Sox9 Increases the Proliferation and Colony-forming Activity of Outer Root Sheath Cells Cultured In Vitro.

BACKGROUND: ß-catenin plays a pivotal role in hair follicle development and hair growth cycle. OBJECTIVE: The aim of this study was to identify ß-catenin-regulated genes in cultured human hair outer root sheath (ORS) cells. METHODS: Primary cultured ORS cells were transduced with recombinant adenovirus expressing N-terminal truncated ß-catenin (constitutive active form), and ß-catenin-regulated genes were identified. RESULTS: Overexpression of the constitutively active form of ß-catenin led to induction of Sox9 expression at both mRNA and protein levels. To investigate the potential role of Sox9, we made the recombinant adenovirus expressing green fluorescent protein-tagged Sox9, and then transduced into cultured ORS cells. Interestingly, Sox9 induced the expression of keratin 15, increased the proliferation of ORS cells in vitro, and enhanced colony-forming activity. CONCLUSION: Our results suggest that Sox9 is a ß-catenin-regulated gene in ORS cells, and has potential importance in the regulation of hair follicle homeostasis.

HDAC inhibitors downregulate MRP2 expression in multidrug resistant cancer cells: implication for chemosensitization.

Although histone deacetylase (HDAC) inhibitors are emerging as a promising class of cancer chemotherapeutic agents, their effects on multidrug resistance (MDR) are poorly understood. In this study, we investigated whether HDAC inhibitors overcome MDR phenotype. HDAC inhibitors suppress the growth of both MDR positive cancer cells KBV20C and its parental cells KB with similar potencies. In parallel, histone acetylation and p21WAF1 expression by the HDAC inhibitors were similarly increased in both cell types, indicating that these HDAC inhibitors are poor substrates of ABC drug transporters and effective in MDR cancer cells. In addition, multidrug resistance protein 2 (MRP2) expression is selectively attenuated by HDAC inhibitors, especially SAHA and TSA, in KBV20C cells, whereas MDR1 and BCRP expressions are not affected. This downregulation of MRP2 contributes to increase in paclitaxel-induced G2/M arrest and apoptosis, which might be due to intracellular accumulation of paclitaxel. Collectively, our data provide a molecular rationale for the application of HDAC inhibitors to overcome MDR in cancer cells.

Role of plasminogen activator inhibitor-2 (PAI-2) in keratinocyte differentiation.

BACKGROUND: Plasminogen activator inhibitor-2 (PAI-2) is an enzyme inhibitor which is involved in various biological processes including cell differentiation, tissue regrowth and regeneration. Although PAI-2 has been originally isolated as an extracellular inhibitor of urokinase plasminogen activator (uPA), recent studies indicate that PAI-2 has other intracellular effects in keratinocyte, such as the component of cornified envelope. OBJECTIVE: The aim of this study is to investigate the expression and functional role of PAI-2 during the keratinocyte differentiation. METHODS: We transduced keratinocytes with adenovirus harboring the expression cassette for PAI-2, then examined the effect on keratinocytes differentiation. RESULTS: When cultured epidermal keratinocytes were treated with 1.2 mM calcium, PAI-2 expression was increased time-dependently at both mRNA and protein levels. The calcium-induced PAI-2 expression was abolished by treatment with p38 MAPK inhibitor, while overexpression of MKK6 led to the increase of PAI-2 expression. When PAI-2 was overexpressed by adenoviral transduction, the expression of keratinocyte differentiation markers such as involucrin, keratin 10 and loricrin was markedly increased. Concomitantly, overexpression of PAI-2 resulted in the retardation of cell growth, with the increase of Rb and p53. CONCLUSION: These results suggest that PAI-2 has a role for promoting the differentiation of epidermal keratinocytes.

Histone deacetylase inhibitor apicidin-mediated drug resistance: involvement of P-glycoprotein.

Multidrug resistance (MDR), which is a significant impediment to the success of cancer chemotherapy, is attributable to the overexpression of membrane transport proteins, such as P-glycoprotein (P-gp), resulting in an increased drug efflux. In this study, we show that the histone deacetylase (HDAC) inhibitor apicidin leads to resistance of HeLa cells to paclitaxel through the induction of P-gp expression. Furthermore, apicidin dramatically increases the release of a fluorescent P-gp substrate, rhodamine 123, from cells. In parallel, apicidin resistance to the apoptotic potential of paclitaxel is associated with induction of P-gp expression in HeLa cells, as evidenced by specific inhibition of P-gp function using either the pharmacological inhibitor verapamil or RNA silencing. We also demonstrate the contribution of apicidin-induced functional P-gp expression to drug resistance using KB cells. Failure of P-gp induction by apicidin does not reverse paclitaxel-induced cytotoxicity in the cells. Although HDAC inhibitors are widely appreciated as a new class of anti-tumor agent, our findings clearly demonstrate that apicidin treatment may lead to P-gp-mediated resistance to other anti-tumor agents, suggesting a need for careful design of clinical applications using HDAC inhibitors.