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Glutathione S-Transferase Expression in Nasopharyngeal Cancer

Anita Jayasurya, MD,PhD; Wai-Ming Yap, MRCPath; Nam-Guan Tan, FRCS; Benny Kwong-Huat Tan, MBBS,PhD; Boon-Huat Bay, MBBS,PhD

Arch Otolaryngol Head Neck Surg. 2002;128:1396-1399.

Background  Glutathione S-transferase (GST-) is an enzyme that catalyzes the conjugation of electrophilic substrates and prevents oxidative damage. Although GST- expression has been analyzed in many cancers, the significance of GST- expression in nasopharyngeal cancer (NPC), a tumor with a high treatment failure rate, is still unclear.

Objective  To elucidate the significance of GST- expression in NPC.

Design  Evaluation of GST- expression in NPC tissue specimens and determination of its relationship with tissue iron (a pro-oxidant) and clinicopathological factors in NPC.

Materials and Methods  Immunohistochemical expression of GST- was carried out in 55 NPC and 4 normal nasopharyngeal tissue sections. Eleven nasopharyngeal biopsy specimens (4 normal and 7 NPC) were analyzed for tissue iron levels. The expression of GST- in NPC was correlated with corresponding tissue iron levels. The relationships between GST- expression with sex, race, tumor stage, cervical nodal status, and clinical staging were also analyzed.

Results  Glutathione S-transferase immunoreactivity was observed in all NPC sections, with the percentage of immunopositive cells ranging from 1.0% to 72.0%. Tissue iron levels were significantly higher in the NPC tissues compared with normal tissues (P = .001). A direct correlation was observed between GST- expression and total and nuclear iron levels in NPC (P = .01 and P = .047, respectively). A significant association was also observed between GST- expression and cervical nodal disease (P = .007).

Conclusions  Nasopharyngeal tumor cells may respond to pro-oxidant conditions by modulating intracellular antioxidant defense. Glutathione S-transferase expression appears to be associated with lymphogenous metastasis in NPC.

From the Departments of Anatomy (Drs Jayasurya and Bay) and Pharmacology (Dr Benny Kwong-Huat Tan), National University of Singapore, Singapore; the Department of Pathology, Tan Tock Seng Hospital, Jalan Tan Tock Seng, Singapore (Dr Yap); and the Department of Otolaryngology, Singapore General Hospital, Singapore (Dr Nam-Guan Tan).