HHLA2 and systemic lupus erythematosus: In addition to high HHLA2 expression groups, our results demonstrated that HHLA2 also regulates many other pathways in low HHLA2 expression groups, such as those involved in steroid hormone biosynthesis in ACC; cytosolic DNA sensing pathway in LAML; amino sugar and nucleotide sugar metabolism in KIRC; histidine metabolism in PAAD; peroxisome in PRAD; and systemic lupus erythematosus in UCEC (Figure 11).