Targeting Immunosuppressive Myeloid Cells and Exhausted CD8+ T Cells Overcomes Radioresistance in NSCLC

PURPOSE/OBJECTIVE(S)

Although stereotactic body radiation therapy (SBRT) has achieved great success in the treatment of non-small cell lung cancer (NSCLC), local relapses still occur and abscopal effects are rarely seen even when combined with immune checkpoint blockers (ICBs). Therefore, it is necessary to thoroughly understand the immune responses after SBRT.

MATERIALS/METHODS

We characterized the dynamic changes of tumor-infiltrating immune cells at early and late time points after SBRT in a therapy-resistant murine tumor model using single-cell transcriptomes and T-cell receptor sequencing.

RESULTS

At the early stage, the innate and adaptive immune systems were activated, including activation of NKs and NKTs, and infiltration of cytotoxic CD8+ T cells. At the late stage, however, the tumor immune microenvironment (TIME) shifted into immunosuppressive properties, containing enrichment of immunosuppressive tumor-associated neutrophils (TANs), M2-like tumor-associated macrophages (TAMs), and terminal exhausted CD8+ T cells. Furthermore, our study revealed that inhibition of CD39 combined with SBRT preferentially reinvigorated exhausted CD8+ T cells and promoted their proliferation, infiltration, and cytotoxicity. Meanwhile, it also promoted M1-like macrophage infiltration and DCs maturation. On the other hand, consequently increased infiltration of immunosuppressive myeloid cells after SBRT could be a potential mechanism mediating CD8+ T cell dysfunction. Moreover, we found that combination treatment with anti-VISTA and SBRT synergistically reduced immunosuppressive myeloid cells, containing TANs, M-MDSCs, and M2-like TAMs, and further activated CD8+ T cells. Clinically, high VISTA expression was associated with poor prognosis in NSCLC patients.

CONCLUSION

Altogether, our data provides deep insight into acquired resistance to SBRT from an immune perspective and presents rational combination strategies.

CaFeFeNbO6 - an iron-based double double perovskite

Ordering of cations is important for controlling properties of ABO₃ perovskites, and CaFeFeNbO₆ is the first example of an Fe-based AA'BB'O₆ double double perovskite, with Ca²⁺/Fe²⁺ ordered on A-site columns, and Fe³⁺/Nb⁵⁺ at the octahedral B-sites. Substantial (37%) antisite disorder of the latter cations leads to spin glassy magnetism below a freezing transition at 12 K. The CaMnFeNbO₆ analogue also shows substantial cation disorder and spin glassy behaviour. Comparison of synthesis pressures for ordered materials based on different A-site transition metals, suggests that pressures of at least 14-18 GPa will be required to discover the expected plethora of double double perovskites based on A' cations smaller than Mn²⁺.

Ang II acutely stimulates Na,K-pump in cells from proximal tubules by increasing its phosphorylation at S938 via a PI3K/AKT pathway

Angiotensin II (Ang II)-dependent stimulation of the AT1 receptor in proximal tubules increases sodium reabsorption and blood pressure. Reabsorption is driven by the Na,K-pump that is acutely stimulated by Ang II, which requires phosphorylation of serine-938 (S938). This site is present in humans and only known to phosphorylated by PKA. Yet, activation of AT1 decreases cAMP required to activate PKA and inhibiting PKA does not block Ang II-dependent phosphorylation of S938. We tested the hypothesis that Ang II-dependent activation is mediated via increased phosphorylation at S938 through a PI3K/AKT-dependent pathway. Experiments were conducted using opossum kidney cells, a proximal tubule cell line, stably co-expressing the AT1 receptor and either the wild-type (α-1.wild-type) or an alanine substituted (α-1.S938A) form of rat kidney Na,K-pump. A 5-min exposure to 10 pM Ang II significantly activated Na,K-pump activity (56%) measured as short-circuit current across polarized α-1.wild-type cells. Wortmannin, at a concentration that selectively inhibits PI3K, blocked that Ang II-dependent activation. Ang II did not stimulate Na,K-pump activity in α-1.S938A cells. Ang II at 10 and 100 pM increased phosphorylation at S938 in α-1.wild-type cells measured in whole cell lysates. The increase was inhibited by wortmannin plus H-89, an inhibitor of PKA, not by either alone. Ang II activated AKT inhibited by wortmannin, not H-89. These data support our hypothesis and show that Ang II-dependent phosphorylation at S938 stimulates Na,K-pump activity and transcellular sodium transport.

Anti-tumor and immune modulating activity of T cell induced tumor-targeting effectors (TITE)

Adoptive transfer of Bispecific antibody Armed activated T cells (BATs) showed promising anti-tumor activity in clinical trials in solid tumors. The cytotoxic activity of BATs occurs upon engagement with tumor cells via the bispecific antibody (BiAb) bridge, which stimulates BATs to release cytotoxic molecules, cytokines, chemokines, and other signaling molecules extracellularly. We hypothesized that the release of BATs Induced Tumor-Targeting Effectors (TITE) by this complex interaction of T cells, bispecific antibody, and tumor cells may serve as a potent anti-tumor and immune-activating immunotherapeutic approach. In a 3D tumorsphere model, TITE showed potent cytotoxic activity against multiple breast cancer cell lines compared to control conditioned media (CM): Tumor-CM (T-CM), BATs-CM (B-CM), BiAb Armed PBMC-CM (BAP-CM) or PBMC-CM (P-CM). Multiplex cytokine analysis showed high levels of Th₁ cytokines and chemokines; phospho-protein signaling array data suggest that the prominent JAK1/STAT1 pathway may be responsible for the induction and release of Th₁ cytokines/chemokines in TITE. In xenograft breast cancer models, IV injections of 10× concentrated TITE (3×/week for 3 weeks; 150 μl TITE/injection) was able to inhibit tumor growth significantly (ICR/scid, p < 0.003; NSG p < 0.008) compared to the control mice. We tested the key components of the TITE for immune activating and anti-tumor activity individually and in combinations, the combination of IFN-γ, TNF-α and MIP-1β recapitulates the key activities of the TITE. In summary, master mix of active components of BATs-Tumor complex-derived TITE can provide a clinically controllable cell-free platform to target various tumor types regardless of the heterogeneous nature of the tumor cells and mutational tumor.

Clinical features and cardiovascular magnetic resonance characteristics in Danon disease

AIMS

To investigate the clinical spectrum, cardiovascular magnetic resonance imaging (cMRI) characteristics, including T1 and extracellular volume fraction, and outcomes of Danon disease to facilitate further understanding of the phenotype of patients with Danon disease.

MATERIALS AND METHODS

The study comprised six male patients 8-23 years old recruited to the study between 2014-2019. The clinical presentation, laboratory examinations, pathology/genetic analysis, electrocardiography (ECG), echocardiography, and cCMRI characteristics were summarised.

RESULTS

Five out of six patients suffered from hypertrophic cardiomyopathy (HCM) phenotype of Danon disease, while one patient had dilated cardiomyopathy (DCM) phenotype. Left ventricular (LV) and left atrial (LA) function were impaired at strain measurement. Diffuse and focal late gadolinium enhancement (LGE) were observed separately in the LV walls of three patients and right ventricular (RV) insertion points of the remaining three patients. Furthermore, values for the native T1 (mean 1313.3 ms) and extracellular volume fraction (ECV; mean 39.17%) of three patients were increased.

CONCLUSIONS

Both dilated and hypertrophic cardiomyopathy may be the phenotypes of Danon disease. Comprehensive cCMRI played a unique role in the diagnosis and grading severity and risk factors of Danon disease in vivo, especially by using robust quantitative strain analysis, T1 mapping, and further ECV calculation.

Clinical use of internal distraction osteogenesis in the rehabilitation of gunshot injuries of the mandible

Rehabilitation of gunshot injuries that require combined reconstruction of bone and soft tissue poses a considerable challenge. We describe three cases of rehabilitation for mandibular defects and deformities caused by gunshot injuries. After debridement, three kinds of internal distractors were used. The bony transport discs were distracted about 10-22mm, and the new bone formed well in the distracted gaps. There was no evidence of infection during the consolidation period or follow up. Aesthetic appearance was also pleasing after treatment. Internal distraction osteogenesis after debridement might be a practical way of synchronously reconstructing bony and soft tissue after mandibular gunshot injuries.

Autophagy attenuates the oxidative stress-induced apoptosis of Mc3T3-E1 osteoblasts

OBJECTIVE

The oxidative stress-induced osteoblast apoptosis plays an important role in the pathological process of osteoporosis, but the roles of autophagy in oxidative stress and apoptosis of osteoblasts remain unclear. This study aimed to observe the role of autophagy in oxidative stress injury of osteoblasts and the relationship between autophagy and apoptosis.

MATERIALS AND METHODS

Mc3T3-E1 cells were stimulated with different concentrations (0.1, 0.5, and 1 mM) of hydrogen peroxide. The cell viability was detected via cell counting kit 8 (CCK8) at different time points (0, 2, 6, 8, and 12 h), the apoptosis was detected via Western blotting and flow cytometry, and the autophagy was detected via macrophage-derived chemokine (MDC) and transmission electron microscope. The changes in expression of autophagy-associated protein, Beclin1, and LC3II/I ratio, were detected via Western blotting. Moreover, the intracellular reactive oxygen species (ROS) level and extracellular superoxide dismutase (SOD) level were observed using the autophagy regulators, rapamycin (Rap) and 3-methyladenine (3-MA), so as to clarify the interaction between autophagy and cellular oxidation.

RESULTS

Hydrogen peroxide-induced apoptosis and autophagy of osteoblasts were in dose- and time-dependent manners; the hydrogen peroxide inhibitors could inhibit the autophagy level, and autophagy inhibitor (3-MA) could significantly enhance the hydrogen peroxide-induced ROS level and apoptosis rate in cells. Besides, Western blotting confirmed that the cleaved caspase-3 and cleaved poly adenosine diphosphate ribose polymerase (PARP) proteins were increased. The autophagy inducer (Rap) partially inhibited the hydrogen peroxide-induced oxidative stress and apoptosis.

CONCLUSIONS

Autophagy inhibits the oxidative stress-mediated apoptosis of osteoblasts, which is a potential target for the osteoporosis treatment.

[Clinicopathological and molecular characteristics of Epstein-Barr virus associated gastric cancer: a single center large sample case investigation]

OBJECTIVE

Epstein-Barr virus associated gastric cancer (EBVaGC) is different from the traditional gastric cancer (Epstein-Barr virus non-associated gastric cancer, EBVnGC), and has unique clinicopathological features. This study investigated the largest single center cancer series so as to establish the clinicopathological and molecular characteristics of EBVaGC in China.

METHODS

A retrospective analysis was conducted on EBVaGC and EBVnGC patients diagnosed at Peking University Cancer Hospital from 2003 to 2018 by comparing their clinicopathological features and prognosis. The gastric cancer (GC) dataset of public database was analyzed to obtain differentially expressed genes. The expression of important genes and their association with prognosis of GC were verified in GC tissues from our hospital.

RESULTS

In this study, 3 241 GC patients were included, and a total of 163 EBVaGC (5.0%) patients were identified. Compared with EBVnGC, EBVaGC was higher in male and younger patients, and positively associated with remnant GC, poorly differentiated adenocarcinoma, and mixed type GC. EBVaGC was inversely related to lymph node metastasis. The 5-year survival rate of EBVnGC and EBVaGC was 59.6% and 63.2% respectively (P<0.05). In order to explore molecular features of EBVaGC, the Cancer Genome Atlas (TCGA) dataset was analyzed (n=240), and 7 404 significant differentially expressed genes were obtained, involving cell proliferation, apoptosis, invasion and metastasis. The down-regulated invasion/metastasis gene SALL4 and the up-regulated immune checkpoint gene PD-L1 were important molecular features of EBVaGC. Validation of these two genes in large GC series showed that the majority of the EBVaGC was SALL4 negative (1/92, 1.1%, lower than EBVnGC, 303/1 727, 17.5%), and that PD-L1 was mostly positive in EBVaGC (81/110, 73.6%, higher than EBVnGC, 649/2 350, 27.6%). GC patients with SALL4 negative and PD-L1 positive were often associated with better prognosis.

CONCLUSION

EBVaGC is a unique subtype of GC with less metastasis and a good prognosis. It also has a distinct molecular background. The down-regulation of invasion/metastasis gene SALL4 and up-regulation of immune checkpoint gene PD-L1 are important molecular features.

Abstract 5036: Induction of highly efficacious anti-tumor activity and modulation of tumor microenvironment: Cell-free off the shelf therapeutic modality

Adoptive transfer of Bispecific antibody Armed activated T cells (BATs) show promising anti-tumor activity in clinical trials in solid tumors. The cytotoxic activity of BATs occur upon engagement with tumor cells via the bispecific antibody bridge which stimulates BATs to release not only the lytic and cytotoxic molecules (perforin/granzyme) but also cytokines, chemokines and other signaling molecules extracellularly. We hypothesized that the release of extracellular soluble factors by this complex interaction of T cells, bispecific antibody, and tumor cells may serve as a potent anti-tumor and immune activating conditioned media (CM). In a 3D tumorsphere model, tumor+BATs-CM (n=10) showed potent cytotoxicity (p&lt;0.001) against multiple breast (MDA-MB-231, BT-20, SK-BR-3 and MCF-7) and other cancer cell lines (p&lt;0.001) compared to control tumor-CM or BATs-CM. Tumor+BATs-CM (n=6) was able to reduce the proportion of CD44hi/CD24lo cancer stem like cells to 0.7% compared to 4.9% in control CM. The addition of tumor+BATs-CM decreased the proportions of T regulatory cells (5% to 1.1%; p&lt;0.02) and myeloid derived suppressor cells (3.8% to 1.2%; p&lt;0.03), but increased activation and proliferation of effector T cells in 3D cultures compared to control CM (n=3). Size based CM factionation showed that most activity is retained in the &lt;50kDa but &gt;10kDa fraction. Multiplex analysis showed high levels of IL-2, IL-15, IFN-γ, TNF-α, GM-CSF, granszyme B (GZB), IL-13, MIP-1β, IP-10, MIG and RANTES. These factors are likely responsible for the cytolytic and immune activating effects. Phospho-specific signaling protein arrays showed enhanced JAK1/STAT-1/STAT-5A, Rac/cdc42/STIM-1) pathways in tumor+BATs-CM (n=3). Exosomal microRNA (miR) in tumor+BAT-CM showed higher expression of several miRs that are associated with T cell function and activation compared to control CM (n=2). Simulations using cocktails of multiple cytokines were done to test anti-tumor activity, IFN-γ/TNF-α/GZB showed potent cytotoxicity directed at breast (58-78%) and pancreatic cancer (50-72%) cell lines compared to 45-65%, 20-27%, 18-25% with IFN-γ, TNF-α and GZB individually, respectively. In a xenograft breast cancer model, IV and intra-tumoral injections of 10x concentrated tumor+BAT-CM (3x/week for 4 weeks;150μl CM/injection) was able to inhibit tumor growth significantly (p&lt;0.01) compared to the control CM treated mice (n=10 mice/group). Therapeutic advantages of CM include: 1) a ready off-the-shelf product; 2) a decrease in regulatory and manufacturing costs. In summary, BATs-Tumor complex derived CM provides a clinically controllable cell-free platform to target various tumor types with diverse anti-cancer immune activating mediators regardless of the heterogeneous nature of the tumor cells and mutational burden as a novel and potent off-the-shelf therapeutic modality.

Citation Format: Archana Thakur, SriVidya Yarlagadda, Kyungmin Ji, Dana L. Schalk, Johnson Ung, Edwin T. Bliemeister, Amro Aboukameel, Eli Casarez, Bonnie F. Sloane, Lawrence G. Lum. Induction of highly efficacious anti-tumor activity and modulation of tumor microenvironment: Cell-free off the shelf therapeutic modality [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 5036.

In Vitro Models for Studying Invasive Transitions of Ductal Carcinoma In Situ

About one fourth of all newly identified cases of breast carcinoma are diagnoses of breast ductal carcinoma in situ (DCIS). Since we cannot yet distinguish DCIS cases that would remain indolent from those that may progress to life-threatening invasive ductal carcinoma (IDC), almost all women undergo aggressive treatment. In order to allow for more rational individualized treatment, we and others are developing in vitro models to identify and validate druggable pathways that mediate the transition of DCIS to IDC. These models range from conventional two-dimensional (2D) monolayer cultures on plastic to 3D cultures in natural or synthetic matrices. Some models consist solely of DCIS cells, either cell lines or primary cells. Others are co-cultures that include additional cell types present in the normal or cancerous human breast. The 3D co-culture models more accurately mimic structural and functional changes in breast architecture that accompany the transition of DCIS to IDC. Mechanistic studies of the dynamic and temporal changes associated with this transition are facilitated by adapting the in vitro models to engineered microfluidic platforms. Ultimately, the goal is to create in vitro models that can serve as a reproducible preclinical screen for testing therapeutic strategies that will reduce progression of DCIS to IDC. This review will discuss the in vitro models that are currently available, as well as the progress that has been made using them to understand DCIS pathobiology.

Breast Cancer: Proteolysis and Migration

Understanding breast cancer cell proteolysis and migration is crucial for developing novel therapies to prevent local and distant metastases. Human cancer cells utilize many biological functions comparable to those observed during embryogenesis conferring the cancer cells with survival advantages. One such advantage is the ability to secrete proteases into the tumor microenvironment in order to remodel the extracellular matrix to facilitate migration. These proteases degrade the extracellular matrix, which initially functions as a barrier to cancer cell escape from their site of origin. The extracellular matrix also functions as a reservoir for growth factors that can be released by the secreted proteases and thereby further aid tumor growth and progression. Other survival advantages of tumor cells include: the ability to utilize multiple modes of motility, thrive in acidic microenvironments, and the tumor cell's ability to hijack stromal and immune cells to foster their own migration and survival. In order to reduce metastasis, we must focus our efforts on addressing the survival advantages that tumor cells have acquired.

Downregulation of Rap1Gap: A Switch from DCIS to Invasive Breast Carcinoma via ERK/MAPK Activation

Diagnosis of breast ductal carcinoma in situ (DCIS) presents a challenge since we cannot yet distinguish those cases that would remain indolent and not require aggressive treatment from cases that may progress to invasive ductal cancer (IDC). The purpose of this study is to determine the role of Rap1Gap, a GTPase activating protein, in the progression from DCIS to IDC. Immunohistochemistry (IHC) analysis of samples from breast cancer patients shows an increase in Rap1Gap expression in DCIS compared to normal breast tissue and IDCs. In order to study the mechanisms of malignant progression, we employed an in vitro three-dimensional (3D) model that more accurately recapitulates both structural and functional cues of breast tissue. Immunoblotting results show that Rap1Gap levels in MCF10.Ca1D cells (a model of invasive carcinoma) are reduced compared to those in MCF10.DCIS (a model of DCIS). Retroviral silencing of Rap1Gap in MCF10.DCIS cells activated extracellular regulated kinase (ERK) mitogen-activated protein kinase (MAPK), induced extensive cytoskeletal reorganization and acquisition of mesenchymal phenotype, and enhanced invasion. Enforced reexpression of Rap1Gap in MCF10.DCIS-Rap1GapshRNA cells reduced Rap1 activity and reversed the mesenchymal phenotype. Similarly, introduction of dominant negative Rap1A mutant (Rap1A-N17) in DCIS-Rap1Gap shRNA cells caused a reversion to nonmalignant phenotype. Conversely, expression of constitutively active Rap1A mutant (Rap1A-V12) in noninvasive MCF10.DCIS cells led to phenotypic changes that were reminiscent of Rap1Gap knockdown. Thus, reduction of Rap1Gap in DCIS is a potential switch for progression to an invasive phenotype. The Graphical Abstract summarizes these findings.

Abstract 2131: Paracrine cytokine pathways mediate metastasis of breast cancer to lymphatics

Lymphatics, rather than blood vessels, are the primary route for breast cancer metastasis. The presence of breast cancer cells in regional lymphatics, i.e., lymphatic metastasis, is an important prognostic factor for patients. Delineating molecular mechanisms by which the breast cancer cells migrate toward and infiltrate into lymphatics is crucial to designing new therapies to prevent metastatic dissemination. To study tumor:lymphatic interactions, we are using a three-dimensional (3D) heterotypic co-culture model of human breast cancer cells (hBCCs) grown with human microvascular lymphatic endothelial cells (hLECs) in novel chambers that we designed and fabricated. These chambers support growth of the 3D co-cultures, live-cell confocal imaging in real time and noninvasive collection of conditioned media for secretomic analyses. We use live-cell assays developed in our laboratory for quantitative analysis of temporal and dynamic changes in BCC:LEC interactions in correspondence with changes in their malignant and proteolytic phenotypes. We cultured hLECs in the presence and absence of human MDA-MB-231 (231) triple-negative BCCs in 3D cultures for 4 days. In mono-cultures, the 231 cells grow in clusters that exhibit a stellate morphology and hLECs form branching networks with central nodes. We observed that the volumes of 3D structures formed by LECs and 231 cells were significantly greater in co-cultures than in mono-cultures of either cell type. In addition, 231 cells infiltrate into the LEC networks with the infiltration increasing over the 4-day period as assessed by the degree of overlap between 231 cells and hLECs in 3D reconstructions of the co-cultures. Moreover, soluble factors from LECs increase invasive outgrowths of 231 structures. This was demonstrated in 231 cells grown in media conditioned by LECs and in parallel co-cultures of 231 cells and LECs. The induction of invasiveness by LEC conditioned media is reduced by boiling and repeated freeze/thawing, suggesting that the active factor(s) is a protein. Our preliminary results suggest that LECs secrete soluble factors that may be therapeutic targets for reducing invasion of BCCs into lymphatic networks.

Citation Format: Kyungmin Ji, Zhiguo Zhao, Kamiar Moin, Yong Xu, Robert J. Gillies, Raymond R. Mattingly, Bonnie F. Sloane. Paracrine cytokine pathways mediate metastasis of breast cancer to lymphatics [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 2131.

Ras and Rap1: A tale of two GTPases

Ras oncoproteins play pivotal roles in both the development and maintenance of many tumor types. Unfortunately, these proteins are difficult to directly target using traditional pharmacological strategies, in part due to their lack of obvious binding pockets or allosteric sites. This obstacle has driven a considerable amount of research into pursuing alternative ways to effectively inhibit Ras, examples of which include inducing mislocalization to prevent Ras maturation and inactivating downstream proteins in Ras-driven signaling pathways. Ras proteins are archetypes of a superfamily of small GTPases that play specific roles in the regulation of many cellular processes, including vesicle trafficking, nuclear transport, cytoskeletal rearrangement, and cell cycle progression. Several other superfamily members have also been linked to the control of normal and cancer cell growth and survival. For example, Rap1 has high sequence similarity to Ras, has overlapping binding partners, and has been demonstrated to both oppose and mimic Ras-driven cancer phenotypes. Rap1 plays an important role in cell adhesion and integrin function in a variety of cell types. Mechanistically, Ras and Rap1 cooperate to initiate and sustain ERK signaling, which is activated in many malignancies and is the target of successful therapeutics. Here we review the role activated Rap1 in ERK signaling and other downstream pathways to promote invasion and cell migration and metastasis in various cancer types.

Live-Cell Imaging of Protease Activity: Assays to Screen Therapeutic Approaches

Methodologies to image and quantify the activity of proteolytic enzymes have been developed in an effort to identify protease-related druggable pathways that are involved in malignant progression of cancer. Our laboratory has pioneered techniques for functional live-cell imaging of protease activity in pathomimetic avatars for breast cancer. We analyze proteolysis in the context of proliferation and formation of structures by tumor cells in 3-D cultures over time (4D). In order to recapitulate the cellular composition and architecture of tumors in the pathomimetic avatars, we include other tumor-associated cells (e.g., fibroblasts, myoepithelial cells, microvascular endothelial cells). We also model noncellular aspects of the tumor microenvironment such as acidic pericellular pH. Use of pathomimetic avatars in concert with various types of imaging probes has allowed us to image, quantify, and follow the dynamics of proteolysis in the tumor microenvironment and to test interventions that impact directly or indirectly on proteolytic pathways. To facilitate use of the pathomimetic avatars for screening of therapeutic modalities, we have designed and fabricated custom 3D culture chambers with multiple wells that are either individual or connected by a channel to allow cells to migrate between wells. Optical glass microscope slides underneath an acrylic plate allow the cultures to be imaged with an inverted microscope. Fluid ports in the acrylic plate are at a level above the 3D cultures to allow introduction of culture media and test agents such as drugs into the wells and the harvesting of media conditioned by the cultures for immunochemical and biochemical analyses. We are using the pathomimetic avatars to identify druggable pathways, screen drug and natural product libraries and accelerate entry of validated drugs or natural products into clinical trials.

Pathomimetic avatars reveal divergent roles of microenvironment in invasive transition of ductal carcinoma in situ

BACKGROUND

The breast tumor microenvironment regulates progression of ductal carcinoma in situ (DCIS) to invasive ductal carcinoma (IDC). However, it is unclear how interactions between breast epithelial and stromal cells can drive this progression and whether there are reliable microenvironmental biomarkers to predict transition of DCIS to IDC.

METHODS

We used xenograft mouse models and a 3D pathomimetic model termed mammary architecture and microenvironment engineering (MAME) to study the interplay between human breast myoepithelial cells (MEPs) and cancer-associated fibroblasts (CAFs) on DCIS progression.

RESULTS

Our results show that MEPs suppress tumor formation by DCIS cells in vivo even in the presence of CAFs. In the in vitro MAME model, MEPs reduce the size of 3D DCIS structures and their degradation of extracellular matrix. We further show that the tumor-suppressive effects of MEPs on DCIS are linked to inhibition of urokinase plasminogen activator (uPA)/urokinase plasminogen activator receptor (uPAR)-mediated proteolysis by plasminogen activator inhibitor 1 (PAI-1) and that they can lessen the tumor-promoting effects of CAFs by attenuating interleukin 6 (IL-6) signaling pathways.

CONCLUSIONS

Our studies using MAME are, to our knowledge, the first to demonstrate a divergent interplay between MEPs and CAFs within the DCIS tumor microenvironment. We show that the tumor-suppressive actions of MEPs are mediated by PAI-1, uPA and its receptor, uPAR, and are sustained even in the presence of the CAFs, which themselves enhance DCIS tumorigenesis via IL-6 signaling. Identifying tumor microenvironmental regulators of DCIS progression will be critical for defining a robust and predictive molecular signature for clinical use.

How to Target Activated Ras Proteins: Direct Inhibition vs. Induced Mislocalization

Oncogenic Ras proteins are a driving force in a significant set of human cancers and wildtype, unmutated Ras proteins likely contribute to the malignant phenotype of many more. The overall challenge of targeting activated Ras proteins has great promise to treat cancer, but this goal has yet to be achieved. Significant efforts and resources have been committed to inhibiting Ras, but these energies have so far made little impact in the clinic. Direct attempts to target activated Ras proteins have faced many obstacles, including the fundamental nature of the gain-of-function oncogenic activity being produced by a loss-of-function at the biochemical level. Nevertheless, there has been very promising recent pre-clinical progress. The major strategy that has so far reached the clinic aimed to inhibit activated Ras indirectly through blocking its post-translational modification and inducing its mislocalization. While these efforts to indirectly target Ras through inhibition of farnesyl transferase (FTase) were rationally designed, this strategy suffered from insufficient attention to the distinctions between the isoforms of Ras. This led to subsequent failures in large-scale clinical trials targeting K-Ras driven lung, colon, and pancreatic cancers. Despite these setbacks, efforts to indirectly target activated Ras through inducing its mislocalization have persisted. It is plausible that FTase inhibitors may still have some utility in the clinic, perhaps in combination with statins or other agents. Alternative approaches for inducing mislocalization of Ras through disruption of its palmitoylation cycle or interaction with chaperone proteins are in early stages of development.

Dynamic microglial modulation of spatial learning and social behavior

Microglia are active players in inflammation, but also have important supporting roles in CNS maintenance and function, including modulation of neuronal activity. We previously observed an increase in the frequency of excitatory postsynaptic current in organotypic brain slices after depletion of microglia using clodronate. Here, we describe that local hippocampal depletion of microglia by clodronate alters performance in tests of spatial memory and sociability. Global depletion of microglia by high-dose oral administration of a Csf1R inhibitor transiently altered spatial memory but produced no change in sociability behavior. Microglia depletion and behavior effects were both reversible, consistent with a dynamic role for microglia in the regulation of such behaviors.

Identification of a novel microRNA important for melanogenesis in alpaca (Vicugna pacos)

The molecular mechanisms underlying the formation of coat colors in animals are poorly understood. Recent studies have demonstrated that microRNA play important roles in the control of melanogenesis and coat color in mammals. In a previous study, we characterized the miRNA expression profiles in alpaca skin with brown and white coat color and identified a novel miRNA (named lpa-miR-nov-66) that is expressed significantly higher in white skin compared to brown skin. The present study was conducted to determine the functional roles of this novel miRNA in the regulation of melanogenesis in alpaca melanocytes. lpa-miR-nov-66 is predicted to target the soluble guanylate cyclase (sGC) gene based on presence of a binding site in the sGC coding sequence (CDS). Overexpression of lpa-miR-nov-66 in alpaca melanocyes upregulated the expression of sGC both at the mRNA and protein level. Overexpression of lpa-miR-nov-66 in melanocyes also resulted in decreased expression of key melanogenic genes including tyrosinase (TYR), tyrosinase related protein 1 (TYRP1), and microphthalmia transcription factor (MITF). Our ELISA assays showed increased cyclic guanosine monophosphate (cGMP) but decreased cyclic adenosine monophosphate (cAMP) production in melanocytes overexpressing lpa-miR-nov-66. In addition, overexpression of lpa-miR-nov-66 also reduced melanin production in cultured melanocytes. Results support a role of lpa-miR-nov-66 in melanocytes by directly or indirectly targeting , which regulates melanogenesis via the cAMP pathway.

Abstract B65: Live-cell imaging of 3D/4D parallel co-cultures of breast carcinoma cells and breast fibroblasts in tissue architecture and microenvironment engineering (TAME) chambers

Interactions among breast carcinoma cells and other cells in the tumor microenvironment, e.g., stromal fibroblasts and immune cells, contribute to malignant progression. We have developed three dimensional (3D) co-culture models and live-cell imaging assays for the analysis of such interactions in real-time, focusing on interactions and associated signaling pathways that might be druggable. Bissell, Brugge and colleagues have elegantly shown that the 3D context of breast cells is essential for their development and neoplastic progression, and the genes down-regulated during acini development in 3D culture are prognostic for clinical outcome of estrogen receptor (ER)-positive and ER-negative breast tumors. We as well as others have demonstrated that 3D cultures of tumor cells can better predict resistance to cytotoxic therapy than 2D monolayer cultures and can be used to identify targets and validate potential therapeutic agents. Nonetheless, in vitro models using only one cell type are at best only partially predictive of in vivo conditions and thus may not be optimal screening platforms for pre-clinical drug discovery. To this end, we have been developing complex 3D co-culture models. We have optimized models that recapitulate in 3D the architecture of the human breast during the transition from normal breast epithelium through pre-malignancy to malignancy and have named them MAME models for mammary architecture and microenvironment engineering models. We have used these models in our laboratory for live-cell imaging and molecular, biochemical and immunochemical analyses in real-time, i.e., 4D (3D + time) of breast tumor cells interacting with other cell types (fibroblasts, myoepithelial cells, lymphatic and blood vessel microvascular endothelial cells, macrophages) in the breast tumor microenvironment. We also developed a live-cell proteolysis assay that allows us to localize and quantify proteolysis and how that is altered by therapeutic approaches and microenvironmental conditions associated with tumors such as acidosis and hypoxia. The MAME models are state-of-the-art in that they allow the analysis of dynamic and temporal processes in live cells and furthermore can be created with all human cells. Thus MAME models provide an alternative to 2D cultures of cancer cells, xenografts of human cancers in mice or transgenic mouse models.

Here we report the development and testing of novel modular chambers designed to allow 3D culture of cancer cells alone or in co-culture (direct and parallel) with other cells over extended periods of time (4D). Because the chambers can be used for cells other than breast, we have designated them tissue architecture and microenvironment engineering (TAME) chambers. With TAME chambers, we have grown for periods ≥60 days human triple negative breast cancer cells, MDA-MB-231, and human breast fibroblasts [normal fibroblasts (NAF98i) and carcinoma-associated fibroblasts (CAF49TKi)]. TAME chambers facilitate collection of conditioned media, without disturbing the cultures, for analyses of dynamic and temporal effects on the secretome; monitoring and quantification by live-cell imaging of dynamic and temporal changes in proliferation, viability, migration, proteolysis and phenotype; regulated introduction of blocking antibodies to cytokines and their receptors; etc. We suggest that TAME chambers will be suitable for high-content imaging and therefore for screening of therapeutic approaches for cancer treatment.

Citation Format: Kyungmin Ji, Zhiguo Zhao, Kamiar Moin, Yong Xu, Bonnie F. Sloane. Live-cell imaging of 3D/4D parallel co-cultures of breast carcinoma cells and breast fibroblasts in tissue architecture and microenvironment engineering (TAME) chambers. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Breast Cancer Research; Oct 17-20, 2015; Bellevue, WA. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(2_Suppl):Abstract nr B65.

Pathomimetic cancer avatars for live-cell imaging of protease activity

Proteases are essential for normal physiology as well as multiple diseases, e.g., playing a causative role in cancer progression, including in tumor angiogenesis, invasion, and metastasis. Identification of dynamic alterations in protease activity may allow us to detect early stage cancers and to assess the efficacy of anti-cancer therapies. Despite the clinical importance of proteases in cancer progression, their functional roles individually and within the context of complex protease networks have not yet been well defined. These gaps in our understanding might be addressed with: 1) accurate and sensitive tools and methods to directly identify changes in protease activities in live cells, and 2) pathomimetic avatars for cancer that recapitulate in vitro the tumor in the context of its cellular and non-cellular microenvironment. Such avatars should be designed to facilitate mechanistic studies that can be translated to animal models and ultimately the clinic. Here, we will describe basic principles and recent applications of live-cell imaging for identification of active proteases. The avatars optimized by our laboratory are three-dimensional (3D) human breast cancer models in a matrix of reconstituted basement membrane (rBM). They are designated mammary architecture and microenvironment engineering (MAME) models as they have been designed to mimic the structural and functional interactions among cell types in the normal and cancerous human breast. We have demonstrated the usefulness of these pathomimetic avatars for following dynamic and temporal changes in cell:cell interactions and quantifying changes in protease activity associated with these interactions in real-time (4D). We also briefly describe adaptation of the avatars to custom-designed and fabricated tissue architecture and microenvironment engineering (TAME) chambers that enhance our ability to analyze concomitant changes in the malignant phenotype and the associated tumor microenvironment.

The experimental autoimmune encephalomyelitis disease course is modulated by nicotine and other cigarette smoke components

Epidemiological studies have reported that cigarette smoking increases the risk of developing multiple sclerosis (MS) and accelerates its progression. However, the molecular mechanisms underlying these effects remain unsettled. We have investigated here the effects of the nicotine and the non-nicotine components in cigarette smoke on MS using the experimental autoimmune encephalomyelitis (EAE) model, and have explored their underlying mechanism of action. Our results show that nicotine ameliorates the severity of EAE, as shown by reduced demyelination, increased body weight, and attenuated microglial activation. Nicotine administration after the development of EAE symptoms prevented further disease exacerbation, suggesting that it might be useful as an EAE/MS therapeutic. In contrast, the remaining components of cigarette smoke, delivered as cigarette smoke condensate (CSC), accelerated and increased adverse clinical symptoms during the early stages of EAE, and we identify a particular cigarette smoke compound, acrolein, as one of the potential mediators. We also show that the mechanisms underlying the opposing effects of nicotine and CSC on EAE are likely due to distinct effects on microglial viability, activation, and function.

Biomimetic tissue-engineered systems for advancing cancer research: NCI Strategic Workshop report

Advanced technologies and biomaterials developed for tissue engineering and regenerative medicine present tractable biomimetic systems with potential applications for cancer research. Recently, the National Cancer Institute convened a Strategic Workshop to explore the use of tissue biomanufacturing for development of dynamic, physiologically relevant in vitro and ex vivo biomimetic systems to study cancer biology and drug efficacy. The workshop provided a forum to identify current progress, research gaps, and necessary steps to advance the field. Opportunities discussed included development of tumor biomimetic systems with an emphasis on reproducibility and validation of new biomimetic tumor models, as described in this report.

Simultaneous integrated boost intensity-modulated radiotherapy for treatment of locally advanced non-small-cell lung cancer: a retrospective clinical study

OBJECTIVE

To evaluate the clinical efficacy and safety of simultaneous integrated boost intensity-modulated radiotherapy (SIB-IMRT) for patients with locally advanced non-small-cell lung cancer (LANSCLC).

METHODS

48 patients with LANSCLC treated with SIB-IMRT from January 2010 to April 2012 were retrospectively analysed. A radiation dose of 45-63 Gy (median dose, 51.58 Gy) was delivered to the planning target volume (1.8-2.0 Gy daily fractions) simultaneously with 55.0-74.2 Gy (median dose, 63 Gy) to the planning gross tumour volume (2.00-2.25 Gy daily fractions). 45 patients received concurrent/sequential chemotherapy. The overall survival (OS), locoregional recurrence-free survival (LRFS) and progression-free survival (PFS) were estimated using the Kaplan-Meier method. Treatment-related pneumonitis and oesophagitis were graded according to the Common Terminology Criteria for Adverse Events v. 4.0.

RESULTS

By 1 July 2013, 29 of the 48 patients were dead. The median follow-up time for the survivors was 28 months (19-44 months). The median OS and PFS were 21 and 14 months, respectively. The median LRFS time was not reached. The 2-year LRFS, OS and PFS were 62.5%, 45.1% and 28.0%, respectively. Two patients experienced Grade 3 treatment-related pneumonitis, two patients experienced Grade 5 treatment-related pneumonitis and two patients had ≥Grade 3 oesophagitis.

CONCLUSION

SIB-IMRT appears to be an effective therapeutic option in patients with LANSCLC and warrants further evaluation with increased number of patients in prospective clinical trials.

ADVANCES IN KNOWLEDGE

This study explores the feasibility of delivering tumoricidal doses of radiation to primary lesions in non-small-cell lung cancer.

Death-associated protein-3, DAP-3, correlates with preoperative chemotherapy effectiveness and prognosis of gastric cancer patients following perioperative chemotherapy and radical gastrectomy

Background:

DAP3 is a member of the death-associated protein (DAP) family and is characterised by proapoptotic function. It is involved in both exogenous and endogenous apoptotic pathways. In our previous studies, apoptotic level was found to be correlated with the effectiveness of preoperative chemotherapy. The effectiveness of preoperative chemotherapy was also associated with the overall effectiveness of the combined therapy and prognosis. The present study aimed to investigate the role of DAP3 in the evaluation of preoperative chemotherapy effectiveness and its ability to predict prognosis in gastric cancer.

Methods:

Quantitative PCR and immunohistochemistry staining were performed in 87 patients who received combined therapy. Knockdown of DAP3 was conducted in gastric cancer cell lines to investigate its impact on cell growth, migration, adhesion and invasion. Tolerance to chemotherapy agents was determined by assessing apoptosis and caspase-3.

Results:

Higher DAP3 expression in gastric tumours was correlated with better prognosis. Knockdown of DAP3 expression promoted cell migration and enhanced resistance to chemotherapy by inhibiting apoptosis.

Conclusion:

DAP3 is a potential molecular marker for response to preoperative chemotherapy and for predicting prognosis in gastric cancer patients treated with neoadjuvant chemotherapy and gastrectomy.

Brain inflammation and microglia: facts and misconceptions

THE INFLAMMATION THAT ACCOMPANIES ACUTE INJURY HAS DUAL FUNCTIONS: bactericidal action and repair. Bactericidal functions protect damaged tissue from infection, and repair functions are initiated to aid in the recovery of damaged tissue. Brain injury is somewhat different from injuries in other tissues in two respects. First, many cases of brain injury are not accompanied by infection: there is no chance of pathogens to enter in ischemia or even in traumatic injury if the skull is intact. Second, neurons are rarely regenerated once damaged. This raises the question of whether bactericidal inflammation really occurs in the injured brain; if so, how is this type of inflammation controlled? Many brain inflammation studies have been conducted using cultured microglia (brain macrophages). Even where animal models have been used, the behavior of microglia and neurons has typically been analyzed at or after the time of neuronal death, a time window that excludes the inflammatory response, which begins immediately after the injury. Therefore, to understand the patterns and roles of brain inflammation in the injured brain, it is necessary to analyze the behavior of all cell types in the injured brain immediately after the onset of injury. Based on our experience with both in vitro and in vivo experimental models of brain inflammation, we concluded that not only microglia, but also astrocytes, blood inflammatory cells, and even neurons participate and/or regulate brain inflammation in the injured brain. Furthermore, brain inflammation played by these cells protects neurons and repairs damaged microenvironment but not induces neuronal damage.

Microglia actively regulate the number of functional synapses

Microglia are the immunocompetent cells of the central nervous system. In the physiological setting, their highly motile processes continually survey the local brain parenchyma and transiently contact synaptic elements. Although recent work has shown that the interaction of microglia with synapses contributes to synaptic remodeling during development, the role of microglia in synaptic physiology is just starting to get explored. To assess this question, we employed an electrophysiological approach using two methods to manipulate microglia in culture: organotypic hippocampal brain slices in which microglia were depleted using clodronate liposomes, and cultured hippocampal neurons to which microglia were added. We show here that the frequency of excitatory postsynaptic current increases in microglia-depleted brain slices, consistent with a higher synaptic density, and that this enhancement ensures from the loss of microglia since it is reversed when the microglia are replenished. Conversely, the addition of microglia to neuronal cultures decreases synaptic activity and reduces the density of synapses, spine numbers, surface expression of AMPA receptor (GluA1), and levels of synaptic adhesion molecules. Taken together, our findings demonstrate that non-activated microglia acutely modulate synaptic activity by regulating the number of functional synapses in the central nervous system.

Periodontal tissue engineering with stem cells from the periodontal ligament of human retained deciduous teeth

BACKGROUND AND OBJECTIVE

Periodontal ligament stem cells from human permanent teeth (PePDLSCs) have been investigated extensively in periodontal tissue engineering and regeneration. However, little knowledge is available on the periodontal ligament stem cells from human retained deciduous teeth (DePDLSCs). This study evaluated the potential of DePDLSCs in periodontal tissue regeneration.

MATERIAL AND METHODS

DePDLSCs were isolated and purified by limited dilution. The characteristics of DePDLSCs were evaluated and compared with PePDLSCs both in vitro and in vivo.

RESULTS

DePDLSCs presented a higher proliferation rate and colony-forming capacity than PePDLSCs in vitro. During the osteogenic induction, alkaline phosphatase (ALP) activity, mineralized matrix formation and expression of mineralization-related genes, including runt-related transcription factor 2 (RUNX2), ALP, collagen type I (COLI) and osteocalcin (OCN) were significantly enhanced in DePDLSCs compared with PePDLSCs. Furthermore, DePDLSC cell sheets showed a stronger synthesis of collagen type I in the extracellular matrix than did PePDLSC cell sheets. After in vivo transplantation, DePDLSC cell sheets recombined with human dentin blocks were able to generate new cementum/periodontal ligament-like tissues.

CONCLUSION

Our findings suggest that DePDLSCs can be used as a promising candidate for periodontal tissue engineering.

p53 opens the mitochondrial permeability transition pore to trigger necrosis

Ischemia-associated oxidative damage leading to necrosis is a major cause of catastrophic tissue loss, and elucidating its signaling mechanism is therefore of paramount importance. p53 is a central stress sensor responding to multiple insults, including oxidative stress to orchestrate apoptotic and autophagic cell death. Whether p53 can also activate oxidative stress-induced necrosis is, however, unknown. Here, we uncover a role for p53 in activating necrosis. In response to oxidative stress, p53 accumulates in the mitochondrial matrix and triggers mitochondrial permeability transition pore (PTP) opening and necrosis by physical interaction with the PTP regulator cyclophilin D (CypD). Intriguingly, a robust p53-CypD complex forms during brain ischemia/reperfusion injury. In contrast, reduction of p53 levels or cyclosporine A pretreatment of mice prevents this complex and is associated with effective stroke protection. Our study identifies the mitochondrial p53-CypD axis as an important contributor to oxidative stress-induced necrosis and implicates this axis in stroke pathology.

Targeted therapy via oral administration of attenuated Salmonella expression plasmid-vectored Stat3-shRNA cures orthotopically transplanted mouse HCC

The development of RNA interference-based cancer gene therapies has been delayed due to the lack of effective tumor-targeting delivery systems. Attenuated Salmonella enterica serovar Typhimurium (S. Typhimurium) has a natural tropism for solid tumors. We report here the use of attenuated S. Typhimurium as a vector to deliver shRNA directly into tumor cells. Constitutively activated signal transducer and activator of transcription 3 (Stat3) is a key transcription factor involved in both hepatocellular carcinoma (HCC) growth and metastasis. In this study, attenuated S. Typhimurium was capable of delivering shRNA-expressing vectors to the targeted cancer cells and inducing RNA interference in vivo. More importantly, a single oral dose of attenuated S. Typhimurium carrying shRNA-expressing vectors targeting Stat3 induced remarkably delayed and reduced HCC (in 70% of mice). Cancer in these cured mice did not recur over 2 years following treatment. These data demonstrated that RNA interference combined with Salmonella as a delivery system may offer a novel clinical approach for cancer gene therapy.

[Zero-stress state of renal artery in spontaneously hypertensive rats]

By observing the opening angle of the renal artery, the zero-stress state of the renal artery was studied in spontaneously hypertensive rats (SHR) prior to and posterior to their hypertension, and the role of endogenous angiotensin II (Ang II) and endothelin (ET) on the zero-stress state was studied by giving SHR Losartan(AT1 receptor antagonist of Ang II) and BMS-182874 (an A type receptor antagonist of ET) respectively. The opening angle of the renal artery in SHR with established hypertension was much greater than that in wistar-Kyoto rats(WKY) (114.2 +/- 42.2 vs 70.2 +/- 30.4, P < 0.01). The opening angles of the renal artery in SHR treated with Losartan and BMS-182874 were much smaller than those in control SHR. The opening angles of the renal artery in Losartan-treated and BMS-182874-treated SHR were 65.9 +/- 32.7 and 66.6 +/- 41.54 respectively. The results suggest that non-unequal growth exists in the renal arterial wall in SHR with established hypertension and the residual stress and strain in SHR are greater than those in age-matched WKY. Endogenous Ang II and ET may play a role in the changes of zero-stress state in SHR with hypertension.

[Remodeling and biomechanical properties of thoracic aorta in spontaneously hypertensive rats]

Morphometry and microstructure of thoracic aorta of spontaneously hypertensive rats (SHR) at different periods before and after hypertension were studied quantitatively by histological method and computer image analysis. We also observed the changes of opening angle in the zero-stress state and the relationship between pressure and diameter in SHR during established hypertension. The results showed that with blood pressure chronically increasing, there was a significant increase in morphometric parameters and microstructure parameters of the thoracic aorta in SHR. The zero-stress state of opening angle in SHR during established hypertension increased significantly. These reults suggest that aortic structural remodeling in hypertension such as thickness of vascular wall and disproportional increase of collagen may lead to decrease in distensibility of the aorta in SHR. The structural remodeling and changes of mechanical properties in aorta may contribute to the important pathophysiology of hypertension-induced complications.

[Sequencing and analysis of the NS5 region of HGV/GBV-C gene]

To study the genomic organization of non structural region 5 of HGV in China, 186 nucleotides of NS5 region of HGV were amplified, cloned and sequenced. The data were analyzed with computer programs. The results indicated that the gene sequence homology between 2 HGV isolates in this study was 95.2%. The comparison of these 2 isolates and 3 foreign isolates reported previously showed that the sequence homology was in the range of 84.4% to 92.4%, and was obvious by divergent from the foreign isolates. The results make us consider that HGV may have different genotypes, after a further inspection into the gene sequence of each region of HGV. The 2 isolates were from the sera collected in 1984, therefore the existence of HGV infection in Harbin was retrospectively traced to 1980s.

Computerized case-based instructional system for computed tomography and magnetic resonance imaging of brain tumors

RATIONALE AND OBJECTIVES

A computerized system that applies the case-based approach to training radiologists to diagnose brain tumors was designed. The authors attempted to provide residents a tool that supports their visual memory and inducts case-based reasoning.

METHODS

A relational database with a digital image library was implemented and incorporated into a computer aided instruction environment based on case presentation. An indexing system was structured around case features (case history and radiologic findings). "If-then" type rules were used to control the search direction within the case library and to generate lists of diagnostic hypotheses. The indexing system was evaluated against cases "known" to the system.

RESULTS

The current case library consists of 122 cases with 640 digitized images (computed tomography and magnetic resonance imaging). The accuracy of retrieval for "known" to the system cases was 80.7%.

CONCLUSIONS

A case library stored on a personal computer can be efficiently searched for a combination of radiologic findings and can offer quality images for comparison to the case in question. A case library is a source of the information that may be used by different teaching applications.