In order to quantify and compare the mRNA expression amounts of each nAChR subunit among human breast cancer cell lines and the normal (nonmalignant) human breast cell lines, real-time quantitative fluorescent PCR were used to detect the mRNA expression level of α3, α4, α5, α7, α9, α10, β2, β3 and β4 nAChR subunits respectively (Figure 2). The gene discussed is IGKV1D-22; the disease is breast cancer.