Localized inhibition of platelets and platelet derived growth factor by a matrix targeted glycan mimetic significantly attenuates liver fibrosis.

New therapeutic strategies are needed for the growing unmet clinical needs in liver disease and fibrosis. Platelet activation and PDGF activity are recognized as important therapeutic targets; however, no therapeutic approach has yet addressed these two upstream drivers of liver fibrosis. We therefore designed a matrix-targeting glycan therapeutic, SBR-294, to inhibit collagen-mediated platelet activation while also inhibiting PDGF activity. Herein we describe the synthesis and characterization of SBR-294 and demonstrate its potential therapeutic benefits in vitro and in vivo. In vitro SBR-294 was found to bind collagen (EC50 = 23 nM), thereby inhibiting platelet-collagen engagement (IC50 = 60 nM). Additionally, SBR-294 was found to bind all PDGF homodimeric isoforms and to inhibit PDGF-BB mediated hepatic stellate cell activation and proliferation. Translating these mechanisms in vivo, SBR-294 reduced fibrosis by up to 54% in the CCl4 mouse model (p = 0.0004), as measured by Sirius red histological analysis. Additional fibrosis measurements were also supportive of the therapeutic benefit in this model. These results support the therapeutic benefit of platelet and PDGF antagonism and warrant further investigation of SBR-294 as a potential treatment for liver fibrosis.

Stress-inducible gene Atf3 in the noncancer host cells contributes to chemotherapy-exacerbated breast cancer metastasis.

Chemotherapy is a double-edged sword. It is anticancer because of its cytotoxicity. Paradoxically, by increasing chemoresistance and cancer metastasis, it is also procancer. However, the underlying mechanisms for chemotherapy-induced procancer activities are not well understood. Here we describe the ability of paclitaxel (PTX), a frontline chemotherapeutic agent, to exacerbate metastasis in mouse models of breast cancer. We demonstrate that, despite the apparent benefit of reducing tumor size, PTX increased the circulating tumor cells in the blood and enhanced the metastatic burden at the lung. At the primary tumor, PTX increased the abundance of the tumor microenvironment of metastasis, a landmark microanatomical structure at the microvasculature where cancer cells enter the blood stream. At the metastatic lung, PTX improved the tissue microenvironment (the "soil") for cancer cells (the "seeds") to thrive; these changes include increased inflammatory monocytes and reduced cytotoxicity. Importantly, these changes in the primary tumor and the metastatic lung were all dependent on Atf3, a stress-inducible gene, in the noncancer host cells. Together, our data provide mechanistic insights into the procancer effect of chemotherapy, explaining its paradox in the context of the seed-and-soil theory. Analyses of public datasets suggest that our data may have relevance to human cancers. Thus, ATF3 in the host cells links a chemotherapeutic agent-a stressor-to immune modulation and cancer metastasis. Dampening the effect of ATF3 may improve the efficacy of chemotherapy.

Transcription factor ATF3 links host adaptive response to breast cancer metastasis.

Host response to cancer signals has emerged as a key factor in cancer development; however, the underlying molecular mechanism is not well understood. In this report, we demonstrate that activating transcription factor 3 (ATF3), a hub of the cellular adaptive response network, plays an important role in host cells to enhance breast cancer metastasis. Immunohistochemical analysis of patient tumor samples revealed that expression of ATF3 in stromal mononuclear cells, but not cancer epithelial cells, is correlated with worse clinical outcomes and is an independent predictor for breast cancer death. This finding was corroborated by data from mouse models showing less efficient breast cancer metastasis in Atf3-deficient mice than in WT mice. Further, mice with myeloid cell-selective KO of Atf3 showed fewer lung metastases, indicating that host ATF3 facilitates metastasis, at least in part, by its function in macrophage/myeloid cells. Gene profiling analyses of macrophages from mouse tumors identified an ATF3-regulated gene signature that could distinguish human tumor stroma from distant stroma and could predict clinical outcomes, lending credence to our mouse models. In conclusion, we identified ATF3 as a regulator in myeloid cells that enhances breast cancer metastasis and has predictive value for clinical outcomes.

Immunohistochemical detection of activating transcription factor 3, a hub of the cellular adaptive-response network.

Activating transcription factor 3 (ATF3) gene encodes a member of the ATF family of transcription factors and is induced by various stress signals, including many of those that induce the unfolded protein response (UPR). Emerging evidence suggests that ATF3 is a hub of the cellular adaptive-response network and studies using various mouse models indicate that ATF3 plays a role in the pathogenesis of various diseases. One way to investigate the potential relevance of ATF3 to human diseases is to determine its expression in patient samples and test whether it correlates with disease progression or clinical outcomes. Due to the scarcity and preciousness of patient samples, methods that can detect ATF3 on archival tissue sections would greatly facilitate this research. In this chapter, we briefly review the roles of ATF3 in cellular adaptive-response and UPR, and then describe the detailed steps and tips that we developed based on general immunohistochemistry (IHC) protocols to detect ATF3 on paraffin embedded sections.

Snail and slug mediate radioresistance and chemoresistance by antagonizing p53-mediated apoptosis and acquiring a stem-like phenotype in ovarian cancer cells.

The transcriptional repressors Snail and Slug contribute to cancer progression by mediating epithelial-mesenchymal transition (EMT), which results in tumor cell invasion and metastases. We extend this current understanding to demonstrate their involvement in the development of resistance to radiation and paclitaxel. The process is orchestrated through the acquisition of a novel subset of gene targets that is repressed under conditions of stress, effectively inactivating p53-mediated apoptosis, while another subset of targets continues to mediate EMT. Repressive activities are complemented by a concurrent derepression of specific genes resulting in the acquisition of stem cell-like characteristics. Such cells are bestowed with three critical capabilities, namely EMT, resistance to p53-mediated apoptosis, and a self-renewal program, that together define the functionality and survival of metastatic cancer stem cells. EMT provides a mechanism of escape to a new, less adverse niche; resistance to apoptosis ensures cell survival in conditions of stress in the primary tumor; whereas acquisition of "stemness" ensures generation of the critical tumor mass required for progression of micrometastases to macrometastases. Our findings, besides achieving considerable expansion of the inventory of direct genes targets, more importantly demonstrate that such elegant cooperative modulation of gene regulation mediated by Snail and Slug is critical for a cancer cell to acquire stem cell characteristics toward resisting radiotherapy- or chemotherapy-mediated cellular stress, and this may be a determinative aspect of aggressive cancer metastases.