Cancer is considered to be a disease closely related to age. Over the age of 65, the risk of multiple cancers and related mortality have increased significantly. However, the complex relationship between aging and cancer is poorly understood. < / P > < p > why is it easy to get cancer when you are older? In a research paper published online today in the leading academic journal Nature, scientists analyzed and compared the blood of the elderly and the young, and put forward a new answer to the question: as we age, metabolic disorders can make the internal environment conducive to tumor progression and invasion. Based on their findings, the researchers also propose a new potential target for cancer treatment. < / P > < p > in their paper, the researchers pointed out that in the past few decades, the relationship between aging and cancer has generally been attributed to the “accumulation of DNA damage” in cells. However, this explanation is not comprehensive, and more and more evidence shows that some factors outside cancer cells are very important for regulating tumor progression. That’s why diet, exercise, and a variety of small molecule drugs that target metabolic processes can affect cancer. < / P > < p > to test this idea, in this study, scientists at Weill Cornell medicine first collected serum from two groups of volunteers, one from 30 healthy donors aged 30 and under, and the other from 30 donors aged 60 or over. They then fed the serum to cancer cells in a dish. < / P > < p > soon, the cancer cells had different changes. Most of the cells treated with the serum from young donors remain in the original state, but most of the cancer cells treated with the serum of the aged donors have changed from epithelial cells to mesenchymal cells, and some proteins related to invasion and metastasis in the cells increase accordingly. In other words, the old serum allows cancer cells to gain the potential of invasion and metastasis. This potential was then validated: after these cancer cells were injected into mice, the serum from the elderly strongly enhanced the ability of cancer cells to colonize the lung and form metastatic lesions. Moreover, the cancer cells cultured in the serum of the elderly were resistant to two commonly used chemotherapy drugs (paclitaxel and carboplatin). < / P > < p > naturally, what are the substances in the serum of the elderly that are rare in the serum of young people and can promote the invasion of cancer cells? After measuring nearly 180 metabolites in the serum of both groups, the researchers noticed a consistent increase in a substance called methylmalonic acid (MMA) in the serum of the elderly. Moreover, the invasion of cancer cells can be increased by treating cancer cells with MMA alone. < / P > < p > MMA is a byproduct of protein and fat decomposition, and its increase may be related to vitamin B12 deficiency and high protein intake. The researchers measured the concentration of MMA and found that in young serum, only 0.1 – 1.5 μ m was found, while that in elderly serum was as high as 15 – 80 μ m, which was dozens to hundreds of times different. Subsequently, gene analysis showed that when the concentration of MMA was high, the expression of transcription factor SOX4 gene was significantly increased. However, many previous studies have found that SOX4 gene can promote tumor progression and metastasis, and its expression level is high in many invasive cancers, which is a sign of poor prognosis. The researchers found that if SOX4 activity was blocked and MMA was added, the migration and invasion of cancer cells did not increase, nor did they show resistance to chemotherapy drugs. Based on the above results, the authors conclude that aging related metabolic disorders play a central role in tumor invasion. Aging can promote the increase of MMA in the blood, and then make cancer cells have the ability to migrate, invade, survive and progress, and shorten the cancer-related survival period. In a review published in nature, Professor Zhang Xiang, an oncologist at Baylor Medical College, pointed out that this study reveals the role of metabolism in the relationship between aging and cancer progression, thus broadening our understanding of cancer risk factors.