Ruiz van Haperen V W, Veerman G, Boven E, Noordhuis P, Vermorken J B, Peters G J
Department of Oncology, Free University Hospital, Amsterdam, The Netherlands.
Biochem Pharmacol. 1994 Oct 7;48(7):1327-39. doi: 10.1016/0006-2952(94)90554-1.
2',2'-Difluorodeoxycytidine (Gemcitabine, dFdC) is a relatively new deoxycytidine antimetabolite, with established activity against ovarian cancer and non-small-cell lung cancer. dFdC is assumed to exert its antitumour effect mainly by incorporation of the triphosphate dFdCTP into DNA. We determined the sensitivity to dFdC of six cell lines derived from solid tumours; two ovarian carcinoma (A2780 and OVCAR-3), two colon carcinoma (WiDr and C26-10) and two squamous cell carcinoma cell lines (UM-SCC-14C and UM-SCC-22B). In vitro sensitivity to dFdC was strongly time dependent. Under all conditions A2780 was the most sensitive cell line with an IC50 (the concentration of dFdC causing 50% growth inhibition) of 31 and 0.6 nM at 1 and 48 hr exposure, respectively. WiDr and C26-10 cells were relatively insensitive, with IC50s of 468 and 1133 nM, respectively, at 1 hr exposure, but of 11 and 6 nM at 48 hr exposure. Accumulation of the triphosphate dFdCTP was also time dependent. After 4 hr exposure to 10 microM dFdC, A2780, WiDr and C26-10 cells accumulated 223, 136 and 267 pmol/10(6) cells, respectively; after 24 hr exposure they accumulated 1045, 619 and 617 pmol/10(6) cells, respectively. A2780 cells retained the high dFdCTP concentration longer than 24 hr. For comparison purposes we also studied dFdCTP kinetics in the corresponding solid tumours, showing the same sensitivity pattern as the cell lines. In general, sensitivity to dFdC in vitro related with dFdCTP accumulation and retention, but in vivo this relation was less clear. Unexpectedly, remarkable in vitro and in vivo changes were observed in the ribonucleotide pools. The most predominant in vitro cell line dependent changes were a decrease in CTP concentrations, accompanied by an increase in UTP and GTP concentrations. In vivo CTP, UTP and GTP pools increased in all tumours. In conclusion, in this study we demonstrate that dFdCTP is accumulated and retained in solid tumours and cell lines. dFdCTP is not only important as a DNA precursor, but also appears to interfere with normal ribonucleotide metabolism.
2',2'-二氟脱氧胞苷（吉西他滨，dFdC）是一种相对较新的脱氧胞苷抗代谢物，对卵巢癌和非小细胞肺癌具有确切疗效。dFdC被认为主要通过将三磷酸dFdCTP掺入DNA来发挥其抗肿瘤作用。我们测定了六种实体瘤来源的细胞系对dFdC的敏感性；两种卵巢癌细胞系（A2780和OVCAR-3）、两种结肠癌细胞系（WiDr和C26-10）以及两种鳞状细胞癌细胞系（UM-SCC-14C和UM-SCC-22B）。体外对dFdC的敏感性强烈依赖时间。在所有条件下，A2780是最敏感的细胞系，在暴露1小时和48小时时的IC50（导致50%生长抑制的dFdC浓度）分别为31 nM和0.6 nM。WiDr和C26-10细胞相对不敏感，在暴露1小时时的IC50分别为468 nM和1133 nM，但在48小时暴露时为11 nM和6 nM。三磷酸dFdCTP的积累也具有时间依赖性。在暴露于10 μM dFdC 4小时后，A2780、WiDr和C26-10细胞分别积累了223、136和267 pmol/10⁶个细胞；在暴露24小时后，它们分别积累了1045、619和617 pmol/10⁶个细胞。A2780细胞保持高dFdCTP浓度的时间超过24小时。为了进行比较，我们还研究了相应实体瘤中的dFdCTP动力学，显示出与细胞系相同的敏感性模式。一般来说，体外对dFdC的敏感性与dFdCTP的积累和保留相关，但在体内这种关系不太明确。出乎意料的是，在核糖核苷酸库中观察到了显著的体外和体内变化。最主要的体外细胞系依赖性变化是CTP浓度降低，同时UTP和GTP浓度增加。在体内，所有肿瘤中的CTP、UTP和GTP库均增加。总之，在本研究中我们证明dFdCTP在实体瘤和细胞系中积累并保留。dFdCTP不仅作为DNA前体很重要，而且似乎还会干扰正常的核糖核苷酸代谢。
