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A novel RAF kinase inhibitor with DFG-out binding mode: high efficacy in BRAF-mutant tumor xenograft models in the absence of normal tissue hyperproliferation

ABSTRACT: Purpose: Seek for differential gene expression in vemurafenib-resistant A375 tumors vs. untreated controls to provide a rationale for resistance mechanism Methods: mRNA profiles of vemurafenib-resistant A375 tumors and untreated control tumors were generated by transcriptome sequencing of A375 melanoma bearing mice. Since our xenograft samples contain a mixture of human and mouse RNAs we mapped RNASeq reads against a hybrid human/mouse genome. We than removed reads of potential mouse origin by taking only reads that map uniquely to human chromosomes. On average 23% of reads were removed as potential mouse reads. We than took the remaining reads (on average 77% per sample) to determine the gene expression levels for each sample. Normalized expression levels of 5 resistant samples were compared to 4 untreated control samples to detect differnetially regulated genes which may contribute to vemurfenib resistance Results: Expression levels of several genes were consistently altered in all resistant samples. Expression of e.g. genes encoding SPRY2, SPRY4, DUSP6, CCND1, PIK3R3, FGFR1, EPHA4, MCL1, and IGF1R was down-regulated, whereas expression of PDGFC, VEGFC, ABCB9 and KITLG was increased. Conclusions: Our study reports several differentially expressed genes which may contribute to vemurafenib resistance in A375 tumor bearing mice

ORGANISM(S): Homo sapiens

PROVIDER: GSE74729 | GEO | 2016/01/01

SECONDARY ACCESSION(S): PRJNA301353

REPOSITORIES: GEO

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Project description:The majority of human melanomas bears BRAF mutations and thus is treated with inhibitors of BRAF, such as vemurafenib. While patients with BRAF mutations often demonstrate an initial dramatic response to vemurafenib, relapse is extremely common. Thus, novel agents are needed for the treatment of these aggressive melanomas. Honokiol is a small molecule compound derived from Magnolia grandiflora that has activity against solid tumors and hematopoietic neoplasms. In order to increase the lipophilicity of honokiol, we have synthesized honokiol DCA, the dichloroacetate ester of honokiol. In addition, we synthesized a novel fluorinated honokiol analog, bis-trifluoromethyl-bis-(4-hydroxy-3-allylphenyl) methane (hexafluoro). Both compounds exhibited activity against A375 melanoma in vivo, but honokiol DCA was more active. Gene arrays comparing treated with vehicle control tumors demonstrated induction of the respiratory enzyme succinate dehydrogenase B (SDHB) by treatment, suggesting that our honokiol analogs induce respiration in vivo. We then examined its effect against a pair of melanomas, LM36 and LM36R, in which LM36R differs from LM36 in that LM36R has acquired vemurafenib resistance. Honokiol DCA demonstrated in vivo activity against LM36R (vemurafenib resistant) but not against parental LM36. Honokiol DCA and hexafluoro inhibited the phosphorylation of DRP1, thus stimulating a phenotype suggestive of respiration through mitochondrial normalization. Honokiol DCA may act in vemurafenib resistant melanomas to increase both respiration and reactive oxygen generation, leading to activity against aggressive melanoma in vivo. Tumors from animals treated with control vehicle, honokiol DCA, and hexafluoro were harvested and snapped-frozen in liquid nitrogen until RNA Extraction. RNA extraction was performed according to the Qiagen RNeasy kit. RNA samples were then submitted to Emory Universityâs Intergrated Genomics Core for RNA quality analysis and gene expression assay. Gene expression analysis was performed using an Illumina HumanHT-12 v3 Expression Bead Chip and Gene Expression Module of Illuminaâs GenomeStudio Software package (v2011.1, Illumina).

Project description:Bevacizumab induces glioblastoma resistance in two in vivo xenograft models. Two cell lines were developed with acquired resistance to bevacizumab. Gene expression difference were analyzed between treated and untreated tumors. Purpose: Antiangiogenic therapy reduces vascular permeability and delays progression but may ultimately promote an aggressive treatment-resistant phenotype. The aim of the present study was to identify mechanisms responsible for glioblastoma resistance to antiangiogenic therapy. Experimental Design: Glioma stem cell (GSC) NSC11 and U87 cell lines with acquired resistance to bevacizumab were developed from orthotopic xenografts in nude mice treated with bevacizumab. Genome-wide analyses were used to identify changes in tumor subtype and specific factors associated with resistance. Results: Mice with established parental NSC11 and U87 cells responded to bevacizumab, whereas glioma cell lines derived at the time of acquired resistance to anti-VEGF therapy were resistant to bevacizumab and did not have prolongation of survival compared to untreated controls. Gene expression profiling comparing anti-VEGF therapy-resistant cell lines to untreated controls demonstrated an increase in genes associated with a mesenchymal origin, cellular migration/invasion, and inflammation. Gene Set Enrichment Analysis (GSEA) demonstrated that bevacizumab-treated tumors showed a highly significant correlation to published mesenchymal gene signatures. Mice bearing resistant tumors showed significantly greater infiltration of myeloid cells in NSC11 and U87 resistant tumors. Invasion-related genes were also upregulated in both NSC11 and U87 resistant cells, which had higher invasion rates in vitro compared with their respective parental cell lines. Conclusions: Our studies identify multiple pro-inflammatory factors associated with resistance and identify a proneural-to-mesenchymal transition (PMT) in tumors resistant to antiangiogenic therapy. Glioma cell lines were injected into the caudate of nude mice and were allowed to grow untreated (samples labeled control) or were treated with 10 mg/kg IP twice weekly with bevacizumab (samples labeled Avastin). At the time of animal death, tumor tissue from the mouse was removed, and RNA was isolated and analyzed using gene expression. U87R and NSC11R represent cells resistant to bevacizumab (Avastin).

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A novel RAF kinase inhibitor with DFG-out binding mode: high efficacy in BRAF-mutant tumor xenograft models in the absence of normal tissue hyperproliferation

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