Mechanisms underlying resistance to cetuximab in the HNSCC cell line: Role of AKT inhibition in bypassing this resistance

Abstract

Abstract. EGFR is frequently overexpressed in head and neck squamous cell cancer (HNSCC). Cetuximab is a monoclonal antibody designed to interact with EGFR, block its activation, reduce the downstream signaling pathways and induce EGFR internalization. This study aims to investigate the role of the EGFR signaling pathway and EGFR internalization in a cetuximab-resistant cell line and to propose a new therapeutic strategy to optimize treatment of HNSCC. The HNSCC cell line, CAL33 was sensitive to gefitinib but resistant to cetuximab. Cetuximab induces an unexpected EGFR phosphorylation in CAL33 cells similarly to EGF but this EGFR activation does not trigger EGFR internalization/degradation, the process currently implicated in the response to cetuximab. Cetuximab inhibits ERK and AKT phosphorylation in cetuximab-sensitive A431 cells, whereas the level of AKT phosphorylation is unmodified in cetuximab-resistant cells. Interestingly, CAL33 cells harbor a PIK3CA mutation. The treatment of CAL33 cells with PI3K inhibitor and cetuximab restores the inhibition of AKT phosphorylation and induces growth inhibition. Our results indicate that EGFR internalization is impaired by cetuximab treatment in CAL33 cells and that the AKT pathway is a central element in cetuximab resistance. The combination of cetuximab with a PI3K inhibitor could be a good therapeutic option in PIK3CA-mutated HNSCC.

Tumor-Specific Antibody, Cetuximab, Enhances the In Situ Vaccine Effect of Radiation in Immunologically Cold Head and Neck Squamous Cell Carcinoma

“…This results from the inability of cetuximab to bind and antagonize mEGFR. In their persistent expression of huEGFR at the plasma membrane but lack of sensitivity to antiproliferative and radiosensitizing effects of cetuximab, these huEGFR-expressing murine tumor models are phenotypically analogous to human HNSCC tumor cells with acquired cetuximab resistance (52,53). We acknowledge many differences between our murine models and clinically acquired resistance to cetuximab in human HNSCC.…”

Treatment effect of buparlisib, cetuximab and irradiation in wild-type or PI3KCA-mutated head and neck cancer cell lines

“…CAL33 cells carry a p53 mutation (codon 175, CGC→CAC) and exhibit high EGFR expression (34,000 fmol/mg protein); they have no intrinsic K-ras or B-raf mutations while presenting a mutation on PI3KCA gene exon 20 (c.3140A>G; p.H1047R) [9,19]. CAL27 cell line was originally isolated from a 56-year-old Caucasian male with a squamous cell carcinoma of the tongue and presents no K-ras, B-raf or PI3KCA mutations [20].…”

“…Its activation is recognized as an important mechanism in tumor progression and resistance to EGFR inhibitors [8,9]. Indeed, in more than 90 % of HNSCC, the PI3K/mTOR signaling pathway resulted to be dysregulated and PI3KCA mutations, leading to kinase constitutive activation, increased PI3K expression, AKT amplification and/or mTOR activation, are reported [10,11].…”

Precision Medicine Approaches to Overcome Resistance to Therapy in Head and Neck Cancers

“…Activation of downstream signaling effectors, such as STAT3 (signal transducer and activator of transcription 3) (77, 84, 101-106), Src Kinases (64,107,108), RAS/MAPK pathways (86,96,(109)(110)(111)(112)(113)(114)(115), and PI3K/Akt/mTOR pathway (102,105,(116)(117)(118)(119)(120)(121)(122)(123)(124)(125)(126)(127) could induce CTX resistance independently of the EGFRligand activation.…”

“…Several genetic alterations causing PI3K/AKT/mTOR activation, such as activating mutations in the oncogene PI3KCA or inactivating mutations in the tumor suppressor protein PTEN, are driving CTX resistance in different HNSCC cell lines (125,127). Indeed, Izumi et al show that loss of PTEN conferred independence from EGFR activity and resistance to EGFR inhibition by CTX in terms of downstream signaling, proliferation, and tumor growth both in vitro and in in vivo xenograft models (119).…”