Hannu Elo

Antitumor activity and metal complexes of the first transition series. Trans-bis(salicylaldoximato)copper(II) and related copper(II) complexes, a novel group of potential antitumor agents

Abstract The antitumor activity of forty nine different metal complexes of the first transition series against mouse leukemia L 1210 cells and of two of the complexes against Ehrlich ascites carcinoma have been tested in vitro by the method described in this paper. Eight complexes showed a 50% inhibition of tumor cell division at concentration level 5–6 μg/ml of the complex for the former and two most effective complexes also for the latter. The trans-bis-(salicylaldoximato)copper(II) and trans-bis(resorcylaldoximato)copper(II) complexes were found to possess the highest antitumor activity.

S-adenosylmethionine decarboxylase as target of chemotherapy

Although ornithine decarboxylase under most conditions is the rate-controlling enzyme of polyamine biosynthesis and thus the most logical target for chemical intervention, the inhibition of the enzyme triggers a series of compensatory reactions all aimed to circumvent the inhibition. These include secondary induction of adenosylmethionine decarboxylase, enhanced accumulation of extracellular polyamines and an overproduction of ornithine decarboxylase resulting from enhanced expression and gene amplification. Thus chemotherapy based on an intervention of polyamine formation has also to be directed to reactions other than the decarboxylation of ornithine. Adenosylmethionine decarboxylase is the second natural target for chemotherapy. Virtually all effective inhibitors of this enzyme are members of the family of bis(guanylhydrazones). Small modifications, such as increased hydrophobicity at the glyoxal portion of the parent compound glyoxal bis(guanylhydrazone), greatly enhance the inhibition of adenosylmethionine decarboxylase and diminish the undesirable inhibition of diamine oxidase. However, although ethylglyoxal and propylglyoxal bis(guanylhydrazone) appear to utilize the putative polyamine carrier for their cellular entry, their cellular accumulation, in contrast to that of glyoxal and methylglyoxal bis(guanylhydrazone), is not stimulated by putrescine and spermidine deprivation produced by inhibitors of ornithine decarboxylase. It is obvious that the cellular accumulation of each of the bis(guanylhydrazones) is determined by their different efflux rates: GBG and MGBG are effectively retained whereas EGBG is rapidly excreted by the tumor cells. GBG and MGBG, but possibly not EGBG, behave as mitochondrial poisons and rapidly produce extensive morphological damage of the mitochondria. The bis(guanylhydrazones) likewise inhibit carnitine-dependent mitochondrial oxidation of long-chain fatty acids, competitively in respect to carnitine. It is possible that this inhibition has something to do with the mitochondrial damage, as carnitine protects tumor cells from the early mitochondrial damage produced by MGBG. Carnitine also protects experimental animals from MGBG-induced acute toxicity and death.

trans-bis(salicylaldoximato)copper(II) and its derivatives as antiproliferative and antineoplastic agents: a review

Abstract The antineoplastic, antiproliferative and other biological properties of the copper(II) chelates of salicylaldoxime and related ligands are reviewed. Original results are reported on the toxicity and some other properties of the compounds, and possible mechanisms of action are discussed.

Diethylglyoxal bis(guanylhydrazone): a novel highly potent inhibitor of S-adenosylmethionine decarboxylase with promising properties for potential chemotherapeutic use.

Diethylglyoxal bis(guanylhydrazone) (DEGBG), a novel analog of the antileukemic agent methylglyoxal bis(guanylhydrazone) (MGBG) was synthesized. It was found to be the most powerful inhibitor of yeast S-adenosylmethionine decarboxylase (AdoMetDC) so far studied (Ki approx. 9 nM). This property, together with the finding that the compound is a weaker inhibitor of intestinal diamine oxidase than are MGBG and its glyoxal, ethylglyoxal and ethylmethylglyoxal analogs, makes the compound a promising candidate as a polyamine antimetabolite for chemotherapy studies. DEGBG was also found to potentiate the antiproliferative effect of the ornithine decarboxylase inhibitor alpha-difluoromethyl ornithine against mouse L1210 leukemia cells in vitro. DEGBG increased several-fold the intracellular putrescine concentration of cultured L1210 cells, just as MGBG and its ethylglyoxal analog are known to do. The results strongly suggest that DEGBG is worth further studies. Combined with previous studies, they also made possible the construction of some empirical rules concerning the structure-activity relationships of bis(guanylhydrazone) type inhibitors of AdoMetDC. The identity of DEGBG was confirmed by a single-crystal X-ray analysis and by 1H- and 13C-NMR spectroscopy. It consisted of the same isomer as MGBG and several of its analogs are known to consist of.

Proton Nuclear Magnetic Resonance Spectroscopy of Bis (Amidinohydrazones) (Bis(Guanylhydrazones)), and Its Use for Studies on the Isomerism and Tautomerism of the Compounds

Abstract The proton NMR spectra of the antileukemic agent glyoxal bis(amidinohydrazone) and of nine alkyl- and dialkylglyoxal analogs thereof, many of which are novel compounds, are reported. Measurements were carried out using both the free bases (in D2O and dimethyl sulfoxide-d6) and their divalent salts (in D2O). Dioxan was a suitable internal standard, while DSS caused extensive precipitation. Most spectra were first-order or nearly so, and the resonances of the various protons could be rigorously

Biochemical Properties and Crystal Structure of Ethylmethylglyoxal Bis(guanylhydrazone) Sulfate — an Extremely Powerful Novel Inhibitor of Adenosylmethionine Decarboxylase

Ethylmethylglyoxal bis(guanylhydrazone) (EMGBG) sulfate, an analog of the well-known antileukemic drug methylglyoxal bis(guanylhydrazone), was synthesized. It was shown to be an extremely powerful competitive inhibitor of eukaryotic S-adenosyimethionine decarboxylase, with an apparent Ki value 12 nᴍ. Thus, it appears to be the most powerful known inhibitor of the enzyme, being almost an order of magnitude more powerful than the corresponding ethylglyoxal derivative. It neither inhibited the proliferation of mouse L1210 leukemia cells in vitro, nor did it potentiate the growth inhibition produced by α-difluoromethyl ornithine. In this respect, its properties are closely related to those of dimethylglyoxal, ethylglyoxal and propylglyoxal bis(guanylhydrazones), while in striking contrast to those of the antiproliferative glyoxal and methylglyoxal analogs. EMGBG also inhibited intestinal diamine oxidase activity (Ki 0.7 μᴍ). EMGBG sulfate was crystallized from water, giving orthorhombic crystals (space group Pbcn). Their crystal and molecular structure was determined by X-ray diffraction methods. The carbon-nitrogen double bonds between the ethylmethylglyoxal part and the aminoguanidine moieties were found to have the same configuration as they are known to have in the salts of glyoxal. methylglyoxal and propylglyoxal bis(guanylhydrazones). The glyoxal bis(guanylhydrazone) chain of the EMGBG cation deviated strongly from planarity, thus differing dramatically from the corresponding chains of the glyoxal, methylglyoxal and propylglyoxal analogs.

Yawning and thermoregulation

Dear Editors, The paper “Excessive yawning and thermoregulation: two case histories of chronic, debilitating bouts of yawning” by Gallup andGallup [1] deals with an interesting and potentially important topic. Yet, there are problems concerning it. The patients never met the investigators, only providing subjective reports. On the basis of the two cases of pathological yawning that may be etiologically unrelated, conclusions are drawn concerning yawning in general. The medical histories contain contradictions, and no details are given concerning blood tests and MRI investigations. Both patients are reported to suffer from excessive yawning in the absence of sleep problems. Yet, both had received sleep-related diagnoses (patient 1 received diagnoses of narcolepsy and excessive daytime sleepiness—and the same diagnoses were ruled out, and patient 2 was diagnosed with sleep apnoea). A high fasting insulin level (patient 1) does not confirm insulin resistance and could result from insulinoma that causes life-threatening hypoglycaemias and would explain the symptoms (inability to walk, feeling ill, and extreme discomfort) and diagnoses (seizure, migraine, and excessive daytime sleepiness) [2–4]. It is not revealed which drug(s) worsened the problem. Metformin worsens hypoglycaemias [5]. The alpha-1-antitrypsin deficiency of patient 2 is important (often related to emphysema/COPD) [6], but this goes unnoticed, and the focus is solely on the putative thermoregulatory role of her yawning. No attention is paid to her obesity and its consequences. It is not always possible to exclude multiple sclerosis at an early stage. Both patients should be encouraged to seek medical assistance. It is not sufficient that they have been “notified of the possible connection to temperature regulation”. The only measurements were performed by one patient under uncontrolled conditions and using uncontrolled methodology (no details given). Oral temperatures do not necessarily reflect core or brain temperature. What exactly is meant by saying “at the beginning and after a number of attacks” is not told, or how attacks were chosen for measurement. Subjectivity may have played a marked role, especially as the patient “can anticipate” the episodes. How she anticipates them is not reported. No conclusions should be based on these sporadic measurements. A 0.4°C decrease of body temperature of a 96.5-kg patient requires the loss of 137 kJ of heat (specific heat capacity of the body 3.56 kJ kgK [7]). During a 5-min bout, the body would thus act as a 460-W heater capable of heating 430 ml of water from 25°C to the boiling point in 5 min (specific heat capacity of water 4.19 kJ kgK [7, 8]). With 15 daily bouts, the extra loss of heat is over 2,000 kJ, and if not compensated for by increased heat production, severe hypothermia will result (6°C decrease daily). If compensated (without extra eating), the increased metabolism will lead to a loss of more than 2 kg of body fat in a month. The obesity of the patient is not in accord with this. Compensation by drinking hot liquids (50°C) would require a daily consumption of ca. 38 l. There are few mechanisms by which the body can lose heat so that its temperature decreases:

Structure of aminoguanidine hemioxalate. Implications for the synthesis of amidinohydrazones

SummaryThe crystal and molecular structure of aminoguanidine hemioxalate, a salt in which aminoguanidine exists in the monocation form, was determined by single crystal X-ray diffraction. The salt crystallizes in the monoclinic space group P2(1)/n with unit cell dimensions ofa=4.95,b=10.46,c=10.40 Å, β=92.57°, andZ=4. The structure contains one oxalate ion for every two CN4H7+ ions, the latter being practically planar. The structure of the monocation is largely similar to those of aminoguanidine dications except that the monocation is devoid of one of the protons attached to the terminal hydrazine nitrogen. This result is of interest considering the synthesis of amidinohydrazones, indicating that the concentration of the active nucleophile is nearly maximal even when aminoguanidine exists in the monocation form. Therefore, the synthesis of amidinohydrazones should be performed in thepH range in which aminoguanidine exists mainly in the monocation form,i.e. at apH higher than 2. There is, however, no need to elevate thepH to values at which a considerable proportion of aminoguanidine exists as the free base.ZusammenfassungDie Kristallstruktur von Aminoguanidinhemioxalat, einem Salz, in dem Aminoguanidin als Monokation existiert, wurde mit Einkristallröntgenmethoden aufgeklärt. Das Salz kristallisiert in der monoklinen Raumgruppe P2(1)/n mit den Zellparameterna=4.95,b=10.46,c=10.40 Å, β=92.57° undZ=4. In der Einheitszelle kommt ein Oxalation auf je zwei flache CN4H7+-Ionen. Die Struktur des Monokations ist bekannten Strukturen des Aminoguanidindikations ähnlich, mit der Ausnahme, daß dem Monokation eines der an das äußere Stickstoffatom der Hydrazingruppe gebundenen drei Protonen fehlt. Dieses Ergebnis ist interessant bezüglich der Synthese von Amidinohydrazonen, da es bedeutet, daß die Konzentration des aktiven Nukleophils auch dann beinahe maximal ist, wenn Aminoguanidin in der Monokationform vorliegt. Synthesen von Amidinohydrazonen sollten daher unter solchen Bedingungen ausgeführt werden, unter denen Aminoguanidin hauptsächlich in der Monokationform existiert (pH höher als 2). Es ist jedoch nicht nötig, beipH-Werten zu arbeiten, die so hoch sind, daß ein bedeutender Teil der Verbindung als freie Base vorliegt.

Carbon-13 NMR Spectroscopy of the Antileukemic Drug MGBG and Related Bis(Amidinohydrazones) [‘Bis(Guanylhydrazones)’]

Abstract The first survey of the carbon-13 NMR spectroscopy of the bis(amidinohydrazones) [‘bis(guanylhydrazones)’] of various glyoxals is reported. The compounds studied included the free base and the dihydrochloride of the investigational antileukemic drug methylglyoxal bis(amidinohydrazone) (MGBG) and the dihydrochloride of the parent compound glyoxal bis(amidinohydrazone), as well as the free bases of seven alkyl- and dialkylglyoxal analogs of these compounds. Spectra were assigned with the aid of off-resonance proton noise decoupled carbon-13 measurements. The results obtained strongly suggest that each of the compounds studied consisted of one of the three or four possible geometrical isomers only, or that (less probably) the isomerization of the compounds is rapid on the NMR time scale. Thus, the results are in line with previous proton NMR and X-ray crystallographic observations, and support the theory that the classical syntheses of the compounds tend to yield

Biochemical characterization of propylglyoxal bis(guanylhydrazone). Facile synthesis of monoalkylglyoxal bis(guanylhydrazones).

Abstract Propylglyoxal Bis(guanylhydrazone). Ethylglyoxal Bis(guanylhydrazone), Adenosylmethionine Decarboxylase Inhibition. Tumor Cells, Cellular Uptake Propylglyoxal bis(guanylhydrazone) sulfate, a novel analog of the well-known antileukemic drug methylglyoxal bis(guanylhydrazone), has been prepared from 2,2-dibromopentanal, and the compound has been characterized biochemically. Although it is a powerful inhibitor of S-adenosylmethionine decarboxylase, its Ki, value (0.2 μᴍ) is considerably higher than that of ethylglyoxal bis(guanylhydrazone) (0.06 μᴍ). The compound is only poorly taken up by tumor cells, and its accumulation is not stimulated by a prior exposure of the tumor cells to di-fluoromethylornithine, a compound that causes polyamine depletion. Thus, the uptake charac teristics of the compound are similar to those of ethylglyoxal bis(guanylhydrazone), but in striking contrast to those of methylglyoxal and glyoxal bis(guanylhydrazones). Since the configuration of the double bonds in glyoxal, methylglyoxal and propylglyoxal bis(guanylhydrazones) has been shown to be identical, the different uptake characteristics are probably only due to differences in side chain size and/or hydrophobicity.