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


OBJECTIVE
To elucidate the significance of GST-pi expression in NPC.


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


METHODS
Immunohistochemical expression of GST-pi 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-pi in NPC was correlated with corresponding tissue iron levels. The relationships between GST-pi expression with sex, race, tumor stage, cervical nodal status, and clinical staging were also analyzed.


RESULTS
Glutathione S-transferase pi 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-pi expression and total and nuclear iron levels in NPC (P =.01 and P =.047, respectively). A significant association was also observed between GST-pi 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 pi expression appears to be associated with lymphogenous metastasis in NPC.
Jayasurya
Anita
A
Department of Anatomy, National University of Singapore, 4 Medical Dr, Blk MD 10, S117 597 Singapore. antbaybh@nus.edu.sg
Yap
Wai-Ming
WM
Tan
Nam-Guan
NG
Tan
Benny Kwong-Huat
BK
Bay
Boon-Huat
BH
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005982:Glutathione Transferase / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D007501:Iron / Q000032:analysis; D008297:Male; D008875:Middle Aged; D009303:Nasopharyngeal Neoplasms / Q000201:enzymology*
D007501:Iron; D005982:Glutathione Transferase