Thesis (Ph. D.)--University of Nevada, Reno, 2008. / "February 2008." Includes bibliographical references (leaves 151-174). Online version available on the World Wide Web.

Thesis (Ph.D.) - University of Queensland, 2005. / Includes bibliography.

Cancer is a major health burden in modern society, costing millions of lives worldwide and negatively impacting many more. With increasing rates of cancer, there is a need for new approaches to its treatment. This is where immunotherapies step in, this a relatively new approach to cancer treatment which caught public’s attention only in recent years. The main goal of these therapies is to enhance and help immune cells to identify and kill tumor cells, thereby initiating the cycle of cancer immunity. In this project LOAd platform viruses were evaluated and compared for their ability to induce oncolysis in cancer cells and ability to produce immunostimulatory molecules. Established LOAd703 virus armed with CD40L and 4-1BBL transgenes was compared to new constructs LOAd732, LOAd780 and LOAd786. All three new viruses are armed with CD40L and 4-1BBL, but also have additional transgenes X, Y and Z, respectively. Specific molecules coded by these transgenes cannot be disclosed at this moment. All viruses demonstrated high competence in oncolysis of A549-lung, T24-bladder and 526-mel melanoma cancer cell lines and were able to express transgenes coding for CD40L and 4-1BBL in all cell lines. New viruses were able to induce expression of new transgenes in infected cells, except for LOAd780 infected cell which had low concentration of protein Y in their supernatants. Also dendritic cells matured using LOAd viruses were able to induce expansion of CMV-specific T cells and a major expansion of natural killer cells.

Oncolytic viruses are characterised by their ability to selectively infect and kill tumour cells. Recently it has emerged that they can exert an additional anticancer mechanism stimulating adaptive immune-mediated cancer cell killing. Enadenotucirev (EnAd, formerly known as ColoAd1), is a chimeric Ad11p/Ad3 virus group B oncolytic adenovirus that binds CD46 and is under development for the systemic treatment of metastatic carcinomas. The central aim of this thesis was to to assess whether EnAd provides an adjuvant effect on tumour-associated antigen presenting cells (APCs) that could drive T_H1 polarisation for an effective anti-tumour immune response. This thesis describes the potent oncolytic properties, fast replication and high numbers of virus progeny production by EnAd in cancer cells. Recombinant EnAd variants were engineered to investigate the roles of the mutant regions in the genome of EnAd, and how these influence the modified phenotype. A chemical drug panel was used to identify pathways and cellular factors involved in cellular production of EnAd, finding that several mTOR inhibitors and microtubule inhibitors could improve virus replication. An in vitro system using partially matured human monocyte-derived dendritic cells (DCs), which displayed a similar phenotype to tumour-infiltrating DCs, was used to explore the effect of EnAd on APC responses. EnAd induced a strong adjuvant effect on these cells by up-regulating surface markers and secretion of pro-inflammatory factors. Further mechanistic experiments, alongside a CAR-binding group C adenovirus 5, indicated these adjuvant effects were virus particle-mediated and dependent on CD46 binding. To understand the functional implications downstream of these interactions, T cell activation and phenotype was assessed using a mixed lymphocyte reaction approach. The data indicated EnAd was a good candidate compared to other adenoviruses, that may steer the response of activated T-cells towards a T_H1 phenotype, for an effective immune response. In conclusion, the potent oncolytic properties of EnAd virus may provide an adjuvant effect on tumour-associated APCs, helping to harness an adaptive immune response.

Treatment of permissive tumours with the oncolytic virus (OV) VSV-Δ51 leads to a robust anti-tumour T cell response, which contributes to efficacy; however, many tumours are not permissive to in vivo treatment with VSV-Δ51. In an attempt to channel the immune stimulatory properties of VSV-Δ51 and broaden the scope of tumours that can be treated by an OV, a potent oncolytic vaccine platform was developed, consisting of tumour cells infected with VSV-Δ51. I demonstrate that prophylactic immunization with this infected cell vaccine (ICV) protected mice from subsequent tumour challenge, and expression of GM-CSF by the virus (VSVgm-ICV) increased efficacy. Immunization with VSVgm-ICV in the VSV-resistant B16-F10 model induced maturation of dendritic cells, natural killer (NK) cells, and T cells. I demonstrate that this approach is robust enough to control the growth of established and spontaneous tumours. This strategy is broadly applicable because of VSV’s extremely broad tropism, allowing nearly all cell types to be infected at high MOIs in vitro, where the virus replication kinetics outpace the cellular IFN response. It is also personalized to the unique tumour antigen(s) displayed by the cancer cell. Histone deacetylase inhibitors (HDIs) can augment viral replication, making them particularly interesting complements to OV therapy. However, the impact of HDIs on the generation and re-stimulation of immune responses remains to be clearly elucidated. Along with my collaborators at McMaster University, I demonstrate that MS-275, but not SAHA, selectively depletes naïve and regulatory lymphocytes. Memory lymphocytes that are being boosted remain unscathed and even have enhanced cytokine production, potentially as a consequence of the depleted lymphocyte compartment. This leads to a delay in anti-VSV neutralizing antibodies and T cell responses. Interestingly, HDI treatment of B16-F10 cells appears to inhibit VSV replication but allows for a longer persistence within the tumour. When used in an oncolytic prime/boost vaccination model, MS-275 potently enhanced survival. Though the anti-tumour immune response is enhanced, a near complete reduction in autoimmune vitiligo is observed with MS-275 administration. Therefore, this HDI uniquely modulates the immune response to enhance anti-tumour immunity and decrease the anti-viral response, while also decreasing autoimmune sequelae.

SMAC mimetic compounds (SMCs) are small molecule antagonists of the Inhibitor of Apoptosis (IAP) family of proteins. Binding of SMCs to the IAPs results in the sensitization of cancer cells to apoptosis in the presence of death ligands, such as tumour necrosis factor alpha (TNFα). I hypothesize that type I interferon (IFN) stimulation in cancer cells and in immune cells leads to the production of TNFα, which can then synergize with SMCs to kill cancer cells. The combined treatment of SMC and IFNα induces tumour regression in mice, and this effect is completely abrogated upon treatment with TNFα-neutralizing antibody. The synergistic effects are mediated by tumour cells and by contribution of immune cells, particularly macrophages and dendritic cells, as the systemic depletion of phagocytic innate immune cells results in an increase in tumour volume following combination treatment. The characterization of immune cell contribution will aid in the translation of the SMC combination therapy into clinical applications for the treatment of cancer.

The most exciting area in current cancer research is immuno-oncology, which aims to develop immunotherapy that activates the human immune system to attack cancers. However, we still lack broadly effective drugs and drug targets for this promising new cancer treatment modality. In an attempt to seek new immuno-oncology drugs that particularly target the antitumor innate immunity, our lab had previously screened traditional Chinese herbal medicine and found that water extract from a medicinal plant, Alocasia Cucullata (AC), has strong anticancer activity in mouse solid tumor models and acts partly by promoting antitumor, proinflammatory macrophages. However, the active components responsible for this exciting immuno-oncology activity and the corresponding immune targets are unknown. Therefore, the aim of my PhD study is to develop chemical biology strategies to isolate and purify the active components of AC from the crude water extract and identify the corresponding cellular targets and mechanisms. Results from my study identified two separable activities and active components, one smaller than 3K and the other larger than 100K, which work synergistically to simulate antitumor macrophages. Further analysis revealed the >100K active component is a large polysaccharide that binds to multiple Toll-like Receptors (TLRs) critical for activating proinflammatory M1-type macrophages. Identity of the Nonetheless, I was able to clean up this fraction by 50 fold and perform RNAseq to examine the innate immune targets of this intriguing drug lead and found it acts to differentiate monocytes to macrophages. Overall my PhD thesis has explored new chemical biology strategies to purify and characterize active components from traditional Chinese medicine towards new drug development and developed a variety of cell-based immune activity assays for identifying and characterizing novel innate immune drug targets and mechanisms

Interleukin-7 (IL-7) increases lymphocyte numbers, a critical feature of immune reconstitution, through mechanisms that are still poorly understood. Part of the problem is that IL-7 is produced in limited amounts by non-lymphoid cells, making in vivo studies of the cytokine's activity a challenge. To overcome this, we developed an in vitro system by which lymphocytes from secondary immune organs could be cultured to produce IL-7 responsive cells. Using this method, we showed that CD8hiCD44hi T cells accumulate in culture with IL-7 from a population of lymph node or splenic cells. These results were validated when a similar lymphocyte subset was found in mice expressing a constitutively active form of STAT5b, a key transducer of IL-7 signals. Interestingly, IL-7-expanded cells also up regulated the activation marker, CD69. The IL-7-derived CD44hiCD69hi cells were not generated from naïve cells, but expanded from an existing population, since culture in IL-7 of naïve lymphocytes from OT-1/Rag1-/- mice did not produce CD44hiCD69hi cells. Using the in vitro culture system to study lymphocytes from mice deficient in the apoptotic protein, BIM, we were able to attribute the expansion of CD8hiCD44hiCD69hi T cells to the proliferative and not survival activity of IL-7. The in vitro culture system provides an important new methodology to examine the activities of this essential as well as immunotherapeutic cytokine.

Indiana University-Purdue University Indianapolis (IUPUI) / Purpose: The purpose was to comprehensively assess the impact of PD-L1 expression on the efficacy of immune checkpoint inhibitors on Overall Survival (OS) and Progression-Free Survival (PFS). Methods: A systematic literature search and review was conducted through June 2019. I searched all eligible randomized controlled trials comparing PD-1/PD-L1 monotherapy to an active comparator in adult patients with advanced cancer across multiple tumor types. The Cochrane risk-of-bias tool was used to assess trial quality. A random-effects model was used for the meta-analysis. Heterogeneity was assessed using Cochran Q statistic and I2 test. Publication bias was assessed by visual inspection of a funnel plot and Begg’s test. Results: I identified and included 23 trials involving 14,434 participants. When stratifying PD-L1 positive (+) and negative (-) patients using varying thresholds of expression, a significant group difference was observed at PD-L1 >1% ( p=0.04; PD-L1(+): HR, 0.72; 95% CI, 0.65-0.79; PD-L1(-): HR,0.83; 95% CI, 0.75-0.91), at PD-L1 >10% (p=0.02; PD-L1(+): HR,0.50; 95% CI, 0.38-0.62; PD-L1 (-): HR, 0.74; 95% CI, 0.57-0.90) and at PD-L1>50% (p=0.01; PD-L1(+): HR,0.59; 95% CI, 0.51-0.68; PD-L1(-): HR, 0.93; 95% CI, 0.71-1.15). Across tumor types, both PD-L1(+) and PD-L1(-) patients treated with an immunotherapy had improved OS compared with patients receiving standard care therapies. A PFS benefit was observed and favored patients treated with a PD-1/PD-L1 inhibitor versus standard of care. However, there was significant heterogeneity and the benefit on PFS was not statistically significant between PD-L1(+) and PD-L1(-) groups using varying cut-off levels of PD-L1 expression. No differences between sub-groups of interest including median follow-up time, type of inhibitor, and line of therapy for either PD-L1(+) or PD-L1(-) patients at 1% cut-off were identified. Conclusion: This study supports the use of PD-L1 as a predictive biomarker of improved response to immunotherapies. As thresholds increase and specifically above the 10% PD-L1 expression threshold, patients who were positive for PD-L1 appeared to have better OS compared to those who were negative for PD-L1. Further investigation is needed to assess the clinical usefulness of PD-L1 at various expression levels with improved technologies that have the potential to enhance assay accuracy and precision.

Tumors induce immune dysfunction through the production of soluble factors that subvert macrophage (Mf) function to favor tumor growth. Previous studies suggested that tumor-induced immune cell dysfunction may be reversible through regimens that disrupt tumor cell suppressor mechanisms and concurrently promote tumoricidal activities. Because the antineoplastic agent paclitaxel (TAXOL) activates Mf function, we studied mechanisms of paclitaxel-mediated cytotoxic and immunostimulatory responses by tumor-induced Mfs. Although tumor-derived factors, including interleukin-10 and transforming growth factor-b1, modulate Mf response to activation signals, paclitaxel partly reverses tumor-induced Mf-mediated suppression of T-cell reactivity through enhanced production of the immunostimulatory cytokine interleukin-12 (IL-12). Concurrently, paclitaxel induces Mf cytotoxic and proinflammatory molecule production, including tumor necrosis factor-a and interleukin-1b. In contrast to its apparent immunotherapeutic effect on Mf populations, paclitaxel's cytostatic mechanisms suppress lymphocyte proliferation and function. We showed that IL-12 can reverse paclitaxel-mediated suppression of T-cell responses in vitro, establishing the foundation for a novel antitumor therapy using paclitaxel in combination with IL-12. We show that the administration of paclitaxel as a chemotherapeutic agent, followed by IL-12 as an immunotherapeutic agent to alleviate paclitaxel-mediated immunosuppression, prolongs survival, reduces tumor progression, and activates immune effector populations in a murine tumor model. These results are the first experimental evidence to suggest that paclitaxel and IL-12 are an effective antitumor modality. Collectively, these studies show that paclitaxel induces multiple antitumor mechanisms that can be enhanced with proper ancillary administration of immunotherapeutic cytokines. / Ph. D.