Macrophage inhibitory cytokine 1 mediates a p53-dependent protective arrest in S phase in response to starvation for DNA precursors

Small-Molecule Allosteric Inhibitors of Human Aspartate Transcarbamoylase Suppress Proliferation of Bone Osteosarcoma Epithelial Cells

Aspartate transcarbamoylase (ATC) is the first committed step in de novo pyrimidine biosynthesis in eukaryotes and plants. A potent transition state analog of human ATCase (PALA) has previously been assessed in clinical trials for the treatment of cancer, but was ultimately unsuccessful. Additionally, inhibition of this pathway has been proposed to be a target to suppress cell proliferation in E. coli, the malarial parasite and tuberculosis. In this manuscript we screened a 70-member library of ATC inhibitors developed against the malarial and tubercular ATCases for inhibitors of the human ATC. Four compounds showed low nanomolar inhibition (IC50 30-120 nM) in an in vitro activity assay. These compounds significantly outperform PALA, which has a triphasic inhibition response under identical conditions, in which significant activity remains at PALA concentrations above 10 μM. Evidence for a druggable allosteric pocket in human ATC is provided by both in vitro enzyme kinetic, homology modeling and in silico docking. These compounds also suppress the proliferation of U2OS osteoblastoma cells by promoting cell cycle arrest in G0/G1 phase. This report provides the first evidence for an allosteric pocket in human ATC, which greatly enhances its druggability and demonstrates the potential of this series in cancer therapy.

Potential Markers to Differentiate Uterine Leiomyosarcomas from Leiomyomas

Uterine leiomyomas (ULM) are the most common benign tumors of the female genitalia, while uterine leiomyosarcomas (ULMS) are rare. The sarcoma is diffuse growth, prone to hematogenous metastasis, and has a poor prognosis. Due to their similar clinical symptoms and morphological features, it is sometimes difficult to distinguish them, and the final diagnosis depends on histological diagnosis. Misdiagnosis of ULM as ULMS will lead to more invasive and extensive surgery when it is not needed, while misdiagnosis of ULMS as ULM may lead to delayed treatment and poor prognosis. This review searched and studied the published articles on ULM and ULMS, and summarized the potential markers for the differential diagnosis of ULMS. These markers will facilitate differential diagnosis and personalized treatment, providing timely diagnosis and potentially better prognosis for patients.

Urinary Growth Differentiation Factor-15 (GDF15) levels as a biomarker of adverse outcomes and biopsy findings in chronic kidney disease

BACKGROUND

Growth Differentiation Factor-15 (GDF15) is a member of the TGF-β superfamily. Increased serum GDF15 has been associated with increased risk of chronic kidney disease (CKD) progression. However, no prior studies have addressed the significance of urinary GDF15 in adult CKD.

METHODS

We measured serum and urinary GDF15 in a prospective cohort of 84 patients who underwent kidney biopsy and assessed their association with outcomes (survival, kidney replacement therapy) during a follow-up of 29 ± 17 months.

RESULTS

There was a statistically significant correlation between serum and urine GDF15 values. However, while serum GDF15 values increased with decreasing glomerular filtration rate, urinary GDF15 did not. Immunohistochemistry located kidney GDF15 expression mainly in tubular cells, and kidney GDF15 staining correlated with urinary GDF15 values. Urine GDF15 was significantly higher in patients with a histologic diagnosis of diabetic nephropathy than in diabetic patients without diabetic nephropathy. This was not the case for serum GDF15. Both serum and urine GDF15 were negatively associated with patient survival in multivariate models. However, when both urine and serum GDF15 were present in the model, lower urine GDF15 predicted patient survival [B coefficient (SEM) - 0.395 (0.182) p 0.03], and higher urine GDF15 predicted a composite of mortality or kidney replacement therapy [0.191 (0.06) p 0.002], while serum GDF15 was not predictive. Decision tree analysis yielded similar results. The area under the curve (AUC) of the receiver operating curve (ROC) for urine GDF15 as a predictor of mortality was 0.95 (95% CI 0.89-1.00, p < 0.001).

CONCLUSIONS

In conclusion, urinary GDF15 is associated with kidney histology patterns, mortality and the need for renal replacement therapy (RRT) in CKD patients who underwent a kidney biopsy.

Review of clinical and emerging biomarkers for early diagnosis and treatment management of pancreatic cancer: towards personalised medicine

Background:

Pancreatic cancer is the 12th most commonly diagnosed cancer and the 3rd leading cause of cancer mortality and accounts for approximately 2·7% of all newly diagnosed cancer cases and 6·4% of all cancer mortalities in Canada. It has a very poor survival rate mainly due to the difficulty of detecting the disease at an early stage. Consequently, in the advancement of disease management towards the concept of precision medicine that takes individual patient variabilities into account, several investigators have focused on the identification of effective clinical biomarkers with high specificity and sensitivity, capable of early diagnosis of symptomatic patients and early detection of the disease in asymptomatic individuals at high risk for developing pancreatic cancer.

Materials and methods:

We searched several databases from August to December 2020 for relevant studies published in English between 2000 and 2020 and reporting on biomarkers for the management of pancreatic cancer. In this narrative review paper, we describe 13 clinical and emerging biomarkers for pancreatic cancers used in screening for early detection and diagnosis, to identify patients’ risk for metastatic disease and subsequent relapse, to monitor patient response to specific treatment and to provide clinicians the possibility of prospectively identifying groups of patients who will benefit from a particular treatment.

Conclusions:

Current and emerging biomarkers for pancreatic cancer with high specificity and sensitivity has the potential to account for individual patient variabilities, for early detection of disease before the onset of metastasis to improve treatment outcome and patients’ survival, help screen high-risk populations, predict prognosis, provide accurate information of patient response to specific treatment and improve patients monitoring during treatment. Thus, the future holds promise for the use of effective clinical biomarkers or a panel of biomarkers for personalised patient-specific targeted medicine for pancreatic cancer.

Retinoids delay cell cycle progression and promote differentiation of intestinal epithelial cells exposed to nutrient deprivation

OBJECTIVE

Vitamin A is commonly recommended as a treatment for diarrhea and undernutrition; however, little is known about the underlying cellular mechanisms. The aim of this study was to investigate the modulation of cell cycle by vitamin A derivatives (retinyl palmitate or retinol) in undernourished intestinal epithelial crypts (IEC-6).

METHODS

IEC-6 cells were exposed to nutrient deprivation (no serum and no glutamine) and supplemented with retinyl palmitate or retinol at a range of 2 to 20 μM. Proliferation, apoptosis/necrosis, cell cycle process, and gene transcription were assessed.

RESULTS

Nutrient deprivation for 6, 12, 24, or 48 h decreased cell proliferation, and retinyl palmitate further decreased it after 24 and 48 h. Apoptosis rates were reduced by undernourishment and further reduced by retinyl palmitate after 48 h; whereas necrosis rates were unaltered. Undernourishment induced overall cell quiescence, increased percentage of cells in G0/G1 phase and decreased percentage of cells in S phase after 12 h and in G2/M phases at 6, 12, and 24 h after treatment. Both retinoids also showed cell quiescence induction with less cells in G2/M phases after 48 h, whereas only retinol showed significant modulation of G0/G1 and S phases. Both retinoids also increased markers of cell differentiation Fabp and Iap gene transcriptions in about fivefold rates after 42 h. Furthermore, specific gene transcriptions related to MAP kinase signaling pathway regulation of cell differentiation and cell cycle regulation were triggered by retinoids in undernourished IEC-6, with higher levels of expression for Atf2 and C-jun genes.

CONCLUSIONS

These findings indicated that both vitamin A derivatives induce further survival mechanisms in undernourished intestinal epithelial crypt cells. These mechanisms include increased cell quiescence, decreased apoptosis, increased cell differentiation, and transcription of genes related to MAP kinase signaling pathway.

Insulin resistance and idiopathic infertility: A potential possible link

Among various health issues, infertility has been always considered as one of the major health problems. Idiopathic infertility is still a matter of debate since the underlying mechanisms stay obscure. Idiopathic infertility is related to expanded chance of metabolic syndrome components, obesity and increased risk of cardiovascular diseases. This study aimed to assess insulin resistance and serum levels of irisin as one of the adipokines in patients with idiopathic infertility. This study included 50 male patients aged 25-50 years old suffering from idiopathic infertility, together with 50 healthy individuals of matched age as controls. Patients showed significantly increased homeostasis model assessment for insulin resistance values than controls. For irisin results, idiopathic infertility patients had significantly decreased values than controls indicating the potential effect of irisin in development of insulin resistance in idiopathic infertility patients.

Renoprotective and Immunomodulatory Effects of GDF15 following AKI Invoked by Ischemia-Reperfusion Injury

BACKGROUND

Gdf15 encodes a TGF-β superfamily member that is rapidly activated in response to stress in multiple organ systems, including the kidney. However, there has been a lack of information about Gdf15 activity and effects in normal kidney and in AKI.

METHODS

We used genome editing to generate a Gdf15 ^nuGFP-CE mouse line, removing Gdf15 at the targeted allele, and enabling direct visualization and genetic modification of Gdf15-expressing cells. We extensively mapped Gdf15 expression in the normal kidney and following bilateral ischemia-reperfusion injury, and quantified and compared renal responses to ischemia-reperfusion injury in the presence and absence of GDF15. In addition, we analyzed single nucleotide polymorphism association data for GDF15 for associations with patient kidney transplant outcomes.

RESULTS

Gdf15 is normally expressed within aquaporin 1-positive cells of the S3 segment of the proximal tubule, aquaporin 1-negative cells of the thin descending limb of the loop of Henle, and principal cells of the collecting system. Gdf15 is rapidly upregulated within a few hours of bilateral ischemia-reperfusion injury at these sites and new sites of proximal tubule injury. Deficiency of Gdf15 exacerbated acute tubular injury and enhanced inflammatory responses. Analysis of clinical transplantation data linked low circulating levels of GDF15 to an increased incidence of biopsy-proven acute rejection.

CONCLUSIONS

Gdf15 contributes to an early acting, renoprotective injury response, modifying immune cell actions. The data support further investigation in clinical model systems of the potential benefit from GDF15 administration in situations in which some level of tubular injury is inevitable, such as following a kidney transplant.

Growth Differentiation Factor-15-Induced Contractile Activity and Extracellular Matrix Production in Human Trabecular Meshwork Cells

Purpose

To determine the role and regulation of growth differentiation factor-15 (GDF-15), a TGF-β-related cytokine in human trabecular meshwork (TM) cells in the context of aqueous humor (AH) outflow and IOP.

Methods

Regulation of expression by external cues, and the distribution and secretion of GDF-15 by human TM primary cell cultures, and the effects of recombinant (r) GDF-15 on TM cell contractile characteristics, actin cytoskeleton, cell adhesion, extracellular matrix (ECM), α-smooth muscle actin (αSMA), SMAD signaling, and gene expression were determined by immunoblot, immunofluorescence, mass spectrometry, cDNA microarray, and real-time quantitative PCR (RT-qPCR) analyses.

Results

Growth differentiation factor-15, a common constituent of ECM derived from the human TM cells, was confirmed to be distributed throughout the conventional aqueous humor outflow pathway of the human eye. Growth differentiation factor-15 protein levels were significantly increased in human TM cells in response to TGF-β2, dexamethasone, endothelin-1, lysophosphatidic acid, TNF-α, IL-1β treatment, and by cyclic mechanical stretch. Stimulation of human TM cells with rGDF-15 caused a significant increase in the formation of actin stress fibers and focal adhesions, myosin light chain phosphorylation, SMAD signaling, gene expression, and the levels of αSMA and ECM proteins.

Conclusions

The results of this study, including a robust induction of GDF-15 expression by several external factors known to elevate IOP, and rGDF-15-induced increase in contractility, cell adhesion, and the levels of ECM proteins and αSMA in TM cells, collectively suggest a potential role for GDF-15 in homeostasis and dysregulation of AH outflow and IOP in normal and glaucomatous eyes, respectively.

Dihydroorotate dehydrogenase (DHODH) inhibitors affect ATP depletion, endogenous ROS and mediate S-phase arrest in breast cancer cells

Dihydroorotate dehydrogenase (DHODH) is the key enzyme in de novo biosynthesis of pyrimidine in both prokaryotes and eukaryotes. The de novo pathway of pyrimidine biosynthesis is essential in cancer cells proliferation. Leflunomide is an approved DHODH inhibitor that has been widely used for the treatment of arthritis. Similarly, brequinar sodium is another DHODH inhibitor that showed anti-tumour effect in MC38 colon carcinoma cells when used in combination with fluorouracil. Despite the potential role of DHODH inhibitors in cancer therapy, their mechanisms of action remain obscure and await further elucidation. Here, we evaluated the effect of DHODH inhibitors on the production of ATP and ROS in sensitive and non-sensitive breast cancer cells. Subsequently, the effects of DHODH inhibitors on cell cycle as well as on signalling molecules such as p53, p65 and STAT6 were evaluated in sensitive T-47D and non-sensitive MDAMB-436 cells. The correlations between DHODH protein expression, proliferation speed and sensitivity to DHODH inhibitors were also investigated in a panel of cancer cell lines. DHODH inhibitors-sensitive T-47D and MDAMB-231 cells appeared to preserve ROS production closely to endogenous ROS level whereas the opposite was observed in non-sensitive MDAMB-436 and W3.006 cells. In addition, we observed approximately 90% of intracellular ATP depletion in highly sensitive T-47D and MDAMB-231 cells compared to non-sensitive MDAMB-436 cells. There was significant over-expression of p53, p65 and STAT6 signalling molecules in sensitive cells which may be involved in mediating the S-phase arrest in cell cycle progression. The current study suggests that DHODH inhibitors are most effective in cells that express high levels of DHODH enzyme. The inhibition of cell proliferation by these inhibitors appears to be accompanied by ROS production as well as ATP depletion. The increase in expression of signalling molecules observed may be due to pyrimidine depletion which subsequently leads to cell cycle arrest at S-phase.

Acquisition of Chemoresistance and Other Malignancy-related Features of Colorectal Cancer Cells Are Incremented by Ribosome-inactivating Stress

Colorectal cancer (CRC) as an environmental disease is largely influenced by accumulated epithelial stress from diverse environmental causes. We are exposed to ribosome-related insults, including ribosome-inactivating stress (RIS), from the environment, dietary factors, and medicines, but their physiological impacts on the chemotherapy of CRC are not yet understood. Here we revealed the effects of RIS on chemosensitivity and other malignancy-related properties of CRC cells. First, RIS led to bidirectional inhibition of p53-macrophage inhibitory cytokine 1 (MIC-1)-mediated death responses in response to anticancer drugs by either enhancing ATF3-linked antiapoptotic signaling or intrinsically inhibiting MIC-1 and p53 expression, regardless of ATF3. Second, RIS enhanced the epithelial-mesenchymal transition and biogenesis of cancer stem-like cells in an ATF3-dependent manner. These findings indicate that gastrointestinal exposure to RIS interferes with the efficacy of chemotherapeutics, mechanistically implying that ATF3-linked malignancy and chemoresistance can be novel therapeutic targets for the treatment of environmentally aggravated cancers.

Anti-Colon Cancer Effects of 6-Shogaol Through G2/M Cell Cycle Arrest by p53/p21-cdc2/cdc25A Crosstalk

Chemopreventive agents can be identified from botanicals. Recently, there has been strong support for the potential of 6-shogaol, a natural compound from dietary ginger (Zingiber officinale), in cancer chemoprevention. However, whether 6-shogaol inhibits the growth of colorectal tumors in vivo remains unknown, and the underlying anticancer mechanisms have not been well characterized. In this work, we observed that 6-shogaol (15 mg/kg) significantly inhibited colorectal tumor growth in a xenograft mouse model. We show that 6-shogaol inhibited HCT-116 and SW-480 cell proliferation with IC50 of 7.5 and 10 μM, respectively. Growth of HCT-116 cells was arrested at the G2/M phase of the cell cycle, primarily mediated by the up-regulation of p53, the CDK inhibitor p21(waf1/cip1) and GADD45α, and by the down-regulation of cdc2 and cdc25A. Using p53(-/-) and p53(+/+) HCT-116 cells, we confirmed that p53/p21 was the main pathway that contributed to the G2/M cell cycle arrest by 6-shogaol. 6-Shogaol induced apoptosis, mainly through the mitochondrial pathway, and the bcl-2 family might act as a key regulator. Our results demonstrated that 6-shogaol induces cancer cell death by inducing G2/M cell cycle arrest and apoptosis. 6-Shogaol could be an active natural product in colon cancer chemoprevention.

Role of GDF15 (growth and differentiation factor 15) in pulmonary oxygen toxicity

GDF15 (growth and differentiation factor 15) is a secreted cytokine, a direct target of p53 and plays a role in cell proliferation and apoptosis. It is induced by oxidative stress and has anti-apoptotic effects. The role of GDF15 in hyperoxic lung injury is unknown. We tested the hypothesis that GDF15 will be induced in vitro, in a model of pulmonary oxygen toxicity, and will play a critical role in decreasing cell death and oxidative stress. BEAS-2B (human bronchial epithelial cells) and human pulmonary vascular endothelial cells (HPMEC) were exposed to hyperoxia, and expression of GDF15 and effect of GDF15 disruption on cell viability and oxidative stress was determined. Furthermore, we studied the effect of p53 knockdown on GDF15 expression. In vitro, both BEAS-2B and HPMEC cells showed a significant increase in GDF15 expression upon exposure to hyperoxia. After GDF15 knockdown, there was a significant decrease in cell viability and increase in oxidative stress compared to control cells transfected with siRNA with a scrambled sequence. Knockdown of p53 significantly decreased the induction of GDF15 by hyperoxia. In conclusion, we show that GDF15 has a pro-survival and anti-oxidant role in hyperoxia and that p53 plays a key role in its induction.

The glucosinolate metabolite 1-methoxy-3-indolylmethyl alcohol induces a gene expression profile in mouse liver similar to the expression signature caused by known genotoxic hepatocarcinogens

SCOPE

Breakdown products of certain glucosinolates induce detoxifying enzymes and demonstrate preventive activities against chemically induced tumourigenesis in animal models. However, other breakdown products are genotoxic. 1-Methoxy-3-indolylmethyl alcohol (1-MIM-OH) is mutagenic in bacterial and mammalian cells upon activation by sulphotransferases and forms DNA adducts in mouse tissues. This effect is enhanced in mice transgenic for human sulphotransferases 1A1/2 (FVB/N-hSULT1A1/2). Therefore, we explored gene expression changes induced by 1-MIM-OH in mouse liver.

METHODS AND RESULTS

FVB/N-hSULT1A1/2 mice were orally treated with 1-MIM-OH for 21 or 90 days, leading to high levels of hepatic 1-MIM-DNA adducts. Genome-wide expression analyses demonstrated no influence on detoxifying enzymes, but up-regulation of many mediators of the tumour suppressor p53 and down-regulation of Fhit and other long genes. While this p53 response might indicate protection, it was unable to prevent the accumulation of DNA adducts. However, various epidemiological studies reported inverse associations between the intake of cruciferous vegetables and cancer. This association may be due to the presence of other glucosinolates with tumour-preventing influences possibly outweighing adverse effects of some metabolites.

CONCLUSION

1-MIM-OH is a genotoxic substance inducing a gene expression profile similar to the expression signature caused by known genotoxic hepatocarcinogens.

Growth differentiation factor-15 as biomarker in uterine sarcomas

OBJECTIVE

The aim of this study was to investigate and validate circulating growth differentiation factor-15 (GDF-15) as a discriminating biomarker between highly malignant uterine sarcomas and benign uterine leiomyomas. In addition, we investigated whether GDF-15 differed between uterine sarcomas and benign adnexal tumors, ovarian or endometrial cancer, and borderline tumors of the ovary.

MATERIALS AND METHODS

Preoperative blood samples from 19 women with a diagnosis of uterine sarcoma were analyzed for GDF-15 with immunoassay and compared with samples from 50 patients operated on for leiomyoma uteri and with samples from 20 premenopausal and 20 postmenopausal controls. Our previously presented preoperative GDF-15 concentrations in women with borderline (n = 43), benign (n = 144), and malignant ovarian tumors (n = 125), as well as endometrial cancer (n = 510), were used for comparison.

RESULTS

The median circulating GDF-15 concentration was elevated in the uterine sarcoma group (943 ng/L) compared with the myoma uteri group (647 ng/L), the premenopausal and postmenopausal controls (363 and 545 ng/L), and the women with benign ovarian tumors (591 ng/L, all P ≤ 0.007) but was not significantly different from the ovarian borderline tumor (718 ng/L) or ovarian (1242 ng/L) or endometrial cancer (1076 ng/L) groups.High GDF-15 levels were significantly associated with leiomyosarcomas (P = 0.036), advanced disease (International Federation of Gynecology and Obstetrics stage III/IV, P = 0.013), large tumors (≥10 cm, P = 0.009), and poor survival (P = 0.022).

CONCLUSIONS

Circulating GDF-15 may be a promising novel biomarker for the preoperative identification of malignant pelvic disease. Further large prospective studies are needed to evaluate the clinical usefulness of GDF-15 as a discriminator between benign leiomyomas and aggressive sarcomas and as a marker to guide surgical and systemic therapy.

A genomics approach identifies senescence-specific gene expression regulation

Replicative senescence is a fundamental tumor-suppressive mechanism triggered by telomere erosion that results in a permanent cell cycle arrest. To understand the impact of telomere shortening on gene expression, we analyzed the transcriptome of diploid human fibroblasts as they progressed toward and entered into senescence. We distinguished novel transcription regulation due to replicative senescence by comparing senescence-specific expression profiles to profiles from cells arrested by DNA damage or serum starvation. Only a small specific subset of genes was identified that was truly senescence-regulated and changes in gene expression were exacerbated from presenescent to senescent cells. The majority of gene expression regulation in replicative senescence was shown to occur due to telomere shortening, as exogenous telomerase activity reverted most of these changes.

Pro-apoptotic action of macrophage inhibitory cytokine 1 and counteraction of activating transcription factor 3 in carrageenan-exposed enterocytes

Carrageenan (CGN), a widely used food additive, has been shown to injure the epithelial barrier in animal models. This type of damage is a clinical feature of inflammatory bowel disease (IBD) in humans. In the present study, the effects of CGN on pro-apoptotic responses associated with macrophage inhibitory cytokine 1 (MIC-1) regulation in human enterocytes were evaluated. CGN up-regulated the expression of MIC-1 that promoted epithelial cell apoptosis. Although MIC-1 induction was dependent on pro-apoptotic p53 protein, the pro-survival protein activating transcription factor 3 (ATF3) was negatively regulated by p53 expression. However, MIC-1 enhanced the expression of the pro-survival protein ATF3 in enterocytes exposed to CGN. Functionally, MIC-1-mediated epithelial cell apoptosis was counteracted by the pro-survival action of ATF3 in response to CGN exposure. These findings demonstrated that the counterbalance between MIC-1 and ATF3 is critical for deciding the fate of enterocytes under the food chemical stress.

Diagnostic performance of serum macrophage inhibitory cytokine-1 in pancreatic cancer: a meta-analysis and meta-regression analysis

Many existing studies have demonstrated that the macrophage inhibitory cytokine-1 (MIC-1) might be a powerful diagnostic biomarker in patients with pancreatic cancer; but individually published results are inconclusive. This meta-analysis aimed to derive a more precise estimation of the diagnostic performance of serum MIC-1 in pancreatic cancer. We searched CISCOM, CINAHL, Web of Science, PubMed, Google Scholar, EBSCO, Cochrane Library, China BioMedicine (CBM), and China National Knowledge Infrastructure (CNKI) databases from their inception through August 1st, 2013. Meta-analysis was performed using Meta-Disc version 1.4 and STATA version 12.0 software. Crude standardized mean difference (SMD) and their 95% confidence intervals (CI) were estimated. Data from selected studies were pooled to yield summary sensitivity, specificity, positive and negative likelihood ratio (LR), diagnostic odds ratio (DOR), and receiver operating characteristic (SROC) curve. Ten case-control studies were included in this meta-analysis with a total of 1235 pancreatic cancer patients and 730 healthy subjects. Our meta-analysis results revealed that serum MIC-1 levels in pancreatic patients were higher than those of healthy subjects (SMD=1.38, 95% CI=1.15-1.62, p<0.001). The area under the SROC curve was 0.92 (SE=0.020); the pooled sensitivity was 0.79 (95% CI=0.77-0.82); and the pooled specificity was 0.86 (95% CI=0.84-0.88). The pooled positive LR was 6.20 (95% CI=1.24-30.91); the pooled DOR was 35.73 (95% CI=18.52-68.93). In conclusion, the present meta-analysis suggests that serum MIC-1 may be a useful diagnostic biomarker with high sensitivity and specificity for identifying pancreatic cancer.

The Role of Dihydroorotate Dehydrogenase in Apoptosis Induction in Response to Inhibition of the Mitochondrial Respiratory Chain Complex III

A mechanism for the induction of programmed cell death (apoptosis) upon dysfunction of the mitochondrial respiratory chain has been studied. Previously, we had found that inhibition of mitochondrial cytochrome bc1, a component of the electron transport chain complex III, leads to activation of tumor suppressor p53, followed by apoptosis induction. The mitochondrial respiratory chain is coupled to the de novo pyrimidine biosynthesis pathway via the mitochondrial enzyme dihydroorotate dehydrogenase (DHODH). The p53 activation induced in response to the inhibition of the electron transport chain complex III has been shown to be triggered by the impairment of the de novo pyrimidine biosynthesis due to the suppression of DHODH. However, it remained unclear whether the suppression of the DHODH function is the main cause of the observed apoptotic cell death. Here, we show that apoptosis in human colon carcinoma cells induced by the mitochondrial respiratory chain complex III inhibition can be prevented by supplementation with uridine or orotate (products of the reaction catalyzed by DHODH) rather than with dihydroorotate (a DHODH substrate). We conclude that apoptosis is induced in response to the impairment of the de novo pyrimidine biosynthesis caused by the inhibition of DHODH. The conclusion is supported by the experiment showing that downregulation of DHODH by RNA interference leads to accumulation of the p53 tumor suppressor and to apoptotic cell death.

Genistein induces G2/M cell cycle arrest and apoptosis via ATM/p53-dependent pathway in human colon cancer cells

Soybean isoflavones have been used as a potential preventive agent in anticancer research for many years. Genistein is one of the most active flavonoids in soybeans. Accumulating evidence suggests that genistein alters a variety of biological processes in estrogen-related malignancies, such as breast and prostate cancers. However, the molecular mechanism of genistein in the prevention of human colon cancer remains unclear. Here we attempted to elucidate the anticarcinogenic mechanism of genistein in human colon cancer cells. First we evaluated the growth inhibitory effect of genistein and two other isoflavones, daidzein and biochanin A, on HCT-116 and SW-480 human colon cancer cells. In addition, flow cyto-metry was performed to observe the morphological changes in HCT-116/SW-480 cells undergoing apoptosis or cell cycle arrest, which had been visualized using Annexin V-FITC and/or propidium iodide staining. Real-time PCR and western blot analyses were also employed to study the changes in expression of several important genes associated with cell cycle regulation. Our data showed that genistein, daidzein and biochanin A exhibited growth inhibitory effects on HCT-116/SW-480 colon cancer cells and promoted apoptosis. Genistein showed a significantly greater effect than the other two compounds, in a time- and dose-dependent manner. In addition, genistein caused cell cycle arrest in the G2/M phase, which was accompanied by activation of ATM/p53, p21waf1/cip1 and GADD45α as well as downregulation of cdc2 and cdc25A demonstrated by q-PCR and immunoblotting assay. Interestingly, genistein induced G2/M cell cycle arrest in a p53-dependent manner. These findings exemplify that isoflavones, especially genistein, could promote colon cancer cell growth inhibition and facilitate apoptosis and cell cycle arrest in the G2/M phase. The ATM/p53-p21 cross-regulatory network may play a crucial role in mediating the anticarcinogenic activities of genistein in colon cancer.

Enteropathogenic Escherichia coli-induced macrophage inhibitory cytokine 1 mediates cancer cell survival: an in vitro implication of infection-linked tumor dissemination

Mucosally adherent Escherichia coli is frequently observed in intestinal surface of patients with colorectal cancer, but rarely in healthy control. Particularly, enteropathogenic Escherichia coli (EPEC) is known to be closely associated with colorectal carcinogenesis in human. In this study, one consequence of EPEC infection in human intestinal cancer cells was induction of macrophage inhibitory cytokine 1 (MIC-1), which is a multifunctional cytokine with biological activities involved in cancer cell growth, differentiation and migration. The present investigation assessed the involvement of MIC-1 protein in EPEC infection-mediated cancer cell survival. The challenge with EPEC induced cancer cell detachment via cytoskeleton rearrangement, which was positively associated with induced MIC-1 expression. Moreover, MIC-1 also mediated RhoA GTPase-linked survival of the detached cancer cells. Blocking of MIC-1 or RhoA activity increased cellular apoptosis of the detached cancer cells. In terms of signaling pathway, MIC-1 triggered transforming growth factorβ-activated kinase 1 (TAK1), which enhanced expression of RhoA GTPase. We conclude that EPEC enhances MIC-1 gene expression in the human intestinal cancer cells, which can be associated with enhanced tumor cell resistance to anchorage-dependent tumor cell death via enhanced TAK1 and RhoA GTPase.

Prolonged NF-κB activation by a macrophage inhibitory cytokine 1-linked signal in enteropathogenic Escherichia coli-infected epithelial cells

Intestinal epithelial activation of nuclear factor kappa B (NF-κB) exerts both detrimental and beneficial functions in response to various luminal insults, including ones associated with mucosa-associated pathogens. Gastrointestinal infection with enteropathogenic Escherichia coli (EPEC) causes severe injuries in epithelial integrity and leads to watery diarrhea. The present study was conducted to investigate the prolonged epithelial responses to persistent EPEC infection via NF-κB activation. EPEC infection led to sustained activation of NF-κB signal in mouse intestinal epithelial cells in vivo and in vitro, which was positively associated with a type III secretion system, whereas early NF-κB is regulated. Moreover, prolonged NF-κB activation was found to be a part of macrophage inhibitory cytokine 1 (MIC-1)-mediated signaling activation, a novel link between NF-κB signaling and infection-associated epithelial stress. EPEC infection induced gene expression of MIC-1, a member of the transforming growth factor β (TGF-β) superfamily, which then activated TGF-β-activated kinase 1 and consequently led to NF-κB activation. Functionally, both EPEC-induced MIC-1 and NF-κB signaling mediated epithelial survival by enhancing the expression of cyclin D1, a target of NF-κB. In summary, the results of the present study suggest that MIC-1 serves as a mediator of prolonged NF-κB activation, which is critical in maintaining gut epithelial integrity in response to infection-induced injuries.

Compound K, a Ginsenoside Metabolite, Inhibits Colon Cancer Growth via Multiple Pathways Including p53-p21 Interactions

Compound K (20-O-beta-D-glucopyranosyl-20(S)-protopanaxadiol, CK), an intestinal bacterial metabolite of ginseng protopanaxadiol saponins, has been shown to inhibit cell growth in a variety of cancers. However, the mechanisms are not completely understood, especially in colorectal cancer (CRC). A xenograft tumor model was used first to examine the anti-CRC effect of CK in vivo. Then, multiple in vitro assays were applied to investigate the anticancer effects of CK including antiproliferation, apoptosis and cell cycle distribution. In addition, a qPCR array and western blot analysis were executed to screen and validate the molecules and pathways involved. We observed that CK significantly inhibited the growth of HCT-116 tumors in an athymic nude mouse xenograft model. CK significantly inhibited the proliferation of human CRC cell lines HCT-116, SW-480, and HT-29 in a dose- and time-dependent manner. We also observed that CK induced cell apoptosis and arrested the cell cycle in the G1 phase in HCT-116 cells. The processes were related to the upregulation of p53/p21, FoxO3a-p27/p15 and Smad3, and downregulation of cdc25A, CDK4/6 and cyclin D1/3. The major regulated targets of CK were cyclin dependent inhibitors, including p21, p27, and p15. These results indicate that CK inhibits transcriptional activation of multiple tumor-promoting pathways in CRC, suggesting that CK could be an active compound in the prevention or treatment of CRC.

PRAP1 is a novel executor of p53-dependent mechanisms in cell survival after DNA damage

p53 has a crucial role in governing cellular mechanisms in response to a broad range of genotoxic stresses. During DNA damage, p53 can either promote cell survival by activating senescence or cell-cycle arrest and DNA repair to maintain genomic integrity for cell survival or direct cells to undergo apoptosis to eliminate extensively damaged cells. The ability of p53 to execute these two opposing cell fates depends on distinct signaling pathways downstream of p53. In this study, we showed that under DNA damage conditions induced by chemotherapeutic drugs, gamma irradiation and hydrogen peroxide, p53 upregulates a novel protein, proline-rich acidic protein 1 (PRAP1). We identified functional p53-response elements within intron 1 of PRAP1 gene and showed that these regions interact directly with p53 using ChIP assays, indicating that PRAP1 is a novel p53 target gene. The induction of PRAP1 expression by p53 may promote resistance of cancer cells to chemotherapeutic drugs such as 5-fluorouracil (5-FU), as knockdown of PRAP1 increases apoptosis in cancer cells after 5-FU treatment. PRAP1 appears to protect cells from apoptosis by inducing cell-cycle arrest, suggesting that the induction of PRAP1 expression by p53 in response to DNA-damaging agents contributes to cancer cell survival. Our findings provide a greater insight into the mechanisms underlying the pro-survival role of p53 in response to cytotoxic treatments.

Expression of NSAID-activated gene-1 by EGCG in head and neck cancer: involvement of ATM-dependent p53 expression

Epigallocatechin-3-gallate (EGCG), a major polyphenolic constituent of green tea, possesses remarkable chemopreventive and therapeutic potential against various types of cancer, including head and neck squamous cell carcinoma (HNSCC). However, the molecular mechanism involved is not completely understood. Nonsteroidal anti-inflammatory drug-activated gene-1 (NAG-1), a transforming growth factor β superfamily protein, is shown to be induced by several antitumorigenic compounds and to exhibit proapoptotic and antitumorigenic activities. In this report, we demonstrate that EGCG transcriptionally induced the expression of NAG-1 during EGCG-induced apoptosis of HNSCC cells. Reporter assays, using the luciferase constructs containing the NAG-1 promoter, demonstrate that p53 is required for EGCG-mediated activation of NAG-1. Overexpression of NAG-1 enhanced the apoptotic effect of EGCG, whereas suppression of NAG-1 expression by small interfering RNA attenuated EGCG-induced apoptosis in HNSCC cells. Subsequently, we found that ataxia-telangiectasia mutated (ATM) plays an important role in activating these proapoptotic proteins (NAG-1 and p53) and cell cycle inhibitor (p21). Furthermore, EGCG significantly inhibited tumor formation as assessed by xenograft models, and this result is accompanied with induction of apoptotic cells and NAG-1 expression in tumor tissue samples. Taken together, these results demonstrate for the first time that EGCG induces apoptosis via ATM/p53-dependent NAG-1 expression in HNSCC, providing an additional mechanistic explanation for the apoptotic activity of EGCG.

N-(phosphonacetyl)-L-aspartate induces TAp73-dependent apoptosis by modulating multiple Bcl-2 proteins: potential for cancer therapy

p53 is essential for the cellular responses to DNA damage that help to maintain genomic stability. However, the great majority of human cancers undergo disruption of the p53-network. Identification and characterization of molecular components important in both p53-dependent and -independent apoptosis might be useful in developing novel therapies for cancers. In the complete absence of p53, cells treated with N-(phosphonacetyl)-L-aspartate (PALA) continue to synthesize DNA slowly and eventually progress through S phase, suffering severe DNA damage that in turn triggers apoptosis, whereas cells with functional p53 undergo growth arrest. In the present study, we investigated apoptotic signaling in response to PALA and the role of p53 expression in this pathway. We found that treatment of cells lacking p53 with PALA induced TAp73, Noxa, and Bim and inactivation of these proteins with dominant negative plasmids or siRNAs significantly inhibited apoptosis, suggesting that PALA-induced apoptosis was mediated via TAp73-dependent expression of Noxa and Bim. However, PALA treatment inhibited the expression of ΔNp73 only in cells lacking p53 but not in cells expressing p53. In addition, PALA treatment inhibited Bcl-2, and overexpression of Bcl-2 significantly inhibited PALA-induced apoptosis. Moreover, expression of p53 in these cells protected them from PALA-induced apoptosis by activating p21, sustaining the expression of ΔNp73 and inhibiting the induction of Noxa and Bim. Taken together, our study identifies novel but opposing roles for the p53 and TAp73 in the induction of Noxa and Bim and regulation of apoptosis. Our data will help to develop strategies to eliminate cancer cells lacking p53 while protecting normal cells with wild-type p53.

Conserved Peptide Upstream Open Reading Frames are Associated with Regulatory Genes in Angiosperms

Upstream open reading frames (uORFs) are common in eukaryotic transcripts, but those that encode conserved peptides occur in less than 1% of transcripts. The peptides encoded by three plant conserved peptide uORF (CPuORF) families are known to control translation of the downstream ORF in response to a small signal molecule (sucrose, polyamines, and phosphocholine). In flowering plants, transcription factors are statistically over-represented among genes that possess CPuORFs, and in general it appeared that many CPuORF genes also had other regulatory functions, though the significance of this suggestion was uncertain (Hayden and Jorgensen, 2007). Five years later the literature provides much more information on the functions of many CPuORF genes. Here we reassess the functions of 27 known CPuORF gene families and find that 22 of these families play a variety of different regulatory roles, from transcriptional control to protein turnover, and from small signal molecules to signal transduction kinases. Clearly then, there is indeed a strong association of CPuORFs with regulatory genes. In addition, 16 of these families play key roles in a variety of different biological processes. Most strikingly, the core sucrose response network includes three different CPuORFs, creating the potential for sophisticated balancing of the network in response to three different molecular inputs. We propose that the function of most CPuORFs is to modulate translation of a downstream major ORF (mORF) in response to a signal molecule recognized by the conserved peptide and that because the mORFs of CPuORF genes generally encode regulatory proteins, many of them centrally important in the biology of plants, CPuORFs play key roles in balancing such regulatory networks.

Inhibitory member of the apoptosis-stimulating protein of p53 (ASPP) family promotes growth and tumorigenesis in human p53-deficient prostate cancer cells

iASPP is a member of the apoptosis-stimulating protein of p53 (ASPP) family and an evolutionarily conserved inhibitor of p53. Higher levels of iASPP proteins were examined in paraffin-embedded sections collected from 30 patients with prostate cancer using an immunohistochemical method. We found that specially knocking down iASPP with lentivirus-mediated small interfering RNA inhibited the growth, in vitro colony-forming capacity and in vivo tumorigenesis of p53-defective prostate cancer cells. Importantly, inhibition of iASPP induced cell apoptosis, which confers the inhibitory effect on cell survival. We conclude that iASPP is essential for prostate cancer cellular proliferation and survival and may be a potential target for the gene therapy for prostate cancer.

Elevated plasma growth differentiation factor-15 correlates with lymph node metastases and poor survival in endometrial cancer

PURPOSE

The study objective was to investigate and validate plasma growth differentiation factor-15 (GDF-15) as a predictor of lymph node metastasis and a poor prognosis in primary endometrial cancer.

EXPERIMENTAL DESIGN

Plasma samples from 510 women treated for endometrial cancer in a primary investigation cohort (n = 44) and a secondary validation cohort (n = 466) were analyzed for GDF-15. Plasma from healthy premenopausal (n = 20) and postmenopausal (n = 20) women, women with borderline (n = 43), benign (n = 144), and malignant ovarian tumors (n = 125) were used for comparison.

RESULTS

Median plasma GDF-15 concentration for the endometrial cancer group was elevated (1,077 ng/L) as compared with pre- and postmenopausal controls (590 and 684 ng/L) and women with benign (591 ng/L) or borderline ovarian tumors (718 ng/L; all P < 0.001), but similar to the ovarian cancer group. In the large validation cohort of endometrial carcinomas, high plasma GDF-15 was significantly associated with International Federation of Gynecology and Obstetrics (FIGO) stage III/IV disease, nonendometrioid histology, high grade, older age, postmenopausal status, and lymph node metastases (all P ≤ 0.001). High GDF-15 was also an independent predictor of poor disease-specific and recurrence-free survival.

CONCLUSIONS

Based on findings indicated in a primary investigation set and confirmed in the large secondary validation set, we report for the first time plasma GDF-15 as a biomarker for endometrial cancer phenotype, including presence of lymph node metastasis and reduced survival. Its applicability as a predictor of metastatic nodes and in monitoring treatment of endometrial cancer needs to be further studied.

Clinical pathological significance of MIC-1 and uPA expression in esophageal squamous cell carcinoma

AIM: To explore the relationship of the protein expression of macrophage inhibitory cytokine-1 (MIC-1) and urokinase plasminogen activator (uPA) with the development, progression, invasion and metastasis of esophageal squamous cell carcinoma (ESCC).

METHODS: The protein expression of MIC-1 and uPA was detected by immunohistochemistry using the streptavidin-peroxidase method in 45 ESCC specimens, 22 tumor-adjacent atypical hyperplastic epithelial specimens and 45 normal esophageal epithelial specimens.

RESULTS: The expression of MIC-1 protein was closely correlated with tumor grade, infiltration, TNM grade and lymphatic metastasis in ESCC (all P < 0.05). The expression of uPA protein was closely correlated with tumor TNM grade and lymphatic metastasis in ESCC (both P < 0.05). The positive rates of MIC-1 expression in ESCC, tumor-adjacent atypical hyperplastic epithelium and normal esophageal epithelium were 64.4% (29/45), 40.9% (9/22) and 13.3% (6/45), respectively, with a significant difference among the three groups (χ² = 24.673, P < 0.01). The positive rates of UPA protein expression in ESCC, tumor-adjacent atypical hyperplastic epithelium and normal esophageal epithelium were 68.9% (31/45), 27.3% (6/22) and 24.4% (11/45), respectively, with a significant difference among the three groups (P < 0.01). There is a positive correlation between the protein expression of MIC-1 and uPA (γ_p = 0.403, P < 0.01).

CONCLUSION: MIC-1 and uPA play important roles in the carcinogenesis, infiltration and metastasis of ESCC. Combined detection of MIC-1 and uPA expression may be a promising molecular parameter for early diagnosis and prognostic evaluation of ESCC.

Growth differentiation factor-15 as a prognostic biomarker in ovarian cancer

OBJECTIVES

There is a need for identification of new biomarkers improving our understanding, diagnosis, and follow-up of ovarian cancer. Growth differentiation factor-15 (GDF-15) is a member of the transforming growth factor-beta superfamily, and GDF-15 overexpression has been found in several cancer forms but has not been explored in ovarian cancer. The aim of the study was to explore preoperative plasma concentration and tissue expression of growth differentiation factor (GDF)-15 in ovarian tumors.

METHODS

GDF-15 concentration was measured by immunoradiometric assay in plasma samples from patients with invasive ovarian cancer (n=125), borderline ovarian tumor (BOT, n=43), and benign ovarian tumor (n=144), from healthy women (n=40), as well as in effusion samples (n=44) from women with advanced ovarian cancer. Sections of ovarian carcinoma (n=20), BOT (n=9), and cystadenoma (n=7) were immunostained for GDF-15.

RESULTS

Median plasma GDF-15 concentration was elevated in ovarian cancer as compared to healthy controls and women with benign ovarian tumors or BOT (p<0.001). GDF-15 plasma concentration correlated inversely with survival time and was an independent predictor of survival, after correction for FIGO stage and age (p=0.01). GDF-15 protein was cytoplasmatically expressed in serous tumor cells and detectable in high concentrations in effusion samples.

CONCLUSION

GDF-15 emerges as a new potential biomarker in ovarian cancer.

Pyrimidine biosynthesis links mitochondrial respiration to the p53 pathway

While many functions of the p53 tumor suppressor affect mitochondrial processes, the role of altered mitochondrial physiology in a modulation of p53 response remains unclear. As mitochondrial respiration is affected in many pathologic conditions such as hypoxia and intoxications, the impaired electron transport chain could emit additional p53-inducing signals and thereby contribute to tissue damage. Here we show that a shutdown of mitochondrial respiration per se does not trigger p53 response, because inhibitors acting in the proximal and distal segments of the respiratory chain do not activate p53. However, strong p53 response is induced specifically after an inhibition of the mitochondrial cytochrome bc1 (the electron transport chain complex III). The p53 response is triggered by the deficiency in pyrimidines that is developed due to a suppression of the functionally coupled mitochondrial pyrimidine biosynthesis enzyme dihydroorotate dehydrogenase (DHODH). In epithelial carcinoma cells the activation of p53 in response to mitochondrial electron transport chain complex III inhibitors does not require phosphorylation of p53 at Serine 15 or up-regulation of p14(ARF). Instead, our data suggest a contribution of NQO1 and NQO2 in stabilization of p53 in the nuclei. The results establish the deficiency in pyrimidine biosynthesis as the cause of p53 response in the cells with impaired mitochondrial respiration.

p53-Dependent p21-mediated growth arrest pre-empts and protects HCT116 cells from PUMA-mediated apoptosis induced by EGCG

The tumor suppressor protein p53 plays a key role in regulation of negative cellular growth in response to EGCG. To further explore the role of p53 signaling and elucidate the molecular mechanism, we employed colon cancer HCT116 cell line and its derivatives in which a specific transcriptional target of p53 is knocked down by homologous recombination. Cells expressing p53 and p21 accumulate in G1 upon treatment with EGCG. In contrast, same cells lacking p21 traverse through the cell cycle and eventually undergo apoptosis as revealed by TUNEL staining. Treatment with EGCG leads to induction of p53, p21 and PUMA in p21 wild-type, and p53 and PUMA in p21(-/-) cells. Ablation of p53 by RNAi protects p21(-/-) cells, thus indicating a p53-dependent apoptosis by EGCG. Furthermore, analysis of cells lacking PUMA or Bax with or without p21 but with p53 reveals that all the cells expressing p53 and p21 survived after EGCG treatment. More interestingly, cells lacking both PUMA and p21 survived ECGC treatment whereas those lacking p21 and Bax did not. Taken together, our results present a novel concept wherein p21-dependent growth arrest pre-empts and protects cells from otherwise, in its absence, apoptosis which is mediated by activation of pro-apoptotic protein PUMA. Furthermore, we find that p53-dependent activation of PUMA in response to EGCG directly leads to apoptosis with out requiring Bax as is the case in response to agents that induce DNA damage. p21, thus can be used as a molecular switch for therapeutic intervention of colon cancer.

Inhibition of de novo purine synthesis in human prostate cells results in ATP depletion, AMPK activation and induces senescence

BACKGROUND

4-[2-(2-Amino-4-oxo-4,6,7,8-tetrahydro-3H-pyrimidino[5,4,6][1,4]thiazin-6-yl)-(S)-ethyl]-2,5-thienoylamino-l-glutamic acid (AG2034), is a classical antifolate shown to be an excellent inhibitor of glycinamide ribonucleotide formyltransferase (GARFT), ultimately inhibiting de novo purine synthesis. We examined some metabolic effects of this drug in prostate cancer cells, LNCaP, versus non-tumorigenic prostatic epithelial cells, RWPE-1.

METHODS AND RESULTS

Cells were cultured in medium containing 10 nM 5-methyl-tetrahydrofolate supplemented with/without 1.7 microM hypoxanthine/1.5 microM thymidine. Cytotoxicity of AG2034 was determined by clonogenic assays. Total ATP was quantified by reverse-phase HPLC and [(14)C]-glycine incorporation and [(3)H]-hypoxanthine conversion into ATP by liquid scintillation counting. Protein expression levels were determined by Western blotting, cell cycle analysis by propidium iodide staining and cell-senescence by beta-galactosidase staining. AG2034 inhibited LNCaP cell proliferation causing death in the absence of hypoxanthine and cytostasis in its presence. However, RWPE-1 cells were resistant to AG2034 when hypoxanthine was present. AG2034 elevates AMP/ATP ratios but is unable to activate AMPK in RWPE-1 when hypoxanthine is present. Drug exposure increased expression levels of p53, p21, p27, and p16 in both cell lines and increased senescence-associated-beta-gal staining in LNCaP with/without hypoxanthine, but primarily in its absence in RWPE-1.

CONCLUSIONS

LNCaP cells primarily depend upon de novo while RWPE-1 cells largely favor salvage synthesis for maintenance of their ATP pools. With AG2034 treatment, ATP synthesis via hypoxanthine salvage is insufficient to support growth of LNCaP but enough to restore ATP levels and support RWPE-1 growth. The anti-proliferative effect of AG2034 involves increasing phosphorylation of AMPK. These results indicate that AG2034 activates p53 and AMPK mediating the induction of signaling pathways leading to senescence.

A novel mechanism of natural vitamin E tocotrienol activity: involvement of ERbeta signal transduction

Vitamin E is a generic term used to indicate all tocopherol (TOC) and tocotrienol (TT) derivates. In the last few years, several papers have shown that a TT-rich fraction (TTRF) extracted from palm oil inhibits proliferation and induces apoptosis in a large number of cancer cells. However, the molecular mechanism(s) involved in TT action is still unclear. In the present study, we proposed for the first time a novel mechanism for TT activity that involves estrogen receptor (ER) signaling. In silico simulations and in vitro binding analyses indicated a high affinity of TTs for ERbeta but not for ERalpha. In addition, in ERbeta-containing MDA-MB-231 breast cancer cells, we demonstrated that TTs increase the ERbeta translocation into the nucleus, which in turn activates estrogen-responsive genes (MIC-1, EGR-1 and cathepsin D), as demonstrated by cell preincubation with the ER inhibitor ICI-182,780. Finally, we observed that TT treatment is associated with alteration of cell morphology, DNA fragmentation, and caspase-3 activation. Altogether, these experiments elucidated the molecular mechanism underling gamma- and delta-TT effects.

Macrophage inhibitory cytokine-1 (MIC-1) and subsequent urokinase-type plasminogen activator mediate cell death responses by ribotoxic anisomycin in HCT-116 colon cancer cells

Ribosome-inactivating stresses possess a potent regulatory activity against tumor cell progression. In this study, we demonstrated that macrophage inhibitory cytokine-1 (MIC-1) and its associated signals determined the colon cancer cell response to the chemical ribotoxic stress. The ribotoxic stress agent anisomycin-induced MIC-1 gene expression which was involved in the ribotoxin-induced apoptotic pathway. MIC-1 was also a critical inducer of apoptosis-related gene products such as activated urokine-type plasminogen activator (PLAU) and PLAU receptor (uPAR). When MIC-1 or PLAU action was repressed in the tumor cells, the chemical ribotoxic stress triggered a survival-related MAP kinase such as ERK. Mechanistically, gene expression of apoptosis-mediator MIC-1 was enhanced by activating transcription factor 3 (ATF-3) via the p38 MAP kinase signaling pathway. Moreover, both promoter activity and mRNA stability of MIC-1 gene were up-regulated by ribotoxic anisomycin via the p38 MAP kinase signaling pathway. In conclusion, ribotoxic anisomycin-induced MIC-1 expression via p38-ATF3 pathway and subsequent apoptosis while suppressing survival ERK signal in the colon cancer cells. The results of this study provide mechanistic insight into tumor cell decision for death or survival pathways in response to ribosome-disrupting stresses from chemotherapeutics.

Identification of macrophage inhibitory cytokine-1 in adipose tissue and its secretion as an adipokine by human adipocytes

Macrophage inhibitory cytokine-1 (MIC-1), a divergent member of the TGF-beta superfamily, is involved in the control of multiple cellular processes and mediates cachexia through the inhibition of appetite. Adipose tissue as an endocrine organ secretes proteins (adipokines) that regulate energy homeostasis and other cellular functions. This study investigated whether MIC-1 is expressed in adipose tissue and whether MIC-1 is a secretory product of adipocytes. Mouse and human adipose tissues were collected from different depots. 3T3-L1 preadipocytes and human preadipocytes were induced to differentiate into adipocytes in cell culture. MIC-1 mRNA was detected in the major mouse adipose depots (epididymal, perirenal, sc). In these depots, MIC-1 gene expression was evident in both isolated mature adipocytes and stromal-vascular cells. In 3T3-L1 adipocytes, MIC-1 mRNA was detected before and after differentiation. MIC-1 mRNA and protein secretion were evident in human preadipocytes as well as differentiated adipocytes. MIC-1 production by human adipocytes was stimulated by H(2)O(2) and 15d-prostaglandin J(2). In addition, recombinant MIC-1 increased adiponectin secretion by differentiated human adipocytes. MIC-1 mRNA and protein were also observed in human sc and visceral fat. MIC-1 mRNA levels were positively correlated with adiponectin mRNA. Moreover, MIC-1 mRNA was negatively associated with body mass index and body fat mass in human subjects. We conclude that MIC-1 is expressed in adipose tissue and secreted from adipocytes and is therefore a new adipokine. MIC-1 may have a paracrine role in the modulation of adipose tissue function and body fat mass.

Glutamine deprivation induces abortive s-phase rescued by deoxyribonucleotides in k-ras transformed fibroblasts

Background

Oncogene activation plays a role in metabolic reprogramming of cancer cells. We have previously shown that K-ras transformed fibroblasts have a stronger dependence on glycolysis and a reduced oxidative phosphorylation ability as compared to their normal counterparts. Another metabolic adaptation of cancer cells, that has long been established, is their propensity to exhibit increased glutamine consumption, although the effects induced by glutamine deprivation on cancer cells are still controversial.

Methodology and Principal Findings

Here, by using nutritional perturbations and molecular physiology, we show that reduction or complete depletion of glutamine availability in K-ras transformed fibroblasts causes a strong decrease of proliferation ability and a slower re-entry of synchronized cells into the cell cycle. The reduced proliferation is accompanied by sustained expression of cyclin D and E, abortive S phase entrance and is dependent on Ras signalling deregulation, since it is rescued by expression of a dominant negative guanine nucleotide exchange factor. The growth potential of transformed cells as well as the ability to execute the G₁ to S transition is restored by adding the four deoxyribonucleotides, indicating that the arrest of proliferation of K-ras transformed cells induced by glutamine depletion is largely due to a reduced supply of DNA in the presence of signalling pathways promoting G₁ to S transition.

Conclusions and Significance

Our results suggest that the differential effects of glutamine and glucose on cell viability are not a property of the transformed phenotype per se, but rather depend on the specific pathway being activated in transformation. For instance, myc-overexpressing cells have been reported to die under glutamine depletion and not under glucose shortage, while the opposite holds for ras-transformed fibroblasts as shown in this paper. These different responses of transformed cells to nutritional stress should be taken into account when designing anti-cancer therapies that aim to exploit metabolic differences between normal and transformed cells.

Influence of inflammation and aging on macrophage inhibitory cytokine-1 gene expression in rat ventral prostate

OBJECTIVES

We have previously reported that the macrophage inhibitory cytokine-1 (MIC-1) gene is downregulated in human symptomatic benign prostatic hyperplasia. The aim of this study was to investigate the histologic changes and MIC-1 gene expression in the prostate of young nonbacterial prostatitis model (Y-NBP) and aging rats.

METHODS

A total of 35 Wistar male rats, 13 weeks old, were castrated and subjected to (a) castration alone for 14 days, (b) Y-NBP-14d (0.25 mg/2 mL/kg beta-estradiol injection for 14 days), or (c) Y-NBP-30d (beta-estradiol injection for 30 days). A total of 5 male rats, 10 months old, were also analyzed. We used 21 male rats, 13 weeks old, who had undergone sham surgery as the controls. The ventral lobes of the prostate were histologically examined with Masson's trichrome staining or immunostaining using an anti-macrophage antibody. The MIC-1 mRNA levels were quantitatively assessed using real-time reverse transcriptase-polymerase chain reaction.

RESULTS

The MIC-1 gene mRNA levels in the castration alone, Y-NBP-14d, and Y-NBP-30d rat prostates were greater than those in the control rats (P < .005). In contrast, those of the 10-month-old rats were lower than those of the controls (P = .0093). The mean stroma-to-epithelium ratio in the Y-NBP-30d rats, 10-month-old rats, and 13-week-old controls was 1.28, 0.26, and 0.10, respectively (Y-NBP-30d vs 10-month-old rats, P = .0008; 10-month-old vs 13-week-old rats, P = .001). The number of infiltrating macrophages in the Y-NBP-14d, Y-NBP-30d, and 10-month-old rats was greater than that of the 13-week-old controls (P < .001).

CONCLUSIONS

Castration causes induction of MIC-1 gene expression. Estradiol treatment has little effect on MIC-1 gene expression but causes a significant increase in the stroma-to-epithelium ratio. The aging rat prostate is more similar to human benign prostatic hyperplasia than is the Y-NBP model in light of MIC-1 gene expression and histologic changes.

Implication of human N-alpha-acetyltransferase 5 in cellular proliferation and carcinogenesis

The N-alpha-acetyltransferase NatB, composed in Saccharomyces cerevisiae by the Nat3p and Mdm20p subunits, is an important factor for yeast growth and resistance to several stress agents. However, the expression and functional role of the mammalian counterpart has not yet been analysed. Here, we report the identification of Nat3p human homologue (hNAT5/hNAT3) and the characterization of its biological function. We found that hNAT5/hNAT3 silencing in HeLa cells results in inhibition of cell proliferation and increased sensitivity to the pro-apoptotic agent MG132. Moreover, inhibition of hNAT5/hNAT3 expression induces p53 activation and upregulation of the antiproliferative protein p21(WAF1/CIP1). The changes of the cellular transcriptome after hNAT5/hNAT3 knockdown confirmed the involvement of this protein in cell growth and survival processes. Among the genes differentially expressed, we observed upregulation of several p53-dependent antiproliferative and pro-apoptotic genes. In the c-myc transgenic mice, which is a model of inducible hepatocarcinoma, we found that hNAT5/hNAT3 was upregulated when the tumour was induced. In accordance with this observation, we noticed increased hNAT5/hNAT3 protein level in neoplastic versus non-neoplastic tissue in a high proportion of patients with hepatocellular carcinoma. Consequently, our results suggest that hNAT5/hNAT3 is required for cellular proliferation and can be implicated in tumour growth.

DNA synthesis from unbalanced nucleotide pools causes limited DNA damage that triggers ATR-CHK1-dependent p53 activation

p53-dependent G(1) and G(2) cell cycle checkpoints are activated in response DNA damage that help to maintain genomic stability. p53 also helps to protect cells from damage that occurs during S phase, for example, when the cells are starved for DNA precursors or irradiated with a low dose of UV. p53 is activated in normal cells starved for pyrimidine nucleotides by treatment with N-(phosphonacetyl)-l-aspartate (PALA). The treated cells progress through a first S phase with kinetics similar to those of untreated cells. However, the DNA of the treated cells begins to become damaged rapidly, within 12 h, as revealed by a comet assay, which detects broken DNA, and by staining for phosphorylated histone H2AX, which accumulates at sites of DNA damage. Because the cells survive, the damage must be reversible, suggesting single-strand breaks or gaps as the most likely possibility. The transiently damaged DNA stimulates activation of ATR and CHK1, which in turn catalyze the phosphorylation and accumulation of p53. Although PALA-induced DNA damage occurs only in dividing cells, the p53 that is activated is only competent to transcribe genes such as p21 and macrophage inhibitory cytokine 1 (whose products regulate G(2) and G(1) or S phase checkpoints, respectively) after the cells have exited the S phase during which damage occurs. We propose that p53 is activated by stimulation of mismatch repair in response to the misincorporation of deoxynucleotides into newly synthesized DNA, long before the lack of pyrimidine nucleoside triphosphates causes the rate of DNA synthesis to slow appreciably.