N3-substituted temozolomide analogs overcome methylguanine-DNA methyltransferase and mismatch repair precipitating apoptotic and autophagic cancer cell death.

Glioblastoma multiforme (GBM) treatment includes temozolomide (TMZ) chemotherapy. O6-Methylguanine lesions are repaired by methylguanine-DNA methyltransferase (MGMT). Response to TMZ requires low MGMT and functional mismatch repair (MMR); resistance, conferred by MGMT or MMR deficiency, represents a barrier to successful treatment. TMZ analogs were synthesized, substituting N3-methyl with propargyl (1) or sulfoxide (2). MTT assays were conducted in SNB19 and U373 isogenic glioma cell lines (V = vector control; M = MGMT-transfected). TMZ potency was reduced >5-fold in SNB19M and U373M cells; in contrast, MGMT-expressing cells were equisensitive as vector controls to analogs 1 and 2 . GI50 values <50 μM of analogs 1 or 2 were detected in V cells possessing acquired TMZ resistance: SNB19VR (hMSH6 loss) and U373VR (MGMT upregulation). Analogs 1 and 2 inhibited MMR-deficient colorectal carcinoma cell growth (irrespective of p53); G2/M cell cycle arrest preceded apoptosis. γH2AX foci inferred the generation of DNA double-strand breaks by analogs 1 and 2 . Acridine orange-stained vesicles, intracellular punctate GFP-LC3 protein and double-membraned autophagosomes indicate that TMZ, 1 and 2 induce autophagy in apoptotis-resistant GBM cells. Analogs 1 and 2 elicit in vitro antitumor activity irrespective of MGMT, MMR and p53. Such imidazotetrazines may treat MGMT+ GBM and possess broader spectrum activity causing apoptosis and autophagy in malignancies which evade apoptosis.

Zhang J ，Hummersone M ，Matthews CS ，Stevens MF ，Bradshaw TD ... -  《-》

Certain imidazotetrazines escape O6-methylguanine-DNA methyltransferase and mismatch repair.

Resistance to temozolomide (TMZ), conferred by O6-methylguanine-DNA methyltransferase (MGMT) or mismatch repair (MMR) deficiency, presents obstacles to successful glioblastoma multiforme (GBM) treatment. Activities of novel TMZ analogs, designed to overcome resistance, were tested against isogenic SNB19 and U373 GBM cell lines (V = vector control, low MGMT; M = MGMT overexpression). TMZ and triazene MTIC demonstrated >9-fold resistance in SNB19M cells (cf SNB19V). N-3 methyl ester analog 11 and corresponding triazene 12 inhibited growth of TMZ-sensitive (V) and TMZ-resistant (M) cells (GI(50) <50 μM). Ethyl ester 13 and triazene 14 gave similar profiles. MMR-deficient colorectal carcinoma cells, resistant to TMZ (GI(50) >500 μM), responded to analog 11 and 13 treatment. Cross-resistance to these agents was not observed in cell lines possessing acquired TMZ resistance (SNB19VR; U373VR). Methyl ester 11 blocked SNB19V, SNB19M and SNB19VR cells in S and G(2)/M, causing dose- and time-dependent apoptosis. DNA damage, recruiting excision repair was detected by alkaline comet assay; H2AX phosphorylation indicated a lethal DNA double-strand break formation following analog 11 exposure. Compounds 11 and 13 demonstrated 3.7- and 5.1-fold enhanced activity in base excision repair-deficient Chinese hamster ovary cells; furthermore, poly (ADP-ribose) polymerase-1 inhibition potentiated HCT-116 cells' sensitivity to analog 11. In conclusion, analogs 11 and 13 exert anticancer activity irrespective of MGMT and MMR.

Zhang J ，Stevens MF ，Hummersone M ，Madhusudan S ，Laughton CA ，Bradshaw TD ... -  《-》

Temozolomide- and fotemustine-induced apoptosis in human malignant melanoma cells: response related to MGMT, MMR, DSBs, and p53.

Naumann SC ，Roos WP ，Jöst E ，Belohlavek C ，Lennerz V ，Schmidt CW ，Christmann M ，Kaina B ... -  《-》

Temozolomide: mechanisms of action, repair and resistance.

Zhang J ，Stevens MF ，Bradshaw TD 《-》

Effect of lomeguatrib-temozolomide combination on MGMT promoter methylation and expression in primary glioblastoma tumor cells.

Taspinar M ，Ilgaz S ，Ozdemir M ，Ozkan T ，Oztuna D ，Canpinar H ，Rey JA ，Sunguroğlu A ，Castresana JS ，Ugur HC ... -  《-》