NKX6-2 and breast cancer: In this study, the IC50 of GTX in A549 cells was 0.46 μM, which was more effective than in HeLa cervical cancer cells or SW1353 chondrosarcoma cells (both IC50 > 90 μM) [19], and equally potent in six breast cancer cell lines (IC50 ranging from 38 to 985 nM) [19].