C3 and neoplasm: Furthermore, high expression levels of C3, C5, C3AR1, and C5AR1 are significantly (p < 0.05) associated with tumor subtypes in KIRC, LUAD, LUSC, and STAD, while tumor stages of BRCA are significantly (p < 0.05) associated with the expression of C3, C5, and C5AR1 (Figure 1C).