A missense mutation, p.V132G, in the X-linked spermine synthase gene (SMS) causes Snyder-Robinson syndrome.

Snyder-Robinson syndrome (SRS, OMIM 309583) is a rare X-linked syndrome characterized by mental retardation, marfanoid habitus, skeletal defects, osteoporosis, and facial asymmetry. Linkage analysis localized the related gene to Xp21.3-p22.12, and a G-to-A transition at point +5 of intron 4 of the spermine synthase gene, which caused truncation of the SMS protein and loss of enzyme activity, was identified in the original family. Here we describe another family with Snyder-Robinson syndrome in two Mexican brothers and a novel mutation (c.496T>G) in the exon 5 of the SMS gene confirming its involvement in this rare X-linked mental retardation syndrome.

New SMS mutation leads to a striking reduction in spermine synthase protein function and a severe form of Snyder-Robinson X-linked recessive mental retardation syndrome.

We report the identification of a novel mutation at a highly conserved residue within the N-terminal region of spermine synthase (SMS) in a second family with Snyder-Robinson X-linked mental retardation syndrome (OMIM 309583). This missense mutation, p.G56S, greatly reduces SMS activity and leads to severe epilepsy and cognitive impairment. Our findings contribute to a better delineation and expansion of the clinical spectrum of Snyder-Robinson syndrome, support the important role of the N-terminus in the function of the SMS protein, and provide further evidence for the importance of SMS activity in the development of intellectual processing and other aspects of human development.

Altered spermidine/spermine N1-acetyltransferase activity as a mechanism of cellular resistance to bis(ethyl)polyamine analogues.

To develop a model system to investigate mechanisms of antiproliferative action of bis(ethyl)polyamine analogues, intermittent analogue treatments followed by recovery periods in drug-free medium were used to select an N(1), N(12)-bis(ethyl)spermine-resistant derivative of the Chinese hamster ovary cell line C55.7. The resulting C55.7Res line was at least 10-fold resistant to N(1),N(12)-bis(ethyl)spermine and N(1), N(11)-bis(ethyl)norspermine. The stability of the resistance in the absence of selection pressure was >/=9 months, indicating that a heritable genotypic change was responsible for the resistance phenotype. Polyamine transport alterations and multi-drug resistance were eliminated as causes of the resistance. Spermidine/spermine N(1)-acetyltransferase (SSAT) activity and regulation were altered in C55.7Res cells as basal activity was decreased, and no activity induction resulted from exposure to analogue concentrations, which caused 300-fold enzyme induction in parental cells. SSAT mRNA levels in the absence and presence of analogue were unchanged, but no SSAT protein was detected in C55.7Res cells. A point mutation, which results in the change leucine156 (a fully conserved residue) to phenylalanine, was identified in the C55.7Res SSAT cDNA. Expression of wtSSAT activity in C55.7Res cells restored sensitivity to bis(ethyl)polyamines. These results provided definitive evidence that SSAT activity is a critical target of the cytotoxic action of these analogues.

Effects of the polyamine analogues N1-ethyl-N11-((cyclopropyl)methyl)-4,8-diazaundecane and N1-ethylN-11-((cycloheptyl)methyl)-4,8-diazaundecane in human prostate cancer cells.

The high levels of polyamines maintained in the prostate suggest that these compounds are important to prostate cell function and that disruption of polyamine metabolism may be an effective way to stop the growth of prostate cancer cells. The unsymmetrically alkylated polyamine analogues N1-ethyl-N11-((cyclopropyl)methyl)-4,8-diazaunde-cane (CPENSpm) and N1-ethyl-N11-((cycloheptyl)methyl)-4,8-diazaundecane (CHENSpm) have been shown previously to have cytotoxic effects in breast and non-small cell lung cancer cells. We have now investigated the responses of three human prostate cancer cell lines, LNCaP, PC3, and Du145, to these polyamine analogues and to the symmetrically alkylated analogue N1,N11-bis(ethyl)norspermine (BE 3-3-3). The Du145 cell line, in which IC50 values ranged from 0.65 to 0.8 microM, was the most sensitive to each of the polyamine analogues, although significant growth inhibition resulted in the other cell lines as well. CPENSpm and BE 3-3-3 but not CHENSpm caused significant decreases in the intracellular spermine and spermidine pools, although all three analogues accumulated to high levels in each of the cell lines. Spermidine/spermine N1-acetyltransferase activity was induced 23-250-fold in response to CPENSpm and BE 3-3-3, but it was not affected by CHENSpm. None of the analogues had significant effects on the activities of ornithine decarboxylase or S-adenosylmethionine decarboxylase. Quantitation of DNA fragmentation indicative of programmed cell death (PCD) showed that both CPENSpm and CHENSpm were effective inducers of PCD in all three prostate cell lines. In contrast, BE 3-3-3 led to PCD only in LNCaP cells. The ability to induce PCD was the only parameter measured that correlated with cell line sensitivity to these polyamine analogues.

Properties and regulation of human spermidine/spermine N1-acetyltransferase stably expressed in Chinese hamster ovary cells.

Spermidine/spermine N1-acetyltransferase (SSAT) appears to be the rate-limiting enzyme of polyamine catabolism, yet studies of its regulation have been limited by the low amounts of SSAT in uninduced cells. A system for studying SSAT was established by stably transfecting Chinese hamster ovary cells with a construct where SSAT cDNA was under control of the cytomegalovirus promoter. Thirteen of 44 clones expressed significantly increased SSAT activity (650-1900 compared with 24 pmol/min/mg protein in control cells). SSAT activity was directly proportional to SSAT protein, which turned over very rapidly (t(1)/(2) of 29 min) and was degraded through the ubiquitin/proteasomal pathway. The increased SSAT activity caused perturbations in polyamine homeostasis and led to a reduction in the rate of growth under clonal conditions. N1,N12-bis(ethyl)spermine greatly increased SSAT activity in controls and SSAT transfected clones (to about 10 and 60 nmol/min/mg protein, respectively). N1, N12-Bis(ethyl)spermine caused an increase in the SSAT half-life and a slight increase in SSAT mRNA, but these changes were insufficient to account for the increase in SSAT protein suggesting that translational regulation of SSAT must also occur.

Clinical aspects of cell death in breast cancer: the polyamine pathway as a new target for treatment.

Because intracellular polyamines have a critical role in cell proliferation and death pathways, the polyamine metabolic pathway represents a potential target for intervention in cancers. A number of polyamine analogues have been identified that downregulate polyamine synthesis and enhance polyamine catabolism, thereby depleting intracellular polyamines. Treatment of human breast cancer cell lines in culture with these analogues has been shown to decrease cell proliferation and induce programmed cell death. Phase I studies with one analogue are now complete, setting the stage for phase II trials to determine efficacy, in addition to preclinical studies to examine combinations of polyamine analogues and conventional cytotoxics.

Paclitaxel induces programmed cell death in MDA-MB-468 human breast cancer cells.

The ability of paclitaxel, one of the most active chemotherapeutic agents against breast cancer, to induce programmed cell death in hormone-independent MDA-MB-468 human breast cancer cells was assessed. Treatment of MDA-MB-468 cells led to growth inhibition, high-molecular-weight and oligonucleosomal DNA fragmentation, and apoptosis-associated morphological changes after either 3- or 24-h exposure to paclitaxel concentrations >/=10 nM. Additionally, cleavage products of poly(ADP-ribose) polymerase and lamin B1, two proteins that are cleaved early in the execution phase of programmed cell death, were detected. Quantitative studies indicated that exposure to paclitaxel for 24 h resulted in more DNA fragmentation than did 3-h exposure. Rapid induction of the early-response gene c-jun but not c-myc was associated with paclitaxel treatment. The ability of paclitaxel to induce high-molecular-weight DNA fragmentation and apoptosis-associated morphological changes in three other breast cancer cell lines was also established. These data suggest that paclitaxel, an agent known to stabilize microtubules and prevent cell division but not to act directly on DNA, induces programmed cell death in breast cancer cells.

Polyamine analogue induction of programmed cell death in human lung tumor cells.

The naturally occurring polyamines putrescine, spermidine, and spermine are required for cell growth. Based on this requirement, several polyamine analogues that interfere with polyamine function and metabolism have been synthesized as antineoplastic agents. The symmetrically substituted N1,N12-bis(ethyl)spermine (BESpm), and unsymmetrically substituted N1-ethyl-N11-[(cyclopropyl)methyl]-4, 8-diazaundecane (CPENSpm) have previously been shown to cause rapid cytotoxicity of NCI H157 cells, with concurrent high induction of the polyamine catabolic enzyme spermidine/spermine N1-acetyltransferase. However, the precise mechanism(s) of the cytotoxic action of the compounds is not known. We now demonstrate that treatment with either BESpm or CPENSpm results in morphological and biochemical changes consistent with the activation of programmed cell death pathways, and that the unsymmetrically substituted CPENSpm more rapidly activates the death program. These studies suggest that the cell type-specific cytotoxicity of these polyamine analogues may be a result of their ability to selectively activate the cell death pathway in sensitive phenotypes and indicate that the relationship between the structure of the polyamine analogues and the ability to induce programmed cell death should be investigated.

Programmed cell death in human breast cancer cells.

The need for improved systemic therapy for breast cancer is great. Cancer growth represents an imbalance between cell proliferation and cell death: thus, effective anti-cancer therapies may act to decrease cell proliferation or increase cell death, or both. This chapter delineates the role of the programmed cell death process in maintaining homeostasis in normal mammary tissues. The preservation of such death pathways in malignant mammary cells and the ability of chemotherapeutic agents to initiate the programmed cell death process in these cells is reviewed. Finally, ongoing research exploring new ways to take advantage of these death pathways in the clinical setting is examined.

Induction of programmed cell death in human breast cancer cells by an unsymmetrically alkylated polyamine analogue.

The need for antineoplastic compounds with novel mechanisms of action is great. One such agent is the recently synthesized polyamine analogue N1-ethyl-N11-((cyclopropyl)methyl)-4,8-diazaundecane (CPENSpm). Exposure of hormone-dependent and -independent human breast cancer cells to 0.1-10 microM CPENSpm led to both growth inhibition and induction of programmed cell death. Fragmentation of DNA to high molecular weight fragments and oligonucleosomal-sized fragments, both characteristic of programmed cell death, was determined to be time and concentration dependent. Depletion of natural polyamine pools and accumulation of the analogue was also demonstrated. These data provide the first evidence that a polyamine analogue induces programmed cell death.

Cross-resistance studies of folylpolyglutamate synthetase-deficient, methotrexate-resistant CCRF-CEM human leukemia sublines.

CCRF-CEM human leukemia sublines resistant to short-term methotrexate (MTX) exposure as a result of decreased folylpolyglutamate synthetase (FPGS) activity were examined for their response to other cytotoxic agents. The R3/7 and R30dm sublines display 25 and 1%, respectively, of the FPGS activity of CCRF-CEM cells as measured with MTX in vitro. Response to agents in outgrowth experiments was examined under both continuous exposure (120 h, where MTX resistance is not observed) and short-term (6-14.5 h) exposure. During continuous exposure to various classes of agents, cross-resistance of R3/7 and R30dm that correlated with FPGS level was not observed, although some minor (< or = 3-fold) stochastic variations in sensitivity were noted. These agents included actinomycin D, Adriamycin, etoposide, vincristine, cisplatin, cytosine arabinoside, 5-fluorouracil, and some other antifolates. Cross-resistance during continuous exposure that did correlate with FPGS level was noted, however, to glutamate-containing thymidylate synthase inhibitors (including ICI D1694) and, to a minor extent, to 6-mercaptopurine and 5-fluorodeoxyuridine. Slight collateral sensitivity during continuous exposure that apparently correlated with FPGS level was noted to the lipid-soluble antifolate trimetrexate and to 5,8-dideazapteroyl-L-ornithine, an FPGS-specific inhibitor. In short-term exposures (where MTX resistance of the sublines is observed), the resistant sublines displayed sensitivity or cross-resistance to each agent that was qualitatively similar to that observed for the same agent in continuous exposure. Because of the requirement for reduced folates in the anti-DNA mechanism of action of fluoropyrimidines and the current clinical use of leucovorin (LV) to enhance their effects, the interaction of LV and fluoropyrimidines was examined. The results suggest that even highly FPGS-deficient cells are as sensitive to the effects of LV modulation as are wild-type cells even at fluoropyrimidine exposure times as short as 4 h.

Decreased folylpolyglutamate synthetase activity as a mechanism of methotrexate resistance in CCRF-CEM human leukemia sublines.

Determinants of methotrexate (MTX) resistance in cell lines resistant to short, but not continuous, MTX exposure were investigated since such lines may have relevance to clinical resistance. CCRF-CEM R30dm (R30dm), cloned from CCRF-CEM R30/6 (a MTX-resistant subline of the CCRF-CEM human leukemia cell line), had growth characteristics similar to CCRF-CEM. R30dm was resistant to a 24-h exposure to levels as high as 300 microM MTX but was as sensitive as CCRF-CEM to continuous MTX exposure. MTX resistance of R30dm was stable for greater than 68 weeks in the absence of selective pressure. Initial velocities of MTX transport were comparable for R30dm and CCRF-CEM, as were dihydrofolate reductase specific activity and MTX binding. A 2-fold thymidylate synthase activity decrease for R30dm from that of CCRF-CEM was not a significant factor in R30dm MTX resistance. Decreased MTX poly(gamma-glutamate) synthesis resulted in lower levels of drug accumulation by R30dm. Decreased polyglutamylation was attributable to folylpolyglutamate synthetase (FPGS) activity in R30dm extracts which was 1, 2, and less than or equal to 10% of CCRF-CEM extracts with the substrates MTX, aminopterin, and naturally occurring folates, respectively. Comparison of cell lines with varying levels of resistance to short term MTX exposure indicated that the extent of MTX resistance was proportional to the reduction of FPGS activity. The evidence supported decreased FPGS activity as the mechanism of resistance to short MTX exposure in the cell lines investigated.

13C-NMR analysis of alanine metabolism by isolated perfused livers from C3HeB/FeJ mice infected with African trypanosomes.

1. Isolated perfused livers from mice infected with Trypanosoma brucei rhodesiense formed substantially more [3-13C]-lactate from [3-13C]-alanine than livers from uninfected mice. Quantities formed by infected livers increased as infection progressed. 2. Infected livers produced more 13C-labeled glutamate and glutamine, with label scrambled between C-2 and C-3. Scrambling also produced [2,3-13C]-aspartate, [2-13C]-alanine and [2-13C]-lactate. Delayed appearance of label in C-4 of glutamate/glutamine in infected livers reflects significant endogenous stores of unlabeled acetyl CoA. 3. Although differences do exist in catabolism of [3-13C]-alanine by perfused livers from infected and control mice, trypanosomiasis does not cause permanent breakdown or blockage of hepatic alanine metabolism.

Childhood serous otitis media: fifteen months' observations of children untreated compared with those receiving an antihistamine-adrenergic combination.

Of 55 patients who had received, in a previously reported double-blind study, either an antihistamine-adrenergic combination or a placebo for three months for serous otitis media, 48 were followed without drug therapy for an additional year. During the follow-up period no differences were detected between the patients who had initially been treated with drugs and those who had received the placebo, as detected by audiometry, tympanometry, parental concern about hearing loss (as detected by the parents themselves or by their children's teachers or primary health care providers), school performance, or recurrences of serous otitis media.

Diagnostic and therapeutic studies in childhood serous otitis media. Results of treatment with an antihistamine-adrenergic combination.

Fifty-five children with their first recognized episodes of serous otitis media were followed over a three-month period. The efficacy of an antihistamine-adrenergic combination (diphenhydramine and pseudoephedrine), the comparative value of various diagnostic studies of middle ear function, and the prognostic importance of information obtained at the first visit were assessed. Compared double-blindly to a placebo, the pharmaceutical preparations did not appear to influence the clinical course, although more drug patients experienced lethargy or relief of symptoms not directly concerned with middle ear function (mainly upper respiratory congestion). The color and extent of motility of the tympanic membrane, but no other pneumatic otoscopic findings, were related to audiometry, whereas tympanometry correlated with the amount of motility and the presence or absence of visible fluid behind the membrane. The patients with the most severe hearing losses or with visible middle ear fluid at their initial visits improved the most, and those who began to be followed in the summer the least. The last finding may be due to a general but unexplained deterioration of childhood serous otitis media during the fall.