RUNX3 expression levels in AML patients and cell lines. (A) RUNX3 mRNA levels in 73 diagnostic BM from AML patients were determined by real-time RT-PCR and normalized using GAPDH. Patients were divided into 4 subgroups: (1) t(8;21)-positive; (2) inv(16)-positive; (3) t(8;21)- and inv(16)-negative M2/M4; and (4) t(8;21)- and inv(16)-negative non-M2/M4. The number of patients in each subgroup is shown. The horizontal line indicates the mean RUNX3/GAPDH ratio. (B) Correlation analysis between RUNX3 mRNA levels and the levels of RUNX1-ETO and CBFβ-MYH11 fusion transcripts. RUNX1-ETO and CBFβ-MYH11 levels in the t(8;21) and inv(16)-positive patients were determined by real-time RT-PCR and normalized using GAPDH. Of the 8 inv(16)-positive patients, 7 cases express the common type A transcript (also expressed by ME-1), and 1 case expresses the type D transcript,³²  which was not amplified by the type A primer set and was excluded from the analysis. r indicates Pearson correlation coefficient. (C) Real-time RT-PCR (top panel) and immunoblot (bottom panel) analysis of RUNX3 expression in Kasumi-1, ME-1, and MV4-11 cell lines, which represent different subgroups of AML. For real-time RT-PCR, results are expressed as mean plus or minus SD from triplicate assays. The mean RUNX3/GAPDH mRNA ratio was 0.002 for ME-1. *P < .001. For immunoblot, the image was assembled from different lanes in the same film.