Effects of Putative Hydroxylated Thalidomide Metabolites on Blood Vessel Density in the Chorioallantoic Membrane (CAM) Assay and on Tumor and Endothelial Cell Proliferation.

Abstract

Angiogenesis, the process of blood vessel formation from pre-formed vessels, has recently become a primary target of anticancer therapy. This is due in part to the finding that removing the blood supply to a tumor can not only prevent further growth but can also starve the existing cells to death.2) In the past several years there have been many potential anti-angiogenic agents developed acting by many mechanisms including interruption of growth factor receptor phosphorylation, [3][4][5] growth factor-receptor binding, 6,7) cell adhesion molecule expression and signaling 8,9) and alterations in endothelial cell apoptosis. 10,11) In addition, several agents such as thalidomide have been shown to inhibit angiogenesis by an as yet not fully understood mechanism.12-18) Furthermore, thalidomide has been shown to reduce tumor growth both in model systems [19][20][21] and in patients. [22][23][24][25][26][27][28] Clinically, however, thalidomide has a fairly weak effect as a monotherapy in patients with solid tumors [22][23][24] but is showing tremendous promise against multiple myeloma.25-28) It has been shown that activation of thalidomide by human or rabbit liver enzymes, but not by rat liver enzymes, significantly enhances the anti-angiogenic effect of the drug in rat aortic sections or isolated endothelial cells.29) This is very interesting because thalidomide is virtually non-toxic to rats when given orally (PO). Intraperitoneal (IP), administration however, commonly associated with "first-pass" hepatic metabolism, 30) recapitulates the teratogenic effect of thalidomide in rats. 31)Kenyon et al. 19) also showed that thalidomide given IP was effective as an anti-angiogenic agent in the mouse corneal model, whereas thalidomide given PO was inactive. In addition, thalidomide teratogenesis was only found to occur after activation of the drug by liver enzymes. 13,[32][33][34][35] Furthermore, in a Xenopus oocyte assay of teratogenesis, activation of thalidomide by a single cytochrome P450 enzyme, CYP2E1, lead to a teratogenic compound whereas unactivated thalidomide was non-teratogenic.35) Thus metabolism of thalidomide is critical to its anti-angiogenic and teratogenic activity. However, the identity of the active anti-angiogenic and teratogenic moiety or moieties of thalidomide are still unknown.The goal of this work was to explore the effect of putative hydroxylated thalidomide metabolites on blood vessel density and target cell proliferation. Since the anti-angiogenic activity of thalidomide was first reported, 36) only a limited number of thalidomide metabolites have been tested for antiangiogenic activity. Figure 1 shows known and hypothesized metabolites of thalidomide (structures M1-M8) based on extensive literature review. [37][38][39][40][41][42][43][44][45] Thalidomide can be metabolized through hydrolysis at the glutarimide and/or phthalimide ring to yield metabolites such as M6-M8. Its hydroxylation can occur on glutarimide or phthalimide ring to yield metabolites M1-M5. Interestingly, only metabolites M5...

Thalidomide Down-Regulates Transcript Levels of GC-Rich Promoter Genes in Multiple Myeloma

“…Despite several studies displaying the need of metabolic activation of racemic Thd, we demonstrated an inhibition of gene transcription with hydrolysis products only (Kenneth et al, 1998). Similar reports regarding the effects of hydroxylation without bioactivation have been published previously (Marks et al, 2002).…”

Isoindolone derivative QSN-10c induces leukemic cell apoptosis and suppresses angiogenesis via PI3K/AKT signaling pathway inhibition

“…Recent research has shown that the drug has antitumoral properties, and promising results from thalidomide treatment in patients with myeloma, myelodysplastic syndrome, and variety of solid tumors has been reported [35] . However, thalidomide has been shown to require bio-activation to exert its anti-angiogenic effect in isolated blood vessels and endothelial cells [36,37] . Moreover, thalidomide displayed varying antiangiogenic activities in endothelial cells (ECs) in the literature [38,39] .…”

A thalidomide analogue within vitroantiproliferative, antimitotic, and microtubule-stabilizing activities

“…Recently, we reported the antiangiogenic activities of several putative metabolites of thalidomide (26). Our ongoing search for potent antiangiogenic thalidomide analogues revealed a compound, 5-hydroxy-(2,6-diisopropylphenyl)-1H-isoindole-1,3-dione (5HPP-33; Fig.…”