PD −1, T-cell immunoglobulin and mucin domain 3 (TIM3), Choline transporter-like protein 4 (CTL4), indoleamine 2,3-dioxygenase (IDO−1), Lymphocyte-activation gene 3 (LAG−3), etc., further leading to T cell depletion and promoting immune suppression and the progression of cholangiocarcinoma (8, 9). The gene discussed is SLC44A4; the disease is cholangiocarcinoma.