VHZ is a novel centrosomal phosphatase associated with cell growth and human primary cancers.
BACKGROUND
VHZ is a VH1-like (member Z) dual specific protein phosphatase encoded by DUSP23 gene. Some of the dual specific protein phosphatases (DSPs) play an important role in cell cycle control and have shown to be associated with carcinogenesis. Here, the expression of VHZ associated with cell growth and human cancers was investigated.


RESULTS
We generated a mouse monoclonal antibody (mAb clone#209) and rabbit polyclonal antibodies (rAb) against VHZ. We performed cell proliferation assay to learn how VHZ is associated with cell cycle by retroviral transduction to express VHZ, VHZ(C95S), and control vector in MCF-7 cells. Overexpression of VHZ [but not VHZ(C95S)] in MCF-7 cells promoted cell proliferation compared to control cells. shRNA-mediated knockdown of VHZ in MCF-7 cells showed that reduction of VHZ resulted in increased G1 but decreased S phase cell populations. Using indirect immunofluorescence, we showed that both exogenous and endogenous VHZ protein was localized at the centrosome in addition to its cytoplasmic distribution. Furthermore, using immunohistochemistry, we revealed that VHZ protein was overexpressed either in enlarged centrosomes (VHZ-centrosomal-stain) of some invasive ductal carcinomas (IDC) Stage I (8/65 cases) or in entire cytoplasm (VHZ-cytosol-stain) of invasive epithelia of some IDC Stage II/III (11/47 cases) of breast cancers examined. More importantly, upregulation of VHZ protein is also associated with numerous types of human cancer, in particular breast cancer. VHZ mAb may be useful as a reagent in clinical diagnosis for assessing VHZ positive tumors.


CONCLUSIONS
We generated a VHZ-specific mAb to reveal that VHZ has a novel subcellular localization, namely the centrosome. VHZ is able to facilitate G1/S cell cycle transition in a PTP activity-dependent manner. The upregulation of its protein levels in primary human cancers supports the clinical relevance of the protein in cancers.
Tang
Jing Ping
JP
Institute of Molecular and Cell Biology, A*STAR (Agency for Science, Technology and Research), Proteos, Singapore.
Tan
Cheng Peow
CP
Li
Jie
J
Siddique
Md Monowarul
MM
Guo
Ke
K
Chan
Siew Wee
SW
Park
Jung Eun
JE
Tay
Wan Ngee
WN
Huang
Zhi Yuan
ZY
Li
Wen Cai
WC
Chen
Jian
J
Zeng
Qi
Q
D000818:Animals; D000911:Antibodies, Monoclonal; D014408:Biomarkers, Tumor / Q000032:analysis* / Q000235:genetics / Q000378:metabolism; D002453:Cell Cycle / Q000235:genetics; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002469:Cell Separation; D018385:Centrosome / Q000201:enzymology*; D054637:Dual-Specificity Phosphatases / Q000235:genetics / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006801:Humans; D006825:Hybridomas; D007150:Immunohistochemistry; D051379:Mice; D008807:Mice, Inbred BALB C; D009369:Neoplasms / Q000235:genetics / Q000378:metabolism*; D011817:Rabbits
D000911:Antibodies, Monoclonal; D014408:Biomarkers, Tumor; C497817:DUSP23 protein, human; D054637:Dual-Specificity Phosphatases