Androgen receptor and enzymes in lymph node metastasis and cancer reoccurrence in triple-negative breast cancer

Background: Triple-negative breast cancer (TNBC) is characterized by the absence of estrogen receptor, progesterone receptor and HER2. TNBCs are a diverse subgroup, but one promising marker and therapeutic target of this breast cancer is the androgen receptor (AR). Previously we demonstrated that AR and cognate intracrine pathways are associated with decreased proliferation in invasive ductal carcinoma with their decrease also detected between organ-confined and invasive diseases. Therefore, in this study, we examined the status of AR and androgen-producing enzymes during the process of metastasis to lymph nodes and cancer recurrence. Materials and Methods: We studied 2 series of patients with TNBC, one from Kumamoto University Hospital composed of 16 matched cases of primary and locally or distal recurrences and the other from Tohoku University Hospital examining 46 lymph node metastasis from 23 patients. In addition to studying concordance in AR expression, we also examined the interactions between AR and Ki-67 labeling index and AR and site of distal metastasis. Results: In both series, AR status was concordant between primary and recurrent/metastatic disease, but coordinated expression of AR and androgenic enzymes was lost during the process. The inverse association between AR and Ki-67, previously reported in invasive ductal carcinoma (IDC), was markedly potentiated in both lymph node and recurrent cancers. In addition, AR expression appeared to have little effect on visceral metastasis but was associated directly with bone metastasis and inversely with brain metastasis. Conclusions: The results of our present study demonstrated that AR remained in the majority of metastatic samples from AR-positive primary TNBCs and that AR manipulation could be exploited in the metastatic settings of TNBC.