To examine whether there is differential expression of EGFR ligands in human tumors, we determined expression levels of TGFA, HB-EGF, NRG1, AREG and EGF by RT-PCR in one normal oral mucosa, two HNSCC tumors taken at the time of diagnosis, and four HNSCC tumors taken at the time of recurrence (Figure 6A and Table 2). The gene discussed is AREG; the disease is head and neck squamous cell carcinoma.