Plasma glutathione S-transferase P1-1 levels in patients with head and neck squamous cell carcinoma

BACKGROUND: Many tumors contain high amounts of the detoxification enzyme glutathione S-transferase P1-1 (GSTP1-1). Elevated levels of GSTP1-1 have also been detected in serum and plasma from patients with gastrointestinal, lung, or head and neck tumors. The authors of this report evaluated the role of GSTP1-1 as a plasma tumor marker in patients with head and neck squamous cell carcinoma (HNSCC) of the larynx, hypopharynx, or oropharnyx and in patients with benign head and neck lesions (BHNL). METHODS: GSTP1-1 levels were measured in EDTA plasma combined with ethylenediaminetetraacetic acid using a recently developed sensitive and specific sandwich enzyme-linked immunoadsorbent assay. A normal reference level with an upper limit of 21.8 microg GSTP1-1 per liter of plasma was calculated from results obtained with samples from 230 blood donors. RESULTS: Median GSTP1-1 levels in samples from 53 patients with oral/oropharyngeal SCC (10.6 microg/L; range, 3.7-46.1 microg/L), 12 patients with hypopharyngeal SCC (11.9 microg/L; range, 5.2-146.6 microg/L), and 28 patients with laryngeal SCC (14.4 microg/L; range, 6.4-141.5 microg/L) were significantly elevated when compared with plasma GSTP1-1 levels in samples from 45 patients with BHNL (8.1 microg/L; range, 3.3-32.3 microg/L; P < 0.0001, P < 0.01, and P < 0.0001, respectively). However, only 6 of 53 patients (11%) with oral/oropharyngeal SCC, 1 of 12 patients (8%) with hypopharyngeal SCC, and 6 of 28 patients (21%) with laryngeal SCC had plasma GSTP1-1 levels above the upper limit of the normal reference level. Thus, only 13 of 93 patients (14%) with HNSCC had elevated plasma GSTP1-1 levels overall. No significant relation between plasma GSTP1-1 levels and TNM classification of the tumors was observed. CONCLUSIONS: GSTP1-1 is not a suitable plasma tumor marker for HNSCC.