Musashi 2 (MSI2) expression as an independent prognostic biomarker in non-small cell lung cancer (NSCLC).

e21583 Background: Non-small cell lung cancer (NSCLC) is the leading cause of cancer-related death in the world, and metastasis is the most common cause of death in lung cancer patients. Musashi-2 (MSI2) is a member of RNA-binding protein family and regulates mRNA translation of numerous intracellular targets, and influences multiple biological processes, including maintenance of stem cell identity. Previously we reported that MSI2 is upregulated in the metastasis-competent NSCLC murine and human cell lines, drives NSCLC metastasis, and is progressively elevated in lung cancer patient samples. This study assessed MSI2 as potential clinical biomarker in NSCLC. Methods: The current study included 40 patients with NSCLC, of whom 15 presented with stage II and III respectively (37,5% each), and 10 patients (25%) had stage IV. All patients received treatment in accordance with the NCCN guidelines, and did not participate in clinical trials. All patient samples were obtained before treatment started. We used immunohistochemical (IHC) approach to measure MSI2 expression on the protein level in matching specimens of normal versus tumor tissues, and primary tumor vs. metastasis, followed by correlative analysis in relation to clinical outcomes. In parallel, clinical correlative analysis of MSI2 mRNA expression was performed in silico using publicly available datasets (TCGA/ICGC) as of January 2020. Results: MSI2 protein expression in patient samples was significantly elevated in NSCLC primary tumors and metastatic sites versus normal tissue (p = 0.03). MSI2 elevated expression positively correlated with a decreased progression free survival (PFS) (p = 0.026) at all stages and overall survival at stage IV (p = 0.013). Elevated MSI2 expression on RNA level was observed in primary tumor versus normal tissue samples in TCGA (p < 0.0001), and positively correlated with decreased OS (p = 0.028). No correlation was observed between MSI2 expression and age, sex, smoking, and treatment type. Conclusions: Elevated MSI2 expression in primary NSCLC tumors is associated with poor prognosis and can be used as a novel potential prognostic biomarker in NSCLC patients. Future studies in an extended patient cohort are strongly warranted.