Increased tumor cell expression of Axl is a marker of aggressive features in breast cancer among African women

Axl, a receptor tyrosine kinase belonging to the Tyro/Axl/Mer (TAM) family, has been shown to be overexpressed in breast cancer with poor outcome. Moreover, Axl was associated with a basal-like phenotype (BLP) in these tumors. Our aim was to investigate Axl expression in breast cancers from an African population since these tumors are known to be aggressive and have a high frequency of the basal-like phenotype. We studied 170 paraffin-embedded breast carcinoma cases by tissue microarrays and immunohistochemical methods. In total, 128 tumor cases (75%) had strong Axl expression and 42 cases (25%) had weak or negative staining. Strong expression of Axl was associated with high tumor grade (p<0.0005), estrogen receptor (ER) negativity (p=0.024), p53 expression (p=0.004), P-cadherin positivity (p=0.017), and basal-like phenotypic profiles BLP2 (p=0.033) and BLP3 (p=0.022). In addition, Axl overexpression also showed an association with markers of tumor cell proliferation and tumor angiogenesis. In conclusion, our findings indicate strong expression of Axl in a high proportion of breast cancer cases among African women and associations with markers of aggressive features, indicating poor prognosis. These findings suggest Axl as a potential therapeutic target in this population.