Inhibition of the p38 MAPK pathway in human CD1c+ Dendritic Cells enhances their function for cancer immunotherapy

Kaur, Aanchal Preet (2021) Inhibition of the p38 MAPK pathway in human CD1c+ Dendritic Cells enhances their function for cancer immunotherapy. PhD thesis, University of Nottingham.

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The success of immune checkpoint inhibitors (ICI) in treating chemo-radiotherapy resistant tumours like melanoma has ignited renewed interest in cancer immunotherapy. Despite the success of ICI, a substantial proportion of patients do not respond. The resistance mechanisms used by tumours to evade ICI-dependent effector mechanisms overlap with those used during the cancer immune-editing process. Furthermore, the severe cytotoxicity that occurs as a consequence of this, complicates the use of these therapies.

Dendritic cells (DC) are the most potent antigen-presenting cells that play essential roles in cancer immunity as they prime naïve T cell responses. ICI therapies that target co-inhibitory receptors re-activate and amplify pre-existing anti-tumour immune responses that were primarily elicited by DC. Enhanced infiltration and activation of tumour-associated DC sensitizes and improves the responsiveness of resistant tumours in checkpoint-resistant patients. These observations suggest that a combination of DC-based and ICI therapies may improve overall response rates and survival in patients with advanced cancer. Moreover, the superior safety profile of adoptively transferred DC vaccines can reduce the occurrence of immune-related adverse effects (irAEs) when in combination with ICI. With the paradigm shift from laboratory-generated DC to naturally circulating DC (nDC) subsets for DC vaccines, the clinical implementation of these vaccines in standard of care regimes for cancer treatment is now a real possibility. While these therapies are currently being assessed in several clinical trials, efforts are being made to improve the functionality and migratory potential of nDC.

In this study, we explore strategies of using small molecule inhibitors to improve the functionality of nDC with a view to enhancing their clinical efficacy. We assessed the frequency and phenotype of nDC subsets in whole blood derived from advanced cancer patients using a multi-parametric flow cytometric assay. The effect of p38 MAPK inhibitors (p38i) on the phenotype and function of isolated nDC subsets was determined in a range of pertinent immune assays. Because of the reported cooperative behaviour of different natural DC subsets, cells were studied either in mono-culture or co-cultures.

Our study shows the suppressed frequency and phenotype of nDC subsets (most notably plasmacytoid DC (pDC), p<0.001) in advanced cancer patients (n=32). In isolated CD1c+ DC, inhibition of the p38 MAPK pathway with highly selective small molecule inhibitors such as BIRB-0796 improved their Th1 inducing cytokine secretion profile by approximately 6-fold (n=20, p<0.05). This correlated with an increase in IL-12p70 secretion and depressed expression of IL-10. In contrast to CD1c+ DC, p38i attenuated the function of pDC or monocyte-derived DC (MoDC). We further demonstrated that p38i augmented CD86 expression and the migratory capability of CD1c+ DC to CCL19 chemokine. An average of 9.09% (p< 0.05) and 18.33% (p<0.001) more of p38i treated cells were observed migrating to CCL19 as compared to mature and immature CD1c+ DC respectively.

These results support a strategy whereby isolated patient’s CD1c+ DC are treated to inhibit the p38 MAPK pathway before adoptive transfer. For the first time we demonstrate here that a combination of p38-inhibited-CD1c+ DC and pDC subsets can be used for the development of nDC vaccines with enhanced functionality, wherein the DC subsets co-operate with each other to induce strong T cell responses. We show that the co-culture of p38-inhibited-CD1c+ DC and pDC subsets induces strong signal 3 cytokine secretion, namely IL-12 and IFN-α, suppresses the secretion of inhibitory IL-10 cytokine and improves expression of the co-stimulatory molecule CD86, important for priming strong anti-tumour Th1 responses. Thus, incorporating p38i in the developmental protocol for nDC vaccines enhances the potency of DC vaccines, a finding that is now due to be investigated in an early-phase clinical trial for patients with ICI-resistant malignant melanoma.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Jackson, Andrew M.
Patel, Poulam M.
Keywords: Dendritic cells; chemotaxis; co-culture; whole blood assay; phenotyping
Subjects: QS-QZ Preclinical sciences (NLM Classification) > QW Microbiology. Immunology > QW501 Immunology
QS-QZ Preclinical sciences (NLM Classification) > QZ Pathology
Faculties/Schools: UK Campuses > Faculty of Medicine and Health Sciences > School of Medicine
Item ID: 65509
Depositing User: Kaur, Aanchal
Date Deposited: 04 Aug 2021 04:42
Last Modified: 31 Dec 2022 04:30

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