MicroRNA-29c and 223 Are
Powerful Prognostic Factors for Chronic Lymphocytic Leukemia and
Improve Risk Stratification When Combined with ZAP70 and LPL in a qPCR
Score
Stamatopoulos B, Meuleman N, Bron D, Haibe-Kains B, Saussoy P, Martiat P and Lagneaux L
Background:
MicroRNAs (or miR) are a novel class of small noncoding RNA involved in
gene regulation. Aberrant microRNA expression has been recently
associated with chronic lymphocytic leukemia (CLL) outcome. Currently,
the heterogeneous evolution of this disease can be predicted by several
prognostic factors. Nevertheless, a better individualization of the
outcome in a given patient is still of utmost interest.
Methods: In the current study, we investigated the expression of
two microRNAs, miR-29c and miR-223, compared them to other biological
or clinical markers and proposed a quantitative real-time PCR (qPCR)
score to better assess CLL outcome. All cut-offs were calculated by ROC
curve analysis maximising the correlation with the immunoglobulin
variable heavy chain (IgVH) mutational status; statistical differences
were evaluated by Mann Whitney test or Kruskal-Wallis test ;
treatment-free (TFS) and overall (OS) survival differences were
investigated by log-rank test or Cox proportional hazard ratio (HR).
Results: miR-29c and miR-223
expression decreased significantly with progression along Binet Stage A
to C (P=0.0010 and P=0.0183, respectively), and were significantly
lower in poor prognosis subgroups defined by cytogenetic abnormalities,
IgVH mutational status, lymphocyte doubling time, solubleCD23,
β2-microglobulin, ζ-associated protein 70 (ZAP70), lipoprotein lipase
(LPL) and CD38 expression. Furthermore, miR-29c and miR-223 could
predict TFS (n=110, P=0.0015 and P<0.0001, respectively) and OS
(n=110, P=0.0234 and P=0.0008, respectively). Regarding all these
results, we developed a qPCR score (from 0 to 4 poor prognostic
markers) combining miR-29c, miR-223, ZAP70 and LPL in order to stratify
treatment and death risk in a 110 patient cohort with a median
follow-up of 72 months (range, 2-312). Patients with a score of 0/4,
1/4, 2/4, 3/4, and 4/4 had a median TFS of >312, 129, 80, 36 and 19
months, respectively (HR=17.00, P<0.0001). Patient with a score of
0-1/4, 2-3/4 and 4/4 had a median OS of >312, 183 and 106 months,
respectively (HR=13.69, P=0.0001). Interestingly, during the first 50
months after diagnosis, only 10% of patients with a 0/4 score required
a treatment, when compared to 100% of the 4/4. Furthermore, during the
total follow-up (312 months), patients with a 4/4 score had a 27-fold
higher risk to be treated and a 31-fold higher risk to die comparing to
patients with a 0/4 score. This score was validated by a 10-fold
cross-validation (prediction accuracy of 82%). Finally, in Binet stage
A patients (n=77), this score remained relevant and significant for TFS
and OS prediction (HR=18.56, P<0.0001 and HR=12.5, P=0.0068,
respectively).
Conclusions: we showed that (i)
miR-29c and miR-223 levels were decreased in poor prognosis patients
regarding several well-known prognostic factors; (ii) a low level of
these two microRNAs is thus associated to disease aggressiveness, tumor
burden and poor clinical evolution; (iii) we also showed that
these two microRNAs could predict TFS and OS; (iv) we proposed a qPCR
score to better individualize evolution of a particular CLL patient.
This score will help to identify patients who will need early therapy
and require thus a closer follow-up.