[Experimental study of anti-tumor immunologic response functions after combined treatment of cryoablation with GM-CSF for colorectal cancer liver metastases].

Abstract

Objective: To assess the anti-tumor immune response after combined cryoablation and granulocyte-macrophage colony-stimulating factor (GM-CSF) treatment. Methods: A mouse model of colorectal liver metastases (CLM) was established using 80 BALB/c mice. All tumor-bearing mice were divided into a control group (n=20), a GM-CSF group (n=20), a cryoablation group (n=20), and a cryoablation+GM-CSF group (n=20). Cryoablation was applied using a 1.7-mm diameter cryosurgery needle from an argon-helium cryosurgery system. Tumor size and survival time were observed. Changes in the number of dendritic cells (DCs) in tumors were assessed by immunohistochemistry. Serum cytokine (IFN-γ, IL-4) levels were analyzed by enzyme-linked immunosorbent assay (ELISA), and the Th1/Th2 ratio was estimated from the IFN-γ/IL-4 ratio. One-way analysis of variance was used for data analysis. Results: Our findings showed that combining cryoablation and GM-CSF synergistically increased infiltrating DC numbers. Among the four groups, cryoablation+GM-CSF group exhibited the highest DC count post-treatment (control group: 1.4±0.5/HPF, GM-CSF group: 15.3±1.8/HPF, cryoablation group: 9.6±1.5/HPF, cryoablation+GM-CSF group:17.4±1.3/HPF; F=138.60,P<0.05). Cryoablation, alone or combined with GM-CSF, elevated serum IFN-γ and reduced serum IL-4. IFN-γ levels of cryoablation group increased from 45.6±2.4 pg/ml to 57.8±3.3 pg/ml,F=170.09,P<0.05,and IFN-γ levels of cryoablation+GM-CSF group increased from 45.6±2.4 pg/ml to 86.3±1.9 pg/ml,F=664.31,P<0.05;and IL-4 levels of cryoablation group decreased from 7.21±0.63 pg/ml to 6.35±0.25 pg/ml,F=5.77,P<0.05,IL-4 levels of cryoablation+GM-CSF group decreased from 7.21±0.63 pg/ml to 6.42±0.21 pg/ml,F=10.93,P<0.05. Conversely, GM-CSF alone decreased serum IFN-γ and increased serum IL-4. Notably, combined cryoablation and GM-CSF significantly boosted Th1/Th2 ratios (cryoablation+GM-CSF group: from 6.32±0.45 to 13.43±0.64; F=379.95,P<0.05). Conclusion: Combined cryoablation with GM-CSF treatment exerted a promising anti-tumor immune effect in the treatment of colorectal cancer liver metastases. This approach increased the number of DCs in the tumor microenvironment and improved the anti-tumor immunologic response in tumor-bearing mice.