Cisplatin regulates the MAPK kinase pathway to induce increased expression of DNA repair gene ERCC1 and increase melanoma chemoresistance. Oncogene. 2012;31:2412-2422. [PMID: 21996734 DOI: 10.1038/onc.2011.426]

TonEBP/NFAT5 expression is associated with cisplatin resistance and migration in macrophage-induced A549 cells

BACKGROUND

Macrophages promote angiogenesis, metastasis, and drug resistance in several cancers. Similarly, TonEBP/NFAT5 induces metastasis in renal carcinoma and colon cancer cells. However, the role of this transcription factor and that of macrophages in lung cancer cells remains unclear. Therefore, this study investigated the effects of macrophages and TonEBP/NFAT5 expression on cisplatin resistance and migration in A549 lung adenocarcinoma cells.

RESULTS

A549 cells were cultured alone or indirectly co-cultured with THP-1-derived macrophages using a transwell culture chamber. Cisplatin-induced cell death was markedly decreased and migration increased in co-cultured A549 cells. Macrophage-conditioned media (CM) showed a similar effect on drug resistance and migration. Cisplatin-induced apoptosis, DNA fragmentation, and cleaved apoptotic proteins PARP and caspase-3 were markedly reduced in macrophage CM-induced A549 cells. Here, ERK, p38, JNK, and NF-κB activities were increased by macrophage CM. Furthermore, the proteins involved in cisplatin resistance and cancer cell migration were identified using specific inhibitors of each protein. ERK and NF-κB inhibition considerably reduced cisplatin resistance. The increase in macrophage CM-induced migration was partially reduced by treatment with ERK, JNK, and NF-κB inhibitors. TonEBP/NFAT5 expression was increased by macrophages, resulting in increased cisplatin resistance, cell migration, and invasion. Moreover, RNAi-mediated knockdown of TonEBP/NFAT5 reduced cisplatin resistance, migration, and invasion in macrophage CM-induced A549 cells.

CONCLUSIONS

These findings demonstrate that paracrine factors secreted from macrophages can change A549 cells, resulting in the induction of drug resistance against cisplatin and migration. In addition, the TonEBP/NFAT5 ratio, increased by macrophages, is an important regulator of the malignant transformation of cells.

Breast cancer: miRNAs monitoring chemoresistance and systemic therapy

With a high mortality rate that accounts for millions of cancer-related deaths each year, breast cancer is the second most common malignancy in women. Chemotherapy has significant potential in the prevention and spreading of breast cancer; however, drug resistance often hinders therapy in breast cancer patients. The identification and the use of novel molecular biomarkers, which can predict response to chemotherapy, might lead to tailoring breast cancer treatment. In this context, accumulating research has reported microRNAs (miRNAs) as potential biomarkers for early cancer detection, and are conducive to designing a more specific treatment plan by helping analyze drug resistance and sensitivity in breast cancer treatment. In this review, miRNAs are discussed in two alternative ways-as tumor suppressors to be used in miRNA replacement therapy to reduce oncogenesis and as oncomirs to lessen the translation of the target miRNA. Different miRNAs like miR-638, miR-17, miR-20b, miR-342, miR-484, miR-21, miR-24, miR-27, miR-23 and miR-200 are involved in the regulation of chemoresistance through diverse genetic targets. For instance, tumor-suppressing miRNAs like miR-342, miR-16, miR-214, and miR-128 and tumor-promoting miRNAs like miR101 and miR-106-25 cluster regulate the cell cycle, apoptosis, epithelial to mesenchymal transition and other pathways to impart breast cancer drug resistance. Hence, in this review, we have discussed the significance of miRNA biomarkers that could assist in providing novel therapeutic targets to overcome potential chemotherapy resistance to systemic therapy and further facilitate the design of tailored therapy for enhanced efficacy against breast cancer.

Engine shutdown: migrastatic strategies and prevention of metastases

Most cancer-related deaths among patients with solid tumors are caused by metastases. Migrastatic strategies represent a unique therapeutic approach to prevent all forms of cancer cell migration and invasion. Because the migration machinery has been shown to promote metastatic dissemination, successful migrastatic therapy may reduce the need for high-dose cytotoxic therapies that are currently used to prevent the risk of metastatic dissemination. In this review we focus on anti-invasive and antimetastatic strategies that hold promise for the treatment of solid tumors. The best targets for migrastatic therapy would be those that are required by all forms of motility, such as ATP availability, mitochondrial metabolism, and cytoskeletal dynamics and cell contractility.

Prognostication of DNA Damage Response Protein Expression Patterns in Chronic Lymphocytic Leukemia

Proteomic DNA Damage Repair (DDR) expression patterns in Chronic Lymphocytic Leukemia were characterized by quantifying and clustering 24 total and phosphorylated DDR proteins. Overall, three protein expression patterns (C1-C3) were identified and were associated as an independent predictor of distinct patient overall survival outcomes. Patients within clusters C1 and C2 had poorer survival outcomes and responses to fludarabine, cyclophosphamide, and rituxan chemotherapy compared to patients within cluster C3. However, DDR protein expression patterns were not prognostic in more modern therapies with BCL2 inhibitors or a BTK/PI3K inhibitor. Individually, nine of the DDR proteins were prognostic for predicting overall survival and/or time to first treatment. When looking for other proteins that may be associated with or influenced by DDR expression patterns, our differential expression analysis found that cell cycle and adhesion proteins were lower in clusters compared to normal CD19 controls. In addition, cluster C3 had a lower expression of MAPK proteins compared to the poor prognostic patient clusters thus implying a potential regulatory connection between adhesion, cell cycle, MAPK, and DDR signaling in CLL. Thus, assessing the proteomic expression of DNA damage proteins in CLL provided novel insights for deciphering influences on patient outcomes and expanded our understanding of the potential complexities and effects of DDR cell signaling.

Effects of Ion-Transporting Proteins on the Digestive System Under Hypoxia

Hypoxia refers to a state of oxygen limitation, which mainly mediates pathological processes in the human body and participates in the regulation of normal physiological processes. In the hypoxic environment, the main regulator of human body homeostasis is the hypoxia-inducible factor family (HIF). HIF can regulate the expression of many hypoxia-induced genes and then participate in various physiological and pathological processes of the human body. Ion-transporting proteins are extremely important types of proteins. Ion-transporting proteins are distributed on cell membranes or organelles and strictly control the inflow or outflow of ions in cells or organelles. Changes in ions in cells are often closely related to extensive physiological and pathological processes in the human body. Numerous studies have confirmed that hypoxia and its regulatory factors can regulate the transcription and expression of ion-transporting protein-related genes. Under hypoxic stress, the regulation and interaction of ion-transporting proteins by hypoxia often leads to diseases of various human systems and even tumors. Using ion-transporting proteins and hypoxia as targets to explore the mechanism of digestive system diseases and targeted therapy is expected to become a new breakthrough point.

Effects of Para-Toluenesulfonamide on Canine Melanoma Xenotransplants in a BALB/c Nude Mouse Model

The pharmacological pathway of para-toluenesulfonamide (PTS) restricts the kinase activity of the mammalian target of rapamycin, potentially leading to reductions in cell division, cell growth, cell proliferation, and inflammation. These pathways have a critical effect on tumorigenesis. We aimed to examine the antitumor effect of PTS or PTS combined with cisplatin on canine melanoma implanted in BALB/c nude mice by estimating tumor growth, apoptosis expression, inflammation, and metastasis. The mice were randomly divided into four groups: control, cisplatin, PTS, and PTS combined with cisplatin. Mice treated with PTS or PTS combined with cisplatin had retarded tumor growth and increased tumor apoptosis through the enhanced expression of cleaved caspase 3 and extracellular signal-regulated kinase phosphorylation, decreased inflammatory cytokine levels, reduced inflammation-related factors, enhanced anti-inflammation-related factors, and inhibition of metastasis-related factors. Mice treated with PTS combined with cisplatin exhibited significantly retarded tumor growth, reduced tumor size, and increased tumor inhibition compared with those treated with cisplatin or PTS alone. PTS or PTS combined with cisplatin could retard canine melanoma growth and inhibit tumorigenesis. PTS and cisplatin were found to have an obvious synergistic tumor-inhibiting effect on canine melanoma. PTS alone and PTS combined with cisplatin may be antitumor agents for canine melanoma treatment.

Extracellular Vesicles and Resistance to Anticancer Drugs: A Tumor Skeleton Key for Unhinging Chemotherapies

Although surgical procedures and clinical care allow reaching high success in fighting most tumors, cancer is still a formidable foe. Recurrence and metastatization dampen the patients’ overall survival after the first diagnosis; nevertheless, the large knowledge of the molecular bases drives these aspects. Chemoresistance is tightly linked to these features and is mainly responsible for the failure of cancer eradication, leaving patients without a crucial medical strategy. Many pathways have been elucidated to trigger insensitiveness to drugs, generally associated with the promotion of tumor growth, aggressiveness, and metastatisation. The main mechanisms reported are the expression of transporter proteins, the induction or mutations of oncogenes and transcription factors, the alteration in genomic or mitochondrial DNA, the triggering of autophagy or epithelial-to-mesenchymal transition, the acquisition of a stem phenotype, and the activation of tumor microenvironment cells. Extracellular vesicles (EVs) can directly transfer or epigenetically induce to a target cell the molecular machinery responsible for the acquisition of resistance to drugs. In this review, we resume the main body of knowledge supporting the crucial role of EVs in the context of chemoresistance, with a particular emphasis on the mechanisms related to some of the main drugs used to fight cancer.

Synergistic effects of natural compounds and conventional chemotherapeutic agents: recent insights for the development of cancer treatment strategies

Cancer is one of the leading causes of death in the world. Chemotherapy is presented as an option for treatment of this disease, however, low specificity, high resistance rates, toxicity and hypersensitivity reactions, make it necessary to search for therapeutic alternatives that increase the selectivity of treatment, reduce the side effects and enhance its antitumor potential. Natural products are accessible, inexpensive and less toxic sources; in addition, they have multiple mechanisms of action that can potentiate the outcome of chemotherapeutics. In this review, we present evidence on the beneficial effect of the interaction of dietary phytochemicals with chemotherapeutical agents for cancer treatment. This effect is generated by different mechanisms of action such as, increased tumoricidal effect via sensitization of cancer cells, reversing chemoresistance through inhibition of several targets involved in the development of drug resistance and, decreasing chemotherapy-induced toxicity in non-tumoral cells by the promotion of repair mechanisms. Studies discussed in this review will provide a solid basis for the exploration of the potential use of natural products in combination with chemotherapeutical agents, to overcome some of the difficulties that arise in the management of cancer patients.

MicroRNAs as the critical regulators of Cisplatin resistance in ovarian cancer cells

BACKGROUND

Ovarian cancer (OC) is one of the leading causes of cancer related deaths among women. Due to the asymptomatic tumor progression and lack of efficient screening methods, majority of OC patients are diagnosed in advanced tumor stages. A combination of surgical resection and platinum based-therapy is the common treatment option for advanced OC patients. However, tumor relapse is observed in about 70% of cases due to the treatment failure. Cisplatin is widely used as an efficient first-line treatment option for OC; however cisplatin resistance is observed in a noticeable ratio of cases. Regarding, the severe cisplatin side effects, it is required to clarify the molecular biology of cisplatin resistance to improve the clinical outcomes of OC patients. Cisplatin resistance in OC is associated with abnormal drug transportation, increased detoxification, abnormal apoptosis, and abnormal DNA repair ability. MicroRNAs (miRNAs) are critical factors involved in cell proliferation, apoptosis, and chemo resistance. MiRNAs as non-invasive and more stable factors compared with mRNAs, can be introduced as efficient markers of cisplatin response in OC patients.

MAIN BODY

In present review, we have summarized all of the miRNAs that have been associated with cisplatin resistance in OC. We also categorized the miRNAs based on their targets to clarify their probable molecular mechanisms during cisplatin resistance in ovarian tumor cells.

CONCLUSIONS

It was observed that miRNAs mainly exert their role in cisplatin response through regulation of apoptosis, signaling pathways, and transcription factors in OC cells. This review highlighted the miRNAs as important regulators of cisplatin response in ovarian tumor cells. Moreover, present review paves the way of suggesting a non-invasive panel of prediction markers for cisplatin response among OC patients.

Adaptive Evolution: How Bacteria and Cancer Cells Survive Stressful Conditions and Drug Treatment

Cancer is characterized by loss of the regulatory mechanisms that preserve homeostasis in multicellular organisms, such as controlled proliferation, cell-cell adhesion, and tissue differentiation. The breakdown of multicellularity rules is accompanied by activation of "selfish," unicellular-like life features, which are linked to the increased adaptability to environmental changes displayed by cancer cells. Mechanisms of stress response, resembling those observed in unicellular organisms, are actively exploited by mammalian cancer cells to boost genetic diversity and increase chances of survival under unfavorable conditions, such as lack of oxygen/nutrients or exposure to drugs. Unicellular organisms under stressful conditions (e.g., antibiotic treatment) stop replicating or slowly divide and transiently increase their mutation rates to foster diversity, a process known as adaptive mutability. Analogously, tumor cells exposed to drugs enter a persister phenotype and can reduce DNA replication fidelity, which in turn fosters genetic diversity. The implications of adaptive evolution are of relevance to understand resistance to anticancer therapies.

Curcumin Regulates ERCC1 Expression and Enhances Oxaliplatin Sensitivity in Resistant Colorectal Cancer Cells through Its Effects on miR-409-3p

Background

Oxaliplatin (L-OHP) resistance is a major obstacle to the effective treatment of colorectal cancer. The resistance mechanism(s) of colorectal tumors to L-OHP may be related to the regulation of ERCC1 by cancer-expressed miRNAs, but no in-depth studies on the miRNAs that affect drug resistance have been performed. Curcumin (Cur) can reverse the drug resistance of cancer cells, but its effects on ERCC1 expression and miRNA profiles in colorectal cancer have not been studied.

Methods

To study the regulation effect of curcumin on ERCC1 expression and its effects on miRNAs, the L-OHP-resistant colorectal cancer cell line HCT116/L-OHP was established. MTT assays were used to evaluate cell proliferation. Flow cytometry was used to investigate apoptotic induction. Western blot and RT-PCR analysis were used to evaluate the expression of drug-associated ERCC1, Bcl-2, GST-π, MRP, P-gp, and survivin.

Results

HCT116//L-OHP cell lines were successfully established. The combination of L-OHP and curcumin could reduce L-OHP resistance in vitro. In addition, combination therapy inhibited the expression of ERCC1, Bcl-2, GST-π, MRP, P-gp, and survivin at the mRNA and protein level. Curcumin was found to inhibit ERCC1 through its ability to modulate miR-409-3p.

Conclusion

Curcumin can overcome L-OHP resistance in colorectal cancer cells through its effects on miR-409-3p mediated ERCC1 expression.

Analytical Challenges in Development of Chemoresistance Predictors for Precision Oncology

Chemoresistance, i.e., tumor insensitivity to chemotherapy, shortens life expectancy of cancer patients. Despite the availability of new treatment options, initial systemic regimens for solid tumors are dominated by a set of standard chemotherapy drugs, and alternative therapies are used only when a patient has demonstrated chemoresistance clinically. Chemoresistance predictors use laboratory parameters measured on tissue samples to predict the patient's response to chemotherapy and help to avoid application of chemotherapy to chemoresistant patients. Despite thousands of publications on putative chemoresistance predictors, there are only about a dozen predictors that are sufficiently accurate for precision oncology. One of the major reasons for inaccuracy of predictors is inaccuracy of analytical methods utilized to measure their laboratory parameters: an inaccurate method leads to an inaccurate predictor. The goal of this study was to identify analytical challenges in chemoresistance-predictor development and suggest ways to overcome them. Here we describe principles of chemoresistance predictor development via correlating a clinical parameter, which manifests disease state, with a laboratory parameter. We further classify predictors based on the nature of laboratory parameters and analyze advantages and limitations of different predictors using the reliability of analytical methods utilized for measuring laboratory parameters as a criterion. Our eventual focus is on predictors with known mechanisms of reactions involved in drug resistance (drug extrusion, drug degradation, and DNA damage repair) and using rate constants of these reactions to establish accurate and robust laboratory parameters. Many aspects and conclusions of our analysis are applicable to all types of disease biomarkers built upon the correlation of clinical and laboratory parameters.

Anti-tumour effects of PIM kinase inhibition on progression and chemoresistance of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a biologically aggressive cancer. Targeted therapy is in need to tackle challenges in the treatment perspective. A growing body of evidence suggests a promising role of pharmacological inhibition of PIM (proviral integration site for Moloney murine leukaemia virus) kinase in some human haematological and solid cancers. Yet to date, the potential application of PIM inhibitors in HCC is still largely unexplored. In the present study we investigated the pre-clinical efficacy of PIM inhibition as a therapeutic approach in HCC. Effects of PIM inhibitors on cell proliferation, migration, invasion, chemosensitivity, and self-renewal were examined in vitro. The effects of PIM inhibitors on tumour growth and chemoresistance in vivo were studied using xenograft mouse models. Potential downstream molecular mechanisms were elucidated by RNA sequencing (RNA-seq) of tumour tissues harvested from animal models. Our findings demonstrate that PIM inhibitors SGI-1776 and PIM447 reduced HCC proliferation, metastatic potential, and self-renewal in vitro. Results from in vivo experiments supported the role of PIM inhibition in suppressing of tumour growth and increasing chemosensitivity of HCC toward cisplatin and doxorubicin, the two commonly used chemotherapeutic agents in trans-arterial chemoembolisation (TACE) for HCC. RNA-seq analysis revealed downregulation of the MAPK/ERK pathway upon PIM inhibition in HCC cells. In addition, LOXL2 and ICAM1 were identified as potential downstream effectors. Taken together, PIM inhibitors demonstrated remarkable anti-tumourigenic effects in HCC in vitro and in vivo. PIM kinase inhibition is a potential approach to be exploited in formulating adjuvant therapy for HCC patients of different disease stages. © 2020 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Unexpected therapeutic effects of cisplatin

Cisplatin is a widely used chemotherapeutic agent that is clinically approved to fight both carcinomas and sarcomas. It has relatively high efficiency in treating ovarian cancers and metastatic testicular cancers. It is generally accepted that the major mechanism of cisplatin anti-cancer action is DNA damage. However, cisplatin is also effective in metastatic cancers and should, therefore, affect slow-cycling cancer stem cells in some way. In this review, we focused on the alternative effects of cisplatin that can support a good therapeutic response. First, attention was paid to the effects of cisplatin at the cellular level such as changes in intracellular pH and cellular mechanical properties. Alternative cellular targets of cisplatin, and the effects of cisplatin on cancer cell metabolism and ER stress were also discussed. Furthermore, the impacts of cisplatin on the tumor microenvironment and in the whole organism context were reviewed. In this review, we try to reveal possible causes of the unexpected effectiveness of this anti-cancer drug.

DNA damage response and resistance of cancer stem cells

The cancer stem cell (CSC) model defines tumors as hierarchically organized entities, containing a small population of tumorigenic CSC, or tumour-initiating cells, placed at the apex of this hierarchy. These cells may share common qualities with chemo- and radio-resistant cancer cells and contribute to self-renewal activities resulting in tumour formation, maintenance, growth and metastasis. Yet, it remains obscure what self-defense mechanisms are utilized by these cells against the chemotherapeutic drugs or radiotherapy. Recently, attention has been focused on the pivotal role of the DNA damage response (DDR) in tumorigenesis. In line with this note, an increased DDR that prevents CSC and chemoresistant cells from genotoxic pressure of chemotherapeutic drugs or radiation may be responsible for cancer metastasis. In this review, we focus on the current knowledge concerning the role of DDR in CSC and resistant cancer cells and describe the existing opportunities of re-sensitizing such cells to modulate therapeutic treatment effects.

Combination of ω-3 fatty acids and cisplatin as a potential alternative strategy for personalized therapy of metastatic melanoma: an in-vitro study

The recently developed therapeutic strategies have led to unprecedented improvements in the control of metastatic melanoma and in the survival of specific subgroups of patients. However, drug resistance, low response rates, and undesired side effects make these treatments not suitable or tolerable for all the patients, and chemotherapeutic treatments appear still indispensable, at least for subgroups of patients. New combinatory strategies are also under investigation as tailored treatments or salvage therapies, including combined treatments of immunotherapy with conventional chemotherapy. On this basis, and in consideration of the antineoplastic properties of ω-3 polyunsaturated fatty acids, we have here investigated the potential of these bioactive dietary factors to revert the resistance frequently exhibited by this form of cancer to cisplatin (CDDP, cis-diamminedichloroplatinum). We demonstrated that docosahexenoic acid (DHA, 22:6ω-3) sensitizes the cells to the CDDP-induced inhibition of cell growth and migration by reverting CDDP effects on DNA damage and ERCC1 expression, as well as on the DUSP6 and p-ERK expressions, which regulate ERCC1 activation upwardly. In line, DUSP6 gene silencing prevented the effect of DHA, confirming that DHA acted on the DUSP6/p-ERK/ERCC1 repair pathways to sensitize melanoma cells to the anticancer effect of CDDP. Similar effects were obtained also with eicosapentaenoic acid (20:5ω-3). Overall, our findings suggest that the combination of CDDP treatment with a dietary supplementation with ω-3 polyunsaturated fatty acids could potentially represent a new therapeutic strategy for overcoming CDDP resistance in metastatic melanoma.

Long noncoding RNA X-inactive specific transcript promotes malignant melanoma progression and oxaliplatin resistance

Long noncoding RNA X-inactive specific transcript (XIST) was confirmed to participate in the development of many cancers. However, the function of XIST in malignant melanoma (MM) remained largely unknown. In the current study, we found that the XIST expression level was upregulated in MM tissues and cell lines. In addition, the growth rate of MM cells transfected with silencing XIST was significantly decreased compared with that with silencing normal control. XIST knockdown inhibited proliferation and migration in MM cells and increased the oxaliplatin sensitivity of oxaliplatin-resistant MM cells. Bioinformatics analysis showed that XIST acts as a molecular sponge for miR-21 and miR-21 directly targets with 3'-UTR of PI3KR1. Furthermore, XIST knockdown inhibited PI3KRI and AKT expression, and promoted Bcl-2 and Bax expression. In short, the current study showed that XIST was a crucial regulator in progression and oxaliplatin resistance of MM, providing a novel insight into the pathogenesis and underlying therapeutic target for MM.

Chemoresistance in gastric cancer is attributed to the overexpression of excision repair cross-complementing 1 (ERCC1) caused by microRNA-122 dysregulation

MicroRNAs are deemed as key regulators of gene expression. In particular, the elevated expression of excision repair cross-complementing 1 (ERCC1) significantly reduced the effectiveness of gastric cancer treatment by cisplatin (CDDP)-based therapies. In this paper, qRT-PCR and western blot were adopted to measure miR-122 and ERCC1 messenger RNA (mRNA) expression in all samples. Luciferase assay was carried out to verify the role of ERCC1 as a target of miR-122. The CCK-8 assay was carried out to study the effect of ERCC1 and miR-122 on cell survival and apoptosis. The results demonstrated that miR-122 expression was reduced in cisplatin-resistant gastric cancer. Using bioinformatic analysis, miR-122 was shown to target the 3'-UTR of human ERCC1. A dual-luciferase assay demonstrated that miR-122 downregulated ERCC1 expression, while the mutations in ERCC1 3'-UTR abolished its interaction with miR-122. Transfection of miR-122 mimics decreased the levels of ERCC1 mRNA and protein expression, while the transfection of miR-122 inhibitors increased the levels of both ERCC1 mRNA and protein expression. Furthermore, we found that overexpressed miR-122 promoted the proliferation of MKN74 cells and reduced their apoptotic by targeting ERCC1. In addition, the levels of miR-122 and ERCC1 were negatively correlated in gastric cancer samples. In summary, the reduced miR-122 expression may play an essential role in the induction of cisplatin-resistance by increasing ERCC1 expression.

Chemoresistance mechanisms of breast cancer and their countermeasures

Chemoresistance is one of the major challenges for the breast cancer treatment. Owing to its heterogeneous nature, the chemoresistance mechanisms of breast cancer are complicated, and not been fully elucidated. The existing treatments fall short of offering adequate solution to drug resistance, so more effective approaches are desperately needed to improve existing therapeutic regimens. To overcome this hurdle, a number of strategies are being investigated, such as novel agents or drug carriers and combination treatment. In addition, some new therapeutics including gene therapy and immunotherapy may be promising for dealing with the resistance. In this article, we review the mechanisms of chemoresistance in breast cancer. Furthermore, the potential therapeutic methods to overcome the resistance were discussed.

Chemoresistance and the Self-Maintaining Tumor Microenvironment

The progression of cancer is associated with alterations in the tumor microenvironment, including changes in extracellular matrix (ECM) composition, matrix rigidity, hypervascularization, hypoxia, and paracrine factors. One key malignant phenotype of cancer cells is their ability to resist chemotherapeutics, and elements of the ECM can promote chemoresistance in cancer cells through a variety of signaling pathways, inducing changes in gene expression and protein activity that allow resistance. Furthermore, the ECM is maintained as an environment that facilitates chemoresistance, since its constitution modulates the phenotype of cancer-associated cells, which themselves affect the microenvironment. In this review, we discuss how the properties of the tumor microenvironment promote chemoresistance in cancer cells, and the interplay between these external stimuli. We focus on both the response of cancer cells to the external environment, as well as the maintenance of the external environment, and how a chemoresistant phenotype emerges from the complex signaling network present.

Assessing Therapeutic Efficacy of MEK Inhibition in a KRASG12C-Driven Mouse Model of Lung Cancer

Purpose: Despite the challenge to directly target mutant KRAS due to its high GTP affinity, some agents are under development against downstream signaling pathways, such as MEK inhibitors. However, it remains controversial whether MEK inhibitors can boost current chemotherapy in KRAS-mutant lung tumors in clinic. Considering the genomic heterogeneity among patients with lung cancer, it is valuable to test potential therapeutics in KRAS mutation-driven mouse models.Experimental Design: We first compared the pERK1/2 level in lung cancer samples with different KRAS substitutions and generated a new genetically engineered mouse model whose tumor was driven by KRAS G12C, the most common KRAS mutation in lung cancer. Next, we evaluated the efficacy of selumetinib or its combination with chemotherapy, in KRASG12C tumors compared with KRASG12D tumors. Moreover, we generated KRASG12C/p53R270H model to explore the role of a dominant negative p53 mutation detected in patients in responsiveness to MEK inhibition.Results: We determined higher pERK1/2 in KRASG12C lung tumors compared with KRASG12D Using mouse models, we further identified that KRASG12C tumors are significantly more sensitive to selumetinib compared with KrasG12D tumors. MEK inhibition significantly increased chemotherapeutic efficacy and progression-free survival of KRASG12C mice. Interestingly, p53 co-mutation rendered KRASG12C lung tumors less sensitive to combination treatment with selumetinib and chemotherapy.Conclusions: Our data demonstrate that unique KRAS mutations and concurrent mutations in tumor-suppressor genes are important factors for lung tumor responses to MEK inhibitor. Our preclinical study supports further clinical evaluation of combined MEK inhibition and chemotherapy for lung cancer patients harboring KRAS G12C and wild-type p53 status. Clin Cancer Res; 24(19); 4854-64. ©2018 AACR.

Accumulation of prohibitin is a common cellular response to different stressing stimuli and protects melanoma cells from ER stress and chemotherapy-induced cell death

Melanoma is responsible for most deaths among skin cancers and conventional and palliative care chemotherapy are limited due to the development of chemoresistance. We used proteomic analysis to identify cellular responses that lead to chemoresistance of human melanoma cell lines to cisplatin. A systems approach to the proteomic data indicated the participation of specific cellular processes such as oxidative phosphorylation, mitochondrial organization and homeostasis, as well as the unfolded protein response (UPR) to be required for the survival of cells treated with cisplatin. Prohibitin (PHB) was among the proteins consistently accumulated, interacting with the functional clusters associated with resistance to cisplatin. We showed PHB accumulated at different levels in melanoma cell lines under stressing stimuli, such as (i) treatment with temozolomide (TMZ), dacarbazine (DTIC) and cisplatin; (ii) serum deprivation; (iii) tunicamycin, an UPR inducer. Prohibitin accumulated in the mitochondria of melanoma cells after cisplatin and tunicamycin treatment and its de novo accumulation led to chemoresistance melanoma cell lines. In contrast, PHB knock-down sensitized melanoma cells to cisplatin and tunicamycin treatment. We conclude that PHB participates in the survival of cells exposed to different stress stimuli, and can therefore serve as a target for the sensitization of melanoma cells to chemotherapy.

Down-regulation of GADD45A enhances chemosensitivity in melanoma

Melanoma is a malignant skin cancer with considerable drug resistance. Increased expression of DNA repair genes have been reported in melanoma, and this contributes to chemotherapy resistance. GADD45A is involved in DNA repair, cell cycle arrest and apoptosis in response to physiologic or environmental stresses. In this study, we investigated the role of GADD45A in chemotherapy response. Firstly, the mRNA expression of profiled DNA repair genes in cisplatin-treated melanoma cells was detected by RT2 profilerTM PCR array. We found the expression of GADD45A upregulated in a dose- and time- dependent manner. In addition, suppression of GADD45A sensitized melanoma cells to cisplatin and enhanced cisplatin-induced DNA damage. Flow cytometry revealed that downregulating GADD45A released cells from cisplatin-induced G2/M arrest and increased apoptosis. By using a MEK inhibitor, GADD45A was shown to be regulated by MAPK-ERK pathway following cisplatin treatment. Thus, the induction of GADD45A might play important roles in chemotherapy response in human melanoma cancer and could serve as a novel molecular target for melanoma therapy.

Differential Regulation of LET-7 by LIN28B Isoform-Specific Functions

The RNA-binding protein LIN28B plays an important role in development, stem cell biology, and tumorigenesis. LIN28B has two isoforms: the LIN28B-long and -short isoforms. Although studies have revealed the functions of the LIN28B-long isoform in tumorigenesis, the role of the LIN28B-short isoform remains unclear and represents a major gap in the field. The LIN28B-long and -short isoforms are expressed in a subset of human colorectal cancers and adjacent normal colonic mucosa, respectively. To elucidate the functional and mechanistic aspects of these isoforms, colorectal cancer cells (Caco-2 and LoVo) were generated to either express no LIN28B or the -short or -long isoform. Interestingly, the long isoform suppressed LET-7 expression and activated canonical RAS/ERK signaling, whereas the short isoform did not. The LIN28B-long isoform-expressing cells demonstrated increased drug resistance to 5-fluorouracil and cisplatin through the upregulation of ERCC1, a DNA repair gene, in a LET-7-dependent manner. The LIN28B-short isoform preserved its ability to bind pre-let-7, without inhibiting the maturation of LET-7, and competed with the LIN28B-long isoform for binding to pre-let-7 Coexpression of the short isoform in the LIN28B-long isoform-expressing cells rescued the phenotypes induced by the LIN28B-long isoform.Implications: This study demonstrates the differential antagonistic functions of the LIN28B-short isoform against the LIN28B-long isoform through an inability to degrade LET-7, which leads to the novel premise that the short isoform may serve to counterbalance the long isoform during normal colonic epithelial homeostasis, but its downregulation during colonic carcinogenesis may reveal the protumorigenic effects of the long isoform. Mol Cancer Res; 16(3); 403-16. ©2018 AACR.

Downregulation of vimentin expression increased drug resistance in ovarian cancer cells

Cisplatin and other platinum-based drugs have been widely used in the treatment of ovarian cancer, but most patients acquire the drug resistance that greatly compromises the efficacy of drugs. Understanding the mechanism of drug resistance is important for finding new therapeutic approaches. In the present study, we found that the expression of vimentin was downregulated in drug-resistant ovarian cancer cell lines A2780-DR and HO-8910 as compared to their respective control cells. Overexpression of vimentin in A2780-DR cells markedly increased their sensitivity to cisplatin, whereas knockdown of vimentin in A2780, HO-8910-PM and HO-8910 cells increased the resistance to cisplatin, demonstrating that vimentin silencing enhanced cisplatin resistance in ovarian cancer cells. Quantitative proteomic analysis identified 95 differentially expressed proteins between the vimentin silenced A2780 cells (A2780-VIM-KN) and the control cells, in which downregulation of endocytic proteins and the upregulation of exocytotic proteins CHMP2B and PDZK1 were proposed to contribute the decreased cisplatin accumulation in vimentin knockdown cells. Silencing of vimentin induced upregulation of cancer stem cell markers and both A2780-DR and A2780-VIM-KN cells were more facile to form spheroids than control cells under serum-free culture condition. Our results also revealed that vimentin knockdown increased the 14-3-3 mediated retention of Cdc25C in the cytoplasm, leading to inactivation of Cdk1 and the prolonged G2 phase arrest that allowed the longer period of time for cells to repair cisplatin-damaged DNA. Taken together, we demonstrated that vimentin silencing enhanced cells' resistance to cisplatin via prolonged G2 arrest and increased exocytosis, suggesting that vimentin is a potential target for treatment of drug resistant ovarian cancer.

Dual-specificity phosphatase 6 (DUSP6): a review of its molecular characteristics and clinical relevance in cancer

Mitogen-activated protein kinases (MAPKs) are the main regulators of cellular proliferation, growth, and survival in physiological or pathological conditions. Aberrant MAPK signaling plays a pivotal role in carcinogenesis, which leads to development and progression of human cancer. Dual-specificity phosphatase 6 (DUSP6), a member of the MAPK phosphatase family, interacts with specifically targeted extracellular signal-regulated kinase 1/2 via negative feedback regulation in the MAPK pathway of mammalian cells. This phosphatase functions in a dual manner, pro-oncogenic or tumor-suppressive, depending on the type of cancer. To date, the tumor-suppressive role of DUSP6 has been demonstrated in pancreatic cancer, non-small cell lung cancer, esophageal squamous cell and nasopharyngeal carcinoma, and ovarian cancer. Its pro-oncogenic role has been observed in human glioblastoma, thyroid carcinoma, breast cancer, and acute myeloid carcinoma. Both roles of DUSP6 have been documented in malignant melanoma depending on the histological subtype of the cancer. Loss- or gain-of-function effects of DUSP6 in these cancers highlights the significance of this phosphatase in carcinogenesis. Development of methods that use the DUSP6 gene as a therapeutic target for cancer treatment or as a prognostic factor for diagnosis and evaluation of cancer treatment outcome has great potential. This review focuses on molecular characteristics of the DUSP6 gene and its role in cancers in the purview of development, progression, and cancer treatment outcome.

Melanoma cells replicate through chemotherapy by reducing levels of key homologous recombination protein RAD51 and increasing expression of translesion synthesis DNA polymerase ζ

BACKGROUND

The global incidence of melanoma has been increasing faster than any other form of cancer. New therapies offer exciting prospects for improved survival, but the development of resistance is a major problem and there remains a need for additional effective melanoma therapy. Platinum compounds, such as cisplatin, are the most effective chemotherapeutics for a number of major cancers, but are ineffective on metastatic melanoma. They cause monofunctional adducts and intrastrand crosslinks that are repaired by nucleotide excision repair, as well as the more toxic interstrand crosslinks that are repaired by a combination of nuclease activity and homologous recombination.

METHODS

We investigated the mechanism of melanoma resistance to cisplatin using a panel of melanoma and control cell lines. Cisplatin-induced changes in levels of the key homologous recombination protein RAD51 and compensatory changes in translesion synthesis DNA polymerases were identified by western blotting and qRT-PCR. Flow cytometry, immunofluorescence and western blotting were used to compare the cell cycle and DNA damage response and the induction of apoptosis in cisplatin-treated melanoma and control cells. Ectopic expression of a tagged form of RAD51 and siRNA knockdown of translesion synthesis DNA polymerase zeta were used to investigate the mechanism that allowed cisplatin-treated melanoma cells to continue to replicate.

RESULTS

We have identified and characterised a novel DNA damage response mechanism in melanoma. Instead of increasing levels of RAD51 on encountering cisplatin-induced interstrand crosslinks during replication, melanoma cells shut down RAD51 synthesis and instead boost levels of translesion synthesis DNA polymerase zeta to allow replication to proceed. This response also resulted in synthetic lethality to the PARP inhibitor olaparib.

CONCLUSIONS

This unusual DNA damage response may be a more appropriate strategy for an aggressive and rapidly growing tumour like melanoma that enables it to better survive chemotherapy, but also results in increased sensitivity of cultured melanoma cells to the PARP inhibitor olaparib.

A regulatory circuit composed of DNA methyltransferases and receptor tyrosine kinases controls lung cancer cell aggressiveness

Overexpression of DNMT1 and KIT is prevalent in lung cancer, yet the underlying molecular mechanisms are poorly understood. While the deregulated activation of DNMT1 or KIT has been implicated in lung cancer pathogenesis, whether and how DNMT1 and KIT orchestrate lung tumorigenesis are unclear. Here, using human lung cancer tissue microarrays and fresh frozen tissues, we found that the overexpression of DNMT1 is positively correlated with the upregulation of KIT in tumor tissues. We demonstrated that DNMT1 and KIT form a positive regulatory loop, in which ectopic DNMT1 expression increases, whereas targeted DNMT1 depletion abrogates KIT signaling cascade through Sp1/miR-29b network. Conversely, an increase of KIT levels augments, but a reduction of KIT expression ablates DNMT1 transcription by STAT3 pathway leading to in-parallel modification of the DNA methylation profiles. We provided evidence that KIT inactivation induces global DNA hypomethylation, restores the expression of tumor suppressor p15INK4B through promoter demethylation; in turn, DNMT1 dysfunction impairs KIT kinase signaling. Functionally, KIT and DNMT1 co-expression promotes, whereas dual inactivation of them suppresses, lung cancer cell proliferation and metastatic growth in vitro and in vivo, in a synergistic manner. These findings demonstrate the regulatory and functional interplay between DNA methylation and tyrosine kinase signaling in propelling tumorigenesis, providing a widely applicable approach for targeting lung cancer.

ISG15 silencing increases cisplatin resistance via activating p53-mediated cell DNA repair

Tumor cells frequently evolved resistance to cisplatin that greatly compromises the efficacy of chemotherapy. Identification of the mechanisms underlying drug resistance is important for developing new therapeutic approaches. ISG15 is found to be elevated in many human carcinomas and cancer cell lines. Here, we identified that the expressions of ISG15 and ISG15-conjugating system were downregulated in drug resistant A549/DDP cells compared to drug sensitive A549 cells. Silencing of ISG15 robustly elevated the resistance to cisplatin, suggesting ISG15 plays an important role in cisplatin resistance. Quantitative proteomics identified 1296 differentially expressed proteins between the control and ISG15 knockdown cells, showing that ISG15 silencing upregulated proteins in p53 pathway, adherens junction and nucleotide excision repair (NER) pathway. We also found that ISG15 silencing induced cell cycle arrest through stabilizing p53 and increasing HnRNP K expression, which allowed the prolonged time for cells to repair cisplatin-damaged DNA. Taken together, we proved that ISG15 downregulation activated the DNA damage/repair pathway to enhance cisplatin resistance in tumor cells.

Functional characterization of a novel transcript of ERCC1 in chemotherapy resistance of ovarian cancer

Approximately 15-20% of ovarian cancer patients receiving platinum-based chemotherapy are primary platinum-resistant. Identification of these patients and transfer to other more effective therapy could reduce the morbidity of ovarian cancer. ERCC1 is a DNA repair gene which can complex with XPF to repair cisplatin-induced DNA damage and cause chemotherapy resistance. In this study, we found a novel ERCC1 transcript initiated upstream of the normal transcription initiation site. The expression of this larger ERCC1 transcript dramatically increased following cisplatin treatment in ovarian cancer cells and was regulated by the MAPK pathway. This phenomenon conferred enhanced cisplatin resistance on ovarian cancer cells, and was confirmed with chemosensitive and chemoresistant patients' samples. Our data suggested that larger ERCC1 transcript levels correlated with the outcome of platinum-based chemotherapy.

Functional characterization of a novel transcript of ERCC1 in chemotherapy resistance of ovarian cancer

Approximately 15-20% of ovarian cancer patients receiving platinum-based chemotherapy are primary platinum-resistant. Identification of these patients and transfer to other more effective therapy could reduce the morbidity of ovarian cancer. ERCC1 is a DNA repair gene which can complex with XPF to repair cisplatin-induced DNA damage and cause chemotherapy resistance. In this study, we found a novel ERCC1 transcript initiated upstream of the normal transcription initiation site. The expression of this larger ERCC1 transcript dramatically increased following cisplatin treatment in ovarian cancer cells and was regulated by the MAPK pathway. This phenomenon conferred enhanced cisplatin resistance on ovarian cancer cells, and was confirmed with chemosensitive and chemoresistant patients' samples. Our data suggested that larger ERCC1 transcript levels correlated with the outcome of platinum-based chemotherapy.

Functional characterization of a novel transcript of ERCC1 in chemotherapy resistance of ovarian cancer

Approximately 15-20% of ovarian cancer patients receiving platinum-based chemotherapy are primary platinum-resistant. Identification of these patients and transfer to other more effective therapy could reduce the morbidity of ovarian cancer. ERCC1 is a DNA repair gene which can complex with XPF to repair cisplatin-induced DNA damage and cause chemotherapy resistance. In this study, we found a novel ERCC1 transcript initiated upstream of the normal transcription initiation site. The expression of this larger ERCC1 transcript dramatically increased following cisplatin treatment in ovarian cancer cells and was regulated by the MAPK pathway. This phenomenon conferred enhanced cisplatin resistance on ovarian cancer cells, and was confirmed with chemosensitive and chemoresistant patients' samples. Our data suggested that larger ERCC1 transcript levels correlated with the outcome of platinum-based chemotherapy.

Combined pitavastatin and dacarbazine treatment activates apoptosis and autophagy resulting in synergistic cytotoxicity in melanoma cells

Melanoma is an aggressive skin cancer and its incidence is increasing faster than any other type of cancer. Whilst dacarbazine (DTIC) is the standard chemotherapy for metastatic melanoma, it has limited success. Statins, including pitavastatin, have been demonstrated to have a range of anti-cancer effects in a number of human cancer cell lines. The present study therefore explored the anti-cancer activity of combined DTIC and pitavastatin in A375 and WM115 human melanoma cells. Cell survival assays demonstrated that combined DTIC and pitavastatin treatment resulted in synergistic cell death. Cell cycle analyses further revealed that this combined treatment resulted in a G1 cell cycle arrest, as well as a sub-G1 population, indicative of apoptosis. Activation of apoptosis was confirmed by Annexin V-fluorescein isothiocyanate/propidium iodide double-staining and an increase in the levels of active caspase 3 and cleaved poly (ADP-ribose) polymerase. Furthermore, it was demonstrated that apoptosis occurs through the intrinsic pathway, evident from the release of cytochrome c. Finally, combined DTIC and pitavastatin treatment was demonstrated to also activate autophagy as part of a cell death mechanism. The present study provides novel evidence to suggest that the combined treatment of DTIC and pitavastatin may be effective in the treatment of melanoma.

Pharmacological inhibition of DUSP6 suppresses gastric cancer growth and metastasis and overcomes cisplatin resistance

Gastric cancer (GC) is the second cause of cancer-related death. Cisplatin (CDDP) is widely used as the standard GC treatment, but relapse and metastasis are common because of intrinsic or acquired drug resistance. The mitogen-activated protein kinase phosphatases (MAPK)-extracellular signal regulated kinases (ERK) pathway contributes to GC progression and drug resistance, but targeting the MAPK-ERK pathway is challenging in GC therapy. Here, we demonstrated that dual-specificity phosphatases 6 (DUSP6) was overexpressed in GC and predicted poor overall survival and progression-free survival. Knockdown DUSP6 inhibited GC proliferation, migration, invasion and induced apoptosis. (E/Z)-BCI hydrochloride (BCI), a DUSP6 small molecule inhibitor, increased the activity of ERK but interestingly decreased the expression of ERK response genes in BGC823, SGC7901 and CDDP-resistant SGC7901/DDP cells. BCI also caused cell death through the DNA damage response (DDR) pathway. Moreover, BCI inhibited cell proliferation, migration and invasion in a receptor-independent manner and enhanced CDDP cytotoxicity at pharmacological concentrations in the GC cells. In vivo experiments further showed that BCI enhances the antitumor effects of CDDP in cell-based xenografts and PDX models. In summary, our findings indicated that disruption of DUSP6 by BCI enhanced CDDP-induced cell death and apoptosis in GC may partly through ERK and DDR pathways. Thus, this study suggests that DUSP6 is a potential prognostic biomarker and a promising target for GC therapy.

The molecular mechanisms of chemoresistance in cancers

Overcoming intrinsic and acquired drug resistance is a major challenge in treating cancer patients because chemoresistance causes recurrence, cancer dissemination and death. This review summarizes numerous molecular aspects of multi-resistance, including transporter pumps, oncogenes (EGFR, PI3K/Akt, Erk and NF-κB), tumor suppressor gene (p53), mitochondrial alteration, DNA repair, autophagy, epithelial-mesenchymal transition (EMT), cancer stemness, and exosome. The chemoresistance-related proteins are localized to extracellular ligand, membrane receptor, cytosolic signal messenger, and nuclear transcription factors for various events, including proliferation, apoptosis, EMT, autophagy and exosome. Their cross-talk frequently appears, such as the regulatory effects of EGFR-Akt-NF-κB signal pathway on the transcription of Bcl-2, Bcl-xL and survivin or EMT-related stemness. It is essential for the realization of the target, individualized and combine therapy to clarify these molecular mechanisms, explore the therapy target, screen chemosensitive population, and determine the efficacy of chemoreagents by cell culture and orthotopic model.

Disruption of DNA repair in cancer cells by ubiquitination of a destabilising dimerization domain of nucleotide excision repair protein ERCC1

DNA repair pathways present in all cells serve to preserve genome stability, but in cancer cells they also act reduce the efficacy of chemotherapy. The endonuclease ERCC1-XPF has an important role in the repair of DNA damage caused by a variety of chemotherapeutic agents and there has been intense interest in the use of ERCC1 as a predictive marker of therapeutic response in non-small cell lung carcinoma, squamous cell carcinoma and ovarian cancer. We have previously validated ERCC1 as a therapeutic target in melanoma, but all small molecule ERCC1-XPF inhibitors reported to date have lacked sufficient potency and specificity for clinical use. In an alternative approach to prevent the repair activity of ERCC1-XPF, we investigated the mechanism of ERCC1 ubiquitination and found that the key region was the C-terminal (HhH)₂ domain which heterodimerizes with XPF. This ERCC1 region was modified by non-conventional lysine-independent, but proteasome-dependent polyubiquitination, involving Lys33 of ubiquitin and a linear ubiquitin chain. XPF was not polyubiquitinated and its expression was dependent on presence of ERCC1, but not vice versa. To our surprise we found that ERCC1 can also homodimerize through its C-terminal (HhH)₂ domain. We exploited the ability of a peptide containing this C-terminal domain to destabilise both endogenous ERCC1 and XPF in human melanoma cells and fibroblasts, resulting in reductions of up to 85% in nucleotide excision repair and near two-fold increased sensitivity to DNA damaging agents. We suggest that the ERCC1 (HhH)₂ domain could be used in an alternative strategy to treat cancer.

A phase I clinical trial of binimetinib in combination with FOLFOX in patients with advanced metastatic colorectal cancer who failed prior standard therapy

Background

This was a first in-human, open-label, dose-escalation phase I study conducted to evaluate the maximum tolerated dose (MTD), safety, and efficacy of the combination of oral binimetinib and FOLFOX.

Materials and Methods

Patients with metastatic colorectal cancer (mCRC) who progressed on prior standard therapies received twice daily binimetinib continuously or intermittently with FOLFOX. Dose-limiting toxicities (DLTs) were assessed in the first 2 cycles of study treatment. Pharmacokinetic (PK) analysis of 5-FU and oxaliplatin was performed at the MTD in an expanded 6 patient cohort.

Results

Twenty-six patients were enrolled and assessed for safety. In the dose-escalation phase, no DLTs were noted in all binimetinib dosing schedules and the MTD of binimetinib in with FOLFOX was 45 mg orally twice daily. There were no significant differences in the PKs of 5-FU or oxaliplatin with or without binimetinib. Continuous dosing of binimetinib produced SD at 2 months in 9 of 13 evaluable patients and a median PFS of 3.5 months. Nine of 10 patients had PD at 2 months on the intermittent arm.

Conclusions

Oral binimetinib and FOLFOX has a manageable toxicity profile and showed some evidence of antitumor activity in heavily pretreated mCRC patients.

Improved prediction of PARP inhibitor response and identification of synergizing agents through use of a novel gene expression signature generation algorithm

Despite rapid advancement in generation of large-scale microarray gene expression datasets, robust multigene expression signatures that are capable of guiding the use of specific therapies have not been routinely implemented into clinical care. We have developed an iterative resampling analysis to predict sensitivity algorithm to generate gene expression sensitivity profiles that predict patient responses to specific therapies. The resultant signatures have a robust capacity to accurately predict drug sensitivity as well as the identification of synergistic combinations. Here, we apply this approach to predict response to PARP inhibitors, and show it can greatly outperforms current clinical biomarkers, including BRCA1/2 mutation status, accurately identifying PARP inhibitor-sensitive cancer cell lines, primary patient-derived tumor cells, and patient-derived xenografts. These signatures were also capable of predicting patient response, as shown by applying a cisplatin sensitivity signature to ovarian cancer patients. We additionally demonstrate how these drug-sensitivity signatures can be applied to identify novel synergizing agents to improve drug efficacy. Tailoring therapeutic interventions to improve patient prognosis is of utmost importance, and our drug sensitivity prediction signatures may prove highly beneficial for patient management.

Heterogeneous nuclear ribonucleoprotein K is associated with poor prognosis and regulates proliferation and apoptosis in bladder cancer

Heterogeneous nuclear ribonucleoprotein K (hnRNPK) is an essential RNA- and DNA-binding protein that regulates diverse biological events, especially DNA transcription. hnRNPK overexpression is related to tumorigenesis in several cancers. However, both the expression patterns and biological mechanisms of hnRNPK in bladder cancer are unclear. We investigated hnRNPK expression by immunohistochemistry in 188 patients with bladder cancer, and found that hnRNPK expression levels were significantly increased in bladder cancer tissues and that high-hnRNPK expression was closely correlated with poor prognosis. Loss- and gain-of-function assays demonstrated that hnRNPK promoted proliferation, anti-apoptosis, and chemoresistance in bladder cancer cells in vitro, and hnRNPK knockdown suppressed tumorigenicity in vivo. Mechanistically, hnRNPK regulated various functions in bladder cancer by directly mediating cyclin D1, G0/G1 switch 2 (G0S2), XIAP-associated factor 1, and ERCC excision repair 4, endonuclease catalytic subunit (ERCC4) transcription. In conclusion, we discovered that hnRNPK plays an important role in bladder cancer, suggesting that it is a potential prognostic marker and a promising target for treating bladder cancer.

Elevated Cellular PD1/PD-L1 Expression Confers Acquired Resistance to Cisplatin in Small Cell Lung Cancer Cells

Although small cell lung cancer (SCLC) is highly responsive to chemotherapies (e.g., cisplatin-etoposide doublet), virtually almost all responsive SCLC patients experience disease recurrence characterized by drug resistance. The mechanisms underlying cisplatin resistance remain elusive. Here we report that cell-intrinsic expression of PD1 and PD-L1, two immune checkpoints, is required for sustained expansion of SCLC cells under cisplatin selection. Indeed, PD1 and PD-L1 were expressed at a higher level in lung cancer cell lines, tumor tissues, and importantly, in SCLC cells resistant to cisplatin (H69R, H82R), when compared to respective controls. Genetic abrogation of PD1 and PD-L1 in H69R and H82R cells decreased their proliferation rate, and restored their sensitivity to cisplatin. Mechanistically, PD-L1 upregulation in H69R and H82R cells was attributed to the overexpression of DNA methyltransferase 1 (DNMT1) or receptor tyrosine kinase KIT, as knockdown of DNMT1 or KIT in H69R and H82R cells led to PD-L1 downregulation. Consequently, combined knockdown of PD-L1 with KIT or DNMT1 resulted in more pronounced inhibition of H69R and H82R cell growth. Thus, cell intrinsic PD1/PD-L1 signaling may be a predictor for poor efficacy of cisplatin treatment, and targeting the cellular PD1/PD-L1 axis may improve chemosensitization of aggressive SCLC.

The synergistic effect of resveratrol in combination with cisplatin on apoptosis via modulating autophagy in A549 cells

Several studies have shown that combination treatment with natural products and chemotherapy agents can improve the sensitivity and cytotoxicity of chemotherapy agents. Resveratrol, a natural product, has many biological effects including antitumor and antiviral activities, as well as vascular protective effect. The aim of this study is to investigate the synergistic anticancer effect of resveratrol in combination with cisplatin and the potential anticancer mechanisms involved in A549 cells. The results obtained from Cell Counting Kit-8 and isobolographic analysis demonstrated that combination of resveratrol and cisplatin resulted in synergistic cytotoxic effects in A549 cells. Results from Hoechst staining, flow cytometry and western blot analysis suggested that resveratrol enhanced cisplatin-mediated apoptosis. Meanwhile, the changes of LC3-II and P62 levels and formation of autophagosome suggested that resveratrol in combination with cisplatin triggered autophagy. More importantly, inhibiting autophagy by 3-methyladenine markedly attenuated the apoptosis caused by combination of resveratrol and cisplatin in A549 cells. Taken together, our study provides the first evidence that resveratrol combined with cisplatin synergistically induce apoptosis via modulating autophagic cell death in A549 cells. These findings also help us to understand the role of natural products in combination with chemotherapy agents in lung cancer.

Cross-reacting material 197, a heparin-binding EGF-like growth factor inhibitor, reverses the chemoresistance in human cisplatin-resistant ovarian cancer

Cross-reacting material 197 (CRM197), a specific HB-EGF inhibitor, has been proven to be a promising antitumor agent for ovarian cancer therapy. Our previous studies have shown that CRM197 has potent antitumor activity in human cisplatin-resistant ovarian cancer. However, the relationship between CRM197 and the resistance to cisplatin remains unclear. Here, we report that CRM197 significantly reverses the resistance to cisplatin in cisplatin-resistant ovarian carcinoma cell line (A2780/CDDP). We established xenograft nude mice models with A2780 and A2780/CDDP cells. Notably, we observed that CRM197 suppresses the expression of HB-EGF and epidermal growth factor receptor in A2780/CDDP cells and xenografts harboring the overexpression of HB-EGF and epidermal growth factor receptor. Experiments conducted in vitro and in vivo suggest that CRM197 markedly downregulates the expression of excision repair cross-complementing group 1 (P = 0.002) and DNA repair capacity in A2780/CDDP tumor (P < 0.001) by inactivation of extracellular signal-regulated kinase signaling, providing novel possible mechanisms for the ability of CRM197 to restore drug sensitivity. These results suggest that CRM197 as an HB-EGF inhibitor might be a cisplatin-chemosensitizing agent for the treatment of ovarian carcinoma with resistance to cisplatin.

Regulatory Roles of MAPK Phosphatases in Cancer

The mitogen-activated protein kinases (MAPKs) are key regulators of cell growth and survival in physiological and pathological processes. Aberrant MAPK signaling plays a critical role in the development and progression of human cancer, as well as in determining responses to cancer treatment. The MAPK phosphatases (MKPs), also known as dual-specificity phosphatases (DUSPs), are a family of proteins that function as major negative regulators of MAPK activities in mammalian cells. Studies using mice deficient in specific MKPs including MKP1/DUSP1, PAC-1/DUSP2, MKP2/DUSP4, MKP5/DUSP10 and MKP7/DUSP16 demonstrated that these molecules are important not only for both innate and adaptive immune responses, but also for metabolic homeostasis. In addition, the consequences of the gain or loss of function of the MKPs in normal and malignant tissues have highlighted the importance of these phosphatases in the pathogenesis of cancers. The involvement of the MKPs in resistance to cancer therapy has also gained prominence, making the MKPs a potential target for anti-cancer therapy. This review will summarize the current knowledge of the MKPs in cancer development, progression and treatment outcomes.

Regulation of Multi-drug Resistance in hepatocellular carcinoma cells is TRPC6/Calcium Dependent

Hepatocellular carcinoma (HCC) is notoriously refractory to chemotherapy because of its tendency to develop multi-drug resistance (MDR), whose various underlying mechanisms make it difficult to target. The calcium signalling pathway is associated with many cellular biological activities, and is also a critical player in cancer. However, its role in modulating tumour MDR remains unclear. In this study, stimulation by doxorubicin, hypoxia and ionizing radiation was used to induce MDR in HCC cells. A sustained aggregation of intracellular calcium was observed upon these stimuli, while inhibition of calcium signalling enhanced the cells' sensitivity to various drugs by attenuating epithelial-mesenchymal transition (EMT), Hif1-α signalling and DNA damage repair. The effect of calcium signalling is mediated via transient receptor potential canonical 6 (TRPC6), a subtype of calcium-permeable channel. An in vivo xenograft model of HCC further confirmed that inhibiting TRPC6 enhanced the efficacy of doxorubicin. In addition, we deduced that STAT3 activation is a downstream signalling pathway in MDR. Collectively, this study demonstrated that the various mechanisms regulating MDR in HCC cells are calcium dependent through the TRPC6/calcium/STAT3 pathway. We propose that targeting TRPC6 in HCC may be a novel antineoplastic strategy, especially combined with chemotherapy.

miR-17-92 plays an oncogenic role and conveys chemo-resistance to cisplatin in human prostate cancer cells

The mir-17-92 cluster consists of six mature miRNAs and is implicated in diverse human cancers by targeting mRNAs involved in distinct pathways that either promote or inhibit carcinogenesis. However, the molecular mechanism underlying the mir-17-92 cluster-mediated pro-tumorigenic or anti-tumorigenic effects has not been clearly elucidated in prostate cancer. In the present study, the role of the mir-17-92 cluster in diverse aspects of prostate cancer cells has been thoroughly investigated. Forced introduction of the mir-17-92 cluster into the androgen-independent DU145 prostate cancer cells evidently promoted cell growth due to disruption of the balance between cellular proliferation and apoptosis. Overexpression of the mir-17-92 cluster significantly improved the migration and invasion of the DU145 cells, attributed to the induction of integrin β-1. Notably, the mir-17-92 cluster conveyed chemo-resistance to cisplatin. We demonstrated that the mir-17-92 cluster suppressed the expression of inhibitor of the AKT signaling pathway and activated the AKT pathway subsequently, which played a central role in regulating cellular proliferation, apoptosis and chemo-resistance. Continuously activated ERK1/2 signaling also contributed importantly to these processes. The present study provides key evidence for crucial oncogenic role of the miR-17-92 cluster in prostate cancer cells. Further investigations are warranted to determine whether miR-17-92 cluster can be targeted for future treatment of human prostate cancer.

Engineered Nanoparticles Against MDR in Cancer: The State of the Art and its Prospective

Cancer is a highly heterogeneous disease at intra/inter patient levels and known as the leading cause of death worldwide. A variety of mono and combinational therapies including chemotherapy have been evolved over the years for its effective treatment. However, advent of chemotherapeutic resistance or multidrug resistance (MDR) in cancer is a major challenge researchers are facing in cancer chemotherapy. MDR is a complex process having multifaceted non-cellular or cellular-based mechanisms. Research in the area of cancer nanotechnology over the past two decade has now proven that the smartly designed nanoparticles help in successful chemotherapy by overcoming the MDR and preferentially accumulate in the tumor region by means of active and passive targeting therefore reducing the offtarget accumulation of payload. Many of such nanoparticles are in different stages of clinical trials as nanomedicines showing promising result in cancer therapy including the resistant cases. Nanoparticles as chemotherapeutics carriers offer the opportunity to have multiple payload of drug and or imaging agents for combinational and theranostics therapy. Moreover, nanotechnology further bring in notice the new treatment strategies such as combining the NIR, MRI and HIFU in cancer chemotherapy and imaging. Here, we discussed the cellular/non-cellular factors constituting the MDR in cancer and the role of nanomedicines in effective chemotherapy of MDR cases of cancers. Moreover, recent advancements like combinational payload delivery and combined physical approach with nanotechnology in cancer therapy have also been discussed.

miR-634 restores drug sensitivity in resistant ovarian cancer cells by targeting the Ras-MAPK pathway

Background

Drug resistance hampers the efficient treatment of malignancies, including advanced stage ovarian cancer, which has a 5-year survival rate of only 30 %. The molecular processes underlying resistance have been extensively studied, however, not much is known about the involvement of microRNAs.

Methods

Differentially expressed microRNAs between cisplatin sensitive and resistant cancer cell line pairs were determined using microarrays. Mimics were used to study the role of microRNAs in drug sensitivity of ovarian cancer cell lines and patient derived tumor cells. Luciferase reporter constructs were used to establish regulation of target genes by microRNAs.

Results

MiR-634 downregulation was associated with cisplatin resistance. Overexpression of miR-634 affected cell cycle progression and enhanced apoptosis in ovarian cancer cells. miR-634 resensitized resistant ovarian cancer cell lines and patient derived drug resistant tumor cells to cisplatin. Similarly, miR-634 enhanced the response to carboplatin and doxorubicin, but not to paclitaxel. The cell cycle regulator CCND1, and Ras-MAPK pathway components GRB2, ERK2 and RSK2 were directly repressed by miR-634 overexpression. Repression of the Ras-MAPK pathway using a MEK inhibitor phenocopied the miR-634 effects on viability and chemosensitivity.

Conclusion

miR-634 levels determine chemosensitivity in ovarian cancer cells. We identify miR-634 as a therapeutic candidate to resensitize chemotherapy resistant ovarian tumors.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-015-0464-4) contains supplementary material, which is available to authorized users.