The study into the role of antioxidants in cancer development, published in PNAS, may also shed light on new therapeutic approaches that involve the blockade of antioxidant-producing systems in cancer cells.
Primary liver cancer—or hepatocellular carcinoma—is the fifth most prevalent cancer in the world, and more than half of new cases occur in Hong Kong and China. It has a high recurrence rate and is refractory to chemotherapy, leading ultimately to death in most patients.
However, the study’s findings suggest that vitamin supplements, which are widely used for extra nutrients by patients in Hong Kong, where liver cancer is the third-deadliest form of the diseases, are harmful in high doses, said Irene Ng Oi-lin, who led the study.
“Liver cancer patients are advised to have a balanced diet and they should note that a high intake of antioxidant supplements may not be beneficial to health,” she said.
“[Cancer patients] might not have to stop taking them, but they need to consider whether they are necessary to continue.”
The animal study showed that while antioxidants were harmful to cancer cells, lowering their growth rate, this effect decreased as more antioxidants were introduced, leading to cancer cell growth.
Liver cancer cells were found to produce more antioxidants, which assist tumour growth, through an enzyme called transketolase. The researchers also found that therapeutically targeting this key enzyme would create metabolic vulnerabilities in cancer cells, making them more sensitive to existing drug treatment.
Though the findings related to liver cancer, the University of Hong Kong team believe the results are applicable to other cancers having the same metabolic pathway, such as colorectal and lung cancers.
“In the long-term, our study can facilitate the development of safer, effective and targeted treatment that can be used in combination with chemotherapy to completely eradicate this deadly disease and benefit liver cancer patients,” said Professor Ng.