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Recent studies have highlighted that androgen receptor (AR) signaling can be bypassed via activation of the glucocorticoid receptor (GR), and that this bypass drives enzalutamide resistance in advanced prostate cancer (PCa). However, the molecular mechanism(s) that drive the switch from AR to GR signaling remain unknown. We have previously reported that TBX2, a developmental T-box transcription factor (TF), is over-expressed in castrate resistant prostate cancer (CRPC) and that TBX2 drives the CRPC phenotype via cell-intrinsic and exosome-mediated paracrine modes. Our current study demonstrates that TBX2, a TF with known repressor and activator functions, may be the molecular switch that represses AR on one hand while activating GR expression on the other to drive CRPC. Mechanistically, our studies revealed a two-tiered mechanism of AR repression by TBX2 wherein TBX2 directly binds to the promoters of AR and GATA2, an AR coregulator, thereby resulting in the repression of AR as well as GATA2. Conversely, our results demonstrate that TBX2 mediates increased expression of GR via directly binding to the GR promoter, and through TBX2-GR functional protein-protein interaction. Our results demonstrate that the TBX2 driven switch from AR to GR signaling results in enzalutamide resistance since GR inhibition in the context of TBX2 over-expression attenuates enzalutamide resistance. Further, we present evidence that SP2509 based allosteric inhibition of Lysine Specific Demethylase 1 (LSD1), a protein that interacts with TBX2 as part of the Co-repressor of RE1-Silencing Transcription Factor (COREST) complex, is able to disrupt TBX2-GR interaction. Taken together, our study has identified TBX2 as the molecular switch that drives AR to GR signaling and thereby confers enzalutamide resistance in CRPC. Furthermore, our study provides key insights into a potential therapeutic strategy of targeting the AR to GR switch wherein SP2509-based allosteric inhibition of TBX2-LSD1 could be harnessed to target the TBX2-GR interaction, thereby resulting in the inhibition of enzalutamide resistance in CRPC.

Invasion assay of ARCaPM-TBX2 and ARCaPM-Neo cells

Legend to Supplementary Figures

Plot showing relative protein expression of TBX2 and WNT3A in human PCa cell lines

Invasion assay of PC3 (TBX2DN+WNT3A, TBX2DN, and Neo)cells with the addition of SFRP-2

Supplementary Materials and Methods

Schematic depiction of WNT3A gene promoter, and ChIP analysis of LNCaP-TBX2 and LNCaP-Neo cells to assess the binding of TBX2 on WNT3A promoter

Micro-CT images of mouse tibiae injected with ARCaPM-TBX2 and ARCaPM-Neo cells

Identification of factors that mediate visceral and bone metastatic spread and subsequent bone remodeling events is highly relevant to successful therapeutic intervention in advanced human prostate cancer. TBX2, a T-box family transcription factor that negatively regulates cell-cycle inhibitor p21, plays critical roles during embryonic development, and recent studies have highlighted its role in cancer. Here, we report that TBX2 is overexpressed in human prostate cancer specimens and bone metastases from xenograft mouse models of human prostate cancer. Blocking endogenous TBX2 expression in PC3 and ARCaPM prostate cancer cell models using a dominant-negative construct resulted in decreased tumor cell proliferation, colony formation, and invasion in vitro. Blocking endogenous TBX2 in human prostate cancer mouse xenografts decreased invasion and abrogation of bone and soft tissue metastasis. Furthermore, blocking endogenous TBX2 in prostate cancer cells dramatically reduced bone-colonizing capability through reduced tumor cell growth and bone remodeling in an intratibial mouse model. TBX2 acted in trans by promoting transcription of the canonical WNT (WNT3A) promoter. Genetically rescuing WNT3A levels in prostate cancer cells with endogenously blocked TBX2 partially restored the TBX2-induced prostate cancer metastatic capability in mice. Conversely, WNT3A-neutralizing antibodies or WNT antagonist SFRP-2 blocked TBX2-induced invasion. Our findings highlight TBX2 as a novel therapeutic target upstream of WNT3A, where WNT3A antagonists could be novel agents for the treatment of metastasis and for skeletal complications in prostate cancer patients. Cancer Res; 77(6); 1331–44. ©2017 AACR.

Quantitative Real-Time RT-PCR and Invasion assay of LNCaP-TBX2 and LNCaP-Neo cells

Cancer Outlier Profile Analysis (COPA) in Oncomine 4.4 showing TBX2 over-expression in PCa microarray data sets

Background: A major obstacle in the treatment of metastatic castrate resistant prostate cancer (mCRPC) is acquired resistance to androgen deprivation therapy (ADT). It is now recognized that ADT, particularly the 2nd generation androgen receptor (AR) antagonists, such as enzalutamide, orchestrate plasticity changes/molecular alterations leading to therapy resistance. It is hypothesized in the field that the emergence of castrate resistance to 2nd generation ADT is driven by a switch/bypass from AR signaling to the glucocorticoid receptor (GR) signaling. Therefore, identifying the molecular mechanisms that concurrently drive the loss of AR and gain of GR signaling may be crucial in devising novel and effective therapeutic modalities against mCRPC. We have previously reported that TBX2, a T-box transcription factor (TF) with both repressor and activator functions, is over-expressed in CRPC and that TBX2 drives PCa bone metastatic progression. In agreement with our findings, a recent report showed that TBX2 is a key TF that drives plasticity associated with CRPC. In this study, we investigated the molecular mechanisms by which TBX2 drives plasticity associated with enzalutamide resistance. Methods: We genetically modulated TBX2 using the dominant negative (DN), sh-RNA, and overexpression (OE) approaches. RNA-seq was performed, and qRT-PCR, Western blot and immunohistochemical (IHC) analyses were used for validation. Further, we performed chromatin immunoprecipitation (ChIP) and site directed mutagenesis (SDM). Results: Using publicly available databases, we observed a negative correlation between TBX2 and AR; and a positive correlation between TBX2 and GR. Strikingly, blocking TBX2 expression in wildtype PC3 human PCa cells that do not express AR mRNA or protein led to a marked elevation of AR signature as assessed by RNA-seq analysis. These results were confirmed/validated at the protein level using additional human PCa cell lines. Further, these results were validated using all three approaches to genetically modulate TBX2, i.e. DN, shRNA, and OE. Further, ChIP and SDM analyses confirmed that TBX2 directly binds and transcriptionally represses AR. Conversely, genetic modulation of TBX2 was positively associated with GR expression, and TBX2 was found to directly bind to the GR promoter. Further, we found that knock-down of GR in LNCaP cells overexpressing TBX2 (LNCaPTBX2OE) reversed enzalutamide resistance that is associated with elevated TBX2 expression. Conclusions: Our studies suggest that TBX2 acts as the molecular switch that on one hand represses AR and on the other hand activates GR. Further our study paves the way for potential therapeutic strategies against the AR/GR switch/bypass in CRPC wherein AR and GR signaling could be co-inhibited through targeting TBX2. Citation Format: Sayanika Dutta, Girijesh Patel, Hamed Khedmatgozar, Daniel Latour, Manisha Tripathi, Srinivas Nandana. TBX2 acts as a molecular switch to downregulate androgen receptor and upregulate glucocorticoid receptor signaling in castrate resistant prostate cancer [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 1445.

Co-expression is a simultaneous expression of two or more proteins. Molecular chaperones are proteins that are naturally produced in the cell and have an essential role in restraining the aggregation of nonnative protein production. Co-expression of target protein alongside molecular chaperones is an efficient way to overcome the problems faced during the expression of recombinant proteins. The present study aims to a co-express protein highly useful in cosmetics, superoxide dismutase (SOD), in the periplasm of E. coli with molecular chaperone Skp. Superoxide dismutase and Skp were placed under the control of the different promoter and terminator systems to maintain separate expression levels. The co-expression of Skp chaperone on cell growth, SOD protein yield, and SOD enzyme activity were evaluated. Skp co-expression was found effective in all three aspects. The yield of Cu-Zn Superoxide dismutase increased from 30.92mg/L to 52.01mg/L when Skp chaperon is co-expressed. No detectable free SOD subunits were observed on western blot, which shows the method of Skp co-expression could be applied to tackle the problem of unprocessed, free protein subunits while expressing the recombinant protein in E. coli periplasm.

Recent studies have shown that exosome secretion by prostate cancer (PCa) cells fosters multiple facets of PCa progression and metastasis, mediated in particular through exosomal micro RNAs (miRs) that dictate gene expression changes. However, the molecular mechanisms through which exosomal miRs orchestrate bone remodeling that facilitates the establishment of a pre-metastatic niche (PMN) at the distant metastatic site i.e. bone remain elusive. We have identified that TBX2, a transcription factor that we previously reported plays a key role in PCa metastasis, represses miR-375-3p thereby resulting in de-repression/upregulation of its target RBPJ, an effector of Notch signaling and an established driver of PCa metastasis. Further, the unbiased identification of miR-375-3p as the topmost miR repressed by TBX2, in combination with experiments that genetically manipulate miR-375-3p in the context of TBX2 modulation, point to a crucial biological function of miR-375-3p as a key mediator in RBPJ regulation exerted by TBX2. In addition, the study highlights a dual level of RBPJ regulation by TBX2/miR-375-3p signaling i.e. via: a) gene expression changes at the intra-cellular or autocrine level, and b) gene expression changes at the distant site of bone metastasis through inter-cellular/endocrine communication via exosomes. Further, the study implicates TBX2high primary PCa cells in directing bone remodeling activity at the distant metastatic site in a paracrine mode via exosomes in addition to our previously reported role of TBX2 in mediating bone remodeling in an autocrine mode that occurs following metastatic dissemination. Taken together, our study unravels the role of TBX2/miR-375-3p/RBPJ signaling in PCa bone metastatic progression. Citation Format: Girijesh Kumar Patel, Sayanika Dutta, Hamed Khedmatgozar, Manisha Tripathi, Srinivas Nandana. TBX2highmiR-375-3plowRBPJhigh signaling drives prostate cancer bone metastatic phenotype via exosomes [abstract]. In: Proceedings of the AACR Special Conference: Cancer Metastasis; 2022 Nov 14-17; Portland, OR. Philadelphia (PA): AACR; Cancer Res 2022;83(2 Suppl_2):Abstract nr B024.

Periodontal diseases can lead to chronic inflammation affecting the integrity of the tooth supporting tissues. Recently, a striking association has been made between periodontal diseases and primary cancers in the absence of a mechanistic understanding. Here we address the effect of periodontal inflammation (PI) on tumor progression, metastasis, and possible underlining mechanisms. We show that an experimental model of PI in mice can promote lymph node (LN) micrometastasis, as well as head and neck metastasis of 4T1 breast cancer cells, both in early and late stages of cancer progression. The cervical LNs had a greater tumor burden and infiltration of MDSC and M2 macrophages compared with LNs at other sites. Pyroptosis and the resultant IL-1β production were detected in patients with PI, mirrored in mouse models. Anakinra, IL-1 receptor antagonist, limited metastasis, and MDSC recruitment at early stages of tumor progression, but failed to reverse established metastatic tumors. PI and the resulting production of IL-1β was found to promote CCL5, CXCL12, CCL2, and CXCL5 expression. These chemokines recruit MDSC and macrophages, finally enabling the generation of a premetastatic niche in the inflammatory site. These findings support the idea that periodontal inflammation promotes metastasis of breast cancer by recruiting MDSC in part by pyroptosis-induced IL-1β generation and downstream CCL2, CCL5, and CXCL5 signaling in the early steps of metastasis. These studies define the role for IL-1β in the metastatic progression of breast cancer and highlight the need to control PI, a pervasive inflammatory condition in older patients.

The current assessment is an undertaking to evaluateand compare variousmorphometric parameters of the Baur catchment. Morphometric analysis of the river basin provides a quantitative description of the drainage system, which is an important aspect of the categorization of the basin (Strahler, 1964).The Baur catchment is located in the outer part of the Lesser Himalaya in the Kumaun region, which is a major part of Western Himalaya.The geographical area of Baur Catchment is 106.233Km2.Morphometric analysis of Baur Catchment includes linear, areal, and relief aspects.The calculation of the morphometric parameter, along with map preparation, was performed with the help of GIS techniques and ancillary material.Most of the area of Baur Catchment is occupied by Siwalik Group (sandstone and clay intercalation with pseudo-conglomerate) of rocks.The entire Baur Catchment has found 6thorder drainage, which reveals sub-dendritic to a dendritic type of drainage pattern. It is observed that the drainage density of the Baur Catchment is 3.525 km/halfkm2. &nbsp

Introduction: Bone is the preferred site of metastasis in about 80% of advanced prostate cancer (PCa) patients. The molecular mechanisms that drive bone metastatic PCa are not well understood. Recent reports have increasingly shed light on the role of cancer-cell-derived extracellular vesicles (exosomes) in driving the metastatic cascade including priming the secondary site for metastatic manifestation. We have previously reported that TBX2 promotes multiple facets of the PCa bone metastatic cascade via a cell-intrinsic manner. In this study, we sought to determine if the bone metastasis promoted by TBX2 is driven by microRNAs (miRs) in an exosome-mediated paracrine manner. Methods: Two converse approaches were utilized for the genetic modulation of TBX2: a) TBX2 was blocked in the metastatic PC3 and C4-2B human PCa cells using a dominant negative (DN) approach, and b) TBX2 was over-expressed in the low-TBX2 expressing LNCaP human PCa cells. Exosomes isolated from TBX2-modulated human PCa cells were added to MC3T3 pre-osteoblastic cells or mouse calvaria bone cells to examine the differential effects of TBX2 modulation on osteoblast or osteoclast differentiation. Next, unbiased next generation sequencing (NGS) was performed to identify the differential miR expression in exosomes derived from the TBX2-blocked PC3 cells. Results: Our results demonstrate that compared with control exosomes, exosomes derived from TBX2-blocked PC3 cells slowed the proliferation and migration/wound healing when added to 22Rv1 cells. Further, compared with control exosomes, exosomes derived from TBX2-blocked C4-2B cells resulted in reduced osteoblast differentiation when added to: a) MC3T3 pre-osteoblastic cells, or b) mouse calvaria bone cells. Along similar lines, when compared with the control exosomes, exosomes derived from TBX2-blocked PC3 and C4-2B cells resulted in reduced osteoclast differentiation when added to bone-marrow derived cells. These results were confirmed by q RT-PCR analysis of the osteoblastic/osteolytic bone markers. In order to identify exosomal miRs downstream of TBX2 signaling, NGS analysis of exosomal miRs obtained from TBX2-blocked PC3 human PCa cells identified miR-375-3p as the top-most differentially-expressed (over-expressed miR) when compared with control exosomes. In silico analysis revealed that miR-375-3p could potentially bind and target the 3’UTR of RBPJ, an established driver of PCa bone metastasis. In agreement, q RT-PCR analysis revealed that rescue of miR-375-3p in TBX2 modulated human PCa cells rescued RBPJ expression. Conclusions: Our studies have identified the exosome-mediated TBX2/miR-375-3p/RBPJ signaling axis as a promoter of the bone-metastatic phenotype in human PCa. Citation Format: Girijesh Kumar Patel, Sayanika Dutta, Hamed Khedmatgozar, Manisha Tripathi, Srinivas Nandana. TBX2 promotes prostate cancer bone-metastatic phenotype through exosomal microRNA-375-3p [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 5999.

Successful visualization of prostate cancer (PCa) tumor margins during surgery remains a major challenge. The visualization of these tumors during surgery via near infrared fluorescence (NIRF) imaging would greatly enhance surgical resection, minimizing tumor recurrence and improving outcome. Furthermore, chemotherapy is typically administered to patients after surgery to treat any missed tumor tissue around the surgical area, minimizing metastasis and increasing patient survival. For these reasons, a theranostics fluorescent nanoparticle could be developed to assist in the visualization of PCa tumor margins, while also delivering chemotherapeutic drug after surgery. Methods: Ferumoxytol (FMX) conjugated to the fluorescent dye and PCa targeting agent, heptamethine carbocyanine (HMC), yielded the HMC-FMX nanoprobe that was tested in vitro with various PCa cell lines and in vivo with both subcutaneous and orthotopic PCa mouse models. Visualization of these tumors via NIRF imaging after administration of HMC-FMX was performed. In addition, delivery of chemotherapeutic drug and their effect on tumor growth was also assessed. Results: HMC-FMX internalized into PCa cells, labeling these cells and PCa tumors in mice with near infrared fluorescence, facilitating tumor margin visualization. HMC-FMX was also able to deliver drugs to these tumors, reducing cell migration and slowing down tumor growth. Conclusion: HMC-FMX specifically targeted PCa tumors in mice allowing for the visualization of tumor margins by NIRF imaging. Furthermore, delivery of anticancer drugs by HMC-FMX effectively reduced prostate tumor growth and reduced cell migration in vitro. Thus, HMC-FMX can potentially translate into the clinic as a nanotheranostics agent for the intraoperative visualization of PCa tumor margins, and post-operative treatment of tumors with HMC-FMX loaded with anticancer drugs.

Heterogeneous prostatic carcinoma-associated fibroblasts (CAF) contribute to tumor progression and resistance to androgen signaling deprivation therapy (ADT). CAF subjected to extended passaging, compared to low passage CAF, were found to lose tumor expansion potential and heterogeneity. Cell surface endoglin (CD105), known to be expressed on proliferative endothelia and mesenchymal stem cells, was diminished in high passage CAF. RNA-sequencing revealed SFRP1 to be distinctly expressed by tumor-inductive CAF, which was further demonstrated to occur in a CD105-dependent manner. Moreover, ADT resulted in further expansion of the CD105+ fibroblastic population and downstream SFRP1 in 3-dimensional cultures and patient-derived xenograft tissues. In patients, CD105+ fibroblasts were found to circumscribe epithelia with neuroendocrine differentiation. CAF-derived SFRP1, driven by CD105 signaling, was necessary and sufficient to induce prostate cancer neuroendocrine differentiation in a paracrine manner. A partially humanized CD105 neutralizing antibody, TRC105, inhibited fibroblastic SFRP1 expression and epithelial neuroendocrine differentiation. In a novel synthetic lethality paradigm, we found that simultaneously targeting the epithelia and its microenvironment with ADT and TRC105, respectively, reduced castrate-resistant tumor progression, in a model where either ADT or TRC105 alone had little effect.

Simple Summary An estimated ~25–30% of patients with advanced prostate cancer (PCa) develop the aggressive and lethal form of the disease known as treatment-induced neuroendocrine prostate cancer (t-NEPC). Owing to lack of treatment options, the identification of the underlying molecular mechanisms that propagate the t-NEPC phenotype is critical towards developing novel therapeutic strategies against advanced PCa. Further, the roles of extracellular vesicles (exosomes) and microRNAs—an increasingly recognized and key mode of propagation of the NEPC phenotype—remain elusive. Our studies reveal that TBX2 promotes SOX2- and N-MYC- driven t-NEPC through regulation of the intermediary factor—miR-200c-3p; and that TBX2/miR-200c-3p/SOX2/MYCN signaling can promote t-NEPC via both intracellular and exosome-mediated intercellular mechanisms. Abstract Deciphering the mechanisms that drive transdifferentiation to neuroendocrine prostate cancer (NEPC) is crucial to identifying novel therapeutic strategies against this lethal and aggressive subtype of advanced prostate cancer (PCa). Further, the role played by exosomal microRNAs (miRs) in mediating signaling mechanisms that propagate the NEPC phenotype remains largely elusive. The unbiased differential miR expression profiling of human PCa cells genetically modulated for TBX2 expression led to the identification of miR-200c-3p. Our findings have unraveled the TBX2/miR-200c-3p/SOX2/N-MYC signaling axis in NEPC transdifferentiation. Mechanistically, we found that: (1) TBX2 binds to the promoter and represses the expression of miR-200c-3p, a miR reported to be lost in castrate resistant prostate cancer (CRPC), and (2) the repression of miR-200c-3p results in the increased expression of its targets SOX2 and N-MYC. In addition, the rescue of mir-200c-3p in the context of TBX2 blockade revealed that miR-200c-3p is the critical intermediary effector in TBX2 regulation of SOX2 and N-MYC. Further, our studies show that in addition to the intracellular mode, TBX2/miR-200c-3p/SOX2/N-MYC signaling can promote NEPC transdifferentiation via exosome-mediated intercellular mechanism, an increasingly recognized and key mode of propagation of the NEPC phenotype.

Our understanding of neuroendocrine prostate cancer (NEPC) has assumed a new perspective in light of the recent advances in research. Although classical NEPC is rarely seen in the clinic, focal neuroendocrine trans-differentiation of prostate adenocarcinoma occurs in about 30% of advanced prostate cancer (PCa) cases, and represents a therapeutic challenge. Even though our knowledge of the mechanisms that mediate neuroendocrine differentiation (NED) is still evolving, the role of androgen deprivation therapy (ADT) as a key driver of this phenomenon is increasingly becoming evident. In this review, we discuss the molecular, cellular, and therapeutic mediators of NED, and emphasize the role of the tumor microenvironment (TME) in orchestrating the phenotype. Understanding the role of the TME in mediating NED could provide us with valuable insights into the plasticity associated with the phenotype, and reveal potential therapeutic targets against this aggressive form of PCa.

Purpose: A successful cancer surgery requires the complete removal of cancerous tissue, while also sparing as much healthy, non-cancerous tissue as possible. To achieve this, an accurate identification of tumor boundaries during surgery is critical, but intra-operative tumor visualization remains challenging. Fluorescence imaging is a promising method to improve tumor detection and delineate tumor boundaries during surgery, but the lack of stable, long-circulating, clinically-translatable fluorescent probes that can identify tumors with high signal-to-noise ratios and low background fluorescence signals have prevented its widespread application. Methods: We screened the optical properties of several fluorescent dyes before and after nanoprobe encapsulation, and then identified nanoprobes with quenched fluorescence that were re-activated upon dye release. The physical and biological properties of these nanoprobes leading to fluorescence activation were investigated in vitro. Further, the cancer imaging properties of both free dyes and nanoprobe-encapsulated dyes were compared in vivo. Results: A novel fluorescent nanoprobe was prepared by combining two FDA-approved agents commonly used in the clinic: Feraheme (FH) and indocyanine green (ICG). The resulting FH-entrapped ICG nanoprobe [FH(ICG)] displayed quenched fluorescence compared to other nanoprobes, and this quenched fluorescence was re-activated in acidic tumor microenvironment conditions (pH 6.8) and upon uptake into cancer cells. Finally, in vivo studies in a prostate cancer mouse model demonstrated that FH(ICG) treatments enhance long-term fluorescence signals in tumors compared to ICG treatments, allowing for fluorescence-guided tumor identification using clinically relevant fluorescence cameras. Conclusions: FH(ICG) nanoprobes were identified as fluorescent nanoprobes with beneficial fluorescence activation properties compared to other FH-entrapped dyes. The activatable nature of this nanoprobe allows for a low background fluorescence signal and high signal-to-noise ratio within a long-circulating nanoagent, which allows for long-term fluorescence signals from tumors that enabled their fluorescence-guided detection. This activatable nanoprobe offers tremendous potential as a clinically translatable image-guided cancer therapy modality that can be prepared in a clinical setting.

Biological interactions between tumor-associated macrophages (TAMs), cancer cells and other cells within the tumor microenvironment contribute to tumorigenesis, tumor growth, metastasis and therapeutic resistance. TAMs can remodel the tumor microenvironment to reduce growth barriers such as the dense extracellular matrix and shift tumors towards an immunosuppressive microenvironment that protects cancer cells from targeted immune responses. Nanoparticles can interrupt these biological interactions within tumors by altering TAM phenotypes through a process called polarization. Macrophage polarization within tumors can shift TAMs from a growth-promoting phenotype towards a cancer cell-killing phenotype that predicts treatment efficacy. Because many types of nanoparticles have been shown to preferentially accumulate within macrophages following systemic administration, there is considerable interest in identifying nanoparticle effects on TAM polarization, evaluating nanoparticle-induced TAM polarization effects on cancer treatment using drug-loaded nanoparticles and identifying beneficial types of nanoparticles for effective cancer treatment. In this review, the macrophage polarization effects of nanoparticles will be described based on their primary chemical composition. Because of their strong macrophage-polarizing and antitumor effects compared to other types of nanoparticles, the effects of iron oxide nanoparticles on macrophages will be discussed in detail. By comparing the macrophage polarization effects of various nanoparticle treatments reported in the literature, this review aims to both elucidate nanoparticle material effects on macrophage polarization and to provide insight into engineering nanoparticles with more beneficial immunological responses for cancer treatment.

Prostate cancer is an androgen-dependent disease subject to interactions between the tumor epithelium and its microenvironment. Here, we found that epigenetic changes in prostatic cancer-associated fibroblasts (CAF) initiated a cascade of stromal-epithelial interactions. This facilitated lethal prostate cancer growth and development of resistance to androgen signaling deprivation therapy (ADT). We identified a Ras inhibitor, RASAL3, as epigenetically silenced in human prostatic CAF, leading to oncogenic Ras activity driving macropinocytosis-mediated glutamine synthesis. Interestingly, ADT further promoted RASAL3 epigenetic silencing and glutamine secretion by prostatic fibroblasts. In an orthotopic xenograft model, subsequent inhibition of macropinocytosis and glutamine transport resulted in antitumor effects. Stromal glutamine served as a source of energy through anaplerosis and as a mediator of neuroendocrine differentiation for prostate adenocarcinoma. Antagonizing the uptake of glutamine restored sensitivity to ADT in a castration-resistant xenograft model. In validating these findings, we found that prostate cancer patients on ADT with therapeutic resistance had elevated blood glutamine levels compared with those with therapeutically responsive disease (odds ratio = 7.451, P = 0.02). Identification of epigenetic regulation of Ras activity in prostatic CAF revealed RASAL3 as a sensor for metabolic and neuroendocrine reprogramming in prostate cancer patients failing ADT.

// Manisha Tripathi 1, * , Srinivas Nandana 1, * , Sandrine Billet 1 , Karen A. Cavassani 1 , Rajeev Mishra 1 , Leland W.K. Chung 1 , Edwin M. Posadas 1 and Neil A. Bhowmick 1, 2 1 Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, California 90048, USA 2 Department of Research, Greater Los Angeles Veterans Administration, Los Angeles, California 90048, USA * These authors have contributed equally to this work Correspondence to: Neil A. Bhowmick, email: neil.bhowmick@cshs.org Edwin M. Posadas, email: Edwin.Posadas@cshs.org Keywords: carcinoma associated fibroblasts, cabozantinib, metastasis, prostate cancer Received: May 30, 2017 Accepted: August 15, 2017 Published: September 23, 2017 ABSTRACT The tumor microenvironment (TME) is increasingly recognized as the arbiter of metastatic progression and drug resistance in advanced prostate cancer (PCa). Cabozantinib is a potent tyrosine kinase inhibitor (TKI) with reported biological activity in the PCa epithelia, but failed to provide an overall survival benefit in phase 3 clinical trials. However, the promising biologic efficacy of the drug in early trials warranted a better understanding of the mechanism of action, with the goal of improving patient selection for TKI-based therapy such as cabozantinib. We found a 100-fold lower cabozantinib IC 50 in macrophages, PCa associated fibroblasts, and bone marrow fibroblasts compared to PCa epithelia. In PCa mouse models, pre-treatment with cabozantinib potentiated osseous and visceral tumor engraftment, suggesting a pro-tumorigenic host response to the drug. We further found that the host effects of cabozantinib impacted bone turnover, but not necessarily tumor expansion. Cabozantinib affected M1 macrophage polarization in mice. Analogously, circulating monocytes from PCa patients treated with cabozantinib, demonstrated a striking correlation of monocyte reprograming with therapeutic bone responsivity, to support patient selection at early stages of treatment. Thus, a re-evaluation of TKI-based therapeutic strategies in PCa can be considered for suitable patient populations based on TME responses.

Identification of factors that mediate visceral and bone metastatic spread and subsequent bone remodeling events is highly relevant to successful therapeutic intervention in advanced human prostate cancer. TBX2, a T-box family transcription factor that negatively regulates cell-cycle inhibitor p21, plays critical roles during embryonic development, and recent studies have highlighted its role in cancer. Here, we report that TBX2 is overexpressed in human prostate cancer specimens and bone metastases from xenograft mouse models of human prostate cancer. Blocking endogenous TBX2 expression in PC3 and ARCaPM prostate cancer cell models using a dominant-negative construct resulted in decreased tumor cell proliferation, colony formation, and invasion in vitro. Blocking endogenous TBX2 in human prostate cancer mouse xenografts decreased invasion and abrogation of bone and soft tissue metastasis. Furthermore, blocking endogenous TBX2 in prostate cancer cells dramatically reduced bone-colonizing capability through reduced tumor cell growth and bone remodeling in an intratibial mouse model. TBX2 acted in trans by promoting transcription of the canonical WNT (WNT3A) promoter. Genetically rescuing WNT3A levels in prostate cancer cells with endogenously blocked TBX2 partially restored the TBX2-induced prostate cancer metastatic capability in mice. Conversely, WNT3A-neutralizing antibodies or WNT antagonist SFRP-2 blocked TBX2-induced invasion. Our findings highlight TBX2 as a novel therapeutic target upstream of WNT3A, where WNT3A antagonists could be novel agents for the treatment of metastasis and for skeletal complications in prostate cancer patients. Cancer Res; 77(6); 1331–44. ©2017 AACR.

Background: Bone metastasis in human prostate cancer remains a major clinical problem since no effective therapy exists. The RANKL/RANK pathway plays a predominant role in the interaction between metastasized prostate cancer cells and osteoclasts that increases the bone turnover. The current therapies, including targeting RANKL with denosumab, address the growth of prostate tumor cells that have already colonized the bone, but are largely ineffective in prolonging the survival of human prostate cancer patients with bone metastasis. Further, a major impediment to prostate cancer bone metastasis research is the lack of an animal model that spontaneously recapitulates human prostate cancer bone metastasis in the context of an intact immune system. Results: To overcome this major limitation, we have developed a novel syngeneic mouse model to study prostate cancer bone metastasis. Both the CXCL12/CXCR4 and RANKL/RANK pathways have been reported to be overexpressed / dysregulated in human prostate cancer bone metastatic samples. Data generated utilizing our immune-intact mouse model shows that the CXCL12/CXCR4 and RANKL/RANK pathways co-operate with each other to drive prostate cancer bone metastasis. Studies have shown that targeting the CXCL12/CXCR4 and RANKL/RANK pathways individually affects the immune system, thereby making our syngeneic mouse model an indispensable tool for studying the critical co-operation between these 2 pathways in the manifestation of human prostate cancer bone metastasis. Extending our earlier findings that RANKL drives PCa metastases in immune-deficient mice (Chu et al., 2014) to immune-intact C57/Bl6 mice, we found that MPC3 mouse PCa cells with RANKL overexpression (MPC3-Luc-GFP-RANKL) develop 70-80% limb and jaw within 4 weeks of intra-cardiac injection in these syngeneic mice. Control MPC3 cells had no bone metastasis. Bone lesions visualized by luciferase imaging and X-ray were confirmed by micro CT and immunohistochemistry. RANKL signaling drove bone and visceral metastases via the downstream CXCL12/CXCR4 signaling axis. MPC3-Luc-GFP-RANKL cells showed increased CXCR4 protein levels by immunohistochemistry. Metastatic bone marrow flush showed dramatically increased levels of CXCL12 mRNA compared with control mice (MPC3-Luc-GFP-EV). Conclusion: In sum, 1) circulating PCa cells induce a marked CXCL12 elevation after colonizing bone, triggering chemotaxis and recruiting CXCR4-positive PCa cells to migrate to bone; and 2) osteomimetic PCa cells with increased RANKL expression interact with osteoclasts to enhance bone resorption and turnover, releasing additional growth factors and chemokines for PCa cell growth and survival in bone. Citation Format: Srinivas Nandana, Murali Gururajan, Manisha Tripathi, Chia-Yi Chu, Haiyen Zhau, Stephen Shiao, Leland Chung. A novel syngeneic mouse model of prostate cancer bone metastasis: Mechanisms of chemotaxis and bone colonization [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 4523.

Juxtacrine signaling with the stromal compartment is important to the development of castrate resistance prostate cancer. We found that Notch signaling is upregulated in prostate cancer associated fibroblasts (CAFs) compared with normal tissue associated fibroblasts (NAFs). Further, inhibition of Notch signaling in CAFs resulted in decreased Wnt signaling and decrease in expression of Notch pathway genes. Interestingly, androgen receptor antagonism resulted in increased Notch signaling and the upregulation of downstream Wnts. Further, generation of chimeric tissue recombinant xenografts with human RV1 prostate cancer epithelia with mouse prostate stromal cells with activated Notch signaling that are derived from NICD transgenic mice resulted in increased tumor size compared with wild type control stromal recombinants. Conversely, recombinants derived from prostatic fibroblasts of RBPJ-knockout mice that have a loss of Notch signaling demonstrated diminished tumorigenesis, compared with xenografts with the wild type fibroblasts. In trying to determine the mediator of Wnt-associated paracrine prostate epithelial expansion, we found downstream YAP activation in the RV1 cells. In a reciprocal epithelial-to-fibroblast communication we found that the RV1 cells treated with conditioned media from NICD fibroblasts showed increased IL-6 expression. Conversely, conditioned media from prostate cancer cells caused increased Notch target gene expression in CAFs, which was blocked upon addition of IL-6 neutralizing antibody. Taken together our results suggest that there is a stromal-derived feed-back - feed-forward signaling loop involving Notch and Wnt ligands that activates YAP in the epithelia for paracrine IL-6-dependent Notch activity back in the stromal fibroblasts. Critically, disruption of this cross-talk in the fibroblasts can potentially limit the gain of stem features and castrate resistance of the adjacent epithelia in halting lethal progression of prostate cancer. Citation Format: Manisha Tripathi, Srinivas Nandana, Jen-Ming Huang, Manabu Kato, Rajeev Mishra, Leland Chung, Li Xin, Neil Bhowmick. Signaling crosstalk within prostate tumor microenvironment mediates castrate resistant disease progression [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 5164.

SummaryUnderstanding the mechanism underlying the regulation of the androgen receptor (AR), a central player in the development of castration-resistant prostate cancer (CRPC), holds promise for overcoming the challenge of treating CRPC. We demonstrate that the ubiquitin ligase Siah2 targets a select pool of NCOR1-bound, transcriptionally-inactive AR for ubiquitin-dependent degradation, thereby promoting expression of select AR target genes implicated in lipid metabolism, cell motility, and proliferation. Siah2 is required for prostate cancer cell growth under androgen-deprivation conditions in vitro and in vivo, and Siah2 inhibition promotes prostate cancer regression upon castration. Notably, Siah2 expression is markedly increased in human CRPCs. Collectively, we find that selective regulation of AR transcriptional activity by the ubiquitin ligase Siah2 is important for CRPC development.

Hemorrhagic cystitis is an inflammatory and ulcerative bladder condition associated with systemic chemotherapeutics, like cyclophosphomide. Earlier, we reported reactive oxygen species resulting from cyclophosphamide metabolite, acrolein, causes global methylation followed by silencing of DNA damage repair genes. Ogg1 (8-oxoguanine DNA glycosylase) is one such silenced base excision repair enzyme that can restore DNA integrity. The accumulation of DNA damage results in subsequent inflammation associated with pyroptotic death of bladder smooth muscle cells. We hypothesized that reversing inflammasome-induced imprinting in the bladder smooth muscle could prevent the inflammatory phenotype. Elevated recruitment of Dnmt1 and Dnmt3b to the Ogg1 promoter in acrolein treated bladder muscle cells was validated by the pattern of CpG methylation revealed by bisulfite sequencing. Knockout of Ogg1 in detrusor cells resulted in accumulation of reactive oxygen mediated 8-Oxo-dG and spontaneous pyroptotic signaling. Histone deacetylase (HDAC) inhibitor, suberoylanilide hydroxamic acid (SAHA), restored Ogg1 expression in cells treated with acrolein and mice treated with cyclophosphamide superior to the standard of care, mesna or nicotinamide-induced DNA demethylation. SAHA restored cyclophosphamide-induced bladder pathology to that of untreated control mice. The observed epigenetic imprinting induced by inflammation suggests a new therapeutic target for the treatment of hemorrhagic cystitis.

The major cellular components of tumor microenvironment, referred to as the cancer stroma, are composed of cancer-associated fibroblasts that support tumor epithelial growth, invasion and therapeutic resistance. Thus when we speak of developing therapies that address tumor heterogeneity it is not only a matter of different mutations within the tumor epithelia. While individual mutations in the stromal compartment are controversial, the heterogeneity in fibroblastic population in a single tumor is not up for debate. Cooperative interaction among heterotypic fibroblasts and tumor cells contribute to cancer progression. Therefore to tackle solid tumors, we need to understand its complex microenvironment. Here we review some seminal developments in the field of tumor microenvironment, mainly focusing on cancer-associated fibroblast.

BACKGROUND Matriptase, a type II transmembrane serine protease, has been linked to initiation and promotion of epidermal carcinogenesis in a murine model, suggesting that deregulation of its role in epithelia contributes to transformation. In human prostate cancer, matriptase expression correlates with progression. It is therefore of interest to determine how matriptase may contribute to epithelial neoplastic progression. One approach for studying this is to identify potential matriptase substrates involved in epithelial integrity and/or transformation like the extracellular matrix macromolecule, laminin-332 (Ln-332), which is found in the basement membrane of many epithelia, including prostate. Proteolytic processing of Ln-332 regulates cell motility of both normal and transformed cells, which has implications in cancer progression.

Purpose: The identification, functional status, distribution, and interactions of immune cells in PCa patients have yet to be fully characterized. Understanding these details could provide key insights as to how promising current and developing immunotherapies might be directed toward PCa. Recruited myeloid cells promote cancer initiation, malignant progression, metastasis, and resistance to therapy in the tumor niche. In the present study, we tested the hypothesis that circulating blood monocytes from advanced prostate cancer (PCa) patients exhibit a tumor-promoting phenotype and directly influence the tumor microenvironment in response to tumor-derived signals. Experimental Design: Monocytes from metastatic (PCa-M) and nonmetastatic (PCa-N) patient blood samples were isolated, cultured, and conditioned media (CM) was obtained. To evaluate the role of monocytes in metastatic behavior of PCa cells, in vitro invasion (via Matrigel) and motility assays (Incucyte Live Cell Analysis System) were performed using monocyte-CM. To identify the candidate PCa-M monocyte-secreted protein(s) that might be implicated in tumor progression, we analyzed the CM using Proteome Profiler Analysis (R&D). Data were validated using ELISA and qPCR. Results: Herein, we report that CM from circulating monocytes in patients with PCa/mCRPC (metastatic castration-resistant PCa) increased motility and invasion of epithelial PCa cells. Proteome Profiler Analysis revealed that monocyte-derived CM from metastatic PCa/mCRPC patients presented high levels of YKL-40 (Chitinase-3-like 1; CHI3L1) when compared with PCa-N patients and healthy controls (HC), classified as individuals with no known history of cancer. The only described receptor for YKL-40, interleukin-13 receptor α2 (IL-13Rα2), was significantly upregulated in ARCaPm cells; accordingly, we observed that the activation of IL-13Rα2 from PCa-M CM increased the invasiveness of ARCaPm. In addition, siRNA directed against this receptor in ARCaPm cells caused a significant reduction in the invasiveness of these cells in the presence of CM from PCa-M patients. Conclusions: We show that circulating monocytes from metastatic PCa/mCRPC patients exert a tumor-promoting role via the secretion of YKL-40, and YKL-40 demands further exploration as a possible therapeutic target in advanced PCa. Citation Format: Karen A. Cavassani, Rebecca Meza, David Habiel, Jie-Fu Chen, Alexander Montes, Manisha Tripathi, Gislaine Martins, Timothy R. Crother, Cory M. Hogaboam, Sungyong You, Neil Bhowmick, Edwin Posadas. Monocytes-produced Chitinase-3-like 1 is a driver of metastatic behavior in advanced prostate cancer patients [abstract]. In: Proceedings of the AACR Special Conference: Prostate Cancer: Advances in Basic, Translational, and Clinical Research; 2017 Dec 2-5; Orlando, Florida. Philadelphia (PA): AACR; Cancer Res 2018;78(16 Suppl):Abstract nr B086.

Purpose: The identification, functional status, distribution, and interactions of immune cells in prostate cancer (PCa) patients have yet to be fully characterized. Understanding these details could provide key insights as to how promising current and developing immunotherapies might be directed toward PCa. Recruited myeloid cells are known to promote cancer initiation, malignant progression, metastasis, and resistance to therapy in the tumor niche. In the present study, we tested the hypothesis that circulating blood monocytes from advanced PCa patients exhibit a protumor phenotype and directly influence the tumor microenvironment in response to tumor-derived signals. Experimental Design: Monocytes from metastatic (PCa-M) and nonmetastatic (PCa-N) patient blood samples were isolated, cultured, and conditioned media (CM) was obtained. To evaluate the role of monocytes in metastatic behaviors of PCa cells, in vitro invasion (via Matrigel) and motility assays (Incucyte® Live Cell Analysis System) were performed using monocyte-CM. To identify the candidate PCa-M monocyte-secreted protein(s) that might be implicated in tumor progression, we analyzed the CM using Proteome Profiler Analysis (R&D). Data were validated using ELISA and qPCR. Results: Herein, we report that CM from circulating monocytes in patients with PCa/mCRPC (metastatic castration-resistant PCa) increased motility and invasion of epithelial PCa cells in vitro. Proteome Profiler Analysis revealed that monocyte-derived CM from metastatic PCa/mCRPC patients presented high levels of Chitinase-3-like 1 (CHI3L1, YKL-40) when compared with PCa-N patients and healthy-control individuals (HC). The only described receptor for CHI3L1, interleukin-13 receptor α2 (IL-13Rα2), was significantly upregulated in the human metastatic prostate cancer cell line, ARCaPM. Accordingly, we observed that the activation of IL-13Rα2 from PCa-M CM increased the invasiveness of ARCaPM cells, and siRNA directed against this receptor significantly reduced invasiveness of these cells in the presence of CM from PCa-M patients. Conclusions: Thus, we show that circulating monocytes from metastatic PCa/mCRPC patients exert a tumor-promoting role via the secretion of CHI3L1, and CHI3L1 demands further exploration as a possible therapeutic target in advanced PCa. Citation Format: Karen A. Cavassani, Rebecca J. Meza, David M. Habiel, Jie-Fu Chen, Alexander Montes, Manisha Tripathi, Gislaine A. Martins, Timothy R. Crother, Sungyong You, Cory M. Hogaboam, Neil Bhowmick, Edwin M. Posadas. Monocyte-produced Chitinase-3-like 1 is a driver of metastatic behavior in prostate cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5208.

Restrictocin, a member of the fungal ribotoxin family, specifically cleaves a single phosphodiester bond in the 28S rRNA and potently inhibits eukaryotic protein synthesis. The long loops in restrictocin molecule have been shown structurally to be involved in target RNA recognition. In this study we have investigated the role of some putative substrate-interacting residues in loops L2 and L4, spanning residues 36-48 and 99-117, respectively in restrictocin catalysis. The residues Lys42, Ser46, Pro48 and Lys111 were individually mutated to alanine to probe their role in restrictocin function. The mutation of Lys111 to alanine, although did not affect the ribonucleolytic activity, rendered the toxin completely inactive in inhibiting translation in HeLa cells as well in an in vitro cell free system. The loop L4 in restrictocin appears to be more critical compared to loop L2 for its interaction with the specific substrate.

Biological control is an accepted important component of current plant disease management strategies. Introduction of bacterized seeds carrying bacterial isolates with proven growth-promotion capabilities and antagonistic characteristics offer a valid alternative to chemical protectants. Root colonization of disease-susceptible (PS 1024) and moderately resistant (PS1042) varieties of soyabean (Glycine Max L) by fluorescent pseudomonad (FLPs) strains GRP3, PEn-4, PRS1, and WRS-24 was studied in relation to natural occurrence of anthracnose caused by Colletotrichum dematium (Pers Ex Fr.) Grove. Rhizoplane population of FLPs was maintained at a critical level (5.3 cfu) up to 30 days of plant growth, followed by a steep decline. Indigenous FLPs population, however, remained nearly unchanged (3.0 to 2.4 log g(-1) root) between 30 days and 75 days of plant growth. The relative FLPs population in rhizosphere was lower than that in rhizoplane. Although intervarietal difference was observed, the root/shoot length remained unaffected. Compared to nonbacterized control, dry root weight was improved by FLPs treatment. Severity of foliar anthracnose was reduced significantly after FLPs treatment in the variety PS 1042. Because the point of FLPs treatment (seed bacterization) was away from the site of disease appearance (leaf), operation of induced systemic resistance in strains PEn-4 and GRP3 appears imminent.

5031 Background: The presence of VM in metastatic, castration-resistant prostate cancer (mCRPC) predicts poor survival. Cabozantinib (cabo) is a multi-kinase inhibitor that has clinical activity that did not improve survival in an unselected mCRPC population. Subgroup analyses suggested that the benefit may exist for patients (pts) with mCRPC-VM. The effect of cabo includes the tumor microenvironment, monocytes in particular, which in turn can alter tumor behavior. Methods: We conducted a single-arm study of cabo in men with mCRPC-VM. Pts received cabo 60 mg daily. Radiographs were used to assess response. Correlative blood samples were collected for the enumeration and characterization of circulating tumor cells using the NanoVelcro Assay and analysis of circulating monocytes by FACS. Results: A total of 17 pts enrolled with 16 evaluable for response. At 12 weeks, 19% experienced partial responses (PR), 44% stable disease (SD), and 38% progressive disease. The clinical benefit rate (PR+SD) at 12 weeks was 63%. Safety profile was consistent with previous reports. CTCs were detected in 80% of pts. NanoVelcro CTC counts showed reduction by week 8 in both PR+SD (88%) and PD (71%) groups with re-emergence at progression. Among pts with liver metastases, very-small-nuclear CTCs ( < 8.5 μm) were seen in 29% of pts with clinical benefit compared to 60% in non-benefiters. Analysis of monocyte polarization after initiation of therapy showed that reduction of M1 polarization was associated with improvement in bone pain and/or bone scan. Conclusions: In heavily-pretreated mCRPC-VM, cabo provided clinical benefit with acceptable toxicity. Circulating biomarkers related to both tumor and microenvironment may be useful in identifying patients who benefit from this type of therapeutic approach. Clinical trial information: NCT01834651.

Our lab has previously reported that the mouse model knocked out for TGF-beta receptor type II in fibroblasts results in castrate resistance of prostate tissues, mediated by paracrine Wnt signaling. We found that antagonizing androgen signaling leads to Wnt ligand expression by prostatic fibroblasts, interestingly dependent on cell-cell contact. This led us to hypothesize that a juxtacrine action within the stromal compartment was important to the development of castrate resistance. Building upon this observation, we found that Notch signaling was upregulated in prostate cancer associated fibroblasts (CAFs) compared with normal tissue associated fibroblasts (NAFs). Further, inhibition of Notch signaling in CAFs, using DAPT, resulted in decrease in Wnt2b and decreased expression of Notch target genes. Similarly, castration or androgen receptor antagonism (i.e. bicalutamide or enzalutamide) resulted in increased Notch signaling and downstream Wnts 2 and 2b up regulation. The further generation of chimeric tissue recombinant xenografts with human RV1 prostate cancer epithelia with mouse prostate stromal cells with activated Notch signaling, derived from NICD transgenic mice resulted in increased tumor size compared with wild type control stromal recombinants. Conversely, recombinants derived from prostatic fibroblasts having a loss of Notch signaling, from RBPJ-knockout mice, had diminished tumorigenesis, compared to xenografts with the wild type fibroblasts counterpart. In trying to determine the mediator of Wnt-associated paracrine prostate epithelial expansion, we found downstream YAP activation in the RV1 cells. In a reciprocal epithelial-to-fibroblast communication we found that the RV1 cells treated with conditioned media from NICD fibroblasts showed increased IL-6 expression. Conversely, conditioned media from prostate cancer cells increased Notch target gene expression in CAFs, which was blocked upon addition of IL-6 neutralizing antibody. Taken together there is a stromal-derived signaling cascade involving Notch and Wnt ligands, that activates YAP in the epithelia for paracrine IL-6-dependent Notch activity back in the stromal fibroblasts. Critically, disruption of this cross-talk in the fibroblasts can limit the gain of stem features and castrate resistance of the adjacent epithelia in halting lethal progression of prostate cancer. This abstract is also presented as Poster A44. Citation Format: Manisha Tripathi, Srinivas Nandana, Jen-Ming Huang, Manabu Kato, Leland W. K. Chung, Rajeev Mishra, Li Xin, Neil Bhowmick. Reciprocal prostate cancer signaling with its microenvironment mediates castrate-resistant disease progression. [abstract]. In: Proceedings of the AACR Special Conference: Function of Tumor Microenvironment in Cancer Progression; 2016 Jan 7–10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2016;76(15 Suppl):Abstract nr PR06.

Therapeutic targeting of the epithelial compartment alone in prostate cancer has resulted in unfavorable outcomes, including the development of resistance. Cabozantinib (XL184), a small molecule inhibitor of tyrosine kinases including c-MET and VEGFR2 has been shown to decrease tumor growth and metastasis. Our working rationale is that therapeutic strategies that target the prostate tumor microenvironment would have improved outcomes compared with those that solely target the cancer epithelia. Cabozantinib is demonstrated to have a role in inhibiting osteoclast and osteoblast differentiation and thereby limit prostate cancer (PCa) bone lesions, as determined by technetium-99 bone scan. However, the ultimate survival benefit of castrate resistant prostate cancer patients treated with cabozantinib has not born out in recent clinical trials for PCa patients with bone metastasis. In this study, utilizing various pre-clinical xenograft mouse models, prostate epithelial cell lines and human and mouse prostate fibroblasts, we investigated the effect of cabozantinib on prostate tumor microenvironment and delineated the cellular targets of cabozantnib. We found that cabozantinib affects prostate stromal cells at a significantly lower concentration compared with epithelial cells in vitro. We found that human cancer associated fibroblasts pre-treated with cabozantinib induced a significantly increased tumor growth in the intra-tibial mouse model of growth in the bone microenvironment. Further, in a novel and surprising discovery, we found that cabozantinib alters the immune microenvironment by reducing the M1 macrophages. However, cabozantinib depleted both basal and luminal epithelial progenitor cells in vivo. Taken together, we found that cabozantnib can have a tumor potentiating role by limiting M1 macrophages, yet the down regulation of carcinoma associated fibroblasts and associated epithelial progenitors could suggest interesting combination therapies. A lower dose of cabozantnib with traditional anti-proliferative therapies, like taxanes or radiation is supported by the pre-clinical experiments. Citation Format: Manisha Tripathi, Srinivas Nandana, Sandrine Billet, Edwin M. Posadas, Leland W.K. Chung, Neil A. Bhowmick. Microenvironment mediates the efficacy of Cabozantinib in prostate cancer. [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 LB-274.

Bone metastasis is a crucial turning point in the progression of PCa and is seen in > 90% of the lethal cases. Identifying factors that mediate the metastatic spread and subsequent remodeling of the bone is highly relevant to successful therapeutic intervention in advanced human prostate cancer (PCa). TBX2, a transcription factor that belongs to the T-box family negatively regulates p21 cell cycle inhibitor and is known to play critical roles during embryonic development and cancer progression. Interestingly, a recent report found TBX2 over-expression in the bone metastases from patients with castrate resistant prostate cancer. We found TBX2 over-expression in human prostate cancer specimens and in aggressive androgen independent human PCa cell lines. Further, we found TBX2 over-expression in bone metastases in multiple xenograft mouse models of human PCa progression. Blocking endogenous TBX2 in PC3 and ARCaPM PCa cells through the use of a dominant negative construct resulted in decreased proliferation, colony formation and invasion in vitro. Utilizing various pre-clinical xenograft mouse models, we found that blocking endogenous TBX2 in PCa cells leads to decreased invasion and abrogation of bone and soft tissue metastasis in vivo. Further, utilizing the intra-tibial mouse model of growth in the bone microenvironment, we found that blocking endogenous TBX2 in PCa cells dramatically reduces bone remodeling. Additionally we found that TBX2 acts upstream of the canonical WNT (WNT3A) signaling in PCa and positively regulates its transcription by binding to its promoter. Further, rescue of WNT3A levels in PCa cells in the context of blocking endogenous TBX2 rescues the metastatic ability of the cells in vivo. Taken together, our findings highlight a novel and critical role of TBX2 in PCa progression, metastasis and the subsequent bone remodeling, and that TBX2 function in PCa is mediated through the canonical WNT signaling. Citation Format: Srinivas Nandana, Manisha Tripathi, Peng Duan, Gina Chu, Haiyen E. Zhau, Robert J. Matusik, Leland W.K. Chung. Blocking endogenous TBX2 abrogates prostate cancer bone metastasis through WNT signaling. [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 4131.

Plant growth promoting Pantoea agglomerans NBRISRM (NBRISRM) was able to produce 60.4 μg/ml indole acetic acid and solubilize 77.5 μg/ml tri-calcium phosphate under in vitro conditions. Addition of 2% NaCl (w/v) in the media induced the IAA production and phosphate solubilization by 11% and 7%, respectively. For evaluating the plant growth promotory effect of NBRISRM inoculation a micro plot trial was conducted using maize and chickpea as host plants. The results revealed significant increase in all growth parameters tested in NBRISRM inoculated maize and chickpea plants, which were further confirmed by higher macronutrients (N, P and K) accumulation as compared to un-inoculated controls. Throughout the growing season of maize and chickpea, rhizosphere population of NBRISRM were in the range 10(7)-10(8) CFU/g soil and competing with 10(7)-10(9) CFU/g soil with heterogeneous bacterial population. Functional richness, diversity, and evenness were found significantly higher in maize rhizosphere as compared to chickpea, whereas NBRISRM inoculation were not able to change it, in both crops as compared to their un-inoculated control. To the best of our knowledge this is first report where we demonstrated the effect of P. agglomerans strain for improving maize and chickpea growth without altering the functional diversity.

The extracellular matrix (ECM) is thought to be an essential component of tissue scaffolding and engineering because it fulfills fundamental functions related to cell adhesion, migration, and three-dimensional organization. Natural ECM preparations, however, are challenging to work with because they are comprised of macromolecules that are large and insoluble in their functional state. Functional fragments of ECM macromolecules are a viable answer to this challenge, as demonstrated by the RGD-based engineered scaffolds, where the tri-peptide, Arg– Gly–Asp (RGD), represents the minimal functional unit of fibronectin and related ECM. Laminins (Ln) are main components of epithelial tissues, since they enter into the composition of basement membranes (BM). Application of Ln to epithelial tissue engineering would be desirable, since they could help mimic ideal functional conditions for both lining and glandular epithelial tissues. However, functional fragments of Ln that could be used in artificial settings have not been characterized in detail. In this paper, we describe the production and application of the recombinant LG4 (rLG4) fragment of laminin-332 (Ln-332), and show that it mimics three fundamental functional properties of Ln-332: integrin mediated cell adhesion, spreading, and migration. Adhesive structures formed by cells on rLG4 closely resemble those formed on Ln-332, as judged by microscopy-based analyses of their molecular composition. As on Ln-332, focal adhesion kinase (FAK) is phosphorylated in cells adhering to rLG4, and colocalized with other focal adhesion components. We conclude that rLG4 could be a useful substitute to recapitulate, in vitro, the tissue scaffolding properties of Ln-332.

Lysophosphatidic acid (LPA) is a bioactive phospholipid that affects various biological functions, such as cell proliferation, migration, survival, wound healing, and tumor invasion through LPA receptors. Previously, we reported that LPA induces A431 colony dispersal, accompanied by disruption of cell-cell contacts and cell migration. However, it remains unclearhowLPA affects cell migration and gene expression during A431 colony dispersal. In this paper, we performed cDNA microarray analysis to investigate this question by comparing gene expression between untreated and LPA-treated A431 cells. Interestingly, these results revealed that LPA treatment upregulates several TGF-β1 target genes, including laminin-332 (Ln-332) components (α3,β3, andγ2 chains). Western blot analysis also showed that LPA increased phosphorylation of Smad2, an event that is carried out by TGF-β1 interactions. Among the genes upregulated, we further addressed the role of Ln-332. Real-time PCR analysis confirmed the transcriptional upregulation of allα3,β3, andγ2 chains of Ln-332 by LPA, corresponding to the protein level increases revealed by western blot. Further, the addition of anti-Ln-332 antibody prevented LPA-treated A431 colonies from dispersing. Taken together, our results suggest that LPA-induced Ln-332 plays a significant role in migration of individual cells from A431 colonies.

Laminins (αβγ heterotrimers) form the basement membrane. They are important for many cell processes, through adhesion and signaling. There are 17 known laminins with different properties, depending on their subunits. Among the many functions fulfilled by laminins, they actively contribute to all stages of cancer progression, from the onset of the disease to the life-threatening development of metastases. At the cellular level, laminins are crucial in helping cells adhere, migrate, and differentiate.

Hepsin, a cell surface protease, is widely reported to be overexpressed in more than 90% of human prostate tumors. Hepsin expression correlates with tumor progression, making it a significant marker and target for prostate cancer. Recently, it was reported that in a prostate cancer mouse model, hepsin up-regulation in tumor tissue promotes progression and metastasis. The underlying mechanisms, however, remain largely uncharacterized. Hepsin transgenic mice displayed reduced laminin-332 (Ln-332) expression in prostate tumors. This is an intriguing cue, since proteolytic processing of extracellular matrix macromolecules, such as Ln-332, is believed to be involved in cancer progression, and Ln-332 expression is lost during human prostate cancer progression. In this study, we provide the first direct evidence that hepsin cleaves Ln-332. Cleavage is specific, since it is both inhibited in a dose-dependent manner by a hepsin inhibitor (Kunitz domain-1) and does not occur when catalytically inactive hepsin is used. By Western blotting and mass spectrometry, we determined that hepsin cleaves the β3 chain of Ln-332. N-terminal sequencing identified the cleavage site at β3 Arg245, in a sequence context (SQLR245↓LQGSCFC) conserved among species and in remarkable agreement with reported consensus target sequences for hepsin activity. In vitro cell migration assays showed that hepsin-cleaved Ln-332 enhanced motility of DU145 prostate cancer cells, which was inhibited by Kunitz domain-1. Further, hepsin-overexpressing LNCaP prostate cancer cells also exhibited increased migration on Ln-332. Direct cleavage of Ln-332 may be one mechanism by which hepsin promotes prostate tumor progression and metastasis, possibly by up-regulating prostate cancer cell motility.