Abstract 3289: Microenvironment modulation and enhancement of cytotoxic therapy by the heparanase inhibitor Roneparstat against human B-non Hodgkin lymphomas

Background: The standard chemotherapy treatment for Non-Hodgkin lymphoma (NHL) consists in the combination of cyclophosphamide, doxorubicin, vincristine and prednisone (CHOP). Because of the relevant treatment-related toxicity and the minor therapeutic effectiveness of CHOP therapy variants, the development of novel therapeutic approaches represents an urgent clinical need. Despite treatment with the anti-CD20 monoclonal antibody Rituximab and CHOP has led to favourable results for CD20+ lymphoma, many patients experienced drug resistance. Based on studies indicating that the malignant behaviour of tumors depends on the interactions between tumor and its microenvironment, we tested the effect of the novel heparanase inhibitor Roneparstat (sigma-tau Research Switzerland) in combination with various clinically relevant agents against B-cell lymphoma models, poorly responsive to conventional agents. Methods: We assessed the CD20 cell surface expression by flow cytometry, the heparanase (HPA-1) expression levels by immunoblotting, the VEGF spontaneous release in cell supernatant by proteome array in B-NHL models. The therapeutic activity was evaluated in SCID mice xenografted with CD20+ and VEGF+ B-NHL models. The efficacy of the drug treatment was estimated as tumor volume inhibition percentage (TVI%), log10 cell kill (LCK) and complete regression (CR). To gain insight the mechanisms underlying the anti-tumor activity of Roneparstat plus rituximab histopathological/immunoistochemical analyses were performed on treated tumors versus controls. Results: In a model of aggressive diffuse large B-cell NHL, except for doxorubicin, the combinations cyclophosphamide, dexamethasone and rituximab exhibited significantly superior efficacy over single-agent therapy. The most impressive enhancement of anti-tumor activity was observed with Roneparstat plus rituximab, with a high rate of complete tumor regressions and no evidence of disease at the end of the experiment in 50% of treated animals. Histological analysis revealed inflammatory cell infiltration, stromal destructuration, most pronounced apoptotic changes in Roneparstat plus rituximab-treated tumors versus controls; stromal architecture analysis showed signs of an altered, incomplete reticulin network suggestive of impaired stromal scaffolding that might have promoted the recruitment of complement components (C1q, C5) within tumors increasing the cytotoxic effect of rituximab. This interpretation was also supported