CLL with double productive IGHV-IGHD-IGHJ rearrangements / Biclonal

Background

  • Double productive IGHV-IGHD-IGHJ rearrangements have been detected in normal as well as malignant B cells. In such cases, typically, only one rearrangement will be translated to protein and expressed on the cell surface as part of BcR, due to allelic exclusion.
  • Lack of allelic exclusion has been reported in, for example, autoreactive B cells, leading to the expression of multiple antigen receptors, probably as an attempt to edit a “deleterious” BcR.
  • Evidence for lack of allelic exclusion (sometimes referred to as “allelic inclusion”) has also been obtained for B cell malignancies, in particular CLL. Indeed, molecular studies have suggested that allelic exclusion may not be absolute in a minority of CLL cases in either the heavy or the light chain loci or both, with continued IG gene rearrangements postulated to occur in the context of (auto)antigen-driven receptor editing.
  • Occasionally, the presence of double productive IGHV-IGHD-IGHJ rearrangements may reflect the existence of biclonal populations in the same patient. Indeed, up to 5% of patients with B cell chronic lymphoproliferative malignancies may display two or more clonal populations.
  • In CLL cases with double IGHV-IGHD-IGHJ rearrangements of discordant IGHV gene mutational status, it is impossible to give a conclusive, prognostically relevant interpretation. Although admittedly rare (29/4154 cases of the present study, ~1%), this situation could create problems, especially if this biomarker is used for risk stratification within clinical trials.

 

Goal

  • To study IGH gene rearrangements at the single cell level after single-cell sorting in CLL cases carrying double productive IGHV-IGHD-IGHJ rearrangements as well as in biclonal (CLL+CLL, CLL+other) cases
  • To collect biologic material (genomic DNA, total cellular RNA, viable/fresh-frozen cells) and clinicobiological information from these cases
  • To assess the prevalence of “real” biclonal CLL cases versus cases expressing double productive IGH rearrangements and define their prognostic significance.

 

Participants

The study will include any ERIC group and/or ERIC member willing to contribute information and biological material.
The analysis will be performed by the groups responsible for the collection and curation of sequence and other clinicobiological information as well as the in vitro studies, as detailed below:

 

Technical details

Cell processing and storage
The amount of cells needed per case is at least 30x106 ficoll-separated mononuclear cells from patients prior to the initiation of any treatment or at least six months off treatment and also showing  >30% CLL cells.
Viable, fresh cells should be frozen in liquid nitrogen in RPMI medium supplemented with 10% DMSO at a concentration of 10x106/tube.

Clinicobiological and sequence data
A template with predefined fields (in Excel format) can be downloaded » here and should be use to exchange data.

 

Time-line

Sample collection: up to March 2013
Data processing and in vitro studies: up to mid 2013 

Coordination

Paolo Ghia,
Kostas Stamatopoulos,