Recurrent activating mutations of CD28 in peripheral T-cell lymphomas

Abstract

Peripheral T-cell lymphomas (PTCLs) comprise a heterogeneous group of mature T-cell neoplasms with a poor prognosis. Recently, mutations in TET2 and other epigenetic modifiers as well as RHOA have been identified in these diseases, particularly in angioimmunoblastic T-cell lymphoma (AITL). CD28 is the major co-stimulatory receptor in T-cells which, upon binding ligand, induces sustained T-cell proliferation and cytokine production when combined with T-cell receptor stimulation. We have identified recurrent mutations in CD28 in PTCLs. Two residues – D124 and T195 – were recurrently mutated in 11.3% of cases of AITL and in one case of PTCL, not otherwise specified (PTCL-NOS). Surface plasmon resonance analysis of mutations at these residues with predicted differential partner interactions showed increased affinity for ligand CD86 (residue D124) and increased affinity for intracellular adaptor proteins GRB2 and GADS/GRAP2 (residue T195). Molecular modeling studies on each of these mutations suggested how these mutants result in increased affinities. We found increased transcription of the CD28-responsive genes CD226 and TNFA in cells expressing the T195P mutant in response to CD3 and CD86 co-stimulation and increased downstream activation of NF-κB by both D124V and T195P mutants, suggesting a potential therapeutic target in CD28-mutated PTCLs.

Recent Progress in the Understanding of Angioimmunoblastic T-cell Lymphoma

“…Half of the samples of AITL and nodal PTCL with TFH phenotype had mutations in genes encoding components of the T-cell Receptor (TCR) signaling pathway in an almost exclusive manner: 48 e.g., PLCgamma, 14%; 48 CD28, 9% -11%; 48,49 FYN, 3% -4%; 27,48 and VAV1 5%. 48 A substantial proportion of these mutations are commonly found in ATLL.…”

“…The T195 mutant was demonstrated to have higher affinity for GADS/GRAP2 and GRB2. 49,53 Both mutants activate downstream transcription of TNFA and CD226, 49 and the NF-κB reporter 49,53 in Jurkat RHOA mutations are shown by integrating the published information for AITL, 13 ATLL, 46 Burkitt's lymphoma, 45 and diffuse-type gastric carcinoma. 44 Four nucleotide-binding domains are indicated by yellow boxes.…”

“…The D124 mutant was found to have higher affinity for its ligands CD80 and CD86. 49 T195 is located between the YMNM-containing SH2-binding motif and proximal PxxPcontaining SH3-binding motif. The T195 mutant was demonstrated to have higher affinity for GADS/GRAP2 and GRB2.…”

“…52 Two residues, p.D124 and p.T195, are recurrently mutated. 48,49 D124 is located close to the C-terminal end of the ligand-binding site. The D124 mutant was found to have higher affinity for its ligands CD80 and CD86.…”

Comment on: Frequent CTLA4-CD28 gene fusion in diverse types of T-cell lymphoma, by Yoo et al.

“…We reanalyzed WES or RNA-seq data from published series of AITL (n=43), PTCL-NOS (n=16), and NKTCL (n= 43) [5][6][7][8][9] (Table 1) and found the CTLA4 exon 3-CD28 exon 4 fusion only in a single sample, which was from an earlier publication by Yoo et al 9 (sample PAT7), out of 9 cases with RNA-seq reported in this earlier paper. Note that this earlier RNA-seq dataset showed a significantly lower frequency (P=0.0055, two-sided binomial test) than reported in their most recent publication.…”