Human breast cancers include cancer stem cell populations as well as nontumorigenic cancer cells. Breast cancer stem cells have self-renewal capability and are resistant to conventional chemotherapy. miRNAs regulate the expression of many target genes; therefore, dysregulation of miRNAs has been associated with the pathogenesis of human diseases, including cancer. However, a role for miRNA dysregulation in stemness and drug resistance has yet to be identified. Members of the miR34 family are reportedly tumor-suppressor miRNAs and are associated with various human cancers. Our results confirm that miR34a expression was downregulated in MCF7/ADR cells compared with MCF7 cells. We hypothesized that this reduction was due to the p53 (TP53) mutation in MCF7/ ADR cells. In this study, we found that primary and mature miR34a were suppressed by treatment with p53 RNAi or the dominant-negative p53 mutant in MCF7 cells. Ectopic miR34a expression reduced cancer stem cell properties and increased sensitivity to doxorubicin treatment by directly targeting NOTCH1. Furthermore, tumors from nude mice treated with miR34a were significantly smaller compared with those of mice treated with control lentivirus. Our research suggests that the ectopic expression of miR34a represents a novel therapeutic approach in chemoresistant breast cancer treatment. Cancer Res; 74(24); 7573-82. Ó2014 AACR.

Background: Receptor of advanced glycation end product (RAGE) mediates not only proinflammatory signaling, but also stimulates cell proliferation and survival-related signaling. Results: Inhibiting RAGE resulted in slowed cyst growth in an autosomal dominant polycystic kidney disease (ADPKD) mouse model and improved renal function. Conclusion: RAGE inhibition is highly effective against cyst enlargement in vivo. Significance: RAGE signaling may play a role in cystogenesis and could be a new therapeutic target for PKD.

Autosomal polycystic kidney disease (ADPKD) is a highly prevalent genetic renal disorder in which epithelial-lining fluid-filled cysts appear in kidneys. It is accompanied by hyperactivation of cell proliferation, interstitial inflammation, and fibrosis around the cyst lining cells, finally reaching end-stage renal disease. Previously, we found high expression of ligands stimulating the receptor for advanced glycation end products (RAGE) in ADPKD mice. Furthermore, gene silencing of RAGE was revealed to cause reduction of cystogenesis via down-regulation of cell proliferation in vitro, and intravenous administration of anti-RAGE adenovirus in vivo also displayed alleviation of the disease. Here, we attempted to identify the role of soluble RAGE (sRAGE) in inhibiting the progression of ADPKD using 2 different ADPKD mouse models. sRAGE is an endogenously expressed form of RAGE that has no membrane-anchoring domain, thereby giving it the ability to neutralize the ligands that stimulate RAGE signals. Both overexpression of sRAGE and sRAGE treatment blocked RAGE-mediated cell proliferation in vitro. In addition, sRAGE-injected ADPKD mice showed reduced cysts accompanied by enhanced renal function, inhibition of cell proliferation, inflammation, and fibrosis. These positive therapeutic effects of sRAGE displayed little liver toxicity, suggesting it as a new potential therapeutic target of ADPKD with low side effects.

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by abnormal proliferation of renal tubular epithelial cells, resulting in the loss of renal function. Despite identification of the genes responsible for ADPKD, few effective drugs are currently available for the disease. Thus finding additional effective drug targets is necessary. The functions of multidrug- resistance-associated protein 3 (MRP3) have been reported only in the field of drug resistance, and the renal functions of MRP3 are mostly unknown. In this study, we found that MRP3 was significantly downregulated in kidneys of human patients with ADPKD and polycystic kidney disease (PKD) mouse models. Our results suggest that downregulated MRP3 stimulated renal epithelial cell proliferation through the B-Raf/MEK/ERK signaling pathway. In contrast, we found that restoring MRP3 reduced cell proliferation and cystogenesis in vitro. These results suggest that the renal function of MRP3 is related to renal cell proliferation and cyst formation and that restoring MRP3 may be an effective therapeutic approach for PKD.

<p>Supplementary Figure 3. The relationship between Notch1 and miR-34 family members.</p>

<p>Supplementary Figure 1. Expression levels of cancer stem cell markers in tumorsphere cells.</p>

<p>Supplementary Figure 4. Overexpression of miR-34a by lentiviral system in primary cells.</p>

<p>Supplementary Figure 1. Expression levels of cancer stem cell markers in tumorsphere cells.</p>