Immune Cell Infiltration in Liver Oligometastasis Microenvironment from Colorectal Cancer: Intratumoral CD8/CD3 Ratio Represents a Valuable Prognostic Index for Patients Undergoing Liver Metastasectomy

Abstract

Background: The overview of the tumor microenvironment on liver oligometastasis from colorectal cancer remains largely unclear. A comprehensive investigation on the immune cell infiltration and its constituent ratio might provide a more accurate and reliable prognostic information for the patients with colorectal liver oligometastasis (CLO) after liver metastasectomy. Methods: A simultaneous detection of immune constituents CD3+, CD8+, Foxp3+ T cells, and α-SMA fibroblast on the liver oligometastasis of 133 patients were conducted by using a five-color immunohistochemical multiplex technique. The immune cells were quantified and tumor-infiltrating lymphocytes (TILs) ratios were subsequently calculated. Correlation analysis was performed using Pearson's correlation. Recurrence-free survival (RFS) and overall survival (OS) for TIL ratios were analyzed using the Kaplan-Meier method and Cox regression models. Results: The number of CD3+, CD8+, and Foxp3+ T cells were significantly fewer in the intratumoral subsection by compared to the peritumoral subsection of metastases. CD3+, CD8+, Foxp3+ T cells, and α-SMA+ fibroblast showed a significantly positive correlation between each other both in the intratumoral and peritumoral subsection of liver metastases. As to the correlation of TIL ratios, only the CD8/CD3 ratio demonstrated a positive correlation in intratumoral and peritumoral metastases (r=0.541, P<0.001). Patients with high intratumoral CD8/CD3 ratio had a significantly higher 3-year RFS (59.0% vs. 47.4%, P = 0.035) and 3-year OS rate (83.3% vs. 65.8%, P = 0.007) than those with low intratumoral CD8/CD3 ratio. Multivariate analyses revealed that intratumoral CD8/CD3 ratio was independently associated with RFS (HR 0.572; 95% CI 0.346-0.948; P = 0.030). Conclusions The current study showed a novel insight into the tumor microenvironment on CLO. The intratumoral CD8/CD3 ratio was found to be a valuable prognostic index for CLO undergoing liver metastasectomy. Funding: This work was supported by grants from the National Natural Science Foundation of China (grant No.81772595), Sun Yat-sen University Clinical Research 5010 Program (grant No. 2015024), Sun Yat-sen University Clinical Research 5010 Program (grant No. 2013013), and Guangzhou Science and Technology Plan Projects (Health Medical Collaborative Innovation Program of Guangzhou) (grant No. 201803040019). Declaration of Interest: The authors declare that they have no conflict of interest. Ethical Approval: All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. This study was approved by the Institutional Research Ethics Committee of Sun Yat-sen University Cancer Center (Approval number: GZR2017-006). Informed consents for using tissue samples before the initial treatment were obtained from the patients.