Risk factors for recurrence after therapeutic lateral neck dissection for primary papillary thyroid cancer

BACKGROUND

Lateral lymph node metastasis is an important prognostic factor and is predictive of tumor recurrence and cause-specific survival in patients with papillary thyroid cancer (PTC). However, the factors predicting recurrence and clinical outcomes after therapeutic lateral neck dissection are not well established. The aims of this study were to evaluate the incidence, pattern, and factors predictive of PTC recurrence after therapeutic lateral neck dissection.

MATERIALS AND METHODS

The records of 126 consecutive patients who underwent total thyroidectomy with therapeutic lateral neck dissection for primary PTC at the National Cancer Center were retrospectively reviewed. The factors predictive of recurrence were determined using both univariate and multivariate analyses considering several clinicopathologic variables.

RESULTS

The median follow-up period was 61.2 months, during which 22 patients (17.5 %) experienced recurrence with 1 death (0.8 %) due to disease. Locoregional recurrence and distant metastasis were found in 20 cases (15.9 %) and 2 cases (1.6 %), respectively. Male gender, aggressive histology, number of lymph node metastases, initial level of T4-off Tg per ng/mL, and ATA risk categories (high risk) were independent risk factors for recurrence. Of note, initial T4-off Tg levels greater than 4.2 ng/mL showed highest sensitivity and specificity in predicting recurrence.

CONCLUSIONS

These results provide useful information regarding the clinical outcomes after therapeutic lateral neck dissection for primary PTC and can be used to identify at-risk patients who need aggressive treatment and intensive surveillance for postoperative recurrence.

HDAC2 provides a critical support to malignant progression of hepatocellular carcinoma through feedback control of mTORC1 and AKT

Aberrant regulation of histone deacetylase 2 (HDAC2) contributes to malignant progression in various cancers, but the underlying mechanism leading to the activation of oncogenic HDAC2 remains unknown. In this study, we show that HDAC2 expression is upregulated in a large cohort of patients with human hepatocellular carcinoma, and that high expression of HDAC2 was significantly associated with poor prognosis of patients with hepatocellular carcinoma. We found that mTORC1/NF-κBp50 signaling is necessary for the growth factor-induced HDAC2 and is sustained in hepatocellular carcinoma, but not in normal hepatic cells. Growth factor-induced mTORC1 activates the nuclear translocation of NF-κBp50, where it binds to the intragenic sequences of the HDAC2 gene and promotes its transcription. Hepatocellular carcinoma tissues derived from chemical-induced mouse and rat liver cancer models validated that mTORC1 activation and NF-κBp50 nuclear translocation are essential for the transcriptional activation of oncogenic HDAC2 in hepatocellular carcinoma. In addition, we demonstrate that HDAC2 is required to maintain mTORC1 activity by stabilizing the mTOR/RAPTOR complex. Elevated expression of HDAC2 triggers a positive feedback loop that activates AKT phosphorylation via the transcriptional modulation of phosphoinositide signaling molecules. Bioinformatics analysis of HDAC2 signature and immunoblot analysis of mesenchymal genes also evidenced that HDAC2 plays a role in the malignant behavior of tumor cells by Snail induction and simultaneously E-cadherin suppression in hepatocellular carcinoma cells. These findings establish a molecular mechanism responsible for the activation of oncogenic HDAC2, which explains how growth factor-induced HDAC2 maintains mitogenic signaling and function during hepatocellular malignant progression and provide a novel strategy for therapeutic intervention in liver cancer. Cancer Res; 74(6); 1728-38. ©2014 AACR.

Respiratory insufficiency and dynamic hyperinflation after rigid bronchoscopy in a patient with relapsing polychondritis -a case report-

Relapsing polychondritis (RP) is an uncommon disease that is characterized by inflammation and destruction of cartilaginous structures. When tracheobronchial tree is involved, respiratory obstructive symptoms can occur. A 35-year-old man, with a previous diagnosis of RP, was scheduled for rigid bronchoscopy to relieve dyspnea, caused by subglottic stenosis. After laser splitting of the subglottic web, the spontaneous respiration of the patient was insufficient, and hypercarbia developed progressively even with assisted ventilation. After 20 minutes of aggressive hyperventilation to reduce end-tidal CO₂ level, sudden extreme tachycardia and hypotension developed. Ventilation rate was reduced and prolonged expiration time was allowed to alleviate a near-tampon status from dynamic hyperinflation. After the hemodynamic status was stabilized, the patient was transferred to the ICU for mechanical ventilation. He received ICU care for 30 days, and now, he was on supportive care on a ward, considering Y stent insertion to prevent luminal collapse from tracheobronchomalacia.

Down-regulation of mortalin exacerbates Aβ-mediated mitochondrial fragmentation and dysfunction

Mitochondrial dynamics greatly influence the biogenesis and morphology of mitochondria. Mitochondria are particularly important in neurons, which have a high demand for energy. Therefore, mitochondrial dysfunction is strongly associated with neurodegenerative diseases. Until now various post-translational modifications for mitochondrial dynamic proteins and several regulatory proteins have explained complex mitochondrial dynamics. However, the precise mechanism that coordinates these complex processes remains unclear. To further understand the regulatory machinery of mitochondrial dynamics, we screened a mitochondrial siRNA library and identified mortalin as a potential regulatory protein. Both genetic and chemical inhibition of mortalin strongly induced mitochondrial fragmentation and synergistically increased Aβ-mediated cytotoxicity as well as mitochondrial dysfunction. Importantly we determined that the expression of mortalin in Alzheimer disease (AD) patients and in the triple transgenic-AD mouse model was considerably decreased. In contrast, overexpression of mortalin significantly suppressed Aβ-mediated mitochondrial fragmentation and cell death. Taken together, our results suggest that down-regulation of mortalin may potentiate Aβ-mediated mitochondrial fragmentation and dysfunction in AD.

TNFα-induced miR-130 resulted in adipocyte dysfunction during obesity-related inflammation

Adipocytes are continuously stimulated by proinflammatory cytokines such as TNFα, which cause adipocyte dysfunction by facilitating the inflammatory response. Although miR-130 was reported to be an important regulator of adipogenesis by targeting PPARγ mRNA, little is known about the mechanisms regulating miR-130 expression during the proinflammatory response. Here, we examined miR-130 levels in white adipose tissue (WAT) from high-fat diet (HFD) mice and TNFα-stimulated adipocytes. Primary transcripts of miR-130 were increased after TNFα stimulation, indicating that induction of miR-130 during the pro-inflammatory response is regulated by a transcriptional event. A chromatin immunoprecipitation assay showed that p65 binding to the promoter regions of miR-130 was enhanced after TNFα treatment. Taken together, our findings suggest that induction of miR-130 by TNFα is responsible for adipocyte dysfunction.

The RNA-binding protein HuD regulates autophagosome formation in pancreatic β cells by promoting autophagy-related gene 5 expression

Tight regulation of autophagy is critical for the fate of pancreatic β cells. The autophagy protein ATG5 is essential for the formation of autophagosomes by promoting the lipidation of microtubule-associated protein LC3 (light chain 3). However, little is known about the mechanisms that regulate ATG5 expression levels. In this study, we investigated the regulation of ATG5 expression by HuD. The association of HuD with ATG5 mRNA was analyzed by ribonucleoprotein complex immunoprecipitation and biotin pulldown assays. HuD expression levels in pancreatic β cells were knocked down via siRNA, elevated by overexpression of a HuD-expressing plasmid. The expression levels of HuD, ATG5, LC3, and β-actin were determined by Western blot and quantitative RT-PCR analysis. Autophagosome formation was assessed by fluorescence microscopy in GFP-LC3-expressing cells and in pancreatic tissues from WT and HuD-null mice. We identified ATG5 mRNA as a post-transcriptional target of the mammalian RNA-binding protein HuD in pancreatic β cells. HuD associated with the 3'-UTR of the ATG5 mRNA. Modulating HuD abundance did not alter ATG5 mRNA levels, but HuD silencing decreased ATG5 mRNA translation, and, conversely, HuD overexpression enhanced ATG5 mRNA translation. Through its effect on ATG5, HuD contributed to the lipidation of LC3 and the formation of LC3-positive autophagosomes. In keeping with this regulatory paradigm, HuD-null mice displayed lower ATG5 and LC3 levels in pancreatic β cells. Our results reveal HuD to be an inducer of ATG5 expression and hence a critical regulator of autophagosome formation in pancreatic β cells.

MiR-101 functions as a tumor suppressor by directly targeting nemo-like kinase in liver cancer

Nemo-like kinase (NLK), an evolutionarily conserved MAP kinase-related kinase, has been reported to be involved in the development of hepatocellular carcinoma (HCC), but the underlying mechanisms leading to oncogenic NLK are poorly understood. A comprehensive microRNA (miRNA) profiling analysis on human HCC tissues identified four downregulated miRNAs that may target NLK. Ectopic expression of miRNA mimics suggested that miR-101 could suppress NLK in HCC cells. Notably, ectopic miR-101 expression repressed cancer cell growth and proliferation and imitated NLK knockdown effect on HCC cells. In conclusion, we suggest that miR-101 functions as a tumor suppressor by regulating abnormal NLK activity in liver.

DNA methylation of MAPK signal-inhibiting genes in papillary thyroid carcinoma

BACKGROUND

The purpose of this study was to identify the DNA methylation status of the mitogen-activated protein kinase (MAPK) signal-inhibiting genes dual-specificity phosphatase 4 (DUSP4) and 6 (DUSP6); and serpin peptidase inhibitor A member 5 (SERPINA5) in thyroid cancer.

MATERIALS AND METHODS

Using 76 papillary thyroid cancer(PTC) tissues and three thyroid cancer cell lines (TPC1, WRO82-1 and XTC), the expression of three genes and DNA methylation were determined by reverse transcription-PCR and methylation-specific PCR.

RESULTS

In all cell lines, the expression of DUSP4 and DUSP6 increased; the corresponding gene promoters were unmethylated. However, SERPINA5 gene expression decreased and SERPINA5 DNA was methylated in the TPC1 cell line. With the de-methylating agent 5'-aza-2'-deoxycytidine, SERPINA5 gene expression was restored. In 82.9% of PTC tissues (63/76), the SERPINA5 DNA promoter was methylated, which was associated with a higher v-raf murine sarcoma viral oncogene homolog B1(BRAF) mutation rate in PTC tissues based on multivariate regression (odds ratio=3.573; 95% confidence interval=1.122-11.379; p=0.031).

CONCLUSION

The expression of the MAPK signal-inhibiting gene SERPINA5 decreased in the TPC1 cell line, SERPINA5 expression was regulated by DNA methylation, which was associated with a higher BRAF mutation rate in PTC.

Inhibition of adipogenesis in 3T3-L1 cells and suppression of abdominal fat accumulation in high-fat diet-feeding C57BL/6J mice after downregulation of hyaluronic acid

OBJECTIVE

Adipogenesis can be spatially and temporally regulated by extracellular matrix (ECM). We hypothesized that the regulation of hyaluronic acid (HA), a component of the ECM, can affect adipogenesis in fat cells. The effects of HA on adipogenesis were investigated in vitro in 3T3-L1 cells and in vivo in high-fat diet-feeding C57BL/6J mice.

METHODS

We investigated the effects of HA by degradation of pre-existing or synthesized HA and artificial inhibition of HA synthesis in adipogenesis.

RESULTS

In vitro adipogenesis in 3T3-L1 cells was inhibited by treating them with exogenous hyaluronidase (HYAL) and with 4-methylumbelliferone, which inhibited the synthesis of HA in a concentration-dependent manner. In vivo, abdominal fat accumulation in high-fat diet-feeding C57BL/6J mice was suppressed by exogenous HYAL 10(4) IU injections, which was associated with reduction of lipid accumulation in liver and increase of insulin sensitivity.

CONCLUSION

Changes in the ECM such as accumulation of high molecular weight of HA by HAS and degradation of HA by endogenous HYAL were essential for adipogenesis both in vitro and in vivo.

TNFα-induced miR-130 resulted in adipocyte dysfunction during obesity-related inflammation

Adipocytes are continuously stimulated by proinflammatory cytokines such as TNFα, which cause adipocyte dysfunction by facilitating the inflammatory response. Although miR-130 was reported to be an important regulator of adipogenesis by targeting PPARγ mRNA, little is known about the mechanisms regulating miR-130 expression during the proinflammatory response. Here, we examined miR-130 levels in white adipose tissue (WAT) from high-fat diet (HFD) mice and TNFα-stimulated adipocytes. Primary transcripts of miR-130 were increased after TNFα stimulation, indicating that induction of miR-130 during the pro-inflammatory response is regulated by a transcriptional event. A chromatin immunoprecipitation assay showed that p65 binding to the promoter regions of miR-130 was enhanced after TNFα treatment. Taken together, our findings suggest that induction of miR-130 by TNFα is responsible for adipocyte dysfunction.

CANCER-SPECIFIC GENE CARRIERS RESPONDING TO CANCER MICROENVIRONMENT: ACIDOSIS AND HYPER-ACTIVATED PROTEIN KINASES

Protein kinase (PK)-responsive gene carriers modified with polyethylene glycol (PEG) chains using an acid-labile linker were developed. These carriers were obtained by modifying the PEG chains and substrate peptides for the PKs (PKA or PKCα) on the branched polyethyleneimine main chain. Polyplexes formed from these carriers and plasmid DNA (pDNA) were stably dispersed under neutral pH medium. The polyplexes were also taken up by cells on the release of the PEG chains under the slightly acidic extracellular pH associated with cancer cells. The polyplexes taken up by cells resulted in gene expression when the substrate peptides were phosphorylated by the intracellular PKs to release pDNA from the polyplexes. These novel gene carriers are expected to be promising for cancer-specific gene therapy via intravenous administration.

Differential protein expression of lymph node metastases of papillary thyroid carcinoma harboring the BRAF mutation

BACKGROUND

The prognostic role of the T1799A BRAF mutation is controversial. We investigated the protein expression in papillary thyroid carcinoma (PTCs) samples harboring the specific mutation using proteomic tools.

MATERIALS AND METHODS

We performed two-dimensional gel electrophoresis to identify differential protein expression regarding lymph node metastasis (LNM). Proteins were identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Immunohistochemical staining was performed for 38 PTCs harboring the mutation. We validated the association between these proteins and clinicopathological factors in a test set of 121 PTCs.

RESULTS

The expression of vimentin was increased in PTCs with LNM, but the one for HSP60, SOD2 and PEBP1 was increased in samples without LNM. HSP60 protein was up-regulated in PTCs without LNM (84.2% vs. 36.8%. p=0.003) and in PTCs without LNM harboring the mutation (58% vs. 41.8%. p=0.003) in the test set as shown by immunohistochemical staining.

CONCLUSION

HSP60 protein expression may inhibit LNM in PTCs harboring the BRAF mutation and may be a useful prognostic marker.

Branched polyethylenimine-based PKCα-responsive gene carriers

We examined in vitro performance of the branched polyethylenimine (bPEI)-based gene carriers which respond to cancer-specific activation of protein kinase Cα (PKCα) to express plasmid DNA. The carriers were synthesized straightforward by using amide bond formation between a peptide terminal carboxyl and a primary amine group of bPEI. To examine the effect of the peptide contents in the carrier, we prepared several carriers with various peptide contents. The obtained polymers form polyplexes with tighter condensation of plasmid DNA than our previous gene carriers. After internalization of the polyplexes via endocytosis, the polyplexes effectively escaped from the endosome into cytosol. Then, the polyplexes showed a clear-cut response to PKCα to release plasmid DNA for gene expression. We determined the optimum contents of the peptides in carriers as 5 mol% to achieve the clear-cut response to PKCα.

Post-transcriptional controls by ribonucleoprotein complexes in the acquisition of drug resistance

Acquisition of drug resistance leads to failure of anti-cancer treatments and therapies. Although several successive chemotherapies are available, along with efforts towards clinical applications of new anti-cancer drugs, it is generally realized that there is a long way to go to treat cancers. Resistance to anti-cancer drugs results from various factors, including genetic as well as epigenetic differences in tumors. Determining the molecular and cellular mechanisms responsible for the acquisition of drug resistance may be a helpful approach for the development of new therapeutic strategies to overcome treatment failure. Several studies have shown that the acquisition of drug resistance is tightly regulated by post-transcriptional regulators such as RNA binding proteins (RBPs) and microRNAs (miRNAs), which change the stability and translation of mRNAs encoding factors involved in cell survival, proliferation, epithelial-mesenchymal transition, and drug metabolism. Here, we review our current understanding of ribonucleoprotein complexes, including RBPs and miRNAs, which play critical roles in the acquisition of drug resistance and have potential clinical implications for cancer.

Changes in the clinicopathological characteristics and outcomes of thyroid cancer in Korea over the past four decades

BACKGROUND

Thyroid cancer has increased globally, with a prominent increase in small, papillary thyroid cancers (PTC). The Korean population has a high iodine intake, high prevalence of BRAF V600E mutations, and family histories of thyroid cancer. We examined the clinicopathological characteristics and outcomes of thyroid cancers in Korean patients over four decades.

METHODS

The medical records of 4500 thyroid cancer patients, between 1962 and 2009 at a single center, including 3147 PTC patients, were reviewed.

RESULTS

The mean age of the patients was 46.8±13.2 years; women accounted for 82.9% of the patients, and the median follow-up duration was 4.8 years (mean 7.0±5.8 years, range 1-43 years). The number of patients visiting the clinic increased from 411 during 1962-1990 to 2900 during 2000-2009. Age at diagnosis increased from 39.6±12.9 to 48.6±12.4 years. The male to female ratio increased from 1:6 to 1:4.5. The proportion of small (<1 cm) tumors increased from 6.1% to 43.1%, and the proportion of cancers with lymph node (LN) involvement or extrathyroidal extension (ETE) decreased from 76.4% to 44.4% and from 65.5% to 54.8% respectively. Although there were decreases in the proportion of LN involvement and ETE, these decreasing rates were not proportional to the expected rates based on the decreased proportion of large tumors. The overall recurrence and mortality rates were 13.3% and 1.4%. The five-year recurrence rate significantly decreased (from 11% to 5.9%), and the five-year mortality also improved (from 1.5% to 0.2%).

CONCLUSIONS

The incidence of thyroid cancer has rapidly increased, with a decrease in tumors of large size, LN involvement, and ETE, although the decreasing rates of LN involvement and ETE were not as prominent as decreasing rates of large size tumors. The mortality and recurrence rates have also decreased. Future long-term follow-up of patients diagnosed in the most recent decade is needed to confirm the prognostic characteristics of Korean PTC patients.

Recent progress of genome study for anaplastic thyroid cancer

Anaplastic thyroid cancer (ATC) belongs to the most malignant and rapidly progressive human thyroid cancers and its prognosis is very poor. Also, it shows high resistance to cancer treatments, so that effective treatment for ATC has not been found to date, and virtually all patients terminate their life rapidly after diagnosis. Although targeted treatment of genetic alterations has emerged as an extremely promising approach to human cancers, such as BRAF in metastatic melanoma, it remains unclear that how commonly genomic alterations are influenced in ATC tumorigenesis. In recent years, genome wide approaches have been exploited to find genetic alterations associated with complex diseases, including cancer. Here, we reviewed the comprehensive genetic alterations in ATC and recent approaches in the context of identifying genomic alterations associated with ATC. Since surprisingly few reports have been published on the genome wide study of ATC, this review puts emphasis on the urgent needs of genomic research for the prevention and treatment of ATC.

Increased arterial stiffness in subjects with impaired fasting glucose

AIMS

The present study investigated the association between fasting glucose and arterial stiffness in subjects with normal fasting glucose (NFG) and impaired fasting glucose (IFG).

METHODS

The study group consisted of 1043 subjects, including 683 subjects with NFG and 360 subjects with IFG (100≤fasting glucose <126 mg/dL). All subjects were evaluated for glucose, insulin, lipid profiles, high sensitivity C-reactive protein (hs-CRP), malondialdehyde (MDA), 8-epi-prostaglandin F2α (8-epi-PGF2α) and brachial-ankle pulse wave velocity (ba-PWV).

RESULTS

MDA (P<0.001) and ba-PWV (P<0.001) in the IFG group were higher than those in the NFG group after adjustment for sex, age, BMI, smoking and drinking, waist, blood pressure, serum lipid profiles. Ba-PWV in the IFG group was still higher than that in the NFG group after further adjustment for hs-CRP, MDA, 8-epi-PGF2α (P=0.031). Through multiple linear regression analysis, ba-PWV was found to be independently and positively associated with fasting glucose, age, systolic blood pressure, triglyceride, hs-CRP and insulin and negatively associated with male:female ratio, BMI.

CONCLUSION

Arterial stiffness was higher in the IFG group than in subjects with NFG even after adjustment for all confounding variables including hs-CRP and oxidative stress markers. In addition, fasting glucose and insulin were positively and independently associated with the ba-PWV in non-diabetic healthy adults.

Post-translational modifications of RNA-binding proteins and their roles in RNA granules

Post-transcriptional processes critically affect eukaryotic gene expression. Cells respond to environmental and intrinsic stresses by arresting global translation and inducing the accumulation of mRNAs into cytoplasmic RNA granules such as stress granules (SGs) and processing bodies (PBs), which are thought to participate in the regulation of translation and degradation of mRNAs. Stresses trigger the formation of SGs and increase PB size and abundance, and the two granules can share specific mRNAs and proteins. The protein content and dynamics of RNA granules have been extensively studied, but the mechanisms of interaction of RNA-binding proteins (RBPs) with binding partners and the signaling pathways that regulate these interactions are poorly understood. Post-translational modification of proteins in RNA granules via phosphorylation, glycosylation and methylation, influences their associations, enzymatic activities and intracellular locations. There is evidence that the post-translational modification of RBPs has a major influence on their binding to mRNA as well as on the assembly of RNA granules. In this review, recent findings concerning the post-translational modification of RBPs and their possible roles in the assembly of RNA granules are discussed.

Urinary cystatin C and tubular proteinuria predict progression of diabetic nephropathy

OBJECTIVE

The aim of this study was to evaluate the association of urinary cystatin C, a tubular damage marker, with the progression of type 2 diabetic nephropathy. RESERCH DESIGN AND METHODS: The baseline values of serum and urinary cystatin C were measured as primary parameters and those of urinary nonalbumin protein (NAP) were measured as secondary parameters. In this prospective observational study, a total of 237 type 2 diabetic patients were followed up for 29 months (13-44 months).

RESULTS

Both the urinary cystatin C-to-creatinine ratio (CCR) and NAP-to-creatinine ratio (NAPCR) were significantly different according to the degree of albuminuria. Both markers had strongly positive correlations at baseline. After adjusting for several clinical factors, both urinary CCR and NAPCR had significant associations with the decline of the estimated glomerular filtration rate (eGFR) (r = 0.160, P = 0.021; r = 0.412, P < 0.001, respectively). Urinary CCR had positive correlations with the decline of eGFR in the subpopulation of patients with eGFR ≥60 mL/min/1.73 m(2). In patients with eGFR ≥60 mL/min/1.73 m(2) and normoalbuminuria, only urinary NAPCR showed a significant association with the decline of eGFR; urinary CCR did not. In multivariate regression analysis, the number of patients who progressed to chronic kidney disease stage 3 or greater was higher in those in the upper tertiles of both the urinary levels of cystatin C and NAP than in those in the lower tertiles.

CONCLUSIONS

The results of this study suggest that urinary cystatin C and NAP may be predictors of the progression of type 2 diabetic nephropathy.

Rhamnogalacturonan II is a Toll-like receptor 4 agonist that inhibits tumor growth by activating dendritic cell-mediated CD8+ T cells

We evaluated the effectiveness of rhamnogalacturonan II (RG-II)-stimulated bone marrow-derived dendritic cells (BMDCs) vaccination on the induction of antitumor immunity in a mouse lymphoma model using EG7-lymphoma cells expressing ovalbumin (OVA). BMDCs treated with RG-II had an activated phenotype. RG-II induced interleukin (IL)-12, IL-1β, tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ) production during dendritic cell (DC) maturation. BMDCs stimulated with RG-II facilitate the proliferation of CD8⁺ T cells. Using BMDCs from the mice deficient in Toll-like receptors (TLRs), we revealed that RG-II activity is dependent on TLR4. RG-II showed a preventive effect of immunization with OVA-pulsed BMDCs against EG7 lymphoma. These results suggested that RG-II expedites the DC-based immune response through the TLR4 signaling pathway.

Activation of de novo GSH synthesis pathway in mouse spleen after long term low-dose γ-ray irradiation

Glutathione (GSH) is an important cellular antioxidant and has a critical role in maintaining the balance of cellular redox. In this study, we investigated the GSH biosynthesis genes involved in the elevation of endogenous GSH levels using an irradiation system with an irradiation dose rate of 1.78 mGy/h, which was about 40,000 times less than the dose rates used in other studies. The results showed that GSH levels were significantly increased in the low-dose (0.02 and 0.2 Gy) irradiated group compared to those in the non-irradiated group, but enzymatic antioxidants such as superoxide dismutase and catalase were not induced at any doses tested. The elevation in GSH was accompanied by elevated expression of glutamate-cysteine ligase modifier subunit, but no changes were observed in the expression of glutamate-cysteine ligase catalytic subunit and thioredoxin in de novo GSH synthesis. In the case of genes involved in the GSH regeneration cycle, the expression of glutathione reductase was not changed after irradiation, whereas glutathione peroxidase was only increased in the 0.2 Gy irradiated group. Collectively, our results suggest that the de novo pathway, rather than the regeneration cycle, may be mainly switched on in response to stimulation with long-term low-dose radiation in the spleen.