Autophagy is originally named as a process of protein recycling. It begins with sequestering cytoplasmic organelles in a membrane vacuole called autophagosome. Autophagosomes then fuse with lysosomes, where the materials inside are degraded and recycled. To date, however, little is known about the role of autophagy in cancer therapy. In this study, we present that temozolomide (TMZ), a new alkylating agent, inhibited the viability of malignant glioma cells in a dose-dependent manner and induced G2/M arrest. At a clinically achievable dose (100 microM), TMZ induced autophagy, but not apoptosis in malignant glioma cells. After the treatment with TMZ, microtubule-associated protein light-chain 3 (LC3), a mammalian homologue of Apg8p/Aut7p essential for amino-acid starvation-induced autophagy in yeast, was recruited on autophagosome membranes. When autophagy was prevented at an early stage by 3-methyladenine, a phosphatidylinositol 3-phosphate kinase inhibitor, not only the characteristic pattern of LC3 localization, but also the antitumor effect of TMZ was suppressed. On the other hand, bafilomycin A1, a specific inhibitor of vacuolar type H(+)-ATPase, that prevents autophagy at a late stage by inhibiting fusion between autophagosomes and lysosomes, sensitized tumor cells to TMZ by inducing apoptosis through activation of caspase-3 with mitochondrial and lysosomal membrane permeabilization, while LC3 localization pattern stayed the same. These results indicate that TMZ induces autophagy in malignant glioma cells. Application of an autophagy inhibitor that works after the association of LC3 with autophagosome membrane, such as bafilomycin A1, is expected to enhance the cytotoxicity of TMZ for malignant gliomas.

/pdf/role-of-autophagy-in-temozolomide-induced-cytotoxicity-for-2pey4bbe5w.pdf

Role of autophagy in temozolomide-induced cytotoxicity for malignant glioma cells

Temozolomide: a review of its discovery, chemical properties, pre-clinical development and clinical trials

Malignant gliomas (glioblastoma multiforme and anaplastic astrocytoma) occur more frequently than other types of primary central nervous system tumors, having a combined incidence of 5-8/100,000 population. Even with aggressive treatment using surgery, radiation, and chemotherapy, median reported survival is less than 1 year. Temozolomide, a new drug, has shown promise in treating malignant gliomas and other difficult-to-treat tumors. Temozolomide, a p.o. imidazotetrazine second-generation alkylating agent, is the leading compound in a new class of chemotherapeutic agents that enter the cerebrospinal fluid and do not require hepatic metabolism for activation. In vitro, temozolomide has demonstrated schedule-dependent antitumor activity against highly resistant malignancies, including high-grade glioma. In clinical studies, temozolomide consistently demonstrates reproducible linear pharmacokinetics with approximately 100% p.o. bioavailability, noncumulative minimal myelosuppression that is rapidly reversible, and activity against a variety of solid tumors in both children and adults. Preclinical studies have evaluated the combination of temozolomide with other alkylating agents and inhibitors of the DNA repair protein O6-alkylguanine alkyltransferase to overcome resistance to chemotherapy in malignant glioma and malignant metastatic melanoma. Temozolomide has recently been approved in the United States for the treatment of adult patients with refractory anaplastic astrocytoma and, in the European Union, for treatment of glioblastoma multiforme showing progression or recurrence after standard therapy. Predictable bioavailability and minimal toxicity make temozolomide a candidate for a wide range of clinical testing to evaluate the potential of combination treatments in different tumor types. An overview of the mechanism of action of temozolomide and a summary of results from clinical trials in malignant glioma are presented here.

https://clincancerres.aacrjournals.org/content/clincanres/6/7/2585.full.pdf

Temozolomide and treatment of malignant glioma.

This invention describes novel pyrazole compounds of formula (IV) wherein Ring D is a 5-7 membered monocyclic ring or 8-10 membered bicyclic ring selected from aryl, heteroaryl, heterocyclyl or carbocyclyl; R?x and Ry? are independently selected from T-R3, or taken together with their intervening atoms to form a fused, unsaturated or partially unsaturated, 5-8 membered ring having 1-3 ring heteroatoms selected from oxygen, sulfur, or nitrogen; and R2, R2', and T, and R3 are as described in the specification. The compounds are useful as protein kinase inhibitors, especially as inhibitors of aurora-2 and GSK-3, for treating diseases such as cancer, diabetes and Alzehimer's disease.

Pyrazole compounds useful as protein kinase inhititors

Temozolomide (TMZ) is the first new chemotherapy agent to be approved for the treatment of high-grade malignant gliomas in more than 20 years This novel oral alkylating agent has demonstrated promising activity not only in brain tumors, but in a variety of solid tumors, including malignant melanoma TMZ is 100% bioavailable when taken orally and, because of its small size and lipophilic properties, it is able to cross the blood-brain barrier Concentrations in the central nervous system are approximately 30% of plasma concentrations Once it has entered the central nervous system, TMZ can be spontaneously converted to the active metabolite These pharmacologic properties make it an ideal agent for treating central nervous system malignancies In patients with advanced metastatic melanoma, brain metastases are a major cause of treatment failure In this setting, TMZ has been shown to be as effective as dacarbazine, with a similar safety profile More importantly, there is evidence to suggest that TMZ-treated patients have a lower incidence of central nervous system relapse compared with dacarbazinetreated patients Therefore, TMZ is actively being investigated for the treatment and prevention of brain metastases in melanoma patients TMZ may become an important part of treatment regimens for advanced metastatic melanoma The Oncologist 2000;5:144-151

Temozolomide, a novel alkylating agent with activity in the central nervous system, may improve the treatment of advanced metastatic melanoma.

Interaction of 5-diazoimidazole-4-carboxamide and alkyl and aryl isocyanates in the dark affords 8-carbamoyl-3-substituted-imidazo[5,1-d]-1,2,3,5-tetrazin-4(3H)-on es. In cold methanol or ethanol, the 3-(2-chloroethyl) derivative 7a decomposes to afford 2-azahypoxanthine (14) and methyl and ethyl N-(2-chloroethyl)carbamates, respectively. Compound 7a has curative activity against L-1210 and P388 leukemia and may act as a prodrug modification of the acyclic triazene 5-[3-(2-chloroethyl)triazen-1-yl]imidazole-4-carboxamide (MCTIC), since it ring opens to form the triazene in aqueous sodium carbonate.

Antitumor imidazotetrazines. 1. Synthesis and chemistry of 8-carbamoyl-3-(2-chloroethyl)imidazo[5,1-d]-1,2,3,5-tetrazin-4(3 H)-one , a novel broad-spectrum antitumor agent.

Mitozolomide (1) and its 3-alkyl congeners ring-open in aqueous sodium carbonate to form 5-(3-alkyltriazen-1-yl)imidazole-4-carboxamides The 3-methyl and 3-ethyl analogues of mitozolomide decompose in alcohols to form 2-azahypoxanthine and 5-amino-1-alkoxycarbonylimidazole-4-carboxamides In hydrazine hydrate mitozolomide yields, principally, 5-azidoimidazole-4-carboxamide, whereas the 3-alkyl-derivatives form 5-amino-4-carbamoylimidazole-1-carbohydrazide5-Diazoimidazole-4-carboxamide, generated by thermolysis of mitozolomide in acetic acid or pyridine, can be trapped by reactive methylenic ketones, nitriles or esters to afford imidazo[1,2,4]triazines

Antitumour imidazotetrazines. Part 12. Reactions of mitozolomide and its 3-alkyl congeners with oxygen, nitrogen, halogen, and carbon nucleophiles

The thermolysis of 4-anilino-1,2,3-benzotriazines and their precursor 3-aryl-1-(2-cyanophenyl)-triazenes in hot formamide to give 3-arylquinazolin-4(3H)-ones in high yield is described. The reaction cannot be extended to the preparation of 2-alkyl-3-arylquinazolinones. In hot acetamide–diglyme 4-(4-nitroanilino)-1,2,3-benzotriazine (5c) gives a high yield of the 3-substituted 4-(4-nitrophenylimino)-3,4-dihydro-1,2,3-benzotriazine (11c).

Triazines and related products. Part 28. Conversion of 3-aryl-1-(2-cyanophenyl)triazenes into 3-arylquinazolin-4(3H)-ones with formamide

5-Diazomidazole-4-carboxamide couples with reactive methylenic substrates to afford a series of imidazolyl-hydrazones which cyclise in acid or alkali to imidazo[5,1-c][1,2,4]triazines. Hydrazones with cyano-substituents cyclise in acid to yield 7-aminoimidazotriazines whereas hydrazones with acetyl groups undergo acidic dehydration to form bicycles with a 7-methylene substituent. In basic conditions, hydrazones with a reactive ester group cyclisa to imidazotriazin-7(4H)-ones with loss of an alcohol moiety. Ethyl 7-amino-3-carbamoylimidazo[5,1-c][1,2,4]-triazine-6-carboxylate hydrolyses in boiling 2N-hydrochloric acid, forms an N-acetyl derivative, and reacts with secondary heteroalicyclic amines to form amides.

Triazines and related products, Part 22. Synthesis and reactions of imidazo[5,1-c][1,2,4]triazines

4-(Substituted)imidazo[5,1-c][1,2,4)triazine-8-carboxamides with ester, ketone, or cyano-groups in the 3-position undergo ring-opening with hydrazine and phenylhydrazine to yield substituted (pyrazol-4-ylidenehydrazino)imidazole-4-carboxamides. In some cases ring cleavage is initiated by attack of the hydrazine at C-4 of the imidazotriazine, and in others by nucleophilic attack at the 3-substituent. Examples of the same series of hydrazones can be prepared by coupling 5-diazoimidazole-4-carboxamide with activated pyrazoles. Diazotised arylamines couple with 5-aminoimidazole-4-carboxamide at C-2 to yield a series of intensely coloured 5-amino-2-arylazoimidazole-4-carboxamides, which can be cyclised to 8-arylazo-9H-purin-6(1H)-ones with ethyl formats in sodium ethoxide, and form mono- or di-acylamino-derivatives in formic acid or acetic anhydride. In no case was it found possible to prepare 2,5-diaminoimidazole-4-carboxamide by reductive cleavage of 5-amino-2-arylazoimidazole-4-carboxamides; only arylamines or unstable hydrazo-intermediates were identified. Reduction of 5-amino-2-(2-cyanophenylazo)imidazole-4-carboxamide with sodium dithionite or with hydrogen over a 10% palladium–charcoal catalyst afforded 5-amino-2-(3-aminoindazol-2-yl)imidazole-4-carboxamide.

Triazines and related products. Part 24. Synthesis of pyrazol-4-ylidenehydrazinoimidazoles by hydrazinolysis of imidazo[5,1-c][1,2,4]-triazines and 2-arylazoimidazoles by diazonium coupling reactions

Ghouse Unissa Baig

Papers

Antitumor imidazotetrazines. 1. Synthesis and chemistry of 8-carbamoyl-3-(2-chloroethyl)imidazo[5,1-d]-1,2,3,5-tetrazin-4(3 H)-one , a novel broad-spectrum antitumor agent.

Antitumour imidazotetrazines. Part 12. Reactions of mitozolomide and its 3-alkyl congeners with oxygen, nitrogen, halogen, and carbon nucleophiles

Triazines and related products. Part 28. Conversion of 3-aryl-1-(2-cyanophenyl)triazenes into 3-arylquinazolin-4(3H)-ones with formamide

Triazines and related products, Part 22. Synthesis and reactions of imidazo[5,1-c][1,2,4]triazines

Triazines and related products. Part 24. Synthesis of pyrazol-4-ylidenehydrazinoimidazoles by hydrazinolysis of imidazo[5,1-c][1,2,4]-triazines and 2-arylazoimidazoles by diazonium coupling reactions