Tocotrienol-rich fraction from annatto ameliorates expression of lysyl oxidase in human osteoblastic MG-63 cells.

Lysyl oxidase (LOX) is required for the formation of bone collagen cross-links. Inactivation of the LOX gene in osteoblasts by DNA methylation and JAK signaling has been reported to cause loss of cross-links and an increased risk of fractures. Tocotrienols (T3s) have proven benefits on bone strength, but their potential effects on LOX remain largely unknown. Thus, the present study investigates the in vitro effects of T3s on LOX expression in human osteoblastic MG-63 cells. Results indicated that Tocotrienol-Rich Fraction (TRF), the δ-T3 rich oil extracted from Annatto was the most effective and significantly increased LOX expression. TRF treatment decreased de-novo methyltransferases (DNMTs), DNMT3A and DNMT3B levels. In addition, TRF significantly inhibited JAK2 activation and decreased expression of Fli1, a transcription factor of DNMTs. We conclude that TRF induced an increase in LOX expression via inhibition of de-novo methylation and reduction of Fli1 expression by the inactivation of JAK2.Abbreviations: CpG: cytosine-guanine dinucleotide; DNMT: DNA methyltransferase; Fli1: friend leukemia virus integration 1; JAK: janus kinase; LOX: lysyl oxidase; PCR: polymerase chain reaction; STAT: signal transducers and activators of transcription; T3s: tocotrienols; TPs: tocopherols; TRF: Tocotrienol-Rich Fraction.

Induction of the connexin 32 gene by epigallocatechin-3-gallate potentiates vinblastine-induced cytotoxicity in human renal carcinoma cells.

BACKGROUND/AIM: Enforced expression of the connexin (Cx) 32 gene, a member of the gap junction gene family and a tumor suppressor gene in human renal cell carcinoma (RCC), enhanced vinblastine (VBL)-induced cytotoxicity in RCC cells due to suppression of multidrug resistance 1 (MDR1) expression. Furthermore, in RCC the Cx32 gene is silenced by hypermethylation of CpG islands in a promoter region of the Cx gene. In this study, we investigated if the green tea polyphenol epigallocatechin-3-gallate (EGCG) could enhance susceptibility of RCC cells (Caki-1, a human metastatic RCC cell) to VBL. METHODS: The effects of EGCG on Caki-1 cells were estimated by WST-1 (cell viability), real-time RT-PCR (mRNA level) and immunoblotting (protein level). We estimated the methylation status in the promoter region of the Cx32 gene in RCC cells by methylation-specific PCR. Each protein function was inhibited by small interfering RNA (siRNA) and specific inhibitors. RESULTS: The EGCG treatment elicited significant upregulation of Cx32 in Caki-1 cells, and the induction of the Cx led to the suppression of MDR1 mRNA expression through inactivation of Src and subsequent activation of c-Jun NH2-terminal kinase (JNK). Chemical sensitivity to VBL in Caki-1 cells was increased by EGCG pretreatment, and this effect was abrogated by siRNA-mediated knockdown of Cx32. CONCLUSION: This study suggests that the restoration of Cx32 by EGCG pretreatment improves chemical tolerance on VBL in Caki-1 cells via the inactivation of Src and the activation of JNK.

Redox-inactive analogue of tocotrienol as a potential anti-cancer agent.

Vitamins are prominent among natural or endogenous compounds that are considered to be beneficial for both prevention and therapy of various human ailments. The vitamin E group of compounds composed of tocopherol and tocotrienol isoforms, has been subsequently proven to have health benefits including antioxidant and related protective properties. However, individual isoforms exhibit a wide-range of antioxidant potencies. Tocotrienol (T3) displays powerful anticancer activity that is often not exhibited by tocopherols, by modulating multiple intracellular signaling pathways associated with tumor cell proliferation and survival. The anticancer effect of T3 remains not fully understood but generally is mediated independently of its antioxidant activity. Further we have synthesized a new redox-inactive analogue of T3, 6-O-carboxypropyl-α-tocotrienol (T3E) showing considerable promise for stronger anticancer potency than its mother compound. In this mini-review, we particularly focus upon the anticancer action of the above active components of vitamin E and describe current research on the anticancer effects of T3 irrespective of antioxidant activity.

Yes is a central mediator of cell growth in malignant mesothelioma cells.

The constitutive activation of the Src family kinases (SFKs) has been established as a poor prognostic factor in malignant mesothelioma (MM), however, the family member(s) which contribute to the malignancy have not been defined. This study aimed to identify the SFK member(s) contributing to cell growth using RNA interference in various MM cell lines. Silencing of Yes but not of c-Src or Fyn in MM cells leads to cell growth suppression. This suppressive effect caused by Yes silencing mainly depends on G1 cell cycle arrest and partly the induction of apoptosis. Also, the knockout of Yes induces the inactivation of ß-catenin signaling and subsequently decreases the levels of cyclin D necessary for G1-S transition in the cell cycle. In addition, Yes knockout has less effect on cell growth suppression in ß-catenin-deficient H28 MM cells compared to other MM cells which express the catenin. Overall, we conclude that Yes is a central mediator for MM cell growth that is not shared with other SFKs such as c-Src.