Synthesis of Methotrexate Polyglutamates in Cultured Human Cells

Abstract

The deqree of FAS positivity was determined by counting 200 hlast cells in the initial bone marrow specimen of 38 childrendm ALL. Each cell was scored on a 0 to 5 scale accordinq to the number of PAS-psitive qranules per cell (0-4). or the presence of 1 or more larqe blocks per cell (5). The patients were stratified into 3 groups accordinq to their mean PAS score. Fourteen children had a low score (mean 65, ranqe 3-150), 12 were intermediate (mea~. 315, range 153-4451. and 12 were high (mean 692, range 465-860). The mean white blood count (WBC) at diaanosis was higher in the low-score qroup compared to the hiqh-score qroup, but thedf* erence was not siqnificant (mO.05); 5/14 low-score patients had an initial WBC below 20,000/mn3, and 3/12 high-score patientsww above 20,000/mm3. There were no sir~nificant differences among tha groups with respect to aqe, h-lobin and platelet levels at* nosis or presence of a mediastinal or abdominal mass. However, 13 of 14 lw-score patients were male, compared to 4/12 and 6/12 in the intermediate and high groups (p<0.05). In addition, 7 of 13 low-score patients were in relapse by 6 months from diaqnosis (yl had an initial WBC below 20,000/mm3), compared to none of the k d z~ mediate and only 1 of the high patients (~(0.05). These results suggest that a low PAS score is related to a poor proqnosis in childhood ALL, regardless of the level of the initial WBC. Fenales tend to have higher PAS scores than males, and also seem to have a better prognosis.

Resistance to antifolates

“…In the case of MTX, only a fair substrate for FPGS, polyglutamyl forms have the same, or only a small increase in, affinity for DHFR (Whitehead, 1977;Domin et al, 1982;Appleman et al, 1988;Kumar et al, 1989). MTX polyglutamates accumulate at different rates in a variety of tumor cells and ultimately become the predominant species and the form of antifolate bound to DHFR (Whitehead, 1977;Rosenblatt et al, 1978a;Schilsky et al, 1980;Matherly et al, 1983). The major impact is the retention and buildup of appreciable levels of polyglutamyl derivatives of the drug in cells (Fry et al, 1982b;Jolivet et al, 1982;Jolivet and Chabner, 1983) with sustained inhibition of DHFR (Rosenblatt et al, 1978b).…”

“…MTX polyglutamates accumulate at different rates in a variety of tumor cells and ultimately become the predominant species and the form of antifolate bound to DHFR (Whitehead, 1977;Rosenblatt et al, 1978a;Schilsky et al, 1980;Matherly et al, 1983). The major impact is the retention and buildup of appreciable levels of polyglutamyl derivatives of the drug in cells (Fry et al, 1982b;Jolivet et al, 1982;Jolivet and Chabner, 1983) with sustained inhibition of DHFR (Rosenblatt et al, 1978b). The level and rapidity of formation of MTX polyglutamates in tumor cells is an important determinant of the pharmacologic activity of this drug (Fabre et al, 1984;Curt et al, 1985).…”

Synthesis, Retention, and Biological Activity of Methotrexate Polyglutamates in Cultured Human Breast Cancer Cells

“…In contrast, [3H]deoxyuridine incorporation and cell growth quickly recovered to normal in the MDA-231 cells following removal of 2 ,uM MTX from the medium after a 24-h incubation. Prolonged inhibition of both thymidylate synthesis and cell growth was observed in this cell line in drug-free medium only after a 24-h incubation with 10 jM MTX, a condition that leads to the synthesis of 11.3 nmol/g of MTX polyglutamates.…”

“…The ZR-75-B cell line is a cloned line derived from the ZR-75-1 cell line (22) and has the same hormonal receptors and responsiveness as the parent cell line. The cells were grown in improved Min 10 ;tM thymidine (dT), and 10 uM deoxyinosine (dl). This medium allowed cell growth to proceed unperturbed in the presence of MTX.…”

Synthesis of Methotrexate Polyglutamates by Bone Marrow Cells from Patients with Leukemia and Lymphoma

“…These folate polyglutamates are believed to be the biologically active forms of the vitamin (1, 4-8, 13, 15-17, 20). Studies from a number of laboratories have established that methotrexate (MTX, amethopterin), an analog of folic acid, is also metabolized to MTX polyglutamates (2,3,10,11,18,22,23). This metabolism has been observed to occur in a number of animal tissues (2,3,23) andin cells in culture (10,11,18,22), and has been detected in human liver following chemotherapy ( 12).…”