promoting agent

[prə-mōtĭng]
n.
  1. A noncarcinogenic substance that enhances tumor production in a tissue previously exposed to subcarcinogenic doses of a carcinogen.initiating agent
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.