Preliminary characterization of FGFR2 expression in SUM-52PEcells. (a) Exon III-specific primers were used in RT-PCR of SUM-52PE RNA.RT-PCR product was then digested with Ava I or Hinc II at 37°C overnightand then resolved on a 3% NuSieve gel. Exon IIIb contains one unique Ava Isite, whereas exon IIIc contains two Hinc II sites, and therefore theproportion of Ava I digest fragments to Hinc II digest fragments determines theproportion of IIIb to IIIc variants present. The presence of 269 and 188 bpfragments generated by Ava I digestion (lane 2) and lack of Hinc II digestedproducts (lane 3) confirms the exclusive presence of exon IIIb in FGFR2variants in the SUM-52PE cell line. (b) SUM-52PE mRNA was reverse transcribedusing an oligo dT primer, and then amplified using a 5' -FGFR2-specificprimer and a 3' -specific primer for C1/C2 or C3. Equimolar amounts ofprimer were used in the PCR reaction, and then 2 or 5 μ l of PCR productwere compared on a 0.8% agarose gel. Lane 1, 2 μ l C1/C2 product; lane 2,5μ l C1/C2 product; lane 3, 2 μ l C3 product; lane 4, 5 μ l C3product.