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R. Foà - Potential role of miRNAS in IgM-mediated signal transduction in normal and neoplastic B cells
Results
We are analyzing preliminary data. In particular,
gene expression profile results have highlighted an
upregulation of genes involved in proliferation, cell
cycle induction and apoptosis only in IgVH-unmu tated CLL cases, while no changes are observed in
IgVH-mutated CLL cases. These data have been
confirmed by evaluating cell cycle progression and
apoptosis function in neoplastic cells following BCR
engagement and suggest that BCR stimulation with
IgM is effective only in IgVH-unmutated CLL. In
particular, we analyzed 6 CLL cases and in 3 with
unmutated IgVH we found an increased number of
cycling cells after IgM stimulation; on the contrary,
no significant differences were observed in mutated
IgVH cases. All data concerning the gene expression
modulation after 24 hours of stimulation are in
agreement with our published data (Guarini et al.,
Blood 2008, 112:782-92). After 48 hours of stimulation,
gene expression profile analysis showed a similar
pattern. No significant changes were observed.
The analysis of miRNA expression profile was performed
in 4 CLL cases, 2 with unmutated IgVH and
2 with mutated IgVH genes, and in a pool of 6 (normal)
B cells samples obtained from healthy donors.
The data are expressed as change fold of unstimu-
98
lated/stimulated cells. The first approach of statistical
elaboration of the results shows that 47 miRNA
are differentially expressed. The differences seem
more significant after 48 hours of IgM stimulation
compared to 24 hours, in particular for mutated
IgV H CLL cells. Normal B cells show minimal
response to IgM stimulation.
The analysis of miRNA profile are preliminary and
must be confirmed in further cases.
During the coming year, the correlation between gene
expression profile and miRNA expression will be
examined and statistically correlated. The analysis of
a positive correlation will evaluate several hypothesis:
1) miRNAs and their host genes: a positive correlation
should be observed in those cases in which the
miRNA resides within the intron of a given gene.
This hypothesis will be tested using the annotations
included in the miRBase website;
2) miRNA promoters: we aim at using computational
tools as TRANSFAC for the search of putative
transcription factor binding sites in the miRNA promoter
regions. The presence of such motifs may be
suggestive of a correlation that will be experimentally
validated;
3) the relationship between a miRNA and a mRNA is
not a direct, but a secondary, target of that miRNA.