Tumor-specific immunity and antiangiogenesis generated by a DNA vaccine encoding calreticulin linked to a tumor antigen

Antigen-specific cancer immunotherapy and antiangiogenesis have emerged as two attractive strategies for cancer treatment. An innovative approach that combines both mechanisms will likely generate the most potent antitumor ef fect. We tested this approach using calreticulin (CRT), which has demonstra ted the ability to enhance MHC class I presentation and exhibit an antiangi ogenic effect. We explored the linkage of CRT to a model tumor antigen, hum an papilloma virus type-16 (HPV-16) E7, for the development of a DNA vaccin e. We found that C57BL/6 mice vaccinated intradermally with CRT/E7 DNA exhi bited a dramatic increase in E7-specific CD8(+)T cell precursors and an imp ressive antitumor effect against E7-expressing tumors compared with mice va ccinated with wild-type E7 DNA or CRT DNA. Vaccination of CD4/CD8 double-de pleted C57BL/6 mice and immunocompromised (BALB/c nu/nu) mice with CRT/E7 D NA or CRT DNA generated significant reduction of lung tumor nodules compare d with wild-type E7 DNA, suggesting that antiangiogenesis may have contribu ted to the antitumor effect. Examination of microvessel density in lung tum or nodules and an in vivo angiogenesis assay further confirmed the antiangi ogenic effect generated by CRT/E7 and CRT. Thus, cancer therapy using CRT l inked to a tumor antigen holds promise for treating tumors by combining ant igen-specific immunotherapy and antiangiogenesis.