Novel actions of the antitumor drugs vinflunine and vinorelbine on microtubules

Vinflunine is a novel Vinca alkaloid presently in Phase I clinical trials. In preclinical studies, it exhibited superior antitumor activity to that of other Vinca alkaloids, including vinorelbine from which it was synthetically derived. Vinca alkaloids appear to inhibit cell proliferation by affecting the dynamics of spindle microtubules. Here we have analyzed the effects of vinflunine and vinorelbine on microtubule dynamic instability and treadmilling and found that these newer drugs exert effects on microtubule dynamics that differ significantly from those of the classic Vinca alkaloid, vinblastine. The major effects of vinflunine and vinorelbine on dynamic instability were a slowing of the microtubule growth rate, an increase in growth duration, and a reduction in shortening duration. In marked contrast to the action of vinblastine, they neither reduced the rate of shortening nor increased the percentage of time the microtubules spent in an attenuated state, neither growing nor shortening detectably. In addition, vinflunine and vinorelbine suppressed treadmilling, but less strongly than vinblastine. The diverse actions of these drugs on microtubules are likely to produce different effects on mitotic spindle function, leading to different effects on cell cycle progression and cell killing. Nontumor cells with normal checkpoint proteins may tolerate the relatively less powerful inhibitory effects of vinflunine and vinorelbine on microtubule dynamics better than the more powerful effects of vinblastine. Thus the unique constellation of effects of vinflunine and vinorelbine on dynamic instability and treadmilling may contribute to their superior antitumor efficacies.     

Down-regulation and promoter methylation of tissue inhibitor of metalloproteinase 3 in choriocarcinoma

OBJECTIVE: To assess the differential gene expression in neoplastic and normal trophoblastic cells and evaluate the effect of methylation on tissue inhibitor of metalloproteinase 3 (TIMP3) expression in choriocarcinoma (CCA) cells. METHODS: The Atlas Human Cancer 1.2 Array (Clontech) was used to compare differential gene expression in a trophoblastic cell line (B6) established from first term placenta with two choriocarcinoma cell lines (JAR and JEG-3). The differentially expressed candidate genes in the placental and malignant trophoblastic cells in these cell lines were confirmed by real-time polymerase chain reaction (PCR), Western blotting and immunohistochemistry. Differential expression of a specific gene, TIMP3, was confirmed by immunohistochemistry using clinical specimens of choriocarcinoma and placenta. The involvement of promoter methylation in suppression of TIMP3 expression in choriocarcinoma was examined using methylation-specific PCR (MSP) and demethylation treatment. RESULTS: Differential expression of 23 genes was observed in choriocarcinoma cell lines compared to the placental trophoblastic cells using the cDNA array analysis (Atlas Human Cancer Array, Clontech). Among these differentially expressed genes, down-regulation of TIMP3, PLAB, IGFBP3 and up-regulation of CCNB1 were confirmed by real-time PCR determination. Reduced expression of TIMP3 was further confirmed in clinical samples of choriocarcinoma by immunohistochemical staining. Methylation of TIMP3 promoter was detected in choriocarcinoma cell lines and clinical samples of choriocarcinoma. Treatment with a demethylation drug, 5-aza-2'-deoxycytidine, in choriocarcinoma cell lines restored TIMP3 expression. CONCLUSION: Down-regulation of TIMP3, PLAB, IGFBP3 and up-regulation of CCNB1 were observed in choriocarcinoma cells compared to placental trophoblasts. Down-regulation of TIMP3 expression was confirmed in clinical specimens of choriocarcinoma and may play a role in its pathogenesis. Promoter methylation of the TIMP3 is involved in suppression of TIMP3 expression. Differentiation expression of TIMP3 in choriocarcinoma may have potential application in clinical diagnosis and patient treatment.     

Considerations in the management of transposed teeth

AIM: To review the management of transposed teeth, and to illustrate the treatment options with four case reports. METHODS: The aetiology and management of transposed teeth are reviewed. Three management options are discussed: correcting the order of transposed teeth, maintaining the order of transposed teeth, and extraction of one of the transposed teeth. Methods of camouflaging transposed teeth are described in detail. The treatment options are illustrated with case reports.     

Hepatic arteriogram for gestational trophoblastic tumor: is it useful?

The presence of liver metastasis will be staged as IV in the FIGO 1992 Gestational Trophoblastic Tumor (GTT) staging. This study was to determine the role of hepatic arteriogram (HAG) in the management of GTT. It is a retrospective analysis of 309 patients treated from 1981 to 2001. Patients were restaged according to the FIGO 1992 classification with or without taking into account the HAG result. Outcome measures including mortality, drug resistance and recurrence of disease, as well as treatment with and without the HAG result were compared. Eighty-one (26.2 percent) patients had HAG and 11 (3.6 percent) also had ultrasound (USG) features of liver metastasis. Interval between diagnosis and treatment were significantly different between USG and HAG positive groups (Mann-Whitney U test, P < 0.05). Seventeen (5.5 percent) of the 309 patients died of the disease and 7 (41.2 percent) of them had liver metastasis. Three (27.3 percent) of the 11 patients who had USG features of liver metastasis died of the disease; mortality is significantly higher than those without USG features of metastasis (Chi-square test, P < 0.05). Patients classified as medium to high risk with or without taking HAG as a feature of liver metastasis were associated with higher mortality and recurrent rate (Chi-square test, P < 0.05). On the other hand, the chance of drug resistance was higher in the medium to high risk group after reclassifying all HAG positive patients as negative for liver metastasis (Chi-square test, P < 0.05). HAG evidence of liver metastasis did not correlate with patient mortality. HAG was not an appropriate investigation in the management of GTT.