Co-stimulatory molecules play an important role in initiating antitumor imm
une responses. Engineered tumor cells expressing co-stimulatory molecules h
ave been used as cancer vaccines in both experimental tumor models and clin
ical trials In this study, we cloned a cDNA gene coding for the mouse co-st
imulatory molecule 4-1BBL by RTPCR. The expression vector pCI-4-1BBL was co
nstructed by DNA recombinant technology and further transfected into a mode
rately immunogenic EL4 and a poorly immunogenic BL6-10 tumor cell line. Exp
ression of the co-stimulatory molecule 4-1BBL is able to induce tumor regre
ssion of EL4/4-1BBL but not BL6-10/4-1BBL tumor cell line in syngeneic BALB
/c mice. The tumor regression which is mainly mediated by CD8(+) T cells fu
rther leads to protective immunity against the parental EL4 tumor. Our resu
lts thus indicate the potential utility of engineered tumor cells expressin
g co-stimulatory molecule 4-1BBL, especially in combination with other co-s
timulatory molecules such as B7-1 in cancer vaccine.