We present a computational study of tissue transcriptomic data of 14 cancer types to address: what may drive cancer cell division? Our analyses point to that persistent disruption of the intracellular pH by Fenton reactions may be at the root of cancer development. Specifically, we have statistically demonstrated that Fenton reactions take place in cancer cytosol and mitochondria across all the 14 cancer types, based on cancer tissue gene-expression data integrated via the Michaelis–Menten equation. In addition, we have shown that (i) Fenton reactions in cytosol of the disease cells will continuously increase their pH, to which the cells respond by generating net protons to keep the pH stable through a combination of synthesizing glycolytic ATPs and consuming them by nucleotide syntheses, which may drive cell division to rid of the continuously synthesized nucleotides; and (ii) Fenton reactions in mitochondria give rise to novel ways for ATP synthesis with electrons ultimately coming from H2O2, largely originated from immune cells. A model is developed to link these to cancer development, where some mutations may be selected to facilitate cell division at rates dictated by Fenton reactions.