HIV-Tat-mediated delivery of an LPTS functional fragment inhibits telomerase activity and tumorigenicity of hepatoma cells.
OBJECTIVE
Human liver-related putative tumor suppressor (LPTS) is a gene that encodes a telomerase inhibitory protein that is similar to human Pin2/TRF1-interacting protein. The LPTS protein binds directly to the telomerase catalytic subunit (human telomerase reverse transcriptase) and suppresses telomerase activity. Telomere maintenance and telomerase activity are required for long-term proliferation of cancer cells, so LPTS might be used in anticancer strategies.


METHODS
The carboxy-terminal (functional) fragment of LPTS was fused to the transactivator of transcription of human immunodeficiency virus (Tat)-an 11-amino acid peptide that translocates across the cell membrane; the TAT-fused C-terminal of LPTS (TAT-LPTS-LC) was purified and transduced into cells. Telomerase activity was identified by using the telomeric repeat amplification protocol. The effects of the TAT-LPTS-LC protein on cell proliferation and death were evaluated by colorimetric tetrazolium salt and flow cytometry analyses. Tumor growth was analyzed in nude mice.


RESULTS
The purified TAT-LPTS-LC protein was efficiently delivered into the cells, where it suppressed telomerase activity and shortened telomere length. TAT-LPTS-LC inhibited proliferation of telomerase-positive hepatocellular carcinoma BEL-7404 and hepatoblastoma HepG2cells and induced their death; however, it had no effect on telomerase-negative liver cell line L02 and osteosarcoma cell line Saos-2. In mice, tumor formations by BEL-7404 cells were suppressed by TAT-LPTS-LC treatments.


CONCLUSIONS
Transduction of hepatoma cells with a fusion protein that contains the C-terminal, functional fragment of LPTS and human immunodeficiency virus Tat (TAT-LPTS-LC) causes telomere shortening, limits proliferation, and inhibits growth of tumors from these cells in mice. TAT-LPTS-LC inhibits telomerase activity and might be developed as an anticancer agent.
Chen
Guangming
G
State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, People's Republic of China.
Da
Liang
L
Wang
Hongfei
H
Xu
Ying
Y
Chen
Guoyuan
G
Sun
Chengfu
C
Wang
Leiming
L
Zhao
Jing
J
Zhang
Fang
F
Feng
Jian
J
Wang
Yifei
Y
Tiollais
Pierre
P
Li
Tsaiping
T
Zhao
Mujun
M
D000818:Animals; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy*; D018797:Cell Cycle Proteins; D016503:Drug Delivery Systems; D006801:Humans; D008113:Liver Neoplasms / Q000188:drug therapy*; D051379:Mice; D008819:Mice, Nude; D011993:Recombinant Fusion Proteins / Q000008:administration & dosage* / Q000235:genetics / Q000378:metabolism; D019098:Telomerase / Q000037:antagonists & inhibitors*; D025521:Tumor Suppressor Proteins / Q000008:administration & dosage* / Q000235:genetics / Q000378:metabolism; D054322:tat Gene Products, Human Immunodeficiency Virus / Q000008:administration & dosage* / Q000235:genetics / Q000378:metabolism
D018797:Cell Cycle Proteins; C440808:PINX1 protein, human; D011993:Recombinant Fusion Proteins; D025521:Tumor Suppressor Proteins; D054322:tat Gene Products, Human Immunodeficiency Virus; D019098:Telomerase