POSSIBLE CANCER EFFECTS. “Few experimental cancer therapies have incited as much debate as vitamin C. More than half of human colorectal cancers (CRCs) carry either KRAS or BRAF mutations and are often refractory to approved targeted therapies. We found that cultured human CRC cells harboring KRAS or BRAF mutations are selectively killed when exposed to high levels of vitamin C.”
http://science.sciencemag.org/content/350/6266/1391