Upregulation of ERK-EGR1-heparanase axis by HDAC inhibitors provides targets for rational therapeutic intervention in synovial sarcoma

Abstract

Background Synovial sarcoma (SS) is an aggressive soft tissue tumor with limited therapeutic options in advanced stage. SS18-SSX fusion oncogenes, which are the hallmarks of SS, cause epigenetic rewiring involving histone deacetylases (HDACs). Promising preclinical studies supporting HDAC targeting for SS treatment were not reflected in clinical trials with HDAC inhibitor (HDACi) monotherapies. We investigated pathways implicated in SS cell response to HDACi to identify vulnerabilities exploitable in combination treatments and improve the therapeutic efficacy of HDACi-based regimens. Methods Antiproliferative and proapoptotic effects of the HDACi SAHA and FK228 were examined in SS cell lines in parallel with biochemical and molecular analyses to bring out cytoprotective pathways. Treatments combining HDACi with drugs targeting HDACi-activated prosurvival pathways were tested in functional assays in vitro and in a SS orthotopic xenograft model. Molecular mechanisms underlying synergisms were investigated in SS cells through pharmacological and gene silencing approaches and validated by qRT-PCR and Western blotting. Results SS cell response to HDACi was consistently characterized by activation of a cytoprotective and auto-sustaining axis involving ERKs, EGR1, and the β-endoglycosidase heparanase, a well recognized pleiotropic player in tumorigenesis and disease progression. HDAC inhibition was shown to upregulate heparanase by inducing expression of the positive regulator EGR1 and by hampering negative regulation by p53 through its acetylation. Interception of HDACi-induced ERK-EGR1-heparanase pathway by cell co-treatment with a MEK inhibitor (trametinib) or a heparanase inhibitor (SST0001/roneparstat) enhanced antiproliferative and pro-apoptotic effects. HDAC and heparanase inhibitors had opposite effects on histone acetylation and nuclear heparanase levels. The combination of SAHA with SST0001 prevented the upregulation of ERK-EGR1-heparanase induced by the HDACi and promoted caspase-dependent cell death. In vivo, the combined treatment with SAHA and SST0001 potentiated the antitumor efficacy against the CME-1 orthotopic SS model as compared to single agent administration. Conclusions The present study provides preclinical rationale and mechanistic insights into drug combinatory strategies based on the use of ERK pathway and heparanase inhibitors to improve the efficacy of HDACi-based antitumor therapies in SS. The involvement of classes of agents already clinically available, or under clinical evaluation, indicates the transferability potential of the proposed approaches.

Potential roles of heparanase in cancer therapy: Current trends and future direction

“…Intriguingly, elimination or inhibition of p53 in several cell types resulted in a significant increase in HPSE expression and enzyme activity (Baraz et al, 2006). Inhibition of histone deacetylases (HDACs) has been shown to enhance proproliferative and antiapoptotic effects by hindering the negative regulation of acetylation of p53 to increase HPSE (Lanzi et al, 2021; Figure 4).…”

“…Notably, elevated HPSE expression has been associated with poor clinical prognosis in cancer patients (Barash et al, 2018; Sun et al, 2017), thus critically supporting the intimate involvement of heparinase in tumor progression. Furthermore, in animal studies, deletion of HPSE by gene silencing or specific inhibitors significantly attenuated tumor growth and dissection (Lanzi et al, 2021; W. Q. Tang & Lin, 2022). For instance, adjuvant HPSE‐1 inhibitor PI‐88 treatment confers significant clinical benefits in patients with hepatocellular carcinoma (C. J. Liu, 2014).…”

“…Furthermore, in animal studies, deletion of HPSE by gene silencing or specific inhibitors significantly attenuated tumor growth and dissection (Lanzi et al, 2021; W. Q. Tang & Lin, 2022).…”

Drug Targeting of Chromosomal Translocations in Fusion-Positive Sarcoma

“…On the other hand, the PAX3-FOXO1 fusion oncogene of alveolar rhabdomyosarcoma recruits master transcription factors MYOG, MYOD, and MYCN to activated gene loci and alters their histone acetylation which enables binding and manipulation of reader proteins such as BRD4 [55]. In synovial sarcomas, SS18-SSX fusion oncogenes, cause epigenetic restructuring involving HDACs [127]. Conversely, EWSR1-FLI1 translocation recruits histone deacetylases and histone demethylase LSD1 to specific gene loci through direct interaction with the NuRD complex, thereby suppressing their expression in Ewing sarcoma [39].…”

“…In the mouse model, combined treatment with SAHA and SST0001 enhanced the antitumor effect compared with single-agent administration. [127]. Thus, it seems very reasonable to advance mediators of epigenetic processes as treatment targets for FP sarcomas.…”