IDDF2024-ABS-0311 RBMX promotes tumor plasticity and immune suppression by activating IL-33/TGF-β signaling niche in colorectal cancer

Background Cancer-cell plasticity plays a pivotal role in shaping the immunosuppressive tumor microenvironment (TME), thereby establishing a reciprocal relationship that sustains tumor plasticity. RNA-binding proteins (RBPs) are critical regulators of cancer. Here, we investigated the effects of RNA binding protein RNA Binding Motif Protein X-Linked (RBMX) in mediating tumor plasticity and immunosuppression in colorectal cancer (CRC). Methods We used quantitative real-time polymerase chain reaction and immunohistochemistry (IHC) analyses to compare RBMX expression between paired CRC samples and nontumor tissues. We determined the effects of RBMX transcriptional activation and knockdown in CRC cell lines via in vitro functional assays. RIP-seq and RNA-seq were employed to unravel the downstream targets of RBMX. Liquid-liquid phase separation was investigated through protein purification and live cell imaging. Results Levels of RBMX mRNA and protein were increased in CRC tissues compared with matched non-tumor tissues (IDDF2024-ABS-0311 Figure 1. RBMX is frequently overexpressed in CRC tissues). Transcriptional activation of RBMX in CRC cells increased their capabilities of proliferation, motility and plasticity, which were impaired in RBMX-silenced cells (IDDF2024-ABS-0311-Figure 2. RBMX expression is associated with capabilities of proliferation motility and plasticity). Integrative analysis of RIP-seq and RNA-seq revealed that RBMX facilitates CRC plasticity through regulating IL33/TGFβ signal transduction (IDDF2024-ABS-0311 Figure 3. RBMX facilitates CRC plasticity through regulating IL33 TGFβ signal transduction, IDDF2024-ABS-0311 Figure 4. RBMX facilitates CRC plasticity through binding to IL33 mRNA and undergoing phase separation). Specifically, RBMX was found to bind to IL33 mRNA and undergo phase separation, forming droplet-shaped condensates that protect IL33 mRNA from degradation (IDDF2024-ABS-0311 Figure 4. RBMX facilitates CRC plasticity through binding to IL33 mRNA and undergoing phase separation). As a downstream target of IL33, the expression level of TGF-β was also elevated by RBMX, contributing to tumor plasticity and immune suppression (IDDF2024-ABS-0311 Figure 3. RBMX facilitates CRC plasticity through regulating IL33 TGFβ signal transduction, IDDF2024-ABS-0311 Figure 4. RBMX facilitates CRC plasticity through binding to IL33 mRNA and undergoing phase separation). Conclusions This study demonstrated that RBMX regulated tumor plasticity and immunosuppression by sustaining the mRNA stability of IL33 and induced TGFβ expression. Targeting RBMX might provide a promising treatment strategy for CRC.