Abstract
BACKGROUND: Human immunological memory is a hallmark of the adaptive immune system and plays an important role in the development of effective immune responses against tumors. In the present study, we aimed to determine the frequencies of CD8(+) memory T cell subsets including T stem cell memory (TSCM) in tumor-draining lymph nodes of patients with breast cancer (BC). METHODS: Mononuclear cells were obtained from axillary lymph nodes of 52 untreated patients with BC and stained for CD8, CCR7, CD45RO, CD95 markers to detect different subtypes of memory cells in the CD8(+) lymphocyte population. Data were acquired on four-color flow cytometer and analyzed with CellQuest Pro software. RESULTS: We observed that 47.65 ± 2.66% of CD8(+) lymphocytes expressed the CD45RO, a marker for memory T cells. Statistical analysis showed that the total frequency of central memory T cells (TCM) and their subset with low CD45RO expression was significantly higher in tumor-involved nodes compared to tumor-free ones (P = 0.024 and P = 0.017, respectively). The level of CD95 expression (based on mean fluorescence intensity) on the surface of TCM, their CD45RO(hi) and CD45RO(low) subsets, and TSCM was higher in patients with stage II compared to those in stage I (P < 0.05). In addition, the percentage of naive CD8(+) T cells was significantly lower in tumor-involved lymph nodes compared to tumor-free ones (P = 0.025). CONCLUSIONS: Our data collectively indicate no significant differences in the frequencies of CD8(+) lymphocytes or their memory subsets in tumor-draining lymph nodes of patients with BC. However, the frequency of CD45(low) TCM was higher in tumor-involved nodes. Along with a decrease in the frequency of naive T cells, the higher frequency of CD45(low) TCM suggests that despite the immune reaction to provide a pool of effective memory cells, it is blocked in early-stage of memory cells' differentiation (CD45RO(low)), probably by tumor-derived suppressive factors. Identifying the molecular and cellular mechanisms behind this suppression can provide invaluable tools for adoptive T cell therapies in cancer.