Relative expression of α-smooth muscle actin and matrix metalloproteinases-2 in ameloblastoma of a black African sub-population.

Abstract

Ameloblastoma although a benign odontogenic tumor, is locally invasive. The abundant presence of myofibroblasts (marked by α-smooth muscle actin [α-SMA]) in the stroma and expression of matrix metalloproteinase-2 (MMP-2) in the neoplastic or stromal cells have been linked with the tumor's ability for both local and distant spread. We aim to estimate the relative expression of α-SMA and MMP-2 in ameloblastoma from a black African subgroup to gauge their relative potential for enhancing local invasiveness and hence, their prospects as possible chemotherapeutic targets. Twenty-five formalin-fixed paraffin-embedded blocks of ameloblastoma cases from Nigeria were prepared for antibody processing to α-SMA (Dako Monoclonal Mouse Anti-Human α-SMA antibody clone 1A4) and MMP-2 (Abcam Mouse Monoclonal Anti-MMP-2 antibody [CA-4001/CA719E3C] ab3158). The score for percentage positivity of the tumor cells and the score for staining intensities were then multiplied in order to generate an immunoreactive score. α-smooth muscle actin was only expressed in the fibrous connective tissues adjacent to the tumor islands while MMP-2 was expressed in the ameloblasts, stellate reticulum, and the connective tissues in varying proportions. All the variants analyzed expressed α-SMA mildly or moderately, except for the follicular variant that either did not express α-SMA or expressed it mildly. The highest number of strong immunoreactivity to MMP-2 in the ameloblast region was found in the plexiform variant. Chemotherapeutic targeting of both molecules may, therefore, be a vital step in the control of local ameloblastoma invasiveness.