High expression of the RNA-binding protein RBPMS2 in gastrointestinal stromal tumors

Abstract

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms of the gastrointestinal tract and are often associated with KIT or PDGFRA gene mutations. GIST cells might arise from the interstitial cells of Cajal (ICCs) or from a mesenchymal precursor that is common to ICCs and smooth muscle cells (SMCs). Here, we analyzed the mRNA and protein expression of RNA-Binding Protein with Multiple Splicing-2 (RBPMS2), an early marker of gastrointestinal SMC precursors, in human GISTs (n=23) by in situ hybridization, quantitative RT-PCR analysis and immunohistochemistry. The mean RBPMS2 mRNA level in GISTs was 42-fold higher than in control gastrointestinal samples (p<0.001). RBPMS2 expression was not correlated with KIT and PDGFRA expression levels, but was higher in GISTs harboring KIT mutations than in tumors with wild type KIT and PDGFRA or in GISTs with PDGFRA mutations that were characterized by the lowest RBPMS2 levels. Moreover, RBPMS2 levels were 64-fold higher in GIST samples with high risk of aggressive behavior than in adult control gastrointestinal samples and 6.2-fold higher in high risk than in low risk GIST specimens. RBPMS2 protein level was high in 87% of the studied GISTs independently of their histological classification. Finally, by inhibiting the KIT signaling pathway in GIST882 cells, we show that RBPMS2 expression is independent of KIT activation. In conclusion, RBPMS2 is up-regulated in GISTs compared to normal adult gastrointestinal tissues, indicating that RBPMS2 might represent a new diagnostic marker for GISTs and a potential target for cancer therapy.

Homodimerization of RBPMS2 through a new RRM-interaction motif is necessary to control smooth muscle plasticity

“…Previous studies demonstrated that post-transcriptional events control the development and the plasticity of different types of smooth muscles through miR or RNA-binding protein expression and function (2,3,7,8,9,11). Among these important players is the RNA-binding protein RBPMS2, which is involved in digestive SMC development and plasticity through the control of BMP signaling activity (9,11).…”

“…Human RBPMS2 cDNA was used as template (11). The substitution of L49 by E or Q in human RBPMS2 was done with the QuikChange site-directed mutagenesis kit and protocol (Stratagene).…”

“…Myc-tagged chick full-length RBPMS2 (RCAS-Myc- RBPMS2 ), GFP (RCAS- GFP ) and Myc-NICD were previously described (9,10,17). All plasmids were checked by DNA sequencing, protein expression and expression plasmids were transfected in the avian DF-1 chicken fibroblast cell line (ATCC-LGC) or human embryonic kidney 293 (HEK293) cell line as previously described (11,18). …”

“…RBPMS2 is an early marker of gastrointestinal smooth muscle precursor cells (9,10), which positively regulates mRNA expression of NOGGIN , the major inhibitor of the bone morphogenetic protein (BMP) pathway, through the formation of a NOGGIN– RBPMS2 ribonucleoprotein complex (9). Ectopic RBPMS2 expression in differentiated digestive SMCs hinders their ability to contract and induces their proliferation leading to their dedifferentiation, demonstrating that RBPMS2 expression has to be tightly regulated to avoid SMC dedifferentiation, as observed in chronic intestinal pseudo-obstruction syndrome (CIPO) and gastro-intestinal stromal tumors (GISTs) (9,11). …”

Identification of the RNA recognition element of the RBPMS family of RNA-binding proteins and their transcriptome-wide mRNA targets

“…Nuclear (Nuc), cytoplasmic (Cyt), and total cell lysate (Tot) fractions were resolved on a 4%-12% SDS-polyacrylamide gel and then probed using an anti-HA antibody targeting FLAG-HA RBPMS and RBPMS2, and antibodies targeting ELAVL1 (HuR), TUBB (β-tubulin), and LMNB1 (lamin B) as controls for the purity of the cytoplasmic and nuclear fractions. Dysregulation of RBPMS family proteins has been reported in cancer (Skawran et al 2008;Miller and Stamatoyannopoulos 2010;Drozdov et al 2012;Hapkova et al 2013; http://www.cbioportal.org/public-portal/) and chronic intestinal pseudo-obstruction (Notarnicola et al 2012). Manipulation of RBPMS levels during embryogenesis suggested functions in X. laevis oocyte maturation (Zearfoss et al 2003), heart and kidney development (Gerber et al 2002), and retinal ganglion cell development (Hornberg et al 2013).…”