As intracellular cAMP levels are determined by the balance of the activities of adenylate cyclases and PDEs, this forskolin concentration might be insufficient to suppress the growth of HeLa cells but sufficient to suppress (by 25–50%) growth of some other mammalian cells such as mouse neuroblastoma/rat glioma hybrid cells, NG108-15 [39], or non-small-cell lung cancer cells, H1299 and A549 [40]. This evidence concerns the gene ADCY1 and central nervous system cancer.