Angiotensin-converting enzyme expression of the lymphoma-associated macrophages in the lymph nodes of Hodgkin's disease.

Objective: Angiotensin-converting enzyme (ACE) is involved in the control of cellular proliferation. Tumor-associated macrophages promote lymphoma pathogenesis via affecting tumor cell growth and associated survival factors. We assessed ACE expression in the neoplastic lymph node microenvironment of Hodgkin's lymphoma (HL), particularly in macrophages and in nonneoplastic lymphoid tissue.

Methods: Paraffin sections of the lymph nodes from randomly selected 20 HL cases with nodular sclerosing and 20 mixed cellular types were included into the study. Five normal tonsils and five lymph nodes showing reactive lymphoid hyperplasia were used as controls. Immunohistochemistry of lymph node biopsies had been performed with monoclonal antibody against human ACE. Sections were evaluated by two pathologists.

Results: ACE-expressing histiocytes were observed in lymph nodes of HL. ACE staining was also observed in the vascular endothelium in all the tissues evaluated. Neoplastic lymphoid tissues and control tissues did not express ACE.

Conclusion: ACE expression of the lymphoma-associated macrophages in the lymph nodes of HL may represent the point of cross-talk between renin-angiotensin system (RAS) and lymphomagenesis. ACE could serve in the pathobiological function of the tissue-based macrophages in tumorigenesis of HL.