FOXO1 repression contributes to block of plasma cell differentiation in classical Hodgkin lymphoma.

The survival of classical Hodgkin lymphoma (cHL) cells depends on activation of NF-κB, JAK/STAT, and IRF4. Whereas these factors typically induce the master regulator of plasma cell (PC) differentiation PRDM1/BLIMP-1, levels of PRDM1 remain low in cHL. FOXO1, playing a critical role in normal B-cell development, acts as a tumor suppressor in cHL, but has never been associated with induction of PC differentiation. Here we show that FOXO1 directly upregulates the full-length isoform PRDM1α in cHL cell lines. We also observed a positive correlation between FOXO1 and PRDM1 expression levels in primary Hodgkin-Reed-Sternberg cells. Further, we show that PRDM1α acts as a tumor suppressor in cHL at least partially by blocking MYC. Here we provide a link between FOXO1 repression and PRDM1α downregulation in cHL and identify PRDM1α as a tumor suppressor in cHL. The data support a potential role for FOXO transcription factors in normal PC differentiation.