Effects of the polyamine analogues BE-4-4-4-4, BE-3-7-3, and BE-3-3-3 on the proliferation of three prostate cancer cell lines

The Emerging Clinical Role of Spermine in Prostate Cancer

Spermine, a member of polyamines, exists in all organisms and is essential for normal cell growth and function. It is highly expressed in the prostate compared with other organs and is detectable in urine, tissue, expressed prostatic secretions, and erythrocyte. A significant reduction of spermine level was observed in prostate cancer (PCa) tissue compared with benign prostate tissue, and the level of urinary spermine was also significantly lower in men with PCa. Decreased spermine level may be used as an indicator of malignant phenotype transformation from normal to malignant tissue in prostate. Studies targeting polyamines and key rate-limiting enzymes associated with spermine metabolism as a tool for PCa therapy and chemoprevention have been conducted with various polyamine biosynthesis inhibitors and polyamine analogues. The mechanism between spermine and PCa development are possibly related to the regulation of polyamine metabolism, cancer-driving pathways, oxidative stress, anticancer immunosurveillance, and apoptosis regulation. Although the specific mechanism of spermine in PCa development is still unclear, ongoing research in spermine metabolism and its association with PCa pathophysiology opens up new opportunities in the diagnostic and therapeutic roles of spermine in PCa management.

Beneficial effects of tea and its polyphenols against prostate cancer

Tea, next to water, is the most widely consumed beverage in the world. Depending upon the level of fermentation, tea can be categorized into three types: green (unfermented), oolong (partially fermented), and black (highly to fully fermented). In general, green tea has been found to be superior to black and oolong tea in terms of antioxidant and health promoting benefits owing to the higher content of (-)-epigallocatechin-3-gallate. Tea polyphenols comprise about one-third of the weight of the dried leaf, and they exhibit biochemical and pharmacological activities including antioxidant activities, inhibition of cell proliferation, induction of apoptosis, cell cycle arrest and modulation of carcinogen metabolism. Several studies demonstrate that most tea polyphenols exert their effects by scavenging reactive oxygen species (ROS) since excessive production of ROS has been implicated in the development of a variety of ailments including cancer of the prostate gland (CaP). Using cell culture and animal model systems, molecular targets for these remarkable beneficial effects of green tea drinking on CaP prevention and therapy have been defined. Geographical and case-control studies are showing that green tea drinking could afford CaP chemopreventive effects in human population. In this review we attempt to summarize the experimental as well as the epidemiological basis for the possible role of tea and its polyphenols for chemoprevention and chemotherapy of CaP.

Analysis of polyamines as markers of (patho)physiological conditions

The aliphatic polyamines, putrescine, spermidine and spermine, are normal cell constituents that play important roles in cell proliferation and differentiation. The equilibrium between cellular uptake and release and the balanced activities of biosynthetic and catabolic enzymes of polyamines are essential for normal homeostasis in the proliferation and functions of cells and tissues. However, the intracellular polyamine content increases in hyperplastic or neoplastic growth. Although the involvement of polyamines in physiological and pathological cell proliferation and differentiation has been well established, the role they play is quite different in relation to cell systems and animal models and is dependent on inducer agents and stimuli. Also, the experimental procedures used to deplete polyamines have been shown to influence the cell responses. In this paper, the assay methods currently in use for polyamines are reviewed and compared with respect to sensitivity, reproducibility and applicability to routine analysis. The relevance of polyamine metabolism and the uptake/release process in many physiological and pathological processes is highlighted, and the cellular polyamine pathways are discussed in relation to the possible diagnostic and therapeutic significance of these mediators.

cis-Unsaturated analogues of 3,8,13,18,23-pentaazapentacosane (BE-4-4-4-4): synthesis and growth inhibitory effects on human prostate cancer cell lines

From the results of our previous physicochemical studies of polyamine-nucleic acid interactions, we concluded that polyamine analogues in cisoidal conformation are capable of wrapping around the major groove of the double helix, of displacing natural polyamines from their nucleic acid binding sites, and of inhibiting cell division. On the basis of this hypothesis, nine unsaturated pentamines, formally derived from the cytotoxic pentamine 3,8,13,18,23-pentaazapentacosane (BE-4-4-4-4), were prepared in an attempt to increase antineoplastic activity. Cis-double bonds were introduced in all possible sites in the saturated pentaazapentacosane structure of BE-4-4-4-4 to yield two pentacosenes, four pentacosadienes, two pentacosatrienes, and one pentacosatetraene. Cis-double bonds should also provide good targets for mixed-function oxidases that might eliminate the accumulation of unsaturated pentamines in serum, thereby reducing systemic toxicity in animals. We determined the ability of these new pentamines to inhibit growth in four cultured human prostate cancer cell lines (LnCap, DU145, PC-3, and DuPro) using a MTT assay. LnCap and DU145 cells were very sensitive, PC-3 cells were relatively resistant, and DuPro cells were intermediate in sensitivity to most of these synthetic pentamines. In all cell lines, pentamines that had unsaturation(s) at the end of the chain showed the highest cell growth inhibitory effects. The cellular uptake, effects on cellular polyamine levels, and cytotoxicity of these pentamines on one representative prostate cancer cell line (DuPro) were further examined with a colony-forming efficiency (CFE) assay. The pentamines with unsaturation(s) at the end of the chain were once again the most cytotoxic among both the saturated (BE-4-4-4-4) and unsaturated analogues. Appreciable amounts of all pentamines entered DuPro cells and depleted cellular polyamine pools by day 6 of treatment. For most pentamines, however, cell growth inhibitory and cytotoxic effects could not be directly correlated either with their cellular uptake or with their ability to deplete cellular polyamine pools. The position of the double bonds in the aliphatic backbone seems to be the most important determinant of cytotoxicity. For some pentamines, however, depletion of cellular polyamines may add to their efficacy.

Conformationally restricted analogues of 1N,14N-bisethylhomospermine (BE-4-4-4): synthesis and growth inhibitory effects on human prostate cancer cells

Twelve analogues of 1N,14N-bisethylhomospermine (BE-4-4-4) with restricted conformations were synthesized in the search for cancer chemotherapeutic agents with higher cytotoxic activities and lower systemic toxicities than BE-4-4-4. The central butane segment of BE-4-4-4 was replaced with a 1,2-substituted cyclopropane ring, a 1,2-substituted cyclobutane ring, and a 2-butene residue. In each case, the cis/trans-isomeric pair was synthesized. Cis-monounsaturation(s) was also introduced at the outer butane segment(s) of BE-4-4-4. The two possible cis-dienes and a cis-triene formally derived from the tetraazaeicosane skeleton of BE-4-4-4 were also prepared. Four cultured human prostate cancer cell lines (LnCap, DU145, DuPro, and PC-3) were treated with the new tetramines to examine their effects on cell growth with a MTT assay. One representative cell line (DuPro) was selected to further study the cellular uptake of the novel tetramines, their effects on intracellular polyamine pools, and their cytotoxicity. All tetramines entered the cells, reduced cellular putrescine and spermidine pools while exerting only a small effect on the spermine pool, inhibited cell growth, and killed 2-3 logs of cells after 6 days of treatment at 10 microM. Four new tetramines, the two cyclopropyl isomers, the trans-cyclobutyl isomer, and the (5Z)-tetraazaeicosene, were more cytotoxic than their saturated counterpart (BE-4-4-4). Their cytotoxicity, however, could not be correlated either with their cellular uptake or with their ability to deplete intracellular polyamine pools. We attribute their cytotoxicity to their specific molecular structures. The cytotoxicity was markedly reduced when the central butane segment was deprived of its rotational freedom by replacing it with a double bond. Introduction of a triple bond or a benzene-1,2-dimethyl residue at the central segment of the polyamine chain, led to complete loss of biological activity. The conformationally restricted alicyclic derivatives were not only more cytotoxic than was the freely rotating BE-4-4-4 by several orders of magnitude but also had much lower systemic toxicities than the latter. Thus, we obtained new tetramines with a wider therapeutic window than BE-4-4-4.

Antitumor activity of the polyamine analog N(1), N(11)-diethylnorspermine against human prostate carcinoma cells

BACKGROUND

Recent studies indicate that N-terminally bis-ethylated-polyamine analogs have significant antitumor activity in several human solid-tumor models. In this study, the in vitro and in vivo antitumor potential of the polyamine analog N(1), N(11)-diethylnorspermine (DENSpm) in human prostate carcinoma cells was examined.

METHODS

The antiproliferative and biochemical effects of DENSpm were tested in four human prostate cancer cell lines, i.e., PC-3, TSU-pr1, DU-145, and JCA-1. The in vivo antitumor potential was explored in two groups of nude mice bearing small or more developed xenografts of the DU-145 cell line. The mice were treated with 40 mg/kg DENSpm, three times per day for two cycles of 6 days, on days 1-6 and 8-13.

RESULTS

In vitro studies showed that all four tested human prostate carcinoma cell lines were sensitive to DENSpm in micromolar concentrations. In tumor-bearing mice, DENSpm clearly prevented tumor growth in both size groups, which became significant after day 17. Treatment with DENSpm evoked intracellular accumulation of the analog and various regulatory responses, e.g., downregulation of the polyamine biosynthesis, the induction of the catabolic enzyme spermidine/spermine N(1)-acetyltransferase (SSAT), and the depletion or decrease of natural polyamines. The cellular sensitivity to growth inhibition by DENSpm only correlated with the degree of ODC inhibition and SSAT induction.

CONCLUSIONS

DENSpm has sustained inhibitory effects on the growth of human prostate carcinoma cells in vitro as well in vivo. This polyamine analog may provide a new tool in the chemotherapy of prostate cancers with various phenotypes.

Antitumor effects of bis(ethyl)polyamine analogs on mammary tumor development in FVB/NTgN (MMTVneu) transgenic mice

We studied the therapeutic potential of two polyamine analogs on breast cancer using FVB/NTgN (MMTVneu), a transgenic mouse model with neu/erb-B2 oncogene overexpression. Treatment was initiated at 31 weeks of age with bis(ethyl)norspermine (BE333) and its higher homolog, BE3333 as i.p. injections once weekly. There was a 40% reduction in the average number of tumors per mouse in both treatment groups, by 10 weeks of treatment. BE3333-treated mice had 70-75% lower tumor volume than controls. Spermidine/spermine acetyl transferase activity was significantly higher in tumor tissues and kidneys of treated animals, whereas polyamine levels were lower than controls. Beneficial effects were also evident from the mortality rates in control and treatment groups. Our results suggest a potential use of selected bis(ethyl) polyamine analogs as antitumor agents in breast cancer.

A novel cytotoxic agent for human carcinoid tumors

BACKGROUND

Conventional adjuvant therapy for advanced carcinoid tumors remains disappointing; novel therapeutic agents are needed. We have shown previously that inhibiting polyamine biosynthesis with alpha-difluoromethylornithine (DFMO) slows the growth of carcinoid tumors. However, the clinical utility of DFMO has been limited by its cytostatic property. Synthetic polyamine analogs such as 1,19-bis(ethylamino)-5,10,15-triazanonadecane (BE-4-4-4-4) appear to be cytotoxic against several human tumors. The purpose of our study was to determine whether BE-4-4-4-4 is a more effective antiproliferative and cytotoxic agent than DFMO on human carcinoid (BON) cells in vitro.

METHODS

BON cells were treated with either 5 mmol/L DFMO, 0.5 to 10 mumol/L BE-4-4-4-4, or vehicle (control). Ornithine decarboxylase activity was determined by the rate of 14CO2 production, and intracellular polyamine levels were determined by chromatography. Cell number and viability were determined by Coulter counter and trypan blue exclusion, respectively.

RESULTS

BE-4-4-4-4 inhibited ornithine decarboxylase activity and depleted all 3 polyamines. BE-4-4-4-4 decreased cell numbers by 81% compared with control and 27% compared with DFMO. BE-4-4-4-4 also induced a 2-fold increase in cell death compared with control or DFMO.

CONCLUSIONS

BE-4-4-4-4 is cytotoxic and more effective than DFMO in inhibiting growth of BON cells. Polyamine analogs such as BE-4-4-4-4 may be effective adjuvant therapeutic agents for advanced carcinoid tumors.