]. We used c-BioPortal to analyze PCK1 alterations in the TCGA liver hepatocellular carcinoma (LIHC) samples.
LinkedOmics
LinkedOmics ((http://www.linkedomics.orglogin.php) is publicly available portal that includes multi-omics data from all 32 TCGA Cancer types [32]. Our study used the LinkInterpreter module to perform enrichment analysis based on Gene Ontology, biological pathways, network modules, among other functional categories.
GeneMANIA
GeneMANIA is a website for constructing protein protein interaction (PPI) network by using a large amount of functional association data [33]. These association data include protein and genetic interactions, pathways, co-expression, co-localization and protein domain similarity. In our study we analyzed PCK1 associated genes networks and the predicted potential functions by using GeneMANIA.
CCLE
CCLE ( https://www.broadinstitute.org/ccle) is a website providing public access to genomic data, analysis, and visualization for about 1,457 cell lines, which was founded by the Broad Institute and the Novartis Institutes for Biomedical Research and its Genomics Institute of the Novartis Research [34]. PCK1 expression at mRNA level in cancer cell lines was investigated by the CCLE dataset.
EMBL-EBI
EMBL-EBI (https://www.ebi.ac.uk) is an open science resource providing information about gene and protein expressions across species and biological conditions such as different tissues, cell types, developmental stages and diseases [35]. PCK1 expression at mRNA level in cancer cell lines was investigated by the EMBL-EBI dataset.