T-Cell Receptor Engagement Confers Resistance to Chemotherapy in T-Cell Lymphoproliferative Disorders

Background: Chemotherapy resistance and primary refractory disease are common among patients with the more common peripheral T-cell lymphomas (TCL) treated with anthracycline-based chemotherapy. Antigen-receptor signaling activates a number of proliferation and survival pathways in normal lymphocytes. When activated in lymphomas, antigen-receptor signaling might confer resistance to chemotherapy. Until recently, the role of antigen-receptor signaling in B-cell malignancies was poorly understood. It is now appreciated that B-cell receptor (BCR) signaling is an important driver of B-cell lymphoma growth and survival, and represents an attractive therapeutic target in these lymphomas. In contrast, the potential role of T-cell receptor (TCR) signaling in T-cell lymphomagenesis is poorly understood. The observation that most (≈95%) TCLs express an intact TCR suggests that malignant T cells, like their B-cell counterparts, may benefit from antigen-receptor signaling.

Methods: TCL cell lines and primary patient specimens were subjected to TCR activation by CD3/CD28 beads. Gene expression profiling was performed by Affymetrix human gene 2.1 ST array at different time points (4, 8, 24 hours) following TCR engagement. Results were further validated by immunophenotyping by flow cytometry, western blot and cytokine measurement by enzyme-linked immunosorbent assay (ELISA). The proliferation and chemoresistance of the TCL cells following TCR engagement were determined by MTT assay.

Results: Microarray gene expression profiling of TCLs showed differential gene expression upon TCR engagement by CD3/CD28 beads at different time points. A total of 1274 genes were differentially expressed commonly in the patient specimens. Some of the differentially expressed genes were confirmed in independent samples by immunophenotyping (CD25, CD30, CD69, CD137, CCR4, GITR) and cytokine (IL2, IL13, IL10, IFNγ) release. Gene enrichment analysis of the common differentially expressed genes showed that pro-proliferation and pro-survival signaling pathways, including TCR (FDR: 0.05%), MAPK (FDR: 2.8%), NFκB (FDR: 0.1%) and cytokines (FDR: 0.03%) were enriched in TCR-engaged TCL cells. The activation of TCR and NFκB signaling in TCR-engaged TCLs was also confirmed by western blot and flow cytometry. More importantly, the proliferation of TCLs increased by 2-4 fold when cocultured with CD3/CD28 beads for 72 hours (p<0.01). In the presence of either vincristine or romidepsin, the viability of TCLs increased by 1.5-4 fold by CD3/CD28 bead treatment (p<0.01). TCR-dependent proliferation and chemoresistance in TCLs was significantly inhibited by agents targeting TCR and NFκB signaling pathways.

Conclusions: T-cell receptor dependent signaling pathways are rational therapeutic targets in the T-cell lymphomas.