Expression analysis of gastric cancer associated genes in BPIFB2 stable cell lines / Nur Amira Zulkifli

Gastric cancer (GC) is one of the leading causes of cancer morbidity worldwide. Most GC cases are detected at a later stage with poor prognosis and much of the molecular mechanism involved is poorly understood. Bactericidal/Permeability-Increasing Fold containing family B member 2 (BPIFB2) belongs to the lipid transfer/lipopolysaccharide binding protein where the gene and protein mainly express in the oral cavity, nasopharyngeal region, and stomach. Currently, limited data is available on BPIFB2. Differential expression of BPIFB2 was reported in diseases such as mucoepidermoid carcinoma and oral squamous cell carcinoma and its exact function and role in GC has never been investigated. However, preliminary gene expression study showed that the gene is differentially expressed in GC tissue. This study aims to investigate the role of BPIFB2 in GC as well as its association with other GC-related genes by using gene expression analysis and to generate GC cell lines stably overexpressing BPIFB2 as in vitro models for GC research. Generation of BPIFB2 expression vector construct (designated MEX6BP2) was carried out using pcDNA™6.2/cLumio™-DEST plasmid and the GC cell lines (AGS, HGC-27, MKN45) were transfected with MEX6BP2 using Turbofect™ transfection reagent. BPIFB2 stable cell lines of AGS, HGC-27 and MKN45 cells were successfully generated whereby the expression vector was integrated into the genome of the cells. Subsequently, fluorescence and confocal microscopy were carried out to determine the localisation of BPIFB2 in the GC cells, the Lumio-tagged BPIFB2 protein were mostly found localised in the cytoplasm. By using real-time QPCR, the baseline and differential expression levels of BPIFB2 in relation to other GC-associated genes were measured. QPCR analysis showed significant increase of BPIFB2 level in the transfected GC cell lines (all having p=.001*) which then caused differential expression of the GC-associated genes. In AGS cells, BPIFB2 overexpression significantly downregulated expression levels of the GC-associated genes, whereby BPIFB1, CDH1, CDH2, SNAI1, and VIM have a p-value of p=.001* while MUC5AC has p=.049*. In HGC-27 cells, upregulation of BPIFB1 (p=.708), CDH2 (p=.075), and SNAI1 (p=.085), were not significant, only CDH1 (p=.015*) upregulation together with VIM (p=.027*) and MUC5AC (p=.001*) downregulation were significant. In MKN45 cells, BPIFB1 (p=.002*), CDH1 (p=.001*), SNAI1 (p=.001*), and VIM (p=.001*) expression levels were increased significantly except for CDH2 (p=.106*) while MUC5AC (p=.001*) was significantly downregulated. In conclusion, we have successfully generated AGS, HGC-27, and MKN45 cell lines stably overexpressing BPIFB2 to be used as in vitro models for GC research. We also demonstrated molecular cross-talking between BPIFB2 and the GC-associated genes in these GC cells and these findings may help in elucidating the exact role and function of BPIFB2 in GC.