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Histone Deacetylase Sirtuin 1 Promotes Loss of Primary Cilia in Cholangiocarcinoma
Kishor Pant1, Estanislao Peixoto1, Seth Richard1
1The Hormel Institute, University of Minnesota, Austin, MN.
Background And Aims:
Sirtuin 1 (SIRT1) is a complex NAD+ -dependent protein deacetylase known to act as a tumor promoter or suppressor in different cancers. Here, we describe a mechanism of SIRT1-induced destabilization of primary cilia in cholangiocarcinoma (CCA).
Approach And Results:
A significant overexpression of SIRT1 was detected in human CCA specimens and CCA cells including HuCCT1, KMCH, and WITT1 as compared with normal cholangiocytes (H69 and NHC). Small interfering RNA (siRNA)-mediated knockdown of SIRT1 in HuCCT1 cells induced cilia formation, whereas overexpression of SIRT1 in normal cholangiocytes suppressed ciliary expression. Activity of SIRT1 was regulated by presence of NAD+ in CCA cells. Inhibition of NAD -producing enzyme nicotinamide phosphoribosyl transferase increased ciliary length and frequency in CCA cells and in SIRT1-overexpressed H69 cells. Furthermore, we also noted that SIRT1 induces the proteasomal mediated degradation of ciliary proteins, including α-tubulin, ARL13B, and KIF3A. Moreover, overexpression of SIRT1 in H69 and NHC cells significantly induced cell proliferation and, conversely, SIRT1 inhibition in HuCCT1 and KMCH cells using siRNA or sirtinol reduced cell proliferation. In an orthotopic transplantation rat CCA model, the SIRT1 inhibitor sirtinol reduced tumor size and tumorigenic proteins (glioma-associated oncogene 1, phosphorylated extracellular signal-regulated kinase, and IL-6) expression.
Conclusions:
In conclusion, these results reveal the tumorigenic role of SIRT1 through modulation of primary cilia formation and provide the rationale for developing therapeutic approaches for CCA using SIRT1 as a target.
Insights
Sirtuin 1 (SIRT1) promotes cholangiocarcinoma (CCA) by destabilizing primary cilia. Inhibiting SIRT1 reduces tumor growth and proliferation, offering a potential therapeutic strategy for CCA.
Area of Science:
- Oncology
- Molecular Biology
- Cell Biology
Background:
- Sirtuin 1 (SIRT1) is an NAD+-dependent deacetylase with dual roles in cancer.
- Primary cilia are crucial cellular antennae involved in signaling pathways.
- Cholangiocarcinoma (CCA) is a challenging cancer with limited therapeutic options.
Purpose of the Study:
- To elucidate the mechanism of SIRT1's role in CCA.
- To investigate the impact of SIRT1 on primary cilia in CCA.
- To evaluate SIRT1 as a potential therapeutic target for CCA.
Main Methods:
- Assessed SIRT1 expression in human CCA tissues and cell lines.
- Utilized siRNA-mediated SIRT1 knockdown and overexpression.
- Measured primary cilia length and frequency.
- Investigated proteasomal degradation of ciliary proteins.
- Evaluated cell proliferation in vitro and tumor growth in an in vivo rat model.
- Administered SIRT1 inhibitor sirtinol.
Main Results:
- SIRT1 is significantly overexpressed in CCA.
- SIRT1 knockdown promotes cilia formation; SIRT1 overexpression suppresses it.
- SIRT1 induces proteasomal degradation of key ciliary proteins (α-tubulin, ARL13B, KIF3A).
- SIRT1 overexpression enhances cell proliferation; SIRT1 inhibition reduces it.
- Sirtinol treatment decreased tumor size and tumorigenic markers in vivo.
Conclusions:
- SIRT1 acts as a tumor promoter in CCA by destabilizing primary cilia.
- Modulation of primary cilia by SIRT1 is a key mechanism in CCA pathogenesis.
- Targeting SIRT1 represents a promising therapeutic strategy for cholangiocarcinoma.
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