Proteomics profiling of CLL versus healthy B-cells identifies putative therapeutic targets and a subtype-independent signature of spliceosome dysregulation

Abstract

Chronic lymphocytic leukaemia (CLL) is a heterogeneous B-cell cancer exhibiting a wide spectrum of disease courses and treatment responses. Molecular characterisation of RNA and DNA from CLL cases has led to the identification of important driver mutations and disease sub-types, but the precise mechanisms of disease progression remain elusive. To further our understanding of CLL biology we performed isobaric labelling and mass spectrometry proteomics on 14 CLL samples, comparing them with B-cells from healthy donors (HDB). Of 8694 identified proteins, ~6000 were relatively quantitated between all samples (q<0.01). A clear CLL signature, independent of subtype, of 544 significantly overexpressed proteins relative to HDB was identified, highlighting establishedhallmarks of CLL (eg. CD5, BCL2, ROR1 and CD23 overexpression). Previously unrecognised surface markers demonstrated overexpression (eg. CKAP4, PIGR, TMCC3 and CD75) and three of these (LAX1, CLEC17A and ATP2B4) were implicated in B-cell receptor signalling, which plays an important role in CLL pathogenesis. Several other proteins (eg. Wee1, HMOX1/2, HDAC7 and INPP5F) were identified with significant overexpression that also represent potential targets. Western blotting confirmed overexpression of a selection of these proteins in an independent cohort. mRNA processing machinery were broadly upregulated across the CLL samples. Spliceosome components demonstrated consistent overexpression (p=1.3x10-21) suggesting dysregulation in CLL, independent of SF3B1 mutations. This study highlights the potential of proteomics in the identification of putative CLL therapeutic targets and reveals a subtype-independent protein expression signature in CLL.

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Identifiers

ORCID for Spiros Garbis: orcid.org/0000-0002-1050-0805

ORCID for Jonathan Strefford: orcid.org/0000-0002-0972-2881

ORCID for Andrew Steele: orcid.org/0000-0003-0667-1596

ORCID for Mark Cragg: orcid.org/0000-0003-2077-089X

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