Evaluation of Tumour Associated Macrophages and Angiogenesis in Ameloblastoma.

Introduction: Ameloblastoma is a locally invasive odontogenic neoplasm that has a high recurrence rate. The invasion of adjacent tissue is supported by angiogenesis stimulated by Tumour-Associated Macrophages (TAMs). TAMs are macrophages modified in the milieu of the tumour microenvironment and have very weak or no ability to present antigens. Thus, there is collaboration between the tumour and the tumour microenvironment to maintain tumour enlargement. TAMs exist as the classically activated M1 macrophages that possess antitumour activity and the otherwise activated M2 macrophages that support tumour invasion and metastasis.

Aim: To investigate the relative expression and topography of TAMs and CD34 in ameloblastoma in order to assess their affiliation and effect on tumour growth.

Materials and Methods: Forty-six Formalin Fixed Paraffin Embedded (FFPE) blocks of ameloblastoma were processed for Abcam Mouse monoclonal Anti-CCR7 antibody, Abcam Rabbit polyclonal Anti-CD206 antibody and Dako Mouse monoclonal Anti-CD34 antibody QBEnd-10. Cytoplasmic/membrane brown staining was taken as positive for all antibodies. The relative percentage of TAMs was classified as: <5%, 5-25%, 25-50% and >50%. TAMs related Microvessel Density (MVD) was evaluated as the mean of the three-recorded values. Cases with no CD34+ vessels adjacent to the TAMs region had MVD score of 0. Simple descriptive statistics was applied.

Results: Macrophages adjacent to peri-tumour islands were marked by CD206 and CCR7 and we noted negligible intra-tumour presence of positive macrophages. The percentage of positive CCR7 immune cells was greater than that for CD206 in 38 (82.6%) cases, approximately equal to CD206 in 6 (13%) cases, and the CD206 expression was more than CCR7 in only 2 (4.3%) cases. In 34 (73.9%) cases, the area of MVD did not overlap with the region of TAMs but in 4 (8.7%) cases (where MVD overlapped TAM1), the average MVD score was 20.

Conclusion: The relative percentage of TAM1 exceeds TAM2 in peri-tumoural areas of ameloblastoma, conferring anti-angiogenic and hence anti-tumour activity on the tumour.