Burkitt-like mutations in the c-myc gene locus in prolymphocytic leukemia.

The c-myc oncogene recently shown to act as a transcription factor, is involved in cellular proliferation. Deregulation of this gene can be one step in malignant transformation. In Burkitt's lymphoma (BL) the c-myc gene is consistently involved in chromosomal translocations and the first exon of the gene has been found to be a frequent target of somatic mutations. These mutations are believed to interfere with normal transcriptional regulation of the gene. We demonstrate a case of the rare prolymphocytic leukemia (PLL), a variant of chronic lymphocytic leukemia (CLL), that shows multiple Burkitt-like mutations in the first exon of c-myc and one nonconservative point mutation in the coding exon 2. Cytogenetic analysis revealed involvement of both chromosomes 8 in chromosomal translocations. Both chromosomes 8 are broken at (q23), the c-myc gene locus. Since the patient's leukemia cells exhibited high expression levels of the mutated allele of the c-myc mRNA, the point mutations alone may have accounted for transcriptional deregulation.