Abstract 4: Intercepting ribosomal protein S6KB1 signaling: Prevention of prostate cancer recurrence

There is an urgent need for innovative strategies such as the discovery of adjuvants that can prevent relapse and improve quality of life for patients treated with radiotherapy. Previously we demonstrated the utility of Nexrutine (Nex) as a neo-adjuvant with radiation. Nex was safe and well tolerated in PCa patients and potentiated radiation response in part through downregulation of ribosomal protein S6K (encoded byRPS6KB1). We now show that RPS6KB1 depleted prostate cancer cells with higher basal levels of γ-H2AX, a marker for DNA double strand breaks (i) are more sensitive to radiation and (ii) form smaller tumors with reduced levels of prostate specific antigen (PSA). Depletion of RPS6KB1 hindered DNA double-strand break repair predominantly through the alternate end-joining pathway, induction of G2/M checkpoint and NFκB pathway activation. Collectively these events led to improved radiation sensitivity. We further identified Berberine (Ber), one of the active constituents of Nex as a potential pharmacological inhibitor of RPS6KB1. In an orthotopic implantation model of C4-2B, treatment with Ber alone or Ber plus radiation decreased PSA levels that was sustained during the course of the experiment. On the other hand animals treated with radiation alone developed recurrent cancer as evidenced by a resurgence of PSA. Animals administered Ber followed by XRT intervention had increased levels of RANTES while there was no change in animals that received XRT followed by Ber. The observed reversal of the Bereffect with the sequence of intervention is statistically significant (p=0.0298). Among animals not subject to XRT, the mean PSA increased in those that did not receive Ber relative to those that did; mean difference=-1.93, 95% CI -3.75 to -0.105, p=0.04 with no significant changes in body weight. Notably,RPS6KB1 mRNA levels increased in tumor samples in patients experiencing biochemical recurrence(BCR). Given that rising PSA following conventional therapeutic approaches such as radiation remain a major clinical challenge, targeting RPS6KB1 signaling with radiation therapy is an attractive strategy to prevent BCR. Supported in part by CPRIT RP190012 (APK).

Citation Format: Addanki Pratap Kumar, Alison Clark, Michelle Villarreal, Sridharan Jayamohan, Shih-Bo Huang, Suleman S. Hussain, Xiaoyu Yang, Paul Rivas, Darpan Patel, Bethany L. Pierce, Shreya Tripathy, Pawel Osmulski, Maria Gaczynska, Lai Zhao, Li-Ju Wang, Yidong Chen, Caroline Xavier Paul Ezhilan, Mohan Natarajan, Joel E. Michalek, Robert L. Reddick, Rita Ghosh. Intercepting ribosomal protein S6KB1 signaling: Prevention of prostate cancer recurrence [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 4.

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.

Evidence for 2-Methoxyestradiol-Mediated Inhibition of Receptor Tyrosine Kinase RON in the Management of Prostate Cancer

2-Methoxyestradiol (2-ME₂) possesses anti-tumorigenic activities in multiple tumor models with acceptable tolerability profile in humans. Incomplete understanding of the mechanism has hindered its development as an anti-tumorigenic compound. We have identified for the first-time macrophage stimulatory protein 1 receptor (MST1R) as a potential target of 2-ME₂ in prostate cancer cells. Human tissue validation studies show that MST1R (a.k.a RON) protein levels are significantly elevated in prostate cancer tissues compared to adjacent normal/benign glands. Serum levels of macrophage stimulatory protein (MSP), a ligand for RON, is not only associated with the risk of disease recurrence, but also significantly elevated in samples from African American patients. 2-ME₂ treatment inhibited mechanical properties such as adhesion and elasticity that are associated with epithelial mesenchymal transition by downregulating mRNA expression and protein levels of MST1R in prostate cancer cell lines. Intervention with 2-ME₂ significantly reduced tumor burden in mice. Notably, global metabolomic profiling studies identified significantly higher circulating levels of bile acids in castrated animals that were decreased with 2-ME₂ intervention. In summary, findings presented in this manuscript identified MSP as a potential marker for predicting biochemical recurrence and suggest repurposing 2-ME₂ to target RON signaling may be a potential therapeutic modality for prostate cancer.

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)

Targeting AXL-JAK1 in tumor and immune ecosystem of lung cancer

Intercellular crosstalk between lung adenocarcinoma cells (LACs) and tumor-associated macrophages (TAMs) has been implicated in promoting cancer metastasis; however, how oncogenic signaling networks corroborate in this tumorigenic process remains unexplored. Our findings suggest that coordinated activation of AXL and JAK1-pSTAT3 signaling engenders a vicious cycle of dependence between LACs and TAMs for tumor progression. AXL-overexpressing LACs polarize TAMs to an M2-like phenotype in a JAK1-STAT3-dependent manner, facilitating the development of a proinflammatory tumor microenvironment. Conversely, M2-like TAMs release Gas6 ligand to enhance AXL-mediated cancer stemness and epithelial-to-mesenchymal transition (EMT) in LACs. Cytometry by time-of-flight (CyTOF) is a single-cell detection technology that allows for measurement of multiple protein markers in diverse cell subpopulations. We designed a 34-antibody CyTOF panel to identify immune cells, stromal cells, epithelial cells, oncogenic signaling, stemness and EMT components for LAC tumor profiling. CyTOF profiling of ~642,241 single cells detected 55 subpopulations among LAC cell lines (n=4 with co-culture conditions) and lung tumors (n=12), which were further differentiated based on their cell types (LACs, TAMs, stromal cells, granulocytes, natural killer, B and T lymphocytes). High AXL expression was noticed in tumor cell subpopulation while high pSTAT3 expression was detected in the TAM subpopulation. Moreover, pSTAT3 expression levels were increased in U937 differentiated macrophage after co-culture with A549 cells. This novel platform may facilitate the optimal selection of lung cancer patients for dual targeting of AXL and JAK1-pSTAT3.

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 5150: Adipose-derived stem cell disruption of gap junction intercellular communication in obesity-associated endometrial cancer

Endometrial cancer is the most common gynecologic cancer. It is divided into two major types, a less aggressive endometrioid type and a more aggressive serous type. Recent clinical observations underscore obesity as a major risk factor for endometrial cancer. In this study, we hypothesized that obesity can result in long term epigenetic modifications in the endometrial compartment, leading to the promotion of endometrial cancer. We examined the role of adipose-derived stem cells (ASCs), which are adipocyte progenitors, in the endometrial tumor microenvironment. By staining for ASCs in a tumor tissue microarray, we observed ASC infiltration that was specific to samples from obese patients, correlating with body mass index (R2=0.77, p<0.001). Using a co-culture system to simulate ASC microenvironmental effects and transcriptomic analysis, we showed that exposure of immortalized endometrial epithelial cells (EECs) to ASC secreted factors led to the repression of cell-cell communication pathways, most notably gap junctions and related factors tight junction proteins TJP and PKC genes. This gene repression was associated with induction of DNA Methylation in the promoter of the major GJ gene GJA1 (encoding connexin 43, Cx43) in the ASC-exposed EECs. Importantly, we further demonstrated this DNA hypermethylation in the promoters of the GJA1, TJP2 and PKC genes in primary endometrial tumors from obese patients compared to non-obese patients. We assessed the effects of epigenetic regulation on gap junction intercellular communication (GJIC) and cell-cell interactions using cellular calcein dye transfer assays and atomic force microscopy (for nano-scale assessment of cell-cell adhesion) by treating endometrial cancer cells with a demethylating agent (DAC). DAC treatment resulted in increased level of cell-cell adhesiveness and communication via gap junction coupling. Specific reactivation of GJA1 (Cx43) by expression vector in endometrial cancer cells led to decreased cellular motility. Because we found that PAI-1 is a major adipokine in the ASC secretome, inhibition of PAI-1 in ASC-exposed EECs led to a cell population expression profile with lower GJ expression, based on single-cell PCR studies. Collectively, the data demonstrate multi-scale regulation of cellular communication via paracrine actions and direct cell-cell coupling via gap junctions by epigenetic silencing influenced by ASCs. This leads to disruption of cellular homeostasis and enhanced motility, promoting endometrial cancer in obese patients.

Citation Format: Li-Ling Lin, Srikanth Polusani, Guangcun Huang, Chun-Lin Lin, Chiou-Miin Wang, Nicholas Lucio, Mikhail Kolonin, Alexes Daquinag, Pawel Osmulski, Bruce Nicholson, Edward Kost, Tim Huang, Nameer B. Kirma. Adipose-derived stem cell disruption of gap junction intercellular communication in obesity-associated endometrial cancer [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 5150.

Proline- and Arginine-Rich Peptides as Flexible Allosteric Modulators of Human Proteasome Activity

Proline- and arginine-rich peptide PR11 is an allosteric inhibitor of 20S proteasome. We modified its sequence inter alia by introducing HbYX, RYX, or RHbX C-terminal extensions (Hb, hydrophobic moiety; R, arginine; Y, tyrosine; X, any residue). Consequently, we were able to improve inhibitory potency or to convert inhibitors into strong activators: the former with an aromatic penultimate Hb residue and the latter with the HbYX motif. The PR peptide activator stimulated 20S proteasome in vitro to efficiently degrade protein substrates, such as α-synuclein and enolase, but also activated proteasome in cultured fibroblasts. The positive and negative PR modulators differently influenced the proteasome conformational dynamics and affected opening of the substrate entry pore. The resolved crystal structure showed PR inhibitor bound far from the active sites, at the proteasome outer face, in the pocket used by natural activators. Our studies indicate the opportunity to tune proteasome activity by allosteric regulators based on PR peptide scaffold.

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.

Crosstalk between RON and androgen receptor signaling in the development of castration resistant prostate cancer

Castrate-resistant prostate cancer (CRPC) is the fatal form of prostate cancer. Although reactivation of androgen receptor (AR) occurs following androgen deprivation, the precise mechanism involved is unclear. Here we show that the receptor tyrosine kinase, RON alters mechanical properties of cells to influence epithelial to mesenchymal transition and functions as a transcription factor to differentially regulate AR signaling. RON inhibits AR activation and subset of AR-regulated transcripts in androgen responsive LNCaP cells. However in C4-2B, a castrate-resistant sub-line of LNCaP and AR-negative androgen independent DU145 cells, RON activates subset of AR-regulated transcripts. Expression of AR in PC-3 cells leads to activation of RON under androgen deprivation but not under androgen proficient conditions implicating a role for RON in androgen independence. Consistently, RON expression is significantly elevated in castrate resistant prostate tumors. Taken together our results suggest that RON activation could aid in promoting androgen independence and that inhibition of RON in combination with AR antagonist(s) merits serious consideration as a therapeutic option during hormone deprivation therapy.

Sustained NFκB inhibition improves insulin sensitivity but is detrimental to muscle health

Older adults universally suffer from sarcopenia and approximately 60-70% are diabetic or prediabetic. Nonetheless, the mechanisms underlying these aging-related metabolic disorders are unknown. NFκB has been implicated in the pathogenesis of several aging-related pathologies including sarcopenia and type 2 diabetes and has been proposed as a target against them. NFκB also is thought to mediate muscle wasting seen with disuse, denervation, and some systemic diseases (e.g., cancer, sepsis). We tested the hypothesis that lifelong inhibition of the classical NFκB pathway would protect against aging-related sarcopenia and insulin resistance. Aged mice with muscle-specific overexpression of a super-repressor IκBα mutant (MISR) were protected from insulin resistance. However, MISR mice were not protected from sarcopenia; to the contrary, these mice had decreases in muscle mass and strength compared to wild-type mice. In MISR mice, NFκB suppression also led to an increase in proteasome activity and alterations in several genes and pathways involved in muscle growth and atrophy (e.g., myostatin). We conclude that the mechanism behind aging-induced sarcopenia is NFκB independent and differs from muscle wasting due to pathologic conditions. Our findings also indicate that, while suppressing NFκB improves insulin sensitivity in aged mice, this transcription factor is important for normal muscle mass maintenance and its sustained inhibition is detrimental to muscle function.

Cholesterol Regulates Monocyte Rolling through CD44 Distribution

Cholesterol is an important risk factor of atherosclerosis, due to its active uptake by monocytes/macrophages. Monocyte recruitment from flowing blood to atherosclerotic foci is the key first step in the development of atherosclerosis. Cholesterol content alters cell membrane stiffness, and lateral lipid and protein diffusion. We hypothesized that cholesterol content will modulate the recruitment of monocytes to inflamed endothelial surface by altering the dynamics of adhesion receptors. We depleted or enriched the cellular cholesterol levels using methyl-β-cyclodextran in freshly isolated human monocytes. We investigated the effect of these changes on the mechanics of monocyte rolling on E-selectin surfaces at 1 dyn/cm² in microchannels. Using imaging flow cytometry and atomic force microscopy, we characterized the distribution of lipid rafts and the E-selectin counterreceptor CD44 on the monocyte surface. We observed that lower levels of cholesterol resulted in the uniform, CD44-mediated rolling of monocytes on the E-selectin-coated surfaces. We also observed that cells depleted of cholesterol had higher membrane fluidity, and more uniform distribution of CD44 counterreceptor, which resulted in smooth motion of the cells compared to cells enriched with cholesterol. This work demonstrates that cholesterol can modulate monocyte adhesion by regulating the receptor mobility, and our results provide insights into the biophysical regulation of inflammation for the better understanding of diseases like atherosclerosis and hypercholesterolemia.

Cellular cholesterol regulates monocyte deformation

The role of cholesterol content on monocyte biomechanics remains understudied despite the well-established link between cholesterol and monocytes/macrophages in atherosclerosis, and the effect on other cell types. In this work, we have investigated the effect of cholesterol on monocyte deformability and the underlying molecular mechanisms. We altered the baseline cholesterol in human monocytic cell line THP-1, and investigated the changes in monocyte deformability using a custom microfluidic platform and atomic force microscopy. We observed that the cholesterol depletion lowered deformability while enrichment increased deformability compared to untreated cells. As a consequence of altered deformability, cholesterol depleted cells spread more on collagen-coated surfaces with elongated morphology, whereas cholesterol enriched cells had a more rounded morphology. We observed that the decreased deformability in cholesterol depleted cells, despite an increase in the fluidity of the membrane, is due to an increase in phosphorylation of Protein Kinase C (PKC), which translates to a higher degree of actin polymerization. Together, our results highlight the importance of biophysical regulation of monocyte response to cholesterol levels.

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 5588: Epithelial-to-mesenchymal markers of circulating tumor cells for detection of castration-resistant prostate cancer

Approximately 30% of prostate cancer (PCa) patients who receive androgen-deprivation therapy experience disease progression, including bone metastasis, in 18-36 months. Clinical diagnosis of this castration resistance is primarily based on a continuous rise in serum PSA levels during therapy. However, the underlying disease progression predates the clinical onset of castration resistance by many months. The clinical challenge is to distinguish indolent vs aggressive cancer for better disease management. During the prostate cancer progression, malignant circulating tumor cells (CTC) shed from the primary site into the bloodstream through epigenetic modifications and an epithelial-to-mesenchymal transition (EMT). Evidence suggests that increased CTCs are present in the blood of castration-resistant PCa patients and can be obtained through routine phlebotomy. EMT changes of CTCs present a great potential for disease prognosis, treatment stratification and subsequent disease monitoring.

We have recently established the combined microfiltration-micromanipulation system (CM2S) to enrich prostate CTCs from blood as published in The Prostate. Our preliminary studies based on a relatively small sample size show that CTCs isolated from advanced PCa patients often lose the typical features of prostate epithelial cells and display incremental EMT-related gene expression signatures, higher elasticity and smoother membrane features. Furthermore, incremental expression of these genes and particular nanomechanical features in CTCs are associated with castration-resistant and metastatic PCa. In this study, we would like expand the sample size to clinically develop this methodology.

CTCs were isolated from patients' blood (∼15 ml) using microfiltration system (ScreenCell). We analyzed castration-sensitive (CS) and castration-resistant (CR) PCa cells and CTCs using high throughput microfluidic single-cell RT-PCR. The data were subject to hierarchical clustering, violin plot and Ingenuity Pathway Analysis (IPA). Increased expression of EMT genes was found in CR PCa cells and CTCs as compared to CS counterparts. IPA indicated that these EMT genes are closely related to AKT, β-catenin, Myc and NFκB pathways. Some of CTCs isolated from patients were subject to nanomechanical and nanochemical analysis using PeakForce QNM Catalyst atomic force microscopy (AFM) (Bruker). CTCs of CR patients are about 3 fold more elastic and 7 fold more adherent than CTCs of CS patients. Additionally, CTCs of CR patients are about 3 fold more deformable than CTCs of CS patients.

In conclusion, we confirmed our previous study with a larger patient sample size. The increased expression of EMT-related genes and nanomechanical and nanochemical phenotypes in CTCs are potential biomarkers for detection of the castration-resistant PCa, treatment stratification and subsequent disease monitoring.

Citation Format: Chun-Liang Chen, Pawel Osmulski, Devalingam Mahalingam, Aaron M. Horning, Rohit R. Jadhav, Anna D. Louie, Chiou-Miin Wang, Tim H.-M. Huang. Epithelial-to-mesenchymal markers of circulating tumor cells for detection of castration-resistant prostate cancer. [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 5588. doi:10.1158/1538-7445.AM2014-5588

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.

Altered composition of liver proteasome assemblies contributes to enhanced proteasome activity in the exceptionally long-lived naked mole-rat

The longest-lived rodent, the naked mole-rat (Bathyergidae; Heterocephalus glaber), maintains robust health for at least 75% of its 32 year lifespan, suggesting that the decline in genomic integrity or protein homeostasis routinely observed during aging, is either attenuated or delayed in this extraordinarily long-lived species. The ubiquitin proteasome system (UPS) plays an integral role in protein homeostasis by degrading oxidatively-damaged and misfolded proteins. In this study, we examined proteasome activity in naked mole-rats and mice in whole liver lysates as well as three subcellular fractions to probe the mechanisms behind the apparently enhanced effectiveness of UPS. We found that when compared with mouse samples, naked mole-rats had significantly higher chymotrypsin-like (ChT-L) activity and a two-fold increase in trypsin-like (T-L) in both whole lysates as well as cytosolic fractions. Native gel electrophoresis of the whole tissue lysates showed that the 20S proteasome was more active in the longer-lived species and that 26S proteasome was both more active and more populous. Western blot analyses revealed that both 19S subunits and immunoproteasome catalytic subunits are present in greater amounts in the naked mole-rat suggesting that the observed higher specific activity may be due to the greater proportion of immunoproteasomes in livers of healthy young adults. It thus appears that proteasomes in this species are primed for the efficient removal of stress-damaged proteins. Further characterization of the naked mole-rat proteasome and its regulation could lead to important insights on how the cells in these animals handle increased stress and protein damage to maintain a longer health in their tissues and ultimately a longer life.

Potential allosteric modulators of the proteasome activity

Proteasome, consisting of a tube-shaped proteolytic core particle and attached to it regulatory modules, is a multifunctional enzymatic complex essential for the ubiquitin-proteasome metabolic pathway. Due to its immense involvement in regulation of cellular physiology, the proteasome is an acknowledged anticancer drug target and potential target to treat inflammatory or degenerative diseases. So far, competitive inhibitors of the core particle gain most consideration as drugs. We postulate that noncompetitively-acting small-molecule compounds would provide excellent means to precisely regulate actions of the proteasome. In this study, we evaluated five short peptides based on sequences of two proteins known to interact with the core proteasome: HIV-1 Tat and PA28/REG activator. We performed Circular Dichroism (CD), Fourier Transformed Infrared Spectroscopy (FTIR), and Nuclear Magnetic Resonance (NMR) analysis, supplemented by MD simulations, and tested influence of the peptides on performance of the core particle active sites and functioning of regulatory modules. We found that PP2-containing Tat peptides are noncompetitive inhibitors of the core, interfering with the actions of PA28alphabeta activator. In addition, at low concentrations the turn-prone Tat2 is able to activate the latent core. The random coil-structured PA28-derived peptides display only weak or nondetectable direct effects on the core activities, exhibiting, however, a positive cooperation with activity-enhancing actions of PA28alphabeta.