Scientists find why obesity can increase your cancer risk

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Obesity is now a global epidemic, and it is increasing people’s risk for cancer.

The National Cancer Institute lists more than a dozen cancers that are associated with overweight and obesity. But how obesity increases cancer risk hasn’t been clear.

In a study from Boston Children’s Hospital, researchers found a direct link—one with possible implications for cancer screening and treatment.

The team focused on one common cancer, breast cancer after menopause, and they provided compelling evidence that obesity may cause previously dormant tumors to trigger the formation of new blood vessels, a process called angiogenesis or neovascularization.

Once nourished with a blood supply, the tumors grow and become more of a threat.

The team then showed, in mice, that giving a drug to inhibit blood vessel formation kept breast tumors in their dormant state.

In the study, the researchers created a complex model involving obese menopausal mice that would allow them to observe tumor neovascularization in real-time.

They then injected human breast tumor cells, bearing an enzyme called luciferase, into the mammary fat pads of both obese and lean mice.

Finally, to detect the invasion of new blood vessels into the tumors, they injected another compound, luciferin, into the animals’ bloodstreams.

When luciferase and luciferin meet, they light up as a bioluminescent signal, indicating that blood vessels have reached the tumor.

The team then tracked subsequent tumor growth through a series of imaging studies.

Initially, the tumors did not light up because no blood vessels (and hence no luciferin) reached them.

But within three to six weeks, blood vessels began invading the tumors of the obese mice, which lit up dramatically. In contrast, tumors in the non-obese mice were still dormant at 12 weeks.

The team found that fat cells from the obese mice were secreting higher levels of compounds that promote angiogenesis: lipocalin-2, vascular endothelial growth factor, and basic fibroblast growth factor.

These apparently enabled the tumors to come out of dormancy and start progressing.

The team also found when the obese mice received sunitinib, a drug that inhibits blood vessel formation, tumor latency was prolonged and tumor-free survival increased.

The lab has now shown in multiple mouse models that such inhibitors can maintain breast tumors in their dormant state.

If you care about cancer, please read studies about vaccine to prevent pancreatic cancer, and vitamin D supplements strongly reduces cancer death.

For more information about weight loss, please see recent studies about why diet drinks make you gain more weight, and honey could help control blood sugar.

The study was conducted by Marsha A. Moses et al and published in the Proceedings of the National Academy of Sciences.

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