DNA Vaccination Controls Her-2+ Tumors that Are Refractory to Targeted Therapies

• Published in: Cancer research (Chicago, Ill.) Vol. 68; no. 18; pp. 7502 - 7511
• Main Authors: WHITTINGTON, Paula J, PIECHOCKI, Marie P, HENG, Henry H, JACOB, Jennifer B, JONES, Richard F, BACK, Jessica B, WEI, Wei-Zen
• Format: Journal Article
• Language: English
• Published: Philadelphia, PA American Association for Cancer Research 15.09.2008
• Subjects: Animals; Antibodies, Monoclonal - immunology; Antibodies, Monoclonal - pharmacology; Antineoplastic agents; Biological and medical sciences; Cancer Vaccines - immunology; Cancer Vaccines - pharmacology; Cell Growth Processes - drug effects; Female; Karyotyping; Mammary Neoplasms, Experimental - enzymology; Mammary Neoplasms, Experimental - genetics; Mammary Neoplasms, Experimental - immunology; Mammary Neoplasms, Experimental - therapy; Medical sciences; Mice; Mice, Inbred BALB C; Pharmacology. Drug treatments; Quinazolines - pharmacology; Receptor, ErbB-2 - biosynthesis; Receptor, ErbB-2 - immunology; Receptor, ErbB-2 - metabolism; Signal Transduction - drug effects; T-Lymphocytes, Cytotoxic - immunology; Tumors; Tyrphostins; Vaccines, DNA - immunology; Vaccines, DNA - pharmacology; Control; Treatment resistance; Treatment; Targeted therapy; Malignant tumor; Genetic vaccine; Cancer
• ISSN: 0008-5472; 1538-7445
• DOI: 10.1158/0008-5472.CAN-08-1489

Her-2/neu(+) tumor cells refractory to antibody or receptor tyrosine kinase inhibitors are emerging in treated patients. To investigate if drug resistant tumors can be controlled by active vaccination, gefitinib and antibody sensitivity of four neu(+) BALB/c mouse mammary tumor lines were compared. Significant differences in cell proliferation and Akt phosphorylation were observed. Treatment-induced drug resistance was associated with increased chromosomal aberrations as shown by spectral karyotyping analysis, suggesting changes beyond neu signaling pathways. When mice were immunized with pneuTM encoding the extracellular and transmembrane domains of neu, antibody and T-cell responses were induced, and both drug-sensitive and drug-resistant tumor cells were rejected. In T-cell-depleted mice, drug-sensitive tumors were still rejected by vaccination, but drug-refractory tumors survived in some mice, indicating their resistance to anti-neu antibodies. To further test if T cells alone can mediate tumor rejection, mice were immunized with pcytneu encoding full-length cytoplasmic neu that is rapidly degraded by the proteasome to activate CD8 T cells without inducing antibody response. All test tumors were rejected in pcytneu-immunized mice, regardless of their sensitivity to gefitinib or antibody. Therefore, cytotoxic T lymphocytes activated by the complete repertoire of neu epitopes were effective against all test tumors. These results warrant Her-2 vaccination whether tumor cells are sensitive or resistant to Her-2-targeted drugs or antibody therapy.