You can read more about the technology on the company web site:
http://www.vitaltherapies.com/technology.html
Note how they call them “immortal” cells rather than cancerous cells.
Quote:
The key to the ELAD system is the proprietary C3A human hepatocyte cell line, licensed from the Wistar Institute in Philadelphia and further developed by Baylor College of Medicine. This is an immortal cell line that is grown in ELAD cartridges, then stored and shipped worldwide from VTI’s San Diego production facility. The cartridges are then incorporated into an extracorporeal blood pumping system at the patient’s bedside. The cells have been shown to perform most of the metabolic functions of normal liver cells in laboratory experiments.