Identifying and targeting key driver genes for collagen production within the 11q13/14 breast cancer amplicon

Genetic studies indicate that breast cancer can be divided into several basic molecular groups. One of these groups, termed IntClust-2, is characterized by amplification of a small portion of chromosome 11 and has a median survival of only five years. Several cancer-relevant genes occupy this portion of chromosome 11, and it is thought that overexpression of a combination of driver genes in this region is responsible for the poor outcome of women in this group. In this study we used a gene editing method to knock out, one by one, each of 198 genes that are located within the amplified region of chromosome 11 and determined how much each of these genes contributed to the survival of breast cancer cells. In addition to well-known drivers such as CCND1 and PAK1 , we identified two different genes ( SERPINH1 and P4HA3 ), that encode proteins involved in collagen synthesis and organization. Using both in vitro and in vivo functional analyses, we determined that P4HA3 and/or SERPINH1 provide a critical driver function on IntClust-2 basic processes, such as viability, proliferation, and migration. Inhibiting these enzymes via genetic or pharmacologic means reduced collagen synthesis and impeded oncogenic signaling transduction in cell culture models, and a small-molecule inhibitor of P4HA3 was effective in treating 11q13 tumor growth in an animal model. As collagen has a well-known association with tissue stiffness and aggressive forms of breast cancer, we believe that the two genes we identified provide an opportunity for a new therapeutic strategy in IntClust-2 breast cancers.

Pulsed low-dose-rate radiation (PLDR) reduces the tumor-promoting responses induced by conventional chemoradiation in pancreatic cancer-associated fibroblasts

Pancreatic cancer is becoming increasingly deadly, with treatment options limited due to, among others, the complex tumor microenvironment (TME). This short communications study investigates pulsed low-dose-rate radiation (PLDR) as a potential alternative to conventional radiotherapy for pancreatic cancer neoadjuvant treatment. Our ex vivo research demonstrates that PLDR, in combination with chemotherapy, promotes a shift from tumor-promoting to tumor-suppressing properties in a key component of the pancreatic cancer microenvironment we called CAFu (cancer-associated fibroblasts and selfgenerated extracellular matrix functional units). This beneficial effect translates to reduced desmoplasia (fibrous tumor expansion) and suggests PLDR's potential to improve total neoadjuvant therapy effectiveness. To comprehensively assess this functional shift, we developed the HOST-Factor, a single score integrating multiple biomarkers. This tool provides a more accurate picture of CAFu function compared to individual biomarkers and could be valuable for guiding and monitoring future therapeutic strategies. Our findings support the ongoing NCT04452357 clinical trial testing PLDR safety and TME normalization potential in pancreatic cancer patients. The HOST-Factor will be used in samples collected from this trial to validate its potential as a key tool for personalized medicine in this aggressive disease.

Trogocytosis of cancer-associated fibroblasts promotes pancreatic cancer growth and immune suppression via phospholipid scramblase anoctamin 6 (ANO6)

In pancreatic ductal adenocarcinoma (PDAC), the fibroblastic stroma constitutes most of the tumor mass and is remarkably devoid of functional blood vessels. This raises an unresolved question of how PDAC cells obtain essential metabolites and water-insoluble lipids. We have found a critical role for cancer-associated fibroblasts (CAFs) in obtaining and transferring lipids from blood-borne particles to PDAC cells via trogocytosis of CAF plasma membranes. We have also determined that CAF-expressed phospholipid scramblase anoctamin 6 (ANO6) is an essential CAF trogocytosis regulator required to promote PDAC cell survival. During trogocytosis, cancer cells and CAFs form synapse-like plasma membranes contacts that induce cytosolic calcium influx in CAFs via Orai channels. This influx activates ANO6 and results in phosphatidylserine exposure on CAF plasma membrane initiating trogocytosis and transfer of membrane lipids, including cholesterol, to PDAC cells. Importantly, ANO6-dependent trogocytosis also supports the immunosuppressive function of pancreatic CAFs towards cytotoxic T cells by promoting transfer of excessive amounts of cholesterol. Further, blockade of ANO6 antagonizes tumor growth via disruption of delivery of exogenous cholesterol to cancer cells and reverses immune suppression suggesting a potential new strategy for PDAC therapy.

Lorazepam Stimulates IL6 Production and Is Associated with Poor Survival Outcomes in Pancreatic Cancer

PURPOSE

This research investigates the association between benzodiazepines (BZD) and cancer patient survival outcomes, the pancreatic cancer tumor microenvironment, and cancer-associated fibroblast (CAF) signaling.

EXPERIMENTAL DESIGN

Multivariate Cox regression modeling was used to retrospectively measure associations between Roswell Park cancer patient survival outcomes and BZD prescription records. IHC, H&E, Masson's trichrome, RNAscope, and RNA sequencing were used to evaluate the impact of lorazepam (LOR) on the murine PDAC tumor microenvironment. ELISA and qPCR were used to determine the impact of BZDs on IL6 expression or secretion by human-immortalized pancreatic CAFs. PRESTO-Tango assays, reanalysis of PDAC single-cell sequencing/TCGA data sets, and GPR68 CRISPRi knockdown CAFs were used to determine the impact of BZDs on GPR68 signaling.

RESULTS

LOR is associated with worse progression-free survival (PFS), whereas alprazolam (ALP) is associated with improved PFS, in pancreatic cancer patients receiving chemotherapy. LOR promotes desmoplasia (fibrosis and extracellular matrix protein deposition), inflammatory signaling, and ischemic necrosis. GPR68 is preferentially expressed on human PDAC CAFs, and n-unsubstituted BZDs, such as LOR, significantly increase IL6 expression and secretion in CAFs in a pH and GPR68-dependent manner. Conversely, ALP and other GPR68 n-substituted BZDs decrease IL6 in human CAFs in a pH and GPR68-independent manner. Across many cancer types, LOR is associated with worse survival outcomes relative to ALP and patients not receiving BZDs.

CONCLUSIONS

We demonstrate that LOR stimulates fibrosis and inflammatory signaling, promotes desmoplasia and ischemic necrosis, and is associated with decreased pancreatic cancer patient survival.

Abstract 6794: SETD2 loss in renal cell carcinoma generates peptides from aberrantly translated retained introns

Introduction: SETD2, a histone H3-K36 trimethyltransferase, is necessary for regulation of proper intron splicing. SETD2 is frequently inactivated in kidney cancer. We hypothesized that SETD2 deficiency would cause aberrant translation of retained introns (ATaRI) that could serve as potential immunotherapeutic targets in SETD2-mutant states.

Methods and Results: We detected increased presence of retained introns in SETD2-mutant vs WT tumors in two publicly available renal cell carcinoma RNA-seq data sets. We hypothesized that if intronic sequences translated into proteins, accumulation of misfolded proteins would activate the Unfolded Protein Response (UPR). The UPR pathway was strongly transcriptionally enriched as measured by GSEA, as were several immunotherapy-relevant pathways, suggesting that tumors are inflamed, possibly related to the antigenic nature of translated introns. To investigate this further, we generated Setd2-isogenic mouse renal cancer cells using CRISPR in the RENCA cell line. RNAseq followed by GSEA confirmed upregulation of UPR pathway transcriptional signature in the Setd2-null condition, supporting our observation in human tumors. Indicators of UPR activation such as cleavage of ATF6 and increase in ATF4 and Xbp1 levels in Setd2 deficient vs. unedited RENCA cells, as well as nuclear translocation of ATF6 in SETD2-mutant human kidney cancer samples validates these findings. We then measured the presence of ATaRI-derived peptides in Setd2-mutant RENCA cells using mass spectrometry, detecting 47 such peptides. Using publicly available proteomics data from one human data set, we preliminarily identified peptides translated from 151 introns that are retained in SETD2-mutant cases. Applying netMHCpan to both the human and murine data, we found that detectable ATaRI peptides were predicted to generate multiple 10-amino acid-long peptides which strongly bind to the 8 murine MHC or to the 20 most common human HLA receptors. We propose that these presentable peptides might activate an immune response to SETD2-mutant renal cell carcinoma.

Conclusions: We identified intron retention which may cause activation of the UPR as a feature of SETD2-mutant kidney cancer. ATaRI peptides are detectable and should be presented to the adaptive immune system. These features may represent a new therapeutic vulnerability for exploitation as a rationale for personalized medicine.

Citation Format: Marya T. Kozinova, Alexander Metz, Robert Uzzo, Janusz Franco-Barraza, Michael Slifker, Jessica Peskin, Angel Fernández Sanromán, Samra Turajlic, Edna Cukierman, Phillip Phillip Abbosh. SETD2 loss in renal cell carcinoma generates peptides from aberrantly translated retained introns. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6794.

Abstract C047: Phospholipid scramblase TMEM16F in cancer associated fibroblasts regulates trogocytosis to sustain critical dependency of pancreatic cancer cells on exogenous lipids

Pancreatic ductal adenocarcinoma (PDAC) cells derive their resistance to therapy and aggressive clinical course from the symbiotic signaling and metabolic interactions with cancer-associated fibroblasts (CAFs). Trogocytosis is a process of “nibbling” of plasma membranes between two living cells. Here, we demonstrate CAFs are the primary recipients of exogenous lipids which they transfer to metabolically “parasitic” PDAC cells via a contact-mediated trogocytosis. Whereas trogocytosis has been described in immune system and in normal development, the biochemical and signaling regulators of trogocytosis between CAFs and PDAC cells have not been defined. Results: We determine that trogocytosis occurs through heterotypic CAF-PDAC cell contacts: membrane blebbing (readily observed in activated CAFs and exaggerated by release of Ca2+ from the ER stores) results in the blebs uptake by the PDAC cells. The CAF blebs express externalized phosphatidylserine (PtdSer), and blockade of PtdSer in vitro transiently deters trogocytic uptake of CAF membranes. Probing a short list of candidate targets involved in regulation of cholesterol trafficking, membrane fusion and membrane protrusions using CRISPRi, has shown that CAFs deficient in CD81, ARF6 or TMEM16F exhibit markedly reduced ability to support the viability of cholesterol-auxotrophic PDAC cells in lipid-poor media. As a promising therapy target, TMEM16F is a Ca2+-regulated scramblase increasing PtdSer on the outer leaflet of the plasma membrane. TMEM16F protein is highly expressed in human PDAC CAFs compared to fibroblasts isolated from the adjacent non-malignant pancreatic tissues. The TMEM16F-null CAFs are unable to sustain of cholesterol-auxotrophic PDAC cells in lipid-poor co-cultures, and do not support the growth of PDAC cells in orthotopic co-implantation model. Furthermore, several clinically available antibiotics used to treat tapeworms are selective TMEM16F inhibitors. One of the widely available TMEM16F inhibitors, niclozamide, is effective in blocking cholesterol transfer from CAFs to PDAC cells in vivo. Conclusion: Our overall model is that activated CAFs initiate trogocytosis by expressing PtdSer as “eat me” signals on the surfaces of their membrane blebs. This process is regulated by Ca2+-dependent phospholipid scramblase TMEM16F which is an attractive drug-amenable target to dismantle the critical metabolic dependency in PDAC on the exogenous lipids. Re-purposing of clinically available TMEM16 inhibitors will make a tangible impact on treatment of PDAC patients in the near term.

Citation Format: Charline Ogier, Alena Klochkova, Linara Gabitova-Cornell, Battuya Bayarmagnai, Diana Restifo, Aizhan Surumbayeva, Debora Barbosa Vendramini-Costa, Ralph Francescone, Janusz Franco-Barraza, Jaye Gardiner, Emmanuelle Nicolas, Andrei Efimov, Elizabeth A. Handorf, Kathy Q. Cai, Bojana Gligorijevic, Edna Cukierman, Igor Astsaturov. Phospholipid scramblase TMEM16F in cancer associated fibroblasts regulates trogocytosis to sustain critical dependency of pancreatic cancer cells on exogenous lipids [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 C047.

Abstract PR017: Stromal Netrin G1 ligand (NGL-1): A new modulator of tumorigenesis and immunosuppression in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is soon to be the second deadliest types of cancer, with a 5-year survival of only 10%. The unique features of PDAC are the expansion of cancer-associated fibroblasts (CAFs), presence of a dense fibrous stroma with high bundled collagen I and immunosuppression, representing a challenge for therapies. Ways to overcome these unique pro-tumor features will be key for the development of better therapeutic strategies for PDAC. Herein we report that, in addition to the identified ectopic expression of NGL-1 in PDAC cells, it is also expressed in the stroma (CAFs and immune cells) of PDAC patients, inversely correlating with overall survival. Stromal NGL-1 was important for tumorigenesis in vivo, as NGL-1 knockout mice (KO) orthotopically allografted with pancreatic cancer cells presented less tumor burden. Further analysis showed that the tumors from KO mice presented more CD8+ T cells and less immunosuppressive cytokines, such as TGFβ. Single cell RNAseq analysis of these tumors showed decreased expression of pro-tumor factors, such as immune checkpoint molecules in T cells and TGFβ related genes across different cellular compartments (epithelial, immune and fibroblasts). In accordance with these results, these tumors presented a limited amount of desmoplastic bundled collagen, suggestive of a TGFβ-deficient environment. In order to further dissect between the NGL-1-dependent contributions of immune vs. local stroma (e.g., CAFs) cells, we generated bone marrow chimeras and performed orthotopic injections to generate tumors. The loss of NGL-1 in each cellular compartment alone failed to phenocopy the full body loss of NGL-1, suggesting that NGL-1 in both immune cells and local stromal are important for tumorigenesis. Functionally, NGL-1 deficient CAFs failed to support the survival of starved PDAC cells in vitro, downregulated important myofibroblastic molecules such as p-smad, and produced less immunosuppressive cytokines, suggesting a role for NGL-1 in key pro-tumor features of CAFs. In fact, the fibroblastic NGL-1 dependent immunomodulatory effects were confirmed with human CD8+ T cells from healthy donors, which lost their cytotoxic profile in the presence of conditioned media (CM) from NGL-1+ CAFs, but were able to keep this profile when exposed to CM from NGL-1 deficient CAFs. Bone marrow derived macrophages from KO mice produced less pro-tumor cytokines and CD8+ T cells lacking NGL-1 proliferated more than those from wild type animals, when stimulated in vitro. Mechanistically, while immune cells and CAFs deficient in NGL-1 are both tumor suppressive, the latter can regain pro-tumor functions in response to TGFβ, explaining the need for a global modulation of NGL-1 expression for an anti-tumor effect. Finally, NGL-1 KO mice orthotopically allografted with PDAC cells responded better (smaller tumors) to chemotherapeutical regimen (FOLFIRINOX) compared to WT animals. All these results point to NGL-1 as a potential new target to modulate immunosuppression and tumorigenesis in pancreatic cancer.

Citation Format: Debora Barbosa Vendramini Costa, Ralph Francescone, Janusz Franco-Barraza, Tiffany Luong, Esteban Martinez, Stephen Sykes, Nina Steele, Marina Pasca di Magliano, Dmitry Zhigarev, Charline Ogier, Huamin Wang, Igor Astsaturov, Kerry Campbell, Edna Cukierman. Stromal Netrin G1 ligand (NGL-1): A new modulator of tumorigenesis and immunosuppression in pancreatic cancer [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 PR017.

NetrinG1+ cancer-associated fibroblasts generate unique extracellular vesicles that support the survival of pancreatic cancer cells under nutritional stress

It is projected that in 5 years, pancreatic cancer will become the second deadliest cancer in the United States. A unique aspect of pancreatic ductal adenocarcinoma (PDAC) is its stroma; rich in cancer-associated fibroblasts (CAFs) and a dense CAF-generated extracellular matrix (ECM). These pathogenic stroma CAF/ECM units cause the collapse of local blood vessels rendering the tumor microenvironment nutrient-poor. PDAC cells are able to survive this state of nutrient stress via support from CAF-secreted material, which includes small extracellular vesicles (sEVs). The tumor-supportive CAFs possess a distinct phenotypic profile, compared to normal-like fibroblasts, expressing NetrinG1 (NetG1) at the plasma membrane, and active Integrin α₅β₁ localized to the multivesicular bodies; traits indicative of poor patient survival. We herein report that NetG1⁺ CAFs secrete sEVs that stimulate Akt-mediated survival in nutrient-deprived PDAC cells, protecting them from undergoing apoptosis. Further, we show that NetG1 expression in CAFs is required for the pro-survival properties of sEVs. Additionally, we report that the above-mentioned CAF markers are secreted in distinct subpopulations of EVs; with NetG1 being enriched in exomeres, and Integrin α₅β₁ being enriched in exosomes. Finally, we found that NetG1 and Integrin α₅β₁ were detected in sEVs collected from plasma of PDAC patients, while their levels were significantly lower in plasma-derived sEVs of sex/age-matched healthy donors. The discovery of these tumor-supporting CAF-EVs elucidates novel avenues in tumor-stroma interactions and pathogenic stroma detection.

Abstract 3649: Stromal netrinG1-ligand (NGL1) constitutes a new modulator of pancreatic cancer immunosuppression

Pancreatic cancer (PC), is currently the third and predicted to soon become the second deadliest cancer in the US. A unique feature of PC is its fibrous tumor microenvironment (TME), marked by the expansion of cancer-associated fibroblasts (CAFs), highly bundled collagen I, and absence or inactivation of antitumor immune cells. As this TME is a physical and biochemical therapeutic barrier, a better understanding of how pro-tumor immunosuppression is modulated constitutes a highly sought-after goal. Herein we report that in addition to the identified ectopic expression of NetrinG1-Ligand (NGL1) in PC cells, NGL1 is detected in both immune cells and CAFs, with increased levels in CAFs associated with short PC patient overall survival. Further, in tumor-bearing mice, fibroblastic NGL1 expression correlates with PC progression while assorted immune cells express high levels of NGL1. To question the pro-PC role of stromal NGL1, we evaluated tumor progression in NGL1 knockout (KO) mice, using orthotopic PC allografts, and observed that tumors were significantly smaller. Single-cell RNA sequencing pointed to downregulation of pro-tumor transcripts in key assorted KO TME cells (e.g., T Cells). We also noted that tumor-bearing KO tissues included a TME with limited immunosuppressive cytokines, increased CD8+ and CD4+ T cells expressing low levels of tumor-promoting factors, and a limited amount of desmoplastic bundled collagen, all suggestive of a TGFβ-deficient milieu. In order to further dissect between the NGL1-dependent contributions of hematopoietic/immune vs. local stroma (e.g., CAFs) cells, we generated bone marrow KO/WT chimeras. Results suggested that loss of NGL1 in one of the two compartments fails to phenocopy the full-body loss of NGL1, and was thus insufficient to hinder PC tumorigenesis. Further, depletion of selected immune cell subsets informed on NGL1-dependent T- and myeloid-cell contributions. Functional assays showed that KO macrophages released limited pro-tumor factors while KO T cells displayed increased proliferation compared to the WTs of both cell types. Fibroblastic NGL1-dependent immuno-regulatory effects were confirmed with human immune cells collected from healthy donors. Mechanistically, while immune cells and CAFs deficient in NGL1 are both tumor-suppressive, the latter can regain pro-tumor functions in response to TGFβ, explaining the chimera and full-body KO results. Finally, KO effects were mirrored in WT CAFs treated with an NGL1-neutralizing molecule. Overall, our data suggest that stromal NGL1 is a novel and targetable modulator of PC immunosuppression

Citation Format: Débora B. Vendramini-Costa, Ralph Francescone, Janusz Franco-Barraza, Tiffany Luong, Esteban Martinez, Stephen Sykes, Nina G. Steele, Benjamin L. Allen, Marina Pasca di Magliano, Dmitry I. Zhigarev, Charline Ogier, Igor Astsaturov, Kathy Q. Cai, Andres J. Klein-Szanto, Huamin Wang, Kerry Campbell, Edna Cukierman. Stromal netrinG1-ligand (NGL1) constitutes a new modulator of pancreatic cancer immunosuppression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3649.

Abstract 1571: Cancer associated fibroblasts sustain critical dependency of pancreatic cancer cells on exogenous lipids

Pancreatic ductal adenocarcinoma (PDAC) cells derive their resistance to therapy and aggressive clinical course from the symbiotic signaling and metabolic interactions with cancer-associated fibroblasts (CAFs). CAFs have been shown to provide nutrients to "parasitic" PDAC cells including water soluble glucose and amino acids. In hypoxic tumor microenvironments, aggressive PDAC are functional auxotroph for lipids, and scavenge exogenous lipids to build cellular membranes. However, the mechanism by which PDAC cells obtain these water-insoluble essential membrane building materials remains poorly understood. To gain insights into the mechanism of lipid scavenging, we generated cholesterol-auxotrophic human and mouse PDAC PDAC cells since cholesterol is the major constituent of lipid cellular membranes. Here, we discovered that PDAC cells utilize CAFs as a main source of lipids in vivo through direct heterotypic cellular contacts. In this process, PDAC cells directly acquire the CAF plasma membrane (PM) via trogocytosis. In response to yet unidentified paracrine “feed me” signals activating CAF-dependent trogocytosis, CAFs upregulate phosphatidylserine (PtdSer) on the outer leaflet of the PM. Consequently, blockade of PtdSer on CAFs partially deterred trogocytic transfer of CAF membranes to PDAC cells in vitro. Furthermore, Ca2+-dependent phospholipid scramblase TMEM16F is a critical regulator of PtdSer externalization. TMEM16F is highly expressed in human PDAC CAFs compared to fibroblasts isolated from the matching adjacent non-malignant pancreatic tissues CAFs deficient in TMEM16F scramblase exhibited markedly reduced ability to support the growth of cholesterol-auxotrophic PDAC cells cultured in lipid depleted media. We propose trogocytosis as a new mode of lipid scavenging by PDAC cells from CAFs involving activation of Ca2+-dependent phospholipid scramblase TMEM16F in CAFs and increased expression of PtdSer as “eat me” signals on CAF PM. To inactivate trogocytosis, we nominate TMEM16F as a plausible PDAC therapy target using clinically available TMEM16 inhibitors with a potential for impact on treatment of PDAC patients in the near term.

Citation Format: Charline Ogier, Alena Klochkova, Battuya Bayarmagnai, Linara Gabitova, Diana Restifo, Aizhan Surumbayeva, Janusz Franco-Barraza, Debora Vendramini Costa, Ralph Francescone, Jaye Gardiner, Emmanuelle Nicolas, Elizabeth A. Handorf, Kathy Q. Cai, Edna Cukierman, Igor Astsaturov. Cancer associated fibroblasts sustain critical dependency of pancreatic cancer cells on exogenous lipids [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1571.

Abstract 3725: SETD2 loss in renal carcinoma cells induces the unfolded protein response

Introduction: SETD2 encodes a histone H3-K36 methyltransferase which is frequently inactivated in clear cell renal carcinomas (ccRCCs) and papillary RCCs via 3p deletion/LOH and deleterious mutations. Histone H3-K36 trimethylation is facilitated by SETD2, which is necessary for proper pre-mRNA intron splicing. Improperly spliced mature mRNA may lead to aberrant translation of retained introns (ATaRI), which represents potential therapeutic vulnerabilities. We explored this hypothesis using real world data and RCC models.

Methods and Results: Gene set enrichment analysis comparing SETD2-mutant to WT tumors using samples from the TCGA KIRC data set revealed that the unfolded protein response (UPR) was strongly enriched, as well as several immunotherapy-relevant pathways. This suggested that peptides arising from ATaRI may be present, since they would not be expected to fold properly and thus need to be addressed by the UPR pathway to maintain homeostasis. To investigate this further, we generated Setd2-isogenic RENCA cells using CRISPR. Knockout was confirmed by sequencing and immunoblot. H3K36 trimethylation was decreased or eliminated in monoclonal knockout cell lines, confirming a functional effect. Markers of UPR activation, including Atf4 and cleaved Atf6, were found to be upregulated in Setd2-mutant RENCA cells compared to controls as measured by immunoblot. Cleaved ATF6 translocates to the nucleus to induce the UPR transcriptional program. Consistent with this, Atf6 was found to localize to the nucleus in Setd2-knockout cells using immunofluorescence (IF). Analysis of tissue microarrays of human SETD2-mutant vs -WT ccRCC revealed increased ATF6 signal in areas with low H3K36 tri-methylation, indicating UPR activation in vivo. Interestingly, CHOP, another downstream effector of the UPR pathway which predominantly regulates cell death, did not become upregulated in Setd2-knockout cells, suggesting activation of a compensatory cell survival pathway. Geldanamycin was shown to destabilize the Perk and Ire1a arms of the UPR, which resulted in increased cell death in Setd2 mutant cells using Cell Titre glo. Additionally, H3K36 trimethylation has been implicated in directing homologous repair of DNA, and blunted responses to agents that induce DNA double-strand breaks of p-Atm, p53, and Rad51 were observed by immunoblot and IF. The inability to detect DNA damage in Setd2 mutant cells however did not confer sensitivity to PARP inhibitors.

Conclusions: We identify activation of the UPR upon Setd2 loss and suggest that activation of part of the UPR pathway may represent a new therapeutic vulnerability for exploitation as a rationale for personalized medicine. We further characterize the altered DNA damage response in the setting of Setd2 loss. We continue to evaluate the generation of peptides arising from ATaRI in Setd2-mutant contexts.

Citation Format: Alexander Metz, Marya Kozinova, Robert Uzzo, Jessica Peskin, Michael Slifker, Janusz Franco-Barraza, Edna Cukierman, Philip Abbosh. SETD2 loss in renal carcinoma cells induces the unfolded protein response [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3725.

Targeting SOX10-deficient cells to reduce the dormant-invasive phenotype state in melanoma

Cellular plasticity contributes to intra-tumoral heterogeneity and phenotype switching, which enable adaptation to metastatic microenvironments and resistance to therapies. Mechanisms underlying tumor cell plasticity remain poorly understood. SOX10, a neural crest lineage transcription factor, is heterogeneously expressed in melanomas. Loss of SOX10 reduces proliferation, leads to invasive properties, including the expression of mesenchymal genes and extracellular matrix, and promotes tolerance to BRAF and/or MEK inhibitors. We identify the class of cellular inhibitor of apoptosis protein-1/2 (cIAP1/2) inhibitors as inducing cell death selectively in SOX10-deficient cells. Targeted therapy selects for SOX10 knockout cells underscoring their drug tolerant properties. Combining cIAP1/2 inhibitor with BRAF/MEK inhibitors delays the onset of acquired resistance in melanomas in vivo. These data suggest that SOX10 mediates phenotypic switching in cutaneous melanoma to produce a targeted inhibitor tolerant state that is likely a prelude to the acquisition of resistance. Furthermore, we provide a therapeutic strategy to selectively eliminate SOX10-deficient cells.

Abstract PR-015: Cancer-associated fibroblasts sustain critical dependency of pancreatic cancer cells on exogenous lipids

Pancreatic ductal adenocarcinoma (PDAC) cells derive their resistance to therapy and aggressive clinical course from the symbiotic signaling and metabolic interactions with cancer-associated fibroblasts (CAFs). CAFs have been shown to provide to metabolically “parasitic” PDAC cells with water-soluble metabolites such as glucose and amino acids, or bulk protein via micropinocytosis. To meet the elevated demands for cellular membrane lipids, cancer cells rely on uptake of the exogenous lipids. However, the mechanism by which PDAC cells obtain water-insoluble essential lipids, such as cholesterol, remains poorly understood. Here, we define CAFs as a main source of lipids for PDAC cells by direct “feeding” of the CAF plasma membrane (PM) to cancer cells via heterotypic cellular contacts, a phenomenon known as trogocytosis. To gain insights into the mechanisms of regulation of CAF trogocytosis, we engineered cholesterol-auxotrophic human and mouse PDAC cells. In the absence of exogenously provided cholesterol, these cancer cells undergo apoptosis, which is completely rescued in CAF co-cultures. Using CRISPRi-mediated depletion in CAFs of select genes involved in cholesterol trafficking, membrane fusion and membrane protrusions, we found that CAFs deficient in CD81, TMEM16F, or ARF6 exhibited markedly reduced ability to support the viability of cholesterol-auxotrophic PDAC cells in lipid-poor media. As a promising therapy target, TMEM16F is a Ca2+-regulated scramblase increasing phosphatidylserine (PtdSer) on the outer leaflet of the PM. TMEM16F protein is highly expressed in human PDAC CAFs compared to fibroblasts isolated from the adjacent non-malignant pancreatic tissues. The TMEM16F-null CAFs are unable to sustain of cholesterol-auxotrophic PDAC cells in lipid-poor co-cultures. Our overall model is that, to initiate trogocytosis, PDAC cells release paracrine “feed me” signals activating Ca2+-dependent phospholipid scramblase TMEM16F. As the result, increased outward expression of PtdSer on CAF PM is a hallmark “eat me” signal that is recognized by the trogocytic PDAC cells. We conclude that trogocytosis is the critical metabolic dependency in PDAC, and nominated TMEM16F as a plausible PDAC therapy target. Re-purposing of clinically available TMEM16 inhibitors will make a tangible impact on treatment of PDAC patients in the near term.

Citation Format: Charline Ogier, Alena Klochkova, Linara Gabitova, Battuya Bayarmagnai, Diana Restifo, Aizhan Surumbayeva, Janusz Franco-Barraza, Ralph Francescone, Debora B. Barbosa Vendramini-Costa, Jaye Gardiner, Emmanuelle Nicolas, Elizabeth A. Handorf, Kathy Q. Cai, Edna Cukierman, Igor Astsaturov. Cancer-associated fibroblasts sustain critical dependency of pancreatic cancer cells on exogenous lipids [abstract]. In: Proceedings of the AACR Virtual Special Conference on Pancreatic Cancer; 2021 Sep 29-30. Philadelphia (PA): AACR; Cancer Res 2021;81(22 Suppl):Abstract nr PR-015.

Abstract PO-096: The synaptic protein Netrin G1 ligand (NGL-1) modulates tumorigenesis and immunosuppression in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest types of cancer, with a 5-year survival of 10%. A major feature of PDAC is the presence of a dense fibrous stroma, due to the expansion of cancer associated fibroblasts (CAFs) and their extracellular matrix. This unique environment represents a challenge for therapies as it promotes immunosuppression, limits access to nutrients, and excludes or inactivates antitumor immune cells. Recently, we identified the ectopic expression of the neuronal protein Netrin G1 Ligand (NGL-1) in PDAC tissue, including its novel expression in immune cells and CAFs. However, the roles of NGL-1 in the tumor microenvironment (TME) of PDAC and in immune cell function are unknown and warranted further investigation. The contribution of NGL-1 to PDAC tumorigenesis was assessed by measuring the expression of NGL-1 in different models of PDAC and by orthotopically injecting PDAC cells in wild type (WT) or NGL-1 full body knockout mice (KO). Using our in vitro 3D system we evaluated if NGL-1+ CAFs, compared to NGL-1 knockdown (KD) CAFs, produced less immunosuppressive factors and were able to rescue PDAC cell survival under nutrient deprivation. For NGL-1 dependent immune cell functions we isolated naïve immune cells from WT and KO mice and performed ex-vivo functional assays. NGL-1 expression in fibroblasts correlated with disease development in different models of PDAC, and myeloid, T and NK cells from tumor bearing mice tended to overexpress NGL-1 when compared with cells from naïve mice. Accordingly, NGL-1 KO mice orthotopically injected with PDAC cells developed smaller tumors with decreased secretion of immunosuppressive factors, increased presence of CD8+ T cells and CD4+ T cells expressing less pro-tumor markers. Single cell RNA sequencing data from tumors from KO mice showed downregulation of pro-tumor genes in different cell populations, with the fibroblastic populations differing between WT and KO mice. In order to evaluate the contribution of the immune system for tumorigenesis in WT and KO mice, we performed bone marrow chimeras and depletion of specific immune cells. Functionally, CD8+ and CD4+ T cells from KO mice proliferated more when stimulated in vitro, suggesting that NGL-1 could represent a functional brake for T cells, inhibiting their anti-tumor capacity. The lack of NGL-1 in stimulated bone marrow-derived macrophages decreased pro-inflammatory cytokine secretion, further suggesting a functional role for NGL-1 in myeloid cells. Of note, NGL-1 KD CAFs did not support PDAC cell survival in vitro and produced less immunosuppressive cytokines, which was phenocopied by the treatment with a peptide targeting NGL-1. Translationally, we assessed the overall survival of 140 PDAC patients according to NGL-1 expression in the TME, where low expression of NGL-1 in CAFs and immune cells correlated with better survival of PDAC patients. Overall, this suggests NGL-1 as potential new target in PDAC, that could be manipulated in different compartments in pancreatic cancer.

Citation Format: Debora Barbosa Vendramini Costa, Ralph Francescone, Janusz Franco-Barraza, Tiffany Luong, Nina Steele, Benjamin Allen, Marina Pasca di Magliano, Charline Ogier, Igor Astsaturov, Kathy Q. Cai, Andres J. Klein-Szanto, Huamin Wang, Kerry Campbell, Edna Cukierman. The synaptic protein Netrin G1 ligand (NGL-1) modulates tumorigenesis and immunosuppression in pancreatic cancer [abstract]. In: Proceedings of the AACR Virtual Special Conference on Pancreatic Cancer; 2021 Sep 29-30. Philadelphia (PA): AACR; Cancer Res 2021;81(22 Suppl):Abstract nr PO-096.

Abstract 3173: NetrinG1's pro-tumor role on stroma-derived extracellular vesicles in pancreatic cancer

Pancreatic Ductal Adenocarcinoma (PDAC) is a devastating disease which is in part driven, and supported by changes in its microenvironment, or stroma. These changes occur early, yet PDAC is usually undetected until the disease has metastasized, causing survival rates to drop dramatically. Therefore, there exists an urgency to detect this disease as early as possible and understand its progression. This project dissects the intercellular communication that exists between the primary stromal component, cancer-associated fibroblasts (CAFs), and PDAC cells. Specifically, we focus on how CAF-secreted extracellular vesicles (EVs) promote PDAC progression, with an additional goal to identify biomarkers suitable to generate a non-invasive “liquid biopsy” test for early PDAC detection and prognosis. PDAC communicates with its microenvironment, in part, through the exchange of specific types of EVs, which include exosomes and recently characterized “ectosomes.”

We observe distinct types of CAF-derived EVs containing unique surface receptors. One novel surface protein, NetrinG1, is expressed on the plasma membrane of pancreatic CAFs, but not their normal/healthy counterparts. Further, PDAC cells, but not healthy pancreatic epithelial cells, upregulate NetrinG1's lone binding partner, suggesting a role for these factors in PDAC-selective EV uptake. Functional assays designed to test PDAC viability in nutrient deprivation show that CAF-EVs are capable of protecting PDAC cells from the induction of programmed cell death. Further, we show NetrinG1's expression in CAFs is necessary for this EV-mediated survival effect. We also determine that NetrinG1 localizes to the novel “ectosome” EV sub-population, suggesting it possesses unique cargo and is packaged into EVs and secreted through a yet-unknown mechanism separate from canonical exosome trafficking. We also determine, that sub-populations of EVs can be “filtered” locally by the extracellular matrix, based on various EV surface markers. This suggests that the extracellular matrix can play an important role in determining the fate of secreted EVs; which has significant implications for what sub-populations maybe be found circulating systemically in blood, or acting locally in the tumor microenvironment.

Pursuing our biomarker goal, we confirm stromal NetrinG1 expression precedes tumorigenesis and are currently seeking to validate the prognostic potential of NetrinG1(+)EVs in blood of PDAC patients. Altogether, this research shines light on a novel mechanism of tumor-stroma communication, and introduces EV biomarkers potentially capable of identifying both early PDAC occurrences and predicted efficacy of certain adjuvant interventions.

Citation Format: Kristopher Raghavan, Debora Vendramini, Ralph Francescone, Janusz Franco-Barraza, Edna Cukierman. NetrinG1's pro-tumor role on stroma-derived extracellular vesicles in pancreatic cancer [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 3173.

Necroptotic astrocytes contribute to maintaining stemness of disseminated medulloblastoma through CCL2 secretion

BACKGROUND

Medulloblastoma (MB) with metastases at diagnosis and recurrence correlates with poor prognosis. Unfortunately, the molecular mechanism underlying metastases growth has received less attention than primary therapy-naïve MB. Though astrocytes have been frequently detected in brain tumors, their roles in regulating the stemness properties of MB stem-like cells (MBSCs) in disseminated lesions remain elusive.

METHODS

Effects of tumor-associated astrocyte (TAA)-secreted chemokine C-C ligand 2 (CCL2) on MBSC self-renewal was determined by immunostaining analysis. Necroptosis of TAA was examined by measuring necrosome activity. Alterations in Notch signaling were examined after inhibition of CCL2. Progression of MBSC-derived tumors was evaluated after pharmaceutical blockage of necroptosis.

RESULTS

TAA, as the essential components of disseminated tumor, produced high levels of CCL2 to shape the inflammation microenvironment, which stimulated the enrichment of MBSCs in disseminated MB. In particular, CCL2 played a pivotal role in maintaining stem-like properties via Janus kinase 2/signal transducer and activator of transcription 3 (JAK2/STAT3)-mediated activation of Notch signaling. Loss of CCL2/C-C chemokine receptor 2 (CCR2) function repressed the JAK2/STAT3-Notch pathway and impaired MBSC proliferation, leading to a dramatic reduction of stemness, tumorigenicity, and metastasizing capability. Furthermore, necroptosis-induced CCL2 release depended on activation of receptor-interacting protein 1 (RIP1)/RIP3/mixed lineage kinase domain-like pseudokinase (MLKL) in TAA, which promoted the oncogenic phenotype. Blockade of necroptosis resulted in CCL2 deprivation and compromised MBSC self-proliferation, indicating MBSCs outsourced CCL2 from necroptotic TAA. Finally, CCL2 was upregulated in high-risk stages of MB, further supporting its value as a prognostic indicator.

CONCLUSION

These findings highlighted the critical role of CCL2/CCR2 in Notch signaling activation in MBSCs and revealed a necroptosis-associated glial cytokine microenvironment driving stemness maintenance in disseminations.Key Points1. TAA-derived CCL2 promoted stemness in disseminated MBSCs through Notch signaling activation via the JAK2/STAT3 pathway.2. TAA released CCL2 in a RIP1/RIP3/MLKL-dependent manner leading to necroptosis.

Abstract PR-006: Pulsed low-dose-rate radiation (PLDR) limits pancreatic pro-tumor stroma aggravation: Pre-clinical basis for an ongoing PLDR trail

Radiation, combined with radio-sensitizing chemotherapy, is used preoperatively as neoadjuvant therapy (NT) for borderline resectable pancreatic ductal adenocarcinoma (PDAC) with the intent of facilitating a curative surgical intervention. PDAC is uniquely characterized by an extensive fibrous microenvironment, desmoplasia, which can unintendedly be aggravated by NT to foster its pro-tumoral function. Radiation, as part of NT, is aimed at providing a margin adjacent to un-resectable vessels and sterilizing regional lymph nodes. Yet, to avoid the unintended desmoplastic aggravation, and because of a risk of toxicities associated with high doses due to the radio-sensitivity of adjacent small bowel and stomach, the total dose of NT radiation delivered to PDAC patients is classically modest. Therefore, NT radiation in PDAC patients is often lower than optimal for effective tumor cell elimination. Pulsed low-dose-rate (PLDR) radiation improves the safety of radiation treatment as it allows time for DNA damage repair in non-tumorous cells/tissues while simultaneously remaining as effective as continuous dose rate (CDR) radiation in cancer cells. In theory, PLDR could be amendable for increased radiation dosage. Of interest, the use of PLDR in pre-clinical animal studies revealed a systemic lowering of transforming growth factor beta (TGFβ), a known immunosuppressive factor. Hence, we posit that since cancer-associated fibroblasts (CAFs) produce TGFβ and constitute one of the most abundant cells in PDAC desmoplasia, variations in TGFβ levels in response to NT will inform on desmoplastic dynamic changes. Our team has developed means to assess CAF functions and activation statuses. These efforts were guided by generating a desmoplastic biomarker signature obtained from patient-harvested CAFs during the production of extracellular matrix (ECM), using our well-established in vitro 3D system. We employed this in vivo-mimetic system to test the hypothesis that PLDR limits pro-tumoral desmoplastic CAF aggravation. As part of the CAF functional signature, we tested levels of immunosuppressive TGFβ secretion, expression of netrin-G1, palladin, and others; together with the biogenesis of unique extracellular vesicles, and the production of ECMs capable of nurturing PDAC cells under starvation. During a 5-day assay, human PDAC 3D ECM producing CAFs were treated with gemcitabine (Gem; 5nm) plus 4Gy or 8Gy PLDR vs. CDR. Results indicated that Gem alone or with CDR indeed aggravated CAF’s pro-PDAC phenotype and function, while Gem combined with PDLR limited and sometimes reverted this functional pro-tumor CAF signature. Based on these results, we are poised to test this functional CAF/desmoplasia signature, as laboratory correlatives, in an ongoing clinical trial at Fox Chase Cancer Center. The phase I trial is a dose-escalation study of PLDR radiation and chemotherapy at standard and intensified doses in preoperative pancreatic cancer patients with toxicity, histopathologic, and CAF-informing translational endpoints.

Citation Format: Janusz Franco-Barraza, Tiffany Luong, Jessica K. Wong, Debora B. Vendramini-Costa, Ralph Francescone, Jaye C. Gardiner, Kristopher S. Raghavan, Joshua E. Meyer, Edna Cukierman. Pulsed low-dose-rate radiation (PLDR) limits pancreatic pro-tumor stroma aggravation: Pre-clinical basis for an ongoing PLDR trail [abstract]. In: Proceedings of the AACR Virtual Special Conference on Radiation Science and Medicine; 2021 Mar 2-3. Philadelphia (PA): AACR; Clin Cancer Res 2021;27(8_Suppl):Abstract nr PR-006.

Abstract PR004: NetrinG1’s pro-tumor role on stroma-derived extracellular vesicles in pancreatic cancer

Pancreatic Ductal Adenocarcinoma (PDAC) is a devastating disease which is, in part, driven and supported by changes in its microenvironment, or stroma. These changes occur early, yet PDAC is usually undetected until the disease has metastasized, causing survival rates to drop dramatically. Therefore, there exists a grave importance to detect this disease as early as possible and understand its progression. This project dissects the intercellular communication that exists between the primary stromal component, cancer-associated fibroblasts (CAFs), and PDAC cells. Specifically, we focus on how CAF-secreted extracellular vesicles (EVs) promote PDAC progression, with an additional goal to identify biomarkers suitable to generate a non-invasive “liquid biopsy” test for early PDAC detection and prognosis. PDAC communicates with its microenvironment, in part, through the exchange of specific types of EVs, which include exosomes and recently characterized “ectosomes.” We observe distinct types of CAF-derived EVs containing unique surface receptors. One novel surface protein, NetrinG1, is expressed on the plasma membrane of pancreatic CAFs, but not their normal/healthy counterparts. Further, PDAC cells, but not healthy pancreatic epithelial cells, upregulate NetrinG1’s lone binding partner, suggesting a role for these factors in PDAC-selective EV uptake. Functional assays designed to test PDAC viability in nutrient deprivation show that CAF-EVs are capable of protecting PDAC cells from the induction of programmed cell death. Further, we show NetrinG1’s expression in CAFs is necessary for this EV-mediated survival effect. We also determine that NetrinG1 localizes to the novel “ectosome” EV sub-population, suggesting it possesses unique cargo and is packaged into EVs and secreted through a yet-unknown mechanism separate from canonical exosome trafficking. We also determine, that sub-populations of EVs can be “filtered” locally by the extracellular matrix, based on various EV surface markers. This suggests that the extracellular matrix can play an important role in determining the fate of secreted EVs; which has significant implications for what sub-populations maybe be found circulating systemically in blood, or acting locally in the tumor microenvironment. Pursuing our biomarker goal, we confirm stromal NetrinG1 expression precedes tumorigenesis and are currently seeking to validate the prognostic potential of NetrinG1(+)-EVs in blood of PDAC patients. Altogether, this research shines light on a novel mechanism of tumor-stroma communication, and introduces EV biomarkers potentially capable of identifying both early PDAC occurrences and predicted efficacy of certain adjuvant interventions.

Citation Format: Kristopher Raghavan, Ralph Francescone, Janusz Franco-Barraza, Edna Cukierman. NetrinG1’s pro-tumor role on stroma-derived extracellular vesicles in pancreatic cancer [abstract]. In: Proceedings of the AACR Virtual Special Conference on the Evolving Tumor Microenvironment in Cancer Progression: Mechanisms and Emerging Therapeutic Opportunities; in association with the Tumor Microenvironment (TME) Working Group; 2021 Jan 11-12. Philadelphia (PA): AACR; Cancer Res 2021;81(5 Suppl):Abstract nr PR004.

Abstract LT019: The synaptic protein netrin G1 ligand (NGL-1) modulates the immunosuppressive environment in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC), one of the deadliest cancers, features a highly immunosuppressive environment, with expansion of cancer-associated fibroblasts (CAFs), and absence/inactivation of antitumor immune cells. Therefore, ways to manipulate this environment, favoring the antitumor cells, will be critical for effective therapies for PDAC. Recently, we identified the neuronal protein Netrin G1 Ligand (NGL-1) to be overexpressed in PDAC tissue, including its novel expression in immune cells and CAFs. However, the role that NGL-1 plays in the tumor microenivronment (TME) is unknown and warrented further investigation. Using wild-type and NGL-1 full body knockout mice orthotopically injected or not with pancreatic tumor cells, we assessed tumorigenesis and secretion of immunosuppresive factors. Moreover, using our in vitro 3D system we explored the ability of NGL-1+ CAFs to rescue PDAC cell survival under nutrient deprivation, their immunosuppressive profile and the ability of a peptide targeting NGL-1 to reverse these features. Finally, we assessed the overall survival of 140 PDAC patients according to NGL-1 expression in the TME. Comparing immune cells from naïve and tumor-bearing mice we observed that myeloid, T and NK cells from tumor-bearing mice tend to overexpress NGL-1. Moreover, CD8+ and CD4+ T cells from NGL-1 KO mice proliferated more when stimulated in vitro, suggesting that NGL-1 could represent a functional brake for T cell activation and proliferation. Interestingly, the absence of NGL-1 in bone marrow-derived macrophages stimulated in vitro led to decreased production of pro-inflammatory cytokines, further suggesting a functional role for NGL-1 in myeloid cells. Importantly, NGL-1 KO mice orthotopically injected with PDAC cells developed smaller tumors and these produced less immunosuppressive factors. In accordance, CAFs lacking NGL-1 were not supportive of PDAC cell survival in vitro and produced less immunosuppressive cytokines, which was phenocopied by the treatment with the peptide targeting NGL-1. Finally, data from PDAC patients showed that low expression of NGL-1 in CAFs and immune cells correlated with better survival of these patients, therefore highlighting NGL-1 as a potential new target that could be manipulated in different compartments in pancreatic cancer (cancer cells, CAFs, immune cells). This represents an innovative perspective for such a complex disease.

Citation Format: Debora Barbosa Vendramini-Costa, Ralph Francescone, Tiffany Luong, Janusz Franco-Barraza, Igor Astsaturov, Kathy Q. Cai, Andres J. Klein-Szanto, Huamin Wang, Kerry Campbell, Edna Cukierman. The synaptic protein netrin G1 ligand (NGL-1) modulates the immunosuppressive environment in pancreatic cancer [abstract]. In: Proceedings of the AACR Virtual Special Conference on the Evolving Tumor Microenvironment in Cancer Progression: Mechanisms and Emerging Therapeutic Opportunities; in association with the Tumor Microenvironment (TME) Working Group; 2021 Jan 11-12. Philadelphia (PA): AACR; Cancer Res 2021;81(5 Suppl):Abstract nr LT019.

Palladin isoforms 3 and 4 regulate cancer-associated fibroblast pro-tumor functions in pancreatic ductal adenocarcinoma

Pancreatic Ductal Adenocarcinoma (PDAC) has a five-year survival under 10%. Treatment is compromised due to a fibrotic-like stromal remodeling process, known as desmoplasia, which limits therapeutic perfusion, supports tumor progression, and establishes an immunosuppressive microenvironment. These processes are driven by cancer-associated fibroblasts (CAFs), functionally activated through transforming growth factor beta1 (TGFβ1). CAFs produce a topographically aligned extracellular matrix (ECM) that correlates with reduced overall survival. Paradoxically, ablation of CAF populations results in a more aggressive disease, suggesting CAFs can also restrain PDAC progression. Thus, unraveling the mechanism(s) underlying CAF functions could lead to therapies that reinstate the tumor-suppressive features of the pancreatic stroma. CAF activation involves the f-actin organizing protein palladin. CAFs express two palladin isoforms (iso3 and iso4) which are up-regulated in response to TGFβ1. However, the roles of iso3 and iso4 in CAF functions remain elusive. Using a CAF-derived ECM model, we uncovered that iso3/iso4 are required to sustain TGFβ1-dependent CAF activation, secrete immunosuppressive cytokines, and produce a pro-tumoral ECM. Findings demonstrate a novel role for CAF palladin and suggest that iso3/iso4 regulate both redundant and specific tumor-supportive desmoplastic functions. This study highlights the therapeutic potential of targeting CAFs to restore fibroblastic anti-tumor activity in the pancreatic microenvironment.

Netrin G1 Promotes Pancreatic Tumorigenesis through Cancer-Associated Fibroblast-Driven Nutritional Support and Immunosuppression

Pancreatic ductal adenocarcinoma (PDAC) has a poor 5-year survival rate and lacks effective therapeutics. Therefore, it is of paramount importance to identify new targets. Using multiplex data from patient tissue, three-dimensional coculturing in vitro assays, and orthotopic murine models, we identified Netrin G1 (NetG1) as a promoter of PDAC tumorigenesis. We found that NetG1+ cancer-associated fibroblasts (CAF) support PDAC survival, through a NetG1-mediated effect on glutamate/glutamine metabolism. Also, NetG1+ CAFs are intrinsically immunosuppressive and inhibit natural killer cell-mediated killing of tumor cells. These protumor functions are controlled by a signaling circuit downstream of NetG1, which is comprised of AKT/4E-BP1, p38/FRA1, vesicular glutamate transporter 1, and glutamine synthetase. Finally, blocking NetG1 with a neutralizing antibody stunts in vivo tumorigenesis, suggesting NetG1 as potential target in PDAC. SIGNIFICANCE: This study demonstrates the feasibility of targeting a fibroblastic protein, NetG1, which can limit PDAC tumorigenesis in vivo by reverting the protumorigenic properties of CAFs. Moreover, inhibition of metabolic proteins in CAFs altered their immunosuppressive capacity, linking metabolism with immunomodulatory function.See related commentary by Sherman, p. 230.This article is highlighted in the In This Issue feature, p. 211.

CD38 in cancer-associated fibroblasts promotes pro-tumoral activity

Primary and metastatic melanoma progression are supported by a local microenvironment comprising, inter alia, of cancer-associated fibroblasts (CAFs). We previously reported in orthotropic/syngeneic mouse models that the stromal ectoenzyme CD38 participates in melanoma growth and metastasis. The results presented here suggest that CD38 is a novel regulator of CAFs' pro-tumorigenic functions. Orthotopic co-implantation of CD38 deficient fibroblasts and B16F10 melanoma cells limited tumor size, compared with CD38-expressing fibroblasts. Intrinsically, CAF-CD38 promoted migration of primary fibroblasts toward melanoma cells. Further, in vitro paracrine effects of CAF-CD38 fostered tumor cell migration and invasion as well as endothelial cell tube formation. Mechanistically, we report that CAF-CD38 drives the protein expression of an angiogenic/pro-metastatic signature, which includes VEGF-A, FGF-2, CXCL-12, MMP-9, and HGF. Data suggest that CAF-CD38 fosters tumorigenesis by enabling the production of pro-tumoral factors that promote cell invasion, migration, and angiogenesis.

IMMU-17. SINGLE-CELL RNA-SEQ REVEALS HIGH-GRADE GLIOMA ASSOCIATED MICROGLIA WITH PROINFLAMMATORY AND STEM-LIKE FEATURES SUPPORT TUMOR PROGRESSION

Poor response of human glioblastoma to current therapies are influenced by tumor microenvironment. Although glioblastoma is recognized by large enrichment of microglia, characterization of diverse cell subsets and their functions remain challenging because of high heterogenicity. Here, we analyzed single-cell transcriptomics to comprehensively map the cell populations and determine the roles of microglia in IDH1/2 wild-type (IDH-wt) glioblastoma progression. Besides finding microglia were significantly enriched in IDH-wt glioblastoma compared to IDH1/2 mutant (IDH-mut) gliomas, we identified a unique high-grade glioma microglia (HGAM) subtype characterized by proinflammatory and stem-like features. In particular, HGAM’s pro-tumoral IL1β secretion is mediated via ApoE-induced activation of NLRP1 inflammasome. HGAM phagocytosed OPC-like malignant cells forming the neoplastic microglia, which presented the stem-like potential giving rise to activated microglia. Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation. Additionally, an intricated evaluation of glioma patients revealed that SETD2 mutation/low-expression correlated with adverse prognosis. Further analysis showed that SETD2 -dificient tumor cells presented hypersensitivity to HGAM-derived IL1β via epigenetic dysregulation of PHF6. Also, SETD2 -deficient tumor cells produced TGF-β1 contributing to microglia activation. Finally, targeting the TGF-β1/TβRI signaling impaired HGAM activation and tumor growth. Our studies identify a unique neoplastic microglia subpopulation and establish cellular basis of interactions with tumor cells important for disease progression.

STEM-30. NECROPTOTIC ASTROCYTES CONTRIBUTE TO MAINTAINING STEMNESS OF DISSEMINATED MEDULLOBLASTOMA THROUGH CCL2 SECRETION

Medulloblastoma (MB) with metastases at diagnosis and recurrence correlates with poor prognosis. Unfortunately, the molecular mechanism underlying metastases growth has received less attention than primary therapy-naïve MB. Though astrocytes have been frequently detected in brain tumors, their roles in regulating the stemness properties of MB stem-like cells (MBSCs) in disseminated lesions remain elusive. Effects of tumor-associated astrocytes (TAA)-secreted CCL2 on MBSCs self-renewal was determined by immunostaining analysis. Necroptosis of TAA was examined by measuring necrosome activity. Alterations in Notch signaling were examined after inhibition of CCL2. Progression of MBSCs-derived tumors was evaluated after pharmaceutical blockage of necroptosis. TAA, as the essential components of disseminated tumor, produced high level of CCL2 to shape inflammation microenvironment, which stimulated the enrichment of MBSCs in disseminated MB. In particular, CCL2 played a pivotal role in maintaining stem-like properties via JAK2/STAT3 mediated activation of Notch signaling. Loss of CCL2/CCR2 function repressed JAK2/STAT3-Notch pathway and impaired MBSCs proliferation, leading to a dramatic reduction of stemness, tumorigenicity and metastasizing capability. Furthermore, necroptosis-induced CCL2 release depended on RIP1/RIP3/MLKL activation in TAA, which promoted the oncogenic phenotype. Blockade of necroptosis resulted in CCL2 deprivation and compromised MBSCs self-proliferation, indicating MBSCs outsourced CCL2 from necroptotic TAA. Finally, CCL2 was upregulated in high-risk stages of MB, further supporting its value as a prognostic indicator. These findings highlighted the critical role of CCL2/CCR2 in Notch signaling activation in MBSCs, and revealed a necroptosis-associated glial cytokine microenvironment driving stemness maintenance in disseminations.

Cholesterol Pathway Inhibition Induces TGF-β Signaling to Promote Basal Differentiation in Pancreatic Cancer

Oncogenic transformation alters lipid metabolism to sustain tumor growth. We define a mechanism by which cholesterol metabolism controls the development and differentiation of pancreatic ductal adenocarcinoma (PDAC). Disruption of distal cholesterol biosynthesis by conditional inactivation of the rate-limiting enzyme Nsdhl or treatment with cholesterol-lowering statins switches glandular pancreatic carcinomas to a basal (mesenchymal) phenotype in mouse models driven by Kras^G12D expression and homozygous Trp53 loss. Consistently, PDACs in patients receiving statins show enhanced mesenchymal features. Mechanistically, statins and NSDHL loss induce SREBP1 activation, which promotes the expression of Tgfb1, enabling epithelial-mesenchymal transition. Evidence from patient samples in this study suggests that activation of transforming growth factor β signaling and epithelial-mesenchymal transition by cholesterol-lowering statins may promote the basal type of PDAC, conferring poor outcomes in patients.

Tumour-reprogrammed stromal BCAT1 fuels branched-chain ketoacid dependency in stromal-rich PDAC tumours

Branched-chain amino acids (BCAAs) supply both carbon and nitrogen in pancreatic cancers, and increased levels of BCAAs have been associated with increased risk of pancreatic ductal adenocarcinomas (PDACs). It remains unclear, however, how stromal cells regulate BCAA metabolism in PDAC cells and how mutualistic determinants control BCAA metabolism in the tumour milieu. Here, we show distinct catabolic, oxidative and protein turnover fluxes between cancer-associated fibroblasts (CAFs) and cancer cells, and a marked reliance on branched-chain α-ketoacid (BCKA) in PDAC cells in stroma-rich tumours. We report that cancer-induced stromal reprogramming fuels this BCKA demand. The TGF-β-SMAD5 axis directly targets BCAT1 in CAFs and dictates internalization of the extracellular matrix from the tumour microenvironment to supply amino-acid precursors for BCKA secretion by CAFs. The in vitro results were corroborated with circulating tumour cells (CTCs) and PDAC tissue slices derived from people with PDAC. Our findings reveal therapeutically actionable targets in pancreatic stromal and cancer cells.

Force-exerting perpendicular lateral protrusions in fibroblastic cell contraction

Aligned extracellular matrix fibers enable fibroblasts to undergo myofibroblastic activation and achieve elongated shapes. Activated fibroblasts are able to contract, perpetuating the alignment of these fibers. This poorly understood feedback process is critical in chronic fibrosis conditions, including cancer. Here, using fiber networks that serve as force sensors, we identify "3D perpendicular lateral protrusions" (3D-PLPs) that evolve from lateral cell extensions named twines. Twines originate from stratification of cyclic-actin waves traversing the cell and swing freely in 3D to engage neighboring fibers. Once engaged, a lamellum forms and extends multiple secondary twines, which fill in to form a sheet-like PLP, in a force-entailing process that transitions focal adhesions to activated (i.e., pathological) 3D-adhesions. The specific morphology of PLPs enables cells to increase contractility and force on parallel fibers. Controlling geometry of extracellular networks confirms that anisotropic fibrous environments support 3D-PLP formation and function, suggesting an explanation for cancer-associated desmoplastic expansion.

Discoidin Domain Receptor 1 (DDR1) Is Necessary for Tissue Homeostasis in Pancreatic Injury and Pathogenesis of Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDA) and chronic pancreatitis are characterized by a dense collagen-rich desmoplastic reaction. Discoidin domain receptor 1 (DDR1) is a receptor tyrosine kinase activated by collagens that can regulate cell proliferation, migration, adhesion, and remodeling of the extracellular matrix. To address the role of DDR1 in PDA, Ddr1-null (Ddr^-/-) mice were crossed with the Kras^G12D/+; Trp53^R172H/+; Ptf1a^Cre/+ (KPC) model of metastatic PDA. Ddr1^-/-; KPC mice progress to differentiated PDA but resist progression to poorly differentiated cancer compared with KPC control mice. Strikingly, severe pancreatic atrophy accompanied tumor progression in Ddr1^-/-; KPC mice. To further explore the effects of Ddr1 ablation, Ddr1^-/- mice were crossed with the Kras^G12D/+; Ptf1a^Cre/+ neoplasia model and subjected to cerulein-induced experimental pancreatitis. Similar to KPC mice, tissue atrophy was a hallmark of both neoplasia and pancreatitis models in the absence of Ddr1. Compared with controls, Ddr1^-/- models had increased acinar cell dropout and reduced proliferation with no difference in apoptotic cell death between control and Ddr1^-/- animals. In most models, organ atrophy was accompanied by increased fibrillar collagen deposition, suggesting a compensatory response in the absence of this collagen receptor. Overall, these data suggest that DDR1 regulates tissue homeostasis in the neoplastic and injured pancreas.

Engineering clinically-relevant human fibroblastic cell-derived extracellular matrices

Three-dimensional (3D) culturing models, replicating in vivo tissue microenvironments that incorporate native extracellular matrix (ECM), have revolutionized the cell biology field. Fibroblastic cells generate lattices of interstitial ECM proteins. Cell interactions with ECMs and with molecules sequestered/stored within these are crucial for tissue development and homeostasis maintenance. Hence, ECMs provide cells with biochemical and biomechanical cues to support and locally control cell function. Further, dynamic changes in ECMs, and in cell-ECM interactions, partake in growth, development, and temporary occurrences such as acute wound healing. Notably, dysregulation in ECMs and fibroblasts could be important triggers and modulators of pathological events such as developmental defects, and diseases associated with fibrosis and chronic inflammation such as cancer. Studying the type of fibroblastic cells producing these matrices and how alterations to these cells enable changes in ECMs are of paramount importance. This chapter provides a step-by-step method for producing multilayered (e.g., 3D) fibroblastic cell-derived matrices (fCDM). Methods also include means to assess ECM topography and other cellular traits, indicative of fibroblastic functional statuses, like naïve/normal vs. inflammatory and/or myofibroblastic. For these, protocols include indications for isolating normal and diseased fibroblasts (i.e., cancer-associated fibroblasts known as CAFs). Protocols also include means for conducting microscopy assessments, querying whether fibroblasts present with fCDM-dependent normal or CAF phenotypes. These are supported by discrete semi-quantitative digital imaging analyses, providing some imaging processing advice. Additionally, protocols include descriptions for effective fCDM decellularization, which renders cellular debris-free patho/physiological in vivo-like scaffolds, suitable as 3D substrates for subsequent cell culturing.

Abstract C06: Cholesterol deprivation induces TGFβ signaling to promote basal differentiation in pancreatic cancer

Oncogenic transformation alters the metabolism of cellular nutrients to sustain tumor growth. We here define a mechanism by which modifications in cholesterol metabolism control the formation of pancreatic ductal adenocarcinoma (PDAC). Disruption of distal cholesterol biosynthesis by means of conditional inactivation of Nsdhl in mice bearing a tumor-inducing Kras mutation (KrasG12D) prevented PDAC formation in the context of a heterozygous Trp53f/+ genotype without impairing normal pancreatic development. In mice with pancreatic Nsdhl ablation and homozygous loss of Trp53, the emerging tumors presented with the aggressive basal (mesenchymal) phenotype as opposed to the classic (glandular) PDAC. This paralleled significantly reduced expression of cholesterol metabolic pathway genes in human basal PDAC subtype. Mechanistically, we demonstrate that genetic or metabolic reduction in cellular cholesterol induces the expression of transforming growth factor beta (TGF) and activates pro-mesenchymal effectors in human and murine PDAC, providing a direct transcriptional mechanism by which cholesterol metabolism can condition tumor differentiation. Activity of TGF beta pathway estimated via pSMAD2 expression in surgical PDAC samples inversely correlated with patients’ blood cholesterol levels, especially in patients taking cholesterol-lowering statins. Conclusions: Low levels of cellular cholesterol induce autocrine TGF beta signaling in PDAC. Malnutrition or cholesterol-lowering statins may be mechanistically linked to basal PDAC differentiation.

Citation Format: Linara Gabitova, Suraj Peri, Ralph Francescone, Janusz Franco-Barraza, Neelima Shah, Emmanuelle Nicolas, Elizabeth A. Handorf, Kathy Q. Cai, Ido Sloma, Rachel Chiaverelli, Richard Moffitt, Erica A. Golemis, Carolyn Fang, Shannon Lynch, Edna Cukierman, Igor Astsaturov. Cholesterol deprivation induces TGFβ signaling to promote basal differentiation in pancreatic cancer [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2019 Sept 6-9; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2019;79(24 Suppl):Abstract nr C06.

Rigidity controls human desmoplastic matrix anisotropy to enable pancreatic cancer cell spread via extracellular signal-regulated kinase 2

It is predicted that pancreatic ductal adenocarcinoma (PDAC) will become the second most lethal cancer in the US by 2030. PDAC includes a fibrous-like stroma, desmoplasia, encompassing most of the tumor mass, which is produced by cancer-associated fibroblasts (CAFs) and includes their cell-derived extracellular matrices (CDMs). Since elimination of desmoplasia has proven detrimental to patients, CDM reprogramming, as opposed to stromal ablation, is therapeutically desirable. Hence, efforts are being made to harness desmoplasia's anti-tumor functions. We conducted biomechanical manipulations, using variations of pathological and physiological substrates in vitro, to culture patient-harvested CAFs and generate CDMs that restrict PDAC growth and spread. We posited that extrinsic modulation of the environment, via substrate rigidity, influences CAF's cell-intrinsic forces affecting CDM production. Substrates used were polyacrylamide gels of physiological (~1.5 kPa) or pathological (~7 kPa) stiffnesses. Results showed that physiological substrates influenced CAFs to generate CDMs similar to normal/control fibroblasts. We found CDMs to be softer than the corresponding underlying substrates, and CDM fiber anisotropy (i.e., alignment) to be biphasic and informed via substrate-imparted morphological CAF aspect ratios. The biphasic nature of CDM fiber anisotropy was mathematically modeled and proposed a correlation between CAF aspect ratios and CDM alignment; regulated by extrinsic and intrinsic forces to conserve minimal free energy. Biomechanical manipulation of CDMs, generated on physiologically soft substrates, leads to reduction in nuclear translocation of pERK1/2 in KRAS mutated pancreatic cells. ERK2 was found essential for CDM-regulated tumor cell spread. In vitro findings correlated with in vivo observations; nuclear pERK1/2 is significantly high in human PDAC samples. The study suggests that altering underlying substrates enable CAFs to remodel CDMs and restrict pancreatic cancer cell spread in an ERK2 dependent manner.

Remodeling of the Collagen Matrix in Aging Skin Promotes Melanoma Metastasis and Affects Immune Cell Motility

Physical changes in skin are among the most visible signs of aging. We found that young dermal fibroblasts secrete high levels of extracellular matrix (ECM) constituents, including proteoglycans, glycoproteins, and cartilage-linking proteins. The most abundantly secreted was HAPLN1, a hyaluronic and proteoglycan link protein. HAPLN1 was lost in aged fibroblasts, resulting in a more aligned ECM that promoted metastasis of melanoma cells. Reconstituting HAPLN1 inhibited metastasis in an aged microenvironment, in 3-D skin reconstruction models, and in vivo. Intriguingly, aged fibroblast-derived matrices had the opposite effect on the migration of T cells, inhibiting their motility. HAPLN1 treatment of aged fibroblasts restored motility of mononuclear immune cells, while impeding that of polymorphonuclear immune cells, which in turn affected regulatory T-cell recruitment. These data suggest that although age-related physical changes in the ECM can promote tumor cell motility, they may adversely affect the motility of some immune cells, resulting in an overall change in the immune microenvironment. Understanding the physical changes in aging skin may provide avenues for more effective therapy for older patients with melanoma. SIGNIFICANCE: These data shed light on the mechanochemical interactions that occur between aged skin, tumor, and immune cell populations, which may affect tumor metastasis and immune cell infiltration, with implications for the efficacy of current therapies for melanoma.See related commentary by Marie and Merlino, p. 19.This article is highlighted in the In This Issue feature, p. 1.

Cancer cell chemokines direct chemotaxis of activated stellate cells in pancreatic ductal adenocarcinoma

The mechanisms by which the extreme desmoplasia observed in pancreatic tumors develops remain unknown and its role in pancreatic cancer progression is unsettled. Chemokines have a key role in the recruitment of a wide variety of cell types in health and disease. Transcript and protein profile analyses of human and murine cell lines and human tissue specimens revealed a consistent elevation in the receptors CCR10 and CXCR6, as well as their respective ligands CCL28 and CXCL16. Elevated ligand expression was restricted to tumor cells, whereas receptors were in both epithelial and stromal cells. Consistent with its regulation by inflammatory cytokines, CCL28 and CCR10, but not CXCL16 or CXCR6, were upregulated in human pancreatitis tissues. Cytokine stimulation of pancreatic cancer cells increased CCL28 secretion in epithelial tumor cells but not an immortalized activated human pancreatic stellate cell line (HPSC). Stellate cells exhibited dose- and receptor-dependent chemotaxis in response to CCL28. This functional response was not linked to changes in activation status as CCL28 had little impact on alpha smooth muscle actin levels or extracellular matrix deposition or alignment. Co-culture assays revealed CCL28-dependent chemotaxis of HPSC toward cancer but not normal pancreatic epithelial cells, consistent with stromal cells being a functional target for the epithelial-derived chemokine. These data together implicate the chemokine CCL28 in the inflammation-mediated recruitment of cancer-associated stellate cells into the pancreatic cancer parenchyma.

Matrix-regulated integrin αvβ5 maintains α5β1-dependent desmoplastic traits prognostic of neoplastic recurrence

Desmoplasia, a fibrotic mass including cancer-associated fibroblasts (CAFs) and self-sustaining extracellular matrix (D-ECM), is a puzzling feature of pancreatic ductal adenocarcinoma (PDACs). Conflicting studies have identified tumor-restricting and tumor-promoting roles of PDAC-associated desmoplasia, suggesting that individual CAF/D-ECM protein constituents have distinguishable tumorigenic and tumor-repressive functions. Using 3D culture of normal pancreatic versus PDAC-associated human fibroblasts, we identified a CAF/D-ECM phenotype that correlates with improved patient outcomes, and that includes CAFs enriched in plasma membrane-localized, active α₅β₁-integrin. Mechanistically, we established that TGFβ is required for D-ECM production but dispensable for D-ECM-induced naïve fibroblast-to-CAF activation, which depends on α_vβ₅-integrin redistribution of pFAK-independent active α₅β₁-integrin to assorted endosomes. Importantly, the development of a simultaneous multi-channel immunofluorescence approach and new algorithms for computational batch-analysis and their application to a human PDAC panel, indicated that stromal localization and levels of active SMAD2/3 and α₅β₁-integrin distinguish patient-protective from patient-detrimental desmoplasia and foretell tumor recurrences, suggesting a useful new prognostic tool.

DOI:http://dx.doi.org/10.7554/eLife.20600.001

Tumors are not entirely made out of cancerous cells. They contain many other components – referred to as tumor stroma – that may either encourage or hinder the tumor’s growth. Tumor stroma includes non-cancerous cells and a framework of fibrous sugary proteins, called the extracellular matrix, which surround and signal to cells while providing physical support.

In the most common and aggressive form of pancreatic cancer, the stroma often makes up the majority of the tumor’s mass. Sometimes the stroma of these pancreatic tumors can protect the cancer cells from anti-cancer drugs. Researchers have therefore been interested in finding out exactly which aspects of the tumor stroma shield and support cancer cells, and which impede their growth and progression. Answering these questions could make it possible to develop new drugs that will change a tumor-supporting stroma into one that hinders the tumor’s growth and spread.

The most abundant cells in the stroma of pancreatic tumors are called cancer-associated fibroblasts. Healthy specialized fibroblasts – known as pancreatic stellate cells – help to build and maintain the ‘normal’ extracellular matrix and so these cells normally restrict a tumor’s development. However, cancer cells can adapt healthy fibroblasts into cancer-associated fibroblasts, which produce an altered extracellular matrix that could allow the tumor to grow.

Franco-Barraza et al. have now compared healthy and cancer-associated fibroblasts from patients’ pancreatic tumors. One of the main differences between these two cell types was the location of the activated form of a molecule called α₅β₁-integrin. Healthy fibroblasts, in a normal extracellular matrix, have active α₅β₁-integrin on the surface of the cell. However, a number of tumor-promoting signals, including some from the altered extracellular matrix, could force the active α₅β₁-integrins to relocate inside the fibroblasts instead. In further experiments, where the activated integrin was retained at the cell surface, the fibroblasts were able to resist the influence of the cancer-associated extracellular matrix. Then again, if the active α₅β₁-integrins were directed inside the cells, healthy cells turned into cancer-associated fibroblasts.

With this information in hand, Franco-Barraza et al. examined tumor samples from over a hundred pancreatic cancer patients using a new microscopy-based technique that distinguishes cancer cells from stroma cells. The analysis confirmed the pattern observed in the laboratory: those patients who appeared to produce more normal extracellular matrix and have active α₅β₁-integrin localized mostly to the surface of the cells survived longer without the cancer returning than those patients who lacked these stroma traits. Samples from patients with kidney cancer also showed similar results and, as before, an altered extracellular matrix was linked to a worse outcome of the disease.

Together these findings suggest that if future studies uncover ways to relocate or maintain active α₅β₁-integrin to the cell surface of fibroblasts they could lead to new treatments to restrict the growth of tumors in cancer patients.

DOI:http://dx.doi.org/10.7554/eLife.20600.002

Preparation of Extracellular Matrices Produced by Cultured and Primary Fibroblasts

Fibroblasts secrete and organize extracellular matrix (ECM), which provides structural support for their adhesion, migration, and tissue organization, besides regulating cellular functions such as growth and survival. Cell-to-matrix interactions are vital for vertebrate development. Disorders in these processes have been associated with fibrosis, developmental malformations, cancer, and other diseases. This unit describes a method for preparing a three-dimensional matrix derived from fibroblastic cells; the matrix is three-dimensional, cell and debris free, and attached to a two-dimensional culture surface. Cell adhesion and spreading are normal on these matrices. This matrix can also be compressed into a two-dimensional matrix and solubilized to study the matrix biochemically. © 2016 by John Wiley & Sons, Inc.

Abstract 2913: Transcriptional reprogramming of pancreatic stroma induces metabolic changes in pancreatic tumor cells

Pancreatic cancer remains one of the most lethal of all solid tumors largely due to an aggressive stroma that constitutes the bulk of the tumor. The notion of a reprogrammed stroma suggests the re-establishment of a physiologically normal tumor microenvironment with quiescent stellate cells and fibroblasts. The induction of a quiescent phenotype hinders the aberrant tumor-stroma crosstalk and enables the increased intratumoral delivery of chemo drugs. A combinatorial transcriptional therapy has proven successful at normalizing the tumor microenvironment by reverting the activated state of stromal cells back to quiescence, both at the phenotypic and genetic levels. Indeed, we have observed a reduction in the activation markers of primary human stellate cells and fibroblasts, accompanied by an increase in the quiescence markers. Observations from methylation/hydroxymethylation profiling and metabolic rewiring through isotopomer flux analysis revealed potential targets for therapeutic intervention. In addition, the differential metabolic rewiring induced by a quiescent stroma in cancer cells suggests a tumor suppressive environment aimed at weakening an otherwise aggressive cancer.

Citation Format: Joelle Baddour, Lifeng Yang, Abhinav Achreja, Seth Padmabandu, Pari Shah, Rebecca N. Curtis, Thomas Plackemeier, Radina Khalid, Juan C. Marini, Janusz Franco-Barraza, Edna Cukierman, Chaoxin Hu, Anirban Maitra, Deepak Nagrath. Transcriptional reprogramming of pancreatic stroma induces metabolic changes in pancreatic tumor cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2913. doi:10.1158/1538-7445.AM2015-2913

Abstract 3379: Metabolic influences of pancreatic tumor microenvironment on pancreatic cancer cell's metabolism

Pancreatic cancer, the most lethal of solid tumors, is associated with a five-year survival rate and high mortality. The lethality of this tumor stems from lack of early symptoms, inability for detection of cancerous pancreatic lesions, and a diagnosis window that is accompanied by tumor resistance and metastasis. The bulk of the tumor mass, the fibrotic stroma, has been deemed an active player in the initiation and progression of pancreatic ductal adinocarcinoma (PDAC). A number of studies have elucidated the interactions between stromal cells and pancreatic cancer cells (PCCs), and the extracellular matrix (ECM) and PCCs. However, the role of the tumor microenvironment on the metabolic machinery of PCCs remains an active field of investigation. In this study, we investigate the effect of pancreatic stellate cells (PSCs), cancer-associated fibroblasts (CAFs), with or without ECM components, in a two-dimensional or three-dimensional setting on the glycolytic and mitochondrial pathways of patient-derived PCCs. The modulation of the expression levels of metabolic enzymes by the tumor microenvironment was also investigated. The metabolic reprogramming induced in PCCs by normal and reactive pancreatic stroma was investigated by isotopomer flux analysis. Our results reveal that pancreatic reactive stroma differentially upregulates glutamine and arginine metabolism in PCCs. The insights obtained from our work will lead to the development of targeted therapies for stroma and pancreatic cancer cells.

Citation Format: Joelle Baddour, Lifeng Yang, Juan C. Marini, Janusz Franco-Barraza, Edna Cukierman, Chaoxin Hu, Anirban Maitra, Deepak Nagrath. Metabolic influences of pancreatic tumor microenvironment on pancreatic cancer cell's metabolism. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3379. doi:10.1158/1538-7445.AM2014-3379

Abstract 137: Tumor-associated ECM induces renal cell carcinoma tumorigenic responses via α6β1-integrin regulation of ITPKA

It is estimated that over 65,150 patients were diagnosed with renal cell carcinoma (RCC) with 13,680 deaths in 2013. Surgery and targeted therapies have limited impact on survival in patients with advanced metastatic RCC. Tumor-stroma plays a pivotal role in RCC tumorigenesis including metastasis. One of the striking features of RCC is a fibro vascular stromal reaction with an altered tumor-associated extracellular matrix (TA-ECM) that directly intercalates with the tumoral epithelia playing a functional role in RCC progression. We previously suggested that stromal activation characterized by the expression of specific tumor-associated stromal proteins and the TA-ECM not only constitutes an independent worse prognostic marker, but also comprises a predictive risk indicator of recurrent RCC.

Our work is based on the fact that stromal-tumor interactions are most readily studied in in vivo-mimetic 3D models. Among the most promising systems are in vitro 3D stromal models developed by our group in which tumor cells are plated within TA-ECMs derived from fibroblasts harvested from surgical tissue samples comprised of patient-matched normal and tumor-associated fibroblasts. We have demonstrated the physiological relevance of this system in vivo and found that mesenchymal RCC stromal cells and matrices are modified during epithelial tumor progression.

Here we show that ECMs produced by normal fibroblasts are restrictive, while syngeneic tumor-associated ECMs induce increased RCC tumorigenic responses including tumor growth, resistance to apoptosis and promotion of invasion. An unbiased gene expression array was conducted using RNA obtained from RCC cells cultured within the assorted ECMs. Classic RCC signaling pathways were evident, and in addition proteins previously unsuspected to play important roles in stromal regulation of RCC progression were identified. Amid these, we observed significant increases in the levels of inositol 1,4,5-trisphosphate 3-kinase-A (IP3KA; also known as ITPKA). Our data suggests that ITPKA's activity is necessary for the above-stated TA-ECM induced tumorigenic responses. The study describes how, in response to tumor-associated but not normal ECM, α6β1-integrin activity regulates ITPKA via increased cytosolic Ca2+ stabilizing constitutive Raf1 and Erk1/2 activities to promote tumorigenic responses. Moreover, in vitro experiments were confirmed using the original patient samples while clinical relevance was established in a well-annotated RCC tissue microarray cohort.

We propose that activated stromal RCC triggers a novel α6β1/ITPKA/Erk1/2 pro-tumorigenic signaling pathway. In consequence, patients presenting activated stroma, together with high tumoral α6β1-integrin and/or ITPKA expression, are predicted to present unfavorable outcomes. This work is expected to facilitate future clinical testing of the new targets to aid development of novel RCC therapeutics.

Citation Format: Vivekanand Gupta, Janusz Franco-Barraza, Neelima Shah, Essel Dulaimi, Yan Zhou, Karthik Devarajan, Kathy Q. Cai, Katherine R. Alpaugh, Robert G. Uzzo, Edna Cukierman. Tumor-associated ECM induces renal cell carcinoma tumorigenic responses via α6β1-integrin regulation of ITPKA. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 137. doi:10.1158/1538-7445.AM2014-137

The wound healing, chronic fibrosis, and cancer progression triad

For decades tumors have been recognized as "wounds that do not heal." Besides the commonalities that tumors and wounded tissues share, the process of wound healing also portrays similar characteristics with chronic fibrosis. In this review, we suggest a tight interrelationship, which is governed as a concurrence of cellular and microenvironmental reactivity among wound healing, chronic fibrosis, and cancer development/progression (i.e., the WHFC triad). It is clear that the same cell types, as well as soluble and matrix elements that drive wound healing (including regeneration) via distinct signaling pathways, also fuel chronic fibrosis and tumor progression. Hence, here we review the relationship between fibrosis and cancer through the lens of wound healing.

Abstract P6-02-05: A novel culturing 3-D model to evaluate the role of tumor microenvironment in IBC

Introduction: Inflammatory breast cancer (IBC) is a highly aggressive form of breast cancer associated with extremely poor outcomes. The clinical and pathological characteristics of the disease are the peculiar invasion of the dermal lymphatics as tumor emboli and the development of early recurrences. We aimed to establish a 3D model to evaluate the role of tumor microenvironment.

Methods: We used human tumor-associated fibroblasts (or fibroblasts derived from metastatic skin) from IBC patients to build a multilayer extracellular matrix structure which effectively mimics aspects of the mesenchymal microenvironment of IBCs. Using this in vivo-like microenvironment we proceeded to test both matrix effects upon IBC's phenotypes and IBC modifications upon the cell-derived 3D matrices.

We seeded the IBC cells into the matrix and cultured for 3 days, then tested the characterization markers cancer cells and ECM e.g. Phalloidin, E-cadherin, Ki67, α5β1 integrin and fibronectin by immunofluorescence and the expression of E-cadherin and vimentin as marker of epithelial-mesenchymal transition (EMT) by western blot.

Results: We divided six IBC cell lines into 2 groups depending on the phenotypes acquired when cultured in the IBC fibroblast-derived ECM. SUM149 (EGF receptor positive and aggressive phenotype), BR016 and LG018 (harvested from patient's pleural effusions) presented a single cell organization with a spindle-like or mesenchymal type (as opposed to cluster) morphology. In comparison, SUM190 (HER2 positive and non aggressive tumorigenesis), MDA-IBC-3 and FC-IBC-02 (abstracted from patient's pleural effusion) presented a phenotype resembling mammospheres or in vivo emboli. Moreover, this last group of cells showed a peculiar capability for ECM modifications which greatly differed from the ECM modifications that were apparent following 3 day culturing of the above mentioned group represented by SUM149. In addition, proliferation measurements by Ki67 expression demonstrated a significant increased in 3D culture for SUM149, BR016 and LG018 compared with that in 2D culture, while no differences in proliferation were observed in the other three cell lines. Moreover, the expression of E-cadherin known to be upregulated in IBC tumors was increased in all cancer cells when seeded into the human fibroblast-derived 3D matrix indicating a potential role of the microenvironment in promoting proliferation, growth and invasion.

Conclusion: The present study demonstrated the establishment of a novel IBC stromal 3D model using extracellular matrix produced from human fibroblasts of patients with advanced IBC. We showed a dynamic interaction between cancer cells and the microenvironment and potential sorting of IBC cells into two discrete groups which also correlate with their aggressive behaviors in vivo. We believe that these system may serve to predict levels of IBC tumorigenesis. We will proceed to further study the two identified responsive phenotypes with the goal of uncovering mechanisms of IBC tumor-stromal interactions and better understand ECM influences upon IBC development and progression. The ultimate goal will be to use the system to study IBC biology and better design drugs that will specifically affect the newly identified phenotypes.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P6-02-05.

FAP-overexpressing fibroblasts produce an extracellular matrix that enhances invasive velocity and directionality of pancreatic cancer cells

BACKGROUND

Alterations towards a permissive stromal microenvironment provide important cues for tumor growth, invasion, and metastasis. In this study, Fibroblast activation protein (FAP), a serine protease selectively produced by tumor-associated fibroblasts in over 90% of epithelial tumors, was used as a platform for studying tumor-stromal interactions. We tested the hypothesis that FAP enzymatic activity locally modifies stromal ECM (extracellular matrix) components thus facilitating the formation of a permissive microenvironment promoting tumor invasion in human pancreatic cancer.

METHODS

We generated a tetracycline-inducible FAP overexpressing fibroblastic cell line to synthesize an in vivo-like 3-dimensional (3D) matrix system which was utilized as a stromal landscape for studying matrix-induced cancer cell behaviors. A FAP-dependent topographical and compositional alteration of the ECM was characterized by measuring the relative orientation angles of fibronectin fibers and by Western blot analyses. The role of FAP in the matrix-induced permissive tumor behavior was assessed in Panc-1 cells in assorted matrices by time-lapse acquisition assays. Also, FAP+ matrix-induced regulatory molecules in cancer cells were determined by Western blot analyses.

RESULTS

We observed that FAP remodels the ECM through modulating protein levels, as well as through increasing levels of fibronectin and collagen fiber organization. FAP-dependent architectural/compositional alterations of the ECM promote tumor invasion along characteristic parallel fiber orientations, as demonstrated by enhanced directionality and velocity of pancreatic cancer cells on FAP+ matrices. This phenotype can be reversed by inhibition of FAP enzymatic activity during matrix production resulting in the disorganization of the ECM and impeded tumor invasion. We also report that the FAP+ matrix-induced tumor invasion phenotype is β1-integrin/FAK mediated.

CONCLUSION

Cancer cell invasiveness can be affected by alterations in the tumor microenvironment. Disruption of FAP activity and β1-integrins may abrogate the invasive capabilities of pancreatic and other tumors by disrupting the FAP-directed organization of stromal ECM and blocking β1-integrin dependent cell-matrix interactions. This provides a novel preclinical rationale for therapeutics aimed at interfering with the architectural organization of tumor-associated ECM. Better understanding of the stromal influences that fuel progressive tumorigenic behaviors may allow the effective future use of targeted therapeutics aimed at disrupting specific tumor-stromal interactions.

Actin cytoskeleton participation in the onset of IL-1beta induction of an invasive mesenchymal-like phenotype in epithelial MCF-7 cells

BACKGROUND

Interleukin 1 beta (IL-1beta) and other inflammatory cytokines are reported to induce phenotypic changes in epithelial breast cancer tumor cells related to increased invasiveness. Mechanisms involved in the process are not well understood.

METHODS

The noninvasive breast cancer epithelial cell line MCF-7 was used to investigate the IL-1beta-induced phenotype. Live cells expressing EGFP-actin were monitored for cell morphology changes and actin cytoskeleton dynamics by time-lapse video microscopy in the presence of IL-1beta and specific inhibitors of actin signaling pathways. Chemotaxis, invasion of Matrigel, MMP activity and expression of S100A4 in cells treated with IL-1beta were assessed by migration assays, zymograms and immunoblots.

RESULTS

Exposure to IL-1beta specifically induced a change in MCF-7 cells from a typical epithelial morphology into elongated cells, showing numerous dynamic actin-rich lamellae and peripheral ruffles characteristic of fibroblasts. These cells could scatter from compact cell colonies and respond to chemoattractants such as the homing-associated chemokine CXCL-12. Pharmacological blockage of actin signaling pathways and negative mutants of RhoGTPases revealed that actin reorganization and enhanced motility are regulated via PI3K/Rac 1 activation. IL-1beta-stimulated cells expressed the metastasis promoter S100A4, increased secretion of active MMP-9 and MMP-2 and invasion of extracellular matrix proteins.

CONCLUSIONS

IL-1beta induces a PI3K/Rac 1-regulated reorganization of the actin cytoskeleton of MCF-7 cells that is required for cell scattering, elongation and migration. The enhanced motility is accompanied by expression of protein markers correlated with invasive behavior.

Effect of pro-inflammatory cytokine stimulation on human breast cancer: implications of chemokine receptor expression in cancer metastasis

Interactions between tumour cells and microenvironments may affect their growth and metastasis formation. In search for a better understanding of the role of cellular mediators in the progression of cancer, we investigated the effect of pro-inflammatory cytokines IL-1, IL-6, TNF-alpha and IFN-gamma on the regulation of expression of chemokine receptors CXCR4, CXCR2, CX3CR1, CCR9, and CCR5 in the human breast cancer cell line MCF-7. Our results showed that IL-1 increased CXCR4 expression whereas TNF-alpha increased CX3CR1, CCR9 and CCR5. Interestingly, this regulation was not homogeneous, emphasizing the inherent heterogeneity in cancer that may be responsive to specific inflammatory microenvironments.

Rho signaling inEntamoeba histolytica modulates actomyosin-dependent activities stimulated during invasive behavior

Interaction of Entamoeba histolytica trophozoites with target cells and substrates activates signaling pathways in the parasite. Phosphorylation cascades triggered by phospho-inositide and adenyl-cyclase-dependent pathways modulate reorganization of the actin cytoskeleton to form structures that facilitate adhesion. In contrast, little is known about participation of Rho proteins and Rho signaling in actin rearrangements. We report here the in vivo expression of at least one Rho protein in trophozoites, whose activation induced actin reorganization and actin-myosin interaction. Antibodies to EhRhoA1 recombinant protein mainly localized Rho in the cytosol of nonactivated amoebae, but it was translocated to vesicular membranes and to some extent to the plasma membrane after treatment with lysophosphatidic acid (LPA), a specific agonist of Rho activation. Activated Rho was identified in LPA-treated trophozoites. LPA induced striking polymerization of actin into distinct dynamic structures. Disorganization of these structures by inhibition of Rho effector, Rho-kinase (ROCK), and by ML-7, an inhibitor of myosin light chain kinase dependent phosphorylation of myosin light chain, suggested that the actin structures also contained myosin. LPA stimulated concanavalin-A-mediated formation of caps, chemotaxis, invasion of extracellular matrix substrates, and erythrophagocytosis, but not binding to fibronectin. ROCK inhibition impaired LPA-stimulated functions and to some extent adhesion to fibronectin. Similar results were obtained with ML-7. These data suggest the presence and operation of Rho-signaling pathways in E. histolytica, that together with other, already described, signaling routes modulate actomyosin-dependent motile processes, particularly stimulated during invasive behavior.