Kim Tae Woo, Ko Seong-Gyu
Department of Biopharmaceutical Engineering, Dongguk University-WISE, Gyeongju, Gyeongbuk 38066, Republic of Korea.
Department of Preventive Medicine, College of Korean Medicine, Kyung Hee University, Seoul 02447, Republic of Korea.
Nutrients. 2024 Dec 14;16(24):4320. doi: 10.3390/nu16244320.
: Peroxisome proliferator-activated receptor γ (PPARγ) plays a key role in mediating anti-inflammatory and anticancer effects in the tumor microenvironment. Kaurenoic acid (KA), a diterpene compound isolated from (L.) Pruski, has been demonstrated to exert anti-inflammatory, anticancer, and antihuman immunodeficiency virus effects. : In this study, we identified KA as a novel activator of PPARγ with potent anti-inflammatory and antitumor effects both in vitro and in vivo. Given the potential of PPARγ regulators in overcoming radioresistance and chemoresistance in cancer therapies, we hypothesized that KA may enhance the efficacy of breast cancer radiotherapy. : In a lipopolysaccharide (LPS)-induced mouse inflammation model, KA treatment reduced the levels of pro-inflammatory cytokines, including COX-2, IL-6, IL-1β, and TNFα. In a xenograft mouse mode of breast cancer, KA treatment inhibited tumor growth. Specifically, KA treatment enhanced caspase-3 activity and cytotoxicity against MDA-MB-231 and MCF-7 breast cancer cells. When KA was co-treated with a caspase inhibitor, Z-VAD-FMK, caspase-dependent apoptosis was suppressed in these cells. KA was found to induce the generation of cytosolic calcium ions (Ca) and reactive oxygen species (ROS), triggering endoplasmic reticulum (ER) stress via the PERK-ATF4-CHOP axis. Hence, the ER stressor thapsigargin (TG) synergized with KA treatment to enhance apoptosis in these cells, while the loss of the PERK or CHOP function inhibited this phenomenon. KA treatment was shown to induce oxidative stress via the NADPH oxidase 4 (NOX4) and stimulate ROS production. Specifically, NOX4 knockdown (KD) and antioxidant treatment (N-acetyl cysteine or diphenyleneiodonium) suppressed such ER stress-mediated apoptosis by inhibiting KA-enhanced caspase-3 activity, cytotoxicity, and intracellular ROS production in the treated cells. In radioresistant MDA-MB-231R and MCF-7R cells, KA combined with 2 Gy radiation overcame radioresistance by upregulating PPARγ and modulating epithelial-mesenchymal transition (EMT) markers, such as E-cadherin, N-cadherin, and vimentin. In PPARγ KD MDA-MB-231R and MCF-7R cells, this phenomenon was inhibited due to reduced PPARγ and NOX4 expression. : In conclusion, these findings demonstrated KA as a novel PPARγ regulator with promising potential to enhance the efficacy of breast cancer radiotherapy.
过氧化物酶体增殖物激活受体γ（PPARγ）在介导肿瘤微环境中的抗炎和抗癌作用中起关键作用。从（L.）Pruski中分离出的二萜类化合物柯桠酸（KA）已被证明具有抗炎、抗癌和抗人类免疫缺陷病毒的作用。：在本研究中，我们确定KA是一种新型的PPARγ激活剂，在体外和体内均具有强大的抗炎和抗肿瘤作用。鉴于PPARγ调节剂在克服癌症治疗中的放射抗性和化学抗性方面的潜力，我们假设KA可能会增强乳腺癌放疗的疗效。：在脂多糖（LPS）诱导的小鼠炎症模型中，KA治疗降低了促炎细胞因子的水平，包括COX-2、IL-6、IL-1β和TNFα。在乳腺癌异种移植小鼠模型中，KA治疗抑制了肿瘤生长。具体而言，KA治疗增强了caspase-3活性以及对MDA-MB-231和MCF-7乳腺癌细胞的细胞毒性。当KA与caspase抑制剂Z-VAD-FMK联合处理时，这些细胞中的caspase依赖性凋亡受到抑制。发现KA可诱导胞质钙离子（Ca）和活性氧（ROS）的产生，通过PERK-ATF4-CHOP轴触发内质网（ER）应激。因此，内质网应激剂毒胡萝卜素（TG）与KA治疗协同作用以增强这些细胞中的凋亡，而PERK或CHOP功能的丧失则抑制了这种现象。KA治疗被证明可通过NADPH氧化酶4（NOX4）诱导氧化应激并刺激ROS产生。具体而言，NOX4基因敲低（KD）和抗氧化剂处理（N-乙酰半胱氨酸或二苯基碘鎓）通过抑制KA增强的caspase-3活性、细胞毒性和处理细胞中的细胞内ROS产生，抑制了这种内质网应激介导的凋亡。在放射抗性的MDA-MB-231R和MCF-7R细胞中，KA与2 Gy辐射联合通过上调PPARγ和调节上皮-间质转化（EMT）标志物，如E-钙黏蛋白、N-钙黏蛋白和波形蛋白，克服了放射抗性。在PPARγ KD的MDA-MB-231R和MCF-7R细胞中，由于PPARγ和NOX4表达降低，这种现象受到抑制。：总之，这些发现证明KA是一种新型的PPARγ调节剂，具有增强乳腺癌放疗疗效的潜在前景。
