Reduction of TSG101 protein has a negative impact on tumor cell growth.
TSG101 was defined originally as a tumor-suppressor gene, raising the expectation that absence of the encoded protein should lead to increased tumor cell growth and, perhaps, increased tumor cell aggressiveness. We have used the RNA interference (RNAi) technique to downregulate TSG101 in PC3 (prostate cancer) and MDA-MB-231 (breast cancer) cells. An approximately 85% selective downregulation at the protein level was achieved in both cell lines over a period of 12 days as detected by Western blotting. This treatment resulted in inhibition of tumor cell growth, with a decreased level of TSG101 causing partial cell cycle arrest at the G(1)/S boundary and a reduction in the rate at which cells passed from G(2) through mitosis and back into G(1). In both cell lines, the percentage of cells in S-phase was reduced significantly at day 4 after the TSG101 siRNA transfection (27% vs. 41% in MDA-MB-231 cells; 22% vs. 39% in PC3 cells). Additionally, RNAi-mediated downregulation of TSG101 reduced the colony formation capacities of both cancer cell lines. Rather more surprisingly, TSG101 downregulation affected the migratory activity of the MDA-MB-231 cells, independent of any effect on proliferation. Thus, in a Transwell assay, after 4-hr incubation, 36.0% of control MDA-MB-231 cells had migrated to the lower chamber vs. 7.3% of TSG101-downregulated cells (p < 0.001; scrambled control, 36.5%). These results show that the TSG101 gene does not comply with the usual characteristics of a tumor-suppressor gene; rather, its expression may be necessary for activities associated with aspects of tumor progression.
Richard Dimbleby Department of Cancer Research/Cancer Research U.K. Laboratory, GKT School of Medicine, St. Thomas' Hospital, London, United Kingdom.
Gang
G
Zhu
Ruth
R
Gilchrist
Nigel
N
Borley
Hsiao Wee
HW
Chng
Mark
M
Morgan
John F
JF
Marshall
Richard S
RS
Camplejohn
Gordon H
GH
Muir
Ian R
IR
Hart
D017209:Apoptosis / Q000502:physiology*; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism*; D002453:Cell Cycle / Q000502:physiology*; D002465:Cell Movement / Q000502:physiology; D003114:Colony-Forming Units Assay; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation; D056827:Endosomal Sorting Complexes Required for Transport; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D016350:Leucine Zippers; D008297:Male; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000494:pharmacology; D016160:Retinoblastoma Protein / Q000378:metabolism; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D000099177:Tsg101 Protein
D004268:DNA-Binding Proteins; D056827:Endosomal Sorting Complexes Required for Transport; D034741:RNA, Small Interfering; D016160:Retinoblastoma Protein; D014157:Transcription Factors; D000099177:Tsg101 Protein