Home>>Signaling Pathways>> DNA Damage/DNA Repair>> DNA Alkylator/Crosslinker>>Temozolomide


Catalog No.: GC13667

Temozolomide is an oral activity alkylating agent that induces the formation of O6-methylguanine in DNA

Temozolomide Chemical Structure

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10mM (in 1mL DMSO)
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Sample solution is provided at 25 µL, 10mM.

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Cell experiment [1]:

Cell lines

U-118 GBM cell line

Preparation Method

Cells were subcultured every 48 h by lifting them up with a cell scrapper. The cells were then centrifuged and resuspended in fresh DMEM. For the experiments, unsynchronized cells were treated with different concentrations of Temozolomide (0, 10, 20, 100, 250 and 500 µM) for 24 and 48 h. Assays were previously performed in the presence of DMSO, which corresponded to each Temozolomide concentration.

Reaction Conditions

0, 10, 20, 100, 250 and 500 µM for 24 and 48 h


The effect of Temozolomide was particularly evident when U-118 cells were incubated with Temozolomide concentrations of >100 µM. When U-118 cells were incubated with Temozolomide (250 µM) the proliferation rate was inhibited by 43.2%, as compared to that observed in the control cells.

Animal experiment [2]:

Animal models

Male B6D2F1 (C57BL/6 × DBA/2) mice

Preparation Method

L5178Y cells (104 in 0.03 mL RPMI-1640) were then injected intracranially, through the center-middle area of the frontal bone to a 2-mm depth, using a 0.1-mL glass microsyringe and a 27-gauge disposable needle. Temozolomide was dissolved in dimethyl-sulfoxide (40 mg/mL), diluted in saline (5 mg/mL), and administered intraperitoneally on day 2 after tumor injection at 100 mg/kg or 200 mg/kg, total dose of 200 mg/kg Temozolomide was divided in 2 doses of 100 mg/kg given on days 2 and 3.

Dosage form

Intraperitoneal injection, 100, 200 mg/kg


Intracranial injection of NU1025, immediately before the administration of 100 or 200 mg/kg Temozolomide, significantly increased lifespans with respect to controls or to groups treated with Temozolomide only. When Temozolomide was fractionated, the ILS obtained with this schedule was higher than that observed when NU1025 was combined with a single injection of Temozolomide.


[1]: Carmo A, Carvalheiro H, Crespo I, et al. Effect of Temozolomide on the U-118 glioma cell line[J]. Oncology letters, 2011, 2(6): 1165-1170.
[2]: Tentori L, Leonetti C, Scarsella M, et al. Combined treatment with Temozolomide and poly (ADP-ribose) polymerase inhibitor enhances survival of mice bearing hematologic malignancy at the central nervous system site[J]. Blood, The Journal of the American Society of Hematology, 2002, 99(6): 2241-2244.


Temozolomide is an oral activity alkylating agent that induces the formation of O6-methylguanine in DNA, which mispairs with thymine during the following cycle of DNA replication, leading to activation of the apoptotic pathways, Temozolomide could crosses the blood-brain barrier and is indicated for malignant gliomas and metastatic melanomas [1]. Temozolomide induced cell cycle arrest at G2/M and to eventually lead to apoptosis [2]. At physiologic pH it is converted to the short-lived active compound, MTIC. MTIC is further hydrolyzed to 5-amino-imidazole-4-carboxamide (AIC) and to methylhydrazine. The cytotoxicity of Temozolomide is mediated by its addition of methyl groups at N7 and O6 sites on guanines and the O3 site on adenines in genomic DNA. Alkylation of the O6 site on guanine leads to the insertion of a thymine instead of a cytosine opposite the methylguanine during subsequent DNA replication, and this can result in cell death [3].

Lymphoma cell counts performed 72 hours after treatment showed that the IC50 of Temozolomide was 44 µM (35-58 µM) when used alone and 16 µM (12-26 µM) when combined with NU1025 [1]. A time-related response in DNA strand-break formation was observed in the U251MG glioblastoma cells treated with Temozolomide (100 µM) alone [4]. Temozolomide was particularly evident when U-118 cells were incubated with Temozolomide concentrations of >100 µM. When U-118 cells were incubated with Temozolomide (250 µM) the proliferation rate was inhibited by 43.2% [5].

Temozolomide consistently demonstrates reproducible linear pharmacokinetics with approximately 100% p.o. bioavailability [6]. In the early stage s.c. implanted SNB-75 astrocytoma model, a 400-mg/kg dose of Temozolomide administered on Day 5 produced 10 of 10 Day 54 tumor-free mice. In later staged s.c. U251 and SF-295 glioblastoma models, a single 600-mg/kg dose produced 9 of 10 Day 86 and 2 of 10 Day 40 tumor-free mice, respectively. In the latter group, a tumor growth delay of >315% was attained [7]. Treatment of CEP 6800 (30 mg/kg) with Temozolomide (17 and 34 mg/kg) resulted in 100% complete regression of U251MG tumors by day 28 versus 60% complete regression caused by Temozolomide alone [4].

[1]. Tentori L, Leonetti C, Scarsella M, et al. Combined treatment with temozolomide and poly (ADP-ribose) polymerase inhibitor enhances survival of mice bearing hematologic malignancy at the central nervous system site[J]. Blood, The Journal of the American Society of Hematology, 2002, 99(6): 2241-2244.
[2]. Baer J C, Freeman A A, Newlands E S, et al. Depletion of O6-alkylguanine-DNA alkyltransferase correlates with potentiation of temozolomide and CCNU toxicity in human tumour cells[J]. British journal of cancer, 1993, 67(6): 1299-1302.
[3]. Lee S Y. Temozolomide resistance in glioblastoma multiforme[J]. Genes & diseases, 2016, 3(3): 198-210.
[4]. Miknyoczki S J, Jones-Bolin S, Pritchard S, et al. Chemopotentiation of temozolomide, irinotecan, and cisplatin activity by CEP-6800, a poly (ADP-ribose) polymerase inhibitor[J]. Molecular cancer therapeutics, 2003, 2(4): 371-382.
[5]. Carmo A, Carvalheiro H, Crespo I, et al. Effect of temozolomide on the U-118 glioma cell line[J]. Oncology letters, 2011, 2(6): 1165-1170.
[6]. Friedman H S, Kerby T, Calvert H. Temozolomide and treatment of malignant glioma[J]. Clinical cancer research, 2000, 6(7): 2585-2597.
[7]. Plowman J, Waud W R, Koutsoukos A D, et al. Preclinical antitumor activity of temozolomide in mice: efficacy against human brain tumor xenografts and synergism with 1, 3-bis (2-chloroethyl)-1-nitrosourea[J]. Cancer research, 1994, 54(14): 3793-3799.

Chemical Properties

Cas No. 85622-93-1 SDF
Chemical Name 3-methyl-4-oxoimidazo[5,1-d][1,2,3,5]tetrazine-8-carboxamide
Canonical SMILES CN1C(=O)N2C=NC(=C2N=N1)C(=O)N
Formula C6H6N6O2 M.Wt 194.15
Solubility ≥ 29.61mg/mL in DMSO Storage Store at -20°C, protect from light, stored under nitrogen
General tips For obtaining a higher solubility , please warm the tube at 37 ℃ and shake it in the ultrasonic bath for a while.Stock solution can be stored below -20℃ for several months.
Shipping Condition Evaluation sample solution : ship with blue ice
All other available size: ship with RT , or blue ice upon request

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Research Update

Evidence-Based Practice: Temozolomide Beyond Glioblastoma

Curr Oncol Rep2019 Mar 5;21(4):30.PMID: 30835007DOI: 10.1007/s11912-019-0783-5

Purpose of review: Temozolomide is a first-line treatment for newly diagnosed glioblastoma. In this review, we will examine the use of temozolomide in other contexts for treating gliomas, including recurrent glioblastoma, glioblastoma in the elderly, diffuse low- and high-grade gliomas, non-diffuse gliomas, diffuse intrinsic pontine glioma (DIPG), ependymoma, pilocytic astrocytoma, and pleomorphic xanthoastrocytoma. Recent findings: Temozolomide improved survival in older patients with glioblastoma, anaplastic gliomas regardless of 1p/19q deletion status, and progressive ependymomas. Temozolomide afforded less toxicity and comparable efficacy to radiation in high-risk low-grade gliomas and to platinum-based chemotherapy in pediatric high-grade gliomas. The success of temozolomide in promoting survival has expanded beyond glioblastoma to benefit patients with non-glioblastoma tumors. Identifying practical biomarkers for predicting temozolomide susceptibility, and establishing complementary agents for chemosensitizing tumors to temozolomide, will be key next steps for future success.

Potential Strategies Overcoming the Temozolomide Resistance for Glioblastoma

Neurol Med Chir (Tokyo)2018 Oct 15;58(10):405-421.PMID: 30249919DOI: 10.2176/nmc.ra.2018-0141

Glioblastoma (GBM) is a highly malignant type of primary brain tumor with a high mortality rate. Although the current standard therapy consists of surgery followed by radiation and temozolomide (TMZ), chemotherapy can extend patient's post-operative survival but most cases eventually demonstrate resistance to TMZ. O6-methylguanine-DNA methyltransferase (MGMT) repairs the main cytotoxic lesion, as O6-methylguanine, generated by TMZ, can be the main mechanism of the drug resistance. In addition, mismatch repair and BER also contribute to TMZ resistance. TMZ treatment can induce self-protective autophagy, a mechanism by which tumor cells resist TMZ treatment. Emerging evidence also demonstrated that a small population of cells expressing stem cell markers, also identified as GBM stem cells (GSCs), contributes to drug resistance and tumor recurrence owing to their ability for self-renewal and invasion into neighboring tissue. Some molecules maintain stem cell properties. Other molecules or signaling pathways regulate stemness and influence MGMT activity, making these GCSs attractive therapeutic targets. Treatments targeting these molecules and pathways result in suppression of GSCs stemness and, in highly resistant cases, a decrease in MGMT activity. Recently, some novel therapeutic strategies, targeted molecules, immunotherapies, and microRNAs have provided new potential treatments for highly resistant GBM cases. In this review, we summarize the current knowledge of different resistance mechanisms, novel strategies for enhancing the effect of TMZ, and emerging therapeutic approaches to eliminate GSCs, all with the aim to produce a successful GBM treatment and discuss future directions for basic and clinical research to achieve this end.

Elucidating the mechanisms of Temozolomide resistance in gliomas and the strategies to overcome the resistance

Biochim Biophys Acta Rev Cancer2021 Dec;1876(2):188616.PMID: 34419533DOI: 10.1016/j.bbcan.2021.188616

Temozolomide (TMZ) is a first-choice alkylating agent inducted as a gold standard therapy for glioblastoma multiforme (GBM) and astrocytoma. A majority of patients do not respond to TMZ during the course of their treatment. Activation of DNA repair pathways is the principal mechanism for this phenomenon that detaches TMZ-induced O-6-methylguanine adducts and restores genomic integrity. Current understanding in the domain of oncology adds several other novel mechanisms of resistance such as the involvement of miRNAs, drug efflux transporters, gap junction's activity, the advent of glioma stem cells as well as upregulation of cell survival autophagy. This review describes a multifaceted account of different mechanisms responsible for the intrinsic and acquired TMZ-resistance. Here, we summarize different strategies that intensify the TMZ effect such as MGMT inhibition, development of novel imidazotetrazine analog, and combination therapy; with an aim to incorporate a successful treatment and increased overall survival in GBM patients.

Pericytes augment glioblastoma cell resistance to temozolomide through CCL5-CCR5 paracrine signaling

Cell Res2021 Oct;31(10):1072-1087.PMID: 34239070DOI: 10.1038/s41422-021-00528-3

Glioblastoma (GBM) is a prevalent and highly lethal form of glioma, with rapid tumor progression and frequent recurrence. Excessive outgrowth of pericytes in GBM governs the ecology of the perivascular niche, but their function in mediating chemoresistance has not been fully explored. Herein, we uncovered that pericytes potentiate DNA damage repair (DDR) in GBM cells residing in the perivascular niche, which induces temozolomide (TMZ) chemoresistance. We found that increased pericyte proportion correlates with accelerated tumor recurrence and worse prognosis. Genetic depletion of pericytes in GBM xenografts enhances TMZ-induced cytotoxicity and prolongs survival of tumor-bearing mice. Mechanistically, C-C motif chemokine ligand 5 (CCL5) secreted by pericytes activates C-C motif chemokine receptor 5 (CCR5) on GBM cells to enable DNA-dependent protein kinase catalytic subunit (DNA-PKcs)-mediated DDR upon TMZ treatment. Disrupting CCL5-CCR5 paracrine signaling through the brain-penetrable CCR5 antagonist maraviroc (MVC) potently inhibits pericyte-promoted DDR and effectively improves the chemotherapeutic efficacy of TMZ. GBM patient-derived xenografts with high CCL5 expression benefit from combined treatment with TMZ and MVC. Our study reveals the role of pericytes as an extrinsic stimulator potentiating DDR signaling in GBM cells and suggests that targeting CCL5-CCR5 signaling could be an effective therapeutic strategy to improve chemotherapeutic efficacy against GBM.

TGF-β1 modulates temozolomide resistance in glioblastoma via altered microRNA processing and elevated MGMT

Neuro Oncol2021 Mar 25;23(3):435-446.PMID: 32813021DOI: 10.1093/neuonc/noaa198

Background: Our previous studies have indicated that miR-198 reduces cellular methylguanine DNA methyltransferase (MGMT) levels to enhance temozolomide sensitivity. Transforming growth factor beta 1 (TGF-β1) switches off miR-198 expression by repressing K-homology splicing regulatory protein (KSRP) expression in epidermal keratinocytes. However, the underlying role of TGF-β1 in temozolomide resistance has remained unknown.
Methods: The distribution of KSRP was detected by western blotting and immunofluorescence. Microarray analysis was used to compare the levels of long noncoding RNAs (lncRNAs) between TGF-β1-treated and untreated cells. RNA immunoprecipitation was performed to verify the relationship between RNAs and KSRP. Flow cytometry and orthotopic and subcutaneous xenograft tumor models were used to determine the function of TGF-β1 in temozolomide resistance.
Results: Overexpression of TGF-β1 contributed to temozolomide resistance in MGMT promoter hypomethylated glioblastoma cells in vitro and in vivo. TGF-β1 treatment reduced cellular MGMT levels through suppressing the expression of miR-198. However, TGF-β1 upregulation did not affect KSRP expression in glioma cells. We identified and characterized 2 lncRNAs (H19 and HOXD-AS2) that were upregulated by TGF-β1 through Smad signaling. H19 and HOXD-AS2 exhibited competitive binding to KSRP and prevented KSRP from binding to primary miR-198, thus decreasing miR-198 expression. HOXD-AS2 or H19 upregulation strongly promoted temozolomide resistance and MGMT expression. Moreover, KSRP depletion abrogated the effects of TGF-β1 and lncRNAs on miR-198 and MGMT. Finally, we found that patients with low levels of TGF-β1 or lncRNA expression benefited from temozolomide therapy.
Conclusions: Our results reveal an underlying mechanism by which TGF-β1 confers temozolomide resistance. Furthermore, our findings suggest that a novel combination of temozolomide with a TGF-β inhibitor may serve as an effective therapy for glioblastomas.


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