Combing with the result of expression profiling analysis, HHLA2 abounds in human normal and malignant tissue, however only differentially expressed in some tumor types (KIRC, COAD etc.)(Supplementary Table 1), the subsequent studies will focus on the unique role of HHLA2 in renal clear cell carcinoma. Here, HHLA2 is linked to clear cell renal carcinoma.