ATP-binding Cassette Subfamily C Member 4 Research Articles

Comparing ATPase activity of ATP-binding cassette subfamily C member 4, lamprey CFTR, and human CFTR using an antimony-phosphomolybdate assay.

Introduction: ATP-binding cassette (ABC) transporters use the hydrolysis of ATP to power the active transport of molecules, but paradoxically the cystic fibrosis transmembrane regulator (CFTR, ABCC7) forms an ion channel. We previously showed that ATP-binding cassette subfamily C member 4 (ABCC4) is the closest mammalian paralog to CFTR, compared to other ABC transporters. In addition, Lamprey CFTR (Lp-CFTR) is the oldest known CFTR ortholog and has unique structural and functional features compared to human CFTR (hCFTR). The availability of these evolutionarily distant orthologs gives us the opportunity to study the changes in ATPase activity that may be related to their disparate functions. Methods: We utilized the baculovirus expression system with Sf9 insect cells and made use of the highly sensitive antimony-phosphomolybdate assay for testing the ATPase activity of human ABCC4 (hABCC4), Lp-CFTR, and hCFTR under similar experimental conditions. This assay measures the production of inorganic phosphate (Pi) in the nanomolar range. Results: Crude plasma membranes were purified, and protein concentration, determined semi-quantitatively, of hABCC4, Lp-CFTR, and hCFTR ranged from 0.01 to 0.36μg/μL. No significant difference in expression level was found although hABCC4 trended toward the highest level. hABCC4 was activated by ATP with the equilibrium constant (Kd) 0.55 ± 0.28mM (n = 8). Estimated maximum ATPase rate (Vmax) for hABCC4 was about 0.2nmol/μg/min when the protein was activated with 1mM ATP at 37°C (n = 7). Estimated maximum ATPase rate for PKA-phosphorylated Lp-CFTR reached about half of hCFTR levels in the same conditions. Vmax for both Lp-CFTR and hCFTR were significantly increased in high PKA conditions compared to low PKA conditions. Maximum intrinsic ATPase rate of hABCC4 in the absence of substrate was twice that of hCFTR when activated in 1mM ATP. Conclusion: The findings here suggest that while both ABCC4 and hCFTR bear one consensus and one degenerate ATPase site, the hCFTR exhibited a reduced intrinsic ATPase activity. In addition, ATPase activity in the CFTR lineage increased from Lp-CFTR to hCFTR. Finally, the studies pave the way to purify hABCC4, Lp-CFTR, and hCFTR from Sf9 cells for their structural investigation, including by cryo-EM, and for studies of evolution in the ABC transporter superfamily.

ABCC4 suppresses glioblastoma progression and recurrence by restraining cGMP-PKG signalling.

Cyclic nucleotides are critical mediators of cellular signalling in glioblastoma. However, the clinical relevance and mechanisms of regulating cyclic nucleotides in glioblastoma progression and recurrence have yet to be thoroughly explored. In silico, mRNA, and protein level analyses identified the primary regulator of cyclic nucleotides in recurrent human glioblastoma. Lentiviral and pharmacological manipulations examined the functional impact of cyclic nucleotide signalling in human glioma cell lines and primary glioblastoma cells. An orthotopic xenograft mice model coupled with aspirin hydrogels verified the in vivo outcome of targeting cyclic nucleotide signalling. Elevated intracellular levels of cGMP, instead of cAMP, due to a lower substrate efflux from ATP-binding cassette sub-family C member 4 (ABCC4) is engaged in the recurrence of glioblastoma. ABCC4 gene expression is negatively associated with recurrence and overall survival outcomes in glioblastoma specimens. ABCC4 loss-of-function activates cGMP-PKG signalling, promoting malignancy in glioblastoma cells and xenografts. Hydrogels loaded with aspirin, inhibiting glioblastoma progression partly by upregulating ABCC4 expressions, augment the efficacy of standard-of-care therapies in orthotopic glioblastoma xenografts. ABCC4, repressing the cGMP-PKG signalling pathway, is a tumour suppressor in glioblastoma progression and recurrence. Aspirin hydrogels impede glioblastoma progression through ABCC4 restoration and constitute a viable translational approach.

Acquisition of drug resistance in endothelial cells by tumor-derived extracellular vesicles and cancer progression.

Angiogenesis by endothelial cells (ECs) is essential for tumor growth. Angiogenesis inhibitors are used in combination with anticancer drugs in many tumor types, but tumors eventually become resistant. Previously, the underlying mechanism for developing drug resistance was considered to be a change in the characteristics of tumor cells whereas ECs were thought to be genetically stable and do not contribute to drug resistance. However, tumor endothelial cells (TECs) have been shown to differ from normal endothelial cells (NECs) in that they exhibit chromosomal abnormalities, angiogenic potential, and drug resistance. Extracellular vesicles (EVs) secreted by tumor cells have recently attracted attention as a factor involved in the acquisition of such abnormalities. Various cells communicate with each other through EVs, and it has been reported that tumor-derived EVs act on other tumor cells or stromal cells to develop drug resistance. Drug-resistant tumor cells confer drug resistance to recipient cells by transporting mRNAs encoding ATP-binding cassette subfamily B member 1 (ABCB1) and ATP-binding cassette subfamily C member 1 (ABCC1) as well as miRNAs involved in signaling such as Akt, drug efflux transporters, and P-glycoprotein modulators via EVs. However, there are limited reports on the acquisition of drug resistance in ECs by tumor-derived EVs. Since drug resistance of ECs may induce tumor metastasis and support tumor cell proliferation, the mechanism underlying the development of resistance should be elucidated to find therapeutic application. This review provides insight into the acquisition of drug resistance in ECs via tumor EVs in the tumor microenvironment.

Macrophages enhance cisplatin resistance in gastric cancer through the transfer of circTEX2.

Cisplatin-based chemotherapy is often used in advanced gastric cancer (GC) treatment, yet resistance to cisplatin may lead to treatment failure. Mechanisms underlying cisplatin resistance remain unclear. Recent evidence highlighted the role of macrophages in cancer chemoresistance. Macrophage-derived exosomes were shown to facilitate intercellular communication. Here, we investigated the cisplatin resistance mechanism based on macrophage-derived exosomes in gastric cancer. Cell growth and apoptosis detection experiments revealed that M2-polarized macrophages increased the resistance of GC cells to cisplatin. qRT-PCR, RNAase R assay, actinomycin D assay and cell nucleo-cytoplasmic separation experiments confirmed the existence of circTEX2 in macrophage cytoplasm, with a higher expression level in M2 macrophages than that in M1 macrophages. Further experiments showed that circTEX2 acted as microRNA sponges for miR-145 and regulated the expression of ATP Binding Cassette Subfamily C Member 1 (ABCC1). Inhibition of the circTEX2/miR-145/ABCC1 axis blocked the cisplatin resistance of gastric cancer induced by M2 macrophages, as evidenced by invitro and invivo experiments. In conclusion, our research suggests that the exosomal transfer of M2 macrophage-derived circTEX2 enhances cisplatin resistance in gastric cancer through miR-145/ABCC1. Additionally, communication between macrophages and cancer cells via exosomes may be a promising therapeutic target for the treatment of cisplatin-resistant gastric cancer.

Evaluation of the FDA-approved kinase inhibitors to uncover the potential repurposing candidates targeting ABC transporters in multidrug-resistant cancer cells: an in silico approach

Multiple drug resistance (MDR) is characterized by the resistance of cancer cells to a broad spectrum of anticancer drugs. The main mechanism underlying the MDR phenotype is the overexpression of ATP-binding cassette (ABC) transporters by promoting active drug efflux from cancer cells. Some small-molecule protein kinase inhibitors have been found to overcome MDR by inhibiting ABC transporters as substrates or modulators. This study investigated the chemical activity of 58 FDA-approved anticancer kinase inhibitors against three multidrug resistance-related proteins. The studied proteins are ATP-Binding Cassette Sub-Family B Member 1 (ABCB1), ATP-Binding Cassette Subfamily C Member 1 (ABCC1), and ATP-binding cassette superfamily G member 2 (ABCG2). The drug-binding domain and ATP binding sites of the proteins were considered the kinase inhibitors’ probable target. High-throughput virtual screening and molecular docking were employed to find the hit drugs, and the drugs with the highest binding affinity were further evaluated using the molecular dynamics (MD) simulation. The virtual screening revealed that several kinase inhibitors could be considered potential inhibitors of ABCB1, ABCC1, and ABCG2, among which larotrectinib, entrectinib, and infigratinib showed the highest binding affinity, respectively. Based on the obtained results from MD simulation, these drugs can form strong interactions with the essential residues of the target proteins. In silico investigation revealed that larotrectinib, entrectinib, and infigratinib can target the key residues of the studied proteins. Therefore, these approved kinase inhibitors could be considered potential therapies for MDR cancers by targeting these transporters. Communicated by Ramaswamy H. Sarma

ABCC4 is a PGE2 efflux transporter in the ovarian follicle: A mediator of ovulation and a potential non-hormonal contraceptive target.

The role of prostaglandins (PGs) in the ovulatory process is known. However, the role of the ATP binding cassette subfamily C member 4 (ABCC4), transmembrane PG carrier protein, in ovulation remains unknown. We report herein that ABCC4 expression is significantly upregulated in preovulatory human granulosa cells (GCs). We found that PGE2 efflux in cultured human GCs is mediated by ABCC4 thus regulating its extracellular concentration. The ABCC4 inhibitor probenecid demonstrated effective blocking of ovulation and affects key ovulatory genes in female mice in vivo. We postulate that the reduction in PGE2 efflux caused by the inhibition of ABCC4 activity in GCs decreases the extracellular concentration of PGE2 and its ovulatory effect. Treatment of female mice with low dose of probenecid as well as with the PTGS inhibitor indomethacin or Meloxicam synergistically blocks ovulation. These results support the hypothesis that ABCC4 has an important role in ovulation and might be a potential target for non-hormonal contraception, especially in combination with PGE2 synthesis inhibitors. These findings may fill the gap in understanding the role of ABCC4 in PGE2 signaling, enhance the understanding of ovulatory disorders, and facilitate the treatment and control of fertility.

CircSETDB1 contributes to paclitaxel resistance of ovarian cancer cells by sponging miR-508-3p and regulating ABCC1 expression

Ovarian cancer is a gynecological tumor with a poor prognosis. The chemotherapy failure and recurrence induced by paclitaxel (Ptx) resistance are the main reason for the failure of ovarian cancer treatment. In this study, we aimed to explore the role of circular RNA (circRNA) in the regulation of Ptx resistance in ovarian cancer. Quantitative reverse transcription PCR was performed to detect the expression of circRNA SET domain bifurcated histone lysine methyltransferase 1 (circSETDB1), microRNA (miR)-508-3p and ATP-binding cassette subfamily C member 1 ( ABCC1 ) mRNA. The effects of circSETDB1 on Ptx resistance were explored by cell counting kit-8, 5-ethynyl-2'-deoxyuridine, and flow cytometry experiments in vitro . The protein level was assessed by western blot. Dual-luciferase reporter and RNA pull-down assays were carried out to confirm the interactions among circSETDB1, miR-508-3p, and ABCC1 . Xenograft tumor experiment was performed to investigate the effect of circSETDB1 on Ptx resistance in vivo . CircSETDB1 was highly expressed in Ptx-resistant ovarian cancer. CircSETDB1 knockdown inhibited cell proliferation viability, half maximal inhibitory concentration value of Ptx, cell cycle progression, and induced cell apoptosis in Ptx-resistant ovarian cancer cells. miR-508-3p was a target of circSETDB1, and inhibition of miR-508-3p overturned the effects of circSETDB1 knockdown on the Ptx resistance of ovarian cancer cells. miR-508-5p could bind to ABCC1 . Overexpression of ABCC1 reversed the effects of circSETDB1 knockdown on the Ptx resistance of ovarian cancer cells. CircSETDB1 knockdown also enhanced Ptx sensitivity in vivo . In conclusion, circSETDB1 regulated Ptx resistance of ovarian cancer by targeting miR-508-3p/ ABCC1 axis.

Effects of 4-n-nonylphenol in liver of male and female viviparous fish (Poecilia vivipara)

4-n-Nonylphenol (NP) is one of the most toxic alkylphenols found in the environment. To evaluate the transcriptional effects of NP in the viviparous fish Poecilia vivipara, a hepatic transcriptome and qPCR analysis of genes were carried out. Guppies separated by sex were injected with two doses of NP (15 μg/g and 150 μg/g) or peanut oil (control). After 24 h, analysis of transcriptional level of Aryl Hydrocarbon Receptor (AhR), Estrogen Nuclear Receptor Alpha (ESR1), Pregnane X Receptor (PXR), Cytochromes P450 (CYP1A, CYP2K1 and CYP3A30), Glutathione S-transferase A3 and Mu 3 (GSTa3 and GSTMu3), SRY-Box Transcription Factor 9 (SOX9), Vitellogenin-1 (VIT), ATP Binding Cassette Subfamily C Member 1 (ABCC1), Multidrug Resistance-Associated Protein 2 (MRP2) and UDP Glucuronosyltransferase Family 1 Member A1 (UGT1A1) was evaluated. 205,046 transcripts were assembled and protein prediction resulted in 203,147 predicted peptides. In females, no significant changes were detected in the transcription of some phase I biotransformation and ABC transporter genes. AhR, PXR, GSTa3 and SOX9 genes where higher in the lower dose group (15 μg/g) compared to control. In male fish, no changes were observed in the transcript levels of the nuclear receptors, in endocrine disruption and phase I biotransformation genes. GSTa3 showed lower transcription in fish treated with both doses. ABCC1 was higher in guppies treated with the lower dose while MRP2 showed less transcripts. This short-term and low-dose exposure to NP caused changes that could serve as early indicators of deleterious processes. These results indicate P. vivipara as a good sentinel in biomonitoring programs.

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

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. 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. 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. 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.

The glucocorticoid transporter ATP-binding cassette subfamily C member 1 (ABCC1) influences adiposity, glucose homeostasis and insulin sensitivity in male mice

The glucocorticoid transporter ATP-binding cassette subfamily C member 1 (ABCC1) influences adiposity, glucose homeostasis and insulin sensitivity in male mice

LncRNA SNHG11 enhances bevacizumab resistance in colorectal cancer by mediating miR-1207-5p/ABCC1 axis.

Long noncoding RNAs (lncRNAs) have been reported to serve as vital regulators in the chemoresistance of human cancers, including colorectal cancer (CRC). In this study, we aimed to explore the functions of lncRNA small nucleolar RNA host gene 11 (SNHG11) in the resistance of CRC to bevacizumab. Quantitative real-time PCR, western blot assay or immunohistochemistry assay were performed to examine the expression of SNHG11, microRNA-1207-5p (miR-1207-5p), ATP binding cassette subfamily C member 1 (ABCC1) and Ki67. Cell Counting Kit-8 assay was conducted to evaluate bevacizumab resistance and cell viability. 5'-ethynyl-2'-deoxyuridine analysis, flow cytometry analysis and wound-healing assay were conducted for cell proliferation, apoptosis and migration, respectively. Dual-luciferase reporter assay and RNA immunoprecipitation assay were employed to analyze the relations among SNHG11, miR-1207-5p and ABCC1. Murine xenograft model assay was employed to analyze bevacizumab resistance in vivo. The exosomes were observed under transmission electron microscopy. SNHG11 was overexpressed in bevacizumab-resistant CRC tissues and cells. Knockdown of SNHG11 restrained bevacizumab resistance, repressed cell proliferation and migration, and promoted apoptosis in bevacizumab-resistant CRC cells. MiR-1207-5p served as the target of SNHG11 and SNHG11 regulated bevacizumab resistance by targeting miR-1207-5p. ABCC1 was the target gene of miR-1207-5p. Overexpression of miR-1207-5p inhibited bevacizumab resistance and cell progression in bevacizumab-resistant CRC cells, with ABCC1 elevation abrogated the impacts. SNHG11 silencing repressed bevacizumab resistance in vivo. In addition, exosomal SNHG11 was upregulated in bevacizumab-resistant CRC cells. SNHG11 contributes to bevacizumab resistance in CRC depending on the modulation of miR-1207-5p and ABCC1.

Circ_0048856 competes with ABCC1 for miR-193a-5p/miR-98-5p binding sites to promote the cisplatin resistance and tumorigenesis in lung cancer

Although cisplatin (DDP)-based therapy is the most predominant chemotherapeutic strategy used for lung cancer, drug resistance usually occurs after several cycle use of it. Circular RNAs (circRNAs) are found to be involved in the chemoresistance in lung cancer. Hence, this study aimed to clarify the role and mechanism of circ_0048856 in lung cancer tumorigenesis and DDP resistance. The levels of circ_0048856, miR-193a-5p, miR-98-5p and ABCC1 (ATP Binding Cassette Subfamily C Member 1) were determined by qRT-PCR and western blotting. In vitro assays were conducted by cell counting kit-8 assay, 5-ethynyl-2’-deoxyuridine (EDU) assay, flow cytometry and transwell assay, respectively. The binding interaction was verified using dual-luciferase reporter assay and RIP assay. In vivo experiment was performed by the establishment of murine xenograft model. Circ_0048856 was highly expressed in DDP-resistant lung cancer tissues and cells. Functionally, circ_0048856 silencing re-sensitized DDP-resistant lung cancer cells to DDP, as well as suppressed cell growth and invasion in lung cancer in vitro and in vivo. Mechanistically, circ_0048856 acted as the sponge for miR-193a-5p or miR-98-5p, which targeted ABCC1. Furthermore, rescue experiments showed that inhibition of miR-193a-5p or miR-98-5p reversed the effects of circ_0048856 knockdown on lung cancer cells. Besides that, overexpression of miR-193a-5p or miR-98-5p suppressed cell tumorigenesis and reduced DDP resistance in lung cancer, which were attenuated by ABCC1 up-regulation. Circ_0048856 knockdown suppressed tumor growth and reduced DDP resistance in lung cancer by miR-193a-5p/ABCC1 or miR-98-5p/ABCC1 axis, indicating a novel strategy for efficient application of DDP in lung cancer.

SUMOylation of methyltransferase-like 3 facilitates colorectal cancer progression by promoting circ_0000677 in an m6 A-dependent manner.

Colorectal cancer (CRC) is one of the major health issues in the world. Circ_0000677 has been shown to be upregulated in CRC with unclarified function and mechanism. Methyltransferase-like 3 (METTL3) acts as a regulator for gene expression via the mechanism of RNA N6 -methyladenosine (m6 A) in different types of cancer, which is under the control of SUMO1-based SUMOylation. We aim to investigate their roles in CRC progression. Quantitative real-time polymerase chain reaction and Western blot were used to detect the expressions of METTL3, circ_0000677, and ATP binding cassette subfamily c member 1(ABCC1) in CRC patients' tissues and cell lines. The functions of ABCC1 and circ_0000677 in CRC were studied by manipulating their level via knocking down or overexpression. RNA pull-down and RNA immunoprecipitation assays were performed to identify the specific binding of target genes. The biological function of SUMOylation of METTL3 was investigated in vivo by xenograft mice tumor model. METTL3, circ_0000677, and ABCC1 were upregulated in CRC patients' samples and cell lines. Circ_0000677 positively regulates CRC cell proliferation and drug resistance via affecting ABCC1 expression. METTL3 facilitated circ_0000677 level via m6 A modification. METTL3 was regulated by SUMO1-mediated SUMOylation in CRC. Mutation of METTL3-K459 could suppress tumor growth in vivo via regulating circ_0000677/ABCC1 axis. Overall, our study revealed that circ_0000677 and its downstream target ABCC1 were upregulated in CRC cells, induced by the METTL3-mediated m6 A modification of circ_0000677 and SUMO1-mediated SUMOylation of METTL3. This work provided a new strategy for the therapeutic treatment of CRC.

NUDT15 is a key genetic factor for prediction of hematotoxicity in pediatric patients who received a standard low dosage regimen of 6-mercaptopurine

6-Mercaptopurine (6-MP) is commonly used for treatment of acute lymphoblastic leukemia (ALL). The incidence of hematotoxicity caused by this drug is quite high in Asians even using a standard low dosage regimen. The present study was aimed to elucidate the impact of thiopurine S-methyltransferase (TPMT), a nucleoside diphosphate-linked moiety X-type motif 15 (NUDT15), inosine triphosphatase (ITPA) and ATP Binding Cassette Subfamily C Member 4 (ABCC4) polymorphisms on hematotoxicity in pediatric patients who received a standard low starting dose of 6-MP. One hundred and sixty-nine pediatric patients were enrolled and their genotypes were determined. Patients who carried NUDT15∗3 and NUDT15∗2 genotypes were at a 10–15 fold higher risk of severe neutropenia than those of the wild-type during the early months of the maintenance phase. Risk of neutropenia was not significantly increased in patients with other NUDT15 variants as well as in patients with TPMT, ITPA or ABCC4 variants. These results suggest that NUDT15 polymorphisms particularly, NUDT15∗3 and NUDT15∗2, play major roles in 6-MP-induced severe hematotoxicity even when using a standard low dosage of 6-MP and genotyping of these variants is necessary in order to obtain precise tolerance doses and avoid severe hematotoxicity in pediatric patients.

ATP-Binding Cassette Subfamily C Member 1 (ABCC1) influences adiposity, glucose homeostasis and insulin sensitivity

ATP-Binding Cassette Subfamily C Member 1 (ABCC1) influences adiposity, glucose homeostasis and insulin sensitivity

Withdrawn: 'Circular RNA PTGR1 regulates 5-FU resistance and development of hepatocellular carcinoma cells by modulating miR-129-5p/ABCC1 axis' by, Xiuxiu Li, and Ti Zhang.

The above article from Cell Biology International, published online as Accepted Article on May 18, 2021, in Wiley Online Library (https://doi.org/10.1002/cbin.11635) has been withdrawn by agreement among the Journal Editor-in-Chief Sergio Schenkmann, and John Wiley & Sons Ltd. on behalf of the International Federation for Cell Biology. The withdrawal has been agreed after a detailed investigation. Several flaws and inconsistencies between results presented and experimental methods described were found, the editors consider the conclusions of this article to be invalid. The authors did not respond when asked to comment on these inconsistencies.

Identification of circ_0058357 as a regulator in non-small cell lung cancer cells resistant to cisplatin by miR-361-3p/ABCC1 axis.

BackgroundDrug resistance is a major clinical drawback behind the failure of chemotherapy in non‐small cell lung cancer (NSCLC). In this study, we undertook to identify the precise role of circular RNA (circRNA) circ_0058357 in the functional properties of DDP‐resistant NSCLC cells.MethodsCirc_0058357, miR‐361‐3p and ATP‐binding cassette (ABC) subfamily C member 1 (ABCC1) were quantified by qRT‐PCR and western blot. Cell survival and viability were gauged by MTT assay. Cell proliferation, apoptosis, invasion and migration were measured by EdU, flow cytometry, transwell and wound‐healing assays, respectively. The direct relationship between miR‐361‐3p and circ_0058357 or ABCC1 was validated by dual‐luciferase reporter assay.ResultsOur data showed that circ_0058357 was highly expressed in DDP‐resistant NSCLC tissues and cells. Inhibition of circ_0058357 repressed cell growth, invasion, migration, and promoted DDP sensitivity and cell apoptosis of H1299/DDP and A549/DDP cells in vitro. Moreover, inhibition of circ_0058357 diminished the growth of A549/DDP cells and sensitized them to the cytotoxic effect of DDP in vivo. Mechanistically, circ_0058357 contained a miR‐361‐3p binding site and miR‐361‐3p was identified as a molecular mediator of circ_0058357 regulation. MiR‐361‐3p suppressed ABCC1 expression by binding to ABCC1 3′UTR, and miR‐361‐3p‐mediated inhibition of ABCC1 affected the growth, invasion, migration, apoptosis and DDP sensitivity of H1299/DDP and A549/DDP cells. Furthermore, circ_0058357 regulated ABCC1 expression by competitively binding to shared miR‐361‐3p.ConclusionsOur findings identified that inhibition of circ_0058357 suppresses the growth and metastasis of H1299/DDP and A549/DDP cells and sensitizes them to DDP therapy partially by targeting the miR‐361‐3p/ABCC1 axis.

MiR-9-5p Mediates ABCC1 to Elevate the Sensitivity of Glioma Cells to Temozolomide.

Chemotherapy combined with surgery is an important clinical treatment for glioma, but endogenous or acquired temozolomide (TMZ) resistance can lead to poor prognosis. microRNA (miR)-9-5p acts in biological function of glioma, but the drug resistance of miR-9-5p in glioma is under exploration. The study intended to test the molecular mechanism of miR-9-5p in glioma cells. MTT assay was applied to investigate the chemosensitivity enhancement of miR-9-5p on TMZ in glioma cells U87-TMZ and U251-TMZ, and in vivo experiments confirmed its role on tumor growth in nude mice. The results of double luciferase reporter gene assay, qRT-PCR and WB indicated that miR-9-5p directly targeted ABCC1 (ATP binding cassette subfamily C member 1) to reduce its expressions. MTT and flow cytometry indicated that elevation of miR-9-5p or down-regulation of ABCC1 could inhibit proliferation-induced apoptosis of drug-resistant cells, and the decrease of miR-9-5p could reverse the reduction of ABCC1 on proliferation-induced apoptosis of drug-resistant cells. In vivo experiments showed that miR-9-5p could promote the anti-tumor role of TMZ. To sum up, the increase of miR-9-5p directly targets ABCC1 and may make glioma cells sensitive to TMZ.

Circular RNAcirc_0076305 Promotes Cisplatin (DDP) Resistance of Non-Small Cell Lung Cancer Cells by Regulating ABCC1 Through miR-186-5p.

Background: Lung cancer is a social problem of increasing concern, and non-small cell lung cancer (NSCLC) accounts for 80%-85% incidence of lung cancer. Cisplatin (DDP) is reported as a first-line chemotherapy drug for NSCLC, but the resistance has became a main obstacle for NSCLC treatment. The high level of circular RNA circ_0076305 was related to the DDP resistance in NSCLC. However, the mechanism of circ_0076305 remains unclear in DDP resistance of NSCLC. Materials and Methods: Exosomes were detected by a transmission electron microscope and nanoparticle tracking analysis. The protein levels of CD63, CD81, P-glycoprotein (P-gp), Lung resistance-related protein, and ATP-binding cassette subfamily C member 1 (ABCC1) were examined by Western blot assay. Circ_0076305, microRNA-186-5p (miR-186-5p), and ABCC1 levels were tested by real-time quantitative polymerase chain reaction. DDP resistance was examined by 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2-H-tetrazolium bromide assay. The binding relationship between miR-186-5p and circ_0076305 or ABCC1 was predicted by circRNA interactome or starBase, and then verified by dual-luciferase reporter and RNA immunoprecipitation assays. The effect of circ_0076305 on DDP resistance in NSCLC was examined by xenograft tumor model in vivo. Results: Circ_0076305 was increased in NSCLC cell-derived exosomes, DDP-resistant NSCLC tissues and cells. Circ_0076305 knockdown elevated DDP sensitivity in vitro. Mechanically, circ_0076305 enhanced ABCC1 expression through sponging miR-186-5p, thus regulating DDP resistance of NSCLC. Furthermore, circ_0076305 silencing improved DDP sensitivity of NSCLC in vivo. Conclusion: The results from this study disclosed that circ_0076305 knockdown improved DDP sensitivity by the miR-186-5p/ABCC1 axis in NSCLC, hinting a potential circRNA-targeted therapy for NSCLC.

Synergistic effects of autophagy inhibitors combined with cisplatin against cisplatin-resistant nasopharyngeal cancer cells.

This study explored the synergistic effects of autophagy inhibitors combined with cisplatin against cisplatin-resistant nasopharyngeal cancer cells by treating HNE-1 and cisplatin (diamminedichloroplatinum; DDP)-resistant HNE1/DDP nasopharyngeal cancer cell lines with DDP, autophagy inhibitors, or a combination of autophagy inhibitors and DDP. Cell viability was determined via MTT (colorimetric) and colony-forming assays, and the rate of apoptosis was determined using propidium iodide (PI) and annexin V double-staining. The expressions of proteins were determined by Western blotting. For our in-vivo studies, a murine xenograft model was established to evaluate the anti-tumor effects of the combination of autophagy inhibitor and DDP. The results showed that treatment with DDP increased the expressions of ATP-binding cassette sub-family B member 1 (ABCB1), ATP Binding Cassette Subfamily C Member 1 (ABCC1), and P-glycoprotein 1 (P-gp) in the HNE1/DDP cell lines. Treatment with chloroquine decreased the expression levels of ABCB1, ABCC1, and P-gp, and increased the formation of LC3-II and the expression levels of p62 in the HNE1/DDP cells. Additionally, the combination of autophagy inhibitors and DDP produced a synergistic effect on DDP-induced cell death and apoptosis. Furthermore, the combination of the autophagy inhibitor and DDP showed significant anti-tumor effects in the xenograft mouse model. In summary, autophagy inhibitors show synergistic anti-tumor effects with DDP in vitro against DDP-resistant nasopharyngeal cancer cells and in vivo in our xenograft murine model.