HHLA2 and breast carcinoma: In addition to the function of HHLA2 in KIRC, the potential mechanism involved in dysregulated expression of HHLA2 is also noteworthy, our result provided a possible explanation for this question, inconsistent with the previous report on breast cancer (44), the epigenetic modification but not copy number variant may be responsible for the dysregulated expression of HHLA2 in KIRC.