Expression of p16INK4A and p14ARF in hematological malignancies

The INK4A/ARF locus yields two tumor suppressors, p16INK4A and p14ARF, and is frequently deleted in human tumors. We studied their mRNA expressions in 41 hematopoietic cell lines and in 137 patients with hematological malignancies; we used a quantitative reverse transcription-PCR assay. Normal peripheral bloods, bone marrow and lymph nodes expressed little or undetectable p16INK4A and p14ARF mRNAs, which were readily detected in 12 and 17 of 41 cell lines, respectively. Patients with hematological malignancies frequently lacked p16INK4A expression (60/137) and lost p14ARF expression less frequently (19/137, 13.9%). Almost all patients without p14ARF expression lacked p16INK4A expression, which may correspond to deletions of the INK4A/ARF locus. Undetectable p16INK4A expression with p14ARF expression in 41 patients may correspond to p16INK4A promoter methylation or to normal expression status of the p16INK4A gene. All patients with follicular lymphoma (FL), myeloma or acute myeloid leukemia (AML) expressed p14ARF while nine of 23 patients with diffuse large B cell lymphoma (DLBCL) lost p14ARF expression. Patients with ALL, AML or blast crisis of chronic myelogenous leukemia expressed abundant p16INK4A mRNAs more frequently than patients with other diseases (12/33 vs 6/104, P < 0.01). Patients with FL and high p14ARF expression had a significantly shorter survival time while survival for patients with DLBCL and increased p14ARF expression tended to be longer. These observations indicate that p16INK4A and p14ARF expression is differentially affected among hemato- logical malignancies and that not only inactivation but also increased expression may have clinical significance.