Cancer chemoresistance; biochemical and molecular aspects: a brief overview

Structural variety and pharmacological potential of naphthylisoquinoline alkaloids

Naphthylisoquinoline alkaloids are a fascinating class of natural biaryl compounds. They show characteristic mono- and dimeric scaffolds, with chiral axes and stereogenic centers. Since the appearance of the last comprehensive overview on these secondary plant metabolites in this series in 1995, the number of discovered representatives has tremendously increased to more than 280 examples known today. Many novel-type compounds have meanwhile been discovered, among them naphthylisoquinoline-related follow-up products like e.g., the first seco-type (i.e., ring-opened) and ring-contracted analogues. As highlighted in this review, the knowledge on the broad structural chemodiversity of naphthylisoquinoline alkaloids has been decisively driven forward by extensive phytochemical studies on the metabolite pattern of Ancistrocladus abbreviatus from Coastal West Africa, which is a particularly "creative" plant. These investigations furnished a considerable number of more than 80-mostly new-natural products from this single species, with promising antiplasmodial activities and with pronounced cytotoxic effects against human leukemia, pancreatic, cervical, and breast cancer cells. Another unique feature of naphthylisoquinoline alkaloids is their unprecedented biosynthetic origin from polyketidic precursors and not, as usual for isoquinoline alkaloids, from aromatic amino acids-a striking example of biosynthetic convergence in nature. Furthermore, remarkable botanical results are presented on the natural producers of naphthylisoquinoline alkaloids, the paleotropical Dioncophyllaceae and Ancistrocladaceae lianas, including first investigations on the chemoecological role of these plant metabolites and their storage and accumulation in particular plant organs.

A second life for MAO inhibitors? From CNS diseases to anticancer therapy

Monoamine oxidases A and B (MAO A, B) are ubiquitous enzymes responsible for oxidative deamination of amine neurotransmitters and xenobiotics. Despite decades of studies, MAO inhibitors (MAOIs) find today limited therapeutic space as second-line drugs for the treatment of depression and Parkinson's disease. In recent years, a renewed interest in MAOIs has been raised up by several studies investigating the role of MAOs, particularly MAO A, in tumor insurgence and progression, and the efficacy of MAOIs as coadjutants in the therapy of chemoresistant tumors. In this survey, we highlight the implication of MAOs in the biochemical pathways of tumorigenesis and review the state-of-the-art of preclinical and clinical studies of MAOIs as anticancer agents used in monotherapy or in combination with antitumor chemotherapeutics.

Dual targeting of Mcl-1 and Bcl-2 to overcome chemoresistance in cervical and colon cancer

After an initial positive response to chemotherapy, cancer patients often become resistant and experience relapse. Our previous research identified eukaryotic translation initiation factor 4E (eIF4E) as a crucial target to overcome chemoresistance. In this study, we delved further into the role and therapeutic potential of myeloid cell leukemia 1 (Mcl-1), an eIF4E-mediated target, in chemoresistance. We showed that the levels of phosphor and total eIF4E, as well as Mcl-1, were elevated in chemoresistant cervical but not colon cancer cells. Mcl-1 inhibitor S64315 decreased Mcl-1 levels in chemoresistant cancer cells, regardless of Mcl-1 upregulation, decreased viability in chemoresistant cancer cells and acted synergistically with chemotherapy drugs. The combined inhibition of Mcl-1 and B-cell lymphoma 2 (Bcl-2), employing both genetic and pharmacological approaches, led to a markedly more substantial decrease in viability compared with the inhibition of either target individually. The combination of S64315 and Bcl-2 inhibitors reduced tumor growth in chemoresistant cervical and colon cancer models without causing general toxicity in mice. This combination also prolonged overall survival compared with using S64315 or venetoclax alone. Our research highlights the therapeutic potential of inhibiting Mcl-1 and Bcl-2 simultaneously in chemoresistant cancers and provides a rationale for initiating clinical trials to investigate the combination of S64315 and venetoclax for the treatment of advanced colon and cervical cancer.

On the mechanism of action of arsenoplatins: arsenoplatin-1 binding to a B-DNA dodecamer

The reaction of Pt-based anticancer agents with arsenic trioxide affords robust complexes known as arsenoplatins. The prototype of this family of anticancer compounds is arsenoplatin-1 (AP-1) that contains an As(OH)2 fragment linked to a Pt(II) moiety derived from cisplatin. Crystallographic and spectrometric studies of AP-1 binding to a B-DNA double helix dodecamer are presented here, in comparison with cisplatin and transplatin. Results reveal that AP-1, cisplatin and transplatin react differently with the DNA model system. Notably, in the AP-1/DNA systems, the Pt-As bond can break down with time and As-containing fragments can be released. These results have implications for the understanding of the mechanism of action of arsenoplatins.

Nasopharyngeal carcinoma: current views on the tumor microenvironment's impact on drug resistance and clinical outcomes

The incidence of nasopharyngeal carcinoma (NPC) exhibits significant variations across different ethnic groups and geographical regions, with Southeast Asia and North Africa being endemic areas. Of note, Epstein-Barr virus (EBV) infection is closely associated with almost all of the undifferentiated NPC cases. Over the past three decades, radiation therapy and chemotherapy have formed the cornerstone of NPC treatment. However, recent advancements in immunotherapy have introduced a range of promising approaches for managing NPC. In light of these developments, it has become evident that a deeper understanding of the tumor microenvironment (TME) is crucial. The TME serves a dual function, acting as a promoter of tumorigenesis while also orchestrating immunosuppression, thereby facilitating cancer progression and enabling immune evasion. Consequently, a comprehensive comprehension of the TME and its intricate involvement in the initiation, progression, and metastasis of NPC is imperative for the development of effective anticancer drugs. Moreover, given the complexity of TME and the inter-patient heterogeneity, personalized treatment should be designed to maximize therapeutic efficacy and circumvent drug resistance. This review aims to provide an in-depth exploration of the TME within the context of EBV-induced NPC, with a particular emphasis on its pivotal role in regulating intercellular communication and shaping treatment responses. Additionally, the review offers a concise summary of drug resistance mechanisms and potential strategies for their reversal, specifically in relation to chemoradiation therapy, targeted therapy, and immunotherapy. Furthermore, recent advances in clinical trials pertaining to NPC are also discussed.

Repositioning of HMG-CoA Reductase Inhibitors as Adjuvants in the Modulation of Efflux Pump-Mediated Bacterial and Tumor Resistance

Efflux pump (EP)-mediated multidrug resistance (MDR) seems ubiquitous in bacterial infections and neoplastic diseases. The diversity and lack of specificity of these efflux mechanisms raise a great obstacle in developing drugs that modulate efflux pumps. Since developing novel chemotherapeutic drugs requires large investments, drug repurposing offers a new approach that can provide alternatives as adjuvants in treating resistant microbial infections and progressive cancerous diseases. Hydroxy-methyl-glutaryl coenzyme-A (HMG-CoA) reductase inhibitors, also known as statins, are promising agents in this respect. Originally, statins were used in the therapy of dyslipidemia and for the prevention of cardiovascular diseases; however, extensive research has recently been performed to elucidate the functions of statins in bacterial infections and cancers. The mevalonate pathway is essential in the posttranslational modification of proteins related to vital eukaryotic cell functions. In this article, a comparative review is given about the possible role of HMG-CoA reductase inhibitors in managing diseases of bacterial and neoplastic origin. Molecular research and clinical studies have proven the justification of statins in this field. Further well-designed clinical trials are urged to clarify the significance of the contribution of statins to the lower risk of disease progression in bacterial infections and cancerous diseases.

Establishment and Characterization of Multi-Drug Resistant p53-Negative Osteosarcoma SaOS-2 Subline

AIM

To establish a p53-negative osteosarcoma (OS) SaOS-2 cellular subline exhibiting resistance to specific chemotherapeutic agents, including topoisomerase II inhibitors, taxanes, and vinca alkaloids.

METHODS

The OS subline exhibiting resistance to the chemotherapeutic agents indicated above was generated by the stepwise treatment of the parental SaOS-2 cell line with increasing concentrations of doxorubicin (Dox) for 5 months. Half-inhibitory concentrations (IC50) for Dox, vinblastine (Vin), and paclitaxel (PTX) were calculated by a colorimetric MTS-based assay. Crystal violet staining was used to assess cellular viability, whereas the proliferation capacities of cancer cells were monitored in real-time by the i-Celligence system. Expression of apoptotic markers (e.g., cleaved PARP and caspase-3), DNA repair proteins (e.g., ATM, DNA-PK, Nbs1, Rad51, MSH2, etc.), and certain ABC transporters (P-glycoprotein, MRP1, ABCG2, etc.) was assessed by western blotting and real-time PCR. Flow cytometry was used to examine the fluorescence intensity of Dox and ABC-transporter substrates (e.g., Calcein AM and CMFDA) and to assess their excretion to define the activity of specific ABC-transporters. To confirm OS resistance to Dox in vivo, xenograft experiments were performed.

RESULTS

An OS subline generated by a stepwise treatment of the parental SaOS-2 cell line with increasing concentrations of Dox resulted in an increase in the IC50 for Dox, Vin, and PTX (~6-, 4-, and 30-fold, respectively). The acquisition of chemoresistance in vitro was also evidenced by the lack of apoptotic markers (e.g., cleaved PARP and caspase-3) in resistant OS cells treated with the chemotherapeutic agents indicated above. The development of the multidrug resistance (MDR) phenotype in this OS subline was due to the overexpression of ABCB1 (i.e., P-glycoprotein) and ABCC1 (i.e., multidrug resistance protein-1, MRP-1), which was evidenced on both mRNA and protein levels. Due to increased expression of MDR-related proteins, resistant OS exhibited an excessive efflux of Dox. Moreover, decreased accumulation of calcein AM, a well-known fluorescent substrate for both ABCB1 and ABCC1, was observed for resistant OS cells compared to their parental SaOS-2 cell line. Importantly, tariquidar and cyclosporin, well-known ABC inhibitors, retained the intensity of Dox-induced fluorescence in resistant SAOS-2 cells. Furthermore, in addition to the increased efflux of the chemotherapeutic agents from Dox-resistant OS cells, we found higher expression of several DNA repair proteins (e.g., Rad51 recombinase, Mre11, and Nbs1, activated forms of ATM, DNA-PK, Chk1, and Chk2, etc.), contributing to the chemoresistance due to the excessive DNA repair. Lastly, the in vivo study indicated that Dox has no impact on the SaOS-2 Dox-R xenograft tumor growth in a nude mouse model.

CONCLUSIONS

An acquired resistance of OS to the chemotherapeutic agents might be due to the several mechanisms undergoing simultaneously on the single-cell level. This reveals the complexity of the mechanisms involved in the secondary resistance of OS to chemotherapies.

Arising Novel Agents in Lung Cancer: Are Bispecifics and ADCs the New Paradigm?

Lung cancer is one of the most common cancers with the highest mortality. Non-small cell lung cancer (NSCLC) contributes to around 85% of lung cancer diagnoses (vs. 15% for small cell lung cancer). The treatment of NSCLC has vastly changed in the last two decades since the development of immunotherapy and targeted therapy against driver mutations. As is the nature of malignancy, cancer cells have acquired resistance to these treatments prompting an investigation into novel treatments and new targets. Bispecific antibodies, capable of targeting multiple substrates at once, and antibody-drug conjugates that can preferentially deliver chemotherapy to tumor cells are examples of this innovation. From our initial evaluation, both treatment modalities appear promising.

miRNAs as potential game-changers in bone diseases: Future medicinal and clinical uses

MicroRNAs (miRNAs), short, highly conserved non-coding RNA, influence gene expression by sequential mechanisms such as mRNA breakdown or translational repression. Many biological processes depend on these regulating substances, thus changes in their expression have an impact on the maintenance of cellular homeostasis and result in the emergence of a variety of diseases. Relevant studies have shown in recent years that miRNAs are involved in many stages of bone development and growth. Additionally, abnormal production of miRNA in bone tissues has been closely associated with the development of numerous bone disorders, such as osteonecrosis, bone cancer, and bone metastases. Many pathological processes, including bone loss, metastasis, the proliferation of osteosarcoma cells, and differentiation of osteoblasts and osteoclasts, are under the control of miRNAs. By bringing together the most up-to-date information on the clinical relevance of miRNAs in such diseases, this study hopes to further the study of the biological features of miRNAs in bone disorders and explore their potential as a therapeutic target.

Enzyme-catalyzed synthesis of selenium-doped manganese phosphate for synergistic therapy of drug-resistant colorectal cancer

BACKGROUND

The development of multidrug resistance (MDR) during postoperative chemotherapy for colorectal cancer substantially reduces therapeutic efficacy. Nanostructured drug delivery systems (NDDSs) with modifiable chemical properties are considered promising candidates as therapies for reversing MDR in colorectal cancer cells. Selenium-doped manganese phosphate (Se-MnP) nanoparticles (NPs) that can reverse drug resistance through sustained release of selenium have the potential to improve the chemotherapy effect of colorectal cancer.

RESULTS

Se-MnP NPs had an organic-inorganic hybrid composition and were assembled from smaller-scale nanoclusters. Se-MnP NPs induced excessive ROS production via Se-mediated activation of the STAT3/JNK pathway and a Fenton-like reaction due to the presence of manganese ions (Mn²⁺). Moreover, in vitro and in vivo studies demonstrated Se-MnP NPs were effective drug carriers of oxaliplatin (OX) and reversed multidrug resistance and induced caspase-mediated apoptosis in colorectal cancer cells. OX@Se-MnP NPs reversed MDR in colorectal cancer by down-regulating the expression of MDR-related ABC (ATP binding cassette) transporters proteins (e.g., ABCB1, ABCC1 and ABCG2). Finally, in vivo studies demonstrated that OX-loaded Se-MnP NPs significantly inhibited proliferation of OX-resistant HCT116 (HCT116/DR) tumor cells in nude mice.

CONCLUSIONS

OX@Se-MnP NPs with simple preparation and biomimetic chemical properties represent promising candidates for the treatment of colorectal cancer with MDR.

Claudins: The Newly Emerging Targets in Breast Cancer

Claudin-low breast cancers are recently described entities showing low expression of certain claudins and cell adhesion molecules. Claudins constitute the backbone of tight junctions (TJs) formed between 2 cells. Their dysregulation plays a vital role in tumorigenesis. First part of the article focuses on the role of claudins in the TJ organization, their structural-functional characteristics, and post-transcriptional and translational modifications. The latter part of the review attempts to summarize existing knowledge regarding the status of claudins in breast cancer. The article also provides an overview of the effect of claudins on tumor progression, metastasis, stemness, chemotherapy resistance, and their crosstalk with relevant signaling pathways in breast cancer. Claudins can act as 2-edged swords in tumors. Some claudins have either tumor-suppressive/ promoting action, while others work as both in a context-dependent manner. Claudins regulate many important events in breast cancer. However, the intricacies involved in their activity are poorly understood. Post-translational modifications in claudins and their impact on TJ integrity, function, and tumor behavior are still unclear. Although their role in adverse events in breast cancer is recognized, their potential to serve as relevant targets for future therapeutics, especially for difficult-to-treat subtypes of the above malignancy, remains to be explored.

UCP2 as a Cancer Target through Energy Metabolism and Oxidative Stress Control

Despite numerous therapies, cancer remains one of the leading causes of death worldwide due to the lack of markers for early detection and response to treatment in many patients. Technological advances in tumor screening and renewed interest in energy metabolism have allowed us to identify new cellular players in order to develop personalized treatments. Among the metabolic actors, the mitochondrial transporter uncoupling protein 2 (UCP2), whose expression is increased in many cancers, has been identified as an interesting target in tumor metabolic reprogramming. Over the past decade, a better understanding of its biochemical and physiological functions has established a role for UCP2 in (1) protecting cells from oxidative stress, (2) regulating tumor progression through changes in glycolytic, oxidative and calcium metabolism, and (3) increasing antitumor immunity in the tumor microenvironment to limit cancer development. With these pleiotropic roles, UCP2 can be considered as a potential tumor biomarker that may be interesting to target positively or negatively, depending on the type, metabolic status and stage of tumors, in combination with conventional chemotherapy or immunotherapy to control tumor development and increase response to treatment. This review provides an overview of the latest published science linking mitochondrial UCP2 activity to the tumor context.

Pump proton inhibitors display anti-tumour potential in glioma

OBJECTIVES

Glioma is one of the most aggressive brain tumours with poor overall survival despite advanced technology in surgical resection, chemotherapy and radiation. Progression and recurrence are the hinge causes of low survival. Our aim is to explain the concrete mechanism in the proliferation and progression of tumours based on tumour microenvironment (TME). The main purpose is to illustrate the mechanism of proton pump inhibitors (PPIs) in affecting acidity, hypoxia, oxidative stress, inflammatory response and autophagy based on the TME to induce apoptosis and enhance the sensitivity of chemoradiotherapy.

FINDINGS

TME is the main medium for tumour growth and progression. Acidity, hypoxia, inflammatory response, autophagy, angiogenesis and so on are the main causes of tumour progress. PPIs, as a common clinical drug to inhibit gastric acid secretion, have the advantages of fast onset, long action time and small adverse reactions. Nowadays, several kinds of literature highlight the potential of PPIs in inhibiting tumour progression. However, long-term use of PPIs alone also has obvious side effects. Therefore, till now, how to apply PPIs to promote the effect of radio-chemotherapy and find the concrete dose and concentration of combined use are novel challenges.

CONCLUSIONS

PPIs display the potential in enhancing the sensitivity of chemoradiotherapy to defend against glioma based on TME. In the clinic, it is also necessary to explore specific concentrations and dosages in synthetic applications.

Negative value of CD10-/CD34- immunophenotype in pediatric leukemia and development of a related cell line model for investigating drug resistance

PURPOSE

Appropriate sub-classification of leukemia according to the immunophenotypic characteristics of the malignant cells may improve therapeutic strategies. The aim of this study was to investigate the prognostic value of CD10/CD34 surface markers in pediatric acute lymphoblastic leukemia (pALL).

PATIENTS AND METHODS

A retrospective cohort study was performed in 79 children with ALL. Possible correlation between leukemia prognosis and CD10 CD34 immunophenotype was assessed using Kaplan-Meier and Cox regression analyses. A CD10- CD34- pre-B-ALL cell line was generated from a patient with resistant ALL. RN95 was characterized using light microscopy, immunophenotyping, karyotyping, and Western blotting. Drug sensitivity and resistant genes' expression profile were assessed using MTT and RT-PCR assays.

RESULTS

Kaplan-Meier analysis showed negative correlation between CD10/CD34 double negativity and patients' 2- and 5-year disease-free survival (DFS). Multivariate analysis indicated that the absence of CD10 and CD34 expression in the ALL patients was an independent negative prognostic marker for 2- and 5-year DFS. A novel cell line model, RN95, was developed with similar immunophenotype from a primary relapsed sample. Cells showed p53 positive functionality and demonstrated partial sensitivity to Vincristine, but complete resistance to Cytarabine. Overexpression of ABCB1, ABCA2, and ABCA3 was detected.

CONCLUSION

In the current study, simultaneous absence of CD10 and CD34 cell surface markers was introduced as an unfavorable prognostic factor in pediatric B-ALL. Moreover, a special cell line was established to help delineation of novel therapeutics for B-ALL drug resistance.

Structure-Activity Relationships of 8-Hydroxyquinoline-Derived Mannich Bases with Tertiary Amines Targeting Multidrug-Resistant Cancer

A recently proposed strategy to overcome multidrug resistance (MDR) in cancer is to target the collateral sensitivity of otherwise resistant cells. We designed a library of 120 compounds to explore the chemical space around previously identified 8-hydroxyquinoline-derived Mannich bases with robust MDR-selective toxicity. We included compounds to study the effect of halogen and alkoxymethyl substitutions in R5 in combination with different Mannich bases in R7, a shift of the Mannich base from R7 to R5, as well as the introduction of an aromatic moiety. Cytotoxicity tests performed on a panel of parental and MDR cells highlight a strong influence of experimentally determined pK_a values of the donor atom moieties, indicating that protonation and metal chelation are important factors modulating the MDR-selective anticancer activity of the studied compounds. Our results identify structural requirements increasing MDR-selective anticancer activity, providing guidelines for the development of more effective anticancer chelators targeting MDR cancer.

Hybrid/Atypical Forms of Circulating Tumor Cells: Current State of the Art

Cancer is one of the most common diseases worldwide, and its treatment is associated with many challenges such as drug and radioresistance and formation of metastases. These difficulties are due to tumor heterogeneity, which has many causes. One may be the cell fusion, a process that is relevant to both physiological (e.g., wound healing) and pathophysiological (cancer and viral infection) processes. This literature review aimed to summarize the existing data on the hybrid/atypical forms of circulating cancer cells and their role in tumor progression. For that, the bioinformatics search in universal databases, such as PubMed, NCBI, and Google Scholar was conducted by using the keywords “hybrid cancer cells”, “cancer cell fusion”, etc. In this review the latest information related to the hybrid tumor cells, theories of their genesis, characteristics of different variants with data from our own researches are presented. Many aspects of the hybrid cell research are still in their infancy. However, with the level of knowledge already accumulated, circulating hybrids such as CAML and CHC could be considered as promising biomarkers of cancerous tumors, and even more as a new approach to cancer treatment.

S-20, a steroidal saponin from the berries of black nightshade, exerts anti-multidrug resistance activity in K562/ADR cells through autophagic cell death and ERK activation

Multidrug resistance (MDR) is a major cause of chemotherapy failure. Adriamycin (ADR) has been widely used to treat cancer, however, as a substrate of the adenosine triphosphate binding cassette (ABC) transporter, it is easy to develop drug resistance during the treatment. Here, we demonstrated that steroidal saponin S-20 isolated from the berries of black nightshade has comparable cytotoxicity in ADR-sensitive and resistant K562 cell lines. Autophagy is generally considered to be a protective mechanism to mediate MDR during treatment. However, we found that S-20-induced cell death in K562/ADR is associated with autophagy. We further explored the underlying mechanisms and found that S-20 induces caspase-dependent apoptosis in ADR-sensitive and resistant K562 cell lines. Most importantly, S-20-induced autophagy activates the ERK pathway and then inhibits the expression of drug resistance protein, which is the main reason to overcome K562/ADR resistance, rather than apoptosis. Taken together, our findings emphasize that S-20 exerts anti-multidrug resistance activity in K562/ADR cells through autophagic cell death and ERK activation, which may be considered as an effective strategy.

Synthesis and characterization of Cu(II)-pyrazole complexes for possible anticancer agents; conformational studies as well as compatible in-silico and in-vitro assays

New pyrazole derivatives were prepared and used to synthesize new bioactive agents from Cu(II) complexes that have OSN donors. Analytical and spectral (IR, UV-Vis, MS, ¹H NMR, ESR & XRD) instruments characterized these complexes as well as their corresponding ligands. The bonding mode has been modified from ligand to ligand and the molar ratio for isolated complexes has also varied (1:1/1:2, M:L). The geometry of isolated complexes was commonly proposed, based on electronic transitions and ESR spectral-parameters. Via computational approaches, these structures were optimized using standard programs (Gaussian 09 & HyperChem 8.1) under the required basis set. Consequently, important physical characteristics have been obtained after finishing the optimization process. Inhibition behavior of all new synthesizes was studied by MOE module as in-silico approach which conducted versus the crystal structure of NUDT5 protein (6gru) of breast cancer cells. The interaction features summarized from docking processes, reveal effective inhibition validity for new Cu(II) complexes versus breast cancer cells. This according to scoring energy values and the stability of docking complexes in true interaction path (bond length ≤3.5 Å) particularly with Cu(II)-L³ and Cu(II)-L⁴ complexes. This reflects the possibility of successful behavior during practical application through in-vitro assay that intended in this study. Finally, the degree of toxicity of such new compounds to the breast cancer cell line was determined by in-vitro screening. To judge perfectly on their toxicity, in-vitro screening must compared to positive control as Doxorubicin (reference drug). IC₅₀ values were calculated and represent Cu(II) complexes as outstanding cytotoxic agents which revealed superiority on the reference drug itself.

Acquired Drug Resistance Enhances Imidazoquinoline Efflux by P-Glycoprotein

Multidrug-Resistant (MDR) cancers attenuate chemotherapeutic efficacy through drug efflux, a process that transports drugs from within a cell to the extracellular space via ABC (ATP-Binding Cassette) transporters, including P-glycoprotein 1 (P-gp or ABCB1/MDR1). Conversely, Toll-Like Receptor (TLR) agonist immunotherapies modulate activity of tumor-infiltrating immune cells in local proximity to cancer cells and could, therefore, benefit from the enhanced drug efflux in MDR cancers. However, the effect of acquired drug resistance on TLR agonist efflux is largely unknown. We begin to address this by investigating P-gp mediated efflux of TLR 7/8 agonists. First, we used functionalized liposomes to determine that imidazoquinoline TLR agonists Imiquimod, Resiquimod, and Gardiquimod are substrates for P-gp. Interestingly, the least potent imidazoquinoline (Imiquimod) was the best P-gp substrate. Next, we compared imidazoquinoline efflux in MDR cancer cell lines with enhanced P-gp expression relative to parent cancer cell lines. Using P-gp competitive substrates and inhibitors, we observed that imidazoquinoline efflux occurs through P-gp and, for Imiquimod, is enhanced as a consequence of acquired drug resistance. This suggests that enhancing efflux susceptibility could be an important consideration in the rational design of next generation immunotherapies that modulate activity of tumor-infiltrating immune cells.

Combination therapy with miR-34a and doxorubicin synergistically induced apoptosis in T-cell acute lymphoblastic leukemia cell line

MicroRNAs are identified to take actively part in the development of different cancers. Reduced expression of tumor suppressor miRNAs leads to cancer cell development, so restoring the expression of these miRNAs can be an appropriate treatment option for cancer. Due to the heterogeneity of cancer cells, single-drug therapy often results in drug resistance. Therefore, the combination of chemotherapy with miRNA can be a powerful strategy for cancer treatment. In the current investigation, miR-34a mimic, and negative control were purchased and transfected using jetPEI reagents. Then the synergic effects of miR-34a in combination with doxorubicin were investigated on cell death of acute T-cell lymphoblastic leukemia Jurkat cell line, as well as the expression of some genes including Caspase-3, Bcl-2, and p53 which are involved in apoptosis. Our outcomes showed that this combination remarkably reduced the expression of the Bcl-2 gene, the target gene of miR-34a. According to the results of the MTT assay, the survival rate was significantly decreased compared to the untreated cells. Results of the flow cytometry assay and DAPI staining demonstrated an increased apoptosis rate of Jurkat cells in combination therapy. Moreover, cell cycle arrest was observed at the G2/M phase in cells that were treated with miR-34a/doxorubicin. Most importantly, we showed that the transfection of the Jurkat cells with miR-34a increased the sensitivity of these cells to doxorubicin. Furthermore, the combination of miR-34a and doxorubicin drug effectively increased apoptosis of treated cells. Therefore, this method can be used as an impressive treatment for T-ALL.

Multifaceted roles of CCL20 (C-C motif chemokine ligand 20): mechanisms and communication networks in breast cancer progression

Emerging studies have demonstrated notable roles of CCL20 in breast cancer progression. Based on these findings, CCL20 has become a potential therapeutic target for cancer immunotherapy. Accordingly, studies utilizing monoclonal antibodies to target CCL20 are currently being experimented. However, the existence of cytokine network in the tumor microenvironment collectively regulates tumor progression. Hence, a deeper understanding of the role of CCL20 and the underlying signaling pathways regulating the functions of CCL20 may provide a novel strategy for therapeutic interventions. This review provides the current knowledge on how CCL20 interacts with breast cancer cells to influence tumor progression via immunosuppression, angiogenesis, epithelial to mesenchymal transition, migration/invasion and chemoresistance. As a possible candidate biomarker, we also reviewed signal pathways and other factors in the tumor microenvironment regulating the tumor-promoting functions of CCL20.These new insights may be useful to design new potent and selective CCL20 inhibitors against breast cancer in the future.

Apoptosis Inducing Activity of Rhinacanthin-C in Doxorubicin-Resistant Breast Cancer MCF-7 Cells

Rhinacanthin-C is a natural bioactive naphthoquinone ester with potential chemotherapeutic value in cancer treatment. In this study, we investigated its apoptotic induction ability and the involved mechanisms through the mitogen-activated protein kinases (MAPK) and protein kinase B/glycogen synthase kinase-3β/nuclear factor erythroid 2-related factor 2 (Akt/GSK-3β/Nrf2) signaling pathways in doxorubicin-resistant breast cancer MCF-7 (MCF-7/DOX) cells. Our 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay showed that rhinacanthin-C (3-28 µM) significantly decreased the viability of MCF-7/DOX cells and potentiated hydrogen peroxide cytotoxicity. This naphthoquinone was able to increase intracellular reactive oxygen species (ROS), as measured by the 2',7'-dichlorofluorescein diacetate (DCFH-DA) assay. This compound increased the number of apoptotic cells by elevating the ratio of apoptotic checkpoint proteins Bax/Bcl-2 and by decreasing the expression of poly(ADP-ribose) polymerase (PARP) protein. Furthermore, Western blotting analyses showed that treatment with rhinacanthin-C (3-28 µM) for 24 h significantly decreased the expression levels of the phosphorylated forms of MAPK proteins (i.e., extracellular signal regulated protein kinase 1/2 (ERK1/2), c-Jun N-terminal kinases (JNK) and p38), Akt, GSK-3β and Nrf2 proteins in MCF-7/DOX cells. Inhibition of the Akt/GSK-3β/Nrf2 pathway led to a significant reduction in heme oxygenase-1 (HO-1) and reduced nicotinamide adenine dinucleotide phosphate (NADP)(H): quinone oxidoreductase 1 (NQO1) proteins. These findings suggested that rhinacanthin-C was able to induce apoptosis in MCF-7/DOX cells through increased ROS production and suppression of the cell survival systems mediated by the MAPKs and Akt/GSK-3β/Nrf2 signaling pathways.

Battling Chemoresistance in Cancer: Root Causes and Strategies to Uproot Them

With nearly 10 million deaths, cancer is the leading cause of mortality worldwide. Along with major key parameters that control cancer treatment management, such as diagnosis, resistance to the classical and new chemotherapeutic reagents continues to be a significant problem. Intrinsic or acquired chemoresistance leads to cancer recurrence in many cases that eventually causes failure in the successful treatment and death of cancer patients. Various determinants, including tumor heterogeneity and tumor microenvironment, could cause chemoresistance through a diverse range of mechanisms. In this review, we summarize the key determinants and the underlying mechanisms by which chemoresistance appears. We then describe which strategies have been implemented and studied to combat such a lethal phenomenon in the management of cancer treatment, with emphasis on the need to improve the early diagnosis of cancer complemented by combination therapy.

Progress in the study of D-α-tocopherol polyethylene glycol 1000 succinate (TPGS) reversing multidrug resistance

Currently, multidrug resistance (MDR) is one of the major reasons for failure in clinical cancer chemotherapy. Overexpression of the ATP binding cassette (ABC) transporter P-glycoprotein (P-gp), which significantly increases the efflux of anticancer drugs from tumor cells, enhances MDR. In the past few decades, four generations of P-gp inhibitors have appeared. However, they are limited in clinical application due to their severe toxic side effects. As a P-gp inhibitor and carrier for loading chemotherapy agents, TPGS has received increasing attention due to its advantages and unique properties of reversing MDR. TPGS is an amphipathic agent that increases the solubility of most chemotherapy drugs and decreases severe side effects. In addition, TPGS is an excellent carrier with P-gp-inhibiting ability. In this review, we summarize the latest articles on TPGS-based nanodelivery systems to prevent MDR.

Rab27B enhances drug resistance in hepatocellular carcinoma by promoting exosome-mediated drug efflux

Liver cancer is a major threat to human life and health, and chemotherapy has been the standard non-surgical treatment for liver cancer. However, the emergence of drug resistance of liver cancer cells has hindered the therapeutic effect of chemical drugs. The discovery of exosomes has provided new insights into the mechanisms underlying tumour cell resistance. In this study, we aimed to determine the proteins associated with drug resistance in tumour cells and to elucidate the underlying mechanisms. We found that Rab27B expression in drug (5-fluorouracil, 5Fu)-resistant Bel7402 (Bel/5Fu) cells increased significantly compared with that in drug-sensitive Bel7402 cells. In addition, Bel/5Fu cells secreted more exosomes under 5Fu stimulation. The number of exosomes secreted by Bel/5Fu cells significantly reduced after knocking down Rab27B, and the cellular concentration of 5Fu increased, enhancing its therapeutic effect. We also found that the administration of classical drug efflux pump (P-glycoprotein, P-gp) inhibitors together with knockdown of Rab27B further improved the therapeutic effects of chemotherapy drugs. In conclusion, our findings suggest that Rab27B could be a new therapeutic target in liver cancer.

Cell fusion in cancer hallmarks: Current research status and future indications

Cell fusion is involved in several physiological processes, such as reproduction, development and immunity. Although cell fusion in tumors was reported 130 years ago, it has recently attracted great interest, with recent progress in tumorigenesis research. However, the role of cell fusion in tumor progression remains unclear. The pattern of cell fusion and its role under physiological conditions are the basis for our understanding of the pathological role of cell fusion. However, the role of cell fusion in tumors and its functions are complicated. Cell fusion can directly increase tumor heterogeneity by forming polyploids or aneuploidies. Several studies have reported that cell fusion is associated with tumorigenesis, metastasis, recurrence, drug resistance and the formation of cancer stem cells. Given the diverse roles cell fusion plays in different tumor phenotypes, methods based on targeted cell fusion have been designed to treat tumors. Research on cell fusion in tumors may provide novel ideas for further treatment.

ent-Kaurane diterpenoids induce apoptosis and ferroptosis through targeting redox resetting to overcome cisplatin resistance

Reactive oxygen species (ROS) induction is an effective mechanism to kill cancer cells for many chemotherapeutics, while resettled redox homeostasis induced by the anticancer drugs will promote cancer chemoresistance. Natural ent-kaurane diterpenoids have been found to bind glutathione (GSH) and sulfhydryl group in antioxidant enzymes covalently, which leads to the destruction of intracellular redox homeostasis. Therefore, redox resetting destruction by ent-kaurane diterpenoids may emerge as a viable strategy for cancer therapy. In this study, we isolated 30 ent-kaurane diterpenoids including 20 new samples from Chinese liverworts Jungermannia tetragona Lindenb and studied their specific targets and possible application in cancer drug resistance through redox resetting destruction. 11β-hydroxy-ent-16-kaurene-15-one (23) possessed strong inhibitory activity against several cancer cell lines. Moreover, compound 23 induced both apoptosis and ferroptosis through increasing cellular ROS levels in HepG2 cells. ROS accumulation induced by compound 23 was caused by inhibition of antioxidant systems through targeting peroxiredoxin I/II (Prdx I/II) and depletion of GSH. Furthermore, compound 23 sensitized cisplatin (CDDP)-resistant A549/CDDP cancer cells in vitro and in vivo by inducing apoptosis and ferroptosis. Thus, the ent-kaurane derivative showed potential application for sensitizing CDDP resistance by redox resetting destruction through dual inhibition of Prdx I/II and GSH in cancer chemotherapy.

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Thirty ent-kaurane diterpenoids were isolated from the Chinese liverworts, Jungermannia tetragona.

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11β-hydroxy-ent-16-kaurene-15-one (23) was identified to induce apoptosis and ferroptosis for the first time.

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Compound 23 could disorder the intracellular redox system by directly targeting Prdx I/II and GSH.

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Compound 23 could sensitize A549/CDDP cancer cells in vitro and in vivo through redox resetting destruction.

Current perspectives on exosomes in the diagnosis and treatment of hepatocellular carcinoma (review)

The prognosis of hepatocellular carcinoma (HCC), a malignant tumor, is poor. Tumor recurrence and metastasis are the major challenges for the treatment of HCC. Various studies have demonstrated that exosomes, which are loaded with various biomolecules including nucleic acids, lipids, and proteins are involved in the recurrence and metastasis of HCC. Additionally, exosomes mediate various biological processes, such as immune response, cell apoptosis, angiogenesis, thrombosis, autophagy, and intercellular signal transduction. In cancer, exosomes regulate cancer cell differentiation, development, and drug resistance. Circular RNAs, microRNAs, and proteins in the exosomes can serve as early diagnostic and prognostic markers for HCC. As exosomes are characterized by low immunogenicity and high stability in the tissues and circulation, they can be used to deliver the drugs in cancer therapies.

Application of CRISPR/Cas9 System to Reverse ABC-Mediated Multidrug Resistance

Multidrug resistance (MDR) is the main obstacle in cancer chemotherapy. ATP-binding cassette (ABC) transporters can transport a wide range of antitumor drugs out of cells, which is the most common reason in the development of resistance to drugs. Currently, various therapeutic strategies are used to reverse MDR, among which CRISPR/Cas9 gene editing technique is expected to be an effective way. Here, we reviewed the research progress of reversing ABC-mediated drug resistance by CRISPR/Cas9 system.

Identification of chemoresistance-associated microRNAs and hub genes in breast cancer using bioinformatics analysis

Breast cancer threatens women's health. Although there are a lot of methods to treat breast cancer, chemotherapy resistance still hinders the effectiveness of treatment. This study attempts to explore the mechanism of chemotherapy resistance from the perspective of miRNA and look for several new targets for developing new drugs. Three datasets (GSE73736, GSE71142 and GSE6434) from Gene Expression Omnibus (GEO) were used for the bioinformatics analysis. Differentially expressed miRNAs (DE-miRNAs) and differentially expressed genes (DE-genes) were obtained by using R package "limma". DAVID tool was used to perform gene ontology annotation analysis (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis for the overlapping genes. Protein-protein interaction (PPI) network was established by STRING database and visualized by software Cytoscape. Hub genes were identified by software Cytoscape. The prognostic value of hub genes was assessed through Kaplan-Meier plotter website. In total, 22 DE-miRNAs, 1932 DE-genes and top 10 hub genes were obtained. The genes were mainly enriched in cell signaling pathways like ErbB signaling pathway and PI3K / AKT/mTOR pathway. These pathways have a significant impact on the proliferation, invasion and drug resistance in cancer. MiRNA-Gene interaction may provide new insight for exploring the mechanism of chemotherapy resistance in breast cancer. Our study ultimately identified effective biomarkers and potential drug targets, which may enhance the effect of chemotherapy in patients with breast cancer.

Inhibition of β-glucosidase overcomes gastric cancer chemoresistance through inducing lysosomal dysfunction

OBJECTIVE

The clinical management of gastric cancer still remains challenge due to its poor response to chemotherapy. Better understanding the underlying mechanisms is required for the identification of more comprehensive therapies to overcome chemoresistance in gastric cancer.

MATERIALS AND METHODS

GBA1 level was systematically analyzed in gastric cancer patients before and after chemotherapy, and gastric cancer cells exposed to long-term chemo agent's treatment. The roles of GBA1 and its downstream mechanisms were investigated using pharmacological and genetic approaches.

RESULTS

We observed the time-dependent upregulation of GBA1 expression and enzyme activity in multiple gastric cancer cell lines in response to prolonged exposure of 5-FU. It is noted that this phenomenon was also observed in gastric cancer patients after chemotherapy. Interestingly, no significant differences on GBA1 expression were detected between normal and malignant gastric tissues. These suggest that the predominant role of GBA1 is in the development of gastric cancer chemoresistance rather than tumorigenesis. Functional analysis demonstrated that GBA1 inhibition suppressed gastric cancer growth and survival without affecting migration, and augmented 5-FU's efficacy. Consistently, GBA1 inhibition was active against 5-FU-resistant gastric cancer cells. Mechanism studies showed that GBA1 inhibition led to loss of lysosomal integrity and function in 5-FU-resistant gastric cancer cells.

CONCLUSIONS

We are the first to show that inhibition of β-glucosidase (encoded by GBA1) sensitizes gastric cancer to chemotherapy. Our findings demonstrate the therapeutic value of inhibiting GBA1 in gastric cancer, particularly in those who develop chemoresistance.

CD13: A Key Player in Multidrug Resistance in Cancer Chemotherapy

Cancer is one of the most serious diseases that are harmful to human health. Systemic chemotherapy is an optimal therapeutic strategy for the treatment of cancer, but great difficulty has been encountered in its administration in the form of multidrug resistance (MDR). As an enzyme on the outer cell surface, CD13 is documented to be involved in the MDR development of tumor cells. In this review, we will focus on the role of CD13 in MDR generation based on the current evidence.

Antitumor Drugs and Their Targets

Through novel methodologies, including both basic and clinical research, progress has been made in the therapy of solid cancer. Recent innovations in anticancer therapies, including immune checkpoint inhibitor biologics, therapeutic vaccines, small drugs, and CAR-T cell injections, mark a new epoch in cancer research, already known for faster (epi-)genomics, transcriptomics, and proteomics. As the long-sought after personalization of cancer therapies comes to fruition, the need to evaluate all current therapeutic possibilities and select the best for each patient is of paramount importance. This is a novel task for medical care that deserves prominence in therapeutic considerations in the future. This is because cancer is a complex genetic disease. In its deadly form, metastatic cancer, it includes altered genes (and their regulators) that encode ten hallmarks of cancer-independent growth, dodging apoptosis, immortalization, multidrug resistance, neovascularization, invasiveness, genome instability, inflammation, deregulation of metabolism, and avoidance of destruction by the immune system. These factors have been known targets for many anticancer drugs and treatments, and their modulation is a therapeutic goal, with the hope of rendering solid cancer a chronic rather than deadly disease. In this article, the current therapeutic arsenal against cancers is reviewed with a focus on immunotherapies.

The Nrf2/PGC1α Pathway Regulates Antioxidant and Proteasomal Activity to Alter Cisplatin Sensitivity in Ovarian Cancer

Drug resistance remains a barrier in the clinical treatment of ovarian cancer. Proteasomal and antioxidant activities play important roles in tumor drug resistance, and increasing evidence suggests the existence of an interaction between antioxidant and proteasomal activities. However, the mechanism of the synergistic effects of proteasomal activity and antioxidation on tumor drug resistance is not completely clear. In this study, we compared two ovarian cancer cells, A2780 and SKOV3 cells. Among them, SKOV3 cell is a human clear cell carcinoma cell line that is resistant to platinum. We found that compared with the findings in A2780 cells, SKOV3 cells were less sensitive to both proteasomal inhibitor and cisplatin. Proteasomal inhibition enhanced the sensitivity of A2780 cells, but not SKOV3 cells, to cisplatin. Notably, the Nrf2-mediated antioxidant pathway was identified as a resistance mechanism in proteasome inhibitor-resistant cells, but this was not the only factor identified in our research. In SKOV3 cells, PGC1α regulated the antioxidant activity of Nrf2 by increasing the phosphorylation of GSK3β, and in turn, Nrf2 regulated the transcriptional activity of PGC1α. Thus, Nrf2 and PGC1α synergistically participate in the regulation of proteasomal activity. Furthermore, the Nrf2/PGC1α pathway participated in the regulation of mitochondrial function and homeostasis, further regulating proteasomal activity in SKOV3 cells. Therefore, exploring the roles of PGC1α and Nrf2 in the regulation of proteasomal activity by antioxidant and mitochondrial functions may provide new avenues for reversing drug resistance in ovarian cancer.

Encorafenib enhances TRAIL-induced apoptosis of colorectal cancer cells dependent on p53/PUMA signaling

TRAIL has been demonstrated to play a critical role in the apoptosis of colorectal cancer (CRC) cells, but drug resistance markedly restricts its therapeutic effects. Objectives: This study aims to investigate whether encorafenib can enhance TRAIL-induced apoptosis of colorectal cancer cells and the underlying mechanism. TRAIL was first used to induce CRC cells. CCK-8 assays were conducted for detecting cell viability of TRAIL-induced CRC cells with encorafenib treatment. Flow cytometry was used to detect the cell apoptosis of CRC cells and western blot was used to measure the expressions of apoptosis-related proteins. The expressions of DR4, DR5, p53, and PUMA were then evaluated by qPCR and western blot. After transfecting the interference plasmid of p53 into CRC cells, the expressions of PUMA and DR5 were further explored. TRAIL reduced the cell viability of CRC cells, and the inhibition was further reinforced under co-treatment of TRAIL and encorafenib. Encorafenib also triggered the promotion of CRC cell apoptosis induced by TRAIL. It was also found that encorafenib exerted its promoting effects on cell apoptosis of CRC cells via the elevation of DR5. Besides, encorafenib administration promoted the expression levels of p53 and PUMA in TRAIL-induced CRC cells. Furthermore, p53 knockdown attenuated the expression of PUMA and DR5 in TRAIL-induced CRC cells treated with encorafenib. This study indicates that encorafenib stimulates TRAIL-induced apoptosis of CRC cells dependent on p53/PUMA signaling, which may provide instructions for the treatment of CRC.

The Combination of the M2 Muscarinic Receptor Agonist and Chemotherapy Affects Drug Resistance in Neuroblastoma Cells

One of the major limits of chemotherapy is depending on the ability of the cancer cells to elude and adapt to different drugs. Recently, we demonstrated how the activation of the M2 muscarinic receptor could impair neuroblastoma cell proliferation. In the present paper, we investigate the possible effects mediated by the preferential M2 receptor agonist arecaidine propargyl ester (APE) on drug resistance in two neuroblastoma cell lines, SK-N-BE and SK-N-BE(2C), a sub-clone presenting drug resistance. In both cell lines, we compare the expression of the M2 receptor and the effects mediated by the M2 agonist APE on cell cycle, demonstrating a decreased percentage of cells in S phase and an accumulation of SK-N-BE cells in G1 phase, while the APE treatment of SK-N-BE(2C) cells induced a block in G2/M phase. The withdrawal of the M2 agonist from the medium shows that only the SK-N-BE(2C) cells are able to rescue cell proliferation. Further, we demonstrate that the co-treatment of low doses of APE with doxorubicin or cisplatin significantly counteracts cell proliferation when compared with the single treatment. Analysis of the expression of ATP-binding cassette (ABC) efflux pumps demonstrates the ability of the M2 agonist to downregulate their expression and that this negative modulation may be dependent on N-MYC decreased expression induced by the M2 agonist. Our data demonstrate that the combined effect of low doses of conventional drugs and the M2 agonist may represent a new promising therapeutic approach in neuroblastoma treatment, in light of its significant impact on drug resistance and the possible reduction in the side effects caused by high doses of chemotherapy drugs.

Selective dysregulation of ABC transporters in methotrexate-resistant leukemia T-cells can confer cross-resistance to cytarabine, vincristine and dexamethasone, but not doxorubicin

Pediatric acute lymphoblastic leukemia (pALL) includes 75 % of childhood leukemias, and methotrexate (MTX) is one of the most effective chemotherapy agents prescribed for pALL treatment. The aim of this study was to establish and characterize an MTX-resistant tumor cell model in order to study the mechanism contributing to drug sensitivity loss in pALL. Parental CCRF-CEM cells were treated with a gradual increasing concentration of MTX from 5 nM to 1.28 μM. The resistant subline was then characterized according to the cellular morphology, cellular growth curves and specific mRNA expression changes associated with drug resistance in ALL. Moreover, in vitro cytotoxicity assays were used to analyze cells relative responsiveness to a set of clinically used anti-ALL chemotherapy drugs. The morphological changes observed in the new R-CCRF-CEM/MVCD subline were associated with dysregulation of the EMT-related genes, Twist1 and CDH1. Cells demonstrated downregulation of ABCC1 and the overexpression of ABCA2, ABCA3, and ABCB1 membrane transporters. However, short treatment of the sensitive and parental cell line with MTX did not affect the expression profiles of the former ABC pumps. Moreover, R-CCRF-CEM/MVCD cells demonstrated cross-resistance to cytarabine (cytosine arabinoside, ara-C), vincristine, and dexamethasone, but not doxorubicin. The induced cross-resistance to specific chemotherapy drugs may possibly be attributed to selective dysregulation of the ABC transporters and EMT-related genes. These data may pave the way for the development of new cancer therapeutic strategies.

Chaetomugilin J Enhances Apoptosis in Human Ovarian Cancer A2780 Cells Induced by Cisplatin Through Inhibiting Pink1/Parkin Mediated Mitophagy

Purpose

The chemoresistance and toxicity of traditional chemotherapeutic drugs have become obstacles to their antitumor effects in ovarian cancers. Therefore, it is particularly important to develop new anticancer drugs to increase target sensitivity and reduce the toxicity of chemotherapy drugs. As key organelles, the endoplasmic reticulum and mitochondria play important role in chemoresistance. Cells become resistant to drugs by maintaining the homeostasis of the endoplasmic reticulum and mitochondria. Chaetomugilin J, a metabolite isolated from Polygonatum sibiricum, belongs to the Chaetomium family and exhibits potent cytotoxicity. In this study, we aimed to explore the mechanistic link between apoptosis and endoplasmic reticulum stress, mitophagy and mitochondrial dysfunction induced by chaetomugilin J combined with cisplatin in the ovarian cancer cell line A2780.

Methods

Chaetomugilin J was identified by chemical methods. Cell viability was measured by an MTT assay. The apoptosis, mitochondrial membrane potential, and intracellular reactive oxygen species (ROS) were examined by flow cytometry. Mitochondrial ROS was measured by a fluorescence microscope with MitoSox staining. Further, the related proteins and overexpression of parkin were detected by Western blot.

Results

Chaetomugilin J combined with low-dose cisplatin decreased cell viability and increased apoptosis in A2780 cells. In addition, intracellular ROS and mitochondrial ROS were increased, while the mitochondrial membrane potential was reduced. The expressions of grp78 and chop were decreased after treatment by chaetomugilin J combined with low-dose cisplatin. Overexpression of parkin attenuated chaetomugilin J combined with cisplatin-induced apoptosis.

Conclusion

Chaetomugilin J combined with cisplatin inhibited pink1/parkin mediated mitophagy increased mitochondrial dysfunction in the A2780 cells and enhanced apoptosis induced by cisplatin in the ovarian cancer cell line A2780. But this process was not related to endoplasmic reticulum apoptotic pathway.

Novel TrxR1 Inhibitors Show Potential for Glioma Treatment by Suppressing the Invasion and Sensitizing Glioma Cells to Chemotherapy

Currently, available glioblastoma (GBM) treatment remains ineffective, with relapse after initial response and low survival rate of GBM patients. The reasons behind limited capacities for GBM treatment are high tumor heterogeneity, invasiveness, and occurrence of drug resistance. Therefore, developing novel therapeutic strategies is of utmost importance. Thioredoxin reductase (TrxR) is a novel, promising target due to its overexpression in many cancer types and important role in cancer progression. Previous research on Ugi-type Michael acceptors–inhibitors of TrxR showed desirable anticancer properties, with significant selectivity toward cancer cells. Herein, two TrxR inhibitors, 5 and 6, underwent in-depth study on multidrug-resistant (MDR) glioma cell lines. Besides the antioxidative effects, 5 and 6 induced cell death, decreased cell proliferation, and suppressed invasion and migration of glioma cells. Both compounds showed a synergistic effect in combination with temozolomide (TMZ), a first-line chemotherapeutic for GBM treatment. Moreover, 5 and 6 affected activity of P-glycoprotein extrusion pump that could be found in cancer cells and in the blood–brain barrier (BBB), thus showing potential for suppressing MDR phenotype in cancer cells and evading BBB. In conclusion, investigated TrxR inhibitors are effective anticancer compounds, acting through inhibition of the thioredoxin system and perturbation of antioxidative defense systems of glioma cells. They are suitable for combining with other chemotherapeutics, able to surpass the BBB and overcome MDR. Thus, our findings suggest further exploration of Ugi-type Michael acceptors–TrxR inhibitors’ potential as an adjuvant therapy for GBM treatment.

Copper Complexes as Anticancer Agents Targeting Topoisomerases I and II

Organometallics, such as copper compounds, are cancer chemotherapeutics used alone or in combination with other drugs. One small group of copper complexes exerts an effective inhibitory action on topoisomerases, which participate in the regulation of DNA topology. Copper complexes inhibitors of topoisomerases 1 and 2 work by different molecular mechanisms, analyzed herein. They allow genesis of DNA breaks after the formation of a ternary complex, or act in a catalytic mode, often display DNA intercalative properties and ROS production, and sometimes display dual effects. These amplified actions have repercussions on the cell cycle checkpoints and death effectors. Copper complexes of topoisomerase inhibitors are analyzed in a broader synthetic view and in the context of cancer cell mutations. Finally, new emerging treatment aspects are depicted to encourage the expansion of this family of highly active anticancer drugs and to expend their use in clinical trials and future cancer therapy.

Deep phylogeny of cancer drivers and compensatory mutations

Driver mutations (DM) are the genetic impetus for most cancers. The DM are assumed to be deleterious in species evolution, being eliminated by purifying selection unless compensated by other mutations. We present deep phylogenies for 84 cancer driver genes and investigate the prevalence of 434 DM across gene-species trees. The DM are rare in species evolution, and 181 are completely absent, validating their negative fitness effect. The DM are more common in unicellular than in multicellular eukaryotes, suggesting a link between these mutations and cell proliferation control. 18 DM appear as the ancestral state in one or more major clades, including 3 among mammals. We identify within-gene, compensatory mutations for 98 DM and infer likely interactions between the DM and compensatory sites in protein structures. These findings elucidate the evolutionary status of DM and are expected to advance the understanding of the functions and evolution of oncogenes and tumor suppressors.

Rochman et al. present deep phylogenies for 84 cancer driver genes and examine the prevalence of driver mutations across gene-species trees. Their results show that driver mutations are rare in species evolution and give insight into the evolution of driver mutations and oncogenes.

Chemotherapy and chemo-resistance in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is closely associated with Epstein-Barr virus (EBV) and occurs frequently in the south of China and Southeast Asian countries. Concurrent chemo-radiotherapy is one of the main treatments for NPC. Although, the combined treatment of chemo-radiotherapy produces a satisfying survival rate, the chemo-resistance arises as a big obstacle in curing recurrent NPC patients. The acquirement of chemo-resistance is usually along with a poor prognosis. So far, the mechanism of chemo-resistance in NPC has not been fully elucidated and there have not been a comprehensive review on this issue. Thus, it is of great significance to summarize the mechanisms involved in NPC chemo-resistance. In this review, the importance and limitations of chemotherapy and the mechanisms of chemo-resistances in NPC were discussed.

Cancer associated fibroblast mediated chemoresistance: A paradigm shift in understanding the mechanism of tumor progression

One of the undeniable issues with cancer eradication is the evolution of chemoresistance in due course of treatment, and the mechanisms of chemoresistance have been the subject of extensive research for several years. The efficacy of chemotherapy is hindered by cancer epithelium, mostly in a cell-autonomous mechanism. However, recently the valid experimental evidence showed that the surrounding tumor microenvironment (TME) is equivalently responsible for the induction of chemoresistance. Of the verities of cells in the tumor microenvironment, cancer-associated fibroblasts (CAFs) are the major cellular component of TME and act as a key regulator in the acquisition of cancer chemoresistance by providing a protective niche to the cancer cells against the anti-cancer drugs. Moreover, the symbiotic relationship between the tumor and CAFs to obtain key resources such as growth factors and nutrients for optimal tumor growth and proliferation favors the chemoresistance phenotype. Here, in this review, we provide an up-to-date overview of our knowledge of the role of the CAFs in inducing chemoresistance and tumor progression. We also further delineated the emerging events leading to the CAF origins and activation of normal fibroblasts to CAFs. Along with this, we also discuss the novel area of research confined to the CAF targeted therapies of cancer. The identification of CAF-specific markers may allow unveiling new targets and avenues for blunting or reverting the detrimental pro-tumorigenic potential of CAFs in the foreseeable future.

Evaluating the role of microRNAs alterations in oral squamous cell carcinoma

Oral squamous cell carcinoma (OSCC) accounts for nearly 90 percent of oral cavity malignancies and is one of the most widespread oral cancers in the world. The microRNAs (miRNAs or miRs) have an important role in cellular processes comprising cell cycle, differentiation, and also apoptosis. MiRNAs are also implicated in the progression of cancers, including OSCC, through a variety of signaling pathways. One of the most significant signaling pathways in OSCC is the PI3K / Akt pathway that has been illustrated to be under the tight regulation of miRNAs. Deregulation or activation of the PI3K / Akt pathway due to mutations has been revealed to be implicated in the development of oral cancer. According to studies, more than 47% of HNSCC and around 38% of OSCC samples indicate at least one molecular alteration in this signaling pathway. The potential of miRNAs for their use as therapeutic tools in the diagnosis as well as treatment of numerous diseases have been confirmed. In the current review, we summarize miRNAs and their possible mechanisms as well as their functions in OSCC advancement and progression.

Administration with hyperoside sensitizes breast cancer cells to paclitaxel by blocking the TLR4 signaling

Breast cancer is a malignancy and one of the most frequent causes of cancer death among women worldwide. Paclitaxel is a common chemotherapeutic drug and has recently been shown to facilitate tumor cell escape during cytotoxic chemotherapy by inducing inflammatory mediators and pro-survival protein expression. Hyperoside is a flavonoid glycoside compound and exerts anti-inflammation, and anti-tumor growth properties. However, its function in breast cancer chemosensitivity remains poorly elucidated. In this study, hyperoside exhibited little cytotoxicity to normal human breast mammary epithelial cell lines, and also protected against paclitaxel-induced cytotoxicity in MCF-10A. Importantly, treatment with hyperoside engendered not only inhibition of cell viability, but also potentiated cancer cell sensitivity to paclitaxel in TLR4-positive breast cancer MDA-MB-231 cells by suppressing cell viability, and increasing cell apoptosis and caspase-3 activity. Nevertheless, although hyperoside exposure restrained cell viability, its treatment presented little effects to paclitaxel sensitivity in TLR4-null HCC1806 cells. Intriguingly, paclitaxel stimulation activated the TLR4-NF-κB signaling, which was reversed after hyperoside administration. Concomitantly, hyperoside also attenuated paclitaxel-mediated anti-apoptotic Bcl-2 expression, but enhanced the effects of paclitaxel on pro-apoptotic Bax expression, and pro-inflammatory cytokine IL-6 and IL-6 levels in MDA-MB-231 cells. Importantly, restoring the TLR4 pathway overturned hyperoside-evoked chemosensitivity to paclitaxel in MDA-MB-231 cells. Thus, hyperoside may elevate breast cancer cell sensitivity to paclitaxel by blocking TLR4 activation-mediated pro-inflammatory and pro-survival approaches, thereby endorsing its usefulness as a promising therapeutic combination to overcome chemosensitivity in breast cancer.

Inhibition of cyclin-dependent kinases by AT7519 enhances nasopharyngeal carcinoma cell response to chemotherapy

BACKGROUND

The poor outcomes in nasopharyngeal carcinoma (NPC) necessitate new treatments. AT7519 is a potent inhibitor of several cyclin-dependent kinases (CDKs) and is currently in the early phase of clinical development for cancer treatment. The potent anti-cancer activities of AT7519 have been reported in various cancers, but not in NPC.

MATERIALS AND METHODS

The effects of AT7519 in NPC were systematically analyzed using cell culture assays and xenograft mouse models. The effects of AT7519 on molecules involved in mRNA transcription were examined.

RESULTS

AT7519, at a nanomolar concentration, significantly inhibits growth via arresting cells at G2/M phase, and induces apoptosis in NPC cells regardless of Epstein-Barr virus (EBV) infection and cellular origin. It also inhibits growth of a subpopulation of cells with highly proliferative and invasive features. Importantly, AT7519 acts synergistically with cisplatin and is effective against chemo-resistant NPC cells. Mechanistically, AT7519 inhibits phosphorylation of Rb, suggesting the inhibition of CDK2 in NPC. It also decreases N-myc level and RNA polymerase II phosphorylation, and inhibits transcription. Consistent with the in vitro findings, we demonstrate that AT7519 is effective as a single agent in two independent NPC xenograft mouse models. The combination of ATP7519 and cisplatin results in greater efficacy than cisplatin alone in inhibiting NPC tumor growth.

CONCLUSIONS

Our work is the first to report anti-NPC activities of AT7519. Our preclinical evidence suggests that AT7519 is a useful addition to overcome NPC chemo-resistance.

Regulation of Integrin Subunit Alpha 2 by miR-135b-5p Modulates Chemoresistance in Gastric Cancer

Chemotherapy has substantially improved gastric cancer (GC) patient outcomes in the past decades. However, the development of chemotherapy resistance has become the major cause of treatment failure. Although numerous molecules have been implicated in GC chemoresistance, its pathological mechanisms are still unclear. Here, we found that integrin subunit alpha 2 (ITGA2) is upregulated in chemoresistant GC cells and that increased ITGA2 levels correlated with the poor prognosis of GC patients who received chemotherapy. ITGA2 overexpression led to elevated chemotherapy resistance and drug-induced apoptosis inhibition in GC cells. ITGA2 knockdown resulted in restored chemosensitivity and increased apoptosis in chemoresistant GC cells both in vitro and in vivo. NanoString analysis revealed a unique signature of deregulated pathway expression in GC cells after ITGA2 silencing. The MAPK/ERK pathway and epithelial-mesenchymal transition (EMT) were found to be downregulated after ITGA2 knockdown. miR-135b-5p was identified as a direct upstream regulator of ITGA2. miR-135b-5p overexpression reduced chemoresistance and induced apoptosis in GC cells and attenuated ITGA2-induced chemoresistance and antiapoptotic effects by inhibiting MAPK signaling and EMT. In conclusion, this study underscored the role and mechanism of ITGA2 in GC and suggested the novel miR-135b-5p/ITGA2 axis as an epigenetic cause of chemoresistance with diagnostic and therapeutic implications.

SRGN crosstalks with YAP to maintain chemoresistance and stemness in breast cancer cells by modulating HDAC2 expression

Background: Chemoresistance is a significant obstacle to the effective treatment of breast cancer (BC), resulting in more aggressive behavior and worse clinical outcome. The molecular mechanisms underlying breast cancer chemoresistance remain unclear. Our microarray analysis had identified the overexpression of a small molecular glycoprotein serglycin (SRGN) in multidrug-resistant BC cells. Here, we aimed to investigate the role of SRGN in chemoresistance of breast cancer and elucidate the underlying mechanisms. Methods: SRNG overexpression was identified using microarray analysis and its clinical relevance was analyzed. To investigate the role of SRGN, we performed various in vitro and in vivo studies, as well as characterization of serum and tissue samples from BC patients. Chemosensitivity measurement, gene expression interference, immunofluorescence staining, mammosphere assay, flow cytometry analysis, luciferase reporter assay, ChIP-qPCR, coimmunoprecipitation, and immunohistochemistry were performed to explore the potential functions and mechanisms of SRGN. Results: We confirmed overexpression of SRGN in chemoresistant BC cells and in serum and tissue samples from BC patients with poor response to chemotherapy. SRGN specifically predicted poor prognosis in BC patients receiving chemotherapy. Mechanistically, SRGN promoted chemoresistance both in vitro and in vivo by cross-talking with the transcriptional coactivator YES-associated protein (YAP) to maintain stemness in BC cells. Ectopic YAP expression restored the effects of SRGN knockdown. Inversely, YAP knockdown rescued the effects of SRGN overexpression. The secreted SRGN triggered ITGA5/FAK/CREB signaling to enhance YAP transcription. Reciprocally, YAP promoted SRGN transcription in a TEAD1-dependent manner to form a feed-forward circuit. Moreover, the YAP/RUNX1 complex promoted HDAC2 transcription to induce chemoresistance and stemness in BC cells. Importantly, the SRGN levels were positively correlated with the YAP and HDAC2 levels in chemoresistant BC tissues. YAP and HDAC2 acted downstream of SRNG and correlated with poor outcomes of BC patients receiving chemotherapy. Conclusions: Our findings clarify the roles and mechanisms of SRGN in mediating chemoresistance in breast cancer and suggest its use a potential biomarker for chemotherapeutic response. We believe that novel therapeutic strategies for breast cancer can be designed by targeting the signaling mediated by the crosstalk between SRGN and YAP.

IRE1α-targeting downregulates ABC transporters and overcomes drug resistance of colon cancer cells

Drug resistance is a big problem in cancer treatment and one of the most prominent mechanisms underlain is overexpression of ATP-binding cassette (ABC) transporters, particularly ABCB1, ABCC1 and ABCG2. Inhibition of ABC transporters is an important approach to overcome drug resistance. The inositol-requiring enzyme 1α (IRE1α), an arm of unfolded protein response (UPR), splices XBP1 mRNA to generate an active transcription factor XBP1s. UPR is implicated in drug resistance. However, the underlying mechanism is unclear. We found that the anticancer drugs such as 5-fluorouracil (5-FU) activated the IRE1α-XBP1 pathway to induce the expression of ABCB1, ABCC1 and ABCG2 in colon cancer cells. Inhibition of IRE1α RNase activity with small molecule 4μ8c suppressed the drug-induced expression of these ABC transporters and sensitized 5-FU-resistant colon cancer cells to drug treatment. In vivo xenograft assay indicates that administration of 4μ8C substantially enhanced the efficacy of 5-FU chemotherapy on 5-FU-resistant colon cancer cells. These results suggest that IRE1α-targeting might be a strategy to cope with drug resistance of colon cancer.

Chemotherapeutic drugs stimulate the release and recycling of extracellular vesicles to assist cancer cells in developing an urgent chemoresistance

Background

Chemotherapy is a widely used treatment for cancer. However, the development of acquired multidrug resistance (MDR) is a serious issue. Emerging evidence has shown that the extracellular vesicles (EVs) mediate MDR, but the underlying mechanism remains unclear, especially the effects of chemotherapeutic agents on this process.

Methods

Extracellular vesicles isolation was performed by differential centrifugation. The recipient cells that acquired ATP-binding cassette sub-family B member 1 (ABCB1) proteins were sorted out from co-cultures according to a stringent multi-parameter gating strategy by fluorescence-activated cell sorting (FACS). The transfer rate of ABCB1 was measured by flow cytometry. The xenograft tumor models in mice were established to evaluate the transfer of ABCB1 in vivo. Gene expression was detected by real-time PCR and Western blotting.

Results

Herein, we show that a transient exposure to chemotherapeutic agents can strikingly increase Rab8B-mediated release of extracellular vesicles (EVs) containing ABCB1 from drug-resistant cells, and accelerate these EVs to circulate back onto plasma membrane of sensitive tumor cells via the down-regulation of Rab5. Therefore, intercellular ABCB1 transfer is significantly enhanced; sensitive recipient cells acquire a rapid but unsustainable resistance to evade the cytotoxicity of chemotherapeutic agents. More fascinatingly, in the xenograft tumor models, chemotherapeutical drugs also locally or distantly increase the transfer of ABCB1 molecules. Furthermore, some Non-small-cell lung carcinoma (NSCLC) patients who are undergoing primary chemotherapy have a rapid increase of ABCB1 protein in their monocytes, and this is obviously associated with poor chemotherapeutic efficacy.

Conclusions

Chemotherapeutic agents stimulate the secretion and recycling of ABCB1-enriched EVs through the dysregulation of Rab8B and Rab5, leading to a significant increase of ABCB1 intercellular transfer, thus assisting sensitive cancer cells to develop an urgent resistant phenotype. Our findings provide a new molecular mechanism of how chemotherapeutic drugs assist sensitive cancer cells in acquiring an urgent resistance.