1144 - Patients with unmutated IgHV_1-69; 1-02; 3-30; 4-39 and high expression of AID enzyme need earlier treatment.

Clinical and molecular heterogeneity is a hallmark of chronic lymphocytic leukemia (CLL). This point is even more complex considering that leukemic cells continuously interact with cells and/or soluble factors from their microenvironment constantly modifying the evolution of the disease. The practical problem of this heterogeneous landscape is that leukemia progression cannot be predicted and it still remains an important unmet clinical need. Among different prognostic tools validated in CLL the mutational IgHV status is recognized as the most reliable molecular prognostic factor. Patients expressing mutated IgHV (M-CLL) develop a more indolent disease, whereas unmutated IgHV (U-CLL) patients display a more aggressive one, often unresponsive to treatment. Despite this categorization and a myriad of other molecules proposed as prognostic markers (CD38, Zap-70, CD49d, CXCL3/4, LPL and others) disease progression and/or treatment requirement still cannot be accurately predicted in many patients.
We and others have described that activation-induced cytidine deaminase (AID) is over-expressed in peripheral blood (PB) of patients with poor clinical outcome and that it is predominantly expressed in U-CLL. Despite AID expression in CLL cells has been linked with disease progression, the role of AID in this leukemia and how its expression is involved during disease evolution remains controversial. To deepen into this question we studied AID expression in relationship with specific IgVH rearrangements that may contribute as prognostic markers. In a cohort of 270 CLL patients diagnosed according to IWCLL diagnostic criteria we analyzed the mutational IgHV status, the fluorescence in-situ hybridization (FISH) abnormalities and AID’s mRNA expression by TaqMan Quantitative-PCR in the PB at diagnosis. Finally, we assessed the prognostic impact of IgHV rearrangements and AID expression levels in time to first treatment (TTFT). Of 270 patients, 172 were men and 98 women, (male-female ratio = 1.75). From these, 153 (57%) were Binet’s stage A, 60 (22%) stage B and 57 (21%) were stage C. IgHV gene status was mutated in 53%, whereas typical cytogenetic aberrations were found in 68%: del(13q14) in 36%, trisomy 12 in 15%, del(11q22) in 10% and del(17p13) in 7%. Median age at diagnosis was 67 years old and median of follow up was 5 years. Our first observation was that positive AID patients in the unmutated group mostly express the rearrangements IgHV_1-02; 1-69; 3-30 and 4-39. However, negative AID U-CLL as well as the M-CLL counterpart (expressing AID or not), remain distributed among the different IgHV rearrangements without any significant selection in the use of a specific IgHV/D/J genes. Prompted by these findings, and also considering previous reports describing the poorest clinical outcome for U-CLL expressing IgHV_1-69, we focused on these 4 unmutated IgHV rearrangements (1-02; 1-69; 3-30 and 4-39, hereafter, Sub-group_1) and compared the prognostic impact on TTFT with those U-CLL, expressing AID or not, but carrying different IgHV rearrangements of the Sub-group_1, (hereafter, mentioned as Sub-group 2). Forest plot of the hazard ratio assessed for association with TTFT by univariate and multivariate analysis were performed. Our results showed that U-CLL group expressing AID with BCR rearrangements corresponding to Sub-group_1 maintained the highest hazard ratio in the final model even after being included in the multivariable analyses del(17p) or Trisomy12. Next, we performed Kaplan-Meier curves analyzing TTFT among the different groups (U-CLL/AIDpos/Sub-group_1; U-CLL/AIDneg/Sub-group_1; U-CLL/AIDpos/Sub-group_2; U-CLL/AIDneg/Sub-group_2). Our results showed statistically significant differences comparing TFTT between the different sub-groups of patients indicating that: U-CLL/AIDpos/Sub-group_1 needed earlier treatment ( TFTT= 7 months, n=44), compared with: U-CLL/AIDpos/Sub-group_2, ( TFTT= 26 months, n=27, p=*); U-CLL/AIDneg/Sub-group_2, ( TFTT= 37 months, n=39, p=***), and U-CLL/AIDneg/Sub-group_1, ( TFTT= 48 months, n=26, p=****), Log-rank (Mantel-Cox) test.
In conclusion, our results highlight the relevance of assessing AID expression in PB of CLL patients in relationship with the mutational IgHV profile with the final goal of identifying the U-CLL/AIDpos/Sub-group_1. Considering our previous study analyzing the South American cohort, n=900 (Stanganelli et al., Hematol. Oncol, 2019), the percentage of patients corresponding to the sub-group_1 is 27%. Hence, we can assume that the new entity described here (U-CLL/AIDpos/Sub-group_1) represents ~15% of the total CLL population, thus, accurate prediction of this sub-group could result in a useful tool to be incorporated in clinical practice after validation.