Washington: Antioxidants may serve as a better treatment strategy for older patients with skin cancer, say scientists, including one of Indian-origin, who have found that aged melanoma tumour cells behave differently than younger ones.
Cancer risk increases with one's age as accumulated damage to our cells and chronic inflammation occur over time. Changes in the micro environment make these older tumour cells more metastatic and more resistant to treatment with
targeted therapies.
"It's fascinating to see that the microenvironment can have such a profound effect on both metastasis, and response to a therapy that is specifically targeted to a mutation in a gene," said lead author Ashani Weeraratna, associate professor
at The Wistar Institute.
Melanoma is the deadliest form of skin cancer, and patients with advanced cases of the disease only have a 20 per cent chance of surviving five years after their diagnosis. Multiple targeted therapies for melanoma have been approved in the last few years, but patients who receive these drugs eventually relapse and become resistant to these treatment options.
While multiple factors may contribute the age-related increases in cancer, for the first time, researchers have pinpointed age-related changes that occur in the
microenvironment of tumour cells.
Cells found in the skin called dermal fibroblasts help the skin recovery from injuries, and can contribute to the growth and invasion of melanoma cells. The researchers used dermal fibroblasts from healthy donors 25-35 years of age or from donors 55-65 years of age to understand what factors contribute to the difference in melanoma progression in ageing cell populations.
They determined that a secreted factor sFRP2 was present in ageing cells. SFRP2 regulates another protein called beta-catenin that blocks the invasion of melanoma cells. In addition, beta-catenin loss has been shown to promote oxidative stress in some cell types.
The researchers showed that in an aged microenvironment, there are fewer scavengers of free oxygen radicals, leading to more activity of reactive oxygen species (ROS). At the same time, the age-induced loss of beta-catenin renders melanoma cells less capable of dealing with ROS, resulting in a genetically unstable tumour.
Treatment resistance experienced by older melanoma patients was found with increased activity of ROS and decreased levels of beta-catenin all contribute to increased resistance to treatment with drugs that inhibit a gene, BRAF, mutated in approximately half of all cases of melanoma.
Researchers also showed how antioxidants might be a more effective strategy for treating older melanoma patients. An antioxidant called N-acetylcysteine (NAC) killed melanoma cells in aged dermal fibroblasts. "Our findings highlight how vital it is to treat that melanoma in an age-appropriate manner," said Amanpreet Kaur, a graduate student in the Weeraratna lab. The study was published in the journal Nature.
