A novel approach to detect resistance mechanisms reveals FGR as a factor mediating HDAC inhibitor SAHA resistance in B‐cell lymphoma

Abstract

Histone deacetylase (HDAC) inhibitors such as suberoylanilide hydroxamic acid (SAHA) are not commonly used in clinical practice for treatment of B‐cell lymphomas, although a subset of patients with refractory or relapsed B‐cell lymphoma achieved partial or complete remissions. Therefore, the purpose of this study was to identify molecular features that predict the response of B‐cell lymphomas to SAHA treatment. We designed an integrative approach combining drug efficacy testing with exome and captured target analysis (DETECT). In this study, we tested SAHA sensitivity in 26 B‐cell lymphoma cell lines and determined SAHA‐interacting proteins in SAHA resistant and sensitive cell lines employing a SAHA capture compound (CC) and mass spectrometry (CCMS). In addition, we performed exome mutation analysis. Candidate validation was done by expression analysis and knock‐out experiments. An integrated network analysis revealed that the Src tyrosine kinase Gardner‐Rasheed feline sarcoma viral (v‐fgr) oncogene homolog (FGR) is associated with SAHA resistance. FGR was specifically captured by the SAHA‐CC in resistant cells. In line with this observation, we found that FGR expression was significantly higher in SAHA resistant cell lines. As functional proof, CRISPR/Cas9 mediated FGR knock‐out in resistant cells increased SAHA sensitivity. In silico analysis of B‐cell lymphoma samples (n = 1200) showed a wide range of FGR expression indicating that FGR expression might help to stratify patients, which clinically benefit from SAHA therapy. In conclusion, our comprehensive analysis of SAHA‐interacting proteins highlights FGR as a factor involved in SAHA resistance in B‐cell lymphoma.

Keywords

• SAHA
• HDAC inhibitor
• FGR
• B-cell lymphoma
• Drug resistance