Cell surface expression of gp96 on tumor cells confers increased immunogenicity and anti-tumor memory. (A) Expression of cell surface gp96 by Meth A-neo and Meth A-96tm cells was analyzed by immunoprecipitation of biotinylated cell surface proteins with avidin, followed by immunoblotting with anti-myc Ab (top panel). As a control, the total cell lysate was blotted for gp96 with anti-gp96 Ab (bottom panel). (B) Efficient rejection of CT-26-96tm (left panel) and Meth A-96tm (right panel) cells, but not of control vector-transfected cells, by wild type syngeneic BALB/c mice. (C) Meth A-96tm immunized mice were re-challenged 90 days later with wild type Meth A. The kinetics of tumor growth were then measured. Each line represents the average growth kinetics of 5 mice. The numbers in parenthesis indicate the number of tumor-free mice in each group at the end of the experiment shown. Two independent experiments yielded similar results.