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Exon4-mutations in KRAS Affect MEK-ERK and Pi3K-AKT Signaling in Multiple Myeloma

ABSTRACT: Approximately 40% of MM cases harbor a point mutation in either KRAS or NRAS. However, it is still unclear whether RAS-mutations are associated with disease outcome. Specifically, no information exists whether KRAS-mutations have an impact on survival in MM patients at diagnosis that were treated with novel agents (e.g. bortezomib, lenalidomide). Targeting KRAS directly for therapeutic purposes is still impossible, but recently the first covalent mutant-specific inhibitor targeting KRASG12C made it into clinical trials. However, other KRAS-hotspot-mutations exist in MM patients, including the less common exon4-mutations. Within the current study, the coding regions of KRAS in 80 MM patients at diagnosis, uniformly treated with bortezomib and high-dose chemotherapy, were deep-sequenced. Moreover, the functional impact of KRASG12A as well as the two exon4-mutations A146T (AMO1) and A146V (MM patient) on different survival pathways was investigated. Specifically, an siRNA-mediated knockdown in AMO1 was performed and KRASWT, KRASG12A, KRAS146T and KRAS146V were overexpressed in the KRASWT cell lines JJN3 and OPM2 using lentiviral transduction and the transposase based Sleeping Beauty system. KRAS-mutations were not associated with survival. Yet, the expression of all KRAS-mutants had an impact on MEK/ERK-signaling in two independent MM cell lines and on AKT/PI3K-signaling in one MM cell line.

PROVIDER: EGAS00001004110 | EGA |

REPOSITORIES: EGA

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Project description:Colorectal cancer (CRC) is still one of the most common causes of cancer-related death worldwide (World Health Organization, Fact sheet NM-BM-0297, October 2011). Though, therapeutic options improved over the past years, the prognosis of metastatic colorectal cancer (mCRC) remains poor with a median survival of 18-21 months. Monoclonal antibodies targeting the epidermal growth factor receptor (EGFR) are used for the palliative treatment of metastatic colorectal cancer (mCRC) carrying a KRAS-wildtype. Among the tumors with a KRAS-wildtype, only 35% respond, and alterations of other signaling molecules and pathways modulate therapeutic response. In this study we analyzed the effect of KRAS-mutations on intracellular signaling cascades to find new therapeutic approaches for patients with mCRC. Reverse-phase protein array and gene array technology was applied to sixteen adenocarcinomas of the sigmoid colon carrying either wildtype (n=8) or mutant (n=8) KRAS. Differential expression was validated on 49 sigmoid cancers by RT-PCR, Western blot and immunohistochemistry. In a screening for members of signaling pathways known to have a high impact on tumor development in colon cancer, we found 14 proteins downregulated in tumors with mutated KRAS. Subsequently, we compared the data of the protein arrays with the results of gene expression arrays performed with the same samples. We confirmed the differential expression of eight genes as a function of the KRAS genotype of the tumor. To further validate the differential expression of these candidates, we performed quantitative expression analysis and immunohistochemical staining of an independent validation series comprising 49 CRC patient samples. It was clearly demonstrated that the expression of EGFR is decreased in colorectal carcinomas with a mutant KRAS genotype. mRNA was obtained from 16 patients with colorectal cancer (8 with and 8 without KRAS-mutation). mRNA was extracted from neoplastic and non-neoplastic colon mucosa and analyzed separately by Affymetrix Human Gene 1.1 ST GeneChips finally generating 32 separate data sets.

Project description:Multiple myeloma (MM) is a malignant disorder characterized by the clonal proliferation of plasma cells (PCs) in the bone marrow (BM). The genetic background and clinical course of the disease are largely heterogeneous, and MM pathophysiology ranges from the premalignant condition of monoclonal gammopathy of undetermined significance (MGUS) to smoldering MM, symptomatic MM, and extramedullary MM/plasma cell leukemia (PCL). Recent genome-wide sequencing efforts have provided the rationale for molecularly aimed treatment approaches, identifying mutations that can be specifically targeted, such as those in the mitogen-activated protein kinase (MAPK) pathway, which represent the most prevalent mutations in MM. Among these, mutations affecting BRAF gene, detected in 4-15% of patients, are of potential immediate clinical relevance due to the availability of effective inhibitors of this serine-threonine kinase which are in fact being explored also in myeloma. In this study, we screened by next generation sequencing (NGS) a large and representative series of intramedullary and extramedullary MM patients, including primary and secondary plasma cell leukemia (pPCL and sPCL, respectively), for mutations in BRAF, NRAS and KRAS genes. We evaluated the relationship of identified variants with other clinical and biological features and determined the transcriptional signature associated with MAPK pathway activation in MM. To identify transcriptomic profiles possibly related to BRAF, NRAS and KRAS mutations found in our study, we investigated by Affymetrix microarray technology a large fraction (n=142) of the samples analyzed by NGS, including wild-type patients for all the three genes and cases carrying mutations in at least one of them. Assuming that alterations present in a very limited number of malignant PCs might not appreciably affect gene expression, we chose to arbitrarily establish 20% as the lower variant allele frequency cut-off to perform supervised analyses.

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Exon4-mutations in KRAS Affect MEK-ERK and Pi3K-AKT Signaling in Multiple Myeloma

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