Anastas Jamie N, Kulikauskas Rima M, Tamir Tigist, Rizos Helen, Long Georgina V, von Euw Erika M, Yang Pei-Tzu, Chen Hsiao-Wang, Haydu Lauren, Toroni Rachel A, Lucero Olivia M, Chien Andy J, Moon Randall T
J Clin Invest. 2014 Jul;124(7):2877-90. doi: 10.1172/JCI70156. Epub 2014 May 27.
About half of all melanomas harbor a mutation that results in a constitutively active BRAF kinase mutant (BRAF(V600E/K)) that can be selectively inhibited by targeted BRAF inhibitors (BRAFis). While patients treated with BRAFis initially exhibit measurable clinical improvement, the majority of patients eventually develop drug resistance and relapse. Here, we observed marked elevation of WNT5A in a subset of tumors from patients exhibiting disease progression on BRAFi therapy. WNT5A transcript and protein were also elevated in BRAFi-resistant melanoma cell lines generated by long-term in vitro treatment with BRAFi. RNAi-mediated reduction of endogenous WNT5A in melanoma decreased cell growth, increased apoptosis in response to BRAFi challenge, and decreased the activity of prosurvival AKT signaling. Conversely, overexpression of WNT5A promoted melanoma growth, tumorigenesis, and activation of AKT signaling. Similarly to WNT5A knockdown, knockdown of the WNT receptors FZD7 and RYK inhibited growth, sensitized melanoma cells to BRAFi, and reduced AKT activation. Together, these findings suggest that chronic BRAF inhibition elevates WNT5A expression, which promotes AKT signaling through FZD7 and RYK, leading to increased growth and therapeutic resistance. Furthermore, increased WNT5A expression in BRAFi-resistant melanomas correlates with a specific transcriptional signature, which identifies potential therapeutic targets to reduce clinical BRAFi resistance.
大约一半的黑色素瘤携带一种突变,该突变导致组成型激活的BRAF激酶突变体(BRAF(V600E/K)),其可被靶向BRAF抑制剂(BRAFis)选择性抑制。虽然接受BRAFis治疗的患者最初表现出可测量的临床改善,但大多数患者最终会产生耐药性并复发。在这里,我们观察到在接受BRAFi治疗出现疾病进展的患者的一部分肿瘤中,WNT5A显著升高。通过用BRAFi进行长期体外处理产生的BRAFi耐药黑色素瘤细胞系中,WNT5A转录本和蛋白质也升高。RNAi介导的黑色素瘤内源性WNT5A减少降低了细胞生长,增加了对BRAFi刺激的凋亡,并降低了促生存AKT信号的活性。相反,WNT5A的过表达促进了黑色素瘤的生长、肿瘤发生和AKT信号的激活。与WNT5A敲低类似,WNT受体FZD7和RYK的敲低抑制了生长,使黑色素瘤细胞对BRAFi敏感,并降低了AKT激活。总之,这些发现表明,慢性BRAF抑制会升高WNT5A表达,其通过FZD7和RYK促进AKT信号传导,导致生长增加和治疗耐药性。此外,BRAFi耐药黑色素瘤中WNT5A表达的增加与特定的转录特征相关,该特征可识别潜在的治疗靶点以降低临床BRAFi耐药性。