Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:5.99.1.3 (topoisomerase)
 9,911 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We describe three patients with advanced Merkel cell carcinoma who were treated with etoposide given orally for recurrent regional lymph node involvement 18 to 30 months after exposure to etoposide given intravenously. Etoposide given orally (100 mg/day) was given for 10 to 14 consecutive days and repeated every 21 to 28 days for a median of three courses (range: two to four). Toxicity was minimal and mainly hematologic. Two patients showed a complete response and one a partial response, all of very rapid onset. All three patients are alive 6, 9, and 42 months from the start of oral treatment. Two remain progression free, and one had a recurrence 1 month after completion of chemotherapy. We suggest that orally administered etoposide, a topoisomerase II inhibitor, has a strong antitumor effect in advanced Merkel cell carcinoma, even in patients previously treated parenterally with the same drug. This action may be explained by the greater dependence of the drug's efficacy on the duration of administration rather than the dose intensity.
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PMID:Oral etoposide for Merkel cell carcinoma in patients previously treated with intravenous etoposide. 1068 81

Merkel cell carcinomas are rare and aggressive tumors about which the expression of cell cycle regulatory proteins are not well known. We evaluated the clinicopathologic features of Merkel cell carcinomas and examined the expression of the cell cycle regulatory markers p27 and S-phase kinase-associated protein 2 (Skp2) and the proliferation markers Ki-67 and DNA topoisomerase II alpha (topo II alpha) in a group of these tumors. Thirty-nine cases of Merkel cell carcinoma were studied, 19 from the Mayo Clinic, Rochester, MN, and 20 from the University of Torino, Torino, Italy. Although the University of Torino patients tended to be slightly older at time of surgery compared to the Mayo Clinic patients, no clinical, pathologic, or immunohistochemical feature was statistically significantly different between the two groups. Of the 39 patients, 20 were male and 19 were female. The age at surgery averaged 72 yr. Formalin-fixed paraffin-embedded archival tissues from the 39 Merkel cell carcinomas were analyzed by immunohistochemistry for p27, Skp2, Ki-67, and topo II alpha with the avidin-biotin peroxidase system. The distribution of immunoreactivity was analyzed by quantifying the percentage of positive nuclei, which was expressed as the labeling index. There was a statistically significant inverse relationship between p27 and Skp2 (p = 0.005). Most tumors with increased levels of Skp2 were associated with reduced p27, and tumors with high levels of p27 expression were associated with reduced levels of Skp2. These results suggest that Skp2 regulates p27 expression in Merkel cell carcinomas. Tumors showing increased Skp2 expression were not always correlated with increased proliferation as evaluated by Ki-67 and topo II alpha, suggesting that Skp2 may be involved in Merkel cell tumorigenesis, but that other factors may also influence cell proliferation in these tumors.
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PMID:Merkel cell carcinomas: expression of S-phase kinase-associated protein 2 (Skp2), p27, and proliferation markers. 1458 67