The controversial results of several studies suggest that certain everyday-use chemicals may be linked to breast cancer. ln recent years, extensive researches have been carried out to under-stand breast carcinogenesis and the hedgehog(Hh) signaling pathway has emerged as a critical determi-nant of human breast cancer. Aberrant Hh signaling in adults results in carcinogenesis, angiogenesis, and metastasis. This review is focused on the Hh signaling pathway and chemicals in the regulation of breast cancer development and provide an updated survey of pre-clinical and clinical trials of novel strategies to target them.

OBJECTIVE To explore the effect of bisphenol A (BPA) on the differentiation potential of embryonic stem cells, and provide an experimental basis for evaluation of safety of BPA. METHODS Mouse embryonic fibroblasts (MEFs) and embryonic stem cells (ESCs) were treated with BPA 0.1, 1, 10, 100 and 1000 μmol.L-1 for 8 d respectively. The viability of MEFs and ESCs was measured by CCK-8 and lC50 was calculated. The mRNA expression of α-myosin heavy chain in ESCs was tested by RT-PCR to determine lD50 . The embryonic body cultured by suspension method was treated with BPA 0.001, 0.01, 0.1 and 1 μmol.L-1 for 10 d respectively. The changes of marked genes in each blastoderm were detected by RT-PCR. RESULTS lC50 of BPA to mouse ESCs was 5.22×10-4 mol.L-1 , and to MEFs was 6. 25 × 10-4 mol.L-1 . lD50 of BPA to mouse ESCs differentiating to cardiomyocytes was 7.0×10-7 mol.L-1 . BPA 0.001 and 0.01 μmol.L-1 upregulated the expression of the marked genes of mesoderm, fetal liver kinase-1 and globin transcription factor 1. CONCLUSION BPA is a strong embry-otoxic compound. BPA of low concentration can promote the differentiation of mouse ESCs to mesoderm.