miR-7 modulates chemoresistance of small cell lung cancer by repressing MRP1/ABCC1

Novel RNA molecular bioengineering technology efficiently produces functional miRNA agents

Genome-derived microRNAs (miRNAs or miRs) govern posttranscriptional gene regulation and play important roles in various cellular processes and disease progression. While chemo-engineered miRNA mimics or biosimilars made in vitro are widely available and used, miRNA agents produced in vivo are emerging to closely recapitulate natural miRNA species for research. Our recent work has demonstrated the success of high-yield, in vivo production of recombinant miRNAs by using human tRNA (htRNA) fused precursor miRNA (pre-miR) carriers. In this study, we aim to compare the production of bioengineered RNA (BioRNA) molecules with glycyl versus leucyl htRNA fused hsa-pre-miR-34a carriers, namely, BioRNAGly and BioRNALeu, respectively, and perform the initial functional assessment. We designed, cloned, overexpressed, and purified a total of 48 new BioRNA/miRNAs, and overall expression levels, final yields, and purities were revealed to be comparable between BioRNAGly and BioRNALeu molecules. Meanwhile, the two versions of BioRNA/miRNAs showed similar activities to inhibit non-small cell lung cancer cell viability. Interestingly, functional analyses using model BioRNA/miR-7-5p demonstrated that BioRNAGly/miR-7-5p exhibited greater efficiency to regulate a known target gene expression (EGFR) than BioRNALeu/miR-7-5p, consistent with miR-7-5p levels released in cells. Moreover, BioRNAGly/miR-7-5p showed comparable or slightly greater activities to modulate MRP1 and VDAC1 expression, compared with miRCURY LNA miR-7-5p mimic. Computational modeling illustrated overall comparable 3D structures for exemplary BioRNA/miRNAs with noticeable differences in htRNA species and payload miRNAs. These findings support the utility of hybrid htRNA/hsa-pre-miR-34a as reliable carriers for RNA molecular bioengineering, and the resultant BioRNAs serve as functional biologic RNAs for research and development.

Promoter A1312C mutation leads to microRNA-7 downregulation in human non-small cell lung cancer

MicroRNA-7 (miRNA-7, miR-7) is a unique class of tumor suppressors, plays an important role in various physiological and pathological processes including human non-small cell lung cancer (NSCLC). In previous works, we revealed that miR-7 could regulate the growth and metastasis of human NSCLC cells. However, the mechanism of dysregulated miR-7 expression in NSCLC remains to be further elucidated. In this study, based on clinical sample analysis, we found that the downregulated expression of miR-7 was dominantly attributed to the decreased level of pri-miR-7-2 in human NSCLC. Furthermore, there were four site mutations in the miR-7-2 promoter sequence. Notably, among these four sites, mutation at -1312 locus (A → C, termed as A1312C mutation) was dominate, and A1312C mutation further led to decreased expression of miR-7 in human NSCLC cells, accompanied with elevated transduction of NDUFA4/ERK/AKT signaling pathway. Mechanistically, homeobox A5 (HOXA5) is the key transcription factors regulating miR-7 expression in NSCLC. A1312C mutation impairs HOXA5 binding, thereby reducing the transcriptional activity of miR-7-2 promoter, resulting in downregulation of miR-7 expression. Together, these data may provide new insights into the dysregulation of specific miRNA expression in NSCLC and ultimately prove to be helpful in the diagnostic, prognostic, and therapeutic strategies against NSCLC.

Drug resistance mechanisms in cancers: Execution of pro-survival strategies

One of the quintessential challenges in cancer treatment is drug resistance. Several mechanisms of drug resistance have been described to date, and new modes of drug resistance continue to be discovered. The phenomenon of cancer drug resistance is now widespread, with approximately 90% of cancer-related deaths associated with drug resistance. Despite significant advances in the drug discovery process, the emergence of innate and acquired mechanisms of drug resistance has impeded the progress in cancer therapy. Therefore, understanding the mechanisms of drug resistance and the various pathways involved is integral to treatment modalities. In the present review, I discuss the different mechanisms of drug resistance in cancer cells, including DNA damage repair, epithelial to mesenchymal transition, inhibition of cell death, alteration of drug targets, inactivation of drugs, deregulation of cellular energetics, immune evasion, tumor-promoting inflammation, genome instability, and other contributing epigenetic factors. Furthermore, I highlight available treatment options and conclude with future directions.

Emerging roles of ncRNAs regulating ABCC1 on chemotherapy resistance of cancer - a review

In the process of chemotherapy, drug resistance of cancer cells is a common and difficult problem of chemotherapy failure, and it is also the main cause of cancer recurrence and metastasis. Non-coding RNAs (ncRNAs) refer to the RNA that does not encode proteins, including microRNA (miRNA), long non-coding RNA (lncRNA) and circularRNA (circRNA), etc. NcRNAs are involved in a series of important life processes and further regulate the expression of ABCC1 by directly or indirectly up-regulating or down-regulating the expression of targeted mRNAs, making cancer cells more susceptible to drug resistance. A growing number of studies have shown that ncRNAs have effects on cancer cell proliferation, invasion, metastasis, and drug sensitivity, by regulating the expression of ABCC1. In this review, we will discuss the emerging roles of ncRNAs regulating ABCC1 in chemotherapy resistance and mechanisms to reverse drug resistance as well as provide potential targets for future cancer treatment.

Non-Coding RNAs as Key Regulators in Lung Cancer

For several decades, most lung cancer investigations have focused on the search for mutations in candidate genes; however, in the last decade, due to the fact that most of the human genome is occupied by sequences that do not code for proteins, much attention has been paid to non-coding RNAs (ncRNAs) that perform regulatory functions. In this review, we principally focused on recent studies of the function, regulatory mechanisms, and therapeutic potential of ncRNAs including microRNA (miRNA), long ncRNA (lncRNA), and circular RNA (circRNA) in different types of lung cancer.

The crosstalk between non-coding RNA polymorphisms and resistance to lung cancer therapies

Lung cancer (LC) is one of the most common cancer-related mortality in the world. Even with intensive multimodality therapies, lung cancer has a poor prognosis and a high morbidity rate. This review focused on the role of non-coding RNA polymorphisms such as lncRNAs and miRNAs in the resistance to LC therapies, which could open promising avenue for better therapeutic response. Of note, there is currently no valid biomarker to predict lung cancer sensitivity in patients during treatment. Since genetic variations cause many challenges in treating patients, genotyping of known polymorphisms must be thoroughly explored to find desirable treatment platforms. With this knowledge, individualized treatments could become more possible in management of LC.

Recombinant Technologies Facilitate Drug Metabolism, Pharmacokinetics, and General Biomedical Research

The development of safe and effective medications requires a profound understanding of their pharmacokinetic (PK) and pharmacodynamic properties. PK studies have been built through investigation of enzymes and transporters that drive drug absorption, distribution, metabolism, and excretion (ADME). Like many other disciplines, the study of ADME gene products and their functions has been revolutionized through the invention and widespread adoption of recombinant DNA technologies. Recombinant DNA technologies use expression vectors such as plasmids to achieve heterologous expression of a desired transgene in a specified host organism. This has enabled the purification of recombinant ADME gene products for functional and structural characterization, allowing investigators to elucidate their roles in drug metabolism and disposition. This strategy has also been used to offer recombinant or bioengineered RNA (BioRNA) agents to investigate the posttranscriptional regulation of ADME genes. Conventional research with small noncoding RNAs such as microRNAs (miRNAs) and small interfering RNAs has been dependent on synthetic RNA analogs that are known to carry a range of chemical modifications expected to improve stability and PK properties. Indeed, a novel transfer RNA fused pre-miRNA carrier-based bioengineering platform technology has been established to offer consistent and high-yield production of unparalleled BioRNA molecules from Escherichia coli fermentation. These BioRNAs are produced and processed inside living cells to better recapitulate the properties of natural RNAs, representing superior research tools to investigate regulatory mechanisms behind ADME. SIGNIFICANCE STATEMENT: This review article summarizes recombinant DNA technologies that have been an incredible boon in the study of drug metabolism and PK, providing investigators with powerful tools to express nearly any ADME gene products for functional and structural studies. It further overviews novel recombinant RNA technologies and discusses the utilities of bioengineered RNA agents for the investigation of ADME gene regulation and general biomedical research.

The Alternating Access Mechanism in Mammalian Multidrug Resistance Transporters and Their Bacterial Homologs

Multidrug resistance (MDR) proteins belonging to the ATP-Binding Cassette (ABC) transporter group play a crucial role in the export of cytotoxic drugs across cell membranes. These proteins are particularly fascinating due to their ability to confer drug resistance, which subsequently leads to the failure of therapeutic interventions and hinders successful treatments. One key mechanism by which multidrug resistance (MDR) proteins carry out their transport function is through alternating access. This mechanism involves intricate conformational changes that enable the binding and transport of substrates across cellular membranes. In this extensive review, we provide an overview of ABC transporters, including their classifications and structural similarities. We focus specifically on well-known mammalian multidrug resistance proteins such as MRP1 and Pgp (MDR1), as well as bacterial counterparts such as Sav1866 and lipid flippase MsbA. By exploring the structural and functional features of these MDR proteins, we shed light on the roles of their nucleotide-binding domains (NBDs) and transmembrane domains (TMDs) in the transport process. Notably, while the structures of NBDs in prokaryotic ABC proteins, such as Sav1866, MsbA, and mammalian Pgp, are identical, MRP1 exhibits distinct characteristics in its NBDs. Our review also emphasizes the importance of two ATP molecules for the formation of an interface between the two binding sites of NBD domains across all these transporters. ATP hydrolysis occurs following substrate transport and is vital for recycling the transporters in subsequent cycles of substrate transportation. Specifically, among the studied transporters, only NBD2 in MRP1 possesses the ability to hydrolyze ATP, while both NBDs of Pgp, Sav1866, and MsbA are capable of carrying out this reaction. Furthermore, we highlight recent advancements in the study of MDR proteins and the alternating access mechanism. We discuss the experimental and computational approaches utilized to investigate the structure and dynamics of MDR proteins, providing valuable insights into their conformational changes and substrate transport. This review not only contributes to an enhanced understanding of multidrug resistance proteins but also holds immense potential for guiding future research and facilitating the development of effective strategies to overcome multidrug resistance, thus improving therapeutic interventions.

Circular RNA circ-CD44 regulates chemotherapy resistance by targeting the miR-330-5p/ABCC1 axis in colorectal cancer cells

BACKGROUND

Colorectal cancer (CRC) is a common malignant tumor worldwide, ranking fourth for incidence. Recently, circular RNAs (circRNAs) have been demonstrated to play a key role in chemotherapy resistance to CRC treatment. Therefore, the role of circ-CD44 is investigated in CRC.

METHODS

The expression levels of circ-CD44, miR-330-5p, and ATP binding cassette subfamily C member 1 (ABCC1) were quantified by real-time quantitative polymerase chain reaction (RT-qPCR) assay. The sensitivity of CRC cells to oxaliplatin (OXA) was assessed by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl-2H-tetrazol-3-ium bromide (MTT) assay. Colony-forming experiment was performed to measure the colony-forming ability of CRC cells. The apoptosis, migration, and invasion of CRC cells were determined by flow cytometry and transwell assays. A xenograft experiment was established to clarify the functional role of circ-CD44 silencing in vivo. The interactional relationship among circ-CD44, miR-330-5p, and ABCC1 was confirmed by dual-luciferase reporter and RNA immunoprecipitation assays. The protein expression of ABCC1 was quantified by western blot assay.

RESULTS

Circ-CD44 was obviously upregulated in OXA-resistant colorectal cancer tissues and cells. Loss-of-function experiments revealed that inhibition of circ-CD44 suppressed proliferation, migration, and invasion while it increased OXA sensitivity and apoptosis in OXA-resistant colorectal cancer cells, which was overturned by suppression of miR-330-5p; besides, silencing of circ-CD44 also slowed the tumor growth in vivo. Additionally, overexpression of miR-330-5p inhibited chemotherapy resistance, proliferation, migration, and invasion while it induced apoptosis by targeting ABCC1.

CONCLUSION

Mechanistically, circ-CD44 functioned as a miRNA sponge for miR-330-5p to upregulate the expression of ABCC1 and regulate chemotherapy resistance in CRC cells.

Recent Advances in Novel Recombinant RNAs for Studying Post-transcriptional Gene Regulation in Drug Metabolism and Disposition

Drug-metabolizing enzymes and transporters are major determinants of the absorption, disposition, metabolism, and excretion (ADME) of drugs, and changes in ADME gene expression or function may alter the pharmacokinetics/ pharmacodynamics (PK/PD) and further influence drug safety and therapeutic outcomes. ADME gene functions are controlled by diverse factors, such as genetic polymorphism, transcriptional regulation, and coadministered medications. MicroRNAs (miRNAs) are a superfamily of regulatory small noncoding RNAs that are transcribed from the genome to regulate target gene expression at the post-transcriptional level. The roles of miRNAs in controlling ADME gene expression have been demonstrated, and such miRNAs may consequently influence cellular drug metabolism and disposition capacity. Several types of miRNA mimics and small interfering RNA (siRNA) reagents have been developed and widely used for ADME research. In this review article, we first provide a brief introduction to the mechanistic actions of miRNAs in post-transcriptional gene regulation of drug-metabolizing enzymes, transporters, and transcription factors. After summarizing conventional small RNA production methods, we highlight the latest advances in novel recombinant RNA technologies and applications of the resultant bioengineered RNA (BioRNA) agents to ADME studies. BioRNAs produced in living cells are not only powerful tools for general biological and biomedical research but also potential therapeutic agents amenable to clinical investigations.

Prognostic value of microRNAs in patients with small cell lung cancer: a meta-analysis

BACKGROUND

An increasing number of studies have shown that microRNAs play an important role in the occurrence and development of small cell lung cancer, which mainly manifest as oncogenic and tumor inhibition. Therefore, microRNAs may affect the survival of patients with small cell lung cancer. In this meta-analysis, we will evaluate the role of microRNAs in the overall survival of patients with small cell lung cancer, which may provide valuable information for the treatment of small cell lung cancer.

METHODS

We searched the PubMed, Embase, and Web of Science online databases to determine the effect of microRNAs on the prognosis of patients with small cell lung cancer. The data and characteristics of each study were extracted, and the hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated to estimate the effect.

RESULTS

A total of 7 articles, involving 427 subjects and 15 studies, were included in this meta-analysis. The pooled HR of the relationship between the microRNA expression level and the overall survival rate of small cell lung cancer patients was 1.25 (95% CI: 1.06-1.47). There was a significant difference in the prognostic value of oncogenic and tumor inhibition microRNAs among patients with small cell lung cancer, with pooled HRs of 1.60 (95% CI: 1.35-1.90) and 0.42 (95% CI: 0.30-0.57), respectively.

CONCLUSIONS

MicroRNAs have a significant impact on the overall survival of small cell lung cancer patients, suggesting that microRNAs can be used as potential prognostic markers and may provide treatment strategies for small cell lung cancer patients.

TRIAL REGISTRATION

The protocol was registered on PROSPERO website with the registration number of CRD42022334363. The relevant registration information can be obtained from the website https://www.crd.york.ac.uk/prospero/#searchadvanced .

Non-coding genome in small cell lung cancer between theoretical view and clinical applications

Small cell lung cancer (SCLC) is a highly aggressive cancer of the neuroendocrine system, characterized by poor differentiation, rapid growth, and poor overall survival (OS) of patients. Despite the recent advances in the treatment of SCLC recently, the 2-year survival rate of patients with the cancer is only 14-15%, occasioned by the acquired resistance to drugs and serious off-target effects. In humans, the coding region is only 2% of the total genome, and 20% of that is associated with human diseases. Beyond the coding genome are RNAs, promoters, enhancers, and other intricate elements. The non-coding regulatory regions, mainly the non-coding RNAs (ncRNAs), regulate numerous biological activities including cell proliferation, metastasis, and drug resistance. As such, they are potential diagnostic or prognostic biomarkers, and also potential therapeutic targets for SCLC. Therefore, understanding how non-coding elements regulate SCLC development and progression holds significant clinical implications. Herein, we summarized the recent discoveries on the relationship between the non-coding elements including long non-coding RNAs (lncRNA), microRNAs (miRNAs), circular RNA (circRNA), enhancers as well as promotors, and the pathogenesis of SCLC and their potential clinical applications.

Role of Nanotechnology in Overcoming the Multidrug Resistance in Cancer Therapy: A Review

Cancer is one of the leading causes of morbidity and mortality around the globe and is likely to become the major cause of global death in the coming years. As per World Health Organization (WHO) report, every year there are over 10 and 9 million new cases and deaths from this disease. Chemotherapy, radiotherapy, and surgery are the three basic approaches to treating cancer. These approaches are aiming at eradicating all cancer cells with minimum off-target effects on other cell types. Most drugs have serious adverse effects due to the lack of target selectivity. On the other hand, resistance to already available drugs has emerged as a major obstacle in cancer chemotherapy, allowing cancer to proliferate irrespective of the chemotherapeutic agent. Consequently, it leads to multidrug resistance (MDR), a growing concern in the scientific community. To overcome this problem, in recent years, nanotechnology-based drug therapies have been explored and have shown great promise in overcoming resistance, with most nano-based drugs being explored at the clinical level. Through this review, we try to explain various mechanisms involved in multidrug resistance in cancer and the role nanotechnology has played in overcoming or reversing this resistance.

Combinatory therapy of MRP1-targeted photoimmunotherapy and liposomal doxorubicin promotes the antitumor effect for chemoresistant small cell lung cancer

Small cell lung cancer (SCLC), considered a mortal recalcitrant cancer, is a severe healthcare issue because of its poor prognosis, early metastasis, drug resistance and limited clinical treatment options. In our previous study, we established a MRP1-targeted antibody-IR700 system (Mab-IR700) for near infrared photoimmunotherapy (NIR-PIT) which exhibited a promising therapeutic effect on drug resistant H69AR cells both in vitro and in vivo, though the tumor growth suppression effect did not last long with a single round of PIT treatment. To achieve a better anticancer effect, we have combined Mab-IR700-mediated NIR-PIT with liposomal doxorubicin (Doxil®) and investigated the in vitro and in vivo cytotoxicity by using a H69AR/3T3 cell co-culture model in which 3T3 cells were used to mimic stromal cells. Cytotoxicity experiments demonstrated the specificity of Mab-IR700 to H69AR cells, while cytotoxicity and flow cytometry experiments confirmed that H69AR cells were doxorubicin-resistant. Compared with Mab-IR700-mediated PIT or Doxil-mediated chemotherapy, the combination therapy exhibited the best cell killing effect in vitro and superior tumor growth inhibition and survival prolongation effect in vivo. Super enhanced permeability and retention (SUPR) effect was observed in both co-culture spheroids and tumor-bearing mice. Owing to an approximately 9-fold greater accumulation of Doxil within the tumors, NIR-PIT combined with Doxil resulted in enhanced antitumor effects compared to NIR-PIT alone. This photoimmunochemotherapy is a practical strategy for the treatment of chemoresistant SCLC and should be further investigated for clinical translation.

MicroRNAs as Predictors of Lung-Cancer Resistance and Sensitivity to Cisplatin

BACKGROUND

Platinum-based chemotherapy, cisplatin (DDP) specifically, is the main strategy for treating lung cancer (LC). However, currently, there is a lack of predictive drug-resistance markers, and there is increased interest in the development of a reliable and sensitive panels of markers for DDP chemotherapy-effectiveness prediction. MicroRNAs represent a perspective pool of markers for chemotherapy effectiveness.

OBJECTIVES

Data on miRNAs associated with LC DDP chemotherapy response are summarized and analyzed.

MATERIALS AND METHODS

A comprehensive review of the data in the literature and an analysis of bioinformatics resources were performed. The gene targets of miRNAs, as well as their reciprocal relationships with miRNAs, were studied using several databases.

RESULTS AND DISCUSSION

The complex analysis of bioinformatics resources and the literature indicated that the expressions of 12 miRNAs have a high predictive potential for LC DDP chemotherapy responses. The obtained information was discussed from the point of view of the main mechanisms of LC chemoresistance.

CONCLUSIONS

An overview of the published data and bioinformatics resources, with respect to the predictive microRNA markers of chemotherapy response, is presented in this review. The selected microRNAs and gene panel have a high potential for predicting LC DDP sensitiveness or DDP resistance as well as for the development of a DDP co-therapy.

Targeting multidrug resistance-associated protein 1 (MRP1)-expressing cancers: Beyond pharmacological inhibition

Resistance to chemotherapy remains one of the most significant obstacles to successful cancer treatment. While inhibiting drug efflux mediated by ATP-binding cassette (ABC) transporters is a seemingly attractive and logical approach to combat multidrug resistance (MDR), small molecule inhibition of ABC transporters has so far failed to confer clinical benefit, despite considerable efforts by medicinal chemists, biologists, and clinicians. The long-sought treatment to eradicate cancers displaying ABC transporter overexpression may therefore lie within alternative targeting strategies. When aberrantly expressed, the ABC transporter multidrug resistance-associated protein 1 (MRP1, ABCC1) confers MDR, but can also shift cellular redox balance, leaving the cell vulnerable to select agents. Here, we explore the physiological roles of MRP1, the rational for targeting this transporter in cancer, the development of small molecule MRP1 inhibitors, and the most recent developments in alternative therapeutic approaches for targeting cancers with MRP1 overexpression. We discuss approaches that extend beyond simple MRP1 inhibition by exploiting the collateral sensitivity to glutathione depletion and ferroptosis, the rationale for targeting the shared transcriptional regulators of both MRP1 and glutathione biosynthesis, advances in gene silencing, and new molecules that modulate transporter activity to the detriment of the cancer cell. These strategies illustrate promising new approaches to address multidrug resistant disease that extend beyond the simple reversal of MDR and offer exciting routes for further research.

Restoring HOXD10 Exhibits Therapeutic Potential for Ameliorating Malignant Progression and 5-Fluorouracil Resistance in Colorectal Cancer

Emerging evidence suggests that hypermethylation of HOXD10 plays an important role in human cancers. However, the biological and clinical impacts of HOXD10 overmethylation and its downstream targets in colorectal cancer remain unknown. We evaluated the methylation level of HOXD10 in paired cancer and normal tissues (n = 42) by using pyrosequencing, followed by validation of the methylation status of HOXD10 from The Cancer Genome Atlas (TCGA) datasets with 302 cancer tissues and 38 normal tissues. The biological function of HOXD10 was characterized in cell lines. We further evaluated the effects of HOXD10 and its targets on chemoresistance in our established resistant cell lines and clinical cohort (n = 66). HOXD10 was found frequently methylated in colorectal cancer, and its hypermethylation correlates with its low expression level, advanced disease, and lymph node metastasis. Functionally, HOXD10 acts as a tumor suppressor gene, in which HOXD10-expressing cells showed suppressed cell proliferation, colony formation ability, and migration and invasion capacity. Mechanistically, DNMT1, DNMT3B, and MeCP2 were recruited in the HOXD10 promoter, and demethylation by 5-Aza-2′-deoxycytidine (5-Aza-CdR) treatment or MeCP2 knockdown can sufficiently induce HOXD10 expression. HOXD10 regulates the expressions of miR-7 and IGFBP3 in a promoter-dependent manner. Restoration of the expression of HOXD10 in 5-fluorouracil (5-FU)-resistant cells significantly upregulates the expressions of miR-7 and IGFBP3 and enhances chemosensitivity to 5-FU. In conclusion, we provide novel evidence that HOXD10 is frequently methylated, silenced, and contributes to the development of colorectal cancers. Restoration of HOXD10 activates the expressions of miR-7 and IGFBP3 and results in an inhibited phenotype biologically, suggesting its potential therapeutic relevance in colorectal cancer (CRC).

MicroRNAs Involved in Small-cell Lung Cancer as Possible Agents for Treatment and Identification of New Targets

Small-cell lung cancer, a neuro-endocrine type of lung cancers, responds very well to chemotherapy-based agents. However, a high frequency of relapse due to adaptive resistance is observed. Immunotherapy-based treatments with checkpoint inhibitors has resulted in improvement of treatment but the responses are not as impressive as in other types of tumor. Therefore, identification of new targets and treatment modalities is an important issue. After searching the literature, we identified eight down-regulated microRNAs involved in radiation- and chemotherapy-induced resistance, as well as three up-regulated and four down-regulated miRNAs with impacts on proliferation, invasion and apoptosis of small-cell lung cancer cells in vitro. Furthermore, one up-regulated and four down-regulated microRNAs with in vivo activity in SCLC cell xenografts were identified. The identified microRNAs are candidates for inhibition or reconstitution therapy. The corresponding targets are candidates for inhibition or functional reconstitution with antibody-based moieties or small molecules.

Role of multidrug resistance-associated proteins in cancer therapeutics: past, present, and future perspectives

Cancer, a major public health problem, is one of the world's top leading causes of death. Common treatments for cancer include cytotoxic chemotherapy, surgery, targeted drugs, endocrine therapy, and immunotherapy. However, despite the outstanding achievements in cancer therapies during the last years, resistance to conventional chemotherapeutic agents and new targeted drugs is still the major challenge. In the present review, we explain the different mechanisms involved in cancer therapy and the detailed outlines of cancer drug resistance regarding multidrug resistance-associated proteins (MRPs) and their role in treatment failures by common chemotherapeutic agents. Further, different modulators of MRPs are presented. Finally, we outlined the models used to analyze MRP transporters and proposed a future impact that may set up a base or pave the way for many researchers to investigate the cancer MRP further.

MiRNA Expression in Neuroendocrine Neoplasms of Frequent Localizations

Neuroendocrine neoplasms (NEN) are infrequent malignant tumors of a neuroendocrine nature that arise in various organs. They occur most frequently in the lungs, intestines, stomach and pancreas. Molecular diagnostics and prognosis of NEN development are highly relevant. The role of clinical biomarkers can be played by microRNAs (miRNAs). This work is devoted to the analysis of data on miRNA expression in NENs. For the first time, a search for specificity or a community of their functional characteristics in different types of NEN was carried out. Their properties as biomarkers were also analyzed. To date, more than 100 miRNAs have been characterized as differentially expressed and significant for the development of NEN tumors. Only about 10% of the studied miRNAs are expressed in several types of NEN; differential expression of the remaining 90% was found only in tumors of specific localizations. A significant number of miRNAs have been identified as potential biomarkers. However, only a few miRNAs have values that characterized their quality as markers. The analysis demonstrates the predominant specific expression of miRNA in each studied type of NEN. This indicates that miRNA’s functional features are predominantly influenced by the tissue in which they are formed.

MRP1-targeted near infrared photoimmunotherapy for drug resistant small cell lung cancer

Small cell lung cancer (SCLC), one of the most aggressive cancers, has a high mortality rate and poor prognosis, and the clinical therapeutic outcomes of multidrug resistant SCLC are even worse. Multidrug resistance protein 1 (MRP1), one of the ATP-binding cassette (ABC) transporter proteins that cause decreased drug accumulation in cancer cells, is overexpressed in drug resistant SCLC cells and could be a promising target for treating the patients suffering from this illness. Near infrared photoimmunotherapy (NIR-PIT) is a newly developed approach for targeted cancer treatment which uses a conjugate of a monoclonal antibody and photoabosorber IR700 followed by NIR light irradiation to induce rapid cancer cell death. In the present study, an anti-MRP1 antibody (Mab) -IR700 conjugate (Mab-IR700) was synthesized, purified and used to treat chemoresistant SCLC H69AR cells that overexpressed MRP1, while non-MRP1-expressing H69 cells were used as a control. Then, the photokilling and tumor suppression effect were separately evaluated in H69AR cells both in vitro and in vivo. Higher cellular delivery of Mab-IR700 was detected in H69AR cells, whereas there was little uptake of IgG-IR700 in both H69 and H69AR cells. Due to the targeting activity of Mab, stronger photokilling effect was found both in H69AR cells and spheroids treated with Mab-IR700, while superior tumor suppression effect was also observed in the mice treated with Mab-IR700 and light illumination. Photoacoustic imaging results proved that oxygen was involved in NIR-PIT treatment, and TUNEL staining images showed the occurrence of cell apoptosis, which was also testified by HE staining. This research provides MRP1 as a novel target for PIT and presents a prospective way for treating drug resistant SCLC and, thus, should be further studied.

Varied clinical significance of ATP-binding cassette C sub-family members for lung adenocarcinoma

Lung adenocarcinoma (LUAD) is a lethal malignancy worldwide and a major public health concern. We explored the potential clinical significance for LUAD of ATP-binding cassette (ABC), sub-family C, consisting of ABCC1-6, 8-12, and cystic fibrosis transmembrane conductance regulator (CFTR).Five hundred LUAD patients from The Cancer Genome Atlas database were used for analysis, including differential expression and diagnostic and prognostic significance. Oncomine and MERAV databases were used to validate differential expression and diagnostic significance. A risk score model was constructed using prognosis-related ABCC members. Prognosis-related genes were further explored to correlate their expression with tumor stage progression. Interaction networks, including biological processes and metabolic pathways, were constructed using Cytoscape software and STRING website.ABCC1-3 consistently showed high expression in tumor tissues (all P ≤ 0.05). Most datasets indicated that ABCC5, 10, and 11 were highly expressed in tumor tissues whereas ABCC6, 9, and CFTR were highly expressed in nontumor tissues (all P ≤ 0.05). Diagnostic significance of ABCC3 and ABCC5 was consistently assessed and validated in three datasets (all area under the curve > 0.700) whereas ABCC6, 8, 10, 11, and CFTR were assessed in The Cancer Genome Atlas dataset and validated in one dataset (all area under the curve > 0.700). Prognostic analysis indicated that ABCC2, 6, and 8 mRNA expression was associated with survival of LUAD (all adjusted P ≤ .037). The risk score model constructed using ABCC2, 6, and 8 suggested prognostic significance for survival predictions. ABCC2 expression was associated with tumor stage, whereas ABCC6 and 8 were not. Interaction networks indicated that they were involved in establishment of localization, ion transport, plasma membrane, apical plasma membrane, adenylyl nucleotide binding, ABC transporters, ABC transporter disorders, ABC-family-protein-mediated transport, and bile secretion.Differentially expressed ABCC2 and ABCC5 might be diagnostic whereas ABCC2, 6, and 8 may be prognostic biomarkers for LUAD, possibly through ABC-family-mediated transporter disorders.

Role of microRNAs in regulating cell proliferation, metastasis and chemoresistance and their applications as cancer biomarkers in small cell lung cancer

Small cell lung cancer (SCLC), a smoking-related highly aggressive neuroendocrine cancer, is characterized by rapid cell proliferation, early metastatic dissemination, and early relapse due to chemoresistance to first-line platinum-doublet chemotherapy. Genomically, SCLC tumors show nearly universal loss of TP53 and RB1 tumor suppressor genes, while gene expression signature classifies them into 4 distinct subgroups based on the expression patterns of lineage transcription factors - ASCL1/ASH1, NEUROD1, YAP-1, and POU2F3. Due to the lack of targetable molecular alterations and clinically useful diagnostic, prognostic and predictive biomarker, there is insignificant progress in the therapeutic management of SCLC patients. Numerous studies have shown a significant involvement of non-coding RNAs in the regulation of cell proliferation, invasion and migration, apoptosis, metastasis, and chemoresistance in various human cancers. In this review, we comprehensively discuss the role of microRNAs (miRNAs) in regulating the aforementioned biological process in SCLC. For this, we searched the scientific literature and selected studies that have evaluated the role of miRNAs in the disease pathogenesis or as a cancer biomarker in SCLC. Our review suggests that several miRNAs are involved in the pathogenesis of SCLC mainly by regulating cell proliferation, metastasis, and chemoresistance. Few studies have also demonstrated the clinical utility of miRNAs in monitoring response to chemotherapy as well as in predicting survival outcomes. However, more in-depth mechanistic studies utilizing in vivo models and multicentric studies with larger patient cohorts are needed before the applications of miRNAs as therapeutic targets or as biomarkers are translated from the laboratory into clinics.

MiR-7 in Cancer Development

MicroRNAs (miRNAs) are short non-coding RNA involved in the regulation of specific mRNA translation. They participate in cellular signaling circuits and can act as oncogenes in tumor development, so-called oncomirs, as well as tumor suppressors. miR-7 is an ancient miRNA involved in the fine-tuning of several signaling pathways, acting mainly as tumor suppressor. Through downregulation of PI3K and MAPK pathways, its dominant role is the suppression of proliferation and survival, stimulation of apoptosis and inhibition of migration. Besides these functions, it has numerous additional roles in the differentiation process of different cell types, protection from stress and chromatin remodulation. One of the most investigated tissues is the brain, where its downregulation is linked with glioblastoma cell proliferation. Its deregulation is found also in other tumor types, such as in liver, lung and pancreas. In some types of lung and oral carcinoma, it can act as oncomir. miR-7 roles in cell fate determination and maintenance of cell homeostasis are still to be discovered, as well as the possibilities of its use as a specific biotherapeutic.

The Role of miRNA-7 in the Biology of Cancer and Modulation of Drug Resistance

MicroRNAs (miRNAs, miRs) are small non-coding RNA (ncRNA) molecules capable of regulating post-transcriptional gene expression. Imbalances in the miRNA network have been associated with the development of many pathological conditions and diseases, including cancer. Recently, miRNAs have also been linked to the phenomenon of multidrug resistance (MDR). MiR-7 is one of the extensively studied miRNAs and its role in cancer progression and MDR modulation has been highlighted. MiR-7 is engaged in multiple cellular pathways and acts as a tumor suppressor in the majority of human neoplasia. Its depletion limits the effectiveness of anti-cancer therapies, while its restoration sensitizes cells to the administered drugs. Therefore, miR-7 might be considered as a potential adjuvant agent, which can increase the efficiency of standard chemotherapeutics.

Transcriptomic silencing as a potential mechanism of treatment resistance

Next-generation sequencing (NGS) has not revealed all the mechanisms underlying resistance to genomically matched drugs. Here, we performed in 1417 tumors whole-exome tumor (somatic)/normal (germline) NGS and whole-transcriptome sequencing, the latter focusing on a clinically oriented 50-gene panel in order to examine transcriptomic silencing of putative driver alterations. In this large-scale study, approximately 13% of the somatic single nucleotide variants (SNVs) were unexpectedly not expressed as RNA; 23% of patients had ≥1 nonexpressed SNV. SNV-bearing genes consistently transcribed were TP53, PIK3CA, and KRAS; those with lower transcription rates were ALK, CSF1R, ERBB4, FLT3, GNAS, HNF1A, KDR, PDGFRA, RET, and SMO. We also determined the frequency of tumor mutations being germline, rather than somatic, in these and an additional 462 tumors with tumor/normal exomes; 33.8% of germline SNVs within the gene panel were rare (not found after filtering through variant information domains) and at risk of being falsely reported as somatic. Both the frequency of silenced variant transcription and the risk of falsely identifying germline mutations as somatic/tumor related are important phenomena. Therefore, transcriptomics is a critical adjunct to genomics when interrogating patient tumors for actionable alterations, because, without expression of the target aberrations, there will likely be therapeutic resistance.

Mechanisms of drugs-resistance in small cell lung cancer: DNA-related, RNA-related, apoptosis-related, drug accumulation and metabolism procedure

Small-cell lung cancer (SCLC), the highest malignant cancer amongst different types of lung cancer, has the feature of lower differentiation, rapid growth, and poor survival rate. Despite the dramatically initial sensitivity of SCLC to various types of treatment methods, including chemotherapy, radiotherapy and immunotherapy, the emergence of drugs-resistance is still a grandly clinical challenge. Therefore, in order to improve the prognosis and develop new therapeutic approaches, having a better understanding of the complex mechanisms of resistance in SCLC is of great clinical significance. This review summarized recent advances in understanding of multiple mechanisms which are involved in the resistance during SCLC treatment, including DNA-related process, RNA-related process, apoptosis-related mechanism, and the process of drug accumulation and metabolism.

Circular RNA cESRP1 sensitises small cell lung cancer cells to chemotherapy by sponging miR-93-5p to inhibit TGF-β signalling

Circular RNAs (circRNAs) are novel RNA molecules that play important roles in chemoresistance in different cancers, including breast and gastric cancers. However, whether circRNAs are involved in the response to chemotherapy in small cell lung cancer (SCLC) remains largely unknown. In this study, we observed that cESRP1 (circular RNA epithelial splicing regulatory protein-1) expression was significantly downregulated in the chemoresistant cells compared with the parental chemosensitive cells. cESRP1 enhanced drug sensitivity by repressing miR-93-5p in SCLC. Cytoplasmic cESRP1 could directly bind to miR-93-5p and inhibit the posttranscriptional repression mediated by miR-93-5p, thereby upregulating the expression of the miR-93-5p downstream targets Smad7/p21(CDKN1A) and forming a negative feedback loop to regulate transforming growth factor-β (TGF-β) mediated epithelial-mesenchymal transition. Furthermore, cESRP1 overexpression and TGF-β pathway inhibition both altered tumour responsiveness to chemotherapy in an acquired chemoresistant patient-derived xenograft model. Importantly, cESRP1 expression was downregulated in SCLC patient tissues and was associated with survival. Our findings reveal, for the first time, that cESRP1 plays crucial a role in SCLC chemosensitivity by sponging miR-93-5p to inhibit the TGF-β pathway, suggesting that cESRP1 may serve as a valuable prognostic biomarker and a potential therapeutic target in SCLC patients.

Prognostic significance and molecular mechanisms of adenosine triphosphate-binding cassette subfamily C members in gastric cancer

Gastric cancer (GC) is one of the major leading causes of tumor-related deaths worldwide. Adenosine triphosphate-binding cassette subfamily C (ABCC) consists of 13 members, ABCC1 to 13, which were examined for their associations with GC.The online Kaplan-Meier Plotter database was used to determine the prognostic significance of ABCC subfamily members in GC. Stratified analyses were performed using gender, disease stage, degree of tumor differentiation, expression of human epidermal growth factor receptor 2 (HER2), and Lauren classification. Molecular mechanisms were examined using the database for annotation, visualization, and integrated discovery database.ABCC1, ABCC3, ABCC7, ABCC8, ABCC9, and ABCC10 expression showed prognostic significance in the whole population and in male and female subpopulations (all P ≤ .05). Furthermore, high expression of most ABCC family members always suggested a poor prognosis, except for ABCC7 (P > .05). Stratified analyses revealed that ABCC1, ABCC3, ABCC7, ABCC8, ABCC9, and ABCC10 expression showed prognostic significance for the whole population, as well as male and female populations. ABCC2 and ABCC9 were significantly correlated with all disease stages, while ABCC2 and ABCC6 were significantly correlated with all Lauren classifications. Expression of ABCC1, ABCC3, ABCC5, ABCC7, ABCC8, ABCC9, and ABCC10 was significantly correlated with either negative or positive of HER2 status (all P ≤ .05). Enrichment analysis indicated that these genes were involved in ATPase activity, transmembrane transport, or were ABC transporters (all P ≤ .05).ABCC1, ABCC3, ABCC7, ABCC8, ABCC9, and ABCC10 may be potential prognosis biomarkers for GC, acting as ABC transporters and via ATPase activity.

Alternative Polyadenylation of ABC Transporters of the C-Family (ABCC1, ABCC2, ABCC3) and Implications on Posttranscriptional Micro-RNA Regulation

ATP-binding cassette (ABC) transporters represent a large group of efflux pumps that are strongly involved in the pharmacokinetics of various drugs and nutrient distribution. It was recently shown that micro-RNAs (miRNAs) may significantly alter their expression as proven, e.g., for miR-379 and ABCC2 However, alternative mRNA polyadenylation may result in expression of 3'-untranslated regions (3'-UTRs) with varying lengths. Thus, length variants may result in presence or absence of miRNA binding sites for regulatory miRNAs with consequences on posttranscriptional control. In the present study, we report on 3'-UTR variants of ABCC1, ABCC2, and ABCC3 mRNA. Applying in vitro luciferase reporter gene assays, we show that expression of short ABCC2 3'-UTR variants leads to a significant loss of miR-379/ABCC2 interaction and subsequent upregulation of ABCC2 expression. Furthermore, we show that expression of ABCC2 3'-UTR lengths varies significantly between human healthy tissues but is not directly correlated to the respective protein level in vivo. In conclusion, the presence of altered 3'-UTR lengths in ABC transporters could lead to functional consequences regarding posttranscriptional gene expression, potentially regulated by alternative polyadenylation. Hence, 3'-UTR length variability may be considered as a further mechanism contributing to variability of ABCC transporter expression and subsequent drug variation in drug response. SIGNIFICANCE STATEMENT: micro-RNA (miRNA) binding to 3'-untranslated region (3'-UTR) plays an important role in the control of ATP-binding cassette (ABC)-transporter mRNA degradation and translation into proteins. We disclosed various 3'-UTR length variants of ABCC1, C2, and C3 mRNA, with loss of mRNA seed regions partly leading to varying and tissue-dependent interaction with miRNAs, as proven by reporter gene assays. Alternative 3'-UTR lengths may contribute to variable ABCC transporter expression and potentially explains inconsistent findings in miRNA studies.

Emerging targets in cancer drug resistance

Drug resistance is a complex phenomenon that frequently develops as a failure to chemotherapy during cancer treatment. Malignant cells increasingly generate resistance to various chemotherapeutic drugs through distinct mechanisms and pathways. Understanding the molecular mechanisms involved in drug resistance remains an important area of research for identification of precise targets and drug discovery to improve therapeutic outcomes. This review highlights the role of some recent emerging targets and pathways which play critical role in driving drug resistance.

MiR-7-5p-mediated downregulation of PARP1 impacts DNA homologous recombination repair and resistance to doxorubicin in small cell lung cancer

Background

Chemo-resistance is one of the major challenges in the therapy of small cell lung cancer (SCLC). Multiple mechanisms are thought to be involved in chemo-resistance during SCLC treatment, but unfortunately, these mechanisms have not been well elucidated. Herein, we investigated the role of miRNA in the resistance of SCLC cells to doxorubicin (Dox).

Methods

MiRNA microarray analysis revealed that several miRNAs, including miR-7-5p, were specifically decreased in Dox-resistant SCLC cells (H69AR) compared to parental cells (H69). The expression level of miR-7-5p was confirmed by qRT-PCR in Dox-resistant cells (H69AR and H446AR cells) and their parental cells. Bioinformatic analysis indicated that poly ADP-ribose polymerase 1 (PARP1) is a direct target of miR-7-5p. The binding sites of miR-7-5p in the PARP1 3′ UTR were verified by luciferase reporter and Western blot assays. To investigate the role of miR-7-5p in the chemo-resistance of SCLC cells to doxorubicin, mimic or inhibitor of miR-7-5p was transfected into SCLC cells, and the effect of miR-7-5p on homologous recombination (HR) repair was analyzed by HR reporter assays. Furthermore, the expression of HR repair factors (Rad51 and BRCA1) induced by doxorubicin was detected by Western blot and immunofluorescent staining in H446AR cells transfected with miR-7-5p mimic.

Results

The expression level of miR-7-5p was remarkably reduced (4-fold) in Dox-resistant SCLC cells (H69AR and H446AR cells) compared with that in parental cells (H69 and H446 cells). Poly ADP-ribose polymerase 1 (PARP1) is a direct target of miR-7-5p, and PARP1 expression was downregulated by miR-7-5p. MiR-7-5p impeded Dox-induced HR repair by inhibiting the expression of HR repair factors (Rad51 and BRCA1) that resulted in resensitizing SCLC cells to doxorubicin.

Conclusions

Our findings provide evidence that miR-7-5p targets PARP1 to exert its suppressive effects on HR repair, indicating that the alteration of the expression of miR-7-5p may be a promising strategy for overcoming chemo-resistance in SCLC therapy.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-5798-7) contains supplementary material, which is available to authorized users.

Edwardsiella tarda-induced miR-7a functions as a suppressor in PI3K/AKT/GSK3β signaling pathway by targeting insulin receptor substrate-2 (IRS2a and IRS2b) in Paralichthys olivaceus

To study the effect of Edwardsiella tarda infection on miRNAs expression profile in Japanese flounder, fish were injected intraperitoneally with E. tarda. The miRNAs involved in regulating immune responses were analyzed by high-throughput sequencing. A total of 164 mature miRNAs were identified, of which 17 miRNAs were differentially expressed (DE miRNAs) after E. tarda infection, indicating that they were immune-related miRNAs. To further examine the relationship between the miRNAs and their predicted target mRNAs, a total of 22 predicted target mRNAs, mainly related to endocytic signaling pathway, NF-κB signaling pathway, and p53 signaling pathway, were detected with miRNA mimics in HEK-293T cells by dual-luciferase reporter experiments. Finally, we confirmed that insulin receptor substrate-2 (IRS2a and IRS2b) were regulated by miR-7a. And the target sites of the 3' untranslated region (UTR) of IRS2a and IRS2b were verified by dual-luciferase reporter experiments. Furthermore, we found that the E. tarda and LPS significantly increased host miR-7a expression. In vivo and in vitro studies revealed that IRS2-mediated PI3K/AKT/GSK3β signaling pathway was suppressed. Taken together, these results implied that miR-7a might be a key regulator of PI3K/AKT/GSK3β signaling pathway via suppressing the IRS2a and IRS2b genes.

Schistosoma japonicum MiRNA-7-5p Inhibits the Growth and Migration of Hepatoma Cells via Cross-Species Regulation of S-Phase Kinase-Associated Protein 2

MicroRNAs (miRNAs) play important roles in human diseases, such as cancer. Human miRNA-7-5p is a tumor suppressor miRNA that inhibits tumor growth by regulating multiple oncogenic signal pathways. Recently, studies revealed that plant miRNAs could regulate mammalian gene expression in a cross-kingdom manner. Schistosoma japonicum miRNA-7-5p (designated as sja-miR-7-5p) is conserved between the parasites and mammals. Thus, we investigated whether sja-miR-7-5p has similar antitumor activity to its mammalian counterpart. We first showed that sja-miR-7-5p was detected in host hepatocytes during S. japonicum infection. The sja-miR-7-5p mimics significantly inhibited the growth, migration, and colony formation of mouse and human hepatoma cell lines in vitro, and induced G1/G0 cell cycle arrest. In a xenograft animal model, the tumor volume and weight were significantly reduced in mice inoculated with hepatoma cells transfected with sja-miR-7-5p mimics compared with those transfected with NC miRNAs. Furthermore, the antitumor activity of sja-miR-7-5p was suggested by cross-species downregulation of the S-phase kinase-associated protein 2 gene in the host. Thus, sja-miR-7-5p is translocated into hepatocytes and exerts its anti-cancer activities in mammals, implying that sja-miR-7-5p might strengthen host resistance to hepatocellular carcinoma during schistosome infection.

Liquid Biopsies for Neuroendocrine Tumors: Circulating Tumor Cells, DNA, and MicroRNAs

Effective management of neuroendocrine tumors depends on early diagnosis, personalized risk stratification, and monitoring response to therapy. During cancer progression, tumors shed circulating tumor cells, circulating tumor DNA, and microRNAs into the bloodstream. Analysis of these biomarkers offers the prospect of a liquid biopsy to predict/monitor therapeutic responses, assess drug resistance, and quantify residual disease. Compared with single-site biopsies, these entities have the potential to inform intratumor heterogeneity and tumor evolution in a reproducible and less invasive way. This article summarizes the state-of-the-art on the potential role of these markers as prognostic and predictive factors in neuroendocrine tumors.

The understanding of circular RNAs as special triggers in carcinogenesis

Circular RNAs (circRNAs) are a large type of noncoding RNAs characterized by their circular shape resulting from covalently closed continuous loops. They are known to regulate gene expression in mammals. These tissue-specific transcripts are largely generated from exonic or intronic sequences of their host genes. Although several models of circRNA biogenesis have been proposed, the understanding of their origin is far from complete. Unlike other noncoding RNAs, circRNAs are widely expressed, highly conserved and stable in cytoplasm, which confer special functionalities to them. They are known to serve as microRNA (miRNA) sponges, regulators of alternative splicing, transcription factors and encode for proteins. The expression of circRNAs is associated with several pathological states and may potentially serve as novel diagnostic or predictive biomarkers. CircRNAs are known to regulate the expression of numerous cancer-related miRNAs. The circRNA-miRNA-mRNA axis is a known regulatory pattern of several cancer-associated pathways, with both agonist and antagonist effects on carcinogenesis. In consideration of their potential clinical relevance, circRNAs are at the center of ongoing research initiatives on cancer prevention and treatment. In this review, we discuss the current understanding of circRNAs and the prospects for their potential clinical application in the management of cancer patients.

DNA Methylation of miR-7 is a Mechanism Involved in Platinum Response through MAFG Overexpression in Cancer Cells

One of the major limitations associated with platinum use is the resistance that almost invariably develops in different tumor types. In the current study, we sought to identify epigenetically regulated microRNAs as novel biomarkers of platinum resistance in lung and ovarian cancers, the ones with highest ratios of associated chemo-resistance.

Methods: We combined transcriptomic data from microRNA and mRNA under the influence of an epigenetic reactivation treatment in a panel of four paired cisplatin -sensitive and -resistant cell lines, followed by real-time expression and epigenetic validations for accurate candidate selection in 19 human cancer cell lines. To identify specific candidate genes under miRNA regulation, we assembled “in silico” miRNAs and mRNAs sequences by using ten different algorithms followed by qRT-PCR validation. Functional assays of site-directed mutagenesis and luciferase activity, miRNAs precursor overexpression, silencing by antago-miR and cell viability were performed to confirm their specificity in gene regulation. Results were further explored in 187 primary samples obtained from ovarian tumors and controls.

Results: We identified 4 candidates, miR-7, miR-132, miR-335 and miR-148a, which deregulation seems to be a common event in the development of resistance to cisplatin in both tumor types. miR-7 presented specific methylation in resistant cell lines, and was associated with poorer prognosis in ovarian cancer patients. Our experimental results strongly support the direct regulation of MAFG through miR-7 and their involvement in the development of CDDP resistance in human tumor cells.

Conclusion: The basal methylation status of miR-7 before treatment may be a potential clinical epigenetic biomarker, predictor of the chemotherapy outcome to CDDP in ovarian cancer patients. To the best of our knowledge, this is the first report linking the regulation of MAFG by miRNA-7 and its role in chemotherapy response to CDDP. Furthermore, this data highlights the possible role of MAFG as a novel therapeutic target for platinum resistant tumors.

The Different Mechanisms of Cancer Drug Resistance: A Brief Review

Anticancer drugs resistance is a complex process that arises from altering in the drug targets. Advances in the DNA microarray, proteomics technology and the development of targeted therapies provide the new strategies to overcome the drug resistance. Although a design of the new chemotherapy agents is growing quickly, effective chemotherapy agent has not been discovered against the advanced stage of cancer (such as invasion and metastasis). The cancer cell resistance against the anticancer agents can be due to many factors such as the individual's genetic differences, especially in tumoral somatic cells. Also, the cancer drug resistance is acquired, the drug resistance can be occurred by different mechanisms, including multi-drug resistance, cell death inhibiting (apoptosis suppression), altering in the drug metabolism, epigenetic and drug targets, enhancing DNA repair and gene amplification. In this review, we outlined the mechanisms of cancer drug resistance and in following, the treatment failures by common chemotherapy agents in the different type of cancers.

MCAM Mediates Chemoresistance in Small-Cell Lung Cancer via the PI3K/AKT/SOX2 Signaling Pathway

Despite favorable responses to initial therapy, small-cell lung cancer (SCLC) relapse occurs within a year and exhibits resistance to multiple drugs. Because of limited accessibility of patient tissues for research purposes, SCLC patient-derived xenografts (PDX) have provided the best opportunity to address this limitation. Here, we sought to identify novel mechanisms involved in SCLC chemoresistance. Through in-depth proteomic profiling, we identified MCAM as a markedly upregulated surface receptor in chemoresistant SCLC cell lines and in chemoresistant PDX compared with matched treatment-naïve tumors. MCAM depletion in chemoresistant cells reduced cell proliferation and reduced the IC₅₀ inhibitory concentration of chemotherapeutic drugs in vitro This MCAM-mediated sensitization to chemotherapy occurred via SOX2-dependent upregulation of mitochondrial 37S ribosomal protein 1/ATP-binding cassette subfamily C member 1 (MRP1/ABCC1) and the PI3/AKT pathway. Metabolomic profiling revealed that MCAM modulated lactate production in chemoresistant cells that exhibit a distinct metabolic phenotype characterized by low oxidative phosphorylation. Our results suggest that MCAM may serve as a novel therapeutic target to overcome chemoresistance in SCLC. Cancer Res; 77(16); 4414-25. ©2017 AACR.

Circulating tumor cells and miRNAs as prognostic markers in neuroendocrine neoplasms

The prognosis of neuroendocrine neoplasms (NENs) is widely variable and has been shown to associate with several tissue- and blood-based biomarkers in different settings. The identification of prognostic factors predicting NEN outcome is of paramount importance to select the best clinical management for these patients. Prognostic markers have been intensively investigated, also taking advantage of the most modern techniques, in the perspective of personalized medicine and appropriate resource utilization. This review summarizes the available data on the possible role of circulating tumor cells and microRNAs as prognostic markers in NENs.

Curcumin exerts its antitumor activity through regulation of miR-7/Skp2/p21 in nasopharyngeal carcinoma cells

Curcumin, a natural polyphenol compound, exhibits tumor suppressive activity in a wide spectrum of cancers, including nasopharyngeal carcinoma cells. However, the exact molecular mechanisms governing this tumor suppressive activity remain elusive. Multiple studies have revealed that miRNAs are critically involved in tumorigenesis, indicating that targeting miRNAs could be a therapeutic strategy for treating human cancer. In the current study, we set out to determine whether curcumin regulates miR-7 expression in nasopharyngeal carcinoma cells. We found that curcumin inhibited cell growth, induced apoptosis, retarded cell migration and invasion, and triggered cell cycle arrest in the human nasopharyngeal carcinoma cell lines CNE1 and CNE2. Importantly, we observed that curcumin upregulated the expression of miR-7 and subsequently inhibited Skp2, a direct miR-7 target. Our results identified that upregulation of miR-7 by curcumin could benefit nasopharyngeal carcinoma patients.

Breviscapine suppresses the growth of non-small cell lung cancer by enhancing microRNA-7 expression

Breviscapine (BVP) has previously been shown to inhibit the proliferation of hepatocellular carcinoma cells. However, little is known about the effects of BVP on non-small cell lung cancer (NSCLC) growth. Here, we aimed to study the effects of BVP on human NSCLC growth. We employed A549, NCL-H460 and A549 cells transfected with microRNA-7 (miR-7) mimic and inhibitor to investigate the effect of BVP on cell proliferation, apoptosis and apoptosis-associated molecules. The results showed that BVP significantly reduced the growth of A549 and NCLH460 cells in a concentration-dependent and time-dependent manner, accompanied by a significant elevation of apoptosis. Additionally, the present study also confirmed that BVP-treated A549 cells showed increased levels of Bax and microRNA-7 (miR-7) and a decreased level of Bcl-2. The up-regulation of miR-7 enhanced the BVP sensitivity of NSCLC cells by suppressing cell proliferation and promoting cell apoptosis, while the inhibition of miR-7 reversed the anti-proliferative pro-apoptotic effects of BVP. Pre-treatment with miR-7 mimics enhanced the BVP-mediated down-regulation of Bax/Bcl-2 in NSCLC cells, while pre-treatment with the miR-7 inhibitor blocked the BVPmediated down-regulation of Bax/Bcl. Taken together, these results confirm that BVP effectively inhibits NSCLC proliferation and that miR-7, as a novel target, is likely involved in BVP-induced growth suppression and the apoptosis of NSCLC cells.

Influence of microRNAs and Long Non-Coding RNAs in Cancer Chemoresistance

Innate and acquired chemoresistance exhibited by most tumours exposed to conventional chemotherapeutic agents account for the majority of relapse cases in cancer patients. Such chemoresistance phenotypes are of a multi-factorial nature from multiple key molecular players. The discovery of the RNA interference pathway in 1998 and the widespread gene regulatory influences exerted by microRNAs (miRNAs) and other non-coding RNAs have certainly expanded the level of intricacy present for the development of any single physiological phenotype, including cancer chemoresistance. This review article focuses on the latest research efforts in identifying and validating specific key molecular players from the two main families of non-coding RNAs, namely miRNAs and long non-coding RNAs (lncRNAs), having direct or indirect influences in the development of cancer drug resistance properties and how such knowledge can be utilised for novel theranostics in oncology.