Dietz, Allan B

Abstract Cancer-associated fibroblasts (CAF) are abundant in the stroma of desmoplastic cancers where they promote tumor progression. CAFs are “activated” and as such may be uniquely susceptible to apoptosis. Using cholangiocarcinoma as a desmoplastic tumor model, we investigated the sensitivity of liver CAFs to the cytotoxic drug navitoclax, a BH3 mimetic. Navitoclax induced apoptosis in CAF and in myofibroblastic human hepatic stellate cells but lacked similar effects in quiescent fibroblasts or cholangiocarcinoma cells. Unlike cholangiocarcinoma cells, neither CAF nor quiescent fibroblasts expressed Mcl-1, a known resistance factor for navitoclax cytotoxicity. Explaining this paradox, we found that mitochondria isolated from CAFs or cells treated with navitoclax both released the apoptogenic factors Smac and cytochrome c, suggesting that they are primed for cell death. Such death priming in CAFs appeared to be due, in part, to upregulation of the proapoptotic protein Bax. Short hairpin RNA-mediated attenuation of Bax repressed navitoclax-mediated mitochondrial dysfunction, release of apoptogenic factors, and apoptotic cell death. In a syngeneic rat model of cholangiocarcinoma, navitoclax treatment triggered CAF apoptosis, diminishing expression of the desmoplastic extracellular matrix protein tenascin C, suppressing tumor outgrowth, and improving host survival. Together, our findings argue that navitoclax may be useful for destroying CAFs in the tumor microenvironment as a general strategy to attack solid tumors. Cancer Res; 73(2); 897–907. ©2012 AACR.

Long-term culture of hepatocyte spheroids with high ammonia clearance is valuable for therapeutic applications, especially the bioartificial liver. However, the optimal conditions are not well studied. We hypothesized that liver urea cycle enzymes can be induced by high protein diet and maintain on a higher expression level in rat hepatocyte spheroids by serum-free medium (SFM) culture and coculture with mesenchymal stromal cells (MSCs). Rats were feed normal protein diet (NPD) or high protein diet (HPD) for 7 days before liver digestion and isolation of hepatocytes. Hepatocyte spheroids were formed and maintained in a rocked suspension culture with or without MSCs in SFM or 10% serum-containing medium (SCM). Spheroid viability, kinetics of spheroid formation, hepatic functions, gene expression, and biochemical activities of rat hepatocyte spheroids were tested over 14 days of culture. We observed that urea cycle enzymes of hepatocyte spheroids can be induced by high protein diet. SFM and MSCs enhanced ammonia clearance and ureagenesis and stabilized integrity of hepatocyte spheroids compared to control conditions over 14 days. Hepatocytes from high protein diet-fed rats formed spheroids and maintained a high level of ammonia detoxification for over 14 days in a novel SFM. Hepatic functionality and spheroid integrity were further stabilized by coculture of hepatocytes with MSCs in the spheroid microenvironment. These findings have direct application to development of the spheroid reservoir bioartificial liver.

Abstract Background and Aims: Cholangiocarcinomas (CCA) are highly desmoplastic tumors containing abundant cancer associated myofibroblasts (CAF). An inverse association between the abundance of CAF and survival has been demonstrated in CCA, suggesting that CAF play a pivotal role in CCA development and progression. The CAF phenotype represents an ‘activated cell state’ and as such may be uniquely susceptible to apoptosis. BH3 mimetics induce apoptosis in cells ‘primed’ for cell death, representing a therapeutic strategy for cancer. Herein we examine whether CAF display a selective sensitivity to the BH3 mimetic ABT-263 and whether ABT-263 induced ablation of CAF reduces tumor growth and progression. Methods: We employed human and rat CAF, myofibroblastic human LX2 cells, human and rat control fibroblasts, the rat cholangiocarcinoma cell line BDEneu and human CCA cell lines for these studies. In-vivo experiments were conducted using a syngeneic, orthotopic rat CCA model. Results: We observed a significant and dose dependent induction of apoptosis by ABT-263 in human and rat primary CAF as well as activated LX2 cells as compared to rat BDEneu and human CCA cell lines. Comparison of Bcl-2 protein expression in quiescent fibroblasts versus CAF demonstrated a consistent upregulation of Bax in the CAF, likely explaining their enhanced sensitivity to pro-death stimuli. Indeed, ABT-263 treatment of CAF was associated with Bax activation as compared to human CCA cell lines. Finally, administration of ABT-263 decreased tumor size and metastasis in a human-like in-vivo rat model of CCA. Analysis of the rat tumors revealed a decrease in Tenascin C positive tumor stroma and an increase of TUNEL-positive apoptotic stromal cells. Conclusions: CCA associated CAF appear to be ‘primed’ for cell death, possibly due to overexpression of the pro-apoptotic Bcl-2 protein Bax. Consequently CAF display increased sensitivity to the BH3 mimetic ABT-263, which selectively depletes them from a rat in-vivo model of CCA, thereby reducing tumor growth and metastasis. Thus targeting CCA tumor stroma by inducing apoptosis in CAF may represent a new therapeutic approach in human CCA. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4905. doi:1538-7445.AM2012-4905

With favorable regenerative and immunotolerant profiles, patient-derived human mesenchymal stem cells (hMSCs) are increasingly considered in cell therapy. Derived from bone marrow (BM) and standardized with culture in fetal bovine serum (FBS), translation of hMSC-based approaches is impeded by protracted expansion times, risk of xenogenic response, and exposure to zoonoses. Here, human platelet lysate adherent to good manufacturing practices (GMP-hPL) provided a nonzoonotic adjuvant that enhanced the capacity of BM-hMSC to proliferate. The nurturing benefit of GMP-hPL was generalized to hMSC from adipose tissue evaluated as an alternative to bone marrow. Long-term culture in GMP-hPL maintained the multipotency of hMSC, while protecting against clonal chromosomal instability detected in the FBS milieu. Proteomic dissection identified TGF-β, VEGF, PDGF, FGF, and EGF as highly ranked effectors of hPL activity, revealing a paradigm of healing that underlies platelet lysate adjuvancy. Thus, GMP-adherent human platelet lysate accelerates hMSC proliferation with no chromosomal aberrancy, through an innate repair paradigm.

AbstractImmunosuppression is a known risk factor for B-cell non-Hodgkin lymphoma (NHL), yet mechanisms of tumor-associated immunosuppression remain to be fully characterized. We examined the immunophenotype of 40 NHL patients and 27 age-matched healthy volunteers to better understand systemic immune suppression. NHL peripheral blood mononuclear cells had significantly decreased interferon-γ production and proliferation. This suppression was not the result of regulatory T cells, interleukin-6 or interleukin-10, as these factors were not different between NHL and healthy volunteers (controls). We were able to restore T-cell proliferation by removing NHL monocytes, suggesting that these monocytes are suppressive. This suppression was mediated in part through arginine metabolism as exogenous arginine supplementation partially overcame monocytes' suppression of T-cell proliferation in vitro and NHL patients had elevated arginase I in their plasma. NHL monocytes had impaired STAT1 phosphorylation and interferon-α production to CpG stimulation and a dendritic cell differentiation deficiency. Further studies demonstrated that monocytes from NHL patients had decreased HLA-DR and Tumor necrosis factor-α receptor II (CD120b) expression compared with controls (CD14+HLA-DRlow/−CD120blow). Patients with increased ratios of CD14+HLA-DRlow/− monocytes had more aggressive disease and suppressed immune functions. In summary, we report that CD14+HLA-DRlow/− monocytes are a major and multifactorial contributor to systemic immunosuppression in NHL.

Abstract Purpose: The mammalian target of rapamycin (mTOR) functions within the phosphoinositide 3-kinase/Akt signaling pathway as a critical modulator of cell survival. Methods: The mTOR inhibitor temsirolimus (CCI-779) was combined with chemoradiotherapy in glioblastoma multiforme (GBM) patients in a dose-escalation phase I trial. The first 12 patients were treated with CCI-779 combined with radiation/temozolomide and adjuvant temozolomide. A second cohort of 13 patients was treated with concurrent CCI-779/radiation/temozolomide followed by adjuvant temozolomide monotherapy. Results: Concomitant and adjuvant CCI-779 was associated with a high rate (3 of 12 patients) of grade 4/5 infections. By limiting CCI-779 treatment to the radiation/temozolomide phase and using antibiotic prophylaxis, the rate of infections was reduced, although 2 of 13 patients developed exacerbation of pre-existing fungal or viral infections. Dose-limiting toxicities were observed in 2 of 13 patients with this modified schedule. Weekly CCI-779 (50 mg/week) combined with radiation/temozolomide is the recommended phase II dose and schedule. The immune profile of patients in the second cohort was assessed before, during, and after CCI-779 therapy. There was robust suppression of helper and cytotoxic T cells, B cells, natural killer, cells and elevation of regulatory T cells during CCI-779/radiation/temozolomide therapy with recovery to baseline levels during adjuvant temozolomide of cytotoxic T cells, natural killer cells, and regulatory T cells. Conclusions: The increased infection rate observed with CCI-779 combined with chemoradiotherapy in GBM was reduced with antibiotic prophylaxis and by limiting the duration of CCI-779 therapy. The combined suppressive effects of CCI-779 and temozolomide therapy on discrete immune compartments likely contributed to the increased infectious risks observed. Clin Cancer Res; 16(22); 5573–80. ©2010 AACR.

Abstract Purpose: Preexisting antiviral antibodies in cancer patients can quickly neutralize oncolytic measles virus (MV) and decrease its antitumor potency. In contrast to “naked” viruses, cell-associated viruses are protected from antibody neutralization. Hence, we hypothesized that measles virotherapy of ovarian cancer in measles-immune mice might be superior if MV-infected mesenchymal stem cell (MSC) carriers are used. Experimental Design: Antimeasles antibodies titers in ovarian cancer patients were determined. The protection of MV by MSC from antimeasles antibodies, the in vivo biodistribution profiles, and tumor infiltration capability of MSC were determined. Measles-naïve or immune tumor–bearing mice were treated with naked virus or MSC-associated virus and mice survivals were compared. Results: MSC transferred MV infection to target cells via cell-to-cell heterofusion and induced syncytia formation in the presence of high titers of antimeasles antibody, at levels that completely inactivated naked virus. Athymic mice bearing i.p. human SKOV3ip.1 ovarian tumor xenografts passively immunized with measles-immune human serum were treated with saline, naked MV, or MV-infected MSC. Bioluminescent and fluorescent imaging data indicated that i.p. administered MSC localized to peritoneal tumors, infiltrated into the tumor parenchyma, and transferred virus infection to tumors in measles naïve and passively immunized mice. Survival of the measles-immune mice was significantly enhanced by treatment with MV-infected MSC. In contrast, survivals of passively immunized mice were not prolonged by treatment with naked virus or uninfected MSC. Conclusions: MSC should be used as carriers of MV for intraperitoneal virotherapy in measles-immune ovarian cancer patients. (Clin Cancer Res 2009;15(23):7246–55)

A variety of nonmalignant cells present in the tumor microenvironment promotes tumorigenesis by stimulating tumor cell growth and metastasis or suppressing host immunity. The role of such stromal cells in T-cell lymphoproliferative disorders is incompletely understood. Monocyte-derived cells (MDCs), including professional antigen-presenting cells such as dendritic cells (DCs), play a central role in T-cell biology. Here, we provide evidence that monocytes promote the survival of malignant T cells and demonstrate that MDCs are abundant within the tumor microenvironment of T cell–derived lymphomas. Malignant T cells were observed to remain viable during in vitro culture with autologous monocytes, but cell death was significantly increased after monocyte depletion. Furthermore, monocytes prevent the induction of cell death in T-cell lymphoma lines in response to either serum starvation or doxorubicin, and promote the engraftment of these cells in nonobese diabetic/severe combined immunodeficient mice. Monocytes are actively recruited to the tumor microenvironment by CCL5 (RANTES), where their differentiation into mature DCs is impaired by tumor-derived interleukin-10. Collectively, the data presented demonstrate a previously undescribed role for monocytes in T-cell lymphoproliferative disorders.

Background and Purpose— Adipose tissue is an abundant source of endothelial cells as well as stem and progenitor cells which can develop an endothelial phenotype. It has been demonstrated that these cells have distinct angiogenic properties in vitro and in vivo. However, whether these cells have the capacity to directly improve large vessel form and function after vascular injury remains unknown. To define whether delivery of adipose-derived endothelial cells (ADECs) would improve healing of injured carotid arteries, a rabbit model of acute arterial injury was used. Methods— Autologous rabbit ADECs were generated using defined culture conditions. To test the ability of ADECs to enhance carotid artery repair, cells were delivered intraarterially after acute balloon injury. Additional delivery studies were performed after functional selection of cells before delivery. Results— After rabbit omental fat harvest and digestion, a proliferative, homogenous, and distinctly endothelial population of ADECs was identified. Direct delivery of autologous ADECs resulted in marked reendothelialization 48 hours after acute vascular injury as compared to saline controls (82.2±26.9% versus 4.2±3.0% P <0.001). Delivery of ADECs that were selected for their ability to take up acetylated LDL significantly improved vasoreactivity and decreased intimal formation after vascular injury. Conclusions— Taken together, these data suggest that ADECs represent an autologous source of proliferative endothelial cells, which demonstrate the capacity to rapidly improve reendothelialization, improve vascular reactivity, and decrease intimal formation in a carotid artery injury model.

Abstract Polarizing effects of productive dendritic cell (DC)–T-cell interactions on DC cytoskeleton have been known in some detail, but the effects on DC membrane have been studied to a lesser extent. We found that T-cell incubation led to DC elongation and segregation of characteristic DC veils to the broader pole of the cell. On the opposite DC pole, we observed a novel membrane feature in the form of bundled microvilli. Each villus was approximately 100 nm in diameter and 600 to 1200 nm long. Microvilli exhibited high density of antigen-presenting molecules and costimulatory molecules and provided the physical basis for the multifocal immune synapse we observed during human DC and T-cell interactions. T cells preferentially bound to this site in clusters often contained both CD4+ and CD8+ T cells.