Metallothionien 3 expression is frequently down-regulated in oesophageal squamous cell carcinoma by DNA methylation.
BACKGROUND
Metallothionein 3 (MT3) inhibits growth in a variety of cell types. We measured MT3 gene expression by RT-PCR, and DNA methylation in the MT3 promoter by combined bisulphite restriction analysis, in four oesophageal cancer cell lines and the resected oesophagus from 64 patients with oesophageal squamous cell carcinoma (SCC).


RESULTS
MT3 expression was not detected in one of the four oesophageal cell lines. The MT3 promoter was methylated in all of the oesophageal cell lines, but the degree of methylation was greater in the non-expressing cell line. After treatment with 5-aza-2'-deoxycytidine there was a reduction in the degree of methylation, and an increase in MT3 expression, in each of the cell lines (p < 0.01). Methylation was detected in 52% (33 of 64) of primary SCC and 3% (2 of 62) of histologically normal resection margins. MT3 expression was measured in 29 tumours, 17 of which had methylation of MT3. The expression of MT3 was significantly less in the methylated tumours compared to either the unmethylated tumours (p = 0.03), or the matched margin (p = 0.0005). There was not a significant difference in MT3 expression between the tumour and the margin from patients with unmethylated tumour. No correlations were observed between methylation of MT3 and survival time, patient age, gender, smoking or drinking history, tumour stage, volume, or lymph node involvement.


CONCLUSIONS
We conclude that MT3 expression is frequently down-regulated in oesophageal SCC, by DNA methylation, but that this is not a prognostic indicator.
Smith
Eric
E
Department of Surgery, The University of Adelaide, Royal Adelaide Hospital, Adelaide, South Australia, 5005, Australia. eric.smith@adelaide.edu.au
Drew
Paul A
PA
Tian
Zi-Qing
ZQ
De Young
Neville J
NJ
Liu
Jun-Feng
JF
Mayne
George C
GC
Ruszkiewicz
Andrew R
AR
Watson
David I
DI
Jamieson
Glyn G
GG
D000328:Adult; D000368:Aged; D002294:Carcinoma, Squamous Cell / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D019175:DNA Methylation; D015536:Down-Regulation / Q000187:drug effects; D004938:Esophageal Neoplasms / Q000235:genetics / Q000378:metabolism*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D008214:Lymphocytes / Q000378:metabolism; D008297:Male; D000090023:Metallothionein 3; D008875:Middle Aged; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics
D000090023:Metallothionein 3; D009419:Nerve Tissue Proteins