PGC-1β regulates HER2-overexpressing breast cancer cells proliferation by metabolic and redox pathways

Breast cancer is a prevalent neoplastic disease among women worldwide which treatments still present several side effects and resistance. Considering that cancer cells present derangements in their energetic homeostasis, and that peroxisome proliferator-activated receptor- gamma coactivator 1 (PGC-1) is crucial for cellular metabolism and redox signaling, the main objective of this study was to investigate whether there is a relationship between PGC-1 expression, the proliferation of breast cancer cells and the mechanisms involved. We initially assessed PGC-1β expression in complementary DNA (cDNA) from breast tumor of patients bearing luminal A, luminal B, and HER2-overexpressed and triple negative tumors. Our data showed that PGC-1β expression is increased in patients bearing HER2-overexpressing tumors as compared to others subtypes. Using quantitative PCR and immunoblotting, we showed that breast cancer cells with HER2-amplification (SKBR-3) have greater expression of PGC-1β as compared to a non-tumorous breast cell (MCF-10A) and higher proliferation rate. PGC-1β expression was knocked down with short interfering RNA in HER2-overexpressing cells, and cells decreased proliferation. In these PGC-1β-inhibited cells, we found increased citrate synthase activity and no marked changes in mitochondrial respiration. Glycolytic pathway was decreased, characterized by lower intracellular lactate levels. In addition, after PGC-1β knockdown, SKBR-3 cells showed increased reactive oxygen species production, no changes in antioxidant activity, and decreased expression of ERRα, a modulator of metabolism. In conclusion, we show an association of HER2-overexpression and PGC-1β. PGC-1β knockdown impairs HER2-overexpressing cells proliferation acting on ERRα signaling, metabolism, and redox balance.

Pharmacognostic and acute toxicological evaluation of Scaptotrigona aff. postica propolis extract in pre-clinical assays

The propolis of Scaptotrigona aff. postica is popularly used in Maranhão State, Brazil, for treating wounds and respiratory illnesses. Nevertheless, little is known about the chemical composition of this propolis and the adverse effects of its use. Hence, this study is a pharmacognostic characterisation of the propolis hydroalcoholic extract (PHE) from S. aff. postica. The methodology consisted of an evaluation of the sensory and chemical parameters. Chemical analysis of PHE indicated high concentrations of phenolic and triterpens substances, and the absence of steroids. Additionally, we evaluated the acute toxicity of propolis using 48 Swiss male and female mice. The animals received single doses of PHE (1000, 2000 or 4000 mg kg⁻¹) orally and were observed for 14 days. After this period, the mice were sacrificed and the blood was used for biochemical and haematological evaluation. PHE did not induce any death, and the acute treatment significantly reduced serum concentrations of alanine aminotransferase and alkaline phosphatase. The resultant data indicate that PHE from S. aff. postica has low toxicity when used orally, even in high doses.