Response Of Pancreatic Ductal Adenocarcinoma Research Articles

Allysine-Targeted Molecular MRI Enables Early Prediction of Chemotherapy Response in Pancreatic Cancer.

Neoadjuvant therapy is routinely used in pancreatic ductal adenocarcinoma (PDAC), but not all tumors respond to this treatment. Current clinical imaging techniques are not able to precisely evaluate and predict the response to neoadjuvant therapies over several weeks. A strong fibrotic reaction is a hallmark of a positive response, and during fibrogenesis, allysine residues are formed on collagen proteins by the action of lysyl oxidases. Here, we report the application of an allysine-targeted molecular MRI probe, MnL3, to provide an early, noninvasive assessment of treatment response in PDAC. Allysine increased 2- to 3-fold after one dose of neoadjuvant therapy with FOLFIRINOX in sensitive human PDAC xenografts in mice. Molecular MRI with MnL3 could specifically detect and quantify fibrogenesis in PDAC xenografts. Comparing the MnL3 signal before and 3 days after one dose of FOLFIRINOX predicted subsequent treatment response. The MnL3 tumor signal increased by 70% from day 0 to day 3 in mice that responded to subsequent doses of FOLFIRINOX, whereas no signal increase was observed in FOLFIRINOX-resistant tumors. This study indicates the promise of allysine-targeted molecular MRI as a noninvasive tool to predict chemotherapy outcomes. Significance: Allysine-targeted molecular MRI can quantify fibrogenesis in pancreatic tumors and predict response to chemotherapy, which could guide rapid clinical management decisions by differentiating responders from nonresponders after treatment initiation.

A targetable secreted neural protein drives pancreatic cancer metastatic colonization and HIF1a nuclear retention.

Pancreatic ductal adenocarcinoma (PDAC) is an increasingly diagnosed cancer that kills 90% of afflicted patients, with most patients receiving palliative chemotherapy. We identified neuronal pentraxin 1 (NPTX1) as a cancer secreted protein that becomes over-expressed in human and murine PDAC cells during metastatic progression and identified adhesion molecule with Ig like domain 2 (AMIGO2) as its receptor. Molecular, genetic, biochemical and pharmacologic experiments revealed that secreted NPTX1 acts cell-autonomously on the AMIGO2 receptor to drive PDAC metastatic colonization of the liver-the primary site of PDAC metastasis. NPTX1-AMIGO2 signaling enhanced hypoxic growth and was critically required for hypoxia induced factor-1a (HIF1a) nuclear retention and function. NPTX1 is over-expressed in human PDAC tumors and upregulated in liver metastases. Therapeutic targeting of NPTX1 with a high-affinity monoclonal antibody substantially reduced PDAC liver metastatic colonization. We thus identify NPTX1-AMIGO2 as druggable critical upstream regulators of the HIF1a hypoxic response in PDAC.

Keratin 17 modulates the immune topography of pancreatic cancer

BackgroundThe immune microenvironment impacts tumor growth, invasion, metastasis, and patient survival and may provide opportunities for therapeutic intervention in pancreatic ductal adenocarcinoma (PDAC). Although never studied as a potential modulator of the immune response in most cancers, Keratin 17 (K17), a biomarker of the most aggressive (basal) molecular subtype of PDAC, is intimately involved in the histogenesis of the immune response in psoriasis, basal cell carcinoma, and cervical squamous cell carcinoma. Thus, we hypothesized that K17 expression could also impact the immune cell response in PDAC, and that uncovering this relationship could provide insight to guide the development of immunotherapeutic opportunities to extend patient survival.MethodsMultiplex immunohistochemistry (mIHC) and automated image analysis based on novel computational imaging technology were used to decipher the abundance and spatial distribution of T cells, macrophages, and tumor cells, relative to K17 expression in 235 PDACs.ResultsK17 expression had profound effects on the exclusion of intratumoral CD8+ T cells and was also associated with decreased numbers of peritumoral CD8+ T cells, CD16+ macrophages, and CD163+ macrophages (p < 0.0001). The differences in the intratumor and peritumoral CD8+ T cell abundance were not impacted by neoadjuvant therapy, tumor stage, grade, lymph node status, histologic subtype, nor KRAS, p53, SMAD4, or CDKN2A mutations.ConclusionsThus, K17 expression correlates with major differences in the immune microenvironment that are independent of any tested clinicopathologic or tumor intrinsic variables, suggesting that targeting K17-mediated immune effects on the immune system could restore the innate immunologic response to PDAC and might provide novel opportunities to restore immunotherapeutic approaches for this most deadly form of cancer.

Abstract 6433: Anti-CD36 monoclonal antibody can sensitize the neoadjuvant chemotherapy response in PDAC by eliminating the senescent tertiary lymphatic structure

Abstract Objective: Pancreatic ductal adenocarcinoma (PDAC) is deadly and aggressive. Neoadjuvant chemotherapy (NAC) may reduce tumor volume and alter the resectability of the tumor. The efficacy of neoadjuvant chemotherapy in patients is still limited. Tertiary lymphoid structures (TLSs) develop in peripheral non-lymphoid tissues and are essential for the immune response and correlate with chemotherapy in various tumor types. However, more research is needed to determine how TLSs affect neoadjuvant chemotherapy in PDAC. We aim to determine how neoadjuvant chemotherapy affects tumor-infiltrating lymphocytes (TLSs) in PDAC patients. We also want to find a biomarker to boost PDAC neoadjuvant chemotherapy response. Methods: We retrospectively collected formalin-fixed paraffin embedded (FFPE) tissues from 115 PDAC patients without preoperative treatment and 72 patients pretreated with neoadjuvant chemotherapy. Multispectral images were processed using AI-powered image analysis software (Tissue Gnostics; Zeiss, Germany). The 10X Genomics platform was used to sequence single cells in tissue samples from five patients who received neoadjuvant chemotherapy (NAC) and five patients who had not received any treatment before analysis (pretreatment naïve, PN). TLS was separated using Laser Microdissection. The mouse model was created by orthotopically injecting tumor cells into the pancreas. Results: Patients who received NAC have a senescent microenvironment. High-throughput single-cell sequencing showed that the senescent gene signature score was enriched in the NAC group, especially in immune cells. The percentage of p16+ CD20+ B cells and P16+ CD3+ T cells in TLSs also increased in the NAC group. Spatial transcriptomics analysis exhibited that CD36 is highly expressed in senescent TLSs, which suggested that CD36 may be a marker for senescent TLSs. Moreover, CD36+ TLSs induced the infiltration of MDSCs and regulatory T cells. CD36+ TLSs were an independent prognostic factor for poor overall survival (OS) (HR=0.67, p=0.002) and progression-free survival (PFS) (HR=0.71, p=0.003). A mice orthotopic xenograft model showed that an anti-CD36 monoclonal antibody eliminated senescent TLSs in pancreatic tissue. MDSCs and Tregs in the surrounding tissue also decreased. Additionally, in vivo KPC mice model showed that the combination of an anti-CD36 and chemotherapy reduced tumor volume and increased survival compared to chemotherapy alone. Conclusion: NAC has the potential to induce the senescence of tumor-associated TLSs, a phenomenon that has been linked to unfavorable prognosis in PDAC. CD36 serves as a viable marker for senescent TLSs that can be targeted. The administration of an anti-CD36 monoclonal antibody can potentially enhance the efficacy of chemotherapy in PDAC by selectively eliminating CD36+ senescent TLSs in mouse models. Citation Format: Jingrui Yan, Tianxing Zhou, Chao Yang, Yongjie Xie, Jun Yu, Jihui Hao. Anti-CD36 monoclonal antibody can sensitize the neoadjuvant chemotherapy response in PDAC by eliminating the senescent tertiary lymphatic structure [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6433.

Abstract 6649: Tumor treating fields (TTFields) induce an anti-tumor immune response in a pancreatic cancer mouse model

Abstract Background: Pancreatic ductal adenocarcinoma (PDAC) is a deadly malignancy with few therapeutic options. Tumor Treating Fields (TTFields) are low-intensity electric fields that disrupt cellular processes critical for cancer cell division and tumor progression and are approved for the treatment of glioblastoma and pleural mesothelioma. A phase 3 clinical trial is in progress to test the efficacy and safety of TTFields concomitant with standard-of-care gemcitabine and nab-paclitaxel (GnP) as front-line treatment of locally advanced PDAC. TTFields have been shown to induce immunogenic cell death (ICD) in cancer cells and elicit a systemic anti-cancer immune response. Accordingly, the benefit of applying TTFields together with immune checkpoint inhibitors (ICI) was demonstrated in a phase 3 study in patients with non-small cell lung carcinoma. This preclinical study investigated TTFields-induced immune responses in PDAC. Methods: An orthotopic PDAC tumor model was established by inoculating 4 × 105 Panc02 pancreatic cancer cells with stable luciferase expression into the pancreas tail of immune-competent C57BL/6 mice. The mice were randomized into four groups following bioluminescence detection of tumor volume: control, TTFields (150 kHz, 10 days), GnP (50 mg/kg for each drug, i.p. injected once a week for a total of two administrations), and GnP + TTFields. At the end of treatment, tumor volume was measured using caliper, and blood was collected for spectral flow cytometry-based immunophenotyping and ELISA testing for the ICD marker HMGB-1. In vitro, Panc02 cells were treated for 72h with TTFields (150 kHz, 1.62 V/cm RMS) and examined by flow cytometry for apoptosis and ATP secretion (using quinacrine staining) and surface exposure of calreticulin. Results: TTFields markedly reduced the tumor size in Panc02 tumor-bearing mice compared to control mice. Analysis of peripheral blood effector (CD62L-CD44+) and central (CD62L+CD44+) memory T cells demonstrated the induction of circulating effector-memory cytotoxic CD8+ T cells. Additionally, serum HMGB-1 concentrations were significantly elevated in mice treated with TTFields compared to control mice, implying the involvement of ICD in the response to TTFields. In vitro, TTFields application induced apoptosis of Panc02 cells and increased ICD, as indicated by increased surface exposure of calreticulin and ATP depletion. When TTFields were used in Panc02 tumor bearing mice concomitantly with GnP, a substantial reduction in tumor size was detected, and a complete tumor regression was observed in a number of mice. Conclusions: Our results suggest that TTFields may enhance the effects of standard-of-care chemotherapy for the treatment of PDAC. Furthermore, TTFields were shown to induce ICD and activate an antitumor immune response in PDAC, supporting future studies evaluating the efficacy of TTFields together with ICI in PDAC. Citation Format: Tal Kan, Tharwat Haj Khalil, Yiftah Barsheshet, Tali Voloshin, Avital Vorontsov, Boris Brant, Lilach Koren, Roni Blatt, Shay Cahal, Efrat Zemer-Tov, Rom Paz, Anat Klein-Goldberg, Catherine Tempel Brami, Sara Jacobovitch, Alexandra Volodin, Bella Koltun, Cfir David, Adi Haber, Moshe Giladi, Uri Weinberg, Yoram Palti. Tumor treating fields (TTFields) induce an anti-tumor immune response in a pancreatic cancer mouse model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6649.

Abstract 2495: CCL3 predicts an exceptional response to TGFβ inhibition in pancreatic ductal adenocarcinoma by sustaining a basal-like ecotype enriched in LIF-producing macrophages

Abstract The TGFβ receptor inhibitor galunisertib (GAL) exhibited promising efficacy in patients with pancreatic ductal adenocarcinoma (PDAC) in the randomized phase 2 H9H-MC-JBAJ study. However, the identification of predictive biomarkers remains of unique importance. We used a 279 multi-analyte panel and confirmed CCL3 as the most significant plasma protein for chemoresistance in patients receiving gemcitabine (GEM) [overall survival (mOS) (95%CI), high vs low, 3.6 (2.5-4.0) vs 10.1 (7.2-17.0) months, HR (95%CI)= 3.92 (2.14-7.20); p&amp;lt;0.001]. GAL dramatically reverted this resistance and CCL3 was the most significant predictive marker for the combination of this agent plus GEM [mOS (95%CI), GAL + GEM vs. placebo + GEM, 9.0 (5.5-12.1) vs 3.6 (2.5-4.0) months, HR (95%CI)= 0.39 (0.23-0.68); p&amp;lt;0.001]. We delved into the mechanisms behind this exceptional response in PDAC with this prognostically negative ecotype sustained by CCL3 in 6 different murine PDAC models. Mice bearing high-Ccl3 tumors had a significantly shorter mOS, a higher infiltration of M2-macrophages (TAMs), and a more mesenchymal/basal-like phenotype than did models with undetectable Ccl3.Ccl3 was stably expressed in DT4313 and PAN610, and silenced in RC416 cells. In co-culture models, DT4313Ccl3 and PAN610Ccl3 had a more mesenchymal phenotype and induced a M2 polarization of RAW264.7 murine TAMs than did controls. Mice bearing DT4313Ccl3 or PAN610Ccl3 tumors had a significantly shorter mOS, an higher infiltration of M2-polarized TAMs and a more mesenchymal/basal-like phenotype than controls. The expression of Tgfβ1 ligand and the phosphorylation of Smad2 were triggered only in TAMs if co-cultured with Ccl3-high RC416scr, DT4313Ccl3 or PAN610Ccl3 cells. This activation of Tgfβ pathway was blocked by maraviroc, a selective inhibitor of Ccl3-receptor Ccr5. In co-culture, GAL reverted the mesenchymal phenotype of PDAC cells and the M2 polarization of TAMs. By using an 111 different cytokine immunoassay, Leukemia Inhibitory Factor (Lif) was the most significantly factor overexpressed by TAMs if stimulated by Ccl3. GAL suppressed this Lif expression. In mice bearing DT4313Ccl3 tumors GEM was ineffective, whereas it prolonged mOS in those with DT4313NTC tumors. Conversely, GAL plus GEM doubled mOS duration vs. GEM, modulated M2- TAMs infiltration, the mesenchymal/basal-like phenotype and plasma Lif only in mice bearing DT4313Ccl3 tumors, but not in those with DT4313NTC controls. In summary, we demonstrated that tumor-derived Ccl3 activates an autocrine Tgfβ signaling in TAMs, triggering their M2-phenotype and secretion of Lif. This Tgfβ-Lif axis sustains paracrinally a mesenchymal/basal-like PDAC ecotype resistant to GEM. Inhibition of Tgfβ signaling modulates this poor prognosis ecotype, and explains the exceptional response to GAL in patients with high-CCL3 PDAC. Citation Format: Silvia Pietrobono, Monica Bertolini, Veronica De Vita, Enza Scarlato, Federica Fazzini, Fabio Sabbadini, Domenico Mangiameli, Alberto Quinzii, Simona Casalino, Davide Melisi. CCL3 predicts an exceptional response to TGFβ inhibition in pancreatic ductal adenocarcinoma by sustaining a basal-like ecotype enriched in LIF-producing macrophages [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2495.

Abstract 6631: Aging influences the pancreatic ductal adenocarcinoma tumor immune microenvironment to promote features of immunosuppression

Abstract Advancing age is the strongest independent risk factor for the development of pancreatic ductal adenocarcinoma (PDAC) and a negative prognostic factor. PDACs are typically immunologically “cold” tumors and do not often respond to currently approved immunotherapy treatment approaches. How aging may alter non-malignant cells, such as fibroblasts and immune cell populations, in the PDAC tumor microenvironment (TME) to decrease anti-tumor immune responses is not understood. We identified that aged microenvironments significantly alter the growth and progression of PDAC tumors. Orthotopic KPC and Panc02 mouse PDAC cell line injections into the pancreata of aged (&amp;gt;64-week-old) compared to young (6-8-week-old) C57BL/6 mice result in more rapid tumor growth and increased frequency of liver metastases in vivo. Tumors from aged mice have high expression of the TGFβ family member GDF-15 and hyperactivation of AKT signaling driven by the release of secreted factors from aged pancreatic fibroblasts. We found that in aged microenvironments there is a marked reduction in the number of CD8+ T cells and an increase in FoxP3+ regulatory T cells in primary orthotopic pancreatic tumors using the KPC and Panc02 models. In addition, we performed portal vein injections to establish liver metastases to study the differences in immune cell infiltration in metastases from young vs. aged microenvironments. Aged mice form more and larger liver metastases compared to young mice, and metastatic lesions in aged mice have decreased CD8+ T cell infiltration when compared to young mice. Since tumors in aged microenvironments have increased AKT activation compared to young microenvironments, we next tested if AKT signaling was sufficient to alter immune cell infiltration in PDAC tumors. In young mice, treatment with recombinant GDF-15, which activates AKT signaling, reduced CD8+ T cell infiltration into tumors. Conversely, in KPC tumors grown in aged mice treated with the AKT inhibitor MK-2206, there was a trend toward increased CD8+ T cell infiltration and a significant reduction in immunosuppressive FoxP3+ Tregs. Together, these data highlight age-dependent differences in the immune infiltration in PDAC tumors. They suggest that activation of AKT signaling can drive features of immunosuppression in PDAC, providing the rationale for targeting AKT signaling to improve antitumor immune responses in PDAC. Citation Format: Emma Kartalia, James M. Leatherman, Jae W. Lee, Elizabeth M. Jaffee, Ashani T. Weeraratna, Daniel J. Zabransky. Aging influences the pancreatic ductal adenocarcinoma tumor immune microenvironment to promote features of immunosuppression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6631.

Group A streptococcal collagen-like protein 1 restricts tumor growth in murine pancreatic adenocarcinoma and inhibits cancer-promoting neutrophil extracellular traps.

Pancreatic ductal adenocarcinoma (PDAC) is a lethal cancer associated with an immunosuppressive environment. Neutrophil extracellular traps (NETs) were initially described in the context of infection but have more recently been implicated in contributing to the tolerogenic immune response in PDAC. Thus, NETs are an attractive target for new therapeutic strategies. Group A Streptococcus (GAS) has developed defensive strategies to inhibit NETs. In the present work, we propose utilizing intra-tumoral GAS injection to stimulate anti-tumor activity by inhibiting cancer-promoting NETs. Mice harboring Panc02 or KPC subcutaneous tumors injected with three different M-type GAS strains. Tumors and spleens were harvested at the endpoint of the experiments to assess bacterial colonization and systemic spread, while sera were analyzed for humoral responses toward the streptococcal antigens, especially the M1 and Scl1 proteins. Role of the streptococcal collagen-like protein 1 (Scl1) in anti-PDAC activity was assessed in vivo after intratumoral injection with M1 GAS wild-type, an isogenic mutant strain devoid of Scl1, or a complemented mutant strain with restored scl1 expression. In addition, recombinant Scl1 proteins were tested for NET inhibition using in vitro and ex vivo assays assessing NET production and myeloperoxidase activity. Injection of three different M-type GAS strains reduced subcutaneous pancreatic tumor volume compared to control in two different murine PDAC models. Limitation of tumor growth was dependent on Scl1, as isogenic mutant strain devoid of Scl1 did not reduce tumor size. We further show that Scl1 plays a role in localizing GAS to the tumor site, thereby limiting the systemic spread of bacteria and off-target effects. While mice did elicit a humoral immune response to GAS antigens, tested sera were weakly immunogenic toward Scl1 antigen following intra-tumoral treatment with Scl1-expressing GAS. M1 GAS inhibited NET formation when co-cultured with neutrophils while Scl1-devoid mutant strain did not. Recombinant Scl1 protein inhibited NETs ex vivo in a dose-dependent manner by suppressing myeloperoxidase activity. Altogether, we demonstrate that intra-tumoral GAS injections reduce PDAC growth, which is facilitated by Scl1, in part through inhibition of cancer promoting NETs. This work offers a novel strategy by which NETs can be targeted through Scl1 protein and potentiates its use as a cancer therapeutic.

Microscopic tumor mapping of post-neoadjuvant therapy pancreatic cancer specimens to predict post-surgical recurrence: A prospective cohort study

BackgroundAlthough various pathological grading systems are available for evaluating the response of pancreatic ductal adenocarcinoma (PDAC) to neoadjuvant therapy (NAT), their prognostic value has not been thoroughly validated. This study examined whether microscopic tumor mapping of post-NAT specimens could predict tumor recurrence. MethodsThis prospective study enrolled 52 patients who underwent pancreaticoduodenectomy after NAT for PDAC between 2019 and 2021. Microscopic mapping was performed to identify residual tumor loci within the tumor bed using 4 mm2 pixels. Patients were divided into small extent (SE; n = 26) and large extent (LE; n = 26) groups using a cutoff value of 226 mm2. The diagnostic performance for predicting tumor recurrence was evaluated using receiver operating characteristic (ROC) curves. ResultsCarbohydrate antigen 19-9 levels were normalised after NAT in more patients in the SE group (SE 21 [80.8%] vs. LE 13 [50.0%]; P = 0.041). Tumor size (P < 0.001), T stage (P < 0.001), positive lymph node yield (P = 0.024), and perineural invasion rate (P = 0.018) were significantly greater in the LE group. The 3-year disease-free survival rate was significantly lower in the LE group (SE 83.3% vs. LE 50.0%, P = 0.004). The area under the ROC curve for mapping extent was 0.743, which was greater than that of the other tumor response scoring systems. ConclusionsMicroscopic tumor mapping of the residual tumor in post-NAT specimens is a significant predictor of post-surgical recurrence, and offers better prognostic performance than the current grading systems.

Abstract 1190 Investigating chemoresistance mechanisms and collateral responses in pancreatic ductal adenocarcinoma

Abstract 1190 Investigating chemoresistance mechanisms and collateral responses in pancreatic ductal adenocarcinoma

Inter-reader variability of imaging biomarkers for therapeutic response in pancreatic ductal adenocarcinoma.

700 Background: Indeterminate borders of pancreatic ductal adenocarcinoma (PDAC) can impair reliability of lesion annotation in imaging assessment of therapeutic response (TR) after neoadjuvant chemotherapy (NAT). Previous work showed that longitudinal image registration algorithms can track treatment-related changes and produce quantitative imaging biomarkers (QIB) for TR that predict overall (OS) and recurrence-free survival (RFS). We compare inter-reader agreements of these biomarkers against conventional RECIST and tumor volume QIB. Methods: N=30 patients enrolled in a Phase II clinical trial comparing outcomes of a NAT regimen were retrospectively analyzed. In baseline and restaging CT, whole pancreas and tumor segmentations and tumor diameters were annotated by 2 expert attending radiologists and 2 novice radiology fellows. For each reader, percent change in tumor diameter (RECIST score), percent change in tumor volume (ΔV), and difference in ratio of tumor burden to pancreas volume (ΔB) were computed as QIB for TR across the NAT interval via two approaches: image registration of the baseline tumor region of interest, and direct segmentation of the PDAC lesion in baseline and restaging images. Inter-reader agreements of RECIST, ΔV, and ΔB QIB from both approaches were compared via concordance correlation coefficient (CCC). Associations with OS and RFS were compared over 5-year follow-up via Harrell’s C-index. Results: Among expert radiologists, RECIST score CCC was 0.77 [95% CI: 0.59-0.88], whereas image registration QIB CCC values were significantly higher (ΔV: 0.95 [0.90-0.98], p=0.002; ΔB: 0.93 [0.86-0.97], p=0.014). ΔV and ΔB QIB measured by direct tumor segmentation had significantly lower CCC than by image registration (p&lt;0.001). Among novice readers, image registration QIB (ΔV: 0.83 [0.67-0.91], ΔB: 0.70 [0.48-0.84]) produced higher agreement than RECIST (0.26 [-0.17-0.61]; p=0.002 and p=0.035), with CCC more similar to expert readers. While image registration QIB did not differ from RECIST in association with RFS, registration-based QIB predicted OS with significantly higher C-index (ΔV: 0.58 [0.56-0.60], p&lt;0.001; ΔB: 0.64 [0.62-0.66], p&lt;0.001) than RECIST (0.50 [0.45-0.55]) among experts. Conclusions: Longitudinal registration of the pancreas yields more consistent QIB for PDAC TR with stronger association to OS outcomes than RECIST. These registration-based QIB aim to advance PDAC management by improving patient-specific discrimination of TR after NAT. [Table: see text]

Abstract B054: Investigating ER stress responses in pancreatic ductal adenocarcinoma under lipid imbalance

Abstract Pancreatic ductal adenocarcinoma (PDAC) is the 4th leading cause of cancer-related death with a five-year survival rate of 10%. Dense desmoplasia results in poor intratumoral perfusion and elevated interstitial fluid pressure, creating regions with severe oxygen and nutrient deprivation. One result is a deficiency in unsaturated fatty acids (uFAs), as the de novo synthesis of uFAs requires oxygen. Our results indicate that PDAC cells experience endoplasmic reticulum (ER) stress and trigger subsequent ER stress responses under uFA limited conditions in vitro. ER stress responses are governed by three major stress sensors: Inositol-requiring enzyme 1𝛼 (IRE1𝛼), PKR-like ER kinase (PERK) and activating transcription factor 6 (ATF6). ER stress responses are also activated in PDAC murine and patient samples. Interestingly, the expression of ER stress markers is much higher in malignant lesions than benign pancreatic intraepithelial neoplasia. In contrast to tumor promoting, we found that PERK, ATF6 and IRE1𝛼 - XBP1 are cytotoxic to PDAC cells in vitro, as their knockout improved viability under stress conditions. Surprisingly, pharmacological inhibitor of XBP1 splicing, B-I09, didn’t recapitulate the results of the genetic approach. While B-I09 has cytoprotective effects in some PDAC lines, it is cytotoxic in others. In addition to inhibiting XBP1 splicing, B-I09 also inhibits regulated IRE1𝛼 dependent decay (RIDD). We speculate that RIDD might have opposite roles to XBP1s, leading to the discrepancy in the cellular phenotypes we observed. Most B-I09 responders are reported to be the basal-like transcriptional subtype. Therefore, we hypothesize that the basal-like subtype is more susceptible to B-I09. So far, we have shown that basal-like patient tumors are significantly enriched in the ER stress response pathways from bulk patient RNA-seq datasets, and we are currently validating this result in the publicly available scRNA-seq datasets from patients which contain basal-like and classical subtypes. We have generated isogenic models with basal-like features, such as epithelial to mesenchymal transition and deltaNP63 overexpression. However, our results suggest that these basal-like features did not sensitize classical PDAC cells to B-I09. Our lab has previously shown that B-I09 is selectively lethal to the MYC-transformed tumors. We are currently testing whether MYC overexpression would sensitize the non-responders to B-I09. It is exciting to see that some of the PDAC lines such as PANC1 and KPC murine line 4662 have reduced viability under B-I09 treatment. However, in our subcutaneous xenograft and allograft experiments, B-I09 only leads to a mild tumor growth suppression, which is unlikely to be therapeutically beneficial by itself. We are currently testing whether XBP1 inhibition could result in an enhanced tumor suppression using OVA antigen stimulated system, as XBP1 inhibition in tumor cells was shown to have tumor-repressing roles via immune system. Citation Format: Yanqing (Christine) Jiang, Xu Han, Nathan Coffey, Mai Wang, John Tobias, Raymond Ng, Carson Poltorack, M. Celeste Simon. Investigating ER stress responses in pancreatic ductal adenocarcinoma under lipid imbalance [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr B054.

Abstract C063: Keratin 17 as a predictor of chemotherapy response in pancreatic ductal adenocarcinoma

Abstract Background: Two chemotherapies based on either gemcitabine- or 5-fluorouracil (5-FU) remain standard-of-care for pancreatic ductal adenocarcinomas (PDACs). Patients, however, differ in response and thus many clinical trials for experimental drugs have failed. Therefore, there is an urgent need to establish clinically deployable and rapid biomarkers to decide the best chemotherapeutic regimen for subgroups of patients and prevent toxic side effects. We previously reported that keratin 17 (K17) expression, detected at either the level of messenger RNA or protein by immunohistochemistry (IHC), is as accurate as molecular subtyping to identify subgroups of PDAC patients with shortest survival. In this work, we determined the predictive value of K17 testing for both chemotherapeutic approaches to treat PDAC. Methods: We profiled keratin 17 (K17) expression, a hallmark biomarker of the basal molecular subtype of PDAC, using immunohistochemistry in two cohorts of formalin-fixed paraffin-embedded PDACs (total n=305). These cases were collected through the Know Your Tumor® initiative and three high-volume treating institutions in the U.S. We performed multivariate predictive analyses and determined the threshold to define positive vs negative test. Results: Patients with advance stage disease, low K17, and treated with 5-FU- chemotherapy had three-times longer survival rates compared to counterparts treated with gemcitabine-based chemotherapy. These results contrast to those found in cases with high K17, where no differences were seen with either regimen. Based on RECIST, 72% of low K17 cases responded to treatment compared to 24% of high K17 cases. Predictive value of K17 was independent of mutation status and clinical variables. Conclusions: Our findings indicate that 5-FU-, rather than gemcitabine- based therapies are more likely to extend survival for patient's tumors expressing low rather than high K17. A K17 IHC test rapid test in PDACs has been patented (US11,092,603) and it is currently being tested in prospective phase II clinical trials (NCT04469556, NCT02047474 and NCT03991962). Results from these trials will test the presented findings. Citation Format: Lyanne Oblein, Lucia Roa, Sruthi Babu, Michael Horowitz, Emanuel Petricoin, Lynn M. Matrisian, Edik Blais, Natalia Marchenko, Felicia Allard, Ali Alkalin, Wei Jiang, Brent Larson, Andrew Hendifar, Vincent Picozzi, Minsig Choi, Luisa Escobar-Hoyos, Kenneth Shroyer. Keratin 17 as a predictor of chemotherapy response in pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr C063.

Abstract B041: Keratin 17 excludes CD8-positive T cells and recruits CD163-positive macrophages in pancreatic ductal adenocarcinoma

Abstract Background. Keratin 17 (K17) is a negative prognostic and predictive biomarker, overexpressed in the biologically most aggressive forms of pancreatic ductal adenocarcinoma (PDAC). In other anatomic sites and disease processes, K17 expression impacts the inflammatory microenvironment, correlating with changes in the expression of inflammatory cytokines and the infiltration of CD8+ T cells. Thus, we hypothesized that K17 expression also impacts the immune response in PDAC. Methods. We aimed to determine the relationship between intratumoral and peritumoral immune cell infiltrates versus K17 expression in tumor cells, using brightfield multiplexed immunohistochemistry (mIHC) and our suite of deep learning tools to quantitatively evaluate the expression of four biomarkers of T-cells and macrophages. The study included a multi-institutional cohort of 235 PDAC cases from Stony Brook University Hospital (n=54), Thomas Jefferson University (n=67), Cedars Sinai Medical Center (n=7) and Know Your Tumor PanCAN-Perthera (n=107). Peritumoral immune cells were scored in zones defined as stromal tissue within ≤25 µm of the closest tumor cell. Intratumor immune cells were defined as those that physically touched or overlapped with tumor cells. Immune cell counts in peritumoral and intratumoral K17-negatvie areas of the tumor were normalized to immune cell counts in K17-positive areas. Results. The density of CD8+ T cells in K17-negative peritumoral zones was greater than in K17-positive peritumoral zones in 82.6% of PDACs. Similarly, the density of intratumoral CD8+ T cells in K17-negative areas was greater than in K17-positive areas in 93.2% of cases. Less striking inverse correlations for immune cell density relative to K17 expression were found for CD4+ peritumor lymphocytes and both intratumoral and peritumor CD16+ macrophages. By contrast, CD163+ (tumor-promoting) macrophages were more numerous in K17+ peritumoral and intratumoral zones. All differences were statistically significant and independent of tumor grade, stage, histologic subtype, and neoadjuvant treatment history (p&amp;lt; 0.0001). Conclusions. Correlations between K17 and inflammatory cells suggests K17 expression negatively influences the number and infiltration of T-cells and contributes to the marked immunosuppressive effect of PDAC. These findings suggest that the biologic impact of K17 goes beyond its role as a negative prognostic biomarker that impacts tumor growth, metastasis, and chemoresistance, to suppress the immune response to PDAC. Understanding how K17 influences immune cell function may inform future immunotherapeutic opportunities for PDAC treatment. Citation Format: Lyanne Oblein, Sruthi Babu, Mariana Torrente-Goncalves, Lucia Roa, Michael Horowitz, Mahmudul Hasan, Danielle Fassler, Jaymie Oentoro, Emanuel Petricoin, Lynn M. Matrisian, Natalia Marchenko, Edik Blais, Felicia Allard, Ali Alkalin, Wei Jiang, Brent Larson, Andrew Hendifar, Chao Chen, Shahira Abousamra, Dimitris Samaras, Tahsin Kurc, Joel Saltz, Luisa Escobar-Hoyos, Kenneth Shroyer. Keratin 17 excludes CD8-positive T cells and recruits CD163-positive macrophages in pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr B041.

HPB P12 Do Chemotherapy Factors or Treatment Intervals Influence Pathological Tumour Response during Neoadjuvant Chemotherapy for Pancreatic Ductal Adenocarcinoma? A Bi-Institutional Study

Abstract Background Pathological response of pancreatic ductal adenocarcinoma (PDAC) to neoadjuvant chemotherapy (NAT) can be assessed using grading systems such as the College of American Pathologists (CAP) system, with favourable regression being associated with improved oncological outcomes. The aim of the study was to investigate factors associated with favourable tumour regression in patients undergoing pancreatoduodenectomy (PD) for PDAC. Methods Patients who received NAT before undergoing PDAC resection at two institutions in the United Kingdom between 2013 and 2021 were reviewed. Interactions between chemotherapy regimens, tumour staging, carbohydrate antigen 19-9 (Ca19-9) levels, perioperative factors and tumour regression grading (TRG) were explored. Results 54 patients were identified who were suitable for inclusion. 12 (22%) patients had a favourable response to NAT according to the CAP grading system. A significantly greater reduction in Ca19-9 observed in the favourable TRG group [mean -2359 U/mL] compared to the unfavourable TRG group [mean -569 U/mL (p&amp;lt;0.001). The type of chemotherapy agent received, the number of cycles or whether the patient had a dose reduction during their NAT course did not differ significantly between the groups. The time from diagnosis to chemotherapy and time from end of chemotherapy to surgery were also similar between the groups. Conclusions In this bi-institutional retrospective study, neither chemotherapy factors nor treatment intervals were not found to be significantly related to pathological tumour response to NAT in PDAC patients undergoing resection. Given that a favourable pathological response has been related to improved oncological outcomes, future research should concentrate on further mechanisms that may influence the response of PDAC tumours to NAT, such as gene expression and the tumour microbiome. Given that NAT is also a relatively new approach, further multicentre collaboration should be encouraged to increase numbers of patients for study.

Type of neoadjuvant treatment strategy is associated with differential pathologic responses in pancreatic ductal adenocarcinoma

BackgroundTumor fibrosis after neoadjuvant treatment (NAT) for pancreatic ductal adenocarcinoma (PDAC) correlates with treatment response. Herein we assessed how different NAT strategies influence pathologic responses and survival. MethodsPatients with surgically resected PDAC who received NAT (1991–2020) were included. Descriptive statistics compared outcomes amongst fibrosis groups (none, minor <50 ​%, partial 51%–94 ​%, major ≥95 ​%) and NAT (chemotherapy alone, chemoradiation, or chemotherapy ​+ ​chemoradiation (total neoadjuvant therapy, TNT)). ResultsPatients with major fibrosis most often received TNT (65.8 ​%, p ​< ​0.001). Major fibrosis was associated with the greatest rate of downstaging (77.8 ​%, p ​< ​0.001), highest R0 margin rate (100 ​%, p ​< ​0.01), and lowest mean positive lymph node ratio (0.80, p ​< ​0.01). Amongst complete responders, 11/14 (78.6 ​%) received TNT. Median overall (66.3 months, p ​= ​0.003) and disease-free (54.7months, p ​= ​0.05) survival were highest with major fibrosis. ConclusionsMajor fibrosis and complete pathologic responses after NAT are most frequent with a TNT strategy and are associated with improved outcomes.

MiR-506 Promotes Antitumor Immune Response in Pancreatic Cancer by Reprogramming Tumor-Associated Macrophages toward an M1 Phenotype.

Pancreatic ductal adenocarcinoma (PDAC) is a highly malignant cancer with a poor prognosis, and effective treatments for PDAC are lacking. In this study, we hypothesized that miR-506 promotes antitumor immune response in PDAC by reprogramming tumor-associated macrophages toward an M1 phenotype to reverse its immunosuppressive tumor microenvironment (TME). First, the relationship between TME and the expression of miR-506 was assessed using clinical samples. Our results provided evidence that lower expression of miR-506 was associated with poor prognosis and immunosuppressive TME in PDAC patients. In addition, miR-506 inhibit the PDAC progression and reversed its immunosuppressive microenvironment in a macrophage-dependent manner. Next, we established a PDAC mouse model by orthotopic injection to further explore the role of miR-506 in vivo. Mechanistic investigations demonstrated that miR-506 could reprogram the polarization of M2-like macrophages toward an M1-like phenotype through targeting STAT3. Meanwhile, miR-506 could also sensitize PDAC to anti-PD-1 immunotherapy, because the tumor microenvironment remodeling effects of miR-506 could reprogram macrophage polarization and subsequently promote cytotoxic T lymphocyte (CTL) infiltration. These findings suggest a relationship between miR-506 and TME, especially M2-like macrophages, thus providing novel insights into mechanisms of tumor progression and potential immunotherapeutic targets for further clinical treatment.

Characterization of acute and subacute immune response to boiling histotripsy ablation of pancreatic adenocarcinoma

Boiling histotripsy (BH) is a cavitation-based pulsed focused ultrasound method of mechanical tissue disintegration. When applied to tumor ablation, BH was shown in a number of preclinical studies to stimulate antitumor immune responses, with the extent and dynamics depending on the tumor microenvironment. In this work, we assessed the response of pancreatic ductal adenocarcinoma (PDAC)—an immunologically “cold” tumor—to BH ablation. C57BL/6J mice (n = 6 per group) were bilaterally subcutaneously grafted with KPC-derived mT4 cell line in the hind limbs. When one of the two tumors reached 8 mm, 80% of its volume was ablated with BH (1.5 MHz, 3 ms pulses, 1% duty cycle, 450 W power, 15 pulses/point). The tumors, inguinal lymph nodes and spleens were harvested at 1-, 3-, and 6-day time points and processed for immune phenotyping through flow cytometry, histology, and immunohistochemistry. At earlier time points, the response within the tumor was dominated by neutrophils, and by day 6—by inflammatory monocytes both in treated and contralateral sides versus sham. Transient increases in B cells, neutrophils, NK, NKT cells, and monocytes were observed in the ipsilateral lymph nodes and in spleens on day 3, and mostly subsided by day 6. These data will inform further studies in optimization of combination therapies for PDAC. [Work supported by Focused Ultrasound Foundation.]

Analyzing Flow Cytometry or Targeted Gene Expression Data Influences Clinical Discoveries-Profiling Blood Samples of Pancreatic Ductal Adenocarcinoma Patients.

Monitoring the therapeutic response of pancreatic ductal adenocarcinoma (PDAC) patients is crucial to determine treatment strategies. Several studies have examined the effectiveness of FOLFIRINOX as a first-line treatment in patients with locally advanced pancreatic cancer, but little attention has been paid to the immunologic alterations in peripheral blood caused by this chemotherapy regimen. Furthermore, the influence of the measurement type (e.g., flow cytometry and targeted gene expression) on the clinical discoveries is unknown. Therefore, we aimed to scrutinize the influence of using flow cytometry or targeted immune gene expression to study the immunological changes in blood samples of PDAC patients who were treated with a single-cycle FOLFIRINOX combined with lipegfilgrastim (FFX-Lipeg). Whole-blood samples from 44 PDAC patients were collected at two time points: before the first FOLFIRINOX cycle and 14 days after the first cycle. EDTA blood tubes were used for multiplex flow cytometry analyses to quantify 18 immune cell populations and for complete blood count tests as the standard clinical routine. The flow cytometry data were analyzed with FlowJo software. In addition, Tempus blood tubes were used to isolate RNA and measure 1230 immune-related genes using NanoString Technology®. Data quality control, normalization, and analysis were performed using nSolver™ software and the Advanced Analysis module. FFX-Lipeg treatment increased the number of neutrophils and monocytes, as shown by flow cytometry and complete blood count in concordance with elevated gene expression measured via targeted gene expression profiling analysis. Interestingly, flow cytometry analysis showed an increase in the number of B and T cells after treatment, while targeted gene expression analysis showed a decrease in B and T cell-specific gene expression. Targeted gene expression complements flow cytometry analysis to provide a comprehensive understanding of the effects of FFX-Lipeg. Flow cytometry and targeted gene expression showed increases in neutrophils and monocytes after FFX-Lipeg. The number of lymphocytes is increased after treatment; nevertheless, their cell-specific gene expression levels are downregulated. This highlights that different techniques influence clinical discoveries. Therefore, it is important to carefully select the measurement technique used to study the effect of a treatment.

Molecular profiling and specific targeting of gemcitabine-resistant subclones in heterogeneous pancreatic cancer cell populations.

Chemotherapy is pivotal in the multimodal treatment of pancreatic ductal adenocarcinoma (PDAC). Technical advances unveiled a high degree of inter- and intratumoral heterogeneity. We hypothesized that intratumoral heterogeneity (ITH) impacts response to gemcitabine treatment and demands specific targeting of resistant subclones. Using single cell-derived cell lines (SCDCLs) from the classical cell line BxPC3 and the basal-like cell line Panc-1, we addressed the effect of ITH on response to gemcitabine treatment. Individual SCDCLs of both parental tumor cell populations showed considerable heterogeneity in response to gemcitabine. Unsupervised PCA including the 1,000 most variably expressed genes showed a clustering of the SCDCLs according to their respective sensitivity to gemcitabine treatment for BxPC3, while this was less clear for Panc-1. In BxPC3 SCDCLs, enriched signaling pathways EMT, TNF signaling via NfKB, and IL2STAT5 signaling correlated with more resistant behavior to gemcitabine. In Panc-1 SCDCLs MYC targets V1 and V2 as well as E2F targets were associated with stronger resistance. We used recursive feature elimination for Feature Selection in order to compute sets of proteins that showed strong association with the response to gemcitabine. The optimal protein set calculated for Panc-1 comprised fewer proteins in comparison to the protein set determined for BxPC3. Based on molecular profiles, we could show that the gemcitabine-resistant SCDCLs of both BxPC3 and Panc-1 are more sensitive to the BET inhibitor JQ1 compared to the respective gemcitabine-sensitive SCDCLs. Our model system of SCDCLs identified gemcitabine-resistant subclones and provides evidence for the critical role of ITH for treatment response in PDAC. We exploited molecular differences as the basis for differential response and used these for more targeted therapy of resistant subclones.