Carboxylesterase 1 regulates peroxisome proliferator-activated receptor gamma to inhibit the growth and metastasis of breast cancer cells.

Breast cancer is a common malignancy in women, and it has an absence of effective therapies. Carboxylesterase 1 (CES1), a member of the carboxylesterase family, has anti-tumor properties in several types of cancer. However, the function of CES1 in breast cancer remains unclear. Peroxisome proliferator-activated receptor gamma (PPARG) is a downstream regulator of CES1 and exhibits anti-breast cancer properties. Both CES1 and PPARG were downregulated in breast cancer tissues. Low CES1 and PPARG expression were linked to poorer breast cancer survival. We constructed CES1 knockdown and overexpression models of breast cancer cells by CES1 overexpressing plasmids and plasmids containing short hairpin RNA. High expression of CES1 inhibited breast cancer cell proliferation, evidenced by diminished cell viability, decreased DNA replication, and G1 phase arrest. CES1 overexpression decreased the protein levels of CDK2, CDK6 and cyclin B1 in breast cancer cells. CES1 inhibited the Bcl-2/Bax axis and increased Cleaved caspase-3 levels. Transwell assays showed that CES1 inhibited cell migration and invasion. CES1 increased E-cadherin protein expression and decreased Vimentin protein expression. CES1 knockdown facilitated the proliferation, migration, and invasion of breast cancer cells. CES1 was found to regulate PPARG expression in breast cancer cells positively. We transfected PPARG-interfering plasmids into breast cancer cells with CES1 overexpression. Inhibition of PPARG abrogated the anti-growth and anti-metastasis functions of CES1 in breast cancer cells. This study elucidates that CES1 inhibits the malignant progression of breast cancer by up-regulating the expression of PPARG.