Inhibiting NR5A2 targets stemness in pancreatic cancer by disrupting SOX2/MYC signaling and restoring chemosensitivity

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is a profoundly aggressive and fatal cancer. One of the key factors defining its aggressiveness and resilience against chemotherapy is the existence of cancer stem cells (CSCs). The important task of discovering upstream regulators of stemness that are amenable for targeting in PDAC is essential for the advancement of more potent therapeutic approaches. In this study, we sought to elucidate the function of the nuclear receptor subfamily 5, group A, member 2 (NR5A2) in the context of pancreatic CSCs.

METHODS

We modeled human PDAC using primary PDAC cells and CSC-enriched sphere cultures. NR5A2 was genetically silenced or inhibited with Cpd3. Assays included RNA-seq, sphere/colony formation, cell viability/toxicity, real-time PCR, western blot, immunofluorescence, ChIP, CUT&Tag, XF Analysis, lactate production, and in vivo tumorigenicity assays. PDAC models from 18 patients were treated with Cpd3-loaded nanocarriers.

RESULTS

Our findings demonstrate that NR5A2 plays a dual role in PDAC. In differentiated cancer cells, NR5A2 promotes cell proliferation by inhibiting CDKN1A. On the other hand, in the CSC population, NR5A2 enhances stemness by upregulating SOX2 through direct binding to its promotor/enhancer region. Additionally, NR5A2 suppresses MYC, leading to the activation of the mitochondrial biogenesis factor PPARGC1A and a shift in metabolism towards oxidative phosphorylation, which is a crucial feature of stemness in PDAC. Importantly, our study shows that the specific NR5A2 inhibitor, Cpd3, sensitizes a significant fraction of PDAC models derived from 18 patients to standard chemotherapy. This treatment approach results in durable remissions and long-term survival. Furthermore, we demonstrate that the expression levels of NR5A2/SOX2 can predict the response to treatment.

CONCLUSIONS

The findings of our study highlight the cell context-dependent effects of NR5A2 in PDAC. We have identified a novel pharmacological strategy to modulate SOX2 and MYC levels, which disrupts stemness and prevents relapse in this deadly disease. These insights provide valuable information for the development of targeted therapies for PDAC, offering new hope for improved patient outcomes. A Schematic illustration of the role of NR5A2 in cancer stem cells versus differentiated cancer cells, along with the action of the NR5A2 inhibitor Cpd3. B Overall survival of tumor-bearing mice following allocated treatment. A total of 18 PDX models were treated using a 2 x 1 x 1 approach (two animals per model per treatment); n=36 per group (illustration created with biorender.com ).

Bcl3 Couples Cancer Stem Cell Enrichment With Pancreatic Cancer Molecular Subtypes

BACKGROUND & AIMS

The existence of different subtypes of pancreatic ductal adenocarcinoma (PDAC) and their correlation with patient outcome have shifted the emphasis on patient classification for better decision-making algorithms and personalized therapy. The contribution of mechanisms regulating the cancer stem cell (CSC) population in different subtypes remains unknown.

METHODS

Using RNA-seq, we identified B-cell CLL/lymphoma 3 (BCL3), an atypical nf-κb signaling member, as differing in pancreatic CSCs. To determine the biological consequences of BCL3 silencing in vivo and in vitro, we generated bcl3-deficient preclinical mouse models as well as murine cell lines and correlated our findings with human cell lines, PDX models, and 2 independent patient cohorts. We assessed the correlation of bcl3 expression pattern with clinical parameters and subtypes.

RESULTS

Bcl3 was significantly down-regulated in human CSCs. Recapitulating this phenotype in preclinical mouse models of PDAC via BCL3 genetic knockout enhanced tumor burden, metastasis, epithelial to mesenchymal transition, and reduced overall survival. Fluorescence-activated cell sorting analyses, together with oxygen consumption, sphere formation, and tumorigenicity assays, all indicated that BCL3 loss resulted in CSC compartment expansion promoting cellular dedifferentiation. Overexpression of BCL3 in human PDXs diminished tumor growth by significantly reducing the CSC population and promoting differentiation. Human PDACs with low BCL3 expression correlated with increased metastasis, and BCL3-negative tumors correlated with lower survival and nonclassical subtypes.

CONCLUSIONS

We demonstrate that bcl3 impacts pancreatic carcinogenesis by restraining CSC expansion and by curtailing an aggressive and metastatic tumor burden in PDAC across species. Levels of BCL3 expression are a useful stratification marker for predicting subtype characterization in PDAC, thereby allowing for personalized therapeutic approaches.

Abstract 5667: Exposure of tumor-associated macrophages to apoptotic pancreatic cancer cells promotes cancer stem cell chemoresistance

Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer related deaths worldwide. This is largely due to the existence of a subpopulation of stem-like cells present within the tumor, known as cancer stem cells (CSCs) that drive metastasis and chemoresistance. In addition, we have now come to realize that the tumor-associated microenvironment not only provides structural support for tumor development, but more importantly the microenvironment provides cues to CSCs that regulate their biological properties. Chemotherapy often leads to apoptosis of cancer cells, and in previous studies we have shown that tumor-associated macrophages (TAMs) exponentially increase following chemotherapy. We hypothesized that TAMs, in response to chemotherapy-induced apoptosis, secrete factors that potentiate PDAC chemoresistance. In line with this hypothesis, we show that monocyte-derived macrophages cultured in the presence of apoptotic PDAC cells polarize towards an M2 pro-tumor phenotype and secrete factors that render naïve PDAC cells, specifically CSCs, resistant to Gemcitabine- or Abraxane-induced apoptosis, irrespective of mutations in p53. Importantly, chemoresistant cells showed increased sphere formation capacity and increased tumorigenesis as measured in an extreme limiting dilution assay in nude mice, confirming an enrichment in CSCs. Moreover, using a syngeneic orthotropic in vivo model of PDAC, we were able to significantly augment the anti-tumor potential of Gemcitabine by pharmacologically eliminating TAMs using clodronate liposomes. To determine the mechanism by which TAMs promote PDAC chemoresistance, we performed proteomic analyses on macrophage conditioned media and identified several proteins specifically induced and secreted when macrophages were co-cultured with apoptotic PDAC cells, including 14-3-3 protein zeta/delta (14-3-3ζ), a major regulator of apoptotic cellular pathways. We present additional data to show that TAM-seceretd 14-3-3ζ promotes CSC chemoresistance. Taken together, the sum of these data highlight a unique regulatory mechanism by which chemotherapy-induced apoptosis acts as a switch to initiate a pro-tumor/anti-apoptotic mechanism in PDAC, challenging the idea that apoptosis of tumor cell is therapeutically beneficial, at least when immune sensor cells, such as macropahges, are present.

Citation Format: Gabriele D'Errico, Mireia Vallespinos, Sonia Alcala, Sandra Valle, Laura Martin-Hijano, Bruno Sainz. Exposure of tumor-associated macrophages to apoptotic pancreatic cancer cells promotes cancer stem cell chemoresistance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5667. doi:10.1158/1538-7445.AM2017-5667

DNMT1 Inhibition Reprograms Pancreatic Cancer Stem Cells via Upregulation of the miR-17-92 Cluster

Pancreatic ductal adenocarcinoma (PDAC) and other carcinomas are hierarchically organized, with cancer stem cells (CSC) residing at the top of the hierarchy, where they drive tumor progression, metastasis, and chemoresistance. As CSC and non-CSC share an identical genetic background, we hypothesize that differences in epigenetics account for the striking functional differences between these two cell populations. Epigenetic mechanisms, such as DNA methylation, play an important role in maintaining pluripotency and regulating the differentiation of stem cells, but the role of DNA methylation in pancreatic CSC is obscure. In this study, we investigated the genome-wide DNA methylation profile of PDAC CSC, and we determined the importance of DNA methyltransferases for CSC maintenance and tumorigenicity. Using high-throughput methylation analysis, we discovered that sorted CSCs have a higher level of DNA methylation, regardless of the heterogeneity or polyclonality of the CSC populations present in the tumors analyzed. Mechanistically, CSC expressed higher DNMT1 levels than non-CSC. Pharmacologic or genetic targeting of DNMT1 in CSCs reduced their self-renewal and in vivo tumorigenic potential, defining DNMT1 as a candidate CSC therapeutic target. The inhibitory effect we observed was mediated in part through epigenetic reactivation of previously silenced miRNAs, in particular the miR-17-92 cluster. Together, our findings indicate that DNA methylation plays an important role in CSC biology and also provide a rationale to develop epigenetic modulators to target CSC plasticity and improve the poor outcome of PDAC patients. Cancer Res; 76(15); 4546-58. ©2016 AACR.

The ever-changing landscape of pancreatic cancer stem cells

Over the past decade, the cancer stem cell (CSC) concept in solid tumors has gained enormous momentum as an attractive model to explain tumor heterogeneity. The model proposes that tumors contain a subpopulation of rare cancer cells with stem-like properties that maintain the hierarchy of the tumor and drive tumor initiation, progression, metastasis, and chemoresistance. The identification and subsequent isolation of CSCs in pancreatic ductal adenocarcinoma (PDAC) in 2007 provided enormous insight into this extremely metastatic and chemoresistant tumor and renewed hope for developing more specific therapies against this disease. Unfortunately, we have made only marginal advances in applying the knowledge learned to the development of new and more effective treatments for pancreatic cancer. The latter has been partly due to the lack of adequate in vitro and in vivo systems compounded by the use of markers that do not reproducibly nor exclusively select for an enriched CSC population. Thus, attempts to define a pancreatic CSC-specific genetic, epigenetic or proteomic signature has been challenging. Fortunately recent advances in the CSC field have overcome many of these challenges and have opened up new opportunities for developing therapies that target the CSC population. In this review, we discuss these current advances, specifically new methods for the identification and isolation of pancreatic CSCs, new insights into the metabolic profile of CSCs at the level of mitochondrial respiration, and the utility of genetically engineered mouse models as surrogate systems to both study CSC biology and evaluate CSC-specific targeted therapies in vivo.

4: REGENERATIVE ASYNCHRONY IS A DRIVER IN CHRONIC INFLAMMATION IN AGING

Purpose of Study

Age-associated chronic diseases are associated with a pro-inflammatory state. It has been challenging to determine cause and effect – do age-associated pathologies increase inflammation or does inflammation induce age-associated pathologies or both? We previously showed that disease-related regenerative asynchrony in repairing lung is the cause of chronic inflammation and fibrosis. Thus, we hypothesized that the aged lung is itself asynchronously regenerating leading to a pro-inflammatory pulmonary milieu.

Methods Used

Tracheas and intra-cardiac blood were harvested from C57BL6 mice in two age groups of both genders. Young mice were between 8 and 20 weeks of age. Aged mice were between 23 and 33 months of age. Tracheal epithelial progenitor cells were isolated and cultured for 6 days with continuous exposure to BrdU. Cellular regeneration was analyzed by flow cytometry for 7-AAD DNA staining in BrdU+ cells. Concentrations of an initial screening set of cytokines in plasma and cell culture supernatants from days 2 and 6 of culture were measured using magnetic bead-based assays.

Summary of Results

Fewer airway epithelial progenitors underwent mitosis from the aged than the young mice (16.9±10.4% vs. 62.2±9.4% of the cultured cells at 6 days). The tracheal epithelial progenitors from aged mice were asynchronously distributed along the cell cycle (G1, S, G2/M: 44, 25, and 31%) compared to those from young mice (62, 14, and 24%). Plasma concentrations of IL-1β, IL-6, TNFα and TGFβ were not significantly different between age groups. Concentrations of TGFβ were significantly different between age groups in supernatant from day 2 (aged=112.43±16.31 pg/mL, young=171.23±13.70 pg/mL; p<0.05) but not from day 6 of culture (aged=159.60±29.83 pg/mL, young=214.15±.94 pg/mL; p=NS). Concentrations of IL-1β were not significantly different between age groups in supernatant from day 2 of culture (aged=2.01±0.23 pg/mL, young=2.10±0.24 pg/mL; p=NS) but remained higher in aged compared to young progenitors on day 6 (aged: 2.17±0.31 pg/mL, young: 1.26±0.10 pg/mL; p<0.05).

Conclusions

Our data support the concept that aging induces progenitor cell mitotic asynchrony. It is possible that this epithelial mitotic asynchrony contributes to the pro-inflammatory state associated with aging, as seen in other chronic inflammatory states.

9: AN IN VIVO MODEL OF HUMAN AIRWAYS FOR INVESTIGATING FIBROSIS

Purpose of Study

Limited models exist to investigate the airway epithelium's role in repair, regeneration, and pathology of chronic obstructive lung diseases. We introduce a human asthmatic airway epithelial xenograft system integrating a proliferating and differentiating airway epithelium with an actively remodeling rodent mesenchyme in an immunocompromised murine host. We hypothesized that epithelial regeneration in asthma induces underlying matrix fibrosis.

Methods Used

Human airway epithelial cells from asthmatic and non-asthmatic donors (n=5 per group) were seeded into decellularized rat tracheas. Tracheas were ligated to a sterile tubing cassette and implanted subcutaneously in the flanks of athymic nude mice. Grafts were harvested at 2, 4, or 6 weeks for analysis of tissue histology, fibrillar collagen deposition, and TGFβ1 activation. Non-transplantable human lungs from asthmatic and non-asthmatic donor FFPE sections were analyzed using similar methods.

Summary of Results

Grafted epithelial cells generated a differentiated epithelium with basal, ciliated, and mucus cells. By 4 weeks post-engraftment, asthmatic-derived epithelia showed decreased numbers of ciliated cells and E-cadherin expression compared to non-asthmatic controls, similar to human lung biopsy tissue. While there was no evidence of matrix remodeling in acellular xenografts, grafts seeded with asthmatic-derived epithelial cells had 3 times as much fibrillar collagen at 6 weeks post-engraftment as non-asthmatic epithelial seeded grafts. This was accompanied by a >2-fold induction of matrix TGFβ1 [with evidence of pSMAD3 activity] in asthmatic grafts at 4 weeks (positive pixels/total field pixels=0.12±0.001 vs. 0.05±0.001; p=0.003) and 6 weeks (0.09±0.02 vs. 0.04±0.01; p=0.044) post-engraftment.

Conclusions

We show in this model that asthmatic epithelium alone is sufficient to drive aberrant mesenchymal remodeling, specifically with fibrillar collagen deposition in asthmatic-derived xenografts.These xenografts are a major advance over current animal models of asthma in that they permit direct assessment of the epithelial-mesenchymal trophic unit.

22: MITOTIC ASYNCHRONY INDUCES A PRO-INFLAMMATORY STATE IN AIRWAY EPITHELIUM

Purpose of Study

Mitotic behaviors are likely important for maintaining and restoring homeostasis in lung diseases with epithelial injury. We recently proposed that regenerative asynchrony in repairing tissue may underlie chronic inflammation and fibrosis, where immune cell infiltration is secondary to pro-inflammatory cross-talk among asynchronously repairing adjacent tissues. Building on our previous finding that regenerative asynchrony is associated with pro-inflammatory/fibrotic cytokine secretion, here we provide proof of cause-and-effect.

Methods Used

In vitro experiments were performed wherein airway epithelial cells were mitotically asynchronous due to disease state and then resynchronized via capture of the G1/S checkpoint via pulse exposure to dexamethasone, simvastatin, or aphidicolin. Experiments utilized a novel method we developed for inducing mitotic asynchrony in normal progenitors. Induced populations were used to elucidate if TGF- β1 plays a role in the resynchronization process.

Summary of Results

Human asthmatic fully-differentiated air–liquid interface airway epithelial mitosis was asynchronous relative to normal epithelia. Mitotic capture increased the percentage of progenitors in G1. This resynchronization in the asthmatic epithelia reduced basolateral TGF-β1 secretion. We next examined whether inducing mitotic asynchrony in normal epithelial cells would result in TGF-β1 secretion. Mitotic asynchrony was induced and samples showed moderate asynchrony at 6 and 12 hours that resolved spontaneously by 48 hours. These cells show elevated TGF-β1 secretion at 12 hours compared to either cell population in isolation. Regulation of TGF-β1 is being investigated as a possible mechanism for synchronization through contact and non-contact dependent experiments. Additionally, blocking TGF-β1 delays resynchronization.

Conclusions

Cumulative analysis shows mitotic synchrony is the homeostatic state in airway epithelial progenitor populations and poorly-synchronized mitosis (as in asthma) induces TGF-β1 secretion and a pro-inflammatory/pro-fibrotic airway. This finding establishes rationale for targeting progenitor cell mitotic behavior rather than immune-mediated inflammation in fibrotic disease.

Microenvironmental hCAP-18/LL-37 promotes pancreatic ductal adenocarcinoma by activating its cancer stem cell compartment

OBJECTIVES

The tumour stroma/microenvironment not only provides structural support for tumour development, but more importantly it provides cues to cancer stem cells (CSCs) that regulate their self-renewal and metastatic potential. This is certainly true for pancreatic ductal adenocarcinomas (PDAC), where tumour-associated fibroblasts, pancreatic stellate cells and immune cells create an abundant paracrine niche for CSCs via microenvironment-secreted factors. Thus understanding the role that tumour stroma cells play in PDAC development and CSC biology is of utmost importance.

DESIGN

Microarray analyses, tumour microarray immunohistochemical assays, in vitro co-culture experiments, recombinant protein treatment approaches and in vivo intervention studies were performed to understand the role that the immunomodulatory cationic antimicrobial peptide 18/LL-37 (hCAP-18/LL-37) plays in PDAC biology.

RESULTS

We found that hCAP-18/LL-37 was strongly expressed in the stroma of advanced primary and secondary PDAC tumours and is secreted by immune cells of the stroma (eg, tumour-associated macrophages) in response to tumour growth factor-β1 and particularly CSC-secreted Nodal/ActivinA. Treatment of pancreatic CSCs with recombinant LL-37 increased pluripotency-associated gene expression, self-renewal, invasion and tumourigenicity via formyl peptide receptor 2 (FPR2)- and P2X purinoceptor 7 receptor (P2X7R)-dependent mechanisms, which could be reversed by inhibiting these receptors. Importantly, in a genetically engineered mouse model of K-Ras-driven pancreatic tumourigenesis, we also showed that tumour formation was inhibited by either reconstituting these mice with bone marrow from cathelicidin-related antimicrobial peptide (ie, murine homologue of hCAP-18/LL-37) knockout mice or by pharmacologically inhibiting FPR2 and P2X7R.

CONCLUSIONS

Thus, hCAP-18/LL-37 represents a previously unrecognised PDAC microenvironment factor that plays a critical role in pancreatic CSC-mediated tumourigenesis.

Intracellular autofluorescence: a biomarker for epithelial cancer stem cells

Cancer stem cells (CSCs) are thought to drive tumor growth, metastasis and chemoresistance. Although surface markers such as CD133 and CD44 have been successfully used to isolate CSCs, their expression is not exclusively linked to the CSC phenotype and is prone to environmental alteration. We identified cells with an autofluorescent subcellular compartment that exclusively showed CSC features across different human tumor types. Primary tumor-derived autofluorescent cells did not overlap with side-population (SP) cells, were enriched in sphere culture and during chemotherapy, strongly expressed pluripotency-associated genes, were highly metastatic and showed long-term in vivo tumorigenicity, even at the single-cell level. Autofluorescence was due to riboflavin accumulation in membrane-bounded cytoplasmic structures bearing ATP-dependent ABCG2 transporters. In summary, we identified and characterized an intrinsic autofluorescent phenotype in CSCs of diverse epithelial cancers and used this marker to isolate and characterize these cells.

Abstract A18: The role of the microenvironment protein cathelicidin LL-37 in pancreatic ductal adenocarcinoma

This abstract is being presented as a short talk in the scientific program. A full abstract is printed in the Proffered Abstracts section (PR1) of the Conference Proceedings.

Citation Format: Bruno Sainz, Jr., Javier Frias, Michele Cioffi, Sonia Alcala, Christopher Heeschen. The role of the microenvironment protein cathelicidin LL-37 in pancreatic ductal adenocarcinoma. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Invasion and Metastasis; Jan 20-23, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;73(3 Suppl):Abstract nr A18.

Abstract PR1: The role of the microenvironment protein cathelicidin LL-37 in pancreatic ductal adenocarcinoma

The tumor-associated microenvironment does not only provide structural support for tumor development, but more importantly the microenvironment provides cues to cancer initiating cells [i.e. cancer stem cells (CSC)] that regulate their self-renewal capacity and metastatic potential. Recent evidence also suggests that inflammatory molecules at the tumor-stroma interface may also play critical roles in the development and progression of numerous tumors, such as pancreatic cancer, and their effects may also be paracrine-mediated. Along these lines, we have discovered that the immuno-modulatory cationic antimicrobial protein 18 (hCAP-18 or LL-37) is highly expressed in microenvironment resident cells (cancer-associated fibroblasts, infiltrating immune cells, and pancreatic stellate cells) of patients with pancreatic cancer. It is also secreted by primary human macrophages co-cultured with pancreatic CSCs. Intriguingly, LL-37 was not detectable in tissue from patients with chronic pancreatitis or pancreatic intraepithelial neoplasia (PanIN) suggesting a bilateral crosstalk between LL-37 producing cells and fully transformed cancer (stem) cells. As we have recently shown a strong role for the tumor stroma and microenvironment-secreted factors in pancreatic CSC self-renewal and invasiveness, LL-37 may represent a new and uncharacterized PDAC microenvironment factor that may play a critical role in pancreatic cancer progression and metastasis. Indeed, treatment of pancreatic CSCs with LL-37 increased CSC pluripotency-associated gene expression, self-renewal, and invasion in vitro as well as tumorigenicity and metastasis in vivo. LL-37 exerted its biological functions through interaction with the G protein—coupled receptor, formyl peptide receptor—like 1, P2X(7) purinergic receptor. In addition, receptor independent activity was mediated by stabilization of the CXCR4 receptor in the cell membrane. Taken together, our data expands our understanding of the tumor microenvironment and the tumor host interactions that perpetuate pancreatic ductal adenocarcinoma. Even more importantly, these studies identify a new tumor-specific factor for identifying malignant lesions in the pancreas and predicting patient outcome. Targeting of LL-37 could improve our therapeutic armamentarium against this deadly disease.

This abstract is also presented as Poster A18.

Citation Format: Bruno Sainz, Jr., Javier Frias, Michele Cioffi, Sonia Alcala, Christopher Heeschen. The role of the microenvironment protein cathelicidin LL-37 in pancreatic ductal adenocarcinoma. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Invasion and Metastasis; Jan 20-23, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;73(3 Suppl):Abstract nr PR1.

Combination of injectable multiple growth factor-releasing scaffolds and cell therapy as an advanced modality to enhance tissue neovascularization

OBJECTIVE

Vasculogenic progenitor cell therapy for ischemic diseases bears great potential but still requires further optimization for justifying its clinical application. Here, we investigated the effects of in vivo tissue engineering by combining vasculogenic progenitors with injectable scaffolds releasing controlled amounts of proangiogenic growth factors.

METHODS AND RESULTS

We produced biodegradable, injectable polylactic coglycolic acid-based scaffolds releasing single factors or combinations of vascular endothelial growth factor, hepatocyte growth factor, and angiopoietin-1. Dual and triple combinations of scaffold-released growth factors were superior to single release. In murine hindlimb ischemia models, scaffolds releasing dual (vascular endothelial growth factor and hepatocyte growth factor) or triple combinations improved effects of cord blood-derived vasculogenic progenitors. Increased migration, homing, and incorporation of vasculogenic progenitors into the vasculature augmented capillary density, translating into improved blood perfusion. Most importantly, scaffold-released triple combinations including the vessel stabilizer angiopoietin-1 enhanced the number of perivascular smooth muscle actin(+) vascular smooth muscle cells, indicating more efficient vessel stabilization.

CONCLUSIONS

Vasculogenic progenitor cell therapy is significantly enhanced by in vivo tissue engineering providing a proangiogenic and provasculogenic growth factor-enriched microenvironment. Therefore, combined use of scaffold-released growth factors and cell therapy improves neovascularization in ischemic diseases and may translate into more pronounced clinical effects.