SULF2 and head and neck squamous cell carcinoma: HNSCC cell lines SCC35 and CAL33 (human squamous cell carcinoma cell lines derived from hypopharynx and oral cavity tumors, respectively) conditioned media was used as the starting material for immuno-affinity purification (IP) of the Sulf-2 protein in complex with its interacting partners (Supplemental Fig. S3).