Department of Oral and Maxillofacial Surgery, School of Dentistry, Showa University, 2-1-1 Kitasenzoku, Ota-ku, Tokyo, 145-8515, Japan.
Cell Oncol (Dordr). 2013 Jun;36(3):233-45. doi: 10.1007/s13402-013-0131-y. Epub 2013 Mar 26.
Tumor protein D54 (TPD54) belongs to the TPD52 family of proteins and is expressed in several types of cancer, including oral squamous cell carcinoma (OSCC). Here, we investigated relationships between various OSCC-related characteristics and TPD54 expression in vitro.
The expression of TPD54 in several OSCC-derived cell lines and normal, non-malignant, cells was assessed. Based on the results obtained, OSCC-derived SAS cells were subsequently subjected to exogenous over-expression of alternative splice variants (ASVs) of TPD54 and to TPD54 knock-down, mediated by siRNA. Next, the role of TPD54 in cellular growth, apoptosis, invasion, migration and extracellular-matrix (ECM)-dependent migration and attachment was investigated, as also the concomitant expression of integrins and integrin-related proteins by the OSCC-derived cells.
Western blot analysis and RT-PCR revealed that several TPD54 ASVs were expressed in the OSCC-derived cell lines tested. Neither exogenous ASV over-expression nor TPD54 knock-down modulated the proliferation or invasion of SAS cells in a monolayer culture assay. However, exogenous ASV over-expression did decrease anchorage-independent growth and TPD54 knock-down did increase anchorage-independent growth, irrespective of caspase activities. The same effects were observed on ECM-dependent cellular migration and cell attachment to the ECM. The expression levels of the major α and β integrin subunits, and of E-cadherin, were found to be similar to those observed in the non-transfected control cells, whereas talin1 expression was found to be increased after TPD54 knock-down. Also Akt was found to be activated after TPD54 knock-down, even in the absence of serum stimulation. Very similar effects were observed in the OSCC-derived cell lines HSC 2 and HSC 3.
Our results show that TPD54 affects OSCC cell attachment to the ECM, OSCC cell migration, and Akt/PKB activation by modulating integrin activation via a talin1-mediated inside-out signal of the ECM. Based on these results, we suggest that TPD54 may serve as a novel biomarker for OSCC and as a putative target for OSCC therapy.
肿瘤蛋白 D54（TPD54）属于 TPD52 蛋白家族，在多种癌症中表达，包括口腔鳞状细胞癌（OSCC）。在这里，我们研究了 TPD54 表达与体外多种 OSCC 相关特征的关系。
评估了几种 OSCC 衍生细胞系和正常、非恶性细胞中 TPD54 的表达。根据获得的结果，随后对 OSCC 衍生的 SAS 细胞进行外源性过表达 TPD54 的替代剪接变体（ASVs）和 TPD54 敲低，由 siRNA 介导。接下来，研究了 TPD54 在细胞生长、凋亡、侵袭、迁移和细胞外基质（ECM）依赖性迁移和附着中的作用，以及 OSCC 衍生细胞中整合素及其相关蛋白的伴随表达。
Western blot 分析和 RT-PCR 显示，在所测试的 OSCC 衍生细胞系中表达了几种 TPD54 ASVs。外源性 ASV 过表达或 TPD54 敲低均未调节 SAS 细胞在单层培养测定中的增殖或侵袭。然而，外源性 ASV 过表达确实减少了非锚定依赖性生长，而 TPD54 敲低增加了非锚定依赖性生长，而与半胱天冬酶活性无关。在 ECM 依赖性细胞迁移和细胞附着到 ECM 中也观察到相同的效果。主要α和β整合素亚基和 E-钙粘蛋白的表达水平与非转染对照细胞观察到的相似，而在 TPD54 敲低后发现 talin1 表达增加。还发现 TPD54 敲低后 Akt 被激活，即使没有血清刺激。在 OSCC 衍生细胞系 HSC2 和 HSC3 中也观察到非常相似的效果。
我们的结果表明，TPD54 通过调节整合素激活，通过 talin1 介导的 ECM 内信号，影响 OSCC 细胞与 ECM 的附着、OSCC 细胞迁移和 Akt/PKB 激活。基于这些结果，我们建议 TPD54 可作为 OSCC 的新型生物标志物和 OSCC 治疗的潜在靶点。
