5-(α-Thyminyl)-5,6-dihydrothymine, also called spore photoproduct or SP, is commonly found in the genomic DNA of UV irradiated bacterial endospores. Despite the fact that SP was discovered nearly 50 years ago, its biochemical impact is still largely unclear due to the difficulty to prepare SP containing oligonucleotide in high purity. Here, we report the first synthesis of the phosphoramidite derivative of dinucleotide SP TpT, which enables successful incorporation of SP TpT into oligodeoxyribonucleotides with high efficiency via standard solid phase synthesis. This result provides the scientific community a reliable means to prepare SP containing oligonucleotides, laying the foundation for future SP biochemical studies. Thermal denaturation studies of the SP containing oligonucleotide found that SP destabilizes the duplex by 10–20 kJ/mole, suggesting that its presence in the spore genomic DNA may alter the DNA local conformation.
Mood stabilizers used for treating bipolar disorder (BD) selectively downregulate arachidonic acid (AA) turnover (deacylation-reacylation) in brain phospholipids, when given chronically to rats. In vitro studies suggest that one of these, valproic acid (VPA), which is teratogenic, reduces AA turnover by inhibiting the brain acyl-CoA synthetase (Acsl)-4 mediated acylation of AA to AA-CoA. We tested whether non-teratogenic VPA analogues might also inhibit Acsl-4 catalyzed acylation, and thus have potential anti-BD action.
Rat Acsl4-flag protein was expressed in E. coli, and the ability of three VPA analogues, propylisopropylacetic acid (PIA), propylisopropylacetamide (PID) and N-methyl-2,2,3,3-tetramethylcyclopropanecarboxamide (MTMCD), and of sodium butyrate, to inhibit conversion of AA to AA-CoA by Acsl4 was quantified using Michaelis-Menten kinetics.
Acsl4-mediated conversion of AA to AA-CoA in vitro was inhibited uncompetitively by PIA, with a Ki of 11.4 mM compared to a published Ki of 25 mM for VPA, while PID, MTMCD and sodium butyrate had no inhibitory effect.
PIA's ability to inhibit conversion of AA to AA-CoA by Acsl4 in vitro suggests that, like VPA, PIA may reduce AA turnover in brain phospholipids in unanesthetized rats, and if so, may be effective as a non-teratogenic mood stabilizer in BD patients.
bipolar disorder; valproate; arachidonic acid; acyl-CoA synthetase 4; mood stabilizer; Acsl4; brain; MTMCD; N-methyl-2,2,3,3-tetramethylcyclopropanecarboxamide; PIA; propylisopropylacetic; PID; propylisopropylacetamide; rat; butyrate; inhibition; uncompetitive; enzyme; anticonvulsant
The 121-nucleotide left-end telomere of Minute Virus of Mice (MVM) can be folded into a Y-shaped hairpin with short axial ears that are highly conserved within genus Parvovirus. To explore their potential role(s) during infection, we constructed infectious plasmid clones that lacked one or other ear. Although these were nonviable when transfected into A9 cells, excision of the viral genome and DNA amplification appeared normal, and viral transcripts and proteins were expressed, but progeny virion production was minimal, supporting the idea of a potential role for the ears in genome packaging. To circumvent the absence of progeny that confounded further analysis of these mutants, plasmids were transfected into 293T cells both with and without an adenovirus helper construct, generating single bursts of progeny. These virions bound to A9 cells and were internalized but failed to initiate viral transcription, protein expression, or DNA replication. No defects in mutant virion stability or function could be detected in vitro. Significantly, mutant capsid gene expression and DNA replication could be rescued by coinfection with wild-type virions carrying a replication-competent, capsid-gene-replacement vector. To pinpoint where such complementation occurred, prior transfection of plasmids expressing only MVM nonstructural proteins was explored. NS1 alone, but not NS2, rescued transcription and protein expression from both P4 and P38 promoters, whereas NS1 molecules deleted for their C-terminal transactivation domain did not. These results suggest that the mutant virions reach the nucleus, uncoat, and are converted to duplex DNA but require an intact left-end hairpin structure to form the initiating transcription complex.
The DNA remodeling enzyme FANCM and its DNA-binding partner, FAAP24, constitute a complex involved in the activation of Fanconi Anemia (FA) DNA damage response mechanism, but neither gene has distinct patient mutants. In this study, we created isogenic models for both FANCM and FAAP24 and investigated their integrated functions in DNA damage response. We found that FANCM and FAAP24 coordinately facilitate FA pathway activation and suppress sister chromatid exchange. Importantly, we show that FANCM and FAAP24 possess non-overlapping functions such that FAAP24 promotes ATR-mediated checkpoint activation particularly in response to DNA crosslinking agents, whereas FANCM participates in recombination-independent interstrand crosslink repair by facilitating recruitment of lesion incision activities which requires its translocase activity. Our data suggest that FANCM and FAAP24 play multiple while not fully epistatic roles in maintaining genomic integrity.
To improve the efficacy of drug delivery, active targeted nanotechnology-based drug delivery systems are gaining considerable attention as they have the potential to reduce side effects, minimize toxicity, and improve efficacy of anticancer treatment. In this work CUR-NPs (curcumin-loaded lipid-polymer-lecithin hybrid nanoparticles) were synthesized and functionalized with ribonucleic acid (RNA) Aptamers (Apts) against epithelial cell adhesion molecule (EpCAM) for targeted delivery to colorectal adenocarcinoma cells. These CUR-encapsulated bioconjugates (Apt-CUR-NPs) were characterized for particle size, zeta potential, drug encapsulation, stability, and release. The in vitro specific cell binding, cellular uptake, and cytotoxicity of Apt-CUR-NPs were also studied. The Apt-CUR-NP bioconjugates exhibited increased binding to HT29 colon cancer cells and enhancement in cellular uptake when compared to CUR-NPs functionalized with a control Apt (P<0.01). Furthermore, a substantial improvement in cytotoxicity was achieved toward HT29 cells with Apt-CUR-NP bioconjugates. The encapsulation of CUR in Apt-CUR-NPs resulted in the increased bioavailability of delivered CUR over a period of 24 hours compared to that of free CUR in vivo. These results show that the EpCAM Apt-functionalized CUR-NPs enhance the targeting and drug delivery of CUR to colorectal cancer cells. Further development of CUR-encapsulated, nanosized carriers will lead to improved targeted delivery of novel chemotherapeutic agents to colorectal cancer cells.
PLGA-lecithin-PEG nanoparticles; curcumin; EpCAM; aptamer; targeted drug delivery
The structure of a spore photoproduct lesion in duplex DNA is described.
The spore photoproduct lesion (SP; 5-thymine-5,6-dihydrothymine) is the dominant photoproduct found in UV-irradiated spores of some bacteria such as Bacillus subtilis. Upon spore germination, this lesion is repaired in a light-independent manner by a specific repair enzyme: the spore photoproduct lyase (SP lyase). In this work, a host–guest approach in which the N-terminal fragment of Moloney murine leukemia virus reverse transcriptase (MMLV RT) serves as the host and DNA as the guest was used to determine the crystal structures of complexes including 16 bp oligonucleotides with and without the SP lesion at 2.14 and 1.72 Å resolution, respectively. In contrast to other types of thymine–thymine lesions, the SP lesion retains normal Watson–Crick hydrogen bonding to the adenine bases of the complementary strand, with shorter hydrogen bonds than found in the structure of the undamaged DNA. However, the lesion induces structural changes in the local conformation of what is otherwise B-form DNA. The region surrounding the lesion differs significantly in helical form from B-DNA, and the minor groove is widened by almost 3 Å compared with that of the undamaged DNA. Thus, these unusual structural features associated with SP lesions may provide a basis for recognition by the SP lyase.
spore photoproduct; DNA; host–guest approach
Exposure to lead (Pb) can induce kidney injury and our recent studies have found that Salvia miltiorrhiza (SM) injection, a traditional Chinese medicine, could protect against the organ injury induced by iron overload. This study was designed to investigate the protective effects of SM injection on nephrotoxicity induced by Pb acetate in mice and to elucidate the potential mechanism(s). Healthy male mice were randomly divided into four groups: control, Pb, low-dose Salvia miltiorrhiza (L-SM), and high-dose Salvia miltiorrhiza (H-SM). SM injection dose dependently reduced the Pb accumulation in the kidney, decreased kidney coefficients, and ameliorated renal structure and function from the morphology analysis. Meanwhile, SM administration downregulated serum levels of blood urea nitrogen (BUN) and creatinine (CR), decreased malondialdehyde (MAD) content, and increased activities of super oxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in the kidney homogenate. Moreover, SM injection reduced the level of renal apoptosis by immunohistochemical staining analysis. Our findings implicate the therapeutic potential of SM injection for Pb-induced nephrotoxicity, which were at least partly due to the decrease of Pb accumulation, inhibition of lipid peroxidation, and suppression of renal apoptosis. These results provided preliminary experimental support for Danshen as a therapeutic drug for Pb poisoning diseases.
Solid pseudopapillary neoplasm of the pancreas (SPN) is a rare low-grade malignant neoplasm. SPN with prominent atypical multinucleated giant tumor cells (MNGTCs) has not been reported.
Methods and results
We identified four cases of SPN with prominent atypical MNGTCs in a cohort of 62 cases of SPN (6.5%). The MNGTCs contained multiple enlarged, hyperchromatic, irregular nuclei with ample eosinophilic cytoplasm, typically present in the solid area of the tumor. The MNGTCs had a typical immunohistochemical profile of the conventional SPN and were positive for vimentin, β-catenin, CD10, and progesterone receptor, but were negative for pan-cytokeratin chromogranin, synaptophysin, trypsin, Ki-67 and CD68 in all four cases. Patients of SPN with prominent MNGTCs were older than those with conventional SPN (p=0.01), tumors were incidentally discovered by imaging studies for an unrelated disease in all four cases, and with a female to male ratio of 1:1. The proliferation index (Ki-67) was <1% in all four cases. None of the three patients, whose follow up information was available, developed recurrence during follow-up of 2.7, 3.8 and 5.0 years.
The presence of MNGTCs in SPN most likely represents degenerative change of the tumor cells and does not seem to affect the prognosis.
solid pseudopapillary neoplasm; multinucleated giant cells; prognosis
Most advanced prostate cancers (PCa) will develop into the castration-resistant stage following androgen deprivation therapy, yet the molecular mechanisms remain unclear. In this study, we found PrLZ, a newly identified Prostate Leucine Zipper gene that is highly expressed in PCa could interact with the androgen receptor (AR) directly leading to enhance AR transactivation in the castration-resistant condition. PrLZ might enhance AR transactivation via a change of AR conformation that leads to promotion of AR nuclear translocation and suppression of AR degradation via modulating the proteasome pathway, which resulted in increased prostate-specific antigen expression and promoted PCa growth at the castration-resistant stage. Clinical PCa sample survey from same-patient paired specimens found increased PrLZ expression in castration-resistant PCa following the classical androgen deprivation therapy. Targeting the AR-PrLZ complex via ASC-J9® or PrLZ-siRNA resulted in suppression of PCa growth in various human PCa cells and in vivo mouse PCa models. Together, these data not only strengthen PrLZ roles in the transition from androgen dependence to androgen independence during the castration-resistant stage, but they may also provide a new potential therapy to battle PCa at the castration-resistant stage.
We have previously used the ATAD5-luciferase high-throughput screening assay to identify genotoxic compounds with potential chemotherapeutic capabilities. The successful identification of known genotoxic agents, including the histone deacetylase inhibitor (HDACi) trichostatin A (TSA), confirmed the specificity of the screen since TSA has been widely studied for its ability to cause apoptosis in cancer cells. Because many cancers have acquired mutations in DNA damage checkpoints or repair pathways, we hypothesized that these cancers may be susceptible to treatments that target compensatory pathways. Here, we used a panel of isogenic chicken DT40 B lymphocyte mutant and human cell lines to investigate the ability of TSA to define selective pathways that promote HDACi toxicity.
HDACi induced a DNA damage response and reduced viability in all repair deficient DT40 mutants although ATM-nulls were least affected. The most dramatic sensitivity was observed in mutants lacking the homology dependent repair (HDR) factor BLM or the non-homologous end-joining (NHEJ) and HDR factors, KU/RAD54, suggesting an involvement of either HDR or NHEJ in HDACi-induced cell death. To extend these findings, we measured the frequencies of HDR and NHEJ after HDACi treatment and monitored viability in human cell lines comparably deficient in HDR or NHEJ. Although no difference in HDR frequency was observed between HDACi treated and untreated cells, HDR-defective human cell lines were clearly more sensitive than wild type. Unexpectedly, cells treated with HDACis showed a significantly elevated NHEJ frequency.
HDACi targeting drugs induced significant increases in NHEJ activity in human cell lines but did not alter HDR frequency. Moreover, HDR is required for cellular resistance to HDACi therapy; therefore, NHEJ does not appear to be a critical axis for HDACi resistance. Rather, HDACi compounds induced DNA damage, most likely double strand breaks (DSBs), and HDR proficiency is correlated with cell survival.
DNA vaccines have evolved greatly over the last 20 years since their invention, but have yet to become a competitive alternative to conventional protein or carbohydrate based human vaccines. Whilst safety concerns were an initial barrier, the Achilles heel of DNA vaccines remains their poor immunogenicity when compared to protein vaccines. A wide variety of strategies have been developed to optimize DNA vaccine immunogenicity, including codon optimization, genetic adjuvants, electroporation and sophisticated prime-boost regimens, with each of these methods having its advantages and limitations. Whilst each of these methods has contributed to incremental improvements in DNA vaccine efficacy, more is still needed if human DNA vaccines are to succeed commercially. This review foresees a final breakthrough in human DNA vaccines will come from application of the latest cutting-edge technologies, including “epigenetics” and “omics” approaches, alongside traditional techniques to improve immunogenicity such as adjuvants and electroporation, thereby overcoming the current limitations of DNA vaccines in humans
DNA vaccine; immunogenicity; adjuvant; epigenetics; RNAi; omics
AIM: To study the clinical outcome of antiviral therapy in hepatitis B-related decompensated cirrhotic patients.
METHODS: Three hundred and twelve patients with decompensated hepatitis B cirrhosis were evaluated in a prospective cohort. With two years of follow-up, 198 patients in the group receiving antiviral therapy with nucleos(t)ide analogues and 39 patients in the control group without antiviral treatment were analysed.
RESULTS: Among the antiviral treatment patients, 162 had a complete virological response (CVR), and 36 were drug-resistant (DR). The two-year cumulative incidence of hepatocellular carcinoma (HCC) in the DR patients (30.6%) was significantly higher than that in both the CVR patients (4.3%) and the control group (10.3%) (P < 0.001). Among the DR patients in particular, the incidence of HCC was 55.6% (5/9) in those who failed rescue therapy, which was extremely high. The rtA181T mutation was closely associated with rescue therapy failure (P = 0.006). The Child-Pugh scores of the CVR group were significantly decreased compared with the baseline (8.9 ± 2.3 vs 6.0 ± 1.3, P = 0.043).
CONCLUSION: This study showed that antiviral drug resistance increased the risk of HCC in decompensated hepatitis B-related cirrhotic patients, especially in those who failed rescue therapy.
Hepatitis B; Decompensated cirrhosis; Nucleos(t)ide analogues; Hepatocellular carcinoma; Drug resistance
Pancreatic cancer is one of the most lethal malignancies, with a prominent desmoplastic reaction as the defining hallmark of the disease. The past several decades have seen dramatic progress in understanding of pancreatic cancer pathogenesis, including the identification of precursor lesions, sequential transformation from normal pancreas to invasive pancreatic cancer and corresponding signature genetic events, and the biological impact of those alterations on malignant behaviors. However, the current therapeutic strategies for epithelial tumor cells, which have exhibited potent antitumor activity in cell culture and animal models, have failed to have significant effects in the clinic. The desmoplastic stroma surrounding pancreatic cancer cells, which accounts for about 90% of a tumor’s mass, clearly is not a passive scaffold for cancer cells but an active contributor to carcinogenesis. Improved understanding of the dynamic interaction between cancer cells and their stroma will be important to designing new, effective therapeutic strategies for pancreatic cancer. This review focuses on the origination of stromal molecular and cellular components in pancreatic tumors, their biological effects on pancreatic cancer cells, and the orchestration between these two components.
Cytokines; growth factors; transcriptional factors; therapy; immunology
High-resolution 2D 13C-13C NMR correlation spectra of uniformly 13C-labeled molecules in solution are obtained by homonuclear 13C-decoupling along both dimensions by the application of indirect covariance NMR to constant-time NMR spectra. The spectra are optimally suited for chemical structure elucidation and molecular identification of the components of complex mixtures, such as ones from uniformly 13C-labeled cell cultures.
Neonatal seizures pose a high risk for adverse outcome in survived infants. While the prognostic value of amplitude-integrated electroencephalogram (aEEG) is well established in neonates with encephalopathy and asphyxia, neonatal seizure studies focusing on the direct correlation between early aEEG measurement and subsequent neurologic outcome are scarce. In this study, the prognostic value of aEEG features was systematically analyzed in 143 full-term neonates to identify prognostic indicators of neurodevelopmental outcome. Neonatal aEEG features of background pattern, cyclicity, and seizure activity, as well as the etiology of neonatal seizures, were significantly associated with neurodevelopmental outcome at one year of age. aEEG background pattern was highly associated with neurologic outcomes (χ2 = 116.9), followed by aEEG cyclicity (χ2 = 87.2) and seizure etiology (χ2 = 79.3). Multiple linear regression showed that the four predictors explained 71.2% of the variation in neurological outcome, with standardized β coefficients of 0.44, 0.24, 0.22, and 0.14 for the predictors of aEEG background pattern, cyclicity, etiology, and aEEG seizure activity, respectively. This clinically applicable scoring system based on etiology and three aEEG indices would allow pediatricians to assess the risk for neurodevelopmental impairment and facilitate an early intervention in newborns developing seizures.
High altitude acclimatization is a series of physiological responses taking places when subjects go to altitude. Many factors could influence these processes, such as altitude, ascending speed and individual characteristics. In this study, based on a repeated measurement design of three sequential measurements at baseline, acute phase and chronic phase, we evaluated the effect of BMI, smoking and drinking on a number of physiological responses in high altitude acclimatization by using mixed model and partial least square path model on a sample of 755 Han Chinese young males. We found that subjects with higher BMI responses were reluctant to hypoxia. The effect of smoking was not significant at acute phase. But at chronic phase, red blood cell volume increased less while respiratory function increased more for smoking subjects compared with nonsmokers. For drinking subjects, red blood cell volume increased less than nondrinkers at both acute and chronic phases, while blood pressures increased more than nondrinkers at acute phase and respiratory function, red blood cell volume and oxygen saturation increased more than nondrinkers at chronic phase. The heavy and long-term effect of smoking, drinking and other factors in high altitude acclimatization needed to be further studied.
A customized metabolomics NMR database, TOCCATA, is introduced, which uses 13C chemical shift information for the reliable identification of metabolites, their spin systems and isomeric states. TOCCATA, whose information was derived from information of the BMRB and HMDB databases and the literature, currently contains 463 compounds and 801 spin systems and it can be used through a publicly accessible web server at http://spinportal.magnet.fsu.edu/toccata/webquery.html. TOCCATA allows the identification of metabolites in the sub-mM concentration range from 13C-13C TOCSY experiments of complex mixtures, which is demonstrated for an E.coli cell lysate, a carbohydrate mixture, and an amino acid mixture, all of which were uniformly 13C-labeled.
Spore photoproduct lyase (SPL) repairs a special thymine dimer 5-thyminyl-5,6-dihydrothymine, which is commonly called spore photoproduct or SP at the bacterial early germination phase. SP is the exclusive DNA photo-damage product in bacterial endospores; its generation and swift repair by SPL are responsible for the spores’ extremely high UV resistance. The early in vivo studies suggested that SPL utilizes a direct reversal strategy to repair the SP in the absence of light. The research in the past decade further established SPL as a radical SAM enzyme, which utilizes a tri-cysteine CXXXCXXC motif to harbor a [4Fe-4S] cluster. At the 1+ oxidation state, the cluster provides an electron to the S-adenosylmethionine (SAM), which binds to the cluster in a bidentate manner as the fourth and fifth ligands, to reductively cleave the C-S bond associated with the sulfonium ion in SAM, generating a reactive 5′-deoxyadenosyl (5′-dA) radical. This 5′-dA radical abstracts the proR hydrogen atom from the C6 carbon of SP to initiate the repair process; the resulting SP radical subsequently fragments to generate a putative thymine methyl radical, which accepts a back-donated H atom to yield the repaired TpT. SAM is suggested to be regenerated at the end of each catalytic cycle; and only a catalytic amount of SAM is needed in the SPL reaction. The H atom source for the back donation step is suggested to be a cysteine residue (C141 in B. subtilis SPL), and the H-atom transfer reaction leaves a thiyl radical behind on the protein. This thiyl radical thus must participate in the SAM regeneration process; however how the thiyl radical abstracts an H atom from the 5′-dA to regenerate SAM is unknown. This paper reviews and discusses the history and the latest progress in the mechanistic elucidation of SPL. Despite some recent breakthroughs, more questions are raised in the mechanistic understanding of this intriguing DNA repair enzyme.
Sepsis in older children and adults modifies immune system function. We compared serotype-specific antibody responses to heptavalent pneumococcal conjugate vaccine (PCV7) in very low birth weight infants (<1500g,VLBW) with and without blood stream infection (BSI) during their birth hospitalization.
Patients and Methods
Retrospective analysis of prospectively collected data for the Neonatal Research Network study of PCV7 responses among VLBWs. Infants received PCV7 at 2, 4, and 6 months after birth with blood drawn 4–6 weeks after 3rd dose. Serotype antibodies were compared between infants with or without a history of BSI. Regression models were constructed with birth-weight groups and other confounding factors identified in the primary study.
244 infants completed the vaccine series and had serum antibody available; 82 had BSI. After adjustment, BSI was not associated with reduced odds of serum antibody ≥0.35μg/mL.
BSI was not associated with reduced odds of WHO-defined protective PCV7 responses in VLBWs.
VLBW; immune response; vaccine; sepsis; blood stream infection
The aim of this study was to test whether a low dose of interferon-α-2b (IFN-α2b) enhances the clinical outcome of docetaxel (DXT) in patients with castration-resistant prostate cancer (CRPC). A prospective controlled trial of 40 CRPC patients receiving 5 mg of prednisone twice daily was conducted, where patients were randomly assigned to be administered 75 mg/m2 DXT plus 3 mIU/m2 IFN-α2b (group A, n=20) or 75 mg/m2 DXT alone (group B, n=20). The prostate-specific antigen (PSA) response, tumor response, progression-free survival (PFS) and overall survival (OS) were evaluated. There was no statistically significant difference in PSA response rate between groups A and B (65 vs. 47.4%, P=0.341). The tumor response rate in group A was significantly greater compared with that in group B (55 vs. 21.1%, P=0.048). The median PFS was longer in group A compared with that in group B (10 vs. 8 months, P=0.043). There was no statistically significant difference in median OS between the two groups (19 vs. 17 months, P=0.348), but one patient displayed a complete tumor response in group A. In groups A and B, transient grade 3 to 4 neutropenia was observed in nine and six patients, grade 3 to 4 anemia was observed in three and five patients, and grade 3 to 4 general fatigue was observed in four and one patient(s), respectively. The proportion of patients with grade 3 to 4 toxicity was not statistically different between the two groups. A low dosage of IFN-α2b may improve the antitumor activity of DXT with an acceptable toxicity profile in patients with CRPC.
castration-resistant prostate cancer; docetaxel; interferon-α-2b
We formulate a multi-matrices factorization model (MMF) for the missing sensor data estimation problem. The estimation problem is adequately transformed into a matrix completion one. With MMF, an n-by-t real matrix, R, is adopted to represent the data collected by mobile sensors from n areas at the time, T1, T2, … , Tt, where the entry, Ri,j, is the aggregate value of the data collected in the ith area at Tj. We propose to approximate R by seeking a family of d-by-n probabilistic spatial feature matrices, U(1), U(2), … , U(t), and a probabilistic temporal feature matrix, V ∈ ℝd×t, where
Rj≈U(j)TTj. We also present a solution algorithm to the proposed model. We evaluate MMF with synthetic data and a real-world sensor dataset extensively. Experimental results demonstrate that our approach outperforms the state-of-the-art comparison algorithms.
matrix factorization; sensor data; probabilistic graphical model; missing estimation
Whether continuous docetaxel (DTX) chemotherapy offers an advantage over intermittent therapy for castration-resistant prostate cancer (CRPC) is unknown. In this study, we evaluated the efficacy, toxicity and quality of life (QoL) of intermittent tri-weekly DTX with bicalutamide in CRPC. Forty-two patients (group A) with CRPC were enrolled. The patients received intravenous DTX (75 mg m−2) once tri-weekly with oral bicalutamide (50 mg) once daily. Patients had a DTX holiday when the prostate-specific antigen (PSA) level declined ≥50%. DTX was restarted in patients with a PSA increase ≥25%. Sixty patients (group B) who had matching characteristics and had continuously received DTX without bicalutamide for 10–12 cycles were also enrolled. There were no statistically significant differences in progression-free survival (8 months vs. 9 months, P=0.866) or overall survival (19 months vs. 21 months, P=0.753) between groups A and B; however, the proportions of patients in group A with all grades of neutropenia (33% vs. 58%, P=0.013) and nausea/vomiting (11% vs. 29%, P=0.024) were significantly less compared to group B. A significant improvement in the global health and fatigue scores was recorded for group A post-chemotherapy compared to pre-chemotherapy (P<0.05). The fatigue, nausea/vomiting and appetite loss scores in group B were increased post-chemotherapy compared to pre-chemotherapy (P<0.05). In conclusion, intermittent tri-weekly DTX plus bicalutamide is well tolerated and has the potential to achieve comparable disease control with an improvement in QoL for patients with CRPC.
androgen; chemotherapy; docetaxel; prostate cancer; safety
Spontaneous DNA breaks instigate genomic changes that fuel cancer and evolution, yet direct quantification of double-strand breaks (DSBs) has been limited. Predominant sources of spontaneous DSBs remain elusive. We report synthetic technology for quantifying DSBs using fluorescent-protein fusions of double-strand DNA end-binding protein, Gam of bacteriophage Mu. In Escherichia coli GamGFP forms foci at chromosomal DSBs and pinpoints their subgenomic locations. Spontaneous DSBs occur mostly one per cell, and correspond with generations, supporting replicative models for spontaneous breakage, and providing the first true breakage rates. In mammalian cells GamGFP—labels laser-induced DSBs antagonized by end-binding protein Ku; co-localizes incompletely with DSB marker 53BP1 suggesting superior DSB-specificity; blocks resection; and demonstrates DNA breakage via APOBEC3A cytosine deaminase. We demonstrate directly that some spontaneous DSBs occur outside of S phase. The data illuminate spontaneous DNA breakage in E. coli and human cells and illustrate the versatility of fluorescent-Gam for interrogation of DSBs in living cells.
Cells have developed a variety of mechanisms for repairing DNA molecules when breaks occur in one or both of the DNA strands. However, we know relatively little about the causes of these breaks, which often occur naturally, or even about how common they are. Learning more about the most common forms of DNA breakage is important because the genomic changes caused by these breaks are driving forces behind both cancer and evolution, including the evolution of drug resistance in bacteria.
Shee et al. have developed a new method for detecting double-strand breaks in both bacterial and mammalian cells. The method involved combining a natural virus protein called Gam with a fluorescent protein called GFP (short for green fluorescent protein) to make a fusion protein called GamGFP. Gam was chosen because it binds only to double-strand breaks, traps double-strand breaks, and does not bind to any proteins. Genetic engineering techniques were used to introduce GamGFP into cells, with DNA breaks in these cells showing up as fluorescent spots when viewed under a microscope.
Shee et al. used this approach to detect double-strand breaks in both Escherichia coli cells and mammalian cells, and to measure the rate of spontaneous DNA breakage in E. coli. The number of double-strand breaks in E. coli was proportional to the number of times the cells had divided, which provides support for DNA replication-dependent models of spontaneous DNA breakage.
The GamGFP method also provided various insights into DNA breaks in mouse and human cells. In particular, Shee et al. found evidence for a mechanism of DNA breakage that appears to be specific to primates. This mechanism involves an enzyme that is only found in the innate immune system of primates removing an amine group from a cytosine. In future, this approach might allow the trapping, mapping and quantification of DNA breaks in all kinds of cells, and the highly specific way GamGFP binds to breaks could make it the preferred tool for studying DNA breakage in mammalian cells.
DNA double-strand breaks; endogenous DNA damage; GFP; fluorescent-protein fusions; spontaneous DNA breaks; synthetic biology; E. coli; Human; Mouse