Abstract. Previous studies indicate that bone morphogenetic protein (BMP) 6 is involved in breast cancer development and progression. However, the mechanism underlying the role of BMP6 in breast cancer cell proliferation, differentiation and chemoresistance remains unknown. In this study, we confirmed that BMP6 expression was downregulated in breast cancer tissues compared with the adjacent normal breast tissues. We further demonstrated that the downregulation of BMP6 was correlated with the estrogen receptor (ER) and progesterone receptor (PR) status, tumor grade and enhanced proliferation (Ki67 proliferation index). In vitro functional experiments showed that the suppression of BMP6 expression by a specific small hairpin (sh)RNA vector led to increased proliferation in the MCF7 breast cancer cell line. Furthermore, knockdown of BMP6 in MCF7 cells enhanced the chemoresistance to doxorubicin by upregulation of mdr-1/P-gp expression and activation of the ERK signaling pathway. Taken together, our data suggest that BMP6 plays a critical role in breast cancer cell aberrant proliferation and chemoresistance and may serve as a novel diagnostic biomarker or therapeutic target for breast cancer.

Abstract. Bone morphogenetic protein 6 (BMP6) is an important regulator of cell growth, differentiation and apoptosis in various types of tumor. In breast cancer, it was considered as a tumor suppressor. Our previous study also confirmed that BMP6 was a critical regulator of breast cancer drug resistance. However, little is known about how its expression is regulated and its mechanisms in breast cancer drug resistance. In the present study, we assessed the DNA methylation regulation of BMP6 based on the presence of a large CpG island in the BMP6 gene promoter. Quantitative DNA methylation analyses showed a significantly increased DNA methylation level in the drug-resistant cell line MCF-7/ADR compared to their parental cells MCF-7. Moreover, the drug-resistant cell line MCF-7/ADR showed an EMT phenotype confirmed by morphology and the expression of EMT marker gene. MCF-7 cells transfected with BMP6-specific shRNA vector also showed an EMT phenotype. The MCF-7/ADR cells treated with the recombinant BMP6 proteins reversed their EMT phenotype. These data indicated that hypermethylation modifications contributed to the regulation of BMP6 and induced an EMT phenotype of breast cancer during the acquisition of drug resistance.

Abstract. Skeletal muscle insulin resistance induced by a high-fat diet has been implicated in the development of type 2 diabetes. However, the precise molecular mechanisms involved are only partially understood. Recently, studies have shown that microRNAs play an important role in insulin resistance in various tissues. In this study, microRNA expression profiles of skeletal muscle of mice fed a high-fat or normal diet were analyzed using microarrays and the results were confirmed by real-time reverse-transcription polymerase chain reaction. Gene Ontology (GO) and pathway mapping tools were employed to analyze systemically the biological processes and signaling pathways affected by the differential expression of microRNAs. In this study, we show that 30 microRNAs are differentially expressed between 2 groups of mice. Compared to the mice fed a normal diet, there were 8 microRNAs up-regulated and 22 microRNAs down-regulated in the highfat diet-fed mice. Furthermore, we confirm that the MAPK signaling pathway highlighted in this study is involved in skeletal muscle insulin resistance. These results indicate that skeletal muscle insulin resistance induced by a high-fat diet is associated with a group of microRNAs. GO and pathway mapping are a valid and effective approach for analyzing the function of microRNAs and the results could be a guideline for further investigation.

One cost-effective way for identifying novel cancer therapeutics is in the repositioning of available drugs for which current therapies are inadequate. Levofloxacin prevents DNA duplication in bacteria by inhibiting the activity of DNA helicase. As eukaryotic cells have similar intracellular biologic characteristics as prokaryotic cells, we speculate that antibiotics inhibiting DNA duplication in bacteria may also affect the survival of cancer cells.Here we report that levofloxacin significantly inhibited the proliferation and clone formation of cancer cells and xenograft tumor growth through cell cycle arrest at G2/M and by enhancing apoptosis. Levofloxacin significantly altered gene expression in a direction favoring anticancer activity. THBS1 and LAPTM5 were dose-dependently upregulated whereas SRD5A3, MFAP5 and P4HA1 were downregulated. Pathway analysis revealed that levofloxacin significantly regulated canonical oncogenic pathways. Specific network enrichment included a MAPK/ apoptosis/cytokine-cytokine receptor interaction pathway network that associates with cell growth, differentiation, cell death, angiogenesis and development and repair processes and a bladder cancer/P53 signaling pathway network mediating the inhibition of angiogenesis and metastasis. THBS1 overlapped in 16 of the 22 enriched apoptotic pathways and the 2 pathways in the bladder cancer/P53 signaling pathway network. P4HA1 enriched in 7 of the top 10 molecular functions regulated by differential downregulated genes. Our results indicate that levofloxacin has broad-spectrum anticancer activity with the potential to benefit cancer patients already treated or requiring prophylaxis for an infectious syndrome. The efficacy we find with levofloxacin may provide insight into the discovery and the design of novel less toxic anticancer drugs. Anti-Cancer Drugs 33: e235-e246

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