TY - JOUR
T1 - Mismatch repair deficiency: a temozolomide resistance factor in medulloblastoma cell lines that is uncommon in primary medulloblastoma tumours
AU - von Bueren, A. O.
AU - Bacolod, M. D.
AU - Hagel, C.
AU - Heinimann, K.
AU - Fedier, A.
AU - Kordes, U.
AU - Pietsch, T.
AU - Koster, J.
AU - Grotzer, M. A.
AU - Friedman, H. S.
AU - Marra, G.
AU - Kool, M.
AU - Rutkowski, S.
PY - 2012
Y1 - 2012
N2 - BACKGROUND: Tumours are responsive to temozolomide (TMZ) if they are deficient in O-6-methylguanine-DNA methyltransferase (MGMT), and mismatch repair (MMR) proficient. METHODS: The effect of TMZ on medulloblastoma (MB) cell killing was analysed with clonogenic survival assays. Expression of DNA repair genes and enzymes was investigated using microarrays, western blot, and immunohistochemistry. DNA sequencing and promoter methylation analysis were employed to investigate the cause of loss of the expression of MMR gene MLH1. RESULTS: Temozolomide exhibited potent cytotoxic activity in D425Med (MGMT deficient, MLH1 proficient; IC50 = 1.7 mu M), moderate activity against D341Med (MGMT proficient, MLH1 deficient), and DAOY MB cells (MGMT proficient, MLH1 proficient). MGMT inhibitor O-6-benzylguanine sensitised DAOY, but not D341Med cells to TMZ. Of 12 MB cell lines, D341Med, D283Med, and 1580WU cells exhibited MMR deficiency due to MLH1 promoter hypermethylation. DNA sequencing of these cells provided no evidence for somatic genetic alterations in MLH1. Expression analyses of MMR and MGMT in MB revealed that all patient specimens (n = 74; expression array, n = 61; immunostaining, n = 13) are most likely MMR proficient, whereas some tumours had low MGMT expression levels (according to expression array) or were totally MGMT deficient (3 out of 13 according to immunohistochemistry). CONCLUSION: A subset of MB may respond to TMZ as some patient specimens are MGMT deficient, and tumours appear to be MMR proficient. British Journal of Cancer (2012) 107, 1399-1408. doi:10.1038/bjc.2012.403 www.bjcancer.com Published online 13 September 2012 (c) 2012 Cancer Research UK
AB - BACKGROUND: Tumours are responsive to temozolomide (TMZ) if they are deficient in O-6-methylguanine-DNA methyltransferase (MGMT), and mismatch repair (MMR) proficient. METHODS: The effect of TMZ on medulloblastoma (MB) cell killing was analysed with clonogenic survival assays. Expression of DNA repair genes and enzymes was investigated using microarrays, western blot, and immunohistochemistry. DNA sequencing and promoter methylation analysis were employed to investigate the cause of loss of the expression of MMR gene MLH1. RESULTS: Temozolomide exhibited potent cytotoxic activity in D425Med (MGMT deficient, MLH1 proficient; IC50 = 1.7 mu M), moderate activity against D341Med (MGMT proficient, MLH1 deficient), and DAOY MB cells (MGMT proficient, MLH1 proficient). MGMT inhibitor O-6-benzylguanine sensitised DAOY, but not D341Med cells to TMZ. Of 12 MB cell lines, D341Med, D283Med, and 1580WU cells exhibited MMR deficiency due to MLH1 promoter hypermethylation. DNA sequencing of these cells provided no evidence for somatic genetic alterations in MLH1. Expression analyses of MMR and MGMT in MB revealed that all patient specimens (n = 74; expression array, n = 61; immunostaining, n = 13) are most likely MMR proficient, whereas some tumours had low MGMT expression levels (according to expression array) or were totally MGMT deficient (3 out of 13 according to immunohistochemistry). CONCLUSION: A subset of MB may respond to TMZ as some patient specimens are MGMT deficient, and tumours appear to be MMR proficient. British Journal of Cancer (2012) 107, 1399-1408. doi:10.1038/bjc.2012.403 www.bjcancer.com Published online 13 September 2012 (c) 2012 Cancer Research UK
U2 - https://doi.org/10.1038/bjc.2012.403
DO - https://doi.org/10.1038/bjc.2012.403
M3 - Article
C2 - 22976800
SN - 0007-0920
VL - 107
SP - 1399
EP - 1408
JO - British journal of cancer
JF - British journal of cancer
IS - 8
ER -