Abstract 1831: Interrogating HER2+ plasticity and lapatinib resistance with MicroEnvironment MicroArrays

Abstract Treatment of HER2+ breast cancer with the targeted therapeutic lapatinib has shown promising results, but faces the major obstacles of de novo and acquired resistance in clinical use. Much of this resistance can be attributed to intratumoral heterogeneity, giving rise to drug resistant cell populations. An important factor of intratumoral heterogeneity is spatial heterogeneity of cancer cells, which results in differential contact with extra cellular matrix (ECM) proteins, stromal cells, and growth factors and signaling molecules within the tumor microenvironment. This can variably alter the intracellular signaling network of cancer cells, modulating cellular plasticity and drug response. To assess the effect cellular interactions with the microenvironment has on lapatinib resistance, we are utilizing MicroEnvironment MicroArrays (MEMA), which consist of combinations of functional ECMs, growth factors, and cytokines printed onto a solid surface, allowing for the simultaneous interrogation of thousands of unique microenvironments in a single assay. We have grown HER2+ breast cancer cells on the MEMA spots, treated with lapatinib, and measured functional response to each protein combination by immunofluorescent assay and high throughput image acquisition and analysis. By focusing on markers of proliferation, apoptosis, and cellular subtype differentiation, we have identified protein combinations that confer resistance to lapatinib. One of the combinations that came out of this preliminary screen is the desmosome protein Desmoglein II and the growth factor HGF, which continued to drive proliferation of HER2+ cells in the presence of lapatinib. Validation experiments found that on their own these two proteins could modulate the differentiation status of HER2+ cells, and combined to provide resistance to lapatinib treatment in traditional cell culture assays. In addition, the extent of drug resistance provided by protein interaction was found to be strongly linked to the differentiation status of the HER2+ cells. Both HGF and Desmoglein II are reported to be important in the progression of breast cancer, but their effect in combination is a novel finding from the use of MEMA analysis. We plan to utilize RNAseq analysis to inform a probabilistic computational model of network signaling to determine what pathways are enhanced by the microenvironment factors, and siRNA knockdown or small molecule inhibitors of identified pathway nodes can then determine which interactions can be targeted to restore drug sensitivity. Citation Format: Spencer Watson, James Korkola, Juha Rantala, Joe Gray. Interrogating HER2+ plasticity and lapatinib resistance with MicroEnvironment MicroArrays. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1831. doi:10.1158/1538-7445.AM2014-1831