DETECTION OF BCL-6 REARRANGEMENTS AND P53 MUTATIONS IN MALT-LYMPHOMAS

Twenty-seven lymphomas of mucosa-associated lymphoid tissue (MALT) der ived from distinct anatomical sites were tested for the presence of ge netic lesions commonly involved in B-cell lymphomagenesis, including a ctivation of proto-oncogenes (BCL-1, BCL-2, BCL-6, and c-MYC), disrupt ion of tumor suppressor loci (p53, 6q), and infection by viruses [Epst ein-Barr virus (EBV), and Kaposi's sarcoma-herpesvirus/human herpesvir us-8 (KSHV/HHV-8)]. Sixteen low-grade and 11 high-grade MALT-lymphomas were included in the study. The presence of genetic lesions was teste d by a combination of molecular approaches, including Southern blot hy bridization, polymerase chain reaction (PCR), and PCR-single strand co nformation polymorphism followed by DNA direct sequencing. Alterations of BCL-1, BCL-2, or c-MYC, as well as infection by KSHV/HHV-8, scored negative in all MALT-lymphomas analysed. Conversely, rearrangements o f BCL-6 and mutations of p53 clustered with a fraction of high-grade M ALT-lymphomas, Deletions of 69 occurred in selected cases of both low- and high-grade MALT-lymphomas, whereas a monoclonal infection by EBV w as restricted to one single patient, These data corroborate the notion that the molecular pathogenesis of MALT-lymphomas differs substantial ly from that of nodal B-cell lymphomas. Occasionally, however, a propo rtion of high-grade MALT-lymphomas may harbor selected genetic lesions among the ones commonly involved in nodal B-cell lymphomagenesis. (C) 1997 Wiley-Liss, Inc.