Hypoxia-inducible factor-1α can reverse the Adriamycin resistance of breast cancer adjuvant chemotherapy by upregulating transferrin receptor and activating ferroptosis.

Breast cancer is a common malignant tumor in women. Ferroptosis, a programmed cell death pathway, is closely associated with breast cancer and its resistance. The transferrin receptor (TFRC) is a key factor in ferroptosis, playing a crucial role in intracellular iron accumulation and the occurrence of ferroptosis. This study investigates the influence and significance of TFRC and its upstream transcription factor hypoxia-inducible factor-1α (HIF1α) on the efficacy of neoadjuvant therapy in breast cancer. The differential gene obtained from clinical samples through genetic sequencing is TFRC. Bioinformatics analysis revealed that TFRC expression in breast cancer was significantly greater in breast cancer tissues than in normal tissues, but significantly downregulated in Adriamycin (ADR)-resistant tissues. Iron-responsive element-binding protein 2 (IREB2) interacts with TFRC and participates in ferroptosis. HIF1α, an upstream transcription factor, positively regulates TFRC. Experimental results indicated higher levels of ferroptosis markers in breast cancer tissue than in normal tissue. In the TAC neoadjuvant regimen-sensitive group, iron ion (Fe2+) and malondialdehyde (MDA) levels were greater than those in the resistant group (all p < .05). Expression levels of TFRC, IREB2, FTH1, and HIF1α were higher in breast cancer tissue compared to normal tissue. Additionally, the expression of the TFRC protein in the TAC neoadjuvant regimen-sensitive group was significantly higher than that in the resistant group (all p < .05), while the difference in the level of expression of IREB2 and FTH1 between the sensitive and resistant groups was not significant (p > .05). The dual-luciferase assay revealed that HIF1α acts as an upstream transcription factor of TFRC (p < .05). Overexpression of HIF1α in ADR-resistant breast cancer cells increased TFRC, Fe2+, and MDA content. After ADR treatment, the cell survival rate decreased significantly, and ferroptosis could be reversed by the combined application of Fer-1 (all p < .05). In conclusion, ferroptosis and chemotherapy resistance are correlated in breast cancer. TFRC is a key regulatory factor influenced by HIF1α and is associated with chemotherapy resistance. Upregulating HIF1α in resistant cells may reverse resistance by activating ferroptosis through TFRC overexpression.

Linc-ROR drive adriamycin resistance by targeting AP-2α/Wnt/ß-catenin axis in hepatocellular carcinoma.

Adriamycin is widely used as a chemotherapeutic strategy for advanced hepatocellular carcinoma (HCC). However, the clinical response was disappointing because of the acquired drug resistance with long-term usage. Revealing the underlying mechanism could provide promising therapeutics for the drug-resistant patients. The recently identified linc-ROR (long intergenic non-protein-coding RNA, regulator of reprogramming) has been found to be an oncogene in various cancers, and it also demonstrated to mediate drug resistance and metastasis. We thereby wonder whether this lincRNA could mediate adriamycin chemoresistance in HCC. In this study, linc-ROR was found to be upregulated in adriamycin-resistant HCC cells. And its overexpression accelerated epithelial-mesenchymal transition (EMT) program and adriamycin resistance. Conversely, its silence suppressed EMT and made HCC cells sensitize to adriamycin in vitro and in vivo. Further investigation revealed that linc-ROR physically interacted with AP-2α, mediated its stability by a post-translational modification manner, and sequentially activated Wnt/ß-catenin pathway. Furthermore, linc-ROR expression was positively associated with ß-catenin expression in human clinical specimens. Taken together, linc-ROR promoted tumorigenesis and adriamycin resistance in HCC via a linc-ROR/AP-2α/Wnt/ß-catenin axis, which could be developed as a potential therapeutic target for the adriamycin-resistant patients.

[Echinacoside hampers malignant progression of breast cancer MCF-7 cells by modulating AKR1B10/ERK signal transduction].

This study analyzes the impact of echinacoside(ECH) in the proliferation, metastasis and adriamycin(ADR) resistance of breast cancer(BC) MCF-7 cells via the modulation of aldo-keto reductase family 1 member 10(AKR1B10)/extracellular signal-regulated kinase(ERK) pathway. The chemical structure of ECH was firstly confirmed. MCF-7 cells were treated with different concentration(0, 10, 20, 40 µg·mL~(-1)) of ECH for 48 h. Western blot was used to analyze expression of AKR1B10/ERK pathway-associated proteins and cell counting kit-8(CCK-8) assay to determine cell viability. MCF-7 cells were collected and classified into control group, ECH group, ECH + Ov-NC group, and ECH + Ov-AKR1B10 group. Then Western blot was employed to analyze the expression of AKR1B10/ERK pathway-associated proteins. CCK-8 and 5-ethynyl-2'-deoxyuridine(EdU) assay were used to examine cell proliferation. Cell migration was appraised with scratch assay, Transwell assay, and Western blot. Eventually, MCF-7 cells were treated with ADR for 48 h to induce ADR resistance. Cell viability was tested by CCK-8 assay and cell apoptosis was estimated based on terminal-deoxynucleoitidyl transferase mediated nick end labeling(TUNEL) assay and Western blot. Based on Protein Data Bank(PDB) and molecular docking, the binding affinity of ECH to AKR1B10 was assessed. Various doses of ECH decreased the expression of AKR1B10/ERK pathway-associated proteins in a dose-dependent manner and declined cell viability compared with the control group. Compared with the control group, 40 µg·mL~(-1) ECH blocked the AKR1B10/ERK pathway in MCF-7 cells and inhibited the proliferation, metastasis and ADR resistance of the cells. Compared with the ECH + Ov-NC group, ECH + Ov-AKR1B10 group showed the recovery of some biological behaviors of MCF-7 cells. ECH also targeted AKR1B10. ECH can inhibit the proliferation, metastasis, and ADR resistance of BC cells by blocking AKR1B10/ERK pathway.

Effect of m6A methyltransferase METTL3 -mediated MALAT1/E2F1/AGR2 axis on adriamycin resistance in breast cancer.

N6-methyladenosine (m6A) methyltransferase METTL3 has been implicated in carcinogenesis, which may be associated the overexpression of MALAT1. However, the downstream mechanics actions remain largely unknown. This study intends to probe the downstream mechanism of the N6-methyladenosine (m6 A) methyltransferase METTL3 and MALAT1 in adriamycin resistance in breast cancer. Through Bioinformatics databases lncMAP, TCGA and GTEx, we predicted the downstream transcription factors E2F1 and AGR2 of MALAT1 in breast cancer. The Cancer Genome Atlas and Genotype-Tissue Expression (GTEx) databases were used to screen the downstream target genes of MALAT1. MeRIP-qPCR was used to detect the m6 A level of MALAT1 in cells. RIP was used to detect the binding between MALAT1 and E2F1, and chromatin immunoprecipitation (ChIP) for the binding of E2F1 to AGR2 promoter. Cell Counting Kit-8 and colony formation assays were used to detect cell viability. Transwell was used to detect cell invasion. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) and western blot were used to detect the expression of related genes and proteins. A nude mouse xenograft tumor model was established to observe the effect of METTL3 on adriamycin resistance of breast cancer. The total survival of mice after exogenous gene silencing was analyzed by the Kaplan-Meier method. METTL3 was highly expressed in adriamycin-resistant breast cancer cells. METTL3 promotes adriamycin resistance in breast cancer cells. METTL3 mediates the expression of MALAT1 in adriamycin-resistant breast cancer through m6 A. MALAT1 increases adriamycin resistance in breast cancer cells by recruiting E2F1 to activate AGR2 transcription. METTL3 can regulate the expression of MALAT1 through m6 A, mediate the E2F1/AGR2 axis, and promote the adriamycin resistance of breast cancer. METTL3 may modify MALAT1 protein through m6 A, recruit E2F1 and activate downstream AGR2 expression, thus promoting adriamycin resistance in breast cancer.

PLAC8 promotes adriamycin resistance via blocking autophagy in breast cancer.

Adriamycin (ADM) is currently one of the most effective chemotherapeutic agents in breast cancer treatment. However, growing resistance to ADM could lead to treatment failure and poor outcome. PLAC8 was reported as a novel highly conserved protein and functioned as an oncogene or tumour suppressor in various tumours. Here, we found higher PLAC8 expression was correlated with worse outcome and aggressive phenotype in breast cancer. Breast cancer patients with higher PLAC8 expression showed potential ADM resistance. In vitro experiments further confirmed that PLAC8 inhibited by siRNA or enforced overexpression by infecting pcDNA3.1(C)-PLAC8 plasmid correspondingly decreased or increased ADM resistance. Subsequently, we demonstrated that ectopic PLAC8 expression in MCF-7/ADMR cell blocked the accumulation of the autophagy-associated protein LC3 and resulted in cellular accumulation of p62. Rapamycin-triggered autophagy significantly increased cell response to ADM, while the autophagy inhibitor 3-MA enhanced ADM resistance. 3-MA and PLAC8 could synergistically cause ADM resistance via blocking the autophagy process. Additionally, the down-regulation of p62 by siRNA attenuated the activation of autophagy and PLAC8 expression in breast cancer cells. Thus, our findings suggest that PLAC8, through the participation of p62, inhibits autophagy and consequently results in ADM resistance in breast cancer. PLAC8/p62 pathway may act as novel therapeutic targets in breast cancer treatment and has potential clinical application in overcoming ADM resistance.

Ursolic acid reduces Adriamycin resistance of human ovarian cancer cells through promoting the HuR translocation from cytoplasm to nucleus.

Ursolic acid (UA) has been shown to suppress various tumor progression, however, its roles in Adriamycin resistance of human ovarian cancer (OC) cells are still unclear. This work aims to investigate the effects of UA on the Adriamycin resistance of human OC cells. Here, we constructed Adriamycin-resistant OC SKOV3-Adr cells and found that UA attenuated Adriamycin resistance in SKOV3-Adr cells. Additionally, UA enhanced Adriamycin sensitivity in the parental SKOV3 and another OC cell line A2780 cells. Mechanistic studies showed that HuR mRNA level was similar between SKOV3 and SKOV3-Adr cells, but the cytoplasmic expression of HuR protein was increased in SKOV3-Adr cells compared with that in SKOV3 cells, and subsequently enhancing the mRNA stability of multidrug resistance gene 1 (MDR1). Moreover, UA had no effects on HuR expression, but promoted the cytoplasm-nucleus translocation of HuR protein, decreased MDR1 mRNA stability and thus reduced MDR1 expression. Furthermore, overexpression of MDR1 rescued the effects of UA on Adriamycin resistance and sensitivity. This work reveals a novel HuR/MDR1 axis responsible for UA-mediated attenuation on Adriamycin resistance in OC cells.

Effect of nucleolin on adriamycin resistance via the regulation of B-cell lymphoma 2 expression in Burkitt's lymphoma cells.

Nucleolin (NCL, C23) is an important nucleocytoplasmic multifunctional protein. Due to its multifaceted profile and high expression in cancer, NCL is considered to be a marker of drug resistance associated with chemotherapy. However, the biochemical mechanisms in which NCL suppresses drug sensitivity in several cancers have yet to be fully elucidated. This study aims to explore the effect of NCL on drug sensitivity and its potential mechanism in CA46 Burkitt's lymphoma (BL) cells. CA46 BL cells were transfected with lentiviruses carrying the NCL gene (CA46-NCL-overexpression, CA46-NCL-OE), or shRNA sequences that target the endogenous NCL gene (CA46-NCL-knockdown, CA46-NCL-KD). Adriamycin (ADM) IC50 levels for CA46-NCL-overexpressed (OE), CA46-NCL-OE control (OEC), CA46-NCL-knockdown (KD), and CA46-NCL-KD control (KDC) cells were 0.68 ± 0.06 µg/ml, 0.68 ± 0.06 µg/ml, 0.68 ± 0.06 µg/ml, and 0.30 ± 0.04 µg/ml, respectively. Apoptosis rates were significantly increased following NCL KD, whereas the opposite effect was noted in OE cells. A significant reduction of B-cell lymphoma 2 (Bcl-2) mRNA and protein levels in KD cells was observed, while OE cells displayed the opposite effect. The stability of Bcl-2 mRNA was influenced by NCL levels, the half-life of which was extended after NCL-OE, whereas it was reduced in KD cells. Finally, results of RNA-immunoprecipitation assays indicated that NCL could bind to Bcl-2 mRNA in CA46 cells. Taken together, these results suggested that NCL could mediate Bcl-2 expression and stability, and thus enhance ADM resistance in CA46 BL cells.

microRNA-129-5p suppresses Adriamycin resistance in breast cancer by targeting SOX2.

Adriamycin resistance is closely related to therapeutic efficacy in breast cancer patients and their prognosis. Increasing evidence has suggested that miRNA functions in Adriamycin resistance in various types of cancer. microRNA-129-5p (miR-129-5p) has been considered a tumor-suppressive miRNA in several cancers, but its potential role in Adriamycin resistance in breast cancer has not been fully elucidate. By qRT-PCR assay, we revealed that the expression of miR-129-5p was significantly decreased in breast cancer tissues and Adriamycin-resistant breast cancer cells (MDA-MB-231/ADR, MCF-7/ADR). CCK-8, colony formation, wound healing, Transwell invasion, and flow cytometric profiles were examined to determine the influence of miR-129-5p on Adriamycin-resistant breast cancer in vitro. The upregulation of miR-129-5p decreased the IC50 concentration of Adriamycin and invasion and promoted the apoptosis of MDA-MB-231/ADR cells in the presence of Adriamycin, whereas the upregulation of Sex-Determining Region Y-Box 2 (SOX2) reversed these effects. A luciferase reporter assay confirmed the binding of miR-129-5p to the 3'UTR of SOX2. Collectively, it was suggested that miR-129-5p suppresses Adriamycin resistance in breast cancer by directly targeting SOX2.

Effects of the Combination of Gliotoxin and Adriamycin on the Adriamycin-Resistant Non-Small-Cell Lung Cancer A549 Cell Line.

Acquired drug resistance constitutes an enormous hurdle in cancer treatment, and the search for effective compounds against resistant cancer is still advancing. Marine organisms are a promising natural resource for the discovery and development of anticancer agents. In this study, we examined whether gliotoxin (GTX), a secondary metabolite isolated from marine-derived Aspergillus fumigatus, inhibits the growth of adriamycin (ADR)-resistant non-small-cell lung cancer (NSCLC) cell lines A549/ADR. We investigated the effects of GTX on A549/ADR cell viability with the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and the induction of apoptosis in A549/ADR cells treated with GTX via fluorescence-activated cell sorting analysis, Hoechst staining, annexin V/propidium iodide staining, tetraethylbenzimidazolylcarbocyanine iodide (JC-1) staining, and western blotting. We found that GTX induced apoptosis in A549/ADR cells through the mitochondria-dependent pathway by disrupting mitochondrial membrane potential and activating p53, thereby increasing the expression levels of p21, p53 upregulated modulator of apoptosis (PUMA), Bax, cleaved poly (ADP-ribose) polymerase (PARP), and cleaved caspase-9. More importantly, we discovered that GTX works in conjunction with ADR to exert combinational effects on A549/ADR cells. In conclusion, our results suggest that GTX may have promising effects on ADR-resistant NSCLC cells by inducing mitochondria-dependent apoptosis and through the combined effects of sequential treatment with ADR.

Solanum nigrum Unripe fruit fraction attenuates Adriamycin resistance by down-regulating multi-drug resistance protein (Mdr)-1 through Jak-STAT pathway.

BACKGROUND: Solanum nigrum, herbal plant that commonly grows in temperate climate zone, has been used as a traditional folk medicine whose ripen fruits were proven to exhibit anti-tumor properties. In traditional Chinese medicine, it has been used for centuries to cure inflammation, edema, mastitis and hepatic cancer and in the Ayurvedic system of traditional medicine in India, S. nigrum is applied against enteric diseases, ulcer, diarrhea and skin diseases. A methanolic glycosidic extract fraction of unripe fruit of S. nigrum (SNME) was investigated for its anticancer property and possible mechanism to surmount adriamycin resistance in NCI/ADR-RES cells. METHODS: The NCI/ADR-RES cells were treated with 7.8125, 15.625, 31.25, 62.5, 125 and 250 µg/ml of methanolic extract of S. nigrum (SNME) for 12, 24 and 48 h, to check the cell viability and proliferation. The cells were also exposed to adriamycin alone or in combination with SNME and the effects on cell growth were determined by MTT. Cell cycle analysis, Ethidium bromide and Acridine orange staining, Annexin-binding efficiency, nuclear condensation and DNA fragmentation of the apoptotic NCI/ADR-RES cells were also determined. To elucidate the relationship between SNME and multi drug resistance, we analyzed the expression levels of Mdr-1, JAK1, STAT3, and pSTAT3 in NCI/ADR-RES cells after treatment with SNME. RESULTS: Results from the cytotoxicity assay showed a direct correlation between the concentration of methanolic glycosidic extract fraction of S. nigrum (SNME) and the surviving cell population. Combination with Adriamycin, SNME exhibits a synergistic action on NCI/ADR-RES cells, giving the first line of evidence to overcoming Adriamycin resistance. The SNME mediated cell growth suppression was proven to be apoptotic, based on results obtained from DNA fragmentation, annexin V apoptosis assaay and PARP cleavage analysis. Looking into the molecular insight SNME surpasses the chemoresistance of NCI/ADR-RES cells by inhibiting the JAK-STAT3 signaling pathway through the down regulation of JAK1, STAT3, pSTAT3, and Mdr1 expression. CONCLUSIONS: Collectively our findings suggest that unripe fruit of Solanum nigrum could possibly be used as a chemosensitizing agent against Adriamycin resistant cancers.

Exosome-Derived MicroRNA-221-3p Desensitizes Breast Cancer Cells to Adriamycin by Regulating PIK3r1-Mediated Glycose Metabolism.

Background: Cancer-derived exosomes facilitate chemoresistance by transferring RNAs, yet their role in exosomal microRNA-221-3p (miR-221-3p) regulation of adriamycin resistance in breast cancer (BC) remains unclear. Methods: Adriamycin-resistant BC cells were developed from MCF-7 and MDA-MB-231 cells by incremental adriamycin exposure. The miR-221-3p levels were quantified by quantitative reverse transcription-polymerase chain reaction. Subsequently, exosomes were isolated and incubated with BC cells, and exosome-mediated adriamycin sensitivity was evaluated using Cell Counting Kit-8, colony formation, and flow cytometry assays. Sensitive cells were cocultured with miR-221-3p inhibitor-treated cells to assess adriamycin resistance. Moreover, the interaction between miR-221-3p and phosphoinositide-3-kinase regulatory subunit 1 (PIK3R1) was validated using a dual luciferase reporter gene assay. Mimics and inhibitors were used to determine the effects of miR-221-3p on adriamycin resistance. Results: Elevated levels of miR-221-3p expression were observed in adriamycin-resistant BC cells and exosomes. Sensitive cells were cocultured with exosomes from resistant cells, resulting in increased half-maximal inhibitory concentration value and proliferation, and reduced adriamycin-induced apoptosis. However, the effects of coculturing sensitive cells with adriamycin-resistant cells were significantly weakened by miR-221-3p inhibitor transfection in adriamycin-resistant cells. PIK3R1 was found to be a target of miR-221-3p, and miR-221-3p mimics enhanced adriamycin resistance in sensitive cells. miR-221-3p inhibitors increased the expression of PIK3R1, p-AKT, c-Myc, HK2, and PKM2, decreased FOXO3 expression, and weakened the adriamycin resistance in resistant cells. Conclusions: miR-221-3p can be transferred between BC cells through exosomes. High levels of miR-221-3p were found to target PIK3R1 and promoted adriamycin resistance in BC cells. [Figure: see text].

PLAGL2 increases adriamycin resistance and EMT in breast cancer cells by activating the Wnt pathway.

BACKGROUND: Adriamycin (ADR) is an effective treatment for breast cancer; nevertheless, it is often linked with acquired resistance in breast cancer cells, reducing ADR's therapeutic efficacy and increasing the risk of recurrence and poor prognosis. It has been revealed that the zinc-finger transcription factor pleomorphic adenoma gene like-2 (PLAGL2) is required for epithelial to mesenchymal transition (EMT) in cancer cells. Recent data indicates that PLAGL2 is also involved in regulating chemotherapeutic drug resistance, albeit the exact mechanism by which this happens remains unknown. OBJECTIVE: This study examines the effect of PLAGL2 on adriamycin resistance and EMT in breast cancer cells. METHODS: The small interfering RNA (siRNA) targeting PLAGL2 was transfected to breast cancer cells to alter PLAGL2 expression. Cell counting kit-8 (CCK-8) and colony formation assay detected cell growth and proliferation rate. Moreover, wound-healing and transwell assays were conducted to evaluate migration and invasion. Western blot (WB) checked the apoptosis and EMT-associated proteins. RESULTS: PLAGL2 expression is associated with breast cancer cells' acquired resistance to ADR in this investigation. Additionally, deletion of PLAGL2 was associated with enhanced sensitivity to ADR, reduced proliferation, migration, and invasion capabilities, increased E-cadherin levels, and reduced Wnt6, ß-catenin, and DVL1 levels in ADR-resistant breast cancer cells (MCF-7/ADR and MDA-MB-231/ADR cells). PLAGL2 could bind to the promoter region of Wnt6 and promote its expression. Additionally, the results of this research established that Wnt signaling is implicated in breast cancer cells' resistance to ADR since BML-284, a Wnt signaling activator partly restored the sensitivity of MCF-7/ADR and MDA-MB-231/ADR cells to ADR. CONCLUSION: PLAGL2 promotes adriamycin resistance and cell aggressiveness in breast cancer cells via activating the Wnt signaling pathway.

Circ_0001667 Promotes Adriamycin Resistance and Malignant Progression via Targeting the miR-193a-5p/Rap2A Molecular Axis in Breast Cancer.

BACKGROUND: The therapeutic effect of adriamycin (ADM) has been limited by chemoresistance in breast cancer (BC). Circular RNAs are involved in resistance regulation by mediating the miRNA/mRNA axis. Circ_0001667 enhanced ADM resistance via the miR-4458/NCOA3 axis in BC. This study was to investigate the other miRNA/mRNA network for circ_0001667. METHODS: The level detection of circ_0001667, microRNA-193a-5p (miR-193a-5p) or Ras-Related Protein 2a (Rap2A) was conducted by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Half inhibitory concentration (IC50) of ADM was detected through cell counting kit-8 (CCK-8) assay. The proliferation analysis was performed by colony formation assay and EdU assay. Flow cytometry was used for assessing apoptosis. Transwell assay was applied for examining cell migration and invasion. The protein detection was carried out by western blot. In vivo assay was performed using xenograft tumor model. Dual-luciferase reporter and RNA immunoprecipitation (RIP) assays were implemented to validate the target interaction. RESULTS: Circ_0001667 was highly expressed in ADM-resistant BC tissues and cells. Downregulation of circ_0001667 reduced ADM resistance and inhibited proliferation, migration, invasion in ADM-resistant BC cells. Tumor growth was repressed by circ_0001667 knockdown in ADM-resistant xenograft model. Circ_0001667 has induced the sponge effect on miR-193a-5p. The circ_0001667 function was partly achieved by targeting miR-193a-5p. Rap2A expression was positively regulated by circ_0001667 through sponging miR-193a-5p. The miR-193a-5p upregulation restrained chemoresistance and BC progression by the downregulation of Rap2A. CONCLUSION: All results unraveled that circ_0001667 contributed to ADM resistance and tumor development in BC via the miR-193a-5p-mediated Rap2A expression change, providing a novel regulatory mechanism for circ_0001667.

Phosphorylated Hsp27 promotes adriamycin resistance in breast cancer cells through regulating dual phosphorylation of c-Myc.

Chemotherapy resistance of breast cancer cells is one of the major factors affecting patient survival rate. Heat shock protein 27 (Hsp27) is a member of the small heat shock protein family that has been reported to be associated with chemotherapy resistance in tumor cells, but the exact mechanism is not fully understood. Here, we explored the regulation of Hsp27 in adriamycin-resistant pathological conditions of breast cancer in vitro and in vivo. We found that overexpression of Hsp27 in MCF-7 breast cancer cells reversed DNA damage induced by adriamycin, and thereby reduced subsequent cell apoptosis. Non-phosphorylated Hsp27 accelerated ubiquitin-mediated degradation of c-Myc under normal physiological conditions. After stimulation with adriamycin, Hsp27 was phosphorylated and translocated from the cytoplasm into the nucleus, where phosphorylated Hsp27 upregulated c-Myc and Nijmegen breakage syndrome 1 (NBS1) protein levels thus leading to ATM activation. We further showed that phosphorylated Hsp27 promoted c-Myc nuclear import and stabilization by regulating T58/S62 phosphorylation of c-Myc through a protein phosphatase 2A (PP2A)-dependent mechanism. Collectively, the data presented in this study demonstrate that Hsp27, in its phosphorylation state, plays a critical role in adriamycin-resistant pathological conditions of breast cancer cells.

B-cell-specific Moloney murine leukemia virus integration site 1 knockdown impairs adriamycin resistance of gastric cancer cells.

BACKGROUND AND STUDY AIMS: The B-cell-specific Moloney murine leukemia virus integration site 1 (BMI-1) is associated with the progression of gastric cancer (GC). However, its role in drug resistance of gastric cancer stem cell (GCSC) remains unclear. This study aimed to explore the biological function of BMI-1 in GC cells and its role in drug resistance of GCSCs. PATIENTS AND METHODS: We assessed BMI-1 expression in the GEPIA database and in our collected samples from patients with GC. We silenced BMI-1 using siRNA to study the cell proliferation and migration of GC cells. We also used Hoechst 33342 staining to verify the effect of adriamycin (ADR) on side population (SP) cells, and measured the effects of BMI-1 on the expression of N-cadherin, E-cadherin, and drug-resistance-related proteins (multidrug resistance mutation 1 and lung resistance-related protein). Finally, we analyzed BMI-1-related proteins uing the STRING and GEPIA databases. RESULTS: BMI-1 mRNA was upregulated in GC tissues and cell lines, especially in MKN-45 and HGC-27 cells. Silencing BMI-1 reduced the proliferation and migration of GC cells. Knocking down BMI-1 significantly decreased epithelial-mesenchymal transition progression, expression levels of drug-resistant proteins, and the number of SP cells in ADR-treated GC cells. Bioinformatics analysis showed that EZH2, CBX8, CBX4, and SUZ12 were positively correlated with BMI-1 in GC tissues. CONCLUSION: Our study demonstrates that BMI-1 affects the cellular activity, proliferation, migration, and invasion of GC cells. Silencing the BMI-1 gene significantly reduces the number of SP cells and the expression of drug-resistant proteins in ADR-treated GC cells. We speculate that inhibition of BMI-1 increases the drug resistance of GC cells by affecting GCSCs, and that EZH2, CBX8, CBX4, and SUZ12 may participate in BMI-1-induced enhancement of GCSC-like phenotype and viability.

HDAC2- and EZH2-Mediated Histone Modifications Induce PDK1 Expression through miR-148a Downregulation in Breast Cancer Progression and Adriamycin Resistance.

BACKGROUND: Breast cancer has one of highest morbidity and mortality rates for women. Abnormalities regarding epigenetics modification and pyruvate dehydrogenase kinase 1 (PDK1)-induced unusual metabolism contribute to breast cancer progression and chemotherapy resistance. However, the role and mechanism of epigenetic change in regulating PDK1 in breast cancer remains to be elucidated. METHODS: Gene set enrichment analysis (GSEA) and Pearson's correlation analysis were performed to analyze the relationship between histone deacetylase 2 (HDAC2), enhancer of zeste homologue 2 (EZH2), and PDK1 in database and human breast cancer tissues. Dual luciferase reporters were used to test the regulation between PDK1 and miR-148a. HDAC2 and EZH2 were found to regulate miR-148a expression through Western blotting assays, qRT-PCR and co-immunoprecipitation assays. The effects of PDK1 and miR-148a in breast cancer were investigated by immunofluorescence (IF) assay, Transwell assay and flow cytometry assay. The roles of miR-148a/PDK1 in tumor growth were investigated in vivo. RESULTS: We found that PDK1 expression was upregulated by epigenetic alterations mediated by HDAC2 and EZH2. At the post-transcriptional level, PDK1 was a new direct target of miR-148a and was upregulated in breast cancer cells due to miR-148a suppression. PDK1 overexpression partly reversed the biological function of miR-148a-including miR-148a's ability to increase cell sensitivity to Adriamycin (ADR) treatment-inhibiting cell glycolysis, invasion and epithelial-mesenchymal transition (EMT), and inducing apoptosis and repressing tumor growth. Furthermore, we identified a novel mechanism: DNMT1 directly bound to EZH2 and recruited EZH2 and HDAC2 complexes to the promoter region of miR-148a, leading to miR-148a downregulation. In breast cancer tissues, HDAC2 and EZH2 protein expression levels also were inversely correlated with levels of miR-148a expression. CONCLUSION: Our study found a new regulatory mechanism in which EZH2 and HDAC2 mediate PDK1 upregulation by silencing miR-148a expression to regulate cancer development and Adriamycin resistance. These new findings suggest that the HDAC2/EZH2/miR-148a/PDK1 axis is a novel mechanism for regulating cancer development and is a potentially promising target for therapeutic options in the future.

RBM38 is negatively regulated by miR-320b and enhances Adriamycin resistance in breast cancer cells.

Breast cancer (BC) is a common type of malignant tumor that is frequently accompanied by drug resistance, which is a significant challenge in the treatment of BC. Adriamycin (ADM) is a commonly used drug for the treatment of BC. The aim of the present study was to demonstrate the association between RNA binding motif protein 38 (RBM38) and ADM resistance in BC. The results revealed that the expression levels of RBM38 were significantly upregulated in ADM-resistant BC tissues and the ADM-resistant cell line, MCF-7/A, as demonstrated using reverse transcription-quantitative PCR and western blotting. In addition, the results of the MTT assay revealed that the overexpression of RBM38 enhanced the resistance of MCF-7/A cells to ADM, promoted invasiveness, as determined using a Transwell assay, inhibited the apoptosis of resistant cells, as determined using flow cytometry, and accelerated cell cycle progression from the G0 to the S phase. The results of the dual luciferase reporter assay demonstrated the binding relationship between microRNA (miR)-320b and RBM38, and the expression levels of miR-320b were significantly downregulated in ADM-resistant BC tissues and MCF-7/A cells. Overexpression of miR-320b reversed ADM resistance, suppressed invasiveness, promoted apoptosis and arrested MCF-7/A cells in the G0 phase. In addition, RBM38 was discovered to be negatively regulated by miR-320b, which was able to restore the sensitivity of BC cells to ADM by downregulating RBM38. Further exploration of the underlying regulatory mechanism revealed that the miR-320b/RBM38 signaling axis mediated the development of ADM resistance in BC by altering the expression of cell cycle-, drug resistance- and PI3K/AKT signaling pathway-related proteins. In conclusion, the results of the present study suggested that RBM38 may be negatively regulated by miR-320b, which accelerates drug resistance in BC.

Ad-Apoptin-hTERTp-E1a Regulates Autophagy Through the AMPK-mTOR-eIF4F Signaling Axis to Reduce Drug Resistance of MCF-7/ADR Cells.

Ad-VT (Ad-Apoptin-hTERTp-E1a) is a type of oncolytic adenovirus with dual specific tumor cell death ability. It can effectively induce cell death of breast cancer cells and has better effect when used in combination with chemotherapy drugs. However, it has not been reported whether Ad-VT reduces the resistance of breast cancer cells to chemotherapy drugs. The purpose of this study is to investigate the effect of Ad-VT on drug resistance of Adriamycin-resistant breast cancer cells. For this, the effects of different doses of Ad-VT on the resistance of breast cancer cells to Adriamycin were analyzed using qualitative and quantitative experiments in vitro and in vivo. The Ad-VT can reduce the resistance of MCF-7/ADR to adriamycin, which is caused by the reduction of MRP1 protein level in MCF-7/ADR cells after treatment with Ad-VT, and MRP1 can be interfered with by autophagy inhibitors. Subsequently, the upstream signal of autophagy was analyzed and it was found that Ad-VT reduced the resistance of cells to doxorubicin by reducing the level of mTOR, and then the analysis of the upstream and downstream proteins of mTOR found that Ad-VT increased the sensitivity of MCF-7/ADR cells to adriamycin by activating AMPK-mTOR-eIF4F signaling axis. Ad-VT can not only significantly induce cell death in MCF-7/ADR cells, but also improved their sensitivity to Adriamycin. Therefore, the combination of Ad-VT and chemotherapy drugs may become a new strategy for the treatment of breast cancer in overcoming Adriamycin resistance.

Adriamycin-resistant cells are significantly less fit than adriamycin-sensitive cells in cervical cancer.

Adriamycin (ADR) is an important chemotherapy agent in many advanced cancers, but the emergence of drug resistance during treatment is a major limitation to its successful use. Recent studies have suggested that drug-resistant cells become less fit and their growth could be inhibited by parental cells without cytotoxic treatment. In this study, we examined the fitness differences between HeLa and HeLa/ADR cells. Compared with the parental cell line, HeLa/ADR cells showed significantly lower growth rates, both in vitro and in vivo. There was no difference in the apoptosis rate between them, but G1 arrest and reduced DNA synthesis were found in HeLa/ADR cells. Further study indicated that HeLa/ADR cells failed to compete for space and nutrition against parental cells in vivo. Taken together, we demonstrate that HeLa/ADR cells are less fit and their growth can be inhibited by parental cells in the absence of ADR; therefore, the maintenance of a certain amount of ADR-sensitive cells during treatment may facilitate the control of the development of ADR resistance.

Small extracellular vesicles deliver TGF-ß1 and promote adriamycin resistance in breast cancer cells.

Chemotherapeutic resistance is a major obstacle in the control of advanced breast cancer (BCa). We have previously shown that small extracellular vesicles (sEVs) can transmit adriamycin resistance between BCa cells. Here, we describe that sEV-mediated TGF-ß1 intercellular transfer is involved in the drug-resistant transmission. sEVs were isolated and characterized from both sensitive and resistant cells. sEVs derived from the resistant cells were incubated with the sensitive cells and resulted in transmitting the resistant phenotype to the recipient cells. Cytokine antibody microarray revealed that most metastasis-associated cytokines present at the high levels in sEVs from the resistant cells compared with their levels in sEVs from the sensitive cells, particularly TGF-ß1 is enriched in sEVs from the resistant cells. The sEV-mediated TGF-ß1 intercellular transfer led to increasing Smad2 phosphorylation and improving cell survival by suppressing apoptosis and enhancing cell mobility. Furthermore, sEV-mediated drug-resistant transmission by delivering TGF-ß1 was validated using a zebrafish xenograft tumor model. These results elaborated that sEV-mediated TGF-ß1 intercellular transfer contributes to adriamycin resistance in BCa.