Inhibition of IGF-IR increases chemosensitivity in human colorectal cancer cells through MRP-2 promoter suppression

Short interfering RNA in colorectal cancer: is it wise to shoot the messenger?

Colorectal cancer (CRC) is the third most common cancer and the leading cause of gastrointestinal cancer death. 90% of people diagnosed with colorectal cancer are over the age of 50; nevertheless, the illness is more aggressive among those detected at a younger age. Chemotherapy-based treatment has several adverse effects on both normal and malignant cells. The primary signaling pathways implicated in the advancement of CRC include hedgehog (Hh), janus kinase and signal transducer and activator of transcription (JAK/STAT), Wingless-related integration site (Wnt)/β-catenin, transforming growth factor-β (TNF-β), epidermal growth factor receptor (EGFR)/Mitogen-activated protein kinases (MAPK), phosphoinositide 3-kinase (PI3K), nuclear factor kappa B (NF-κB), and Notch. Loss of heterozygosity in tumor suppressor genes like adenomatous polyposis coli, as well as mutation or deletion of genes like p53 and Kirsten rat sarcoma viral oncogene (KRAS), are all responsible for the occurrence of CRC. Novel therapeutic targets linked to these signal-transduction cascades have been identified as a consequence of advances in small interfering RNA (siRNA) treatments. This study focuses on many innovative siRNA therapies and methodologies for delivering siRNA therapeutics to the malignant site safely and effectively for the treatment of CRC. Treatment of CRC using siRNA-associated nanoparticles (NPs) may inhibit the activity of oncogenes and MDR-related genes by targeting a range of signaling mechanisms. This study summarizes several siRNAs targeting signaling molecules, as well as the therapeutic approaches that might be employed to treat CRC in the future.

Recent update on application of dihydromyricetin in metabolic related diseases

As a new type of natural flavonoids, dihydromyricetin (DMY) has attracted more and more attention. It has a series of pharmacological effects, such as anti-inflammatory, anti-tumor, anti-oxidation, antibacterial and so on, and it is almost no toxicity and with excellent safety. Therefore, even if the bioavailability is poor, it is often added to daily food, beverages and even medicines. In recent years, some researchers have found that DMY can treat some diseases by anti-oxidation, anti-inflammation, promoting cell death and regulate the activity of lipid and glucose metabolism. In addition, the mechanism of DMY on these diseases was also related to the signal pathway of AMPK, PI3K/Akt, PPAR and the participation of microRNAs. This review describes the mechanism of DMY in metabolic related diseases from three aspects: metabolic diseases, liver diseases, and cancers, hoping to provide some new ideas for clinical researches.

Help or hindrance: The obesity paradox in cancer treatment response

Obesity is a rising epidemic, the influence of which on cancer development, progression as well as its impact on current standard of care cancer treatments is profound with many facets. Obesity is emerging as a modulating factor in many cancer therapies, such as chemotherapy, radiotherapy, immunotherapy and combination therapies. It has been reported to diminish the efficacy of some treatments but has also been alluded to being protective in terms of reduced treatment toxicities, thus the evolution of the obesity paradox. The obese tumour microenvironment influences treatment response through modulation of a series of aspects, including altered adipocyte secretome, angiogenesis, hypoxia, fibrosis, free fatty acid uptake as well as a modulated immune landscape. However, the influence of these underlying mechanisms on cancer treatment response and the biological action of adipose tissue is still largely unknown. Elucidation of these facets may lead to the enhanced efficacy of current treatment options or the identification of novel methods to combat cancer in the obese tumour microenvironment.

Chemoprotective and chemosensitizing effects of apigenin on cancer therapy

BACKGROUND

Therapeutic resistance to radiation and chemotherapy is one of the major obstacles in cancer treatment. Although synthetic radiosensitizers are pragmatic solution to enhance tumor sensitivity, they pose concerns of toxicity and non-specificity. In the last decades, scientists scrutinized novel plant-derived radiosensitizers and chemosensitizers, such as flavones, owing to their substantial physiological effects like low toxicity and non-mutagenic properties on the human cells. The combination therapy with apigenin is potential candidate in cancer therapeutics. This review explicates the combinatorial strategies involving apigenin to overcome drug resistance and boost the anti-cancer properties.

METHODS

We selected full-text English papers on international databases like PubMed, Web of Science, Google Scholar, Scopus, and ScienceDirect from 1972 up to 2020. The keywords included in the search were: Apigenin, Chemoprotective, Chemosensitizing, Side Effects, and Molecular Mechanisms.

RESULTS

In this review, we focused on combination therapy, particularly with apigenin augmenting the anti-cancer effects of chemo drugs on tumor cells, reduce their side effects, subdue drug resistance, and protect healthy cells. The reviewed research data implies that these co-therapies exhibited a synergistic effect on various cancer cells, where apigenin sensitized the chemo drug through different pathways including a significant reduction in overexpressed genes, AKT phosphorylation, NFκB, inhibition of Nrf2, overexpression of caspases, up-regulation of p53 and MAPK, compared to the monotherapies. Meanwhile, contrary to the chemo drugs alone, combined treatments significantly induced apoptosis in the treated cells.

CONCLUSION

Briefly, our analysis proposed that the combination therapies with apigenin could suppress the unwanted toxicity of chemotherapeutic agents. It is believed that these expedient results may pave the path for the development of drugs with a high therapeutic index. Nevertheless, human clinical trials are a prerequisite to consider the potential use of apigenin in the prevention and treatment of various cancers. Conclusively, the clinical trials to comprehend the role of apigenin as a chemoprotective agent are still in infancy.

Circulating non-coding RNAs as new biomarkers and novel therapeutic targets in colorectal cancer

Colorectal cancer (CRC) is one of the most common malignant tumors, and a large number of patients are diagnosed and die every year. Due to the lack of appropriate diagnosis, prediction and treatment, early diagnosis rate of CRC is low and the prognosis is poor. Studies have found that abnormally expressed non-coding RNAs (ncRNAs) (including microRNAs (miRNAs), circular RNAs (circRNAs) and long non-coding RNAs (lncRNAs),etc.) play an important regulatory role in the occurrence and development of CRC. Some studies have shown that they are stable in the blood and can be detected repeatedly. They are expected to be non-invasive biomarkers for early diagnosis, prognosis evaluation, and prediction of drug sensitivity of CRC, as well as potential applications in the treatment of CRC.

RNA-Binding Protein Polymorphisms as Novel Biomarkers to Predict Outcomes of Metastatic Colorectal Cancer: A Meta-analysis from TRIBE, FIRE-3, and MAVERICC

RNA-binding proteins (RBPs) regulate many posttranscriptional cellular activities. Accumulating evidence suggests associations between RBPs with colonic tumorigenesis and chemosensitivity. We investigated the prognostic and predictive values of SNPs of genes encoding RBPs in metastatic colorectal cancer (mCRC), using clinical and genomic data from three randomized clinical trials of standard first-line chemotherapy for mCRC (TRIBE, FIRE-3, and MAVERICC). Genomic DNA extracted from blood samples was genotyped using an OncoArray. We tested 30 candidate SNPs of 10 major RBP-related genes with additive models. Prognostic values were estimated by meta-analysis approach. Treatment-by-SNP interactions were tested to estimate predictive values for targeted drugs and cytotoxic backbone chemotherapies. This study included 884 patients. The meta-analysis revealed prognostic values of LIN28B rs314277 [HR, 1.26; 95% confidence interval (CI), 1.06-1.49, P = 0.005, FDR-adjusted P = 0.072 for overall survival (OS)] and LIN28B rs314276 (HR, 1.25; 95% CI, 1.08-1.44, P = 0.002, FDR-adjusted P = 0.062 for OS). Although some SNPs showed potentially predictive values, these associations were not confirmed after FDR adjustment. In conclusion, the results of this study are warranting additional studies to provide the evidence that RBP-related SNPs may be associated with the prognosis of patients with mCRC treated with standard first-line chemotherapies. In addition, further studies are warranted to study the predictive value.

Dihydromyricetin reverses MRP2-induced multidrug resistance by preventing NF-κB-Nrf2 signaling in colorectal cancer cell

BACKGROUD

Dihydromyricetin (DMY), a natural flavonoid compound from the leaves of the Chinese medicinal herb Vitis heyneana, has been shown to have the potential to combat chemoresistance by inhibiting Nrf2/MRP2 signaling in colorectal cancer (CRC) cells. However, the precise underlying molecular mechanism and its therapeutic target are not well understood.

PURPOSE

Our study aims to investigate the effects of DMY on multidrug resistance (MDR), and elucidate the underlying mechanisms.

STUDY DESIGN

In vitro, HCT116/OXA and HCT8/VCR cells were employed as our MDR models. The cells were treated with DMY (50 µM) or MK-571 (50 µM) plus oxaliplatin (OXA) (10 µM) or vincristine (VCR) (10 µM) for 48 h. In vivo, we used BALB/c mice as a CRC xenograft mouse model. BALB/c mice were given DMY (100 mg/kg), OXA (5 mg/kg) and DMY (100 mg/kg) combined with OXA (5 mg/kg) via intraperitoneal route every 2 days per week for 4 weeks.

METHODS

We used MTT and colony forming assays to detect DMY's ability to reverse MDR. Flow cytometric analysis was used to detect apoptosis. Immunocytochemistry was used to detect the localization of Nrf2 and NF-κB/p65. Western blot, qRT-PCR and reporter gene assays were employed to measure the protein and gene transcriptional levels (MRP2, Nrf2, NF-κB/p65). Moreover, chromatin immunoprecipitation (ChIP) assay was used to investigate the endogenous promoter occupancy of NF-κB/p65. Finally, immunohistochemistry and TUNEL staining were used to detect protein expression and apoptosis in vivo.

RESULTS

DMY restored chemosensitivity (OXA and VCR) by inhibiting both MRP2 expression and its promoter activity in HCT116/OXA and HCT8/VCR cell lines. Furthermore, DMY could inhibit NF-κB/p65 expression, reducing NF-κB/p65 translocation to the nucleus to silence Nrf2 signaling, which is necessary for MRP2 expression. Overexpressing NF-κB/p65 expression reduced the reversal effect of DMY. In addition, NF-κB/p65 regulated Nrf2 expression by directly binding to its specific promoter region and activating its transcription. Finally, we proved that the combination of OXA and DMY has a synergistic tumor suppression effect in vivo.

CONCLUSION

Our study provided a novel mechanism of DMY boosted chemosensitivity in human CRC. The downstream signals of DMY, NF-κB or Nrf2 could also be potential targets for the treatment of CRC.

MicroRNA-Assisted Hormone Cell Signaling in Colorectal Cancer Resistance

Despite substantial progress in cancer therapy, colorectal cancer (CRC) is still the third leading cause of cancer death worldwide, mainly due to the acquisition of resistance and disease recurrence in patients. Growing evidence indicates that deregulation of hormone signaling pathways and their cross-talk with other signaling cascades inside CRC cells may have an impact on therapy resistance. MicroRNAs (miRNAs) are small conserved non-coding RNAs thatfunction as negative regulators in many gene expression processes. Key studies have identified miRNA alterations in cancer progression and drug resistance. In this review, we provide a comprehensive overview and assessment of miRNAs role in hormone signaling pathways in CRC drug resistance and their potential as future targets for overcoming resistance to treatment.

Growth Hormone Upregulates Mediators of Melanoma Drug Efflux and Epithelial-to-Mesenchymal Transition In Vitro and In Vivo

Simple Summary

Growth hormone (GH) action is strongly implicated in the progression and therapy resistance in several types of solid tumors which overexpress the GH receptor (GHR). The aim of our study was to characterize the effects of GH and its downstream effector insulin-like growth factor 1 (IGF-1) on melanoma using in vitro and in vivo models. We confirmed an IGF-1-independent role of elevated circulating GH in upregulating key mechanisms of therapy resistance and malignancy with analyses conducted at the molecular and cellular level. We identified that GH upregulates key mechanisms of therapy resistance and metastases in melanoma tumors in an IGF-1 dependent and independent manner by upregulating multidrug efflux pumps and EMT transcription factors. Our study reveals that GH action renders an intrinsic drug resistance phenotype to the melanoma tumors—a clinically crucial property of GH verifiable in other human cancers with GHR expression.

Abstract

Growth hormone (GH) and the GH receptor (GHR) are expressed in a wide range of malignant tumors including melanoma. However, the effect of GH/insulin-like growth factor (IGF) on melanoma in vivo has not yet been elucidated. Here we assessed the physical and molecular effects of GH on mouse melanoma B16-F10 and human melanoma SK-MEL-30 cells in vitro. We then corroborated these observations with syngeneic B16-F10 tumors in two mouse lines with different levels of GH/IGF: bovine GH transgenic mice (bGH; high GH, high IGF-1) and GHR gene-disrupted or knockout mice (GHRKO; high GH, low IGF-1). In vitro, GH treatment enhanced mouse and human melanoma cell growth, drug retention and cell invasion. While the in vivo tumor size was unaffected in both bGH and GHRKO mouse lines, multiple drug-efflux pumps were up regulated. This intrinsic capacity of therapy resistance appears to be GH dependent. Additionally, epithelial-to-mesenchymal transition (EMT) gene transcription markers were significantly upregulated in vivo supporting our current and recent in vitro observations. These syngeneic mouse melanoma models of differential GH/IGF action can be valuable tools in screening for therapeutic options where lowering GH/IGF-1 action is important.

Manipulation of Metabolic Pathways and Its Consequences for Anti-Tumor Immunity: A Clinical Perspective

In the relatively short history of anti-tumor treatment, numerous medications have been developed against a variety of targets. Intriguingly, although many anti-tumor strategies have failed in their clinical trials, metformin, an anti-diabetic medication, demonstrated anti-tumor effects in observational studies and even showed its synergistic potential with immune checkpoint inhibitors (ICIs) in subsequent clinical studies. Looking back from bedside-to-bench, it may not be surprising that the anti-tumor effect of metformin derives largely from its ability to rewire aberrant metabolic pathways within the tumor microenvironment. As one of the most promising breakthroughs in oncology, ICIs were also found to exert their immune-stimulatory effects at least partly via rewiring metabolic pathways. These findings underscore the importance of correcting metabolic pathways to achieve sufficient anti-tumor immunity. Herein, we start by introducing the tumor microenvironment, and then we review the implications of metabolic syndrome and treatments for targeting metabolic pathways in anti-tumor therapies. We further summarize the close associations of certain aberrant metabolic pathways with impaired anti-tumor immunity and introduce the therapeutic effects of targeting these routes. Lastly, we go through the metabolic effects of ICIs and conclude an overall direction to manipulate metabolic pathways in favor of anti-tumor responses.

Role of anabolic agents in colorectal carcinogenesis: Myths and realities (Review)

Colorectal cancer (CRC) is one of the four leading causes of cancer‑related mortality worldwide. Even though over the past few decades the global scientific community has made tremendous efforts to understand this entity, many questions remain to be raised on this issue and even more to be answered. Epidemiological findings have unveiled numerous environmental and genetic risk factors, each one contributing to a certain degree to the final account of new CRC cases. Moreover, different trends have been revealed regarding the age of onset of CRC between the two sexes. That, in addition to newly introduced therapeutic approaches for various diseases based on androgens, anti‑androgens and anabolic hormones has raised some concerns regarding their possible carcinogenic effects or their synergistic potential with other substances/risk factors, predisposing the individual to CRC. Notably, despite the intense research on experimental settings and population studies, the conclusions regarding the majority of anabolic substances are ambiguous. Some of these indicate the carcinogenic properties of testosterone, dihydrotestosterone (DHT), growth hormone and insulin‑like growth factor (IGF) and others, demonstrating their neutral nature or even their protective one, as in the case of vitamin D. Thus, the synergistic nature of anabolic substances with other CRC risk factors (such as type 2 diabetes mellitus, metabolic syndrome and smoking) has emerged, suggesting a more holistic approach.

Transport-Mediated Oxaliplatin Resistance Associated with Endogenous Overexpression of MRP2 in Caco-2 and PANC-1 Cells

Our recent publications showed that multidrug resistance protein 2 (MRP2, encoded by the ABCC2 gene) conferred oxaliplatin resistance in human liver cancer HepG2 cells. However, the contribution of MRP2 to oxaliplatin resistance remains unclear in colorectal and pancreatic cancer lines. We investigated the effects of silencing MRP2 by siRNA on oxaliplatin accumulation and sensitivity in human colorectal cancer Caco-2 cells and pancreatic cancer PANC-1 cells. We characterized the effects of oxaliplatin on MRP2 ATPase activities using membrane vesicles. Over-expression of MRP2 (endogenously in Caco-2 and PANC-1 cells) was associated with decreased oxaliplatin accumulation and cytotoxicity, but those deficits were reversed by inhibition of MRP2 with myricetin or siRNA knockdown. Silencing MRP2 by siRNA increased oxaliplatin-induced apoptotic rate in Caco-2 and PANC-1 cells. Oxaliplatin stimulated MRP2 ATPase activity with a concentration needed to reach 50% of the maximal stimulation (EC₅₀) value of 8.3 ± 0.7 µM and Hill slope 2.7. In conclusion, oxaliplatin is a substrate of MRP2 with possibly two binding sites, and silencing MRP2 increased oxaliplatin accumulation and cytotoxicity in two widely available gastrointestinal tumour lines (PANC-1 and Caco-2).

Identification of MRP2 as a targetable factor limiting oxaliplatin accumulation and response in gastrointestinal cancer

Oxaliplatin is important for the clinical treatment of colorectal cancer and other gastrointestinal malignancies, but tumour resistance is limiting. Several oxaliplatin transporters were previously identified but their relative contributions to determining oxaliplatin tumour responses and gastrointestinal tumour cell sensitivity to oxaliplatin remains unclear. We studied clinical associations between tumour expression of oxaliplatin transporter candidate genes and patient response to oxaliplatin, then experimentally verified associations found with MRP2 in models of human gastrointestinal cancer. Among 18 oxaliplatin transporter candidate genes, MRP2 was the only one to be differentially expressed in the tumours of colorectal cancer patients who did or did not respond to FOLFOX chemotherapy. Over-expression of MRP2 (endogenously in HepG2 and PANC-1 cells, or induced by stable transfection of HEK293 cells) decreased oxaliplatin accumulation and cytotoxicity but those deficits were reversed by inhibition of MRP2 with myricetin or siRNA knockdown. Mice bearing subcutaneous HepG2 tumour xenografts were sensitised to oxaliplatin antitumour activity by concurrent myricetin treatment with little or no increase in toxicity. In conclusion, MRP2 limits oxaliplatin accumulation and response in human gastrointestinal cancer. Screening tumour MRP2 expression levels, to select patients for treatment with oxaliplatin-based chemotherapy alone or in combination with a MRP2 inhibitor, could improve treatment outcomes.

Dihydromyricetin reverses MRP2-mediated MDR and enhances anticancer activity induced by oxaliplatin in colorectal cancer cells

Dihydromyricetin (DMY), extracted from the Chinese herbal medicine Ampelopsis grossedentata, possesses antitumor potential in different types of human cancer cells. Hence, its effects on drug resistance and molecular mechanisms in colorectal cancer (CRC) are still unknown. In our present study, we observed that DMY enhanced the chemosensitivity to oxaliplatin (OXA). DMY increased OXA-induced apoptosis and reduced 5(6)-carboxy-2',7'-dichlorofluorescein accumulation in OXA-resistant CRC HCT116/L-OHP cells. Our mechanistic study suggested that DMY treatment inhibited multidrug resistance protein 2 (MRP2) expression levels and promoter activity, indicating that DMY reduced not only MRP2 transcriptional and translational levels but also its function. Additional experiments indicated that the nuclear translocation of nuclear factor-erythroid 2 p45 related factor 2, a MRP2 regulator, was also inhibited by DMY. In summary, our study provided the first direct evidence that the inhibitory effects of DMY on MRP2 expression in OXA-resistant CRC cells were closely associated with the inhibition of nuclear factor-erythroid 2 p45 related factor 2 signaling. DMY could be a potential candidate for CRC chemotherapy.

Function of insulin-like growth factor 1 receptor in cancer resistance to chemotherapy

Drug resistance is a primary cause of chemotherapeutic failure; however, how this resistance develops is complex. A comprehensive understanding of chemotherapeutic resistance mechanisms may aid in identifying more effective drugs and improve the survival rates of patients with cancer. Insulin-like growth factor 1 receptor (IGF1R), a member of the insulin receptor family, has been extensively assessed for biological activity, and its putative contribution to tumor cell development and progression. Furthermore, researchers have attended to drugs that target IGF1R since IGF1R functions as a membrane receptor. However, how IGF1R participates in chemotherapeutic resistance remains unclear. Therefore, the present study described the IGF1R gene and its associated signaling pathways, and offered details of IGF1R-induced tumor chemoresistance associated with promoting cell proliferation, inhibition of apoptosis, regulation of ATP-binding cassette transporter proteins and interactions with the extracellular matrix. The present study offered additional explanations for tumor chemotherapy resistance and provided a theoretical basis of IGF1R and its downstream pathways for future possible chemotherapy treatment options.

Insulin-Like Growth Factor (IGF) Pathway Targeting in Cancer: Role of the IGF Axis and Opportunities for Future Combination Studies

Despite a strong preclinical rationale for targeting the insulin-like growth factor (IGF) axis in cancer, clinical studies of IGF-1 receptor (IGF-1R)-targeted monotherapies have been largely disappointing, and any potential success has been limited by the lack of validated predictive biomarkers for patient enrichment. A large body of preclinical evidence suggests that the key role of the IGF axis in cancer is in driving treatment resistance, via general proliferative/survival mechanisms, interactions with other mitogenic signaling networks, and class-specific mechanisms such as DNA damage repair. Consequently, combining IGF-targeted agents with standard cytotoxic agents, other targeted agents, endocrine therapies, or immunotherapies represents an attractive therapeutic approach. Anti-IGF-1R monoclonal antibodies (mAbs) do not inhibit IGF ligand 2 (IGF-2) activation of the insulin receptor isoform-A (INSR-A), which may limit their anti-proliferative activity. In addition, due to their lack of specificity, IGF-1R tyrosine kinase inhibitors are associated with hyperglycemia as a result of interference with signaling through the classical metabolic INSR-B isoform; this may preclude their use at clinically effective doses. Conversely, IGF-1/IGF-2 ligand-neutralizing mAbs inhibit proliferative/anti-apoptotic signaling via IGF-1R and INSR-A, without compromising the metabolic function of INSR-B. Therefore, combination regimens that include these agents may be more efficacious and tolerable versus IGF-1R-targeted combinations. Herein, we review the preclinical and clinical experience with IGF-targeted therapies to-date, and discuss the rationale for future combination approaches as a means to overcome treatment resistance.

Inhibition of airway remodeling and inflammation by isoforskolin in PDGF-induced rat ASMCs and OVA-induced rat asthma model

Isoforskolin (ISOF) has been reported to play an important role in many illnesses including respiratory, cardiovascular and ophthalmologic diseases. In our study, we aimed to investigate how ISOF regulates airway remodeling and inflammation in asthma. Based on SO₂-stimulated mouse cough model, we assessed the role of ISOF in cough and secretion of phlegm. Afterwards, platelet derived growth factor (PDGF)-induced primary rat airway smooth muscle cell (ASMC) model and ovalbumin (OVA)-induced rat asthma model were used to continue our following research. Our results showed that ISOF could prolong the cough latent period, reduce the cough times in two minutes, and increase the excretion of red phenol, which suggested the antitussive and expectorant effects of ISOF. Besides, ISOF pretreatment reversed the hypotonicity and cytoskeleton remodeling in PDGF-induced ASMCs, and reduced mucus hypersecretion and collagen overdeposition in OVA-induced rat asthma model, which indicated its inhibition on airway remodeling in vitro and in vivo. Moreover, ISOF reduced the invasion of inflammatory cells into bronchoalveolar lavage fluid (BALF) and lungs, which revealed its inhibitory role in airway inflammation. The down-regulation of transforming growth factor β1 (TGF-β1) and interleukin-1β (IL-1β) upon ISOF treatment might be responsible for its anti-remodeling and anti-inflammation roles. In conclusion, ISOF can reduce cough and sputum, as well as inhibit airway remodeling and inflammation by regulating the expression of TGF-β1 and IL-1β. These data indicate the potency of ISOF in treating asthma and also provide insights into the development of new anti-asthma agent.

Targeting miR-21 decreases expression of multi-drug resistant genes and promotes chemosensitivity of renal carcinoma

Renal cell carcinoma, the most common neoplasm of adult kidney, accounts for about 3% of adult malignancies and is usually highly resistant to conventional therapy. MicroRNAs are a class of small non-coding RNAs, which have been previously shown to promote malignant initiation and progression. In this study, we focused our attention on miR-21, a well described oncomiR commonly upregulated in cancer. Using a cohort of 99 primary renal cell carcinoma samples, we showed that miR-21 expression in cancer tissues was higher than in adjacent non-tumor tissues whereas no significant difference was observed with stages, grades, and metastatic outcome. In vitro, miR-21 was also overexpressed in renal carcinoma cell lines compared to HK-2 human proximal tubule epithelial cell line. Moreover, using Boyden chambers and western blot techniques, we also showed that miR-21 overexpression increased migratory, invasive, proliferative, and anti-apoptotic signaling pathways whereas opposite results were observed using an anti-miR-21-based silencing strategy. Finally, we assessed the role of miR-21 in mediating renal cell carcinoma chemoresistance and further showed that miR-21 silencing significantly (1) increased chemosensitivity of paclitaxel, 5-fluorouracil, oxaliplatin, and dovitinib; (2) decreased expression of multi-drug resistance genes; and (4) increased SLC22A1/OCT1, SLC22A2/OCT2, and SLC31A1/CTR1 platinum influx transporter expression. In conclusion, our results showed that miR-21 is a key actor of renal cancer progression and plays an important role in the resistance to chemotherapeutic drugs. In renal cell carcinoma, targeting miR-21 is a potential new therapeutic strategy to improve chemotherapy efficacy and consequently patient outcome.

Redox Control of Multidrug Resistance and Its Possible Modulation by Antioxidants

Clinical efficacy of anticancer chemotherapies is dramatically hampered by multidrug resistance (MDR) dependent on inherited traits, acquired defence against toxins, and adaptive mechanisms mounting in tumours. There is overwhelming evidence that molecular events leading to MDR are regulated by redox mechanisms. For example, chemotherapeutics which overrun the first obstacle of redox-regulated cellular uptake channels (MDR1, MDR2, and MDR3) induce a concerted action of phase I/II metabolic enzymes with a temporal redox-regulated axis. This results in rapid metabolic transformation and elimination of a toxin. This metabolic axis is tightly interconnected with the inducible Nrf2-linked pathway, a key switch-on mechanism for upregulation of endogenous antioxidant enzymes and detoxifying systems. As a result, chemotherapeutics and cytotoxic by-products of their metabolism (ROS, hydroperoxides, and aldehydes) are inactivated and MDR occurs. On the other hand, tumour cells are capable of mounting an adaptive antioxidant response against ROS produced by chemotherapeutics and host immune cells. The multiple redox-dependent mechanisms involved in MDR prompted suggesting redox-active drugs (antioxidants and prooxidants) or inhibitors of inducible antioxidant defence as a novel approach to diminish MDR. Pitfalls and progress in this direction are discussed.

Modulation of sensitivity and resistance to multikinase inhibitors by microenvironmental platelet factors in HCC

INTRODUCTION

Response of a tumor to chemotherapy or multikinase inhibitor therapy has been traditionally thought to be a reflection of the sum of the characteristics of both the drug and of the tumor cell resistance mechanisms. More recently, there has been a growing awareness of the role of non-tumor factors-both cellular and humoral-in the tumor microenvironment that can increase or decrease the tumor cellular responses to the therapy. This article focuses on platelet factors in clinical HCC and experimental evidence that they provide growth stimulants that can antagonize the growth inhibitory effects of therapy.

AREAS COVERED

Review of the mechanisms of multikinase cancer growth inhibitors and of the role of platelets in providing growth factors that can antagonize their effects.

EXPERT OPINION

These new ideas and data show that the response of a tumor to multikinase inhibitors or chemotherapy may be strongly influenced by microenvironmental factors. Conversely, antagonists to these environmental factors, such as EGFR inhibitors and IGF1-R inhibitors, might be expected to augment the anti-tumor effect of both chemotherapy and multikinase inhibitors.

The Insulin/IGF System in Colorectal Cancer Development and Resistance to Therapy

The insulin/insulin-like growth factor (IGF) system is a major determinant in the pathogenesis and progression of colorectal cancer (CRC). Indeed, several components of this signaling network, including insulin, IGF-1, IGF-2, the IGF-binding proteins, the insulin receptor (IR), the IGF-1 receptor (IGF-1R), and IR substrate proteins 1 and 2 contribute to the transformation of normal colon epithelial cells. Moreover, the insulin/IGF system is also implicated in the development of resistance to both chemotherapeutic drugs and epidermal growth factor receptor targeted agents. The identification of hybrid receptors comprising both the IR and IGF-1R adds further complexity to this signaling network. Thus, a comprehensive understanding of the biological functions performed by each component of the insulin/IGF system is required to design successful drugs for the treatment of CRC patients.

Resveratrol induces AMPK-dependent MDR1 inhibition in colorectal cancer HCT116/L-OHP cells by preventing activation of NF-κB signaling and suppressing cAMP-responsive element transcriptional activity

Resveratrol, a natural polyphenolic compound found in foods and beverages, has attracted increasing attention in recent years because of its potent chemopreventive and anti-tumor effects. In this study, the effects of resveratrol on the expression of P-glycoprotein/multi-drug resistance protein 1 (P-gp/MDR1), and the underlying molecular mechanisms, were investigated in oxaliplatin (L-OHP)-resistant colorectal cancer cells (HCT116/L-OHP). Resveratrol downregulated MDR1 protein and mRNA expression levels and reduced MDR1 promoter activity. It also enhanced the intracellular accumulation of rhodamine 123, suggesting that resveratrol can reverse multi-drug resistance by downregulating MDR1 expression and reducing drug efflux. Resveratrol treatment also reduced nuclear factor-κB (NF-κB) activity, reduced phosphorylation levels of IκBα, and reduced nuclear translocation of the NF-κB subunit p65. Moreover, downregulation of MDR1 expression and promoter activity was mediated by resveratrol-induced AMP-activated protein kinase (AMPK) phosphorylation. The inhibitory effects of resveratrol on MDR1 expression and cAMP-responsive element-binding protein (CREB) phosphorylation were reversed by AMPKα siRNA transfection. We found that the transcriptional activity of cAMP-responsive element (CRE) was inhibited by resveratrol. These results demonstrated that the inhibitory effects of resveratrol on MDR1 expression in HCT116/L-OHP cells were closely associated with the inhibition of NF-κB signaling and CREB activation in an AMPK-dependent manner.

Modulation of Regorafenib effects on HCC cell lines by epidermal growth factor

PURPOSE

Blood platelet numbers are correlated to growth and aggressiveness of several tumor types, including hepatocellular carcinoma (HCC). We previously found that platelet lysates (hPLs) also stimulated growth and migration, and antagonized the growth-inhibitory and apoptotic effects of both Sorafenib and Regorafenib, two multikinase inhibitors, on three HCC cell lines. In this study, in vitro function of human epidermal growth factor (EGF) with and without Sorafenib or Regorafenib was investigated.

METHODS

An ELISA kit was used to evaluate the EGF concentrations in hPLs. In vitro function of EGF was assessed with proliferation MTT test. Apoptosis assay, scratch assays, and Transwell assays were performed for apoptosis, invasion, and migration, respectively. MAPK Activation Kit was used to explore MAPK phosphorylation.

RESULTS

EGF antagonized the growth inhibition of Regorafenib on three HCC cell lines. Regorafenib-mediated growth inhibition was blocked by 70 % when the cells were pre-treated with EGF. EGF also blocked Regorafenib-induced apoptosis, as well as Regorafenib-induced decreases in cell migration and invasion. The EGF effects were in turn antagonized by concomitant addition to the cultures of EGF receptor antagonist Erlotinib, showing that the EGF receptor was involved in the mechanisms of EGF-mediated blocking of Regorafenib effects. Erlotinib also partially blocked the effects of hPLs in antagonizing Regorafenib-mediated growth inhibition, showing that EGF was an important component of hPL actions.

CONCLUSIONS

All these results show that EGF antagonized Regorafenib-mediated growth and migration inhibition and apoptosis induction in HCC cells and reinforce the idea that microenvironment can influence cancer drug actions.

Insulin-like growth factor (IGF) signaling in tumorigenesis and the development of cancer drug resistance

One of the greatest obstacles to current cancer treatment efforts is the development of drug resistance by tumors. Despite recent advances in diagnostic practices and surgical interventions, many neoplasms demonstrate poor response to adjuvant or neoadjuvant radiation and chemotherapy. As a result, the prognosis for many patients afflicted with these aggressive cancers remains bleak. The insulin-like growth factor (IGF) signaling axis has been shown to play critical role in the development and progression of various tumors. Many basic science and translational studies have shown that IGF pathway modulators can have promising effects when used to treat various malignancies. There also exists a substantial body of recent evidence implicating IGF signaling dysregulation in the dwindling response of tumors to current standard-of-care therapy. By better understanding both the IGF-dependent and -independent mechanisms by which pathway members can influence drug sensitivity, we can eventually aim to use modulators of IGF signaling to augment the effects of current therapy. This review summarizes and synthesizes numerous recent investigations looking at the role of the IGF pathway in drug resistance. We offer a brief overview of IGF signaling and its general role in neoplasia, and then delve into detail about the many types of human cancer that have been shown to have IGF pathway involvement in resistance and/or sensitization to therapy. Ultimately, our hope is that such a compilation of evidence will compel investigators to carry out much needed studies looking at combination treatment with IGF signaling modulators to overcome current therapy resistance.

Knockdown of β3GnT8 reverses 5-fluorouracil resistance in human colorectal cancer cells via inhibition the biosynthesis of polylactosamine-type N-glycans

Aberrant glycosylation is known to be associated with cancer chemoresistance. β-1,3-N-acetyl-glucosaminyltransferase (β3GnT)8, which synthesizes polylactosamine on β1-6 branched N-glycans, is dramatically upregulated in colorectal cancer (CRC). 5-Fluorouracil (5-FU) resistance remains a major obstacle to the chemotherapy of CRC. However, little is known with regard to the correlation between 5‑FU resistance and the expression of β3GnT8 in CRC. In this study, a 5-FU‑resistant cell line (SW620/5-FU) was generated, and 50% inhibition concentration (IC50) of 5-FU was determined by MTT assay. Flow cytometry and lectin blot analysis were performed to detect the alteration of polylactosamine structures. Quantitative RT-‑PCR and western blot analysis were used to identify and evaluate candidate genes involved in the synthesis of polylactosamine in SW620/5-FU cells. We found polylactosamine chains were significantly increased in SW620/5-FU cells. Inhibition of the biosynthesis of polylactosamine by 3'-azidothymidine (AZT) was able to reduce 5-FU tolerance. Further studies showed that β3GnT8 expression was also upregulated in 5-FU‑resistant cancer cells, and knockdown of β3GnT8 by RNA interference reversed 5-FU resistance through, at least partly, by suppressing the formation of polylactosamine. In conclusion, the alteration of β3GnT8 in CRC cells correlates with tumor sensitivity to the chemotherapeutic drug and has significant implication for the development of new treatment strategies.

Post-transcriptional regulation of the tumor suppressor miR-139-5p and a network of miR-139-5p-mediated mRNA interactions in colorectal cancer

MicroRNAs play key roles in many biological processes, and are frequently dysregulated in tumor cells. However, there are few studies on how microRNAs are dysregulated. miR-139-5p, an important tumor suppressor, is often underexpressed in gastrointestinal cancer cells. Here, we describe post-transcriptional regulation of this intronic microRNA in human colorectal cancer. miR-139-5p is expressed independently of its overexpressed host gene PDE2A in colorectal cancer tissues and cell lines. The miR-139-5p target genes IGF1R, ROCK2 and RAP1B exert regulatory effects on the miR-139-5p expression level, relying on their ability to compete for miR-139-5p binding. These overexpressed target genes also regulate each others' protein levels through 3'-UTRs, thus regulating tumor cell growth and motility properties. Our study provides a mechanistic, experimentally validated rationale for intronic microRNA dysregulation in colorectal cancer, revealing novel oncogenic roles of IGF1R, ROCK2 and RAP1B 3'-UTRs.

Regulation of SOD2 and β-arrestin1 by interleukin-6 contributes to the increase of IGF-1R expression in docetaxel resistant prostate cancer cells

Although several mechanisms behind resistance to docetaxel in castration-refractory prostate cancer (CRPC) have been investigated, molecular determinants of evolved resistance are still not entirely understood. Proteomics-based analysis in this study revealed that SOD2, associated with downregulation of reactive oxygen species (ROS), was significantly up-regulated in docetaxel-resistant (PC3/Doc) cells if compared to sensitive cells, and the expression of redox-regulated genes such as IGF-1R, CXCR4, and BCL2 was increased as well. Forced expression of SOD2 in sensitive cells led to the increase of IGF-1R and association with drug resistance, whereas silencing of SOD2 resulted in the decrease of IGF-1R at the protein level in resistant cells. Further study revealed that SOD2 acted as a negative regulator of β-arrestin1 that is an important adaptor responsible for degradation of IGF-1R via the changes in ROS, as evidenced by observations that an antioxidant agent substantially attenuated β-arrestin1 expression in vitro and in vivo. Finally, we found that blocking of IL6 that was up-regulated in resistant cells resulted in attenuation of SOD2 and STAT3, and simultaneously in increased expression of β-arrestin1. The modulation consequently led to the decreased IGF-1R at both protein and transcription levels. Together, our data provide a novel explanation that high level of IL6 stimulated SOD2 expression that, at least partially, contributed to the low level of ROS that would likely result in a sustained increase in the expression of IGF-1R through abolishment of β-arrestin1 in docetaxel resistant cells.

Antagonism of sorafenib and regorafenib actions by platelet factors in hepatocellular carcinoma cell lines

BACKGROUND

Platelets are frequently altered in hepatocellular carcinoma (HCC) patients. Platelet lysates (hPL) can enhance HCC cell growth and decrease apoptosis. The aims were to evaluate whether hPL can modulate the actions of sorafenib or regorafenib, two clinical HCC multikinase antagonists.

METHODS

Several human HCC cell lines were grown in the presence and absence of sorafenib or regorafenib, with or without hPL. Growth was measured by MTT assay, apoptosis was assessed by Annexin V and by western blot, and autophagy and MAPK growth signaling were also measured by western blot, and migration and invasion were measured by standard in vitro assays.

RESULTS

Both sorafenib and regorafenib-mediated inhibition of cell growth, migration and invasion were all antagonized by hPL. Drug-mediated apoptosis and decrease in phospho-ERK levels were both blocked by hPL, which also increased anti-apoptotic phospho-STAT, Bax and Bcl-xL levels. Preliminary data, obtained with epidermal growth factor (EGF) and insulin-like growth factor-I (IGF-I), included in hPL, revealed that these factors were able to antagonized sorafenib in a proliferation assay, in particular when used in combination.

CONCLUSIONS

Platelet factors can antagonize sorafenib or regorafenib-mediated growth inhibition and apoptosis in HCC cells. The modulation of platelet activity or numbers has the potential to enhance multikinase drug actions.

Chrysin enhances sensitivity of BEL-7402/ADM cells to doxorubicin by suppressing PI3K/Akt/Nrf2 and ERK/Nrf2 pathway

Nuclear factor-E2-related factor 2 (Nrf2) is an important cytoprotective transcription factor which plays a key role in antioxidant and detoxification processes. Recent studies have reported that development of chemoresistance is associated with the constitutive activation of the Nrf2-mediated signaling pathway in many types of cancer cells. Here, we investigated whether Nrf2 was associated with drug resistant in doxorubicin resistant BEL-7402 (BEL-7402/ADM) cells, and if chrysin could reverse drug resistance in BEL-7402/ADM cells. We found that remarkable higher level of Nrf2 and its target proteins in BEL-7402/ADM cells compared to BEL-7402 cells. Similarly, intracellular Nrf2 protein level was significantly decreased and ADM resistance was partially reversed by Nrf2 siRNA in BEL-7402/ADM cells. chrysin is a potent Nrf2 inhibitor which sensitizes BEL-7402/ADM cells to ADM and increases intracellular concentration of ADM. Mechanistically, chrysin significantly reduced Nrf2 expression at both the mRNA and protein levels through down-regulating PI3K-Akt and ERK pathway. Consequently, expression of Nrf2-downstream genes HO-1, AKR1B10, and MRP5 were reduced and the Nrf2-dependent chemoresistance was suppressed. In conclusion, these results clearly indicate that activation of Nrf2 is associated with drug resistance in BEL-7402/ADM cells and chrysin may be an effective adjuvant sensitizer to reduce anticancer drug resistance by down-regulating Nrf2 signaling pathway.

Application of RNA interference in research of multidrug resistance in colorectal cancer: Recent progress

Colorectal cancer is one of the most common malignant digestive tract tumors in the world. Chemotherapy is the main treatment for colorectal cancer. However, multidrug resistance of tumor cells hinders its treatment. RNA interference, which allows specifically inhibiting the expression of multidrug genes, has been gradually applied to gene treatment for multidrug resistance. This paper aims to summarize the progress of application of RNA interference in research of multidrug resistance in colorectal cancer.

Lack of association between expression of MRP2 and early relapse of colorectal cancer in patients receiving FOLFOX-4 chemotherapy

Recurrence following failure of chemotherapy limits the application of high doses of anticancer drugs currently used for eliminating cancerous cells. It has been identified that ATP-binding cassette (ABC) multidrug transporters are associated with chemoresistance, which is a major obstacle in cancer therapy. The present study aimed to investigate the association of pretherapeutic multidrug resistance-associated protein 2 (MRP2) expression with response to chemotherapy in stage II/III colorectal cancer (CRC). Protein expression was determined by immunohistochemical analysis of 50 archival samples from patients who had not received preoperative chemotherapy and radiotherapy. All patients were treated with 5-fluorouracil/leucovorin (FL) plus oxaliplatin (FOLFOX-4) regimen for 6 months following curative resection. During the 12 months of follow-up, local and distant recurrences were observed in 15 (30%) cases, of which 5 occurred at the time of chemotherapy. MRP2 expression was observed in 24 (48%) and 7 (14%) cases in the tumor tissues and matched normal tissues, respectively. A significant difference was observed between the positive expression frequency in the tumor tissues compared to the surrounding normal mucosa (P=0.003). The incidence of recurrence and metastasis for patients in the MRP2-positive group was lower than that in the MRP2-negative group (P>0.05); however, all 5 cases who demonstrated recurrence during their treatment were MRP2-positive (P=0.022). MRP2 expression was not correlated with the clinicopathological markers in this group of patients. Kaplan-Meier analysis revealed that MRP2 expression was not associated with a shorter disease-free survival or overall survival of patients (P>0.05). The results of this study indicated that MRP2 is overexpressed in the course of CRC development and progression. However, expression of MRP2 was not associated with recurrence of patients treated with FL and oxaliplatin in the population studied.