Purpose

Traditional treatment regimens for advanced prostate cancer, especially castration-resistant prostate cancer, result in low survival times with severe side effects. Therefore, new treatment options are required. Vitamin C (VC) has been identified as a promising anti-cancer agent of which the effects depend on the accumulation of H₂O₂ that is produced through autoxidation. Sulfasalazine (SAS), a cystine transporter (X_c⁻) inhibitor, is known to suppress cellular glutathione (GSH) biosynthesis. Here, we hypothesized that targeting the X_c⁻ transporter via SAS may improve the anti-cancer activity of VC through regulating GSH biosynthesis, which in turn may result in the accumulation of reactive oxygen species (ROS).

Methods

The anti-cancer effect of VC and/or SAS on prostate cancer cells was assessed using WST-8, colony formation and annexin V-FITC/PI FACS assays. Changes in cellular ROS and GSH levels were determined to verify our hypothesis. Finally, BALB/c nude mice bearing prostate cancer xenografts were used to assess the anti-cancer effects of single or combined VC and SAS therapies.

Results

We found that SAS could potentiate the short- and long-term cytotoxicity of VC in prostate cancer cells. We also found that the synergistic effect of SAS and VC led to significant cellular GSH depletion, resulting in increased ROS accumulation. This synergistic effect could be reversed by the antioxidant N-acetyl-L-cysteine (NAC). The synergistic effect of SAS and VC was also noted in prostate cancer xenografts and correlated with immunohistochemistry results.

Conclusions

Our results strongly indicate that SAS, a relatively non-toxic drug that targets cystine transporters, in combination with VC may be superior to their single applications in the treatment of prostate cancer.

中文翻译：

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Xc抑制剂柳氮磺吡啶可通过谷胱甘肽依赖性机制改善前列腺癌细胞中药理维生素C的抗癌作用。

目的

晚期前列腺癌，特别是去势抵抗性前列腺癌的传统治疗方案导致生存时间短，并具有严重的副作用。因此，需要新的治疗选择。维生素C（VC）被认为是一种有前途的抗癌药，其作用取决于通过自氧化产生的H ₂ O ₂的积累。柳氮磺吡啶（SAS），胱氨酸转运体（X _Ç ^- ）抑制剂，是已知的以抑制细胞谷胱甘肽（GSH）的生物合成。在这里，我们假设针对X _Ç ^- 通过SAS转运蛋白可以通过调节GSH生物合成来改善VC的抗癌活性，进而可能导致活性氧（ROS）的积累。

方法

使用WST-8，集落形成和膜联蛋白V-FITC / PI FACS分析评估了VC和/或SAS对前列腺癌细胞的抗癌作用。确定细胞中ROS和GSH水平的变化以验证我们的假设。最后，将携带前列腺癌异种移植物的BALB / c裸鼠用于评估单一或组合的VC和SAS治疗的抗癌作用。

结果

我们发现，SAS可以增强VC在前列腺癌细胞中的短期和长期细胞毒性。我们还发现SAS和VC的协同作用导致细胞GSH明显耗竭，从而导致ROS积累增加。抗氧化剂N-乙酰基-L-半胱氨酸（NAC）可以逆转这种协同作用。在前列腺癌异种移植物中也注意到了SAS和VC的协同作用，并且与免疫组织化学结果相关。

结论

我们的结果有力地表明，与胱氨酸结合的SAS是靶向胱氨酸转运蛋白的相对无毒的药物，可能优于其在前列腺癌治疗中的单一应用。