Correlation Between Clinical Features, CRLF2 Expression and Copy Number Alterations In Acute Lymphoblastic Leukemia

Acute lymphoblastic leukemia (ALL) is a heterogeneous disease comprising different genetic abnormalities. An increased cytokine receptor-like factor 2 (CRLF2) expression is associated with activating the JAK-STAT pathway and activation and leukemia initiation. Several studies have shown that some first events are insufficient to cause the development of ALL and other genetic changes are required. In 60% of cases, the altered genes are involved in lymphoid maturation (PAX, IKZF1, EBF, LEF1, BTALA/CD200, TOX), cell cycle control and tumour suppression (CDKN2A/B, PTEN, RB), or transcription factors and coactivators (ETV6, ERG, TBL1XR1). But the prognostic significance of deregulated CRLF2 mRNA expression in patients with CNA in the genes previously mentioned is not fully identified.

To analyze the frequency and prognostic significance of deregulated expression of  CRLF2 and the copy number alterations (CNA) in EBFF1, IKZF1, JAK2, CDKN, PAX, ETV, BTG1 and RB in a series of ALL patients enrolled in BFM, SHOP or PETHEMA clinical trials.

Bone Marrow samples at diagnosis from 69 ALL patients treated in Hospital Universitario 12 de Octubre, between January 2001 and December 2012, were studied by Multiplex ligation- dependent probe amplifications (MLPA) method was used to detect deletions or duplications of IKZF1, PAX5, ETV6, RB1, BTG1, EBF1 and CDKN2A-CDKN2B genes (SALSA MLPA kit P335-B1 ALL-IKZF1; MRC- Holland). Raw data was analyzed using Coffalyzer software (MRC-Holland)

The median age was 22 years (0.9-88), 40 (58%) male and 29 (42%) female, median WBC count 70,753 x10⁹/L (1,000 – 633,780). B-ALL subtype in 64 cases (92%) and T-ALL subtype in 5 cases (8%). Cytogenetics: 10 normal (14.5%), 16 hyperdiploid (20,5%), 8 t(9;22)(10.3%),4 cases 11q23/MLL (5.1%), and 24 (30.8%) with  other translocations or deletions and no growth (23.1%).  Cytogenetics risk was favourable in 25 cases (26.6%), intermediate in 10 cases (10.6%) and poor in 25 cases (26.6%). CRLF2 expression and CAN results are shown in table 1. CRFL2 over expression was found in 18 cases (23%), it was associated with deletions of IKZF1 (p0.013). Deletions of CDNK were associated with T-ALL subtype (p0.049) and with a tendency to deletions TEL group (p0.081). Deletions of PAX were associated with JAK2 deletions (p0.027) and with a tendency to IKZF1 deletions (p0.064). Rb deletions were associated with ph+ ALL (p0.001) and it had a tendency to the risk of death. Other molecular alterations found were gains of gen EBF 2 (2.6%), IKZF 2 (2.6%), CDKN 4 (5.1%), PAX 5(6.4%), BTG   2 (2.6%), RB 2 (2.6%). There was no association between hyperdiploid karyotype and any of the gene gains analyzed. Regarding survival, CDKN deletions 2A/ B were associated with decreasing of progression free survival P (0.051), independent of the presence of Ph chromosome. Deletions of IKZF1 showed an increased risk of death (p0.011) and tendency for deletions of PAX (p0.064).

Our findings are consistent with those of other published series. CDKN deletions 2A / B were associated with a decreased progression free survival, independent of the presence of Ph chromosome as described in other series. RB deletions are associated with ph + and have not been described previously, but these findings must be confirm with additional studies.

No relevant conflicts of interest to declare.