ABSTRACT
Immune checkpoints represent a group of inhibitory receptor molecules that are expresses in the surface of immune cells and play a pivotal role in maintaining immune homeostasis. In recent years, several key immune checkpoint molecules such as CTLA-4 and PD-1, has been found to exist in some kinds of tumor cells. These ectopic expressed checkpoint molecules are named as “cancer cell-intrinsic immune checkpoint molecules”. Although our understanding on cancer cell-intrinsic immune checkpoint molecules is quite limited, emerging evidence suggests that the expression and the biological functions of such molecules in different types of cancer cells are heterozygous and diverse. In particular, the discovery of “adaptive immune-independent” regulation on cancer cell behaviors would potentially benefit to design a customized cancer immune therapy, as well as to develop new therapeutic strategies for cancer. In this review, we will briefly describe the timeline of the studies, deeply discuss the complicated biological functions and the regulatory mechanisms (CTLA-4 and PD-1 as representative examples). And finally we put forward a research perspective on cancer cell-intrinsic immune checkpoint molecules. This review aims to present and promote the studies of cancer cell-intrinsic immune checkpoint molecules to the broad scientific community.