In this study we demonstrate that a commonly applied clinical schedule of conventional low-dose fractionated irradiation (daily fractions of 2 Gy for 5 days per week, up to 6 weeks) induces an intrinsic type I interferon (IFN) response in tumor cells that is characterized by an increased expression of interferon stimulated genes (ISGs). This evidence concerns the gene STING1 and neoplasm.