Summary
The tubulin-binding natural product combretastatin A-4 (CA-4) was tested for antitumor activity against fresh human tumors in vitro and 2 mouse tumors, both in vitro and in vivo. In colony forming assays using 10% fetal bovine serum, CA-4 was inhibitory in 27/40 human ovary cancers with a mean IC50 of 3.18 μg/mL for a 1-hour exposure (n = 35 specimens) and 0.27 μg/mL for a continuous exposure to CA-4 for 11–14 days (n = 5 specimens). Murine B-16 melanoma and P-388 leukemia were also highly sensitive to CA-4 in vitro with an identical IC50 value of 0.0007 μg/mL for continuous drug exposure for 8 days. Comparable in vitro cell culture studies performed in serum concentrations higher than 10%, revealed a significant loss of cytotoxic potency. Using the same reversed-phase HPLC technique as developed for paclitaxel, CA-4 was shown to bind to serum proteins (≥30,000 mw) > 99% and to albumin approximately 70%. CA-4 was only marginally active (25% increased lifespan) in DBA/2 mice bearing P-388 leukemia who were given doses of 100 mg/kg IP on either days, 1, 5 and 9 (p = 0.075 by Wilcoxon analysis) or on consecutive days 1–9 (p = 0.19 compared to control). A higher IP dose of 150 mg/kg on days 1, 5 and 9 did not delay subcutaneous B-16 melanoma tumor growth in C57/Bl mice. These findings demonstrate a substantial loss of antitumor efficacy for CA-4 in physiologic serum concentrations in vitro. No consistent antitumor activity was observed in two murine tumor models in vivo.
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Pettit GR, Singh SB, Niven ML, Hamel E, Schmidt JM: Isolation, structure, and synthesis of combretastatins A-1 and B-1, potent new inhibitors of microtubule assembly, derived from Combretum caffrum. J Nat Prod 50(1):119–131, 1987
Pettit GR, Singh SB, Niven ML, Schmidt JM: Cell growth inhibitory dihydrophenanthrene and phenanthrene constituents of the African tree Combretum caffrum. Can J Chem 66:406–413, 1988
Hamel E, Ho HH, Kang GJ, Lin CM: Cornigerine, a potent antimitotic Colchicum alkaloid of unusual structure: interactions with tubulin. Biochem Pharmacol 37:2445–2449, 1988
Pettit GR, Singh SB, Hamel E, Lin CM, Alberts DS, Garcia-Kendall D: Isolation and structure of the strong cell growth and tubulin inhibitor combretastatin A-4. Experientia 45:209–211, 1989
McGown AT, Fox BW: Differential cytotoxicity of combretastatins A-1 and A-4 in two daunorubicin-resistant P388 cell lines. Cancer Chemother Pharmacol 26:79–81, 1990
El-Zayat AAE, Degen D, Drabek S, Clark GM, Pettit GR, Von Hoff DD: In vitro evaluation of the antineoplastic activity of combretastatin A-4, a natural product from Combretum caffrum (arid shrub). Anti-Cancer Drugs 4:19–25, 1993
Hamburger A, Salmon SE: Primary bioassay of human myeloma stem cells. Science 197:461–463, 1977
Salmon SE, Hamburger AW, Soehnlen B, Durie BG, Alberts DS, Moon TE: Quantitation of differential sensitivity of human tumor stem cells to anticancer drugs. N Engl J Med 298:1321–1327, 1978
Salmon SE, Liu RM, Casazza AM: Evaluation of new anthracycline analogs with the human tumor stem cell assay. Cancer Chemother Pharmacol 6(2):103–109, 1981
Salmon SE, Young L, Lebowitz J, Thomson S, Einsphar J, Tong T, Moon TE: Evaluation of an automated image analysis system for counting human tumor colonies. Intl J Cell Cloning 2:142–160, 1984
Mosmann T: Rapid colorimetric assay for cellular growth and survival: application to proliferation and cytotoxicity assays. J Immunol Meth 65:55–63, 1983
Skehan P, Storeng R, Scudiero D, Monks A, McMahon J, Vistica D, Warren JT, Bokesch H, Kenney S, Boyd MR: New colorimetric cytotoxicity assay for anticancer-drug screening. J Natl Cancer Inst 82:1107–1112, 1990
Griswold DP Jr: Consideration of the subcutaneously implanted B16 melanoma as a screening model for potential anticancer agents. Cancer Chemother Rep 3 (Part 2, No. 1):315–324, 1972
Corbett TH, Griswold DP Jr, Roberts BJ, Peckham JC, Schabel FM Jr: Biology and therapeutic response of a mouse mammary adenocarcinoma (16/C) and its potential as a model for surgical adjuvant chemotherapy. Cancer Treat Rep 62(10):1471–1488, 1978
Gehan EA: A generalized Wilcoxon test for comparing arbitrarily single-censored samples. Biometrika 52:203–210, 1965
Jackson DV, Bender RA: Cytotoxic thresholds of vincristine in L1210 murine leukemia and a human lymphoblastic cell line in vitro. Cancer Res 39:4346–4349, 1979
Cahan MA, Walter KA, Colvin OM, Brem H: Cytotoxicity of taxol in vitro against human and rat malignant brain tumors. Cancer Chemother Pharmacol 33:441–444, 1994
Georgiadis MS, Russell E, Johnson BE: Prolonging the exposure of human lung cancer cell lines to paclitaxel improves the cytotoxicity. Proc Am Assoc Cancer Res 35:341, 1994
Johnson IS, Armstrong JG, Gorman M, Burnett JP Jr: The vinca alkaloids: a new class of oncolytic agents. Cancer Res 23:1390–1427, 1963
National Cancer Institute Clinical Brochure; Taxol (NSC-125973). Division of Cancer Treatment, N.C.I., Bethesda, MD, Sept. 1983, pp 6–12
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Dorr, R.T., Dvorakova, K., Snead, K. et al. Antitumor activity of combretastatin-A4 phosphate, a natural product tubulin inhibitor. Invest New Drugs 14, 131–137 (1996). https://doi.org/10.1007/BF00210783
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DOI: https://doi.org/10.1007/BF00210783