13Q DELETIONS IN LYMPHOID MALIGNANCIES

Previous studies have indicated that a candidate tumor suppressor gene resides telomeric of the RB1 gene at 13q14, a region that is commonly deleted in B-cell chronic lymphocytic leukemia (B-CLL). In this study , we have evaluated the frequency and minimal region of overlap for 13 q deletions in malignant cells from various lymphoid neoplasms. We obs erved losses at 13q14 in 33/75 (44%) B-CLL cases, four of 16 (25%) non -Hodgkin's lymphoma (NHL) cases, eight of 29 (28%) patients with acute lymphocytic leukemia (ALL), and one of 15 T-cell lines. In some ALL c ases, inactivation of the RB1 gene is suggested as the important event in the 13q deletions. The most commonly deleted marker in CLL and NHL was D13S319, between RBkpt and the D13S25 loci. Homozygous deletions of this marker were observed in 10 of 75 B-CLL cases, in six of which the homozygous deletions included only the D13S319 locus. Our data sug gest that 13q deletions are common in lymphoid neoplasms, and that del etion of a candidate tumor suppressor gene(s) in the vicinity of the D 13S319 marker is a tumorigenic event in these diseases. (C) 1995 by Th e American Society of Hematology.