Predominant VH1-69 IgBCR Clones Show Higher Expression of CD5 in Heterogeneous Chronic Lymphocytic Leukemia Populations.

Domenico Maisano,Annamaria Aloisio,Federico Chiurazzi,Ileana Quinto,Giuseppe Fiume,Eleonora Vecchio,Enrico Iaccino,Massimo Gentile,Nancy Nisticò,Selena Mimmi,Mariangela Scalise,Erika De Sensi,Alessandro D’Ambrosio,Vincenzo Dattilo

doi:10.3389/fonc.2021.703254

Abstract

The immunoglobulin B cell receptor (IgBCR) expressed by chronic lymphocytic leukemia (CLL) B cells plays a pivotal role in tumorigenesis, supporting neoplastic transformation, survival, and expansion of tumor clones. We demonstrated that in the same patient, two or more CLL clones could coexist, recognized by the expression of different variable regions of the heavy chain of IgBCR, composing the antigen-binding site. In this regard, phage display screening could be considered the easier and most advantageous methodology for the identification of small peptide molecules able to mimic the natural antigen of the tumor IgBCRs. These molecules, properly functionalized, could be used as a probe to specifically identify and isolate single CLL subpopulations, for a deeper analysis in terms of drug resistance, phenotype, and gene expression. Furthermore, CLL cells express another surface membrane receptor, the CD5, which is commonly expressed by normal T cells. Piece of evidence supports a possible contribution of CD5 to the selection and maintenance of autoreactivity in B cells and the constitutive expression of CD5 on CLL cells could induce pro-survival stimuli. In this brief research report, we describe a peptide-based single-cell sorting using as bait the IgBCR of tumor cells; in the next step, we performed a quantitative analysis of CD5 expression by qRT-PCR related to the expressed IgBCR. Our approach could open a new perspective for the identification, isolation, and investigation of all subsets of IgBCR-related CLL clones, with particular attention to the more aggressive clones.

Highlights

CD5 is a membrane surface receptor expressed by thymocytes, mature T cells, B1a subset of B cells, and leukemic B cells of chronic lymphocytic leukemia (B-CLL) disease [1, 2]
CD5 is not expressed in normal B cells, except the B1 subgroup, while it is mostly expressed in B-CLL cells [2]; this suggests a possible critical role of CD5 in self-maintenance and progression of neoplastic B cells [5, 6]
We firstly analyzed by qRT-PCR the CD5 expression levels in total CD5 positive B-CLL cells of CLL1 and CLL5 patients at different times of disease

Summary

Introduction

CD5 is a membrane surface receptor expressed by thymocytes, mature T cells, B1a subset of B cells, and leukemic B cells of chronic lymphocytic leukemia (B-CLL) disease [1, 2]. CD5 is not expressed in normal B cells, except the B1 subgroup, while it is mostly expressed in B-CLL cells [2]; this suggests a possible critical role of CD5 in self-maintenance and progression of neoplastic B cells [5, 6]. This hypothesis is supported by the evidence that CD5 activates multiple signaling pathways, including mitogen-activated protein kinase (MAPK) (Ras/Erk) pathway, the Ca2+–calmodulin–calcineurin–NFAT pathway, and the PI3-K/Akt/mTOR pathway [7]. In transgenic mice, the expression of CD5 correlates with the self-reactivity in B cell populations, supporting a possible contribution to the selection and maintenance of autoreactivity in B cells [8]

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Results

Conclusion