Increased TOX expression associates with exhausted T cells in patients with multiple myeloma

Abstract

Previous studies have shown increased aberrant expression of immune checkpoint (IC) proteins, such as programmed cell death receptor-1 (PD-1) and T cell immunoglobulin mucin-domain-containing-3 (Tim-3) on T cells from patients with multiple myeloma (MM), which result in T cell exhaustion and dysfunction. However, little is known about the mechanism regulating aberrant IC protein expression. In this study, we analyzed the expression of TOX (thymocyte selection-associated HMG BOX), a crucial transcription factor involved in T cell exhaustion, and its co-expression with PD-1, Tim-3, and CD244 in T cell subsets by multi-color fluorescent flow cytometry in peripheral blood (PB) and bone marrow (BM) samples from patients with MM. Significantly, the percentage of TOX + CD3 +/CD4 +/CD8 + T cells was increased, and similarly, higher numbers of TOX co-expression with PD-1, Tim-3, and CD244 on CD3 +/CD4 +/CD8 + T cells were found. Interestingly, the numbers of TOX +, TOX + PD-1 +, and TOX + Tim-3 + regulatory T (Treg) cells also significantly increased in both the PB and BM of MM patients. In summary, we for the first time observed increased TOX expression concurrent with PD-1, Tim-3, and CD244 on T cells, which may contribute to T cell exhaustion and impair their function in MM. Thus, TOX may be considered a potential target for reversing T cell exhaustion and improving T cell function in MM.

Different expression patterns of VISTA concurrent with PD-1, Tim-3, and TIGIT on T cell subsets in peripheral blood and bone marrow from patients with multiple myeloma

“…It is known that T cell dysfunction is related to the cancer immune microenvironment ( 19 ). In previous studies, researchers have observed a greater impact on T cell suppression in BM compared with that in PB in leukemia and MM patients, which was evident from the higher percentage of PD-1+/Tim-3+ T cells in the BM ( 4 , 42 , 43 ). Interestingly, these results unlike the findings of higher PD-1+/Tim-3+ T cells and TOX+ T cells in BM compared with that in PB in MM patients ( 10 , 42 , 43 ).…”

“…It has been reported that Tregs accumulate in MM, and this is closely related to high mortality and reduced survival time, which is consistent with our findings (45, 47, 48). In addition, we previously reported higher expression of immune inhibitory proteins including PD-1, Tim-3, and TOX in Tregs in hematologic malignancies that negatively impact T cell immunosuppressive functions (4,36,42). Anna et al found that patients with MM with higher frequencies of Tregs had inferior survival and a distinct Treg immune checkpoint profile (i.e., increased PD-1, LAG-3) (49).…”

“…In previous studies, researchers have observed a greater impact on T cell suppression in BM compared with that in PB in leukemia and MM patients, which was evident from the higher percentage of PD-1+/Tim-3+ T cells in the BM (4,42,43). Interestingly, these results unlike the findings of higher PD-1+/Tim-3+ T cells and TOX+ T cells in BM compared with that in PB in MM patients (10,42,43). In this study, we found a higher trend of VISTA+ T cells and VISTA+PD-1+/Tim-3+/TIGIT+ T cells present in PB compared to BM and an even higher percentage of PD-1+, Tim-3+, and TIGIT+ T cells was confirmed in BM compared with PB in MM patients, and the latter is consistent with previous findings (8,39).…”

TOX regulates T lymphocytes differentiation and its function in tumor

“…TOX exhausts CD8 + T lymphocytes in mouse models (infection ( 13 – 15 ) or tumor models) or human cancers, including melanoma, non-small cell lung carcinoma ( 16 ), colorectal cancer ( 17 ), liver cancer ( 18 ), bladder cancer, oral squamous cell carcinoma ( 19 ), acute myeloid leukemia ( 18 , 20 ), multiple myeloma ( 21 ), and non-Hodgkin’s lymphoma ( 22 ) ( Figure 1 ) ( Table 1 ).…”

“…Higher counts of TOX + Treg subsets in the bone marrow may be helpful in mediating immunosuppressive microenvironment in the bone marrow ( 7 ). The proportion of the TOX + Treg subgroup is increased in patients with non-Hodgkin’s lymphoma ( 22 ), multiple myeloma (MM) ( 21 ), or de novo AML ( 18 ), and this phenomenon results in Treg activation instead of Treg exaustion. Fusobacterium nucleatum may aggravate rectal cancer by inhibiting antitumor T cell-mediated adaptive immunity.…”