Dai Liu

Regression of established hepatocellular carcinoma is induced by chemoimmunotherapy in an orthotopic murine model.

The high rate of mortality and frequent incidence of recurrence associated with hepatocellular carcinoma (HCC) reveal the need for new therapeutic approaches. In this study we evaluated the efficacy of a novel chemoimmunotherapeutic strategy to control HCC and investigated the underlying mechanism that increased the antitumor immune response. We developed a novel orthotopic mouse model of HCC through seeding of tumorigenic hepatocytes from SV40 T antigen (Tag) transgenic MTD2 mice into the livers of syngeneic C57BL/6 mice. These MTD2‐derived hepatocytes form Tag‐expressing HCC tumors specifically within the liver. This approach provides a platform to test therapeutic strategies and antigen‐specific immune‐directed therapy in an immunocompetent murine model. Using this model we tested the efficacy of a combination of oral sunitinib, a small molecule multitargeted receptor tyrosine kinase (RTK) inhibitor, and adoptive transfer of tumor antigen‐specific CD8+ T cells to eliminate HCC. Sunitinib treatment alone promoted a transient reduction in tumor size. Sunitinib treatment combined with adoptive transfer of tumor antigen‐specific CD8+ T cells led to elimination of established tumors without recurrence. In vitro studies revealed that HCC growth was inhibited through suppression of STAT3 signaling. In addition, sunitinib treatment of tumor‐bearing mice was associated with suppression of STAT3 and a block in T‐cell tolerance. Conclusion: These findings indicate that sunitinib inhibits HCC tumor growth directly through the STAT3 pathway and prevents tumor antigen‐specific CD8+ T‐cell tolerance, thus defining a synergistic chemoimmunotherapeutic approach for HCC. (HEPATOLOGY 2012;55:141–152)

Successful chemoimmunotherapy against hepatocellular cancer in a novel murine model.

BACKGROUND & AIMS We have established a clinically relevant animal model of hepatocellular cancer (HCC) in immune competent mice to elucidate the complex dialog between host immunity and tumors during HCC initiation and progression. Mechanistic findings have been leveraged to develop a clinically feasible anti-tumor chemoimmunotherapeutic strategy. METHODS Intraperitoneal injection of carbon tetrachloride and intrasplenic inoculation of oncogenic hepatocytes were combined to induce progressive HCCs in fibrotic livers of immunocompetent mice. Immunization and adoptive cell transfer (ACT) were used to dissect the tumor antigen-specific immune response. The ability of the tyrosine kinase inhibitor sunitinib to enhance immunotherapy in the setting of HCC was evaluated. RESULTS This new mouse model mimics human HCC and reflects its typical features. Tumor-antigen-specific CD8+ T cells maintained a naïve phenotype and remained responsive during early-stage tumor progression. Late tumor progression produced circulating tumor cells, tumor migration into draining lymph nodes, and profound exhaustion of tumor-antigen-specific CD8+ T cells associated with accumulation of programmed cell death protein 1 (PD-1)hi CD8+ T cells and regulatory T cells (Tregs). Sunitinib-mediated tumoricidal effect and Treg suppression synergized with antibody-mediated blockade of PD-1 to powerfully suppress tumor growth and activate anti-tumor immunity. CONCLUSION Treg accumulation and upregulation of PD-1 provide two independent mechanisms to induce profound immune tolerance in HCC. Chemoimmunotherapy using Food and Drug Administration-approved sunitinib with anti-PD-1 antibodies achieved significant tumor control, supporting translation of this approach for the treatment of HCC patients. LAY SUMMARY In the current study, we have established a clinically relevant mouse model which mimics human liver cancer. Using this unique model, we studied the response of the immune system to this aggressive cancer. Findings from this trial have led to the development of an innovative and clinically feasible chemoimmunotherapeutic strategy.

Nonblocking Monoclonal Antibody Targeting Soluble MIC Revamps Endogenous Innate and Adaptive Antitumor Responses and Eliminates Primary and Metastatic Tumors

Purpose: The human tumor-derived soluble MHC I-chain–related molecule (sMIC) is highly immune suppressive in cancer patients and correlates with poor prognosis. However, the therapeutic effect of targeting sMIC has not been determined, due to the limitation that mice do not express homologs of human MIC. This study is to evaluate the therapeutic effect of a monoclonal antibody (mAb) targeting sMIC in a clinically relevant transgenic animal model. Experimental Design: We treated the engineered MIC-expressing “humanized” TRAMP/MIC bitransgenic mice at advanced disease stages with a sMIC-neutralizing nonblocking anti-MIC mAb and assessed the therapeutic efficacy and associated mechanisms. Results: A sMIC-neutralizing nonblocking anti-MIC mAb effectively induced regression of primary tumors and eliminated metastasis without inducing systemic toxicity. The therapeutic effect is conferred by revamping endogenous antitumor immune responses, exemplified by restoring natural killer (NK) cell homeostasis and function, enhancing susceptibility of MIC+-tumor cells to NK cell killing, reviving and sustaining antigen-specific CD8 T-cell responses, augmenting CD4 T cells to Th1 responses, priming dendritic cells for antigen presentation, and remodeling tumor microenvironment to be more immune reactive. Conclusions: Therapy with a sMIC-neutralizing nonblocking anti-MIC mAb can effectuate antitumor immune responses against advanced MIC+ tumors. Our study provided strong rationale for translating sMIC-neutralizing therapeutic mAb into clinics, either alone or in combination with current ongoing standard immunotherapies. Clin Cancer Res; 21(21); 4819–30. ©2015 AACR.

Immune-based Therapy Clinical Trials in Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) is the second leading cause of cancer-related mortality and continues to increase. Current standard of care for patients with HCC only provides limited therapeutic benefit. Development of innovative strategies is urgently needed. Experience with immunotherapy in HCC is quite early, but rapidly rise in the recent 15 years. Multifaceted immune-based approaches have shown efficacy in achieving disease regression, representing the most promising new treatment approach. Here, we classify the ongoing or completed clinical trials in HCC in terms of the immune strategies to be used and assess their clinical outcomes. The generated information may be helpful in the design of future immune-based therapies for achieving ideal tumor control and maximizing anti-tumor immunity.

Antibody-mediated neutralization of soluble MIC significantly enhances CTLA4 blockade therapy

Cooperative therapeutic effect of anti-CTLA4 and anti-sMIC antibodies. Antibody therapy targeting cytotoxic T lymphocyte–associated antigen 4 (CTLA4) elicited survival benefits in cancer patients; however, the overall response rate is limited. In addition, anti-CTLA4 antibody therapy induces a high rate of immune-related adverse events. The underlying factors that may influence anti-CTLA4 antibody therapy are not well defined. We report the impact of a cancer-derived immune modulator, the human-soluble natural killer group 2D (NKG2D) ligand sMIC (soluble major histocompatibility complex I chain–related molecule), on the therapeutic outcome of anti-CTLA4 antibody using an MIC transgenic spontaneous TRAMP (transgenic adenocarcinoma of the mouse prostate)/MIC tumor model. Unexpectedly, animals with elevated serum sMIC (sMIChi) responded poorly to anti-CTLA4 antibody therapy, with significantly shortened survival due to increased lung metastasis. These sMIChi animals also developed colitis in response to anti-CTLA4 antibody therapy. Coadministration of an sMIC-neutralizing monoclonal antibody with the anti-CTLA4 antibody alleviated treatment-induced colitis in sMIChi animals and generated a cooperative antitumor therapeutic effect by synergistically augmenting innate and adoptive antitumor immune responses. Our findings imply that a new combination therapy could improve the clinical response to anti-CTLA4 antibody therapy. Our findings also suggest that prescreening cancer patients for serum sMIC may help in selecting candidates who will elicit a better response to anti-CTLA4 antibody therapy.

Nanoliposome C6-Ceramide Increases the Anti-tumor Immune Response and Slows Growth of Liver Tumors in Mice

BACKGROUND & AIMS Ceramide, a sphingolipid metabolite, affects T-cell signaling, induces apoptosis of cancer cells, and slows tumor growth in mice. However, it has not been used as a chemotherapeutic agent because of its cell impermeability and precipitation in aqueous solution. We developed a nanoliposome-loaded C6-ceremide (LipC6) to overcome this limitation and investigated its effects in mice with liver tumors. METHODS Immune competent C57BL/6 mice received intraperitoneal injections of carbon tetrachlo-ride and intra-splenic injections of oncogenic hepatocytes. As a result, tumors resembling human hepatocellular carcinomas developed in a fibrotic liver setting. After tumors formed, mice were given an injection of LipC6 or vehicle via tail vein every other day for 2 weeks. This was followed by administration, also via tail vein, of tumor antigen-specific (TAS) CD8+ T cells isolated from the spleens of line 416 mice, and subsequent immunization by intraperitoneal injection of tumor antigen-expressing B6/WT-19 cells. Tumor growth was monitored with magnetic resonance imaging. Tumor apoptosis, proliferation, and AKT expression were analyzed using immunohistochemistry and immunoblots. Cytokine production, phenotype, and function of TAS CD8+ T cells and tumor-associated macrophages (TAMs) were studied with flow cytometry, real-time polymerase chain reaction (PCR), and ELISA. Reactive oxygen species (ROS) in TAMs and bone marrow-derived macrophages, induced by colony stimulating factor 2 (GMCSF or CSF2) or colony stimulating factor 1 (MCSF or CSF1), were detected using a luminescent assay. RESULTS Injection of LipC6 slowed tumor growth by reducing tumor cell proliferation and phosphorylation of AKT, and increasing tumor cell apoptosis, compared with vehicle. Tumors grew more slowly in mice given the combination of LipC6 injection and TAS CD8+ T cells followed by immunization compared with mice given vehicle, LipC6, the T cells, or immunization alone. LipC6 injection also reduced numbers of TAMs and their production of ROS. LipC6 induced TAMs to differentiate into an M1 phenotype, which reduced immune suppression and increased activity of CD8+ T cells. These results were validated by experiments with bone marrow-derived macrophages induced by GMCSF or MCSF. CONCLUSIONS In mice with liver tumors, injection of LipC6 reduces the number of TAMs and the ability of TAMs to suppress the anti-tumor immune response. LipC6 also increases the anti-tumor effects of TAS CD8+ T cells. LipC6 might therefore increase the efficacy of immune therapy in patients with hepatocellular carcinoma.

Sunitinib represses regulatory T cells to overcome immunotolerance in a murine model of hepatocellular cancer

ABSTRACT Successful development of immunotherapeutic strategies for hepatocellular cancer (HCC) has been impeded by limited understanding of tumor-induced profound tolerance and lack of a clinically faithful HCC model. Recently, we developed a novel model that recapitulates typical features of human HCC. Using this clinically relevant model, we demonstrate that tumor growth impairs host immunity and causes a profound exhaustion of tumor antigen-specific (TAS) CD8+ T cells. Increase in frequency and suppressive function of regulatory T cells (Tregs) is critically involved in this tumor-induced immune dysfunction. We further demonstrate that sunitinib suppresses Tregs and prevents tumor-induced immune tolerance, allowing TAS immunization to activate endogenous CD8+ T cells. As a result, this combinational strategy delays tumor growth. Importantly, the additional integration of exogenous naïve TAS CD8+ T cells by adoptive cell transfer (ACT) leads to the elimination of the established tumors without recurrence and promotes long-term survival of the treated mice. Mechanistically, sunitinib treatment primes the antitumor immune response by significantly decreasing Treg frequency, reducing TGF-β and IL-10 production by Tregs, and also protecting TAS CD8+ T cells from tumor-induced deletion in the setting of HCC. Taken together, sunitinib quantitatively and qualitatively modifies Tregs to overcome tumor-induced immune deficiency, suggesting the potential of sunitinib as a therapeutic immune activator for HCC control.

A Selenium Containing Inhibitor for the Treatment of Hepatocellular Cancer

Hepatocellular carcinoma (HCC) is the third most deadly cancer in the world. New treatment strategies are desperately needed due to limited standard therapies. Activation of the Erk, Akt, and STAT3pathways is implicated in the prognosis of HCC. The Se,Se′-1,4-phenylenebis(1,2-ethanediyl) bisisoselenourea (PBISe), is a selenium-containing MAPK and PI3 kinase inhibitor, effectively inhibit tumorigenesis in a variety of experimental models. The aim of our study is to demonstrate the potential role of PBISe in the treatment of HCC. The anti-proliferative and pro-apoptotic ability of PBISe is studied in vitro in four human HCC cell lines and in vivo in a spontaneous murine HCC model. Inhibition of cancer growth was performed by cell viability assay and apoptosis by caspase 3/7, PARP cleavage, annexin-V, and TUNEL assays. Role of PBISe on PI3 kinase, MAPK and STAT3 signaling is determined by Western blotting. In vivo effects of PBISe on tumor sizes were monitored using MRI in a spontaneous murine HCC. Liver tissues from the PBISe-treated mice are analyzed for angiogenesis, proliferation, and signaling pathway markers. Overall, PBISe activated caspase-3/7 and increased DNA fragmentation, which is positively correlated with the increased PARP cleavage. PBISe promoted apoptosis by inhibiting PI3K, MAPK, and STAT3 signaling with significant reduction in the tumor sizes (p < 0.007). PBISe-treated tumors reduced survival marker PCNA, and angiogenesis markers Vegf-A, Vegf-R3 and CD34. These results demonstrate the chemotherapeutic effects of PBISe, by inhibiting tumor growth and facilitating tumor apoptosis for HCC treatment.

Development of inCVAX, In situ Cancer Vaccine, and Its Immune Response in Mice with Hepatocellular Cancer

Manipulation of immune system toward the rejection of established cancers has become the standard of care in some patients. Here we propose the development of an in situ autologous cancer vaccine, inCVAX, for the treatment of hepatocellular cancer (HCC). inCVAX is based on the induction of local immunogenic cancer cell death combined with local dendritic cell stimulation by intratumoral injection of the immune-activator N-dihydro-galacto-chitosan (GC). In a first set of experiments, cellular and molecular studies were performed to investigate the effect of inCVAX on immune activation in a murine model of HCC that we previously developed. Once large tumors were formed in mice, the tumor is surgically exposed and a laser fiber was inserted into the center of an individual tumor mass. Using a 10 mm diffuser tip, laser irradiation of 1.5 W was applied to heat the tumor at different durations (6-10 min) to assess tolerability of photothermal application at different temperatures. The laser application was followed by immediate injection of GC, and each mouse received one laser treatment and one GC injection. ELISA was used to assess the level of cytokines; immunohistochemical staining was conducted to analyze the effect of inCVAX on immune cell tumor-filtration and expression of tumor-specific antigens (TSAs) and tumor-associated antigens (TAAs). Results indicate that survival correlated to thermal exposure. At lower temperatures the photothermal effect was sufficient to induce tumor necrosis, but without obvious complication to the mice, although at these temperatures the treatment didn’t alter the level of TSAs and TAAs, so further optimization is suggested. Nevertheless, in response to the inCVAX treatment, cytotoxic cytokine IFN-γ was significantly increased, but suppressive cytokine TGF-β was dramatically reduced. Furthermore, inCVAX prompted tumor infiltration of CD3+, CD4+, and CD8+ T cells; but modulated macrophage subsets differently. In conclusion, while the protocol needs further optimization, it would appear that inCVAX for the treatment of HCC activates an immune response in tumor-bearing mice, which in turn may have potential for the treatment of HCC.

Abstract 4004: Development of a successful combination therapy for hepatocellular cancer by targeting Treg and PD-1

We have established a clinically relevant murine model to reveal tumor-induced immunotoerance in hepatocellular carcinoma (HCC). Critical factors are targeted to develop immune-based therapies for HCC control. Intrasplenic (ISPL) inoculation of oncogenic hepatocytes and intraperitoneal (IP) injection of carbon tetrachloride (CCl4) are combined to induce progressive HCCs in fibrotic livers of immunocompetent mice. We characterize the features of this model, examine tumor-antigen-specific (TAS) immunity during tumor initiation and progression, and identify the critical factors in tumor-induced immune tolerance. The established murine model recapitulates human HCC and reflects its typical features. TAS CD8+ T cells initially maintain a naive phenotype and function in early-stage tumor-bearing mice, then become profound exhaustion with the tumor progression to the advanced stage. The deep immunosuppression is associated with the significant upregulation of Programmed cell death protein 1(PD-1), Cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and the increase of Tregs. While the changes in Tregs and PD-1 are systemic, they are particularly pronounced in the tumor microenvironment. Sunitinib-mediated reduction of Treg together with antibody-mediated blockade of PD-1 synergistically suppress tumor growth and activate anti-tumor immunity. Our data provide evidence that oncogenic hepatocytes escape immune surveillance during tumor initiation via immune ignorance, while later-stage established HCCs evade immune destruction via tumor-induced immunotolerance. Synergy of sunitinib and anti-PD-1 Ab generates favorable effect on suppressing tumor growth and activating anti-tumor immunity. This combinational strategy has high translational potential in HCC treatment. Citation Format: Dai Liu, Guangfu Li, Timothy Cooper, Eric Kimchi, Xiaoqiang Qi, Ningfei Li, Don Rockey, Todd Schell, Kevin Staveley-O’Carroll. Development of a successful combination therapy for hepatocellular cancer by targeting Treg and PD-1. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4004.