GREB1: An evolutionarily conserved protein with a glycosyltransferase domain links ERα glycosylation and stability to cancer.

What covalent modifications control the temporal ubiquitination of ERα and hence the duration of its transcriptional activity remain poorly understood. We show that GREB1, an ERα-inducible enzyme, catalyzes O-GlcNAcylation of ERα at residues T553/S554, which stabilizes ERα protein by inhibiting association with the ubiquitin ligase ZNF598. Loss of GREB1-mediated glycosylation of ERα results in reduced cellular ERα levels and insensitivity to estrogen. Higher GREB1 expression in ERα+ve breast cancer is associated with greater survival in response to tamoxifen, an ERα agonist. Mice lacking Greb1 exhibit growth and fertility defects reminiscent of phenotypes in ERα-null mice. In summary, this study identifies GREB1, a protein with an evolutionarily conserved domain related to DNA-modifying glycosyltransferases of bacteriophages and kinetoplastids, as the first inducible and the only other (apart from OGT) O-GlcNAc glycosyltransferase in mammalian cytoplasm and ERα as its first substrate.

Telomerase reverse transcriptase promotes cancer cell proliferation by augmenting tRNA expression.

Transcriptional reactivation of telomerase reverse transcriptase (TERT) reconstitutes telomerase activity in the majority of human cancers. Here, we found that ectopic TERT expression increases cell proliferation, while acute reductions in TERT levels lead to a dramatic loss of proliferation without any change in telomere length, suggesting that the effects of TERT could be telomere independent. We observed that TERT determines the growth rate of cancer cells by directly regulating global protein synthesis independently of its catalytic activity. Genome-wide TERT binding across 5 cancer cell lines and 2 embryonic stem cell lines revealed that endogenous TERT, driven by mutant promoters or oncogenes, directly associates with the RNA polymerase III (pol III) subunit RPC32 and enhances its recruitment to chromatin, resulting in increased RNA pol III occupancy and tRNA expression in cancers. TERT-deficient mice displayed marked delays in polyomavirus middle T oncogene-induced (PyMT-induced) mammary tumorigenesis, increased survival, and reductions in tRNA levels. Ectopic expression of either RPC32 or TERT restored tRNA levels and proliferation defects in TERT-depleted cells. Finally, we determined that levels of TERT and tRNA correlated in breast and liver cancer samples. Together, these data suggest the existence of a unifying mechanism by which TERT enhances translation in cells to regulate cancer cell proliferation.

Telomerase regulates MYC-driven oncogenesis independent of its reverse transcriptase activity.

Constitutively active MYC and reactivated telomerase often coexist in cancers. While reactivation of telomerase is thought to be essential for replicative immortality, MYC, in conjunction with cofactors, confers several growth advantages to cancer cells. It is known that the reactivation of TERT, the catalytic subunit of telomerase, is limiting for reconstituting telomerase activity in tumors. However, while reactivation of TERT has been functionally linked to the acquisition of several "hallmarks of cancer" in tumors, the molecular mechanisms by which this occurs and whether these mechanisms are distinct from the role of telomerase on telomeres is not clear. Here, we demonstrated that first-generation TERT-null mice, unlike Terc-null mice, show delayed onset of MYC-induced lymphomagenesis. We further determined that TERT is a regulator of MYC stability in cancer. TERT stabilized MYC levels on chromatin, contributing to either activation or repression of its target genes. TERT regulated MYC ubiquitination and proteasomal degradation, and this effect of TERT was independent of its reverse transcriptase activity and role in telomere elongation. Based on these data, we conclude that reactivation of TERT, a direct transcriptional MYC target in tumors, provides a feed-forward mechanism to potentiate MYC-dependent oncogenesis.

Quantitative assessment of telomerase components in cancer cell lines.

Besides its canonical function of catalyzing the formation of telomeric repeats, many groups have recently reported non-canonical functions of hTERT in particular, and telomerase in general. Regulating transcription is the central basis of non-canonical functions of telomerase. However, unlike reverse transcriptase activity of telomerase that requires only a few molecules of enzymatically active hTERT, non-canonical functions of hTERT or other telomerase components theoretically require several hundred copies. Here, we provide the first direct quantification of all the telomerase components in human cancer cell lines. We demonstrate that telomerase components do not exist in a 1:1 stoichiometric ratio, and there are several hundred copies of hTERT in cells. This provides the molecular basis of hTERT to function in other signaling cascades, including transcription.

A Novel Anti-Cancer Agent, 1-(3,5-Dimethoxyphenyl)-4-[(6-Fluoro-2-Methoxyquinoxalin-3-yl)Aminocarbonyl] Piperazine (RX-5902), Interferes With ß-Catenin Function Through Y593 Phospho-p68 RNA Helicase.

1-(3,5-Dimethoxyphenyl)-4-[(6-fluoro-2-methoxyquinoxalin-3-yl)aminocarbonyl] piperazine (RX-5902) exhibits strong growth inhibition in various human cancer cell lines with IC50 values ranging between 10 and 20 nM. In this study, we demonstrate that p68 RNA helicase is a cellular target of RX-5902 by the drug affinity responsive target stability (DARTS) method, and confirmed the direct binding of (3) H-labeled RX-5902 to Y593 phospho-p68 RNA helicase. We further demonstrated RX-5902 inhibited the ß-catenin dependent ATPase activity of p68 RNA helicase in an in vitro system. Furthermore, we showed that treatment of cancer cells with RX-5902 resulted in the downregulation of the expression of certain genes, which are known to be regulated by the ß-catenin pathway, such as c-Myc, cyclin D1 and p-c-Jun. Therefore, our study indicates that the inhibition of Y593 phospho-p68 helicase - ß-catenin interaction by direct binding of RX-5902 to Y593 phospho-p68 RNA helicase may contribute to the anti-cancer activity of this compound.

Hispolon decreases melanin production and induces apoptosis in melanoma cells through the downregulation of tyrosinase and microphthalmia-associated transcription factor (MITF) expressions and the activation of caspase-3, -8 and -9.

Hispolon is one of the most important functional compounds that forms Phellinus linteus (Berkeley & Curtis) Teng. Hispolon has antioxidant, anti-inflammatory, antiproliferative and anticancer effects. In this study, we analyzed the functions of hispolon on melanogenesis and apoptosis in B16-F10 melanoma cells. The results demonstrated that hispolon is not an enzymatic inhibitor for tyrosinase; rather, it represses the expression of tyrosinase and the microphthalmia-associated transcription factor (MITF) to reduce the production of melanin in α-melanocyte-stimulating hormone (α-MSH)-stimulated B16-F10 cells at lower concentrations (less than 2 µM). In contrast, at higher concentration (greater than 10 µM), hispolon can induce activity of caspase-3, -8 and -9 to trigger apoptosis of B16-F10 cells but not of Detroit 551 normal fibroblast cells. Therefore, we suggest that hispolon has the potential to treat hyperpigmentation diseases and melanoma skin cancer in the future.

Kinetic study on the tyrosinase and melanin formation inhibitory activities of carthamus yellow isolated from Carthamus tinctorius L.

Carthamus yellow (CY) is the major component of the yellow pigments of Carthamus tinctorius L. CY has been extensively used as a natural color additive for food and cosmetics. Here, our results demonstrate that carthamus yellow reduced the activity of mushroom tyrosinase in a dose-dependent manner with a half maximal inhibitory concentration (IC(50)) value of approximately 1.01 ± 0.03 mg/mL. A kinetic study of carthamus yellow on tyrosinase exhibited a mode of competitive inhibition with a Ki of 0.607 mg/mL. Moreover, cell viability analysis indicated that carthamus yellow used at concentrations of 1.0-4.0 mg/mL had no cytotoxicity in B16F10 melanoma cells. Melanin content analysis showed that melanin production in B16F10 melanoma cells treated with 4 mg/mL carthamus yellow can decrease to 82.3 ± 0.4% of the levels of melanin production of untreated cells. Thus, carthamus yellow has the potential to become a useful skin-whitening agent in the future.

Association of body mass index and depressive symptoms in a Chinese community population: results from the Health Promotion Knowledge, Attitudes, and Performance Survey in Taiwan.

BACKGROUND: The association between obesity and depression remains equivocal. The aims of this study were to examine the association between body mass index (BMI) and depressive symptoms in the Chinese adult population. METHODS: In this study, data from the Health Promotion Knowledge, Attitudes, and Performance Survey, conducted in 2002 among 20,385 Taiwanese adults (aged 18-64 years), were used. Depressive symptoms were assessed by the Taiwanese Depression Questionnaire (cut off point 19). Weight status was categorized as underweight (BMI < 18.5 kg/m²), normal weight (BMI 18.5- 23.9 kg/m²), overweight (BMI 24-26.9 kg/m²), and obese (BMI ≥ 27 kg/m²). RESULTS: Bivariate analyses revealed that underweight men and women had higher risks of depressive symptoms than normal weight individuals. After controlling for education, income, occupation, smoking status, marital status, presence of chronic disease, exercise, and weight control measures, we found that underweight men were significantly more likely to have depressive symptoms than normal weight men (Adjusted odds ratio [AOR] 2.68, 95% confidence interval [CI] 1.85-3.88). On the contrary, obese women were significantly less likely to have depressive symptoms than normal weight women (AOR 0.62, 95% CI 0.46-0.83). CONCLUSION: The associations of BMI and depressive symptoms were different between genders. Underweight men ran a higher risk of depression than normal weight men, and overweight women had a lower risk than normal weight women. These findings support the "jolly fat" hypothesis among the adult population in the Chinese community.

The effect of calcium score on the diagnostic accuracy of coronary computed tomography angiography.

The influence of coronary calcification on the diagnostic performance of coronary computed tomography angiography (CTA) remains controversial. This study attempts to assess the effect of coronary calcium score (CS) on the diagnostic accuracy of detecting coronary artery disease (CAD) using 64-row multidetector computed tomography (MDCT). Over a period of 2 years and 9 months, 113 symptomatic patients (37-87 year-old, mean 62.3, 92 males) underwent 64-row MDCT for coronary CS and CTA. All had conventional coronary angiography (CCA) within 90 (mean 9.6) days. Coronary CTA was evaluated with CCA as the gold standard. Of 113 patients, 18 patients had a CS of 0, 18 had scores between 1 and 100, 27 between 101 and 400, and 50 had scores >400. With respect to patient-based analysis, the accuracy of CTA was 90.3%, the sensitivity was 95%, and the specificity was 78.8%. Regarding patients with CS > 400, the accuracy, sensitivity, and specificity were 92, 95.6, and 60%, respectively. On vessel-based analysis, the specificity of CTA in different vessels with CS < [double bond] 400 and CS > 400 was as follows: right coronary artery 87.1% versus 87.5% (P = 0.924); left main artery 94.8% versus 66.7% (P = 0.173); left anterior descending artery 77.1% versus 27.3% (P = 0.001); and left circumflex artery 83.3% versus 42.8% (P = 0.011). A high CS does not significantly affect the diagnostic accuracy and sensitivity of CTA; however, it significantly decreases the specificity, particularly the left anterior descending and left circumflex arteries.