Biomedical subjects

A F Chambers

Publications and source records attributed to A F Chambers.

At least 37 records · Page 2Linked to original sources

PubMed2000

Antibodies to different peptides in osteopontin reveal complexities in the various secreted forms.

We have generated synthetic peptides corresponding to various portions of human osteopontin (OPN) and have immunized rabbits and mice with these peptides to generate polyclonal and monoclonal antibodies specific to human OPN. We then generated six distinct sandwich enzyme-linked immunoabsorbent assay (ELISA) systems by using different pairs of polyclonal and monoclonal antibodies against human OPN. These systems allowed us to detect not only various isoforms and truncated forms of recombinant OPN, but also the glycosylated form of native urinary OPN. Most importantly, tumor-derived OPN was differentially detected by the six ELISA systems. The ELISA systems that we have developed will be useful for clarifying the functional roles for OPN in vivo in various physiologic and pathologic conditions.

Adult↗

PubMed2000

Transforming JB6 cells exhibit enhanced integrin-mediated adhesion to osteopontin.

Transformation of preneoplastic epidermal JB6 cells with tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate (TPA) is an in vitro model of late-stage tumor promotion. Osteopontin (OPN) is a secreted, adhesive protein that is highly expressed in JB6 cells with TPA treatment, and its expression persists for at least 4 days, which is the time required for subsequent expression of transformed phenotype. These observations suggest that OPN may play a role in promoting JB6 cell transformation. To function in transformation of JB6 cells, OPN must bind to the surface of the JB6 cell and subsequently signal within the cell. Therefore, we investigated whether JB6 cells adhere to OPN and, if so, to which surface receptors. TPA-treated JB6 cells had significantly (P < 0.05) increased adherence to OPN compared with dimethylsulfoxide-treated control cells. Enhanced attachment of JB6 cells to OPN was also observed after treatment with another tumor promoter phorbol dibutyrate but not with nontumor promoters (phorbol and 1alpha,25-dihydroxyvitamin D(3)), suggesting that tumor promoters specifically modulate attachment to OPN. The argininylglycylaspartic acid (RGD) cell-binding region of OPN mediates attachment of TPA-treated JB6 cells because RGD, but not argininylglycylglutamic acid (RGE), peptides inhibited adherence of these cells to OPN in a dose-dependent manner. Flow cytometric analyses, blocking adhesion assay using anti-alpha(v) antibody, and co-immunoprecipitation assay all indicated that TPA-treated cells had similar levels of alpha(v) and beta(5) but decreased levels of beta(1) compared with untreated cells and that cell adhesion to OPN is most likely mediated through the alpha(v)beta(5). Furthermore, calphostin C, a specific protein kinase C (PKC) inhibitor, decreased TPA-treated JB6 cell adhesion to OPN by 50%, suggesting that TPA increased integrin affinity or avidity for OPN through a PKC-mediated pathway. Collectively, these results indicate that transforming JB6 cells adhere to OPN through its RGD sequence. The most likely OPN receptor is the alpha(v)beta(5) integrin, which increases the affinity or avidity for OPN through a PKC-dependent pathway rather than increasing the number of receptors.

Animals↗

PubMed1999

Osteopontin induces increased invasiveness and plasminogen activator expression of human mammary epithelial cells.

Osteopontin (OPN) has been associated with enhanced malignancy in breast cancer, but its functional role in this disease is poorly understood. To study the effect of OPN on cellular invasiveness, basal OPN expression was first assessed in members of a progression series of human mammary epithelial cell lines (21PT: immortalized, non-tumorigenic; 21NT: weakly tumorigenic; 21MT-1: tumorigenic, weakly metastatic; MDA-MB-435 cells: tumorigenic, highly metastatic). The two lines which expressed lowest basal levels of OPN (21PT, 21NT) were then examined for up-regulation of invasive behavior in response to exogenous or transfected (endogenous) OPN. Both 21PT and 21NT showed increased invasiveness through Matrigel when human recombinant (hr)OPN was added to the lower chamber of transwells. Both also showed a cell migration response to hrOPN. Populations of 21PT and 21NT cells stably transfected with an OPN-expression vector showed higher levels of cell invasiness than control vector transfectants. Examination of transfectants for mRNA of a number of secreted proteases showed that only urokinase-type plasminogen activator (uPA) expression was closely associated with OPN expression and cellular invasiveness. Treatment of the parental 21PT and 21NT cells with exogenous hrOPN resulted in increased uPA mRNA expression and increased urokinase activity of the conditioned media. Both increased cell migration and induction of uPA expression are thus potential mechanisms of increased invasiness of breast epithelial cells in response to OPN.

Breast↗

PubMed1999

Detection of various epitopes of murine osteopontin by monoclonal antibodies.

We immunized rats with recombinant murine osteopontin protein and obtained four monoclonal antibodies recognizing distinct epitopes of murine osteopontin. OPN1.2 recognized the amino-terminal half of OPN, while OPN2.2, OPN2.3, and OPN3.1 recognized the carboxy-terminal half of OPN. The epitope recognized by OPN2.2 was destroyed by further cleavage of the carboxy half of OPN. The epitope recognized by OPN2.3 was located in the amino-terminal end of the carboxy half of OPN, whereas that recognized by OPN3.1 was located in the carboxy-terminal end of the carboxy half of OPN. OPN1.2 and OPN2.2 recognized thrombin-cleaved osteopontin, whereas thrombin-cleaved osteopontin was not recognized by OPN2.3 and OPN3.1. Thus, these monoclonal antibodies will be useful in structure/function studies of the role of osteopontin in murine models of disease.

Animals↗

PubMed1999

CD44 variants but not CD44s cooperate with beta1-containing integrins to permit cells to bind to osteopontin independently of arginine-glycine-aspartic acid, thereby stimulating cell motility and chemotaxis.

The expression of osteopontin (OPN), CD44 variants, and integrins has been correlated with tumorigenesis and metastasis. Here we show that these proteins cooperate to enhance cell motility. First, we demonstrate that several different CD44 variants bind to OPN in an arginine-glycineaspartic acid-independent manner, but that the standard form of CD44 does not. These CD44 variants bind to both the amino- and COOH-terminal portions of OPN independently of the arginine-glycine-aspartic acid sequence, suggesting that multiple domains on OPN can be bound by the CD44 variants. Antibodies directed against the integrin beta1 subunit are able to inhibit this binding. The binding of CD44 variants to OPN is significantly augmented by both anti-CD44s and anti-CD44v antibodies. This augmentation by anti-CD44 antibodies is OPN specific and, again, can be blocked by anti-beta1 antibodies. Finally, we show that OPN binding by CD44 variants/beta1-containing integrins promotes cell spreading, motility, and chemotactic behavior.

Animals↗

PubMed1999

Serum bound forms of PSP94 (prostate secretory protein of 94 amino acids) in prostate cancer patients.

PSP94 (prostate secretory protein of 94 amino acids) was regarded as a possible prostate cancer marker, however, it has been controversial. All prior studies were designed to test the free form in serum using antibodies to PSP94. Results presented here demonstrate that PSP94 exists in prostate cancer patients in two forms, free and bound, and that the majority is present as serum bound complexes. This result was demonstrated by using both native and SDS-PAGE analyses of serum proteins from prostate cancer patients. Chromatographic separation of serum total proteins by a molecular sieve column generated two peaks (peak I and II), which were reactive with rabbit antiserum to human PSP94 in Western blot experiments. Peak I was eluted before the IgG fraction at a molecular weight larger than 150 kDa, and peak II appeared after serum albumin ( approximately 67 kDa) was eluted. By using a biotinylated PSP94 as an indicator of the free form of PSP94, we demonstrate that peak I contains serum PSP94-bound complexes and peak II is likely the free form of serum PSP94. Since the molecular weight of serum PSP94-bound complexes is close to IgG during molecular sieve separation, serum PSP94 complexes were further purified through two rounds of protein A column separation, followed by DEAE-ion exchange column chromatography. In vitro dissociation tests of the purified PSP94-bound complexes showed that the binding of serum PSP94-complexes is probably via disulfide bonds and is chemically stable. The results presented here indicate that serum PSP94-bound complexes must be considered in evaluating the clinical utility of PSP94 as a prostate cancer marker.

Antibodies↗

PubMed1999

Metastasis Research Society VII International Congress (Part II). 7-10 October 1998, San Diego, CA, USA.

The Metastasis Research Society (MRS) has held its International Congress every two years since 1986, and alternates between European and North American meeting venues. The next MRS International Congress will be held in London, UK in the year 2000, and will be hosted by the current MRS President, Dr. Suzanne Eccles (Institute of Cancer Research, Sutton, UK). Dr. Eccles took over from the out-going President, Dr. William Stetler-Stevenson (National Institutes of Health, Bethesda, MD, USA), at the San Diego meeting. Information on joining the Metastasis Research Society, which includes a subscription to the Society's journal, Clinical and Experimental Metastasis, can be obtained from Dr. Eccles (suzan@icr.ac.uk) or from the newly-elected Secretary/Treasurer Dr. Danny Welch (Hershey, PA, USA; drw9@psu.edu). The meeting was organized by Darwin Medical Communications Ltd (Gill Heaton, Oxford, UK), who have placed the full program on the meeting web site (http:@www.sparks.co.uk/mrs). It is envisaged that full abstracts of all the presentations will be placed on the Metastasis Research Society web site, which is currently under construction. Corporate sponsors for the San Diego meeting included Agouron Pharmaceuticals, Becton Dickinson & Co, Zeneca Pharma SA, Schering AG, AntiCancer Inc, Oncogene Research Products, Daiichi Seiyaku Co Ltd and Novartis Pharma AG.

California↗

PubMed1999

The matrix metalloproteinase inhibitor batimastat inhibits angiogenesis in liver metastases of B16F1 melanoma cells.

Matrix metalloproteinases (MMPs) have been shown to contribute functionally to tumor metastasis. MMP inhibitors are thus being assessed for clinical utility as anti-metastatic therapeutics. Batimastat (BB-94) is a synthetic MMP inhibitor that has been shown to inhibit tumor growth and metastasis in mice. Here we assessed the ability of batimastat to inhibit liver metastases of murine B16F1 cells, after injection of cells in mice via mesenteric vein to target the liver. We then determined which of the sequential steps in metastasis were affected by batimastat, in order to identify its mechanism of action in vivo. Intravital videomicroscopy was used to assess the effect on extravasation, and a 'cell accounting' procedure was used to determine the effect on initial survival of cells. Stereological quantification of functional blood vessels was used to determine the effect on tumor vascularity, thereby avoiding problems associated with immunohistochemical detection of liver sinusoidal endothelial cells. We found that batimastat (50 mg/kg i.p. 5 h prior to and after cell injection, daily thereafter) resulted in a 23% reduction in mean diameter of liver metastases (equivalent to a 54% reduction in tumor volume), while not reducing the number of metastases. Extravasation of cells from the liver circulation was not affected: at 8, 24 and 48 h after injection of cells, the same proportion of cells had extravasated from treated vs. control mice. Batimastat also did not inhibit early survival of cells. However, batimastat-treated mice had a significantly reduced percentage vascular volume within liver metastases, indicating inhibition of angiogenesis. This study demonstrates in vivo that the mechanism by which batimastat limits growth of B16F1 metastases in liver is not by affecting extravasation, but by inhibiting angiogenesis within metastases. This finding suggests that MMP inhibitors may be appropriate for use in patients with metastatic cells that have already extravasated in secondary sites.

Animals↗

PubMed1999

Angiogenesis as a target for breast cancer therapy.

Angiogenesis, the development of new blood vessels, is crucial for the growth of both primary tumors and metastases beyond a minimal size and the vasculature of tumors facilitates their metastatic spread. Inhibition of angiogenesis is thus seen as a potentially useful approach to anti-metastasis therapy, and is an area of active research and development. Here we discuss this therapeutic approach in the context of breast cancer. An overview of the contribution of angiogenesis to tumor development is provided and current treatment options for breast cancer are briefly summarized. Assessment of angiogenesis in primary breast tumors has been shown to provide independent prognostic information. There are opportunities for the application of anti-angiogenesis therapeutic strategies in the treatment of breast cancer. Clinical trial design must take into account the unique properties of anti-angiogenic agents to fully assess their potential clinical benefit.

Angiogenesis Inhibitors↗

PubMed1999

Reduced tolerance to acute renal ischemia in mice with a targeted disruption of the osteopontin gene.

BACKGROUND: Mice with a targeted disruption of the osteopontin gene through homologous recombination in embryonic stem cells have recently been generated and shown to be characterized by unaltered fertility and normal embryonic and postnatal development, including renal development, but altered osteoclastogenesis from spleen progenitors. The lack of detectable pathological manifestations in kidneys of mice with the targeted disruption of the osteopontin gene (opn -/-) makes them an excellent model for studies of pathophysiological processes that are thought to be accompanied by changes in renal osteopontin expression. It has previously been suggested that osteopontin may play an important role in the pathophysiology of acute renal failure, thus prompting this study. METHODS: Wild-type and opn -/- mice were subjected to 30 minutes of renal ischemia and were studied 24 hours later. RESULTS: Control opn +/+ mice showed a significant retention of blood urea nitrogen and creatinine, which is indicative of the development of ischemic acute renal dysfunction. This was accompanied by a 2.7-fold increase in the immunodetectable osteopontin compared with sham-operated control. Animals with the disrupted osteopontin gene exhibited ischemia-induced renal dysfunction, which was twice as pronounced as that observed in mice with the intact osteopontin response to stress. In addition, the structural damage to the ischemic kidneys obtained from opn -/- mice was more pronounced than that observed in similarly treated wild-type mice. This was associated with the augmented expression of inducible nitric oxide synthase and the prevalence of nitrotyrosine residues in kidneys from opn -/- mice versus wild-type counterparts. In vitro studies with proximal tubular cells subjected to hypoxia in the presence of OPN, but not OPN with deleted arginine-glycine-aspartic acid (RGD) domain, resulted in cytoprotection. CONCLUSIONS: The comparative analysis of functional and morphological sequelae of acute renal ischemia in opn +/+ and opn -/- mice provides strong evidence of renoprotective action of osteopontin in acute ischemia.

Acute Disease↗

PubMed1999

O(6)-methylguanine-DNA methyltransferase activity, p53 gene status and BCNU resistance in mouse astrocytes.

We observed previously that wild-type p53 rendered neonatal mouse astrocytes resistant to 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) in a gene dose-dependent fashion. This effect of p53 appeared to be unrelated to its cell cycle regulation or apoptotic functions. Because in many cell types O(6)-methylguanine-DNA methyltransferase (MGMT)-mediated DNA repair is an important mechanism of resistance to nitrosoureas, we measured MGMT activity in wild-type, heterozygous and p53 knockout neonatal mouse astrocytes. Wild-type p53 astrocytes had significantly greater MGMT activity than either heterozygous or p53 knockout astrocytes: MGMT activity was approximately 5-fold greater in wild-type p53 astrocytes than in p53 knockout cells. However, despite successful depletion of MGMT activity in wild-type astrocytes by O(6)-benzylguanine (BG), resistance to BCNU persisted unchanged. Moreover, we excluded the possibility that continued resistance to BCNU at the concentrations used could be explained by a compensatory induction of MGMT triggered by exposure to either BCNU or BG. Although these studies support a role for p53 regulation of MGMT in neonatal mouse astrocytes, BCNU resistance in wild-type cells appears to be mediated by a non-MGMT mechanism. Nevertheless, regulation of DNA repair by MGMT may be another mechanism by which alterations of the p53 gene promote tumor initiation or progression.

Animals↗

PubMed1999

Tumour metastasis to the liver, and the roles of proteinases and adhesion molecules: new concepts from in vivo videomicroscopy.

Most preclinical studies of tumour metastasis and effects of molecular interventions have been based on end point assays, and little is known about the fate of cells at sequential steps in the metastatic process. In vivo videomicroscopy permits direct observations of sequential steps in hematogenous metastasis as they occur in living animals over time. These steps include initial arrest of cells in the microcirculation, extravasation, postextravasation migration and growth in the target organ. In the mouse liver model, cells are arrested in periportal sinusoids based on size restriction, survive in the circulation and extravasate into the tissue by 48 to 72 h regardless of metastatic potential. Thereafter, cells may migrate to preferred sites for growth. Critical steps responsible for cell losses and metastatic inefficiency occur at the level of postextravasation cell growth. Many extravasated cells may remain dormant, and growth to form micrometastases is initiated in only a small subset of cells. Most early micrometastases may disappear after a few days, and only a small subset continue growth into macroscopic tumours. Angiogenesis is a prerequisite for continued growth of metastases, as shown previously by others. Integrin based interventions can modulate postextravasation cell migration and cell growth. Matrix metalloproteinase inhibitors can inhibit tumour angiogenesis and thus reduce growth. Key targets against which future therapeutic strategies should be directed include the initiation and maintenance of growth of micrometastases, and the activation of dormant solitary cells.

Animals↗

PubMed1999

Cellular expression of green fluorescent protein, coupled with high-resolution in vivo videomicroscopy, to monitor steps in tumor metastasis.

High resolution intravital videomicroscopy has provided a powerful tool for directly observing steps in the metastatic process, and for clarifying molecular mechanisms of metastasis and modes of action of anti-metastasis therapeutics. Cells previously have been identified in vivo using exogenously added fluorescent labels, limiting observations to a few cell divisions, or by natural markers (e.g. melanin) expressed only by specific cell types. Here we tested the utility of stable green fluorescent protein (GFP)-transfected cells for monitoring and quantifying sequential steps in the metastatic process. Using CHO-K1 cells that stably express GFP, we document the visualization and quantification by intravital videomicroscopy of sequential steps in metastasis within mouse liver, from initial arrest of cells in the microvasculature to the growth and angiogenesis of metastases. Individual, non-dividing cells, as well as micro- and macrometastases could clearly be detected and quantified, as could fine cellular details such as pseudopodial projections, even after extended periods of in vivo growth. We quantified the size distribution of micrometastases and their locations relative to the liver surface using 50 micrometer thick formalin-fixed tissue sections. The data suggest preferential growth and survival of micrometastases near the liver surface. Furthermore, we observed a small population of single cells that persisted over the 11 day observation period, which may represent dormant cells with potential for subsequent proliferation. This study demonstrates the advantages of GFP-expressing cells, coupled with real-time high resolution videomicroscopy, for long-term in vivo studies to visualize and quantify sequential steps of the metastatic process.

Animals↗

PubMed1999

The metastatic process: basic research and clinical implications.

Metastatic spread of cancer is responsible for most deaths due to cancer. An understanding of the process of metastasis at a level sufficient to permit the development of effective antimetastatic therapies thus has the potential to make an impact on mortality from cancer. Recent experimental studies using in vivo videomicroscopy, which have allowed direct observation and quantification of steps in metastasis as they occur in vivo, have led to new insights into the metastatic process and steps that result in metastatic inefficiency. It is important to learn if these findings are relevant to clinical cancer. If these experimental results reflect the situation that occurs during metastasis of human cancers, there are clinical implications that deserve evaluation. In this Commentary, these results are discussed in the context of human cancer, and the possible clinical implications of the experimental findings are considered. The findings are also discussed in the context of results that suggest that the timing of breast cancer surgery during the menstrual cycle in premenopausal women may affect probability of survival, and possible implications of the findings for tumor dormancy are discussed.

Animals↗

PubMed1998

Osteopontin expression in a group of lymph node negative breast cancer patients.

The aim of this study was to examine the cellular distribution of osteopontin (OPN) protein [by immunohistochemical (IHC) analysis] and mRNA [by in situ hybridization (ISH)] in the primary tumors of lymph node negative (LNN) breast cancer patients and to determine whether the level of immunodetectable OPN may be associated with tumor aggressiveness. We examined OPN levels in tumors from 154 patients with LNN breast cancer who were followed for a median of 7 years (range 1.7-16.3 years). IHC staining for OPN was seen in tumor infiltrating macrophages and lymphocytes in 70% of these tumors, and in the carcinoma cells themselves in 26%. ISH was performed to determine cellular distribution of OPN mRNA expression in sections from selected tumors. OPN mRNA was detected in groups of tumor cells, individual tumor cells and tumor infiltrating macrophages and lymphocytes. Matched sections showed that some tumor cells with IHC staining for OPN protein were also positive for OPN mRNA by ISH, in contrast with previous studies which have shown OPN mRNA expression only in tumor infiltrating inflammatory cells. Our results thus indicate that OPN protein can be produced by breast cancer cells in vivo and suggest that it may also be taken up from the environment (i.e., secreted by inflammatory cells or other tumor cells). Tumor cell IHC staining intensity was then assessed using a semiquantitative scoring system. Univariate analysis showed tumor cell OPN positivity above an optimized cutpoint to be significantly associated with decreased disease-free survival (DFS) and overall survival (OS). The results of this pilot study thus suggest that the ability of breast cancer cells to either synthesize OPN or to bind and sequester OPN from the microenvironment may be associated with tumor aggressiveness and poor prognosis.

Adult↗

PubMed1998

Activation of MMP-2 by human GCT23 giant cell tumour cells induced by osteopontin, bone sialoprotein and GRGDSP peptides is RGD and cell shape change dependent.

We show that osteopontin (OPN), bone sialoprotein (BSP) and GRGDSP peptides, in solution, induce activation of metalloproteinase-2 (MMP-2) secreted by human GCT23 giant cell tumour cells. Activation of MMP-2 is RGD sequence dependent, possibly involves anti-alphaVbeta3 integrins, is preceded by a change from spread to rounded cell morphology and is mimicked by the actin depolymerising agent cytochalasin B. Cells that had spread on OPN, BSP and GRGDSP substrata failed to activate MMP-2, but subsequent addition of soluble GRGDSP induced rounding and MMP-2 activation. Activation induced by GRGDSP and cytochalasin B was cell mediated, inhibited by EDTA, tissue inhibitor of metalloproteinase-2 (TIMP-2) and carboxyl terminal MMP-2 consistent with a role for membrane type (MT)-MMP but did not involve urokinase, plasmin or thrombin activity. Activation induced by GRGDSP and cytochalasin B, but not cell rounding, was inhibited by herbimycin A, cycloheximide and actinomycin D, suggesting a role for tyrosine kinases, protein and RNA synthesis, but was not associated with changes in mRNA for MT-MMP-1, MMP-1, MMP-2, TIMP-1 or TIMP-2. GRGDSP and cytochalasin B enhanced levels of membrane-associated pro- and active form MMP-1 and MMP-2 but not MT-MMP-1, stimulated cell surface MMP-1 staining and induced that of MT-MMP-1, MMP-2 and TIMP-2. This was consistent with the possible relocation of constitutive MT-MMP-1 to the cell surface as a prerequisite for subsequent cell surface MMP-2/TIMP-2/MT-MMP-1 complex formation and to the potential induction of conditions favourable for reciprocal cell surface MMP-1/MMP-2 activation. Our data provide a novel insight into interactions between RGD containing bone matrices, GCT cells and MMPs of potential relevance to GCT pathology.

Carcinoma, Giant Cell↗

PubMed1998

Expression of genes that contribute to proliferative and metastatic ability in breast cancer resected during various menstrual phases.

BACKGROUND: Retrospective studies show significant improvements in survival among women who had breast cancer resected during the luteal phase of their menstrual cycle compared with the follicular phase. We hypothesised that tumour tissue would show cyclical changes in expression of genes whose products might contribute to metastatic potential. METHODS: We studied 32 premenopausal women with operable breast cancer. We assayed hormones to define more accurately the menstrual phase during which surgery was done. We used northern blot analysis of RNA from fresh-frozen tumour specimens to study the patterns of expression of genes for proteolytic enzymes (cysteine proteinase cathepsin L and aspartyl proteinase cathepsin D; matrix metalloproteinases MMP-9 and MMP-2), tissue inhibitors of metalloproteinases TIMP-1 and TIMP-2, and TP53. RESULTS: There was a significantly higher level of expression of RNA for cathepsin L, MMP-9, and TP53 (p=0.005, 0.03, 0.03, respectively) in tumours that were resected during the follicular and periovulatory phases of the menstrual cycle than at other times in the cycle. A similar but non-significant trend was seen for MMP-2 and cathepsin D. A non-significant trend in the opposite direction was seen for TIMP-1 and TIMP-2. INTERPRETATION: We found that tumour expression of genes that may contribute to proliferative capacity and metastatic potential can change in breast cancer during the course of the menstrual cycle. The finding could provide a molecular explanation for the reports of improved survival in some breast-cancer patients whose tumours were removed during the luteal phase of the menstrual cycle. Larger studies are required to extend our study, assess mechanisms of gene regulation, and verify any relevant influence in long-term survival.

Adult↗

PubMed1998

Coordinate expression of OPN and associated receptors during monocyte/macrophage differentiation of HL-60 cells.

Promyelocytic leukemia HL-60 cells promoted by PMA to differentiate along the monocyte pathway adhere to tissue culture plates. To explore the regulation of adhesion molecules in cells promoted to differentiate, the expression and secretion of osteopontin (OPN) and expression of associated cell surface receptors, CD44 and integrin subunits alpha(v), beta3, beta1, were examined. Results were as follows: 1) PMA induced OPN mRNA and OPN secretion into media; 2) untreated cells expressed beta1 and CD44 mRNA, and PMA induced alpha(v), and beta3 mRNA and increased beta1 and CD44 mRNA expression; 3) PMA increased levels of alpha(v), beta3, beta1 and CD44 protein on the cell surface; and 4) retinoic acid, which promotes granulocytic differentiation of HL-60 cells, did not affect OPN, alpha(v), beta3, beta1, or CD44 mRNA or protein expression. These data suggest that induction of OPN and associated receptors may play a role during monocytic differentiation of HL-60 cells.

Cell Differentiation↗