Anti-tumor effects of chimeric T7 phage nanoparticles.
(A) Tumor incidence of the immunized mice in prophylactic setting. Seven days after the last boost, mice were challenged subcutaneously with 5×105 TUBO breast cancer cells and monitored for palpable tumors for six weeks. As shown, 83% of mice (5 out of 6 mice) did not develop TUBO tumors and remained tumor-free until the end of study (day 42) (log-rank test, P = 0.004, compared to negative controls). In contrast, with p66 peptide-CFA/IFA emulsion only 33% survival rate was achieved (log-rank test, P = 0.04, compared to negative controls. All mice in T7-p66x2, p66x2+FA and T7-wt+p66 groups showed fast-growing tumors and had to be euthanized. (B) Therapeutic efficacy of the chimeric T7 phage nanoparticles. Before initiation of the immunization schedule, BALB/c mice were implanted with 5×105 TUBO cells in the right flank. After developing palpable tumors of ∼3 mm in diameter, vaccination was started in the opposite flank and tumor sizes were recorded regularly as described. Immunization of mice with T7-p66 nanoparticles successfully resulted in regression of the established tumors in four out of six mice. The other two animals had ulcerated tumors and had to be euthanized by day 28. In contrast, only two out of six mice vaccinated with p66 peptide plus Freund's adjuvant (p66+FA group) was able to significantly control tumor growth by day 80; even though the tumors were not completely eradicated at the end of study. Furthermore, these mice had a greater mean tumor volume compared to T7-p66-injected animals throughout the monitoring period. All control mice as well as those vaccinated with T7-p66x2 or p66x2+FA succumbed to TUBO tumors.