Use of in vitro Primary Culture Models to investigate the activity of Standard and Novel Therapies in Haematological Malignancies

Abstract

Despite improved treatments for Non-Hodgkin’s Lymphoma (NHL) and Multiple Myeloma (MM), most patients eventually relapse and these diseases remain largely incurable. This has precipitated recent research into more clinically relevant in vitro models to enable development of more effective therapies. We have validated and standardised two in vitro primary culture models using tumour samples derived from patients with NHL, Chronic Lymphocytic Leukaemia (CLL) and MM. Several novel findings have been demonstrated. In vitro sensitivity of primary NHL cells cocultured in a CD40L model predicted clinical response to bortezomib in patients receiving the drug in a phase II trial. In vitro sensitivity correlated with CD40 expression, identifying a potential surrogate biomarker for response to bortezomib. The novel HDAC inhibitor, UCL67022 was 10-fold more potent than vorinostat in NHL and produced synergy when combined with bortezomib. UCL67022 maintained its potency in primary MM samples grown in an HS-5 stromal model. It modulated cytokine secretion resulting in downregulation of cytokine-induced signalling pathways (JAK/STAT3). A novel Hsp90 inhibitor, KW-2478 maintained activity in the HS-5 model and enhanced the activity of bortezomib and melphalan. Hsp70 was identified as a potential surrogate biomarker to monitor the combinatorial effect in future clinical trials. A highly synergistic and schedule-dependent cytotoxic effect occurred when primary MM cells were pre-treated with melphalan followed by bortezomib, with important implications for future clinical trial design. IL-6, IL-8 and VEGF levels correlated with resistance to bortezomib and melphalan and were associated with activation of JAK/STAT, MAPK and PI3K/Akt signalling pathways. Antibody neutralization of IL-6, IL-8 and VEGF resulted in restoration of drug sensitivity. We have therefore demonstrated the ability of primary culture models to predict response to chemotherapy, to identify therapeutically beneficial novel agents and to enable study of tumour microenvironmental interactions responsible for drug resistance in patients with haematological malignancies.