SUMO E3 ligase mediates androgen receptor transcription to promote tamoxifen resistance of breast cancer / 中国临床药理学与治疗学

AIM: To investigate the mechanism of the involvement of SUMO-ylated Androgen receptor (AR) in tamoxifen resistance and the role of SUMO inhibitor ginkgolic acid in resistance. METHODS: Real-Time PCR was used to detect AR mRNA levels in parental cells MCF-7W and drug-resistant cells MCF-7R, AR protein levels and SUMO levels in MCF-7W and MCF-7R cells was performed by western blot, and CB/IP was applied to detect AR interacts with SUMOE3 ligase PIAS1 and HSP27 in MCF-7R cell chromatin, the transcriptional activity of SUMO AR was also evaluated by the fluorescent reporter gene experiment, the CCK-8 method and the trypan blue exclusion method were used to detect cell viability and cell viability respectively. RESULTS: The mRNA and protein expression levels of AR in MCF-7R cells were significantly higher than those in MCF-7W cells (P<0.05), and there was highly SUMOylated AR in MCF-7R cells. Further research found that there had an obvious interaction between AR and SUMO E3 ligase PIAS1 and HSP27, that was, the SUMOylated AR was modified by E3 ligase. Moreover, androgen R1881 could enhance the transcriptional activity of the SUMOylated AR in a concentration-dependent manner. Compared with ginkgo acid alone, 10 μmol/L of ginkgolic acid combined with 10 μmol/L of enzalutamide treated MCF-7R cells for 3 days, the cell number was significantly reduced, and the number of cell death increased significantly (P<0.05). CONCLUSION: The resistance mechanism of tamoxifen may be due to the enhanced AR transcription and activity increased by the hyperactive SUMOylated AR, SUMO inhibitor ginkgolic acid combined with AR antagonist enzalutamide can be a new strategy for the treatment of tamoxifen resistance.

Effect of Shugan Yishen Prescription on Tamoxifen-resistant Cell Line from Exosome-mediated Crosstalk in Breast Cancer Microenvironment / 中国实验方剂学杂志

Objective:To explore the effect of Shugan Yishen prescription（SGYS） on the tamoxifen （TAM） -resistant cell line LCC9 by the intervention of exosome-mediated crosstalk in the breast cancer microenvironment. Method:Four groups of serum were set up， specifically， a blank group， a TAM （2 mg·kg^-1·d^-1） group，an SGYS（113.2 g·kg^-1·d^-1） group，and a combination group. The exosomes of LCC9 cells were extracted by ultracentrifugation and identified by transmission electron microscopy （TEM），nanoparticle tracking analysis （NTA）， and Western blot. Then the collected LCC9 exosomes （LCC9-EXO） were co-cultured with bone marrow mesenchymal stem cells（BMMSCs），and 10% of the above four groups of serum were added to the co-culture system. After 48 hours of co-culture，the exosomes of BMMSCs （BMMSCs-EXO） were extracted and incubated with LCC9 cells. Fluorescence microscope was used to observe the uptake of exosomes by cells. Cell counting kit-8 （CCK-8） assay，flow cytometry， and Transwell assay were used to detect the effects of drug-containing serum in the four groups on the proliferation，apoptosis， and migration of LCC9 cells. Western blot was used to detect the protein expression of CD24，CD44，human epidermal growth factor 2（HER2）， and estrogen receptor <italic>α</italic> （ER<italic>α</italic>） in each group. Result:Fluorescence microscope observed that LCC9-EXO could be taken up by BMMSCs，and BMMSCs-EXO could be taken up by LCC9 cells. CCK-8 assay revealed that compared with the TAM group，the SGYS group and the combination group showed reduced cell proliferation ability at each period （<italic>P</italic><0.05），especially the combination group，but no statistically significant difference between the SGYS group and the combination group was observed （<italic>P</italic><0.05）. Flow cytometry revealed that compared with the TAM group，the SGYS group and the combination group showed increased levels of apoptosis （<italic>P</italic><0.05）. Transwell assay revealed that compared with the TAM group，the SGYS group and the combination group showed decreased cell migration ability （<italic>P</italic><0.05）. Western blot revealed that compared with the TAM group，the SGYS group and the combination group showed up-regulated expression of ERα and CD24（<italic>P</italic><0.05），and down-regulated expression of HER2 and CD44 （<italic>P</italic><0.05）. The effect of the combination group on protein expression was superior to that of the SGYS group （<italic>P</italic><0.05）. Conclusion:SGYS reverses the TAM resistance of LCC9 cells by interfering with the crosstalk between BMMSCs-EXO and LCC9-EXO.

Inhibition of EGFR and HER2 in Tamoxifen-resistant T47D:A18/4-OHT Breast Cancer Cells

PURPOSE: Tamoxifen has been prescribed as a very effective hormonal agent not only for the treatment of breast cancer, but also for the prevention of the disease. The development of resistance to tamoxifen is one of the most important obstacles to hormonal therapy of breast cancer. HER2 or EGFR expression has been reported to be associated with the development of tamoxifen resistance. This study was performed to evaluate the effect of HER2 and EGFR inhibition on tamoxifen resistance using tamoxifen-resistant breast cancer cells (T47D:A18/4-OHT cells). METHODS: Tamoxifen-resistant T47D:A18/4-OHT cells were established by long-term treatment of 1micrometer 4-hydroxytamoxifen on T47D:A18 human breast cancer cells. The effect of HER2 and EGFR inhibition was investigated by the use of a cell proliferation assay with treatment of trastuzumab, a monoclonal antibody to the extracellular domain of the human HER2 receptor, and ZD1839, an ERFR tyrosine kinase inhibitor. RESULTS: In contrast to T47D:A18 cells, T47D:A18/4-OHT cells showed estrogen-independent proliferation and partial regulation by treatment with tamoxifen. With a single treatment of trastuzumab or ZD1839, T47D:A18/4-OHT cell growth was reduced to 77.8% (P=0.15) or 74.4% (P=0.034) respectively, as compared to untreated cells. Combinational treatment with 1 nM estradiol resulted in a further reduction of T47D:A17 cell proliferation by 83.6% (P=0.002) for trastuzumab and 77.7% (P=0.047) for ZD1839, as compared to the single treatments. CONCLUSION: Tamoxifen resistance could be partially regulated by inhibition of HER2 or EGFR in T47D:A18/4-OHT cells, especially in combination with a low dose of estradiol. This effect may provide an important clue to overcome tamoxifen resistance in the treatment of breast cancer.

Tamoxifen Resistance and Crosstalk of Signal Transduction in Breast Cancer / 한국유방암학회지

In the hormonal therapy of breast cancer, tamoxifen is currently the standard treatment for estrogen receptor (ER)-positive patients. A response to tamoxifen has been reported in only 2/3 of patients treated with tamoxifen, with the other 1/3 regarded as tamoxifen resistant. In addition, this resistance could play a significant role in the recurrence or metastasis of breast cancer. Overcoming tamoxifen resistance would be an important advance in the conquest of breast cancer. With the recent rapid development of molecular biology, various pathways in signal transduction are known to be related with tamoxifen resistance, and crosstalk between the ER and growth factor receptor (GFR) pathways has been reported as the main mechanism in the development of tamoxifen resistance. In this paper, the crosstalk between the ER and GFR pathways has been summarized with respect to the signal transduction of cancer cells, and this concept could be useful in overcoming tamoxifen resistance due to the blocking of multiple pathways with new targeted agents.

Tamoxifen Resistance and Crosstalk of Signal Transduction in Breast Cancer / 한국유방암학회지

In the hormonal therapy of breast cancer, tamoxifen is currently the standard treatment for estrogen receptor (ER)-positive patients. A response to tamoxifen has been reported in only 2/3 of patients treated with tamoxifen, with the other 1/3 regarded as tamoxifen resistant. In addition, this resistance could play a significant role in the recurrence or metastasis of breast cancer. Overcoming tamoxifen resistance would be an important advance in the conquest of breast cancer. With the recent rapid development of molecular biology, various pathways in signal transduction are known to be related with tamoxifen resistance, and crosstalk between the ER and growth factor receptor (GFR) pathways has been reported as the main mechanism in the development of tamoxifen resistance. In this paper, the crosstalk between the ER and GFR pathways has been summarized with respect to the signal transduction of cancer cells, and this concept could be useful in overcoming tamoxifen resistance due to the blocking of multiple pathways with new targeted agents.