Moreover, McEwan et al. reported that combination of the PDE4 inhibitor rolipram and low doses of the adenylate cyclase activator forskolin resulted in colon cancer cell growth inhibition implicating that these cells are addicted to maintenance of low cAMP concentrations in a compartment that is regulated by PDE4 [45]. The gene discussed is PDE4A; the disease is malignant colon neoplasm.