Clinical characteristics and genetic analysis of a Chinese pedigree affected with mitochondrial DNA depletion syndrome due to compound heterozygous variants of RRM2B gene / 中华医学遗传学杂志

OBJECTIVE@#To analyze the clinical characteristics and pathogenic gene in a Chinese pedigree affected with mitochondrial DNA depletion syndrome 8A (MTDPS8A).@*METHODS@#Whole exome sequencing was carried out for the patient. Sanger sequencing was used to verify the results, and PolyPhen-2 and PROVEAN software were used to predict the impact of amino acid changes on the function of the protein.@*RESULTS@#The patient, a two-month-old female, was admitted to the hospital for poor milk intake and poor mental response. Her clinical manifestations included feeding difficulty, shortness of breath and low muscle tone. Auxiliary laboratory test indicated that the infant was underdeveloped with abnormal liver, kidney, and heart functions accompanied by hyperlacticacidemia. She responded poorly to treatment and eventually died. Sequencing revealed that the child has carried compound heterozygous missense variants of the RRM2B gene, namely c.16delA (p.R6Gfs*22) and c.175G>C (p.A59P), which were respectively inherited from her father and mother, and both were newly discovered pathologic variants.@*CONCLUSION@#The c.16delA and c.175G>C compound heterozygous variants of the RRM2B gene probably underlay the pathogenesis of MTDPS8A. Above finding has strengthened the understanding of the clinical feature and genetic etiology of this disease and expanded the mutation spectrum of the RRM2B gene.

Silencing RRM1 gene reverses paclitaxel resistance in human breast cancer cell line MCF- 7/R by inducing cell apoptosis / 南方医科大学学报

OBJECTIVE@#To investigate the effects of ribonucleotide reductase catalytic subunit M1 (RRM1) gene silencing on drug resistance of human breast cancer cell line MCF-7/R.@*METHODS@#We established a paclitaxel-resistant breast cancer MCF-7 cell line (MCF-7/R) by exposing the cells to high-concentration paclitaxel in a short time. Small interfering RNAs (siRNAs) targeting RRM1 were designed to silence RRM1 expression in human breast cancer MCF-7/R cells. MTT assay was used to detect the IC values and the sensitivity to paclitaxel in the cells with or without siRNA transfection. The changes in the proliferative activity of MCF7 and MCF-7/R cells following RRM1 gene silencing were evaluated using EdU assay. Flow cytometry was used to analyze the cell apoptosis and cell cycle changes. We assessed the effect of RRM1 gene silencing and paclitaxel on the tumor growth in a nude mouse model bearing subcutaneous xenografts with or without siRNA transfection.@*RESULTS@#We detected significantly higher expressions of RRM1 at both the mRNA and protein levels in the drug-resistant MCF- 7/R cells than in the parental MCF-7 cells ( < 0.01). Transfection with the specific siRNAs significantly reduced the expression of RRM1 in MCF-7/R cells ( < 0.05), which showed a significantly lower IC value of paclitaxel than the cells transfected with the negative control siRNA ( < 0.05). RRM1 silencing significantly inhibited the proliferation ( < 0.01) and enhanced the apoptosis-inducing effect of paclitaxel in MCF-7/R cells ( < 0.001); RRM1 silencing also resulted in obviously reduced Akt phosphorylation, suppressed Bcl-2 expression and promoted the expression of p53 protein in MCF-7/R cells. In the tumor-bearing nude mice, the volume of subcutaneously transplanted tumors was significantly smaller in MCF-7/R/siRNA+ PTX group than in the other groups ( < 0.001).@*CONCLUSIONS@#RRM1 gene silencing can reverse paclitaxel resistance in human breast cancer cell line MCF-7/R by promoting cell apoptosis.

SATB1 promotes the malignant of human non-Hodgkin lymphoma by activating the ribonucleotide reductase small subunit M2 / 中南大学学报(医学版)

To explore the role of the special AT rich sequence binding protein-1 (SATB1) and ribonucleotide reductase M2 (RRM2) in enhancing malignant progression of non-Hodgkin lymphoma (NHL). 
 Methods: A total of 42 NHL and 42 chronic lymphadenitis patients were recruited. The protein expressions of SATB1 and RRM2 in cervical lymph nodes were determined by Western blot. After overexpression of SATB1, siSATB1 or siRRM2, the mRNA levels of SATB1 and RRM2 in cells were analyzed via RT-PCR, the cell proliferation was evaluated via MTT and EdU assays, while the migration and invasion of cells were assessed by transwell assays.
 Results: Compared with chronic lymphadenitis, the expressions of SATB1 and RRM2 in NHL patients were up-regulated. There was positive correlation between SATB1 and RRM2 in NHL patients. RRM2 mRNA level was up-regulated after transfection of SATB1 and down-regulated after transfection of siSATB1. Overexpression of SATB1 increased tumor cell proliferation, migration and invasion, while knockdown of RRM2 reversed those phenomena.
 Conclusion: SATB1 functions as an oncogene and promotes tumor cell proliferation, migration and invasion by up-regulation of RRM2 in NHL.

Functions of Herpesvirus-Encoded Homologs of the Cellular Ribonucleotide Reductase Large Subunit

Deoxyribonucleotides (dNTPs) are important for the efficient growth of DNA viruses. Therefore, many DNA viruses have strategies for the upregulation of cellular dNTP levels. Both α- and γ-herpesviruses encode functional homologs of cellular dNTP anabolic enzymes, including the class I ribonucleotide reductase (RNR) large (R1) and small (R2) subunits, whereas β-herpesviruses modulate host cells to induce genes that increase dNTP levels. Interestingly, β-herpesviruses still express the nonfunctional RNR R1 subunit. However, it is not clear why β-herpesviruses still carry inactive R1 homologs. Recently, the R1 homologs of herpesviruses have been shown to inhibit innate immune signaling pathways. In particular, both functional and nonfunctional R1 homologs target receptor-interacting protein kinase 1 (RIP1) and inhibit RIP1-mediated signaling pathways to promote viral replication. Here, we summarize recent findings on the activity of herpesviral R1 homologs and discuss their roles in the regulation of innate immune signaling pathways.

Essential functions of iron-requiring proteins in DNA replication, repair and cell cycle control

Eukaryotic cells contain numerous iron-requiring proteins such as iron-sulfur (Fe-S) cluster proteins, hemoproteins and ribonucleotide reductases (RNRs). These proteins utilize iron as a cofactor and perform key roles in DNA replication, DNA repair, metabolic catalysis, iron regulation and cell cycle progression. Disruption of iron homeostasis always impairs the functions of these iron-requiring proteins and is genetically associated with diseases characterized by DNA repair defects in mammals. Organisms have evolved multi-layered mechanisms to regulate iron balance to ensure genome stability and cell development. This review briefly provides current perspectives on iron homeostasis in yeast and mammals, and mainly summarizes the most recent understandings on iron-requiring protein functions involved in DNA stability maintenance and cell cycle control.

Long-Term Follow-Up Result of Hydroxyurea Chemotherapy for Recurrent Meningiomas

OBJECTIVE: Meningiomas represent 18-20% of all intracranial tumors and have a 20-50% 10-year recurrence rate, despite aggressive surgery and irradiation. Hydroxyurea, an inhibitor of ribonucleotide reductase, is known to inhibit meningioma cells by induction of apoptosis. We report the long-term follow-up result of hydroxyurea therapy in the patients with recurrent meningiomas. METHODS: Thirteen patients with recurrent WHO grade I or II meningioma were treated with hydroxyurea (1000 mg/m2/day orally divided twice per day) from June 1998 to February 2012. Nine female and 4 male, ranging in age from 32 to 83 years (median age 61.7 years), were included. Follow-up assessment included physical examination, computed tomography, and magnetic resonance imaging (MRI). Standard neuro-oncological response criteria (Macdonald criteria) were used to evaluate the follow-up MRI scans. The treatment was continued until there was objective disease progression or onset of unmanageable toxicity. RESULTS: Ten of the 13 patients (76.9%) showed stable disease after treatment, with time to progression ranging from 8 to 128 months (median 72.4 months; 6 patients still accruing time). However, there was no complete response or partial response in any patients. Three patients had progressive disease after 88, 89, 36 months, respectively. There was no severe (Grade III-IV) blood systemic disorders and no episodes of non-hematological side effects. CONCLUSION: This study showed that hydroxyurea is a modestly active agent against recurrent meningiomas and can induce long-term stabilization of disease in some patients. We think that hydroxyurea treatment is well tolerated and convenient, and could be considered as an alternative treatment option in patients with recurrent meningiomas prior to reoperation or radiotherapy.

Comparative Analysis of the Three Classes of Archaeal and Bacterial Ribonucleotide Reductase from Evolutionary Perspective

The Ribonucleotide reductases (RNR) are essential enzymes that catalyze the conversion of nucleotides to deoxynucleotides in DNA replication and repair in all living organisms. The RNRs operate by a free radical mechanism but differ in the composition of subunit, cofactor required and regulation by allostery. Based on these differences the RNRs are classified into three classes-class I, class II and class III which depend on oxygen, adenosylcobalamin and S-adenosylmethionine with an iron sulfur cluster respectively for radical generation. In this article thirty seven sequences belonging to each of the three classes of RNR were analyzed by using various tools of bioinformatics. Phylogenetic analysis, dot-plot comparisons and motif analysis was done to identify a number of differences in the three classes of RNRs. In this research article, we have attempted to decipher evolutionary relationship between the three classes of RNR by using bioinformatics approach.

Low productivity of ribonucleotide reductase in Saccharomyces cerevisiae increases sensitivity to stannous chloride

Ribonucleotide reductase (RNR) of the yeast Saccharomyces cerevisiae is a tetrameric protein complex, consisting of two large and two small subunits. The small subunits Y2 and Y4 form a heterodimer and are encoded by yeast genes RNR2 and RNR4, respectively. Loss of Y4 in yeast mutant rnr4delta can be compensated for by up-regulated expression of Y2, and the formation of a small subunit Y2Y2 homodimer that allows for a partially functional RNR. However, rnr4delta mutants exhibit slower growth than wild-type (WT) cells and are sensitive to many mutagens, amongst them UVC and photo-activated mono- and bi-functional psoralens. Cells of the haploid rnr4delta mutant also show a 3- to 4-fold higher sensitivity to the oxidative stress-inducing chemical stannous chloride than those of the isogenic WT. Both strains acquired increased resistance to SnCl2 with age of culture, i.e., 24-h cultures were more sensitive than cells grown for 2, 3, 4, and 5 days in liquid culture. However, the sensitivity factor of three to four (WT/mutant) did not change significantly. Cultures of the rnr4delta mutant in stationary phase of growth always showed higher frequency of budding cells (budding index around 0.5) than those of the corresponding WT (budding index <0.1), pointing to a delay of mitosis/cytokinesis.

Promoter Polymorphism of RRM1 Gene in Korean Lung Cancer Population / 결핵및호흡기질환

BACKGROUND: LOH11A is a region with frequent allele loss (>75%) in lung cancer that is located on the centromeric part of chromosome 11p15.5. Clinical and cell biological studies suggest that this region contains a gene associated with metastatic tumor spread. RRM1 encoding the M1 subunit of ribonucleotide reductase, which is an enzyme that catalyses the rate-limiting step in deoxyribonucleotide synthesis, is located in the LOH11A region. METHODS: Polymorphisms were found at nucleotide position (-)37 (C/A) and (-)524 (C/T) from the beginning of exon 1 of the RRM1 gene that might regulate the expression of RRM1. We studied the polymorphisms in 127 Korean individuals (66 lung cancer and 61 normal controls) and compared with those of 140 American patients with lung cancer. RESULTS: CC, AC and AA were found at the (-)37 position in 64(50.4%), 55(43.3%), and 8(6.3%) out of 127 Korean individuals (66 cancer, 61 non-cancer patients), respectively. There was a similar frequency of allele A at (-)37 in the American(27.9%) and Korean population(28.0%). CC, CT and TT was found at the (-)524 position in 24(18.9%), 44(34.6%), and 59(46.5%) out of the 127 Korean individuals, respectively. There was a similar frequency of allele C at (-)524 in the American(34.6%) and Korean population(36.2%).There was no difference in the frequency of the (-)37 and (-)524 genotypes between the cancer and non-cancer group. However there was a significant correlation of the genotypes between (-)37 and (-)524 (p<0.001), which suggests the possible coordination of these polymorphisms in the regulation of the promoter activity of the RRM1 gene. CONCLUSION: RRM1 promoter polymorphisms were not found to be significant risk factors for lung cancer. However, a further study of the promoter activity and expression of the RRM1 gene according to the pattern of the polymorphism will be needed.

Expression of R2 protein in gestational trophoblastic diseases / 浙江大学学报·医学版

<p><b>OBJECTIVE</b>To study the expression of the small subunit ribonucleotide reductase (R2) in gestational trophoblastic diseases (GTD) and to assess its prognostic value.</p><p><b>METHODS</b>The expression of R2 was detected with immunohistochemical method in 15 cases of normal villi, 38 cases of hydatidiform mole (HM), 42 cases of invasive moles (IM) and 18 cases of choriocarcinoma (CC).</p><p><b>RESULTS</b>R2 expression in HM, IM and CC was significantly increased compared with that of normal villi (P=0.000). There were no significant differences in R2 protein expression among HM, IM and CC. Among 38 cases of HM, R2 expression in 8 cases with malignant transformation was significantly higher than in 30 cases of non-malignant transformation mole (P=0.02). Preoperative chemotherapy of gestational trophoblastic tumor including IM and CC did not influence the R2 expression. Compared with patients of stage I (WHO), the R2 protein in gestational trophoblastic tumor (GTT) patients of stage III or stage II was significantly increased (P=0.023 and P=0.038, respectively). The value of R2 in GTT patients with middle or high risk in WHO prognostic scoring system was higher than in the patients with low risk (P=0.018 and P=0.006, respectively).</p><p><b>CONCLUSION</b>R2 expression in GTD is increased, which may be associated with the hyperplasia of trophoblasts, malignant transformation of hydatidiform mole and drug resistance of trophoblastic tumor.</p>

Combination of Mutated Herpes Simplex Virus (G207) with Radiation for the Treatment of Squamous Cell Carcinoma of the Head and Neck / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: G207 virus is an ideal candidate of oncolytic viral therapy. It is a multi-gene mutant of HSV-1 with a deletion at the gamma34.5 loci and a LacZ gene insertion in the ICP6 gene, encoding the HSV ribonucleotide reductase. Ionizing radiation induces the growth arrest-inducible gene, Gadd34, a protein that correlates with apoptosis following radiation and has homology with the G207 gamma34.5 gene. It is hypothesized that the combination of radiotherapy with G207 virus may have a synergic effect on viral replication and efficacy. The purpose of this study is to evaluate the combination of the cytotoxic G207 virus with radiation therapy to treat head and neck tumors. MATERIALS AND METHOD: Five human SCCHN cell lines and one murine SCC cell line were utilized in this study. There were two groups of cells: control cells received no irradiation while the second group was irradiated with 400 cGy. Cells were infected with G207 vectors at a multiplicity of infection (MOI) of 0.1. Cytotoxicity assay was performed for 5 days. Cells and culture medium supernatant were collected and viral titers determined by plaque forming units on Vero cells. To evaluate infection efficiency, X-gal staining was performed at 24hr post infection. RESULTS: All head and neck squamous cancer cell lines tested demonstrated an increased susceptibility to the combination of G207 virus with radiation therapy when compared with each single modality (more than additive effect, p<0.05). Even though cell lines such as SCC25, MSKQLL2, or SCCVII were radioresistant, the combination of G207 with radiation therapy showed significantly increased cytotoxic effect. X-gal staining and viral growth curve studies demonstrated that G207 replications in radiated cell lines were not decreased as compared with non-radiated ones. CONCLUSION: The results provide preliminary support for the use of G207 oncolytic virus as a radiation adjuvant in treatment of head and neck cancer. The combination of radiation and oncolytic viral gene therapy may eventually be useful in treating patients with radio-resistant, non-resectable disease, and patients with a high probability of contracting postoperative microscopic residual diseases.

Hydroxyurea Therapy in Hemoglobin Madrid Patients / 대한혈액학회지

Unstable hemoglobins (Hb) are variants of adult Hb that tend to precipitate and form insoluble inclusions (Heinz bodies) within red blood cells (RBC) and RBC precursors. More than 100 structurally different unstable Hb variants showing broad spectrum of manifestations from asymptomatic to severe hemolytic anemia and dyserythropoiesis have been discovered. Hydroxyurea is a potent ribonucleotide reductase inhibitor and have been proposed as a new therapy for beta chain hemoglobinopathies through activation of gamma chain synthesis. We treated two patients (A : son, B : father) with highly unstable Hb diagnosed as Hb Madrid [Beta 115(G17)Ala->Pro] by direct DNA sequencing and restriction enzyme analysis. Our patients received hydroxyurea in dosages varying from 0.75g to 1.3g daily for 89 weeks. We could not show the clinical and hematological improvements after hydroxyurea therapy in thses patients. Optimization of dosage and long term side effects of hydroxyurea should be studied further.

A Case of Hydroxyurea-Induced Cutaneous Ulceration and Squamous Cell Carcinoma / 대한피부과학회지

Hydroxyurea, one of conventional chemotherapies in chronic myelogenous leukemia(CML) and polycythemia vera, inhibits ribonucleotide reductase, which catalyzes the rate-limiting step in the de novo synthesis of deoxynucleotide triphosphates required for DNA synthesis. Various cutaneous side effects due to hydroxyurea have been reported as follows; alopecia, diffuse hyperpigmentation, scaling, poikiloderma, atrophy of the skin and subcutaneous tissues, nail changes with multiple pigmented nail bands or brittleness, erythema and scaling of acral sites simulating chronic dermatomyositis, lichen planus-like lesions, or skin tumors on the UV-light exposed areas.A 72-year-old woman, receiving hydroxyurea for CML during 5 years, revealed hydroxyurea dermopathy such as scaly papules, poikilodermatous patches, and acral ulceration, and unusually developed squamous cell carcinoma. This is a rare case of hydroxyurea dermopathy and the first case of squamous cell carcinoma by hydroxyurea in Korea.

Gemcitabine Therapy in Patients with Advanced Pancreatic Cancer

BACKGROUND: Advanced, unresectable pancreatic cancer is an extremely aggressive disease. The 5-year survival rate for pancreatic cancer is only less than 5%. Current therapeutic options for patients with locally advanced or metastatic disease are limited. This analysis is a retrospective evaluation of the efficacy and toxicity of gemcitabine regimen as first-line chemotherapy in patients with advanced pancreatic cancer. METHODS: Seventeen chemotherapy-na ve patients with advanced or recurred pancreatic cancer were consecutively treated. Gemcitabine was diluted in normal saline and administered intravenously over 1 hour. Gemcitabine 1,000 mg/m2 was administered once weekly for 3 out of every 4 weeks. RESULTS: The median age of patients was 55 years (range 44~82 years). Based on RECIST criteria, there were 5 cases of stable disease (45%) and 6 cases of progressive disease (55%) among the 11 assessable patients. The median survival time was 189 days (range, 84 to 409 days), the 1 year survival rate was 18% in all 17 patients. Grade 3~4 toxic side effect was leucopenia only (29%) and was easily managed without infection. CONCLUSION: Gemcitabine is well tolerated, but has no objective response in advanced pancreatic cancer.