Researchers shed light on how diet influences cancer development

NUMEROUS studies have linked high-calorie diets to increased risk of cancer. But in a new study, researchers have found that switching from a low- to high-calorie diet can either encourage tumor growth or reduce it.

    Researchers say they have uncovered how changing from a low- to high-calorie diet affects cancer development.

      The association between diet and cancer has long been investigated by researchers. The general consensus is that unhealthy diets may contribute to cancer development, while healthy diets may prevent it.

     Last year, it was reported that a low-fat diet supplemented with omega-3 may reduce prostate cancer risk. And another study published this week linked a reduction in dietary fat intake to improved survival rates for women with hormone-unrelated breast cancer.

      But the team involved in this latest study – led by Prof. Roberto Coppari of the Faculty of Medicine at the University of Geneva in Switzerland – notes that the mechanisms by which diet influences tumor growth is unclear, and this is something they set out to investigate.

      Specifically, the researchers focused on tumors driven by mutations in the KRAS gene, which are often found in lung, pancreas and colon cancers.

    Coppari and his team wanted to see how switching from a diet low in calories to a high-calorie diet affects tumor growth in the lungs.

High-calorie diet increases stress in endoplasmic reticulum of cells

      The results of the study – published in the journal Cell Metabolism – revealed that conversion from a low- to high-calorie diet appeared to reduce tumor growth when the high-calorie diet was adopted before tumors started to grow. If the switch from a low- to high-calorie diet took place after tumor growth began, it boosted their growth further.

    On further analysis, the team found that a change in diet triggered an increase in stress in the endoplasmic reticulum – an area in cells that regulates protein organization. A rise in stress in this area increases expression of chaperones, which are molecules that aid protein function.

    The researchers note that too much of a stress increase in the endoplasmic reticulum can cause cells to die, making the cells unable to spur tumor growth. This may explain why changing to a high-calorie diet reduced tumor growth.

    The team says changing to a high-calorie diet after tumor growth started, however, may fuel further growth because the tumor cells have already adapted to an increase in endoplasmic reticulum stress; more stress encourages further tumor cell proliferation.

    Commenting on their findings, co-first study author Giorgio Ramadori, of the University of Geneva, says: “Our study does not show that, by eating junk food, people would be protected from lung cancer.

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