The microsatellite instable subset of colorectal cancer is a particularly good candidate for checkpoint blockade...

Area of Science:

• Oncology
• Immunology
• Cancer Research

Background:

• Microsatellite instable (MSI) colorectal cancer features an active Th1/CTL immune microenvironment, likely due to numerous tumor neoantigens.
• However, MSI colorectal cancer also exhibits elevated expression of checkpoint molecules (PD-1, PD-L1, CTLA-4, LAG-3, IDO), creating an immunosuppressive environment.
• This immunosuppression may enable MSI tumors to evade immune cell-mediated destruction.

Purpose of the Study:

• To investigate the immune microenvironment of microsatellite instable (MSI) colorectal cancer.
• To evaluate the potential of MSI colorectal cancer as a candidate for checkpoint immunotherapy.

Main Methods:

• Analysis of immune cell infiltration and checkpoint molecule expression in MSI colorectal cancer.
• Comparison of immune profiles between MSI and microsatellite stable (MSS) colorectal cancer.

Main Results:

• MSI colorectal cancer demonstrates an active immune microenvironment rich in neoantigens.
• High expression of PD-1, PD-L1, CTLA-4, LAG-3, and IDO was observed in MSI tumors.
• These factors contribute to an immunosuppressive microenvironment, potentially aiding immune evasion.

Conclusions:

• Despite limited response to PD-1 pathway immunotherapy in colorectal cancer generally, the MSI subset presents a strong rationale for checkpoint immunotherapy.
• Targeting these checkpoint molecules may overcome immune evasion in MSI colorectal cancer.