MMSET deregulation affects cell cycle progression and adhesion regulons in t(4;14) myeloma plasma cells.
BACKGROUND
The recurrent immunoglobulin translocation, t(4;14)(p16;q32) occurs in 15% of multiple myeloma patients and is associated with poor prognosis, through an unknown mechanism. The t(4;14) up-regulates fibroblast growth factor receptor 3 (FGFR3) and multiple myeloma SET domain (MMSET) genes. The involvement of MMSET in the pathogenesis of t(4;14) multiple myeloma and the mechanism or genes deregulated by MMSET upregulation are still unclear.


METHODS
The expression of MMSET was analyzed using a novel antibody. The involvement of MMSET in t(4;14) myelomagenesis was assessed by small interfering RNA mediated knockdown combined with several biological assays. In addition, the differential gene expression of MMSET-induced knockdown was analyzed with expression microarrays. MMSET gene targets in primary patient material was analyzed by expression microarrays.


RESULTS
We found that MMSET isoforms are expressed in multiple myeloma cell lines, being exclusively up-regulated in t(4;14)-positive cells. Suppression of MMSET expression affected cell proliferation by both decreasing cell viability and cell cycle progression of cells with the t(4;14) translocation. These findings were associated with reduced expression of genes involved in the regulation of cell cycle progression (e.g. CCND2, CCNG1, BRCA1, AURKA and CHEK1), apoptosis (CASP1, CASP4 and FOXO3A) and cell adhesion (ADAM9 and DSG2). Furthermore, we identified genes involved in the latter processes that were differentially expressed in t(4;14) multiple myeloma patient samples.


CONCLUSIONS
In conclusion, dysregulation of MMSET affects the expression of several genes involved in the regulation of cell cycle progression, cell adhesion and survival.
Brito
Jose L R
JL
Institute for Cancer Research, Section of Haemato-Oncology, London, UK.
Walker
Brian
B
Jenner
Matthew
M
Dickens
Nicholas J
NJ
Brown
Nicola J M
NJ
Ross
Fiona M
FM
Avramidou
Athanasia
A
Irving
Julie A E
JA
Gonzalez
David
D
Davies
Faith E
FE
Morgan
Gareth J
GJ
D002448:Cell Adhesion; D002453:Cell Cycle; D045744:Cell Line, Tumor; D002877:Chromosomes, Human / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic; D011495:Histone-Lysine N-Methyltransferase / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D009101:Multiple Myeloma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D015996:Survival Rate; D015854:Up-Regulation
D020033:Protein Isoforms; D034741:RNA, Small Interfering; D012097:Repressor Proteins; D011495:Histone-Lysine N-Methyltransferase; C419586:NSD2 protein, human