Local ablative therapies and the effect on antitumor immune responses in pancreatic cancer - A review

Pancreatic ductal adenocarcinoma (PDAC) is a devastating disease, projected to rank as the second most prevalent cause of cancer-related mortality by 2030. Despite significant progress in advances in surgical techniques and chemotherapy protocols, the overall survival (OS) remains to be less than 10 % for all stages combined. In recent years, local ablative techniques have been introduced and utilized as additional therapeutic approaches for locally advanced pancreatic cancer (LAPC), with promising results with respect to local tumor control and OS. In addition to successful cytoreduction, there is emerging evidence that local ablation induces antitumor immune activity that could prevent or even treat distant metastatic tumors. The enhancement of antitumor immune responses could potentially make ablative therapy a therapeutic option for the treatment of metastatic PDAC. In this review, we summarize current ablative techniques used in the management of LAPC and their impact on systemic immune responses.

Pressure-Enabled Drug Delivery (PEDD) of a class C TLR9 agonist in combination with checkpoint inhibitor therapy in a murine pancreatic cancer model

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Background: Systemic immunotherapy has had limited clinical benefit in pancreatic ductal adenocarcinoma (PDAC). This is thought to be due to its desmoplastic immunosuppressive tumor microenvironment in addition to high intratumoral pressures that limit drug delivery. Recent pre-clinical cancer models and early-phase clinical trials have demonstrated the efficacy of toll-like receptor 9 agonists (TLR9a), including the synthetic CpG oligonucleotide SD101, to stimulate innate and adaptive immune cells and eliminate suppressive myeloid cells. We hypothesized that Pressure Enabled Drug Delivery (PEDD) via Pancreatic Retrograde Venous Infusion (PRVI) of a TLR9a would improve responsiveness to systemic anti-programmed death receptor-1 (PD-1) checkpoint inhibitor therapy in a murine orthotopic PDAC model. Methods: Murine PDAC (KPC4580P) tumors were implanted into the pancreatic tails of C57BL/6J mice and treated 8 days after implantation. Mice were assigned to PRVI saline (pSAL, n=9), systemic anti-PD1 100 mcg/mouse on Day 0, 2 and 4 (sAPD1, n = 6), 30mcg PRVI TLR9a (pTLR9a, n=9), 30mcg systemic TLR9a (sTLR9a, n=7) on Day 0, and combination 30mcg PRVI TLR9a on Day 0 and systemic anti-PD1 100 mcg/mouse on Day 0, 2 and 4 (COMBO, n =9). Fluorescently-labeled TLR9a (radiant efficiency [RE]) was measured on day 1. Blood and tumors were collected at necropsy 12 days after infusion. Results: All mice survived to necropsy. Site of tumor fluorescence measurements revealed higher intensity fluorescence in pTLR9a compared to sTLR9a (7.5x10^5 vs. 2.4x10^5 RE, p= 0.048). Significantly lower MDSCs in the COMBO vs. pSAL are shown. Tumor weights were significantly lower in the COMBO group compared to pSAL (400 vs. 964 mg, p=0.003), and were also lower, although not significantly, than in the pTLR9a (400 vs. 518mg, p=0.50), and sAPD1 (400 vs. 645 mg, p = 0.70) groups. Conclusions: PEDD of TLR9a by PRVI with systemic anti-PD-1 demonstrated improved PDAC tumor control. These results support study of this combination therapy in PDAC patients and expansion of ongoing PEDD clinical trials. [Table: see text]

Inhibition of SUMOylation modulates the immunosuppressive microenvironment of pancreatic cancer

Objective

Pancreatic cancer (PC) is a highly aggressive disease that is poorly responsive to available immunotherapy approaches, such as checkpoint inhibitors. Post-translational protein modification (PTM) by small ubiquitin-like modifier (SUMO) is upregulated in cancer, and high expression of SUMOylation-related factors correlates with poor survival in PC. TAK-981 is a novel inhibitor of SUMOylation that has demonstrated induction of anti-tumor immune responses in preclinical models. Our hypothesis is that TAK-981 will decrease SUMOylated proteins and subsequently modulate the tumor microenvironment to increase anti-tumor immunity.

Methods

In order to recapitulate the microenvironment of human PC, a 3-dimensional organoid cell line derived from a genetically-engineered “KPC” mouse was used. Organoids were injected orthotopically into the head of the pancreas via laparotomy. Once tumors reached 5–7 mm in diameter on ultrasound imaging, mice were randomized to one of two treatment groups: Control/Vehicle versus TAK-981 (15 mg/kg) delivered daily via intraperitoneal injection. Tumors were harvested on day 14 for gene expression analysis by quantitative real time PCR (RT-qPCR).

Results

Tumor growth (Fig. 1) in the TAK-981 15 mg/KG daily group (mean + SD volume = 207 + 109 mm3) was significantly inhibited compared to the vehicle group (595 + 141 mm3, p < 0.01). Immunohistochemical staining for CD 31 (Fig. 2) and Caspase 3 indicated a reduction of angiogenesis and increased apoptosis of tumor cells, consistent with the well-established roles of SUMOylation in angiogenesis and tumorigenesis. Gene expression analysis of tumor lysates showed a 26-fold increase in expression of Interferon beta (p<0.05), and an almost 2-fold increase in expression of genes related to dendritic cell activation, including CD80 (p<0.05) and CD86 (p=0.14) in the TAK-981 group, suggesting a modulation of the immune microenvironment.

Conclusion

Our results suggest that the inhibition of SUMOylation with TAK-981 is associated with improved local tumor control and changes in the immunosuppressive tumor microenvironment. We expect that TAK-981 will improve PC responsiveness to immunotherapy, such as with checkpoint inhibitors.

Abstract 1610: Local delivery of anti CTLA4 mediates cDC1 dependent eradication of HNSCC with limited IRAEs in a preclinical model of oral squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) ranks 6th in cancer incidence worldwide and has a five-year survival rate of only 63%. Despite advances in curative-intent therapies over the past three decades, rates of recurrence exceed 50% and long-term toxicities remain unacceptably morbid. Immunotherapies - principally immune checkpoint inhibitors (ICI) such as αPD-1 and αCTLA-41 antibodies which restore endogenous antitumor T cell immunity - offer the greatest promise for achieving durable response in HNSCC. However, the clinical application of ICI has been limited by immune-related adverse events (irAEs), which is a consequence of compromised peripheral immune tolerance after ICI therapy. Although irAEs are often reversible they can become severe, at best prompting premature termination of therapy or at worst becoming life-threatening. To address the off-target irAEs inherent to systemic ICI therapy, we developed a novel, local delivery strategy based upon an array of soluble microneedles (MN). Leveraging our recently reported syngeneic, tobacco-signature murine HNSCC model, we characterized the αCTLA-41 anti-tumor response as both CD8 T cell- and conventional dendritic cell type 1-dependent. When comparing αCTLA-4 therapy delivered in the traditional systemic format or with our local-MN delivery system, we found that while both routes of delivery led to >90% tumor responses, local-MN delivery achieved responses with lower total dosing while also limiting distribution of αCTLA-41 antibody from areas distal to draining lymphatic basins. Employing the previously described Foxp3-GFP-DTR GEMM developed for interrogation of murine irAEs, we found that local-MN protected animals from irAEs observed with systemic therapy. Taken together, our findings support the exploration of the microneedle array as a viable delivery strategy for ICI treatment in HNSCC.

Citation Format: Mara Gilardi, Zhiyong Wang, Victoria H. Wu, Miguel Angel Lopez-Ramirez, Fernando Soto-Alvarez, Robert Saddawi-Konefka, Dana Steffen, Marco Proietto, Zbigniew Mikulski, Haruka Miki, Jayanth Shankara Narayanan, Alfredo Molinolo, Joseph Wang, J. Silvio Gutkind. Local delivery of anti CTLA4 mediates cDC1 dependent eradication of HNSCC with limited IRAEs in a preclinical model of oral squamous cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1610.

Inhibition of SUMOylation enhances responses to irreversible electroporation in pancreatic cancer

Objective

The revolutionary results of immunotherapy have not yet translated to pancreatic cancer (PC).

Irreversible electroporation (IRE) is a non-thermal ablative therapy that can generate tumor-specific immune responses, yet not sufficient to eradicate distant metastatic disease. Post-translational protein modification (PTM) by small ubiquitin-like modifier (SUMO) is involved in carcinogenesis and PD-L1 mediated immunosuppression. TAK-981 is a novel inhibitor of SUMOylation that has demonstrated induction anti-tumor immune responses in preclinical models. Our hypothesis is that TAK-981 will augment the effects of IRE in an immunocompetent orthotopic mouse model of PC.

Methods

The PC cell line (KPC4580P) was derived from an autochthonous tumor arising in a genetically engineered mouse model (KPC). The tumors were implanted orthotopically into the pancreas via laparotomy. Once tumors reached 5-7 mm in diameter, mice were randomized to one of four treatment groups: IRE alone, TAK-981 alone, IRE + TAK-981, or no treatment. IRE versus sham laparotomy (150 x 90 microsec pulses at 1500 V/cm) was performed once through second laparotomy. TAK-981 (7.5mg/kg) versus vehicle was delivered via subcutaneous injection twice weekly x four doses, starting on the day of IRE. Tumors were harvested on day 14 for flow cytometric analysis.

Results

Ultrasound was performed on days 8, 14 and 20 after initiation of treatment. Tumor growth in the IRE + TAK-981 group was significantly inhibited compared to sham-treated tumors (Fig. 1, *p=0.0002), and this effect persisted to day 20, even after treatment with TAK-981 was stopped on day 11 (p < 0.01). Flow cytometry revealed a greater than 2-fold increase in CD8+ T-cells (Fig. 2a, *p <0.05) and 4-fold increase in IFN-gamma+ CD8+ T-cells (Fig. 2b, *p=0.01) in tumors treated with the combination relative to sham-treated tumors.

Conclusion

Our results suggest that the combination of IRE with TAK-981 is associated with better local tumor control and a significant increase of CD8+ T-cells and IFN-gamma+ CD8+ T-cells. We expect that this combination might contribute systemic immune responses that would prevent or even eradicate distant metastasis. Given that immunosuppression mediated by PD-L1 is regulated by ubiquitination and is seen in 50% of PC tumors, targeting PTM with TAK-981 might also render PC responsive to immunotherapy with checkpoint inhibitors.

Comparison of gemcitabine delivery and tumor response in a pressurized pancreatic retrograde venous infusion versus systemic infusion in an orthotopic murine model

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Background: Pancreatic ductal adenocarcinoma (PDAC) is associated with limited response to systemic therapy (ST). Elevated tumor interstitial fluid pressures (IFP) inhibit penetration of ST. Regional Pressure Enabled Drug Delivery has recently demonstrated improved response for liver tumors in a clinical trial. However, this delivery method has not been evaluated in PDAC. We compared gemcitabine (Gem) by systemic delivery vs. a novel pressurized Pancreatic Retrograde Venous Infusion (PRVI) method in an orthotopic PDAC mouse model. Methods: PDAC murine cell line (KPC4580P) tumors were transplanted onto the pancreatic tail of C57BL/6J mice. Groups of 15 mice were randomly assigned to PRVI Gem, PRVI saline (Control), or intraperitoneal Gem (Systemic) groups. Five mice from the PRVI and Systemic groups were randomly selected after one hour post infusion to evaluate Gem tumor concentrations by liquid chromatography - tandem mass spectrometry (ng/mg), and the remainder of mice were euthanized after 7 days to evaluate treatment response. Results: Tumor concentrations of Gem were significantly higher following PRVI compared to Systemic (128 vs. 19, p < 0.01) at one hour after treatment. Seven days after treatment, PRVI Gem mice demonstrated lower mean tumor volume (mm3) than Systemic Gem and Control mice (274 vs. 857 vs. 629, p < 0.01), respectively. Histologic evaluation of tumors demonstrated decreased cellularity in the PRVI Gem mice compared to Systemic and Control mice (35 vs. 78 vs. 71%, p = 0.01), respectively. No differences were seen in Ki67% or immune cell infiltrate between groups. Conclusions: PRVI delivery resulted in increased PDAC Gem concentrations and improved treatment responses with decreased tumor burden and cellularity. These findings suggest that pressurized regional chemotherapy infusion overcomes the elevated PDAC IFP and justifies additional translational pre-clinical studies with other chemotherapeutics (including immunomodulating antibodies) with different physicochemical properties.

Abstract B78: Irreversible electroporation (IRE) acts as an “in situ vaccine” and induces antitumor immune responses in pancreatic cancer

Introduction: Cancer immunotherapy has made waves of progress in recent years with the advent of checkpoint inhibitor therapies against several cancers. However, pancreatic cancer (PC), a disease which kills approximately 40,000 patients each year in the US, has successfully evaded immunotherapy approaches. PC hosts a notoriously immunosuppressive microenvironment comprised of an abundance of immunosuppressive tumor associated macrophages, myeloid derived suppressor cells (MDSCs) and regulatory T-cells with a scarcity of effector CD8+ T-cells. Irreversible electroporation (IRE) is a non-thermal ablation technique that induces tumor cell death without destruction of adjacent collagenous structures. Unlike thermal ablation techniques, IRE results in a gradual apoptotic cell death and is currently in clinical use for selected patients with locally advanced PC. We hypothesize that the abundant release of antigens by IRE can induce an “in situ vaccination” effect that can elicit adaptive T-cell-mediated anti-tumor immune responses.

Methods: We have developed a robust syngeneic immunocompetent mouse model of PC using a cell line established from a tumor arising in a LSL-KrasG12D/+; LSL-Trp53R172H/+; PDX1Cre/+; LSL-ROSA26 Luc/+ mouse (KPC). We have utilized the ECM 830 square wave pulse generator to deliver IRE (100 μsec pulses of electricity at 1500 V/cm using a two-needle array probe) to subcutaneous tumors measuring 5-7 mm in diameter. The effects of IRE on primary tumor growth and secondary tumor challenge were observed. Flow cytometry-based immunoprofiling studies of tumors at one week post-IRE were performed in triplicate and presented as mean difference between IRE and no treatment (standard error). *P&lt;0.01 by student’s t-test was considered statistically significant.

Results: Vaccination studies with irradiated KPC cells confirmed that they were immunogenic in C57BL/6 mice. In preliminary studies, we identified the minimal IRE dose to induce tumor regression to be 150 pulses, with complete regression in 3 of 9 tumors (33%). Survival was prolonged in the IRE groups, particularly in mice with complete regression. This outcome was confirmed to be immune-mediated, as IRE of tumor-bearing immunodeficient Rag-1-/- mice, which lack functional T and B cell components, results in progressive outgrowth with similar kinetics as untreated mice. When immunocompetent mice with tumor regression were re-challenged two weeks later with 105 cells injected into the contralateral flank, we observed no growth in the secondary tumors, confirming adaptive immune activation post-IRE. Tumor immunoprofiling revealed a 43±2%* decrease in the number of tumor-infiltrating MDSCs (CD11b+/CD11c+/Gr-1hi) post-IRE, with a similar decrease in the respective tumor draining inguinal lymph nodes. An increase in total tumor infiltrating lymphocytes (TILs) was also observed, including an 18±2%* increase in CD8+ TILs and a concomitant large increase (2.5 fold*) in PD-1+/CD8+ double positive T-cells.

Conclusion: These results suggest that IRE is capable of triggering an antitumor immune response that contributes to the local effects of IRE and inhibits growth of secondary tumor re-challenge. IRE affects the composition of immune cells in the tumor microenvironment, including a large increase in PD-1+/CD8+ TILs. These effects may be augmented by combining IRE with checkpoint blockade, which is a focus of our ongoing studies.

Citation Format: Jayanth Shankara Narayanan, Tomoko Hayashi, Aaron M. Miller, Stephen P. Schoenberger, Rebekah R. White. Irreversible electroporation (IRE) acts as an “in situ vaccine” and induces antitumor immune responses in pancreatic cancer [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2017 Oct 1-4; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2018;6(9 Suppl):Abstract nr B78.