Williams J A, Dillehay L E, Tabassi K, Sipos E, Fahlman C, Brem H
Department of Oncology, Johns Hopkins Oncology Center, Baltimore, MD 21287-5001, USA.
J Neurooncol. 1997 May;32(3):181-92. doi: 10.1023/a:1005704913330.
The potential of halogenated pyrimidines for the radiosensitization of human malignant gliomas remains unrealized. To assess the role of local delivery for radiosensitization, we tested a synthetic, implantable biodegradable polymer for the controlled release of 5-iodo-2'-deoxyuridine (IUdR) both in vitro and in vivo and the resultant radiosensitization of human malignant glioma xenografts in vivo.
In vitro: To measure release, increasing (10%, 30%, 50%) proportions (weight/weight) of IUdR in the polyanhydride [(poly(bis(p-carboxyphenoxy)-propane) (PCPP): sebacic acid (SA) (PCPP : SA ratio 20:80)] polymer discs were incubated (1 ml phosphate-buffered saline, 37 degrees C). The supernatant fractions were serially assayed using high performance liquid chromatography. To measure modulation of release, polymer discs were co-loaded with 20 microCi 5-125-iodo-2'-deoxyuridine (125-IUdR) and increasing (10%, 30%, or 50%) proportions of D-glucose. To test radiosensitization, cells (U251 human malignant glioma) were sequentially exposed to increasing (0 or 10 microM) concentrations of IUdR and increasing (0, 2.5, 5.0, or 10 Gy) doses of acute radiation. In vivo. To measure release, PCPP : SA polymer discs having 200 microCi 125-IUdR were surgically placed in U251 xenografts (0.1-0.2 cc) growing in the flanks of nude mice. The flanks were reproducibly positioned over a collimated scintillation detector and counted. To measure radiosensitization, PCPP : SA polymer discs having 0% (empty) or 50% IUdR were placed in the tumor or contralateral flank. After five days, the tumors were acutely irradiated (500 cGy x 2 daily fractions).
In vitro: Intact IUdR was released from the PCPP : SA polymer discs in proportion to the percentage loading. After 4 days the cumulative percentages of loaded IUdR that were released were 43.7 +/- 0.1, 70.0 +/- 0.2, and 90.2 +/- 0.2 (p < 0.001 ANOVA) for the 10, 30, and 50% loadings. With 0, 10, 30, or 50% D-glucose co-loading, the cumulative release of 125-IUdR from PCPP : SA polymers was 21, 70, 92, or 97% (p < 0.001), respectively, measured 26 days after incubation. IUdR radiosensitized U251 cells in vitro. Cell survival (log10) was -2.02 +/- 0.02 and -3.68 +/- 0.11 (p < 0.001) after the 10 Gy treatment and no (control) or 10 microM IUdR exposures, respectively. In vivo: 125-IUdR Release: The average counts (log10 cpm +/- SEM) (hours after implant) were 5.2 +/- 0.05 (0.5), 4.3 +/- 0.07 (17), 3.9 +/- 0.08 (64), and 2.8 +/- 0.06 (284). Radiosensitization: After intratumoral implantation of empty polymer or intratumoral 50% IUdR polymer, or implantation of 50% IUdR polymers contralateral to tumors the average growth delays of tumors to 4 times the initial volumes were 15.4 +/- 1.8, 20.1 + 0.1, and 20.3 + 3.6 (mean + SEM) days, respectively (p = 0.488 one-way ANOVA). After empty polymer and radiation treatments, no tumors regressed and the growth delay was 31.1 + 2.1 (p = 0.046 vs. empty polymer alone) days. After implantation of 50% IUdR polymers either contralateral to the tumors or inside the tumors, followed by radiation, tumors regressed; growth delays to return to the initial average volumes of 14.0 + 3.6 or 24.2 + 0.2 (p < 0.01) days, respectively.
Synthetic, implantable biodegradable polymers hold promise for the controlled release and local delivery of IUdR for radiosensitization of gliomas.
卤代嘧啶对人类恶性胶质瘤进行放射增敏的潜力尚未得到充分发挥。为评估局部给药在放射增敏中的作用，我们在体外和体内测试了一种可植入的合成生物可降解聚合物，用于5-碘-2'-脱氧尿苷（IUdR）的控释，并观察其对体内人恶性胶质瘤异种移植瘤的放射增敏效果。
体外实验：为测定释放情况，将不同比例（10%、30%、50%，重量/重量）的IUdR加入聚酸酐[聚（双（对羧基苯氧基）丙烷）（PCPP）：癸二酸（SA）（PCPP:SA比例为20:80）]聚合物圆盘，于1ml磷酸盐缓冲液中在37℃孵育。上清液用高效液相色谱法连续测定。为测定释放调节情况，聚合物圆盘共负载20微居里的5-125-碘-2'-脱氧尿苷（125-IUdR）和不同比例（10%、30%或50%）的D-葡萄糖。为测试放射增敏作用，将细胞（U251人恶性胶质瘤细胞）依次暴露于不同浓度（0或10微摩尔）的IUdR和不同剂量（0、2.5、5.0或10戈瑞）的急性辐射。体内实验：为测定释放情况，将含有200微居里125-IUdR的PCPP:SA聚合物圆盘手术植入裸鼠侧腹生长的U251异种移植瘤（0.1 - 0.2立方厘米）中。侧腹可重复定位在准直闪烁探测器上进行计数。为测定放射增敏作用，将含0%（空白）或50% IUdR的PCPP:SA聚合物圆盘置于肿瘤或对侧腹。5天后，肿瘤接受急性照射（500厘戈瑞×每天2次分割剂量）。
体外实验：完整的IUdR从PCPP:SA聚合物圆盘中按负载百分比释放。4天后，10%、30%和50%负载量的IUdR累积释放百分比分别为43.7±0.1、70.0±0.2和90.2±0.2（方差分析p<0.001）。分别共负载0%、10%、30%或50% D-葡萄糖时，孵育26天后，PCPP:SA聚合物中125-IUdR的累积释放率分别为21%、70%、92%或97%（p<0.001）。IUdR在体外使U251细胞放射增敏。10戈瑞照射且未暴露（对照）或暴露于10微摩尔IUdR后，细胞存活率（log10）分别为-2.02±0.02和-3.68±0.11（p<0.001）。体内实验：125-IUdR释放：植入后不同时间（小时）的平均计数（log10每分钟计数±标准误）为5.2±0.05（0.5）、4.3±0.07（17）、3.9±0.08（64）和2.8±0.06（284）。放射增敏：肿瘤内植入空白聚合物或肿瘤内植入50% IUdR聚合物，或在肿瘤对侧植入50% IUdR聚合物后，肿瘤体积增大至初始体积4倍时的平均生长延迟分别为15.4±1.8、20.1±0.1和20.3±3.6（平均值±标准误）天（单向方差分析p = 0.488）。空白聚合物与放疗联合处理后，无肿瘤消退，生长延迟为31.1±2.1天（与单独使用空白聚合物相比p = 0.046）。在肿瘤对侧或肿瘤内植入50% IUdR聚合物后再进行放疗，肿瘤消退；生长延迟恢复至初始平均体积的时间分别为14.0±3.6或24.2±0.2天（p<0.01）。
合成的、可植入的生物可降解聚合物有望用于IUdR的控释和局部给药，以实现对胶质瘤的放射增敏。
