FDG-PET lymphoma demonstration project invitational workshop

The proceedings of a workshop focusing on a project to evaluate the use of fluorodeoxyglucose-positron emission tomography (FDG-PET) as a tool to measure treatment response in non-Hodgkin lymphoma (NHL) are described. Sponsored by the Leukemia & Lymphoma Society, the Foundation of the National Institutes of Health, and the National Cancer Institute, and attended by representatives of the Food and Drug Administration, the Centers for Medicare and Medicaid Services, and scientists and clinical researchers from academia and the pharmaceutical and medical imaging industries, the workshop reviewed the etiology and current standards of care for NHL and proposed the development of a clinical trial to validate FDG-PET imaging techniques as a predictive biomarker for cancer therapy response. As organized under the auspices of the Oncology Biomarker Qualification Initiative, the three federal health agencies and their private sector and nonprofit/advocacy group partners believe that FDG-PET not only demonstrates the potential to be used for the diagnosis and staging of many cancers but in particular can provide an early indication of therapeutic response that is well correlated with clinical outcomes for chemotherapy for this common form of lymphoma. The development of standardized criteria for FDG-PET imaging and establishment of procedures for transmission, storage, quality assurance, and analysis of PET images afforded by this demonstration project could streamline clinical trials of new treatments for more intractable forms of lymphoma and other cancers and, hence, accelerate new drug approvals.

Prediction of collagen orientation in articular cartilage by a collagen remodeling algorithm

OBJECTIVE

Tissue engineering is a promising method to treat damaged cartilage. So far it has not been possible to create tissue-engineered cartilage with an appropriate structural organization. It is envisaged that cartilage tissue engineering will significantly benefit from knowledge of how the collagen fiber orientation is directed by mechanical conditions. The goal of the present study is to evaluate whether a collagen remodeling algorithm based on mechanical loading can be corroborated by the collagen orientation in healthy cartilage.

METHODS

According to the remodeling algorithm, collagen fibrils align with a preferred fibril direction, situated between the positive principal strain directions. The remodeling algorithm was implemented in an axisymmetric finite element model of the knee joint. Loading as a result of typical daily activities was represented in three different phases: rest, standing and gait.

RESULTS

In the center of the tibial plateau the collagen fibrils run perpendicular to the subchondral bone. Just below the articular surface they bend over to merge with the articular surface. Halfway between the center and the periphery, the collagen fibrils bend over earlier, resulting in a thicker superficial and transitional zones. Near the periphery fibrils in the deep zone run perpendicular to the articular surface and slowly bend over to angles of -45 degrees and +45 degrees with the articular surface.

CONCLUSION

The collagen structure as predicted with the collagen remodeling algorithm corresponds very well with the collagen structure in healthy knee joints. This remodeling algorithm is therefore considered to be a valuable tool for developing loading protocols for tissue engineering of articular cartilage.

A composition-based cartilage model for the assessment of compositional changes during cartilage damage and adaptation

OBJECTIVE

The composition of articular cartilage changes with progression of osteoarthritis. Since compositional changes are associated with changes in the mechanical properties of the tissue, they are relevant for understanding how mechanical loading induces progression. The objective of this study is to present a computational model of articular cartilage which enables to study the interaction between composition and mechanics.

METHODS

Our previously developed fibril-reinforced poroviscoelastic swelling model for articular cartilage was combined with our tissue composition-based model. In the combined model both the depth- and strain-dependencies of the permeability are governed by tissue composition. All local mechanical properties in the combined model are directly related to the local composition of the tissue, i.e., to the local amounts of proteoglycans and collagens and to tissue anisotropy.

RESULTS

Solely based on the composition of the cartilage, we were able to predict the equilibrium and transient response of articular cartilage during confined compression, unconfined compression, indentation and two different 1D-swelling tests, simultaneously.

CONCLUSION

Since both the static and the time-dependent mechanical properties have now become fully dependent on tissue composition, the model allows assessing the mechanical consequences of compositional changes seen during osteoarthritis without further assumptions. This is a major step forward in quantitative evaluations of osteoarthritis progression.

Depth-dependent Compressive Equilibrium Properties of Articular Cartilage Explained by its Composition

For this study, we hypothesized that the depth-dependent compressive equilibrium properties of articular cartilage are the inherent consequence of its depth-dependent composition, and not the result of depth-dependent material properties. To test this hypothesis, our recently developed fibril-reinforced poroviscoelastic swelling model was expanded to include the influence of intra- and extra-fibrillar water content, and the influence of the solid fraction on the compressive properties of the tissue. With this model, the depth-dependent compressive equilibrium properties of articular cartilage were determined, and compared with experimental data from the literature. The typical depth-dependent behavior of articular cartilage was predicted by this model. The effective aggregate modulus was highly strain-dependent. It decreased with increasing strain for low strains, and increases with increasing strain for high strains. This effect was more pronounced with increasing distance from the articular surface. The main insight from this study is that the depth-dependent material behavior of articular cartilage can be obtained from its depth-dependent composition only. This eliminates the need for the assumption that the material properties of the different constituents themselves vary with depth. Such insights are important for understanding cartilage mechanical behavior, cartilage damage mechanisms and tissue engineering studies.

Detection of malignant hematopoietic cells in cerebral spinal fluid previously diagnosed as atypical or suspicious

BACKGROUND

Involvement of the cerebrospinal fluid (CSF) by hematopoietic malignancies may be difficult to document by morphology alone. In cases with low numbers of cells or ambiguous morphology, the diagnoses of "atypical" or "suspicious" may be used. The significance of these diagnostic terms in this scenario has not been well established.

METHODS

Between January 2000 and July 2004, 32 patients with known lymphoma or leukemia and an initial diagnosis of "atypical" or "suspicious" using morphologic criteria were identified. Subsequent flow cytometry (FC) and cytologic data from these patients were evaluated.

RESULTS

Of the 32 patients with an initial diagnosis of "atypical" or "suspicious," 40.6% (n = 13) had negative first and subsequent FC and morphologic evaluation of their CSF samples with follow-up up to 1 year. Nineteen patients (59.4%) had malignant hematopoietic cells identified in subsequent CSF samples by cytology and/or FC.

CONCLUSIONS

In patients with a previous history of lymphoma or a hematopoietic malignancy, a majority of the patients (59.4%) with an "atypical" or "suspicious" diagnosis on CSF will ultimately have malignant cells identified in the CSF by cytology and/or FC. Many of these patients can be identified more expediently with the concurrent utilization of flow cytometry.

Fluorodeoxyglucose positron emission tomography (FDG-PET) for monitoring lymphadenopathy in the autoimmune lymphoproliferative syndrome (ALPS)

Autoimmune lymphoproliferative syndrome (ALPS) is associated with mutations that impair the activity of lymphocyte apoptosis proteins, leading to chronic lymphadenopathy, hepatosplenomegaly, autoimmunity, and an increased risk of lymphoma. We investigated the utility of fluorodeoxyglucose positron emission tomography (FDG-PET) in discriminating benign from malignant lymphadenopathy in ALPS. We report that FDG avidity of benign lymph nodes in ALPS can be high and, hence, by itself does not imply presence of lymphoma; but FDG-PET can help guide the decision for selecting which of many enlarged nodes in ALPS patients to biopsy when lymphoma is suspected.

The role of computational models in the search for the mechanical behavior and damage mechanisms of articular cartilage

Articular cartilage plays a vital role in the function of diarthrodial joints. Due to osteoarthritis degeneration of articular cartilage occurs. The initial event that triggers the pathological process of cartilage degeneration is still unknown. Cartilage damage due to osteoarthritis is believed to be mechanically induced. Hence, to investigate the initiation of osteoarthritis the stresses and strains in the cartilage must be determined. So far the most common method to accomplish that is finite element analysis. This paper provides an overview of computational descriptions developed for this purpose, and what they can be used for. Articular cartilage composition and structure are discussed in relation with degenerative changes, and how these affect mechanical properties.

A comparison between mechano-electrochemical and biphasic swelling theories for soft hydrated tissues

Biological tissues like intervertebral discs and articular cartilage primarily consist of interstitial fluid, collagen fibrils and negatively charged proteoglycans. Due to the fixed charges of the proteoglycans, the total ion concentration inside the tissue is higher than in the surrounding synovial fluid (cation concentration is higher and the anion concentration is lower). This excess of ion particles leads to an osmotic pressure difference, which causes swelling of the tissue. In the last decade several mechano-electrochemical models, which include this mechanism, have been developed. As these models are complex and computationally expensive, it is only possible to analyze geometrically relatively small problems. Furthermore, there is still no commercial finite element tool that includes such a mechano-electrochemical theory. Lanir (Biorheology, 24, pp. 173-187, 1987) hypothesized that electrolyte flux in articular cartilage can be neglected in mechanical studies. Lanir's hypothesis implies that the swelling behavior of cartilage is only determined by deformation of the solid and by fluid flow. Hence, the response could be described by adding a deformation-dependent pressure term to the standard biphasic equations. Based on this theory we developed a biphasic swelling model. The goal of the study was to test Lanir's hypothesis for a range of material properties. We compared the deformation behavior predicted by the biphasic swelling model and a full mechano-electrochemical model for confined compression and 1D swelling. It was shown that, depending on the material properties, the biphasic swelling model behaves largely the same as the mechano-electrochemical model, with regard to stresses and strains in the tissue following either mechanical or chemical perturbations. Hence, the biphasic swelling model could be an alternative for the more complex mechano-electrochemical model, in those cases where the ion flux itself is not the subject of the study. We propose thumbrules to estimate the correlation between the two models for specific problems.

A fibril-reinforced poroviscoelastic swelling model for articular cartilage

From a mechanical point of view, the most relevant components of articular cartilage are the tight and highly organized collagen network together with the charged proteoglycans. Due to the fixed charges of the proteoglycans, the cation concentration inside the tissue is higher than in the surrounding synovial fluid. This excess of ion particles leads to an osmotic pressure difference, which causes swelling of the tissue. The fibrillar collagen network resists straining and swelling pressures. This combination makes cartilage a unique, highly hydrated and pressurized tissue, enforced with a strained collagen network. Many theories to explain articular cartilage behavior under loading, expressed in computational models that either include the swelling behavior or the properties of the anisotropic collagen structure, can be found in the literature. The most common tests used to determine the mechanical quality of articular cartilage are those of confined compression, unconfined compression, indentation and swelling. All theories currently available in the literature can explain the cartilage response occurring in some of the above tests, but none of them can explain these for all of the tests. We hypothesized that a model including simultaneous mathematical descriptions of (1) the swelling properties due to the fixed-change densities of the proteoglycans and (2) the anisotropic viscoelastic collagen structure, can explain all these test simultaneously. To study this hypothesis we extended our fibril-reinforced poroviscoelastic finite element model with our biphasic swelling model. We have shown that the newly developed fibril-reinforced poroviscoelastic swelling (FPVES) model for articular cartilage can simultaneously account for the reaction force during swelling, confined compression, indentation and unconfined compression as well as the lateral deformation during unconfined compression. Using this theory it is possible to analyze the link between the collagen network and the swelling properties of articular cartilage.

The molecular basis of antiphospholipid syndrome

We herein review evidence that the phospholipid-binding protein beta2 glycoprotein-1 (beta2GPI) is a causative autoantigen in APS. Recent work suggests that the molecular regions in beta2GPI that facilitate autoimmunization are those that promote binding to negatively charged phospholipids by means of strong positive (anionic) charge and hydrophobicity. Although many common infections can cause antiphospholipid antibodies to be produced in humans, such postinfectious aPL are rarely associated with thromboses or pregnancy morbidity, the central features of antiphospholipid syndrome (APS). We propose that the causes of APS include those infectious agents that mimic the above molecular domains in beta2GPI. In people who are susceptible to APS, tolerance to self-beta2GPI and phospholipids is likely to be broken by foreign bacterial or viral proteins that contain such beta2GPI-like epitopes.

Flow cytometric immunophenotypic profiles of mature gamma delta T-cell malignancies involving peripheral blood and bone marrow

BACKGROUND

In this study we compared clinical findings with flow cytometric immunophenotypic results in a series of patients with aggressive and indolent gamma delta T-cell malignancies with peripheral blood and/or bone marrow involvement.

METHODS

Gamma delta T-cell malignancies were detected based on flow cytometric demonstration of an abnormal T-cell population staining positive with T-cell receptor gamma delta and confirmed by morphologic and clinical reviews. Clinical data were obtained through chart review and discussion with the patients' physicians.

RESULTS

Blood or bone marrow involvement was present in all patients. Hepatosplenic and cutaneous gamma delta T-cell lymphomas had an aggressive clinical course, whereas the gamma delta T-cell large granular lymphocyte (LGL) leukemias had an indolent course. Expressions of CD5, CD8, CD16, and CD57 differed in gamma delta T-cell LGL leukemia compared with hepatosplenic and cutaneous gamma delta T-cell lymphomas.

CONCLUSIONS

Gamma delta T-cell malignancies have a poor prognosis with the exception of gamma delta T-cell LGL leukemia (indolent process). Because CD57 expression is specific for gamma delta T-cell LGL leukemias, expression of this antigen may be associated with a more indolent clinical course. Because cutaneous gamma delta T-cell lymphoma can present with peripheral blood involvement, flow cytometric evaluation of peripheral blood is important in staging these patients.

Utilization of polymerase chain reaction on archival cytologic material: a comparison with fresh material with special emphasis on cerebrospinal fluids

Use of the polymerase chain reaction (PCR) for the detection of B- and T-cell clonality, Epstein-Barr virus (EBV) and Human Herpes Virus 8 (HHV 8) infection is gaining increasing importance as a diagnostic modality. These tests are usually performed on fresh specimens. There are instances when fresh material is not available and there is a clinical utility for the performance of PCR on archival material via slide scrape lysates (SSL). However, the suitability of archival material may be questioned. Records were searched for all archival cytology cases submitted for SSL molecular diagnostics tests since 1998. Results for each case were analyzed for PCR amplification status and individual test results. A randomly chosen control group of equivalent cytologic samples submitted fresh was evaluated for comparison of amplification status. In all, 241 PCR runs were performed on SSL of archival material from 112 cytologic samples (89 cerebrospinal fluids (CSFs), 13 fine-needle aspirates (FNAs), 10 effusions). Out of these samples, 95 (85%) had amplifiable DNA, as assessed by a positive reaction for glyceraldehyde phosphate dehydrogenase (GAPDH). For the control group, 320 PCR runs were performed on 112 fresh cytologic samples (89 CSFs, 13 FNAs, 10 effusions). In total, 102 samples (91%) had amplifiable DNA. There was no statistical difference in the amplification yield between the two groups (P = 0.2177). A morphologic review of 16 of the 17 SSL archival cytologic cases that did not show amplification revealed 11/16 to be of sparse cellularity. Molecular diagnostic tests are performed routinely on fresh cytologic samples with excellent results. At times critical decisions on patient care may need to be made when fresh tissue is not available for molecular diagnostic tests. SSL of archival cytologic material can be used with excellent results for molecular diagnostic tests when fresh material is not available or when the cytologic diagnosis needs further clarification.

Autoreactive, cytotoxic T lymphocytes specific for peptides derived from normal B-cell differentiation antigens in healthy individuals and patients with B-cell malignancies

PURPOSE

To investigate potential immunotherapeutic strategies in B lymphocytic malignancies we looked for CTLs recognizing CD19 and CD20 epitopes.

EXPERIMENTAL DESIGN

Three CD19 and CD20 peptides binding to HLA-A*0201 were identified and used to detect peptide specific CTLs by a quantitative real-time PCR to measure IFN-gamma mRNA expression in 23 healthy individuals and 28 patients (18 chronic lymphocytic leukemia (CLL), 7 follicular lymphoma, 2 acute lymphocytic leukemia, and 1 large cell lymphoma). Peptide-specific CTLs were expanded in culture with CD40-activated B cells to test lytic activity in three patients.

RESULTS

In healthy individuals, CD8+ T-cell responses were detected in one to CD19(74-82), in three to CD20(127-135), and three to CD20(188-196). Seven of 27 patients (6 with CLL) had CD8+ T cells recognizing CD19(74-82). Seven patients responded to CD20(127-135) and three to CD20(188-196). All were CLL patients. CD19(74-82)-specific CTLs from three patients were expanded over 4 weeks. These cells were HLA-A*0201 specific and lytic for peptide-loaded antigen-presenting cells but not to malignant or unpulsed B cells.

CONCLUSIONS

CTLs that recognize CD19 and CD20 epitopes exist in healthy individuals and may be increased in CLL patients. They are of low avidity and require high doses of peptide for activation. Strategies to increase T-cell avidity would be necessary for T-cell immunotherapeutic approaches using the peptides studied.

Stresses in the local collagen network of articular cartilage: a poroviscoelastic fibril-reinforced finite element study

Osteoarthritis (OA) is a multifactorial disease, resulting in diarthrodial joint wear and eventually destruction. Swelling of cartilage, which is proportional to the amount of collagen damage, is an initial event of cartilage degeneration, so damage to the collagen fibril network is likely to be one of the earliest signs of OA cartilage degeneration. We propose that the local stresses and strains in the collagen fibrils, which cause the damage, cannot be determined dependably without taking the local arcade-like collagen-fibril structure into account. We investigate this using a poroviscoelastic fibril-reinforced FEA model. The constitutive fibril properties were determined by fitting numerical data to experimental results of unconfined compression and indentation tests on samples of bovine patellar articular cartilage. It was demonstrated that with this model the stresses and strains in the collagen fibrils can be calculated. It was also exhibited that fibrils with different orientations at the same location can be loaded differently, depending on the local architecture of the collagen network. To the best of our knowledge, the present model is the first that can account for these features. We conclude that the local stresses and strains in the articular cartilage are highly influenced by the local morphology of the collagen-fibril network.

Recombinant immunotoxins for treating cancer

Recombinant immunotoxins are antibody-toxin chimeric molecules that kill cancer cells via binding to a surface antigen, internalization and delivery of the toxin moiety to the cell cytosol. In the cytosol, toxins catalytically inhibit a critical cell function and cause cell death. The antibody portion of the chimera targets antigens that are expressed preferentially on the surface of cancer cells. Truncated versions of either diphtheria toxin (DT) or Pseudomonas exotoxin (PE) can be used to construct fusions with cDNAs encoding antibody fragments or cell-binding ligands. Recombinant immunotoxins are routinely produced in E. coli and purified using standard chromatographic methods. Before they can be evaluated for anticancer activity in humans, recombinant immunotoxins undergo extensive preclinical testing. Immunotoxins must demonstrate cell-killing activity in tissue culture, antitumor activity in an animal model and have favorable pharmacokinetic and toxicity profiles. Candidate molecules with favorable characteristics are then evaluated in clinical trials. Here we report on the initial evaluation of BL22, a recombinant immunotoxin targeted to CD22 expressed on the surface of B-cell malignancies.

A computational model for collagen fibre remodelling in the arterial wall

As the interaction between tissue adaptation and the mechanical condition within tissues is complex, mathematical models are desired to study this interrelation. In this study, a mathematical model is presented to investigate the interplay between collagen architecture and mechanical loading conditions in the arterial wall. It is assumed that the collagen fibres align along preferred directions, situated in between the principal stretch directions. The predicted fibre directions represent symmetrically arranged helices and agree qualitatively with morphometric data from literature. At the luminal side of the arterial wall, the fibres are oriented more circumferentially than at the outer side. The discrete transition of the fibre orientation at the media-adventitia interface can be explained by accounting for the different reference configurations of both layers. The predicted pressure-radius relations resemble experimentally measured sigma-shaped curves. As there is a strong coupling between the collagen architecture and the mechanical loading condition within the tissue, we expect that the presented model for collagen remodelling is useful to gain further insight into the processes involved in vascular adaptation, such as growth and smooth muscle tone adaptation.