α-TEA plus cisplatin reduces human cisplatin-resistant ovarian cancer cell tumor burden and metastasis

A novel nonhydrolyzable ether-linked acetic acid analog of vitamin E, 2,5,7,8-tetramethyl-2R-(4R,8R,12-trimethyltridecyl)-chroman-6-yloxyacetic acid (α-TEA) in combination with cisplatin, reduces tumor burden of A2780/cp70 (cp70) cisplatin-resistant human ovarian cancer cells xenografted into immune compromised nude mice. Two xenograft studies were conducted using cp70 cells stably expressing green fluorescent protein (cp70-GFP) subcutaneously transplanted into NU/NU mice. For studies 1 and 2, α-TEA was formulated in liposomes and delivered by aerosol such that approximately 36 μg and 72 pg of α-TEA were deposited in the respiratory tract of each mouse each day, respectively. Cisplatin at 5 mg/kg was administered by intraperitoneal injections once weekly for the first 3 weeks in Study 1 and on the third and 10th days following treatment initiation in Study 2. The combination α-TEA + cisplatin treatment reduced tumor burden and metastasis of cp70-GFP cells in comparison to control mice or mice treated with α-TEA or cisplatin singly. A significant reduction (P < 0.001) in growth of subcutaneous transplanted tumors was obtained with α-TEA + cisplatin for both studies. Visible metastases were observed in the lungs of animals from control and cisplatin-treated groups but not in animals from the α-TEA- or α-TEA + cisplatin-treated groups. The α-TEA + cisplatin significantly reduced the total number of lung and axillary lymph node micrometastasis (P < 0.03 and P < 0.0001, respectively). Analyses of tumor sections showed the α-TEA + cisplatin treatment group, in comparison to control, to have a significantly lower level of cell proliferation (Ki-67 staining; P < 0.0001) and a significantly higher level of apoptosis (terminal deoxy-nucleotidyl transferase-mediated nick end labeling [TUNEL]; P < 0.0001). In summary, combinations of α-TEA + cisplatin significantly reduced tumor burden and metastases in a xenograft model of cisplatin-resistant human ovarian cancer cells. These data show promise for combination α-TEA + cisplatin chemotherapy for ovarian cancer.