Cyclin-dependent kinases (cdk) play an essential role in the intracellular control of the cell division cycle (cdc). These kinases and their regulators are frequently deregulated in human tumours. Enzymatic screening has recently led to the discovery of specific inhibitors of cyclin-dependent kinases, such as butyrolactone I, flavopiridol and the purine olomoucine. Among a series of C2, N6, N9-substituted adenines tested on purified cdc2kyclin B, 2-(1-ethyl-2-hydroxyethylamino)-6-benzylamino-9-isopropylpurine (roscovitine) displays high efficiency and high selectivity towards some cyclin-dependent kinases. The kinase specificity of roscovitine was investigated with 25 highly purified kinases (including protein kinase A, G and C isoforms, myosin light-chain kinase, casein kinase 2, insulin receptor tyrosine kinase, c-src, v-abl). Most kinases are not significantly inhibited by roscovitine. cdc2kyclin B, cdk2kyclin A, cdk2lcyclin E and cdkSlp35 only are substantially inhibited (IC,, values of 0.65, 0.7, 0.7 and 0.2 pM, respectively). cdk4kyclin D1 and cdk6kyclin D2 are very poorly inhibited by roscovitine (IC,, > 100 pM). Extracellular regulated kinases erkl and erk2 are inhibited with an IC,, of 34 pM and 14 pM, respectively. Roscovitine reversibly arrests starfish oocytes and sea urchin embryos in late prophase. Roscovitine inhibits in vitro M-phase-promoting factor activity and in vitro DNA synthesis in Xenopus egg extracts. It blocks progesterone-induced oocyte maturation of Xenopus oocytes and in vivo phosphorylation of the elongation factor eEF-1. Roscovitine inhibits the proliferation of mammalian cell lines with an average IC,,] of 16 pM. In the presence of roscovitine L1210 cells arrest in G1 and accumulate in G2. In vivo phosphorylation of vimentin on Ser55 by cdc2kyclin B is inhibited by roscovitine. Through its unique selectivity for some cyclin-dependent kinases, roscovitine provides a useful antimitotic reagent for cell cycle studies and may prove interesting to control cells with deregulated cdc2, cdk2 or cdk5 kinase activities.

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Polyamine contents were assessed by mass spectrometry in 233 current foods and beverages. In order to reduce gut polyamine uptake, a polyamine reduced diet (PRD) and partial intermittent intestinal tract decontamination (PIITD) with neomycin or nifuroxazide was proposed as nutritional therapy to 33 prostate carcinoma patients, 30 of whom with hormone refractory prostate cancer (HRPC). Mean PRD observance was 22 +/- 19 (median: 16; range: 3-72) months. 10, 8 and 3 patients were respectively on PRD for more than 30, 36 and 64 months. No diet toxicity was observed. 8 patients had moderate intestinal intolerance due to PIITD which was interrupted. No significant differences in body weight, blood counts or serum protein levels were observed during the follow-up of patients under PRD. Performance status and pain scores were relatively stable during the trial with improved pain scores at 6 months. A PRD associated with intermittent PIITD is a safe and well observed nutritional regimen and long term observance is possible.