Bedside RNA stabilizing kit systems for gene expression analysis of acute leukemias: influence of non-neoplastic white blood cells

Frequent loss of RAF kinase inhibitor protein expression in acute myeloid leukemia

RAF kinase inhibitor protein (RKIP) is a negative regulator of the RAS-mitogen-activated protein kinase/extracellular signal-regulated kinase signaling cascade. We investigated its role in acute myeloid leukemia (AML), an aggressive malignancy arising from hematopoietic stem and progenitor cells (HSPCs). Western blot analysis revealed loss of RKIP expression in 19/103 (18%) primary AML samples and 4/17 (24%) AML cell lines but not in 10 CD34+ HSPC specimens. In in-vitro experiments with myeloid cell lines, RKIP overexpression inhibited cellular proliferation and colony formation in soft agar. Analysis of two cohorts with 103 and 285 AML patients, respectively, established a correlation of decreased RKIP expression with monocytic phenotypes. RKIP loss was associated with RAS mutations and in transformation assays, RKIP decreased the oncogenic potential of mutant RAS. Loss of RKIP further related to a significantly longer relapse-free survival and overall survival in uni- and multivariate analyses. Our data show that RKIP is frequently lost in AML and correlates with monocytic phenotypes and mutations in RAS. RKIP inhibits proliferation and transformation of myeloid cells and decreases transformation induced by mutant RAS. Finally, loss of RKIP seems to be a favorable prognostic parameter in patients with AML.

Transcriptional profiling of peripheral blood cells in clinical pharmacogenomic studies

Peripheral blood represents an attractive tissue source in clinical pharmacogenomic studies, given the feasibility of its collection from patients and its potential as a sentinel tissue to monitor perturbations of physiology in many disease states. The hypothesis is that the circulating blood cells monitor the physiological state of the organism and alter their transcriptome in response to this surveillance. However, the successful implementation of transcriptional profiling of peripheral blood cells in clinical trials represents a tremendous technical challenge for several reasons, including controlling the pre-analytical variables associated with sample processing and the interpretation of gene expression signatures generated from the complex mixture of cell types in blood. Multiple approaches for identifying transcriptomes in peripheral blood cells exist and each method is associated with significant advantages and disadvantages. Nonetheless, a growing number of studies are rapidly identifying transcriptional biomarkers in peripheral blood cells that may function as biomarkers of disease, evidence of pharmacodynamic effect, or even predictors of clinical outcomes and risk of toxicity. This review highlights the major approaches employed in global transcriptional profiling of peripheral blood cells and summarizes the available literature of initial studies in the growing field of hemogenomics. The overall purpose of the review is to focus on the development and application of technologies for the use of peripheral blood cells as a sentinel or surrogate tissue to measure disease state and drug response.