Method for treating and prognosing cancer

A method of treating cancer in a subject in need thereof, wherein the method comprises:

• i) determining the interaction level between DNMT3A/ISGF3gamma proteins in a sample from said patient,
• ii) comparing said interaction level with a predetermined reference value, wherein the predetermined reference value is the interaction level of the DNMT3A/ISGF3gamma proteins in a healthy subject or a mean interaction level of the DNMT3A/ISGF3gamma proteins in a population of healthy individuals, and
• iii) if the interaction level of the DNMT3A/ISGF3gamma proteins from the patient is higher than the predetermined reference value, administering a therapeutically effective amount of a compound which is a DNMT3A/ISGF3gamma antagonist reducing the interaction between DNMT3A and ISGF3gamma proteins, wherein said DNMT3A/ISGF3γ antagonist is peptide comprising an amino acid sequence RPMPRLTFQAGDPYYI (SEQ ID NO:1) or a function-conservative variant thereof, wherein said function-conservative variant comprises the amino acid sequence RPMPRLTFQAGDPYYI (SEQ ID NO:1) with 1, 2, 3, 4, or 5 amino acids that differ from RPMPRLTFQAGDPYYI (SEQ ID NO:1), and wherein said peptide or function-conservative variant thereof is of less than 50 amino acids.