The effects of structural analogs of putrescine on proliferation, morphology and karyotype of glioblastoma cells in culture

Abstract

In a previous study, we identified regions on the surface of tumor cells which act as acceptor sites for putrescine (Put) and studied the competition between structural analogs of Put (N,N'-tetramethyl-alpha,omega-diaminoalkanes) and Put bound to latex microspheres. A chain of four to seven carbons was necessary for inhibition of Put-latex binding to the cell surface of human glioblastoma (U251) cells. We show here that under the experimental conditions, N,N'-tetramethyl-1,4-butanediamine and N,N'-tetramethyl-1,7-heptanediamine exhibit an antitumor effect. In a first step (1-48 h after treatment), cells exposed to these compounds show large intracellular vacuoles. We failed to detect any acid phosphatase activity in these intracellular structures revealing that they were not lysosomes. Electron microscopy observations argue for the conclusion that these vacuoles are an hypertrophy of the endoplasmic reticulum (ER) and/or of the Golgi vesicles. Our hypothesis is that this typical effect of the analogs reveals that ER could be a physiological target of endogenous polyamines. At a later stage (6 days after treatment), the cells undergo morphological and biochemical changes: thin and long expansions characterize the cells and the GFA protein is overexpressed. Correlated to both these effects, karyotypic modifications are found in chromosomes 3 and 6. These changes evoke a differentiation of the treated cells. The work provides evidence that N-methylated polyamine analogs taking the place of endogenous putrescine demonstrate a hopeful antitumor effect.

Polyamine-dependent alterations in the structure of microfilaments, golgi apparatus, endoplasmic reticulum, and proteoglycan synthesis in BHK cells

“…Swelling of Golgi apparatus was previously observed using transmission electron microscopy in lymphocytes treated with DFMO or ethylglyoxal bis(guanylhydrazone) [Sakamaki et al, 1989] and was accompanied by a reduced activity of galactosyltransferase, a Golgi marker enzyme. By transmission electron microscopy, swelling of endoplasmic reticulum, transport vesicles, Golgi apparatus, or secretory vesicles was also observed in glioblastoma cells treated with putrescine analogues (N,Ntetramethyl-a,v-diaminoalkanes) [Quemener et al, 1993]. We used a ceramide and a lectin with binding sites on the medial and trans cisternae of the Golgi apparatus and observed that Golgi apparatus was enlarged and partly shifted towards the periphery of the cell.…”

“…Disturbances in the organization of cytoskeleton, notably the microfilament system, may lead to malignant cell transformation [Rao and Cohen, 1991]. There is evidence that polyamine deprivation is accompanied by structural alterations in the cytoskeleton [Balasundaram et al, 1991;Pohjanpelto et al, 1981;Pomidor et al, 1995] and Golgi apparatus [Allen, 1988;Quemener et al, 1993;Sakamaki et al, 1989]. On the other hand, remodeling of the cytoskeleton can affect the activity of ornithine decarboxylase [Pomidor et al, 1995].…”