GTP-binding proteins (G proteins) couple cell surface receptors to gen
eration of a variety of intracellular second messengers. The mutant G
protein products may be responsible for trapping the protein in its ac
tive and subsequently the abnormal growth of malignant cells and dysfu
nction. We present recent examples of G protein gene mutations in ovar
ian tumors and illustrate how such defects might lead to abnormal tumo
r proliferation.