Abstract
Characteristic behaviors of head and neck squamous cell carcinoma (HNSCC) include a propensity to occur as multiple synchronous and metachronous tumors, frequent recurrence and metastasis. Early detection of HNSCC and monitoring its recurrence are necessary to improve prognosis. Hyaluronic acid (HA), a component of extracellular matrix, promotes metastasis. Small fragments of HA stimulate angiogenesis. HA fragments are generated when hyaluronidase (HAase), an endoglycosidase, degrades the HA polymer. Using the HA test (an ELISA‐like assay) we found that saliva HA levels are 4.9‐fold elevated in 11 HNSCC patients (2841 ± 887 ng/mg protein) when compared to 6 normal controls (579.3 ± 122.6 ng/mg protein; p = 0.00238). HNSCC patients included in our study were patients with cancers of the oral cavity (n = 4), pharynx (n = 7) and larynx (n = 1). The HA levels were also elevated in MDA‐1483, FaDu and HEp‐2 cell lines when compared to the transformed keratinocyte line HEK‐001. Saliva HAase levels measured using the HAase test (an ELISA‐like assay) were 3.7‐fold elevated in HNSCC patients (10.4 ± 1.4 mU/mg protein) when compared to normal controls (2.8 ± 0.7 mU/mg protein; p = 0.0028). MDA‐1483 and HEp‐2 cells secreted 7‐ to 11‐fold higher levels of HAase in their conditioned media (CM) when compared to FaDu cells, and the latter secreted 1.5‐fold more HAase than HEK‐001 cells. Reverse transcriptase (RT)‐PCR analysis detected the expression of full‐length HYAL1 type HAase transcript in tumor cells. None of the cells exhibited the expression of PH20 in RT‐PCR analysis. Immunoblot analysis confirmed the expression of a ∼55 kDa HYAL‐related protein in tumor cell CM and in patients' saliva. The pH activity profile and optimum (pH 4.4) of the HAase activity present in HNSCC patients' or normal saliva and that secreted in the CM of tumor cells closely resembled that of the partially purified HYAL1 type HAase. The profiles of HA species in HNSCC patients' and normal saliva are different. The high‐stage HNSCC patients' saliva contains a high‐molecular‐mass HA species and HA fragments, in addition to the HA species present in the normal individual's saliva. These results show that HYAL1 is the major tumor‐derived HAase expressed in HNSCC. Furthermore, HA and HAase may be sensitive and specific markers for detecting HNSCC and monitoring its recurrence. Further studies are needed to confirm these preliminary studies. © 2003 Wiley‐Liss, Inc.