Department of Pharmacology, School of Medicine, Dongguk University, Gyeongju, Gyeongsangbuk-do 38066, Republic of Korea.
Department of Radiation Oncology, School of Medicine, Dongguk University, Gyeongju, Gyeongsangbuk-do 38066, Republic of Korea.
Biochem Pharmacol. 2021 Oct;192:114718. doi: 10.1016/j.bcp.2021.114718. Epub 2021 Aug 3.
The development of radioresistance during radiotherapy is a major cause of tumor recurrence and metastasis. To provide new insights of the mechanisms underlying radioresistance, we established radioresistant cell lines derived from two different subtypes of breast cancer cells, HER2-positive SK-BR-3 and ER-positive MCF-7 breast cancer cells, by exposing cells to 48 ~ 70 Gy of radiation delivered at 4-5 Gy twice weekly over 9 ~ 10 months. The established radioresistant SK-BR-3 (SR) and MCF-7 (MR) cells were resistant not only to a single dose of radiation (2 Gy or 4 Gy) but also to fractionated radiation delivered at 2 Gy/day for 5 days. Furthermore, these cells exhibited tumor-initiating potential in vivo and high CD24-/CD44 + ratio. To identify novel therapeutic molecular targets, we analyzed differentially expressed genes in both radioresistant cell lines and found that the expression of ACSL4 was significantly elevated in both cell lines. Targeting ACSL4 improved response to irradiation and inhibited migration activities. Furthermore, inhibition of ACLS4 using ASCL4 siRNA or triacsin C suppressed FOXM1 expression, whereas inhibition of FOXM1 using thiostrepton did not affect ACSL4 expression. Targeting the ACSL4-FOXM1 signaling axis by inhibiting ASCL4 or FOXM1 overcame the radioresistance by suppressing DNA damage responses and inducing apoptosis. This is the first study to report that ACSL4 plays a crucial role in mediating the radioresistance of breast cancer by regulating FOXM1. We propose the ACSL4-FOXM1 signaling axis be considered a novel therapeutic target in radioresistant breast cancer and suggest treatment strategies targeting this signaling axis might overcome breast cancer radioresistance.
放射治疗过程中放射抗性的发展是肿瘤复发和转移的主要原因。为了提供放射抗性潜在机制的新见解，我们通过暴露细胞于 48 至 70Gy 的辐射下，建立了源自两种不同亚型乳腺癌细胞（HER2 阳性 SK-BR-3 和 ER 阳性 MCF-7 乳腺癌细胞）的放射抗性细胞系，两次每周，历时 9 至 10 个月。建立的放射抗性 SK-BR-3（SR）和 MCF-7（MR）细胞不仅对单次剂量的辐射（2Gy 或 4Gy）具有抗性，而且对 2Gy/天的分次辐射也具有抗性，共 5 天。此外，这些细胞在体内具有肿瘤起始潜力和高 CD24-/CD44+比率。为了鉴定新的治疗分子靶标，我们分析了两种放射抗性细胞系中的差异表达基因，发现 ACSL4 的表达在两种细胞系中均显著升高。靶向 ACSL4 可提高对辐射的反应并抑制迁移活性。此外，使用 ACSL4 siRNA 或三乙酰精氨酸 C 抑制 ACLS4 表达，而使用 thiostrepton 抑制 FOXM1 表达不影响 ACSL4 表达。通过抑制 ASCL4 或 FOXM1 抑制 ACSL4-FOXM1 信号通路，可通过抑制 DNA 损伤反应和诱导细胞凋亡来克服放射抗性。这是第一项报道 ACSL4 通过调节 FOXM1 在介导乳腺癌放射抗性中起关键作用的研究。我们提出 ACSL4-FOXM1 信号通路可被视为放射抗性乳腺癌的新治疗靶点，并建议针对该信号通路的治疗策略可能克服乳腺癌放射抗性。
