The invention relates to a method of preventing, inhibiting, arresting or reversing tumorigenesis in a cell as well as a method of inducing apoptosis in a tumor cell. The method includes increasing the amount and/or the activity of a DACT protein, or a functional fragment thereof, in the cell. Also provided is a pharmaceutical composition that comprises a compound of general formula (I), wherein A is CH or N, R1, R4 and R5 are independent from each other H, an aliphatic group, an alicyclic group, an aromatic group, an arylaliphatic group, and an arylalicyclic group comprising 0-3 heteroatoms. The heteroatoms may be N, O, S, or Si. R4 and R5 may optionally be linked so as to define an aliphatic hydrocarbyl bridge. R2 is H or a halogen such as F, Cl, Br or L. R3 is H, F, Cl or an aliphatic or arylaliphatic group that includes 1-8 main chain carbon atoms and 0-3 heteroatoms. The pharmaceutical composition also comprises a histone deacetylase inhibitor.