Mental health problems and correlates among 746 217 college students during the coronavirus disease 2019 outbreak in China

AIMS

Coronavirus disease 2019 (COVID-19) pandemic is a major public health concern all over the world. Little is known about the impact of COVID-19 pandemic on mental health in the general population. This study aimed to assess the mental health problems and associated factors among a large sample of college students during the COVID-19 outbreak in China.

METHODS

This cross-sectional and nation-wide survey of college students was conducted in China from 3 to 10 February 2020. A self-administered questionnaire was used to assess psychosocial factors, COVID-19 epidemic related factors and mental health problems. Acute stress, depressive and anxiety symptoms were measured by the Chinese versions of the impact of event scale-6, Patient Health Questionnaire-9 and Generalized Anxiety Disorder-7, respectively. Univariate and hierarchical logistic regression analyses were performed to examine factors associated with mental health problems.

RESULTS

Among 821 218 students who participated in the survey, 746 217 (90.9%) were included for the analysis. In total, 414 604 (55.6%) of the students were female. About 45% of the participants had mental health problems. The prevalence rates of probable acute stress, depressive and anxiety symptoms were 34.9%, 21.1% and 11.0%, respectively. COVID-19 epidemic factors that were associated with increased risk of mental health problems were having relatives or friends being infected (adjusted odds ratio = 1.72-2.33). Students with exposure to media coverage of the COVID-19 ≥3 h/day were 2.13 times more likely than students with media exposure <1 h/day to have acute stress symptoms. Individuals with low perceived social support were 4.84-5.98 times more likely than individuals with high perceived social support to have anxiety and depressive symptoms. In addition, senior year and prior mental health problems were also significantly associated with anxiety or/and depressive symptoms.

CONCLUSIONS

In this large-scale survey of college students in China, acute stress, anxiety and depressive symptoms are prevalent during the COVID-19 pandemic. Multiple epidemic and psychosocial factors, such as family members being infected, massive media exposure, low social support, senior year and prior mental health problems were associated with increased risk of mental health problems. Psychosocial support and mental health services should be provided to those students at risk.

The GADD45 inhibition of Cdc2 kinase correlates with GADD45-mediated growth suppression

Cell cycle growth arrest is an important cellular response to genotoxic stress. Gadd45, a p53-regulated stress protein, plays an important role in the cell cycle G(2)-M checkpoint following exposure to certain types of DNA-damaging agents such as UV radiation and methylmethane sulfonate. Recent findings indicate that Gadd45 interacts with Cdc2 protein and inhibits Cdc2 kinase activity. In the present study, a series of Myc-tagged Gadd45 deletion mutants and a Gadd45 overlapping peptide library were used to define the Gadd45 domains that are involved in the interaction of Gadd45 with Cdc2. Both in vitro and in vivo studies indicate that the interaction of Gadd45 with Cdc2 involves a central region of the Gadd45 protein (amino acids 65-84). The Cdc2-binding domain of Gadd45 is also required for Gadd45 inhibition of Cdc2 kinase activity. Sequence analysis of the central Gadd45 region reveals no homology to inhibitory motifs of known cyclin-dependent kinase inhibitors, indicating that the Cdc2-binding and -inhibitory domains on Gadd45 are a novel motif. The peptide containing the Cdc2-binding domain (amino acids 65-84) disrupted the Cdc2-cyclin B1 protein complex, suggesting that dissociation of this complex results from a direct interaction between the Gadd45 and Cdc2 proteins. GADD45-induced cell cycle G(2)-M arrest was abolished when its Cdc2 binding motif was disrupted. Importantly, a short term survival assay demonstrated that GADD45-induced cell cycle G(2)-M arrest correlates with GADD45-mediated growth suppression. These findings indicate that the cell cycle G(2)-M growth arrest mediated by GADD45 is one of the major mechanisms by which GADD45 suppresses cell growth.

Longitudinal trajectories of post-traumatic stress disorder symptoms among adolescents after the Wenchuan earthquake in China

BACKGROUND

This study examines the patterns and predictors of post-traumatic stress disorder (PTSD) symptom trajectories among adolescent survivors following the Wenchuan earthquake in China.

METHOD

A total of 1573 adolescent survivors were followed up at 6, 12, 18 and 24 months post-earthquake. Participants completed the Posttraumatic Stress Disorder Self-Rating Scale (PTSD-SS), Adolescent Self-Rating Life Events Checklist, Social Support Rate Scale, and the Simplified Coping Style Questionnaire. Distinct patterns of PTSD symptom trajectories were established through grouping participants based on time-varying changes of developing PTSD (i.e. reaching the clinical cut-off on the PTSD-SS). Multivariate logistic regressions were used to examine predictors for trajectory membership.

RESULTS

PTSD prevalence rates at 6, 12, 18 and 24 months were 21.0, 23.3, 13.5 and 14.7%, respectively. Five PTSD symptom trajectories were observed: resistance (65.3% of the sample), recovery (20.0%), relapsing/remitting (3.3%), delayed dysfunction (4.2%) and chronic dysfunction (7.2%). Female gender and senior grade were related to higher risk of developing PTSD symptoms in at least one time point, whereas being an only child increased the possibility of recovery relative to chronic dysfunction. Family members' injury/loss and witness of traumatic scenes could also cause PTSD chronicity. More negative life events, less social support, more negative coping and less positive coping were also common predictors for not developing resistance or recovery.

CONCLUSIONS

Adolescents' PTSD symptoms showed an anniversary reaction. Although many adolescents remain euthymic or recover over time, some adolescents, especially those with the risk factors noted above, exhibit chronic, delayed or relapsing symptoms. Thus, the need for individualized intervention with these adolescents is indicated.

Enzymatic characterization of FliI. An ATPase involved in flagellar assembly in Salmonella typhimurium

FliI is a protein needed for flagellar assembly in Salmonella typhimurium. It shows sequence similarity to the catalytic beta subunit of the F0F1-ATPase and is even more closely related to putative ATPases in Type III bacterial secretory pathways. A His-tagged version of FliI, which was fully functional in complementation tests, was purified to homogeneity. It had an ATPase activity of 0.16 s-1 at 25 degrees C and pH 7, and a Km for ATP of 0.3 mM; Mg2+ was required. The activity was not affected by inhibitors of the F-, V- or P-type ATPases, or inhibitors of the Type I or Type II bacterial secretory pathways. Mutations K188I and Y363S decreased the ATPase activity about 100-fold, increased the Km about 10-fold, blocked flagellar assembly, and were dominant. Other FliI mutations that disrupted flagellar protein export were found near the N terminus; they permitted essentially wild-type ATPase activity, were not dominant, and showed a dosage-dependent phenotype. We propose that FliI has a C-terminal ATPase domain and an N-terminal domain that interacts with other components in the flagellum-specific export apparatus.

The FliP and FliR proteins of Salmonella typhimurium, putative components of the type III flagellar export apparatus, are located in the flagellar basal body

Most of the structural components of the flagellum of Salmonella typhimurium are exported through a flagellum-specific pathway, which is a member of the family of type III secretory pathways. The export apparatus for this process is poorly understood. A previous study has shown that two proteins, about 23 and 26 kDa in size and of unknown genetic origin, are incorporated into the flagellar basal body at a very early stage of flagellar assembly. In the present study, we demonstrate that these basal body proteins are FliP (in its mature form after signal peptide cleavage) and FliR respectively. Both of these proteins have homologues in other type III secretion systems. By placing a FLAG epitope tag on FliR and the MS-ring protein FliF and immunoblotting isolated hook basal body complexes with anti-FLAG monoclonal antibody, we estimate (using the FLAG-tagged FliF as an internal reference) that the stoichiometry of FliR is fewer than three copies per basal body. An independent estimate of stoichiometry was made using data from an earlier quantitative radiolabelling analysis, yielding values of around four or five subunits per basal body for FliP and around one subunit per basal body for FliR. Immunoelectron microscopy using anti-FLAG antibody and gold-protein A suggests that FliR is located near the MS ring. We propose that the flagellar export apparatus contains FliP and FliR and that this apparatus is embedded in a patch of membrane in the central pore of the MS ring.

Nup50, a nucleoplasmically oriented nucleoporin with a role in nuclear protein export

We present here a detailed analysis of a rat polypeptide termed Nup50 (formerly NPAP60) that was previously found to be associated with the nuclear pore complex (F. Fan et al., Genomics 40:444-453, 1997). We have found that Nup50 (and/or a related 70-kDa polypeptide) is present in numerous rat cells and tissues. By immunofluorescence microscopy, Nup50 was found to be highly concentrated at the nuclear envelope of rat liver nuclei, whereas in cultured NRK cells it also is abundant in intranuclear regions. On the basis of immunogold electron microscopy of both rat liver nuclear envelopes and NRK cells, we determined that Nup50 is specifically localized in the nucleoplasmic fibrils of the pore complex. Microinjection of anti-Nup50 antibodies into the nucleus of NRK cells resulted in strong inhibition of nuclear export of a protein containing a leucine-rich nuclear export sequence, whereas nuclear import of a protein containing a classical nuclear localization sequence was unaffected. Correspondingly, CRM1, the export receptor for leucine-rich export sequences, directly bound to a fragment of Nup50 in vitro, whereas several other import and export receptors did not significantly interact with this fragment. Taken together, our data indicate that Nup50 has a direct role in nuclear protein export and probably serves as a binding site on the nuclear side of the pore complex for export receptor-cargo complexes.

Vascular endothelial growth factor receptor-1 mediates migration of human colorectal carcinoma cells by activation of Src family kinases

Vascular endothelial growth factor (VEGF) is the predominant pro-angiogenic cytokine in human malignancy, and its expression correlates with disease recurrence and poor outcomes in patients with colorectal cancer. Recently, expression of vascular endothelial growth factor receptors (VEGFRs) has been observed on tumours of epithelial origin, including those arising in the colon, but the molecular mechanisms governing potential VEGF-driven biologic functioning in these tumours are not well characterised. In this report, we investigated the role of Src family kinases (SFKs) in VEGF-mediated signalling in human colorectal carcinoma (CRC) cell lines. Vascular endothelial growth factor specifically activated SFKs in HT29 and KM12L4 CRC cell lines. Further, VEGF stimulation resulted in enhanced cellular migration, which was effectively blocked by pharmacologic inhibition of VEGFR-1 or Src kinase. Correspondingly, migration studies using siRNA clones with reduced Src expression confirmed the requirement for Src in VEGF-induced migration in these cells. Furthermore, VEGF treatment enhanced VEGFR-1/SFK complex formation and increased tyrosine phosphorylation of focal adhesion kinase, p130 cas and paxillin. Finally, we demonstrate that VEGF-induced migration is not due, at least in part, to VEGF acting as a mitogen. These results suggest that VEGFR-1 promotes migration of tumour cells through a Src-dependent pathway linked to activation of focal adhesion components that regulate this process.

Endothelial cell survival and apoptosis in the tumor vasculature

Angiogenesis is essential for the growth and metastasis of solid tumors. The balance of endothelial cell (EC) proliferation and apoptosis is a major determinant in tumor angiogenesis. Recently, several studies demonstrated that numerous angiogenic factors not only induce angiogenesis but also function as EC survival factors. Vascular endothelial growth factor (VEGF), a potent angiogenic factor, is also an EC survival factor in embryonic vasculogenesis and tumor angiogenesis. VEGF activates specific intracellular survival pathways in ECs including Bcl-2, A1, IAP, Akt, and Erk. Integrins may function as EC survival factors by preventing anoikis by enhancing binding to the extracellular matrix. In addition, integrins may function in concert with VEGF to promote EC survival. Angiopoietin-1 (Ang-1) has recently been shown to stabilize EC networks by binding to the EC-specific tyrosine kinase receptor Tie-2. Pericytes also function as EC survival factors, by cell-cell contact, secretion of survival factors, or both. Targeting any of the above mechanisms for EC survival may provide novel antineoplastic strategies.

The FliO, FliP, FliQ, and FliR proteins of Salmonella typhimurium: putative components for flagellar assembly

The flagellar genes fliO, fliP, fliQ, and fliR of Salmonella typhimurium are contiguous within the fliLMNOPQR operon. They are needed for flagellation but do not encode any known structural or regulatory components. They may be involved in flagellar protein export, which proceeds by a type III export pathway. The genes have been cloned and sequenced. The sequences predict proteins with molecular masses of 13,068, 26,755, 9,592, and 28,933 Da, respectively. All four gene products were identified experimentally; consistent with their high hydrophobic residue content, they segregated with the membrane fraction. From N-terminal amino acid sequence analysis, we conclude that fliO starts immediately after fliN rather than at a previously proposed site downstream. FliP existed in two forms, a 25-kDa form and a 23-kDa form. N-terminal amino acid analysis of the 23-kDa form demonstrated that it had undergone cleavage of a signal peptide--a rare process for prokaryotic cytoplasmic membrane proteins. Site-directed mutation at the cleavage site resulted in impaired processing, which reduced, but did not eliminate, complementation of a fliP mutant in swarm plate assays. A cloned fragment encoding the mature form of the protein could also complement the fliP mutant but did so even more poorly. Finally, when the first transmembrane span of MotA (a cytoplasmic membrane protein that does not undergo signal peptide cleavage) was fused to the mature form of FliP, the fusion protein complemented very weakly. Higher levels of synthesis of the mutant proteins greatly improved function. We conclude that, for insertion of FliP into the membrane, cleavage is important kinetically but not absolutely required.

Induction of neuropilin-1 and vascular endothelial growth factor by epidermal growth factor in human gastric cancer cells

The epidermal growth factor receptor (EGF-R) pathway plays a pivotal role in the progression of human gastric cancer. The angiogenic factor vascular endothelial growth factor (VEGF) has been shown to be induced by EGF in various cancer cell lines. Neuropilin-1 (NRP-1) acts as a coreceptor for VEGF-165 and increases its affinity for VEGF receptor 2 (VEGFR-2) in endothelial cells. Furthermore, NRP-1 has been found to be expressed by tumour cells and has been shown to enhance tumour angiogenesis and growth in preclinical models. We examined the expression of NRP-1 mRNA and EGF-R protein in seven human gastric cancer cell lines. NRP-1 expression was expressed in five of seven cell lines, and EGF-R expression closely mirrored NRP-1 expression. Moreover, in EGF-R-positive NCI-N87 and ST-2 cells, EGF induced both NRP-1 and VEGF mRNA expression. C225, a monoclonal antibody to EGF-R, blocked EGF-induced NRP-1 and VEGF expression in NCI-N87 cells in a dose-dependent manner. The treatment of NCI-N87 cells with EGF resulted in increases in phosphorylation of Erk1/2, Akt, and P38. Blockade of the Erk, phosphatidylinositol-3 kinase/Akt, or P38 pathways in this cell line prevented EGF induction of NRP-1 and VEGF. These results suggest that regulation of NRP-1 expression in human gastric cancer is intimately associated with the EGF/EGF-R system. Activation of EGF-R might contribute to gastric cancer angiogenesis by a mechanism that involves upregulation of VEGF and NRP-1 expression via multiple signalling pathways.

Overexpression of neuropilin-1 promotes constitutive MAPK signalling and chemoresistance in pancreatic cancer cells

Neuropilin-1 (NRP-1) is a novel co-receptor for vascular endothelial growth factor (VEGF). Neuropilin-1 is expressed in pancreatic cancer, but not in nonmalignant pancreatic tissue. We hypothesised that NRP-1 expression by pancreatic cancer cells contributes to the malignant phenotype. To determine the role of NRP-1 in pancreatic cancer, NRP-1 was stably transfected into the human pancreatic cancer cell line FG. Signal transduction was assessed by Western blot analysis. Susceptibility to anoikis (detachment induced apoptosis) was evaluated by colony formation after growth in suspension. Chemosensitivity to gemcitabine or 5-fluorouracil (5-FU) was assessed by MTT assay in pancreatic cancer cells following NRP-1 overexpression or siRNA-induced downregulation of NRP-1. Differential expression of apoptosis-related genes was determined by gene array and further evaluated by Western blot analysis. Neuropilin-1 overexpression increased constitutive mitogen activated protein kinase (MAPK) signalling, possibly via an autocrine loop. Neuropilin-1 overexpression in FG cells enhanced anoikis resistance and increased survival of cells by >30% after exposure to clinically relevant levels of gemcitabine and 5-FU. In contrast, downregulation of NRP-1 expression in Panc-1 cells markedly increased chemosensitivity, inducing >50% more cell death at clinically relevant concentrations of gemcitabine. Neuropilin-1 overexpression also increased expression of the antiapoptotic regulator, MCL-1. Neuropilin-1 overexpression in pancreatic cancer cell lines is associated with (a) increased constitutive MAPK signalling, (b) inhibition of anoikis, and (c) chemoresistance. Targeting NRP-1 in pancreatic cancer cells may downregulate survival signalling pathways and increase sensitivity to chemotherapy.

Overview of angiogenesis: Biologic implications for antiangiogenic therapy

Tumor angiogenesis is essential for the growth of primary and metastatic tumors. This process requires the coordinated activities of multiple factors and cell types. For tumors to develop a neovascular blood supply, tumor cells and host cells must secrete proangiogenic factors that offset the activities of inhibitory angiogenic factors. In addition, the newly derived tumor endothelium must respond to signals in the microenvironment to survive under conditions such as hypoxia and acidity. Moreover, because the process of angiogenesis is regulated by redundant factors and pathways, inhibition of any single pathway is likely to select for cells whose angiogenesis is driven by other factors. Because antiangiogenic therapy is unlikely to induce tumor regression, the criteria for efficacy must be evaluated by means other than the standard criteria used to evaluate cytotoxic chemotherapy. Understanding the basic principles that drive tumor angiogenesis will lead to the development of therapies that will likely prolong survival without the toxicity associated with standard chemotherapy.

Biochemical and genetic characterization of the action of triclosan on Staphylococcus aureus

Triclosan, a widely used antibacterial agent, possesses potent activity against Staphylococcus aureus. This study reports on an investigation of the antibacterial target of triclosan in this pathogen. A strain of S. aureus overexpressing the enoyl-[acyl-carrier-protein] reductase (FabI), demonstrated by Western immunoblotting, gave rise to an increase in the MIC of triclosan, while susceptibilities to a range of unrelated antibacterials were unaffected. There are approximately 12 000 molecules of FabI per cell in mid-log phase growth. This number increased by approximately three- to four-fold in the S. aureus FabI overexpressor. Triclosan selectively inhibited the incorporation of [(14)C]acetate into TCA-precipitable product, an indicator of fatty acid biosynthesis. Furthermore, it inhibited de novo fatty acid biosynthesis in this organism. In vitro, triclosan inhibited recombinant, purified S. aureus FabI with an IC(50) of approximately 1 microM. The combination of these biochemical and genetic data provide further evidence that the mode of action of triclosan in S. aureus is via inhibition of FabI.

Transcription factors Oct-1 and NF-YA regulate the p53-independent induction of the GADD45 following DNA damage

The p53-regulated GADD45 gene is one of the important players in cellular response to DNA damage, and probably involved in the control of cell cycle checkpoint, apoptosis and DNA repair. There are both the p53-dependent and -independent pathways that regulate GADD45 induction. Following ionizing radiation, induction of the GADD45 gene is regulated by p53 through the p53-binding motif located in the third intron of the GADD45 gene. In contrast, GADD45 induction by methyl methanesulfonate (MMS), UV radiation (UV), and medium starvation is independent of p53 status although p53 may contribute to these responses. However, the regulatory elements that control the p53-independent induction of GADD45 remain uncertain. In this report, we have performed detailed analyses to characterize the responsive components that are required for the induction of the GADD45 promoter. We have found that the region between -107 and -62 of the GADD45 promoter is crucial for the induction. Sequence analysis indicates that there are two OCT-1 sites and one CAAT box located in this region. Site-directed mutations of both OCT-1 and CAAT motifs substantially abrogate the induction of the GADD45 promoter by DNA damage. In addition, both Oct-1 protein (binding to OCT-1 site) and NF-YA protein (binding to CAAT box) are induced after cell exposure to DNA damaging agents. Moreover, the Electrophoretic Mobility Shift Assay (EMSA) has demonstrated the direct bindings of Oct-1 and NF-YA proteins to their consensus sequences in the GADD45 promoter. Therefore, these results have presented the novel observation that transcription factors Oct-1 and NF-YA participate in the cellular response to DNA damage and are involved in the regulation of stress-inducible genes.

Differential expression of angiopoietin-1 and angiopoietin-2 in colon carcinoma. A possible mechanism for the initiation of angiogenesis

BACKGROUND

Angiopoietin-1 (Ang-1) and angiopoietin-2 (Ang-2) are important regulators of endothelial cell (EC) survival. Current models suggest that an increase in Ang-2 expression in ECs leads to the initiation of angiogenesis. The authors hypothesized that the imbalance of Ang-1 and Ang-2 activities in colon carcinoma leads to a net gain in Ang-2 function.

METHODS

Reverse transcriptase-polymerase chain reaction (RT-PCR) analyses and immunofluorescent double-staining were performed to examine human colon carcinoma cell lines, surgical specimens, normal mucosa, and liver metastases for the expression of Ang-1 and Ang-2.

RESULTS

RT-PCR analyses revealed that 7 of 18 colon carcinoma cell lines expressed Ang-1, and 14 of 18 colon carcinoma cell lines expressed Ang-2 (P < 0.05). Of the surgical specimens from patients with colon carcinoma, 6 of 11 specimens expressed Ang-1, and 11 of 11 specimens expressed Ang-2 (P < 0.05). However, Ang-1 and Ang-2 were expressed with relative equal frequency in normal mucosa (P = 0.62). Immunofluorescent staining (n = 20 specimens) revealed the presence of Ang-2 protein in normal mucosa and tumor epithelium, but Ang-1 was expressed only in normal mucosa. A similar pattern was found for hepatic colorectal metastases. Double staining for Ang-1 or Ang-2 and cytokeratin-22 (an epithelial marker) demonstrated that Ang-1 was produced by uninvolved, normal colonic epithelium, whereas Ang-2 was produced by normal and malignant colonic epithelium.

CONCLUSIONS

In patients with colon carcinoma, Ang-2 is expressed ubiquitously in tumor epithelium, whereas expression of Ang-1 in tumor epithelium is rare. The net gain of Ang-2 activity is possibly an initiating factor for tumor angiogenesis.

Regulated gene expression in Staphylococcus aureus for identifying conditional lethal phenotypes and antibiotic mode of action

Selectively regulating gene expression in bacteria has provided an important tool for studying gene function. However, well-regulated gene control systems have been restricted primarily for use in laboratory non-pathogenic strains of bacteria (e.g. Escherichia coli, Bacillus subtilis). The development of analogous systems for use in bacterial pathogens such as Staphylococcus aureus would significantly enhance our ability to examine the contribution of any given gene product to pathogen growth and viability. In this report, we adapt, examine and compare three regulated gene expression systems in S. aureus, which had previously been used in B. subtilis. We demonstrate that all three systems function and exhibit titratable induction, together covering a dynamic range of gene expression of approximately 3000-fold. This dynamic range correlates well with the physiological expression levels of cellular proteins. Importantly, we show that one of these systems, the Spac system, is particularly useful for examining gene essentiality and creating specific conditional lethal phenotypes. Moreover, we find that titration of selective target gene products using this system allows direct demonstration of antibiotic mode of action.

Vascular endothelial growth factor is upregulated by interleukin-1 beta in human vascular smooth muscle cells via the P38 mitogen-activated protein kinase pathway

Small tumor vessels are composed of endothelial cells (ECs) and vascular smooth muscle cells (VSMCs). These cells have been shown to communicate with each other via cytokine signaling during neovascularization. We previously demonstrated that interleukin-1 beta (IL-1 beta) leads to induction of vascular endothelial growth factor (VEGF) in human colon carcinoma cells. As pericytes play a role in regulating EC function, we hypothesized that IL-1 beta may mediate EC survival by induction of VEGF in a paracrine manner. We investigated the effects of IL-1 beta on VEGF expression in human VSMCs (hVSMCs) and the signal transduction pathways that may be involved. Treatment of hVSMCs with IL-1 beta induced VEGF expression in a time- and concentration-dependent manner and increased both the VEGF promoter activity and the mRNA half-life. Treatment with IL-1 beta induced the expression of P38 mitogen-activated protein kinase (MAPK) within 5 min but did not activate extracellular signal-regulated kinases (Erk)-1/2, c-jun amino terminal kinase (JNK), or Akt. SB203580, a specific P38 MAPK inhibitor, blocked the ability of IL-1 beta to induce VEGF mRNA and promoter activity. Conditioned media from hVSMCs pretreated with IL-1 beta prevented apoptosis of ECs, an effect that was partially abrogated by VEGF-neutralizing antibodies. These data demonstrate that IL-1 beta may induce VEGF in hVSMCs, and suggest that this paracrine signaling pathway, may prevent, in part, apoptosis of ECs.

BRCA1 activation of the GADD45 promoter

Breast cancer susceptibility gene BRCA1 has been implicated in the control of gene regulation and such regulated genes are thought to mediate the biological role of BRCA1. Overexpression of BRCA1 induces GADD45, a p53-regulated and stress-inducible gene. However, the molecular mechanism by which BRCA1 induces the expression GADD45 remains unclear. In this report, we have shown that the GADD45 promoter is strongly activated following expression of wild-type BRCA1. In contrast, both the tumor-derived BRCA1 mutants (p1749R and Y1853insA) and truncated BRCA1 mutant protein (Delta500 - 1863 BRCA1), which lack transactivation activity, were unable to activate the GADD45 promoter, indicating that the BRCA1-mediated activation of the GADD45 promoter requires normal transcriptional properties of BRCA1. BRCA1 did not induce the c-Jun and c-fos promoters, which rules out a general effect of BRCA1 on other immediate-responsive genes. Expression of the human papillomavirus E6 and the dominant-negative mutant p53 proteins had no effect on the induction of the GADD45 promoter by BRCA1, suggesting that activation of the GADD45 promoter by BRCA1 is independent of cellular p53 function. With the 5'-deletion analysis, the BRCA1-responsive element of the GADD45 promoter was mapped at the region from -121 to -75. Disruption of this region resulted in the abrogation of BRCA1 activation of the GADD45 promoter. Taken together, these results demonstrate that the mechanism by which BRCA1 induces GADD45 is mainly through the transactivation of the GADD45 promoter, further demonstrating the evidence that GADD45 acts as one of the BRCA1-regulated genes. Oncogene (2000) 19, 4050 - 4057.

Cannabinoid receptor down-regulation without alteration of the inhibitory effect of CP 55,940 on adenylyl cyclase in the cerebellum of CP 55,940-tolerant mice

The objective of this study was to determine whether the development of tolerance to CP 55,940, a potent cannabinoid agonist, was due to changes in the receptor or second messenger system. ICR mice treated with CP 55,940 (2 mg/kg) twice a day for 6 and one-half days developed a high degree of tolerance to the pharmacological effects of CP 55,940. The ability of CP 55,940 to produce motor hypoactivity, hypothermia and immobility was reduced 163-, 97- and 19-fold, respectively. Evaluation of 3H-CP 55,940 binding to rat brain membranes indicated no difference in receptor affinity between the vehicle- and CP 55,940-treated animals. However, these binding studies revealed a 50% decrease in receptor number in the cerebellum of the CP 55,940-tolerant mice. Although cAMP is generally considered to be the second messenger for cannabinoid receptors, little difference was observed in the inhibitory effects of CP 55,940 on adenylyl cyclase activity in cerebellum between vehicle and drug-treated mice. However, there was an increase in receptor mRNA which suggests a compensation for receptor loss. There are several possible explanation for these results. There may be sufficient spare receptors such that CP 55,940-tolerant mice are capable of producing a maximal effect on the second messenger system. On the other hand, one could conclude that cannabinoid receptor down-regulation does not account for the development of tolerance to all of the effects of CP 55,940 in mice.

Chronic exposure of colorectal cancer cells to bevacizumab promotes compensatory pathways that mediate tumour cell migration

BACKGROUND

Bevacizumab (Bev), a monoclonal antibody to vascular endothelial growth factor (VEGF), is used in combination with chemotherapy for the treatment of metastatic colorectal cancer (CRC). The effects of Bev on angiogenesis have been well described, but the direct effect of Bev on tumour cells is unknown. This study was carried out to determine the molecular and phenotypic changes in CRC cells after chronic Bev exposure in vitro.

METHODS

Human CRC cell lines were chronically exposed (3 months) to Bev in vitro to develop Bev-adapted (Bev-A) cell lines. Vascular endothelial growth factor family members were determined by reverse transcription-polymerase chain reaction and western blotting. Migration and invasion was determined using standard in vitro assays. Intravenous injection of tumour cells was carried out to evaluate metastatic potential in mice.

RESULTS

Bevacizumab-adapted cells were found to be more migratory and invasive than control cells (P<0.001). Bevacizumab-adapted cells showed higher levels of VEGF-A, -B, -C, placental growth factor (PlGF), VEGF receptor-1 (VEGFR-1) and phosphorylation of VEGFR-1. Furthermore, treatment with SU5416, a VEGFR protein tyrosine kinase inhibitor, led to significantly decreased cell migration in vitro (P<0.001). Bevacizumab-adapted cells were more metastatic in vivo (P<0.05).

CONCLUSION

Chronic exposure of CRC cells to Bev (1) increased expression of VEGF-A, -B, -C, PlGF, VEGFR-1 and VEGFR-1 phosphorylation, (2) increased tumour cell migration and invasion, and (3) metastatic potential in vivo. Our study shows the functional significance of autocrine VEGF signalling in CRC cells.

Development of behavioral tolerance to delta 9-THC without alteration of cannabinoid receptor binding or mRNA levels in whole brain

The effect of repetitive administration of delta-9-tetrahydrocannabinol (delta 9-THC) in mice on behavioral and biochemical tolerance was determined in this study. Mice were injected twice daily with 10 mg/kg delta 9-THC for 6.5 days. On day 8, spontaneous activity was assessed or whole-brain homogenates were prepared for the cannabinoid receptor binding and mRNA studies. Although a twenty-sevenfold tolerance to delta 9-THC was observed in the behavioral assay, there was no significant alteration in receptor binding or mRNA levels.

An aspartate residue in yeast alcohol dehydrogenase I determines the specificity for coenzyme

In the three-dimensional structures of enzymes that bind NAD or FAD, there is an acidic residue that interacts with the 2'- and 3'-hydroxyl groups of the adenosine ribose of the coenzyme. The size and charge of the carboxylate might repel the binding of the 2'-phosphate group of NADP and explain the specificity for NAD. In the NAD-dependent alcohol dehydrogenases, Asp-223 (horse liver alcohol dehydrogenase sequence) appears to have this role. The homologous residue in yeast alcohol dehydrogenase I (residue 201 in the protein sequence) was substituted with Gly, and the D223G enzyme was expressed in yeast, purified, and characterized. The wild-type enzyme is specific for NAD. In contrast, the D223G enzyme bound and reduced NAD+ and NADP+ equally well, but, relative to wild-type enzyme, the dissociation constant for NAD+ was increased 17-fold, and the reactivity (V/K) on ethanol was decreased to 1%. Even though catalytic efficiency was reduced, yeast expressing the altered or wild-type enzyme grew at comparable rates, suggesting that equilibration of NAD and NADP pools is not lethal. Asp-223 participates in binding NAD and in excluding NADP, but it is not the only residue important for determining specificity for coenzyme.

Chemoresistant colorectal cancer cells and cancer stem cells mediate growth and survival of bystander cells

BACKGROUND

Recent studies suggest that cancer stem cells (CSCs) mediate chemoresistance, but interestingly, only a small percentage of cells in a resistant tumour are CSCs; this suggests that non-CSCs survive by other means. We hypothesised that chemoresistant colorectal cancer (CRC) cells generate soluble factors that enhance survival of chemonaive tumour cells.

METHODS

Chemoresistant CRC cells were generated by serial passage in oxaliplatin (Ox cells). Conditioned media (CM) was collected from parental and oxaliplatin-resistant (OxR) cells. CRC cells were treated with CM and growth and survival were assessed. Tumour growth rates were determined in nude mice after cells were treated with CM. Mass spectrometry (MS) identified proteins in CM. Reverse phase protein microarray assays determined signalling effects of CM in parental cells.

RESULTS

Oxaliplatin-resistant CM increased survival of chemo-naive cells. CSC CM also increased growth of parental cells. Parental and OxR mixed tumours grew larger than tumours composed of parental or OxR cells alone. Mass spectrometry detected unique survival-promoting factors in OxR CM compared with parental CM. Cells treated with OxR CM demonstrated early phosphorylation of EGFR and MEK1, with later upregulation of total Akt .We identified progranulin as a potential mediator of chemoresistance.

CONCLUSION

Chemoresistant tumour cells and CSCs may promote resistance through soluble factors that mediate survival in otherwise chemosensitive tumour cells.

Photothermal-reinforced and glutathione-triggered in Situ cascaded nanocatalytic therapy

Tumor microenvironment (TME)-responsive nanoformulations that catalyze a cascade of intracellular redox reactions showed promise for tumor treatment with high specificity and efficiency. In this study, we report Cu²⁺-doped zeolitic imidazolate frameworks-coated polydopamine nanoparticles (PDA@Cu/ZIF-8 NPs) for glutathione-triggered and photothermal-reinforced sequential catalytic therapy against breast cancer. In the TME, the PDA@Cu/ZIF-8 NPs could initially react with antioxidant glutathione (GSH), inducing GSH depletion and Cu⁺ generation. Whereafter, the generated Cu⁺ would catalyze local H₂O₂ to produce highly toxic hydroxyl radicals (·OH) through an efficient Fenton-like reaction even in weakly acidity. Importantly, the PDA could exert excellent photothermal conversion effect to simultaneously accelerate GSH consumption and improve the Fenton-like reaction for further expanding the intracellular oxidative stress, which innovatively achieves a synergistic photothermal-chemodynamic therapy for highly efficient anticancer treatment.