A simple method for preparing 5-fluorouracil surface-functionalized selenium nanoparticles (5FU-SeNPs) with enhanced anticancer activity has been demonstrated in the present study. Spherical SeNPs were capped with 5FU through formation of Se-O and Se-N bonds and physical adsorption, leading to the stable structure of the conjugates. 5FU surface decoration significantly enhanced the cellular uptake of SeNPs through endocytosis. A panel of five human cancer cell lines was shown to be susceptible to 5FU-SeNPs, with IC(50) values ranging from 6.2 to 14.4 μM. Despite this potency, 5FU-SeNP possesses great selectivity between cancer and normal cells. Induction of apoptosis in A375 human melanoma cells by 5FU-SeNPs was evidenced by accumulation of sub-G1 cell population, DNA fragmentation, and nuclear condensation. The contribution of the intrinsic apoptotic pathway to the cell apoptosis was confirmed by activation of caspase-9 and depletion of mitochondrial membrane potential. Pretreatment of cells with a general caspase inhibitor z-VAD-fmk significantly prevented 5FU-SeNP-induced apoptosis, indicating that 5FU-SeNP induced caspase-dependent apoptosis in A375 cells. Furthermore, 5FU-SeNP-induced apoptosis was found dependent on ROS generation. Our results suggest that the strategy to use SeNPs as a carrier of 5FU could be a highly efficient way to achieve anticancer synergism. 5FU-SeNPs may be a candidate for further evaluation as a chemopreventive and chemotherapeutic agent for human cancers, especially melanoma.

The growth-promoting effect of Id-1 (inhibitor of differentiation/DNA binding) has been demonstrated in a number of human cancers. However, the mechanisms responsible for its action are not clear. In this study, we report that in prostate cancer cells, Id-1 promotes cell survival through activation of nuclear factor-jB (NF-jB) signalling pathway. After stable expression of Id-1 protein in LNCaP cells, we found that the Id-1 transfectants showed increased resistance to apoptosis induced by TNFa through inactivation of Bax and caspase 3. In addition, in the LNCaP cells expressing ectopic Id-1 protein, we also observed increased NF-jB transactivation activity and nuclear translocation of the p65 and p50 proteins, which was accompanied by upregulation of their downstream effectors Bcl-xL and ICAM-1. These results indicate that the Id-1-induced antiapoptotic effect may be via NF-jB signalling transduction pathway in these cells. In addition, inactivation of Id-1 by its antisense oligonucleotide and retroviral construct in DU145 cells resulted in the decrease of nuclear level of p65 and p50 proteins, which was associated with increased sensitivity to TNFa-induced apoptosis. Our results strongly suggest that Id-1 may be one of the upstream regulators of NF-jB and activation of NF-jB signalling pathway may be essential for Id-1 induced cell proliferation through protection against apoptosis. Our findings also suggest a potential therapeutic strategy in which inactivation of Id-1 may lead to sensitization of prostate cancer cells to chemotherapeutic drug-induced apoptosis.

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 g-tocotrienol was most potent, which resulted in induction of apoptosis as evidenced by activation of pro-caspases and the presence of sub-G 1 cell population. Examination of the pro-survival genes revealed that the g-tocotrienol-induced cell death was associated with suppression of NF-kB, EGF-R and Id family proteins (Id1 and Id3). Meanwhile, g-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 g-tocotrienol. Interestingly, g-tocotrienol treatment led to suppression of mesenchymal markers and the restoration of E-cadherin and g-catenin expression, which was associated with suppression of cell invasion capability. Furthermore, a synergistic effect was observed when cells were cotreated with g-tocotrienol and Docetaxel. Our results suggested that the antiproliferative effect of g-tocotrienol act through multiplesignalling pathways, and demonstrated for the first time the anti-invasion and chemosensitisation effect of g-tocotrienol against PCa cells.

Our results suggest that over expression of Id-1 may have important roles in the development of prostate cancer. The potential use of Id-1 protein as a marker for prostate cancer should be further explored.