N6-Isopentenyladenosine (1, iPA) is a member of the cytokinin family, plant hormones that regulate cell growth and differentiation. iPA is the only known cytokinin existing in animal cells in a free form, as a mononucleotide in cytoplasm, or bound to t-RNA. At present, the biological role and the mechanism of action of iPA in mammalians cells are not fully understood. It has been demonstrated that iPA is able to inhibit protein prenylation1 and competes for nucleoside transport.2 Spinola3 et al. have recently demonstrated that iPA exerts a potent in vitro anticancer activity on human epithelial cancer cell lines while it has a slight effect on tumour growth in rodents. This lack of in vivo activity could be related to the short plasma half-life of iPA, as it is well known for other nucleosides. With the aim of identifying compounds endowed with in vitro and in vivo antiproliferative activity, we have investigated structural modifications of iPA. Initially, we have synthesized a few acyclonucleosides that are characterized by the presence of an acyclic component, structurally resembling part of the ribose moiety in iPA. Proliferation, clonogenicity, and gene expression profile analysis were evaluated in human epithelial cancer cell lines derived from different tumours. The results showed that the iPA ribofuranosidic ring is pivotal for its biological activity.4 Starting from these results we have synthesized iPA analogues in which the hydroxyl group in 2′, 3′ and 5′ positions were replaced by a hydrogen group in order to verify the importance of each hydroxyl group of the furanosidic moiety for the activity of iPA. Then other analogues where the base adenine was substituted by inosine were synthesized (O-isopentenylinosine and its deoxy-derivatives). All compounds were in vitro tested using T24 cell line and the proliferation assay was carried out in the presence and absence of serum. No activity was found for the tested compounds, except 3′ deoxy-iPA, that was able to cause cell death of quiescent cultures. We have also synthesized iPA analogues in which the N6-position was differently substituted with the aim of verify the importance of the isopentenyl chain for the activity of the molecule. Preliminary results of in vitro assays using these compounds (T24 cell line, proliferation assay in presence and absence of serum) allowed us to select some compounds with cytotoxicity as high as iPA. With these molecules we have performed additional experiments in order to clarify the mechanism of action of iPA and its derivatives. We are now studying the synthesis of analogues of iPA in which the furanosidic moiety is replaced by a hydroxylated cyclopentane in order to obtain more stable compounds replacing the β-N-glycosidic bond (N-C-O) by a N-C-C bond to increase the resistance to enzymatic hydrolysis. [1] Laezza C., Notarnicola M., Caruso M.G., Messa C., Macchia M., Bertini S., Minutolo F., Portella G., Fiorentino L., Stingo S., Bifulco M.; N6-isopentenyladenosine arrests tumor cell proliferation by inhibiting farnesyl diphosphate synthase and protein prenylation. The FASEB J. 2006, 20, 412. [2] Hakala M.T., Slocum H.K., Gryko G.J.; N6-(Δ2-Isopentenyl)adenosine an inhibitor of cellular transport of uridine and cytidine. J.Cell Physiol. 1975, 86, 281. [3] Spinola M., Colombo F., Falvella F.S., Dragani T.A.; N6-isopentenyladenosine: a potential therapeutic agent for a variety of epithelial cancers. Int. J. Cancer 2007, 120, 2744. [4] Colombo F., Favella F.S., Tortoreto M., Pratesi G., Ciuffreda P., Ottria R., Santaniello E., Cicatiello L., Weisz A. & Dragani T.A.; Pharmacogenomics and analogues of the antitumor agent N6-isopentenyladenosine. Int. J. Cancer 2009, 124, 2179

Isopentenyladenosine analogues as potential antitumor agents : synthesis and structure-activity relationships / R. Ottria. ((Intervento presentato al 22. convegno Riunione Nazionale “A. Castellani” dei Dottorandi di Ricerca in Discipline Biochimiche tenutosi a Brallo di Pregola nel 2009.

Isopentenyladenosine analogues as potential antitumor agents : synthesis and structure-activity relationships

R. Ottria
Primo
2009

Abstract

N6-Isopentenyladenosine (1, iPA) is a member of the cytokinin family, plant hormones that regulate cell growth and differentiation. iPA is the only known cytokinin existing in animal cells in a free form, as a mononucleotide in cytoplasm, or bound to t-RNA. At present, the biological role and the mechanism of action of iPA in mammalians cells are not fully understood. It has been demonstrated that iPA is able to inhibit protein prenylation1 and competes for nucleoside transport.2 Spinola3 et al. have recently demonstrated that iPA exerts a potent in vitro anticancer activity on human epithelial cancer cell lines while it has a slight effect on tumour growth in rodents. This lack of in vivo activity could be related to the short plasma half-life of iPA, as it is well known for other nucleosides. With the aim of identifying compounds endowed with in vitro and in vivo antiproliferative activity, we have investigated structural modifications of iPA. Initially, we have synthesized a few acyclonucleosides that are characterized by the presence of an acyclic component, structurally resembling part of the ribose moiety in iPA. Proliferation, clonogenicity, and gene expression profile analysis were evaluated in human epithelial cancer cell lines derived from different tumours. The results showed that the iPA ribofuranosidic ring is pivotal for its biological activity.4 Starting from these results we have synthesized iPA analogues in which the hydroxyl group in 2′, 3′ and 5′ positions were replaced by a hydrogen group in order to verify the importance of each hydroxyl group of the furanosidic moiety for the activity of iPA. Then other analogues where the base adenine was substituted by inosine were synthesized (O-isopentenylinosine and its deoxy-derivatives). All compounds were in vitro tested using T24 cell line and the proliferation assay was carried out in the presence and absence of serum. No activity was found for the tested compounds, except 3′ deoxy-iPA, that was able to cause cell death of quiescent cultures. We have also synthesized iPA analogues in which the N6-position was differently substituted with the aim of verify the importance of the isopentenyl chain for the activity of the molecule. Preliminary results of in vitro assays using these compounds (T24 cell line, proliferation assay in presence and absence of serum) allowed us to select some compounds with cytotoxicity as high as iPA. With these molecules we have performed additional experiments in order to clarify the mechanism of action of iPA and its derivatives. We are now studying the synthesis of analogues of iPA in which the furanosidic moiety is replaced by a hydroxylated cyclopentane in order to obtain more stable compounds replacing the β-N-glycosidic bond (N-C-O) by a N-C-C bond to increase the resistance to enzymatic hydrolysis. [1] Laezza C., Notarnicola M., Caruso M.G., Messa C., Macchia M., Bertini S., Minutolo F., Portella G., Fiorentino L., Stingo S., Bifulco M.; N6-isopentenyladenosine arrests tumor cell proliferation by inhibiting farnesyl diphosphate synthase and protein prenylation. The FASEB J. 2006, 20, 412. [2] Hakala M.T., Slocum H.K., Gryko G.J.; N6-(Δ2-Isopentenyl)adenosine an inhibitor of cellular transport of uridine and cytidine. J.Cell Physiol. 1975, 86, 281. [3] Spinola M., Colombo F., Falvella F.S., Dragani T.A.; N6-isopentenyladenosine: a potential therapeutic agent for a variety of epithelial cancers. Int. J. Cancer 2007, 120, 2744. [4] Colombo F., Favella F.S., Tortoreto M., Pratesi G., Ciuffreda P., Ottria R., Santaniello E., Cicatiello L., Weisz A. & Dragani T.A.; Pharmacogenomics and analogues of the antitumor agent N6-isopentenyladenosine. Int. J. Cancer 2009, 124, 2179
2009
Isopentenyladenosine analogues as potential antitumor agents : synthesis and structure-activity relationships / R. Ottria. ((Intervento presentato al 22. convegno Riunione Nazionale “A. Castellani” dei Dottorandi di Ricerca in Discipline Biochimiche tenutosi a Brallo di Pregola nel 2009.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/65575
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