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  IN THIS Article
 ::  Introduction
 ::  Material and methods
 ::  Results
 ::  Discussion
 ::  References

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Year : 1985  |  Volume : 31  |  Issue : 3  |  Page : 123-7

Effects of anticancer drugs on folate disposition and excretion.







How to cite this article:
Gokhale S V, Ganu U K, Ambaye R Y. Effects of anticancer drugs on folate disposition and excretion. J Postgrad Med 1985;31:123


How to cite this URL:
Gokhale S V, Ganu U K, Ambaye R Y. Effects of anticancer drugs on folate disposition and excretion. J Postgrad Med [serial online] 1985 [cited 2014 Nov 26];31:123. Available from: http://www.jpgmonline.com/text.asp?1985/31/3/123/5399




  ::   Introduction Top

The nutritional status of cancer patients may be affected due to a variety of factors like poor intake, poor absorption and poor retention. The tumour, by itself or through tumour-associated hormones, may increase the requirements of specific vitamins.[6] Circulating levels of thiamine were found to be low in patients having either bronchogenic carcinoma or carcinoma of the breast. They were found to be depleted further during the treatment with 5-fluorouracil.[2],[3]
Folic acid deficiency is common in patients with head and neck cancer and also occurs in patients with liver cancer.[17] Low serum folate levels have also been reported in patients with leukaemias,[14],[19],[20] lymphomas,[14],[20] and carcinoma.[7],[12]
Barford et al,[1] in their studies in normal Wistar rats, showed that methotrexate (MTX) affects the uptake of [14]C and [3]H-Folic acid in a dose-dependent manner.
The folates, on reduction in the body, participate in various single carbon transfer reactions.[13] It was thought to be of interest to see how the folate disposition and excretion are affected by cytotoxic anticancer drugs in tumour-bearing animals.

  ::   Material and methods Top

Anticancer drugs
5-Fluorouracil (5-FU) and cyclophosphamide (CTX) were purchased from Biochem Pharmaceutical Industries, Bombay, India; while methotrexate (MTX) was obtained from Lederle Parenterals Inc; Carolina, Peurto Rico 00630, U.S.A. All drugs were in sterile injection vials, ready for use. Dilutions, when necessary, were made with normal saline.
Tritium labelled folic acid
[3]H-Folic acid (2500 mCi/mmol), labelled non-specifically, was purchased from the Bhabha Atomic Research Centre, Trombay, Bombay, India.
Animals and tumours
C57BL/6 male mice (6-8 weeks old and 20-25 g in weight) were used. Lewis Lung Carcinoma (LL), maintained subcutaneously by serial transplantations,[9] was used for the uptake studies.
Methodology
C57BI,/6 mice, bearing a 14-day-old LL tumour, were randomized, divided into four groups of six mice each and fed colony diet (Composition: Cracked wheat (70%), cracked Bengal gram (20%), yeast powder (4%), fish meal (5%), shark liver oil (0.25%) and sesame oil (0.75%). The mice in the treated-groups received, as a single injection, one of the following anticancer drugs by i.p. route: 5-FU (250 mg/kg); MTX (12.5 mg/kg) or CTX (180 mg/kg); while those in the control group received the vehicle by the same route. Twenty-four hours after drug treatment, each mouse received 5 Ci of [3]H-folic acid by the oral route and the animals were kept in metabolic cages. Diet was withheld; while water was given ad libitum during the period in metabolic cages.
Urine was collected in two aliquots, 0-6 hours and 6-24 hours and the animals were killed at the end of 24 hours. The liver and tumours were taken out separately into beakers, chopped fine and lyophylised.
The percentage folate uptake and excretion were determined by counting the lyophilised tissue and the urine in a Beckman LS-100 scintillation counter. Fifty l urine was counted as such in 10 ml of Bray's scintillation mixture,[5] while the lyophylised tissue (about 15-20 mg) was first digested with 0.2 ml of 2N KOH.[11] The volume of urine was non-quenching whereas the quenching due to KOH was corrected by the use of internal standard method.[15]
The per cent folate uptake by the liver was calculated per tissue as a whole. However, the tumour levels were calculated on per g tumour weight basis to account for the variation in the tumour weight due to the drug treatment.

  ::   Results Top

The liver folate uptake in the case of 5-FU treated mice was significantly higher than that in controls (p < 0.001) [Table - 1]. However, the tumour uptake of the 5-FU treated group was not significantly higher than the control [Table - 2]. The urinary excretion of the label in control and 5-FU treated mice was comparable [Table - 3]
In the case of MTX-treated mice, the liver folate uptake of the treated group was significantly lower than the control group (p < 0.001) [Table - 1] The difference in the tumour uptake values of the treated and control groups was not statistically significant [Table - 2] However, an increased urinary excretion of the label was observed in the MTX-treated mice [Table - 3].
As regards the CTX-treated mice, although the liver uptake of the labelled folate was higher in the drug-treated group than that in the controls, it was not statistically significant [Table - 1]. Urinary excretion in CTX-treated mice was slightly lower when compared with that in the control animals [Table - 3].
The levels of labelled folate in the CTX-treated LL tumours, however, were higher, the values being statistically significant (p < 0.025) [Table - 2]

  ::   Discussion Top

The increased liver folate levels in 5FU treated mice could be explained. on the basis of the mechanism of action of the drug. The formation of a covalently bound ternary complex of 5-FU, 5, 10-methyleneTHF and thymidylate synthetase is necessary for the cytotoxicity of 5-FU.[16],[22] In fact, due to the deprivation of reduced folate by MTX, activity of the combination of MTX followed by 5-FU was found to be less than additive in some schedules.[21],[24]
Further, it has been shown by in vitro studies using S-180 and HEP-2 cell lines that the sensitivity of the cells is not related to the intracellular levels of 5-FU, but coincides with high levels of folates.[4] Evans et al[8] have shown maximum potentiation of growth inhibition by 5-FU when used in combination with excess folates. Higher intracellular levels of 5, 10-methylene THF are necessary for the pharmacological action of FdUMP with thymidylate synthetase, which can be a limiting factor under certain conditions. Further, potentiation of anticancer activity of 5FU with leucovorin against Friend leukaemia virus could be due to the over coming of this limitation in the metabolic activity.[23]
Machover et al[18] observed that some colorectal tumours, which were previously resistant to 5-FU were rendered sensitive to the drug when used in combination with high doses of folinic acid.
Our studies show a larger amount of the labelled- folate in the liver of mice treated with 5-FU [Table - 1]. Weber,[25] in his studies with different hepatoma cell lines and having different growth rates, has shown a definite link between the increased growth rate and the thymidylate synthetase activity.
The foregoing facts conclusively show the presence of reduced folates as a prerequisite for the anticancer activity of 5FU. The concomitant administration of leucovorin with 5-FU could be avoided here by administering folic acid, as the reducing capacity of the host is not affected by 5-FU. Avoiding the use of leucovorin is also desirable due to its high cost and less stability. Liver is endowed with a high amount of dihydrofolate reductase. Hence, the results suggest a possible use of 5-FU in combination with high doses of folic acid in hepatomas.
5-FU is weakly active against Lewis lung carcinoma.[10] Our studies do not show a significant difference in the tumour uptake values of folic acid in the control and 5-FU treated mice [Table - 2].
As regards CTX, the folate levels of the drug-treated animal tumours were significantly higher than the untreated control tumours [Table - 2]. It would be of interest to see as to why there should be an increased demand for folic acid.
Our results of increased urinary excretion of folic acid [Table - 3] and lower uptake by the liver [Table - 1] in the case of MTX-treated mice are predictable on the basis of literature reports.[1] Folate levels in tumours of MTX-treated and control (non-treated) animals did not show statistically significant difference [Table - 2]

  ::   References Top

1.Barford, P. A., Blair, J. A. and Malghani M. A. K.: The effect of methotrexate on folate metabolism in the rat. Brit. J Cancer, 41: 816-820, 1980.  Back to cited text no. 1    
2.Basu, T. K.: Significance of vitamins in cancer. Oncology: 33: 183-187, 1976.   Back to cited text no. 2    
3.Basu, T. K., Dickerson, J. W. T., Raven, R. W. and Williams, D. C.: The thiamine status of patients with cancer as determined by the red cell transketolase activity. Internal. J. Vitamin Nutr. Res., 44: 53-58, 1974.  Back to cited text no. 3    
4.Berger, S. H., Yin, M. B., Whalen, J. A. and Hakala, M. T.: Role of folate (FA) and dUMP in response to 5-Fluoropyrimidines. Proc. Amer. Assoc. Cancer Res. AACR Abstracts, 17, Abstr. No. 652, 1981.  Back to cited text no. 4    
5.Bray, G. A.: A simple liquid scintillator for counting aqueous solutions in a liquid scintillation counter, Anal. Biochem., 1: 279-285, 1960.  Back to cited text no. 5    
6.Dickerson, J. W. T. and Basu, T. K.: Specific vitamin deficiencies and their significance in patients with cancer and receiving chemotherapy. In "Nutrition and Cancer." Editor: M. Winick, M., A. Wiley-Interscience Publication, New York, 1977, pp. 95-104.  Back to cited text no. 6    
7.Einhorn, J. and Reizenstein, P, G.: Metabolic studies on folic acid in malignancy. Cancer Res., 26: 340-343, 1966.  Back to cited text no. 7    
8.Evans, R. M., Laskin, J. D. and Hakala, M. T.: Effect of excess folate and deoxyinosine on the activity and site of action of 5-fluorouracil. Cancer Res., 41: 3288-3295, 1981.  Back to cited text no. 8    
9.Geran, R. I., Greenberg, N. H., Macdonald, M. M., Schumacher, A. M. and Abott, B. J.: Protocols for screening chemical agents and natural products against animal tumours and other biological systems. Cancer Chemother. Rep. (Part 3), 3: 1-103, 1972.  Back to cited text no. 9    
10.Goldin, A., Venditti, J. M., MacDonald, J. S., Muggia E. M., Henney, J. F. and Devita, V. T. Jr,: Current results, of the screening programme at the Division of Cancer Treatment, National Cancer Institute. Eur, J. Cancer, 17: 129-142, 1981.  Back to cited text no. 10    
11.Hansen, D. L. and Busch, E. T.: Improved solubilization procedures for liquid scintillation. counting of biological material. Anal. Biochem., 18: 320-332', 1967.   Back to cited text no. 11    
12.Hellman, S., Iannotti, A. T. and Bertino, J. R.: Determinations of the levels of serum folate in patients with carcinoma of the head and neck treated with methotrexate. Cancer Res., 24: 105-113 1964.  Back to cited text no. 12    
13.Herbert, V. and Das, K. C.: The role of vitamin B12 and folic acid in hemato- and other cell-poiesis. In: "Vitamins and Hormones." Editors: P. L. Munson, E. Diezfalusy, J. Glover and R. E. Olson, Academic Press, New York, 1976, Vol. 34, pp. 1-30.  Back to cited text no. 13    
14.Hoogstraten, B., Baker, H. and Reizenstein, R.: Correlation between folic acid activity and response to antifolate therapy. Abstract presented at the fourth Annual Meeting of the American Society of Hematology on 27th November, 1961, Blood, 18: 787, 1961.  Back to cited text no. 14    
15.Kobayashi, Y. and Mudsley, D. V.: Practical aspects of liquid scintillation counting. In, "Methods of Biochemical Analysis." Editor: D. Glick, Interscience Publishers, New York, 1969, Vol. 17: pp. 55-133.  Back to cited text no. 15    
16.Langenback, R. J., Daneberg, P. V. and Heidelberger, C.: Thymidylate synthetase mechanism of inhibition by 5-fluoro2-deoxyvridylate. BBRC., 48: 1565-1571. 1972.  Back to cited text no. 16    
17.Laszlo, J.: Haematological effects of cancer. In, "Cancer Medicine," 2nd Edition, Editors: J. H. Holland and E. Frei, Lea and Febiger, Philadelphia, 1982, pp. 1275-1288.  Back to cited text no. 17    
18.Machover, D., Schwarzenberg, L., Goldschmidt, E., Tourani J. M., Michalski, B., Hayat, M., Dorval, T., Misset, J. L., Jasmine, C., Maral, R. and Mathe, G.: Treatment of advanced colorectal and gastric adenocarcinomas with 5-fluorour racil combined with high dose of folinic acid; A pilot study. Cancer Treat. Rep., 66: 1803-1807, 1982.  Back to cited text no. 18    
19.Rao, P. B. R., Langerlof, B., Einhorn, J. and Reizensterin, P. G.: Low serum folic acid levels in malignancy. Lancet, 1: 1193-1194, 1963.  Back to cited text no. 19    
20.Rao, P. B. R., Langerlof, B., Einhorn, J. and Reizensterin, P. G.: Folic acid activity in leukaemia and cancer. Cancer Res., 25: 221-224, 1965.  Back to cited text no. 20    
21.Tattersall, M. H. N., Jackson, R. C., Connors, T. A. and Harrap, K. R.: Combination chemotherapy: The interaction of methotrexate and 5-fluorouracil. Europ. J. Cancer, 9: 733-739, 1973.   Back to cited text no. 21    
22.Ullman, B., Lee, M., Martin, D. W. (Jr.) and Santi, D. V.: Cytotoxicity of 5fluoro-2-deoxy-uridine requirement for reduced folate co-factors and antagonism by methotrexate Proc. Natl. Acid. Sci., (U.S.A.), 75: 980-983, 1978.  Back to cited text no. 22    
23.Waxman, S. and Bruckner, H.: The enhancement of 5-fluorouracil antimetabolic activity by leucovorin, menadione and a-tocopherol. Eur. J. Cancer and Clin. Oncol., 18: 685-692, 1982.  Back to cited text no. 23    
24.Waxman, S., Rubinoff, M., Greenspan, E, and Bruckner, H.: Interaction of methotrexate (MTX) and 5-fluorouracil (5-FU): Effects on de novo DNA synthesis. Proc. Amer. Assoc. Cancer Res., AACR Abstracts, Vol. 17: Abstract No. 628, 1976, p. 157.  Back to cited text no. 24    
25.Weber, G.: Enzymology of cancer calls (First of Two Parts). New Engl. J. Med., 296: 480-493, 1977.  Back to cited text no. 25    

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Online since 12th February '04
2004 - Journal of Postgraduate Medicine
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