Quantification of CXCR4 and β-actin mRNA

Expression level of mRNAs of CXCR4 and β-actin was evaluated in AGS cells. The reverse transcription-polymerase chain reaction (RT-PCR) procedures were carried out as previously reported [19 (link)]. Briefly, RNA was isolated using RNA extraction kit (Bioflux, Basel, Switzerland) and then transcribed into cDNA using Bioneer kit (Bioneer, Daejeon, South Korea). The RT-PCR was performed using primer sequences for human CXCR4 and β-actin (housekeeping gene) as listed in Table 1 and a thermocycler (Mastercycler, Eppendorf, Westbury, NY). Finally PCR products were electrophoresed on a 2% agarose gel containing ethidium bromide and gels were visualized under ultraviolet light using gel Documentation System (Bio-Rad, München, Germany).