Unexpectedly, the anti-progranulin Ab detected the 88 kDa progranulin as well as a distinct 105 kDa progranulin isoform (Figure 11A): AML patient samples (n = 9) in which NGR-peptide-1 induced cell death (> 20%) expressed both isoforms or the 88 kDa isoform alone (Figure 11A), whereas NGR-peptide-1-resistant samples (n = 4) preferentially expressed the 105 kDa isoform (Figure 11A). The gene discussed is RTN4R; the disease is acute myeloid leukemia.