A tentative scheme for luteolin regulation of the IGF-IR signaling pathway in HT-29 human colon cancer cells. Luteolin reduces the secretion of IGF-II and levels of IGF-IR mRNA and protein, which leads to a reduction in IGF-IR phosphorylation and a subsequent inhibition of PI3K/Akt and ERK1/2/CDC25c activation. Additionally, luteolin directly inhibits PI3K activity. These changes in IGF-I signaling contribute to luteolin-induced apoptosis and cell cycle arrest in HT-29 cells. *From our previously published results .