Andrographolide derivatives inhibit guanine nucleotide exchange and abrogate oncogenic Ras function by Hocker, Harrison J., Cho, Kwang Jin, Chen, Chung Ying K., Rambahal, Nandini, Sagineedu, Sreenivasa Rao, Shaari, Khozirah, Stanslas, Johnson, Hancock, John F., Gorfe, Alemayehu A.