ETV6-NTRK3–Mediated Breast Epithelial Cell Transformation Is Blocked by Targeting the IGF1R Signaling Pathway

Abstract

The insulin-like growth factor (IGF) 1 receptor (IGF1R) is an important therapeutic target under study in many cancers. Here, we describe a breast cancer model based on expression of the ETV6-NTRK3 (EN) chimeric tyrosine kinase that suggests novel therapeutic applications of IGF1R inhibitors in secretory breast cancers. Originally discovered in congenital fibrosarcomas with t(12;15) translocations, EN was identified subsequently in secretory breast carcinoma (SBC) which represent a variant of invasive ductal carcinoma. Because fibroblast transformation by EN requires the IGF1R axis, we hypothesized a similar dependency may exist in mammary cells and, if so, that IGF1R inhibitors might be useful to block EN-driven breast oncogenesis. In this study, we analyzed EN expressing murine and human mammary epithelial cell lines for transformation properties. Various IGF1R signaling inhibitors, including the dual specificity IGF1R/insulin receptor (INSR) inhibitor BMS-536924, were then tested for effects on three-dimensional Matrigel cell growth, migration, and tumor formation. We found that EN expression increased acinar size and luminal filling in Matrigel cultures and promoted orthotopic tumor growth in mice. Tumors were well differentiated and nonmetastatic, similar to human SBC. The known EN effector pathway, PI3K-Akt, was activated in an IGF1-or insulin-dependent manner. BMS-536924 blocked EN transformation in vitro, whereas BMS-754807, another IGIFR/INSR kinase inhibitor currently in clinical trials, significantly reduced tumor growth in vivo. Importantly, EN model systems mimic the clinical phenotype observed in human SBC. Moreover, EN has a strict requirement for IGF1R or INSR in breast cell transformation. Thus, our findings strongly encourage the evaluation of IGF1R/INSR inhibitors to treat EN-driven breast cancers.

A tripartite complex composed of ETV6-NTRK3, IRS1 and IGF1R is required for ETV6-NTRK3-mediated membrane localization and transformation

“…Moreover, BMS-536924 dramatically reduced soft agar colony formation of EN-transformed cells (Supplementary Figure S4c). This is supported by our recent report that BMS-536924 blocks EN transformation of breast epithelial cells in vitro, and that the related compound, BMS-754807, significantly reduces ENdriven tumor growth in vivo (Tognon et al, 2011). Taken together, these results strongly indicate that IGF1R kinase activity is essential for EN transformation, which is consistent with a model whereby EN is maintained in plasma membrane complexes in association with IRS1 and IGF1R.…”

Mammary Analogue Secretory Carcinoma of Salivary Gland Origin: An Update and Expanded Morphologic and Immunohistochemical Spectrum of Recently Described Entity

“…The presence of ETV6-NTRK3 fusion gene has not been demonstrated in any other salivary gland tumor so far. The ETV6-NTRK3 translocation is not entirely specific for MASC, as it has been identified in a range of neoplasms including congenital fibrosarcoma, congenital cellular mesoblastic nephroma, and acute myeloid leukemia [23]. Moreover, in the context of breast malignancies, the presence of ETV6-NTRK3 translocation seems to be restricted to secretory breast cancer [7].…”

The Insulin Receptor/Insulin-Like Growth Factor Receptor Family as a Therapeutic Target in Oncology

“…Other candidate predictive biomarkers are under investigation, including, for example, the presence of certain transforming fusion proteins that seem to have a requirement for IGF-IR activation (60). In contrast, although not investigated in clinical trial specimens, it is highly plausible that the presence of activating mutations downstream of the IGF-IR, such as those resulting in constitutive rather than ligand-dependent activation of phosphoinositide 3-kinase, would confer resistance to receptor targeting.…”