HER Family Blockade in Head and Neck Squamous Cell Carcinoma: Couple Therapy Efficacy of Cetuximab and Pertuzumab Combined With Photon Irradiation

Purpose/Objective(s) Head and neck squamous cell carcinoma (HNSCC) is a malignancy still associated with severe mortality, due to loco-regional recurrences or distant metastasis. Head and neck cancer stem cells (CSCs) are highly resistant to treatment and have large migratory abilities. These particular properties could explain treatment resistances in this location. If EGFR is strongly overexpressed in 80-100% of HNSCC, HER2 and HER3 seem to be also expressed in these lines. The aim of the present study was to explore the efficacy of HER1-2-3 blockade through cetuximab-pertuzumab association with or without photon irradiation on the proliferation and migration/invasion capabilities of a HNSCC chemo and radio resistant human cell line (SQ20B) and its corresponding stem cell line (SQ20B/CSCs). Materials/Methods SQ20B/CSCs subpopulation was isolated through double cell sorting: side population (SP) (Hoechst exclusion) and CD44 staining: SP/CD44High. SQ20B and SQ20B/CSCs proliferation was studied after treatment with cetuximab 5nM + pertuzumab 20mg/mL treatment +/- 10Gy photon irradiation. Invasion and migration were assessed with scratch wound assay with or without matrigel. EGFR, phospho-EGFR (Tyr1068), HER2 and HER3 basal protein expression was studied. Activation or inhibition of RAS/MAPK and AKT-mTOR downstream signaling cascade was studied through phospho-AKT (Ser473), phospho-MEK1/2(Ser217/221) expression exposed to combined treatments. Results Cetuximab strongly inhibits SQ20B proliferation, migration and invasion when it has a small effect on SQ20B/CSCs. Cetuximab-pertuzumab treatment combined with radiation has a potent significant inhibitory effect on SQ20B and SQ20B/CSCs proliferation, migration and invasion. EGFR is overexpressed in SQ20B, and under-expressed in SQ20B/CSCs, while HER2 and HER3 are expressed equivalently in both populations in basal conditions. Phospho-AKT is strongly expressed in SQ20B, at the opposite of SQ20B/CSCs which express phospho-MEK1/2. Cetuximab-pertuzumab treatment combination with 10Gy photon irradiation switches off both phospho-AKT and phospho-MEK1/2 expression in the two populations. Conclusion Cetuximab-pertuzumab couple pan-HER treatment combined with photon irradiation significantly inhibits proliferation, invasion and migration of SQ20B HNSCC cell line and its CSCs subpopulation, through both AKT-mTOR and Ras-MAPK downstream signaling blockade. HER family seems to be a promising therapeutic target in HNSCC.