Loss of bHLH transcription factor E2A activity in primary effusion lymphoma confers resistance to apoptosis.

Similar to classical Hodgkin lymphoma (HL) tumour cells, primary effusion lymphoma (PEL) originates from mature B cells but displays a non-B cell phenotype, the mechanisms and consequences of which are not yet understood. This study showed that PEL lacked DNA binding activity of the B cell-determining transcription factors E2A, EBF and Pax5. PEL overexpressed the E2A antagonists ABF-1 and Id2, which have been described to block the B-cell differentiation program in classical HL. However, in contrast to HL cells, B lineage-inappropriate genes were not similarly upregulated in PEL, and reconstitution of B cell-specific E2A homodimer activity in PEL induced apoptosis. These data demonstrate that lineage infidelity in PEL is not as pronounced as in HL, and that the loss of the B cell-specific transcription factor E2A in PEL is implicated in apoptosis protection.