Abstract 4847: Identifying molecular targets and mechanisms of treatment resistance in inflammatory breast cancer (IBC) using next-generation sequencing (NGS) and reverse-phase protein microarrays (RPMA)

Abstract

Background Inflammatory Breast Cancer (IBC) is a clinicopathologic entity characterized by rapid progression and poor prognosis, even with the advent of targeted therapies and a multimodal approach. Gene expression profiles of IBC tumors vs. non-IBC demonstrated that HER2+ IBC have increased mTOR signaling compared to non-IBC (Iwamoto et al). mTOR activation is a mechanism for both HER-2 targeted and endocrine resistance. Combining the molecular diagnostics of next-generation sequencing (NGS) and reverse-phase protein microarray (RPMA) may identify additional therapeutic targets as well as mechanisms of resistance to targeted therapy. Methods This is an observational analysis of 12 IBC patients who had tissue biopsy after progression on standard therapies. All patients had tissue analysis by NGS and RPMA. NGS was performed by either FoundationOne™ or our in-house hot spot panel of 45 genes. RPMA was performed using TheraLink™ to identify expression of cancer-related phosphoproteins; it quantifies HER1, HER2, and HER3 receptor overexpression, and evaluates for phosphorylation of the receptor which indicates activation. Phosphorylation of HER downstream signaling pathways such as JAK2, AKT/mTOR and MEK1/2 are also detected. Subset of 7 patients had AR, MET, ALK and PDL1 expression evaluation. Results All patients had IBC and 75% had metastatic disease. 17% of patients were ER+/HER2-, 42% ER+/HER2+, 25% ER-/HER2+, and 17% TNBC. All HER2+ patients by IHC had activation of HER2 on RPMA, and 75% of those patients had confirmed ERBB2 amplification on NGS. 75% of patients had mTOR activation on RPMA, 78% of whom had a concomitant alteration in the PIK3CA pathway on NGS. 71% of the patients evaluated had ALK expression and 80% of those patients had concomitant mTOR activation. Also, both TNBCs had HER2 activation by RPMA. HER2 targeted therapy was continued on 2 patients after RPMA confirmed activation of HER2. 4 patients were initiated on combinations with an mTOR inhibitor, Everolimus (Afinitor®), and one of whom initially obtained a clinical response, upon progression had repeat RPMA demonstrating only persistent mild activation of mTOR with a decrease in downstream proteins. Another patient with TNBC IBC who underwent 3 lines of neoadjuvant therapy prior to surgery was found to have HER1, HER2, HER3 and mTOR activation; she was started on adjuvant lapatinib and capecitabine and remains with no recurrent disease. Conclusions Patients with IBC often have activation of members of the HER family and mTOR pathway indicating molecular targets and potential mechanisms of resistance in IBC. The concomitant use of NGS and RPMA is an intriguing approach to molecular diagnostics as they provide complimentary data on molecular pathways activation which expands therapeutic options, predicts treatment-sensitivity and selects more effective combinations. Citation Format: Laura K. Austin, Keithe Shensky, Juan Palazzo, Tiffany Avery, Rebecca Jaslow, Corrine Ramos, Nicholas Hoke, Emanuel Petricoin, Massimo Cristofanilli. Identifying molecular targets and mechanisms of treatment resistance in inflammatory breast cancer (IBC) using next-generation sequencing (NGS) and reverse-phase protein microarrays (RPMA). [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4847. doi:10.1158/1538-7445.AM2015-4847