Comparison of Radiosensitization by HDAC Inhibitors CUDC-101 and SAHA in Pancreatic Cancer Cells

Simone Moertl,Sarah Payer,Rosemarie Kell,Natasa Anastasov,Michael J Atkinson,Klaudia Winkler

doi:10.3390/ijms20133259

Simone Moertl, Sarah Payer + Show 4 more

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https://doi.org/10.3390/ijms20133259

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Abstract

Pancreatic cancer has a poor prognosis. New treatment options are urgently required to improve patient outcomes. One promising new class of anticancer drugs are synthetic histone deacetylase inhibitors (HDACi) which modulate chromatin structure and gene expression by blocking histone deacetylation. In this study, we aimed at comparing the in vitro capacities of the HDACi SAHA and CUDC-101 to increase radiosensitivity of human pancreatic tumor cell lines. Therefore, three pancreatic cancer cell lines (Su.86.86, MIA Paca-2, T3M-4) were treated with SAHA (1.5–5 µM) or CUDC-101 (0.25–3 µM) and after 24 h irradiated. Cell proliferation, clonogenic survival and apoptosis was determined. Additionally, cell lysates were investigated for the expression of apoptosis-related proteins. CUDC-101 and SAHA increased the radiation sensitivity of pancreatic tumor cell lines in a dose-dependent manner. This was evidenced by cell proliferation and clonogenic survival. Furthermore, enhanced radiation sensitivity after CUDC-101 or SAHA treatment was confirmed for Su.86.86 and T3M-4 cells in a 3-D microtissue approach. Increased amounts of subG1 cells and diminished full length PARP-1 suggest increased radiation-induced apoptosis after SAHA or CUDC-101 treatment. The comparison of both inhibitors in these assays manifested CUDC-101 as more potent radiosensitizer than SAHA. In line, western blot quantification of the apoptosis-inhibitory proteins XIAP and survivin showed a stronger down-regulation in response to CUDC-101 treatment than after SAHA application. These proteins may contribute to the synergy between HDAC inhibition and radiation response. In conclusion, these preclinical results suggest that treatment with the HDAC inhibitors CUDC-101 or SAHA can enhance radiation-induced cytotoxicity in human pancreatic cells. However, comparison of both inhibitors identified the multi target inhibitor CUDC-101 as more potent radiosensitizer than the HDAC inhibitor SAHA.

Highlights

Pancreatic cancer is one of the most lethal cancers worldwide with a 5-year survival rate under 5% and a median survival of 8–12 months [1,2]
Previous studies have shown that XIAP and survivin were overexpressed in pancreatic cancer and were closely associated with cell proliferation and chemoresistance to the standard chemotherapeutic gemcitabine [34]. They are both acknowledged as radioresistance factor with potential as a predictive molecular marker for metastases and cancer patient survival following radiation therapy [35,36]. According to these findings we suggest that CUDC-101 or SAHA trigger a reduction of the antiapoptotic proteins XIAP and survivin which leads to increased radiation sensitivity through enhanced apoptosis
As survivin expression is lower after CUDC-101 than after SAHA treatment while p53 is similar after both inhibitors we suggest further regulatory mechanisms after CUDC-101 treatment (Figure 6 and Figure S2B)

Summary

Introduction

Pancreatic cancer is one of the most lethal cancers worldwide with a 5-year survival rate under 5% and a median survival of 8–12 months [1,2]. Since pancreatic cancer frequently develops therapy resistance, new agents and treatment modalities that increase tumor sensitivity and overcome drug resistance are needed [4]. Histone deacetylase inhibitors (HDACi) are anti-cancer drugs targeting protein acetylation [5,6]. HDACs can regulate the activity and metabolism of other proteins and substrates, to further broaden their biological impact [7,8]. By these means, HDAC inhibitors exert multiple cellular effects including cell cycle arrest, DNA repair, proliferation, autophagy, reactive oxygen species generation, apoptosis and angiogenesis [6]

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