Biophysical phenotype mixtures reveal advantages for tumor muscle invasion in vivo

Bladder, colon, gastric, prostate, and uterine cancers originate in organs surrounded by laminin-coated smooth muscle. In human prostate cancer, tumors that are organ confined, without extracapsular extension through muscle, have an overall cancer survival rate of up to 97% compared with 32% for metastatic disease. Our previous work modeling extracapsular extension reported the blocking of tumor invasion by mutation of a laminin-binding integrin called α6β1. Expression of the α6AA mutant resulted in a biophysical switch from cell-ECM (extracellular matrix) to cell-cell adhesion with drug sensitivity properties and an inability to invade muscle. Here we used different admixtures of α6AA and α6WT cells to test the cell heterogeneity requirements for muscle invasion. Time-lapse video microscopy revealed that tumor mixtures self-assembled into invasive networks in vitro, whereas α6AA cells assembled only as cohesive clusters. Invasion of α6AA cells into and through live muscle occurred using a 1:1 mixture of α6AA and α6WT cells. Electric cell-substrate impedance sensing measurements revealed that compared with α6AA cells, invasion-competent α6WT cells were 2.5-fold faster at closing a cell-ECM or cell-cell wound, respectively. Cell-ECM rebuilding kinetics show that an increased response occurred in mixtures since the response was eightfold greater compared with populations containing only one cell type. A synthetic cell adhesion cyclic peptide called MTI-101 completely blocked electric cell-substrate impedance sensing cell-ECM wound recovery that persisted in vitro up to 20 h after the wound. Treatment of tumor-bearing animals with 10 mg/kg MTI-101 weekly resulted in a fourfold decrease of muscle invasion by tumor and a decrease of the depth of invasion into muscle comparable to the α6AA cells. Taken together, these data suggest that mixed biophysical phenotypes of tumor cells within a population can provide functional advantages for tumor invasion into and through muscle that can be potentially inhibited by a synthetic cell adhesion molecule.

Abstract LB233: Cancer cell invasion through a complex and dynamic smooth muscle microenvironment

The cancer-prone peripheral zone of the human prostate is a fibromuscular stroma bounded by a laminin-rich smooth muscle capsule. Aggressive tumors traverse the muscle to escape organ confinement, but the determinants of cell migration through this complex and highly elastic environment are not well understood. We modeled smooth muscle invasion using a unique in vivo model to test the role of mechanosensing, laminin-binding integrins (α6β1 and α3β1), collect cells successful in traversing smooth muscle, and identify transcriptomes involved in this complex invasive process.

From the DU145 prostate cancer cell line (expressing integrins α3 and α6), we generated homozygous knockouts for genes ITGA6 (α6KO) and ITGA3 (α3KO). We tested for the ability to create 3D invasive cellular networks and measured biophysical features by electric cell-substrate impedance sensing. Muscle invasion was tested in vivo by injecting cells into the intraperitoneal cavity of male NSG mice. The cells colonized the inferior side of the respiratory diaphragm and invaded through to the superior surface after 6 weeks. We analyzed diaphragms by number of invasion sites and average invasion depth. A series of clones were also grown from wild-type, DU145 cells that had completely traversed the diaphragm muscle.

Cells expressing integrins α6 and α3 produced 3D invasive networks on laminin-containing Matrigel and invaded into the diaphragm muscle in vivo. α6KO cells did not produce networks or invade muscle. Surprisingly, knockout of α3 increased 3D invasive networks, decreased cell-cell impedance, and altered in vivo muscle invasion. The results suggest that the integrins α6 and α3 are involved in the invasion of prostate cancer cells through a dynamic smooth muscle layer.

The mechanosensing integrins are central to a variety of cell signaling programs. To further explore the transcriptional regulators of the muscle invasion process, we isolated RNA from cancer cells colonizing the inferior, superior surface and the intact diaphragm. Whole genome RNAseq revealed 1330 differentially expressed genes (DEGs) between inferior cells and cancer cells within the diaphragm, 788 DEGs between cells on the inferior and superior diaphragm surface, and 241 DEGs between cancer cells within the diaphragm and cells that reached the superior surface (padj <0.05, |fold change| >=1.3). Ingenuity Pathway Analysis revealed alterations in pathways including prostate cancer signaling, integrin signaling, other known cancer-related processes, and others.

Through this in vivo assay we have the unique ability to parse out unexplored patterns of changes that occur in early muscle invasive disease to improve prostate cancer patient selection for curative treatment versus active surveillance.

These studies were supported by NCI F30CA247106, P30CA23074, and R01CA24226. K.D.M is additionally supported by the ARCS Foundation Phoenix Chapter.

Citation Format: Kendra D. Marr, Hina Arif-Tiwari, Jaime M. Gard, Noel E. Warfel, Raymond B. Nagle, Anne E. Cress. Cancer cell invasion through a complex and dynamic smooth muscle microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr LB233.

A Method to Reuse Archived H&E Stained Histology Slides for a Multiplex Protein Biomarker Analysis

Archived Hematoxylin and Eosin (H&E) stained pathology slides are routinely stored to index formalin-fixed paraffin-embedded (FFPE) sample tissue blocks. FFPE blocks are clinically annotated human tumor specimens that can be valuable in studies decades after the tissue is collected. If stored properly, they have the potential to yield a valuable number of serial sectioned slides for diagnostic or research purposes. However, some retrospective studies are limited in scope because the tissue samples have been depleted or not enough material is available in stored blocks for serial sections. The goal of these studies was to determine if archived H&E-stained slides can be directly reutilized by optimizing methods to de-stain and then re-stain the H&E stained slides to allow the detection of several biomarkers of interest using a conjugated antibody with chromogen multiplex immunohistochemistry procedure. This simple but innovative procedure, combined with image analysis techniques, demonstrates the ability to perform precise detection of relevant markers correlated to disease progression in initially identified tumor regions in tissue. This may add clinical value in retaining H&E slides for further use.

Kallikrein 6 protease advances colon tumorigenesis via induction of the high mobility group A2 protein

Kallikrein-related peptidase 6 (KLK6) overexpression is commonly observed in primary tumors of colorectal cancer (CRC) patients and has been associated with tumor aggressiveness, metastasis, and poor prognosis. We previously established a unique contribution of KLK6 in colon cancer metastasis via a specific network of microRNAs and mRNAs. Here we evaluated the cellular functions of KLK6 protease in Caco-2 colon adenocarcinoma cell line after introduction of the enzymatically active or inactive form of the enzyme. We found that proteolytically active KLK6 increased Caco-2 cells invasiveness in vitro and decreased the animal survival in the orthotopic colon cancer model. The active KLK6 induced phosphorylation of SMAD 2/3 proteins leading to the altered expression of the epithelial-mesenchymal transition (EMT) markers. KLK6 overexpression also induced the RNA-binding protein LIN28B and high-mobility group AT-hook 2 (HMGA2) transcription factor, two essential regulators of cell invasion and metastasis. In the CRC patients, KLK6 protein levels were elevated in the non-cancerous distant and adjacent tissues, compared to their paired tumor tissues (p < 0.0001 and p = 0.0157, respectively). Patients with mutant K-RAS tumors had significantly higher level of KLK6 protein in the luminal surface of non-cancerous distant tissue, compared to the corresponding tissues of the patients with K-RAS wild type tumors (p ≤ 0.05). Furthermore, KLK6 and HMGA2 immunohistochemistry (IHC) scores in patients' tumors and paired adjacent tissues positively correlated (Spearman correlation P < 0.01 and p = 0.03, respectively). These findings demonstrate the critical function of the KLK6 enzyme in colon cancer progression and its contribution to the signaling network in colon cancer.

Centrosome loss results in an unstable genome and malignant prostate tumors

Localized, nonindolent prostate cancer (PCa) is characterized by large-scale genomic rearrangements, aneuploidy, chromothripsis, and other forms of chromosomal instability (CIN), yet how this occurs remains unclear. A well-established mechanism of CIN is the overproduction of centrosomes, which promotes tumorigenesis in various mouse models. Therefore, we developed a single-cell assay for quantifying centrosomes in human prostate tissue. Surprisingly, centrosome loss-which has not been described in human cancer-was associated with PCa progression. By chemically or genetically inducing centrosome loss in nontumorigenic prostate epithelial cells, mitotic errors ensued, producing aneuploid, and multinucleated cells. Strikingly, transient or chronic centrosome loss transformed prostate epithelial cells, which produced highly proliferative and poorly differentiated malignant tumors in mice. Our findings suggest that centrosome loss could create a cellular crisis with oncogenic potential in prostate epithelial cells.

Gene Editing of α6 Integrin Inhibits Muscle Invasive Networks and Increases Cell-Cell Biophysical Properties in Prostate Cancer

Human prostate cancer confined to the gland is indolent (low-risk), but tumors outside the capsule are aggressive (high-risk). Extracapsular extension requires invasion within and through a smooth muscle-structured environment. Because integrins respond to biomechanical cues, we used a gene editing approach to determine if a specific region of laminin-binding α6β1 integrin was required for smooth muscle invasion both in vitro and in vivo. Human tissue specimens showed prostate cancer invasion through smooth muscle and tumor coexpression of α6 integrin and E-cadherin in a cell-cell location and α6 integrin in a cell-extracellular matrix (ECM) distribution. Prostate cancer cells expressing α6 integrin (DU145 α6WT) produced a 3D invasive network on laminin-containing Matrigel and invaded into smooth muscle both in vitro and in vivo. In contrast, cells without α6 integrin (DU145 α6KO) and cells expressing an integrin mutant (DU145 α6AA) did not produce invasive networks, could not invade muscle both in vitro and in vivo, and surprisingly formed 3D cohesive clusters. Using electric cell-substrate impedance testing, cohesive clusters had up to a 30-fold increase in normalized resistance at 400 Hz (cell-cell impedance) as compared with the DU145 α6WT cells. In contrast, measurements at 40,000 Hz (cell-ECM coverage) showed that DU145 α6AA cells were two-fold decreased in normalized resistance and were defective in restoring resistance after a 1 μmol/L S1P challenge as compared with the DU145 α6WT cells. The results suggest that gene editing of a specific α6 integrin extracellular region, not required for normal tissue function, can generate a new biophysical cancer phenotype unable to invade the muscle, presenting a new therapeutic strategy for metastasis prevention in prostate cancer. SIGNIFICANCE: This study shows an innovative strategy to block prostate cancer metastasis and invasion in the muscle through gene editing of a specific α6 integrin extracellular region.

Integrin α6β4E variant is associated with actin and CD9 structures and modifies the biophysical properties of cell-cell and cell-extracellular matrix interactions

Integrin α6β4 is an essential, dynamic adhesion receptor for laminin 332 found on epithelial cells, required for formation of strong cell–extracellular matrix (ECM) adhesion and induced migration, and coordinated by regions of the β4C cytoplasmic domain. β4E, a unique splice variant of β4 expressed in normal tissue, contains a cytoplasmic domain of 231 amino acids with a unique sequence of 114 amino acids instead of β4C’s canonical 1089 amino acids. We determined the distribution of α6β4E within normal human glandular epithelium and its regulation and effect on cellular biophysical properties. Canonical α6β4C expressed in all basal cells, as expected, while α6β4E expressed within a subset of luminal cells. α6β4E expression was induced by three-dimensional culture conditions, activated Src, was reversible, and was stabilized by bortezomib, a proteasome inhibitor. α6β4C expressed in all cells during induced migration, whereas α6β4E was restricted to a subset of cells with increased kinetics of cell–cell and cell–ECM resistance properties. Interestingly, α6β4E presented in “ringlike” patterns measuring ∼1.75 × 0.72 microns and containing actin and CD9 at cell–ECM locations. In contrast, α6β4C expressed only within hemidesmosome-like structures containing BP180. Integrin α6β4E is an inducible adhesion isoform in normal epithelial cells that can alter biophysical properties of cell–cell and cell–ECM interactions.

A method of quantifying centrosomes at the single-cell level in human normal and cancer tissue

Centrosome abnormalities are emerging hallmarks of cancer. The overproduction of centrosomes (known as centrosome amplification) has been reported in a variety of cancers and is currently being explored as a promising target for therapy. However, to understand different types of centrosome abnormalities and their impact on centrosome function during tumor progression, as well as to identify tumor subtypes that would respond to the targeting of a centrosome abnormality, a reliable method for accurately quantifying centrosomes in human tissue samples is needed. Here, we established a method of quantifying centrosomes at a single-cell level in different types of human tissue samples. We tested multiple anti-centriole and pericentriolar-material antibodies to identify bona fide centrosomes and multiplexed these with cell border markers to identify individual cells within the tissue. High-resolution microscopy was used to generate multiple Z-section images, allowing us to acquire whole cell volumes in which to scan for centrosomes. The normal cells within the tissue serve as internal positive controls. Our method provides a simple, accurate way to distinguish alterations in centrosome numbers at the level of single cells.

The Tumor Microenvironments of Lethal Prostate Cancer

Localized prostate cancer (confined to the gland) generally is considered curable, with nearly a 100% 5-year-survival rate. When the tumor escapes the prostate capsule, leading to metastasis, there is a poorer prognosis and higher mortality rate, with 5-year survival dropping to less than 30%. A major research question has been to understand the transition from indolent (low risk) disease to aggressive (high risk) disease. In this chapter, we provide details of the changing tumor microenvironments during prostate cancer invasion and their role in the progression and metastasis of lethal prostate cancer. Four microenvironments covered here include the muscle stroma, perineural invasion, hypoxia, and the role of microvesicles in altering the extracellular matrix environment. The adaptability of prostate cancer to these varied microenvironments and the cues for phenotypic changes are currently understudied areas. Model systems for understanding smooth muscle invasion both in vitro and in vivo are highlighted. Invasive human needle biopsy tissue and mouse xenograft tumors both contain smooth muscle invasion. In combination, the models can be used in an iterative process to validate molecular events for smooth muscle invasion in human tissue. Understanding the complex and interacting microenvironments in the prostate holds the key to early detection of high-risk disease and preventing tumor invasion through escape from the prostate capsule.

A new species of Euchaetes Harris from southern Arizona (Erebidae, Arctiinae)

Euchaetesnancyaesp. n. is described from southeastern Arizona. Although superficially similar to species of Pygarctia Grote, structural and molecular variation shows it to be most closely related to Euchaeteshelena (Cassino). Adults, genitalic structure, eggs, and first instar larvae are described and illustrated. The larval host plant remains unknown. Euchaeteshelena is confirmed as occurring in Mexico.

Abstract 2106: Focal gene expression profiling of counterstained FFPE with correlation to morphology using TempO-Seq

We previously reported on use of the whole transcriptome TempO-Seq® assay to profile gene expression from 1 mm2 focal areas of 5 µm thick FFPE sections of normal and cancerous tissue to identify disease biomarkers and mechanistic pathways. We are now presenting data demonstrating that the TempO-Seq assay can be performed as an “in situ” assay on slides by an automated slide stainer, followed by counterstaining. Then, using an automated digital imaging platform, areas as small as 30 μm in diameter within the FFPE section can be profiled, permitting the gene expression data to be correlated directly to the specific morphology of that focal area. The pathologist uses a computer interface to select areas for profiling during the course of the histologic examination of the section, and then the TempO-Seq probes are automatically recovered from those region(s) of interest. After depositing them into PCR tubes, the assay is completed with PCR amplification and sample barcoding before pooling the samples into a library for sequencing. Analysis of the sequencing data is carried out automatically to report results. There is no use of laser capture or destruction of the tissue. The TempO-Seq processed slides can be archived and additional areas may be sampled at a later date. In this study, we sample replicate areas of matched normal vs. cancerous tissue, measuring gene biomarkers of clinical utility, gene fusions, and SNPs. We present gene expression profiles for replicate areas of pure stroma, single normal glands, single high-grade PIN glands, and single cancerous glands from prostate FFPE, demonstrating the statistical power of the TempO-Seq in situ assay as well as the correlation to focal histology and the use of focal differential expression to elucidate molecular pathways involved in the transition from normal tissue to cancer. We report measurements of clinically relevant biomarkers and signatures from clinical FFPE samples, plus therapeutic targets and drug resistance genes. This new approach demonstrates that complex molecular tests can be carried out by any pathologist in their own lab, and makes moot the issues of “% cancer” and amount of tissue required for testing. The approach we present brings extraction-free complex molecular testing of FFPE into the pathology lab and takes molecular pathology to a new level of simplicity, focal precision and correlation to morphology.

Citation Format: Elliot Imler, Milos Babic, Deanna Adams, Peter Shepard, Joanne Yeakley, Raymond B. Nagle, Bruce Seligmann. Focal gene expression profiling of counterstained FFPE with correlation to morphology using TempO-Seq [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 2106.

Novel Regulation of Integrin Trafficking by Rab11-FIP5 in Aggressive Prostate Cancer

The laminin-binding integrins, α3β1 and α6β1, are needed for tumor metastasis and their surface expression is regulated by endocytic recycling. β1 integrins share the Rab11 recycling machinery, but the trafficking of α3β1 and α6β1 are distinct by an unknown mechanism. Using a mouse PDX tumor model containing human metastatic prostate cancer, Rab11 family interacting protein 5 (Rab11-FIP5) was identified as a lead candidate for α6β1 trafficking. Rab11-FIP5 and its membrane-binding domain were required for α6β1 recycling, without affecting the other laminin-binding integrin (i.e., α3β1) or unrelated membrane receptors like CD44, transferrin receptor, or E-cadherin. Depletion of Rab11-FIP5 resulted in the intracellular accumulation of α6β1 in the Rab11 recycling compartment, loss of cell migration on laminin, and an unexpected loss of α6β1 recycling in cell-cell locations. Taken together, these data demonstrate that α6β1 is distinct from α3β1 via Rab11-FIP5 recycling and recycles in an unexpected cell-cell location.Implications: Rab11-FIP5-dependent α6β1 integrin recycling may be selectively targeted to limit migration of prostate cancer cells into laminin-rich tissues. Mol Cancer Res; 16(8); 1319-31. ©2018 AACR.

Does Mutated K-RAS Oncogene Attenuate the Effect of Sulindac in Colon Cancer Chemoprevention?

The NSAID sulindac has been successfully used alone or in combination with other agents to suppress colon tumorigenesis in patients with genetic predisposition and also showed its efficacy in prevention of sporadic colon adenomas. At the same time, some experimental and clinical reports suggest that a mutant K-RAS oncogene may negate sulindac antitumor efficacy. To directly assess sulindac activity at suppressing premalignant lesions carrying K-RAS mutation, we utilized a novel mouse model with an inducible colon-specific expression of the mutant K-ras oncogene (K-ras^G12D ). Tumor development and treatment effects were monitored by minimally invasive endoscopic Optical coherence tomography. Expression of the mutant K-ras allele accelerated azoxymethane (AOM)-induced colon carcinogenesis in C57BL/6 mice, a strain otherwise resistant to this carcinogen. Sulindac completely prevented AOM-induced tumor formation in K-ras wild-type (K-ras wt) animals. In K-ras^G12D -mutant mice, a 38% reduction in tumor number, an 83% reduction in tumor volume (P ≤ 0.01) and an increase in the number of adenoma-free mice (P = 0.04) were observed. The partial response of K-Ras^G12D animals to sulindac treatment was evident by the decrease in mucosal thickness (P < 0.01) and delay in progression of the precancerous aberrant crypt foci to adenomas. Molecular analyses showed significant induction in cyclooxygenase 2 (COX-2), cleaved caspase-3 (CC3), and Ki-67 expression by AOM, but not sulindac treatment, in all genotypes. Our data underscore the importance of screening for K-RAS mutations in individuals with colon polyps to provide more personalized interventions targeting mutant K-RAS signaling pathways. Cancer Prev Res; 11(1); 16-26. ©2017 AACR.

Characterization of Laminin Binding Integrin Internalization in Prostate Cancer Cells

Laminin binding integrins α6 (CD49f) and α3 (CD49c) are persistently but differentially expressed in prostate cancer (PCa). Integrin internalization is an important determinant of their cell surface expression and function. Using flow cytometry, and first order kinetic modeling, we quantitated the intrinsic internalization rates of integrin subunits in a single cycle of internalization. In PCa cell line DU145, α6 integrin internalized with a rate constant (k_actual ) of 3.25 min^-1 , threefold faster than α3 integrin (1.0 min^-1 ), 1.5-fold faster than the vitronectin binding αv integrin (CD51) (2.2 min^-1 ), and significantly slower than the unrelated transferrin receptor (CD71) (15 min^-1 ). Silencing of α3 integrin protein expression in DU145, PC3, and PC3B1 cells resulted in up to a 1.71-fold increase in k_actual for α6 integrin. The internalized α6 integrin was targeted to early endosomes but not to lamp1 vesicles. Depletion of α3 integrin expression resulted in redistribution of α6β4 integrin to an observed cell-cell staining pattern that is consistent with a suprabasal distribution observed in epidermis and early PIN lesions in PCa. Depletion of α3 integrin increased cell migration by 1.8-fold, which was dependent on α6β1 integrin. Silencing of α6 integrin expression however, had no significant effect on the k_actual of α3 integrin or its distribution in early endosomes. These results indicate that α3 and α6 integrins have significantly different internalization kinetics and that coordination exists between them for internalization. J. Cell. Biochem. 118: 1038-1049, 2017. © 2016 Wiley Periodicals, Inc.

A basal cell defect promotes budding of prostatic intraepithelial neoplasia

Basal cells in a simple secretory epithelium adhere to the extracellular matrix (ECM), providing contextual cues for ordered repopulation of the luminal cell layer. Early high-grade prostatic intraepithelial neoplasia (HG-PIN) tissue has enlarged nuclei and nucleoli, luminal layer expansion and genomic instability. Additional HG-PIN markers include loss of α6β4 integrin or its ligand laminin-332, and budding of tumor clusters into laminin-511-rich stroma. We modeled the invasive budding phenotype by reducing expression of α6β4 integrin in spheroids formed from two normal human stable isogenic prostate epithelial cell lines (RWPE-1 and PrEC 11220). These normal cells continuously spun in culture, forming multicellular spheroids containing an outer laminin-332 layer, basal cells (expressing α6β4 integrin, high-molecular-weight cytokeratin and p63, also known as TP63) and luminal cells that secrete PSA (also known as KLK3). Basal cells were optimally positioned relative to the laminin-332 layer as determined by spindle orientation. β4-integrin-defective spheroids contained a discontinuous laminin-332 layer corresponding to regions of abnormal budding. This 3D model can be readily used to study mechanisms that disrupt laminin-332 continuity, for example, defects in the essential adhesion receptor (β4 integrin), laminin-332 or abnormal luminal expansion during HG-PIN progression.

Schwann Cells Increase Prostate and Pancreatic Tumor Cell Invasion Using Laminin Binding A6 Integrin

Human pancreatic and prostate cancers metastasize along nerve axons during perineural invasion. The extracellular matrix laminin class of proteins is an abundant component of both myelinated and non-myelinated nerves. Analysis of human pancreatic and prostate tissue revealed both perineural and endoneural invasion with Schwann cells surrounded or disrupted by tumor, respectively. Tumor and nerve cell co-culture conditions were used to determine if myelinating or non-myelinating Schwann cell (S16 and S16Y, respectively) phenotype was equally likely to promote integrin-dependent cancer cell invasion and migration on laminin. Conditioned medium from S16 cells increased tumor cell (DU145, PC3, and CFPAC1) invasion into laminin approximately 1.3-2.0 fold compared to fetal bovine serum (FBS) treated cells. Integrin function (e.g., ITGA6p formation) increased up to 1.5 fold in prostate (DU145, PC3, RWPE-1) and pancreatic (CFPAC1) cells, and invasion was dependent on ITGA6p formation and ITGB1 as determined by function-blocking antibodies. In contrast, conditioned medium isolated from S16Y cells (non-myelinating phenotype) decreased constitutive levels of ITGA6p in the tumor cells by 50% compared to untreated cells and decreased ITGA6p formation 3.0 fold compared to S16 treated cells. Flow cytometry and western blot analysis revealed loss of ITGA6p formation as reversible and independent of overall loss of ITGA6 expression. These results suggest that the myelinating phenotype of Schwann cells within the tumor microenvironment increased integrin-dependent tumor invasion on laminin.

The Cohesive Metastasis Phenotype in Human Prostate Cancer

A critical barrier for the successful prevention and treatment of recurrent prostate cancer is detection and eradication of metastatic and therapy-resistant disease. Despite the fall in diagnoses and mortality, the reported incidence of metastatic disease has increased 72% since 2004. Prostate cancer arises in cohesive groups as intraepithelial neoplasia, migrates through muscle and leaves the gland via perineural invasion for hematogenous dissemination. Current technological advances have shown cohesive-clusters of tumor (also known as microemboli) within the circulation. Circulating tumor cell (CTC) profiles are indicative of disseminated prostate cancer, and disseminated tumor cells (DTC) are found in cohesive-clusters, a phenotypic characteristic of both radiation- and drug-resistant tumors. Recent reports in cell biology and informatics, coupled with mass spectrometry, indicate that the integrin adhesome network provides an explanation for the biophysical ability of cohesive-clusters of tumor cells to invade thorough muscle and nerve microenvironments while maintaining adhesion-dependent therapeutic resistance. Targeting cohesive-clusters takes advantage of the known ability of extracellular matrix (ECM) adhesion to promote tumor cell survival and represents an approach that has the potential to avoid the progression to drug- and radiotherapy-resistance. In the following review we will examine the evidence for development and dissemination of cohesive-clusters in metastatic prostate cancer.

Abstract 1840: Differential expression and mechanistic pathways of prostate cancer identified from FFPE tissue using surrogate or whole transcriptome TempO-Seq targeted gene expression assays

Highly sensitive and quantitative whole transcriptome and surrogate transcriptome targeted sequencing TempO-Seq assays were used to profile gene expression from 1 mm sq focal areas of FFPE sections (5 μm thick) of normal and cancerous tissue within the same prostate. The whole transcriptome assay directly measures changes within the whole transcriptome. The surrogate assay targets fewer genes yet permits in silico extrapolation to identify changes across the whole transcriptome. Both approaches identified differentiating biomarkers and mechanistic pathways in prostate cancer, both corroborating what has been reported and adding new mechanistic insights which will be discussed. These new observations likely result from the sensitivity of the TempO-Seq assays and their robust performance measuring gene expression from focal areas of FFPE, which in turn permit improved isolation of histology. Benefits derived from the TempO-Seq platform which will be discussed are:

1) Insensitivity to RNA degradation (measurements from intact RNA RIN = 9.1 correlate to measurements from degraded RNA RIN = 3.0, R2 = 0.97).

2) Does not require RNA extraction. Measures total RNA from FFPE samples, both soluble RNA in the lysate and crosslinked insoluble RNA.

3) Simple capture-free ligation-based assay protocol, without 3’ or 5’ bias to the probes used to measure each gene. No requirement for poly-adenylation or capture of the RNA (typically required in ligation-based assays).

4) Single base specificity derived from the specificity of probe ligation.

5) Misligation rates &lt;0.01% (unlike other ligation-based assays where misligation can be as great as 30%) enable no sample background controls to be run with typical counts of 0 for most genes and 1 to 3 counts for a few genes.

6) High signal-to-noise provides single cell sensitivity and ability to measure differential gene expression from small focal areas of tissue.

7) Excellent reproducibility (average ∼5% CV) between biological replicates across all expressed genes results in high significance of even small fold change differences.

8) Sequencing only the ligated probes complementary to a 50-base sequence of each gene eliminates the need for bioinformatics to analyze the sequencing data. Pooling of samples into a single sequencing run permits 42 or 865 surrogate samples and 8 or 153 whole transcriptome samples to be sequenced at the same time on the MiSeq or NextSeq, respectively, at an average of 250 counts/expressed gene. In combination, this results in low sequencing cost/sample without sacrifice of information or quality.

9) Simple, robust protocol requires only a PCR or qPCR instrument, and access to a sequencer.

Citation Format: Milos Babic, Peter Shepard, Joanne Yeakley, Ruchir Shah, Deepak Mav, Raymond B. Nagle, Bruce Seligmann. Differential expression and mechanistic pathways of prostate cancer identified from FFPE tissue using surrogate or whole transcriptome TempO-Seq targeted gene expression assays. [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 1840.

Laminin-binding integrin gene copy number alterations in distinct epithelial-type cancers

BACKGROUND

The laminin-binding integrin (LBI) family are cell adhesion molecules that are essential for invasion and metastasis of human epithelial cancers and cell adhesion mediated drug resistance. We investigated whether copy number alteration (CNA) or mutations of a five-gene signature (ITGB4, ITGA3, LAMB3, PLEC, and SYNE3), representing essential genes for LBI adhesion, would correlate with patient outcomes within human epithelial-type tumor data sets currently available in an open access format.

METHODS

We investigated the relative alteration frequency of an LBI signature panel (integrin β4 (ITGB4), integrin α3 (ITGA3), laminin β3 chain (LAMB3), plectin (PLEC), and nesprin 3 (SYNE3)), independent of the epithelial cancer type, within publically available and published data using cBioPortal and Oncomine software. We rank ordered the results using a 20% alteration frequency cut-off and limited the analysis to studies containing at least 100 samples. Kaplan-Meier survival curves were analyzed to determine if alterations in the LBI signature correlated with patient survival. The Oncomine data mining tool was used to compare the heat map expression of the LBI signature without SYNE3 (as this was not included in the Oncomine database) to drug resistance patterns.

RESULTS

Twelve different cancer types, representing 5,647 samples, contained at least a 20% alteration frequency of the five-gene LBI signature. The frequency of alteration ranged from 38.3% to 19.8%. Within the LBI signature, PLEC was the most commonly altered followed by LAMB3, ITGB4, ITGA3, and SYNE3 across all twelve cancer types. Within cancer types, there was little overlap of the individual amplified genes from each sample, suggesting different specific amplicons may alter the LBI adhesion structures. Of the twelve cancer types, overall survival was altered by CNA presence in bladder urothelial carcinoma (p=0.0143*) and cervical squamous cell carcinoma and endocervical adenocarcinoma (p=0.0432*). Querying the in vitro drug resistance profiles with the LBI signature demonstrated a positive correlation with cells resistant to inhibitors of HDAC (Vorinostat, Panobinostat) and topoisomerase II (Irinotecan). No correlation was found with the following agents: Bleomycin, Doxorubicin, Methotrexate, Gemcitabine, Docetaxel, Bortezomib, and Shikonen.

CONCLUSIONS

Our work has identified epithelial-types of human cancer that have significant CNA in our selected five-gene signature, which was based on the essential and genetically-defined functions of the protein product networks (in this case, the LBI axis). CNA of the gene signature not only predicted overall survival in bladder, cervical, and endocervical adenocarcinoma but also response to chemotherapy. This work suggests that future studies designed to optimize the gene signature are warranted.

GENERAL SIGNIFICANCE

The copy number alteration of structural components of the LBI axis in epithelial-type tumors may be promising biomarkers and rational targets for personalized therapy in preventing or arresting metastatic spread.

Time-serial Assessment of Drug Combination Interventions in a Mouse Model of Colorectal Carcinogenesis Using Optical Coherence Tomography

Optical coherence tomography (OCT) is a high-resolution, nondestructive imaging modality that enables time-serial assessment of adenoma development in the mouse model of colorectal cancer. In this study, OCT was utilized to evaluate the effectiveness of interventions with the experimental antitumor agent α-difluoromethylornithine (DFMO) and a nonsteroidal anti-inflammatory drug sulindac during early [chemoprevention (CP)] and late stages [chemotherapy (CT)] of colon tumorigenesis. Biological endpoints for drug interventions included OCT-generated tumor number and tumor burden. Immunochistochemistry was used to evaluate biochemical endpoints [Ki-67, cleaved caspase-3, cyclooxygenase (COX)-2, β-catenin]. K-Ras codon 12 mutations were studied with polymerase chain reaction-based technique. We demonstrated that OCT imaging significantly correlated with histological analysis of both tumor number and tumor burden for all experimental groups (P < 0.0001), but allows more accurate and full characterization of tumor number and burden growth rate because of its time-serial, nondestructive nature. DFMO alone or in combination with sulindac suppressed both the tumor number and tumor burden growth rate in the CP setting because of DFMO-mediated decrease in cell proliferation (Ki-67, P < 0.001) and K-RAS mutations frequency (P = 0.04). In the CT setting, sulindac alone and DFMO/sulindac combination were effective in reducing tumor number, but not tumor burden growth rate. A decrease in COX-2 staining in DFMO/sulindac CT groups (COX-2, P < 0.01) confirmed the treatment effect. Use of nondestructive OCT enabled repeated, quantitative evaluation of tumor number and burden, allowing changes in these parameters to be measured during CP and as a result of CT. In conclusion, OCT is a robust minimally invasive method for monitoring colorectal cancer disease and effectiveness of therapies in mouse models.

Combined micro CT and histopathology for evaluation of skeletal metastasis in live animals

Bone is a favored site for solid tumor metastasis, especially among patients with breast, lung or prostate carcinomas. Micro CT is a powerful and inexpensive tool that can be used to investigate tumor progression in xenograft models of human disease. Many previous studies have relied on terminal analysis of harvested bones to document metastatic tumor activity. The current protocol uses live animals and combines sequential micro CT evaluation of lesion development with matched histopathology at the end of the study. The approach allows for both rapid detection and evaluation of bone lesion progression in live animals. Bone resident tumors are established either by direct (intraosseous) or arterial (intracardiac) injection, and lesion development is evaluated for up to eight weeks. This protocol provides a clinically relevant method for investigating bone metastasis progression and the development of osteotropic therapeutic strategies for the treatment of bone metastases.

Nanoparticle delivery of an AKT/PDK1 inhibitor improves the therapeutic effect in pancreatic cancer

The K-ras mutation in pancreatic cancer can inhibit drug delivery and increase drug resistance. This is exemplified by the therapeutic effect of PH-427, a small molecule inhibitor of AKT/PDK1, which has shown a good therapeutic effect against a BxPC3 pancreatic cancer model that has K-ras, but has a poor therapeutic effect against a MiaPaCa-2 pancreatic cancer model with mutant K-ras. To increase the therapeutic effect of PH-427 against the MiaPaCa-2 pancreatic cancer model with mutant K-ras, we encapsulated PH-427 into poly(lactic-co-glycolic acid) nanoparticles (PNP) to form drug-loaded PH-427-PNP. PH-427 showed a biphasic release from PH-427-PNP over 30 days during studies in sodium phosphate buffer, and in vitro studies revealed that the PNP was rapidly internalized into MiaPaCa-2 tumor cells, suggesting that PNP can improve PH-427 delivery into cells harboring mutant K-ras. In vivo studies of an orthotopic MiaPaCa-2 pancreatic cancer model showed reduced tumor load with PH-427-PNP as compared with treatment using PH-427 alone or with no treatment. Ex vivo studies confirmed the in vivo results, suggesting that PNP can improve drug delivery to pancreatic cancer harboring mutant K-ras.

Intracellular modifiers of integrin alpha 6p production in aggressive prostate and breast cancer cell lines

Cancer metastasis is a multi-step process in which tumor cells gain the ability to invade beyond the primary tumor and colonize distant sites. The mechanisms regulating the metastatic process confer changes to cell adhesion receptors including the integrin family of receptors. Our group previously discovered that the α6 integrin (ITGA6/CD49f) is post translationally modified by urokinase plasminogen activator (uPA) and its receptor, urokinase plasminogen activator receptor (uPAR), to form the variant ITGA6p. This variant of ITGA6 is a cleaved form of the receptor that lacks the ligand-binding domain. Although it is established that the uPA/uPAR axis drives ITGA6 cleavage, the mechanisms regulating cleavage have not been defined. Intracellular integrin dependent "inside-out" signaling is a major regulator of integrin function and the uPA/uPAR axis. We hypothesized that intracellular signaling molecules play a role in formation of ITGA6p to promote cell migration during cancer metastasis. In order to test our hypothesis, DU145 and PC3B1 prostate cancer and MDA-MB-231 breast cancer cell lines were treated with small interfering RNA targeting actin and the intracellular signaling regulators focal adhesion kinase (FAK), integrin linked kinase (ILK), and paxillin. The results demonstrated that inhibition of actin, FAK, and ILK expression resulted in significantly increased uPAR expression and ITGA6p production. Inhibition of actin increased ITGA6p, although inhibition of paxillin did not affect ITGA6p formation. Taken together, these results suggest that FAK and ILK dependent "inside-out" signaling, and actin dynamics regulate extracellular production of ITGA6p and the aggressive phenotype.

Abstract 3152: Integrin α6β1 dependent collective cell migration in prostate cancer metastasis

Investigating the metastasis tactics of cancer cells show some cancers migrate using epithelial to mesenchymal transition (EMT) while others, such as prostate cancer, use collective migration similar to embryonic tubulogenesis. In human tissue specimens, collective migration originates from pre-malignant prostate intraepithelial neoplasia (PIN), occurs in invasive adenocarcinoma and persists in prostate cancer metastatic bone lesions. Successful collective migration requires cell attachment to the surrounding extracellular matrix (ECM), via adhesion receptors, specifically integrins. In prostate cancer, the laminin binding integrins α6β1 and α3β1 are expressed throughout disease progression including metastases. The laminin receptor α6β1 has been shown to be a determinant of prostate tumor cell aggressiveness. Integrin α6β1 undergoes a post-translational modification mediated by the serine protease, urokinase plasminogen activator (uPA) and its receptor uPAR, resulting in a variant form called α6pβ1. In this study, we optimized the growth and retrieval of tumor cells from 3-dimensional matrigel cultures, to determine the role of integrin α6β1, α6pβ1 and α3β1 in DU145 prostate tumor cell collective migration. The DU145 prostate tumor cells embedded in growth factor reduced matrigel, grew robust networks within 24 hours and contained extensive branching structures. The network formation was shown to be dependent on integrin α6β1 expression as determined by specific knockdown of α6β1 over a 24 hour period using 25nM siRNA targeting. Interestingly, the knockdown of α3β1 integrin had no observable effect on the networks. The networks produced by the DU145 cells contained pericellular proteolysis activity along the branches of collective cells as well as at the leading tips of the branches. Laminin 332, its receptor integrin α6β1, and uPAR co-localized on the membranes between cells traveling collectively. Induced production of integrin α6pβ1 increased branching network formation, while blockage of integrin α6pβ1 production impaired collective migration via reduced network formation. Taken together, these observations suggest that collective cell migration through tubulogenesis requires cell adhesion to laminin via integrin α6β1 and production of the α6pβ1 structural variant facilitates this process. Ongoing work is using the model to identify candidate molecular effectors of tubulogenesis as well as pharmacological approaches to block the process and prevent tumor progression. Supported in part by NIH grants CA 23074 and CA 159406.

Citation Format: Cynthia S. Rubenstein, Jaime Gard, Raymond B. Nagle, Terry H. Landowski, Anne E. Cress. Integrin α6β1 dependent collective cell migration in prostate cancer metastasis. [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 3152. doi:10.1158/1538-7445.AM2014-3152

Abstract 4979: A6B1 integrin internalization is increased by loss of A3B1 expression and promotes migration of human prostate cancer cells

Laminin binding integrins, A3B1 and A6B1 drive in part, cancer cell migration and metastasis. Cell migration requires dynamic internalization and recycling of surface integrins. However, whether laminin binding integrin internalization is coordinately or independently controlled is not known. In this study, we quantitated the internalization of integrin A3 and A6 and whether crosstalk influences their respective internalization and subsequent cancer cell migration.

We quantitated the internalization of A6 and A3 integrins, using fluorophore conjugated antibody based internalization assays and flow cytometry. In the prostate cancer cell line DU145, we observed constitutive internalization of integrin A6 with a surface half-life of approximately 30 minutes as compared to &gt;70 minutes for integrin A3, 45 minutes for unrelated integrin Av or 10 minutes for the unrelated transferrin receptor. Silencing A3 integrin expression resulted in a 10 percent increase in the total amount of internalized A6 integrin, with a decreased surface half-life of 20 minutes. The internalized A6 integrin showed intracellular punctate staining colocalized with the early endosome marker EEA1 and Rab4 containing vesicles. Increased integrin A6 internalization led to 40% increase in migration which was dependent on A6B1 integrin. Silencing integrin A6 expression, however, did not affect the internalization of A3 integrin indicating a unidirectional regulation of integrin internalization. The changes in the integrin internalization could be clearly ascribed to alpha subunits, as the obtained half-life of A6 and A3 integrins were independent of antibody used or integrin engagement by ligand mimetic peptides. Taken together, these data indicate that A6B1 and A3B1 integrins have different internalization kinetics and the presence of integrin A3 decreased integrin A6 internalization and ensuing cell migration. These data are consistent with previous observations in normal systems suggesting that A3B1 provides a provisional matrix during early stages of wound healing, requiring subsequent stable adhesion complexes and integrin A6 function. In cancer, the loss of A3 integrin and the increased internalization of A6 integrin may account for the “wounds that won't heal” phenotype and provide a strategy for biological intervention to block tumor progression.

(Supported in part by NIH Grants CA23074 and CA159406 and the TACMASS core service of the Arizona Cancer Center)

Citation Format: Lipsa Das, Todd A. Anderson, Jaime M.c. Gard, Isis C. Sroka, Stephanie R. Strautman, Raymond B. Nagle, Beatrice S. Knudsen, Anne Cress. A6B1 integrin internalization is increased by loss of A3B1 expression and promotes migration of human prostate cancer cells. [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 4979. doi:10.1158/1538-7445.AM2014-4979

Increased aPKC Expression Correlates with Prostatic Adenocarcinoma Gleason Score and Tumor Stage in the Japanese Population

Background. Levels of the protein kinase aPKC have been previously correlated with prostate cancer prognosis in a British cohort. However, prostate cancer incidence and progression rates, as well as genetic changes in this disease, show strong ethnic variance, particularly in Asian populations. Objective. The aim of this study was to validate association of aPKC expression with prostatic adenocarcinoma stages in a Japanese cohort. Methods. Tissue microarrays consisting of 142 malignant prostate cancer cases and 21 benign prostate tissues were subject to immunohistological staining for aPKC. aPKC staining intensity was scored by three independent pathologists and categorized as absent (0), dim (1+), intermediate (2+), and bright (3+). aPKC staining intensities were correlated with Gleason score and tumor stage. Results. Increased aPKC staining was observed in malignant prostate cancer, in comparison to benign tissue. Additionally, aPKC staining levels correlated with Gleason score and tumor stage. Our results extend the association of aPKC with prostate cancer to a Japanese population and establish the suitability of aPKC as a universal prostate cancer biomarker that performs consistently across ethnicities.

Targeting integrin α6 stimulates curative-type bone metastasis lesions in a xenograft model

Laminin-binding integrin receptors are key mediators of epithelial cell migration and tumor metastasis. Recent studies have demonstrated a role for the α6 integrin (ITGA6/CD49f) in maintaining stem cell compartments within normal bone marrow and in residency of tumors metastatic to bone. In this study, we tested a function-blocking antibody specific for ITGA6, called J8H, to determine if preexisting cancer lesions in bone could be slowed and/or animal survival improved. Human prostate tumors were established by intracardiac injection into male SCID mice and treatment with J8H antibody was initiated after 1 week. Tumor progression was monitored by micro-computed tomography (CT) imaging of skeletal lesions. Animals that received weekly injections of the anti-ITGA6 antibody showed radiographic progression in only 40% of osseous tumors (femur or tibia), compared with control animals, where 80% of the lesions (femur or tibia) showed progression at 5 weeks. Kaplan-Meier survival analysis demonstrated a significant survival advantage for J8H-treated animals. Unexpectedly, CT image analysis revealed an increased proportion of bone lesions displaying a sclerotic rim of new bone formation, encapsulating the arrested lytic lesions in animals that received the anti-ITGA6 antibody treatment. Histopathology of the sclerotic lesions demonstrated well-circumscribed tumor within bone, surrounded by fibrosis. These data suggest that systemic targeting of the ITGA6-dependent function of established tumors in bone may offer a noncytotoxic approach to arrest the osteolytic progression of metastatic prostate cancer, thereby providing a new therapeutic strategy for advanced disease.

Serum protein acidic and rich in cysteine (SPARC) as a prognostic marker in soft tissue sarcomas

BACKGROUND

Serum protein acidic and rich in cysteine (SPARC) is a matricellular secreted glycoprotein that performs several cellular functions and has been implicated in tumorigenesis in a variety of tumor types. The chemotherapeutic agent nanoparticle albumin-encapsulated (NAB)-paclitaxel has been postulated to exploit SPARC expression to target neoplastic cells. SPARC's role, and potentially the role of NAB-paclitaxel, in the highly heterogeneous class of soft-tissue sarcomas (STS) has not been investigated. Our objective was to explore the pattern of SPARC expression and its prognostic significance in STS.

METHODS

27 tissue specimens representing various STS histologies were stained for SPARC expression by immunohistochemistry (IHC). Staining intensity was scored blindly. Survival was determined from patients' medical records and analyzed using Kaplan-Meier and log-rank with respect to SPARC expression level.

RESULTS

Elevated SPARC expression was observed in 15/27 (56%) specimens. Overall patient survival segregated strongly based on levels of SPARC expression. Patients who expressed low-to-moderate levels of SPARC exhibited median survival of 22.1 months, while the median survival of patients with moderate-to-high expression levels was 4.4 months (log rank; p = 0.0016).

CONCLUSIONS

SPARC expression is elevated in a significant proportion of STS specimens analyzed in this study, but it does not appear to correlate with specific STS histologies. Given our limited sample size, we cannot draw definitive conclusions regarding association of SPARC with STS subtype. Overall survival segregates strongly by degree of SPARC expression, with elevated expression being adverse. If validated in a larger study, our results suggest that trials in STS with agents potentially targeting SPARC, such as NAB-paclitaxel, should be stratified by SPARC expression level.

Differences in characteristics of men with localised prostate cancer who demonstrate low, intermediate or high prostate-specific antigen velocity

BACKGROUND

Current diagnostic tools are inadequate for reliable prediction of prostate cancer (PCa) aggressiveness in patients with localised disease. This results in many patients being exposed to potentially unnecessary invasive treatment and its associated morbidities. In order to develop appropriate treatment strategies, it is essential to understand the differences between patients who will develop aggressive disease and those who will not.

METHODS

A longitudinal study was conducted in men with localised PCa on active surveillance for their disease in which 140 subjects were followed every 3 months for up to 5 years. Change in prostate-specific antigen (PSA) over time (PSA velocity) was used as a marker for PCa progression. Subjects were categorised as slow, intermediate and fast progressors based on tertiles of PSA velocity. Differences in baseline markers were investigated using logistic regressions. Two approaches were used, slow progressors were compared with fast progressors (model 1) and slow progressors were compared with combination of intermediate and fast progressors (model 2).

RESULTS

Aspirin was negatively associated with high PSA velocity in model 1 (odds ratio (95% confidence interval): 0.24 (0.06, 0.94), P-value = 0.04) and model 2 (odds ratio = 0.22 (0.08, 0.59), P-value = 0.003), whereas smoking was positively associated with high PSA velocity in model 1 (1.03 (0.92, 1.13), P-value = 0.01).

CONCLUSIONS

These findings highlight the role of aspirin and smoking in PCa progression. They have potential towards risk stratification as well as PCa prevention and hence need to be investigated further.

ERG overexpression and PTEN status predict capsular penetration in prostate carcinoma

BACKGROUND

This study examines the combined effect of two common genetic alterations, ERG and PTEN, in prostate carcinoma progression.

METHODS

Prostate tissue from 90 patients having unilateral capsular penetrating lesions, and a contra-lateral organ confined second lesion, were examined by immunohistochemistry for the expression of the TMPRSS2:ERG transformation product ERG and the loss of expression of PTEN, a powerful phosphatase inhibiting the PI3 kinase pathway. Multivariate logistic regression was carried out to analyze the data.

RESULTS

After adjusting for Gleason score, the odds of having capsular penetration were 5.19 times higher (P = 0.015) for ERG+/PTEN- group as compared to the wild type (ERG-/PTEN+).

CONCLUSIONS

This study presents the first evidence that ERG over expression and PTEN deletion is associated with greater risk of capsular penetration. Although further studies are needed, these results have the potential to change clinical assessment for prostate cancer.

Serum protein acidic and rich in cysteine (SPARC) as a prognostic marker in soft tissue sarcoma

10581

Background: SPARC is a matricellular secreted glycoprotein that performs several functions, including modulating cellular adhesion and proliferation. It has been implicated in tumorigenesis and identified as an adverse prognostic factor in a number of cancers. The specific mechanisms involved have yet to be identified. Agents targeting SPARC-expressing tumors, such as nanoparticle albumin-bound-paclitaxel (NAB-P), have been developed. Soft tissue sarcomas (STS) represent a heterogeneous group of tumors with inadequate systemic therapies. Our objective was to explore the pattern of SPARC expression and its prognostic significance in STS. Methods: Formalin-fixed paraffin-embedded tissue sections were stained by immunohistochemistry using a mouse monoclonal antibody for SPARC (Abnova). Staining intensity was scored blindly. Patient survival was determined from patients’ medical records. Kaplan-Meier and log-rank analyses were used to compare survival by SPARC expression level. Results: 27 tissue specimens of various STS subtypes were investigated (Table). Elevated SPARC expression was observed in 56% of specimens, but did not correlate with underlying histology. Overall survival segregated into 2 groups based on SPARC levels. Patients who expressed low-to-moderate levels of SPARC exhibited median survival of 22.1 months, while the median survival of patients with moderate-to-high expression levels was 4.4 months (log rank; p=0.0016). Conclusions: A significant proportion of STS specimens exhibit elevated SPARC expression. Elevated SPARC does not correlate with underlying histology, although analysis of a greater number of specimens might reveal subtypes with more frequently elevated expression. Overall survival segregates strongly by degree of SPARC expression, with elevated expression being adverse. Our results suggest that analysis in STS of agents targeting SPARC, such as NAB-P, should be stratified by extent of SPARC expression. [Table: see text]

Phase 3 clinical trial investigating the effect of selenium supplementation in men at high-risk for prostate cancer

PURPOSE

This study was conducted to investigate the effect of Se supplementation on prostate cancer incidence in men at high risk for prostate cancer.

METHODS

A Phase 3 randomized, double-blind, placebo-controlled clinical trial was conducted in 699 men at high risk for prostate cancer (prostate specific antigen (PSA) >4 ng/ml and/or suspicious digital rectal examination and/or PSA velocity >0.75 ng/ml/year), but with a negative prostate biopsy. Participants were randomized to receive daily oral placebo (N = 232), 200 µg selenium (N = 234), or 400 µg selenium (N = 233) as selenized yeast. They were followed every 6 months for up to 5 years. The time to diagnosis of prostate cancer was compared between treatment groups using the Cox proportional hazards model.

RESULT

Compared to placebo, the hazard ratios [95% confidence intervals] for risk of developing prostate cancer in the selenium 200 µg/day or the selenium 400 µg/day group were 0.94 [0.52, 1.7] and 0.90 [0.48, 1.7], respectively. PSA velocity in the selenium arms was not significantly different from that observed in the placebo group (P = 0.18 and P = 0.17, respectively).

CONCLUSION

Selenium supplementation appeared to have no effect on the incidence of prostate cancer in men at high risk. In conjunction with results of other studies, these data indicate that selenium supplementation may not have a role in prostate cancer chemoprevention.

Abstract 4345: Inadequate repair of ionizing radiation damage: A consequence of the invasive tumor phenotype

A major characteristic of the transition of prostatic intraepithelial neoplasia (PIN) to invasive prostate cancer is the progressive loss of laminin 322 in the basal lamina and loss of A6B4 integrin, a laminin 322 adhesion receptor in the basal cells. Previous work from our group reported that the loss of interaction with laminin 322 decreased the ability of normal prostate cells to respond to DNA damage. The defect was manifested as an alteration of an ionizing radiation (IR) induced G2 progression block. In this study, the goal was to determine if an invasive phenotype of human tumor cells, expressing A6B1 integrin, a laminin 511 adhesion receptor, influenced a DNA damage response (DDR) to IR. DU145 tumor cells were grown on laminin 511 and DDR was determined under conditions of stimulated invasion via HGF. The DDR endpoint chosen was the production, resolution and persistence of nuclear H2AX phosphorylation foci as an indicator of damage, repair and inadequate repair, respectively. Similar to a recent report, we observed a fast and transient phosphorylation of H2AX in response to IR within the basal cells of the normal human prostate epithelium that was both dose and time dependent. Utilizing tissue culture conditions, we determined that under optimal growth conditions on laminin 511 there was a dose and time response of H2AX phosphorylation in response to IR treatment. Under conditions of HGF stimulation, the persistence of H2AX foci 24 hours after IR was two to four fold higher as compared to unstimulated cells. The amplified persistence of H2AX foci was observed at 1, 2, 4, 6 and 8 Gy at both 24 and 36 hours after IR treatment. Current studies are determining if the inadequate repair response to IR under conditions of stimulated invasion results in an increased tumor cell killing or an increased genomic instability of surviving tumor cells. (Supported in part by NIH Cancer Center Core Grant CA 23074 and DOD grant W81XWH-10-1-0496)

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4345. doi:1538-7445.AM2012-4345

Randomized, double-blind, placebo-controlled trial of polyphenon E in prostate cancer patients before prostatectomy: evaluation of potential chemopreventive activities

Compelling preclinical and pilot clinical data support the role of green tea polyphenols in prostate cancer prevention. We conducted a randomized, double-blind, placebo-controlled trial of polyphenon E (enriched green tea polyphenol extract) in men with prostate cancer scheduled to undergo radical prostatectomy. The study aimed to determine the bioavailability of green tea polyphenols in prostate tissue and to measure its effects on systemic and tissue biomarkers of prostate cancer carcinogenesis. Participants received either polyphenon E (containing 800 mg epigallocatechin gallate) or placebo daily for 3 to 6 weeks before surgery. Following the intervention, green tea polyphenol levels in the prostatectomy tissue were low to undetectable. Polyphenon E intervention resulted in favorable but not statistically significant changes in serum prostate-specific antigen, serum insulin-like growth factor axis, and oxidative DNA damage in blood leukocytes. Tissue biomarkers of cell proliferation, apoptosis, and angiogenesis in the prostatectomy tissue did not differ between the treatment arms. The proportion of subjects who had a decrease in Gleason score between biopsy and surgical specimens was greater in those on polyphenon E but was not statistically significant. The study's findings of low bioavailability and/or bioaccumulation of green tea polyphenols in prostate tissue and statistically insignificant changes in systemic and tissue biomarkers from 3 to 6 weeks of administration suggests that prostate cancer preventive activity of green tea polyphenols, if occurring, may be through indirect means and/or that the activity may need to be evaluated with longer intervention durations, repeated dosing, or in patients at earlier stages of the disease.

Association of obesity and smoking with PSA and PSA velocity in men with prostate cancer

Significant number of prostate tumors are slow growing and could probably be left untreated. However, many are aggressive and can spread rapidly causing patient suffering and/or death. Current technology does not allow physicians to differentiate between slow growing and aggressive tumors at diagnosis. Hence, many patients are exposed to invasive treatment and its associated morbidities such as incontinence and impotence. Markers that enable differentiation between slow and fast progressing cancer will allow physicians to prevent unnecessary treatments on men who may not need them, and focus on the men with aggressive disease. A longitudinal study was conducted (N = 140) using mixed effects regression models to determine the association of obesity and smoking toward prostate cancer progression. These models account for correlation because of repeated measures over time, thus, using maximum amount of information provided by the subject. Estimates thus obtained are more robust and reliable than those obtained using data from a single time point. Rate of change of prostate-specific antigen (PSA) over time (PSA velocity) was used as a measure of prostate cancer progression. Results indicate that PSA velocity of overweight and obese subjects (0.59 and 1.05 ng/mL/year) was not significantly different as compared with normal weight subjects (p values .91 and .31, respectively). For men in the highest tertile of pack-years of smoking, PSA velocity was significantly higher as compared with never smokers 1.57 ng/mL/year (p = .04). Further studies with larger sample sizes and study designs specific to above exposures are needed before recommendations can be made to reduce weight or reduce/quit smoking.

ERK crosstalks with 4EBP1 to activate cyclin D1 translation during quinol-thioether-induced tuberous sclerosis renal cell carcinoma

The mammalian target of rapamycin (mTOR) and mitogen-activated protein kinase signaling cascades have been implicated in a number of human cancers. The tumor suppressor gene tuberous sclerosis-2 (Tsc-2) functions as a negative regulator of mTOR. Critical proteins in both pathways are activated following treatment of Eker rats (Tsc-2(EK/+)) with the nephrocarcinogen 2,3,5-tris-(glutathion-S-yl)hydroquinone (TGHQ), which also results in loss of the wild-type allele of Tsc-2 in renal preneoplastic lesions and tumors. Western blot analysis of kidney tumors formed following treatment of Tsc-2(EK/+) rats with TGHQ for 8 months revealed increases in B-Raf, Raf-1, pERK, cyclin D1, 4EBP1, and p-4EBP1-Ser65, -Thr70, and -Thr37/46 expression. Similar changes are observed following TGHQ-mediated transformation of primary renal epithelial cells derived from Tsc-2(EK/+) rats (quinol-thioether rat renal epithelial [QTRRE] cells) that are also null for tuberin. These cells exhibit high ERK, B-Raf, and Raf-1 kinase activity and increased expression of all p-4EBP1s and cyclin D1. Treatment of the QTRRE cells with the Raf kinase inhibitor, sorafenib, or the MEK1/2 kinase inhibitor, PD 98059, produced a significant decrease in the protein expression of all p-4EBP1s and cyclin D1. Following siRNA knockdown of Raf-1, Western blot analysis revealed a significant decrease in Raf-1, cyclin D1, and all p-4EBP1 forms noted above. In contrast, siRNA knockdown of B-Raf resulted in a nominal change in these proteins. The data indicate that Raf-1/MEK/ERK participates in crosstalk with 4EBP1, which represents a novel pathway interaction leading to increased protein synthesis, cell growth, and kidney tumor formation.

Abstract 1534: Laminin binding integrin functions in human bone metastatic cancer

Laminin binding integrins are major determinants of cancer cell migration, invasion and metastasis. In human prostate cancer, both A6B1 and A3B1 laminin-binding integrins are expressed on tumor cell surfaces as observed in either prostatectomy or needle biopsy specimens. In human breast cancer, the A6 integrin is expressed in both primary tumors and in metastatic lesions. Integrin A6B1 is post-translationally modified on the tumor cell surface by urokinase-type plasminogen activator (uPA), producing a structural variant, A6pB1. While the A6pB1 form is devoid of the ligand binding domain, A3B1 is fully functional and not subject to cleavage. In this study, we observed the continued expression of the A6B1 integrin on tumor cell surfaces within human bone metastatic lesions as well as in human tumor xenografts growing within bone. The cleavage function of the A6 integrin was found to be constitutively expressed on nine different cancer cell lines derived from breast, prostate, lung, pancreatic tumors. Interestingly, five different normal cell types expressing the adhesion active A6B1 integrin did not have the constitutive cleavage function. However, the cleavage function in normal cells was inducible by the exogenous addition of uPA. Selection of successive bone resident cancer cells selects for constitutive cleavage of A6 integrin and increasing expression of A3B1 integrin. Taken together, these data suggest that the cleavage function is constitutively activated in cancer specimens and opens the possibility cleavage mediated release from laminin binding may be coordinated with A3 dependent adhesion. (Supported in part by CA23752 and the TACMASS core service of the Arizona Cancer Center).

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1534. doi:10.1158/1538-7445.AM2011-1534

Abstract 1543: Potential role of Schwann cells and laminin adhesion in prostate cancer perineural invasion

Prostate tumor cell migration and invasion of prostatic nerves, a process known as perineural invasion (PNI), is a major route for extracapsular extension during prostate cancer metastasis. The clinical significance of perineural invasion as a predictor for poor patient outcome has been extensively documented. The laminin family of extracellular matrix glycoproteins lines the neural route and plays a prominent role in the development and maintenance of the peripheral nervous system. Evidence has shown that the laminin receptor integrin α6β1 promotes prostate tumor cell migration and invasion in aggressive disease. We hypothesize that α6β1 regulates prostate cancer perineural invasion by regulating laminin dependent adhesion and migration on nerves.

In this study we demonstrate remarkable integrin α6 expression in prostate tumors undergoing active perineural invasion using immunohistochemical analysis of human prostate tumors. The expression of integrin α6 correlates with expression of the laminin subunits α5 and γ1 which comprise laminin-511, the major ligand for integrin α6β1. The laminin extracellular matrix on the peripheral nerves of the prostate is derived from Schwann cells during the myelination process. We demonstrate here that Schwann cells are highly expressed in prostatic nerves using immunohistochemical analysis of the Schwann cell specific marker S-100, suggesting that tumor cells invade myelinated nerves. We also demonstrate two specific patterns of prostate tumor nerve invasion along prostatic nerves. Invasion along the external surface of the nerve sheath or in the perineural space maintains nerve structure while invasion of the endoneural space disrupts nerve structure and displaces Schwann cells. This suggests that tumor interactions with nerves and Schwann cells may illicit nerve damage during the PNI process.

Using a DU-145 prostate tumor and neuron/glial cell in vitro co-culture model we demonstrate that DU-145 cells (cytokeratin positive) migrate towards glial cells (GFAP positive) and neurons (Beta-III tubulin positive) isolated from dorsal root ganglia of male SCID mice. Mature cultures of the prostate tumor cells and neuron/glial cells demonstrate distinct islands of growth. The patterns of colony formation were non-random and interspersed colonies of tumor and nerve cells were not observed. Taken together, our immunohistochemical results suggest that perineural invasion of laminin coated nerves is regulated by the laminin adhesion receptor α6β1. Our in vitro model system demonstrates that tumor cells migrate to neuron/glial cells and dominate the co-culture, correlating with our immunohistochemical data. We expect that blocking α6β1 function in this system will impede prostate tumor cell migration and invasion in the nerve environment.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1543. doi:10.1158/1538-7445.AM2011-1543

Overexpression of tumor vascular endothelial growth factor A may portend an increased likelihood of progression in a phase II trial of bevacizumab and erlotinib in resistant ovarian cancer

PURPOSE

This phase II trial evaluated bevacizumab plus erlotinib in platinum-resistant ovarian cancer; exploratory biomarker analyses, including that of tumor vascular endothelial growth factor A (VEGF-A), were also done.

EXPERIMENTAL DESIGN

Forty heavily pretreated patients received erlotinib (150 mg/d orally) and bevacizumab (10 mg/kg i.v.) every 2 weeks until disease progression. Primary end points were objective response rate and response duration; secondary end points included progression-free survival (PFS), toxicity, and correlations between angiogenic protein levels, toxicity, and efficacy.

RESULTS

Grade 3 toxicities included skin rash (n = 6), diarrhea (n = 5), fatigue (n = 4), and hypertension (n = 3). Grade 4 toxicities were myocardial infarction (n = 1) and nasal septal perforation (n = 1). Only one grade 3 fistula and one grade 2 bowel perforation were observed. Nine (23.1%) of 39 evaluable patients had a response (median duration, 36.1+ weeks; one complete response), and 10 (25.6%) patients achieved stable disease, for a disease control rate of 49%. Median PFS was 4 months, and 6-month PFS was 30.8%. Biomarker analyses identified an association between tumor cell VEGF-A expression and progression (P = 0.03); for every 100-unit increase in the VEGF-A score, there was a 3.7-fold increase in the odds of progression (95% confidence interval, 1.1-16.6).

CONCLUSIONS

Bevacizumab plus erlotinib in heavily pretreated ovarian cancer patients was clinically active and well tolerated. Erlotinib did not seem to contribute to efficacy. Our study raises the intriguing possibility that high levels of tumor cell VEGF-A, capable of both autocrine and paracrine interactions, are associated with resistance to bevacizumab, emphasizing the complexity of the tumor microenvironment.

The laminin binding integrin alpha6beta1 in prostate cancer perineural invasion

Metastasizing prostate tumor cells invade along nerves innervating the encapsulated human prostate gland in a process known as perineural invasion. The extracellular matrix laminin class of proteins line the neural route and tumor cells escaping from the gland express the laminin binding integrin alpha6beta1 as a prominent cell surface receptor. Integrin alpha6beta1 promotes aggressive disease and supports prostate tumor cell metastasis to bone. Laminins and their integrin receptors are necessary for the development and maintenance of the peripheral nervous system, indicating the potential role for integrin receptors in directing prostate tumor cell invasion on nerves during perineural invasion.

Effect of aspirin, other NSAIDs, and statins on PSA and PSA velocity

BACKGROUND

Aspirin, other non-steroidal anti-inflammatory drugs (NSAIDs), and statins have been associated with lower risk of prostate cancer and its progression, though results have been inconsistent.

METHODS

Data from 140 men with prostate cancer enrolled in a Phase 2 clinical trial of selenium to prevent prostate cancer progression were analyzed to determine association between aspirin, other NSAIDs, or statin use with baseline serum prostate-specific antigen (PSA) levels and PSA velocity (rate of PSA change over time) using repeated measures over an average follow-up time of 3.2 years. Multiple linear regression and mixed effects models were used to model the association of medication use with PSA at baseline and with PSA velocity, respectively.

RESULTS

Baseline PSA levels were significantly lower in aspirin users compared to non-users (5.17 ng/ml vs. 7.58 ng/ml, P = 0.001). This association was statistically significant in never smokers (aspirin users vs. non-users: 4.19 ng/ml vs. 8.24 ng/ml, P = 0.004) but not in ever smokers (aspirin users vs. non-users: 5.52 ng/ml vs. 7.3 ng/ml, P = 0.101). Statin and other NSAID use was not associated with baseline PSA. Aspirin, statin, or other NSAID use at baseline demonstrated a non-significant negative association with PSA velocity.

CONCLUSION

These findings support an effect of aspirin use on PSA, particularly among never smokers. However, they do not suggest a protective effect on the disease and support previous findings that aspirin use may mask accurate measurement of PSA warranting consideration of washout procedures prior to testing.

Abstract 2722: Development of automated methods of in-situ hybridization for the detection of ETS gene re-arrangements in FFPE biopsy and archived prostatectomy specimens

Abstract

Prostate cancer (PCa) is the most common visceral neoplasm in men. In most cases, the disease is slowly progressive. Five year survival with organ-confined disease is 100%, while even distal spread is 32%. ETS gene re-arrangements in PCa have been shown to be associated with disease progression and have therapeutic and diagnostic implications.

The goal of this study was to develop methods of automated in-situ hybridization to detect the ETS gene re-arrangements in formalin fixed, paraffin-embedded (FFPE) prostate tissue. Methods were developed on the Ventana Benchmark®XT and Discovery®XT instruments for prostate cancer cell line xenografts, including VCap, LnCaP and H660, as well as for primary biopsy and archived prostatectomy specimens.

Key modules in the protocol have been evaluated and modified both in manual (offline) and automated (online) process of method development. Specific protocols were developed for deparaffinization, antigen retrieval, DNA denaturation, probe hybridization, sample washing, and detection with Quantum Dots (Qdots). Six different FISH probes specific for 3′ ERG, 5′ ERG, 5′ SLC45A3, and 3′ETV1 were used in assay development. Probe hybridization time was held to 8 hours, with overnight completion of the fully automated protocol.

Assay conditions on both instruments were similar for xenografts and in archived prostectomy specimens; however increased stringency of target retrieval was required for processing of the biopsy specimens. This adjustment was necessary to compensate for the tendency of biopsy specimens to become overly fixed during procurement and routine shipping and handling. In addition we observed that the presence of commonly used detergents in washing buffers post-hybridization may increase background staining with QDots.

In conclusion, we have developed fully automated protocols for the processing of clinically relevant tissue specimens. The xenograft cell line controls developed as a part of this study may also enable evaluation of assay performance in routine specimen processing for the detection of the ETS genes in biopsies and in prostatectomies.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2722.

Abstract 534: Invasive human prostate cancer and integrin cleavage: Potential role of uPAR contributed by macrophages

Laminin binding integrins are major determinants of cancer cell migration, invasion and metastasis. Our previous work showed that integrin α6β1 is cleaved on the tumor cell surface by urokinase-type plasminogen activator (uPA), producing a structural variant, α6pβ1. Urokinase plasminogen activator receptor (uPAR) is a regulatory determinant for α6 integrin cleavage since uPAR interacts with integrin and activates uPA. Previous work by others has shown that both human tumor tissue and tumor infiltrating macrophages express uPAR . In the present study, we investigated the potential of uPAR to co-localize with α6β1 integrin in human prostate cancer cells (DU-145) and whether uPAR expressed on the macrophage cell surface mediates integrin α6β1 cleavage. The results indicated uPAR and integrin α6β1 were co-expressed in invasive human prostate carcinoma. Co-localization of uPAR and integrin α6β1 occurred in some tumor cells in vitro, consistent with reports indicating a variable distribution in human tumors. The culture of macrophages with tumor cells resulted in an increased cleavage of integrin α6 as detected by immuno precipitation followed by western blot analysis. Taken together, these data suggest that integrin α6 cleavage is directed by the receptor for uPA, uPAR, contributed either by the tumor cell itself or tumor cell contact with macrophages. (Supported in part by CA 56666, CA23752, T34 GM008718 and the TACMASS core service of the Arizona Cancer Center)

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 534.

Phase II study of erlotinib in patients with locally advanced or metastatic papillary histology renal cell cancer: SWOG S0317

PURPOSE

Patients with advanced papillary renal cell cancer (pRCC) have poor survival after systemic therapy; the reported median survival time is 7 to 17 months. In this trial, we evaluated the efficacy of erlotinib, an oral epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor in patients with advanced pRCC, a tumor type associated with wild-type von Hippel Lindau gene.

PATIENTS AND METHODS

Patients with histologically confirmed, advanced, or metastatic pRCC were treated with erlotinib 150 mg orally once daily. A RECIST (Response Evaluation Criteria in Solid Tumors) response rate (RR) of > or = 20% was considered a promising outcome. Secondary end points included overall survival and 6-month probability of treatment failure.

RESULTS

Of 52 patients registered, 45 were evaluable. The overall RR was 11% (five of 45 patients; 95% CI, 3% to 24%), and the disease control rate was 64% (ie five partial response and 24 stable disease). The median overall survival time was 27 months (95% CI, 13 to 36 months). Probability of freedom from treatment failure at 6 months was 29% (95% CI, 17% to 42%). There was one grade 5 adverse event (AE) of pneumonitis, one grade 4 thrombosis, and nine other grade 3 AEs.

CONCLUSION

Although the RECIST RR of 11% did not exceed prespecified estimates for additional study, single-agent erlotinib yielded disease control and survival outcomes of interest with an expected toxicity profile. The design of future trials of the EGFR axis in pRCC should be based on preclinical or molecular data that define appropriate patient subgroups, new drug combinations, or potentially more active alternative schedules.

Human Cell Surface Receptors as Molecular Imaging Candidates for Metastatic Prostate Cancer

Existing clinical imaging procedures lack sensitivity and specificity in detecting early prostate cancer bone metastatic lesions. In this study, we developed a highly reproducible bone metastasis xenograft model and identified possible molecular imaging candidates for detecting early bone metastatic lesions. Bone trophic human prostate cells (PC-3B1) were isolated and characterized for their ability to reach bone after intracardiac injection into SCID mice. The appearances of skeletal metastases were evaluated using digital radiographic imaging and confirmed by necropsy and histology. The PC-3B1 cells retain a bone homing phenotype after long term propagation in tissue culture and exhibit progressive bone lesions within 3 weeks following intracardiac injection. Comparative transcription signatures of PC-3 and PC-3B1 cells were determined using a cancer specific microarray and confirmed by RT-PCR analysis. The analysis identified increased expression of four cell surface molecules in PC-3B1 cells that may be suitable as molecular imaging candidates to detect bone micro metastases.

Design and activity of a murine and humanized anti-CEACAM6 single-chain variable fragment in the treatment of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDA) is a lethal disease, with surgery being the only curative modality for localized disease, and gemcitabine with or without erlotinib remains the standard of therapy for unresectable or metastatic disease. CEACAM6 is overexpressed in human PDA independent of stage or grade and causes anoikis resistance when dysregulated. Because murine monoclonal antibody 13-1 possesses target-specific cytotoxicity in human PDA cell lines, we designed a humanized anti-CEACAM6 single-chain variable fragment (scFv) based on monoclonal antibody 13-1. PEGylation of the glycine-serine linker was used to enhance plasma half-life. These scFvs bound CEACAM6 with high affinity, exhibited cytotoxic activity, and induced dose-dependent poly(ADP-ribose) polymerase cleavage. Murine PDA xenograft models treated with humanized scFv alone elicited tumor growth inhibition, which was enhanced in combination with gemcitabine. Immunohistochemistry showed significant apoptosis, with inhibition of angiogenesis and proliferation, and preservation of the target. Collectively, our results have important implications for the development of novel antibody-based therapies against CEACAM6 in PDA.

The role of alpha 6 integrin in prostate cancer migration and bone pain in a novel xenograft model

Of the estimated 565,650 people in the U.S. who will die of cancer in 2008, almost all will have metastasis. Breast, prostate, kidney, thyroid and lung cancers metastasize to the bone. Tumor cells reside within the bone using integrin type cell adhesion receptors and elicit incapacitating bone pain and fractures. In particular, metastatic human prostate tumors express and cleave the integrin A6, a receptor for extracellular matrix components of the bone, i.e., laminin 332 and laminin 511. More than 50% of all prostate cancer patients develop severe bone pain during their remaining lifetime. One major goal is to prevent or delay cancer induced bone pain. We used a novel xenograft mouse model to directly determine if bone pain could be prevented by blocking the known cleavage of the A6 integrin adhesion receptor. Human tumor cells expressing either the wildtype or mutated A6 integrin were placed within the living bone matrix and 21 days later, integrin expression was confirmed by RT-PCR, radiographs were collected and behavioral measurements of spontaneous and evoked pain performed. All animals independent of integrin status had indistinguishable tumor burden and developed bone loss 21 days after surgery. A comparison of animals containing the wild type or mutated integrin revealed that tumor cells expressing the mutated integrin resulted in a dramatic decrease in bone loss, unicortical or bicortical fractures and a decrease in the ability of tumor cells to reach the epiphyseal plate of the bone. Further, tumor cells within the bone expressing the integrin mutation prevented cancer induced spontaneous flinching, tactile allodynia, and movement evoked pain. Preventing A6 integrin cleavage on the prostate tumor cell surface decreased the migration of tumor cells within the bone and the onset and degree of bone pain and fractures. These results suggest that strategies for blocking the cleavage of the adhesion receptors on the tumor cell surface can significantly prevent cancer induced bone pain and slow disease progression within the bone. Since integrin cleavage is mediated by Urokinase-type Plasminogen Activator (uPA), further work is warranted to test the efficacy of uPA inhibitors for prevention or delay of cancer induced bone pain.

Differential localization of MT1-MMP in human prostate cancer tissue: role of IGF-1R in MT1-MMP expression

BACKGROUND

MT1-MMP is a metalloproteinase involved in prostate cancer metastasis. The IGF-1R is a tyrosine kinase receptor involved with tumor progression and metastasis. The purpose of this investigation was to examine MT1-MMP and IGF-1R expression and localization in prostate cancer tissues and explore the role of IGF-1R in regulating MT1-MMP in prostate cancer cell lines.

METHODS

Immunohistochemistry was utilized to study MT1-MMP and IGF-1R expression in human prostate tissues. IGF-1R regulation of MT1-MMP expression was determined by gene promoter analysis, quantitative RT-PCR and Western blot analysis following pharmacological inhibition of the receptor in PC-3N cells and treatment of LNCaP cells with androgen and IGF-1.

RESULTS

MT1-MMP expression was high in the apical regions of the luminal cells in PIN and prostate cancer and less intense in the basalateral regions of benign tissues. IGF-1R was expressed primarily in the basal cells of normal glands and highly expressed in prostate cancer. Inhibition of IGF-1R in PC-3N cells decreased MT1-MMP expression and treatment of LNCaP cells with a synthetic androgen and IGF-1 increased MT1-MMP expression.

CONCLUSIONS

These data demonstrate that MT1-MMP is highly expressed in the apical cytoplasmic regions of the luminal cells in PIN and prostate cancer when compared to basalateral cytoplasmic membrane staining in benign glands. Additionally, we demonstrate that IGF-1R is highly expressed in human prostate carcinoma. These findings suggest that MT1-MMP localization and IGF-1R expression in prostate carcinoma could be predictive biomarkers for aggressive disease and support IGF-1R as a promising therapeutic target to decrease processes of prostate cancer metastasis.