Studying the Molecular Regulatory Mechanisms, Clinical Significance, and Therapeutic Potential of Igf2 Mrna-Binding Protein 3 (Igf2bp3) in Hepatocellular Carcinoma

Carcinogenesis of hepatocellular carcinoma (HCC) is a multi-step and complex process mainly caused by activation of oncogenes or deregulation of tumor suppressor genes. Therefore, it is important to identify the novel HCC-associated genes and provide the new molecular mechanisms for the pathogenesis of HCC. To identify novel genes involved in HCC, we analyze the gene expression profiles using microarray analysis in HCC patients. Among the top ranking of the potentially upregulated candidate genes, we focus on IGF2BP3 based on its characterization of the oncofetal protein. We further confirm the upregulated levels of IGF2BP3 mRNA in HCC tumors, and demonstrate that high levels of IGF2BP3 significantly correlate with poor overall survival in patients with HCC. Meanwhile, the trait of bad overall survival is also observed in a cohort of HCC patients from Kaplan Meier plotter. Moreover, IGF2BP3 protein are strongly expressed in the tumor compared to their paired adjacent non-tumorous liver specimens of HCC patients and liver tumor of HBxTg mice. Knockdown of IGF2BP3 greatly inhibits cell proliferation and anchorage-independent tumor growth in HCC. By luciferase reporter gene assays, we find that the fragments 734 to +165 is critical for activation of IGF2BP3 expression. Interestingly, HCC cells expressing CD driven by IGF2BP3 promoter are sensitive to 5-FC, suggesting that IGF2BP3 promoter is potentially developed for a novel selective gene-directed enzyme prodrug therapy (GDEPT). To date, the upstream and downstream regulatory mechanisms of IGF2BP3 have not yet been extensively studied in HCC. In this project, we thus have five aims to dissect the regulatory mechanisms of IGF2BP3, address the clinical significance of its regulatory axis, and develop targeted therapies in HCC. Aim 1. To identify the regulatory factors involving in transcriptional regulation of IGF2BP3 expression in HCC. Aim 2. To identify and reveal the roles of IGF2BP3’s target RNAs in promoting HCC. Aim 3. To assess the clinical importance between IGF2BP3 and its regulatory axis in patients with HCC. Aim 4. To develop the potential small molecule therapies for IGF2BP3 in the treatment of HCC. Aim 5. Aim 5. To optimize and evaluate the anti-tumor applications of IGF2BP3 promoter using gene-directed enzyme prodrug therapy (GDEPT). Our studies will discover a novel insight into molecular regulatory mechanisms by which IGF2BP3 expressions are upregulated by the transcriptional regulators and subsequently control target RNAs to promote the tumorigenesis of HCC. These findings will further provide a significant step forward in development of potential IGF2BP3-specific inhibitors, IGF2BP3 promoter-based GDEPT, and a useful diagnostic marker in prediction of outcome and prognosis in HCC.