Eradication of hepatoma and colon cancer in mice with Flt3L gene therapy in combination with 5-FU

We developed a recombinant defective adenovirus with an insert of gene encoding extracellular domain of mouse Flt3L (Ad-mFlt3L) under control of cytomegalovirus promoter to investigate the biological efficacy of Flt3L in combination with chemotherapeutical drug, 5-FU, in eliciting an effective anti-cancer immunity in mouse hepatoma and colon cancer model systems. The constructed Ad-mFlt3L efficiently infected hepatoma and colon cancer cells both in vitro and in vivo, leading to a high production of mFlt3L proteins in association with accumulation of DCs, NK cells and lymphocytes in local tumor tissues. Administration of Ad-mFlt3L can protect bone marrow injury caused by 5-Fu and stimulates proliferation and maturation of lymphocytes, APCs and NKs. Intratumoral injection of Ad-mFlt3L followed by an intraperitoneal administration of 5-Fu significantly inhibited tumor growth and cured established tumors. Adenovirus mediated Flt3L gene therapy synergies with chemotherapeutic drug, 5-Fu, in elicitation of long-lasting antitumor immunity. The tumor specific immunity can be adoptively transferred into naive animals successfully by transfusion of CD3(+) CD8(+) T cells from the treated mice. The data suggests that adenovirus mediated Flt3L gene therapy in combination with 5-Fu chemotherapy may open a new avenue for development of anti-cancer chemogenetherapy.