The wikipedia article ( https://en.wikipedia.org/wiki/Senolytic ) cites https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4748967/ from December 2015, so the concept is at least that old.

I've talked to researchers in the bio field dealing with immortal cells. Those cells are apparently dangerous to touch because they will give you cancer.

My remembrance is that Campisi and others were thinking about them since at least the early 2000s.