MX1 and breast cancer: We analyzed the mRNA expression of the isoforms of β-hCG (CGB5 and CGB7) in a panel of breast, ovarian and prostate cancer cell lines and found that breast cancer cells harboring mutations in BRCA1 as shown in parenthesis, HCC1937 (5382insC), SUM149 (2288delT) and MX1 (33636delGAAA) express high levels of β-hCG, whereas β-hCG expression is barely detectable in cell lines possessing wild-type BRCA1 (MCF7, SKBR3, T47D, DU145, and OVCAR8) (Figure 1a).