They migrate in groups of at least 23 members, moving in an autonomous and seemingly random, but perfectly coordinated and compact way.

A group leader indicates the movement strategies and migration route. To ensure the effectiveness of migration, the role of leader, more exposed to environmental factors, is constantly rotated among group members, allowing them to rest.

Only in this way are they able to reach their destination and proliferate.

This is not a description of the behaviour of a flock of birds or a school of sardines, but of cancerous B-cells, a typical example of “liquid tumours” such as lymphomas.

Using a combination of cutting-edge technologies, a team of researchers at the FIRC Institute of Molecular Oncology (IFOM) and the University of Milan, led by Professor Giorgio Scita, has managed for the first time to "sketch" the behaviour of aggregated cancer cells, which exhibit different characteristics than non-aggregated cells.

Cells aggregated in "flocks" are more sensitive to migratory stimuli from chemokines, their molecular "fuel", and thus acquire the ability to invade tissues more effectively, to resist cell death and, in the end, to reach lymph nodes and colonise distant organs, causing metastasis.

Cell aggregation is observed in lymphomas and chronic leukaemias, but is also typical of solid tumours such as breast cancer, colon cancer and melanoma.

Understanding why and how they aggregate and identifying potential disruptive factors could contribute significantly to the identification of targeted therapies.

"We worked to identify the molecular mechanisms and biological processes that increase the migration potential and resistance in collective aggregations compared to solitary cancer cells," explained Prof Scita, of IFOM and the University of Milan, Italy. 

Analysing these migrating cells using physical parameters similar to those used in animal behaviour research, the researchers found that the cancer cells have behavioural and relational dynamics identical to those typical of migratory birds or sardines, which tend to move in groups to confuse an attacker.

"We observed that, whereas the individual components appear move in a random fashion, in reality they maintain perfect coordination in the way they migrate," says Prof Scita.

"There are lead cells that drive the movement... but within the group there is constant substitution of the leader cells with follower cells." 

This continuous rotation moves fresh cancer cells, which have not been weakened by the journey, to the outside of the "flock."

The "flock" itself pauses when concentrations of chemokines grow scarce, allowing the group to sample the environment, locate higher concentrations of "fuel," and change course.

"It emerges that there is a flawless cell-cell communication mechanism behind this ability to aggregate and migrate efficiently," Prof Scita says.

"Prospectively, the clinical objective will be to identify an inhibitor that interferes with this intercellular communication mechanism, disrupting the group and eliminating or reducing migration and chemotaxis." 

Source: IFOM