Two-color FISH analysis of normal lymphocytes and 2 MM cell lines. (A) P1 clones containing the c-maf gene (red signal) and chromosome 16 sequences from the JJN3 MM t(14;16) breakpoint (green signal) were hybridized to metaphase chromosomes (counterstained blue) and interphase nuclei from normal lymphocytes. The signals colocalize at chromosome band 16q23. (B) A chromosome 14 painting probe (red signal) and a c-maf P1 clone (green signal) were hybridized to metaphase chromosomes from the OCI-My5 MM cell line. There are no normal copies of chromosome 14 or 16. One copy of c-maf (arrowhead) has been translocated to the telomeric end of chromosome 14 at band q32, consistent with a t(14;16)(q32;q23) translocation, involving the IgH locus and c-maf, respectively. A second copy of c-maf (arrow) is translocated to a structurally altered, unidentified chromosome. (C) A chromosome 22 painting probe (red signal) and a c-maf P1 clone (green signal) were hybridized to metaphase chromosomes from the 8226 MM cell line. There are 4 copies of the c-maf gene, 2 of which have chromosome 22 sequences translocated telomeric to c-maf (arrowhead), whereas 2 are on a normal chromosome 16 (arrow). The breakpoint on chromosome 22 is consistent with a t(16;22)(q23;q11) translocation near the c-maf and IgL, λ loci, respectively.