Early effects of low dose C ion or x-ray irradiation on peripheral blood lymphocytes of patients with alimentary tract cancer

Abstract

The aim of this study was to examine the early effects of low dose (12)C(6+) irradiation or X-ray on peripheral blood lymphocytes (PBL) of patients with alimentary tract cancer and to explore mechanisms that may be involved in an antitumor immune response. We found that the percentage of T lymphocyte subsets, the mRNA expression levels of IL-2 and IFN-γ in PBL, and their protein levels in supernatant were significantly increased 24 hours after exposure to low dose radiation. The effects were more pronounced in the group receiving 0.05Gy (12)C(6+) ion irradiation than the group receiving X-ray irradiation. There was no significant change in the percentage of NK cell subsets and TNF-α production of PBL. Our study suggests that low dose irradiation could alleviate immune suppression caused by tumor burden and that the effect was more pronounced for 0.05Gy high linear energy transfer (LET) (12)C(6+) irradiation.

Keywords: 12C6+; X-ray; alimentary tract cancer; low dose irradiation; peripheral blood cells.

FIGURE 1.

Change in percentage of T and NK cells subsets of PBL and CD4⁺:CD8⁺ T lymphocytes ratio at 24 hours after irradiation with 0.05Gy X-ray or ¹²C⁶⁺ ions. (A) PBL of patients with esophageal cancer (B) PBL of patients with colon cancer (C) PBL of patients with gastric cancer (D) CD4⁺:CD8⁺ T lymphocytes ratio (*p<0.05, **p<0.01, ***p<0.001 vs. 0Gy; n=40). The significance among radiated groups was determined by ANOVA.

FIGURE 2.

The change in Real-time PCR cycle threshold values in PBL at 24 hours after irradiation with 0.05Gy X-ray or ¹²C⁶⁺ ions. (A–C) Expression levels of IFN-γ, IL-2 and TNF-α in PBL of patients with esophageal cancer (D–F) Expression levels of IFN-γ, IL-2 and TNF-α in PBL of patients with colon cancer (G–I) Expression levels of IFN-γ, IL-2 and TNF-α in PBL of patients with gastric cancer were shown as medians (lines), 25^th percentile to the 75^th percentile (boxes) and ranges (whiskers) for 40 samples. (*p<0.05, **p<0.01, ***p<0.001 vs. 0Gy; n=40). The significance among radiated groups was determined by ANOVA.

FIGURE 3.

The change in protein levels of cytokines in supernatant of HPBL at 24 hours after irradiation with X-ray or ¹²C⁶⁺ ions. (A–C) Protein levels of IFN-γ, IL-2 and TNF-α in supernatant of HPBL of patients with esophageal cancer (D–F) Protein levels of IFN-γ, IL-2 and TNF-α in supernatant of PBL of patients with colon cancer (G–I) Protein levels of IFN-γ, IL-2 and TNF-α in supernatant of PBL of patients with gastric cancer (*p<0.05,**p<0.01,***p<0.001 vs. 0Gy; n=40). The significance among radiated groups was determined by ANOVA.