Lack of BIC and microRNA miR-155 Expression in Primary Cases of Burkitt Lymphoma.

We previously demonstrated a high expression of primary-microRNA BIC (pri-miRNA-155) in Hodgkin lymphoma (HL) and lack of expression in most non-Hodgkin lymphoma subtypes including some Burkitt lymphoma (BL) cases. Recently, a high expression of BIC was reported in BL in comparison to pediatric leukemia and normal peripheral blood samples. In this study we extended our series of BL cases and cell lines for BIC expression by RNA in-situ hybridization (ISH) and quantitative (q)RT-PCR. Both BIC RNA-ISH and qRT-PCR revealed no or only low levels of BIC in 25 BL tissues, including 7 Epstein-Barr virus (EBV) positive cases, compared to HL and normal controls. In agreement with these findings, Northern blotting revealed absence of miR-155 in BL tissues. EBV negative and EBV latency type I BL cell lines also showed very low BIC and miR-155 expression levels as compared to HL cell lines. Higher levels of BIC and miR-155 were detected in in vitro transformed lymphoblastoid EBV latency type III BL cell lines. An association of latency type III infection and induction of BIC was supported by consistent expression of BIC in 11 and miR-155 in 2 posttransplantation lymphoproliferative disorder (PTLD) cases. In summary, we demonstrated that expression of BIC and miR-155 is not a common finding in BL. Expression of BIC and miR-155 in 3 latency type III EBV positive BL cell lines and in all primary PTLD cases suggests a possible role for EBV latency type III specific proteins in the induction of BIC expression.