Nano-enabled pancreas cancer immunotherapy using immunogenic cell death and reversing immunosuppression

Abstract

While chemotherapy delivery by nanocarriers has modestly improved the survival prospects of pancreatic ductal adenocarcinoma (PDAC), additional engagement of the immune response could be game changing. We demonstrate a nano-enabled approach for accomplishing robust anti-PDAC immunity in syngeneic mice through the induction of immunogenic cell death (ICD) as well as interfering in the immunosuppressive indoleamine 2,3-dioxygenase (IDO) pathway. This is accomplished by conjugating the IDO inhibitor, indoximod (IND), to a phospholipid that allows prodrug self-assembly into nanovesicles or incorporation into a lipid bilayer that encapsulates mesoporous silica nanoparticles (MSNP). The porous MSNP interior allows contemporaneous delivery of the ICD-inducing chemotherapeutic agent, oxaliplatin (OX). The nanovesicles plus free OX or OX/IND-MSNP induce effective innate and adaptive anti-PDAC immunity when used in a vaccination approach, direct tumor injection or intravenous biodistribution to an orthotopic PDAC site. Significant tumor reduction or eradication is accomplishable by recruiting cytotoxic T lymphocytes, concomitant with downregulation of Foxp3+ T cells.

Breast Cancer Chemo-immunotherapy through Liposomal Delivery of an Immunogenic Cell Death Stimulus Plus Interference in the IDO-1 Pathway

“…The first step toward constructing a dual-delivery carrier was the covalent conjugation of IND (I-methyl- d -tryptophan or 1- d -MT) to 1-palmitoyl-2-hydroxy- sn -glycero-3-phosphocholine (PL) to form an IND-PL prodrug, as schematically explained Figure 3A and Figure S3A. 22 IND-PL self-assembles into a liposome (Figure 3A), which is constructed as outlined in Figure 3B. 22 This requires mixing and suspension of IND-PL, cholesterol, and DSPE-PEG 2K in an organic solvent, which is evaporated from the bottom of a round-bottom flask to form a uniform lipid film.…”

“…22 IND-PL self-assembles into a liposome (Figure 3A), which is constructed as outlined in Figure 3B. 22 This requires mixing and suspension of IND-PL, cholesterol, and DSPE-PEG 2K in an organic solvent, which is evaporated from the bottom of a round-bottom flask to form a uniform lipid film. Various molar ratios of IND-PL, cholesterol, and DSPE-PEG 2K were tested to obtain optimal lipid bilayer stability and carrier size (Figure S4).…”

“…We have also demonstrated in an orthotopic pancreas cancer (PC) model that it is possible to provide an effective ICD stimulus by using a mesoporous silica nanoparticle (MSNP) for delivery of oxaliplatin, which as a free drug was incapable of triggering an immunogenic response in vivo . 22 All considered, these findings suggest that the use of a nanocarrier to improve the PK and tumor drug concentration of ICD-inducing chemotherapeutic agents could provide an effective means for initiating chemo-immunotherapy, which will be difficult to achieve on a reproducible basis by free drugs. Another potential advantage of using a nanocarrier is the ability to co-deliver synergistic drug combinations for improving treatment efficacy, as demonstrated in the PC tumor model, where contemporaneous delivery of 1-methyl- d -tryptophan (aka indoximod, IND) and oxaliplatin by the MSNP carrier triggered a synergistic immunotherapy response.…”

“…24−27 Moreover, the delayed release of adjuvant stimuli, such as high mobility group box 1 protein (HMGB1; a TLR-4 ligand) and ATP (a danger signal that activates the NRLP3 inflammasome), provides additional stimuli for dendritic cell maturation and the ability to present tumor antigens to naïve T-cells. 21,22,28−31 ICD provides a deliberate means of triggering TIL recruitment prior to response boosting by additional immune modulators, including antibodies that bind immune checkpoint receptors or metabolic immune surveillance pathways that prevent effective T-cell priming. 32 An important example is the indoleamine 2,3-dioxygenase (IDO-1) pathway that is overexpressed at the BC tumor site.…”

“…Another potential advantage of using a nanocarrier is the ability to co-deliver synergistic drug combinations for improving treatment efficacy, as demonstrated in the PC tumor model, where contemporaneous delivery of 1-methyl- d -tryptophan (aka indoximod, IND) and oxaliplatin by the MSNP carrier triggered a synergistic immunotherapy response. 22 Not only did the indoximod strongly synergize with oxaliplatin in calreticulin expression, but it also provided effective interference in the IDO-1 immune suppressive pathway, which is regionally overexpressed at the PC tumor site. 22 The immunosuppressive effects of IDO-1 is due to its enzymatic conversion of tryptophan to kynurenine, resulting in tryptophan insufficiency, which interferes in the mTOR pathway or activation of the serine/threonine-protein kinase, GCN2 (general control nonderepressible), or kynurenine in excess, which activates the aryl hydrocarbon receptor (AhR) pathway.…”