We found that this polyphenol phytoalexin suppressed constitutive STAT3 (tyrosine residue 705 and serine residue 727) and STAT5 (tyrosine residue 694 and 699) activation in RCC in parallel with the inhibition of JAK1, JAK2, and c-Src activation. The gene discussed is STAT5A; the disease is renal cell carcinoma.