γ-Tocotrienol suppresses prostate cancer cell proliferation and invasion through multiple-signalling pathways

Tocotrienol-rich fraction (TRF) has demonstrated antiproliferative effect on prostate cancer (PCa) cells. To elucidate this anticancer property in PCa cells, this study aimed, first, to identify the most potent isomer for eliminating PCa cells; and second, to decipher the molecular pathway responsible for its activity. Results showed that the inhibitory effect of γ-tocotrienol was most potent, which resulted in induction of apoptosis as evidenced by activation of pro-caspases and the presence of sub-G1 cell population. Examination of the pro-survival genes revealed that the γ-tocotrienol-induced cell death was associated with suppression of NF-κB, EGF-R and Id family proteins (Id1 and Id3). Meanwhile, γ-tocotrienol treatment also resulted in the induction of JNK-signalling pathway and inhibition of JNK activity by a specific inhibitor (SP600125) was able to partially block the effect of γ-tocotrienol. Interestingly, γ-tocotrienol treatment led to suppression of mesenchymal markers and the restoration of E-cadherin and γ-catenin expression, which was associated with suppression of cell invasion capability. Furthermore, a synergistic effect was observed when cells were co-treated with γ-tocotrienol and Docetaxel. Our results suggested that the antiproliferative effect of γ-tocotrienol act through multiple-signalling pathways, and demonstrated for the first time the anti-invasion and chemosensitisation effect of γ-tocotrienol against PCa cells

Abnormal Dosage Compensation of Reporter Genes Driven by the Drosophila Glass Multiple Reporter (GMR) Enhancer-Promoter

In Drosophila melanogaster the male specific lethal (MSL) complex is required for upregulation of expression of most X-linked genes in males, thereby achieving X chromosome dosage compensation. The MSL complex is highly enriched across most active X-linked genes with a bias towards the 3′ end. Previous studies have shown that gene transcription facilitates MSL complex binding but the type of promoter did not appear to be important. We have made the surprising observation that genes driven by the glass multiple reporter (GMR) enhancer-promoter are not dosage compensated at X-linked sites. The GMR promoter is active in all cells in, and posterior to, the morphogenetic furrow of the developing eye disc. Using phiC31 integrase-mediated targeted integration, we measured expression of lacZ reporter genes driven by either the GMR or armadillo (arm) promoters at each of three X-linked sites. At all sites, the arm-lacZ reporter gene was dosage compensated but GMR-lacZ was not. We have investigated why GMR-driven genes are not dosage compensated. Earlier or constitutive expression of GMR-lacZ did not affect the level of compensation. Neither did proximity to a strong MSL binding site. However, replacement of the hsp70 minimal promoter with a minimal promoter from the X-linked 6-Phosphogluconate dehydrogenase gene did restore partial dosage compensation. Similarly, insertion of binding sites for the GAGA and DREF factors upstream of the GMR promoter led to significantly higher lacZ expression in males than females. GAGA and DREF have been implicated to play a role in dosage compensation. We conclude that the gene promoter can affect MSL complex-mediated upregulation and dosage compensation. Further, it appears that the nature of the basal promoter and the presence of binding sites for specific factors influence the ability of a gene promoter to respond to the MSL complex