Targeting cancer cells and tumor microenvironment in preclinical and clinical models of Hodgkin lymphoma using the dual PI3K{delta}/{gamma} inhibitor RP6530

Purpose: Tumor-associated macrophages (TAMs) and the hyperactivation of phosphoinositide 3-kinase(PI3K)/AKT pathway are involved in the pathogenesis of Hodgkin lymphoma (HL) and affect disease outcome. Since the and isoforms of PI3K are overexpressed in Hodgkin/Reed-Sternberg (HRS) cells and the tumor microenvironment (TME), we propose that the PI3K/ inhibitor RP6530 might affect both HRS cells and TME, ultimately leading to an enhanced antitumor response. Experimental design: HL cell lines (L-540, KM-H2 and L-428) and primary human macrophages were used to investigate the activity of RP6530 in vitro and in vivo in HL cell line xenografts. Results: In vitro, RP6530 besides killing and inhibiting the proliferation of HL cells, downregulated lactic acid metabolism, switching the activation of macrophages from an immunosuppressive M2-like phenotype to a more inflammatory M1-like state. By RNA sequencing, we define tumor glycolysis as a specific PI3K/-dependent pathway implicated in the metabolic reprogramming of cancer cells. We identify the metabolic regulator Pyruvate Kinase M2 (PKM2) as the main mediator of tumor-induced immunosuppressive phenotype of macrophages. Furthermore, we show in human tumor xenografts that RP6530 repolarizes TAMs into pro-inflammatory macrophages and inhibits tumor vasculature, leading to tumor regression. Interestingly, HL patients experiencing objective responses (CR and PR) in a phase 1 trial using RP6530 showed a significant inhibition of circulating MDSCs and an average mean reduction in serum TARC levels of 40% (range, 4-76%). Conclusions: Our results support PI3K/ inhibition as a novel therapeutic strategy that targets both malignant cells and the TME to treat HL patients.

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