CTLA4 and colorectal carcinoma: also reported a significant positive correlation between PDCD1 and several transcription factors, including NR4A1, BATF, and VDR. Due to the persistent stimuli of tumor antigens, tumor-reactive CD103+CD39+CD8+ T cells in CRC tumor microenvironments display exhausted phenotypes with high expression of CTLA4, HAVCR2, LAYN, and TOX (117).