Unexpected favorable outcome in a patient with high grade B-cell lymphoma with abnormalities of MYC, BCL6 and BCL2 loci

Chromosomal Aberration t(14;17)(q32;q21) Simultaneously Activates HOXB5 and miR10a in Triple-Hit B-Cell Lymphoma

BCL2, BCL6 and MYC are major oncogenes in B-cell lymphoma. Their aberrant activation frequently occurs via chromosomal translocations which juxtapose light or heavy chain immunoglobulin (IG) genes to BCL2 and MYC or fuse diverse partner genes with BCL6. So-called double-hit lymphomas usually carry BCL2 and MYC rearrangements, while triple-hit lymphomas additionally bear BCL6-fusions. All these translocations are of diagnostic relevance and usually denote poor prognosis. Here, we genomically characterized classic follicular lymphoma (FL) cell line SC-1, thereby identifying t(14;18)(q32;q21) juxtaposing IGH and BCL2, t(8;14)(q24;q32) juxtaposing IGH and MYC, and t(3;3)(q25;q27) fusing MBNL1 to BCL6. In addition, we found that SC-1 carries a novel chromosomal rearrangement, t(14;17)(q32;q21), which, though present at establishment, has remained unreported until now. We further show that t(14;17)(q32;q21) juxtaposes IGH with the HOXB gene cluster at 17q21 and affect the oncogenic activation of both homeobox gene HOXB5 and neighboring micro-RNA gene miR10a. Moreover, we detected aberrant overexpression of HOXB5 in subsets of Burkitt lymphoma, FL, and multiple myeloma patients, confirming the clinical relevance of its deregulation. In SC-1, HOXB5 activation was additionally supported by co-expression of hematopoietic stem cell factor ZNF521, indicating an aberrant impact in cell differentiation. Functional investigations showed that HOXB5 represses the apoptotic driver BCL2L11 and promotes survival in the presence of etoposide, and that miR10a inhibits BCL6 and may thus play an oncogenic role in later stages of lymphomagenesis. Collectively, we characterize triple-hit B-cell line SC-1 and identify the aberrant expression of HOXB5 and miR10a, both novel oncogenes in B-cell lymphoma.