Lin S, Zhu Y, Ji C, et al. - Silencing METTL3 lowers miR-222-3p expression and consequently stimulates serine/threonine stress kinase 4 (STK4) expression, repressing thyroid carcinoma (TC) malignancy and metastasis.

• The expression of METTL3 was higher in TC, which was associated with a poor prognosis for TC patients.

• Increased METTL3 expression hastened the malignant behaviors of TC cells.

• Mechanistically, METTL3 induced miR-222-3p expression by mediating the m6A modification of pri-miR-222-3p.

• STK4 was targeted and inversely regulated by miR-222-3p.

• METTL3 knockdown increased STK4 expression via downregulating miR-222-3p, decreasing TC cell malignancy as well as tumor growth and lung metastasis in nude mice.