Differential cellular zinc levels in metastatic and primary nasopharyngeal carcinoma.

Zinc levels are known to be elevated in certain cancer tissues. In this study, zinc content in metastatic and primary nasopharyngeal carcinoma (NPC) cells were quantitated by X-ray microanalysis at the ultrastructural level. Zinc levels of cancer cells derived from the cervical lymph node of a patient with metastatic carcinoma and that from the nasopharynx biopsy of another NPC patient with no clinical evidence of secondary spread, were analyzed. X-ray microanalysis revealed significantly higher cellular zinc levels in metastatic NPC cells. Zinc is a known anti-apoptotic agent and tumor response to radiotherapy is linked with apoptosis or programmed cell death. Raised zinc levels observed here could provide the biological basis for the observation of a higher percentage of distant metastasis in cervical node positive NPC patients treated by radiotherapy (the mainstay of treatment for NPC) as compared to those without regional nodal disease.