BACR 6: Expression of the transcription factor NFIL3 contributes to malignant B-cell survival in multiple myeloma and Hodgkin lymphomas

Simon Brooks1,Duncan Gascoyne1,Linden Lyne1,Demin Li1,Elizabeth Soilleux1,Alison Banham1

1University of Oxford, Oxford, UK

Presenting date: Monday 2 November
Presenting time: 13.10-14.00

Background

Aberrant gene expression profiles characterise many haematological malignancies. B-cell program inhibition by factors such as ID2 and ABF-1 is a hallmark of Hodgkin’s lymphoma (HL); suggesting inhibitors of B-cell commitment functionally contribute to lymphoma pathogenesis. NFIL3/E4BP4 has reported roles in various immune cells. Its overexpression in murine haematopoietic progenitor cells reduces the B-cell population, suggesting Nfil3 inhibits B-cell development. To date, NFIL3 has not been studied in lymphoma.

Method

NFIL3 expression in cell lines, normal human tissues and primary biopsies was characterised using immunohistochemistry and Western blot. NFIL3 transcript expression was analysed by qPCR in cell lines. siRNA-mediated NFIL3 depletion and plasmid-mediated overexpression was used to assess its function in cell lines. Differentially expressed genes following NFIL3 depletion were identified by Affymetrix transcriptome microarray.

Results

NFIL3 in normal tissues was largely restricted to the cytoplasm of infiltrating immune cells, including plasma cells. In haematological cell lines and primary patients’ samples nuclear NFIL3 expression was observed in primary mediastinal B-cell lymphoma (PMBCL), HL and multiple myeloma (MM). Some MM exhibited cytoplasmic positivity. Other B- and T-cell malignancies lacked NFIL3 expression. NFIL3 depletion reduced cell viability by ~30% in MM cell lines, with HL cell lines showing less effect at 48 hours post-transfection. In the case of MM, this was found to be at least in part due to a reduction in proliferation. Microarray profiling of the MM cell lines has identified differentially expressed genes, several of which have relevance to MM biology.

Conclusion

The pattern of NFIL3 expression in PMBCL, HL and MM correlates with their lack or down-regulation of BCR signalling components. The reduced cell viability on silencing suggests NFIL3 is important for tumour cell survival, and the underlying mechanism is being investigated further. Modulating NFIL3 or activity of its targets may have future therapeutic potential in these diseases.