Oral cancer diagnosis via a ferrocenylnaphthalene diimide-based electrochemical telomerase assay.

BACKGROUND

Telomerase is regarded as a good marker for cancer because it is unregulated in most tumor cells compared with normal cells. We evaluated telomerase activity in the lysate of tumor tissue and surrounding cells of oral cancer patients by an electrochemical technique, dubbed the electrochemical telomerase assay (ECTA).

METHODS

The assay used ferrocenylnaphthalene diimide (FND) as the probe. Electrochemical telomerase substrate (ETS) primer immobilized on the electrode was elongated by telomerase and FND bound to the product to give rise to a current. The data were standardized with the change in current before and after the elongation, respectively.

RESULTS

The change in current increased more than 30% in biopsy samples from most cancer patients, whereas the increase was 20% or lower in most healthy individuals. On the basis of this difference individual clinical samples were judged telomerase positive, ambiguous, or negative. The positive rates in the cancerous tissues and exfoliated cells (EOCs) of the patients were 85% and 90%, respectively, whereas the corresponding values were 50% and 10% by the telomerase repeat amplification protocol. Furthermore, the positive rate for the ECTA was 100% in early tumors smaller than 2 cm, and 95% and 82% of biopsy and exfoliated cells of healthy individuals were correctly judged as negative. Fifty-six unknown samples with EOCs tested were correctly judged to be cancerous or normal in 84% of cases.

CONCLUSIONS

The ECTA yielded high hit rates for cancerous and normal cells, especially in EOCs, results indicating that this minimally invasive test is suitable for oral cancer diagnosis.