EphA2 Immunoconjugate as Molecularly Targeted Chemotherapy for Ovarian Carcinoma

• Published in: JNCI : Journal of the National Cancer Institute Vol. 101; no. 17; pp. 1193 - 1205
• Main Authors: Lee, Jeong-Won, Han, Hee Dong, Shahzad, Mian M. K., Kim, Seung Wook, Mangala, Lingegowda S., Nick, Alpa M., Lu, Chunhua, Langley, Robert R., Schmandt, Rosemarie, Kim, Hye-Sun, Mao, Shenlan, Gooya, John, Fazenbaker, Christine, Jackson, Dowdy, Tice, David A., Landen, Charles N., Coleman, Robert L., Sood, Anil K.
• Format: Journal Article
• Language: English
• Published: Cary, NC Oxford University Press 02-09-2009; Oxford Publishing Limited (England)
• Subjects: Animals; Antibodies, Monoclonal - pharmacology; Antineoplastic agents; Antineoplastic Agents - pharmacology; Antineoplastic Agents - therapeutic use; Apoptosis - drug effects; Binding sites; Biological and medical sciences; Blotting, Western; Cell Line, Tumor; Cell Survival - drug effects; Cellular biology; Chemotherapy; Female; Fluorescent Antibody Technique; Humans; Immunoconjugates - pharmacology; Immunoconjugates - therapeutic use; Immunohistochemistry; In Situ Nick-End Labeling; Medical sciences; Mice; Molecular biology; Oligopeptides - pharmacology; Oligopeptides - therapeutic use; Ovarian cancer; Ovarian Neoplasms - drug therapy; Ovarian Neoplasms - immunology; Pharmacology. Drug treatments; Platelet Endothelial Cell Adhesion Molecule-1 - analysis; Proliferating Cell Nuclear Antigen - analysis; Receptor, EphA2 - analysis; Receptor, EphA2 - antagonists & inhibitors; Receptor, EphA2 - immunology; Tumors; Xenograft Model Antitumor Assays; Human; Ovary carcinoma; Phenylalanine; Targeted therapy; Ovary cancer; Rodentia; trk receptor; Malignant tumor; Immunoconjugate; Female genital diseases; Ovarian diseases; Vertebrata; Chemotherapy; Mammalia; Treatment; Cancerology; Mouse; Aminoacid; Animal; Established cell line; Cancer
• ISSN: 0027-8874; 1460-2105
• DOI: 10.1093/jnci/djp231

Background EphA2 is overexpressed in many types of human cancer but is absent or expressed at low levels in normal epithelial tissues. We investigated whether a novel immunoconjugate containing an anti-EphA2 monoclonal antibody (1C1) linked to a chemotherapeutic agent (monomethyl auristatin phenylalanine [MMAF]) through a noncleavable linker maleimidocaproyl (mc) had antitumor activity against ovarian cancer cell lines and tumor models. Methods Specificity of 1C1-mcMMAF was examined in EphA2-positive HeyA8 and EphA2-negative SKMel28 ovarian cancer cells by antibody binding and internalization assays. Controls were phosphate-buffered saline (PBS), 1C1, or control IgG-mcMMAF. Viability and apoptosis were investigated in ovarian cancer cell lines and tumor models (10 mice per group). Antitumor activities were tested in the HeyA8-luc and SKOV3ip1 orthotopic mouse models of ovarian cancer. Endothelial cells were identified by use of immunohistochemistry and anti-CD31 antibodies. All statistical tests were two-sided. Results The 1C1-mcMMAF immunoconjugate specifically bound to EphA2-positive HeyA8 cells but not to EphA2-negative cells and was internalized by HeyA8 cells. Treatment with 1C1-mcMMAF decreased the viability of HeyA8-luc cells in an EphA2-specific manner. In orthotopic mouse models, treatment with 1C1-mcMMAF inhibited tumor growth by 85%–98% compared with that in control mice (eg, for weight of HeyA8 tumors, 1C1-mcMMAF = 0.05 g and control = 1.03 g; difference = 0.98 g, 95% confidence interval [CI] = 0.40 to 1.58 g; P = .001). Even in bulkier disease models with HeyA8-luc cells, 1C1-mcMMAF treatment, compared with control treatment, caused regression of established tumors and increased survival of the mice (eg, 1C1-mcMMAF vs control, mean = 60.6 days vs 29.4 days; difference = 31.2 days, 95% CI = 27.6 to 31.2 days; P = .001). The antitumor effects of 1C1-mcMMAF therapy, in SKOV3ip1 tumors, for example, were statistically significantly related to decreased proliferation (eg, 1C1-mcMMAF vs control, mean = 44.1% vs 55.8% proliferating cells; difference = 11.7%, 95% CI = 2.45% to 20.9%; P = .01) and increased apoptosis of tumor cells (eg, 1C1-mcMMAF vs control, mean = 8.6% vs 0.9% apoptotic cells; difference = 7.7%, 95% CI = 3.8% to 11.7%; P < .001) and of mouse endothelial cells (eg, 1C1-mcMMAF vs control, mean 2.8% vs 0.4% apoptotic endothelial cells; difference = 2.4%, 95% CI = 1.4% to 4.6%; P = .034). Conclusion The 1C1-mcMMAF immunoconjugate had antitumor activity in preclinical models of ovarian carcinoma.