Antagonists of IGF:Vitronectin Interactions Inhibit IGF-I–Induced Breast Cancer Cell Functions

Abhishek S Kashyap,Ola Söderberg,Gaëlle Cane,Ali Shokoohmand,Manaswini Sivaramakrishnan,Zee Upton,Gary K Shooter,Brett G Hollier,David I Leavesley,Tristan I Croll,Jacqui Mcgovern

doi:10.1158/1535-7163.mct-15-0907

Abhishek S Kashyap, Ola Söderberg + Show 9 more

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https://doi.org/10.1158/1535-7163.mct-15-0907

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Abstract

We provide proof-of-concept evidence for a new class of therapeutics that target growth factor:extracellular matrix (GF:ECM) interactions for the management of breast cancer. Insulin-like growth factor-I (IGF-I) forms multiprotein complexes with IGF-binding proteins (IGFBP) and the ECM protein vitronectin (VN), and stimulates the survival, migration and invasion of breast cancer cells. For the first time we provide physical evidence for IGFBP-3:VN interactions in breast cancer patient tissues; these interactions were predominantly localized to tumor cell clusters and in stroma surrounding tumor cells. We show that disruption of IGF-I:IGFBP:VN complexes with L(27)-IGF-II inhibits IGF-I:IGFBP:VN-stimulated breast cancer cell migration and proliferation in two- and three-dimensional assay systems. Peptide arrays screened to identify regions critical for the IGFBP-3/-5:VN and IGF-II:VN interactions demonstrated IGFBP-3/-5 and IGF-II binds VN through the hemopexin-2 domain, and VN binds IGFBP-3 at residues not involved in the binding of IGF-I to IGFBP-3. IGFBP-interacting VN peptides identified from these peptide arrays disrupted the IGF-I:IGFBP:VN complex, impeded the growth of primary tumor-like spheroids and, more importantly, inhibited the invasion of metastatic breast cancer cells in 3D assay systems. These studies provide first-in-field evidence for the utility of small peptides in antagonizing GF:ECM-mediated biologic functions and present data demonstrating the potential of these peptide antagonists as novel therapeutics. Mol Cancer Ther; 15(7); 1602-13. ©2016 AACR.

Highlights

The insulin-like growth factors Insulinlike growth factor-I (IGF-I) and IGF-II form multiprotein complexes with the extracellular matrix (ECM) protein vitronectin (VN), with IGF-II binding VN directly [1] whereas IGF-I binds VN via IGF-binding proteins (IGFBP) -2, -3, -4, and -5 [2]
Comparison of the Proximity Ligation Assay (PLA) immunoreactivity with hematoxylin and eosin (H&E) staining indicated that the VN:IGFBP-3 complex was tumor associated (Fig. 1D and E) and interestingly, was more strongly associated with tumor cell clusters invading into the stroma (Fig. 1C and D; arrows)
IGF-I has been implicated in conferring increased motility and survival advantage in certain tumor cells [27], whereas the expression of activated IGF-1R has been reported in invasive breast cancer [32]

Summary

Introduction

The insulin-like growth factors IGF-I and IGF-II form multiprotein complexes with the extracellular matrix (ECM) protein vitronectin (VN), with IGF-II binding VN directly [1] whereas IGF-I binds VN via IGF-binding proteins (IGFBP) -2, -3, -4, and -5 [2]. Biochemically validated in vitro, the physical interaction of VN with IGF family members remains to be investigated in human tissues. IGF-I: Note: Supplementary data for this article are available at Molecular Cancer Therapeutics Online (http://mct.aacrjournals.org/). Current address for A.S. Kashyap: Cancer Immunology, Department of Biomedicine, University Hospital Basel, Switzerland; and current address for D.I. Leavesley and Z.

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