498P - Differences in tumor immune microenvironment and clinical outcomes between right and left colon cancer

Background

Colorectal cancer located in the right and left side are referred to as right colon cancer (RCC) and left colon cancer (LCC), respectively. Increasing evidence reveals that the RCC and LCC having different features with regards to both physiological and molecular characteristics, and, they are different in treatment strategy and prognosis. However, there is insufficient data to explain these differences from the perspective of tumor immune microenvironment. Therefore, we evaluated immune status of tumor microenvironment to explain the differences between LCC and RCC, and explore the prognosis of colorectal cancer from immune microenvironment.

Methods

We collected tissue samples of 50 colorectal cancer patients from May 2017 to December 2018, and detected expression of PD-L1 by using Dako PD-L1 IHC 22C3 pharmDx, and CD8⁺ T cells, two subtypes of tumor associated macrophages (TAM) and two subtypes of NK cells infiltrated in the tumor biopsies by multiple fluorescence immunohistochemistry (mICH). Follow-up data of these patients were analyzed. Statistical analysis was performed using GraphPad Prism (version 7.01) and SPSS version 21.0 (SPSS,Inc.).

Results

CD56^bright NK and CD56^dim NK cells, M1 and M2 TAM, CD8⁺T cells were found both in intratumoral region and tumor rim of colorectal cancer patients (n=50), both CD8⁺T cells and TAM exist more in RCC than LCC tumor tissue, while only NK cells especially CD56^dim NK cells were less infiltrated in tumor of RCC than LCC(p<0.01). Patients with more CD56^dim NK cells infiltration shown better prognosis, that is, have longer progression free survival (p<0.005). What’s more, no positive expression of PD-L1 was detected in the tumor tissue of all patients (Tumor Proportion Score, TPS<1%).

Conclusions

Better prognosis for LCC than RCC was repeatedly reported, we found that more CD56^dim NK cells infiltration in LCC than RCC, although more CD8⁺T cells and TAM (both M1 and M2) infiltration were found in RCC than LCC. In addition to PD-1 / PD-L1, other immune escape mechanism should be explored more in colorectal cancer, and CD56^dim NK cells infiltration should be considered as more valuable prognostic biomarker in colorectal cancer.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

H. Zhang, X. She, X. Shen, D. Huang: Full/Part-time employment: 3D Medicines Inc. All other authors have declared no conflicts of interest.