Background Cancer immunotherapy (CIT) has substantially improved the survival of cancer patients. However, according to recent studies, liver metastasis was reported to predict worse outcomes for CIT. The main objective of the study is to evaluate the differences in the immune microenvironment (IME) between the primary lung cancer (PL) and synchronous liver metastasis (LM) using a multispectral imaging system.
Methods Six immune markers (CD4, CD8, CTLA-4, granzyme B (GZB), Foxp3 and PD-L1) were analyzed using a multiplex IHC system and inForm program (Akoya) on paired lung-liver samples of 10 patients. Cells were categorized into tumor nest and stroma, and cell counts per unit area were measured for comparison.
Results The number of tumor-infiltrating cytotoxic T cells (TIL) in PL (262.5 cells/mm2) was higher than that of LM (113.3 cells/mm2). Additionally, the ratio between the number of TIL and non-TIL was greater in PL (0.31) compared to that of LM (0.26). A similar trend appeared for Helper T cells and regulatory T cells (Treg), as PL consisted of higher numbers of T cells (791.8 Helper T cells/mm2, 195.7 Treg/mm2) than LM (626.3 Helper T cells/mm2, 121.3 Treg/mm2). However, cytotoxic T cells exhibiting GZB+ and CTLA-4- were fewer in PL (140.2 cells/mm2) than in LM (203.3 cells/mm2), and the ratio is 0.69. The mean number of GZB+ TIL in PL (32.5 cells/mm2) was lower than in LM (35.3 cells/mm2), and their proportions among total TIL counts were 0.12 and 0.31, respectively. In PL, GZB+: GZB- ratio is 0.16 while the ratio is 1.91 for LM. A fewer number of TILs exhibiting GZB suggests that PL has lower efficiency in immune response than LM. Another crucial checkpoint receptor that inhibits immune response, CTLA-4, was more prevalent in PL, with CTLA-4+: CTLA-4- ratio in Treg being 0.36 in PL, compared to 0.11 in LM. The tumor proportion score (TPS) of PD-L1 was higher in PL than LM (40.0 vs. 6.6).
Conclusions In our study, we showed the differences in the numbers of TIL or regulatory T cells and expressions of immune checkpoint receptors (PD-L1, CTLA-4), which significantly influence outcomes for CIT. The study is ongoing to confirm different IME between the PL and LM groups in a larger tumor cohort.
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