Myricetin Induces Apoptosis of Human Anaplastic Thyroid Cancer Cells via Mitochondria Dysfunction

Abstract

Aim: Thyroid cancer is the most common endocrine malignancy, with an increasing incidence worldwide. Most thyroid cancers are well differentiated and have a favorable outcome. However, undifferentiated thyroid cancers are one of the most lethal human malignancies. Anaplastic thyroid cancer (ATC) accounts for 2% of all thyroid cancers, and its median survival rate is low. ATC is responsible for more than one-third of thyroid cancer-related deaths. Myricetin is a flavonol compound found in walnuts, herbs, and various berries and is known to induce apoptotic death of various types of cancer cells. However, an anticancer effect of myricetin against human anaplastic thyroid cancer (HATCs) cells has not been demonstrated.

Materials and methods: In the present study, the anticancer effects and mechanism of action of myricetin were examined using SNU-80 HATC cells. SNU-80 HATC cells were treated with various concentrations of myricetin and compared with untreated controls.

Results: Myricetin significantly reduced HATC cell proliferation, by approximately 70%. A substantial proportion of dead cells exhibited arrest in the sub-G₁ phase. Myricetin also exhibited cytotoxicity and induced DNA condensation in SNU-80 HATC cells in a dose-dependent manner. The mechanism of myricetin-induced cell death involved an increase in the activation of caspase cascades and the Bax:Bcl-2 ratio at a concentration of 100 μM. Myricetin also induced the release of apoptosis-inducing factor (AIF) from mitochondria into the cytosol and altered the mitochondrial membrane potential.

Conclusion: Our results indicate that myricetin is a potent inducer of HATC cell death and may thus prove useful in the development of therapeutic agents for HATC.

Keywords: Bax/BcL-2 ratio; Myricetin; cell cycle; human anaplastic thyroid cancer cells.