The present invention relates to an in vitro method for determine the prognosis of the survival time of a patient suffering from a cancer comprising the steps consisting of i) determining the expression level of the couple DNMT3A/ISGF3γ in a sample from said patient, ii) comparing said expression level with a predetermined reference value and iii) providing a good prognosis when the expression level is lower than the predetermined reference value and a poor prognosis when the expression level is higher than the predetermined reference value. The invention also relates a compound which is a DNMT3A/ISGF3γ antagonist or a compound which is a DNMT3A/ISGF3γ gene expression inhibitor for use in the treatment and prevention of cancer.