Grem J L, Daychild P, Drake J, Geoffroy F, Trepel J B, Pirnia F, Allegra C J
NCI-Navy Medical Oncology Branch, Bethesda, MD 20889-5105.
Biochem Pharmacol. 1994 Nov 29;48(11):2117-26. doi: 10.1016/0006-2952(94)90513-4.
We examined the cytotoxicity, biochemical effects and metabolism of 4-methoxy-8-(beta-D-ribofuranosylamino)pyrimido[5,4-d]pyrimidine (MRPP), a synthetic nucleoside inhibitor of phosphoribosylpyrophosphate synthetase, in HCT 116 human colorectal cancer cells. A 4-hr exposure to 1 and 10 microM MRPP inhibited cell growth over a 72-hr period by 76 and 89%, and inhibited clonogenic capacity by 36 and 65%, respectively. MRPP was avidly metabolized to the 5'-monophosphate derivative (MRPP-MP), and MRPP-MP formation increased with increasing MRPP exposure (microM.hr). MRPP-MP was stable, and the intracellular half-life was in excess of 48 hr. A 4-hr exposure to 10 microM MRPP resulted in significant decreases in ATP, UTP, GTP, CTP, dATP, dTTP, and PRPP pools. Near maximal ribonucleotide triphosphate depletion was achieved with > or = 24 microM.hr MRPP, and growth inhibition as a function of MRPP microM.hr closely reflected the biochemical effects. Ribonucleotide triphosphate pools remained depleted for up to 48 hr after drug removal, apparently as a consequence of the prolonged retention of MRPP-MP. MRPP (10 microM) inhibited the salvage of [3H]guanine, [3H]adenine and [3H]guanosine, and concurrent exposure to MRPP and either 100 microM adenine, hypoxanthine, or guanine did not reverse ATP or GTP depletion. Concurrent exposure to 10 microM MRPP and either 10 microM adenosine, uridine or thymidine was accompanied by repletion of ATP, UTP, and dTTP pools, respectively, but depletion of other nucleotide pools was not corrected. In contrast, 10 microM guanosine did not correct GTP depletion in the presence of MRPP. The combination of 10 microM each of thymidine, uridine, adenosine and guanosine during and following a 24-hr exposure to MRPP provided partial protection against 0.1 or 1 microM MRPP, but did not affect the cytotoxicity associated with 10 microM MRPP. MRPP is a novel antimetabolite that inhibits both de novo and salvage pathways for purine synthesis and de novo pyrimidine synthesis.
我们研究了4-甲氧基-8-（β-D-呋喃核糖基氨基）嘧啶并[5,4-d]嘧啶（MRPP），一种磷酸核糖焦磷酸合成酶的合成核苷抑制剂，对HCT 116人结肠癌细胞的细胞毒性、生化效应和代谢情况。暴露于1和10微摩尔/升的MRPP 4小时，在72小时内分别抑制细胞生长76%和89%，并分别抑制克隆形成能力36%和65%。MRPP被迅速代谢为5'-单磷酸衍生物（MRPP-MP），且MRPP-MP的形成随着MRPP暴露量（微摩尔·小时）的增加而增加。MRPP-MP很稳定，细胞内半衰期超过48小时。暴露于10微摩尔/升的MRPP 4小时导致ATP、UTP、GTP、CTP、dATP、dTTP和PRPP库显著减少。当MRPP达到≥24微摩尔·小时时，核糖核苷酸三磷酸几乎耗尽，且生长抑制与MRPP微摩尔·小时的关系密切反映了生化效应。药物去除后，核糖核苷酸三磷酸库在长达48小时内仍处于耗尽状态，这显然是由于MRPP-MP的长时间滞留所致。MRPP（10微摩尔/升）抑制了[3H]鸟嘌呤、[3H]腺嘌呤和[3H]鸟苷的补救合成，同时暴露于MRPP和100微摩尔/升的腺嘌呤（或次黄嘌呤或鸟嘌呤）并不能逆转ATP或GTP的消耗。同时暴露于10微摩尔/升的MRPP和10微摩尔/升的腺苷（或尿苷或胸苷）分别伴随着ATP、UTP和dTTP库的补充，但其他核苷酸库的消耗并未得到纠正。相比之下，在存在MRPP的情况下，10微摩尔/升的鸟苷并不能纠正GTP的消耗。在24小时暴露于MRPP期间及之后，同时给予10微摩尔/升的胸苷、尿苷、腺苷和鸟苷，可对0.1或1微摩尔/升的MRPP提供部分保护，但不影响与10微摩尔/升MRPP相关的细胞毒性。MRPP是一种新型抗代谢物，它抑制嘌呤合成的从头合成途径和补救途径以及嘧啶的从头合成途径。
