Proposed mechanism of therapeutic selectivity for 9-β-D-arabinofuranosyl-2-fluoroadenine against murine leukemia based upon lower capacities for transport and phosphorylation in proliferative intestinal epithelium compared to tumor cells Journal Article
| Authors: | Barrueco, J. R.; Jacobsen, D. M.; Chang, C. H.; Brockman, R. W.; Sirotnak, F. M. |
| Article Title: | Proposed mechanism of therapeutic selectivity for 9-β-D-arabinofuranosyl-2-fluoroadenine against murine leukemia based upon lower capacities for transport and phosphorylation in proliferative intestinal epithelium compared to tumor cells |
| Abstract: | Studies have examined transport and phosphorylation of 9-β-D-arabi-nofhranosyl-2-fluoroadenine (F-Ara-A), a deaminase resistant adenosine analogue, as mechanisms that could mediate the observed therapeutic efficacy of this agent against murine tumor models. Earlier finds by Avramis and Plunkett (Cancer Res., 42: 2587–2591, 1982) showed markedly less accumulation in vivo of administered F-Ara-A as cytotoxic triphosphate in gastrointestinal mucosa and bone marrow compared to P388 cells. We have pursued the basis for this difference in Vitro using LI 210 ascites and proliferative epithelial cells (85-95% crypt cells) isolated from mouse small intestine as representative sample populations of drug-sensitive tumor and drug-limiting normal regenerative host tissue. Using a rapid sampling technique, linear initial rates of substrate uptake were established at 25°C for radiolabeled F-Ara-A and adenosine at a concentration range of 1–1000 μm. The relationship between velocity of initial transport and substrate concentration is indicative of Michaelis-Menten saturation kinetics for both substrates. Competition studies between F-Ara-A and adenosine suggest a common route of entry for both substrates in crypt epithelial cells. Results from double-reciprocal analysis of the velocity versus concentration data are consistent with a simple carrier-mediated facilitated diffusion process with Km V25max and K1 values of 317 ± 44 (SE) μm 49 ± 7 nmol/s/g dry weight, and 301 ± 34 μm for F-Ara-A, and 264 ± 14 μm 44 ± 5 nmol/s/g dry weight, and 225 ± 44 μm for adenosine, respectively. The presence of a single low-affinity carrier in the proliferative epithelial cells contrasts sharply with the high affinity (K.68 ± 14 μm; V25max, 48 ± 4 nmol/s/g dry weight) and low-affinity (K., 326 ± 48 μm; V25max 124 ± 44 nmol/s/g dry weight) routes of entry documented for LI 210 cells. This differential in transport kinetics conveys a 7-to 8-fold greater capacity to LI 210 ascites compared with crypt epithelial cells for uptake of the antitumor agent F-Ara-A. At pharmacologically achievable concentrations of F-Ara-A and in view of this differential, influx of F-Ara-A would be more rate limiting to phosphorylation of F-Ara-A in epithelial cells than in LI 210 cells. Metabolism studies with LI 210 ascites and proliferative intestinal epithelial cells show that intracellular phosphorylation of F-Ara-A is also elevated in LI 210 cells. High-performance liquid chromatography analysis of extracts from cells incubated with 120 μm [3H]F-Ara-A showed substantial production of F-Ara-adenosine 5'-monophosphate, F-Ara-A-adenosine 5'-diphosphate, and the cytotoxic metabolite F-Ara-adenosine 5'-triphosphate in LI 210 cells but little F-Ara-adenosine 5'-monophosphate, F-Ara-adenosine 5'-diphosphate, and no F-Ara-adenosine 5'-triphos-phate in epithelial cells. Overall, the rate of phosphorylated product formation from [3H]F-Ara-A was 9-to 12-fold lower in proliferative intestinal epithelial cells than in L1210 cells. When resuspended in drug-free media, L1210 cells cleared [3H]F-Ara-A and dephosphorylated preformed products more rapidly than epithelial cells but still maintained. © 1987, American Association for Cancer Research. All rights reserved. |
| Keywords: | cancer chemotherapy; leukemia; unclassified drug; fludarabine; nonhuman; comparative study; mouse; animal; metabolism; mice; in vitro study; drug selectivity; phosphorylation; mice, inbred strains; kinetics; drug mechanism; tumor cell; organ specificity; drug derivative; antibody specificity; drug metabolism; drug cytotoxicity; radioisotope; epithelium; mouse strain; small intestine; intestine, small; therapy; biological transport; vidarabine; pharmacokinetics; intestine mucosa; tritium; transport at the cellular level; intoxication; digestive system; intestine epithelium; leukemia l1210; priority journal; article; support, non-u.s. gov't; support, u.s. gov't, p.h.s.; leukemia l 1210; blood and hemopoietic system; fludarabine h 3 |
| Journal Title: | Cancer Research |
| Volume: | 47 |
| Issue: | 3 |
| ISSN: | 0008-5472 |
| Publisher: | American Association for Cancer Research |
| Date Published: | 1987-02-01 |
| Start Page: | 700 |
| End Page: | 706 |
| Language: | English |
| PUBMED: | 3802076 |
| PROVIDER: | scopus |
| DOI/URL: | |
| Notes: | Article -- Export Date: 5 February 2021 -- Source: Scopus |
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