Levels of TCL1 in CLL correlate with other features of aggressive disease. (A) Increased expression of TCL1 (graded on immunoblots after normalization to β-actin levels) significantly correlated with tumor-cell ZAP70 immunohistochemical expression, unmutated IGHV gene mutational status, surface CD38 levels, and deletions of the chromosome 11q22-23 region. (B) TCL1 levels, using a 4-tier score described in “Methods,” showed a strong positive correlation with the percentage of sIgM⁺ CLL cells analyzed at the time of TCL1 measurement.