EphA2 immunoconjugate as molecularly targeted chemotherapy for ovarian carcinoma.
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).


CONCLUSIONS
The 1C1-mcMMAF immunoconjugate had antitumor activity in preclinical models of ovarian carcinoma.
Lee
Jeong-Won
JW
Department of Gynecologic Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA.
Han
Hee Dong
HD
Shahzad
Mian M K
MM
Kim
Seung Wook
SW
Mangala
Lingegowda S
LS
Nick
Alpa M
AM
Lu
Chunhua
C
Langley
Robert R
RR
Schmandt
Rosemarie
R
Kim
Hye-Sun
HS
Mao
Shenlan
S
Gooya
John
J
Fazenbaker
Christine
C
Jackson
Dowdy
D
Tice
David A
DA
Landen
Charles N
CN
Coleman
Robert L
RL
Sood
Anil K
AK
D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D005260:Female; D005455:Fluorescent Antibody Technique; D006801:Humans; D018796:Immunoconjugates / Q000494:pharmacology* / Q000627:therapeutic use; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D051379:Mice; D009842:Oligopeptides / Q000494:pharmacology* / Q000627:therapeutic use; D010051:Ovarian Neoplasms / Q000188:drug therapy* / Q000276:immunology*; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000032:analysis; D018809:Proliferating Cell Nuclear Antigen / Q000032:analysis; D036104:Receptor, EphA2 / Q000032:analysis / Q000037:antagonists & inhibitors* / Q000276:immunology; D023041:Xenograft Model Antitumor Assays
D000911:Antibodies, Monoclonal; D000970:Antineoplastic Agents; D018796:Immunoconjugates; D009842:Oligopeptides; D019408:Platelet Endothelial Cell Adhesion Molecule-1; D018809:Proliferating Cell Nuclear Antigen; D036104:Receptor, EphA2; C495575:monomethyl auristatin E