The Genomic Grade Index predicts postoperative clinical outcome in patients with soft-tissue sarcoma.

Background: Soft-tissue sarcomas (STSs) are a group of rare, heterogeneous, and aggressive tumors, with high metastatic risk and relatively few efficient systemic therapies. We hypothesized that the Genomic Grade Index (GGI), a 108-gene signature previously developed in early-stage breast cancer, might improve the prognostic assessment of patients with early-stage STS. Patients and methods: We collected gene expression and clinicopathological data of 678 operated STS, and searched for correlations between the GGI-based classification and clinicopathological variables, including the metastasis-free survival (MFS). Results: Based on GGI, 275 samples (41%) were classified as 'GGI-low' and 403 (59%) as 'GGI-high'. The 'GGI-high' class was more associated with poor-prognosis features than the 'GGI-low' class: pathological grade 3 (P = 9.50E-11), undifferentiated sarcomas and leiomyosarcomas (P < 1.00E-06), location in extremities (P < 1.00E-06), and complex genetic profile (P = 2.1E-20). The 5-year MFS was 53% (95%CI 47-59) in the 'GGI-high' class versus 78% (95%CI 72-85) in the 'GGI-low' class (P = 3.02E-11), with a corresponding hazard ratio for metastatic relapse equal to 2.92 (95%CI 2.10-4.07; P = 2.23E-10). In multivariate analysis, the GGI-based classification remained significant, whereas the pathological grade did not. In fact, the GGI-based classification stratified the patients with pathological grades 1 and 2 and those with pathological grade 3 in two classes with different 5-year MFS. Comparison of the GGI and CINSARC multigene signatures revealed similar correlations with clinicopathological variables, which were, however, stronger with GGI than with CINSARC, a strong concordance (71%) in terms of low-risk or high-risk classifications, and independent prognostic value for MFS in multivariate analysis, suggesting complementary prognostic information. Conclusion: GGI refines the prediction of MFS in operated STS and might improve the tailoring of adjuvant chemotherapy. Further clinical validation is warranted in larger retrospective, then prospective series, as well as the functional validation of relevant genes that could provide new therapeutic targets.

SLC28A3 genotype and gemcitabine rate of infusion affect dFdCTP metabolite disposition in patients with solid tumours.

BACKGROUND: Gemcitabine is used for the treatment of several solid tumours and exhibits high inter-individual pharmacokinetic variability. In this study, we explore possible predictive covariates on drug and metabolite disposition. METHODS: Forty patients were enrolled. Gemcitabine and dFdU concentrations in the plasma and dFdCTP concentrations in peripheral blood mononuclear cell were measured to 72 h post infusion, and pharmacokinetic parameters were estimated by nonlinear mixed-effects modelling. Patient-specific covariates were tested in model development. RESULTS: The pharmacokinetics of gemcitabine was best described by a two-compartment model with body surface area, age and NT5C2 genotype as significant covariates. The pharmacokinetics of dFdU and dFdCTP were adequately described by three-compartment models. Creatinine clearance and cytidine deaminase genotype were significant covariates for dFdU pharmacokinetics. Rate of infusion of <25 mg m(-2) min(-1) and the presence of homozygous major allele for SLC28A3 (CC genotype) were each associated with an almost two-fold increase in the formation clearance of dFdCTP. CONCLUSION: Prolonged dFdCTP systemic exposures (≥72 h) were commonly observed. Infusion rate <25 mg m(-2) min(-1) and carriers for SLC28A3 variant were each associated with about two-fold higher dFdCTP formation clearance. The impacts of these covariates on treatment-related toxicity in more selected patient populations (that is, first-line treatment, single disease state and so on) are not yet clear.

Conventional protein kinase C plays a critical role in negative regulation of CD98-induced homotypic aggregation.

CD98, a heterodimeric type II transmembrane protein, is involved in many different cellular events, ranging from amino acid transport to cell-cell adhesion. Little is known about the positive and negative signalling pathways involved in these responses. Therefore, we examined the role of conventional protein kinase C (PKC) isoforms during CD98-induced intracellular signalling and homotypic aggregation of U937 cells. The CD98-induced aggregation was enhanced by the general protein kinase inhibitors GF109203X and staurosporin, and by specific PKC-alpha/-beta peptide inhibitor 19-27, but inhibited by PKC activators such as phorbol 12-myristate 13-acetate (PMA). PMA-inhibition was reversed by PKC inhibitors recognising the ATP-binding site in PKC (e.g. staurosporin, GF109203X and Go6983). Inhibitors which bind to diacylglycerol (DAG) or Ca(2+)-binding sites of PKC (calphostin C and Go6967) had no effect. PMA-induced translocation of conventional PKC (cPKC) isozymes (alpha, beta and gamma), but decreased the expression of PKC-delta, which plays an important role in CD98-induced homotypic aggregation. PMA treatment also suppressed the surface level of CD98 but not CD29, CD18 and CD147, dose- and time-dependently. These data provide evidence that PMA-responsive cPKC isoforms (alpha, beta and gamma) play a key role in negative regulation of CD98 signalling and homotypic aggregation.

Reversal of hemodialysis granulocytopenia and pulmonary leukostasis: A clinical manifestation of selective down-regulation of granulocyte responses to C5adesarg.

The transient granulocytopenia of hemodialysis results indirectly from plasma complement activation by dialyzer cellophane membranes. The C5a(desarg) so produced can induce reversible granulocyte aggregation in vitro and in vivo, and we hypothesized that the pulmonary leukostasis responsible for the granulocytopenia results from embolization of aggregates formed under the influence of C5a(desarg) produced in the dialyzer. These studies were designed to measure C5a(desarg) generation during dialysis by granulocyte aggregometry and to determine the reason for the transience of the leukostasis. C5a(desarg) generation was equally evident throughout dialysis, persisting well after granulocytopenia had reversed, and dialyzer-induced complement activation was insufficient to produce significant depletion of plasma complement titers. That granulocyte deactivation might be responsible for the transience was suggested by the absence of the usual granulocytopenia in a patient with uniquely high levels of C5a(desarg) in his predialysis plasma. Granulocytes drawn from seven stable uremic patients after granulocytopenia had reversed exhibited a dose-related, selective and irreversible refractoriness to stimulation with C5a(desarg), but their responses to n-formyl-Met-Leu-Phe remained normal. Identical deactivation was produced in normal cells by short- or long-term exposure of C5a(desarg) in vitro. These studies suggest that C5a(desarg) is indeed generated by the dialyzer throughout hemodialysis and that the transience of the leukostasis and granulocytopenia is due to selective down-regulation of cellular responses to C5a(desarg)-a phenomenon that hitherto has been described only in vitro and that may be important in limiting the deleterious effects of adherent granulocytes on the endothelium in patients with intravascular complement activation.

Corticosteroids block binding of chemotactic peptide to its receptor on granulocytes and cause disaggregation of granulocyte aggregates in vitro.

Inhibition of complement-mediated granulocyte aggregation has recently been proposed as a mechanism of action of high-dose corticosteroids in shock states. Postulating that such inhibition might be effected through alteration of receptors function, we examined the effect of methylprednisolone (MP), hydrocortisone (HC), and dexamethasone (DEX) on the extent and kinetics of binding of the synthetic chemotaxin f-methionine-leucine-phenylalanine (FMLP) to its specific receptor on the granulocyte surface. Dose-dependent inhibition of binding was observed at corticosteroid concentrations paralleling plasma levels achieved with 30 mg/kg intravenous bolus therapy; the order of potency was MP greater than HC greater than DEX. Receptor number was unaffected by steroid exposure, but the steroids effected a decrease in association rate constant for the FMLP-receptor interaction (35% of N for 0.2 mg/ml MP), leading to decreased receptor-ligand affinity. Dissociation kinetics, as examined by cold-chase experiments, were unaltered by the corticosteroids. Furthermore, in addition to the inhibition of aggregation previously reported, aggregated granulocytes were found to disaggregate upon addition of corticosteroids; the order of potency was again MP greater than HC greater than DEX, with an MP concentration of approximately 2-3 mg/ml required to effect complete disaggregation. We conclude that corticosteroids can displace FMLP from the granulocyte surface by slowing association while allowing dissociation to proceed; altered kinetics of receptor-FMLP interaction may explain both the inhibition of granulocyte aggregation and granulocyte disaggregation. If these observations also hold for physiologic stimuli (such as C5adesarginine, which behaves similarly with respect to aggregation, inhibition, and disaggregation), such kinetic changes may be important in the clinical effects of very high-dose corticosteroids such as are administered in shock.

Proteinase 3. A distinct human polymorphonuclear leukocyte proteinase that produces emphysema in hamsters.

Studies were designed to explore the possibility that human polymorphonuclear leukocyte granule constituents in addition to elastase (HLE) had the potential to cause emphysema. A two-step purification of three serine proteinases was developed. Granule extract proteins were initially separated by dye-ligand affinity chromatography. Fractions eluted were divided into four pools. Hamsters were given a single intratracheal instillation of saline +/- 0.1 mg protein of each pool. While pool 2 contained HLE and cathepsin G, the most dramatic bullous emphysema developed in animals treated with pool 4. The esterase from pool 4, designated proteinase 3 (PR-3) was purified, characterized in vitro, and tested for its ability to cause emphysema. PR-3 is a neutral serine proteinase with isoenzyme forms. Its ability to degrade elastin at pH 6.5 is slightly greater than that of HLE, but it is less active than HLE at pH 7.4 or 8.9. PR-3 has weak activity against azocasein. Its ability to degrade hemoglobin is intermediate to that of HLE and cathepsin G at pH 7.4. PR-3 has no activity against chromogenic substrates specific for HLE or cathepsin G. Its pI is substantially less than HLE or cathepsin G. It is also immunologically distinct from HLE. It induces emphysema in hamsters commensurate with that of HLE. We conclude that PR-3 may be important in the pathogenesis of human emphysema.

Clusterin promotes the aggregation and adhesion of renal porcine epithelial cells.

The function of clusterin, a heterodimeric glycoprotein markedly induced in renal and other organ injuries, is unclear. Since renal injury is accompanied by alterations in cell attachment, it is possible that clusterin functions to promote cell-cell and cell-substratum interactions. In this study, a single cell suspension of renal epithelial (LLC-PK1) cells was treated with purified human clusterin, resulting in time- and dose-dependent cell aggregation. Electron microscopy of the cell aggregates demonstrated cell junction and lumen formation. To determine the effect of clusterin on cell adhesion, tissue culture plates were coated with clusterin, fibronectin, PBS, or albumin. Clusterin and fibronectin promoted cell adhesion to the same extent. The adhesion to clusterin was dose dependent and specific, as a monoclonal antibody against clusterin inhibited cell adhesion to clusterin but not fibronectin. Perterbations of the cytoskeleton may underlie the alterations in cell attachment which occur in renal injury. Induction of clusterin mRNA was seen after disruption of both microtubules and microfilaments and after inhibition of cell-substratum interactions. In conclusion, clusterin is a potent renal epithelial cell aggregation and adhesion molecule. We speculate that clusterin functions to promote cell-cell and cell-substratum interactions which are perturbed in the setting of renal injury, thereby preserving the integrity of the renal epithelial barrier.

Changes in the cell surface protein composition of human alveolar macrophages induced by smoking.

The cell surface proteins of human alveolar macrophages obtained from nonsmokers have been compared to those of alveolar macrophages obtained from smokers. Proteins of nonsmokers' alveolar macrophages surface labeled with 125I differed from those of smokers' alveolar macrophages, as shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Three major radiolabeled proteins with molecular weights of 183,000, 80,000, and 30,000 were identified in fresh smokers' cells. The major radiolabeled protein of nonsmokers' macrophages had an apparent molecular weight of approximately 183,000. Affinity chromatography suggested the Mr 183,000 protein is a mannose receptor. In contrast, the molecular weight of the major radiolabeled protein of smokers' alveolar macrophages was approximately 30,000; the Mr 183,000 protein was less prominent. When nonsmokers' alveolar macrophages were cultured in vitro before 125I labeling, the cell surface protein pattern changed to resemble that of smokers' alveolar macrophages; the Mr 183,000 protein could no longer be detected on the cell surface, whereas a Mr 80,000 protein was increased in quantity and a new Mr 30,000 protein was detected. Nonadherent macrophages showed similar changes in their surface-labeled proteins but also contained a new prominently labeled Mr 70,000 protein. Limited proteolysis peptide mapping with five different enzymes did not reveal any evidence of homology among the Mr 183,000, 80,000, 70,000, and 30,000 proteins. The differences in cell surface protein composition between alveolar macrophages of smokers and nonsmokers may reflect their functional capabilities or their state of "activation" and may be mechanistically important in the development of various pulmonary diseases seen in smokers including cancer. These results also demonstrate that major changes in the surface proteins of the human alveolar macrophage plasma membrane can occur rapidly following manipulation.

Subcellular localization of CD66, CD67, and NCA in human neutrophils.

CD66 and CD67 are granulocyte-specific activation antigens; their surface expression is up-regulated when neutrophils are activated. CD66 antibodies recognize an approximately 180-kd neutrophil surface protein that is also recognized by anti-carcinoembryonic antigen (CEA) antibodies and is therefore a nonspecific cross-reacting antigen (NCA). CD67 antibodies recognize an approximately 100-kd neutrophil surface protein that is attached to the membrane via a glycosyl-phosphatidylinositol anchor. To identify an intracellular pool from which CD66 and CD67 could be up-regulated, the subcellular distribution of proteins recognized by CD66 and CD67 monoclonal antibodies and polyclonal anti-CEA was studied. Neutrophil plasma membranes, granules, and cytoplasm were prepared by nitrogen cavitation and differential centrifugation and then analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting. Most of the 180-kd protein recognized by CD66 antibodies and the 100-kd protein recognized by CD67 antibodies were located in the secondary granule fraction, with lesser amounts detectable in the plasma membrane fraction. Several NCA species ranging from approximately 40 to 200 kd were identified, and the distribution of these NCAs was different in the primary granules, secondary granules, and plasma membrane fractions. The major NCAs in the plasma membrane fraction were of approximately 95 to 100 and approximately 180 to 200 kd; the secondary granule fraction contained major NCAs of approximately 42, 85, 95 to 100, and 180 to 200 kd. NCAs were also detected in the primary granule fraction, the most prominent being of approximately 90-100 kd; no NCA of approximately 180 to 200 kd was detected in the primary granules. The presence of CD66, CD67, and NCAs in the secondary granules suggests secondary granules as a likely source from which these antigens could be recruited to the cell surface with activation. The potential role for NCAs in the primary granules is unknown.

Subcellular localization of glycosphingolipids in human neutrophils.

The subcellular distribution of five major glycosphingolipids (GSLs) in human neutrophils was analyzed. The neutrophils were isolated from the blood of six donors and subdivided in three fractions containing the cell membranes, and the primary and the secondary granules, respectively. The separation was confirmed with antibodies detecting established subcellular fraction-specific molecules. The two main neutral GSLsGalbeta1-4Glcbeta1-1'Cer (lactosylceramide, LacCer) and nLc4Cer (paragloboside, PG) and the three gangliosides IV3NeuAcnLc4Cer (2-3SPG), IV6NeuAcnLc4Cer (2-6SPG), and VI3NeuAcnLc6Cer (2-3SnHC) were quantitated using the immunochemical digoxigenin (DIG) staining procedure. Secondary granules contained the highest amount of these GSLs. They are followed by the primary granules and the cell membranes. Based on this quantitation, we conclude that the majority of the GSLs of neutrophils occur intracellularly. These findings are in striking contrast to the general assumption of GSLs being mainly concentrated in the cell membrane.

Identification of the major glycosyl-phosphatidylinositol anchored proteins on the surface of human neutrophils.

A novel mechanism of protein attachment to cell membranes involving the covalent linkage of the protein through an oligosaccharide to phosphatidylinositol has recently been defined. Many proteins that are anchored to the cell membrane by this mechanism can be released by treatment with phosphatidylinositol-specific phospholipase C (PI-PLC). Monoclonal antibodies are useful as probes in the study of the roles of cell-surface components in neutrophil function. Many monoclonal antibodies that bind to human neutrophils react with the oligosaccharide lacto-N-fucopentaose III (CD15 antibodies). Human neutrophil surface proteins identified by 125I surface-labeling using lactoperoxidase were examined for PI-PLC sensitivity, to identify the major surface proteins of human neutrophils that are anchored by a glycosyl-phosphatidylinositol linkage. The major surface-labeled protein identified by lactoperoxidase-catalyzed iodination was a approximately 68-90-kDa protein. Three major surface proteins identified by 125I-surface labeling of approximately 68-90, 57, and 33-kDa were released by PI-PLC treatment. Immunoprecipitation and subsequent gel electrophoresis of proteins from neutrophils labeled with 125I revealed a previously unidentified 98-115-kDa protein specifically reactive with CD15 antibodies that was released from the cell by treatment with PI-PLC. The roles of these proteins in neutrophil function remain to be determined.

Neutrophil-specific antigen NB1 is anchored via a glycosyl-phosphatidylinositol linkage.

Neutrophil-specific alloantibodies and the antigens they recognize are important in clinical medicine but little is known about the structure of these antigens. Alloimmunization to the antigen NB1 is a clinically important cause of neonatal neutropenia and leukocyte-mediated transfusion reactions. A novel mechanism of protein attachment to cell membranes involving the covalent linkage of the protein through an oligosaccharide to phosphatidylinositol has recently been defined. Many proteins which are anchored to the cell membrane by this mechanism can be released by treatment with phosphatidylinositol-specific phospholipase C (PI-PLC). The 58-64-kDa human neutrophil surface protein which contains the NB1 antigen was labeled with 125I by using lactoperoxidase and examined for PI-PLC sensitivity. The 58-64-kDa protein was specifically released from the cell by treatment with PI-PLC, and the mobility of the protein under non-denaturing conditions using non-ionic detergent was increased by treatment with PI-PLC. Surface expression of the NB1 antigen was slightly up-regulated by treatment with the chemotactic peptide f-met-leu-phe. Removal of N-linked carbohydrates with endoglycosidase-F decreased the apparent molecular weight of the protein to approximately 45-kDa. The data suggest that most of the 58-64-kDa protein bearing the neutrophil-specific antigen NB1 is anchored to the membrane through a glycosyl-phosphatidylinositol linkage.

Preparation and characterization of a monoclonal antibody that inhibits human neutrophil elastase activity.

Neutrophil proteases are believed to play a role in the pathogenesis of a variety of human diseases. While many studies of proteases in models of disease have focused on elastase, neutrophils contain several proteases some of which share a high degree of homology. This report describes the production and characterization of an IgG1 murine monoclonal antibody (AHN-10) that reacts with human neutrophil elastase but not with the other major neutrophil neutral proteases: cathepsin G, proteinase 3, collagenase, or the newly purified neutral protease, esterase N. AHN-10 inhibited the elastinolytic activity of purified human neutrophil elastase and could detect elastase in alcohol-fixed cytospin preparations. The epitope recognized by AHN-10 was resistant to treatment with NaIO4, suggesting that the epitope is not a carbohydrate. AHN-10 should be useful for the immunolocalization of neutrophil elastase in tissue specimens and as a stable source of characterized antibody for quantitative identification of neutrophil elastase.

Identification and purification of the human myeloid differentiation antigen recognized by monoclonal antibody AHN-7.

This report describes the characterization and expression of a human myeloid differentiation antigen defined by use of an IgG1 monoclonal antibody (AHN-7). This antibody binds to many granulocytic precursors in normal marrow, to most but not all granulocyte-macrophage progenitors (CFU-GM), and to approximately half of nonlymphoid leukemia specimens. The protein antigens recognized by AHN-7 were purified from 35S-labelled HL-60 cells by antibody affinity column chromatography. The molecule reacting with AHN-7 was markedly heterogeneous, appearing as several forms ranging in pl from 4.5 to 6.4 with apparent molecular weights from 43,000 to 68,000. The molecules were not disulfide-linked. Proteins bearing the antigen were minor components of the plasma membrane. The antigen was expressed by normal human peripheral blood neutrophils, monocytes, eosinophils, and basophils, and weakly on a small percentage of lymphocytes; it was not detected in red blood cells, platelets, or the majority of lymphocytes. The antibody also bound to a variety of human myeloid leukemia cell lines but not to any lymphoid leukemia cell line tested. AHN-7 had no effect on several in vitro neutrophil functions tested.

Preparation and characterization of monoclonal antibodies to human neutrophil cathepsin G, lactoferrin, eosinophil peroxidase, and eosinophil major basic protein.

This report describes the production and characterization of five murine monoclonal antibodies that react with granule proteins of human granulocytes. Monoclonal antibody AHN-11 (IgG2a) reacted specifically with neutrophil cathepsin G; no reactivity with the homologous neutrophil neutral proteases, elastase, proteinase 3, or esterase N was detected. Antibodies AHN-9 (IgG1) and AHN-9.1 (IgG2b) each reacted with different epitopes on human lactoferrin, but not with the homologous protein transferrin. Two IgG1 antibodies, AHE-1 and AHE-2, reacted specifically with eosinophils; AHE-1 reacted strongly with eosinophil peroxidase but not eosinophil major basic protein while AHE-2 recognized eosinophil major basic protein but not eosinophil peroxidase. All five antibodies could detect their respective antigens in alcohol-fixed cytospin preparations. These antibodies should be useful for immunolocalization and quantification of their respective antigens as well as for other studies of the roles of these proteins in granulocyte function and differentiation.

CD66a, CD66b, CD66c, and CD66d each independently stimulate neutrophils.

Four members of the carcinoembryonic antigen family, CD66a, CD66b, CD66c, and CD66d, are expressed on human neutrophils. In neutrophils these proteins are activation antigens in that their surface expression is increased following stimulation. To examine their potential role in neutrophil signaling, the effects on neutrophil adhesion to human umbilical vein endothelial cells of a panel of well-characterized CD66 mAbs was tested. CD66a, CD66b, CD66c, and CD66d antibodies each increased neutrophil adhesion to human umbilical vein endothelial cell monolayers. This increase in neutrophil adhesion caused by CD66 antibodies was blocked by a CD18 antibody and associated with up-regulation of CD11/CD18 on the neutrophil surface. This increase in neutrophil adhesion required physiological extracellular calcium concentrations at or near the time of CD66 antibody binding to the neutrophil. The incubation of CD66 antibodies with neutrophils in the absence of calcium for 10 min before repletion of calcium resulted in no increase in neutrophil adhesion. The data suggest that CD66a, CD66b, CD66c, and CD66d antibody binding to the neutrophil surface triggers a transient activation signal that requires extracellular calcium and regulates the adhesive activity of CD11/CD18. Sequential desensitization experiments indicated that CD66a, CD66b, CD66c, and CD66d can each independently transmit signals in neutrophils.

CD43 is associated with tyrosine kinase activity in human neutrophils.

CD43 appears to be involved in signal transduction, however, the mechanism of this function is unknown. Protein kinase activity was detected in neutrophils associated with CD43. Most of the protein kinase activity associated with these antigens was tyrosine kinase activity. The src family kinases lyn and hck were found to account for much of the associated tyrosine kinase activity. The data suggest that associated tyrosine kinase activity may play a role in signal transduction via CD43 to regulate other cell functions.

CD63 associates with CD11/CD18 in large detergent-resistant complexes after translocation to the cell surface in human neutrophils.

CD63 antibody binding to the neutrophil surface triggers a transient activation signal that regulates the adhesive activity and surface expression of CD11/CD18. Gel permeation chromatography demonstrated that all of the cell surface CD11/CD18 associated with CD63 eluted in the void volume, indicating that they were present in large detergent-resistant complexes. In contrast, the majority of the total cellular CD63, CD11 and CD18, which are largely intracellular, was not present in complexes. The data suggest that intracellular CD11, CD18 and CD63 are not in detergent-resistant complexes, but enter such complexes following translocation to the cell surface.

Tyrosine kinase activity is associated with CD44 in human neutrophils.

CD44 appears to be involved in signal transduction, however, the mechanism of this function is unclear. Protein kinase activity was detected in neutrophils associated with CD44. Most of the protein kinase activity associated with these antigens was tyrosine kinase activity. Src family kinases lyn and hck were found to account for much of the associated tyrosine kinase activity. The data suggest that associated tyrosine kinase activity may play a role in signal transduction from CD44 in neutrophils to regulate other cell functions.

Association of beta 1 integrin with protein kinase activity in large detergent resistant complexes.

Integrins play a critical role in cell adhesion and mediate cell signaling. This report identifies the association of serine protein kinase activity with the beta 1 integrin by immunoprecipitation and phosphoamino acid analysis techniques. Reprecipitation techniques suggested that the serine kinase activity was not a member of the protein kinase C family. By gel filtration, most of the protein kinase activity associated with beta 1 integrin as well as most of the cell-surface beta 1 integrin was present in large detergent resistant complexes. These results suggest that serine protein kinase activity associated with the beta 1 integrin may play a role in signaling via the beta 1 integrin.