Next, the ratio of Ex4a(+)WT1 isoform to 17AA(+) WT1 isoform was determined by RT-PCR using Ex4-forward and Ex6-reverse primer pair in WT1-expressing cancer cell lines (LU99B and K562) and determined to be approximately 1/2 and 1/4 in LU99B and K562 cancer cells, respectively (Fig 4D). This evidence concerns the gene WT1 and cancer.