Title: The Relationship Between CD44, EGFR, and c-MET Expression in Patients With Locally Advanced p16-Positive and p16-Negative Head and Neck Squamous Cell Carcinoma
Abstract: CD44 is a cell surface glycoprotein known to be a cancer stem marker in head and neck squamous cell carcinoma (HNSCC). It is involved in tumor growth, metastasis, and self-renewal. c-MET is a marker of poor prognosis and may have stem cell capacity in HNSCC. Combined CD44/c-MET signaling can drive repopulation in cell culture. The relationship between c-MET and CD44 expression in HNSCC patient tissue is unknown. We examined the association between CD44 and c-MET in relation to p16 and the epidermal growth factor receptor (EGFR) in a cohort of HNSCC patients treated with chemoradiation. Immunohistochemical staining of CD44, p16, EGFR, and c-MET was performed on a tissue microarray consisting of tumors from 103 locally advanced HNSCC patients treated with definitive chemoradiation. Tissue cores were graded by 2 blinded pathologists. p16 was graded as positive (3+ or 2+ in ≥50% of tumor cells) or negative. Positive EGFR expression was defined as any 3+ or 1+/2+ in ≥50% of tumor cells. High c-MET expression was defined as any 3+ and CD44 high expression was defined as 2+/3+ in ≥50% of tumor cells. CD44 expression was correlated with p16, EGFR, and c-MET, locoregional control (LRC), distant metastases (DM), disease-free survival (DFS), and overall survival (OS). Univariate and multivariate analyses (MVA) were performed. CD44 high expression was present in 37% of patients. Fifty-two percent of patients were p16 positive, including 78% of oropharynx tumors. Fifty-four percent of patients were positive for EGFR, and 36% were classified as high c-MET expression. High CD44 expression was associated with higher T stage (P=.01), nonoropharynx primaries (P<.001), p16-negative (P<.001), and EGFR-positive tumors (P<.001). High CD44 expression was highly correlated with c-MET expression with 58% of CD44 high-expressing tumors having high c-MET expression compared to 23% of CD44 low-expressing tumors (P<.001). Twenty-one percent of all patients had both high CD44 and high c-MET expression, and 17% of all patients had a combination of p16-negative, EGFR-positive, high c-MET, and high CD44 expression. On univariate analysis, high CD44 expression predicted for worse LRC (hazard ratio [HR]: 2.40; 95% confidence interval [CI]: 1.14 to 5.05; P=.021), DFS (HR: 2.50; 95% CI: 1.25 to 4.04; P=.007) and OS (HR: 2.02, 95% CI: 1.02 to 4.00; P=.044) but not DM (P=.69). Patients with both high CD44 and c-MET expression had a dismal prognosis, with a 2-year DFS of 31% compared to 69% in the rest of the cohort (P=.003). On MVA, after adjusting for site, T stage, smoking history, and EGFR status, high c-MET (P=.040) and negative p16 status (P<.001) predicted for worse DFS, while high CD44 expression did not (P=.80). High CD44 expression is associated with high c-MET expression, p16-negative tumors, and EGFR-positive tumors. The combination of these markers predict for poor prognosis in HNSCC patients treated with chemoradiation.