Among the limited set of genes associated with MD oncogenicity, MDV-miR-M4, a highly expressed viral ortholog of the oncogenic miR-155, has received extensive attention due to its direct role in the induction of lymphomas.
Moreover, miR155 enhanced lymphoma cell PD-L1 expression, recruited CD8+T cells by PD-1/PD-L1 interaction and inhibited CD8+T cell function via dephosphorylating AKT and ERK.
These findings provide important insights that will improve our understanding of miR-155 control in B cell malignancies.<b>IMPORTANCE</b> MicroRNA miR-155 is expressed at high levels in many human cancers, particularly lymphomas.
miR-155, a microRNA associated with poor prognosis in lymphoma and leukaemia, has been implicated in the progression of mycosis fungoides (MF), the most common form of cutaneous T-cell lymphoma (CTCL).
These results indicated that LMP1 and miR-155 may be novel and reliable biomarkers for the prognostic prediction of lymphoma, and will potentially be analyzed in the future to evaluate patient prognosis.
A number of studies have shown that miR-155can not only regulate cell proliferation, apoptosis and lymphoma progression, but also plays an important part in various other physiological and pathological processes.
Knock-in mice with a LAT mutation impairing calcium flux develop a fatal CD4+ lymphoproliferative disease. miR-155 is a microRNA that is correlated with hyperproliferation in a number of cancers including lymphomas and leukemias and is overexpressed in mutant LAT T cells.
To test if methylation of miR-155-3p was MCL-specific, miR-155-3p methylation was tested in an additional 191 B-cell, T-cell and NK-cell NHLs, yielding miR-155-3p methylation in 66(34.6%) including 36(27%) non-MCL B-cell, 24(53%) T-cell and 6(46%) of NK-cell lymphoma.
Relevant clinical variables were retrieved in a subset of 57 patients (28 cutaneous marginal zone B-cell lymphomas and 29 primary cutaneous centrofollicular lymphomas). miR-150 was upregulated in cutaneous marginal zone B-cell lymphomas relative to primary cutaneous centrofollicular lymphoma samples (false discovery rate <0.05). miR-155 and miR-150 expression levels were associated with progression-free survival in a univariate Cox regression analysis (P<0.1).
Dysregulation of other miRNA, including miR-21, miR-29, miR-150 and miR-155, have also been shown to play crucial roles in the pathogenesis of aggressive transformed, high-grade and refractory lymphomas.
Furthermore, this effect may contribute to lymphoma cell dissemination and aggressiveness, characteristic of activated B cell-like diffuse large B-cell lymphoma typically expressing high levels of miR-155 and lacking HGAL expression.
We recently reported that overexpression of miR-21 and/or miR-155 leads to activation of the phosphoinositide 3-kinase (PI3K)-AKT pathway in malignant lymphomas expressing CD3(-)CD56(+) natural killer (NK) cell antigen.
This loss of oncogenicity appeared to be primarily due to the single miRNA within the cluster, miR-M4, the ortholog of cellular miR-155, since its deletion or a 2-nucleotide mutation within its seed region was sufficient to inhibit the induction of lymphomas.
Collectively, these results provide important new insight into the pathogenesis of NK-cell lymphoma/leukemia and suggest targeting miR-21 and/or miR-155 may represent a useful approach to treating NK-cell lymphoma/leukemia.