Abstract C62: Attacking the most downstream “gatekeeper” signaling module in the oncogenic ERBB/K-RAS signaling pathway to block tumorigenesis and metastasis in human cancer
Authors: Bian Minglei , Liao Yang , Zheleva Vasilena , Gao Xiaofei , Urban Zena M. , Njogu Monicah M. , Odanga Justin J. , Isbell Andrew J. , Schmidt Rebecca L. , Takahashi Rie , Perry Roger R. , Hoefer Richard A. , Smyrk Thomas C. , Petersen Gloria M. , Tang Amy H. 
Published: August 2014

Abstract
Hyperactive ERBB/K-RAS signaling is a major menace that drives aggressive tumor growth and metastasis in human cancer. Currently, there are no effective ways to treat late-stage and relapsed human cancers that have oncogenic ERBB/K-RAS mutations that often confer drug resistance, aggressive tumor growth, systemic metastasis, and poor clinical outcome. Therefore, finding novel approaches and new drug targets to inhibit oncogenic ERBB/K-RAS activation is an urgent goal and the major challenge in cancer therapy and treatment. Instead of targeting an upstream signaling module such as EGFR/HER2/KRAS/B-RAF, we targeted the most downstream signaling module in the EGFR/HER2/K-RAS pathway called the SIAH-dependent proteolytic machinery. SIAHs are the human homologs of Seven-In-Absentia (SINA), an evolutionarily conserved RING E3 ligase, an essential downstream signaling module and a critical “gatekeeper” required for proper EGFR/HER2/K-RAS/B-RAF signal transduction. Guided by the insights and fundamental principles learned from the Drosophila RAS signaling pathway, we conducted preclinical studies to dissect SIAH function in the context of ERBB/K-RAS-mediated tumorigenesis and metastasis in human cancer cells and human cancer biospecimens. We found that (1) SIAH is a great prognostic and predictive biomarker for human cancer, and (2) inhibiting SIAH function is highly effective to block tumorigenesis and metastasis against the well-established, late-stage and metastatic pancreatic cancer and triple negative breast cancer (TNBC). These findings demonstrate that SIAH is an attractive and logical new therapeutic target for novel anti-ERBB/oncogenic K-RAS and anticancer therapy in human cancer. Through our work, SIAH has emerged as a new and effective drug target against oncogenic ERBB/K-RAS activation in human cancer cells. Using anti-SIAH molecules to block K-RAS signaling in human cancer is an excellent example of science going “from the bench (basic research in fruit flies) to the bedside (preclinical studies and ultimately clinical trials)”. As a highly evolutionarily conserved E3 ligase and the most downstream “gatekeeper” of EGFR/HER2/K-RAS/B-RAF signaling pathway, SIAH is uniquely and logically positioned to become a next-generation anti-ERBB/anti-K-RAS drug target. Our preclinical studies have demonstrated that “SIAH-dependent proteolysis” is indeed an Achilles' heel in human cancer. Knowledge gained from our study has great promise and immediate translational values. Anti-SIAH-based small molecule inhibitors may aid in expanding our arsenal of novel anticancer therapies. By attacking the oncogenic ERBB/K-RAS/B-RAF pathway using multi-pronged synergistic inhibitions at upstream (EGFR/HER2 membrane receptors), midstream (K-RAS/B-RAF/MEK/mTOR) and downstream (SIAH E3 ligase) signaling modules in parallel, we will be in a position to control the late-stage, relapsed and metastatic human cancers. If successful, we hope to develop anti-SIAH-based therapy and translate our findings to the cancer clinics to treat cancer patients with metastatic diseases in the near future.
Citation Format: Minglei Bian, Yang Liao, Vasilena Zheleva, Xiaofei Gao, Zena M. Urban, Monicah M. Njogu, Justin J. Odanga, Andrew J. Isbell, Rebecca L. Schmidt, Rie Takahashi, Roger R. Perry, Richard A. Hoefer, Thomas C. Smyrk, Gloria M. Petersen, Amy H. Tang. Attacking the most downstream “gatekeeper” signaling module in the oncogenic ERBB/K-RAS signaling pathway to block tumorigenesis and metastasis in human cancer. [abstract]. In: Proceedings of the Third AACR International Conference on Frontiers in Basic Cancer Research; Sep 18-22, 2013; National Harbor, MD. Philadelphia (PA): AACR; Cancer Res 2013;73(19 Suppl):Abstract nr C62.