CD80 and cancer: Moreover, some negative regulatory co-stimulatory molecules such as B7 family ligands B7-H3 and B7-H4, have been found abnormally expressed in human RCC tissues, and their expression levels in cancer tissues are significantly associated with cancer progression and poor prognosis, indicating that such negative regulatory co-stimulatory molecules can be used as important biomarkers and therapeutic targets against RCC [17, 18].