Antagonism between the RNA-binding protein Musashi1 and miR-137 and its potential impact on neurogenesis and glioblastoma development.

RNA-binding proteins (RBPs) and miRNAs are critical gene expression regulators that interact with one another in cooperative and antagonistic fashions. We identified Musashi1 (Msi1) and miR-137 as regulators of a molecular switch between self-renewal and differentiation. Msi1 and miR-137 have opposite expression patterns and functions, and Msi1 is repressed by miR-137. Msi1 is a stem-cell protein implicated in self-renewal while miR-137 functions as a proneuronal differentiation miRNA. In gliomas, miR-137 functions as a tumor suppressor while Msi1 is a prooncogenic factor. We suggest that the balance between Msi1 and miR-137 is a key determinant in cell fate decisions and disruption of this balance could contribute to neurodegenerative diseases and glioma development. Genomic analyses revealed that Msi1 and miR-137 share 141 target genes associated with differentiation, development, and morphogenesis. Initial results pointed out that these two regulators have an opposite impact on the expression of their target genes. Therefore, we propose an antagonistic model in which this network of shared targets could be either repressed by miR-137 or activated by Msi1, leading to different outcomes (self-renewal, proliferation, tumorigenesis).

Patient-derived conditionally reprogrammed cells maintain intra-tumor genetic heterogeneity.

Preclinical in vitro models provide an essential tool to study cancer cell biology as well as aid in translational research, including drug target identification and drug discovery efforts. For any model to be clinically relevant, it needs to recapitulate the biology and cell heterogeneity of the primary tumor. We recently developed and described a conditional reprogramming (CR) cell technology that addresses many of these needs and avoids the deficiencies of most current cancer cell lines, which are usually clonal in origin. Here, we used the CR cell method to generate a collection of patient-derived cell cultures from non-small cell lung cancers (NSCLC). Whole exome sequencing and copy number variations are used for the first time to address the capability of CR cells to keep their tumor-derived heterogeneity. Our results indicated that these primary cultures largely maintained the molecular characteristics of the original tumors. Using a mutant-allele tumor heterogeneity (MATH) score, we showed that CR cells are able to keep and maintain most of the intra-tumoral heterogeneity, suggesting oligoclonality of these cultures. CR cultures therefore represent a pre-clinical lung cancer model for future basic and translational studies.

Gene Expression Profiling Reveals Regulation of ERK Phosphorylation by Androgen-Induced Tumor Suppressor U19/EAF2 in the Mouse Prostate.

U19/EAF2 is regulated by androgens in the prostate and capable of regulating transcriptional elongation of RNA Pol II via interaction with the ELL family proteins. Inactivation of U19/EAF2 induces tumorigenesis in multiple organs; however the mechanism of U19/EAF2 tumor suppression remains unclear. To elucidate potential mechanisms of U19/EAF2 action, we performed cDNA microarray analysis and identified 164 mRNA transcripts regulated by U19/EAF2 in the mouse ventral prostate. Bioinformatics analysis indicated that U19/EAF2 knockout activates the RAS-BRAF-ERK signaling pathway, which is known to play important roles in carcinogenesis. qPCR verified increased expression of BRAF mRNA, and immunostaining and Western blot analysis demonstrated increased expression of p-ERK at the protein level suggested U19/EAF2 knockout activates this important pathway. These findings indicate that loss of EAF2 up-regulates transcription of RAS cascade genes including Grb2, PI3K, and BRAF, leading to elevated p-ERK levels, which may represent a major functional role of U19/EAF2 in the prostate. Furthermore, these observations suggest that U19/EAF2 is a key player in crosstalk between androgen receptor and the RAS-BRAF-ERK signaling pathway.