PTHrP Overexpression Increases Sensitivity of Breast Cancer Cells to Apo2L/TRAIL

Metformin prevention of doxorubicin resistance in MCF-7 and MDA-MB-231 involves oxidative stress generation and modulation of cell adaptation genes

Metformin was shown to sensitize multidrug resistant breast cancer cells; however, the mechanisms involved in this capacity need to be clarified. We investigated oxidative stress and inflammatory-related pathways during the induction of doxorubicin resistance in MCF-7 and MDA-MB-231 human breast cancer cells (DOX-res group), and evaluated metformin-induced cellular responses that resulted in the prevention of doxorubicin resistance (Met-DOX group). Microarray analysis demonstrated that DOX-res changed the expression of genes involved in oxidative stress (OS) and the TGF- β1 pathway. The DOX-res group presented increased thiols and reduced lipoperoxidation, increased levels of nitric oxide, nuclear NF-kB and Nrf2, and reduced nuclear p53 labelling. Analysis of the TGF-β1 signaling pathway by RT-PCR array showed that DOX-res developed adaptive responses, such as resistance against apoptosis and OS. Metformin treatment modified gene expression related to OS and the IFN-α signaling pathway. The Met-DOX group was more sensitive to DOX-induced OS, presented lower levels of nitric oxide, nuclear NF-kB and Nrf2, and increased nuclear p53. Analysis of the IFN-α signaling pathway showed that Met-DOX presented more sensitivity to apoptosis and OS. Our findings indicate that metformin is a promising tool in the prevention of chemoresistance in patients with breast cancer submitted to doxorubicin-based treatments.

NanoTRAIL-Oncology: A Strategic Approach in Cancer Research and Therapy

TRAIL is a member of the tumor necrosis factor superfamily that can largely trigger apoptosis in a wide variety of cancer cells, but not in normal cells. However, insufficient exposure to cancer tissues or cells and drug resistance has severely impeded the clinical application of TRAIL. Recently, nanobiotechnology has brought about a revolution in advanced drug delivery for enhanced anticancer therapy using TRAIL. With the help of materials science, immunology, genetic engineering, and protein engineering, substantial progress is made by expressing fusion proteins with TRAIL, engineering TRAIL on biological membranes, and loading TRAIL into functional nanocarriers or conjugating it onto their surfaces. Thus, the nanoparticle-based TRAIL (nanoTRAIL) opens up intriguing opportunities for efficient and safe bioapplications. In this review, the mechanisms of action and biological function of TRAIL, as well as the current status of TRAIL treatment, are comprehensively discussed. The application of functional nanotechnology combined with TRAIL in cancer therapy is also discussed.

Calcium-Sensing Receptor Promotes Breast Cancer by Stimulating Intracrine Actions of Parathyroid Hormone-Related Protein

Parathyroid hormone-related protein (PTHrP) contributes to the development and metastatic progression of breast cancer by promoting hypercalcemia, tumor growth, and osteolytic bone metastases, but it is not known how PTHrP is upregulated in breast tumors. Here we report a central role in this process for the calcium-sensing receptor, CaSR, which enables cellular responses to changes in extracellular calcium, through studies of CaSR-PTHrP interactions in the MMTV-PymT transgenic mouse model of breast cancer and in human breast cancer cells. CaSR activation stimulated PTHrP production by breast cancer cells in vitro and in vivo Tissue-specific disruption of the casr gene in mammary epithelial cells in MMTV-PymT mice reduced tumor PTHrP expression and inhibited tumor cell proliferation and tumor outgrowth. CaSR signaling promoted the proliferation of human breast cancer cell lines and tumor cells cultured from MMTV-PyMT mice. Further, CaSR activation inhibited cell death triggered by high extracellular concentrations of calcium. The actions of the CaSR appeared to be mediated by nuclear actions of PTHrP that decreased p27(kip1) levels and prevented nuclear accumulation of the proapoptotic factor apoptosis inducing factor. Taken together, our findings suggest that CaSR-PTHrP interactions might be a promising target for the development of therapeutic agents to limit tumor cell growth in bone metastases and in other microenvironments in which elevated calcium and/or PTHrP levels contribute to breast cancer progression. Cancer Res; 76(18); 5348-60. ©2016 AACR.

Decorin-induced proliferation of avian myoblasts involves the myostatin/Smad signaling pathway

Decorin, a small leucine-rich proteoglycan as a component of the extracellular matrix, plays an important role in the skeletal muscle development. It has been reported that decorin promoted proliferation and differentiation of muscle cells by restraining myostatin activity in rodents. However, the effects and mechanisms of decorin on avian myoblast proliferation are not understood clearly. Thus, in our research, decorin overexpressing and knocking-down quail myoblast-7 (QM7) myoblasts were established to explore the effects of decorin on avian myoblast proliferation by flow cytometry. The results showed that overexpression of decorin enhanced the proliferation of QM7 myoblasts, which was accompanied by the upregulation of follistatin and primary muscle regulatory factors (i.e., myogenic factor 5, myogenic factor 1, myogenin), and downregulation of myostatin expression, as well as the decreased phosphorylation level of SMAD family member 3 (Smad3). In line with expectations, decorin RNAi displayed an opposite effect on the proliferation and gene expression pattern of QM7 cells. In conclusion, our in vitro studies suggested the decorin-mediated myostatin/Smad signaling pathway might be involved in the regulation of avian myoblast proliferation.