Thomas Mark, Davis Tanja, Nell Theo, Sishi Balindiwe, Engelbrecht Anna-Mart
Department of Physiological Sciences, Faculty of Natural Sciences, Stellenbosch University, Stellenbosch, South Africa.
African Cancer Institute (ACI), Department of Global Health, Faculty of Medicine and Health Sciences, Stellenbosch University, Tygerberg, South Africa.
Front Cell Dev Biol. 2020 Oct 15;8:565915. doi: 10.3389/fcell.2020.565915. eCollection 2020.
Many clinical trials are beginning to assess the effectiveness of compounds known to regulate autophagy in patients receiving anti-cancer chemotherapy. However, autophagy inhibition, through exogenous inhibitors, or activation, through starvation, has revealed conflicting roles in cancer management and chemotherapeutic outcome. This study aimed to assess the effect of amino acid starvation on doxorubicin-treated breast cancer cells by assessing the roles of autophagy and apoptosis. An breast cancer model consisting of the normal breast epithelial MCF12A and the metastatic breast cancer MDAMB231 cells was used. Apoptotic and autophagic parameters were assessed following doxorubicin treatments, alone or in combination with bafilomycin, ATG5 siRNA or amino acid starvation. Inhibition of autophagy, through ATG5 siRNA or bafilomycin treatment, increased caspase activity and intracellular doxorubicin concentrations in MCF12A and MDAMB231 cells during doxorubicin treatment. While amino acid starvation increased autophagic activity and decreased caspase activity and intracellular doxorubicin concentrations in MCF12A cells, no changes in autophagic parameters or caspase activity were observed in MDAMB231 cells. Our data showed that 24 h protein starvation during high dose doxorubicin treatment resulted in increased survival of tumor-bearing GFP-LC3 mice. Results from this study suggest that short term starvation during doxorubicin chemotherapy may be a realistic avenue for adjuvant therapy, especially with regards to the protection of non-cancerous cells. More research is however, needed to fully understand the regulation of autophagic flux during starvation.
许多临床试验开始评估已知可调节自噬的化合物在接受抗癌化疗患者中的有效性。然而，通过外源性抑制剂抑制自噬或通过饥饿激活自噬，在癌症管理和化疗结果中显示出相互矛盾的作用。本研究旨在通过评估自噬和凋亡的作用来评估氨基酸饥饿对阿霉素处理的乳腺癌细胞的影响。使用了由正常乳腺上皮MCF12A和转移性乳腺癌MDAMB231细胞组成的乳腺癌模型。在阿霉素单独或与巴弗洛霉素、ATG5小干扰RNA（siRNA）或氨基酸饥饿联合处理后，评估凋亡和自噬参数。在阿霉素处理期间，通过ATG5 siRNA或巴弗洛霉素处理抑制自噬，可增加MCF12A和MDAMB231细胞中的半胱天冬酶活性和细胞内阿霉素浓度。虽然氨基酸饥饿增加了MCF12A细胞中的自噬活性，降低了半胱天冬酶活性和细胞内阿霉素浓度，但在MDAMB231细胞中未观察到自噬参数或半胱天冬酶活性的变化。我们的数据表明，在高剂量阿霉素处理期间24小时的蛋白质饥饿导致荷瘤GFP-LC3小鼠的存活率增加。本研究结果表明，阿霉素化疗期间的短期饥饿可能是辅助治疗的一个现实途径，特别是在保护非癌细胞方面。然而，需要更多的研究来充分了解饥饿期间自噬通量的调节。
