HeLa cells, which are named for Henrietta Lacks, the original donor, play a central role in modern cancer research due to their lack of a cellular-termination switch. Most cells divide a set number of times before dying, but cells of the HeLa line divide continuously, rendering them effectively immortal, and giving cancer researchers a stable baseline of identical cells for experiments.
The first cells of the HeLa line were harvested from Henrietta Lacks, a cancer patient, in 1951. Billions of HeLa cells, weighing approximately 20 tons, have since been cultured and distributed to medical research laboratories around the world. Research involving HeLa cells has generated over 11,000 patents, and the line was instrumental in developing treatments for cancer, AIDS and polio, as well as being used to test the safety of pharmaceuticals and consumer products.
HeLa cells' immortality is the result of an unusual division sequence. In normal cells, chromosomes are bound at their tips by sequences called telomeres. Telomeres usually shorten with each cell division until the cell dies. HeLa cells, which were cultured from an unusually aggressive form of cancer, possess an active protein, called telomerase, which helps replenish the telomeres. As a result, HeLa cells have no internal mechanism for terminating cell division, allowing them to reproduce endlessly.