Ribonucleotide Reductase M1 Research Articles

Predictive and prognostic roles of ribonucleotide reductase M1 in pancreatic cancer: A Meta-analysis

Predictive and prognostic roles of ribonucleotide reductase M1 in pancreatic cancer: A Meta-analysis

RRM1 modulates mitotane activity in adrenal cancer cells interfering with its metabolization

The anti-proliferative activity of mitotane (o,p′DDD) in adrenocortical cancer is mediated by its metabolites o,p′DDE and o,p′DDA. We previously demonstrated a functional link between ribonucleotide reductase M1(RRM1) expression and o,p′DDD activity, but the mechanism is unknown. In this study we assessed the impact of RRM1 on the bioavailability and cytotoxic activity of o,p′DDD, o,p′DDE and o,p′DDA in SW13 and H295R cells. In H295R cells, mitotane and its metabolites showed a similar cytotoxicity and RRM1 expression was not influenced by any drug. In SW13 cells, o,p′DDA only showed a cytotoxic activity and did not modify RRM1 expression, whereas the lack of sensitivity to o,p′DDE was associated to RRM1 gene up-modulation, as already demonstrated for o,p′DDD. RRM1 silencing in SW13 cells increased the intracellular transformation of mitotane into o,p′DDE and o,p′DDA. These data demonstrate that RRM1 gene interferes with mitotane metabolism in adrenocortical cancer cells, as a possible mechanisms of drug resistance.

RRM2 (ribonucleotide reductase M2)

Ribonucleotide reductase subunit M2 (RRM2) is located in chromosome-2 p25-p24, converts ribonucleotides to deoxynucleotides which is required for DNA polymerization and repair. It has been shown that RMM2 plays a key role in DNA synthesis, cell growth, and drug resistance of cancer cells. There is accumulating evidence that alteration in the expression level of RRM2 can have a substantial impact on the biological characteristics of cancer cells, including tumor initiation and progression, suggesting its role as a prognostic factor and a possible therapeutic target for cancer therapy. Therefore, this review highlights several recent and clinically relevant aspects of the expression and function of RRM2 in human cancer.

Downregulation of thymidylate synthase and E2F1 by arsenic trioxide in mesothelioma.

Malignant pleural mesothelioma is a global health issue. Arsenic trioxide (ATO) has been shown to suppress thymidylate synthase (TYMS) in lung adenocarcinoma and colorectal cancer, and induce apoptosis in acute promyelocytic leukemia. With TYMS as a putative therapeutic target, the effect of ATO in mesothelioma was therefore studied. A panel of 5 mesothelioma cell lines was used to study the effect of ATO on cell viability, protein expression, mRNA expression and TYMS activity by MTT assay, western blot, qPCR and tritium-release assay, respectively. The knockdown of TYMS and E2F1 was performed with a specific siRNA. Phosphatidylserine externalization and mitochondrial membrane depolarization were measured by AnnexinV and JC-1 staining respectively. The invivo effect of ATO was studied using a nude mouse xenograft model. Application of ATO demonstrated anticancer effects in the cell line model with clinically achievable concentrations. Downregulation of TYMS protein (except H226 cells and 1.25µM ATO in H2052 cells) and mRNA expression (H28 cells), pRB1 (H28 cells) and E2F1 and TYMS activity (except H226 cells) were also evident. E2F1 knockdown decreased cell viability more significantly than TYMS knockdown. In general, thymidine kinase 1, ribonucleotide reductase M1, c-myc and skp2 were downregulated by ATO. p-c-Jun was downregulated in H28 cells while upregulated in 211H cells. Phosphatidylserine externalization, mitochondrial membrane depolarization, downregulation of Bcl-2 and Bcl-xL, and upregulation of Bak and cleaved caspase-3 were observed. In the H226 xenograft model, the relative tumor growth was aborted, and E2F1 was downregulated while cleaved caspase-3 was elevated and localized to the nucleus in the ATO treatment group. ATO has potent antiproliferative and cytotoxic effects in mesothelioma invitro and invivo, partially mediated through E2F1 targeting (less effect through TYMS targeting). There is sound scientific evidence to support the clinical application of ATO in treatment of mesothelioma.

Abstract 4227: The ribonucleotide reductase inhibitor Didox reverses tamoxifen resistance in breast cancer cells

Abstract Tamoxifen is the most prescribed endocrine therapy for estrogen receptor positive breast cancer patients. The emergence of endocrine resistance is a major hurdle in achieving a successful clinical outcome. Many advances have been made over the past few years to understand the biology of tamoxifen resistance. Activation of the AKT kinase is one of the primary mechanisms of intrinsic tamoxifen resistance. Previously, we reported that the Ribonucleotide Reductase M2 (RRM2) subunit is upregulated in AKT induced tamoxifen resistance and that inhibition of RRM2 by siRNA mediated interference reduces tamoxifen induced cell proliferation. In this study, we report that the inhibition of RRM2 by the small molecule inhibitor of ribonucleotide reductase activity Didox (3, 4-dihydroxybenzohydroxamic acid), significantly reduced tamoxifen induced cell proliferation in AKT overexpressing cells and tamoxifen resistant tumors generated by these cells. As well, Didox in combination with tamoxifen also inhibited cell proliferation in acquired tamoxifen resistant breast cancer cell lines. Employing comprehensive cell culture and in vivo models, we demonstrate that combining tamoxifen with Didox may reverse tamoxifen resistance in AKT expressing breast cancer cells. Citation Format: Khyati N. Shah, Howard L. Elford, Jesika S. Faridi. The ribonucleotide reductase inhibitor Didox reverses tamoxifen resistance in breast cancer cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4227. doi:10.1158/1538-7445.AM2014-4227

E2F1 downregulation by arsenic trioxide in lung adenocarcinoma.

Lung cancer is one of the most common cancers worldwide. Arsenic trioxide (ATO) has been approved by the US Food and Drug Administration for the treatment of acute promyelocytic leukemia. Nonetheless preliminary data have suggested potential activity of ATO in solid tumors including lung cancer. This study aimed to examine the underlying mechanisms of ATO in the treatment of lung adenocarcinoma. Using a panel of 7 lung adenocarcinoma cell lines, the effects of ATO treatment on cell viability, expression of E2F1 and its downstream targets, phosphatidylserine externalization, mitochondrial membrane depolarization and alteration of apoptotic/anti-apoptotic factors were studied. Tumor growth inhibition in vivo was investigated using a nude mouse xenograft model. ATO decreased cell viability with clinically achievable concentrations (8 µM) in all cell lines investigated. This was accompanied by reduced expression of E2F1, cyclin A2, skp2, c-myc, thymidine kinase and ribonucleotide reductase M1, while p-c-Jun was upregulated. Cell viability was significantly decreased with E2F1 knockdown. Treatment with ATO resulted in phosphatidylserine externalization in H23 cells and mitochondrial membrane depolarization in all cell lines, associated with truncation of Bid, downregulation of Bcl-2, upregulation of Bax and Bak, caspase-9 and -3 activation and PARP cleavage. Using the H358 xenograft model, the tumor growth was suppressed in the ATO treatment group during 8 days of treatment, associated with downregulation of E2F1 and upregulation of truncated Bid and cleaved caspase-3. In conclusion, ATO has potent in vitro and in vivo activity in lung adenocarcinoma, partially mediated through E2F1 downregulation and apoptosis.

A prospective study of biomarker-guided chemotherapy in patients with non-small cell lung cancer.

Purpose To assess the therapeutic value of biomarker-guided chemotherapy in patients with advanced non-small cell lung cancer (NSCLC).MethodsEighty-five NSCLC patients at stage IIIb or IV were divided into two groups based on the feasibility of biomarker analysis. Group A included patients with biomarker data (n = 41); Group B were patients without biomarker results (n = 44). Tumor samples obtained by fiberoptic bronchoscopy and computerized tomography-guided needle biopsy were analyzed by immunohistochemistry for intratumoral level of excision repair cross-complementing gene 1 (ERCC1), ribonucleotide reductase M1 (RRM1), and β-tubulin III. Chemotherapy regimens in Group A were determined according to the status of molecular signatures, whereas a standard gemcitabine plus cisplatin regimen was used for Group B. Tumor response, patient survival, and adverse effects were monitored for both groups.ResultsThe overall response rate, defined as complete response plus partial response, was 56.1 % for Group A, significantly higher than that in Group B (31.8 %; P = 0.024). The median progression-free survival (PFS) time was 5.2 months for Group A, significantly longer than that of Group B (4.1 months; P = 0.026). The 1-year survival rate of Group A was 65.9 %, significantly higher than that of Group B (40.9 %; P = 0.021), whereas the median overall survival times were 13.5 versus 12.5 months for Groups A and B, respectively (P = 0.483). The adverse effects in the two groups were essentially the same.ConclusionsBiomarker-tailored chemotherapy based on ERCC1, RRM1, and β-tubulin III expression showed significantly increased response rate, median PFS time, and 1-year survival rate in patients with NSCLC.

Molecular Profiling of Infiltrating Urothelial Carcinoma of Bladder and Nonbladder Origin

BackgroundInfiltrating UC represents the second most common genitourinary malignancy. Advanced UC has a poor prognosis and new treatments are needed. Molecular profiling of UC might identify biomarkers associated with targeted therapies or chemotherapeutics, providing physicians with new treatment options. Materials and MethodsFive hundred thirty-seven cases of locally advanced or metastatic UC of the bladder, 74 nonbladder, and 55 nonurothelial bladder cancers were profiled using mutation analysis, in situ hybridization, and immunohistochemistry assays for biomarkers predictive of therapy response. ResultsMolecular profiling of UC showed high overexpression of topoisomerase 2α, common phosphatidylinositol-4,5-bisphosphate 3-kinase, catalytic subunit alpha and/or phosophatase and tensin homolog (PTEN) alterations in nonbladder (27%) and bladder UC (21%), and rare gene mutations across subtypes. Compared with nonbladder, bladder UC consistently exhibited more frequent abnormal protein expression, including HER2 (10% vs. 3%; P = .04), tyrosine protein c-Kit receptor kinases (11% vs. 5%), c-Met proto-oncogene, receptor tyrosine kinases (25% vs. 8%), androgen receptor (16% vs. 6%), O(6)-methylguanine-methyltransferase (63% vs. 43%), ribonucleotide reductase M1 (32% vs. 11%), Serum protein acidic and rich in cysteine (SPARC) (69% vs. 33%), and topoisomerase 1 (63% vs. 39%). Bladder UC also exhibited increased amplification of HER2 (12% vs. 2%; P = .06). ConclusionComprehensive molecular profiling of UC identified a large number of biomarkers aberrations that might direct treatment in conventional chemotherapies and targeted therapies, not currently recommended in this population. As a group, bladder UC exhibited higher levels of actionable biomarkers, suggesting that UC from different primary sites and non-UC are driven by different molecular pathways. These differences could have clinical implications resulting in different treatment regimens depending on the site of origin of UC.

Primary identification of genomic markers of drug sensitivity for individualized therapy in 38 children with extracranial malignant solid tumors

Objective To identify the significance of genomic markers of drug sensitivity for individualized therapy in children with extracranial malignant solid tumors. Methods The surgical specimens and peripheral blood samples in 38 children with refractory extracranial malignant solid tumors were collected between Apri.2011 and Apri.2013.The genomic markers of anticancer drug sensitivity were examined, including gene expression or mutation of 15 chemotherapeutic agents and two targeted drugs by methods of immunohistochemical staining, enzyme linked immunosorbent assay, fluorescence in situ hybridization, polymerase chain reaction amplification and sequencing. Results Among all of 38 samples, 35 were firstly surgical specimens and 3 secondary surgical specimens, and 3 of them were peripheral blood samples.The tumor tissue of the targets for chemotherapeutic agents such as topoisomerase ⅡA (TOPO ⅡA) in 34 cases, Tubulinβ3 in 32 cases, excision repair cross-complementing 1 (ERCC1) in 28 cases, topoisomerase Ⅰ(TOPO Ⅰ) in 28 cases, O6-methylguanine-DNA methyltransferase (MGMT) in 20 cases, thymidylate synthase (TS) in 13 cases and ribonucleotide reductase M1 (RRM1)in 6 cases were examined.The 68.75% samples were fluo-rouracil and pemetrexed sensitivity, 66.67% samples gemcitabine sensitivity, 56.25% samples vincristine(VCR) sensitivity; while 67.65% had low sensitivity to anthracycline/etoposide, 64.29% had low sensitivity to platinum and topotecan/irinotecan; 63.64% had low sensitivity to temozolomide(TMZ). What's more, the peripheral blood of the targets for chemotherapeutic agents such as CYP2C9*3 genotypes in 33 cases and dihydrofolate reductase (DHFR C829T) genotypes in 14 cases were detected, and found that 100.00% and 93.33% of samples had cyclophosphamide and methotrexate sensitivity, respectively.Furthermore, peripheral blood was used to test the targets for chemotherapy toxicity and found that 100.00% of cyclophosphamide and methotrexate toxicity were weak, 76.19% of irinotecan and etoposide toxicity was weak.Additionally, tumor tissues of the genomic markers for targeted drugs, such as vascular endothe-lial growth factor receptor -2 (VEGFR-2) in 15 cases, epidermal growth factor receptor (EGFR) in 5 cases and intercellular cell adhesion molecule-1 in 10 cases, were examined.Up to 68.00% samples were detected sensitive to Bevacizumab.EGFR was not amplified in any case studied and Tyrosine kinase inhibitor response was invalid.On the basis of the above test results, therapeutic strategy for the patients who had unsatisfactory curative effect and then they achieved preliminary effect were promptly adjusted. Conclusions This study firstly examined the genomic markers of drug sensitivity in children with extracranial malignant solid tumors, which provide laboratory basis for individualized treatment selection and drug side effects prediction. Key words: Child; Extracranial malignant solid tumors; Genomic markers of drug sensitivity; Individualized therapy

Targeting the Warburg effect with a novel glucose transporter inhibitor to overcome gemcitabine resistance in pancreatic cancer cells.

Gemcitabine resistance remains a significant clinical challenge. Here, we used a novel glucose transporter (Glut) inhibitor, CG-5, as a proof-of-concept compound to investigate the therapeutic utility of targeting the Warburg effect to overcome gemcitabine resistance in pancreatic cancer. The effects of gemcitabine and/or CG-5 on viability, survival, glucose uptake and DNA damage were evaluated in gemcitabine-sensitive and gemcitabine-resistant pancreatic cancer cell lines. Mechanistic studies were conducted to determine the molecular basis of gemcitabine resistance and the mechanism of CG-5-induced sensitization to gemcitabine. The effects of CG-5 on gemcitabine sensitivity were investigated in a xenograft tumor model of gemcitabine-resistant pancreatic cancer. In contrast to gemcitabine-sensitive pancreatic cancer cells, the resistant Panc-1 and Panc-1(GemR) cells responded to gemcitabine by increasing the expression of ribonucleotide reductase M2 catalytic subunit (RRM2) through E2F1-mediated transcriptional activation. Acting as a pan-Glut inhibitor, CG-5 abrogated this gemcitabine-induced upregulation of RRM2 through decreased E2F1 expression, thereby enhancing gemcitabine-induced DNA damage and inhibition of cell survival. This CG-5-induced inhibition of E2F1 expression was mediated by the induction of a previously unreported E2F1-targeted microRNA, miR-520f. The addition of oral CG-5 to gemcitabine therapy caused greater suppression of Panc-1(GemR) xenograft tumor growth in vivo than either drug alone. Glut inhibition may be an effective strategy to enhance gemcitabine activity for the treatment of pancreatic cancer.

Targeting ribonucleotide reductase M2 subunit by small interfering RNA exerts anti-oncogenic effects in gastric adenocarcinoma.

Ribonucleotide reductase M2 subunit(RRM2) is one of the two subunits of human ribonucleotide reductase which plays a critical role in tumor progression. The aim of the present study was to analyze its expression, clinical significance and biological functions in gastric adenocarcinoma. We observed the upregulation of RRM2 mRNA and protein in all nine gastric cancer cell lines examined. In paired primary gastric cancers, both mRNA and protein levels of RRM2 were significantly upregulated in tumors compared with the corresponding non-tumorous gastric tissues. RRM2 protein expression correlated with higher tumor grade, advanced T stage and poor disease-specific survival. RRM2 knockdown in gastric cancer cell lines AGS, MKN1 and MKN28 significantly suppressed cell proliferation, inhibited monolayer colony formation, reduced cell invasion and induced apoptosis. Downregulation of RRM2 suppressed xenograft formation invivo. Collectively, these findings suggest that RRM2 plays a crucial role in gastric tumorigenesis and may serve as a potential prognostic marker and therapeutic target in gastric cancer.

The Expression of Ribonucleotide Reductase M2 in the Carcinogenesis of Uterine Cervix and Its Relationship with Clinicopathological Characteristics and Prognosis of Cancer Patients

BackgroundTo investigate the implication of ribonucleotide reductase M2 (RRM2) in the carcinogenesis of uterine cervix and its relationship with clinicopathological characteristics and prognosis of cancer patients.Methodology and Principal FindingsThe impact of RRM2 on cell viability was investigated in SiHa cervical cancer cells after RRM2 knockdown and the addition of cisplatin, which induces inter- and intra-strand DNA crosslinks. RRM2 immunoreactivity was evaluated by semi-quantitative H score among 29 normal, 30 low-grade dysplasia, 30 high-grade dysplasia and 103 invasive cancer tissue specimens of the uterine cervix, using tissue microarrays. RRM2 was then correlated with the clinicopathological variables of cervical cancer and patient survival. A greater toxic effect on cell viability using cisplatin was reflected by the greater reduction in RRM2 protein expression in SiHa cells. The RRM2 expression in cancer tissues was higher than that in high-grade dysplasia, low-grade dysplasia or normal cervical tissues. RRM2 upregulation was correlated with deep stromal invasion, large tumors and parametrial invasion and predicted poor survival.ConclusionsRRM2 is a new molecular marker for the diagnosis and clinical outcomes of cervical cancer. It is involved in cervical carcinogenesis and predicts poor survival, and may be a potential therapeutic target including in cisplatin treatment.

Ubiquitination and Degradation of Ribonucleotide Reductase M1 by the Polycomb Group Proteins RNF2 and Bmi1 and Cellular Response to Gemcitabine

Ribonucleotide reductase M1 (RRM1) is required for mammalian deoxyribonucleotide (dNTP) metabolism. It is the primary target of the antimetabolite drug gemcitabine, which is among the most efficacious and most widely used cancer therapeutics. Gemcitabine directly binds to RRM1 and irreversibly inactivates ribonucleotide reductase. Intra-tumoral RRM1 levels are predictive of gemcitabine’s therapeutic efficacy. The mechanisms that regulate intracellular RRM1 levels are largely unknown. Here, we identified the E3 ubiquitin-protein ligases RNF2 and Bmi1 to associate with RRM1 with subsequent poly-ubiquitination at either position 48 or 63 of ubiquitin. The lysine residues 224 and 548 of RRM1 were identified as major ubiquitination sites. We show that ubiquitinated RRM1 undergoes proteasome-mediated degradation and that targeted post-transcriptional silencing of RNF2 and Bmi1 results in increased RRM1 levels and resistance to gemcitabine. Immunohistochemical analyses of 187 early-stage lung cancer tumor specimens revealed a statistically significant co-expression of RRM1 and Bmi1. We were unable to identify suitable reagents for in situ quantification of RNF2. Our findings suggest that Bmi1 and possibly RNF2 may be attractive biomarkers of gemcitabine resistance in the context of RRM1 expression. They also provide novel information for the rational design of gemcitabine-proteasome inhibitor combination therapies, which so far have been unsuccessful if given to patients without taking the molecular context into account.

AKT-Induced Tamoxifen Resistance Is Overturned by RRM2 Inhibition

Acquired tamoxifen resistance develops in the majority of hormone-responsive breast cancers and frequently involves overexpression of the PI3K/AKT axis. Here, breast cancer cells with elevated endogenous AKT or overexpression of activated AKT exhibited tamoxifen-stimulated cell proliferation and enhanced cell motility. To gain mechanistic insight on AKT-induced endocrine resistance, gene expression profiling was performed to determine the transcripts that are differentially expressed post-tamoxifen therapy under conditions of AKT overexpression. Consistent with the biologic outcome, many of these transcripts function in cell proliferation and cell motility networks and were quantitatively validated in a larger panel of breast cancer cells. Moreover, ribonucleotide reductase M2 (RRM2) was revealed as a key contributor to AKT-induced tamoxifen resistance. Inhibition of RRM2 by RNA interference (RNAi)-mediated approaches significantly reversed the tamoxifen-resistant cell growth, inhibited cell motility, and activated DNA damage and proapoptotic pathways. In addition, treatment of tamoxifen-resistant breast cancer cells with the small molecule RRM inhibitor didox significantly reduced in vitro and in vivo growth. Thus, AKT-expressing breast cancer cells upregulate RRM2 expression, leading to increased DNA repair and protection from tamoxifen-induced apoptosis. These findings identify RRM2 as an AKT-regulated gene, which plays a role in tamoxifen resistance and may prove to be a novel target for effective diagnostic and preventative strategies.

ERCC1 and BRCA1 mRNA expressions are associated with clinical outcome of non-small cell lung cancer treated with platinum-based chemotherapy

We conducted a perspective study to investigate whether the expression of excision repair cross-complementing 1 (ERCC1), xeroderma pigmentosum group G (XPG), breast cancer 1 (BRCA1), and ribonucleotide reductase M1 (RRM1) is correlated with clinical outcome of non-small cell lung cancer (NSCLC). Patients with histologically confirmed inoperable stages IIIB and IV NSCLC were collected and followed up until January 2012. Relative cDNA quantification for ERCC1, XPG, BRCA1, and RRM1 was performed using a fluorescence-based, real-time detection method. Cox regression analysis indicated that a high level of ERCC1 was associated with shorter overall survival (OS) and progression-free survival (PFS) times when compared with low expression, with adjusted hazard ratios (HRs) (95% confidence interval (CI)) of 2.25 (1.18-4.39) and 2.63 (1.33-5.25), respectively. High expression of BRCA1 was correlated with shorter OS and PFS times when compared with low expression, and the adjusted HRs (95% CI) were 3.29 (1.72-6.39) and 5.94 (2.80-13.06), respectively. Moreover, we found a significant correlation between BRCA1 expression and age (χ(2) = 4.14, P = 0.04) and stage (χ(2) = 5.26, P = 0.02). Our results suggest that ERCC1 and BRCA1 mRNA expressions are associated with PFS and OS in advanced NSCLC patients treated with platinum-based chemotherapy.

The Conserved Lys-95 Charged Residue Cluster Is Critical for the Homodimerization and Enzyme Activity of Human Ribonucleotide Reductase Small Subunit M2

Ribonucleotide reductase (RR) catalyzes the reduction of ribonucleotides to deoxyribonucleotides for DNA synthesis. Human RR small subunit M2 exists in a homodimer form. However, the importance of the dimer form to the enzyme and the related mechanism remain unclear. In this study, we tried to identify the interfacial residues that may mediate the assembly of M2 homodimer by computational alanine scanning based on the x-ray crystal structure. Co-immunoprecipitation, size exclusion chromatography, and RR activity assays showed that the K95E mutation in M2 resulted in dimer disassembly and enzyme activity inhibition. In comparison, the charge-exchanging double mutation of K95E and E98K recovered the dimerization and activity. Structural comparisons suggested that a conserved cluster of charged residues, including Lys-95, Glu-98, Glu-105, and Glu-174, at the interface may function as an ionic lock for M2 homodimer. Although the measurements of the radical and iron contents showed that the monomer (the K95E mutant) was capable of generating the diiron and tyrosyl radical cofactor, co-immunoprecipitation and competitive enzyme inhibition assays indicated that the disassembly of M2 dimer reduced its interaction with the large subunit M1. In addition, the immunofluorescent and fusion protein-fluorescent imaging analyses showed that the dissociation of M2 dimer altered its subcellular localization. Finally, the transfection of the wild-type M2 but not the K95E mutant rescued the G1/S phase cell cycle arrest and cell growth inhibition caused by the siRNA knockdown of M2. Thus, the conserved Lys-95 charged residue cluster is critical for human RR M2 homodimerization, which is indispensable to constitute an active holoenzyme and function in cells.

Identification of ribonucleotide reductase M2 as a potential target for pro-senescence therapy in epithelial ovarian cancer

Epithelial ovarian cancer (EOC) is the leading cause of gynecological-related cancer deaths in the United States. There is, therefore, an urgent need to develop novel therapeutic strategies for this devastating disease. Cellular senescence is a state of stable cell growth arrest that acts as an important tumor suppression mechanism. Ribonucleotide reductase M2 (RRM2) plays a key role in regulating the senescence-associated cell growth arrest by controlling biogenesis of 2'-deoxyribonucleoside 5′-triphosphates (dNTPs). The role of RRM2 in EOC remains poorly understood. Here we show that RRM2 is expressed at higher levels in EOCs compared with either normal ovarian surface epithelium (P < 0.001) or fallopian tube epithelium (P < 0.001). RRM2 expression significantly correlates with the expression of Ki67, a marker of cell proliferation (P < 0.001). Moreover, RRM2 expression positively correlates with tumor grade and stage, and high RRM2 expression independently predicts a shorter overall survival in EOC patients (P < 0.001). To delineate the functional role of RRM2 in EOC, we knocked down RRM2 expression in a panel of EOC cell lines. Knockdown of RRM2 expression inhibits the growth of human EOC cells. Mechanistically, RRM2 knockdown triggers cellular senescence in these cells. Notably, this correlates with the induction of the DNA damage response, a known mediator of cellular senescence. These data suggest that targeting RRM2 in EOCs by suppressing its activity is a novel pro-senescence therapeutic strategy that has the potential to improve survival of EOC patients.

Ribonucleotide reductase M2 (RRM2; R2)

Ribonucleotide reductase M2 (RRM2; R2)

Inhibition of hepatocellular carcinoma growth using immunoliposomes for co-delivery of adriamycin and ribonucleotide reductase M2 siRNA

The chemotherapy combined with gene therapy has received great attention. We developed targeted LPD (liposome-polycation-DNA complex) conjugated with anti-EGFR (epidermal growth factor receptor) Fab' co-delivering adriamycin (ADR) and ribonucleotide reductase M2 (RRM2) siRNA (ADR-RRM2-TLPD), to achieve combined therapeutic effects in human hepatocellular carcinoma (HCC) overexpressing EGFR. The antitumor activity and mechanisms of ADR-RRM2-TLPD were investigated. The results showed that RRM2 expression was higher in HCC than in non-HCC tissue, and RRM2 siRNA inhibited HCC cell proliferation, suggesting that RRM2 is a candidate target for HCC therapy. ADR-RRM2-TLPD delivered ADR and RRM2 siRNA to EGFR overexpressing HCC cells specifically and efficiently both in vitro and in vivo, resulting in enhanced therapeutic effects (cytotoxicity, apoptosis and senescence-inducing activity) compared with single-drug loaded or non-targeted controls, including ADR-NC-TLPD (targeted LPD co-delivering ADR and negative control siRNA), RRM2-TLPD (targeted LPD delivering RRM2 siRNA) and ADR-RRM2-NTLPD (non-targeted LPD co-delivering ADR and RRM2 siRNA). Mechanism studies showed that p21 is involved in the combined therapeutic effect of ADR-RRM2-TLPD. The average weight of the orthotopic HCC in mice treated with ADR-RRM2-TLPD was significantly lighter than that of mice treated with other controls. Thus, ADR-RRM2-TLPD represents a potential strategy for combined therapy of HCC overexpressing EGFR.

Phase II trial of customized first line chemotherapy according to ERCC1 and RRM1 SNPs in patients with advanced non-small-cell lung cancer

ObjectivesCustomized chemotherapy has several advantages: patients are more likely to be treated with the most effective agents and can be spared the toxicity of ineffective drugs. Based on the literature, excision repair cross complementation group 1 (ERCC1) and ribonucleotide reductase M1 (RRM1) genes represent predictive biomarkers of response to platinum compound and gemcitabine, in NSCLC. Materials and methodsWe had planned a phase II trial (Simon design) to evaluate combination chemotherapy according to single nucleotide polymorphisms (SNPs) of ERCC1 (118T/C and 8092C/A) and RRM1 (−37C/A and −524T/C) in naïve patients affected by advanced NSCLC. ERCC1 and RRM1 SNPs assessment was performed in peripheral blood lymphocytes (PBLs). Combination chemotherapy was selected based on ERCC1 and RRM1 SNPs: we assume that patients with one or two C alleles at position 118 and with one or two A alleles at position 8092 in ERCC1 gene would correspond to Cisplatin non-responder and than with two A alleles at −37 and two C alleles at −524 in RRM1 gene to gemcitabine non-responder. Four schedules were provided: cisplatin+gemcitabine, cisplatin+docetaxel, gemcitabine+docetaxel; docetaxel+vinorelbine. Primary endpoint was overall response (ORR) in the intention-to-treat population. Results42 patients were enrolled from January 2010 to November 2011; 40 patients received at least 1 cycle of chemotherapy; median age was 66 years (range: 47–72); 36(90%) had stage IV, 4(10%) IIIB; 23(58%) had adenocarcinoma, 14(35%) squamous carcinoma. Twenty-five (62%) patients received treatment A, 3(8%) treatment B, 11(28%) treatment C, 1(23%) treatment D. ORR was 55%, analysis in squamous patients subgroups showed 71.4% ORR. The median follow-up was 19.7 months, PFS was 23 weeks (95% CI=15–26) and OS was 40.4 weeks (95% CI=32–55). Treatment was well tolerated. ConclusionWe observed an increase of ORR in NSCLC patients when they were treated with chemotherapy according to ERCC1 and RRM1 SNPs status.