Wnt Signaling Pathway Inhibition Enhances Efficacy of Cetuximab

Abstract

Objectives:

1) Investigate whether Wnt pathway inhibition via a small molecule inhibitor, ICG-001, enhances cetuximab efficacy in head and neck squamous cell carcinoma (HNSCC). 2) Elucidate the mechanism of cetuximab sensitization and increased cell death that results from ICG-001/cetuximab cotreatment.

Methods:

HNSCC cell line SCC-15 was grown for 24 hours then incubated with: ICG-001, cetuximab, or both for 48-72 hrs. Cells grown in media alone served as control. Cell proliferation was analyzed using WST-1 and clonogenic assays. The mechanism of ICG-001/cetuximab interaction was investigated using reverse transcription polymerase chain reaction (RT-PCR), Western blot, immunohistochemistry, and TUNEL staining.

Results:

SCC-15 cells treated with ICG-001/cetuximab demonstrated significantly decreased viability (19.9%) as determined by WST-1 assay compared to control (100%), cetuximab (90.3%), or ICG-001 (35.1%) treatment (P < 0.05). Additionally, clonogenic assay demonstrated that combination ICG-001/cetuximab treatment led to significantly decreased cell proliferation (2.6%) compared to control (100%) or monotherapy (cetuximab 94.3%; ICG-001 20.2%; P < 0.05). ICG-001 treatment resulted in increased epidermal growth factor receptor (EGFR) expression, as demonstrated by Western blot, RT-PCR, and immunohistochemistry. TUNEL-positive cells were shown to be significantly increased in both ICG-001 and ICG-001/cetuximab treatment groups. Additionally, combination therapy increased levels of cleaved caspase-3, a marker of apoptosis.

Conclusions:

ICG-001/cetuximab cotreatment results in cetuximab sensitization and increased cell death in HNSCC in vitro. Increased EGFR expression and pathway dependence leading to cetuximab vulnerability, along with increased apoptosis, play a major role in this observed effect. ICG-001/cetuximab cotreatment represents a potential novel therapy in HNSCC management which may offer superior outcomes with fewer side effects compared to existing first-line treatment.