ATM and cancer: As similar effects of caffeine treatment were observed on irradiated HeLa cells, the potential of caffeine as a DNA damage-sensitizing agent in cancer cells is considered high, because the caffeine treatment targets one of the earliest steps in homologous recombination, independently of ATM/ATR inhibition (the PI3 kinase in mammalian cells corresponding to Mec1 and Tel1 kinases from the budding yeast) [57].