Department of Surgery, University Medical Centre Utrecht, Utrecht, The Netherlands.
Br J Surg. 2012 Apr;99(4):567-75. doi: 10.1002/bjs.8668. Epub 2012 Feb 13.
Radiofrequency ablation (RFA) is a common procedure for the management of colorectal liver metastases. RFA-generated lesions are surrounded by a rim of hypoxia that is associated with aggressive outgrowth of intrahepatic micrometastases. Hypoxia-activated prodrugs such as tirapazamine are designed selectively to induce apoptosis in tumour cells under hypoxic conditions. Therefore, it was hypothesized that tirapazamine may have therapeutic value in limiting hypoxia-associated tumour outgrowth following RFA.
Murine C26 and MC38 colorectal cancer cells were grown under hypoxia and normal oxygenation in vitro, and treated with different concentrations of tirapazamine. Apoptosis and cell cycle distribution were assessed by western blot and fluorescence-activated cell sorting analysis. Proliferative capacity was tested by means of colony-formation assays. Mice harbouring microscopic colorectal liver metastases were treated with RFA, followed by a single injection of tirapazamine (60 mg/kg) or saline. Tumour load was assessed morphometrically 7 days later.
Tirapazamine induced apoptosis of colorectal tumour cells under hypoxia in vitro. Under normal oxygenation, tirapazamine caused a G2 cell cycle arrest from which cells recovered partly. This reduced, but did not abolish, colony-forming capacity. A single dose of tirapazamine largely prevented accelerated outgrowth of hypoxic micrometastases following RFA. Tirapazamine administration was associated with minimal toxicity.
Tirapazamine induced apoptosis in colorectal cancer cells in a hypoxia-dependent manner and potently suppressed hypoxia-associated outgrowth of liver metastases with limited toxicity. This warrants further study to assess the potential value of tirapazamine, or other hypoxia-activated prodrugs, as adjuvant therapeutics following RFA treatment of colorectal liver metastases.
射频消融（RFA）是治疗结直肠癌肝转移的常用方法。RFA 产生的病变周围存在缺氧环，与肝内微转移的侵袭性生长有关。替拉扎胺等缺氧激活前药旨在选择性地在缺氧条件下诱导肿瘤细胞凋亡。因此，假设替拉扎胺在限制 RFA 后与缺氧相关的肿瘤生长方面可能具有治疗价值。
在体外低氧和正常氧条件下培养小鼠 C26 和 MC38 结直肠癌细胞，并给予不同浓度的替拉扎胺。通过 Western blot 和荧光激活细胞分选分析评估细胞凋亡和细胞周期分布。通过集落形成测定评估增殖能力。将患有微小结直肠癌肝转移的小鼠用 RFA 治疗，然后单次注射替拉扎胺（60mg/kg）或生理盐水。7 天后通过形态计量学评估肿瘤负荷。
替拉扎胺在体外低氧条件下诱导结直肠肿瘤细胞凋亡。在正常氧合条件下，替拉扎胺导致 G2 细胞周期阻滞，部分细胞从中恢复。这降低了，但没有消除集落形成能力。单次给予替拉扎胺可显著防止 RFA 后缺氧微转移的加速生长。替拉扎胺给药与最小毒性相关。
替拉扎胺以缺氧依赖的方式诱导结直肠癌细胞凋亡，并强烈抑制肝转移的缺氧相关生长，毒性有限。这需要进一步研究，以评估替拉扎胺或其他缺氧激活前药作为 RFA 治疗结直肠癌肝转移后的辅助治疗的潜在价值。
