Association between oxidative stress, mitochondrial function of peripheral blood mononuclear cells and gastrointestinal cancers

Abstract

Background: The incidence and mortality rate of gastrointestinal cancers are high worldwide. Increasing studies have illustrated that the occurrence, progression, metastasis and prognosis of cancers are intimately linked to the immune system. Mitochondria, as the main source of cellular energy, play an important role in maintaining the physiological function of immune cells. However, the relationship between mitochondrial function of immune cells and tumorigenesis has not yet been systematically investigated.

Methods: A total of 150 cases, including 60 healthy donors and 90 primary gastrointestinal cancer patients without anti-tumor treatments (30 with gastric cancer, 30 with liver cancer and 30 with colorectal cancer) were involved in our study. The oxidant/antioxidant and cytokine levels in plasma, the ROS level, mitochondrial function and apoptosis ratio of peripheral blood mononuclear cells (PBMCs) were evaluated.

Results: The imbalance between oxidant and antioxidant in plasma was discovered in the primary gastrointestinal cancer patients. The levels of cell reactive oxygen species (ROS) and mitochondrial ROS in PBMCs of primary gastrointestinal cancers were significantly increased compared with that in healthy donors. Meanwhile, the ATP content, the mtDNA copy number and the mitochondrial membrane potential (MMP) in PBMCs of patients with primary gastrointestinal cancers were lower than those in control group. The decreased MMP also occurred in immune cells of gastrointestinal cancers, including T cell, B cell, NK cell and monocyte. Furthermore, the PBMCs apoptosis ratio of primary gastrointestinal cancer patients was significantly higher than that of control group. Importantly, an increase of IL-2 and IL-6 and a decrease of IgG in plasma were found in the patients with primary gastrointestinal cancers. These changes of mitochondrial function in immune cells were consistent among primary gastrointestinal cancers without anti-tumor treatments, such as liver cancer, gastric cancer and colorectal cancer.

Conclusion: Our study demonstrated that the imbalance of oxidation/antioxidation in primary gastrointestinal cancer patients without anti-tumor treatments results in excessive ROS. The oxidative stress was associated to the mitochondrial dysfunction, the apoptosis of immune cells and eventually the abnormal immune function in primary gastrointestinal cancers. The application of immune cell mitochondrial dysfunction into clinical evaluation is anticipated.

Keywords: Gastrointestinal cancers; Mitochondrial dysfunction; PBMCs.

Fig. 1

Overview of the study design. A total of 150 cases, including 60 controls and 90 primary gastrointestinal cancer patients without anti-tumor treatments (30 with gastric cancer, 30 with liver cancer and 30 with colorectal cancer) were involved in our study. Plasma was isolated to detect the oxidative stress parameter and the levels of cytokines. PBMCs was isolated to detect the level of ROS, mtROS, MMP, ATP content, the mtDNA copy number and apoptosis. PBMCs, peripheral blood mononuclear cells; T-AOC, total antioxidant capacity; GSH-Px, glutathione peroxidase; MDA, malondialdehyde; IL-2, interleukin 2; IL-6, interleukin 6; TNF-α, tumor necrosis factor α; TNF-β, tumor necrosis factor β; IgG, immunoglobulin G; MMP, mitochondrial membrane potential; ROS, reactive oxygen species; ATP, adenosine triphosphate

Fig. 2

The oxidant and antioxidant level of the primary gastrointestinal cancer patients without anti-tumor treatments and healthy people. A The level of T-AOC of plasma in primary gastrointestinal cancer patients diagnosed for the first time and healthy people. B The GSH-Px activity of plasma in primary gastrointestinal cancer patients diagnosed for the first time and healthy people. C The content of MDA of plasma in primary gastrointestinal cancer patients diagnosed for the first time and healthy people. D The PBMCs ROS level were detected by flow cytometric analysis. E The level of PBMCs ROS in primary gastrointestinal cancer patients diagnosed for the first time and healthy people. F Ontology terms and KEGG pathways of the up-regulated genes between four cancer types and their paired normal tissues. G Heatmaps illustrating the average expression of these pathways-related genes in tumors and paired normal tissues. Values in the graphs represent the mean ± standard deviation; the symbol (***) indicates a significant increase compared with the control group (P < 0.001)

Fig. 3

The mitoROS and ATP content of PBMCs in the primary gastrointestinal cancer patients without anti-tumor treatments and healthy people. A The PBMCs mitoROS level were detected by flow cytometric analysis. B The level of mitoROS of PBMCs in the primary gastrointestinal cancer patients diagnosed for the first time and healthy people. C The content of ATP of PBMCs in the primary gastrointestinal cancer patients diagnosed for the first time and healthy people. Values in the graphs represent the mean ± standard deviation; the symbol (***) indicates a significant increase compared with the control group (P < 0.001)

Fig. 4

The mitochondrial membrane potential (MMP) of T cells and B cells in the primary gastrointestinal cancer patients without anti-tumor treatments and healthy people. A The MMP level were detected by flow cytometric analysis. B The MMP level of T cells (CD3⁺CD19⁻) in the primary gastrointestinal cancer patients diagnosed for the first time and healthy people. C The MMP level of B cells (CD3⁻CD19⁺) in the primary gastrointestinal cancer patients diagnosed for the first time and healthy people. D The MMP level of PBMCs in the primary gastrointestinal cancer patients diagnosed for the first time and healthy people. Values in the graphs represent the mean ± standard deviation; the symbol (***) indicates a significant increase compared with the control group (P < 0.001)

Fig. 5

The mitochondrial membrane potential (MMP) of NK cells and monocytes in the primary gastrointestinal cancer patients without anti-tumor treatments and healthy people. A The MMP level of NK cells (CD3⁻CD56⁺) were detected by flow cytometric analysis. B The MMP level of T cells (CD3⁻CD56⁺) in the primary gastrointestinal cancer patients diagnosed for the first time and healthy people. C The MMP level of monocytes (CD14⁺) were detected by flow cytometric analysis. D The MMP level of monocytes (CD14⁺) in the primary gastrointestinal cancer patients diagnosed for the first time and healthy people. Values in the graphs represent the mean ± standard deviation; the symbol (***) indicates a significant increase compared with the control group (P < 0.001)

Fig. 6

The apoptosis ratio of PBMCs in the primary gastrointestinal cancer patients without anti-tumor treatments and healthy people. A The apoptosis of PBMCs were detected by flow cytometric analysis. B The apoptosis ratio of PBMCs in the primary gastrointestinal cancer patients diagnosed for the first time and healthy people. Values in the graphs represent the mean ± standard deviation; the symbol (***) indicates a significant increase compared with the control group (P < 0.001)

Fig. 7

The level of Immune inflammatory factor in the primary gastrointestinal cancer patients without anti-tumor treatments and healthy people. A The level of IL-6 in plasma. B The level of IL-2 in plasma. C The level of IgG in plasma. D The level of TNF-α in plasma. E The level of TNF-β in plasma. Values in the graphs represent the mean ± standard deviation; the symbol (***) indicates a significant increase compared with the control group (P < 0.001)