FDA; Use of cancer cells in vaccines is risky.

FDA: Scientific understanding of neoplastic processes and viral-induced carcinogenesis has rapidly advanced, as has the ability to detect and identify infectious, oncogenic agents and other types of adventitious agents that may potentially contaminate cell substrates. These factors underscore the need for developing a regulatory framework in which the relative benefits and risks in using tumorigenic cell lines for vaccine production can be carefully and cautiously revisited.
http://www.fda.gov/ohrms/dockets/ac/01/briefing/3750b1_01.htm