Pre-operative intracellular glutathione levels of peripheral monocytes as a biomarker to predict survival of colorectal cancer patients

Abstract

The ability to predict anti-tumor immune responses at local tumor growing sites using only peripheral blood specimens would be helpful in determining therapeutic options for patients with solid tumors. Here, we show that the glutathione intracellular content (icGSH) of peripheral monocytes (Mo) correlates positively with T cell infiltration within tumor islets and overall survival in patients with colorectal carcinoma. IcGSH redox status was determined in CD14(+) Mo prior to surgery by staining with monochlorobimane. The tumor-infiltrating T cells (TIL) were quantified as CD45RO(+) T cells in resected tumors using paraffin sections. A positive association was found between the GSH index and TIL in tumor islets (P < 0.001). The 50% cut-off value for the GSH index, that is the determinant between TIL presence or absence in tumor islets, was calculated to be almost 0.7 through logistic regression analysis. Mo with a GSH index of > or =0.7 were termed reductive (R)-Mo, and those with <0.7 were designated as oxidative (O)-Mo. Cox's proportional hazards regression analysis of patients with R-Mo or O-Mo prior to surgery, and the presence or absence of TIL, was found to correlate significantly with the overall survival rate of stage II and III patients. Kaplan-Meier analysis also showed a significant correlation. These results indicate that the Mo icGSH index is a useful biomarker parameter for better understanding the host/tumor relationship prior to surgery, thereby enabling the development of an individual patient-oriented therapeutic strategy.

Fig. 1

a Comparison of GSH index and TIL in tumor islets. The mean value of the GSH index in patients whose tumor cell islets were infiltrated with TIL was significantly higher than in patients without TIL (absence of TIL, 0.561 ± 0.052 vs. presence of TIL, 1.035 ± 0.051). b Comparison of the icGSH index of Mo and TIL in tumor islets of two patients with colon cancer (left panel 53 years old, female, stage II; right panel 62 years old, female, stage II). Bar 50 μm. Upper panels MCB staining of the Mo (GSH index of left panel: 1.07 vs. right panel: 0.41). Lower panels Histological section of CD45RO⁺ T cells in tumor islets (left panel: several TIL in tumor islets ↑). On the right-hand side there is no TIL into the tumor islets

Fig. 2

a Kaplan–Meier analyses of stage II and III colorectal cancer patients (n = 23): patients with R-Mo (GSH ≥ 0.7) or O-Mo (GSH < 0.7) plotted separately (P = 0.0009). b Kaplan–Meier analyses of stage II and III colorectal cancer patients (n = 23): patients with or without intratumoral T cells plotted separately (P = 0.0048)

Fig. 3

a Comparison of T cell stimulatory activity of O-Mo and R-Mo in vitro. R-Mo (GSH ≥ 0.7) stimulate T cells more strongly compared with O-Mo (GSH < 0.7) (O-Mo; 829.0 ± 152.0 vs. R-Mo; 1314.3 ± 136.4 pg/ml, P = 0.036). b Effect of OK-432 administration on a the GSH index and b T cell stimulatory activity of Mo in vitro. After OK-432 administration, GSH indices increased dramatically compared to pre-therapy (b-1) (before: 0.923 ± 0.046 vs. after: 1.039 ± 0.035, P = 0.041). T cell stimulatory activity of Mo increased after OK-432 treatment (b-2) (before: 626.8 ± 152.8 vs. after: 1271.9 ± 153.7 pg/ml, P = 0.003)