STAT3 inhibition using shRNA inhibits GBM proliferation, cell migration, ... glioma lines from humans, mice, and rats (U251, GL26, and CNS-â1, respectively).
AACR Abstract 2015 STAT3 inhibition using shRNA inhibits GBM proliferation, cell migration, anchorage-‐independent growth of mouse, rat, and human stem-‐like cells in vitro; and it induces long term survival and anti-‐ GBM immunity in vivo. Nathan VanderVeen1,2, Nicholas Raja1,2, Elizabeth Yi1,2, James Curtin3,4, Peter Chockley1,2, Hikmat Assi1,2, John Savakus1,2, Tom Mikkelsen5, Sam Rabkin6, Pedro R. Lowenstein1,2, Maria G. Castro1,2* 1
Department of Neurosurgery, 2Department of Cell and Developmental Biology, The University of Michigan School of Medicine. 3Gene Therapeutics Research Institute, Department of Biomedical Sciences; Cedars Sinai Medical Center. 4Department of Medicine, Department of Molecular and Medical Pharmacology, The Brain Research Institute, and Jonsson Comprehensive Cancer Center, David Geffen School of Medicine, UCLA. 5Department of Neurology, Henry Ford Hospital. 6Brain Tumor Research Center, Massachusetts General Hospital. The purpose of this study was to elucidate the role of Signal Transducers and Activators of Transcription 3 (STAT3) signaling on the tumor microenvironment in the presence of the most commonly occurring and aggressive primary brain tumor, Glioblastoma Multiforme (GBM), ahead of preclinical evaluations for a novel STAT3-‐targetted strategy for GBM. GBM is genetically heterogeneous, but always overexpresses genes that are vital to cell cycle regulation, growth and proliferation, cell invasion, and angiogenesis. STAT proteins are transcription factors associated with gene regulation and expression signatures that are implicated in many of the same mechanisms that allow human GBMs to flourish in the tumor microenvironment. STAT3 has been implicated as a central mechanism in tumor-‐induced immunosuppression in GBM and other cancers. We studied the effects of STAT3 inhibition via shRNA down-‐regulation of the gene in vivo and in vitro using primary glioma cell lines (HF2303 & MGG8) in conjunction with other glioma lines from humans, mice, and rats (U251, GL26, and CNS-‐1, respectively). In this study, we found that glioma cell lines with down-‐regulated STAT3 signaling exhibit delayed tumor growth rate, increased apoptosis, recruitment of an immune-‐mediated anti-‐tumor response, anchorage dependence, and an increase in survival rates with tumor cells treated both pre-‐ and post-‐implantation (in an in vivo rat model). Our data indicate that STAT3 has a profound influence on the tumor microenvironment in GBM that prevents the body from clearing brain tumors. Down-‐regulating this signaling pathway using gene therapeutic strategies allows for profound infiltration of immune cells, an increase in apoptosis, and a decrease in proliferation that leads to the tumors demise, with an associated development of an anti-‐tumor immunity that prevents tumor recurrence. Given the phenotype of STAT3 inhibition in in vitro assays and its success with in vivo survival rates, STAT3 inhibition proves to be an attractive system for preclinical studies as a potent therapeutic target for GBM.
