Abstract A01: Pharmacological approaches to metastatic disease using an Inflammatory Breast Cancer model

Goal of Study: The lymphovascular embolus is a marker of breast cancer aggressiveness, recurrence, metastatic progression and therapeutic failure. This is especially reflective in inflammatory breast cancer (IBC) which presents as florid intravasation in situ of the lymphovasculature by tumor emboli. This study utilizes a novel 3-dimensional (3D) in vitro and in vivo model of IBC to systematically and strategically develop pharmacological approaches in the treatment of both IBC and metastatic disease. Background: Intravasation, the rate-limiting step of metastasis, is extremely important in tumor progression and expansion, yet the mechanism underlying intravasation is still poorly understood. The consequence of intravasation is the resultant lymphovascular embolus – the key defining feature of metastasis. This is most prevalent in IBC, the most lethal form of breast cancer. Clinical IBC features, erythema, peau d9orange (dimpling of thickened skin) and warmth are due to the IBC signature phenotype, namely extensive intravasation in situ of the lymphatic and blood vessels by tumor emboli. Nearly 100% of all women with IBC have lymph node involvement and approximately 25% of patients with IBC have distant metastases at diagnosis. The IBC xenograft model, MARY-X, has precisely captured the IBC phenotype, where the tumor emboli grow exclusively within the murine lymphatic and blood vessels and exhibit erythema of the overlying skin. MARY-X is an invaluable preclinical IBC model and an overall model of metastasis providing a means to validate and translate therapeutic strategies. MARY-X, in vitro, is a cellular derivative of primary tumor explants. These tumor cells form tight, compact aggregates of cells termed “MARY-X spheroids”. Comparable to human IBC emboli, a persistent, over-expression of an intact E-cadherin/α, β-catenin axis mediates the compaction of both in vitro and in vivo MARY-X spheroids and tumor emboli, respectively. These comparative architectural features (i.e. mimics the in vivo metastasis) of the spheroid of MARY-X provide an in vitro model with tractable in vivo applications. Research Strategy: By exploiting the MARY-X in vitro 3-D model, high throughput (HTP) screening is performed to systematically probe the factors involved in maintenance of tumor emboli architecture as it pertains to sensitivity/resistance to therapeutics in an overall effort to develop efficacious therapeutics for treatment of IBC and metastatic disease. Additionally, MARY-X spheroids co-cultured with bone marrow derived cells (BMDCs) in matrigel overlays are employed to assess targeting of mediators of crosstalk between tumor spheroid/embolus soluble factors (e.g. cytokines, exosomes) and the microenvironment. Soluble factors identified as mediators (i.e. targets) of metastatic progression, that showed the most promise in the HTP screen, are further validated in the in vivo preclinical model, MARY-X. A significant decrease in vessel density of the MARY-X tumor will be indicative of successful blocking of this ‘crosstalk’ i.e. lymphovasculogenesis or the formation of lymphovascular emboli (i.e. intravasation) – the defining feature of metastatic disease. Preliminary Data and Conclusions: Preliminary data show that dissolution of the spheroid/embolus augment apoptotic effects of chemo/irradiation therapy. Suggesting that apoptosis resistance of lymphovascular emboli may be independent of traditional apoptotic mechanisms. Therefore, therapy evasion, in part, is due to formation and maintenance of the architectural features of the lymphovascular embolus. In addition, abrogation of ‘crosstalk’ has proven to hinder the establishment of lymphovascular emboli. Citation Format: Mary L. Alpaugh, Emmanuel Theodorakis. Pharmacological approaches to metastatic disease using an Inflammatory Breast Cancer model. [abstract]. In: Proceedings of the AACR Special Conference: The Translational Impact of Model Organisms in Cancer; Nov 5-8, 2013; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2014;12(11 Suppl):Abstract nr A01.