The design, computer modeling, solution structure, and biological evaluation of synthetic analogs of bryostatin 1

Abstract

The bryostatins are a unique family of emerging cancer chemotherapeutic candidates isolated from marine bryozoa. Although the biochemical basis for their therapeutic activity is not known, these macrolactones exhibit high affinities for protein kinase C (PKC) isozymes, compete for the phorbol ester binding site on PKC, and stimulate kinase activity in vitro and in vivo. Unlike the phorbol esters, they are not first-stage tumor promoters. The design, computer modeling, NMR solution structure, PKC binding, and functional assays of a unique class of synthetic bryostatin analogs are described. These analogs (7b, 7c, and 8) retain the putative recognition domain of the bryostatins but are simplified through deletions and modifications in the C4-C14 spacer domain. Computer modeling of an analog prototype (7a) indicates that it exists preferentially in two distinct conformational classes, one in close agreement with the crystal structure of bryostatin 1. The solution structure of synthetic analog 7c was determined by NMR spectroscopy and found to be very similar to the previously reported structures of bryostatins 1 and 10. Analogs 7b, 7c, and 8 bound strongly to PKC isozymes with K i ‫؍‬ 297, 3.4, and 8.3 nM, respectively. Control 7d, like the corresponding bryostatin derivative, exhibited weak PKC affinity, as did the derivative, 9, lacking the spacer domain. Like bryostatin, acetal 7c exhibited significant levels of in vitro growth inhibitory activity (1.8-170 ng͞ml) against several human cancer cell lines, providing an important step toward the development of simplified, synthetically accessible analogs of the bryostatins.

Bryostatin Enhancement of Memory inHermissenda

“…The dose response results with Hermissenda were congruous with the published data for several model systems (Favit et al, 1998;Wender et al, 1998;Etcheberrigaray et al, 2004;Scioletti et al, 2004;Alkon et al, 2005). Subnanogram concentrations of bryostatin administered before paired associative conditioning up-regulated PKC activity, and specifically for Hermissenda, enhanced both acquisition and retention initiated by suboptimal paired CS/US training regimes.…”

Conformationally Constrained Analogues of Diacylglycerol (DAG). 16. How Much Structural Complexity Is Necessary for Recognition and High Binding Affinity to Protein Kinase C?

“…PK-CR Binding Affinities (Ki) and log P for R-Alkylidene "Reversed Ester" Lactones (Z-and E-Isomers) fit calculated for two subgroups (Z-and E-isomers) of DAG-lactones selected from Table 1. For the R-alkylidene branched series (13)(14)(15)(16)(17)(18)(19)(20)(21)(22), the curves revealed that affinity for PK-C reaches a maximum at ca. log P ) 6 for both Z-and E-isomers.…”

“…Binding affinity (log 1/Ki) versus partition coefficients (log P) in octanol/water. The red (Z-isomers) and green (E-isomers) curves correspond to the R-alkylidene branched series (13)(14)(15)(16)(17)(18)(19)(20)(21)(22), and the black (Z-isomers) and blue (E-isomers) curves correspond to the acyl branched series (23-30). reproduced well the position, orientation, and hydrogenbonding network of the original crystal structure. 27 Except for the "reversed ester" lactones 69 and 70, which docked almost exclusively in an sn-2 mode, the program engendered both sn-1 and sn-2 binding modes in different ratios depending on the size, stereochemistry, and shape of the R 1 and R 2 groups on the DAGlactones (Table 3).…”

Nature: a vital source of leads for anticancer drug development

“…These have resulted in the preparation of compounds, bryologs (Fig. 3), with greater potency than bryostatin 1 in in vitro cell line assays (Wender et al 1998a(Wender et al , 1998b(Wender et al , 1999(Wender et al , 2002(Wender et al , 2003a(Wender et al , 2003bWender and Lippa 2000). Use of molecular probes has demonstrated the presence of a putative type I polyketide synthase gene fragment in the microbial flora (Candidatus Endobugula sertula) of colonies of the host bryozoan producing bryostatin, but shown to be absent in the corresponding flora of non-producers (Sudek et al 2007;Piel 2006).…”