ETS1 promotes chemoresistance and invasion of paclitaxel-resistant, hormone-refractory PC3 prostate cancer cells by up-regulating MDR1 and MMP9 expression.

ETS1, which belongs to the ETS transcription factor family, plays important roles in diverse aspects of cancer such as drug resistance and metastasis. In the present study, we examined the functional roles of ETS1 in paclitaxel resistance and invasion using human prostate cancer PC3 cells and paclitaxel-resistant PC3PR cells established from PC3 cells. Our results showed that ETS1mRNA and protein expression was markedly up-regulated in paclitaxel-resistant PC3PR cells compared with paclitaxel-sensitive PC3 cells. The mRNA levels of MDR1 as well as MMP1, MMP3, MMP9 and uPA were positively correlated with that of ETS1. In PC3PR cells, silencing of ETS1 expression by siRNAs inhibited the activity of the MDR1 promoter containing ETS binding sites, reduced the mRNA and protein levels of MDR1 and suppressed paclitaxel resistance. Furthermore, ETS1 knockdown decreased secretion of MMP9 as well as its intracellular mRNA level, and dramatically inhibited invasion of PC3PR cells. Our results suggest that ETS1 promotes paclitaxel resistance and invasion in part by up-regulating MDR1 and MMP9 expression. Taken together, a novel therapeutic strategy targeting the ETS1 gene could be designed to overcome chemoresistance and metastasis of taxane-resistant, hormone-refractory prostate cancer.

Kato T ，Fujita Y ，Nakane K ，Kojima T ，Nozawa Y ，Deguchi T ，Ito M ... -  《-》

MiR-34a attenuates paclitaxel-resistance of hormone-refractory prostate cancer PC3 cells through direct and indirect mechanisms.

Patients with hormone-refractory prostate cancer are treated with taxane drugs, but eventually become drug resistant. We aimed to elucidate the molecular mechanisms underlying paclitaxel resistance of hormone-refractory prostate cancer with a special focus on the roles of miR-34a and SIRT1. Paclitaxel-resistant cells (PC3PR) were generated from hormone-refractory PC3 cells. The expression levels of mRNA and miRNA were determined by reverse transcriptase PCR and those of protein were by Western blot analysis. Transfection of miRNA precursor or siRNA was performed using the liposome-mediated method. MiR-34a over-expression and SIRT1 knockdown attenuated paclitaxel resistance of PC3PR cells. MiR-34a expression was reduced in PC3PR cells compared with PC3 cells, while the expression levels of HuR and Bcl2 as well as SIRT1 were elevated in PC3PR cells. Luciferase reporter assays revealed that both SIRT1 3'-UTR and promoter activities were higher in PC3PR cells than in PC3 cells. Introduction of miR-34a precursor into PC3PR cells resulted in decreases in HuR, Bcl2, and SIRT1 expression and inhibition of the SIRT1 3'-UTR activity. HuR knockdown reduced SIRT1 and Bcl2 expression. These results suggest that miR-34a not only directly but also indirectly via regulating HuR expression acts on the 3'-UTR of SIRT1 and Bcl2 mRNAs, thereby controlling their expression. Thus, in PC3PR cells, reduced expression of miR-34a confers paclitaxel resistance via up-regulating SIRT1 and Bcl2 expression. MiR-34a and its downstream targets SIRT1 and Bcl2 play important roles in the development of paclitaxel resistance, all of which can be useful biomarkers and promising therapeutic targets for the drug resistance in hormone-refractory prostate cancer.

Kojima K ，Fujita Y ，Nozawa Y ，Deguchi T ，Ito M ... -  《-》

Drug resistant breast cancer cells overexpress ETS1 gene.

Multidrug resistance (MDR) is resistance to wide range of structurally unrelated anticancer agents. MDR is a serious limitation to the effective chemotherapy. Involvement of ETS1 overexpression in upregulation of MDR1 gene expression is implicated. In the present study the aim was to assess the involvement of ETS1 and the genes, which encode the proteins interacting with ETS1 in drug resistant MCF-7 breast cancer cells. Drug resistant sublines to paclitaxel (MCF-7/Pac), docetaxel (MCF-7Doc), vincristine (MCF-7/Vinc) and doxorubicin (MCF-7/Dox) that were developed from sensitive MCF-7 cells (MCF-7/S) were used. cDNA microarray analysis was performed for the RNA samples of sensitive and resistant cells in duplicate experiments. GeneSpring GX 7.3.1 Software was used in data analysis. Microarray data was supported by immunocytochemistry and western blot for drug resistance protein, P-gp, encoded by MDR1 gene. According to microarray data MDR1 and ETS1 genes were highly overexpressed in all of the resistant sublines. Matrix metalloproteinase-1 gene (MMP-1) was also tremendously upregulated only in vincristine resistant cells. Immunocytochemistry and western blot results confirmed that P-gp was highly overexpressed in resistant sublines compared to original MCF-7 cells. High ETS1 expression levels in all resistant MCF-7 sublines may lead to the upregulation of the transcription of MDR1 gene. Overexpression of ETS1 gene in resistant cells may have contributed to the development of resistance in the cells. Furthermore, the significant upregulation of MMP1 and MMP9 in MCF-7/Vinc may also be related to an acquired invasive behavior of MCF-7 cell line due to vincristine treatment.

Kars MD ，Işeri OD ，Gündüz U 《-》

CCR1/CCL5 interaction promotes invasion of taxane-resistant PC3 prostate cancer cells by increasing secretion of MMPs 2/9 and by activating ERK and Rac signaling.

Castration-refractory prostate cancer (CRPC) is treated with taxane-based chemotherapy, but eventually becomes drug resistant. It is thus essential to identify novel therapeutic targets for taxane resistance in CRPC patients. We investigated the role of the chemokine (C-C motif) receptor 1 (CCR1) and its ligand, chemokine (C-C motif) ligand 5 (CCL5), in taxane-resistant CRPC using paclitaxel-resistant prostate cancer cells (PC3PR) established from PC3 cells. We found that the expression levels of CCR1 mRNA and protein were up-regulated in PC3PR cells compared to PC3 cells. In order to investigate the role of increased CCR1 in PC3PR cells, we stimulated cells with CCL5, one of the chemokine ligands of CCR1. In CCL5-stimulated PC3PR cells, siRNA-mediated knockdown of CCR1 expression reduced phosphorylation of ERK1/2 and Rac1/cdc42. Furthermore, CCR1 knockdown and MEK1/2 inhibition decreased CCL5-stimulated secretion of MMPs 2 and 9, which play important roles in cancer cell invasion and metastasis. In the Matrigel invasion assay, knockdown of CCR1 and inhibition of the ERK and Rac signaling pathways significantly decreased the number of invading cells. Finally, the serum CCL5 protein level as measured by ELISA was not different among the three groups of patients: those with negative prostate biopsy, those at initial diagnosis of prostate cancer, and those with taxane-resistant prostate cancer. These results demonstrated for the first time that the interaction of CCR1 with CCL5 caused by increased expression of CCR1 promotes invasion of PC3PR cells by increasing secretion of MMPs 2 and 9 and by activating ERK and Rac signaling. Our findings suggest that CCR1 could be a novel therapeutic target for taxane-resistant CRPC.

Kato T ，Fujita Y ，Nakane K ，Mizutani K ，Terazawa R ，Ehara H ，Kanimoto Y ，Kojima T ，Nozawa Y ，Deguchi T ，Ito M ... -  《-》

The establishment of two paclitaxel-resistant prostate cancer cell lines and the mechanisms of paclitaxel resistance with two cell lines.

Takeda M ，Mizokami A ，Mamiya K ，Li YQ ，Zhang J ，Keller ET ，Namiki M ... -  《-》