Adenylate cyclase 9 expression level is associated with hormone receptor-positive breast cancer and predicts patient prognosis.

Adenylate cyclase family members have recently received attention as novel therapeutic targets. However, the significance of adenylate cyclase 9 (ADCY9) in breast cancer has not been elucidated. Here, we evaluated <i>ADCY9</i> expression in breast cancer (BC) cell lines, and polymerase chain reaction array analysis was performed to determine the correlations between <i>ADCY9</i> expression levels and 84 tumor-associated genes. The association of <i>ADCY9</i> messenger RNA (mRNA) expression levels in clinical breast cancer specimens with patients' clinicopathological factors and prognosis was evaluated. The database of cancer cell line showed that estrogen receptor-positive and progesterone receptor-positive cells expressed higher <i>ADCY9</i> mRNA levels. <i>ADCY9</i> expression showed positive correlations with several oncogenes, such as <i>TGFB1, CDKN1A,</i> and <i>BAX</i> in the polymerase chain reaction array analysis. We defined the ratio of <i>ADCY9</i> mRNA expression levels in breast cancer and adjacent noncancerous tissues as the "C/N ratio". Among 149 patients with BC, estrogen receptor-positive and progesterone receptor-positive patients exhibited higher C/N ratios than estrogen receptor-negative and progesterone receptor-negative patients, respectively. Patients in the lowest C/N ratio quartile experienced shorter prognosis periods. The C/N ratio of <i>ADCY9</i> was found as an independent prognostic factor for disease-free survival. Thus, <i>ADCY9</i> expression is high in hormone receptor-positive breast cancer, and its low expression indicates a poor prognosis in patients with breast cancer.