The present invention relates to at least one modulator of PP2A or at least one modulator of PP2A-like phosphatase or at least one modulator of PP2A and PP2A-like phosphatase or a combination of said modulators for use in the treatment of a disease characterized by an alteration in the DNA damage response. The present invention also relates to a method to identify a subject to be treated with a PP2A modulator comprising detecting in the genome of said patient a mutation in PP2A.