Resistance In Breast Carcinoma Cells Research Articles

Transcription factor STAT4 counteracts radiotherapy resistance in breast carcinoma cells by activating the MALAT1/miR-21-5p/THRB regulatory network.

Considering the limited research and the prevailing evidence of STAT4's tumor-suppressing role in breast carcinoma (BC) or in breast radiotherapy (RT) sensitivity requires more in-depth exploration. Our study delves into how STAT4, a transcription factor, affects BC cell resistance to radiotherapy by regulating the MALAT1/miR-21-5p/THRB axis. Bioinformatics analysis was performed to predict the regulatory mechanisms associated with STAT4 in BC. Subsequently, we identified the expression profiles of STAT4, MALAT1, miR-21-5p, and THRB in various tissues and cell lines, exploring their interactions and impact on RT resistance in BC cells. Moreover, animal models were established with X-ray irradiation for further validation. We discovered that STAT4, which is found to be minimally expressed in breast carcinoma (BC) tissues and cell lines, has been associated with a poorer prognosis. In vitro cellular assays indicated that STAT4 could mitigate radiotherapy resistance in BC cells by transcriptional activation of MALAT1. Additionally, MALAT1 up-regulated THRB expression by adsorbing miR-21-5p. As demonstrated in vitro and in vivo, overexpressing STAT4 inhibited miR-21-5p and enhanced THRB levels through transcriptional activation of MALAT1, which ultimately contributes to the reversal of radiotherapy resistance in BC cells and the suppression of tumor formation in nude mice. Collectively, STAT4 could inhibit miR-21-5p and up-regulate THRB expression through transcriptional activation of MALAT1, thereby mitigating BC cell resistance to radiotherapy and ultimately preventing BC development and progression.

FTO-mediated epigenetic upregulation of LINC01559 confers cell resistance to docetaxel in breast carcinoma by suppressing miR-1343-3p.

This study was to explore the regulatory effect of long non-coding RNA LINC01559 on Docetaxel resistance in breast carcinoma (BCa) and its underlying mechanism. In the present study, we found that LINC01559 expression was elevated and LINC01559 overexpression facilitated docetaxel resistance in BCa cells. Moreover, it was revealed that the upregulation of LINC01559 in BCa cells was induced by FTO-mediated demethylation in an m6A-YTHDF2-dependent manner. Additionally, Dual-luciferase reporter assay confirmed the binding ability between LINC01559 and miR-1343-3p, and Pearson correlation analysis showed a negative correlation between them. Particularly, miR-1343-3p inhibition partly abolished the suppression on docetaxel resistance in BCa cells caused by LINC01559 knockdown. To sum up, FTO-mediated epigenetic upregulation of LINC01559 promoted cell resistance to Docetaxel in BCa by negatively regulating miR-1343-3p.

Shear stress promotes anoikis resistance of cancer cells via caveolin-1-dependent extrinsic and intrinsic apoptotic pathways.

Circulating tumor cells (CTCs) need to acquire resistance to anoikis to survive after they experience fluid shear stress in the circulatory and lymphatic systems. However, the mechanism by which tumor cells resist anoikis under shear stress conditions remains unknown. Here, we found that the application of low shear stress (LSS; 2 dyn/cm2 ) to human breast carcinoma cells (MDA-MB-231) resulted in increased anoikis resistance when tumor cells were grown under anchorage-independent conditions. Caveolin-1 (Cav-1), the major component of plasma membrane caveolae, was overexpressed in LSS-treated cells and prevented tumor cells from anoikis, while depletion of Cav-1 restored sensitivity to anoikis. LSS-induced dissociation of Cav-1-Fas inhibited formation of the death-inducing signaling complex, caspase-8 activation, and rendered tumor cells resistant to anoikis. Likewise, LSS blocked the mitochondrial pathway through promotion of integrin β1-focal adhesion kinase-mediated multicellular aggregation and suppression of truncated BIDtranslocation mediated crosstalk between the extrinsic and intrinsic apoptotic pathways. Our findings provide insights into the mechanisms by which LSS induces anoikis resistance in breast carcinoma cells through inhibition of Cav-1-dependent extrinsic and intrinsic apoptotic pathways, and serves as a potential therapeutic target for CTCs and metastatic breast cancer.

Screening of deoxyribozyme with high reversal efficiency against multidrug resistance in breast carcinoma cells

Specific inhibition of P-glycoprotein (Pgp) expression, which is encoded by multidrug resistance gene-1 (MDR1), is considered a well-respected strategy to overcome multidrug resistance (MDR). Deoxyribozymes (DRz) are catalytic nucleic acids that could cleave a target RNA in sequence-specific manner. However, it is difficult to select an effective target site for DRz in living cells. In this study, target sites of DRz were screened according to MDR1 mRNA secondary structure by RNA structure analysis software. Twelve target sites on the surface of MDR1 mRNA were selected. Accordingly, 12 DRzs were synthesized and their suppression effect on the MDR phenotype in breast cancer cells was confirmed. The results showed that 4 (DRz 2, 3, 4, 9) of the 12 DRzs could, in a dose-dependent response, significantly suppress MDR1 mRNA expression and restore chemosensitivity in breast cancer cells with MDR phenotype. This was especially true of DRz 3, which targets the 141 site purine-pyrimidine dinucleotide. Compared with antisense oligonucleotide or anti-miR-27a inhibitor, DRz 3 was more efficient in suppressing MDR1 mRNA and Pgp protein expression or inhibiting Pgp function. The chemosensitivity assay also proved DRz 3 to be the best one to reverse the MDR phenotype. The present study suggests that screening targets of DRzs according to MDR1 mRNA secondary structure could be a useful method to obtain workable ones. We provide evidence that DRzs (DRz 2, 3, 4, 9) are highly efficient at reversing the MDR phenotype in breast carcinoma cells and restoring chemosensitivity.

Mechanism governing reversal of multidrug resistance in human breast carcinoma cells by chelerythrine.

To explore the mechanism governing the reversal of multidrug resistance in human breast carcinoma cells by chelerythrine. Reverse transcription-polymerase chain reaction (RT-PCR) and Western blot were used to determine the expressions of protein kinase Cα (PKCα) and multidrug resistance-related genes ABCG2, ABCC1, MDR1, and P-glycoprotein (P-gp) in MCF-7Taxol cells after treatment with chelerythrine and phorbol-12-myristate-13-acetate (PMA). Also, the antitumor effect of PMA or chelerythrine and effects of PKCα activator or inhibitor in combination with paclitaxel or adriamycin on multidrug resistance in MCF-7Taxol cells were evaluated by MTT. RT-PCR or Western blot showed that the expressions of MDR1 and P-gp were significantly higher in MCF-7Taxol cells exposed to PMA stimuli (both P0.05). PKCα inhibitor chelerythrine can reverse multidrug resistance in breast carcinoma cells by inhibiting the expressions of MDR1 and P-gp expression in vitro.

Downregulation of miR-21 Enhances Chemotherapeutic Effect of Taxol in Breast Carcinoma Cells

The successful of anti-cancer treatment are often limited by the development of drug resistance. Recent work has highlighted the involvement of non-coding RNAs, microRNAs(miRNAs) in cancer development, and their possible involvement in the evolution of drug resistance has been proposed. In this study, we combine taxol chemotherapy and miR-21 inhibitor treatment via polyamidoamine (PAMAM) dendrimers vector to evaluate the effects of combination therapy on suppression of breast cancer cells. The 50% inhibitory concentration (IC50) values for taxol were significantly decreased to a greater extent in the cells transfected with miR-21 inhibitor compared with cells treated with taxol alone. Taxol treatment also increased the percentage of apoptotic breast cancer cells in miR-21 inhibitor transfected cells compared with control cells. Furthermore, treatment of the miR-21 inhibitor-transfected cells with the anti-cancer drugs taxol resulted in significantly reduced cell viability and invasiveness compared with control cells. These results indicated that the miR-21 plays an important role in the resistance of breast carcinoma cells to chemotherapeutic drugs. Therefore, miR-21 inhibitor gene therapy combined with taxol chemotherapy might represent a promising novel therapeutic approach for the treatment of breast malignancies.

Reversal effect of MDR1 and MDR3 gene silencing by shRNA on resistance of breast carcinoma cells to adriamycin

Objective To investigate the effect of MDR1 and MDR3 gene silence by shRNA of human breast carcinoma cell line MCF-7/Adr,and explore the role of MDR1 and MDR3 in adriamycin-resistance of breast carcinoma cells. Methods shRNA plasmid vector specifically targeting MDR1 and MDR3 gene was transfected into cells. The control group was transfected with empty vector. The concentration of adriamycin was detected by the flow cytometry (FCM). Cell apoptosis was analysed by FITC-Annexin-V/PI double staining. Cell viability and the IC50 of adriamycin on MCF-7/Adr cells were determined by MTT method. MDR1 and MDR3 mRNA were assessed by RT-PCR. P-gp expression was detectedby immunochemistry. Results After treatment with ABCB1 and ABCB4 shRNA plasmid vector, the apoptosis of MCF-7/Adr cells was (30.21±1.65)%and (22.07±2.17)% respectively. Compared with untransfecedgroup and empty vector transfection group the difference was significant(P＜0.01). MDR1 and MDR3 shRNAcould increase cellular adriamycin accumulation of MCF-7/Adr cells. MCF-7/Adr cells viability and the IC50were significantly decreased after transfection. Compared with untransfeced group and empty vector transfectiongroup, the mRNA level of MDR1 and MDR3 in MCF-7/Adr cells were decreased by (89.5±0.8)%and(85.1±1.2)%, the reduction of MDR1 and MDR3 mRNA was in a time-dependent manner. Immunochemistry proved that the expression of p-gp was significantly inhibited. Compared with untransfeced group and empty vector transfection group the difference was significant (P＜0.05). Conclusion The shRNA can effectively and specifically silence the expression of MDR1 and MDR3 gene, reverse the adriamycin-resistance mediated by P-gp in MCF-7/Adr cells. The reversal effect of adriamycin-resistance by shRNA of MDR1 is more effective than that of MDR3. Key words: Drug resistance, neoplasm; Epirubicin; Apoptosis; shRNA

Reversal of drug resistance in breast carcinoma cells by anti-mdr1 ribozyme regulated by the tumor-specific MUC-1 promoter

Multidrug resistance (MDR) is a serious obstacle for cancer chemotherapy. The aim of this study was to reverse MDR of breast carcinoma cells specifically by degrading mdr1 mRNA with anti-mdr1 ribozyme. Our strategy was to limit the expression of ribozyme to only breast-derived cells, but not other type of cells. The results showed the recombinant ribozyme pEGFP-RZmuc was expressed in two kinds of breast carcinoma cells, but not in non-breast-derived cancer cells. Evaluation of chemosensitivity showed that a 15-fold reduction in drug resistance for Adriamycin and a 32-fold reduction in drug resistance for Vinblastine were observed in the transfected cells. Our results demonstrate the efficacy and selectivity of pEGFP-RZmuc to reverse MDR in drug resistant breast carcinoma cells in vitro.

Construction of glucosylceramide synthase-specific siRNA expression vector and its efficiency in reversal of drug resistance in breast carcinoma cells

To construct a glucosylceramide synthase (GCS)-specific small interfering RNA (siRNA) expression vector and to investigate the inhibitory effect of this siRNA on GCS expression and drug resistance in breast carcinoma cells. Two GCS gene-specific siRNAs were designed and cloned into the expression vector pSUPER to generate the plasmids pSUPER-GCS1 and pSUPER-GCS2. Human adriamycin (ADM)-resistant breast carcinoma cells of the line MCF-7/ADR and human adriamycin-sensitive breast carcinoma cells of the line MCF-7 were cultured and transfected with pSUPER-GCS1, pSUPER-GCS2, and blank vector pSUPER as controls. The expression of GCS mRNA was assayed by RT-PCR and the expression of GCS protein was observed by flow cytometry. The 50% inhibition concentration of ADM on MCF-7/ADR cells was evaluated by MTT method. Flow cytometry was performed to determine the ratio of apoptosis. Double enzyme digestion analysis and DNA sequencing confirmed that pSUPER-GCS1 and pSUPER-GCS2 were successfully constructed. The GCS protein positive rate of the MCF-7/ADR cells 48 hours after transfection with pSUPER-GCS1 and pSUPER-GCS2 were 8.3% +/- 1.0% and 9.2% +/- 0.8% respectively, significantly lower than that before transfection (68.3% +/- 0.6%), with a inhibition rate of 89.4% and 88.5% respectively (both P < 0.01). Forty-eight hours after transfection with pSUPER-GCS1 and pSUPER-GCS2, the relative reversal rates of sensitivity to ADM of the MCF-7/ADR cells were 93.7% and 91.6%. Flow cytometry showed that the apoptotic rate of the MCF-7/ADR cells was 0.80 +/- 0.06 before transfection, 15.38 +/- 1.16 after transfection with pSUPER-GCS1 and 13.92 +/- 1.73 after transfection with pSUPER-GCS2 (both P < 0.05), and was 0.87 +/- 0.12 in the cells transfected with blank vector (P > 0.05). A GCS-specific small interfering RNA expression vector has been constructed successfully that suppresses the GCS expression and reverses the multidrug resistance in breast carcinoma cells by increasing the ratio of apoptosis in drug-resistant cells.