Deficiency of TTYH1 Expression Reduces the Migration and Invasion of U2OS Human Osteosarcoma Cells.

The Tweety homolog (TTYH) chloride channel family is involved in oncogenic processes including cell proliferation, invasion, and colonization of cancers. Among the TTYH family, TTYH1 is highly expressed in several cancer cells, such as glioma, breast, and gastric cancer cells. However, the role of TTYH1 in the progression of osteosarcoma remains unknown. Here, we report that deficient TTYH1 expression results in the inhibition of the migration and invasion of U2OS human osteosarcoma cells. We found that TTYH1 was endogenously expressed at both mRNA and protein levels in U2OS cells and that these channels were located at the plasma membrane of the cells. Moreover, we found that silencing of the TTYH1 with small interfering RNA (siRNA) resulted in a decrease in the migration and invasion of U2OS cells, while the proliferation of the cells was not affected. Additionally, treatment with TTYH1 siRNA significantly suppressed the mRNA expression of epithelial−mesenchymal transition (EMT)-regulated transcription factors such as Zinc E-Box Binding Homeobox 1 (ZEB1) and SNAIL. Most importantly, the expression of matrix metalloproteinase (MMP)-2, MPP-9, and N-cadherin was dramatically reduced following the silencing of TTYH1. Taken together, our findings suggest that silencing of TTYH1 expression reduces migration and invasion of U2OS cells and that TTYH1 may act as a potential molecular target for osteosarcoma treatment.

Upregulated TTYH2 expression is critical for the invasion and migration of U2OS human osteosarcoma cell lines.

Ion channels have recently emerged as stable biomarkers and anticancer targets particularly when the applications of the currently available therapeutic regimens are limited, as in case of osteosarcoma, a malignant bone tumor. Here, we evaluated the expression of TTYH2, a presumably calcium-activated chloride channel, in a human osteosarcoma cell line U2OS. We used small-interfering RNA (siRNA)-mediated gene silencing to demonstrate the downregulation in the expression of TTYH2 that resulted in the decrease in the invasion and migration, but not proliferation, of U2OS cells. The expression levels of Slug and ZEB1, the transcription factors involved in epithelial-mesenchymal transition, significantly reduced after TTYH2 silencing. Based on these results, we suggest that TTYH2 may serve as a novel target for the treatment of osteosarcoma.

Suppression of the ERK-SRF axis facilitates somatic cell reprogramming.

The molecular mechanism underlying the initiation of somatic cell reprogramming into induced pluripotent stem cells (iPSCs) has not been well described. Thus, we generated single-cell-derived clones by using a combination of drug-inducible vectors encoding transcription factors (Oct4, Sox2, Klf4 and Myc) and a single-cell expansion strategy. This system achieved a high reprogramming efficiency after metabolic and epigenetic remodeling. Functional analyses of the cloned cells revealed that extracellular signal-regulated kinase (ERK) signaling was downregulated at an early stage of reprogramming and that its inhibition was a driving force for iPSC formation. Among the reprogramming factors, Myc predominantly induced ERK suppression. ERK inhibition upregulated the conversion of somatic cells into iPSCs through concomitant suppression of serum response factor (SRF). Conversely, SRF activation suppressed the reprogramming induced by ERK inhibition and negatively regulated embryonic pluripotency by inducing differentiation via upregulation of immediate early genes, such as c-Jun, c-Fos and EGR1. These data reveal that suppression of the ERK-SRF axis is an initial molecular event that facilitates iPSC formation and may be a useful surrogate marker for cellular reprogramming.