Dennis Jones (Boston University), Zixiong Wang (Boston University), Ivy Chen (Massachusetts General Hospital), Sue Zhang (Boston University), Rohin Banerji (Boston University), Pin-Ji Lei (Massachusetts General Hospital), Hengbo Zhou (Massachusetts General Hospital), Victoria Xiao (Massachusetts General Hospital), Cecilia Kwong (Massachusetts General Hospital), Jan Van Wijnbergen (Massachusetts General Hospital), Ethel Pereira (Massachusetts General Hospital), Benjamin Vakoc (Massachusetts General Hospital), Peigen Huang (Massachusetts General Hospital), Hadi Nia (Boston University), Timothy Padera (Massachusetts General Hospital)
The sina qua non of inflammatory breast cancer (IBC) is numerous tumor emboli especially within overlying dermal lymphatics. The explanation remains a mystery. In human studies comparing IBC with non-IBC, although common tumor parameters such as Ki-67 index, mitotic count and nuclear size show a close overlap, there is a dramatic exponential difference in embolic density in IBC v non-IBC. Using contrasting properties of two IBC xenografts, Mary-X and Karen-X, this study offers a novel explanation and proposed mechanism to explain the very high embolic numbers in IBC. The explanation is geometric budding of emboli. Mary-X exhibits florid lymphovascular invasion in vivo which give rise to high numbers of CTCs and pulmonary metastases whereas Karen-X lacks these features. Mary-X also gives rise to compact spheroids in vitro which exhibit dramatic budding whereas Karen-X exhibits only loose non-budding aggregates. Furthermore Mary-X emboli also bud into daughter emboli in vivo. The mechanism that regulates the compactness of the spheroids as well as the emboli involves the generation of E-cad/NTF1, a calpain-mediated cleavage product of membrane E-cadherin. Inhibiting the generation of E-cad/NTF1 by blocking either the calpain site of cleavage (SC) or the site of binding (SB) with specific decapeptides both reduces spheroid compactness and decreases budding. Since E-cad/NFT1 retains the p120ctn binding site but loses both the β-catenin and α-binding sites, promoting its 360° distribution around the cell’s membrane, the varying levels of expression of this truncated molecule may trigger budding of both the spheroids as well as the emboli. Recurrent and geometric budding of parental emboli into daughter emboli then would account for the plethora of IBC tumor emboli seen in patients.
Support or Funding Information
This work was supported by the Department of Defense Breast Cancer Research Program Grants BC990959, BC024258, BC053405, The work was also supported by the California University of Science and Medicine and the Dr. Carolyn S. Glaubensklee Endowed Cancer Center Directorship.
lt;pgt;This work was supported by the Department of Defense Breast Cancer Research Program Grants BC990959, BC024258, BC053405, The work was also supported by the California University of Science and Medicine and the Dr. Carolyn S. Glaubensklee Endowed Cancer Center Directorship.amp;nbsp; lt;/pgt;
Complete Budding. Complete budding of Mary-X with phase contrast (A, B, C) and single label E-cadherin immunofluorescence (D, E, F). DAPI was used as a nuclear counterstain. Scale bars are provided.; Single and Double Label Immunofluorescent Xenograft Studies. Lymphovascular tumor emboli in Mary-X (E, F, G, H) and their absence in Karen-X (A, B, C, D) are depicted. Additional studies of tumor emboli exhibiting green immunofluorescence (I) within podoplanin-positive lymphovascular channels exhibiting red immunofluorescence (J) with DAPI used as a nuclear counterstain (K) and merged composite image (L) show dynamic embolic budding. Scale bars are provided.
