Abstract B038: Toll like receptor 4 (TLR4) agonism by lipopolysaccharide (LPS) in pancreatic cancer model stimulates anti-tumor immunity in CD4+T cell dependent fashion

Introduction: Pancreatic cancer, one of the most lethal malignancies, has a 5-year overall survival of approximately 10%. It is an immunologically cold tumor and is poorly responsive to immunotherapy. Globally, researchers are in quest of immunomodulatory modalities to improve the therapeutic response. lipopolysaccharide (LPS), a known toll like receptor 4 (TLR4) agonist is known to activate immune response. Here, we evaluate the effect of LPS mediated TLR4 agonism on the anti-tumor immune machinery of pancreatic cancer. Methods: We implanted KPC (Kras LSL-G12D; Trp53 LSL-R172H/+; Pdx1Cre/+) pancreatic cancer cells in C57BL/6 mice subcutaneously. The animals were treated intraperitoneally with LPS (1mg/kg) or saline (control) at day 10 and 17. Tumor samples were isolated at endpoint and were analyzed using flow cytometry and real time polymerase chain reaction (RT-PCR) for infiltration of immunocytes and expression of immune-associated genes respectively. Functional response of CD4+ T-cells to tumor antigen re-challenge was assessed by measuring interferon-γ (IFN-γ) release in-vitro. In another experiment, LPS or saline treatment was administered along with depletion of CD4+ or CD8+ T-cells employing monoclonal antibodies. CD4+ T-cells extracted from spleens of tumor bearing control or LPS treated mice were subjected to Calcein AM based cytotoxicity assay. Cytotoxicity assay was also performed by blocking major histo-compatibility II (MHCII) on KPC cells. Results: LPS administration in tumor bearing mice significantly reduced the tumor burden as compared to control group. Flow cytometry on tumor samples revealed increased infiltration of CD4+ T-cells in LPS group whereas CD8+ T-cell repertoire was unaffected. Tumor samples from the LPS group showed higher expression of genes for anti-tumor cytokines such as IFN-γ, granzymes and perforin. Depletion of CD4+ T cells, but not CD8+ T cells attenuated the effect of LPS on tumor growth. When the splenic CD4+ T-cells from both groups were pulsed with KPC cell lysate, LPS treated mice derived CD4+ T-cells demonstrated a greater ability to secrete IFN-γ. Splenic CD4+ T-cells from LPS treated mice showed significantly higher cytotoxicity against KPC cells as compared to control CD4+ T-cells. However, blocking MHCII molecules on KPC cells reduced the cytotoxicity in CD4+ T-cells derived from LPS treated mice. This suggests that CD4 cytotoxicity ensues in an MHCII dependent manner. Conclusions: LPS treatment reduces tumor burden in the subcutaneous tumor model of pancreatic cancer by upregulating the infiltration of CD4+ T-cells and translating them to a cytotoxic phenotype. It also stimulates the upregulation of anti-tumor immunity related cytokines in the tumor microenvironment. We have also found that the cytotoxic CD4+ T cells terminate the pancreatic cancer cells in an MHCII dependent manner. Therefore, our findings provide a novel insight into how “TLR4 agonism can stimulate CD4+ T-cell mediated antitumor immunity”, which can be harnessed as a potential source for pancreatic cancer immunotherapy.

Citation Format: Utpreksha Vaish, Anthony R. Ferrantella, Tejeshwar Jain, Prateek Sharma, Srikanth Iyer, Vikas Dudeja. Toll like receptor 4 (TLR4) agonism by lipopolysaccharide (LPS) in pancreatic cancer model stimulates anti-tumor immunity in CD4+T cell dependent fashion [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer; 2022 Sep 13-16; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2022;82(22 Suppl):Abstract nr B038.

Utility of routine intraoperative cholangiogram during cholecystectomy in children: A nationwide analysis of outcomes and readmissions

PURPOSE

This study aims to determine postoperative outcomes and readmissions in pediatric cholecystectomy with routine intraoperative cholangiogram (IOC) utilization.

METHODS

The Nationwide Readmissions Database 2010-2014 was queried for all pediatric cholecystectomies. A propensity score-matched analysis (PSMA) with over 30 covariates was performed between cholecystectomy alone (CCY) versus those with routine IOC (CCY + IOC, no biliary obstruction, dilatation, or pancreatitis). χ² analysis or Mann-Whitney U were used for statistical analysis with p < 0.05 set as significant.

RESULTS

34,390 cholecystectomies were performed: 92% were laparoscopic, most were teenage females (75%, 15 years [13-17]) and did not undergo IOC (75%). Postoperative mortality rate was 0.1%. The PSMA cohort comprised of 1412 CCY and 1453 CCY + IOC. Patients with CCY alone had higher rates of 30-day (7% vs 5%), 1-year readmissions (13% vs 11%) and had higher rates of overall complications (22% vs 12%) compared with CCY + IOC, all p < 0.05. Although uncommon, bile duct injuries were more prevalent in CCY (2% vs 0%, p < 0.001), while there was no difference in readmissions for retained stones. Resource utilization was increased in CCY patients, likely due to increased complication rates.

CONCLUSION

This nationwide PSMA suggests pediatric CCY with routine IOC is associated with decreased readmissions, overall resource utilization, complications, and bile duct injuries.

TYPE OF STUDY

Retrospective Comparative Study.

LEVEL OF EVIDENCE

Level III.

Abstract B111: Vaccination against TAP downregulation-induced neoantigens to prevent future tumor development in the setting of recurrence or premalignancy

Development of therapeutic strategies to prevent recurrence in cancer patients, or tumor progression in individuals at high risk of developing cancer, has been challenging given the long and often unpredictable time to the emergence of the malignant tumors. Mutation-generated neoantigens represent the most potent antigens to induce antitumor immunity, yet the ability to predict which neoantigens will be expressed in future tumors is at present not an option.To overcome the limitations of targeting mutated neoantigens, we have developed a simple and broadly applicable approach to induce neoantigens in tumor cells in situ by reducing the expression of peptide transporter TAP, whereby a TAP-specific siRNA is targeted to tumor cells in mice by conjugation to a broad-range nucleolin-binding aptamer. Nucleolin, normally expressed in the cytoplasm and nucleolus of all somatic cells, is translocated to the cell surface of most murine and human tumors and hence could serve as an almost universal target to deliver therapeutics to tumors in vivo. Previous results have demonstrated that genetic ablation of TAP not only inhibits the canonical antigen processing pathway but also upregulates alternative pathways presenting new epitopes, essentially neoantigens, that can be recognized by the immune system to elicit effective CD8+ T-cell responses. Such epitopes are shared among all (tumor) cells in which TAP is downregulated, corresponding to the functional equivalent of clonal mutation-generated neoantigens. Our study shows that transiently increasing the neoantigen burden of tumor cells in situ by targeted downregulation of TAP represent a potent way of generating antitumor immunity in the absence of measurable toxicity.Exploiting the ability to induce neoantigens in situ, we are developing a novel vaccination strategy targeting potent neoantigens to control the growth of the future tumors—whereby mice in remission or with premalignant lesions are first vaccinated against TAP downregulation-induced neoantigens, and when or if tumor develops the same antigens are induced in the tumor, termed prorapeutic vaccination (prophylactic + therapeutic). To induce an immune response against TAP downregulation-induced neoantigens, mice were vaccinated with TAP siRNAs that are targeted to DC in situ by conjugation to a short CpG oligonucleotide leading to the downregulation of TAP, expression of neoantigens, as well as activation of the DC, and thereby priming of a potent T-cell response. To induce neoantigens in the future tumors, the TAP siRNA is targeted to the developing tumor lesion by conjugation to the nucleolin (Nucl) aptamer. Both Nucl and CpG targeted siRNA are administered systemically via intraperitoneal injection to reach the disseminated tumor lesions and resident DC present throughout the body. In murine models of recurrence and premalignant disease, prorapeutic vaccination elicited an adaptive and innate antitumor immune response and inhibited tumor growth. The prorapeutic vaccination approach was more effective than vaccinating against prototypic mutated neoantigens, and did not elicit measurable autoimmune toxicity, in stark contrast to a comparatively therapeutic dose of CTLA-4.The ability to vaccinate against experimentally induced neoantigens using a broadly applicable procedure with two chemically synthesized reagents, introduces a new paradigm in cancer immunotherapy of vaccinating against neoantigens induced in future tumors, to prevent recurrence in patients in remission or preventing tumor development in individuals at high risk of developing cancer.

Citation Format: Greta Garrido Hidalgo, Brett Schrand, Ailem Rabasa, Agata Levay, Tal Gefen, Giri Bhuwan Bhuwan, Anthony R. Ferrantella, Vikas Dudeja, Koen Marijt, Thorbald T. van Hall, Eli Gilboa. Vaccination against TAP downregulation-induced neoantigens to prevent future tumor development in the setting of recurrence or premalignancy [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr B111.