Methoxyamine sensitizes the resistant glioblastoma T98G cell line to the alkylating agent temozolomide

Author(s)

Montaldi, Ana P. ^[1] ; Sakamoto-Hojo, Elza T. ^{[1, 2]}

Affiliation

^[1] Univ Sao Paulo, Fac Med Ribeirao Preto, Dept Genet, BR-14040901 Ribeirao Preto, SP - Brazil

^[2] Univ Sao Paulo, Fac Philosophy Sci & Letters, Dept Biol, BR-14040901 Ribeirao Preto, SP - Brazil

• Document type: Journal article
• Source: CLINICAL AND EXPERIMENTAL MEDICINE; v. 13, n. 4, p. 279-288, NOV 2013.
• Web of Science Citations: 13

Abstract

Chemoresistance represents a major obstacle to successful treatment for malignant glioma with temozolomide. N (7)-methyl-G and N (3)-methyl-A adducts comprise more than 80 % of DNA lesions induced by temozolomide and are processed by the base excision repair, suggesting that the cellular resistance could be caused, in part, by this efficient repair pathway, although few studies have focused on this subject. The aim of this study was to evaluate the cellular responses to temozolomide treatment associated with methoxyamine (blocker of base excision repair) in glioblastoma cell lines, in order to test the hypothesis that the blockage of base excision repair pathway might sensitize glioblastoma cells to temozolomide. For all the tested cell lines, only T98G showed significant differences between temozolomide and temozolomide plus methoxyamine treatment, observed by reduced survival rates, enhanced the levels of DNA damage, and induced an arrest at G2-phase. In addition, similar to 10 % of apoptotic cells (sub-G1 fraction) were observed at 48 h. Western blot analysis demonstrated that APE1 and FEN1 presented a slightly reduced expression levels under the combined treatment, probably due to AP sites blockade by methoxyamine, thus causing a minor requirement of base excision repair pathway downstream to the AP removal by APE1. On the other hand, PCNA expression in temozolomide plus methoxyamine-treated cells does not rule out the possibility that such alteration might be related to the blockage of cell cycle (G2-phase), as observed at 24 h of recovery time. The results obtained in the present study demonstrated the efficiency of methoxyamine to overcome glioblastoma resistance to temozolomide treatment. (AU)

• FAPESP's process: 09/10925-6 - Responses to knock-down strategies for DNA repair genes and transcription factors on the chemo- and/or radioresistance of glioblastoma cells
• Grantee: Elza Tiemi Sakamoto Hojo
• Support Opportunities: Regular Research Grants
• FAPESP's process: 09/10106-5 - Influence of APE1/REF-1 gene in the responses of cell lines from glioblastoma after treatment with temozolomide
• Grantee: Ana Paula de Lima Montaldi
• Support Opportunities: Scholarships in Brazil - Doctorate