Chromosome 1 abnormalities in multiple myeloma.

Multiple myeloma (MM) is a malignancy of the terminally-differentiated B cells and accounts for 10% of all hematological malignancies. Chromosome 1 aberrations are frequently described, the short arm being preferentially involved in deletions and the long arm in gains. The abnormalities were identified in the bone marrow of 37 MM patients by conventional cytogenetics. Fluorescence in situ hybridization (FISH) was used to confirm the presence of the abnormalities and to better characterize them. Chromosome 1 abnormalities were grouped into 4 categories: balanced translocations, deletions, amplifications and jumping translocations (JT). Breakpoints involved in balanced translocations were randomly distributed. The smallest region of overlap for deletions was 1p11 --> 1p21 (present in 27% of the patients) and for gains 1q31 --> 1qter (present in 54% of the patients). The whole long arm was found to be the donor segment for the majority of patients with JT, the most frequent recipients being chromosomes 16 and 19. Our results share some similarities with those obtained for 143 published patients studied by FISH. Band 1p21 was found to be frequently deleted, leading to the assumption that a 1p deletion could lead to hemizygosity of at least 1 tumor suppressor gene. Two regions of 1q showed preferential gains: q12 to q22 and q31 to q42; these amplifications could induce the overexpression of 1 or more oncogenes. In conclusion, our results confirm that chromosome 1 abnormalities play an important role in the pathogenesis of multiple myeloma.