Effects of caffeic acid phenethyl ester on cytotoxicity, antimetastasis, antiproliferative activity, apoptosis, oxidative stress, and mitochondrial membrane potential in thyroid cancer cell line

A comprehensive analysis of global cancer incidence data reveals a significant increase in thyroid cancer cases across all racial and gender groups. In particular, the incidence of thyroid cancer has increased to become the fifth most common cancer among women. The objective of this study was to examine the cytotoxic impact of Caffeic Acid Phenethyl Ester (CAPE), a natural compound derived from Apis mellifera honey bees with a lipophilic molecular structure that facilitates cellular penetration, on the TPC-1 human papillary thyroid cancer cell line via the mitochondrial membrane potential (MMP, Δψm) pathway. The cytotoxic effect of CAPE on the TPC-1 cell line was evaluated using MTT and crystal violet assays. The degree of apoptotic activity was determined by ELISA, a method used to analyse the levels of Bax, Bcl-2, Caspase-3, Caspase-8, Caspase-9 and Apaf-1. The effect on thyroid cancer cell mitochondria was investigated through the analysis of JC-1 fluorescent probed-MMP, ROMO-1 and mitochondrial ATP-synthase activities. The analysis of ROS and 8-OHdG was conducted to assess the extent of oxidative stress and DNA damage. The analysis of lactate dehydrogenase (LDH) was employed as a marker of both cytotoxicity and cellular membrane damage. In order to ascertain the anti-metastatic activity, cell migration and colony formation assays were conducted. The Giemsa staining method was selected for cytomorphological analysis. In light of the findings indicating that CAPE treatment at varying doses over a 48-hour period demonstrated cytotoxic activity in TPC-1 cells, the IC50 value of 25 µM was selected as the effective dose for subsequent experiments. A reduction in Bcl-2 levels and a statistically significant increase in the activation of key components Bax, Caspase-3, -8, -9 and Apaf-1 indicated that CAPE-induced cell death was apoptosis-dependent. This study demonstrated that CAPE caused mitochondrial depolarisation in mitochondrial membrane potential (Δψm), a marker of early apoptosis, and a significant decrease in mitochondrial ATP-synthase. Furthermore, CAPE induced a significant increase in intracellular ROS, ROMO-1 levels and 8-OHdG DNA damage, accompanied by a significant increase in extracellular LDH concentration leaking through cellular membranes. In particular, CAPE, which exhibited anti-metastatic properties by showing a marked inhibitory effect on cell migration and colony formation, also caused cytomorphological changes. In conclusion, the results revealed that CAPE demonstrated activity in both intrinsic and extrinsic apoptotic pathways triggered by increased ROS, ROMO-1 and extracellular LDH through modulation of mitochondrial pathways associated with MMP depolarisation and ATP synthase blockade in TPC-1 cells. However, further in vivo research is required to comprehensively evaluate the potential interactions and safety of CAPE, which was observed to cause cytomorphological changes in human papillary thyroid carcinoma cells.