300 oranges may impair cancer cells

ISLAMABAD: The power of vitamin C could one day be harnessed to fight colorectal cancer, according to a new study published.

The equivalent of 300 oranges-concentration of vitamin C killed colorectal cancer cells. Colorectal cancer (CRC) is the third most common cancer in the US, with about 93,090 new cases each year. Around 50 percent of those cases involve mutations in the KRAS and BRAF genes-these forms of the disease are more aggressive and do not respond well to current therapies or chemotherapy.

Vitamin C is generally thought to improve health because of its antioxidant effect, which prevents or delays some types of cell damage. However, a team led by Dr Lewis Cantley of Weill Cornell Medicine in New York, discovered that in the case of the KRAS and BRAF forms of the CRC, the opposite was true. In these cancer cells, high dose of vitamin C caused oxidation, resulting in what could be a beneficial effect for patients.

They found that in cell cultures and mice, high doses of vitamin C – equivalent to around 300 oranges – impaired the growth of KRAS and BRAF mutant colorectal tumors. They now hope that the findings could lead to the development of new treatments and provide critical insights into who would most benefit from them.

In an oxygen-rich environment such as human arteries, a fraction of vitamin C, also called ascorbic acid, becomes oxidised and is transformed into a new compound called dehydroascorbic acid (DHA).

Scientists have known for some time that a specific membrane protein, known as glucose transporter GLUT1, enables both glucose and DHA to enter cells, but that ascorbic acid cannot do so. What DHA does once inside the cells remained a mystery. The current study reveals that DHA acts as a Trojan horse. Once inside, natural antioxidants in the cancer cell attempt to convert the DHA back to ascorbic acid-in the process, these antioxidants are depleted, and the cell dies from oxidative stress.

Dr Cantley explained that many normal cells express GLUT1, but KRAS- and BRAF-mutant cancer cells typically have much higher levels, since they need a high rate of glucose uptake for survival and growth.

KRAS- and BRAF-mutant cells also produce more reactive oxygen species than normal cells, and so they need more antioxidants in order to survive. This combination of characteristics makes these cancer cells particularly vulnerable to DHA.

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