Synergistic efficacy of combined EGFR and HDAC inhibitors overcomes tolerance to EGFR monotherapy in salivary mucoepidermoid carcinoma

• Main Authors: Amelio, A.L (Author), Castilho, R.M (Author), do Nascimento-Filho, C.H.V (Author), Liu, P. (Author), Musicant, A.M (Author), Parag-Sharma, K. (Author), Tasoulas, J. (Author), Twomey, C. (Author), Zhu, Z. (Author)
• Format: Article
• Language: English
• Published: Elsevier Ltd 2021
• Subjects: amino acid sequence; apoptosis; Article; cancer stem cell; carcinogenicity; Carcinoma, Mucoepidermoid; caspase 3; caspase 7; cell cycle arrest; cell cycle G1 phase; Cell Line, Tumor; cell proliferation; cell survival; cell viability; cisplatin; colony formation; controlled study; cudc 101; CUDC-101; data analysis software; drug cytotoxicity; Drug synergy; drug tolerance; Drug tolerance; EGFR; EGFR protein, human; emetine; enzyme activation; epidermal growth factor receptor; epidermal growth factor receptor kinase inhibitor; ErbB Receptors; erlotinib; exon; genetics; HDAC; Head and neck cancer; histone acetylation; histone deacetylase inhibitor; Histone Deacetylase Inhibitors; human; human cell; Humans; IC50; Lynx; metabolism; monotherapy; Mucoepidermoid carcinoma; mucoepidermoid tumor; pathology; phenotype; priority journal; Salivary cancer; Salivary Gland Neoplasms; salivary gland tumor; signal transduction; synergistic effect; tumor cell line; tumor spheroid; unclassified drug; upregulation; vorinostat
• Online Access: View Fulltext in Publisher

 Objectives: Mucoepidermoid carcinoma (MEC) is the most common type of salivary gland malignancy. Advanced or high-grade MECs are refractory to chemotherapy, often leading to tumor recurrence/metastasis and abysmal ~35% 5-year survival. Causal links have been established between Epithelial Growth Factor Receptor (EGFR) activation and poor outcome. Herein we investigated the therapeutic efficacy of EGFR inhibition against MEC using in vitro pre-clinical models. Materials and Methods: Five human MEC cell lines were used in cell viability, cytotoxicity, apoptosis, cell cycle, 2D-clonogenicity, and 3D-spheroid formation assays following treatment with Erlotinib (EGFR inhibitor), SAHA (Histone Deacetylase inhibitor; HDAC) and CUDC-101 (dual EGFR-HDAC inhibitor). Effects on MEC cancer stem cells were evaluated using flow cytometry. Gene expression and pathway regulation were evaluated via qPCR and Western blot, respectively. Results: MEC cells enter a quiescent, non-proliferative yet rapidly reversible drug tolerant state upon EGFR inhibition. Despite robust suppression of MEC cell proliferation, no discernable apoptosis is detected. Combination of EGFR and HDAC inhibitors exhibits synergistic effects, exerting ~5-fold more potent cell cytotoxicity compared to HDAC or EGFR monotherapy. CUDC-101, a single molecule with dual EGFR-HDAC inhibitor moieties, exerts irreversible and potent cytotoxic activity against MEC cells and blunts MEC cancer stem-cell tumorigenicity. Conclusion: MEC cells are intrinsically tolerant to EGFR inhibition. Combining EGFR and HDAC inhibitors exerts synergistic and potent cytotoxic effects, suggesting that EGFR inhibitors still hold significant promise against MEC. Future studies are needed to assess the applicability and efficacy of dual EGFR-HDAC inhibitors for the clinical management of MEC. © 2021 Elsevier Ltd