School of Pharmacy, Curtin Health Innovation Research Institute, Curtin University, Perth, WA 6845, Australia.
Stem Cell and Cancer Biology Laboratory, School of Biomedical Sciences, Curtin Health Innovation Research Institute, Curtin University, Perth, WA 6845, Australia.
Int J Oncol. 2017 Jul;51(1):362-368. doi: 10.3892/ijo.2017.4011. Epub 2017 May 18.
Secreted frizzled related proteins (SFRPs) are a family of Wnt regulators which are frequently downregulated in cancers. In malignant mesothelioma (MM), downregulation of SFRP4 has been reported as a mechanism which contributes to aberrant activation of oncogenic Wnt signaling. Here we investigated the biological consequences of SFRP4 in two mesothelioma cell models where this protein is downregulated. We used recombinant SFRP4 and transient overexpression to study changes in proliferation, migration and downstream signaling. We found that recombinant SFRP4 inhibited both proliferation and migration of MM cells as well as abrogating the stimulatory effect of recombinant Wnt3a. Morphologically SFRP4 induced a cytotoxic effect distinct from apoptosis and consistent with mitotic catastrophe. Overexpression of SFRP4 in these cell lines displayed similar effects as endogenous protein on cell viability, migration and nuclear morphology. We also used expression constructs to examine the role of the SFRP4 cysteine rich domain (CRD) and a netrin-like domain (NLD) in these effects. Interestingly, we found it was the NLD which mediated the biological effects of SFRP4 in these cells. Our results indicate that SFRP4 inhibits mesothelioma proliferation, migration and activates alternative cell death pathways. The finding that the NLD is responsible for these has broader implications for this protein family. Overall this study suggests that the Wnt pathway may prove a promising target for therapy in mesothelioma.
分泌型卷曲相关蛋白（SFRPs）是 Wnt 调节因子家族的一员，其在癌症中常被下调。在恶性间皮瘤（MM）中，SFRP4 的下调被报道为导致致癌性 Wnt 信号异常激活的机制之一。在这里，我们在两个 SFRP4 蛋白下调的间皮瘤细胞模型中研究了 SFRP4 的生物学后果。我们使用重组 SFRP4 和瞬时过表达来研究增殖、迁移和下游信号的变化。我们发现重组 SFRP4 抑制了 MM 细胞的增殖和迁移，并阻断了重组 Wnt3a 的刺激作用。形态上，SFRP4 诱导了一种不同于细胞凋亡的细胞毒性作用，与有丝分裂灾难一致。在这些细胞系中过表达 SFRP4 对细胞活力、迁移和核形态显示出与内源性蛋白相似的效果。我们还使用表达构建体研究了 SFRP4 半胱氨酸丰富域（CRD）和神经导向因子样域（NLD）在这些效应中的作用。有趣的是，我们发现正是 NLD 介导了 SFRP4 在这些细胞中的生物学效应。我们的结果表明，SFRP4 抑制间皮瘤增殖、迁移并激活替代细胞死亡途径。发现 NLD 负责这些功能对这个蛋白家族具有更广泛的意义。总的来说，这项研究表明 Wnt 通路可能是间皮瘤治疗的一个有前途的靶点。
