Novel vitamin E analogue and 9-nitro-camptothecin administered as liposome aerosols decrease syngeneic mouse mammary tumor burden and inhibit metastasis
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To test the anticancer properties of a nonhydrolyzable ether-linked acetic acid analogue of vitamin E, 2,5,7,8-tetramethyl-2R-(4R,8R,12-trimethyltridecyl)chroman-6-yloxyacetic acid (α-TEA), and a derivative of camptothecin, 9-nitrocamptothecin (9-NC) singly and in combination against mouse mammary tumor cells (line 66 clone 4 stably transfected with green fluorescent protein; 66c1-4-GFP) cultured in vitro or transplanted subcutaneously into the inguinal region of female BALB/c mice to form established tumors.
Following in vitro treatment of 66cl-4-GFP cells with α-TEA and suboptimal concentrations of 9-NC, singly or in combination, apoptosis was measured by morphological evaluation of nuclei stained with 4′,6-diamidino-2-phenylindole (DAPI), and DNA synthesis arrest was measured by tritiated thymidine uptake. For in vivo analyses α-TEA and 9-NC, both water-insoluble compounds, were formulated into liposomes using dilauroylphosphatidylcholine and administered by aerosol to deliver doses calculated to be 36 and 0.4 μg/mouse per day, respectively, (singly or each separately for combined treatments) 7 days per week.
Treatment of 66cl-4-GFP cells in culture for 3 days with a combination of α-TEA (10 μg/ml; singly produces 38% apoptosis), and suboptimal concentrations of 9-NC (15.6, 31.3, 62.5, or 125 ng/ml; singly produce 2–7% apoptosis), produced 47%, 58%, 64%, and 69% apoptosis. Likewise, combinations of α-TEA + 9-NC inhibited DNA synthesis more than either agent administered singly. A significant reduction (P<0.001) in growth of subcutaneous transplanted tumors was observed with liposome-formulated and aerosolized delivery of α-TEA + 9-NC to BALB/c mice. The incidence of macroscopic lung metastasis was 83% in control vs 8% in α-TEA-, 9-NC-, or combination-treated mice. Fluorescence microscopic examination of lungs and axillary and brachial lymph nodes showed a statistically significant decrease in metastasis observed in α-TEA-, 9-NC-, and combination- vs control-treated animals. Analyses of primary tumor tissue for proliferation and apoptosis showed treatment groups to have lower Ki-67 and higher terminal deoxynucleotidyl transferase-mediated nick end labeling, respectively. Treatments showed no measurable effects on two angiogenesis parameters, namely intratumoral blood volume as assessed by hemoglobin content and intratumoral blood vessel density as assessed with CD31 staining.
Combination treatments enhanced antiproliferative and proapoptotic activities in cell culture, and when formulated in liposomes and delivered via aerosolization to treat an aggressive and metastatic syngeneic murine mammary tumor, the combination treatment showed a significant reduction in tumor volume in comparison to either treatment alone. Mechanistically, it appears that neither enhanced apoptosis, reduced cell proliferation, nor reduced blood vessel density can fully account for the enhanced effects of the combination treatment.
- Novel vitamin E analogue and 9-nitro-camptothecin administered as liposome aerosols decrease syngeneic mouse mammary tumor burden and inhibit metastasis
Cancer Chemotherapy and Pharmacology
Volume 54, Issue 5 , pp 421-431
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- Vitamin E analogue α-TEA
- Syngeneic mouse mammary cancer model
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- 1. Cancer Prevention Fellowship Program, National Cancer Institute, NIH, DHHS, 6120 Executive Boulevard, Suite T-41, Bethesda, MD 20892, USA
- 2. Harvard Medical School, 4 Blackfan Circle, Boston, MA 02115, USA
- 3. School of Biological Sciences, University of Texas, Austin, TX 78712, USA
- 4. Department of Chemistry, Brock University, St Catharines, ON, Canada, L2S 3A1
- 5. Department of Cellular and Structural Biology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229, USA
- 6. Department of Molecular Physiology and Biophysics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
- 7. Department of Molecular Virology and Microbiology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
- 8. Division of Nutrition, University of Texas, Austin, TX 78712, USA