In vivo induction of resistance to gemcitabine results in increased expression of ribonucleotide reductase subunit M1 as the major determinant

Aberrant transcription factors in the cancers of the pancreas

Transcription factors (TFs) are essential for proper activation of gene set during the process of organogenesis, differentiation, lineage specificity. Reactivation or dysregulation of TFs regulatory networks could lead to deformation of organs, diseases including various malignancies. Currently, understanding the mechanism of oncogenesis became necessity for the development of targeted therapeutic strategy for different cancer types. It is evident that many TFs go awry in cancers of the pancreas such as pancreatic ductal adenocarcinoma (PDAC) and pancreatic neuroendocrine neoplasms (PanNENs). These mutated or dysregulated TFs abnormally controls various signaling pathways in PDAC and PanNENs including RTK, PI3K-PTEN-AKT-mTOR, JNK, TGF-β/SMAD, WNT/β-catenin, SHH, NOTCH and VEGF which in turn regulate different hallmarks of cancer. Aberrant regulation of such pathways have been linked to the initiation, progression, metastasis, and resistance in pancreatic cancer. As of today, a number of TFs has been identified as crucial regulators of pancreatic cancer and a handful of them shown to have potential as therapeutic targets in pre-clinical and clinical settings. In this review, we have summarized the current knowledge on the role and therapeutic usefulness of TFs in PDAC and PanNENs.

Inhibitors of the Cancer Target Ribonucleotide Reductase, Past and Present

Ribonucleotide reductase (RR) is an essential multi-subunit enzyme found in all living organisms; it catalyzes the rate-limiting step in dNTP synthesis, namely, the conversion of ribonucleoside diphosphates to deoxyribonucleoside diphosphates. As expression levels of human RR (hRR) are high during cell replication, hRR has long been considered an attractive drug target for a range of proliferative diseases, including cancer. While there are many excellent reviews regarding the structure, function, and clinical importance of hRR, recent years have seen an increase in novel approaches to inhibiting hRR that merit an updated discussion of the existing inhibitors and strategies to target this enzyme. In this review, we discuss the mechanisms and clinical applications of classic nucleoside analog inhibitors of hRRM1 (large catalytic subunit), including gemcitabine and clofarabine, as well as inhibitors of the hRRM2 (free radical housing small subunit), including triapine and hydroxyurea. Additionally, we discuss novel approaches to targeting RR and the discovery of new classes of hRR inhibitors.

Association between TOP2A, RRM1, HER2, ERCC1 expression and response to chemotherapy in patients with non-muscle invasive bladder cancer

Purpose

This study aimed to detect the expression levels of topoisomerase IIα (TOP2A), ribonucleotide reductase catalytic subunit M1 (RRM1),c-erbB-2 (HER2) and excision repair cross complementing group 1 (ERCC1) in non-muscular invasive bladder cancer (NMIBC) and explore the correlation between the expression of these genes and NMBIC sensitivity to pirarubicin or gemcitabine treatment.

Materials and methods

NMIBC patient tissues and the bladder cancer cell lines BIU-87 and KK47 were selected for the exploration of drug sensitivity in vitro. Immunohistochemistry was used to examine protein expression in tissues. Reverse transcription-polymerase chain reaction (RT-qPCR) and a Western blot assay were used to detect the mRNA and protein levels in cells. The cell IC50 value was evaluated by an MTT assay. Flow cytometry was used to sort the cell subpopulations.

Results

In the pirarubicin-treated group, the patients with high TOP2A expression experienced lower recurrence rates than those with low TOP2A expression, whereas TOP2A and HER2 co-expression resulted in higher recurrence rates. The patients with low RRM1 expression, especially those with low ERCC1 expression, experienced lower recurrence rates than the patients with high RRM1 expression in the gemcitabine-treated group. Tumour cells with high TOP2A expression were highly sensitive to pirarubicin, and TOP2A⁺ HER2^- cells were more sensitive to pirarubicin than TOP2A⁺ HER2⁺ cells. Cells with low RRM1 expression levels were sensitive to gemcitabine, and RRM1⁻ERCC1^- cells were more sensitive to gemcitabine than RRM1⁻ERCC1⁺ cells.

Conclusion

High TOP2A expression or low RRM1 expression could predict the sensitivity of NMIBC to pirarubicin or gemcitabine treatment. HER2 and ERCC1 expression may affect the effect of TOP2A and RRM1, thus affecting the efficacy of chemotherapeutic drugs.

Resistance to Gemcitabine in Pancreatic Ductal Adenocarcinoma: A Physiopathologic and Pharmacologic Review

Pancreatic ductal adenocarcinoma (PDAC) is a very aggressive tumor with a poor prognosis and inadequate response to treatment. Many factors contribute to this therapeutic failure: lack of symptoms until the tumor reaches an advanced stage, leading to late diagnosis; early lymphatic and hematic spread; advanced age of patients; important development of a pro-tumoral and hyperfibrotic stroma; high genetic and metabolic heterogeneity; poor vascular supply; a highly acidic matrix; extreme hypoxia; and early development of resistance to the available therapeutic options. In most cases, the disease is silent for a long time, andwhen it does become symptomatic, it is too late for ablative surgery; this is one of the major reasons explaining the short survival associated with the disease. Even when surgery is possible, relapsesare frequent, andthe causes of this devastating picture are the low efficacy ofand early resistance to all known chemotherapeutic treatments. Thus, it is imperative to analyze the roots of this resistance in order to improve the benefits of therapy. PDAC chemoresistance is the final product of different, but to some extent, interconnected factors. Surgery, being the most adequate treatment for pancreatic cancer and the only one that in a few selected cases can achieve longer survival, is only possible in less than 20% of patients. Thus, the treatment burden relies on chemotherapy in mostcases. While the FOLFIRINOX scheme has a slightly longer overall survival, it also produces many more adverse eventsso that gemcitabine is still considered the first choice for treatment, especially in combination with other compounds/agents. This review discusses the multiple causes of gemcitabine resistance in PDAC.

Cytoplasmic RRM1 activation as an acute response to gemcitabine treatment is involved in drug resistance of pancreatic cancer cells

Background

RRM1 is functionally associated with DNA replication and DNA damage repair. However, the biological activity of RRM1 in pancreatic cancer remains undetermined.

Methods

To determine relationships between RRM1 expression and the prognosis of pancreatic cancer, and to explore RRM1 function in cancer biology, we investigated RRM1 expression levels in 121 pancreatic cancer patients by immunohistochemical staining and performed in vitro experiments to analyze the functional consequences of RRM1 expression.

Results

Patients with high RRM1 expression had significantly poorer clinical outcomes (overall survival; p = 0.006, disease-free survival; p = 0.0491). In particular, high RRM1 expression was also associated with poorer overall survival on adjuvant chemotherapy (p = 0.008). We found that RRM1 expression was increased 24 hours after exposure to gemcitabine and could be suppressed by histone acetyltransferase inhibition. RRM1 activation in response to gemcitabine exposure was induced mainly in the cytoplasm and cytoplasmic RRM1 activation was related to cancer cell viability. In contrast, cancer cells lacking cytoplasmic RRM1 activation were confirmed to show severe DNA damage. RRM1 inhibition with specific siRNA or hydroxyurea enhanced the cytotoxic effects of gemcitabine for pancreatic cancer cells.

Conclusions

Cytoplasmic RRM1 activation is involved in biological processes related to drug resistance in response to gemcitabine exposure and could be a potential target for pancreatic cancer treatment.

Chemotherapeutic drugs: Cell death- and resistance-related signaling pathways. Are they really as smart as the tumor cells?

Chemotherapeutic drugs kill cancer cells or control their progression all over the patient's body, while radiation- and surgery-based treatments perform in a particular site. Based on their mechanisms of action, they are classified into different groups, including alkylating substrates, antimetabolite agents, anti-tumor antibiotics, inhibitors of topoisomerase I and II, mitotic inhibitors, and finally, corticosteroids. Although chemotherapeutic drugs have brought about more life expectancy, two major and severe complications during chemotherapy are chemoresistance and tumor relapse. Therefore, we aimed to review the underlying intracellular signaling pathways involved in cell death and resistance in different chemotherapeutic drug families to clarify the shortcomings in the conventional single chemotherapy applications. Moreover, we have summarized the current combination chemotherapy applications, including numerous combined-, and encapsulated-combined-chemotherapeutic drugs. We further discussed the possibilities and applications of precision medicine, machine learning, next-generation sequencing (NGS), and whole-exome sequencing (WES) in promoting cancer immunotherapies. Finally, some of the recent clinical trials concerning the application of immunotherapies and combination chemotherapies were included as well, in order to provide a practical perspective toward the future of therapies in cancer cases.

STIM1 Mediates Calcium-Dependent Epigenetic Reprogramming in Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) displays a dismal prognosis due to late diagnosis and high chemoresistance incidence. For advanced disease stages or patients with comorbidities, treatment options are limited to gemcitabine alone or in combination with other drugs. While gemcitabine resistance has been widely attributed to the levels of one of its targets, RRM1, the molecular consequences of gemcitabine resistance in PDAC remain largely elusive. Here we sought to identify genomic, epigenomic, and transcriptomic events associated with gemcitabine resistance in PDAC and their potential clinical relevance. We found that gemcitabine-resistant cells displayed a coamplification of the adjacent RRM1 and STIM1 genes. Interestingly, RRM1, but not STIM1, was required for gemcitabine resistance, while high STIM1 levels caused an increase in cytosolic calcium concentration. Higher STIM1-dependent calcium influx led to an impaired endoplasmic reticulum stress response and a heightened nuclear factor of activated T-cell activity. Importantly, these findings were confirmed in patient and patient-derived xenograft samples. Taken together, our study uncovers previously unknown biologically relevant molecular properties of gemcitabine-resistant tumors, revealing an undescribed function of STIM1 as a rheostat directing the effects of calcium signaling and controlling epigenetic cell fate determination. It further reveals the potential benefit of targeting STIM1-controlled calcium signaling and its downstream effectors in PDAC. SIGNIFICANCE: Gemcitabine-resistant and some naïve tumors coamplify RRM1 and STIM1, which elicit gemcitabine resistance and induce a calcium signaling shift, promoting ER stress resistance and activation of NFAT signaling.

Y box binding protein 1 (YB-1) oncoprotein at the hub of DNA proliferation, damage and cancer progression

The Y Box binding protein 1 (YB-1) belongs to the highly conserved Cold Shock Domain protein family and is a major component of messenger ribonucleoprotein particles (mRNPs) in various organisms and cells. Cold Shock proteins are multifunctional nucleic acids binding proteins involved in a variety of cellular functions. Biological activities of YB-1 range from the regulation of transcription, splicing and translation, to the orchestration of exosomal RNA content. The role of YB-1 in malignant cell transformation and fate transition is the subject of intensive investigation. Besides, emerging evidence indicates that YB-1 participates in several DNA damage repair pathways as a non-canonical DNA repair factor thus pointing out that the protein can allow cancer cells to evade conventional anticancer therapies and avoid cell death. Here, we will attempt to collect and summarize the current knowledge on this subject and provide the basis for further lines of inquiry.

Comparison of the different mechanisms of cytotoxicity induced by checkpoint kinase I inhibitors when used as single agents or in combination with DNA damage

Inhibition of the DNA damage response is an emerging strategy to treat cancer. Understanding how DNA damage response inhibitors cause cytotoxicity in cancer cells is crucial to their further clinical development. This review focuses on three different mechanisms of cell killing by checkpoint kinase I inhibitors (CHK1i). DNA damage induced by chemotherapy drugs, such as topoisomerase I inhibitors, results in S and G2 phase arrest. Addition of CHK1i promotes cell cycle progression before repair is completed resulting in mitotic catastrophe. Ribonucleotide reductase inhibitors such as gemcitabine also arrest cells in S phase by preventing dNTP synthesis. Addition of CHK1i re-activates the DNA helicase to unwind DNA, but in the absence of dNTPs, this leads to excessive single-strand DNA that exceeds the protective capacity of the single-strand-binding protein RPA. Unprotected DNA is subjected to nuclease cleavage, resulting in replication catastrophe. CHK1i alone also kills a subset of cell lines through MRE11 and MUS81-mediated DNA cleavage in S phase cells. The choice of mechanism depends on the activation state of CDK2. Low level activation of CDK2 mediates helicase activation, cell cycle progression, and both replication and mitotic catastrophe. In contrast, high CDK2 activity is required for sensitivity to CHK1i as monotherapy. This high CDK2 activity threshold usually occurs late in the cell cycle to prepare for mitosis, but in CHK1i-sensitive cells, high activity can be attained in early S phase, resulting in DNA cleavage and cell death. This sensitivity to CHK1i has previously been associated with endogenous replication stress, but the dependence on high CDK2 activity, as well as MRE11, contradicts this hypothesis. The major unresolved question is why some cell lines fail to restrain their high CDK2 activity and hence succumb to CHK1i in S phase. Resolving this question will facilitate stratification of patients for treatment with CHK1i as monotherapy.

Development of gemcitabine-resistant patient-derived xenograft models of pancreatic ductal adenocarcinoma

AIM

Gemcitabine is a frontline agent for locally-advanced and metastatic pancreatic ductal adenocarcinoma (PDAC), but neither gemcitabine alone nor in combination produces durable remissions of this tumor type. We developed three PDAC patient-derived xenograft (PDX) models with gemcitabine resistance (gemR) acquired in vivo, with which to identify mechanisms of resistance relevant to drug exposure in vivo and to evaluate novel therapies.

METHODS

Mice bearing independently-derived PDXs received 100 mg/kg gemcitabine once or twice weekly. Tumors initially responded, but regrew on treatment and were designated gemR. We used immunohistochemistry to compare expression of proteins previously associated with gemcitabine resistance [ribonucleotide reductase subunit M1 (RRM1), RRM2, human concentrative nucleoside transporter 1 (hCNT1), human equilibrative nucleoside transporter 1 (hENT1), cytidine deaminase (CDA), and deoxycytidine kinase (dCK)] in gemR and respective gemcitabine-naive parental tumors.

RESULTS

Parental and gemR tumors did not differ in tumor cell morphology, amount of tumor-associated stroma, or expression of stem cell markers. No consistent pattern of expression of the six gemR marker proteins was observed among the models. Increases in RRM1 and CDA were consistent with in vitro-derived gemR models. However, rather than the expected decreases of hCNT1, hENT1, and dCK, gemR tumors expressed no change in or higher levels of these gemR marker proteins than parental tumors.

CONCLUSION

These models are the first PDAC PDX models with gemcitabine resistance acquired in vivo. The data indicate that mechanisms identified in models with resistance acquired in vitro are unlikely to be the predominant mechanisms when resistance is acquired in vivo. Ongoing work focuses on characterizing unidentified mechanisms of gemR and on identifying agents with anti-tumor efficacy in these gemR models.

Identification of chemoresistance-related mRNAs based on gemcitabine-resistant pancreatic cancer cell lines

Gemcitabine (GEM) alone and GEM-based chemotherapy are the preferred regimens for treating advanced unresectable and metastatic pancreatic cancer (PC). However, these treatments have limited efficacy due to acquired resistance of cancer cells to chemotherapy, the mechanisms of which are not fully understood. In this study, we established two stable multidrug-resistant cell lines, BxPC-3-GR and CFPAC-1-GR, from their corresponding parental cells through exposure to GEM following a stepwise incremental dosing strategy. The GEM IC₅₀ values of BxPC-3-GR and CFPAC-1-GR increased 112-fold and 210-fold, respectively, compared to parental cell lines. In vitro and in vivo experiments confirmed that both GEM-resistant cell subgroups declined in proliferative capacity, but were more resistant to GEM. Unlike CFPAC-1-GR, BxPC-3-GR exhibited enhanced migratory and invasive properties compared with BxPC-3 in vitro. We also compared differentially expressed mRNA profiles between parental and GEM-resistant cells using transcriptome sequencing. RRM1, STIM1, and TRIM21 were significantly upregulated in both GEM-resistant cell lines and confirmed to be associated with the degree of GEM resistance by quantitative reverse-transcription polymerase chain reaction and western blot analysis. These three genes were more highly expressed in PC tissues and potentially regarded as prognostic biomarkers through database mining. Thus, our findings provide chemo-resistant cell models to better understand the underlying mechanisms of chemoresistance, and to explore potential biomarkers for GEM response in PC patients.

CX-5461 Inhibits Pancreatic Ductal Adenocarcinoma Cell Growth, Migration and Induces DNA Damage

Background: Inhibition of ribosome biogenesis has recently emerged as a promising strategy for the treatment of metastatic tumors. The RNA polymerase I inhibitor CX-5461 has shown efficacy in a panel of cancer types and is currently being tested in clinical trials. However, further preclinical studies to unravel molecular mechanisms underlying the activity of this drug are warranted. Methods: In this study, we have investigated the effects of CX-5461 on cell growth and migration of pancreatic cancer cells by the sulforhodamine-B and wound healing assay, respectively. Furthermore, we assessed the expression of epithelial-to-mesenchymal transition (EMT) genes by qRT-PCR, while protein expression of DNA damage marker phospho-H2A.X was studied by Western blot and immunofluorescence. Results: CX-5461 inhibits pancreatic cancer cell growth in the nanomolar range and inhibits the migratory capability of the cells. Additionally, CX-5461 induced expression of EMT factor SNAI1 and caused DNA double-strand breaks as measured by increased expression of phospho-H2A.X. Conclusion: This study demonstrated that CX-5461 is active against pancreatic cancer cells and modulation of EMT factors, as well as increased expression of phospho-H2A.X, support further pre-/clinical investigations, including the analyses of these markers.

RRM1 predicts clinical outcome of high-and intermediate-risk non-muscle-invasive bladder cancer patients treated with intravesical gemcitabine monotherapy

Background

The expression level of ribonucleotide reductase subunit M1 (RRM1) is closely related to the effect of gemcitabine-based therapy in advanced bladder cancer. However, the value of RRM1 expression in predicting progression-free survival in non-muscle-invasive bladder cancer (NMIBC) patients treated with intravesical gemcitabine chemotherapy has not been elucidated.

Methods

This study randomly assigned 162 patients to either the RRM1-known group or the unknown group. We collected cancer tissues from 81 patients to evaluate the mRNA expression of RRM1 by using liquid chip technology. All patients were diagnosed and then treated with intravesical gemcitabine monotherapy immediately after transurethral resection of the bladder tumour (TURBT).

Results

RRM1 expression was high in 21% (17/81) of patients. The RRM1 mRNA level was not correlated with sex, age, weight, performance status, or CUA/EAU risk (p > 0.05). Progression-free survival (PFS) was significantly longer for patients with low RRM1 expression than for patients with high and unknown RRM1 expression (p = 0.009). Additionally, the 1- and 2-year relapse rates also differed according to RRM1 expression level. The 1-year relapse rates for RRM1-low, RRM1-high and RRM1-unknown patients were 0, 17.7 and 6.2% (p = 0.009), while the 2-year relapse rates for these groups were 3.1, 29.4, and 11.1% (p = 0.005), respectively.

Conclusions

This preliminary study showed that low RRM1 expression was associated with longer progression-free survival and lower 1-year/2-year relapse rates in NMIBC patients treated with intravesical gemcitabine monotherapy, despite the need for further verification with large sample sizes and considering more mixed factors and biases.

Oncolytic Ad co-expressing decorin and Wnt decoy receptor overcomes chemoresistance of desmoplastic tumor through degradation of ECM and inhibition of EMT

Pancreatic cancer is a highly lethal disease. Excessive accumulation of tumor extracellular matrix (ECM) and epithelial-to-mesenchymal transition (EMT) phenotype are two main contributors to drug resistance in desmoplastic pancreatic tumors. To overcome desmoplasia and chemoresistance of pancreatic cancer, we utilized an oncolytic adenovirus (Ad) co-expressing decorin and soluble Wnt decoy receptor (HEmT-DCN/sLRP6). An orthotopic pancreatic xenograft tumor model was established in athymic nude mice using Mia PaCa-2 cells, and the antimetastatic and antitumor efficacy of systemically administered HEmT-DCN/sLRP6 was evaluated. Immunohistochemical analysis of tumor tissues was performed to assess ECM degradation, induction of apoptosis, viral dispersion, and inhibition of the Wnt/β-catenin signaling pathway. HEmT-DCN/sLRP6 effectively degraded tumor ECM and inhibited EMT, leading to enhanced viral distribution, induction of apoptosis, and attenuation of tumor cell proliferation in tumor tissue. HEmT-DCN/sLRP6 prevented metastasis of pancreatic cancer. Importantly, HEmT-DCN/sLRP6 sensitized pancreatic tumor to gemcitabine treatment. Furthermore, HEmT-DCN/sLRP6 augmented drug penetration and dispersion within pancreatic tumor xenografts and patient-derived tumor spheroids. Collectively, these results illustrate that HEmT-DCN/sLRP6 can enhance the dispersion of both oncolytic Ad and a chemotherapeutic agent in chemoresistant and desmoplastic pancreatic tumor, effectively overcoming the preexisting limitations of standard treatments.

[Silencing RRM1 gene reverses paclitaxel resistance in human breast cancer cell line MCF- 7/R by inducing cell apoptosis]

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 IC₅₀ 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 (P < 0.01). Transfection with the specific siRNAs significantly reduced the expression of RRM1 in MCF-7/R cells (P < 0.05), which showed a significantly lower IC₅₀ value of paclitaxel than the cells transfected with the negative control siRNA (P < 0.05). RRM1 silencing significantly inhibited the proliferation (P < 0.01) and enhanced the apoptosis-inducing effect of paclitaxel in MCF-7/R cells (P < 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 (P < 0.001).

CONCLUSIONS

RRM1 gene silencing can reverse paclitaxel resistance in human breast cancer cell line MCF-7/R by promoting cell apoptosis.

Role of hepatocyte nuclear factor 4 alpha in cell proliferation and gemcitabine resistance in pancreatic adenocarcinoma

Background

Hepatocyte nuclear factor 4α (HNF4α) is a tissue-specific transcription factor that regulates the expression of numerous genes in hepatocytes and pancreatic β cells. HNF4α has been reported to affect cell proliferation and chemoresistance in several cancers. However, the role of HNF4α in pancreatic adenocarcinoma (PDAC) has not been studied extensively and remains unclear.

Methods

By utilizing immunohistochemical (IHC) staining, we measured the expression of HNF4α in PDAC tissues. By silencing HNF4α in PDAC cell lines, we assessed the impact of HNF4α on pancreatic cancer cell proliferation and gemcitabine sensitivity. We used CCK8 and colony formation assays to examine the effect of HNF4α on cell proliferation. A flow cytometry assay was used to assess cell apoptosis. The expression of gemcitabine-related genes was detected by quantitative real‑time PCR (qRT-PCR) and Western blotting. IHC was utilized to assess the correlation between HNF4α and human equilibrative nucleoside transporter 1 (hENT1) expression in PDAC patients. Chromatin immunoprecipitation (ChIP) and dual‑luciferase reporter assays were used to confirm that hENT1 is a target gene of HNF4α.

Results

Increased HNF4α expression was detected in PDAC tissues; patients with higher HNF4α expression displayed worse prognosis. To elucidate the function of HNF4α, we examined its role in pancreatic cancer cell proliferation, apoptosis and gemcitabine resistance. In HNF4α-silenced Capan-1 and MiaPaCa-2 cells, we observed decreased cell proliferation and increased sensitivity to gemcitabine compared to those of controls. The mechanism of HNF4α in gemcitabine-related chemosensitivity was then explored. In response to HNF4α silencing, the expression levels of gemcitabine-related proteins, hENT1 and deoxycytidine kinase (dCK) were significantly increased. Additionally, hENT1 was negatively correlated with HNF4α in PDAC tissue samples. Moreover, we identified hENT1 as a downstream target of HNF4α.

Conclusion

HNF4α is a prognostic marker for overall survival, is required for pancreatic cancer cell proliferation and promotes resistance to gemcitabine by downregulating hENT1. Therefore, targeting HNF4α might reverse gemcitabine resistance and provide novel treatment strategies for PDAC.

Electronic supplementary material

The online version of this article (10.1186/s12935-019-0767-4) contains supplementary material, which is available to authorized users.

GPR55 signalling promotes proliferation of pancreatic cancer cells and tumour growth in mice, and its inhibition increases effects of gemcitabine

The life expectancy for pancreatic cancer patients has seen no substantial changes in the last 40 years as very few and mostly just palliative treatments are available. As the five years survival rate remains around 5%, the identification of novel pharmacological targets and development of new therapeutic strategies are urgently needed. Here we demonstrate that inhibition of the G protein-coupled receptor GPR55, using genetic and pharmacological approaches, reduces pancreatic cancer cell growth in vitro and in vivo and we propose that this may represent a novel strategy to inhibit pancreatic ductal adenocarcinoma (PDAC) progression. Specifically, we show that genetic ablation of Gpr55 in the KRASWT/G12D/TP53WT/R172H/Pdx1-Cre+/+ (KPC) mouse model of PDAC significantly prolonged survival. Importantly, KPC mice treated with a combination of the GPR55 antagonist Cannabidiol (CBD) and gemcitabine (GEM, one of the most used drugs to treat PDAC), survived nearly three times longer compared to mice treated with vehicle or GEM alone. Mechanistically, knockdown or pharmacologic inhibition of GPR55 reduced anchorage-dependent and independent growth, cell cycle progression, activation of mitogen-activated protein kinase (MAPK) signalling and protein levels of ribonucleotide reductases in PDAC cells. Consistent with this, genetic ablation of Gpr55 reduced proliferation of tumour cells, MAPK signalling and ribonucleotide reductase M1 levels in KPC mice. Combination of CBD and GEM inhibited tumour cell proliferation in KPC mice and it opposed mechanisms involved in development of resistance to GEM in vitro and in vivo. Finally, we demonstrate that the tumour suppressor p53 regulates GPR55 protein expression through modulation of the microRNA miR34b-3p. Our results demonstrate the important role played by GPR55 downstream of p53 in PDAC progression. Moreover our data indicate that combination of CBD and GEM, both currently approved for medical use, might be tested in clinical trials as a novel promising treatment to improve PDAC patients' outcome.

RRM1 expression and the clinicopathological characteristics of patients with non-small cell lung cancer treated with gemcitabine

Background

The usefulness of ribonucleotide reductase catalytic subunit M1 (RRM1) for predicting the therapeutic effects of gemcitabine-containing chemotherapy in patients with non-small cell lung cancer (NSCLC) remains controversial. RRM1-positive patients show unique clinicopathological features.

Methods

Here, we performed a meta-analysis to systematically evaluate the relationship between RRM1 expression and the clinicopathological characteristics of NSCLC patients treated with gemcitabine-containing regimens. A comprehensive electronic and manual search was performed to identify relevant articles. The pooled relative risk (RR) and 95% CI were used to estimate the relation between the clinicopathological characteristics of NSCLC patients and RRM1 expression.

Results

The study included 31 observational studies and 3,667 patients. The analysis showed no significant association between RRM1 expression and pathological type, stage, and smoking status; however, RRM1 positivity was significantly lower in women than in men (43.0% vs 51.7%, RR=0.84, 95% CI: 0.74-0.94, P=0.004).

Conclusion

The present pooled analyses demonstrated that RRM1 positivity in women with advanced NSCLC was associated with a higher rate of response to gemcitabine-containing regimens. Immunohistochemistry may be valuable to prescreen for RRM1 expression in clinical practice, whereas PCR can be routinely used as a verification method. These findings will help design suitable molecular-targeted therapies for NSCLC.

Nucleobase and Nucleoside Analogues: Resistance and Re-Sensitisation at the Level of Pharmacokinetics, Pharmacodynamics and Metabolism

Antimetabolites, in particular nucleobase and nucleoside analogues, are cytotoxic drugs that, starting from the small field of paediatric oncology, in combination with other chemotherapeutics, have revolutionised clinical oncology and transformed cancer into a curable disease. However, even though combination chemotherapy, together with radiation, surgery and immunotherapy, can nowadays cure almost all types of cancer, we still fail to achieve this for a substantial proportion of patients. The understanding of differences in metabolism, pharmacokinetics, pharmacodynamics, and tumour biology between patients that can be cured and patients that cannot, builds the scientific basis for rational therapy improvements. Here, we summarise current knowledge of how tumour-specific and patient-specific factors can dictate resistance to nucleobase/nucleoside analogues, and which strategies of re-sensitisation exist. We revisit well-established hurdles to treatment efficacy, like the blood-brain barrier and reduced deoxycytidine kinase activity, but will also discuss the role of novel resistance factors, such as SAMHD1. A comprehensive appreciation of the complex mechanisms that underpin the failure of chemotherapy will hopefully inform future strategies of personalised medicine.

Quantification and expert evaluation of evidence for chemopredictive biomarkers to personalize cancer treatment

Predictive biomarkers have the potential to facilitate cancer precision medicine by guiding the optimal choice of therapies for patients. However, clinicians are faced with an enormous volume of often-contradictory evidence regarding the therapeutic context of chemopredictive biomarkers.

We extensively surveyed public literature to systematically review the predictive effect of 7 biomarkers claimed to predict response to various chemotherapy drugs: ERCC1-platinums, RRM1-gemcitabine, TYMS-5-fluorouracil/Capecitabine, TUBB3-taxanes, MGMT-temozolomide, TOP1-irinotecan/topotecan, and TOP2A-anthracyclines. We focused on studies that investigated changes in gene or protein expression as predictors of drug sensitivity or resistance. We considered an evidence framework that ranked studies from high level I evidence for randomized controlled trials to low level IV evidence for pre-clinical studies and patient case studies.

We found that further in-depth analysis will be required to explore methodological issues, inconsistencies between studies, and tumor specific effects present even within high evidence level studies. Some of these nuances will lend themselves to automation, others will require manual curation. However, the comprehensive cataloging and analysis of dispersed public data utilizing an evidence framework provides a high level perspective on clinical actionability of these protein biomarkers. This framework and perspective will ultimately facilitate clinical trial design as well as therapeutic decision-making for individual patients.

Superresolution imaging of individual replication forks reveals unexpected prodrug resistance mechanism

Many drugs require extensive metabolism en route to their targets. High-resolution visualization of prodrug metabolism should therefore utilize analogs containing a small modification that does not interfere with its metabolism or mode of action. In addition to serving as mechanistic probes, such analogs provide candidates for theranostics when applied in both therapeutic and diagnostic modalities. Here a traceable mimic of the widely used anticancer prodrug cytarabine (ara-C) was generated by converting a single hydroxyl group to azide, giving "AzC." This compound exhibited the same biological profile as ara-C in cell cultures and zebrafish larvae. Using azide-alkyne "click" reactions, we uncovered an apparent contradiction: drug-resistant cells incorporated relatively large quantities of AzC into their genomes and entered S-phase arrest, whereas drug-sensitive cells incorporated only small quantities of AzC. Fluorescence microscopy was used to elucidate structural features associated with drug resistance by characterizing the architectures of stalled DNA replication foci containing AzC, EdU, γH2AX, and proliferating cell nuclear antigen (PCNA). Three-color superresolution imaging revealed replication foci containing one, two, or three partially resolved replication forks. Upon removing AzC from the media, resumption of DNA synthesis and completion of the cell cycle occurred before complete removal of AzC from genomes in vitro and in vivo. These results revealed an important mechanism for the low toxicity of ara-C toward normal tissues and drug-resistant cancer cells, where its efficient incorporation into DNA gives rise to highly stable, stalled replication forks that limit further incorporation of the drug, yet allow for the resumption of DNA synthesis and cellular division following treatment.

Nimbolide reduces CD44 positive cell population and induces mitochondrial apoptosis in pancreatic cancer cells

Pancreatic ductal adenocarcinoma (PDAC) is highly aggressive disease and current treatment regimens fail to effectively cure PDAC. Development of resistance to current therapy is one of the key reasons for this outcome. Nimbolide (NL), a triterpenoid obtained from Azadirachta indica, exhibits anticancer properties in various cancer including PDAC cells. However, the underlying mechanism of this anticancer agent in PDAC cells remains undefined. We show that NL exerts a higher level of apoptotic cell death compared to the first-line agent gemcitabine for PDAC, as well as other anticancer agents including sorafenib and curcumin. The anticancer efficacy of NL was further evidenced by a reduction in the CD44⁺ as well as cancer stem-like cell (CSC) population, as it causes decreased sphere formation. Mechanistically, the anticancer efficacy of NL associates with reduced mutant p53 as well as increased mitochondrial activity in the form of increased mitochondrial reactive oxygen species and mitochondrial mass. Together, this study highlights the therapeutic potential of NL in mutant p53 expressing pancreatic cancer.

Cytolytic virus activation therapy and treatment monitoring for Epstein-Barr virus associated nasopharyngeal carcinoma in a mouse tumor model

Undifferentiated nasopharyngeal carcinoma (NPC) is 100% associated with Epstein‐Barr virus (EBV). Expression of viral proteins in the tumor cells is highly restricted. EBV reactivation by CytoLytic Virus Activation (CLVA) therapy triggers de novo expression of early viral kinases (PK and TK) and uses antiviral treatment to kill activated cells. The mechanism of tumor elimination by CLVA was analyzed in NPC mouse model using C666.1 cells. Valproic acid (VPA) was combined with gemcitabine (GCb) to stimulate EBV reactivation, followed by antiviral treatment with ganciclovir (GCV). A single cycle of CLVA treatment resulted in specific tumor cell killing as indicated by reduced tumor volume, loss of EBV‐positive cells in situ, and paralleled by decreased EBV DNA levels in circulation, which was more pronounced than treatment with GCb alone. In vivo reactivation was confirmed by presence of lytic gene transcripts and proteins in tumors 6 days after GCb/VPA treatment. Virus reactivation was visualized by [¹²⁴I]‐FIAU accumulation in tumors using PET‐scan. This studied showed that CLVA therapy is a potent EBV‐specific targeting approach for killing tumor cells. The [¹²⁴I]‐FIAU appears valuable as PET tracer for studies on CLVA drug dosage and kinetics in vivo, and may find clinical application in treatment monitoring.

Pharmacological factors affecting accumulation of gemcitabine's active metabolite, gemcitabine triphosphate

Gemcitabine is an anticancer agent acting against several solid tumors. It requires nucleoside transporters for cellular uptake and deoxycytidine kinase for activation into active gemcitabine-triphosphate, which is incorporated into the DNA and RNA. However, it can also be deaminated in the plasma. The intracellular level of gemcitabine-triphosphate is affected by scheduling or by combination with other chemotherapeutic regimens. Moreover, higher concentrations of gemcitabine-triphosphate may affect the toxicity, and possibly the clinical efficacy. As a consequence, different nucleoside analogs have been synthetized with the aim to increase the concentration of gemcitabine-triphosphate into cells. In this review, we summarize currently published evidence on pharmacological factors affecting the intracellular level of gemcitabine-triphosphate to guide future trials on the use of new nucleoside analogs.

Enhancing Drug Efficacy and Therapeutic Index through Cheminformatics-Based Selection of Small Molecule Binary Weapons That Improve Transporter-Mediated Targeting: A Cytotoxicity System Based on Gemcitabine

The transport of drug molecules is mainly determined by the distribution of influx and efflux transporters for which they are substrates. To enable tissue targeting, we sought to develop the idea that we might affect the transporter-mediated disposition of small-molecule drugs via the addition of a second small molecule that of itself had no inhibitory pharmacological effect but that influenced the expression of transporters for the primary drug. We refer to this as a “binary weapon” strategy. The experimental system tested the ability of a molecule that on its own had no cytotoxic effect to increase the toxicity of the nucleoside analog gemcitabine to Panc1 pancreatic cancer cells. An initial phenotypic screen of a 500-member polar drug (fragment) library yielded three “hits.” The structures of 20 of the other 2,000 members of this library suite had a Tanimoto similarity greater than 0.7 to those of the initial hits, and each was itself a hit (the cheminformatics thus providing for a massive enrichment). We chose the top six representatives for further study. They fell into three clusters whose members bore reasonable structural similarities to each other (two were in fact isomers), lending strength to the self-consistency of both our conceptual and experimental strategies. Existing literature had suggested that indole-3-carbinol might play a similar role to that of our fragments, but in our hands it was without effect; nor was it structurally similar to any of our hits. As there was no evidence that the fragments could affect toxicity directly, we looked for effects on transporter transcript levels. In our hands, only the ENT1-3 uptake and ABCC2,3,4,5, and 10 efflux transporters displayed measurable transcripts in Panc1 cultures, along with a ribonucleoside reductase RRM1 known to affect gemcitabine toxicity. Very strikingly, the addition of gemcitabine alone increased the expression of the transcript for ABCC2 (MRP2) by more than 12-fold, and that of RRM1 by more than fourfold, and each of the fragment “hits” served to reverse this. However, an inhibitor of ABCC2 was without significant effect, implying that RRM1 was possibly the more significant player. These effects were somewhat selective for Panc cells. It seems, therefore, that while the effects we measured were here mediated more by efflux than influx transporters, and potentially by other means, the binary weapon idea is hereby fully confirmed: it is indeed possible to find molecules that manipulate the expression of transporters that are involved in the bioactivity of a pharmaceutical drug. This opens up an entirely new area, that of chemical genomics-based drug targeting.

Molecular alterations contributing to pancreatic cancer chemoresistance

Pancreatic ductal adenocarcinoma (PDAC) is one of the most common causes of cancer-related death all over the world. This disease is difficult to treat and patients have an overall 5-year survival rate of less than 5%. Although two drugs, gemcitabine (GEM) and 5-fluorouracil (5-FU) have been shown to improve the survival rate of patients systematically, they do not increase general survival to a clinically acceptable degree. Lack of ideal clinical response of pancreatic cancer patients to chemotherapy is likely to be due to intrinsic and acquired chemoresistance of tumor cells. Various mechanisms of drug resistance have been investigated in pancreatic cancer, including genetic and epigenetic changes in particular genes or signaling pathways. In addition, evidence suggests that microRNAs (miRNAs) play significant roles as key regulators of gene expression in many cellular processes, including drug resistance. Understanding underlying genes and mechanisms of drug resistance in pancreatic cancer is critical to develop new effective treatments for this deadly disease. This review illustrates the genes and miRNAs involved in resistance to gemcitabine in pancreatic cancer.

Lung cancer: Biology and treatment options

Lung cancer remains the leading cause of cancer mortality in men and women in the U.S. and worldwide. About 90% of lung cancer cases are caused by smoking and the use of tobacco products. However, other factors such as radon gas, asbestos, air pollution exposures, and chronic infections can contribute to lung carcinogenesis. In addition, multiple inherited and acquired mechanisms of susceptibility to lung cancer have been proposed. Lung cancer is divided into two broad histologic classes, which grow and spread differently: small-cell lung carcinomas (SCLCs) and non-small cell lung carcinomas (NSCLCs). Treatment options for lung cancer include surgery, radiation therapy, chemotherapy, and targeted therapy. Therapeutic-modalities recommendations depend on several factors, including the type and stage of cancer. Despite the improvements in diagnosis and therapy made during the past 25 years, the prognosis for patients with lung cancer is still unsatisfactory. The responses to current standard therapies are poor except for the most localized cancers. However, a better understanding of the biology pertinent to these challenging malignancies, might lead to the development of more efficacious and perhaps more specific drugs. The purpose of this review is to summarize the recent developments in lung cancer biology and its therapeutic strategies, and discuss the latest treatment advances including therapies currently under clinical investigation.

Potent effect of adenoviral vector expressing short hairpin RNA targeting ribonucleotide reductase large subunit M1 on cell viability and chemotherapeutic sensitivity to gemcitabine in non-small cell lung cancer cells

BACKGROUND

Ribonucleotide reductase large subunit (RRM1) is the main enzyme responsible for synthesis of the deoxyribonucleotides used during DNA synthesis. It is also a cellular target for gemcitabine (GEM). Overexpression of RRM1 is reportedly associated with resistance to GEM and the poor prognosis for many types of malignant tumours. Aim of the present study is to establish gene therapy against RRM1-overexpressing tumours.

METHOD

An adenoviral vector that encoded a short hairpin siRNA targeting the RRM1 gene (Ad-shRRM1) was constructed. Two RRM1-overexpressing non-small cell lung cancer (NSCLC) lines, MAC10 and RERF-LC-MA, were used. Finally, a human tumour xenograft model in nude mice was prepared by subcutaneously implanting tumours derived from RERF-LC-MA cells.

RESULTS

Ad-shRRM1 effectively downregulated RRM1 mRNA and protein in both types of NSCLC cells and significantly reduced the percentage of viable cells as detected by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay (p<0.005). Caspase 3/7 analysis revealed that transfection with Ad-RRM1 increased the percentage of apoptotic cells in culture containing either type of RRM1-overexpressing cell (p<0.001). Treatment with Ad-shRRM1 exerted a potent antitumour effect against the RRM1-overexpressing RERF-LC-MA xenografts (p<0.05). Furthermore, Ad-shRRM1-mediated inhibition of RRM1 specifically increased sensitivity to gemcitabine of each type of RRM1-overexpressing tumour cell. Combination treatment with Ad-shRRM1 and GEM exerted significantly greater inhibition on cell proliferation than Ad-shRRM1 or GEM treatment alone.

CONCLUSION

RRM1 appeared to be a promising target for gene therapy, and Ad-shRRM1 had strong antitumour effects, specifically anti-proliferative and pro-apoptotic effects, against NSCLC cells that overexpressed RRM1. Combination therapy with Ad-shRRM1 and GEM may become a new treatment option for patients with NSCLC.

Predictive and Prognostic Value of Ribonucleotide Reductase Regulatory Subunit M1 and Excision Repair Cross-Complementation Group 1 in Advanced Urothelial Carcinoma (UC) Treated with First-Line Gemcitabine Plus Platinum Combination Chemotherapy

Preclinical and clinical studies have suggested that expression of ribonucleotide reductase regulatory subunit M1 (RRM1) and excision repair cross-complementation group 1 (ERCC1) is associated with resistance to gemcitabine and cisplatin, respectively. We evaluated the significance of RRM1 and ERCC1 expression to predict tumor response to gemcitabine plus platinum chemotherapy (GP) and survival in advanced UC. We retrospectively collected tumor samples and reviewed clinical data of 53 patients with unresectable or metastatic UC, who were treated with first-line GP. RRM1 and ERCC1 expression were measured by immunohistochemistry. Among 53 patients, 12 (22.6%) and 26 (49.1%) patients had tumors that demonstrated a high expression for RRM1 and ERCC1, respectively. Twenty-nine (70.7%) of 41 patients with low RRM1 expression achieved a clinical response (complete + partial responses), but only 3 (25.0%) of 12 patients with high RRM1 expression achieved a clinical response after GP (P=0.007). Nineteen (70.4%) of 27 patients with low ERCC1 expression achieved a clinical response, while 13 (50.0%) of 26 patients with high ERCC1 expression achieved a clinical response (P=0.130). High RRM1 expression was associated with shorter progression free survival and overall survival (PFS P=0.006, OS P=0.006). Multivariate analysis confirmed that patients with high RRM1 expression had a significantly greater risk of progression and death than those with low RRM1 expression. ERCC1 status was not a significant predictor for PFS and OS. RRM1 expression was predictive and prognostic of clinical outcome in advanced UC treated with gemcitabine plus platinum combination chemotherapy.

ERCC1 and RRM1 as a predictive parameter for non-small cell lung, ovarian or pancreas cancer treated with cisplatin and/or gemcitabine

Background

We aimed to investigate the impact of RRM1 and ERCC1 expression on response to cisplatin and/or gemcitabine chemotherapy in patients with lung, ovarian or pancreatic cancer.

Material and methods

Patients with lung, ovarian or pancreatic cancer, who used cisplatin and/or gemcitabine therapy were included; hospital files were examined and RRM1 and ERCC1 expression were evaluated with an immunohistochemical method on tissue cross sections from paraffin blocks of the tumour.

Results

Out of 89 patients, 51%, 30% and 19% had lung, ovarian and pancreatic cancer, respectively. The response rates to the therapy in patients with lung and ovarian cancer having low ERCC1 expression were 62% and 90%, respectively (p = 0.028 and p = 0.044, respectively). No significant association was found between ERCC1 expression and response to therapy in patients with pancreatic cancer (p = 0.354). Therapeutic response rates in patients with lung and pancreatic cancer with low RRM1 expression were 60% and 82%, respectively. Survival rates were higher in patients with lung cancer in which ERCC1 and RRM1 expressions were low. Median survival duration in patients with ovarian cancer showing low ERCC1 and RRM1 expressions was longer than that seen in patients with high expressions. Although no significant correlation was found between ERCC1 and the survival in ovarian cancer (p = 0.183), there was a significant correlation between RRM1 expression and survival in patients with pancreatic cancer (p = 0.005).

Conclusions

Our results suggest a predictive value of ERCC1 in lung and ovarian cancers, and also RRM1 in lung and pancreatic cancers.

ATM, THMS, and RRM1 protein expression in nasopharyngeal carcinomas treated with curative intent

BACKGROUND

In advanced nasopharyngeal carcinoma (NPC), biomarkers may help predict survival.

METHODS

Tumoral expression of ataxia-telangiectasia mutated (ATM), thymidylate synthetase (THMS), and ribonucleotide reductase subunit M1 (RRM1), was correlated with survival in patients with nonmetastatic NPC using quantitative fluorescence immunohistochemistry with automated quantitative digital image analysis.

RESULTS

Of the 146 patients included, 58 patients (40%) received concurrent chemoradiation therapy; the remainder was treated with radiation. Overall survival (OS) at 5 years was 71% (95% confidence interval [CI], 62% to 78%); disease-free survival (DFS) was 48% (95% CI, 39% to 57%). OS worsened for increasing values of ATM (hazard ratio [HR], 2.83; 95% CI, 1.01-7.94; p = .049) for values greater than the 75th percentile compared to less than the 25th percentile, but improved for tumors with higher THMS levels (HR, 0.44; 95% CI, 0.20-0.94; p = .033) for values greater than the 25th percentile compared to less than or equal to the 25th percentile. RRM1 was not associated with OS (p = .748). No biomarkers were associated with DFS.

CONCLUSION

In our cohort, relative overexpression of ATM and low THMS levels were associated with worse OS. © 2015 Wiley Periodicals, Inc. Head Neck 38: E384-E391, 2016.

Zidovudine, an anti-viral drug, resensitizes gemcitabine-resistant pancreatic cancer cells to gemcitabine by inhibition of the Akt-GSK3β-Snail pathway

Pancreatic cancer is one of the most difficult malignancies to treat owing to the rapid acquisition of resistance to chemotherapy. Gemcitabine, a first-line treatment for pancreatic cancer, prolongs patient survival by several months, and combination treatment with gemcitabine and other anti-cancer drugs in the clinic do not show any significant effects on overall survival. Thus, identification of a drug that resensitizes gemcitabine-resistant pancreatic cancer to gemcitabine and a better understanding of the molecular mechanisms of gemcitabine resistance are critical to develop new therapeutic options for pancreatic cancer. Here, we report that zidovudine resensitizes gemcitabine-resistant pancreatic cancer to gemcitabine as shown by screening a compound library, including clinical medicine, using gemcitabine-resistant cells. In analyzing the molecular mechanisms of zidovudine effects, we found that the epithelial-to-mesenchymal transition (EMT)-like phenotype and downregulation of human equilibrative nucleoside transporter 1 (hENT1) are essential for the acquisition of gemcitabine resistance, and zidovudine restored these changes. The chemical biology investigations also revealed that activation of the Akt-GSK3β-Snail1 pathway in resistant cells is a key signaling event for gemcitabine resistance, and zidovudine resensitized resistant cells to gemcitabine by inhibiting this activated pathway. Moreover, our in vivo study demonstrated that co-administration of zidovudine and gemcitabine strongly suppressed the formation of tumors by gemcitabine-resistant pancreatic cancer and prevented gemcitabine-sensitive pancreatic tumors from acquiring gemcitabine-resistant properties, inducing an EMT-like phenotype and downregulating hENT1 expression. These results suggested that co-treatment with zidovudine and gemcitabine may become a novel therapeutic strategy for pancreatic cancer by inhibiting chemoresistance-specific signaling.

Importance of excision repair cross-complementation group 1 and ribonucleotide reductase M1 as prognostic biomarkers in malignant pleural mesothelioma treated with platinum-based induction chemotherapy followed by surgery

OBJECTIVES

Survival and response to platinum-based induction chemotherapy are heterogeneous among patients with malignant pleural mesothelioma. The aim of the present study was to assess the prognostic role of DNA repair markers, such as excision repair cross-complementation group 1 and ribonucleotide reductase M1, in multimodally treated patients with malignant pleural mesothelioma.

METHODS

Tumor tissue of a malignant pleural mesothelioma cohort (n = 107) treated with platinum/gemcitabine (n = 46) or platinum/pemetrexed (n = 61) induction chemotherapy followed by extrapleural pneumonectomy was assembled on a tissue microarray. Immunohistochemical expression of excision repair cross-complementation group 1 (nuclear) and ribonucleotide reductase M1 (nuclear and cytoplasmic) was assessed for its prognostic impact (association with overall survival or freedom from recurrence).

RESULTS

Patients with high nuclear ribonucleotide reductase M1 expression before chemotherapy showed significantly longer freedom from recurrence (P = .03). When specifically analyzed in the subgroup of patients receiving platinum/gemcitabine followed by extrapleural pneumonectomy, high nuclear ribonucleotide reductase M1 was associated with prolonged freedom from recurrence (P = .03) and overall survival (P = .02). Low excision repair cross-complementation group 1 expression in prechemotherapy tumor tissues was associated with significantly longer freedom from recurrence (P = .04). Nuclear ribonucleotide reductase M1 and excision repair cross-complementation group 1 were independent prognosticators of freedom from recurrence in addition to pT stage in multivariate analysis.

CONCLUSIONS

In the present study, nuclear ribonucleotide reductase M1 and excision repair cross-complementation group 1 expression were identified as independent prognosticators for freedom from recurrence of malignant pleural mesothelioma in patients undergoing induction chemotherapy followed by extrapleural pneumonectomy.

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.

Predicting chemosensitivity to gemcitabine and cisplatin based on gene polymorphisms and mRNA expression in non-small-cell lung cancer cells

Aim: We used a panel of 17 non-small-cell lung cancer cell lines to investigate whether the presence of polymorphisms in the RRM1, ERCC1, ABCB1 and MTHFR genes and alterations in their mRNA expression can affect the in vitro chemosensitivity to cisplatin and gemcitabine. Materials & methods: Polymorphisms in these genes were evaluated by direct sequencing. mRNA expression levels were assessed by realtime PCR. In vitro chemosensitivity to cisplatin and gemcitabine was expressed as IC50 values, using the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay. Results: There was a significant, positive correlation between RRM1 mRNA expression and IC50 values for gemcitabine (r = 0.6533, p = 0.0045), and there was a significant, negative correlation between ABCB1 mRNA expression and IC50 values for cisplatin (r = -0.5459, p = 0.0287). When examining the association between the polymorphisms and IC50, we found that only the MTHFR 1298A>C polymorphism showed a tendency to be more chemosensitive to gemcitabine (p = 0.0440). Conclusion: These in vitro results suggest that mRNA expression levels of the RRM1 and ABCB1 genes may be useful indicators of chemosensitivity to gemcitabine and cisplatin, respectively. The MTHFR 1298A>C polymorphism was associated with gemcitabine chemosensitivity, which require further functional analysis with co-expressed genes and should be explored in prospective clinical studies to determine its potential clinical application as a predictive biomarker.

Original submitted 11 February 2014; Revision submitted 3 November 2014

Pegylated arginine deiminase synergistically increases the cytotoxicity of gemcitabine in human pancreatic cancer

Background

Pancreatic ductal adenocarcinoma has proven to be one of the most chemo-resistant among all solid organ malignancies. Several mechanisms of resistance have been described, though few reports of strategies to overcome this chemo-resistance have been successful in restoring sensitivity to the primary chemotherapy (gemcitabine) and enter the clinical treatment arena.

Methods

We examined the ability of cellular arginine depletion through treatment with PEG-ADI to alter in vitro and in vivo cytotoxicity of gemcitabine. The effect on levels of key regulators of gemcitabine efficacy (e.g. RRM2, hENT1, and dCK) were examined.

Results

Combination of PEG-ADI and gemcitabine substantially increases growth arrest, leading to increased tumor response in vivo. PEG-ADI is a strong inhibitor of the gemcitabine-induced overexpression of ribonucleotide reductase subunit M2 (RRM2) levels both in vivo and in vitro, which is associated with gemcitabine resistance. This mechanism is through the abrogation of the gemcitabine-mediated inhibitory effect on E2F-1 function, a transcriptional repressor of RRM2.

Conclusion

The ability to alter gemcitabine resistance in a targeted manner by inducing metabolic stress holds great promise in the treatment of advanced pancreatic cancer.

Liver kinase B1 enhances chemoresistance to gemcitabine in breast cancer MDA-MB-231 cells

Liver kinase B1 (LKB1) is a well-known tumor suppressor gene in a variety of human cancers, including breast cancer. However, its role in gemcitabine resistance is unclear. Since gemcitabine in combination with other chemotherapeutic reagents is the first-line treatment in advanced breast cancer, the aim of the present study was to determine the effect of ectopic expression of LKB1 on chemosensitivity to gemcitabine in the breast cancer MDA-MB-231 cell line. Increasing the expression of LKB1 was found to directly correlate with gemcitabine chemoresistance. Although LKB1 suppressed the cell proliferation rate and clonogenicity in the absence of gemcitabine, it increased the median inhibitory concentration of gemcitabine and clonogenicity of cells in the presence of gemcitabine. Mechanistic analysis indicated that LKB1 was able to protect cells from DNA damage caused by gemcitabine. Furthermore, it was found that LKB1 induced a significant upregulation of cytidine deaminase expression, an important enzyme that accelerates gemcitabine catabolization. Overall, dual characteristics of LKB1 were identified: Suppressing cell growth in normal conditions and enhancing chemoresisitance to gemcitabine, possibly by accelerating degradation of gemcitabine, and protecting cells from DNA damage caused by gemcitabine.

A phase 2 cooperative group adjuvant trial using a biomarker-based decision algorithm in patients with stage I non-small cell lung cancer (SWOG-0720, NCT00792701)

BACKGROUND

This cooperative group adjuvant phase 2 trial in patients with completely resected stage I non-small cell lung cancer with tumor diameters measuring ≥ 2 cm was designed to assess the feasibility and preliminary efficacy of assigning patients to therapy or observation using a molecularly based decision algorithm.

METHODS

At least a lobectomy and sampling of recommended mediastinal lymph node stations, good Zubrod performance status, adequate organ function, and a formalin-fixed and paraffin-embedded tumor specimen were required. Excision repair cross-complementing group 1 (ERCC1) and ribonucleotide reductase M1 (RRM1) were analyzed using immunofluorescence-based in situ automated quantitative image analysis and categorized as high or low using prespecified cutoff values. Patients with high ERCC1 and RRM1 were assigned to observation and all others to 4 cycles of cisplatin and gemcitabine. Feasibility was defined as treatment assignment within 84 days from surgery in > 85% of patients. Secondary objectives were to estimate the 2-year survival.

RESULTS

Treatment assignment met the feasibility criteria in 88% of eligible patients (71 of 81 patients). The collective 2-year disease-free and overall survival rates were 80% and 96%, respectively. Protein levels for RRM1 fell within the previously established range, ERCC1 levels were slightly lower than expected, and they were significantly correlated (correlation coefficient, 0.4). The rates of assignment of patients to observation (22%) and chemotherapy (78%) were as expected.

CONCLUSIONS

Gene expression analysis for treatment assignment is feasible. Survival results are encouraging and require future validation. Real-time performance of quantitative in situ ERCC1 and RRM1 analysis requires further development.

Gemcitabine: metabolism and molecular mechanisms of action, sensitivity and chemoresistance in pancreatic cancer

Gemcitabine is the first-line treatment for pancreatic adenocarcinoma, but is increasingly used to treat breast, bladder, and non-small cell lung cancers. Despite such broad use, intrinsic and acquired chemoresistance is common. In general, the underlying mechanisms of chemoresistance are poorly understood. Here, current knowledge of gemcitabine metabolism, mechanisms of action, sensitivity and chemoresistance reported over the past two decades are reviewed; and we also offer new perspectives to improve gemcitabine efficacy with particular reference to the treatment of pancreatic cancer.

Ribonucleotide reductase and cancer: biological mechanisms and targeted therapies

Accurate DNA replication and repair is essential for proper development, growth and tumor-free survival in all multicellular organisms. A key requirement for the maintenance of genomic integrity is the availability of adequate and balanced pools of deoxyribonucleoside triphosphates (dNTPs), the building blocks of DNA. Notably, dNTP pool alterations lead to genomic instability and have been linked to multiple human diseases, including mitochondrial disorders, susceptibility to viral infection and cancer. In this review, we discuss how a key regulator of dNTP biosynthesis in mammals, the enzyme ribonucleotide reductase (RNR), impacts cancer susceptibility and serves as a target for anti-cancer therapies. Because RNR-regulated dNTP production can influence DNA replication fidelity while also supporting genome-protecting DNA repair, RNR has complex and stage-specific roles in carcinogenesis. Nevertheless, cancer cells are dependent on RNR for de novo dNTP biosynthesis. Therefore, elevated RNR expression is a characteristic of many cancers, and an array of mechanistically distinct RNR inhibitors serve as effective agents for cancer treatment. The dNTP metabolism machinery, including RNR, has been exploited for therapeutic benefit for decades and remains an important target for cancer drug development.

RRM1 and RRM2 pharmacogenetics: association with phenotypes in HapMap cell lines and acute myeloid leukemia patients

BACKGROUND

Ribonucleotide reductase catalyzes an essential step in the cellular production of deoxyribonucleotide triphosphates and has been associated with clinical outcome in cancer patients receiving nucleoside analog-based chemotherapy.

MATERIALS & METHODS

In the current study, we sequenced the genes RRM1 and RRM2 in genomic DNA from HapMap cell lines with European (Utah residents with northern and western European ancestry [CEU]; n = 90) or African (Yoruba people in Ibadan, Nigeria [YRI]; n = 90) ancestry.

RESULTS

We identified 44 genetic variants including eight coding SNPs in RRM1 and 15 SNPs including one coding SNP in RRM2. RRM1 and RRM2 mRNA expression levels were significantly correlated with each other in both CEU and YRI lymphoblast cell lines, and in leukemic blasts from acute myeloid leukemia (AML) patients (AML97, n = 89; AML02, n = 187). Additionally, RRM1 expression was higher among patient features indicative of a high relapse hazard. We evaluated SNPs within the RRM1 and RRM2 genes in the HapMap lymphoblast cell lines from CEU and YRI panels for association with expression and cytarabine chemosensitivity. SNPs of potential significance were further evaluated in AML patients. RRM1 SNPs rs1042919 (which occurs in linkage disequilbrium with multiple other SNPs) and promoter SNP rs1561876 were associated with intracellular 1-β-D-arabinofuranosyl-CTP levels, response after remission induction therapy, risk of relapse and overall survival in AML patients receiving cytarabine and cladribine.

CONCLUSION

These results suggest that SNPs within ribonucleotide reductase might be helpful predictive markers of response to nucleoside analogs and should be further validated in larger cohorts.

Response to first-line chemotherapy in patients with non-small cell lung cancer according to RRM1 expression

Background

The response to cytotoxic chemotherapy varies greatly in patients with advanced non-small cell lung cancer (NSCLC), and molecular markers may be useful in determining a preferable therapeutic approach for individual patients. This retrospective study was performed to evaluate the predictive value of ribonucleotide reductase regulatory subunit M1 (RRM1) on the therapeutic efficacy of platinum-based chemotherapy in patients with NSCLC.

Methods

Patients with advanced NSCLC who received platinum doublet chemotherapy (n = 229) were included in this retrospective study, and their clinical outcomes were analyzed according to RRM1 expression.

Results

In patients receiving gemcitabine-based therapy, the disease control rate (DCR) and progression-free survival (PFS) of patients with RRM1-negative tumors were significantly higher than in patients with RRMI-positive tumors (P = 0.041 and P = 0.01, respectively), and multivariate analysis showed that RRM1 expression was an independent prognostic factor (P = 0.013). No similar differences were found in patients receiving docetaxel- or vinorelbine-based therapy. In RRM1-positive patients, the DCRs for docetaxel and vinorelbine were higher than for gemcitabine (P = 0.047 and P = 0.047, respectively), and docetaxel and vinorelbine showed a longer PFS than gemcitabine-based chemotherapy (P = 0.012 and P = 0.007). No similar differences were found among patients with RRM1-negative tumors.

Conclusions

Negative RRM1 expression in advanced NSCLC is associated with a higher response rate to gemcitabine-based chemotherapy. In patients with RRM1-positive tumors, docetaxel and vinorelbine showed a higher therapeutic efficacy than gemcitabine-based therapy. Additional prospective studies are needed to investigate the predictive meaning of RRM1 in the response to chemotherapy.

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.

First-line gemcitabine plus cisplatin in nonsmall cell lung cancer patients

Aim. To evaluate the predictive value of RRM1, ERCCl, and BRCA1 expression in Chinese NSCLC patients treated with gemcitabine and cisplatin. Methods. Real-time fluorescent quantitative PCR was used to determine the RRM1, ERCC1, and BRCA1 mRNA expression levels of peripheral blood in late-stage NSCLC patients. The relationship between peripheral blood and mRNA expression in tumor tissues was analyzed further. Results. In terms of the tumor susceptibility to chemotherapy, the response rate in the low-RRM1-expression group was significantly greater than in the high-expression group (52.9% versus 5.9%, χ² test, P = 0.007). Subjects with low peripheral blood RRM1 expression survived longer than those with high RRM1 expression (15.5 versus 12.0 months, logrank 3.980, P = 0.046). Linear correlations were observed between peripheral blood and tumor tissue expression levels for RRM1 (R² = 0.045, P = 0.048) and BRCA1 (R² = 0.021, P = 0.001). Conclusion. Our study demonstrates increased survival and superior efficacy of gemcitabine and cisplatin combination chemotherapy in the treatment of NSCLC patients with low peripheral blood RRM1 expression. The linear correlations of the relative expression of mRNA were observed between peripheral blood and tumor tissue expression levels for RRM1 and BRCA1. RRM1 gene expression may contribute to chemotherapy sensitivity and may be an indicator of survival. It was significant to individual chemotherapy of patients with advanced NSCLC who do not have sufficient tumor tissue.

RC-3095, a gastrin-releasing peptide receptor antagonist, synergizes with gemcitabine to inhibit the growth of human pancreatic cancer CFPAC-1 in vitro and in vivo

OBJECTIVES

Pancreatic cancer remains a lethal disease. In this study, we investigated the efficacy of a combination of gastrin-releasing peptide receptor antagonist RC-3095 and gemcitabine on pancreatic cancer CFPAC-1.

METHODS

The antiproliferation effects of RC-3095, gemcitabine, or the combination on pancreatic cancer were monitored in vitro. Nude mice bearing xenografts of CFPAC-1 cell received injections of the vehicle (control), RC-3095 (20 μg, subcutaneously, daily), gemcitabine (15 mg/kg, intraperitoneally, every 3 days), or the combination of RC-3095 and gemcitabine for 4 weeks. The histological changes and protein expression were tested using immunohistochemistry and Western blotting.

RESULTS

Treatment with the combination in culture exhibited a powerful inhibition effect on CFPAC-1 cell proliferation. In xenograft mice model, RC-3095 or gemcitabine significantly reduced the volume and weight of tumors after 4 weeks of treatment, as compared with controls. The combination more potently inhibited the tumor growth than either agent used individually. Immunohistochemistry and Western blotting showed gastrin-releasing peptide receptor/bombesin receptor subtype-3 positive cells and protein expression in tumors decreased by treatment with RC-3095 or gemcitabine alone or greater in combination.

CONCLUSIONS

Our data suggested that the combination could be considered for the possible new approaches for treatment of pancreatic cancers.

Protein profiling of ovarian cancers by immunohistochemistry to identify potential target pathways

Background

To determine the protein expression profile (PEP) of primary and recurrent ovarian cancer patients in order to predict therapeutic targets for chemotherapy.

Methods

Tissue samples were submitted for PEP in two formats, including formalin-fixed paraffin-embedded tissue for immunohistochemistry (IHC) and fresh frozen tissue for oligonucleotide microarray (MA) gene expression assays. Specimens were analyzed for 18 protein markers and 88 MA genes. A series of Generalized Linear Models (GLM) was used to predict the proportion of positive results by histology for each biomarker.

Results

Four hundred and twenty-eight specimens were analyzed for IHC and 67 specimens for MA analysis. The majority of specimens, 82%, were serous histology and 35.3% of specimens were poorly differentiated. Sixty percent of specimens were advanced stage, 62% were from a primary diagnosis, and 53% were obtained from a metastatic site. BCRP, ER, MGMT, and RRM1 proteins were overexpressed in 85%, 47%, 93%, and 47% of serous carcinomas, respectively. The MGMT and RRM1 biomarkers were significantly overexpressed in serous (p < .001) and endometrioid (p = .01) histologies when compared to clear cell histology. MGMT was significantly elevated in 93% of serous and endometrioid samples, compared to 62% of samples with clear cell histology. Those proteins most often underexpressed included Her2/neu, SPARC, and c-kit, seen in less than 1%, 4%, and 5% of specimens, respectively.

Conclusions

PEP is a reliable and effective way of analyzing ovarian cancer specimens. PEP target identification does not appear to vary significantly with site evaluated, ovarian or other abdominal pelvic tissue, or primary versus recurrent disease. Variability in the expression of drug targets, including BCRP, ER, MGMT, and RRM1 could impact decision making pertaining to which therapeutic strategies carry the best chances for controlling disease.

Electronic supplementary material

The online version of this article (doi:10.1186/2053-6844-1-4) contains supplementary material, which is available to authorized users.