Optical coherence tomography for presurgical delineation of basal cell carcinomas on the face-A comparison with histopathology.

BACKGROUND: To minimize the risk of incomplete excision of basal cell carcinomas (BCC) the macroscopic tumor margins should be adequately defined. Optical coherence tomography (OCT) is a non-invasive imaging tool that can provide structural and vascular information about skin cancer lesions. The study objective was to compare the presurgical delineation of facial BCC by clinical examination, histopathology, and OCT imaging in tumors undergoing full excision. METHODS: Ten patients with BCC lesions on the face were examined clinically, with OCT and histopathology at 3-mm intervals, from the clinical lesion border and beyond the resection line. The OCT scans were evaluated blinded and a delineation estimate of each BCC lesion was made. The results were compared to the clinical and histopathologic results. RESULTS: OCT evaluations and histopathology were in agreement in 86.6% of the collected data points. In three cases the OCT scans estimated a reduction of the tumor size compared to the clinical tumor border set by the surgeon. CONCLUSION: The results of this study support the notion that OCT can have a role in the clinical daily practice by aiding clinicians in delineating BCC lesions before surgery.

Interventions to prevent preterm delivery in women with short cervix before fetoscopic laser surgery for twin-twin transfusion syndrome.

OBJECTIVE: Preoperative short cervical length (CL) remains a major risk factor for preterm birth after laser surgery for twin-twin transfusion syndrome (TTTS), but the optimal intervention to prolong pregnancy remains elusive. The objective of this study was to compare secondary methods for the prevention of preterm birth in twin pregnancies with TTTS undergoing fetoscopic laser photocoagulation (FLP), in the setting of a short cervix at the time of FLP, in five North American Fetal Treatment Network (NAFTNet) centers. METHODS: This was a secondary analysis of data collected prospectively at five NAFTNet centers, conducted from January 2013 to March 2020. Inclusion criteria were a monochorionic diamniotic twin pregnancy complicated by TTTS, undergoing FLP, with preoperative CL < 30 mm. Management options for a short cervix included expectant management, vaginal progesterone, pessary (Arabin, incontinence or Bioteque cup), cervical cerclage or a combination of two or more treatments. Patients were not included if the intervention was initiated solely on the basis of having a twin gestation rather than at the diagnosis of a short cervix. Demographics, ultrasound characteristics, operative data and outcomes were compared. The primary outcome was FLP-to-delivery interval. Propensity-score matching was performed, with each treatment group matched (1:1) to the expectant-management group for CL, in order to estimate the effect of each treatment on the FLP-to-delivery interval. RESULTS: A total of 255 women with a twin pregnancy complicated by TTTS and a short cervix undergoing FLP were included in the study. Of these, 151 (59%) were managed expectantly, 32 (13%) had vaginal progesterone only, 21 (8%) had pessary only, 21 (8%) had cervical cerclage only and 30 (12%) had a combination of treatments. A greater proportion of patients in the combined-treatment group had had a prior preterm birth compared with those in the expectant-management group (33% vs 9%; P = 0.01). Mean preoperative CL was shorter in the pessary, cervical-cerclage and combined-treatment groups (14-16 mm) than in the expectant-management and vaginal-progesterone groups (22 mm for both) (P < 0.001). There was no significant difference in FLP-to-delivery interval between the groups, nor in gestational age at delivery or the rate of live birth or neonatal survival. Vaginal progesterone was associated with a decrease in the risk of delivery before 28 weeks' gestation compared with cervical cerclage and combined treatment (P = 0.03). Using propensity-score matching for CL, cervical cerclage was associated with a reduction in FLP-to-delivery interval of 13 days, as compared with expectant management. CONCLUSIONS: A large proportion of pregnancies with TTTS and a short maternal cervix undergoing FLP were managed expectantly for a short cervix, establishing a high (62%) risk of delivery before 32 weeks in this condition. No treatment that significantly improved outcome was identified; however, there were significant differences in potential confounders and there were also likely to be unmeasured confounders. Cervical cerclage should not be offered as a secondary prevention for preterm birth in twin pregnancies with TTTS and a short cervix undergoing FLP. A large randomized controlled trial is urgently needed to determine the effects of treatments for the prevention of preterm birth in these pregnancies. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

[Expression of cancer testis (CT) antigens in pediatric and adolescent melanomas]. / Expression von Cancer-Testis(CT)-Antigenen in Melanomen des Kindes- und Jugendalters.

BACKGROUND: One of the main problems in the diagnostics of pediatric melanomas is the differentiation from benign dermal lesions typical for this age group, such as Spitz nevus. The biological behavior of pediatric melanomas differs considerably from that of melanomas in adults. MATERIAL AND METHODS: Cancer testis (CT) antigens are named after their typical expression pattern since they are present in various types of malignant tumors but in normal adult tissues are solely expressed in testicular germ cells. Because of this tumor-associated expression pattern, CT antigens are regarded as potential targets for vaccine-based immunotherapy of cancer and might be used as diagnostic tools in surgical pathology. In adults, melanoma is among the tumors showing a high incidence of CT antigen expression; however, while there is ample knowledge about adult melanomas, little is known about the presence of CT antigens in pediatric melanomas. Consequently, the expression of CT antigens MAGE-A1, MAGE-A4, CT7/MAGE-C1, NY-ESO-1, and GAGE was analyzed in a series of pediatric melanomas. The study was restricted to cases of metastatic disease and/or fatal outcome. A total of 12 cases were available and immunohistochemically analyzed with monoclonal antibodies (mAb). RESULTS: The expression of CT antigens was generally low and present in only 4 of 12 cases. This is in stark contrast to the expression of these antigens in adult melanomas. Moreover, the extent of expression was very limited with most cases showing only a focal CT antigen expression and only marked in very small tumor areas (<5%). CONCLUSION: Despite the low case numbers this study indicates that CT antigens are most likely not useful as diagnostic markers in pediatric melanomas or as targets for vaccine-based immunotherapy. It supports the notion that pediatric melanomas show a different biological behavior than their adult counterparts.

A monoclonal antibody interferes with TIMP-2 binding and incapacitates the MMP-2-activating function of multifunctional, pro-tumorigenic MMP-14/MT1-MMP.

Matrix metalloproteinases (MMPs) and, especially membrane type 1 (MT1)-MMP/MMP-14, are promising drug targets in malignancies. In contrast with multiple small-molecule and protein pan-inhibitors of MT1-MMP cleavage activity, the murine 9E8 monoclonal antibody targets the MMP-2-activating function of cellular MT1-MMP alone, rather than the general proteolytic activity and the pro-migratory function of MT1-MMP. Furthermore, the antibody does not interact in any detectable manner with other members of the membrane type (MT)-MMP family. The mechanism of this selectivity remained unknown. Using mutagenesis, binding and activity assays, and modeling in silico, we have demonstrated that the 9E8 antibody recognizes the MT-loop structure, an eight residue insertion that is specific for MT-MMPs and that is distant from the MT1-MMP active site. The binding of the 9E8 antibody to the MT-loop, however, prevents tissue inhibitor of metalloproteinases-2 (TIMP-2) association with MT1-MMP. As a result, the 9E8 antibody incapacitates the TIMP-2-dependent MMP-2-activating function alone rather than the general enzymatic activity of human MT1-MMP. The specific function of the 9E8 antibody we determined directly supports an essential, albeit paradoxical, role of the protein inhibitor (TIMP-2) in MMP-2 activation via a unique membrane-tethered mechanism. In this mechanism, the formation of a tri-molecular MT1-MMPTIMP-2MMP-2 complex is required for both the capture of the soluble MMP-2 proenzyme by cells and then its well-controlled conversion into the mature MMP-2 enzyme. In sum, understanding of the structural requirements for the 9E8 antibody specificity may pave the way for the focused design of the inhibitory antibodies against other individual MMPs.

MyMiCROscope: intelligent virtual microscopy in a blended learning model at Ulm University.

The growing diversity among students and the rapid increase in new technologies entering the system of higher education, demand reconsideration of traditional learning methods. To improve the individual student's learning situation we developed and integrated a novel virtual microscope, MyMiCROscope, into a face-to-face approach for teaching microscopic anatomy. The intelligent virtual microscope has not only enabled self-directed learning of the students at their individual learning speed independent of time and place but also offered new possibilities to interact with the user because it implements systematic annotations accessible from different operational levels. Furthermore the alteration of a sole instructor-led course into a blended learning model resulted in a change of the learning behaviour of the students: group work and social interactions were facilitated. The results of this study show the advantages that intelligent virtual microscopy incorporates for self-directed learning and that blended learning in undergraduate medical education is able to fulfil the individual needs of the students and support social interactions without disregarding practical skills.

Placental dysferlin expression is reduced in severe preeclampsia.

Dysferlin (DYSF) and myoferlin (MYOF), members of the ferlin family of membrane proteins, are co-expressed in human placental syncytiotrophoblast (STB). Although the role of these ferlin proteins in the placenta has yet to be established, it has been suggested that DYSF and MYOF may contribute to the stability of the apical STB plasma membrane. The release of STB-derived cellular debris increases in the setting of preeclampsia (PE), suggesting relative destabilization of the hemochorial interface. To test whether PE was associated with alterations in placental expression of DYSF and/or MYOF, a cross-sectional study was performed using specimens of villous placenta collected form women with severe PE (n=10) and normotensive controls (n=10). DYSF and MYOF expression were examined using quantitative real-time RT-PCR, immunoblotting, and immunofluorescence labeling of tissue specimens. Placental DYSF expression was 57% lower at the mRNA level (p=0.03) and 38% lower at the protein level (p=0.026) in severe PE as compared to normotensive subjects. There were no differences in placental MYOF protein or mRNA expression between these groups. No appreciable changes in the distribution of DYSF or MYOF within placental villi was observed in PE relative to control specimens. We conclude that DYSF expression is reduced in severe PE relative to gestational age-matched controls. As DYSF has a role in membrane repair, these data suggest a role for DYSF in the stability of the apical STB plasma membrane and may account, at least in part, for the increased shedding of microparticles from this membrane in PE.

The lethal paraphiliac syndrome: accidental autoerotic deaths in four women and a review of the literature.

Four previously unpublished cases of female asphyxiophilia are presented. All women were found immobilised by obviously self-tied ropes, string or handcuffs. The women, who were alone at the time of death, died of a lethal paraphilia. The autopsies revealed asphyxiation as the cause of death, caused in two cases by suffocation as a result of hanging and strangulation and in the other two cases by plastic bags placed over the individuals head. In one case there was additional evidence at the scene that the deceased had inhaled ether. In none of the four cases was there any indication that the asphyxiation was due to homicide or suicide. Thus they can be described as accidental autoerotic deaths (AAD). The four cases closely mirror findings from scenes of male AADs, although autoerotic practices are generally believed to be rarer among females than in males.

The urokinase plasminogen activator receptor-associated protein/endo180 is coexpressed with its interaction partners urokinase plasminogen activator receptor and matrix metalloprotease-13 during osteogenesis.

The urokinase plasminogen activator receptor-associated protein/Endo180 (uPARAP/Endo180) is a newly discovered member of the macrophage mannose receptor family that was reported to interact with ligand-bound urokinase plasminogen activator receptor (uPAR), matrix metalloprotease-13 (MMP-13), and collagen V on the cell surface. We have determined the sites of expression of this novel receptor during murine postimplantation development. uPARAP/Endo180 was expressed in all tissues undergoing primary ossification, including the developing bones of the viscerocranium and calvarium that ossify intramembranously, and developing long bones undergoing endochondral ossification. uPARAP/Endo180 mRNA was expressed by both immature osteoblasts and by mature osteocalcin-producing osteoblasts-osteocytes, and was coexpressed with MMP-13. Interestingly, osteoblasts also expressed uPAR. Besides bone-forming tissues, uPARAP/Endo180 expression was detected only in a mesenchymal condensation of the midbrain and in the developing lungs. The data suggest a function of this novel protease receptor in bone development, possibly mediated through its interactions with uPAR, MMP-13, or collagen V.

Urokinase-catalysed cleavage of the urokinase receptor requires an intact glycolipid anchor.

Urokinase (uPA) has the striking ability to cleave its receptor, uPAR, thereby inactivating the binding potential of this molecule. Here we demonstrate that the glycosylphosphatidylinositol (GPI) anchor of uPAR, which is attached to the third domain, is an important determinant in governing this reaction, even though the actual cleavage occurs between the first and second domains. Purified full-length GPI-anchored uPAR (GPI-uPAR) proved much more susceptible to uPA-mediated cleavage than recombinant truncated soluble uPAR (suPAR), which lacks the glycolipid anchor. This was not a general difference in proteolytic susceptibility since GPI-uPAR and suPAR were cleaved with equal efficiency by plasmin. Since the amino acid sequences of GPI-uPAR and suPAR are identical except for the C-terminal truncation, the different cleavage patterns suggest that the two uPAR variants differ in the conformation or the flexibility of the linker region between domains 1 and 2. This was supported by the fact that an antibody to the peptide AVTYSRSRYLE, amino acids 84-94 in the linker region, recognizes GPI-uPAR but not suPAR. This difference in the linker region is thus caused by a difference in a remote hydrophobic region. In accordance with this model, when the hydrophobic lipid moiety was removed from the glycolipid anchor by phospholipase C, low concentrations of uPA could no longer cleave the modified GPI-uPAR and the reactivity to the peptide antibody was greatly decreased. Naturally occurring suPAR, purified from plasma, was found to have a similar resistance to uPA cleavage as phospholipase C-treated GPI-uPAR and recombinant suPAR.

The urokinase receptor associated protein (uPARAP/endo180): a novel internalization receptor connected to the plasminogen activation system.

The urokinase-mediated plasminogen activation system plays a central role in the extracellular proteolytic degradation reactions in cancer invasion. In this review article we discuss a number of recent findings identifying a new cellular receptor protein, uPARAP, that interacts with components of this proteolytic system. uPARAP is a high molecular weight type-1 membrane protein, belonging to the macrophage mannose receptor protein family. On the surface of certain cells, uPARAP forms a ternary complex with the pro-form of the urokinase-type plasminogen activator (uPA) and its primary receptor (uPAR). While the biological consequences of this reaction have not yet been verified experimentally, a likely event is ligand internalization because uPARAP is a constitutively recycling internalization receptor. uPARAP also binds at least one component, collagen type V, in the extracellular matrix meshwork, pointing to a potential role in proteolytic substrate presentation. Additional ligands have been proposed, including collagenase-3 and glycoproteins capable of interacting with one of the multiple carbohydrate recognition-type domains of uPARAP. In various adult tissues uPARAP is present on fibroblasts, macrophages and a subset of endothelial cells. In fetal tissues the protein has also been demonstrated in certain bone forming regions. Hypotheses on the physiological function of uPARAP include regulatory roles in extracellular proteolysis. This type of function would be likely to direct the local turnover of proteases and their substrate degradation products and thus may add to the complicated interplay between several cell types in governing restricted tissue degradation.

Differential binding of urokinase and peptide antagonists to the urokinase receptor: evidence from characterization of the receptor in four primate species.

The urokinase plasminogen activator receptor (uPAR) is a membrane protein active in localizing the plasminogen activation cascade system on the cell surface. The resulting pericellular proteolytic activity is responsible for degradation reactions in the extracellular matrix that are needed for the invasion of cancer cells, thus making uPAR a potential target for anti-invasive therapy based on binding antagonists. A remarkable property of the uPA-uPAR system is a pronounced species specificity in ligand recognition. We have now cloned and studied uPAR from four primate species and show that even though these sequences contain very few substitutions relative to the human uPAR, the receptor protein products differ markedly in terms of ligand selectivity. Thus, a well described competitive peptide antagonist directed against the human uPAR reacts with only one of the monkey receptors (chimpanzee uPAR), in spite of the fact that uPAR from all of the four species cross-reacts with human uPA. Notably, uPAR from African green monkey, which is completely devoid of reactivity with the peptide, contains only three substitutions relative to chimpanzee uPAR in the molecular regions critical for binding. These findings aid the elucidation of the structure/function relationship of uPAR and, unexpectedly, identify a structural distinction governing the binding of uPA and a very similar peptide antagonist.

Plasminogen-independent initiation of the pro-urokinase activation cascade in vivo. Activation of pro-urokinase by glandular kallikrein (mGK-6) in plasminogen-deficient mice.

The plasminogen activation (PA) system is involved in the degradation of fibrin and various extracellular matrix proteins, taking part in a number of physiological and pathological tissue remodeling processes including cancer invasion. This system is organized as a classical proteolytic cascade, and as for other cascade systems, understanding the physiological initiation mechanism is of central importance. The attempts to identify initiation routes for activation of the proform of the key enzyme urokinase-type plasminogen activator (pro-uPA) in vivo have been hampered by the strong activator potency of the plasmin, that is generated during the progress of the cascade. Using gene-targeted mice deficient in plasminogen (Plg -/- mice) [Bugge, T. H., Flick, M. J., Daugherty, C. C., and Degen, J. L. (1995) Genes Dev. 9, 794-807], we have now demonstrated and identified a component capable of initiating the cascade by activating pro-uPA. The urine from Plg -/- mice contained active two-chain uPA as well as a proteinase capable of activating exogenously added pro-uPA. The active component was purified and identified by mass spectrometry-based peptide mapping as mouse glandular kallikrein mGK-6 (true tissue kallikrein). The pro-uPA converting activity of the mGK-6 enzyme, as well as its ability to cleave a synthetic substrate for glandular kallikrein, was inhibited by the serine proteinase inhibitor leupeptin but not by other serine proteinase inhibitors such as aprotinin, antithrombin III, or alpha(1)-antitrypsin. We suggest that mouse glandular kallikrein mGK-6 is an activator of pro-uPA in the mouse urinary tract in vivo. Since this kallikrein is expressed in a number of tissues and also occurs in plasma, it can also be considered a candidate for a physiological pro-uPA activator in other locations.

A urokinase receptor-associated protein with specific collagen binding properties.

The plasminogen activation cascade system, directed by urokinase and the urokinase receptor, plays a key role in extracellular proteolysis during tissue remodeling. To identify molecular interaction partners of these trigger proteins on the cell, we combined covalent protein cross-linking with mass spectrometry based methods for peptide mapping and primary structure analysis of electrophoretically isolated protein conjugates. A specific tri-molecular complex was observed upon addition of pro-urokinase to human U937 cells. This complex included the urokinase receptor, pro-urokinase, and an unknown, high molecular weight urokinase receptor-associated protein. The tryptic peptide mixture derived from a cross-linked complex of pro-urokinase and the latter protein was analyzed by nanoelectrospray tandem mass spectrometric sequencing. This analysis identified the novel protein as the human homologue of a murine membrane-bound lectin with hitherto unknown function. The human cDNA was cloned and sequenced. The protein, designated uPARAP, is a member of the macrophage mannose receptor protein family and contains a putative collagen-binding (fibronectin type II) domain in addition to 8 C-type carbohydrate recognition domains. It proved capable of binding strongly to a single type of collagen, collagen V. This collagen binding reaction at the exact site of plasminogen activation on the cell may lead to adhesive functions as well as a contribution to cellular degradation of collagen matrices.

[The hospital autopsy. An important factor in hospital quality assurance]. / Hospitalsobduktionen. En vaesentlig faktor i sygehusenes kvalitetssikring.

The frequency of hospital autopsies declined after a new autopsy law was introduced in 1990. The purpose of the study was to evaluate the frequency of autopsy over a six month period in Copenhagen county. We compared the causes of death recorded on death certificates with autopsy findings. One thousand seven hundred and four hospital deaths were followed by 534 (31%) autopsies. Neither age of the decreased nor length of the admission seemed to influence the autopsy frequency. In 20% of the autopsies we found valuable new informations compared to the causes of death recorded on the death certificates.

Evaluation of pneumonia diagnosis in intensive care patients.

The aims of this study were to investigate the frequency of bronchopneumonia diagnosed by histological criteria among autopsied intensive care unit (ICU) patients and to compare these with rates of pneumonia diagnosed by conventional clinical methods. The study material comprised 141 autopsied ICU patients from 7 ICUs in university hospitals in Copenhagen from a 1-y period. A total of 20 lung tissue specimens were sampled from each patient and the histopathological diagnoses were classified as no, mild, moderate or severe bronchopneumonia. Inter-observer variation was calculated using kappa statistics. Demographic data and diagnoses of pneumonia were registered from the patient files. Twenty-six percent of the patients had pneumonia diagnosed whilst in the ICU. Histological evidence of pneumonia, found for every second patient, was regarded as the gold standard. Diagnosis of pneumonia in the ICU had a sensitivity of 29% and if diagnoses of pneumonia during the month before ICU-admission were included, a sensitivity of 60% was found. Specificity for pneumonia diagnosed in the ICU was 77%. The percentage of all ICU-patients with pneumonia was calculated to be between 36% and 56%, depending on the extent of excess mortality attributable to pneumonia. Pulmonary segments with histologically diagnosed pneumonic lesions were distributed diffusely, although the upper segments tended to be affected less. Nearly all patients had other histopathological findings than bronchopneumonia. The reliability coefficient among the 6 pathologists was found to be moderately good (kappa = 0.45).

Different mechanisms are involved in the antibody mediated inhibition of ligand binding to the urokinase receptor: a study based on biosensor technology.

Certain monoclonal antibodies are capable of inhibiting the biological binding reactions of their target proteins. At the molecular level, this type of effect may be brought about by completely different mechanisms, such as competition for common binding determinants, steric hindrance or interference with conformational properties of the receptor critical for ligand binding. This distinction is central when employing the antibodies as tools in the elucidation of the structure-function relationship of the protein in question. We have studied the effect of monoclonal antibodies against the urokinase plasminogen activator receptor (uPAR), a protein located on the surface of various types of malignant and normal cells which is involved in the direction of proteolytic degradation reactions in the extracellular matrix. We show that surface plasmon resonance/biomolecular interaction analysis (BIA) can be employed as a highly useful tool to characterize the inhibitory mechanism of specific antagonist antibodies. Two inhibitory antibodies against uPAR, mAb R3 and mAb R5, were shown to exhibit competitive and non-competitive inhibition, respectively, of ligand binding to the receptor. The former antibody efficiently blocked the receptor against subsequent ligand binding but was unable to promote the dissociation of a preformed receptor-ligand complex. The latter antibody was capable of binding the preformed complex, forming a transient trimolecular assembly, and promoting the dissociation of the uPA/uPAR complex. The continuous recording of binding and dissociation, obtained in BIA, is central in characterizing these phenomena. The identification of a non-competitive inhibitory mechanism against this receptor reveals the presence of a determinant which influences the binding properties of a remote site in the molecular structure and which could be an important target for a putative synthetic antagonist.

[Intestinal ganglioneuromatosis--a rare cause of chronic diarrhea]. / Intestinal ganglioneuromatose--en sjoelden årsag til kronisk diaré.

A case of intestinal ganglioneuromatosis is reported. The symptoms were watery diarrhoea and abdominal pain of several months duration. Endoscopic examination of the oesophagus, ventricle, duodenum, colon and rectum was normal. Mucosal biopsies from colon and rectum revealed ganglia cells and thin nerve fibres in the lamina mucosa, giving the diagnosis ganglioneuromatosis. As a consequence of the diagnosis thyroid scintigraphy, CT-scanning of the thyroid and adrenal glands and measurement of serum calcitonin and gastrin were performed. The tests revealed an intrathoracic nodular struma, and beyond this no abnormalities. The relation of intestinal ganglioneuromatosis to Multiple Endocrine Neoplasia type II b is discussed and the necessity of performing mucosal-biopsy from endoscopically normal colonic mucosa in cases of chronic diarrhoea is emphasised.

Rheumatoid nodules of the larynx.

A 67-year-old woman with rheumatoid arthritis was hospitalized because of dysphagia and severe nodulosis. Over a two-year period the patient had been treated with methotrexate. A computed tomography (CT) scan of the neck showed a 2 x 2 cm large tumour behind the top left lateral thyroid cartilage. A biopsy taken during direct laryngoscopy showed it was a rheumatic nodule. Treatment with colchicine reduced the patient's dysphagia. As methotrexate is used increasingly in the treatment of rheumatoid arthritis and as this particular drug causes rheumatic nodules in five to 10 per cent of the patients, it must be foreseen that the incidence of nodules in the upper airways will increase.

ELISA for complexes between urokinase-type plasminogen activator and its receptor in lung cancer tissue extracts.

A sandwich-type ELISA has been developed for the assessment of complexes between urokinase-type plasminogen activator (uPA) and its receptor (uPAR) in extracts of squamous cell lung carcinomas. The assay is based on a combination of rabbit polyclonal anti-uPA antibodies and a biotinylated mouse anti-uPAR monoclonal antibody (MAb). The detection limit of the assay is approximately 0.5 fmol/ml. A linear dose-response is obtained with up to 40 fmol/ml of uPA:uPAR complexes, while uPA and uPAR separately do not cause any response in the ELISA. A buffer which has been used previously for optimal extraction of uPAR yields the highest amounts of uPA:uPAR complexes. Absorption of tumor extracts with anti-uPA or anti-uPAR MAbs results in a complete disappearance of the ELISA signal, demonstrating the specificity of the ELISA. The recovery of chemically cross-linked uPA:uPAR complexes added to tumor extracts varies between 80% and 105%. The intra- and inter-assay variation coefficients are 5.3% and 9.8%, respectively. Furthermore, a peptide antagonist for uPAR was employed to evaluate de novo uPA:uPAR complex formation during tumor tissue extraction and the immunoassay procedure. Our results strongly indicate that de novo complex formation is a major factor to consider and that complexes analyzed in the presence of this antagonist represent original uPA:uPAR complexes present prior to tumor tissue processing. The present ELISA appears suitable for studying the potential prognostic impact of uPA:uPAR complexes in lung tumor tissue as well as other types of cancer.