Therapeutic potential of curcumin in human prostate cancer. II. Curcumin inhibits tyrosine kinase activity of epidermal growth factor receptor and depletes the protein.

Purpose: In a search for alternative and preventive therapies for prostate cancer, attention was focused on the ways in which curcumin (Turmeric), used in food and medicine in India for centuries, could interfere with the growth factor signaling pathways in both androgen-dependent and androgen-independent prostate cancer cells, as exemplified by the epidermal growth factor receptor (EGF-R) signaling.

Materials and methods: The androgen-sensitive LNCaP and androgen-insensitive PC-3 cell lines were grown in 5 to 50 microM curcumin and analyzed for EGF-R protein by Western blotting and for EGF-R tyrosine kinase activity.

Results: Curcumin was a potent inhibitor of EGF-R signaling, and it accomplished this effect by three different means (1) down regulating the EGF-R protein; (2) inhibiting the intrinsic EGF-R tyrosine kinase activity; and (3) inhibiting the ligand-induced activation of the EGF-R.

Conclusions: These results, taken together with our previous results that curcumin can induce apoptosis in both androgen-dependent and androgen-independent prostate cancer cells, support our view that curcumin may be a novel modality by which one can interfere with the signal transduction pathways of the prostate cancer cell and prevent it from progressing to its hormone-refractory state.