REIC/Dkk-3 overexpression downregulates P-glycoprotein in multidrug-resistant MCF7/ADR cells and induces apoptosis in breast cancer

Abstract

The overexpression of reduced expression in immortalized cells (REIC)/Dickkopf-3 (Dkk-3), a tumor suppressor gene, induced apoptosis in human prostatic and testicular cancer cells. The aim of this study is to examine the potential of REIC/Dkk-3 as a therapeutic target against breast cancer. First, the in vitro apoptotic effect of Ad-REIC treatment was investigated in breast cancer cell lines and the adenovirus-mediated overexpression of REIC/Dkk-3 was thus found to lead to apoptotic cell death in a c-Jun-NH 2 -kinase (JNK) phosphorylaion-dependent manner. Moreover, an in vivo apoptotic effect and MCF/Wt tumor growth inhibition were observed in the mouse model after intratumoral Ad-REIC injection. As multidrug resistance (MDR) is a major problem in the chemotherapy of progressive breast cancer, the in vitro effects of Ad-REIC treatment were investigated in terms of the sensitivity of multidrug-resistant MCF7/ADR cells to doxorubicin and of the P-glycoprotein expression. Ad-REIC treatment in MCF7/ADR cells also downregulated P-glycoprotein expresssion through JNK activation, and sensitized its drug resistance against doxorubicin. Therefore, not only apoptosis induction but also the reversal of anticancer drug resistance was achieved using Ad-REIC. We suggest that REIC/Dkk-3 is a novel target for breast cancer treatment and that Ad-REIC might be an attractive agent against drug-resistant cancer in combination with conventional antineoplastic agents.

REIC/Dkk-3 stable transfection reduces the malignant phenotype of mouse prostate cancer RM9 cells

“…The suppression of tumor growth was further confirmed in an in vivo situation using an orthotopic tumor model. These phenomena were consistent with other published studies (3,5,9,10,(15)(16)(17)(18), showing that ectopic expression of REIC/ Dkk-3 induces apoptosis and inhibits cell proliferation in various cancer cells. Therefore, the lack or absence of endogenous REIC/Dkk-3 expression in RM9 cancer cells seems to be important for the cellular effects induced by the REIC/Dkk-3 overexpression.…”

“…REIC/Dkk-3 expression is down-regulated in a broad range of cancer cell lines and clinical cancer materials (2)(3)(4)(5)(6)(7)(8)(9)(10). The expression of the human REIC/Dkk-3 gene is significantly down-regulated in human prostate cancer specimens in comparison to normal human prostate tissue at the protein level (5).…”

“…The apoptotic cells were determined by Hoechst 33342 staining under fluorescence microscopy and the apoptotic cell rate was calculated (10). The dye solution was added into the culture medium and then cells were incubated for 10 min.…”

Internalization of REIC/Dkk-3 protein by induced pluripotent stem cell-derived embryoid bodies and extra-embryonic tissues

“…The induction of apoptosis was demonstrated to be selective, i.e., efficient killing of cancer cells with only a marginal effect on normal counterparts (2). In addition, Ad-REIC reversed resistance of cancer cells to anti-cancer drugs via down-regulation of P-glycoprotein (9). Furthermore, we recently showed that Ad-REIC has an indirect host-mediated anti-tumor activity in vivo by the induction of IL-7 (10).…”

Expression of tumor suppressor REIC/Dkk-3 by a newly improved adenovirus vector with insertion of a hTERT promoter at the 3′-side of the transgene

“…Therefore, REIC was designated as REIC/Dkk-3. Previous studies by our group have demonstrated that overexpression of REIC/Dkk-3 by an adenovirus (Ad)-REIC vector resulted in a therapeutic effect against numerous human cancer subtypes via a mechanism triggered by endoplasmic reticulum (ER) stress-mediated c-Jun N-terminal kinase (JNK) activation (3)(4)(5)(6).…”