Fig S1: Ibrutinib induces apoptosis and inhibits proliferation of Mino and Rec-1 cells but the effect is impaired by stromal cells. Fig S2: Stromal cells confer ibrutinib resistance by a tumor cell non-autonomous mechanism. Fig S3: Disrupting MCL cell interaction with stromal cells by blocking the adhesion molecule VLA4 overcomes ibrutinib resistance in vitro. Fig S4: Attachment to stromal cells supports MCL cell regrowth after ibrutinib removal. Fig S5: Stromal cells do not influence ibrutinib-mediated down-regulation of NF-κB target genes but impair ibrutinib-mediated down-regulation of pAKT signaling. Fig S6: p110α inhibition overcomes stromal cell-mediated ibrutinib resistance by restoring the ability of ibrutinib to down-regulate pAKT levels. Fig S7: Effects of ibrutinib or BYL719 on mice weight and expression of NF-kB target genes in the MCL tumors. Fig S8: p110α inhibitor BYL719 or ibrutinib do not induce MS-5 stromal cell apoptosis.

Supplementary Table S1 showing QPCR primers used in the study

Supplementary Materials and Methods

Mantle cell lymphoma (MCL) is a non-Hodgkin lymphoma with one of the highest male-to-female incidence ratios. The reason for this is not clear, but epidemiological as well as experimental data have suggested a role for estrogens, particularly acting through estrogen receptor β (ESR2). To study the ESR2 effects on MCL progression, MCL cells sensitive and resistant to the Bruton tyrosine kinase inhibitor ibrutinib were grafted to mice and treated with the ESR2-selective agonist diarylpropionitrile (DPN). The results showed that the DPN treatment of mice grafted with both ibrutinib-sensitive and -resistant MCL tumors resulted in impaired tumor progression. To identify the signaling pathways involved in the impaired tumor progression following ESR2 agonist treatment, the transcriptome and ESR2 binding to target genes were investigated by genome-wide chromatin immunoprecipitation in Granta-519 MCL tumors. DPN-regulated genes were enriched in several biological processes that included cell–cell adhesion, endothelial–mesenchymal transition, nuclear factor-kappaB signaling, vasculogenesis, lymphocyte proliferation, and apoptosis. In addition, downregulation of individual genes, such as SOX11 and MALAT1, that play a role in MCL progression was also observed. Furthermore, the data suggested an interplay between the lymphoma cells and the tumor microenvironment in response to the ESR2 agonist. In conclusion, the results clarify the mechanisms by which estrogens, via ESR2, impair MCL tumor progression and provide a possible explanation for the sex-dependent difference in incidence. Furthermore, targeting ESR2 with a selective agonist may be an additional option when considering the treatment of both ibrutinib-sensitive and -resistant MCL tumors.

The cellular and molecular mechanisms of immunomodulatory actions of glucocorticoids (GC) remain to be identified. Using our experimental findings, a mathematical model based on a system of ordinary differential equations for characterization of the regulation of anti-tumor immune activity by the both direct and indirect GC effects was generated to study the effects of GC treatment on effector CD8+ T cells, GC-generated tolerogenic dendritic cells (DC), regulatory T cells and the growth of lymphoma cells. In addition, we compared the data from in vivo and in silico experiments. The mathematical simulations indicated that treatment with GCs may suppress anti-tumor immune response in a dose-dependent manner. The model simulations were in line with earlier experimental observations of inhibitory effects of GCs on T and NK cells and DCs. The results of this study might be useful for predicting clinical outcomes in patients receiving GC therapy.

Abstract Acquired resistance to cancer drugs is common, also for modern targeted drugs like the Bruton tyrosine kinase (BTK) inhibitor ibrutinib, a new drug approved for the treatment of the highly aggressive and relapsing mantle cell lymphoma (MCL). The tumor microenvironment often impacts negatively on drug response. Here, we demonstrate that stromal cells protect MCL cells from ibrutinib-induced apoptosis and support MCL cell regrowth after drug removal by impairing ibrutinib-mediated downregulation of PI3K/AKT signaling. Importantly, the stromal cell–mediated ibrutinib resistance was overcome in vitro by inhibiting AKT activity using the PI3K catalytic p110α subunit–specific inhibitor BYL719. This was seen both for MCL cell lines and primary MCL cells. Furthermore, inhibition of p110α activity by BYL719 potentiated the ability of ibrutinib to inhibit MCL tumor growth in vivo in a mouse xenograft model. The stromal cell–mediated ibrutinib resistance was found to be due to a direct interaction with MCL cells and involves the integrin VLA-4, as disrupting stromal cell–MCL cell interaction using a VLA-4 blocking antibody abrogated the ibrutinib resistance. This suggests that combined treatment with ibrutinib and a p110α inhibitor, alternatively by disrupting stromal cell–MCL cell interaction, may be a promising therapeutic strategy to overcome stromal cell–mediated ibrutinib resistance in MCL. Mol Cancer Ther; 17(5); 1090–100. ©2018 AACR.

Background/Aim: Recent epidemiological data indicate that lymphoid tumors may be influenced by estrogens. The effects of estrogens are mediated via nuclear estrogen receptors alpha (ER alpha) and beta (ER beta). This study investigated the potential functions of ligand-activated ERs in chronic lymphocytic leukemia (CLL). Materials and Methods: The ER mRNA expression in B lymphocytes isolated from patients with CLL was analyzed by quantitative real-time polymerase chain reaction. To evaluate the effects of ER beta signaling, primary CLL cells and CLL-derived MEC1 cells were treated with selective ER beta agonists. Results: The mRNA expression of ER alpha, ER beta 1 and its splice variant ER beta 2 was detected in CLL cells. Selective ER beta agonist 2,3-bis(4-hydroxy-phenyl)-propionitrile induced apoptosis in primary CLL cells and suppressed the growth of CLL-derived MEC1 cells. Conclusion: A suppressive effect of ER beta agonists on the growth of ER beta-expressing CLL cells was found, indicating that ER beta may be considered as a potential therapeutic target in CLL.

Glucocorticoids (GCs) act via the intracellular glucocorticoid receptor (GR), which can regulate the expression of target genes. With regard to the immune system, GCs may affect both innate and adaptive immunity. Our study analyzed the immunoregulatory effects of dexamethasone (Dex) treatment on splenic T, Treg, NK and NKT cells by treating C57Bl6 mice with various doses of Dex. We observed that treatment with Dex decreased the number of NK cells in the spleen and suppressed their activity. In particular, the expression of both Ly49G and NKG2D receptors was decreased by Dex. However, Dex did not affect the population of NKT cells. With regard to splenic T cells, our results show a dose-dependent reduction in CD3+, CD4+, CD8+, CD44+ and CD8+CD122+ T cells, but a stimulatory effect on CD4+CD25+ regulatory T cells by Dex treatment. In addition, treatment with Dex suppressed anti-tumor immune response in a mouse EG7 tumor model. We conclude that Dex may suppress both T- and NK-mediated immunity.

Well-defined physiological functions of estrogens are mediated via nuclear estrogen receptors α (ESR1) and β (ESR2). With regard to hematological malignancies, expression of ESR2 has been found in both B and T cell lymphomas. In addition to endogenous estrogens or selective ESR2 agonists, ESR2 signaling may be affected by both environmental synthetic estrogen-mimicking compounds and dietary phytoestrogens. In the present study, we demonstrate that oral exposure with either the synthetic compound bisphenol A (BPA) or the dietary phytoestrogen genistein reduced the growth of grafted murine T cell (EG7) and human B cell (Granta-519 mantle cell) lymphomas which both express ESR2. Suppression of lymphoma growth was due to reduced proliferation (BPA and genistein) and induction of apoptosis (genistein). Inhibition of lymphoma growth was seen at a BPA dose of 50 µg/kg body weight (BW)/day considered to be safe human exposure dose or a genistein dose of 1 mg/kg BW/day orally, which is reached in soy-rich diets. Thus, our study indicates that the environmental xenoestrogens BPA and genistein have anti-proliferative effects on ESR2-expressing lymphomas. Our data suggest that phytoestrogens may be considered as a dietary supplement for lymphoma patients and possibly for prevention of lymphoid malignancies.

Immunosuppressive functions of glucocorticoids (GC) can be mediated via various mechanisms, including the modulation of dendritic cells (DC). Our study investigates the effects of tolerogenic GC-treated DCs on NK and T cell anti-tumor responses in OT-1/Rag-/- mice, expressing a transgenic TCR in CD8+ T cells. The effects caused by GC-treated DCs were compared to the responses to immunogenic, CpG-activated DCs. The effects of DCs on anti-tumor immune responses were analyzed using the EG7 tumor model, where the tumor cells express the peptide epitope recognized by OT-1 T cells. We observed that immunization with CpG and peptide-treated DCs protected against tumor growth by activation of NK cell response. Also, immunogenic DCs induced the expansion of cytotoxic CD8+OT-1 cells, expressing activation markers CD44 and CD69 and producing IFNγ. In contrast, the peptide and GC-treated DCs in OT-1 mice increased the numbers of immature Mac-1+CD27- NK cells as well as Foxp3+ and IL-10 secreting CD8+OT-1 cells with suppressive properties. We conclude that the generation of tolerogenic DCs is one of many immunosuppressive mechanisms that can be induced by GC. Our study demonstrated that tolerogenic DCs modify anti-tumor immune response by suppressing NK cell activity and stimulating the formation of IL-10-secreting CD8+ Tregs.

Diffuse large B-cell lymphoma (DLBCL) shows a higher incidence in males versus females. Epidemiological studies have shown that female gender is a favorable prognostic factor, which may be explained by estrogens. Here we show that when grafting human DLBCL cells to immunocompromised mice, tumor growth in males is faster. When treating mice grafted with either germinal center or activated B-cell like DLBCL cells with the selective estrogen receptor beta (ER beta) agonist diarylpropionitrile, tumor growth was significantly inhibited. Furthermore, nuclear ER beta 1 expression analysis in primary DLBCL's by immunohistochemistry revealed expression in 89% of the cases. Nuclear ERb1 expression was in a univariate and multivariate analysis, an independent prognostic factor for adverse progression-free survival in Rituximab-chemotherapy treated DLBCL (p = 0.02 and p = 0.04, respectively). These results suggest that estrogen signaling through ERb1 is an interesting future therapeutic target for treatment of DLBCL, and that ERb1 expression can be used as a prognostic marker.

Most lymphomas show higher incidence and poorer prognosis in males compared to females. However, the endocrine contribution to this gender difference is not entirely known. Here we show that castration accelerates lymphoma growth in C57BL6 male mice grafted with murine EG7 T cell lymphoma cells. However, the androgen receptor antagonist Bicalutamide did not affect lymphoma growth, suggesting no impact of androgen receptor signaling on lymphoma progression. In contrast, inhibition of androgen-to-estrogen conversion by the aromatase inhibitor (AI) Letrozole induced faster lymphoma growth in mice, suggesting that androgens impact lymphoma growth through its conversion to estrogens. This was supported by the inability of dihydrotestosterone, which is not converted to estrogens by aromatase, to influence lymphoma growth in castrated male mice. Lymphoma growth was also stimulated in immunocompromised mice grafted with human B cell lymphoma (Granta-519) and treated with either reversible or irreversible AIs, showing that the blockage of estrogen synthesis caused enhanced growth of both murine T and human B cell lymphomas and with different AIs. Additionally, AI-treated EG7 lymphomas showed accelerated growth not only in male but also in intact female mice. Altogether, our results demonstrate that aromatase inhibition accelerates lymphoma growth but not androgens per se, highlighting a protective role of estrogens in lymphoma pathogenesis. These results also raise concern that the use of AIs in women with breast cancer might enhance lymphoma progression.

Glucocorticoids (GCs) strongly impact on different T cell subsets inducing generally immunosuppressive effects, whereas much less is known about the effect of GC on natural killer (NK) cells. The aims of this study were to investigate the effects of GC on T cell functions, including T cell-mediated anti-tumor immune response, and on NK cells. We have used lck-GR mice, which overexpress a transgenic rat GR in both T and NK cells. These mice were found to have decreased both CD4(+) and CD8(+) T cell populations in the periphery. In contrast, both NK and NKT cells were found in normal numbers in lck-GR mice. To identify genes and pathways affected by GR overexpression in our system in T cells, we have compared gene expression profiles in wild-type and lck-GR T cells. Among the genes upregulated in T cells from lck-GR mice, the microarray analysis has identified genes regulating expansion of regulatory T cells. The analysis of genes downregulated in lck-GR mice has identified genes and gene associated with the regulation of immune response. With regard to the effects on T cell functions in lck-GR mice, transgenic expression of GR had a suppressive effect on killer cell activity in vitro. In addition, lck-GR mice showed an increased tumor growth in murine tumor model in vivo, which may be a possible consequence of reduced T cell numbers and activity. We conclude that an increased expression of the GR strongly affects numbers and possibly functions of T cell subsets, but has little effect on NK cells.

Most lymphomas show an increased incidence and poorer prognosis in males vs females, suggesting endocrine regulation. We have previously shown that tumor growth in vivo of a murine T-cell-derived lymphoma is repressed following activation of estrogen receptor β (ERβ, ESR2). By using ERβ-deficient mice, we now demonstrate that this inhibition is mediated via a direct effect on the tumor cells and not on the microenvironment. Furthermore, we show that the growth-suppressing effects of ERβ agonist are also valid for human B-cell lymphomas as demonstrated in tumors derived from Granta-519 mantle cell lymphoma (MCL) and Raji Burkitt lymphoma (BL) cells. In Granta-519 MCL tumors, activation of ERβ reduced expression of BAFF and GRB7, 2 important molecules involved in B-cell proliferation and survival. Importantly, activation of ERβ inhibited angiogenesis and lymphangiogenesis, possibly mediated by impaired vascular endothelial growth factor C expression. Furthermore, using disseminating Raji BL cells, we show that ERβ activation reduces dissemination of grafted Raji BL tumors. We also show by immunohistochemistry that ERβ is expressed in primary MCL tissue. These results suggest that targeting ERβ with agonists may be valuable in the treatment of some lymphomas, affecting several aspects of the malignant process, including proliferation, vascularization, and dissemination.