Division of Translational Science, National Cancer Center, Goyang, Republic of Korea.
Department of Pathology, National Cancer Center, Goyang, Republic of Korea.
Cancer Lett. 2021 Jun 28;508:59-72. doi: 10.1016/j.canlet.2021.03.011. Epub 2021 Mar 23.
The loss of cell-matrix interactions induces apoptosis, known as anoikis. For successful distant metastasis, circulating tumor cells (CTCs) that have lost matrix attachment need to acquire anoikis resistance in order to survive. Cell aggregate formation confers anoikis resistance, and CTC clusters are more highly metastatic compared to single cells; however, the molecular mechanisms underlying this aggregation are not well understood. In this study, we demonstrated that cell detachment increased cell aggregation and upregulated fibronectin (FN) levels in lung and breast cancer cells, but not in their normal counterparts. FN knockdown decreased cell aggregation and increased anoikis. In addition, cell detachment induced cell-cell adhesion proteins, including E-cadherin, desmoglein-2, desmocollin-2/3, and plakoglobin. Interestingly, FN knockdown decreased the levels of desmoglein-2, desmocollin-2/3, and plakoglobin, but not E-cadherin, suggesting the involvement of desmosomal junction in cell aggregation. Accordingly, knockdown of desmoglein-2, desmocollin-2, or plakoglobin reduced cell aggregation and increased cell sensitivity to anoikis. Previously, we reported that NADPH oxidase 4 (Nox4) upregulation is important for anoikis resistance. Nox4 inhibition by siRNA or apocynin decreased cell aggregation and increased anoikis with the downregulation of FN, and, consequently, decreased desmoglein-2, desmocollin-2/3, or plakoglobin. The coexpression of Nox4 and FN was found to be significant in lung and breast cancer patients, based on cBioPortal data. In vivo mouse lung metastasis model showed that FN knockdown suppressed lung metastasis and thus enhanced survival. FN staining of micro tissue array revealed that FN expression was positive for human lung cancer (61%) and breast cancer (58%) patients. Furthermore, the expression levels of FN, desmoglein-2, desmocollin-2, and plakoglobin were significantly correlated with the poor survival of lung and breast cancer patients, as per the Kaplan-Meier plotter analysis. Altogether, our data suggest that FN upregulation and enhanced desmosomal interactions are critical for cell aggregation and anoikis resistance upon cell detachment.
细胞-基质相互作用的丧失会诱导细胞凋亡，称为凋亡。为了实现成功的远处转移，已经失去基质附着的循环肿瘤细胞 (CTC) 需要获得抗凋亡能力才能存活。细胞聚集体的形成赋予了抗凋亡能力，并且与单个细胞相比，CTC 簇具有更高的转移性；然而，这种聚集的分子机制尚不清楚。在这项研究中，我们证明了细胞分离会增加肺癌和乳腺癌细胞的细胞聚集并上调纤连蛋白 (FN) 水平，但对其正常对应物没有影响。FN 敲低会减少细胞聚集并增加凋亡。此外，细胞分离诱导细胞-细胞粘附蛋白，包括 E-钙粘蛋白、桥粒蛋白-2、桥粒蛋白-2/3 和斑联蛋白。有趣的是，FN 敲低降低了桥粒蛋白-2、桥粒蛋白-2/3 和斑联蛋白的水平，但不降低 E-钙粘蛋白的水平，表明桥粒连接参与了细胞聚集。因此，桥粒蛋白-2、桥粒蛋白-2/3 或斑联蛋白的敲低减少了细胞聚集并增加了细胞对凋亡的敏感性。此前，我们报道 NADPH 氧化酶 4 (Nox4) 的上调对于抗凋亡很重要。siRNA 或 apocynin 抑制 Nox4 减少了细胞聚集并增加了凋亡，同时下调了 FN，从而降低了桥粒蛋白-2、桥粒蛋白-2/3 或斑联蛋白的水平。根据 cBioPortal 数据，发现 Nox4 和 FN 的共表达在肺癌和乳腺癌患者中具有重要意义。体内小鼠肺转移模型表明，FN 敲低抑制了肺转移并因此提高了存活率。微组织阵列的 FN 染色显示 FN 表达阳性见于 61%的肺癌和 58%的乳腺癌患者。此外，根据 Kaplan-Meier 绘图器分析，FN、桥粒蛋白-2、桥粒蛋白-2/3 和斑联蛋白的表达水平与肺癌和乳腺癌患者的不良预后显著相关。总的来说，我们的数据表明，FN 的上调和增强的桥粒相互作用对于细胞分离后细胞聚集和抗凋亡至关重要。
