Using an altered version of the smallpox vaccine, an experimental cancer vaccine from Jennerex Inc. extended the lives of liver cancer patients as much as 14 months, according to a paper published Sunday in the journal Nature Medicine. Showing that some of the toughest-to-treat patients with one of the most aggressive cancers may live longer than with today’s treatments could help privately held Jennerex of San Francisco raise more money as it races against Amgen Inc. (NASDAQ: AMGN) and other…