How old were the donors? The cells have only about 50 cycles from birth to death.

Cancer cells do not undergo senescence without a stress. Therefore, share your culture conditions or any treatments. If your cells died, this does not mean that cells died because of cellular senescence. Senescent cells remain metabolically active and if the medium is changed routinely when needed, cells can stay alive for a long period of time.

Dear Heba,

Divaker is right, this is probably not their senescence but some kind of response to culture conditions. Established cancer cell lines bear genetic abnormalities which help them to grow vigorously in vitro for long periods of time. Cancer cells obtained from primary tumors are far more sensitive to environmental insult. If you want to check if senescence was involved, try to examine how big was the fraction of SA-b-Gal-positive/Ki67-negative/gammaH2A.X-positive cells in your culture (vs. control cells - just after their isolation from a tumor mass).

Good luck