TY - JOUR
T1 - Synergistic effect of 5-fluorouracil and N-(phosphonacetyl)-l-aspartate on cell growth and ribonucleic acid synthesis in a human mammary carcinoma
AU - Ardalan, Bach
AU - Glazer, Robert I.
AU - Kensler, Thomas W.
AU - Jayaram, Hiremagalur N.
AU - van Pham, Tu
AU - Macdonald, John S.
AU - Cooney, David A.
PY - 1981/8/1
Y1 - 1981/8/1
N2 - The biological effects of N-(phosphonacetyl)-l-aspartate (PALA) and 5-fluorouracil (5-FU) were examined singly, and in combination, on the growth of a human mammary carcinoma (MDA) cell line in culture. All combinations of 5-FU (2.5 × 10-7 to 1.5 × 10-5M) and PALA (6.0 × 10-5 to 3.6 × 10-3 M) resulted in synergistic inhibition of cell growth as revealed by a 50 per cent isobologram.To examine the biochemical basis for the synergism, measurements of the incorporation of [3H]-5-FU into total non-poly(A)- and poly(A)-RNA, and of the simultaneous incorporation of [14C]deoxyguanosine and [3H]deoxyuridine into DNA, were determined. The combination of 3.7 × 10-5M PALA and 1 × 10-6 M 5-FU produced 65-85 per cent inhibition of cell growth after continuous treatment for 13 days. Treatment of the cells for 3 or 24 hr with the same drug regimen produced approximately a 170 per cent increase in the incorporation of 1 × 10-6M [3H]-5-FU into poly(A)RNA in comparison to [3H]-5-FU treatment alone; exposure for 24 hr to 3.7 × 10-5 M PALA and 1 × 10-6 M [3H]-5-FU resulted in a 285 per cent increase in the incorporation of [3H]-5-FU into non-poly(A)RNA. The incorporation of either [14C]deoxyguanosine or [3H]deoxyuridine into DNA was not inhibited by this drug regimen; however, the incorporation of [3H]deoxyuridine into DNA was elevated significantly upon 12 or 24 hr of exposure to PALA alone. PALA and 5-FU treatment resulted in a 75 per cent reduction in the concentration of UTP and no change in the concentration of 5-fluorouridine-5′triphosphate 5-FUTP) versus 5-FU treatment alone. Thus, the proportion of 5-FUTP in the total 5FUTP + UTP pool was enhanced more than 3-fold by the combination regimen. These results indicate that the synergistic effect of the combination of PALA and 5-FU on the growth of MDA cells correlates with an increased proportion of 5-FUTP in the pyrimidine nucleotide pool and, consequently, with an enhanced incorporation of 5-FU into RNA, but not with inhibition of DNA synthesis.
AB - The biological effects of N-(phosphonacetyl)-l-aspartate (PALA) and 5-fluorouracil (5-FU) were examined singly, and in combination, on the growth of a human mammary carcinoma (MDA) cell line in culture. All combinations of 5-FU (2.5 × 10-7 to 1.5 × 10-5M) and PALA (6.0 × 10-5 to 3.6 × 10-3 M) resulted in synergistic inhibition of cell growth as revealed by a 50 per cent isobologram.To examine the biochemical basis for the synergism, measurements of the incorporation of [3H]-5-FU into total non-poly(A)- and poly(A)-RNA, and of the simultaneous incorporation of [14C]deoxyguanosine and [3H]deoxyuridine into DNA, were determined. The combination of 3.7 × 10-5M PALA and 1 × 10-6 M 5-FU produced 65-85 per cent inhibition of cell growth after continuous treatment for 13 days. Treatment of the cells for 3 or 24 hr with the same drug regimen produced approximately a 170 per cent increase in the incorporation of 1 × 10-6M [3H]-5-FU into poly(A)RNA in comparison to [3H]-5-FU treatment alone; exposure for 24 hr to 3.7 × 10-5 M PALA and 1 × 10-6 M [3H]-5-FU resulted in a 285 per cent increase in the incorporation of [3H]-5-FU into non-poly(A)RNA. The incorporation of either [14C]deoxyguanosine or [3H]deoxyuridine into DNA was not inhibited by this drug regimen; however, the incorporation of [3H]deoxyuridine into DNA was elevated significantly upon 12 or 24 hr of exposure to PALA alone. PALA and 5-FU treatment resulted in a 75 per cent reduction in the concentration of UTP and no change in the concentration of 5-fluorouridine-5′triphosphate 5-FUTP) versus 5-FU treatment alone. Thus, the proportion of 5-FUTP in the total 5FUTP + UTP pool was enhanced more than 3-fold by the combination regimen. These results indicate that the synergistic effect of the combination of PALA and 5-FU on the growth of MDA cells correlates with an increased proportion of 5-FUTP in the pyrimidine nucleotide pool and, consequently, with an enhanced incorporation of 5-FU into RNA, but not with inhibition of DNA synthesis.
UR - http://www.scopus.com/inward/record.url?scp=0019502887&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0019502887&partnerID=8YFLogxK
U2 - 10.1016/0006-2952(81)90221-5
DO - 10.1016/0006-2952(81)90221-5
M3 - Article
C2 - 7295324
AN - SCOPUS:0019502887
SN - 0006-2952
VL - 30
SP - 2045
EP - 2049
JO - Biochemical Pharmacology
JF - Biochemical Pharmacology
IS - 15
ER -