Detection of KK-LC-1 Protein, a Cancer/Testis Antigen, in Patients with Breast Cancer.

Background: Kita-Kyushu lung cancer antigen-1 (KK-LC-1) is a cancer/testis antigen and predominant target for cancer immunotherapy. Its detection is only established based on gene expression. In this study, we established a monoclonal antibody against KK-LC-1 to detect its protein expression in formalist fixed samples. Materials and Methods: The monoclonal antibody against KK-LC-1 was evaluated and the detection of KK-LC-1 between gene expression and protein expression was compared in patients with breast cancer. The monoclonal antibody clone 34B3, which we established, stained testicular germ cells positively. Results: The rates of detection of KK-LC-1 gene and protein expression were 11.8% and 52.9%, respectively. Protein expression was detected in all triple-negative breast cancer cases studied (n=8). Furthermore, KK-LC-1 was detected in all tumours without oestrogen receptor expression. Conclusion: This study indicated that KK-LC-1 expression was detected in breast cancer, especially in oestrogen receptor-negative subtypes.