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Cooper, Zachary A.

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Cooper

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Zachary A.

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Cooper, Zachary A.
Author's Publications: search.filters.isAuthorOfPublication.4236e964-3403-4bb0-8670-c7ebfeed03d4

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    PDGFRα up-regulation mediated by sonic hedgehog pathway activation leads to BRAF inhibitor resistance in melanoma cells with BRAF mutation
    (Impact Journals LLC, 2014) Sabbatino, Francesco; Wang, YangYang; Wang, Xinhui; Flaherty, Keith; Yu, Ling; Pepin, David; Scognamiglio, Giosue'; Pepe, Stefano; Kirkwood, John M.; Cooper, Zachary A.; Frederick, Dennie T.; Wargo, Jennifer Ann; Ferrone, Soldano; Ferrone, Cristina
    Control of BRAF(V600E) metastatic melanoma by BRAF inhibitor (BRAF-I) is limited by intrinsic and acquired resistance. Growth factor receptor up-regulation is among the mechanisms underlying BRAF-I resistance of melanoma cells. Here we demonstrate for the first time that PDGFRα up-regulation causes BRAF-I resistance. PDGFRα inhibition by PDGFRα-specific short hairpin (sh)RNA and by PDGFRα inhibitors restores and increases melanoma cells' sensitivity to BRAF-I in vitro and in vivo. This effect reflects the inhibition of ERK and AKT activation which is associated with BRAF-I resistance of melanoma cells. PDGFRα up-regulation is mediated by Sonic Hedgehog Homolog (Shh) pathway activation which is induced by BRAF-I treatment. Similarly to PDGFRα inhibition, Shh inhibition by LDE225 restores and increases melanoma cells' sensitivity to BRAF-I. These effects are mediated by PDGFRα down-regulation and by ERK and AKT inhibition. The clinical relevance of these data is indicated by the association of PDGFRα up-regulation in melanoma matched biopsies of BRAF-I +/- MEK inhibitor treated patients with shorter time to disease progression and less tumor regression. These findings suggest that monitoring patients for early PDGFRα up-regulation will facilitate the identification of those who may benefit from the treatment with BRAF-I in combination with clinically approved PDGFRα or Shh inhibitors.
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    Tumor microenvironment induces innate RAF-inhibitor resistance through HGF secretion
    (2012) Straussman, Ravid; Morikawa, Teppei; Shee, Kevin; Barzily-Rokni, Michal; Qian, Zhi Rong; Du, Jinyan; Davis, Ashli; Mongare, Margaret M.; Gould, Joshua; Frederick, Dennie T.; Cooper, Zachary A.; Chapman, Paul B.; Solit, David B.; Ribas, Antoni; Lo, Roger S.; Flaherty, Keith; Ogino, Shuji; Wargo, Jennifer Ann; Golub, Todd
    Drug resistance remains a vexing problem in the treatment of cancer patients. While many studies have focused on cell autonomous mechanisms of drug resistance, we hypothesized that the tumor microenvironment may confer innate resistance to therapy. Here we developed a co-culture system to systematically assay the ability of 23 stromal cell types to influence the innate resistance of 45 cancer cell lines to 35 anti-cancer drugs. We found that stroma-mediated resistance is surprisingly common – particularly to targeted agents. We further characterized the stroma-mediated resistance of BRAF-mutant melanoma to RAF inhibition because most of these patients exhibit some degree of innate resistance1-4. Proteomic analysis showed that stromal secretion of the growth factor hepatocyte growth factor (HGF) resulted in activation of the HGF receptor MET, reactivation of the MAPK and PI3K/AKT pathways, and immediate resistance to RAF inhibition. Immunohistochemistry confirmed stromal HGF expression in patients with BRAF-mutant melanoma and a statistically significant correlation between stromal HGF expression and innate resistance to treatment. Dual inhibition of RAF and MET resulted in reversal of drug resistance, suggesting RAF/MET combination therapy as a potential therapeutic strategy for BRAF-mutant melanoma. A similar resistance mechanism was uncovered in a subset of BRAF-mutant colorectal and glioblastoma cell lines. More generally, these studies indicate that the systematic dissection of tumor-microenvironment interactions may reveal important mechanisms underlying drug resistance.
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    Combining targeted therapy and immune checkpoint inhibitors in the treatment of metastatic melanoma
    (Chinese Anti-Cancer Association, 2015) Kim, Teresa; Amaria, Rodabe N.; Spencer, Christine; Reuben, Alexandre; Cooper, Zachary A.; Wargo, Jennifer A.
    Melanoma is the deadliest form of skin cancer and has an incidence that is rising faster than any other solid tumor. Metastatic melanoma treatment has considerably progressed in the past five years with the introduction of targeted therapy (BRAF and MEK inhibitors) and immune checkpoint blockade (anti-CTLA4, anti-PD-1, and anti-PD-L1). However, each treatment modality has limitations. Treatment with targeted therapy has been associated with a high response rate, but with short-term responses. Conversely, treatment with immune checkpoint blockade has a lower response rate, but with long-term responses. Targeted therapy affects antitumor immunity, and synergy may exist when targeted therapy is combined with immunotherapy. This article presents a brief review of the rationale and evidence for the potential synergy between targeted therapy and immune checkpoint blockade. Challenges and directions for future studies are also proposed.