Gemcitabine resistance mediated by ribonucleotide reductase M2 in lung squamous cell carcinoma is reversed by GW8510 through autophagy induction

Pharmacogenomic study of gemcitabine efficacy in patients with metastatic pancreatic cancer: A multicenter, prospective, observational cohort study (GENESECT study)

BACKGROUND

Genetic polymorphisms of molecules are known to cause individual differences in the therapeutic efficacy of anticancer drugs. However, to date, germline mutations (but not somatic mutations) for anticancer drugs have not been adequately studied. The objective of this study was to investigate the association between germline polymorphisms of gemcitabine metabolic and transporter genes with carbohydrate antigen 19-9 (CA 19-9) response (decrease ≥50% from the pretreatment level at 8 weeks) and overall survival (OS) in patients with metastatic pancreatic cancer who receive gemcitabine-based chemotherapy.

METHODS

This multicenter, prospective, observational study enrolled patients with metastatic pancreatic cancer patients who were receiving gemcitabine monotherapy or gemcitabine plus nanoparticle albumin-bound paclitaxel combination chemotherapy. Thirteen polymorphisms that may be involved in gemcitabine responsiveness were genotyped, and univariate and multivariate logistic regression analyses were used to determine the association of these genotypes with CA 19-9 response and OS. The significance level was set at 5%.

RESULTS

In total, 180 patients from 11 hospitals in Japan were registered, and 159 patients whose CA 19-9 response could be assessed were included in the final analysis. Patients who had a CA 19-9 response had significantly longer OS (372 vs. 241 days; p = .007). RRM1 2464A>G and RRM2 175T>G polymorphisms suggested a weak association with CA 19-9 response and OS, but it was not statistically significant. COX-2 -765G>C polymorphism did not significantly correlate with CA 19-9 response but was significantly associated with OS (hazard ratio, 2.031; p = .019).

CONCLUSIONS

Genetic polymorphisms from the pharmacokinetics of gemcitabine did not indicate a significant association with efficacy, but COX-2 polymorphisms involved in tumor cell proliferation might affect OS.

GINS2 promotes the progression of human HNSCC by altering RRM2 expression

INTRODUCTION

GINS2 exerts a carcinogenic effect in multiple human malignancies, while it is still unclear that the potential roles and underlying mechanisms of GINS2 in HNSCC.

METHODS

TCGA database was used to screen out genes with significant differences in expression in HNSCC. Immunohistochemistry and qRT-PCR were used to measure the expression of GINS2 in HNSCC tissues and cells. GINS2 was detected by qRT-PCR or western blot after knockdown or overexpression. Celigo cell counting, MTT, colony formation, and flow cytometric assay were used to check the ability of proliferation and apoptosis. Bioinformatics and microarray were used to screen out the downstream genes of GINS2.

RESULTS

GINS2 in HNSCC tissues and cells was up-regulated, which was correlated with poor prognosis. GINS2 gene expression was successfully inhibited and overexpressed in HNSCC cells. Knockdown of GINS2 could inhibit proliferation and increase apoptosis of cells. Meanwhile, overexpression of GINS2 could enhance cell proliferation and colony formation. Knockdown of RRM2 may inhibit HNSCC cell proliferation, while overexpression of RRM2 rescued the effect of reducing GINS2 expression.

CONCLUSION

Our study reported the role of GINS2 in HNSCC for the first time. The results demonstrated that in HNSCC cells, GINS2 promoted proliferation and inhibited apoptosis via altering RRM2 expression. Therefore, GINS2 might play a carcinogen in HNSCC, and become a specific promising therapeutic target.

Ribonucleotide reductase M2 (RRM2): Regulation, function and targeting strategy in human cancer

Ribonucleotide reductase M2 (RRM2) is a small subunit in ribonucleotide reductases, which participate in nucleotide metabolism and catalyze the conversion of nucleotides to deoxynucleotides, maintaining the dNTP pools for DNA biosynthesis, repair, and replication. RRM2 performs a critical role in the malignant biological behaviors of cancers. The structure, regulation, and function of RRM2 and its inhibitors were discussed. RRM2 gene can produce two transcripts encoding the same ORF. RRM2 expression is regulated at multiple levels during the processes from transcription to translation. Moreover, this gene is associated with resistance, regulated cell death, and tumor immunity. In order to develop and design inhibitors of RRM2, appropriate strategies can be adopted based on different mechanisms. Thus, a greater appreciation of the characteristics of RRM2 is a benefit for understanding tumorigenesis, resistance in cancer, and tumor microenvironment. Moreover, RRM2-targeted therapy will be more attention in future therapeutic approaches for enhancement of treatment effects and amelioration of the dismal prognosis.

RRM2‑mediated Wnt/β‑catenin signaling pathway activation in lung adenocarcinoma: A potential prognostic biomarker

The present study aimed to investigate the role and mechanism of action of ribonucleotide reductase M2 (RRM2) in lung adenocarcinoma and its potential as a therapeutic target. Data of patients with lung adenocarcinoma from The Cancer Genome Atlas database were collected and analyzed to evaluate the potential of RRM2 as a biomarker. The expression of RRM2 was evaluated in the A549 cell line and its cisplatin-resistant A549/DDP cell line derivative by western blot and reverse transcription-quantitative PCR. The study also investigated cell proliferation and the mechanism by which RRM2 controls cellular cisplatin resistance using CCK-8 and colony-formation assays. In addition, cell migration was assessed using Transwell assays, and the cell cycle and apoptosis were examined using flow cytometry. RRM2 was highly expressed in lung adenocarcinoma and was associated with the clinical TMN stage. Functional enrichment analysis showed that RRM2 was enriched in the cell cycle. Immune cell infiltration analysis identified 12 types of immune cell that exhibited differences between patients expressing different levels of RRM2. Cellular assays revealed higher levels of RRM2 expression in A549/DDP cells than A549 cells, and its expression was induced by cisplatin. RRM2 knockdown decreased cell proliferation and migration, accelerated apoptosis and caused cell cycle arrest in the S-phase, increasing the sensitivity of A549 and A549/DDP cells to cisplatin through the Wnt/β-catenin signaling pathway. Overexpression of β-catenin reduced the effects of RRM2 knockdown on A549 cells. Lung adenocarcinoma growth may be influenced by RRM2 through the Wnt/β-catenin signaling pathway, suggesting a potential pathway for cancer progression.

Molecular mechanism by which RRM2-inhibitor (cholagogue osalmid) plus bafilomycin A1 cause autophagic cell death in multiple myeloma

Despite significant improvement in the prognosis of multiple myeloma (MM), the disease remains incurable; thus, more effective therapies are required. Ribonucleoside-diphosphate reductase subunit M2 (RRM2) is significantly associated with drug resistance, rapid relapse, and poor prognosis. Previously, we found that 4-hydroxysalicylanilide (osalmid), a specific inhibitor of RRM2, exhibits anti-MM activity in vitro, in vivo, and in human patients; however, the mechanism remains unclear. Osalmid inhibits the translocation of RRM2 to the nucleus and stimulates autophagosome synthesis but inhibits subsequent autophagosome-lysosome fusion. We confirm that RRM2 binds to receptor-interacting protein kinase 3 (RIPK3) and reduces RIPK3, inhibiting autophagosome-lysosome fusion. Interestingly, the combination of osalmid and bafilomycin A1 (an autophagy inhibitor) depletes RIPK3 and aggravates p62 and autophagosome accumulation, leading to autophagic cell death. Combination therapy demonstrates synergistic cytotoxicity both in vitro and in vivo. Therefore, we propose that combining osalmid and bafilomycin A1(BafA1) may have clinical benefits against MM.

USP12 promotes nonsmall cell lung cancer progression through deubiquitinating and stabilizing RRM2

RRM2 is the catalytic subunit of ribonucleotide reductase (RNR), which catalyzes de novo synthesis of deoxyribonucleotide triphosphates (dNTPs) and plays critical roles in cancer cell proliferation. RRM2 protein level is controlled by ubiquitination mediated protein degradation system; however, its deubiquitinase has not been identified yet. Here we showed that ubiquitin-specific peptidase 12 (USP12) directly interacts with and deubiquitinates RRM2 in non-small cell lung cancer (NSCLC) cells. Knockdown of USP12 causes DNA replication stress and retards tumor growth in vivo and in vitro. Meanwhile, USP12 protein levels were positively correlated to RRM2 protein levels in human NSCLC tissues. In addition, high expression of USP12 was associated with poor prognosis in NSCLC patients. Therefore, our study reveals that USP12 is a RRM2 regulator and targeting USP12 could be considered as a potential therapeutical strategy for NSCLC treatment.

Chemoresistance Mechanisms in Non-Small Cell Lung Cancer-Opportunities for Drug Repurposing

Globally, lung cancer contributes significantly to the public health burden-associated mortality. As this form of cancer is insidious in nature, there is an inevitable diagnostic delay leading to chronic tumor development. Non-small cell lung cancer (NSCLC) constitutes 80-85% of all lung cancer cases, making this neoplasia form a prevalent subset of lung carcinoma. One of the most vital aspects for proper diagnosis, prognosis, and adequate therapy is the precise classification of non-small cell lung cancer based on biomarker expression profiling. This form of biomarker profiling has provided opportunities for improvements in patient stratification, mechanistic insights, and probable druggable targets. However, numerous patients have exhibited numerous toxic side effects, tumor relapse, and development of therapy-based chemoresistance. As a result of these exacting situations, there is a dire need for efficient and effective new cancer therapeutics. De novo drug development approach is a costly and tedious endeavor, with an increased attrition rate, attributed, in part, to toxicity-related issues. Drug repurposing, on the other hand, when combined with computer-assisted systems biology approach, provides alternatives to the discovery of new, efficacious, and safe drugs. Therefore, in this review, we focus on a comparison of the conventional therapy-based chemoresistance mechanisms with the repurposed anti-cancer drugs from three different classes-anti-parasitic, anti-depressants, and anti-psychotics for cancer treatment with a primary focus on NSCLC therapeutics. Certainly, amalgamating these novel therapeutic approaches with that of the conventional drug regimen in NSCLC-affected patients will possibly complement/synergize the existing therapeutic modalities. This approach has tremendous translational significance, since it can combat drug resistance and cytotoxicity-based side effects and provides a relatively new strategy for possible application in therapy of individuals with NSCLC.

High expression of RRM2 mediated by non-coding RNAs correlates with poor prognosis and tumor immune infiltration of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is known to have a poor prognosis. Accumulating evidence indicates that RRM2 plays a critical role in the occurrence and progression of multiple human cancers. However, the knowledge about RRM2 in HCC is still insufficient, and further research is needed. Here, we first analyzed the expression and prognosis of RRM2 using TCGA and GTEx data, and found that RRM2 may play a potential carcinogenic role in HCC. Then, through a series of comprehensive analysis, including expression analysis, correlation analysis or survival analysis, non-coding RNAs (ncRNAs) that regulate RRM2 overexpression were identified. Finally, MIR4435-2HG/CYTOR were observed to be the most promising upstream lncRNAs for the miR-125b-5p/RRM2 axis in HCC. In addition, RRM2 expression was significantly positively related to immune cell infiltration, immune cell biomarker or immune checkpoint expression in HCC. Altogether, the upregulation of RRM2 mediated by ncRNAs correlates with poor prognosis and tumor immune infiltration of HCC.

Cyclin-Dependent Kinase Inhibitors Function as Potential Immune Regulators via Inducing Pyroptosis in Triple Negative Breast Cancer

Background

Immunotherapy is the most promising treatment in triple-negative breast cancer (TNBC), and its efficiency is largely dependent on the intra-tumoral immune cells infiltrations. Thus, novel ways to assist immunotherapy by increasing immune cell infiltrations were highly desirable.

Methods

To find key immune-related genes and discover novel immune-evoking molecules, gene expression profiles of TNBC were downloaded from Gene Expression Omnibus (GEO). Single-sample gene set enrichment analysis (ssGSEA) and Weighted Gene Co-expression Network Analysis (WGCNA) were conducted to identified hub genes. The CMap database was used subsequently to predicate potential drugs that can modulate the overall hub gene expression network. In vitro experiments were conducted to assess the anti-tumor activity and the pyroptosis phenotypes induced by GW-8510.

Results

Gene expression profiles of 198 TNBC patients were downloaded from GEO dataset GSE76124, and ssGSEA was used to divide them into Immune Cell Proficiency (ICP) group and Immune Cell Deficiency (ICD) group. Hub differential expressed gene modules between two groups were identified by WGCNA and then annotated by Gene Ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis. A cyclin-dependent kinase (CDK) 2 inhibitor, GW-8510 was then identified by the CMap database and further investigated. Treatment with GW-8510 resulted in potent inhibition of TNBC cell lines. More importantly, in vitro and in vivo studies confirmed that GW-8510 and other CDK inhibitors (Dinaciclib, and Palbociclib) can induce pyroptosis by activating caspase-3 and GSDME, which might be the mechanism for their immune regulation potentials.

Conclusion

GW-8510, as well as other CDK inhibitors, might serve as potential immune regulators and pyroptosis promotors in TNBC.

RRM2 Mediates the Anti-Tumor Effect of the Natural Product Pectolinarigenin on Glioblastoma Through Promoting CDK1 Protein Degradation by Increasing Autophagic Flux

The natural product pectolinarigenin exerts anti-inflammatory activity and anti-tumor effects, and exhibits different biological functions, particularly in autophagy and cell cycle regulation. However, the antineoplastic effect of pectolinarigenin on glioblastoma (GBM) remains unclear. In the present study, we found that pectolinarigenin inhibits glioblastoma proliferation, increases autophagic flux, and induces cell cycle arrest by inhibiting ribonucleotide reductase subunit M2 (RRM2), which can be reversed by RRM2 overexpression plasmid. Additionally, pectolinarigenin promoted RRM2 protein degradation via autolysosome-dependent pathway by increasing autophagic flow. RRM2 knockdown promoted the degradation of CDK1 protein through autolysosome-dependent pathway by increasing autophagic flow, thereby inhibiting the proliferation of glioblastoma by inducing G2/M phase cell cycle arrest. Clinical data analysis revealed that RRM2 expression in glioma patients was inversely correlated with the overall survival. Collectively, pectolinarigenin promoted the degradation of CDK1 protein dependent on autolysosomal pathway through increasing autophagic flux by inhibiting RRM2, thereby inhibiting the proliferation of glioblastoma cells by inducing G2/M phase cell cycle arrest, and RRM2 may be a potential therapeutic target and a prognosis and predictive biomarker in GBM patients.

Comprehensive Analysis of Cell Cycle-Related Genes in Patients With Prostate Cancer

This study aimed to identify critical cell cycle-related genes (CCRGs) in prostate cancer (PRAD) and to evaluate the clinical prognostic value of the gene panel selected. Gene set variation analysis (GSVA) of dysregulated genes between PRAD and normal tissues demonstrated that the cell cycle-related pathways played vital roles in PRAD. Patients were classified into four clusters, which were associated with recurrence-free survival (RFS). Moreover, 200 prognostic-related genes were selected using the Kaplan-Meier (KM) survival analysis and univariable Cox regression. The prognostic CCRG risk score was constructed using random forest survival and multivariate regression Cox methods, and their efficiency was validated in Memorial Sloan Kettering Cancer Center (MSKCC) and GSE70770. We identified nine survival-related genes: CCNL2, CDCA5, KAT2A, CHTF18, SPC24, EME2, CDK5RAP3, CDC20, and PTTG1. Based on the median risk score, the patients were divided into two groups. Then the functional enrichment analyses, mutational profiles, immune components, estimated half-maximal inhibitory concentration (IC50), and candidate drugs were screened of these two groups. In addition, the characteristics of nine hub CCRGs were explored in Oncomine, cBioPortal, and the Human Protein Atlas (HPA) datasets. Finally, the expression profiles of these hub CCRGs were validated in RWPE-1 and three PRAD cell lines (PC-3, C4-2, and DU-145). In conclusion, our study systematically explored the role of CCRGs in PRAD and constructed a risk model that can predict the clinical prognosis and immunotherapeutic benefits.

Large-scale and high-resolution mass spectrometry-based proteomics profiling defines molecular subtypes of esophageal cancer for therapeutic targeting

Esophageal cancer (EC) is a type of aggressive cancer without clinically relevant molecular subtypes, hindering the development of effective strategies for treatment. To define molecular subtypes of EC, we perform mass spectrometry-based proteomic and phosphoproteomics profiling of EC tumors and adjacent non-tumor tissues, revealing a catalog of proteins and phosphosites that are dysregulated in ECs. The EC cohort is stratified into two molecular subtypes-S1 and S2-based on proteomic analysis, with the S2 subtype characterized by the upregulation of spliceosomal and ribosomal proteins, and being more aggressive. Moreover, we identify a subtype signature composed of ELOA and SCAF4, and construct a subtype diagnostic and prognostic model. Potential drugs are predicted for treating patients of S2 subtype, and three candidate drugs are validated to inhibit EC. Taken together, our proteomic analysis define molecular subtypes of EC, thus providing a potential therapeutic outlook for improving disease outcomes in patients with EC.

Diversity of structures and functions of oxo-bridged non-heme diiron proteins

Oxo-bridged diiron proteins are a distinct class of non-heme iron proteins. Their active sites are composed of two irons that are coordinated by amino acid side chains, and a bridging oxygen that interacts with each iron. These proteins are members of the ferritin superfamily and share the structural feature of a four α-helix bundle that provides the residues that coordinate the irons. The different proteins also display a wide range of structures and functions. A prototype of this family is hemerythrin, which functions as an oxygen transporter. Several other hemerythrin-like proteins have been described with a diversity of functions including oxygen and iron sensing, and catalytic activities. Rubrerythrins react with hydrogen peroxide and rubrerythrin-like proteins possess a rubredoxin domain, in addition to the oxo-bridged diiron center. Other redox enzymes with oxo-bridged irons include flavodiiron proteins that act as O₂ or NO reductases, ribonucleotide reductase and methane monooxygenase. Ferritins have an oxo-bridged diiron in the ferroxidase center of the protein, which plays a role in the iron storage function of these proteins. There are also bacterial ferritins that exhibit catalytic activities. The structures and functions of this broad class of oxo-bridged diiron proteins are described and compared in this review.

LncRNA MITA1 promotes gefitinib resistance by inducing autophagy in lung cancer cells

Lung cancer is a major health challenge worldwide. Gefitinib, a tyrosine kinase inhibitor (TKI), is the common therapeutic drug used in advanced non-small-cell lung cancer (NSCLC). However, it is eventually bound to face the problem of acquired drug resistance. In this work, we investigated the role of lncRNA MITA1 in the acquisition of gefitinib resistance in NSCLC and uncovered the possible underlying molecular mechanism of the same. Experiments were carried out using the HCC827 and HCC827GR cells. These were transfected with pcDNA-MITA1 or si-MITA1 and treated with gefitinib. Subsequently, lncRNA MITA1 mediated effect on cell viability and apoptosis were studied using the MTT and flow cytometry assays. Furthermore, using qRT-PCR, Western blotting, and immunofluorescence assays, the regulatory association between lncRNA MITA1 and markers of autophagy (LC3, Beclin-1, and p62) were examined by estimating their cellular protein levels. Also, these results were verified in the presence of an autophagy inhibitor bafilomycin A1. We found that MITA1 was highly upregulated in the gefitinib-resistant NSCLC cells, indicating the regulatory role of MITA1 in gefitinib resistance. Mechanistically, upregulated MITA1 led to gefitinib resistance by suppressing apoptosis, increasing cell viability, and inducing autophagy. Furthermore, these results were true when tested in the presence of bafilomycin A1. Our results suggest that MITA1 by inducing autophagy could be a key regulator of gefitinib resistance in NSCLC.

Mechanisms of resistance to chemotherapy in non-small cell lung cancer

Non-small cell lung cancer (NSCLC), which represents 80-85% of lung cancer cases, is one of the leading causes of human death worldwide. The majority of patients undergo an intensive and invasive treatment regimen, which may include radiotherapy, chemotherapy, targeted therapy, immunotherapy, or a combination of these, depending on disease stage and performance status. Despite advances in therapeutic regimens, the 5-year survival of NSCLC is approximately 20-30%, largely due to diagnosis at advanced stages. Conventional chemotherapy is still the standard treatment option for patients with NSCLC, especially those with advanced disease. However, the emergence of resistance to chemotherapeutic agents (chemoresistance) poses a significant obstacle to the management of patients with NSCLC. Therefore, to develop efficacious chemotherapeutic approaches for NSCLC, it is necessary to understand the mechanisms underlying chemoresistance. Several mechanisms are known to mediate chemoresistance. These include altered cellular targets for chemotherapy, decreased cellular drug concentrations, blockade of chemotherapy-induced cell cycle arrest and apoptosis, acquisition of epithelial-mesenchymal transition and cancer stem cell-like phenotypes, deregulated expression of microRNAs, epigenetic modulation, and the interaction with tumor microenvironments. In this review, we summarize the mechanisms underlying chemoresistance and tumor recurrence in NSCLC and discuss potential strategies to avoid or overcome chemoresistance.

Screening a Prognosis-Related Target Gene in Patients with HER-2-Positive Breast Cancer by Bioinformatics Analysis

OBJECTIVE

The objective of the present study was to determine a target gene and explore the molecular mechanisms involved in the pathogenesis of HER-2-positive breast cancer.

METHODS

Three RNA expression profiles obtained from the Gene Expression Omnibus (GEO) and the Cancer Genome Atlas (TCGA) were used to identify differentially expressed genes (DEGs) using the R software. A protein-protein interaction network was then constructed, and hub genes were determined. Subsequently, the relationship between clinical parameters and hub genes was examined to screen for target genes. Next, DNA methylation and genomic alterations of the target gene were evaluated. To further explore potential molecular mechanisms, a functional enrichment analysis of genes coexpressed with the target gene was performed.

RESULTS

The differential expression analysis revealed 217 DEGs in HER-2-positive breast cancer samples compared to normal breast tissues. RRM2 was the only hub gene closely associated with lymphatic metastasis and the patients' prognosis. Additionally, RRM2 was found to be consistently amplified and negatively associated with the level of methylation. Functional enrichment analysis showed that the coexpressed genes were mainly involved in cell cycle regulation.

CONCLUSIONS

RRM2 was identified as a target gene associated with the initiation, progression, and prognosis of HER-2-positive breast cancer, which may be considered as a new biomarker and therapeutic target.

A Novel Autophagy-Related IncRNAs Signature for Prognostic Prediction and Clinical Value in Patients With Pancreatic Cancer

Autophagy is an important bioprocess throughout the occurrence and development of cancer. However, the role of autophagy-related lncRNAs in pancreatic cancer (PC) remains obscure. In the study, we identified the autophagy-related lncRNAs (ARlncRNAs) and divided the PC patients from The Cancer Genome Atlas into training and validation set. Firstly, we constructed a signature in the training set by the least absolute shrinkage and selection operator penalized cox regression analysis and the multivariate cox regression analysis. Then, we validated the independent prognostic role of the risk signature in both training and validation set with survival analysis, receiver operating characteristic analysis, and Cox regression. The nomogram was established to demonstrate the predictive power of the signature. Moreover, high risk scores were significantly correlated to worse outcomes and severe clinical characteristics. The Pearson’s analysis between risk scores with immune cells infiltration, tumor mutation burden, and the expression level of chemotherapy target molecules indicated that the signature could predict efficacy of immunotherapy and targeted therapy. Next, we constructed an lncRNA–miRNA–mRNA regulatory network and identified several potential small molecule drugs in the Connectivity Map (CMap). What’s more, quantitative real-time PCR (qRT-PCR) analysis showed that serum LINC01559 could serve as a diagnostic biomarker. In vitro analysis showed inhibition of LINC01559 suppressed PC cell proliferation, migration, and invasion. Additionally, silencing LINC01559 suppressed gemcitabine-induced autophagy and promoted the sensitivity of PC cells to gemcitabine. In conclusion, we identified a novel ARlncRNAs signature with valuable clinical utility for reliable prognostic prediction and personalized treatment of PC patients. And inhibition of LINC01559 might be a novel strategy to overcome chemoresistance.

Inhibiting RRM2 to enhance the anticancer activity of chemotherapy

RRM2, the small subunit of ribonucleotide reductase, is identified as a tumor promotor and therapeutic target. It is common to see the overexpression of RRM2 in chemo-resistant cancer cells and patients. RRM2 mediates the resistance of many chemotherapeutic drugs and could become the predictor for chemosensitivity and prognosis. Therefore, inhibition of RRM2 may be an effective means to enhance the anticancer activity of chemotherapy. This review tries to discuss the mechanisms of RRM2 overexpression and the role of RRM2 in resistance to chemotherapy. Additionally, we compile the studies on small interfering RNA targets RRM2, RRM2 inhibitors, kinase inhibitors, and other ways that could overcome the resistance of chemotherapy or exert synergistic anticancer activity with chemotherapy through the expression inhibition or the enzyme inactivation of RRM2.

Downregulation of RRM2 Attenuates Retroperitoneal Liposarcoma Progression via the Akt/mTOR/4EBP1 Pathway: Clinical, Biological, and Therapeutic Significance

Background

Retroperitoneal liposarcoma (RLPS) is a rare tumor with high recurrence rate. Ribonucleotide reductase small subunit M2 (RRM2) protein is essential for DNA synthesis and replication. Our previous study has demonstrated that RRM2 downregulation inhibited the proliferation of RLPS cells, but further association between RRM2 and RLPS and relevant mechanisms remains to be explored.

Methods

RRM2 expression was evaluated in RLPS tumor tissues and cell lines by using real-time PCR and immunohistochemical analysis. The effect of RRM2 downregulation on cell proliferation, apoptosis, cell cycle, cell migration and invasion was tested by lentivirus. The effect of RRM2 inhibition on tumor growth in vivo was assessed by using patient-derived tumor xenograft (PDX) of RLPS and RRM2 inhibitor. The underlying mechanisms of RRM2 in RLPS were explored by protein microarray and Western blotting.

Results

The results showed that RRM2 mRNA expression was higher in RLPS tissues than in normal fatty tissues (P<0.001). RRM2 expression was higher in the dedifferentiated, myxoid/round cell, and pleomorphic subtypes (P=0.027), and it was also higher in the high-grade RLPS tissues compared to that in the low-grade RLPS tissues (P=0.004). There was no correlation between RRM2 expression and overall survival (OS) or disease-free survival (DFS) in this group of RLPS patients (P>0.05). RRM2 downregulation inhibited cell proliferation, promoted cell apoptosis, facilitated cell cycle from G1 phase to S phase and inhibited cell migration and invasion. Inhibition of RRM2 suppressed tumor growth in NOD/SCID mice. Protein microarray and Western blot verification showed that activity of Akt/mammalian target of rapamycin/eukaryotic translation initiation factor 4E binding protein 1 (Akt/mTOR/4EBP1) pathway was downregulated along with RRM2 downregulation.

Conclusion

RRM2 was overexpressed in RLPS tissues, and downregulation of RRM2 could inhibit RLPS progression. In addition, suppression of RRM2 is expected to be a promising treatment for RLPS patients.

Bisdemethoxycurcumin Enhances the Sensitivity of Non-small Cell Lung Cancer Cells to Icotinib via Dual Induction of Autophagy and Apoptosis

Non-small cell lung cancer (NSCLC) with epidermal growth factor receptor (EGFR) wild-type is intrinsic resistance to EGFR-tyrosine kinase inhibitors (TKIs). In this study, we assessed whether the combination of bisdemethoxycurcumin (BDMC) and icotinib could surmount primary EGFR-TKI resistance in NSCLC cells and investigated its molecular mechanism. Results showed that the combination of BDMC and icotinib produced potently synergistic growth inhibitory effect on primary EGFR-TKI-resistant NSCLC cell lines H460 (EGFR wild-type and K-ras mutation) and H1781 (EGFR wild-type and Her2 mutation). Compared with BDMC or icotinib alone, the two drug combination induced more significant apoptosis and autophagy via suppressing EGFR activity and interaction of Sp1 and HDCA1/HDCA2, which was accompanied by accumulation of reactive oxygen species (ROS), induction of DNA damage, and inhibition of cell migration and invasion. ROS inhibitor (NAC) and autophagy inhibitors (CQ or 3-MA) partially reversed BDMC plus icotinib-induced growth inhibitory effect on the NSCLC cells. Meanwhile, co-treatment with NAC attenuated the two drug combination-induced autophagy, apoptosis, DNA damage and decrease of cell migration and invasion ability. Also, 3-MA or CQ can abate the combination treatment-induced apoptosis and DNA damage, suggesting that there is crosstalk between different signaling pathways in the effect produced by the combination treatment. Our data indicate that BMDC has the potential to improve the treatment of primary EGFR-TKI resistant NISCLC that cannot be controlled with single-target agent, such as icotinib.

Curcumin overcome primary gefitinib resistance in non-small-cell lung cancer cells through inducing autophagy-related cell death

BACKGROUND

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) are being wildly used as target therapy in non-small-cell lung cancer (NSCLC). However, NSCLC patients with wild-type EGFR and KRAS mutation are primary resistant to EGFR-TKIs such as gefitinib. Curcumin has been known as a potential therapeutic agent for several major human cancers. In this study, we investigated the effect of curcumin on the reversal of gefitinib resistance in NSCLC cells as well as their molecular bases.

METHODS

H157 (wild-type EGFR and KARS mutation) and H1299 (wild-type EGFR and HRAS mutation) cells were treated with gefitinib or curcumin alone, or the two combination, and then cell viability, EGFR activity, expressions of Sp1 and Sp1-dependent proteins and receptor tyrosine kinases, markers of autophagy and apoptosis were examined by using CCK-8, colony formation, immunoblot, quantitative PCR, immunofluoscence, and flow cytometry assays. Also xenograft experiments were conduced to test the synergism of curcumin to gefitinib.

RESULTS

Our results showed that curcumin significantly enhanced inhibitory effect of gefitinib on primary gefitinib-resistant NSCLC cell lines H157 and H1299. Combination treatment with curcumin and gefitinib markedly downregulated EGFR activity through suppressing Sp1 and blocking interaction of Sp1 and HADC1, and markedly suppressed receptor tyrosine kinases as well as ERK/MEK and AKT/S6K pathways in the resistant NSCLC cells. Meanwhile, combination treatment of curcumin and gefitinib caused dramatic autophagy induction, autophagic cell death and autophagy-mediated apoptosis, compared to curcumin or gefitinib treatment alone, as evidenced by the findings that curcumin and gefitinib combination treatment-produced synergistic growth inhibition and apoptosis activation can be reversed by pharmacological autophagy inhibitors (Baf A1 or 3-MA) or knockdown of Beclin-1 or ATG7, also can be partially returned by pan-caspase inhibitor (Z-VAD-FMK) in H157 and H1299 cells. Xenograft experiments in vivo yielded similar results.

CONCLUSIONS

These data indicate that the synergism of curcumin on gefitinib was autophagy dependent. Curcumin can be used as a sensitizer to enhance the efficacy of EGFR-TKIs and overcome the EGFR-TKI resistance in NSCLC patients with wild-type EGFR and/or KRAS mutation.

SiRNA-Mediated RRM2 Gene Silencing Combined with Cisplatin in the Treatment of Epithelial Ovarian Cancer In Vivo: An Experimental Study of Nude Mice

Introduction: We aimed to explore small interfering (si)RNA silencing of ribonucleotide reductase M2 (RRM2) gene combined with cisplatin for the treatment of human ovarian cancer in nude mice models of subcutaneous transplantation of tumor cells. Methods: After conventional cultivation of human ovarian cancer cell line SKOV3 in vitro, SKOV3 cells were injected into the right back of nude mice by subcutaneous injection to establish the subcutaneous tumor models. Twenty-four tumor-burdened rats were randomly divided into four groups (n=6): siRNA group, siRNA in combination with cisplatin group, cisplatin group, and control group. Intraperitoneal injection of cisplatin and subcutaneous injection of siRNA were performed weekly. Tumor volume was measured, and tumor growth inhibition rate was calculated. RRM2 expression at the mRNA and protein levels was detected by reverse transcription-polymerase chain reaction and immunohistochemistry. Results: In the siRNA group, the tumor volume and tumor growth inhibition rate were 249.60±20.46 mm³ and 36.39%, respectively. The tumor growth inhibition rate and tumor volume were significantly different between the siRNA and control groups (p<0.05). In the cisplatin group, the tumor volume and tumor growth inhibition rate were 249.86±12.46 mm³ and 41.10%, respectively. The tumor growth inhibition rate and tumor volume were significantly different between the cisplatin and control groups (p<0.05). In the siRNA + cisplatin group, the tumor volume reduced to 180.84±16.25 mm³ and the tumor growth inhibition rate was increased to 64.33%, which were significantly different compared with the control group (p<0.01). Significant downregulation of RRM2 mRNA and protein expression in the tumor tissues was detected by reverse transcription polymerase chain reaction and immunohistochemistry assay (p<0.05). Discussion: siRNA alone or combined with cisplatin can effectively inhibit the growth of human ovarian cancer in nude mice models of subcutaneous transplantation of tumor cells. RRM2 gene silencing may be a potential treatment regimen for ovarian cancer in future.