Bajalovic Natasa, Or Yu Zuan, Woo Amanda R E, Lee Shi Hao, Lin Valerie C L
School of Biological Sciences, Nanyang Technological University, Singapore 637511, Singapore.
Biomedicines. 2022 Aug 2;10(8):1860. doi: 10.3390/biomedicines10081860.
The widely reported conflicting effects of progestin on breast cancer suggest that the progesterone receptor (PR) has dual functions depending on the cellular context. Cell models that enable PR to fully express anti-tumoral properties are valuable for the understanding of molecular determinant(s) of the anti-tumoral property. This study evaluated whether the expression of high levels of PR in MCF-7 cells enabled a strong anti-tumoral response to progestin. MCF-7 cells were engineered to overexpress PRB by stable transfection. A single dose of Promegestone (R5020) induced an irreversible cell growth arrest and senescence-associated secretory phenotype in MCF-7 cells with PRB overexpression (MCF-7PRB cells) but had no effect on MCF-7 cells with PRA overexpression. The growth-arresting effect was associated with downregulations of cyclin A2 and B1, CDK2, and CDK4 despite an initial upregulation of cyclin A2 and B1. R5020 also induced an evident activation of Nuclear Factor κB (NF-κB) and upregulation of interleukins IL-1α, IL-1β, and IL-8. Although R5020 caused a significant increase of CD24+CD44+ cell population, R5020-treated MCF-7PRB cells were unable to form tumorspheres and underwent massive apoptosis, which is paradoxically associated with marked downregulations of the pro-apoptotic proteins BID, BAX, PARP, and Caspases 7 and 8, as well as diminution of anti-apoptotic protein BCL-2. Importantly, R5020-activated PRB abolished the effect of estrogen. This intense anti-estrogenic effect was mediated by marked downregulation of ERα and pioneer factor FOXA1, leading to diminished chromatin-associated ERα and FOXA1 and estrogen-induced target gene expression. In conclusion, high levels of agonist-activated PRB in breast cancer cells can be strongly anti-tumoral and anti-estrogenic despite the initial unproductive cell cycle acceleration. Repression of ERα and FOXA1 expression is a major mechanism for the strong anti-estrogenic effect.
广泛报道的孕激素对乳腺癌的矛盾作用表明，孕激素受体（PR）根据细胞环境具有双重功能。能够使PR充分发挥抗肿瘤特性的细胞模型对于理解抗肿瘤特性的分子决定因素很有价值。本研究评估了MCF-7细胞中高水平PR的表达是否能使其对孕激素产生强烈的抗肿瘤反应。通过稳定转染使MCF-7细胞过表达PRB。单剂量的普罗美孕酮（R5020）在过表达PRB的MCF-7细胞（MCF-7PRB细胞）中诱导了不可逆的细胞生长停滞和衰老相关分泌表型，但对过表达PRA的MCF-7细胞没有影响。尽管细胞周期蛋白A2和B1最初上调，但生长停滞效应与细胞周期蛋白A2和B1、CDK2和CDK4的下调有关。R5020还诱导了核因子κB（NF-κB）的明显激活以及白细胞介素IL-1α、IL-1β和IL-8的上调。尽管R5020导致CD24+CD44+细胞群体显著增加，但经R5020处理的MCF-7PRB细胞无法形成肿瘤球并发生大量凋亡，这与促凋亡蛋白BID、BAX、PARP以及半胱天冬酶7和8的显著下调以及抗凋亡蛋白BCL-2的减少自相矛盾地相关。重要的是，R5020激活的PRB消除了雌激素的作用。这种强烈的抗雌激素作用是由ERα和先驱因子FOXA1的显著下调介导的，导致与染色质相关的ERα和FOXA1以及雌激素诱导的靶基因表达减少。总之，尽管最初细胞周期加速无效，但乳腺癌细胞中高水平的激动剂激活的PRB可具有强烈的抗肿瘤和抗雌激素作用。ERα和FOXA1表达的抑制是强烈抗雌激素作用的主要机制。
