Abstract:
Carbonyl scavengers, which have been recognized for their ability to react with reactive carbonyl species, have been implicated as agents that can accelerate or induce the death of abnormal cells without having a parallel effect on normal cells. As such, they are useful therapeutic agents in cases where the acceleration or induction of cell death is desirable, such as in cells where the normal apoptotic pathways have been disrupted and where hyperproliferative cell growth occurs.

Description:
RELATED APPLICATION 
     This application is a continuation in part of application Ser. No. 60/549,805, filed Mar. 2, 2004, and incorporated by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to methods for inducing cell death, via using carbonyl scavengers, such as dicarbonyl scavengers. 
     BACKGROUND AND PRIOR ART 
     The rising incidence of skin disorders, including non-melanoma disorders, as well as melanoma skin cancer, has been well documented, as has the continued lack of effective treatments of premalignant and malignant stages of skin cancer. 
     Diegpen, et al.,  Br. J. Dermatology  146: 1–6 (2002), have documented non-melanoma skin cancer, or “NMSC,” as the most common type of cancer affecting Caucasian populations. Approximately 80% of NMSCs are basal cell carcinomas, and 20% are squamous cell carcinomas. The condition known as actinic keratosis is a precancerous condition, which may develop into squamous cell carcinoma. The rate of progression to the invasive, squamous cell carcinoma, is estimated to range to up to 20% per year. See May,  J. Am. Acad. Dermatol.  42: 8–10 (2000). 
     While melanoma represents only about 5% of all skin cancers in the U.S., it accounts for nearly 80% of skin cancer deaths. Early diagnosis leads to a high rate of cure by surgical excision; however, malignant melanoma has a very high tendency for invasion and to metastasize. Melanoma cells are highly resistant toward chemotherapy, all forms of therapeutic induction of apoptosis, as well as to any form of therapy. 
     It has recently been observed that cellular carbonyl stress, mediated by endogenous, reactive carbonyl species, or “RCS,” especially dicarbonyl compounds, including glyoxal, methylglyoxal, and malondialdelhyde, which are formed during glycolysis and lipid peroxidation, are implicated in both proliferative signaling, and metastasis of human tumor cells. See, e.g., Taguchi, et al.,  Nature  405(6784):354–60 (2000). 
     RCS—derived protein epitopes, referred to as “advanced glycation end products,” or “AGEs,” which are formed via reaction between RCS and tissue proteins, are found in abundance in melanoma, and AGEs are potent ligands of RAGE, which is a membrane receptor involved in melanoma proliferation and metastasis. See, e.g., Abe et al.,  J. Invest. Dermatol.  122(2), 461–467 (2004). 
     There is accumulating evidence to support the view that RCS which originate constitutively from increased tumor cells glycolysis, and mitochondrial lipid peroxidation, are small molecular anti-apoptotic modulators which suppress mitochondrial permeability transition pore opening, via covalent modifications. See, e.g., Speer, et al.,  J. Biol. Chem.  278(37), 34757–63. 
     Wondrak, et al.,  Biochem. Pharmacol.  7105: 1–13 (2002), have identified a series of very effective, non-toxic carbonyl scavengers, as being useful in therapeutic intervention of cellular carbonyl stress. This reference is incorporated by reference, as are U.S. Pat. No. 6,716,635, issued Apr. 6, 2004 and U.S. Pat. No. 6,417,235, issued Jul. 9, 2002. The &#39;635 patent in particular gives a detailed explanation of RCS and RAGE compounds, mechanisms of action, how they are formed, and so forth. 
     It has now been found that these carbonyl scavengers have pronounced, apoptosis inducing impact on melanoma and other cancer cells, but not normal cells. This is a feature of the invention, as is set out in the examples which follow. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  depicts a comparison of induced apoptosis using D-penicillamine on malignant melanoma cell lines, of murine (B16) and human (G-361, A-375, LOX) cell lines. In this figure, “C” refers to a control while “P” refers to treatment with D-penicillamine. 
         FIG. 2  summarizes the results of experiments on premalignant, immortalized human keratinocytes, following exposure to D-penicillamine. 
         FIG. 3  shows the induction of apoptosis in malignant, human squamous cell carcinoma line A431, following exposure to D-penicillamine, as well as to D-penicillamine methyl ester. 
         FIG. 4  presents a summary of results using D-penicillamine, N-acetyl-D-penicillamine and aminoguanidine on epithelial carcinoma cell lines. 
         FIG. 5  compares induced apoptosis in human melanoma line A375 and normal fibroblast cell line CF3. The compound used was the lipophilic derivative of D-penicillamine, 3-mercaptoleucine. 
         FIG. 6  shows that a structural requirement exists for carbonyl scavenger activity, where D-penicillamine, aminoguanidine, N-acetyl-D-penicillamine, and penicillamine disulfide were tested. 
         FIG. 7  shows the efficacy of compounds in accordance with the invention, in selectively eliminating malignant melanoma cells from a mix of normal and malignant cells. 
         FIG. 8  shows that the apoptotic mechanism involves depolarization of the mitochondrial transmembrane potential. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     EXAMPLE 1 
     This example delineates experiments which showed that 3-mercapto-D-valine (“D-penicillamine”) induced apoptosis of malignant cell lines. 
     The murine melanoma cell line B16 was used, as were three human melanoma lines, i.e., G-361, A-375, and LOX. Samples of the cells were exposed to 10 mM of D-penicillamine continuously, over a 24 hour period. Apoptosis was measured using a standard assay, i.e., flow cytometric staining using annexin V-FITC/propidium iodide. As a control, normal human skin fibroblasts, i.e., “CF3” cells, were used. 
     The results, presented in  FIG. 1 , show control runs (no compound), and test runs (with compound), on the top and bottom, respectively. It is clear from these figures that apoptosis was induced in the malignant cells, while there was no change in the normal, CF3 cells. 
     In experiments not depicted in the figures, 3-mercaptoisoleucine yielded similar results. 
     EXAMPLE 2 
     In these experiments, D-penicillamine was added, at a concentration of 12.5 mM, to premalignant, immortalized human keratinocytes, or “HaCaT” cells, and the exposure was Continuous over 24 hours. 
     In  FIG. 2 , the control (no compound) is on the left and test compound D-penicillaminie&#39;s effect is shown on the right. Again, apoptosis is indicated. 
     EXAMPLE 3 
     This set of experiments utilized both D-penicillamine, and its more lipophilic derivative, D-penicillamine methyl ester. 
     To make the derivative, 18 ml of SOCl 2  in 75 ml of MeOH which had been stored at −10° C. was stirred, and varying amounts of D-penicillamine (15 g, 100.5 mmol) were added. Stirring continued while the mixture reached room temperature. The mixture was refluxed for 60 hours, and solvent was then evaporated, leaving a crude product (15.2 g, 93.3 mmol), which was dissolved in methanol, then crystallized with addition of ether. Crystallized product was collected, and dried under a vacuum, leaving 7.6 g of pure product. Its structure was confirmed by &#39;H-NMR and mass spectrometry. The m/z calculated for C 6 H 14 O 2 NS was 164.1 [M+H] + , observed 164.1. 
     In each case, 10 mM of the test compound was used, over 24 hours, on human A431 cells, and apoptosis was measured as described, supra. 
     In  FIG. 3 , “D-P” refers to D-penicillamine, while “D-P—OCH 3 ” is the methyl ester. A stronger apoptotic effect was seen with the ester. 
     EXAMPLE 4 
     The efficacy of the compounds on other cancers, epithelial cancers in particular, was determined. Human HeLa cervical adenocarcinoma cells were used, and tested with D-penicillamine, at 10 mM, and aminoguanidine, at 25 mM. These were tested with N-acetyl-D-penicillamine, which does not function as a carbonyl scavenger. 
       FIG. 4  presents the results of these experiments with the control (“C”), D-penicillamaine (“D-P”), N-acetyl-D-Penicillamine (“NAP”) and aminoguanidine (“AG”). Both D-penicillamine and aminoguanidine, known as carbonyl scavengers, were apoptosis inducers, while NAP was not. 
     EXAMPLE 5 
     3-methyl-3-ethyl-L-cysteine (3-mercaptoisoleucine, or “MEC”) is a more lipophilic carbonyl scavenger than those tested previously. As increased lipophilicity can be desirable in topical delivery systems, it was of interest to test this compound. 
     MEC was synthesized, to 95% purity, in accordance with Leach, B. E. et al. “Synthesis of D, L-penicillamine from N-acetyl-D, L-penicillamine” in Clarke, H. T. ed.,  The Chemistry of Penicillin , (Princeton University Press, 1949), Pg. 466, and its structure was confirmed by &#39;H-NMR. 
     Malignant human melanoma cells A375, and normal fibroblasts (CF3), were tested, using 10 mM of MEC, with 24 hours of exposure. 
     Pronounced induction of apoptosis was seen in the malignant cells, but none was observed in the normal cells, as is seen in  FIG. 5 . 
     EXAMPLE 6 
     These experiments were designed to determine if there was a structure/function relationship. In other words, it was of interest to determine if activity as a carbonyl scavenger, but not as antioxidant, was important for anticancer activity. 
     The compound D-penicillamine (D-P), aminoguanidine (AG), N-acetyl-D-penicillamine (NAP), N-acetyl-L-cysteine (NAC), and penicillamine disulfide (PSS) were tested. D-P, NAC and NAP are known as antioxidants. D-P and aminoguanidine are known as carbonyl scavengers. 
     In tests on human melanoma cell line G-361, only D-P and AG induced apoptosis. These results suggest that there is a structural requirement for primary amino and thiol substituents, and that antioxidant activity does not correlate with apoptogenicity.  FIG. 6  summarizes these results. 
     EXAMPLE 7 
     The therapeutic potential of carbonyl scavengers in treating cancer was shown in these experiments. 
     A dermal melanoma reconstruct was made, where both CF3 fibroblast and A375 melanoma cells were embedded in a collagen matrix. Seventy two hours after “seeding” in the matrix, the melanoma cells have proliferated extensively, as the controls show, in  FIG. 7 . Treatment with 12.5 mM of D-P, however, eliminated the melanoma cells and maintained the structure integrity of the fibroblast collagen network. 
     EXAMPLE 8 
     These experiments show that the preferential apoptosis that the carbonyl scavenger treatment induced occurred with depolarization of mitochondrial transmembrane potential “ΔΨm.” The potentiometric dye JC-1 was used, following Reers, et al.,  Biochemistry  30 (18): 4480–6 (1991). The dye was administered 24 hours after 10 mM of D-penicillamine was added to medium. RCS pretreatment involved the use of 5 mM of phenylglyoxal, for 15 minutes, followed by washing with PBS and addition of fresh medium. 
       FIG. 8  indicates, quite clearly, that mitochondrial transmembrane potential was lost, when cells were treated with the carbonyl scavenger and that mitochondrial transmembrane potential was preserved when cells were pretreated with phenylglyoxal and then treated with the carbonyl scavenger. 
     The foregoing disclosure sets forth features of the invention, which are methods for inducing cell death via the administration to a subject of a carbonyl scavenger, in an amount and in a manner sufficient to induce death of the cells to which the scavenger is administered. 
     In practice, the carbonyl scavenger is administered to a subject for whom the enhancement of cell death is desirable. Non-cancerous, precancerous and cancerous hyperproliferative cell disorders are encompassed by the invention, as are conditions where an inappropriate and/or abnormal increase in cells are seen, examples being inflammatory hyperproliferative states, benign prostate hyperplasia, Barrett&#39;s esophagus, virally induced plantar and genital warts, actinic keratosis, nonmelanoma and melanoma skin cancer. The evidence presented supra shows that the scavengers only function as cell death inducers in abnormal cells. Hence, there is no issue as to provoking premature or inappropriate death of normal cells. 
     The carbonyl scavenger used may be any of those discussed and exemplified supra. Other carbonyl scavengers may be identified and used. U.S. Pat. No. 6,716,635, supra, incorporated by reference, teaches how to identify such compounds. 
     Modes of administration can vary. Topical administration in, e.g., the form of a lotion, créme, wash, roll-on, soap, etc., is one preferred form of administration, but intradermal, subdermal, intramuscular, intravenous, oral, sublingual, etc. The form of delivery will vary, depending upon the condition being treated. 
     Other aspects of the invention will be clear to the skilled artisan, and need not be reiterated here. 
     The terms and expression which have been employed are used as terms of description and not of limitation, and there is no intention in the use of such terms and expression of excluding any equivalents of the features shown and described or portions thereof, it being recognized that various modifications are possible with the scope of the invention.