Ex vivo drug testing of patient-derived lung organoids to predict treatment responses for personalized medicine

Lung cancer is the leading cause of global cancer-related mortality resulting in ∼ 1.8 million deaths annually. Systemic, molecular targeted, and immune therapies have provided significant improvements of survival outcomes for patients. However, drug resistance usually arises and there is an urgent need for novel therapy screening and personalized medicine. 3D patient-derived organoid (PDO) models have emerged as a more effective and efficient alternative for ex vivo drug screening than 2D cell culture and patient-derived xenograft (PDX) models. In this review, we performed an extensive search of lung cancer PDO-based ex vivo drug screening studies. Lung cancer PDOs were successfully established from fresh or bio-banked sections and/or biopsies, pleural effusions and PDX mouse models. PDOs were subject to ex vivo drug screening with chemotherapy, targeted therapy and/or immunotherapy. PDOs consistently recapitulated the genomic alterations and drug sensitivity of primary tumors. Although sample sizes of the previous studies were limited and some technical challenges remain, PDOs showed great promise in the screening of novel therapy drugs. With the technical advances of high throughput, tumor-on-chip, and combined microenvironment, the drug screening process using PDOs will enhance precision care of lung cancer patients.

Phagocytosis-initiated tumor hybrid cells acquire a c-Myc-mediated quasi-polarization state for immunoevasion and distant dissemination

While macrophage phagocytosis is an immune defense mechanism against invading cellular organisms, cancer cells expressing the CD47 ligand send forward signals to repel this engulfment. Here we report that the reverse signaling using CD47 as a receptor additionally enhances a pro-survival function of prostate cancer cells under phagocytic attack. Although low CD47-expressing cancer cells still allow phagocytosis, the reverse signaling delays the process, leading to incomplete digestion of the entrapped cells and subsequent tumor hybrid cell (THC) formation. Viable THCs acquire c-Myc from parental cancer cells to upregulate both M1- and M2-like macrophage polarization genes. Consequently, THCs imitating dual macrophage features can confound immunosurveillance, gaining survival advantage in the host. Furthermore, these cells intrinsically express low levels of androgen receptor and its targets, resembling an adenocarcinoma-immune subtype of metastatic castration-resistant prostate cancer. Therefore, phagocytosis-generated THCs may represent a potential target for treating the disease.

AXL-initiated paracrine activation of pSTAT3 enhances mesenchymal and vasculogenic supportive features of tumor-associated macrophages

Tumor-associated macrophages (TAMs) are integral to the development of complex tumor microenvironments (TMEs) and can execute disparate cellular programs in response to extracellular cues. However, upstream signaling processes underpinning this phenotypic plasticity remain to be elucidated. Here, we report that concordant AXL-STAT3 signaling in TAMs is triggered by lung cancer cells or cancer-associated fibroblasts in the cytokine milieu. This paracrine action drives TAM differentiation toward a tumor-promoting "M2-like" phenotype with upregulation of CD163 and putative mesenchymal markers, contributing to TAM heterogeneity and diverse cellular functions. One of the upregulated markers, CD44, mediated by AXL-IL-11-pSTAT3 signaling cascade, enhances macrophage ability to interact with endothelial cells and facilitate formation of primitive vascular networks. We also found that AXL-STAT3 inhibition can impede the recruitment of TAMs in a xenograft mouse model, thereby suppressing tumor growth. These findings suggest the potential application of AXL-STAT3-related markers to quantitatively assess metastatic potential and inform therapeutic strategies in lung cancer.

Contacts with Macrophages Promote an Aggressive Nanomechanical Phenotype of Circulating Tumor Cells in Prostate Cancer

Aggressive tumors of epithelial origin shed cells that intravasate and become circulating tumor cells (CTC). The CTCs that are able to survive the stresses encountered in the bloodstream can then seed metastases. We demonstrated previously that CTCs isolated from the blood of prostate cancer patients display specific nanomechanical phenotypes characteristic of cell endurance and invasiveness and patient sensitivity to androgen deprivation therapy. Here we report that patient-isolated CTCs are nanomechanically distinct from cells randomly shed from the tumor, with high adhesion as the most distinguishing biophysical marker. CTCs uniquely coisolated with macrophage-like cells bearing the markers of tumor-associated macrophages (TAM). The presence of these immune cells was indicative of a survival-promoting phenotype of "mechanical fitness" in CTCs based on high softness and high adhesion as determined by atomic force microscopy. Correlations between enumeration of macrophages and mechanical fitness of CTCs were strong in patients before the start of hormonal therapy. Single-cell proteomic analysis and nanomechanical phenotyping of tumor cell-macrophage cocultures revealed that macrophages promoted epithelial-mesenchymal plasticity in prostate cancer cells, manifesting in their mechanical fitness. The resulting softness and adhesiveness of the mechanically fit CTCs confer resistance to shear stress and enable protective cell clustering. These findings suggest that selected tumor cells are coached by TAMs and accompanied by them to acquire intermediate epithelial/mesenchymal status, thereby facilitating survival during the critical early stage leading to metastasis. SIGNIFICANCE: The interaction between macrophages and circulating tumor cells increases the capacity of tumor cells to initiate metastasis and may constitute a new set of blood-based targets for pharmacologic intervention.

Androgen deprivation-induced elevated nuclear SIRT1 promotes prostate tumor cell survival by reactivation of AR signaling

The NAD⁺-dependent deacetylase, Sirtuin 1 (SIRT1) is involved in prostate cancer pathogenesis. However, the actual contribution is unclear as some reports propose a protective role while others suggest it is harmful. We provide evidence for a contextual role for SIRT1 in prostate cancer. Our data show that (i) mice orthotopically implanted with SIRT1-silenced LNCaP cells produced smaller tumors; (ii) SIRT1 suppression mimicked AR inhibitory effects in hormone responsive LNCaP cells; and (iii) caused significant reduction in gene signatures associated with E2F and MYC targets in AR-null PC-3 and E2F and mTORC1 signaling in castrate-resistant ARv7 positive 22Rv1 cells. Our findings further show increased nuclear SIRT1 (nSIRT1) protein under androgen-depleted relative to androgen-replete conditions in prostate cancer cell lines. Silencing SIRT1 resulted in decreased recruitment of AR to PSA enhancer selectively under androgen-deprivation conditions. Prostate cancer outcome data show that patients with higher levels of nSIRT1 progress to advanced disease relative to patients with low nSIRT1 levels. Collectively, we demonstrate that lowering SIRT1 levels potentially provides new avenues to effectively prevent prostate cancer recurrence.

Abstract B29: AXL Inhibitor TP-0903 attenuates TGFβ-Hippo signaling in lung adenocarcinoma cells

Background: Non-small cell lung cancer (NSCLC) is a molecularly heterogeneous disease with a high propensity for drug resistance and metastasis. AXL, a member of the Tyro3-AXL-Mer (TAM) family of receptor tyrosine kinases, is a central regulator of epithelial-to-mesenchymal transition (EMT) and enables tumor cells to invade and acquire drug resistance. AXL is overexpressed in NSCLC and its expression correlates positively with tumor invasion, drug resistance, and negatively predicts overall survival. We mechanistically interrogated the effects of the AXL inhibitor, TP-0903, on EMT in NSCLC cells using transcriptomic and proteomic profiling.

Methods: Atomic force microscopy, Western blot analysis, RNA sequencing, and mass cytometry (CyTOF) were used to evaluate the phenotypic, transcriptomic, and proteomic profiles of A549 cells treated with 40 nM TP-0903 or shAXL knockdown. A549 and H1650 NSCLC xenograft models were used to explore the consequences of AXL inhibition in vivo.

Results: As expected, TP-0903 treatment attenuated AXL signaling and downstream phosphorylation in the A549 cells. Interestingly, the treatment also reduced gene expression responses to TGFβ-Hippo signaling by disrupting the transcriptional complexes formed by SMAD2/3, SMAD4, YAP1, and TAZ. Consistent with AXL inhibition, TP-0903 reversed the mesenchymal phenotype in A549 and H2009 cell lines and decreased their migratory potential in culture. The CyTOF analysis on TP-0903-treated cells identified resistant clones overexpressing TGFβ receptor II (TGFBR2) and TAZ proteins and displaying hybrid EMT phenotypes. TP-0903 was also active in suppressing A549 or H1650 tumor growth in vivo.

Conclusions: We are the first to report the interplay between AXL and TGFβ-Hippo signaling axis. TP-0903 has excellent therapeutic promise in NSCLC and we speculate that TP-0903 can target mesenchymal transitional states in NSCLC, possibly through the inhibition of the AXL-TGFβ-Hippo signaling axis.

Citation Format: Josephine A. Taverna, Chia-Nung Hung, Chun-Lin Lin, Pawel A. Osmulski, Maria E. Gaczynska, Chiou-Miin Wang, Nicholas D. Lucio, Meizhen Chen, Chih-Wei Chou, Alia Nazarullah, Shellye R. Lampkin, Lianquin Qiu, David J. Bearss, Steve Warner, Lars Mouritsen, Mark Wade, Daniel DeArmond, Ruben Mesa, Nameer Kirma, Tim H.-M. Huang. AXL Inhibitor TP-0903 attenuates TGFβ-Hippo signaling in lung adenocarcinoma cells [abstract]. In: Proceedings of the AACR Special Conference on the Hippo Pathway: Signaling, Cancer, and Beyond; 2019 May 8-11; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(8_Suppl):Abstract nr B29.

SAT-114 Loss of DHEA-Targeting SULT2b1b Sulfotransferase Exacerbates Aggressive Traits of Prostate Cancer

The prostate-expressed sulfotransferase SULT2B1b (SULT2B) regulates intracrine androgen homeostasis by mediating 3β-sulfation of DHEA, thus reducing the precursor pool in the androgen biosynthesis pathway. We explored how loss of SULT2B might influence prostate cancer progression. Results show that SULT2B ablation in castration-resistant prostate cancer (CRPC) cells, generated by stable RNA interference or gene knockout, led to robust activation of the ERK1/2 Map kinase survival signal and induction of epithelial to mesenchymal transition (EMT). EMT activation was concluded on the basis of increased levels of vimentin (a mesenchymal protein) and the EMT-activating transcription factors SNAI1 (Snail) and TWIST1, shown by Western blotting, mass spectrometry and single-cell mass cytometry. Loss of SULT2B was associated with enhanced motility and invasive activity of CRPC cells in vitro and their growth escalation in vivo as xenografts. Higher invasion and metastasis potential of SULT2B-ablated CRPC cells was further indicated by results that these cells are less adhesive (i.e. easily detachable) and less stiff (i.e. more pliable) based on atomic force microscopy analysis of individual cells. Notably, AKR1C3, an aldo-keto reductase, which is elevated frequently in advanced prostate cancer, showed marked upregulation in SULT2B-deficient cells. AKR1C3 regulates androgen receptor (AR) signaling by promoting androgen biosynthesis and functioning as an AR-selective coactivator. While levels of AR and DHT did not change, AR activity was elevated, since PSA and FKBP5 mRNA induction by DHT-activated AR was several fold higher in SULT2B-silenced cells. The DHT-metabolizing AKR1C2 aldo-keto reductase was also upregulated, which likely accounts for a steady-state androgen level despite elevated AKR1C3 expression. Phosphorylation of ERK decreased in AKR1C3-silenced cells, signifying a causal link between AKR1C3 upregulation and ERK1/2 activation. SULT2B was undetectable immunohistochemically in tissue microarrays of clinical CRPC metastases, while SULT2B-negative samples showed AKR1C3-positive immunostaining. Primary prostate cancer exhibited variable, Gleason score independent SULT2B levels -- varying from strong positive to significantly reduced or undetectable. The reciprocal expression pattern for SULT2B and AKR1C3 in clinical CRPC suggests that AKR1C3 upregulation, ERK1/2 activation and increased aggressive traits of SULT2B-ablated cells, observed in vitro in cell models, may be clinically significant. Pathways regulating the inhibitory SULT2B-AKR1C3 axis may inform new avenue(s) for delaying disease progression in SULT2B-deficient prostate cancer.Funding Support: 1I01BX000280, VA (BC); W81XWH-14-1-0606, DOD (BC); IK6 BX004207, VA (BC); P50 CA97186, NIH & W81XWH-12-1-0208, DOD (EAM)

Single-Cell Proteomic Profiling Identifies Combined AXL and JAK1 Inhibition as a Novel Therapeutic Strategy for Lung Cancer

Cytometry by time-of-flight (CyTOF) simultaneously measures multiple cellular proteins at the single-cell level and is used to assess intertumor and intratumor heterogeneity. This approach may be used to investigate the variability of individual tumor responses to treatments. Herein, we stratified lung tumor subpopulations based on AXL signaling as a potential targeting strategy. Integrative transcriptome analyses were used to investigate how TP-0903, an AXL kinase inhibitor, influences redundant oncogenic pathways in metastatic lung cancer cells. CyTOF profiling revealed that AXL inhibition suppressed SMAD4/TGFβ signaling and induced JAK1-STAT3 signaling to compensate for the loss of AXL. Interestingly, high JAK1-STAT3 was associated with increased levels of AXL in treatment-naïve tumors. Tumors with high AXL, TGFβ, and JAK1 signaling concomitantly displayed CD133-mediated cancer stemness and hybrid epithelial-to-mesenchymal transition features in advanced-stage patients, suggesting greater potential for distant dissemination. Diffusion pseudotime analysis revealed cell-fate trajectories among four different categories that were linked to clinicopathologic features for each patient. Patient-derived organoids (PDO) obtained from tumors with high AXL and JAK1 were sensitive to TP-0903 and ruxolitinib (JAK inhibitor) treatments, supporting the CyTOF findings. This study shows that single-cell proteomic profiling of treatment-naïve lung tumors, coupled with ex vivo testing of PDOs, identifies continuous AXL, TGFβ, and JAK1-STAT3 signal activation in select tumors that may be targeted by combined AXL-JAK1 inhibition. SIGNIFICANCE: Single-cell proteomic profiling of clinical samples may facilitate the optimal selection of novel drug targets, interpretation of early-phase clinical trial data, and development of predictive biomarkers valuable for patient stratification.

Inhibitory Interplay of SULT2B1b Sulfotransferase with AKR1C3 Aldo-keto Reductase in Prostate Cancer

SULT2B1b (SULT2B) is a prostate-expressed hydroxysteroid sulfotransferase, which may regulate intracrine androgen homeostasis by mediating 3β-sulfation of dehydroepiandrosterone (DHEA), the precursor for 5α-dihydrotestosterone (DHT) biosynthesis. The aldo-keto reductase (AKR)1C3 regulates androgen receptor (AR) activity in castration-resistant prostate cancer (CRPC) by promoting tumor tissue androgen biosynthesis from adrenal DHEA and also by functioning as an AR-selective coactivator. Herein we report that SULT2B-depleted CRPC cells, arising from stable RNA interference or gene knockout (KO), are markedly upregulated for AKR1C3, activated for ERK1/2 survival signal, and induced for epithelial-to-mesenchymal (EMT)-like changes. EMT was evident from increased mesenchymal proteins and elevated EMT-inducing transcription factors SNAI1 and TWIST1 in immunoblot and single-cell mass cytometry analyses. SULT2B KO cells showed greater motility and invasion in vitro; growth escalation in xenograft study; and enhanced metastatic potential predicted on the basis of decreased cell stiffness and adhesion revealed from atomic force microscopy analysis. While AR and androgen levels were unchanged, AR activity was elevated, since PSA and FKBP5 mRNA induction by DHT-activated AR was several-fold higher in SULT2B-silenced cells. AKR1C3 silencing prevented ERK1/2 activation and SNAI1 induction in SULT2B-depleted cells. SULT2B was undetectable in nearly all CRPC metastases from 50 autopsy cases. Primary tumors showed variable and Gleason score (GS)-independent SULT2B levels. CRPC metastases lacking SULT2B expressed AKR1C3. Since AKR1C3 is frequently elevated in advanced prostate cancer, the inhibitory influence of SULT2B on AKR1C3 upregulation, ERK1/2 activation, EMT-like induction, and on cell motility and invasiveness may be clinically significant. Pathways regulating the inhibitory SULT2B-AKR1C3 axis may inform new avenue(s) for targeting SULT2B-deficient prostate cancer.

Pipecolic esters as minimized templates for proteasome inhibition

Allosteric regulators of clinically important enzymes are gaining popularity as alternatives to competitive inhibitors. This is also the case for the proteasome, a major intracellular protease and a target of anti-cancer drugs. All clinically used proteasome inhibitors bind to the active sites in catalytic chamber and display a competitive mechanism. Unfortunately, inevitable resistance associated with this type of inhibition drives the search for non-competitive agents. The multisubunit and multicatalytic "proteolytic machine" such as the proteasome is occasionally found to be affected by agents with other primary targets. For example the immunosuppressive agent rapamycin has been shown to allosterically inhibit the proteasome albeit at levels far higher than its mTOR related efficacy. As part of an ongoing program to search for novel proteasome-targeting pharmacophores, we identified the binding domain of rapamycin as required for proteasome inhibition even without the macrocyclic context of the parent compound. By subsequent structure-activity relationship studies, we generated a pipecolic ester derivative compound 3 representing a new class of proteasome inhibitors. Compound 3 affects the core proteasome activities and proliferation of cancer cells with low micromolar/high nanomolar efficacy. Molecular modeling, atomic force microscopy imaging and biochemical data suggest that compound 3 binds into one of intersubunit pockets in the proteasomal α ring and destabilizes the α face and the gate. The α face is used as a docking area for proteasome-regulating protein modules and the gate is critical for controlling access to the catalytic chamber. Thus, the pipecolic ester template elicits a new and attractive mechanism for proteasome inhibition distinct from classical competitive drugs.

Abstract 2193: AXL inhibitor TP-0903 attenuates AXL-TGFbeta Hippo signaling axis in lung adenocarcinoma cells

Background: Non-small cell lung cancer (NSCLC) is a molecularly heterogeneous disease with a high propensity for drug resistance and metastasis. AXL, a member of the Tyro3-AXL-Mer family of receptor tyrosine kinases, is a central regulator of epithelial-to-mesenchymal transition (EMT) and enables tumor cells to invade and acquire drug resistance. AXL is overexpressed in lung tumors, correlates positively with tumor invasion, drug resistance, and negatively predicts overall survival. We mechanistically interrogate the effects of AXL inhibitor TP-0903 on EMT in lung adenocarcinoma cells using transcriptomic and proteomic profiling.

Methods: Atomic force microscopy, Western blot analysis, RNA sequencing and mass cytometry (CyTOF) were all used to scrutinize the biomechanical properties, phenotypic, transcriptomic and proteomic profiles of A549 cells treated with 40nM TP0903 or shAXL knockdown.

Results: TP-0903 attenuates total AXL/AXL phosphorylation and blunts transcriptional responses to TGFβ-Hippo signaling by disrupting the transcriptional complexes formed by SMAD2/3, SMAD4, YAP1 and TAZ. AXL knockdown or TP-0903 reverses EMT phenotype and reduces migration potential in A549 and H2009 adenocarcinoma cell lines. CyTOF data also identified resistant clones that overexpress TGFβ receptor II, TAZ protein and display hybrid EMT phenotypes.

Conclusions: We are the first to report the interplay between AXL and TGFβ-Hippo signaling axis. TP-0903 study agent has excellent therapeutic promise in NSCLC and we speculate that TP-0903 drug can target epithelial to mesenchymal transitional states in lung cancer cells possibly through the inhibition of the AXL-TGFβ-Hippo signaling axis.

Citation Format: Josephine Amalia Taverna, Chia-Nung Hung, Chun-Lin Lin, Pawel Osmulski, Meizhen Chen, Chiou-Miin Wang, Nicholas L. L. Lucio, Nameer Kirma, Chih-Wei Chou, Maria E. Gaczynska, Alia Nazarullah, Mark Wade, Lars Mouritsen, Tim Huang. AXL inhibitor TP-0903 attenuates AXL-TGFbeta Hippo signaling axis in lung adenocarcinoma cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2193.

Abstract 2766: Amplification-associated upregulation of genes involved in oxidative phosphorylation for disseminated prostate cancer cells

Purpose: Little is known about adaptive selection of tumor cells transiting from in situ proliferation to distant colonization through blood circulation. This study used genomic, transcriptomic, and biophysical analyses at single-cell levels to explore biological and physical properties of circulating tumor cells (CTCs) undergoing hemodynamic stress. The aims are trying to understand how CTCs strive to survive in the bloodstream and to develop strategies for therapeutic intervention.

Experimental Design: We compared genomic profiles of CTCs in blood and primary tumor cells shed in urine of prostate cancer patients to identify amplified regions preferentially retained in CTCs. Single-cell RNA-seq was used to confirm amplification-associated overexpression of genes in CTCs.

Results: Among 261 recurrently amplified genomic regions in the analysis, 70 were found predominantly shown in CTCs relative to primary tumor cells. In line with the results at the genomic level, the transcriptomic data of CTCs demonstrate a great amount of cells showing high expression levels in the oxidative phosphorylation (OXPHOS) pathway compared to other hallmark gene sets. The finding suggests that tumor cells with these pre-existing genomic alterations were adaptively selected for transcription reprogramming during blood circulation. Specifically, amplified genes associated with OXPHOS were exploited by CTCs for alternative fuels. As to the upstream of this transcription event, we found the expression of MEN1, encoding menin known to form a transcription factor complex with the mixed-lineage leukemia protein (MLL) in prostate cancer cells, was positively correlated with 11 of the 14 OXPHOS loci in the Cancer Genomic Atlas prostate cancer cohort. In vitro assay showed that MEN1 knockdown by shRNA resulted in attenuation of both mRNA and protein expression of OXPHOS loci in PC-3 cells. Taken together pre-existing amplification of OXPHOS loci can be used as a transcription apparatus by menin for metabolic reprogramming of tumor cells in response to harsh microenvironments in the bloodstream.

Conclusions: Single-cell profiling identified signaling pathways that are crucial for CTCs to survive in the bloodstream. The finding suggests that a metabolic shift from Warburg to OXPHOS metabolism can be associated with a hybrid mesenchymal-epithelial phenotype of CTCs. Moreover, the study demonstrates the feasibility of routinely conducting single-cell analysis of exfoliated tumor cells for minimally invasive monitoring of disease progression and treatment response in prostate cancer patients

Citation Format: Chun-Lin Lin, Tan Xi, Chia-Nung Hung, Pawel A. Osmulski, Chih-Wei Chou, Meizhen Chen, Chiou-Miin Wang, Kohzoh Mitsuya, Nameer Kirma, Maria E. Gaczynska, Chun-Liang Chen, Tim H.-M. Huang. Amplification-associated upregulation of genes involved in oxidative phosphorylation for disseminated prostate cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2766.

Adipokines Deregulate Cellular Communication via Epigenetic Repression of Gap Junction Loci in Obese Endometrial Cancer

Emerging evidence indicates that adipose stromal cells (ASC) are recruited to enhance cancer development. In this study, we examined the role these adipocyte progenitors play relating to intercellular communication in obesity-associated endometrial cancer. This is particularly relevant given that gap junctions have been implicated in tumor suppression. Examining the effects of ASCs on the transcriptome of endometrial epithelial cells (EEC) in an in vitro coculture system revealed transcriptional repression of GJA1 (encoding the gap junction protein Cx43) and other genes related to intercellular communication. This repression was recapitulated in an obesity mouse model of endometrial cancer. Furthermore, inhibition of plasminogen activator inhibitor 1 (PAI-1), which was the most abundant ASC adipokine, led to reversal of cellular distribution associated with the GJA1 repression profile, suggesting that PAI-1 may mediate actions of ASC on transcriptional regulation in EEC. In an endometrial cancer cohort (n = 141), DNA hypermethylation of GJA1 and related loci TJP2 and PRKCA was observed in primary endometrial endometrioid tumors and was associated with obesity. Pharmacologic reversal of DNA methylation enhanced gap-junction intercellular communication and cell-cell interactions in vitro. Restoring Cx43 expression in endometrial cancer cells reduced cellular migration; conversely, depletion of Cx43 increased cell migration in immortalized normal EEC. Our data suggest that persistent repression by ASC adipokines leads to promoter hypermethylation of GJA1 and related genes in the endometrium, triggering long-term silencing of these loci in endometrial tumors of obese patients. SIGNIFICANCE: Studies reveal that adipose-derived stem cells in endometrial cancer pathogenesis influence epigenetic repression of gap junction loci, which suggests targeting of gap junction activity as a preventive strategy for obesity-associated endometrial cancer.

TGF-β signal rewiring sustains epithelial-mesenchymal transition of circulating tumor cells in prostate cancer xenograft hosts

Activation of TGF-β signaling is known to promote epithelial-mesenchymal transition (EMT) for the development of metastatic castration-resistant prostate cancer (mCRPC). To determine whether targeting TGF-β signaling alone is sufficient to mitigate mCRPC, we used the CRISPR/Cas9 genome-editing approach to generate a dominant-negative mutation of the cognate receptor TGFBRII that attenuated TGF-β signaling in mCRPC cells. As a result, the delicate balance of oncogenic homeostasis is perturbed, profoundly uncoupling proliferative and metastatic potential of TGFBRII-edited tumor xenografts. This signaling disturbance triggered feedback rewiring by enhancing ERK signaling known to promote EMT-driven metastasis. Circulating tumor cells displaying upregulated EMT genes had elevated biophysical deformity and an increase in interactions with chaperone macrophages for facilitating metastatic extravasation. Treatment with an ERK inhibitor resulted in decreased aggressive features of CRPC cells in vitro. Therefore, combined targeting of TGF-β and its backup partner ERK represents an attractive strategy for treating mCRPC patients.

Anticancer applications of allosteric inhibitors of proteasome

e23066

Background: Proteasome as a hub protease of the ubiquitin proteasome pathway is an established anticancer drug target. Several drugs that inhibit proteasome are currently used to successfully treat aggressive blood cancers. These drugs are based on their competition with protein substrates of proteasome. However, efficacy of these drugs toward solid cancers is inadequate. Besides, the side effects and developing drug resistance are increasingly hampering the therapy. Therefore, there is an unmet challenge to develop new types of proteasome targeting compounds that are efficient against solid cancers and utilize other mechanisms to stop proteasome. Here we present a compound with a novel molecular mechanism, potentially bypassing limitations of the available drugs. Methods: We rationally designed and synthesized a series of small molecule “B” compounds, derivatives of a binding domain of seco-rapamycin that noncompetitively interfere with peptidase activities of proteasome. We tested effects of the compounds in vitro on purified proteasome, in cellulo with selected cancer cell lines and in a xenograft mouse model of prostate cancer. Results: We found that compound B1 binds to the catalytic core of proteasome far from the catalytic sites, destabilizes assembly of the 26S proteasome responsible for digest of polyUb substrates and allosterically inhibits its proteolytic activities. Molecularly, B1 impedes the gating mechanism responsible for substrate uptake as found with AFM. Tryptophan fluorescence indicates that B1 changes proteasome fold and the binding mode of competitive inhibitors. B1 substantially decreases viability of selected cancer cell lines and shifts their mechanical phenotype toward noncancerous status. B1 synergizes with bortezomib decreasing the IC50 5-10 fold. In a xenograft hormone resistant prostate cancer model, B1 treatment leads to shrinkage of the tumor size, decreases enumeration of aggressive, EpCAM+ CTCs and shifts the macrophage profile toward predator M1 type. Conclusions: B1 compounds constitute a new class of noncompetitive allosteric inhibitors of proteasome that could be useful to develop to treat aggressive prostate cancers alone or in synergy with competitive inhibitors.

EpCAM-Regulated Transcription Exerts Influences on Nanomechanical Properties of Endometrial Cancer Cells That Promote Epithelial-to-Mesenchymal Transition

Overexpression of epithelial cell adhesion molecule (EpCAM) has been implicated in advanced endometrial cancer, but its roles in this progression remain to be elucidated. In addition to its structural role in modulating cell-surface adhesion, here we demonstrate that EpCAM is a regulatory molecule in which its internalization into the nucleus turns on a transcription program. Activation of EGF/EGFR signal transduction triggered cell-surface cleavage of EpCAM, leading to nuclear internalization of its cytoplasmic domain EpICD. ChIP-seq analysis identified target genes that are coregulated by EpICD and its transcription partner, LEF-1. Network enrichment analysis further uncovered a group of 105 genes encoding functions for tight junction, adherent, and cell migration. Furthermore, nanomechanical analysis by atomic force microscopy revealed increased softness and decreased adhesiveness of EGF-stimulated cancer cells, implicating acquisition of an epithelial-mesenchymal transition (EMT) phenotype. Thus, genome editing of EpCAM could be associated with altering these nanomechanical properties towards a less aggressive phenotype. Using this integrative genomic-biophysical approach, we demonstrate for the first time an intricate relationship between EpCAM-regulated transcription and altered biophysical properties of cells that promote EMT in advanced endometrial cancer. Cancer Res; 76(21); 6171-82. ©2016 AACR.

Abstract 2871: Dual role of EpCAM cleavage in adhesion attenuation and transcription enhancement for cell migration

Epithelial cell adhesion molecule (EpCAM), a membrane protein known to modulate cell-cell adhesion, is also a regulatory molecule internalized into the nucleus for transcriptional control of gene expression. Here we demonstrate that activated EGF/EGFR is a signaling factor to drive the cleavage of the extracellular fragment EpEX culminating in removal of cell-surface EpCAM as monitored with recognition atomic force microscopy (AFM). As a result, internalization of the cytoplasmic domain EpICD leads to formation of transcription factor complexes with LEF1 that regulate gene transcription for enhancing mobility functions of cancer cells. Comprehensive probing with AFM further reveals increased elasticity and decreased adhesiveness of these cells, implicating acquisition of an epithelial-mesenchymal transition phenotype. While EpCAM cleavage contributes to the loss of cell-surface adhesiveness, its internalized EpICD additionally regulates targets for promoting cell migration. Thus, this EGF/EGFR-modulated action on structural EpCAM and regulatory EpICD can enhance invasion potential of transformed cells.

Citation Format: Ya-Ting Hsu, Pawel A. Osmulski, Yao Wang, Yi-Wen Huang, Lu Liu, Jianhua Ruan, Victor X. Jin, Nameer B. Kirma, Maria E. Gaczynska, Tim H.M. Huang. Dual role of EpCAM cleavage in adhesion attenuation and transcription enhancement for cell migration. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2871.

Interplay between Structure and Charge as a Key to Allosteric Modulation of Human 20S Proteasome by the Basic Fragment of HIV-1 Tat Protein

The proteasome is a giant protease responsible for degradation of the majority of cytosolic proteins. Competitive inhibitors of the proteasome are used against aggressive blood cancers. However, broadening the use of proteasome-targeting drugs requires new mechanistic approaches to the enzyme's inhibition. In our previous studies we described Tat1 peptide, an allosteric inhibitor of the proteasome derived from a fragment of the basic domain of HIV-Tat1 protein. Here, we attempted to dissect the structural determinants of the proteasome inhibition by Tat1. Single- and multiple- alanine walking scans were performed. Tat1 analogs with stabilized beta-turn conformation at positions 4-5 and 8-9, pointed out by the molecular dynamics modeling and the alanine scan, were synthesized. Structure of Tat1 analogs were analyzed by circular dichroism, Fourier transform infrared and nuclear magnetic resonance spectroscopy studies, supplemented by molecular dynamics simulations. Biological activity tests and structural studies revealed that high flexibility and exposed positive charge are hallmarks of Tat1 peptide. Interestingly, stabilization of a beta-turn at the 8-9 position was necessary to significantly improve the inhibitory potency.

Nanomechanical biomarkers of single circulating tumor cells for detection of castration resistant prostate cancer

BACKGROUND

Emerging evidence shows that nanomechanical phenotypes of circulating tumor cells (CTC) could become potential biomarkers for metastatic castration resistant prostate cancer (mCRPC).

METHODS

To determine the nanomechanical phenotypes of CTCs we applied atomic force microscopy (AFM) employing the PeakForce quantitative nanomechanical (QNM) imaging. We assessed biophysical parameters (elasticity, deformation, and adhesion) of 130 CTCs isolated from blood samples from five castration sensitive (CS) and 12 castration resistant prostate cancer (CRPCa) patients.

RESULTS

We found that CTCs from CRPCa patients are three times softer, three times more deformable, and seven times more adhesive than counterparts from CSPCa patients. Both nonsupervised hierarchical clustering and principle component analysis show that three combined nanomechanical parameters could constitute a valuable set to distinguish between CSPCa and CRPCa.

CONCLUSIONS

[corrected] Our study indicates that nanomechanical phenotypes of CTCs may serve as novel and effective biomarkers for mCRPC.

Single-cell analysis of circulating tumor cells identifies cumulative expression patterns of EMT-related genes in metastatic prostate cancer

BACKGROUND

Prostate tumors shed circulating tumor cells (CTCs) into the blood stream. Increased evidence shows that CTCs are often present in metastatic prostate cancer and can be alternative sources for disease profiling and prognostication. Here we postulate that CTCs expressing genes related to epithelial-mesenchymal transition (EMT) are strong predictors of metastatic prostate cancer.

METHODS

A microfiltration system was used to trap CTCs from peripheral blood based on size selection of large epithelial-like cells without CD45 leukocyte marker. These cells individually retrieved with a micromanipulator device were assessed for cell membrane physical properties using atomic force microscopy. Additionally, 38 CTCs from eight prostate cancer patients were used to determine expression profiles of 84 EMT-related and reference genes using a microfluidics-based PCR system.

RESULTS

Increased cell elasticity and membrane smoothness were found in CTCs compared to noncancerous cells, highlighting their potential invasiveness and mobility in the peripheral circulation. Despite heterogeneous expression patterns of individual CTCs, genes that promote mesenchymal transitioning into a more malignant state, including IGF1, IGF2, EGFR, FOXP3, and TGFB3, were commonly observed in these cells. An additional subset of EMT-related genes (e.g., PTPRN2, ALDH1, ESR2, and WNT5A) were expressed in CTCs of castration-resistant cancer, but less frequently in castration-sensitive cancer.

CONCLUSIONS

The study suggests that an incremental expression of EMT-related genes in CTCs is associated with metastatic castration-resistant cancer. Although CTCs represent a group of highly heterogeneous cells, their unique EMT-related gene signatures provide a new opportunity for personalized treatments with targeted inhibitors in advanced prostate cancer patients.

DNA-looping by RXR Tetramers Permits Transcriptional Regulation “at a Distance”

RXR, a member of the superfamily of nuclear hormone receptors, regulates gene transcription in response to 9-cis-retinoic acid. We previously showed that, among nuclear receptors, RXR is unique in that it self-associates into homotetramers, and that these tetramers dissociate rapidly upon ligation. Here, we report that binding of RXR tetramers to DNA containing two RXR response elements results in a dramatic DNA-looping. RXR can thus juxtapose distant DNA sequences, enabling transcriptional regulation by far-upstream factors. We show that RXR functions as a DNA architectural factor and that, while this activity is regulated by 9-cis-retinoic acid, it is distinct from and independent of the receptor's intrinsic transcriptional activity. The data establish RXR as the first identified architectural factor whose activity is regulated by a small ligand, and demonstrate a novel mechanism of transcriptional regulation by retinoids.