For cancerous cells in the body, it seems there is safety in numbers. Researchers from a newly published study investigated the unique advantage cancer cell clusters have over single cancer cells in their ability to metastasize and spread cancer from one part of the body to another. However, with this enhanced understanding of cluster cells’ abilities comes a potential solution.
Cancer metastasizes when either a single cancerous cell or a cluster of cells breaks away from the original tumor and enters the body’s circulation, like one car or a caravan of cars may leave one area and merge onto a highway on the way to a new destination. However, unlike the cars, once the cancer cell reaches its new destination, it sets up camp and triggers the growth of a new tumor, now making a person’s case of cancer twice as dangerous.
Clusters may have higher “metastatic potential” than single cells; the new study investigates why that is. Interestingly, clusters have also been associated with resistance to chemotherapy in the past.
With studies of various animal models in the context of lung cancer metastasis rates and severity, researchers quickly found that the metastatic potential associated with clusters was due to their increased resistance to natural killer (NK) cells. It appeared that NK cells were more efficient at clearing out single cancer cells attempting metastasis as opposed to clusters.
NK cells are immune cells responsible for cancer surveillance and destruction. They are part of the innate immune response, a non-specific, first response to pathogenic infections and cancer. NK cells release molecules toxic to cancerous cells in response to recognition of certain cell surface molecules designating cancerous cells as a target.
Researchers found that clusters seem to be uniquely able to suppress NK cell activity. Cancer cells display certain cell surface molecules that impact NK cell activity. Researchers found that cancer cell clusters display more surface molecules that suppress NK cell activity than molecules that increase their activity.
Interestingly, this mechanism or a similar mechanism may also be employed to elicit the chemotherapy-resistant effect associated with cancer cell clusters.
Now, with a new understanding of how and why metastasis potential can vary in different cases of cancer, researchers are considering enhancing NK cell activity to combat cluster cell resistance.