Formation of a hybrid bcl-2/immunoglobulin transcript as a result of t(14;18) chromosomal translocation.

Specific chromosomal changes are consistently associated with several morphologically or histologically distinct forms of cancer [1]. In a few hematolymphoid malignancies, chromosomal translocations are known to occur near or within the cytologic loci for cellular homologues of retroviral-encoded oncogenes [2]. For example, both the c-abl and c-myc proto-oncogenes are targets for interchromosomal translocations in chronic myelogous leukemia and Burkitt's lymphoma, respectively [3, 4]. Recent molecular studies have elucidated the structural consequences that chromosomal translocations have upon these cellular proto-oncogenes [5-7]. However, most of the recurring chromosomal translocations which have been described, particularly in hematolymphoid malignancies, do not result in structural alterations of cellular homologues for known retroviral oncogenes. Presumably these cytogenetic abnormalities affect cellular genes which have not been transduced by retroviruses and therefore remain largely undefined. One approach toward isolation and characterization of these candidate human proto-oncogenes is to clone from appropriate tumors chromosomal transloca-