This chapter provides a comprehensive overview of immune checkpoint expression in cancer, exploring the complex interplay between the immune system and tumor development. It begins by introducing the concept of cancer immunoediting and its three phases: elimination, equilibrium, and escape. The chapter then explores the composition and characteristics of the tumor microenvironment, discussing various immune cell populations and their roles in tumor progression or suppression. A significant portion of the chapter is dedicated to examining specific immune checkpoint molecules, including CTLA-4, PD-1/PD-L1, TIM-3, LAG-3, TIGIT, CD96, PVRIG, CD244, BTLA, and members of the B7 family. For each checkpoint, the chapter explores its expression patterns in different cancer types, its impact on prognosis, and its potential as a therapeutic target. It also covers emerging checkpoint molecules and their potential significance in cancer immunotherapy. Additionally, the chapter discusses the CD39/CD73/adenosine pathway and the CD47/SIRPα axis to highlight their roles in immune evasion and their potential as therapeutic targets. Throughout the chapter, the complex interactions between various checkpoint molecules and their ligands are examined to emphasize the multifaceted nature of immune regulation in the tumor context. It provides insights into how these checkpoints contribute to T cell exhaustion and tumor escape mechanisms, as well as their implications for developing more effective cancer immunotherapies.