Abstract 5232: Lymphovascular breast carcinoma tumoral emboli beget emboli through stem-cell initiated self-budding histogenesis

Abstract

Abstract Previous studies in our laboratory have indicated that the lymphovascular embolus is not simply a cellular fragment that detaches from the main tumor passively but represents an active clonal selection for a stem cell phenotype exhibiting enhanced stem cell signaling and survival pathways. Lymphovascular emboli exhibit increased resistance to chemotherapy and patients with large numbers of lymphovascular emboli exhibit decreased disease-free survival and poorer prognosis. Florid lymphovascular emboli is the diagnostic signature of inflammatory breast cancer (IBC) and other aggressive metastasizing cancers. The emboli have been presumed to form as a result of lymphovascular invasion but this event is thought to be rare and therefore would not alone explain the large number of emboli observed in IBC and other highly metastatic carcinomas. The reasons why some patients exhibit large numbers of lymphovascular emboli whereas other patients exhibit only rare numbers remain unknown. We wanted to specifically address this question and thus carried out both animal and in vitro imaging studies with our human xenograft model of inflammatory breast cancer, MARY-X, which exhibits florid emboli in mice and gives rise to high density spheroids in vitro. We also carried out morphometric studies on the density of human lymphovascular emboli in 25 IBC and 250 non-IBC cases and subsequent laser capture microdissection. Animal and in vitro multicolor imaging studies using anti-E-cadherin and anti-podoplanin showed evidence of self-budding histogenesis within the lymphovascular spaces with one parent embolus giving rise to daughter emboli. Correspondingly, budding spheroidgenesis was observed in vitro. Density studies of tumoral emboli in the human cases showed their numbers distributed over an exponential rather than linear range. By both RT-PCR and IHC, emboli compared to their non-embolic invasive carcinoma areas exhibited five-ten fold higher stem cell markers including Stellar, H19, Rex-1, Nestin, CD133 and Aldehyde Dehydrogenase 1 (ALDH1) as well as stem cell transcriptional determinants including OCT4, SOX2 and Nanog, and stem cell signaling pathways, eg., Bmi-1, Hedgehog and Notch3. These studies, while not explaining the genesis of the initial embolus, show conclusively that emboli beget emboli through stem-cell initiated self-budding histogenesis. It is this later process which is the more important one because it accounts for the exponential numbers of emboli seen in the human cases which exhibit aggressive behavior. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5232. doi:10.1158/1538-7445.AM2011-5232