Bioengineering fluorescent virus-like particle/RNAi nanocomplexes act synergistically with temozolomide to eradicate brain tumors

The proof-of-concept strategy in this study based on biodegradable and biocompatible self-assembling fluorescent virus-like particle/RNAi nanocomplexes (VLP/RNAi) produced in Escherichia coli (E. coli) followed by surface modification with a cell-penetrating peptide (CPP) and an apolipoprotein E peptide (ApoEP) (dP@VLP/RNAi), which can cross the blood-brain barrier (BBB) to inhibit the DNA repair mechanism and act synergistically with temozolomide (TMZ) for promoting clinical chemotherapy has achieved good therapeutic effects towards malignant brain tumors. The synergistic value of this study's design was verified in intracranial mouse models of glioblastomas (GBMs). Intravenous administration of this formulation enhanced the curative efficacy of TMZ by downregulating the hepatocyte growth factor receptor (c-MET) gene in GBM U87 cells. Furthermore, upon gene-chemotherapy, the methylated DNA in GBM U87 cells was significantly enhanced by inhibiting the DNA repair mechanism, leading to significant brain tumor suppression. The results of this study could be critical for the design of RNAi-based genetic therapeutics for promoting chemotherapy against brain tumors.

Development of a standardized and effect-optimized herbal extract of Wedelia chinensis for prostate cancer

Herbal medicine is a popular complementary or alternative treatment for prostate cancer. Wedelia chinensis has at least three active compounds, wedelolactone, luteolin, and apigenin synergistically inhibiting prostate cancer cell growth in vitro. Here, we report a systematic study to develop a standardized and effect-optimized herbal extract, designated as W. chinensis extract (WCE) to facilitate its future scientific validation and clinical use. Ethanolic extract of dried W. chinensis plant was further condensed, acid hydrolyzed, and enriched with preparative chromatography. The chemical compositions of multiple batches of the standardized preparation WCE were quantified by LC/MS/MS, and biological activities were analyzed by in vitro and in vivo assays. Furthermore, the pharmacokinetics of the holistic WCE were compared with the combination of the equivalent principal active compounds through oral administration. The results indicated that quantitative chemical assay and PSA (prostate-specific antigen)-reporter assay together are suitable to measure the quality and efficacy of a standardized Wedelia extract on a xenograft tumor model. The presence of minor concomitant compounds in WCE prolonged the systemic exposure to the active compounds, thus augmented the anti-tumor efficacy of WCE. In conclusion, a combination of LC/MS/MS and PSA reporter assay is suitable to qualify a standardized preparation of WCE. Furthermore, the pharmacokinetics and oral bioavailability of active compounds demonstrate that holistic WCE exerted additional pharmacological synergy beyond the multi-targeted therapeutic effects caused by more than one active compound. WCE merits a higher priority to be studied for use in prostate cancer treatment.

Signal transduction triggered by iron to induce the nuclear importation of a Myb3 transcription factor in the parasitic protozoan Trichomonas vaginalis

Iron was previously shown to induce rapid nuclear translocation of a Myb3 transcription factor in the protozoan parasite, Trichomonas vaginalis. In the present study, iron was found to induce a transient increase in cellular cAMP, followed by the nuclear influx of Myb3, whereas the latter was also induced by 8-bromo-cyclic AMP. Iron-inducible cAMP production and nuclear influx of Myb3 were inhibited by suramin and SQ22536, respective inhibitors of the Gα subunit of heterotrimeric G proteins and adenylyl cyclases. In contrast, the nuclear influx of Myb3 induced by iron or 8-bromo-cAMP was delayed or inhibited, respectively, by H89, the inhibitor of protein kinase A. Using liquid chromatography-coupled tandem mass spectrometry, Thr(156) and Lys(143) in Myb3 were found to be phosphorylated and ubiquitinated, respectively. These modifications were induced by iron and inhibited by H89, as shown by immunoprecipitation-coupled Western blotting. Iron-inducible ubiquitination and nuclear influx were aborted in T156A and K143R, but T156D was constitutively ubiquitinated and persistently localized to the nucleus. Myb3 was phosphorylated in vitro by the catalytic subunit of a T. vaginalis protein kinase A, TvPKAc. A transient interaction between TvPKAc and Myb3 and the phosphorylation of both proteins were induced in the parasite shortly after iron or 8-bromo-cAMP treatment. Together, these observations suggest that iron may induce production of cAMP and activation of TvPKAc, which then induces the phosphorylation of Myb3 and subsequent ubiquitination for accelerated nuclear influx. It is conceivable that iron probably exerts a much broader impact on the physiology of the parasite than previously thought to encounter environmental changes.

Structural basis for catalysis and ubiquitin recognition by the severe acute respiratory syndrome coronavirus papain-like protease

Papain‐like protease (PL^pro) is one of two cysteine proteases involved in the proteolytic processing of the polyproteins of Severe acute respiratory syndrome coronavirus (SARS‐CoV). PL^pro also shows significant in vitro deubiquitinating and de‐ISGylating activities, although the detailed mechanism is still unclear. Here, the crystal structure of SARS‐CoV PL^pro C112S mutant in complex with ubiquitin (Ub) is reported at 1.4 Å resolution. The Ub core makes mostly hydrophilic interactions with PL^pro, while the Leu‐Arg‐Gly‐Gly C‐terminus of Ub is located in the catalytic cleft of PL^pro, mimicking the P4–P1 residues and providing the first atomic insights into its catalysis. One of the O atoms of the C‐terminal Gly residue of Ub is located in the oxyanion hole consisting of the main‐chain amides of residues 112 and 113. Mutations of residues in the PL^pro–Ub interface lead to reduced catalytic activity, confirming their importance for Ub binding and/or catalysis. The structure also revealed an N‐cyclohexyl‐2‐aminethanesulfonic acid molecule near the catalytic triad, and kinetic studies suggest that this binding site is also used by other PL^pro inhibitors. Overall, the structure provides a foundation for understanding the molecular basis of coronaviral PL^pro catalysis.

Differential domain structure stability of the severe acute respiratory syndrome coronavirus papain-like protease

Papain-like protease (PLpro) from severe acute respiratory syndrome (SARS) coronavirus is one of the two proteases involved in the proteolytic processing of the virion polyproteins. In addition, PLpro shows significant in vitro deubiquitinating and de-ISGylating activities. All these findings demonstrated the multifunctional nature of the PLpro. Here we report the sensitivity of PLpro to denaturant urea. An increase in urea concentration induced a reversible biphasic unfolding of the enzyme. Differently, the unfolding of the catalytic triad region located within the palm and thumb domains followed a monophasic unfolding curve. Further observations suggest that the zinc-binding domain may start to unfold during the first transition. An 80% lost of its enzymatic activity at a urea concentration lower than 1 M showed a close correlation with unfolding of the zinc-binding domain. The enzyme was also characterized in terms of hydrophobicity and size-and-shape distribution. We have demonstrated that PLpro displayed differential domain structure stability and molten globule state in its folding. These studies will not only assist in our understanding of the folding of this viral enzyme, but also that of other deubiquitinating enzymes with a similar scaffold.

Resistance to apoptosis induced by alkylating agents in v-Ha-ras-transformed cells due to defect in p53 function

In this study, we examined the susceptibility of various oncogene-transformed NIH/3T3 cells to apoptosis induced by alkylating agents. Only v-Ha-ras-transformed cells showed marked resistance to apoptotic death induced by these drugs. Upon treatment with methylmethane sulfonate (MMS), NIH/3T3 cells exhibited normal G1 checkpoint function accompanied by the accumulation of p53 and p21CIP1/WAF1 protein. However, no such effects were observed in v-Ha-ras-transformed cells. To further examine the functional status of p53 in ras-transformed cells, we determined the DNA sequence, protein half-life, protein-complexing activity, and specific DNA-binding activity of p53. The results showed that ras transformants and parental NIH/3T3 cells had the same p53 protein half-life of 40 min or less, the same normal wild-type p53 cDNA sequence, and the same coimmunoprecipitable cellular proteins complexed with p53. In electrophoretic mobility gel-shift assays, however, nuclear extracts of cells treated with MMS, ras-transformed cells, and normal cells displayed distinct patterns of binding between p53 and its consensus binding site. Furthermore, western blot analysis showed that the bcl-2 and bax proteins were constitutively elevated in ras-transformed cells but not in parental NIH/ 3T3 cells. Heat-shock protein 70 (hsp70), which has been found to be negatively regulated by wild-type p53, was also dramatically induced in ras-transformed cells but not in NIH/3T3 cells in response to MMS. Thus, our data suggest that an activated ras oncogene can suppress alkylating agent-induced apoptotic cell death by means of a defect in the signal transduction pathway regulating p53 function and alteration in the expression of apoptotic (bax) or anti-apoptotic proteins (bcl-2 and hsp70).

Differential induction of apoptosis in oncogene-transformed NIH 3T3 cells by methylmethanesulfonate

Cellular oncogenes have been shown to play crucial roles in the cell death process induced by cytotoxic agents. In this study, we have demonstrated that v-H-ras transformed NIH 3T3 cells but not other transformants (v-raf, v-src, v-erbB-2, v-fes and v-mos) exhibited a survival advantage to treatment by a DNA-damaging agent, methylmethanesulfonate (MMS). Subsequently, the biochemical and morphologic criteria of MMS-treated cells were examined. It was found that MMS induced v-H-ras transformants to go through necrosis, but it induced other transformed cells to undergo apoptosis. The levels of glutathione (GSH) within each transformant as well as in NIH 3T3 cells, were determined. The results showed that GSH levels within ras transformants were 2- to 7-fold higher than the levels in other transformants and normal NIH 3T3 cells. By using the GSH synthesis inhibitor buthionine sulfoximine, GSH levels were artificially reduced. This depletion, however, made ras transformed cells more sensitive to MMS killing, but the mode of cell death was still necrosis. Western blot analysis demonstrated that the anti-apoptotic protein Bcl-2 was constitutively expressed in ras transformed cells but not in NIH 3T3 or other transformed cells. The level of Bcl-2 was correlated with the resistant phenotype of ras transformants during MMS treatment. These observations suggest that GSH and Bcl-2 levels may cooperatively confer the resistant phenotype of ras transformants in response to MMS. In addition, the mode of cell death may possibly be determined at least in part by Bcl-2 protein.

Distinct p53-mediated G1/S checkpoint responses in two NIH3T3 subclone cells following treatment with DNA-damaging agents

N3T3 and P-3T3 cells, originally isolated from a NIH3T3 cell clone on the basis of their negative and positive transformation by v-Abl, v-Src and Bcr-Abl, were previously found to show distinct cyclin activity changes following 12-O-tetradecanoylphorbol-13-acetate (TPA) treatment, which is anti-mitogenic for N-3T3 cells and mitogenic for P-3T3 cells. We have found in this study that, while the G1/S arrest and cell death induced by serum starvation and TPA treatment in N-3T3 cells did not involve p53-mediated checkpoint or apoptosis, N-3T3 and P-3T3 cells evidently responded differently in these aspects of cell cycle regulation to DNA-damaging agents, methylmethane sulfonate (MMS) and gamma-radiation. In N-3T3 cells, DNA damages elicit cell growth arrest at G1/S transition with concomitant accumulation of p53 and p53-inducible Waf1/Cip1 proteins and also signs of apoptosis such as DNA ladder patterns and apoptotic (subgenomic) peak in flow cytograph. Conversely, P-3T3 cells treated with the DNA-damaging agents showed no cell cycle interruption nor accumulation of p53 or Waf1/Cip1. However, both P-3T3 and N-3T3 cells showed the same p53 protein half-life of 40 min or less, the same wild-type p53 DNA sequence and the same co-immunoprecipitable cellular proteins in complexes with p53, suggesting that an alteration in a signal transduction pathway upstream of p53 might account for the evasion of p53-mediated G1 checkpoint in P-3T3 cells.

Characterization of a cloned pR72H probe for Vibrio parahaemolyticus detection and development of a nonisotopic colony hybridization assay

Vibrio parahaemolyticus is a halophilic bacterium often found in shellfish and is an important causative agent of food poisoning in Taiwan. A rapid and efficient detection method is required to identify this foodborne pathogen. A 0.76-Kb HindIII DNA fragment was cloned from the chromosomal DNA of V. parahaemolyticus strain no. 93, designated as pR72H fragment, was used as a polynucleotide probe. It was labeled with digoxigenin-11-dUTP (DIG) by the random primer-labeling method. The sensitivity and specificity of the digoxigenin-labeled 0.76-Kb DNA probe was determined by colony hybridization assay. Under stringent hybridization conditions, 122 of 124 isolates of V. parahaemolyticus showed positive hybridization reaction with DIG-0.76-Kb DNA probe; the negative strains were attributed to slow growth. The DIG-0.76-Kb probe did not hybridize with 86 isolates of other vibrios and a number of other enterics as well as nonenteric microorganisms. The sensitivity and specificity of this DIG probe are 98% and 100%, respectively. This nonisotopic colony hybridization assay can be very useful for routine monitoring of V. parahaemolyticus in the food industry, environmental analysis and clinical laboratories.