(FORTUNE Magazine) – The possibility that Interleukin-2, a substance produced by the body's immune system, could cure cancer excited doctors and companies that genetically engineer it (FORTUNE, November 25). Four weeks after FORTUNE released its cover story, the New England Journal of Medicine published an encouraging report on IL-2. Though the findings are preliminary, and one patient using the treatment has died, Wall Street went wild. Cetus Corp. and Immunex Corp. saw trading volume increase tenfold and their stock prices double from a month earlier. Stocks of companies working on different lines of cancer research shot up too. ''People pressed the trigger without knowing where they were aiming,'' says Robert Kupor, a security analyst with Cable Howse & Ragen in Seattle.