In particular, with regard to the NOTCH-activating compounds, histone deacetylase inhibitors and valproic acid (VA) showed an in vitro antineoplastic effect in neuroendocrine cell lines (gastrointestinal carcinoid, broncopulmonary carcinoid and in human medullary thyroid cancer cell lines), inducing NOTCH1 mRNA expression through activator protein (AP) transcription factor binding [114]. Here, NOTCH1 is linked to medullary thyroid gland carcinoma.