Abstract 814: Novel strategy for aptamer-directed nanovesicle targeting in cholangiocarcinoma

Background: Cholangiocarcinoma (CCA) is a heterogeneous malignancy arising from the biliary epithelium. Its diverse molecular landscape and aggressive biology render many anti-cancer therapies ineffective. Nanovesicle technology provides an opportunity for therapeutic inhibition of oncogenic targets that have been previously classified as undruggable. EpCAM is an epithelial-specific, transmembrane glycoprotein with increased expression in human and murine CCA which can be used for nanovesicle targeting. As a proof of concept study, we designed and validated a novel strategy to direct therapeutic milk-derived nanovesicles (tMNVs) to CCA tumors.

Methods: tMNVs were decorated with RNA nanoparticles containing a validated aptamer (EpDT3) against EpCAM conjugated to a cholesterol-triethylene-glycol (TEG) scaffold containing an Alexa647 fluorophore. Human and murine CCA cell lines were treated with aptamer directed tMNVs and assessed for nanovesicle uptake by fluorescent microscopy. CCA tumor tissue, derived from orthotopic implantation of a syngeneic CCA cell line, SB1, into a C57BL/6 mouse, was collected and treated with either aptamer-directed or bare tMNVs ex vivo, and compared with adjacent normal liver tissue. Flow cytometry was utilized to characterize tMNVs absorption profile. C57BL/6 mice who had previously undergone SB1 orthotopic and flank implantation were treated with aptamer-directed tMNVs by tail-vein injection and subsequently euthanized. Tissue was collected for biodistribution analyses by fluorescent microscopy. The experiment was repeated in NOD-scid mice following orthotopic implantation of patient derived xenograft (PDX) CCA tumor.

Results: Both human and murine CCA cells treated with aptamer-directed tMNVs demonstrated high fluorescent signal consistent with tMNV absorption within 12 hours of application. Flow cytometry analysis showed aptamer-directed tMNVs were absorbed at a higher proportion by CCA tumors than bare tMNVs ex vivo. Aptamer-directed tMNVs also had better absorption by CCA tumors compared to adjacent normal liver tissue. Following treatment with aptamer-directed or bare tMNVs in vivo, fluorescent microscopy demonstrated that aptamer-directed tMNVs were significantly better absorbed in the orthotopic SB1 tumors, followed by the subcutaneous tumors. Minimal fluorescent signal was noted in the normal adjacent liver. Orthotopically implanted PDX tumors also demonstrated high fluorescent signals following intravenous treatment with aptamer-directed tMNVs.

Conclusions: Utilizing a novel targeting strategy, we were able to design tMNVs capable of reliably and specifically targeting CCA in preclinical models. This work is foundational to the future application of nanovesicle technology in the CCA treatment paradigm.

Citation Format: Mincheng Yu, Jennifer L. Tomlinson, Emilien J. Loeuillard, Ryan D. Watkins, Caitlin B. Conboy, Shohei Takaichi, Nathan W. Werneburg, Roberto Alva-Ruiz, Amro Abdelrahman, Danielle M. Carlson, Jingchun Yang, Sumera I. Ilyas, Gregory J. Gores, Tushar Patel, Rory L. Smoot. Novel strategy for aptamer-directed nanovesicle targeting in cholangiocarcinoma [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 814.

R-Spondins 2 and 3 Are Overexpressed in a Subset of Human Colon and Breast Cancers

Wnt signaling is activated in many cancer types, yet targeting the canonical Wnt pathway has been challenging for cancer therapy. The pathway might be effectively targeted at many levels depending on the mechanism by which it has become hyperactive. Recently, mouse genetic screens have found that R-spondins (RSPOs) act as oncogenes. Evidence includes recurrent genomic rearrangements that led to increased RSPO2 or RSPO3 expression in human colorectal adenocarcinomas, exclusive of APC mutations. RSPOs modulate Wnt signaling to promote epithelial cell proliferation and survival. These secreted proteins modulate Wnt signaling by binding to G-coupled receptors LGR4/5/6, ultimately inhibiting frizzled membrane clearance by RNF43 and ZNRF3. They also exert their function independent of leucine-rich repeat-containing, G protein-coupled receptors (LGRs) by binding to ZNRF3 and RNF43. This results in increased β-catenin concentration that, after translocation to the nucleus, acts as a transcriptional coactivator of genes necessary for proliferation and cell survival. In this article, we aimed to identify the role of RSPOs in colon and breast cancers by using in silico and in vitro studies. We found that expression of RSPO2 and RSPO3 at high levels characterized a subset of colorectal cancers (CRCs). RSPO2 expression was found to characterize a subset of triple-negative breast cancers. In both instances, increased expression of RSPOs was associated with an activated Wnt signaling gene expression profile. Furthermore, knockdown of RSPO2 decreased Wnt signaling and proliferation in human breast cancer cells. Our findings show and confirm that RSPO2 and RSPO3 expression is upregulated in a subset of colorectal adenocarcinomas and breast cancers and that both are attractive druggable oncoprotein targets against such cancers. We also describe novel fusion transcripts that occur in CRC.

The YAP-Interacting Phosphatase SHP2 Can Regulate Transcriptional Coactivity and Modulate Sensitivity to Chemotherapy in Cholangiocarcinoma

The Hippo pathway effector Yes-associated protein (YAP) is localized to the nucleus and transcriptionally active in a number of tumor types, including a majority of human cholangiocarcinomas. YAP activity has been linked to chemotherapy resistance and has been shown to rescue KRAS and BRAF inhibition in RAS/RAF-driven cancers; however, the underlying mechanisms of YAP-mediated chemoresistance have yet to be elucidated. Herein, we report that the tyrosine phosphatase SHP2 directly regulates the activity of YAP by dephosphorylating pYAPY357 even in the setting of RAS/RAF mutations, and that diminished SHP2 phosphatase activity is associated with chemoresistance in cholangiocarcinomas. A screen for YAP-interacting tyrosine phosphatases identified SHP2, and characterization of cholangiocarcinomas cell lines demonstrated an inverse relationship between SHP2 levels and pYAPY357. Human sequencing data demonstrated lower SHP2 levels in cholangiocarcinomas tumors as compared with normal liver. Cell lines with low SHP2 expression and higher levels of pYAPY357 were resistant to gemcitabine and cisplatin. In cholangiocarcinomas cells with high levels of SHP2, pharmacologic inhibition or genetic deletion of SHP2 increased YAPY357 phosphorylation and expression of YAP target genes, including the antiapoptotic regulator MCL1, imparting resistance to gemcitabine and cisplatin. In vivo evaluation of chemotherapy sensitivity demonstrated significant resistance in xenografts with genetic deletion of SHP2, which could be overcome by utilizing an MCL1 inhibitor. IMPLICATIONS: These findings demonstrate a role for SHP2 in regulating YAP activity and chemosensitivity, and suggest that decreased phosphatase activity may be a mechanism of chemoresistance in cholangiocarcinoma via a MCL1-mediated mechanism.

Immunobiology of cholangiocarcinoma

Cholangiocarcinoma (CCA) represents a heterogeneous group of epithelial tumours that are classified according to anatomical location as intrahepatic (iCCA), perihilar (pCCA), or distal (dCCA). Although surgical resection and liver transplantation following neoadjuvant therapy are potentially curative options for a subset of patients with early-stage disease, the currently available medical therapies for CCA have limited efficacy. Immunotherapeutic strategies such as immune checkpoint blockade (ICB) harness the host immune system to unleash an effective and durable antitumour response in a subset of patients with a variety of malignancies. However, response to ICB monotherapy has been relatively disappointing in CCA. CCAs are desmoplastic tumours with an abundant tumour immune microenvironment (TIME) that contains immunosuppressive innate immune cells such as tumour-associated macrophages and myeloid-derived suppressor cells. A subset of CCAs may be classified as immune 'hot' tumours with a high density of CD8+ T cells and enhanced expression of immune checkpoint molecules. Immune 'hot' tumour types are associated with higher response rates to ICB. However, the suboptimal response rates to ICB monotherapy in human clinical trials of CCA imply that the preponderance of CCAs are immune 'cold' tumours with a non-T cell infiltrated TIME. An enhanced comprehension of the immunobiology of CCA, particularly the innate immune response to CCA, is essential in the effort to develop effective combination immunotherapeutic strategies that can target a larger subset of CCAs.

R-spondin 2 Drives Liver Tumor Development in a Yes-Associated Protein-Dependent Manner

Each year, more than 25,000 people succumb to liver cancer in the United States, and this neoplasm represents the second cause of cancer-related death globally. R-spondins (RSPOs) are secreted regulators of Wnt signaling that function in development and promote tissue stem cell renewal. In cancer, RSPOs 2 and 3 are oncogenes first identified by insertional mutagenesis screens in tumors induced by mouse mammary tumor virus and by transposon mutagenesis in the colonic epithelium of rodents. RSPO2 has been reported to be activated by chromosomal rearrangements in colorectal cancer and overexpressed in a subset of hepatocellular carcinoma. Using human liver tumor gene expression data, we first discovered that a subset of liver cancers were characterized by high levels of RSPO2 in contrast to low levels in adjacent nontumor tissue. To determine if RSPOs are capable of inducing liver tumors, we used an in vivo model from which we found that overexpression of RSPO2 in the liver promoted Wnt signaling, hepatomegaly, and enhanced liver tumor formation when combined with loss of transformation-related protein 53 (Trp53). Moreover, the Hippo/yes-associated protein (Yap) pathway has been implicated in many human cancers, influencing cell survival. Histologic and gene expression studies showed activation of Wnt/β-catenin and Hippo/Yap pathways following RSPO2 overexpression. We demonstrate that knockdown of Yap1 leads to reduced tumor penetrance following RSPO2 overexpression in the context of loss of Trp53. Conclusion: RSPO2 overexpression leads to tumor formation in the mouse liver in a Hippo/Yap-dependent manner. Overall, our results suggest a role for Yap in the initiation and progression of liver tumors and uncover a novel pathway activated in RSPO2-induced malignancies. We show that RSPO2 promotes liver tumor formation in vivo and in vitro and that RSPO2's oncogenic activity requires Hippo/Yap activation in hepatocytes. Both RSPO2 and YAP1 are suggested to represent novel druggable targets in Wnt-driven tumors of the liver.

Simple and efficient methods for enrichment and isolation of endonuclease modified cells

The advent of Transcription Activator-Like Effector Nucleases (TALENs), and similar technologies such as CRISPR, provide a straightforward and cost effective option for targeted gene knockout (KO). Yet, there is still a need for methods that allow for enrichment and isolation of modified cells for genetic studies and therapeutics based on gene modified human cells. We have developed and validated two methods for simple enrichment and isolation of single or multiplex gene KO's in transformed, immortalized, and human progenitor cells. These methods rely on selection of a phenotypic change such as resistance to a particular drug or ability to grow in a selective environment. The first method, termed co-transposition, utilizes integration of a piggyBac transposon vector encoding a drug resistance gene. The second method, termed co-targeting, utilizes TALENs to KO any gene that when lost induces a selectable phenotype. Using these methods we also show removal of entire genes and demonstrate that TALENs function in human CD34⁺ progenitor cells. Further, co-transposition can be used to generate conditional KO cell lines utilizing an inducible cDNA rescue transposon vector. These methods allow for robust enrichment and isolation of KO cells in a rapid and efficient manner.

Abstract A242: R-spondin 2 drives Wnt signaling and tumor formation in breast and liver cancer

Background: R-spondins are secreted agonists of Wnt signaling that function in development and promote tissue stem cell proliferation. Rspo2 was identified as a candidate oncogene in intestinal tumors via a Sleeping Beauty transposon insertional mutagenesis screen in mice (1). Further, oncogenic activation of RSPO2 and RSPO3 mediated by recurrent genomic rearrangements has been identified in human colorectal cancer (2). The purpose of the current study was to determine if R-spondins function as oncogenes in other cancer types characterized by active Wnt signaling.

Methods: R-spondin mRNA expression was determined in primary human breast tumors and adjacent normal tissue by quantitative RT-PCR. Affymetrix microarrays were used to assay gene expression and classify by molecular subtype human hepatocellular carcinomas compared to pre-malignant lesions and normal livers. RSPO2 was depleted or overexpressed in breast cell lines by stable transduction with anti-RSPO2 shRNA or RSPO2 cDNA. Resulting changes in gene expression and proliferation were measured by qRT-PCR and MTS assay respectively. RSPO2 was somatically overexpressed in murine liver by hydrodynamic injection and Fah selection in an Fah-null model. Subsequent gene expression studies were conducted by qRT-PCR and immunohistochemistry.

Results: RSPO2 was highly expressed in 12% of primary human breast tumors compared to adjacent normal tissue. Similarly, RSPO2 expression was elevated in the subset of primary human liver cancers with activated Wnt/beta-catenin signaling. In human breast cancer cells with elevated RSPO2 expression, RSPO2 knockdown decreased Wnt signaling and proliferation, while RSPO2 overexpression in a non-tumorigenic breast epithelial cell line potentiated Wnt signaling. Overexpression of RSPO2 in the mouse liver increased Wnt signaling and promoted an enlarged liver phenotype and tumor formation.

Conclusions: These data strongly suggest that RSPO2 is a driver of human breast and liver cancer. Future work will further characterize signaling pathways implicated in RSPO-driven phenotypes, and develop targeted therapy to inhibit RSPO signaling.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):A242.

Citation Format: Caitlin B. Conboy, Bobbi R. Tschida, Hsiangyu Hu, Michael B. Burns, Nuri A. Temiz, Timothy Kuka, Vincent W. Keng, Sara Toffanin, Reuben S. Harris, Josep Llovet, Timothy K. Starr, David A. Largaespada. R-spondin 2 drives Wnt signaling and tumor formation in breast and liver cancer. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr A242.

Canonical Wnt/β-catenin signaling drives human schwann cell transformation, progression, and tumor maintenance

Genetic changes required for the formation and progression of human Schwann cell tumors remain elusive. Using a Sleeping Beauty forward genetic screen, we identified several genes involved in canonical Wnt signaling as potential drivers of benign neurofibromas and malignant peripheral nerve sheath tumors (MPNSTs). In human neurofibromas and MPNSTs, activation of Wnt signaling increased with tumor grade and was associated with downregulation of β-catenin destruction complex members or overexpression of a ligand that potentiates Wnt signaling, R-spondin 2 (RSPO2). Induction of Wnt signaling was sufficient to induce transformed properties in immortalized human Schwann cells, and downregulation of this pathway was sufficient to reduce the tumorigenic phenotype of human MPNST cell lines. Small-molecule inhibition of Wnt signaling effectively reduced the viability of MPNST cell lines and synergistically induced apoptosis when combined with an mTOR inhibitor, RAD-001, suggesting that Wnt inhibition represents a novel target for therapeutic intervention in Schwann cell tumors.

Abstract 108: Functional characterization of WAC, a candidate tumor suppressor gene in colorectal cancer

Broadening our understanding of the genetic basis of cancer will facilitate construction of relevant pre-clinical models and provide novel targets for drug development. To identify genes that contribute to the initiation or progression of colorectal cancer (CRC) when mutated or dysregulated, we recently conducted a set of forward genetic screens using transposon insertional mutagenesis to drive intestinal tumor formation in mice. These studies were designed to identify novel cancer genes that function in a wildtype genetic context or cooperate with known predisposing alleles (ApcMin/+ or Trp53R270H/+). Over 150 genes were identified, including several known to be important in human CRC (eg. APC, PTEN, and FBXW7) and many novel candidate cancer genes. WW domain containing adaptor with coiled-coil (WAC), is a gene not previously associated with cancer that was identified in all three screens. While the function of WAC is incompletely understood, previous reports indicate that the WAC protein participates in multiple cellular processes, including golgi biogenesis, modulation of gene expression, and induction of p21CIP1 expression and cell cycle arrest in response to DNA damage. In this study, we evaluated the role of WAC in cellular transformation by depleting WAC in mouse colonic epithelial cells conditionally immortalized by expression of a temperature sensitive SV40 large T antigen. In this model, loss of WAC expression increased anchorage-independent growth of colonic epithelial cells in cooperation with mutant APC. In human CRC samples, resequencing the WAC gene identified non-silent mutations in 2 of 74 samples. Further, CRC-associated WAC mutants were found to be functionally deficient in induction of p21CIP1 in a zebrafish embryo model. These data are consistent with the model that WAC functions as a tumor suppressor in the colonic epithelium.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 108. doi:1538-7445.AM2012-108

Determination of halothane distribution in the rat head using 19F NMR technique

The distribution of halothane in the rat head was examined with 19F NMR rotating-frame zuegmatography and 2DFT 19F NMR imaging. The rotating frame experiments were conducted at varying times following anesthesia to assess the time dependence of the halothane distribution. The results of these experiments demonstrate that halothane and halothane metabolite are unequally partitioned through the rat tissues examined. 19F spin-echo imaging experiments were conducted immediately following anesthesia. The results of these experiments are compared with those of the spectroscopic technique.

New NMR probe designs for neonatal, immature and adult heart research. With a brief review

We present three new radiofrequency probes for nuclear magnetic resonance (NMR) research with perfused rabbit hearts at different maturational ages. The objective of the double-tunable, cylindrical-window probe design was to achieve a highly homogeneous magnetic field throughout the 16, 25 or 30 mm diameter usable volume for consistency of comparison of measurements obtained from neonate, immature and adult rabbit hearts, respectively. This probe design tunes to 23-Sodium for rapid shimming and then, to 31-Phosphorus for measurements of pH and high energy phosphate metabolites. All three probes yielded excellent signal-to-noise ratios and radiofrequency operating characteristics. We introduce these new probes here in the context of a brief review of other state-of-the-art designs for in vitro and in vivo cardiovascular research.

In vivo 19F-NMR study of halothane distribution in brain

Halothane distribution and elimination from rabbit brain was studied in vivo using 19F-NMR spectroscopy. Two exponential decay functions for the anesthetic were observed in the clearance curve. They are assigned to halothane in brain held in two distinct chemical environments characterized by different chemical shifts, and half-lives (25 and 320 min). A nonvolatile halothane metabolite with a half-life of several days was found to be present in rabbit brains. The in vivo results were corroborated by ex vivo experiments on excised brain tissue. Halothane was distributed in all of the major cell subfractions, whereas the metabolite was present predominantly in the cytoplasm.

In vivo 19F-NMR study of isoflurane elimination from brain

The time course of isoflurane elimination from rabbit brain was studied in vivo with 19F-NMR spectroscopy. Two exponential decay functions with different time constants were observed and assigned to two distinct brain compartments. Isoflurane has a 26 min time constant for one compartment (similar to a value of 25 min with halothane) but 174 min in the second one, compared with 320 min for halothane. The shorter half-life for isoflurane may be due to lower solubility of this agent in brain tissue. Comparison of isoflurane 19F chemical shifts in solvents in isolated brain lipids and in whole brain tissue indicates that the anesthetic present in the brain exists in a single environment (on the NMR time scale), which is a weighted average of both hydrophilic and hydrophobic environments.

Noninvasive in vivo demonstration of 2-fluoro-2-deoxy-D-glucose metabolism beyond the hexokinase reaction in rat brain by 19F nuclear magnetic resonance spectroscopy

The metabolism of 2-fluoro-2-deoxy-D-glucose (FDG) in vivo was observed noninvasively in rat brain using 19F nuclear magnetic resonance (NMR) spectroscopy following an intravenous injection of FDG (400 mg/kg). At 3 h after infusion, four resonances with discrete chemical shifts were resolved. Chemical shift analysis of these resonances suggested the chemical identity of two of the resonances to be FDG and/or FDG-6-phosphate and 2-fluoro-2-deoxy-delta-phosphogluconolactone and/or 2-fluoro-2-deoxy-6-phosphogluconate. The chemical identities of the other two resonances remain to be elucidated. The present study indicates that the metabolism of FDG in vivo is more extensive than is previously recognized and demonstrates the feasibility of using 19F NMR spectroscopy to follow the 19F-containing metabolites of FDG in vivo.

31P surface-coil NMR analysis of metabolic status in KHJJ tumors

Noninvasive monitoring of the effects of treatment on cancer tissue is fundamental to the development of rational radioimmunotherapy (RIT) schemes employing radiolabeled monoclonal antibodies or antibody fragments specific for human cancer. Recent advances in nuclear magnetic resonance spectroscopy make it an attractive candidate for sequential, topical monitoring by 31P NMR of metabolic events during RIT. Preliminary to this effort, we examined the metabolic competence of the well-characterized, murine KHJJ tumor in situ in BALB/c mice using 31P surface-coil NMR. The ATP/Pi ratio in tumor volumes ranging from 100 to 800 mm3 showed that tumors over this range of sizes were able to maintain high levels of ATP relative to Pi. As the tumor volume increased above 1 cm3, ATP/Pi levels indicated poor metabolic competence. This lack of metabolic competence was correlated with histological evidence of tissue necrosis and vascular disintegration. The T1 values of assigned phosphorus metabolites were established. Intracellular pH, as determined from the chemical shift of Pi, was found to vary in these tumors from 7.1 in rapidly metabolizing tissue to 6.6 in necrotic tumors.