Molecular aspects of cancer cell resistance to chemotherapy

BCc1, the novel antineoplastic nanocomplex, showed potent anticancer effects in vitro and in vivo

Purpose

In spite of all the efforts and researches on anticancer therapeutics, an absolute treatment is still a myth. Therefore, it is necessary to utilize novel technologies in order to synthesize smart multifunctional structures. In this study, for the first time, we have evaluated the anticancer effects of BCc1 nanocomplex by vitro and in vivo studies, which is designed based on the novel nanochelating technology.

Methods

Human breast adenocarcinoma cell line (MCF-7) and mouse embryonic fibroblasts were used for the in vitro study. Antioxidant potential, cell toxicity, apoptosis induction, and CD44 and CD24 protein expression were evaluated after treatment of cells with different concentrations of BCc1 nanocomplex. For the in vivo study, mammary tumor-bearing female Balb/c mice were treated with different doses of BCc1 and their effects on tumor growth rate and survival were evaluated.

Results

BCc1 decreased CD44 protein expression and increased CD24 protein expression. It induced MCF-7 cell apoptosis but at the same concentrations did not have negative effects on mouse embryonic fibroblasts viability and protected them against oxidative stress. Treatment with nanocomplex increased survival and reduced the tumor size growth in breast cancer-bearing balb/c mice.

Conclusion

These results demonstrate that BCc1 has the capacity to be assessed as a new anticancer agent in complementary studies.

The role of exosomes in tumor progression and metastasis (Review)

Tumor cells have developed various mechanisms in defense against applied treatment, which prevent their total elimination from an organism. One of the underestimated mechanisms of defense is secretion of highly specialized double-membrane structures called exosomes. They play a crucial role in the control of the local microenvironment and intracellular communication. It has been shown that the exosomes can be carriers of various proteins, lipids, miRNAs and mRNAs. There are extensive data concerning the influence and participation by exosomes in metastasis and cancer progression. It has been demonstrated that exosomes are involved in multidrug resistance mechanisms, radiation-induced bystander effect and epithelial-mesenchymal transition. Furthermore, exosomes are able to form a premetastatic niche and enable the escape of cancer cells from recognition by host immune cells. Moreover, exosomes are responsible for the formation of vessels. This indicates the significance of secreted extracellular vesicles in the development and prognosis of cancer. The aim of the present review is to briefly describe the role of exosomes in tumor biology.

Silencing of MicroRNA-21 confers the sensitivity to tamoxifen and fulvestrant by enhancing autophagic cell death through inhibition of the PI3K-AKT-mTOR pathway in breast cancer cells

Tamoxifen (TAM) and fulvestrant (FUL) represent the major adjuvant therapy to estrogen receptor-alpha positive (ER(+)) breast cancer patients. However, endocrine resistance to TAM and FUL is a great impediment for successful treatment. We hypothesized that miR-21 might alter the sensitivity of breast cancer cells to TAM or FUL by regulating cell autophagy. Using the ER(+) breast cancer cells, we knockdown miR-21.by transfection with miR-21 inhibitor, then the cells were exposed to TAM or FUL and the percentages of apoptosis and autophagy were determined. Knockdown of miR-21 significantly increased the TAM or FUL-induced apoptosis in ER(+) breast cancer cells. Further, silencing of miR-21 in MCF-7 cells enhanced cell autophagy at both basal and TAM or FUL-induced level. The increase of autophagy in miR-21-knockdown MCF-7 cells was also indicated by increase of beclin-1, LC3-II and increased GFP-LC3 dots. Importantly, knockdown of miR-21 contributed to autophagic cell death, which is responsible for part of TAM induced cell death in miR-21 inhibitor-transfected cells. Further analysis suggested that miR-21 inhibitor enhance autophagic cell death through inhibition of PI3K-AKT-mTOR pathway. MiR-21 coordinated the function of autophagy and apoptosis by targeting Phosphatase and tensin homolog (PTEN) through inhibition of PI3K-AKT-mTOR pathway. In conclusion, silencing of miR-21 increased the sensitivity of ER(+) breast cancer cells to TAM or FUL by increasing autophagic cell death. Targeting autophagy-related miRNAs is a potential strategy for overcoming endocrine resistance to TAM and FUL.

Antimitotic drugs in the treatment of cancer

Cancer is a complex disease since it is adaptive in such a way that it can promote proliferation and invasion by means of an overactive cell cycle and in turn cellular division which is targeted by antimitotic drugs that are highly validated chemotherapy agents. However, antimitotic drug cytotoxicity to non-tumorigenic cells and multiple cancer resistance developed in response to drugs such as taxanes and vinca alkaloids are obstacles faced in both the clinical and basic research field to date. In this review, the classes of antimitotic compounds, their mechanisms of action and cancer cell resistance to chemotherapy and other limitations of current antimitotic compounds are highlighted, as well as the potential of novel 17-β estradiol analogs as cancer treatment.

Role of microRNAs in chemoresistance

Drug resistance is a major problem in the treatment of cancer patients. Resistance can develop after prolonged cycles of chemotherapy or can be present intrinsically in the patient. There is an emerging role of microRNAs (miRNAs) in resistance to cancer treatments. miRNAs are small non-coding RNAs that are evolutionarily conserved and also involved as regulators of gene expression through the silencing of mRNA targets. They are involved in many different cancer types and a plethora of mechanisms have been postulated for the roles that miRNAs play in the development of drug resistance. Hence, miRNA-based gene therapy may provide a novel approach for the future of cancer therapy. This review focuses on an overview of recent findings on the role of miRNAs in the resistance to chemotherapy in different tumours.

Synthesis and evaluation of bis-thiazole derivatives as new anticancer agents

New bis-thiazole derivatives (1-10) were synthesized via the ring closure of 1,1'-(3,3'-dimethoxybiphenyl-4,4'-diyl)bis(thiourea) with phenacyl bromides and evaluated for their cytotoxic effects on A549 human lung adenocarcinoma, C6 rat glioma, 5RP7 H-ras oncogene transformed rat embryonic fibroblast and NIH/3T3 mouse embryonic fibroblast cell lines using MTT assay. DNA synthesis inhibitory effects of these compounds were investigated. Each derivative was also evaluated for its ability to inhibit AChE and BuChE using a modification of Ellman's spectrophotometric method. Among these compounds, 3,3'-dimethoxy-N(4),N(4)'-bis(4-(4-bromophenyl)thiazol-2-yl)-[1,1'-biphenyl]-4,4'-diamine (5) can be identified as the most promising anticancer agent due to its notable inhibitory effects on A549 and C6 cell lines and low toxicity to NIH/3T3 cell lines. Compound 5 exhibited anticancer activity against A549 and C6 cell lines with IC50 values of 37.3 ± 6.8 μg/mL and 11.3 ± 1.2 μg/mL, whereas mitoxantrone showed anticancer activity against A549 and C6 cell lines with IC50 values of 15.7 ± 4.0 μg/mL and 11.0 ± 1.7 μg/mL, respectively. Furthermore, compound 5 showed DNA synthesis inhibitory activity against A549 cell line.

Identification of the specific epigenetic alterations associated with chemo-resistance via reprogramming of cancer cells

BACKGROUND

Chemo-resistance is the main obstacle in cancer therapy, limiting the effectiveness of drug treatment. Epigenetics-mediated changes are suggested as a critical factor paying the chemo-resistance phenotype. Since epigenetic modulations are a reversible phenomenon, reversion of epigenetic changes represents a promising therapeutic approach for cancer. However, heterogeneity in epigenetic marks in tumor cells makes it difficult to identify the specific epigenetic aberrations contributing to chemo-resistance. Our hypothesis aimed to explore this issue to add therapeutic options for cancer.

PRESENTATION OF THE HYPOTHESIS

Epigenetic alterations, the main mediator of cellular reprogramming, occur rapidly upon exposure to chemotherapy. Recent studies have demonstrated that reprogramming resets/erases the epigenetic marks established during differentiation to specific somatic cell types. To overcome the heterogeneous nature of cancer cells, we will attempt to make homogenous cancer cell colonies by reprogramming. Comparison of the drug-resistant cancer cells obtained from these colonies to parent cancer cells and reprogrammed cancer cells is an effective way to determine the precise epigenetic alterations underlying specific chemo-resistance.

TESTING THE HYPOTHESIS

Cellular reprogramming of cancer cells led to generation of homogenous colonies. Following lineage specification and long term drug treatment, the obtained drug resistance cells will be compared with parent cancer cells for whole genome epigenetic signature.

IMPLICATIONS OF THE HYPOTHESIS

A key implication of this hypothesis is that determination of the usefulness of cellular reprogramming of cancer cells enabling the identification of specific epigenetic modulation associated with particular drug resistance will enable exploration of new research avenues for cancer treatment.

Synthesis and Evaluation of New Pyrazoline Derivatives as Potential Anticancer Agents

New pyrazoline derivatives were synthesized and evaluated for their cytotoxic effects on AsPC-1 human pancreatic adenocarcinoma, U87 and U251 human glioblastoma cell lines. 1-[((5-(4-Methylphenyl)-1,3,4-oxadiazol-2-yl)thio)acetyl]-3-(2-thienyl)-5-(4-chlorophenyl)-2-pyrazoline (11) was found to be the most effective anticancer agent against AsPC-1 and U251 cell lines, with IC50 values of 16.8 µM and 11.9 µM, respectively. Tumor selectivity of compound 11 was clearly seen between Jurkat human leukemic T-cell line and human peripheral blood mononuclear cells (PBMC). Due to its promising anticancer activity, compound 11 was chosen for apoptosis/necrosis evaluation and DNA-cleavage analysis in U251 cells. Compound 11-treated U251 cells exhibited apoptotic phenotype at low concentration (1.5 µM). DNA-cleaving efficiency of this ligand was more significant than cisplatin and was clearly enhanced by Fe(II)-H₂O₂-ascorbic acid systems. This result pointed out the relationship between the DNA cleavage and the cell death.

Potential of four marine-derived fungi extracts as anti-proliferative and cell death-inducing agents in seven human cancer cell lines

OBJECTIVE

To evaluate the in vitro anticancer activity of crude ethyl acetate extracts of the culture of four marine-derived fungi Aspergillus similanensis KUFA 0013 (E1), Neosartorya paulistensis KUFC 7897 (E2), Neosartorya siamensis KUFA 0017 (E4) and Talaromyces trachyspermus KUFC 0021 (E3) on a panel of seven human cancer cell lines.

METHODS

Effects on cell proliferation, induction of DNA damage and cell death were assessed by MTT and clonogenic assays, comet assay and nuclear condensation assay, respectively.

RESULTS

The proliferation of HepG2, HCT116 and A375 cells decreased after incubation with the extracts E2 and E4. The anti-proliferative effect was confirmed by morphologic alterations and by clonogenic assay. Both extracts also induced cell death in HepG2 and HCT116 cells. Doxorubicin was used as a positive control and showed in vitro anticancer activity.

CONCLUSIONS

This study demonstrated, for the first time, that extracts of Neosartorya paulistensis and Neosartorya siamensis have selective anti-proliferative and cell death activities in HepG2, HCT16 and A375 cells. The bioactivity of these extracts suggests a potential for biotechnological applications and substantiates that both should be further considered for the elucidation of the molecular targets and signal transduction pathways involved.

Influence of the proton pump inhibitor lansoprazole on distribution and activity of doxorubicin in solid tumors

Cellular causes of resistance and limited drug distribution within solid tumors limit therapeutic efficacy of anticancer drugs. Acidic endosomes in cancer cells mediate autophagy, which facilitates survival of stressed cells, and may contribute to drug resistance. Basic drugs (e.g. doxorubicin) are sequestered in acidic endosomes, thereby diverting drugs from their target DNA and decreasing penetration to distal cells. Proton pump inhibitors (PPIs) may raise endosomal pH, with potential to improve drug efficacy and distribution in solid tumors. We determined the effects of the PPI lansoprazole to modify the activity of doxorubicin. To gain insight into its mechanisms, we studied the effects of lansoprazole on endosomal pH, and on the spatial distribution of doxorubicin, and of biomarkers reflecting its activity, using in vitro and murine models. Lansoprazole showed concentration-dependent effects to raise endosomal pH and to inhibit endosomal sequestration of doxorubicin in cultured tumor cells. Lansoprazole was not toxic to cancer cells but potentiated the cytotoxicity of doxorubicin and enhanced its penetration through multilayered cell cultures. In solid tumors, lansoprazole improved the distribution of doxorubicin but also increased expression of biomarkers of drug activity throughout the tumor. Combined treatment with lansoprazole and doxorubicin was more effective in delaying tumor growth as compared to either agent alone. Together, lansoprazole enhances the therapeutic effects of doxorubicin both by improving its distribution and increasing its activity in solid tumors. Use of PPIs to improve drug distribution and to inhibit autophagy represents a promising strategy to enhance the effectiveness of anticancer drugs in solid tumors.

Reversal of microRNA-150 silencing disadvantages crizotinib-resistant NPM-ALK(+) cell growth

The regulatory microRNA miR-150 is involved in the development of hemopathies and is downregulated in T-lymphomas, such as anaplastic large-cell lymphoma (ALCL) tumors. ALCL is defined by the presence or absence of translocations that activate the anaplastic lymphoma kinase (ALK), with nucleophosmin-ALK (NPM-ALK) fusions being the most common. Here, we compared samples of primary NPM-ALK(+) and NPM-ALK(-) ALCL to investigate the role of miR-150 downstream of NPM-ALK. Methylation of the MIR150 gene was substantially elevated in NPM-ALK(+) biopsies and correlated with reduced miR-150 expression. In NPM-ALK(+) cell lines, DNA hypermethylation-mediated miR-150 repression required ALK-dependent pathways, as ALK inhibition restored miR-150 expression. Moreover, epigenetic silencing of miR-150 was due to the activation of STAT3, a major downstream substrate of NPM-ALK, in cooperation with DNA methyltransferase 1 (DNMT1). Accordingly, miR-150 repression was turned off following treatment with the DNMT inhibitor, decitabine. In murine NPM-ALK(+) xenograft models, miR-150 upregulation induced antineoplastic activity. Treatment of crizotinib-resistant NPM-ALK(+) KARPAS-299-CR06 cells with decitabine or ectopic miR-150 expression reduced viability and growth. Altogether, our results suggest that hypomethylating drugs, alone or in combination with other agents, may benefit ALK(+) patients harboring tumors resistant to crizotinib and other anti-ALK tyrosine kinase inhibitors (TKIs). Moreover, these results support further work on miR-150 in these and other ALK(+) malignancies.

Chemoresistance, cancer stem cells, and miRNA influences: the case for neuroblastoma

Neuroblastoma is a type of cancer that develops most often in infants and children under the age of five years. Neuroblastoma originates within the peripheral sympathetic ganglia, with 30% of the cases developing within the adrenal medulla, although it can also occur within other regions of the body such as nerve tissue in the spinal cord, neck, chest, abdomen, and pelvis. MicroRNAs (miRNAs) regulate cellular pathways, differentiation, apoptosis, and stem cell maintenance. Such miRNAs regulate genes involved in cellular processes. Consequently, they are implicated in the regulation of a spectrum of signaling pathways within the cell. In essence, the role of miRNAs in the development of cancer is of utmost importance for the understanding of dysfunctional cellular pathways that lead to the conversion of normal cells into cancer cells. This review focuses on highlighting the recent, important implications of miRNAs within the context of neuroblastoma basic research efforts, particularly concerning miRNA influences on cancer stem cell pathology and chemoresistance pathology for this condition, together with development of translational medicine approaches for novel diagnostic tools and therapies for this neuroblastoma.

Enzyme-instructed self-assembly: a multistep process for potential cancer therapy

The central dogma of the action of current anticancer drugs is that the drug tightly binds to its molecular target for inhibition. The reliance on tight ligand-receptor binding, however, is also the major root of drug resistance in cancer therapy. In this article, we highlight enzyme-instructed self-assembly (EISA)-the integration of enzymatic transformation and molecular self-assembly-as a multistep process for the development of cancer therapy. Using apoptosis as an example, we illustrate that the combination of enzymatic transformation and self-assembly, in fact, is an inherent feature of apoptosis. After the introduction of EISA of small molecules in the context of supramolecular hydrogelation, we describe several key studies to underscore the promises of EISA for developing cancer therapy. Particularly, we will highlight that EISA allows one to develop approaches to target "undruggable" targets or "untargetable" features of cancer cells and provides the opportunity for simultaneously interacting with multiple targets. We envision that EISA, used separately or in combination with current anticancer therapeutics, will ultimately lead to a paradigm shift for developing anticancer medicine that inhibit multiple hallmark capabilities of cancer.

Non-Toxic Metabolic Management of Metastatic Cancer in VM Mice: Novel Combination of Ketogenic Diet, Ketone Supplementation, and Hyperbaric Oxygen Therapy

The Warburg effect and tumor hypoxia underlie a unique cancer metabolic phenotype characterized by glucose dependency and aerobic fermentation. We previously showed that two non-toxic metabolic therapies - the ketogenic diet with concurrent hyperbaric oxygen (KD+HBOT) and dietary ketone supplementation - could increase survival time in the VM-M3 mouse model of metastatic cancer. We hypothesized that combining these therapies could provide an even greater therapeutic benefit in this model. Mice receiving the combination therapy demonstrated a marked reduction in tumor growth rate and metastatic spread, and lived twice as long as control animals. To further understand the effects of these metabolic therapies, we characterized the effects of high glucose (control), low glucose (LG), ketone supplementation (βHB), hyperbaric oxygen (HBOT), or combination therapy (LG+βHB+HBOT) on VM-M3 cells. Individually and combined, these metabolic therapies significantly decreased VM-M3 cell proliferation and viability. HBOT, alone or in combination with LG and βHB, increased ROS production in VM-M3 cells. This study strongly supports further investigation into this metabolic therapy as a potential non-toxic treatment for late-stage metastatic cancers.

Phenotypic switch of CD8(+) T cells reactivated under hypoxia toward IL-10 secreting, poorly proliferative effector cells

CD8(+) T cells controlling pathogens or tumors must function at sites where oxygen tension is frequently low, and never as high as under atmospheric culture conditions. However, T-cell function in vivo is generally analyzed indirectly, or is extrapolated from in vitro studies under nonphysiologic oxygen tensions. In this study, we delineate the role of physiologic and pathologic oxygen tension in vitro during reactivation and differentiation of tumor-specific CD8(+) T cells. Using CD8(+) T cells from pmel-1 mice, we observed that the generation of CTLs under 5% O2, which corresponds to physioxia in lymph nodes, gave rise to a higher effector signature than those generated under atmospheric oxygen fractions (21% O2). Hypoxia (1% O2) did not modify cytotoxicity, but decreasing O2 tensions during CTL and CD8(+) tumor-infiltrating lymphocyte reactivation dose-dependently decreased proliferation, induced secretion of the immunosuppressive cytokine IL-10, and upregulated the expression of CD137 (4-1BB) and CD25. Overall, our data indicate that oxygen tension is a key regulator of CD8(+) T-cell function and fate and suggest that IL-10 release may be an unanticipated component of CD8(+) T cell-mediated immune responses in most in vivo microenvironments.

miR-23b-3p regulates the chemoresistance of gastric cancer cells by targeting ATG12 and HMGB2

Chemotherapy is an important treatment modality for gastric cancer (GC); however, it usually fails because of drug resistance, especially multidrug resistance (MDR). Previously, we found a novel subset of MDR-associated microRNAs (miRNAs) through high-throughput functional screening. In this report, we investigated the exact roles and mechanisms of miR-23b-3p in the MDR of GC. Using gain or loss-of-function in in vitro and in vivo experiments, we found that overexpression of miR-23b-3p reversed cancer cell resistance to multiple chemotherapeutics in vitro and sensitize tumors to chemotherapy in vivo. Reporter gene assay and western blot analysis showed that ATG12 and HMGB2 were the direct targets of miR-23b-3p. Meanwhile, ATG12 and HMGB2 were positively associated with the occurrence of autophagy. Reducing the expression of these target genes by siRNA or inhibition of autophagy both sensitized GC cells to chemotherapy. These findings suggest that a miR-23b-3p/ATG12/HMGB2/autophagy-regulatory loop has a critical role in MDR in GC. In addition, miR-23b-3p could be used as a prognostic factor for overall survival in GC. In conclusion, our data demonstrated that miR-23b-3p inhibited autophagy mediated by ATG12 and HMGB2 and sensitized GC cells to chemotherapy, and suggested the potential application of miR-23b-3p in drug resistance prediction and treatment.

Resistance acquisition to MDM2 inhibitors

Various experimental strategies aim to (re)activate p53 signalling in cancer cells. The most advanced clinically are small-molecule inhibitors of the autoregulatory interaction between p53 and MDM2 (murine double minute 2). Different MDM2 inhibitors are currently under investigation in clinical trials. As for other targeted anti-cancer therapy approaches, relatively rapid resistance acquisition may limit the clinical efficacy of MDM2 inhibitors. In particular, MDM2 inhibitors were shown to induce p53 mutations in experimental systems. In the present article, we summarize what is known about MDM2 inhibitors as anti-cancer drugs with a focus on the acquisition of resistance to these compounds.

New trends in guided nanotherapies for digestive cancers: A systematic review

Digestive tract tumors are among the most common and deadliest malignancies worldwide, mainly due to late diagnosis and lack of efficient therapeutics. Current treatments essentially rely on surgery associated with (neo)adjuvant chemotherapy agents. Despite an upfront response, conventional drugs often fail to eliminate highly aggressive clones endowed with chemoresistant properties, which are responsible for tumor recurrence and disease dissemination. Synthetic drugs also present severe adverse systemic effects, hampering the administration of biologically effective dosages. Nanoencapsulation of chemotherapeutic agents within biocompatible polymeric or lipid matrices holds great potential to improve the pharmacokinetics and efficacy of conventional chemotherapy while reducing systemic toxicity. Tagging nanoparticle surfaces with specific ligands for cancer cells, namely monoclonal antibodies or antibody fragments, has provided means to target more aggressive clones, further improving the selectivity and efficacy of nanodelivery vehicles. In fact, over the past twenty years, significant research has translated into a wide array of guided nanoparticles, providing the molecular background for a new generation of intelligent and more effective anti-cancer agents. Attempting to bring awareness among the medical community to emerging targeted nanopharmaceuticals and foster advances in the field, we have conducted a systematic review about this matter. Emphasis was set on ongoing preclinical and clinical trials for liver, colorectal, gastric and pancreatic cancers. To the best of our knowledge this is the first systematic and integrated overview on this field. Using a specific query, 433 abstracts were gathered and narrowed to 47 manuscripts when matched against inclusion/exclusion criteria. All studies showed that active targeting improves the effectiveness of the nanodrugs alone, while lowering its side effects. The main focus has been on hepatocarcinomas, mainly by exploring glycans as homing molecules. Other ligands such as peptides/small proteins and antibodies/antibody fragments, with affinity to either tumor vasculature or tumor cells, have also been widely and successfully applied to guide nanodrugs to gastrointestinal carcinomas. Conversely, few solutions have been presented for pancreatic tumors. To this date only three nanocomplexes have progressed beyond pre-clinical stages: i) PK2, a galactosamine-functionalized polymeric-DOX formulation for hepatocarcinomas; ii) MCC-465, an anti-(myosin heavy chain a) immunoliposome for advanced stage metastatic solid tumors; and iii) MBP-426, a transferrin-liposome-oxaliplatin conjugate, also for advanced stage tumors. Still, none has been approved for clinical use. However, based on the high amount of pre-clinical studies showing enthusiastic results, the number of clinical trials is expected to increase in the near future. A more profound understanding about the molecular nature of chemoresistant clones and cancer stem cell biology will also contribute to boost the field of guided nanopharmacology towards more effective solutions.

Overexpression of long non-coding RNA PVT1 in gastric cancer cells promotes the development of multidrug resistance

BACKGROUND

The development of multidrug resistance (MDR) is a crucial problem of therapy failure in gastric cancer, which results in disease recurrence and metastasis. Plasmacytoma variant translocation 1 (PVT-1), a long non-coding RNA (lncRNA), was previously found to be increased in gastric cancer patients and regulated the chemotherapy sensitivity in pancreatic cancer cells. However, the role of PVT1 in multidrug resistant Gastric cancer remains largely unexplored.

METHODS

In this study, the mRNA levels of PVT1 in gastric cancer tissues of cisplatin-resistant patients and two kinds of cisplatin-resistant cells BGC823/DDP and SGC7901/DDP were detected by qRT-PCR. The influence of PVT1 knockdown or overexpression on anticancer drug resistance was assessed by measuring the cytotoxicity of cisplatin and the rate of apoptosis detected by CCK-8 assay and flow cytometry, respectively. Further, we investigated the expression levels of MDR1, MRP, mTOR and HIF-1α by qRT-PCR and western blotting.

RESULTS

PVT-1 was highly expressed in gastric cancer tissues of cisplatin-resistant patients and cisplatin-resistant cells. In addition, BGC823/DDP and SGC7901/DDP cells transfected with PVT-1 siRNA and treated with cisplatin exhibited significant lower survival rate and high percentage of apoptotic tumor cells. While, PVT1 overexpression exhibit the anti-apoptotic property in BGC823 and SGC7901 cells transfected with LV-PVT1-GFP and treated with cisplatin. Moreover, qRT-PCR and western blotting revealed that PVT1 up-regulation increased the expression of MDR1, MRP, mTOR and HIF-1α.

CONCLUSIONS

Overexpression of LncRNA PVT1 in gastric carcinoma promotes the development of MDR, suggesting an efficacious target for reversing MDR in gastric cancer therapy.

miRNA-196b inhibits cell proliferation and induces apoptosis in HepG2 cells by targeting IGF2BP1

Background

Tumor hypoxia is one of the features of tumor microenvironment that contributes to chemoresistance. miRNAs have recently been shown to play important roles in tumorigenesis and drug resistance. Moreover, hypoxia also regulates the expression of a series of miRNAs. However, the interaction between chemoresistance, hypoxia and miRNAs has not been explored yet. The aim of this study is to understand the mechanisms activated/inhibited by miRNAs under hypoxia that induce resistance to chemotherapy-induced apoptosis.

Methods

TaqMan low-density array was used to identify changes in miRNA expression when cells were exposed to etoposide under hypoxia or normoxia. The effects of miR-196b overexpression on apoptosis and cell proliferation were studied in HepG2 cells. miR-196b target mRNAs were identified by proteomic analysis, luciferase activity assay, RT-qPCR and western blot analysis.

Results

Results showed that hypoxia down-regulated miR-196b expression that was induced by etoposide. miR-196b overexpression increased the etoposide-induced apoptosis and reversed the protection of cell death observed under hypoxia. By a proteomic approach combined with bioinformatics analyses, we identified IGF2BP1 as a potential target of miR-196b. Indeed, miR-196b overexpression decreased IGF2BP1 RNA expression and protein level. The IGF2BP1 down-regulation by either miR-196b or IGF2BP1 siRNA led to an increase in apoptosis and a decrease in cell viability and proliferation in normal culture conditions. However, IGF2BP1 silencing did not modify the chemoresistance induced by hypoxia, probably because it is not the only target of miR-196b involved in the regulation of apoptosis.

Conclusions

In conclusion, for the first time, we identified IGF2BP1 as a direct and functional target of miR-196b and showed that miR-196b overexpression reverses the chemoresistance induced by hypoxia. These results emphasize that the chemoresistance induced by hypoxia is a complex mechanism.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-015-0349-6) contains supplementary material, which is available to authorized users.

Metabolic and hypoxic adaptation to anti-angiogenic therapy: a target for induced essentiality

Anti-angiogenic therapy has increased the progression-free survival of many cancer patients but has had little effect on overall survival, even in colon cancer (average 6-8 weeks) due to resistance. The current licensed targeted therapies all inhibit VEGF signalling (Table 1). Many mechanisms of resistance to anti-VEGF therapy have been identified that enable cancers to bypass the angiogenic blockade. In addition, over the last decade, there has been increasing evidence for the role that the hypoxic and metabolic responses play in tumour adaptation to anti-angiogenic therapy. The hypoxic tumour response, through the transcription factor hypoxia-inducible factors (HIFs), induces major gene expression, metabolic and phenotypic changes, including increased invasion and metastasis. Pre-clinical studies combining anti-angiogenics with inhibitors of tumour hypoxic and metabolic adaptation have shown great promise, and combination clinical trials have been instigated. Understanding individual patient response and the response timing, given the opposing effects of vascular normalisation versus reduced perfusion seen with anti-angiogenics, provides a further hurdle in the paradigm of personalised therapeutic intervention. Additional approaches for targeting the hypoxic tumour microenvironment are being investigated in pre-clinical and clinical studies that have potential for producing synthetic lethality in combination with anti-angiogenic therapy as a future therapeutic strategy.

Intensified antineoplastic effect by combining an HDAC-inhibitor, an mTOR-inhibitor and low dosed interferon alpha in prostate cancer cells

A significant proportion of men diagnosed with prostate cancer (PCa) eventually develop metastatic disease, which progresses to castration resistance, despite initial response to androgen deprivation. As anticancer therapy has become increasingly effective, acquired drug resistance has emerged, limiting efficacy. Combination treatment, utilizing different drug classes, exemplifies a possible strategy to foil resistance development. The effects of the triple application of the histone deacetylase (HDAC) inhibitor valproic acid (VPA), the mammalian target of rapamycin inhibitor everolimus and low dosed interferon alpha (IFNα) on PCa cell growth and dissemination capacity were investigated. For that purpose, the human PCa cell lines, PC-3, DU-145 and LNCaP were treated with the combined regimen or separate single agents. Cell growth was investigated by the MTT dye reduction assay. Flow cytometry served to analyse cell cycle progression. Adhesion to vascular endothelium or immobilized collagen, fibronectin and laminin was quantified. Migration and invasion characteristics were determined by the modified Boyden chamber assay. Integrin α and β subtypes were investigated by flow cytometry, western blotting and RT-PCR. Integrin related signalling, Epidermal Growth Factor Receptor (EGFr), Akt, p70S6kinase and extracellular signal-regulated kinases (ERK)1/2 activation were also assessed. The triple application of VPA, everolimus and low dosed IFNα blocked tumour cell growth and dissemination significantly better than any agent alone. Antitumour effects were associated with pronounced alteration in the cell cycle machinery, intracellular signalling and integrin expression profile. Combining VPA, everolimus and low dosed IFNα might be a promising option to counteract resistance development and improve outcome in PCa patients.

Diameter-dependent release of a cisplatin pro-drug from small and large functionalized carbon nanotubes

The use of platinum-based chemotherapeutic drugs in cancer therapy still suffers from severe disadvantages, such as lack of appropriate selectivity for tumor tissues and insurgence of multi-drug resistance. Moreover, drug efficacy can be attenuated by several mechanisms such as premature drug inactivation, reduced drug uptake inside cells and increased drug efflux once internalized. The use of functionalized carbon nanotubes (CNTs) as chemotherapeutic drug delivery systems is a promising strategy to overcome such limitations due to their ability to enhance cellular internalization of poorly permeable drugs and thus increase the drug bioavailability at the diseased site, compared to the free drug. Furthermore, the possibility to encapsulate agents in the nanotubes' inner cavity can protect the drug from early inactivation and their external functionalizable surface is useful for selective targeting. In this study, a hydrophobic platinum(IV) complex was encapsulated within the inner space of two different diameter functionalized multi-walled CNTs (Pt(IV)@CNTs). The behavior of the complexes, compared to the free drug, was investigated on both HeLa human cancer cells and RAW 264.7 murine macrophages. Both CNT samples efficiently induced cell death in HeLa cancer cells 72 hours after the end of exposure to CNTs. Although the larger diameter CNTs were more cytotoxic on HeLa cells compared to both the free drug and the smaller diameter nanotubes, the latter allowed a prolonged release of the encapsulated drug, thus increasing its anticancer efficacy. In contrast, both Pt(IV)@CNT constructs were poorly cytotoxic on macrophages and induced negligible cell activation and no pro-inflammatory cytokine production. Both CNT samples were efficiently internalized by the two types of cells, as demonstrated by transmission electron microscopy observations and flow cytometry analysis. Finally, the platinum levels found in the cells after Pt(IV)@CNT exposure demonstrate that they can promote drug accumulation inside cells in comparison with treatment with the free complex. To conclude, our study shows that CNTs are promising nanocarriers to improve the accumulation of a chemotherapeutic drug and its slow release inside tumor cells, by tuning the CNT diameter, without inducing a high inflammatory response.

mTORC1 upregulation via ERK-dependent gene expression change confers intrinsic resistance to MEK inhibitors in oncogenic KRas-mutant cancer cells

Cancer cells harboring oncogenic BRaf mutants, but not oncogenic KRas mutants, are sensitive to MEK inhibitors (MEKi). The mechanism underlying the intrinsic resistance to MEKi in KRas-mutant cells is under intensive investigation. Here, we pursued this mechanism by live imaging of extracellular signal-regulated kinases (ERK) and mammalian target of rapamycin complex 1 (mTORC1) activities in oncogenic KRas or BRaf-mutant cancer cells. We established eight cancer cell lines expressing Förster resonance energy transfer (FRET) biosensors for ERK activity and S6K activity, which was used as a surrogate marker for mTORC1 activity. Under increasing concentrations of MEKi, ERK activity correlated linearly with the cell growth rate in BRaf-mutant cancer cells, but not KRas-mutant cancer cells. The administration of PI3K inhibitors resulted in a linear correlation between ERK activity and cell growth rate in KRas-mutant cancer cells. Intriguingly, mTORC1 activity was correlated linearly with the cell growth rate in both BRaf-mutant cancer cells and KRas-mutant cancer cells. These observations suggested that mTORC1 activity had a pivotal role in cell growth and that the mTORC1 activity was maintained primarily by the ERK pathway in BRaf-mutant cancer cells and by both the ERK and PI3K pathways in KRas-mutant cancer cells. FRET imaging revealed that MEKi inhibited mTORC1 activity with slow kinetics, implying transcriptional control of mTORC1 activity by ERK. In agreement with this observation, MEKi induced the expression of negative regulators of mTORC1, including TSC1, TSC2 and Deptor, which occurred more significantly in BRaf-mutant cells than in KRas-mutant cells. These findings suggested that the suppression of mTORC1 activity and induction of negative regulators of mTORC1 in cancer cells treated for at least 1 day could be used as surrogate markers for the MEKi sensitivity of cancer cells.

Preclinical evaluation of cyclin dependent kinase 11 and casein kinase 2 survival kinases as RNA interference targets for triple negative breast cancer therapy

Introduction

Targeted therapies for aggressive breast cancers like triple negative breast cancer (TNBC) are needed. The use of small interfering RNAs (siRNAs) to disable expression of survival genes provides a tool for killing these cancer cells. Cyclin dependent kinase 11 (CDK11) is a survival protein kinase that regulates RNA transcription, splicing and mitosis. Casein kinase 2 (CK2) is a survival protein kinase that suppresses cancer cell death. Eliminating the expression of these genes has potential therapeutic utility for breast cancer.

Methods

Expression levels of CDK11 and CK2 mRNAs and associated proteins were examined in breast cancer cell lines and tissue arrays. RNA expression levels of CDC2L1, CDC2L2, CCNL1, CCNL2, CSNK2A1, CSNK2A2, and CSNK2B genes in breast cancer subtypes were analyzed. Effects following transfection of siRNAs against CDK11 and CK2 in cultured cells were examined by viability and clonal survival assays and by RNA and protein measures. Uptake of tenfibgen (TBG) nanocapsules by TNBC cells was analyzed by fluorescence-activated cell sorting. TBG nanocapsules delivered siRNAs targeting CDK11 or CK2 in mice carrying TNBC xenograft tumors. Transcript cleavage and response parameters were evaluated.

Results

We found strong CDK11 and CK2 mRNA and protein expression in most human breast cancer cells. Immunohistochemical analysis of TNBC patient tissues showed 100% of tumors stained positive for CDK11 with high nuclear intensity compared to normal tissue. The Cancer Genome Atlas analysis comparing basal to other breast cancer subtypes and to normal breast revealed statistically significant differences. Down-regulation of CDK11 and/or CK2 in breast cancer cells caused significant loss of cell viability and clonal survival, reduced relevant mRNA and protein expression, and induced cell death changes. TBG nanocapsules were taken up by TNBC cells both in culture and in xenograft tumors. Treatment with TBG- siRNA to CDK11 or TBG- siRNA to CK2αα’ nanocapsules induced appropriate cleavage of CDK11 and CK2α transcripts in TNBC tumors, and caused MDA-MB-231 tumor reduction, loss of proliferation, and decreased expression of targeted genes.

Conclusions

CDK11 and CK2 expression are individually essential for breast cancer cell survival, including TNBC. These genes serve as promising new targets for therapeutic development in breast cancer.

Vascular-promoting therapy reduced tumor growth and progression by improving chemotherapy efficacy

In this issue of Cancer Cell, Wong and colleagues describe a novel approach of increasing the number of functional blood vessels in tumors using a low-dose therapy regimen of Cilengtide and Verapamil. This method enhanced gemcitabine delivery, uptake, and metabolism within tumor cells to reduce tumor growth and progression.

Mining the Breast Cancer Proteome for Predictors of Drug Sensitivity

Approximately 20 drugs have been approved by the FDA for breast cancer treatment, yet predictive biomarkers are known for only a few of these. The identification of additional biomarkers would be useful both for drugs currently approved for breast cancer treatment and for new drug development. Using glycoprotein expression data collected via mass spectrometry, in conjunction with statistical models constructed by elastic net or lasso regression, we modeled quantitatively the responses of breast cancer cell lines to ~90 drugs. Lasso and elastic net regression identified HER2 as a predictor protein for lapatinib, afatinib, gefitinib and erlotinib, which target HER2 or the EGF receptor, thus providing an internal control for the approach. Two additional protein datasets and two RNA datasets were also tested as sources of predictor proteins for modeling drug sensitivity. Protein expression measured by mass spectrometry gave models with higher coefficients of determination than did reverse phase protein array (RPPA) predictor data. Further, cross validation of the elastic net models shows that, for many drugs, the prediction error is lower when the predictor data is from proteins, rather than mRNA expression measured on microarrays. Drugs that could be modeled effectively include PI3K inhibitors, Akt inhibitors, paclitaxel and docetaxel, rapamycin, everolimus and temsirolimus, gemcitabine and vinorelbine. Strikingly, this modeling approach with protein predictors often succeeds for drugs that are targeted agents, even when the nominal target is not in the dataset.

Differentially expressed proteins in human MCF-7 breast cancer cells sensitive and resistant to paclitaxel

Resistance of cancer cells to chemotherapeutic agents is one of the main causes of treatment failure. In order to detect proteins potentially involved in the mechanism of resistance to taxanes, we assessed differences in protein expression in MCF-7 breast cancer cells that are sensitive to paclitaxel and in the same cells with acquired resistance to paclitaxel (established in our lab). Proteins were separated using two-dimensional electrophoresis. Changes in their expression were determined and proteins with altered expression were identified using mass spectrometry. Changes in their expression were confirmed using western blot analysis. With these techniques, we found three proteins expressed differently in resistant MCF-7 cells, i.e., thyroid hormone-interacting protein 6 (TRIP6; upregulated to 650%), heat shock protein 27 (HSP27; downregulated to 50%) and cathepsin D (downregulated to 28%). Silencing of TRIP6 expression by specific siRNA leads to decreased number of grown resistant MCF-7 cells. In the present study we have pointed at some new directions in the studies of the mechanism of resistance to paclitaxel in breast cancer cells.

Nonclinical reproductive and developmental safety evaluation of the MAGE-A3 Cancer Immunotherapeutic, a therapeutic vaccine for cancer treatment

We assessed potential toxic effects of the MAGE-A3 Cancer Immunotherapeutic on female fertility and embryo-fetal, pre- and post-natal development in rats and on male fertility in rats and monkeys. Three groups of 48 female (Study 1) or 22 male (Study 2) CD rats received 5 or 3 injections of 100μL of saline, AS15 immunostimulant, or MAGE-A3 Cancer Immunotherapeutic (MAGE-A3 recombinant protein combined with AS15) at various timepoints pre- or post-mating. Male Cynomolgus monkeys (Study 3) received 8 injections of 500μL of saline (n=2) or the MAGE-A3 Cancer Immunotherapeutic (n=6) every 2 weeks. Rats were sacrificed on gestation day 20 or lactation day 25 (Study 1) or 9 weeks after first injection (Study 2) and monkeys, 3 days or 8 weeks after last injection. Injections were well tolerated. Female rat mating performance or fertility, pre- and post-natal survival, offspring development up to 25 days of age, and male mating performance (rats) or fertility parameters (rats and monkeys) were unaffected.

Nanoscale drug delivery for taxanes based on the mechanism of multidrug resistance of cancer

Taxanes are one type of the most extensively used chemotherapeutic agents to treat cancers. However, their clinical use is severely limited by intrinsic and acquired resistance. A diverse variety of mechanisms has been implicated about taxane resistance, such as alterations of drug targets, overexpression of efflux transporters, defective apoptotic machineries, and barriers in drug transport. The deepening understanding of molecular mechanisms of taxane resistance has spawned a number of targets for reversing resistance. However, circumvention of taxane resistance would not only possess therapeutic potential, but also face with clinical challenge, which accelerates the development of optimal nanoscale delivery systems. This review highlights the current understanding on the mechanisms of taxane resistance, and provides a comprehensive analysis of various nanoscale delivery systems to reverse taxane resistance.

Achyranthes aspera root extracts induce human colon cancer cell (COLO-205) death by triggering the mitochondrial apoptosis pathway and S phase cell cycle arrest

Achyranthes aspera (AA) has been used traditionally for the cure of various disorders. However, the action of root extracts of AA as anticancer agent and its cellular mechanism remain unclear. The aim was to screen the antitumor effect of ethanolic (EAA) and aqueous (AAA) root extracts on the growth of colon cancer COLO-205 cells by testing their cytotoxicity, followed by their effect on clonogenicity, migration, and induction of apoptosis. Mechanisms leading to apoptosis and cell cycle arrest were also investigated by expression studies of caspase-9, caspase-3, Bax, Bcl-2, p16, p21, and p27 genes, followed by flow cytometric analysis for cell cycle distribution. Cytotoxicity screening of AA extracts indicated greater cytotoxic activity of AAA extract against COLO-205 cells. A series of events marked by apoptosis revealed loss of cell viability, chromatin condensation, and DNA fragmentation in AAA treated cells to a greater extent. The mRNA expression levels of caspase-9, caspase-3, Bax, p16, p21, and p27 were markedly increased in the AAA treated cells, along with decreased Bcl-2 expression. The cell cycle arrest at S phase was detected by flow cytometric analysis after treatment with AAA. Overall the study signifies the aqueous extracts as a promising therapeutic candidate against cancer.

[Role of HRI in apoptosis resistance]

When exposed to environmental stresses, cells activate defence mechanisms to adapt stress and inhibit apoptotic pathways leading to their survival. Stressed cells also reduce their general metabolism in part by inhibiting mRNA translation, thereby saving energy needed to repair stress-induced damages. Under stress conditions, the inhibition of mRNA translation occurs mainly at its initiation step through the phosphorylation of the translation initiation factor eIF2α. One of the four kinases known to phosphorylate eIF2α is heme-regulated inhibitor (HRI). The activation of HRI occurs under conditions of heme deficiency, oxidative stress and treatment with anti-cancer drugs such as proteasome inhibitors. In this article, we discuss the role of HRI in promoting cell resistance to stress-mediated apoptosis.

Translational research in oncology--10 years of progress and future prospects

International efforts to sequence the genomes of various human cancers have been broadly deployed in drug discovery programmes. Diagnostic tests that predict the value of the molecularly targeted anticancer agents used in such programmes are conceived and validated in parallel with new small-molecule treatments and immunotherapies. This approach has been aided by better preclinical cancer models; an enhanced appreciation of the complex interactions that exist between tumour cells and their microenvironment; the elucidation of interactions between many of the genetic drivers of cancer, including oncogenes and tumour suppressors; and recent insights into the genetic heterogeneity of human tumours made possible by extraordinary improvements in DNA-sequencing techniques. These advances are being employed in the first generation of genomic clinical trials that will examine the feasibility of matching a broad range of systemic therapies to specific molecular tumour characteristics. More-extensive molecular characterization of tumours and their supporting matrices are anticipated to become standard aspects of oncological practice, permitting continuous molecular re-evaluations of human malignancies on a patient-by-patient and treatment-by-treatment basis. We review selected developments in translational cancer biology, diagnostics, and therapeutics that have occurred over the past decade and offer our thoughts on future prospects for the next few years.

The specific alteration of histone methylation profiles by DZNep during early zebrafish development

Early embryo development constitutes a unique opportunity to study acquisition of epigenetic marks, including histone methylation. This study investigates the in vivo function and specificity of 3-deazaneplanocin A (DZNep), a promising anti-cancer drug that targets polycomb complex genes. One- to two-cell stage embryos were cultured with DZNep, and subsequently evaluated at the post-mid blastula transition stage for H3K27me3, H3K4me3 and H3K9me3 occupancy and enrichment at promoters using ChIP-chip microarrays. DZNep affected promoter enrichment of H3K27me3 and H3K9me3, whereas H3K4me3 remained stable. Interestingly, DZNep induced a loss of H3K27me3 and H3K9me3 from a substantial number of promoters but did not prevent de novo acquisition of these marks on others, indicating gene-specific targeting of its action. Loss/gain of H3K27me3 on promoters did not result in changes in gene expression levels until 24h post-fertilization. In contrast, genes gaining H3K9me3 displayed strong and constant down-regulation upon DZNep treatment. H3K9me3 enrichment on these gene promoters was observed not only in the proximal area as expected, but also over the transcription start site. Altered H3K9me3 profiles were associated with severe neuronal and cranial phenotypes at day 4-5 post-fertilization. Thus, DZNep was shown to affect enrichment patterns of H3K27me3 and H3K9me3 at promoters in a gene-specific manner.

Regulation of cell transformation by Rb-controlled redox homeostasis

Rb is a tumor suppressor, and regulates various biological progresses, such as cell proliferation, development, metabolism and cell death. In the current study, we show that Rb knockout in 3T3 cells leads to oxidative redox state and low mitochondrial membrane potential by regulating mitochondrial activity. Our results indicate that Rb plays an important role in controlling redox homeostasis. More importantly, the functions of Rb in modulating cell proliferation, death and transformation are, at least in part, mediated by its controlling cellular redox state. In addition, our results also suggest that the cellular redox state possibly determines various biological activities, including cell survival, death and transformation, where Rb is functioning as a regulator of redox homeostasis.