Neuroblastoma (NB) is an embryonal tumor arising from the sympathetic central nervous system. The epidermal growth factor (EGF) plays a role in NB growth and metastatic behavior. Recently, we have demonstrated that cathepsin D (CD) contrasts EGF-induced NB cell growth in 2D by downregulating EGFR/MAPK signaling. Aggressive NB is highly metastatic to the bone and the brain. In the metastatic process, adherent cells detach to form clusters of suspended cells that adhere once they reach the metastatic site and form secondary colonies. Whether CD is involved in the survival of metastatic NB clones is not known. Therefore, in this study, we addressed how CD differentially affects cell growth in suspension versus the adherent condition. To mimic tumor heterogeneity, we co-cultured transgenic clones silenced for or overexpressing CD. We compared the growth kinetics of such mixed clones in 2D and 3D models in response to EGF, and we found that the Over CD clone had an advantage for growth in suspension, while the CD knocked-down clone was favored for the adherent growth in 2D. Interestingly, on switching from 3D to 2D culture conditions, the expression of E-cadherin and of N-cadherin increased in the KD-CD and Over CD clones, respectively. The fact that CD plays a dual role in cancer cell growth in 2D and 3D conditions indicates that during clonal evolution, subclones expressing different level of CD may arise, which confers survival and growth advantages depending on the metastatic step. By searching the TCGA database, we found up to 38 miRNAs capable of downregulating CD. Interestingly, these miRNAs are associated with biological processes controlling cell adhesion and cell migration. The present findings support the view that during NB growth on a substrate or when spreading as floating neurospheres, CD expression is epigenetically modulated to confer survival advantage. Thus, epigenetic targeting of CD could represent an additional strategy to prevent NB metastases.
神经母细胞瘤（NB）是一种起源于交感神经中枢神经系统的胚胎性肿瘤。表皮生长因子（EGF）在NB的生长和转移行为中发挥重要作用。近期，我们通过下调EGFR/MAPK信号通路，证实组织蛋白酶D（CD）在二维培养中能抑制EGF诱导的NB细胞生长。侵袭性NB易发生骨与脑转移。在转移过程中，贴壁细胞脱离基质形成悬浮细胞簇，抵达转移部位后重新贴壁形成继发集落。目前尚不清楚CD是否参与转移性NB克隆的存活。因此，本研究探讨了CD在悬浮与贴壁条件下对细胞生长的差异化影响。为模拟肿瘤异质性，我们共培养CD基因沉默与过表达的转基因克隆株。通过比较这些混合克隆在二维和三维模型中对EGF反应的生长动力学，发现过表达CD克隆在悬浮生长中具有优势，而CD敲低克隆更适应二维贴壁生长。值得注意的是，当培养条件从三维转换为二维时，KD-CD克隆中E-钙黏蛋白表达上调，而过表达CD克隆中N-钙黏蛋白表达增加。CD在二维与三维条件下对癌细胞生长的双重调控作用表明，在克隆进化过程中可能出现表达不同CD水平的亚克隆，这些亚克隆根据转移阶段的需求获得相应的生存与生长优势。通过检索TCGA数据库，我们鉴定出38种能够下调CD的miRNA。值得注意的是，这些miRNA与调控细胞黏附和迁移的生物学过程密切相关。本研究证实，在基质依赖性生长或悬浮神经球扩散过程中，NB通过表观遗传调控CD表达以获得生存优势。因此，靶向CD的表观遗传调控可能成为预防NB转移的新策略。
肿瘤(癌症)患者之家