In the 2C group, the amount of RAD9A protein increased 1.76- and 1.63-fold at 1 h and 4 h, respectively, implying a lower induction (−1.44x, p = 0.012 at 4 h) by DNA damage in childhood cancer patients with a second tumor. The gene discussed is RAD9A; the disease is childhood malignant neoplasm.