Circadian disruption may promote breast cancer spread via a damaged gut

Could circadian disruption provide a double hit to promote the spread and invasiveness of Breast Cancer?  A couple of studies published recently seem to suggest so.  A study published in May showed that decreased expression of Per2, one of the primary clock genes, plays a role in Breast Cancer.  This study indicated that the mechanism is likely via managing cellular repair and replication.

A study published more recently in the journal Cancer Research found that an inflamed gut increased the spread and invasiveness of hormone receptor-positive breast cancer in mice.  This could also tie in to circadian rhythms because circadian disruption alters gut homeostasis by increasing inflammation in the gut.

Thus, circadian disruption may cause a double hit to the body by altering cellular health and replication at the local tissue level as well as systemically by increasing inflammation in the gut.  So what to do?

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Optimizing circadian rhythms

Circadian rhythms help govern a large part of your physiology, from cellular metabolism and replication to tissue homeostasis.  Ultimately, circadian rhythms help separate use and repair at the cellular level.  This is fundamentally important to health and Cancer prevention because having use and repair at the same time can cause DNA damage which can ultimately lead to the creation of tumorous cells.

The creation of tumor cells isn’t a rare thing; everyone makes them every day.  But our immune system swoops in and takes care of these cells by either forcing them in to programmed cell death, or promoting senescence which prevents them from replicating.

So circadian rhythms provide defense at both the cellular and systemic level to minimize both the production of tumor cells as well as their spread throughout the body.  But in order for this to happen, you have to send the right signals to the body so you can synchronize the various clocks in your cells and tissues with one another to optimize function.

Circadian disruption and Cancer: A case for miscommunication?

We have a master clock in our brain that is sensitive to changes in light.  This master clock also has some level of control over other clocks located in each of our organs, called peripheral clocks.  In fact, each one of our cells has an internal clock.

When our master clock is synchronized with our peripheral clocks, and the peripheral clocks are synchronized with one another, our circadian rhythms are optimized.  This allows each of our tissues to communicate properly with one another, and allows our immune system to patrol at the proper time to terminate cancerous cells.

However, when our clocks are out of sync, this can cause tissues to become inflamed and impair the immune system, particularly when we have inflammation in the gut as 80% of the immune system is found in the gut. Inflammation beginning in the gut can enter the systemic circulation

As a result, cells can become tumorous and are allowed to proliferate in each of our tissues because our normally efficient ability to remove cancerous cells is impaired.  This is a double-hit that you absolutely want to avoid.


When we expose ourselves to light at improper times, eat food at improper times, consume too much food, get inadequate physical activity or perform it at the wrong time, poorly manage stress, or get inadequate sleep, this can cause circadian disruption.  Under circadian disruption, multiple factors conspire to increase our risk of Cancer.

There is ample evidence in mice that optimizing circadian rhythms can reduce the risk of metabolic diseases and Cancer.  Studies are currently underway in humans to see if avoiding circadian disruption by optimizing circadian rhythms can be useful for us. A recent study found that activating the circadian clock regulators REV-ERBa & REV-ERBb was lethal to Cancer cells and senescent cells.

In the meantime, it seems most prudent to work on things like developing a circadian schedule of exposures to reduce the risk for various Cancers.

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