SULF1 and neoplasm: While our previous research confirmed that the SULF2 isoform of heparan 6‐O‐endosulfatases promotes tumor cell growth and invasion in HNSCC [12, 13], we detected only minimal amounts of the SULF1 isoform within the cancer cells themselves even though SULF1 is one of the most consistently upregulated proteins in the HNSCC tumor tissues [12, 14].