The Natural Estrogen Receptor Beta Agonist Silibinin as a Promising Therapeutic Tool in Diffuse Large B-cell Lymphoma.

BACKGROUND/AIM: About 40% of patients with diffuse large cell lymphoma (DLBCL) still have a poor prognosis. Additionally, DLBCL patients treated with doxorubicin are at risk of cardiac failure. Growing evidence suggests an antitumor and cardioprotective activity exerted by estrogen via its binding to estrogen receptor (ER) ß. The aim of this study was to evaluate the anticancer activity of the phytoestrogen silibinin, an ERß selective agonist, on DLBCL growth, and its potential cardioprotective effect. MATERIALS AND METHODS: DLBCL cell lines SUDHL-8, SUDHL-6, and RIVA were used. The anti-tumor activity of silibinin was also evaluated in vivo in NOD/SCID/IL2Rg-/- (NSG) xenografted mice. AC16 human ventricular cardiomyocytes were used to investigate the cardioprotective effects of silibinin. RESULTS: In vitro silibinin induced apoptosis and autophagy, and blocked tumor cell proliferation, also protecting AC16 cardiomyocytes from doxorubicin-induced toxicity. In vivo silibinin induced cell death and autophagy, and reduced tumor volume. CONCLUSION: Silibinin represents a promising therapeutic tool.

Targeting Cancer Cells and Tumor Microenvironment in Preclinical and Clinical Models of Hodgkin Lymphoma Using the Dual PI3Kδ/γ Inhibitor RP6530.

PURPOSE: Tumor-associated macrophages (TAMs) and the hyperactivation of the PI3K/AKT pathway are involved in the pathogenesis of Hodgkin lymphoma and affect disease outcome. Because the δ and γ isoforms of PI3K are overexpressed in Hodgkin/Reed-Sternberg (HRS) cells and the tumor microenvironment (TME), we propose that the PI3Kδ/γ inhibitor RP6530 might affect both HRS cells and TME, ultimately leading to an enhanced antitumor response. EXPERIMENTAL DESIGN: Hodgkin lymphoma 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 Hodgkin lymphoma cell line xenografts. RESULTS: In vitro, RP6530 besides killing and inhibiting the proliferation of Hodgkin lymphoma 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 PI3Kδ/γ-dependent pathway implicated in the metabolic reprogramming of cancer cells. We identify the metabolic regulator pyruvate kinase M2 as the main mediator of tumor-induced immunosuppressive phenotype of macrophages. Furthermore, we show in human tumor xenografts that RP6530 repolarizes TAMs into proinflammatory macrophages and inhibits tumor vasculature, leading to tumor regression. Interestingly, patients with Hodgkin lymphoma experiencing objective responses (complete response and partial response) in a phase I trial using RP6530 showed a significant inhibition of circulating myeloid-derived suppressor cells and an average mean reduction in serum thymus and activation-regulated chemokine levels of 40% (range, 4%-76%). CONCLUSIONS: Our results support PI3Kδ/γ inhibition as a novel therapeutic strategy that targets both malignant cells and the TME to treat patients with Hodgkin lymphoma.

Estrogen receptor ß ligation inhibits Hodgkin lymphoma growth by inducing autophagy.

Although Hodgkin lymphoma (HL) is curable with current therapy, at least 20% of patients relapse or fail to make complete remission. In addition, patients who achieve long-term disease-free survival frequently undergo infertility, secondary malignancies, and cardiac failure, which are related to chemotherapeutic agents and radiation therapies. Hence, new therapeutic strategies able to counteract the HL disease in this important patient population are still a matter of study. Estrogens, in particular 17ß-estradiol (E2), have been suggested to play a role in lymphoma cell homeostasis by estrogen receptors (ER) ß activation. On these bases, we investigated whether the ligation of ERß by a selective agonist, the 2,3-bis(4-hydroxyphenyl)-propionitrile (DPN), could impact HL tumor growth. We found that DPN-mediated ERß activation led to a reduction of in vitro cell proliferation and cell cycle progression by inducing autophagy. In nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice engrafted with HL cells, ERß activation by DPN was able to reduce lymphoma growth up to 60% and this associated with the induction of tumor cell autophagy. Molecular characterization of ERß-induced autophagy revealed an overexpression of damage-regulated autophagy modulator 2 (DRAM2) molecule, whose role in autophagy modulation is still debated. After ERß activation, both DRAM2 and protein 1 light chain 3 (LC3), a key actor in the autophagosome formation, strictly interacted each other and localized at mitochondrial level.Altogether these results suggest that targeting ERß with selective agonists might affect HL cell proliferation and tumor growth via a mechanism that brings into play DRAM2-dependent autophagic cascade.

Dual PI3K/ERK inhibition induces necroptotic cell death of Hodgkin Lymphoma cells through IER3 downregulation.

PI3K/AKT and RAF/MEK/ERK pathways are constitutively activated in Hodgkin lymphoma (HL) patients, thus representing attractive therapeutic targets. Here we report that the PI3K/ERK dual inhibitor AEZS-136 induced significant cell proliferation inhibition in L-540, SUP-HD1, KM-H2 and L-428 HL cell lines, but a significant increase in necroptotic cell death was observed only in two out of four cell lines (L-540 and SUP-HD1). In these cells, AEZS-136-induced necroptosis was associated with mitochondrial dysfunction and reactive oxygen species (ROS) production. JNK was activated by AEZS-136, and AEZS-136-induced necroptosis was blocked by the necroptosis inhibitor necrostatin-1 or the JNK inhibitor SP600125, suggesting that JNK activation is required to trigger necroptosis following dual PI3K/ERK inhibition. Gene expression analysis indicated that the effects of AEZS-136 were associated with the modulation of cell cycle and cell death pathways. In the cell death-resistant cell lines, AEZS-136 induced the expression of immediate early response 3 (IER3) both in vitro and in vivo. Silencing of IER3 restored sensitivity to AEZS-136-induced necroptosis. Furthermore, xenograft studies demonstrated a 70% inhibition of tumor growth and a 10-fold increase in tumor necrosis in AEZS-136-treated animals. Together, these data suggest that dual PI3K/ERK inhibition might be an effective approach for improving therapeutic outcomes in HL.