Abstract
Immune dysfunction in patients with multiple myeloma (MM) includes TGF-β induced dendritic cell dysfunction, regulatory T cell (Tregs)/Th17 cell imbalance, accumulation of Tregs and myeloid derived suppressor cells. These tumor-induced dysfunctions may contribute to immune escape and even suppress immune cells introduced in adoptive cellular immunotherapy. CD28 independent T cells of the effector memory (TEM) and CD45RA+ effector memory (TEMRA) population were shown to accumulate with age and contribute to the immunosuppressive tumor microenvironment in several solid tumors and hematological cancers. Especially in the CD8+ population, the loss of CD28 is associated with high cytotoxicity and regulatory function while showing high diversity and defective antigen-induced proliferation. In the CD4 subset, regulatory and senescent T cells were studied extensively, while in the CD8 positive subset their heterogeneity is still not clearly defined. Their potential immunosuppressive role and distribution in healthy individuals (HI) as well as patients with multiple myeloma (MM) remains to be observed. Furthermore, a recently characterized CD8+CD28- NK-like T cell subset showing expression of NK-related inhibitory receptors and TCR independent effector function is potentially of interest in the progression of MM. In the present study, we compared the changes of distribution of CD8+CD25+ and CD8+FOXP3+ regulatory T cells (Treg), CD28-CD57+ senescent T cells (Tsen), and CD8+KIR/NK2GA+EOMES+ NK-like T in peripheral blood (PB) between HI and patients with MM by multicolour flow cytometry (Gating strategy shown in Figure 1A). When comparing 35 HIs (Median age is 54) and 14 MM patients (Median age is 52), it was shown that there is no significant change in the proportion of senescent T cells in CD8 (P = 0.2452), TEM/CD8 (P = 0.1686) and TEMRA/CD8 (P = 0.4861) between HIs and the MM group, while both the CD25+FOXP3+ regulatory T cells of the CD4 population (P = 0.0031) and CD28-FOXP3+ regulatory T cells of the CD8 population (P = 0.0014) were shown to increase. There is no significant difference in the percentages of KIR/NK2GA+EOMES+ in the CD8 T cell and TEMRA/CD8 T cell population between HIs and the MM group. Remarkably, although there was no overall increase in senescent T cell in MM patients, senescent CD8+NK2GA+EOMES+ NK-like T cells increased in MM patients in comparison to HIs (P = 0.0068) (Figure 1B). In conclusion, the increase of regulatory T cells of both the CD4 and CD8 population as well as the increase of senescent NK-like T cells in the CD8 population potentially contributes to cancer progression through creation of suppressive microenvironments. Moreover, we found that regulatory CD8 T cells and CD8 NK-like T cells only contribute to a small part of the overall CD28- senescent T cell pool.
No relevant conflicts of interest to declare.
