Clinical and Molecular Oncology Laboratory, Division of Oncology, Department of Medicine, University of Patras, Patras, Greece.
Department of Surgery, Memorial Sloan Kettering Cancer Center, New York, NY, USA.
Oncogene. 2018 Sep;37(37):5101-5114. doi: 10.1038/s41388-018-0324-y. Epub 2018 May 29.
The RANK/RANKL axis emerges as a key regulator of breast cancer initiation, progression, and metastasis. RANK-c is a RANK receptor isoform produced through alternative splicing of the TNFRSF11A (RANK) gene and a dominant-negative regulator of RANK-induced nuclear factor-κB (NF-κB) activation. Here we report that RANK-c transcript is expressed in 3.2% of cases in The Cancer Genome Atlas breast cancer cohort evenly between ER-positive and ER-negative cases. Nevertheless, the ratio of RANK to RANK-c (RANK/RANK-c) is increased in ER-negative breast cancer cell lines compared to ER-positive breast cancer cell lines. In addition, forced expression of RANK-c in ER-negative breast cancer cell lines inhibited stimuli-induced NF-κB activation and attenuated migration, invasion, colony formation, and adhesion of cancer cells. Further, RANK-c expression in MDA-MB-231 cells inhibited lung metastasis and colonization in vivo. The RANK-c-mediated inhibition of cancer cell aggressiveness and nuclear factor-κB (NF-κB) activation in breast cancer cells seems to rely on a RANK-c/TNF receptor-associated factor-2 (TRAF2) protein interaction. This was further confirmed by a mutated RANK-c that is unable to interact with TRAF2 and abolishes the ability to attenuate NF-κB activation, migration, and invasion. Additional protein interaction characterization revealed epidermal growth factor receptor (EGFR) as a novel interacting partner for RANK-c in breast cancer cells with a negative effect on EGFR phosphorylation and EGF-dependent downstream signaling pathway activation. Our findings further elucidate the complex molecular biology of the RANKL/RANK system in breast cancer and provide preliminary data for RANK-c as a possible marker for disease progression and aggressiveness.
RANK/RANKL 轴作为乳腺癌发生、进展和转移的关键调节因子出现。RANK-c 是通过 TNFRSF11A（RANK）基因的选择性剪接产生的 RANK 受体同工型，是 RANK 诱导的核因子-κB（NF-κB）激活的显性负调节剂。在这里，我们报告 RANK-c 转录本在癌症基因组图谱乳腺癌队列中的 3.2%的病例中表达，在 ER 阳性和 ER 阴性病例之间均匀分布。然而，与 ER 阳性乳腺癌细胞系相比，RANK 与 RANK-c 的比例（RANK/RANK-c）在 ER 阴性乳腺癌细胞系中增加。此外，在 ER 阴性乳腺癌细胞系中强制表达 RANK-c 抑制了刺激诱导的 NF-κB 激活，并减弱了癌细胞的迁移、侵袭、集落形成和黏附。此外，RANK-c 在 MDA-MB-231 细胞中的表达抑制了体内肺癌转移和定植。RANK-c 在乳腺癌细胞中对癌细胞侵袭性和核因子-κB（NF-κB）激活的抑制似乎依赖于 RANK-c/TNF 受体相关因子-2（TRAF2）蛋白相互作用。这进一步通过不能与 TRAF2 相互作用并消除减弱 NF-κB 激活、迁移和侵袭能力的突变型 RANK-c 得到证实。进一步的蛋白质相互作用特征表明，表皮生长因子受体（EGFR）是乳腺癌细胞中 RANK-c 的一个新的相互作用伙伴，对 EGFR 磷酸化和 EGF 依赖性下游信号通路激活有负作用。我们的发现进一步阐明了 RANKL/RANK 系统在乳腺癌中的复杂分子生物学，并为 RANK-c 作为疾病进展和侵袭性的可能标志物提供了初步数据。
