Tumor heterogeneity is an active process maintained by a mutant EGFR-induced cytokine circuit in glioblastoma

Maria-del-Mar Inda; Rudy Bonavia; Akitake Mukasa; Yoshitaka Narita; Dinah W.Y. Sah; Scott Vandenberg; Cameron Brennan; Terrance G. Johns; Robert Bachoo; Philipp Hadwiger; Pamela Tan; Ronald A. DePinho; Webster Cavenee; Frank Furnari

doi:10.1101/gad.1890510

Tumor heterogeneity is an active process maintained by a mutant EGFR-induced cytokine circuit in glioblastoma

¹Ludwig Institute for Cancer Research, University of California at San Diego, La Jolla, California 92093, USA;
²Department of Neurosurgery, The University of Tokyo, Tokyo 113-8655, Japan;
³Neurosurgery Division, National Cancer Center Hospital, Tokyo 104-0045, Japan;
⁴Alnylam Pharmaceuticals, Inc., Cambridge, Massachusetts 02142, USA;
⁵Department of Pathology, School of Medicine, University of California at San Diego, La Jolla, California 92093, USA;
⁶Department of Neurosurgery, Memorial Sloan-Kettering Cancer Center, New York, New York 10065, USA;
⁷Monash Institute of Medical Research, Monash University, Clayton 3168, Australia;
⁸Department of Neurology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA;
⁹Alnylam Europe AG, 95326 Kulmbach, Germany;
¹⁰Department of Medical Oncology, Belfer Institute for Applied Cancer Science, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115, USA;
¹¹Department of Medicine, Belfer Institute for Applied Cancer Science, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115, USA;
¹²Department of Genetics, Belfer Institute for Applied Cancer Science, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115, USA;
¹³Cancer Center, University of California at San Diego, La Jolla, California 92093, USA

↵14 These authors contributed equally to this work.

Abstract

Human solid tumors frequently have pronounced heterogeneity of both neoplastic and normal cells on the histological, genetic, and gene expression levels. While current efforts are focused on understanding heterotypic interactions between tumor cells and surrounding normal cells, much less is known about the interactions between and among heterogeneous tumor cells within a neoplasm. In glioblastoma multiforme (GBM), epidermal growth factor receptor gene (EGFR) amplification and mutation (EGFRvIII/ΔEGFR) are signature pathogenetic events that are invariably expressed in a heterogeneous manner. Strikingly, despite its greater biological activity than wild-type EGFR (wtEGFR), individual GBM tumors expressing both amplified receptors typically express wtEGFR in far greater abundance than the ΔEGFR lesion. We hypothesized that the minor ΔEGFR-expressing subpopulation enhances tumorigenicity of the entire tumor cell population, and thereby maintains heterogeneity of expression of the two receptor forms in different cells. Using mixtures of glioma cells as well as immortalized murine astrocytes, we demonstrate that a paracrine mechanism driven by ΔEGFR is the primary means for recruiting wtEGFR-expressing cells into accelerated proliferation in vivo. We determined that human glioma tissues, glioma cell lines, glioma stem cells, and immortalized mouse Ink4a/Arf^−/− astrocytes that express ΔEGFR each also express IL-6 and/or leukemia inhibitory factor (LIF) cytokines. These cytokines activate gp130, which in turn activates wtEGFR in neighboring cells, leading to enhanced rates of tumor growth. Ablating IL-6, LIF, or gp130 uncouples this cellular cross-talk, and potently attenuates tumor growth enhancement. These findings support the view that a minor tumor cell population can potently drive accelerated growth of the entire tumor mass, and thereby actively maintain tumor cell heterogeneity within a tumor mass. Such interactions between genetically dissimilar cancer cells could provide novel points of therapeutic intervention.