Although many cells do die on their own, all somatic cells that divide have the ability to undergo senescence.
“We were not sure if they were doing something important.” Despite self-disabling the ability to replicate, senescent cells stay metabolically active, often continuing to perform basic cellular functions.
Senescent cells have also been identified in the placenta and embryo, where they seem to guide the formation of temporary structures before being cleared out by other cells.
In 2008, three research groups, including Campisi’s at the Buck Institute for Research on Aging in Novato, California, revealed that senescent cells excrete a glut of molecules-including cytokines, growth factors and proteases-that affect the function of nearby cells and incite local inflammation.
In support of that idea, a large collaboration of researchers found this year that removing senescent cells right after chemotherapy, in mouse models for skin and breast cancer, makes the cancer less likely to spread. The lack of universal features makes it hard to take inventory of senescent cells.
Kirkland, together with collaborators at the Sanford Burnham Medical Research Institute in La Jolla, California, initially attempted a high-throughput screen to quickly identify a compound that would kill senescent cells.
Finally, senolytic drugs will clear only senescent cells that are already present-they won’t prevent the formation of such cells in the future, which means that senescence can continue to perform its original tumour-suppressing role in the body.