Angiogenesis, Metastasis, and the Cellular Microenvironment Regulation of Inflammatory Breast Cancer Cell Invasion through Akt1/PKBa Phosphorylation of RhoC GTPase Heather L. Lehman 1,2 , Steven J. Van Laere 4,5 , Cynthia M. van Golen 3 , Peter B. Vermeulen 5 , Luc Y. Dirix 5 , and Kenneth L. van Golen 1,2 Abstract With a 42% and 18% 5- and 10-year respective disease-free survival rate, inflammatory breast cancer (IBC) is arguably the deadliest form of breast cancer. IBC invades the dermal lymphatic vessels of the skin overlying the breast and as a consequence nearly all women have lymph node involvement and 1/3 have gross distant metastases at the time of diagnosis. One year after diagnosis 90% of patients have detectable metastases, making IBC a paradigm for lymphovascular invasion. Understanding the underlying mechanisms of the IBC metastatic phenotype is essential for new therapies. Work from our laboratory and others show distinct molecular differences between IBC and non-IBCs (nIBCs). Previously we showed that RhoC GTPase is a metastatic switch responsible for the invasive phenotype of IBC. In this study we integrate observations made in IBC patients with in vitro analysis. We show that the PI3K/Akt signaling pathway is crucial in IBC invasion. Key molecules involved in cytoskeletal control and cell motility are specifically upregulated in IBC patients compared with stage and cell-type- of-origin matched nIBCs patients. Distinctively, RhoC GTPase is a substrate for Akt1 and its phosphorylation is absolutely essential for IBC cell invasion. Further our data show that Akt3, not Akt1 has a role in IBC cell survival. Together our data show a unique and targetable pathway for IBC invasion and survival. Mol Cancer Res; 10(10); 1306–18. Ó2012 AACR. Introduction Inflammatory breast cancer (IBC) is a phenotypically distinct and exceptionally lethal form of breast cancer characterized by rapid progression and poor prognosis. The term IBC was first coined in 1924 to describe a locally advanced breast cancer with unique clinical features includ- ing, skin erythema and thickening, nipple retraction, and peau d'aurange (1). IBC is clinically distinguished by rapid onset of primary skin changes, typically occurring within twelve weeks and progression to Stage IIIb/IV disease within 6 months (2–4). By definition, IBC is a T4d tumor at diagnosis and typically affects younger women, often during their childbearing years (5). Although the actual numbers are disputed by the IBC community, current SEER data suggests that IBC accounts for 1% to 5% of all newly diagnosed breast cancers in the United States annually (6). Despite significant improve- ments in the disease-free survival rates of non-IBC (nIBC) patients, IBC patient survival rates remain low, with a 5-year disease-free survival rate of less than 40%, in comparison to the 90% of nIBC (4, 7–9). The poor prognosis is due to infiltration of tumor emboli that metastasize within the dermal lymphatic vessels of the skin overlying the breast (3, 4). Although notable progress has been made in the last decade in the study of IBC, elucidating the molecular mechanisms involved in driving IBC metastasis is essential for improved treatment. It is suggested that IBC dissemi- nates passively through the dermal lymphatic vessels (10). However, work by our laboratory and others suggest that this is not the case. Our laboratory has previously identified genes involved in IBC invasion; RhoC GTPase has an essential role in driving the metastatic phenotype of IBC, being over- expressed in >90% of IBC tumors as compared with stage- matched nIBC tumors (11, 12). RhoC GTPase dynamically reorganizes the actin cyto- skeleton and controls nearly all aspects of cellular motility (13–16). RhoC GTPase overexpression leads to transfor- mation of immortalized human mammary epithelial cells with an invasive phenotype similar to that of IBC (17). RhoC also promotes metastasis in other invasive cancers, including pancreatic ductal adenocarcinoma (18), lung cancer (19), and melanoma (20). The phosphoinositide 3-kinase (PI3K)/Akt signaling pathway plays a role in enhancing cancer cell motility, Authors' Affiliations: 1 Department of Biological Sciences, University of Delaware; 2 The Center for Translational Cancer Research, The Helen F. Graham Cancer Center, Newark; 3 Department of Biological Science, Del- aware State University, Delaware; 4 Laboratory of Gynecological Oncology, Department of Oncology, Catholic University Leuven, Leuven; 5 Transla- tional Cancer Research Unit, Oncology Center, AZ Sint-Augustinus, Wilrijk, Belgium H.L. Lehman and S.J. Van Laere contributed equally to the preparation of this manuscript. Corresponding Author: Department of Biological Sciences, The Univer- sity of Delaware, 320 Wolf Hall, Newark, DE 19716. Phone (302) 831-2669; Fax (302) 831-2281; E-mail: klvg@udel.edu doi: 10.1158/1541-7786.MCR-12-0173 Ó2012 American Association for Cancer Research. Molecular Cancer Research Mol Cancer Res; 10(10) October 2012 1306 on October 3, 2021. © 2012 American Association for Cancer Research. mcr.aacrjournals.org Downloaded from Published OnlineFirst August 15, 2012; DOI: 10.1158/1541-7786.MCR-12-0173