Unmutated IGHV1-69/D3-16/J3 Stereotyped HCDR3 Rearrangements (Subset 6) Are Associated with Indolent Disease Course and Have Outcome Independent of Mutational Status In Early Stage CLL (Rai 0)

IGHV1-69 gene identifies the most frequent IGHV gene in chronic lymphocytic leukemia (CLL) and identifies the paradigm of unmutated CLL (U-CLL), being used in roughly 1/3 U-CLL. It is often rearranged to form subsets of stereotyped HCDR3 patterns, likely selected and transformed from the natural naïve B-cell repertoire (Blood. 2010; 115:71-7). Being unmutated, IGHV1-69 CLL are hypothetically expected to have competent tumor B-cell receptors (BCR) and to progress more rapidly. However, it has not been investigated if progression occurs similarly in all the subsets.

we aimed to investigate the prognostic significance of mutational status and of stereotypic B-cell receptors in IGHV1-69+ CLL.

Nucleotide sequences of the tumor IGHV1-69/D/J rearrangement, clinical and molecular prognostic parameters at diagnosis and clinical status at follow-up of 294 IGHV1-69+ CLL patients were obtained from 22 hematological Institutions in Italy. CLL B-cell derived IGHV1-69 rearrangements were scanned for HCDR3 stereotypic patterns and assigned to subsets according to the criteria by Murray et al (Blood. 2008; 111: 1524–1533). Enpoint of outcome was time to progression requiring first treatment according to NCI criteria (TTFT) in Rai stage 0 CLL.

Of 294 IGHV1-69+ CLL, 264 (89,8%) were unmutated, 168 (57,1%) were assigned to subsets, of which subsets 7 (n=23, 7,8%), 6 (17, 5,8%), 3 (13, 4,4%), 5 (10, 3,4%) and 9 (10, 3,4%) were the most frequent. CD38, ZAP70, normal or sole del13, +12, del11 and del17p scored positive in 109/264 (58,7%), 139/245 (56,7%), 128/248 (50,5%), 51/248 (20,6%), 43/248 (17,3%) and 34/248 (13,7%). CLLs were reclassified as 18 (6,1%) clinical MBL, 101 (34,4%) Rai 0, 155 (52,7%) Rai I-II and 20 (6,8%) Rai III-IV CLL. Subset 6 was also UM in 16/17 (94,1%) cases. Prevalence of CD38 (p<.001), ZAP70 (p=.016), normal or sole del13 (p<.001), +12 (p=.026), del11 (p=.011), and clinical high risk CLL (p=.025) were lower in IGHV1-69 M-CLL than in IGHV1-69 U-CLL. TTFT was significantly shorter in stage 0 IGHV1-69 U-CLL than in IGHV1-69 M-CLL (49 vs 144 months, p<.001, while it was not different between CLL assigned or not to subsets (65 vs 55 months, p=.346). However, specific analysis of individual subsets revealed differential outcomes (p=.005). Among all, it emerged that subset 6 had a TTFT equivalent to IGHV1-69 M-CLL (p=.29) and significantly longer than stage 0 IGHV1-69 U-CLL (median not reached vs 48 months, p=.017).

our analysis documents and confirms that unmutated status of IGHV, and not stereotypy, is a relevant prognosticator of outcome (TTFT) in CLL. In the IGHV1-69 CLL it exclude a role of IGHV gene use for CLL progression. However, the good prognosis of Rai 0 U-CLL assigned to subset 6 suggests a differential clinical benign course of this particular subset, irrelevant of unmutated status. One possibility is that the IGHV1-69/D3-16/J3 rearrangements of subset 6 produce a tumor-specific BCR with stereotypic HCDR3 patterns that are anergized by antigen while circulating in the peripheral blood in early stage (Rai 0) CLL.

No relevant conflicts of interest to declare.