Figure 1
Figure 1. CEACAM1 expression in endothelial cells of tumor-associated lymphatics. (A) Lymphatics (Ly) in surrounding tumor cell–free area of testicular seminoma exhibit CEACAM1 immunostaining, while middle-sized (Bv) and small (→) blood vessels remain negative. (B) Lymphatics (→) containing clusters of seminoma (Tu) are positive for CEACAM1. (C) No immunostaining could be detected in control sections of testicular tumor tissue. (D) Similarly, in prostate carcinoma, lymphatics (Ly) of tumor-surrounding area, far from tumor area, express CEACAM1. (E) Endothelia of lymphatics (Ly) in close approximation to carcinoma-in-situ cells (…) in a seminiferous tubule exhibit CEACAM1 immunostaining, while neighboring blood vessels (Bv) are negative for CEACAM1 at this phase of tumor development. (F) Granulocytes (→) within the blood vessel lumen are stained as expected. In the invasive bladder cancer, CEACAM1 immunostaining is visible in endothelia of lymphatics (→) containing tumor cell groups (Tu) similar to testicular seminoma in panel B. Similar cells are positive for CD34 (→), indicating their endothelial origin (G); they also exhibit VEGFR-3 (Flt-4; →; H). (I) Double-immunostaining using CEACAM1 antibody 4D1/C2 and VEGFR-3 antibody demonstrates the co-localization of both (→), suggesting the lymphatic character of these cells. Sections in panels A-I are counterstained with calcium red. Immunofluorescence staining for CEACAM1 in a healthy area of human prostate demonstrates the expected localization in the healthy epithelium (J), while neighboring large and small lymphatics from the same area, which are marked by staining for podoplanin (K), do not exhibit CEACAM1. Double-immunofluorescence staining for CEACAM1 and podoplanin in prostate cancer tissue shows clear staining for CEACAM1 (L) and for podoplanin (M) in the same lymphatic vessels, as it is also confirmed by overlay (N). In a further tumor-associated lymphatic vessel, both CEACAM1 (O) and podoplanin (P) are present, but remarkably, single endothelial cells () integrated into the lymphatic endothelium exhibit only CEACAM1 (green fluorescence staining; Q).

CEACAM1 expression in endothelial cells of tumor-associated lymphatics. (A) Lymphatics (Ly) in surrounding tumor cell–free area of testicular seminoma exhibit CEACAM1 immunostaining, while middle-sized (Bv) and small (→) blood vessels remain negative. (B) Lymphatics (→) containing clusters of seminoma (Tu) are positive for CEACAM1. (C) No immunostaining could be detected in control sections of testicular tumor tissue. (D) Similarly, in prostate carcinoma, lymphatics (Ly) of tumor-surrounding area, far from tumor area, express CEACAM1. (E) Endothelia of lymphatics (Ly) in close approximation to carcinoma-in-situ cells (…) in a seminiferous tubule exhibit CEACAM1 immunostaining, while neighboring blood vessels (Bv) are negative for CEACAM1 at this phase of tumor development. (F) Granulocytes (→) within the blood vessel lumen are stained as expected. In the invasive bladder cancer, CEACAM1 immunostaining is visible in endothelia of lymphatics (→) containing tumor cell groups (Tu) similar to testicular seminoma in panel B. Similar cells are positive for CD34 (→), indicating their endothelial origin (G); they also exhibit VEGFR-3 (Flt-4; →; H). (I) Double-immunostaining using CEACAM1 antibody 4D1/C2 and VEGFR-3 antibody demonstrates the co-localization of both (→), suggesting the lymphatic character of these cells. Sections in panels A-I are counterstained with calcium red. Immunofluorescence staining for CEACAM1 in a healthy area of human prostate demonstrates the expected localization in the healthy epithelium (J), while neighboring large and small lymphatics from the same area, which are marked by staining for podoplanin (K), do not exhibit CEACAM1. Double-immunofluorescence staining for CEACAM1 and podoplanin in prostate cancer tissue shows clear staining for CEACAM1 (L) and for podoplanin (M) in the same lymphatic vessels, as it is also confirmed by overlay (N). In a further tumor-associated lymphatic vessel, both CEACAM1 (O) and podoplanin (P) are present, but remarkably, single endothelial cells () integrated into the lymphatic endothelium exhibit only CEACAM1 (green fluorescence staining; Q).

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