Cancer cell

In 2017, actor and singer Olivia Newton-John announced that she had breast cancer for the third time. Two years later, she began suffering from back pain and had to cancel her tour dates. Her doctors initially thought sciatica was the culprit, then realized her cancer had spread to her bones. The famous Grease the singer died at home in Southern California in August 2022 at age 73.

Scientists are learning more about how and where cancer spreads. Metastatic breast cancer (MBC), the kind that Newton-John had, usually spread to the bones, brain, liver or lungs. MBC is a deadly disease and half of all women do not live three years after diagnosis. Less than 26 percent of women survive five years after diagnosis.

For most patients, there is no cure for MBC. Scientists are trying to learn more about how cancer-spreading cells function to stop MBC before it starts. A new studypublished in Naturediscovered when cancer-spreading cells are at their worst, which could help researchers work toward a cure.

Dormant cells

There are several ways that cancer spreads to other organs. For many MBC patients, circulating tumor cells (CTCs) are to blame. These cells are shed from the breast tumor, enter the bloodstream, make their way to other organs and wreak havoc.

Learning found that these cells are most active when a person sleeps. The researchers took blood samples from 30 Swiss women who had been hospitalized with breast cancer. Nine of the women had stage IV MBC and discontinued treatment. The rest had early, non-metastatic breast cancer and were preoperative.

The researchers collected one sample at 4 am and a second sample at 10 am. The team then analyzed the blood to see if CTCs were more prevalent in the overnight or morning sample.

The difference in the number of CTCs found in blood samples is night and day. Almost 80 percent of the CTCs came from the 4 a.m. sample, when patients were at rest.

The research team then repeated the experiment with mice. First, they implanted breast cancer tumors into the mice. Later, they took daytime and nighttime blood samples. Because mice are nocturnal and prefer to rest during the day and then go about their mouse business after nightfall, the researchers sought to see if CTCs were more present in blood taken while the mice were “at rest” or ” active’.

Almost all (more than 90 percent) of the CTCs in the mouse blood samples came from the resting period. But are these dormant cells more capable of spreading cancer?

Skillful distributors

To find out which type of CTC is more adept at spreading cancer, the scientists added fluorescent markers to distinguish the rest from the active CTCs. They injected both types of cells back into the mice.

Most of the CTCs that contributed to new tumors did come from the rest of the sample—meaning that these cells weren’t just more abundant, they were also more potent.

The research team also analyzed the gene expression of each cell type, and it appeared that the CTCs released during rest were consistent with genes involved in cell mutation and mitosis.

Why this happens is still one of the questions that scientists ponder. They believe that the remaining CTCs respond to the cycle of hormones released each day in relation to our sleep and wake patterns. This means that these cancer-spreading cells know when the body is asleep and when it is awake.

Knowing when the body releases these problematic cells may one day help researchers identify treatments that target the released CTCs at the exact time when they are causing the most damage. And since breast cancer isn’t the only type of cancer that metastasizes, there’s hope that scientists can use this as a guide when studying the spread of other types of cancer.

Until then, cancer patients are advised not to skimp on sleep. There is no research to suggest that less sleep means less time for dormant cells to proliferate.

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