Differential expression of metallothionein 1 and 2 isoforms in breast cancer lines with different invasive potential: identification of a novel nonsilent metallothionein-1H mutant variant.
Metallothionein (MT), a low-molecular weight protein with pleiotropic functions, is believed to play an important role in tumorigenesis. The aim of this study was to compare the expression of functional MT-1 and MT-2 mRNA isoforms in five breast cancer cell lines ranging from noninvasive MCF7 breast cancer cells to highly aggressive MDA-MB-231 breast cancer cells together with breast myoepithelial cells in vitro by conventional semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and quantitative real-time RT-PCR. The MT-2A isoform was observed to be differentially upregulated in the invasive phenotype. The MT-1E isoform was found to be present in estrogen receptor-negative breast cancer cell lines (MDA-MB-231 and Hs578T) but not detectable in the estrogen receptor-positive cell lines (T47D, MCF7, and ZR75-1 cells). Only the myoepithelial cells exhibited the presence of the MT-1G transcript. Direct sequencing of the RT-PCR products revealed the occurrence of a variant MT-1H isoform with changes in amino acid residues in the protein sequence and notable differences in the predicted secondary protein structure. The observations in this study are relevant to the development of novel approaches to metastatic breast cancer disease, and may herald the search for novel MT mutants and the elucidation of their biological roles.
Department of Microbiology, Human Genome Laboratory, Faculty of Medicine, National University of Singapore, 4 Medical Drive, S-117 597 Singapore, Republic of Singapore..
Siew-Kian
SK
Tai
Owen June-Keong
OJ
Tan
Vincent Tak-Kwong
VT
Chow
Rongxian
R
Jin
J Louise
JL
Jones
Puay-Hoon
PH
Tan
Anita
A
Jayasurya
Boon-Huat
BH
Bay
D001943:Breast Neoplasms / Q000378:metabolism* / Q000473:pathology*; D002460:Cell Line; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry; D008668:Metallothionein / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics*; D009154:Mutation; D009362:Neoplasm Metastasis; D020033:Protein Isoforms / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics*; D017433:Protein Structure, Secondary / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction
D020033:Protein Isoforms; D012333:RNA, Messenger; D008668:Metallothionein