Defining optimal parameters to maximize the effect of electrochemotherapy on lung cancer cells whilst preserving the integrity of immune cells.

Electrochemotherapy (ECT) is becoming an established therapy for melanoma and is under investigation for application in additional cancer types. One potential cancer type that may benefit from ECT is lung cancer as lung cancer treatments remain unable to deliver long-lasting treatment responses. Given the importance of the immune system in lung cancer, here we have also examined the impact of ECT on immune populations. The impact of electroporation and ECT on three human lung cancer cell lines (A549, H460, SK-MES 1), one murine cell line (LLC) and murine T cells, dendritic cells and macrophages was examined. The viability, metabolic activity and recovery potential post-treatment of all cell types was determined to evaluate the potential utility of ECT as a lung cancer treatment. Our findings demonstrate that cisplatin at 11 µM would be the suggested drug of choice when using ECT for lung cancer treatment. Our study also shows that T cells are not impacted by any tested condition, whilst dendritic cells and macrophages are significantly negatively impacted by electric field strengths surpassing 800 V/cm in vitro. Therefore, current ECT protocols (using 1000 V/cm in vivo) might need to adapted to improve viability of the immune population, thus improving therapy outcomes.

Electrochemotherapy and immune interactions; A boost to the system?

Electrochemotherapy (ECT), the application of an electric impulse to deliver chemotherapy drugs into cells, has been in clinical trials since the early 1990s and has been used for a variety of different malignancies including melanoma and sarcoma. A standard operating procedure for the use of ECT in clinical settings has been established since 2006. ECT is very effective in reducing the local tumour burden via T-cell dependent killing of the cancer cells; however abscopal effects are not consistently observed. Currently little is known or understood about how ECT affects the immune cell population within the treated tumour and how these changes could impact the immune response. In this manuscript, we will review the current knowledge on ECT in the context of its interactions with the immune system and discuss how the gained knowledge could be harnessed to develop a potent ECT-immune co-treatment combination (Electroimmunotherapy).

Electroporation of suspension cell lines - A proposed assay set for optimizations.

To make in vitro single cell electroporation protocols more comparable between various cancer types and groups, we propose a set of assays to test a range of electric field strengths at the start of any new project to determine the optimal electric field strength for a given cell line. While testing a range of electric field strengths, we kept the other ESOPE parameters constant (8 pulses, 100 µs pulse duration, 1 Hz pulse frequency). Basic assays were employed to measure short-term viability, effectiveness of treatment, metabolic activity, and recovery potential post-treatment to determine the optimal field strength for a particular cell line. Six cancer cell lines were tested, three of human (A549, A375 and Pan02) and three murine (LLC, B16F10 and MIA-PACA2). Our findings demonstrate that the optimal electroporation setting while keeping with all other ESOPE parameters are 800 V/cm for A549 and Pan02, 700 V/cm for A375, Mia-PACA2, and B16F10, and 1300 V/cm for LLC. Having an agreed upon set of assays to determine each cell lines optimal electric field strength should allow an improve translation of findings between cell lines for in vitro work from various groups and potentially improve translation into the clinic.

Interleukin-15 in cancer immunotherapy: IL-15 receptor complex versus soluble IL-15 in a cancer cell-delivered murine leukemia model.

Cytokines of the common γ-chain receptor family such as IL-15 are vital with respect to activating immune cells, sustaining healthy immune functions, and augmenting the anti-tumor activity of effector cells, making them ideal candidates for cancer immunotherapy. IL-15, either in its soluble form (IL-15sol) or complexed with IL-15Rα (IL-15Rc), has been shown to exhibit potent anti-tumor activities in various experimental cancer studies. Here we describe the impact of intraperitoneal IL-15 in a cancer cell-delivered IL-15 immunotherapy approach using the 70Z/3-L leukemia mouse model. Whereas both forms of IL-15 led to significantly improved survival rates compared to the parent cell line, there were striking differences in the extent of the improved survival: mice receiving cancer cells secreting IL-15sol showed significantly longer survival and protective long-term immunity compared to those producing IL-15Rc. Interestingly, injection of leukemia cells secreting IL-15sol lead to heightened expansion of CD4+ and CD8+ T-cell populations in the peritoneum compared to IL-15Rc. Cell-secreted IL-15Rc resulted in an influx and/or expansion of NK1.1+ cells in the peritoneum which was much less pronounced in the IL-15sol model. Furthermore, IL-15Rc but not IL-15sol lead to T-cell exhaustion and disease progression. To our knowledge, this is the first study detailing a significantly different biological effect of cell-delivered IL-15sol versus IL-15Rc in a mouse cancer immunotherapy study.

Hypoxia potentiates monocyte-derived dendritic cells for release of tumor necrosis factor α via MAP3K8.

Dendritic cells (DCs) constantly sample peripheral tissues for antigens, which are subsequently ingested to derive peptides for presentation to T cells in lymph nodes. To do so, DCs have to traverse many different tissues with varying oxygen tensions. Additionally, DCs are often exposed to low oxygen tensions in tumors, where vascularization is lacking, as well as in inflammatory foci, where oxygen is rapidly consumed by inflammatory cells during the respiratory burst. DCs respond to oxygen levels to tailor immune responses to such low-oxygen environments. In the present study, we identified a mechanism of hypoxia-mediated potentiation of release of tumor necrosis factor α (TNF-α), a pro-inflammatory cytokine with important roles in both anti-cancer immunity and autoimmune disease. We show in human monocyte-derived DCs (moDCs) that this potentiation is controlled exclusively via the p38/mitogen-activated protein kinase (MAPK) pathway. We identified MAPK kinase kinase 8 (MAP3K8) as a target gene of hypoxia-induced factor (HIF), a transcription factor controlled by oxygen tension, upstream of the p38/MAPK pathway. Hypoxia increased expression of MAP3K8 concomitant with the potentiation of TNF-α secretion. This potentiation was no longer observed upon siRNA silencing of MAP3K8 or with a small molecule inhibitor of this kinase, and this also decreased p38/MAPK phosphorylation. However, expression of DC maturation markers CD83, CD86, and HLA-DR were not changed by hypoxia. Since DCs play an important role in controlling T-cell activation and differentiation, our results provide novel insight in understanding T-cell responses in inflammation, cancer, autoimmune disease and other diseases where hypoxia is involved.

Ethylene, an early marker of systemic inflammation in humans.

Ethylene is a major plant hormone mediating developmental processes and stress responses to stimuli such as infection. We show here that ethylene is also produced during systemic inflammation in humans and is released in exhaled breath. Traces of ethylene were detected by laser spectroscopy both in vitro in isolated blood leukocytes exposed to bacterial lipopolysaccharide (LPS) as well as in vivo following LPS administration in healthy volunteers. Exposure to LPS triggers formation of ethylene as a product of lipid peroxidation induced by the respiratory burst. In humans, ethylene was detected prior to the increase of blood levels of inflammatory cytokines and stress-related hormones. Our results highlight that ethylene release is an early and integral component of in vivo lipid peroxidation with important clinical implications as a breath biomarker of bacterial infection.