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PLEKHG5 stabilized by HDAC2-related deacetylation is the master regulator of sorafenib resistance in HCC

ABSTRACT: Objective: Advanced HCC patients have few choices for life-prolonging therapy due to the high incidence of drug resistance. This study aimed to clarify the mechanism of sorafenib resistance and seek more effective treatments.Design:Two sorafenib-resistant (SR) cell lines were established to study the mechanism of drug resistance. RNA sequencing was used to characterize the global transcriptional consequences of sorafenib resistance, and immunoprecipitation-mass spectrometry (IP-MS) was performed to identify specific acetylation sites.Results： We found that Rho-GTPases were upregulated in SR cells and that PLEKHG5 was most abundantly expressed among all Rho GEFs (activators of Rho-GTPases). PLEKHG5 knockdown increased HCC cell sensitivity to sorafenib and inhibited the activation of Rac1 and downstream AKT/NF-κB signaling, while overexpression of PLEKHG5 reduced sorafenib sensitivity, which suggested that PLEKHG5 activation could be targeted to limit sorafenib resistance. IP-MS confirmed that three lysine sites in PH domain of PLEKHG5 could be acetylated, and their acetylation levels were correlated with PLEKHG5 stability. Further study demonstrated that HDAC2 interacted with PLEKHG5 to deacetylate lysine sites within the PH domain and maintain its stability. Finally, both knockout of HDAC2 and treatment with the selective HDAC2 inhibitor CAY10683 reduced PLEKHG5 protein levels and thereby enhanced the sensitivity of HCC to sorafenib in vivo and in vitro.Conclusion.:PLEKHG5 plays a key role in the occurrence of sorafenib resistance by activating Rac1/AKT/NF-κB signaling. HDAC2 regulates PLEKHG5 protein stability by regulating the acetylation level of its PH domain, and thus HDAC2 may be a potential therapeutic target for overcoming PLEKHG5-mediated sorafenib resistance in HCC.

ORGANISM(S): Homo sapiens

PROVIDER: GSE176151 | GEO | 2021/06/05

REPOSITORIES: GEO

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Project description:OBJECTIVE: Sorafenib is effective in hepatocellular carcinoma (HCC), but patients ultimately present disease progression. Molecular mechanisms underlying acquired resistance are still unknown. Herein, we characterize the role of tumor-initiating cells (T-ICs) and signaling pathways involved in sorafenib resistance. DESIGN: HCC xenograft mice treated with sorafenib (n=22) were explored for responsiveness (n=5) and acquired resistance (n=17). Mechanism of acquired resistance were assessed by: 1) Role of T-ICs by in vitro sphere formation and in vivo tumorigenesis assays using NOD/SCID mice, 2) Activation of alternative signaling pathways and 3) Efficacy of anti-FGF and anti-IGF drugs in experimental models. Gene expression (microarray, qRT-PCR) and protein analyses (immunohistochemistry, western blot) were conducted. A novel gene signature of sorafenib resistance was generated and tested in 2 independent cohorts. RESULTS: Sorafenib-acquired resistance tumors showed significant enrichment of T-ICs (164 cells needed to create a tumor) vs. sorafenib-sensitive tumors (13400 cells) and non-treated tumors (1292 cells), p<0.001. Tumors with sorafenib-acquired resistance were enriched with IGF and FGF signaling cascades (FDR<0.05). In vitro, cells derived from sorafenib-acquired resistant tumors and two sorafenib-resistant HCC cell lines were responsive to IGF or FGF inhibition. In vivo, FGF blockade delayed tumor growth and improved survival in sorafenib-resistant tumors. A sorafenib-resistance 175-gene signature was characterized by enrichment of progenitor-cell features, aggressive tumoral traits and predicted poor survival in 2 cohorts (n=442 HCC patients). CONCLUSION: Acquired resistance to sorafenib is driven by tumor initiating cells with enrichment of progenitor markers and activation of IGF and FGF signaling. Inhibition of these pathways would benefit a subset of patients after sorafenib progression. Transcriptomic profile of subcutaneous Huh7 cells-derived tumors treated with sorafenib that developed acquired resistance to the drug (n=4), remain responsive to sorafenib (n=3) or were treated with brivanib after development of resistance (n=3). Gene profiling of hepatospheres generated from tumors with acquired resistance to sorafenib (n=3) and non-treated tumors (n=3) was also analyzed.

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PLEKHG5 stabilized by HDAC2-related deacetylation is the master regulator of sorafenib resistance in HCC

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