The CancerWeb Report, What's New In Cancer: December, 1996
Head and Neck Cancer

• A predictor of response to platinum-based chemotherapy - An article by researchers at Georgetown University in Washington, DC described a striking relationship between the levels of an enzyme, glutathione S-transferase (frequently called GST), in tumor specimens from patients with head and neck cancers, and their response to chemotherapy regimens that included cisplatin. GST is generally considered to be an enzyme that protects cells from damaging substances by combining them with glutathione, a protective sulfur-containing compound built up of amino acids. In their report, which appeared in the November, 1996 issue of Clinical Cancer Research, these doctors described an overall response rate in 51 patients of 48%. This broke down into 88% for those with low GST levels and only 19% for those with high scores, as determined by immunological staining techniques, making the low GST group nearly 5 times more likely to respond to chemotherapy. Among 33 patients in relapse the difference was even more pronounced, with response rates of 70% for low GST patients versus 8.6% for those with high GST scores. High levels of GST presumably provide the tumor cells with greater ability to withstand the stress of the toxic chemotherapy regimen, although it has not yet been determined whether it plays a direct role in inhibiting the action of cisplatin. (Noshimura, Clin Cancer Res 2:1859, 1996)

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• Telomerase activity may indicate the degree of malignancy of cancer of the larynx - Telomerase is an enzyme which repairs and maintains the protective ends of chromosomes. Except for reproductive cells, normal human cells do not have detectable amounts of this enzyme, so with time, wear, and repeated replication of the main chromosome chain, the ends of normal chromosomes become shorter (see earlier issues of CancerWeb Report for more discussion of this; for example Volume 1, Number 3, November 1995 under Carcinogenesis, and Volume 2, Number 6, June 1996 under Bladder Cancer). An article about this enzyme in relation to cancer of the larynx was published in the November, 1996 issue of Clinical Cancer Research. In an examination of 36 laryngeal cancer specimens from 35 patients, doctors at the Catholic University of St Cuore in Rome found that telomerase was present in 89% of the tumors at levels which increased as the stage of the disease became more advanced. Of the four tumor samples in which the enzyme could not be detected, it appeared that there was an inhibitor of the enzyme in two of them which prevented it from being measured. They also found that in 16 of 21 patients telomerase was detectable in the apparently normal mucosal areas surrounding the tumor. The assay of this enzyme activity may be useful in assessing the stage and spread of this cancer. (Hohaus, Clin Cancer Res 2:1895, 1996)

  Editor's Comment: - Telomerase activity prevents the aging or senescence of cells by restoring the damaged ends of chromosomes. Acquisition of this activity is part of the immortalization' process that is intimately involved in converting a normal cell with a finite capacity to divide into a malignant one capable of proliferating indefinitely. This study does show that in the laryngeal mucosa telomerase activity appears in cells before their actual appearance becomes definitely malignant. Thus it may be an early marker of precancerous changes in this tissue, as well as being an indicator of the degree of malignancy of a tumor.