Biomedical subjects

D T Graves

Publications and source records attributed to D T Graves.

At least 37 records · Page 2Linked to original sources

PubMed1999

Interleukin-1 and tumor necrosis factor activities partially account for calvarial bone resorption induced by local injection of lipopolysaccharide.

The present study was undertaken to test the hypothesis that tumor necrosis factor (TNF) and/or interleukin-1 (IL-1) activity mediates lipopolysaccharide (LPS)-induced bone resorption in vivo. To test this hypothesis, Escherichia coli LPS or Porphyromonas gingivalis LPS was injected into the subcutaneous tissues overlying mouse calvariae. Histological sections, prepared from the center of the lesion, were stained for tartrate-resistant acid phosphatase, and histomorphometric analysis was performed to quantify the osteoclast number and the area of bone resorption. In time course experiments using normal mice, a peak of bone resorption occurred 5 days after endotoxin stimulation. In dose-response experiments, IL-1 receptor type 1 deletion (IL-1R(-/-)), TNF double-receptor p55/p75 deletion (TNF p55(-/-)/p75(-/-)), combined TNF p55 and IL-1 receptor type 1 deletion (TNF p55(-/-)/IL-1R(-/-)), and IL-1beta-converting enzyme-deficient (ICE(-/-)) mice and the respective wild-type mice were injected with 500, 100, or 20 micrograms of P. gingivalis LPS and sacrificed 5 days after LPS injection. At the highest dose (500 micrograms), significant decreases in osteoclast number occurred in mutant mice compared to wild-type mice: (i) a 64% reduction for the TNF p55(-/-)/IL-1R(-/-) mice, (ii) a 57% reduction for the IL-1R(-/-) mice, (iii) a 41% reduction for the TNF p55(-/-)/p75(-/-) mice, and (iv) a 38% reduction for the ICE(-/-) mice. At the two lower doses, bone resorption was apparent but no significant differences between mutant and wild-type animals were observed. The present data indicate that at higher doses, LPS-induced bone resorption is substantially mediated by IL-1 and TNF receptor signaling. Furthermore, IL-1 receptor signaling appears to be slightly more important than TNF receptor signaling. At lower LPS doses, other pathways leading to osteoclast activity that are independent of TNF and IL-1 are involved.

Animals↗

PubMed1999

Regulated expression of MCP-1 by osteoblastic cells in vitro and in vivo.

Inflammation is characterized by the recruitment of leukocytes from the vasculature. Recent studies have implicated chemokines as an important class of mediators that function principally to stimulate leukocyte recruitment, and in some cases, leukocyte activity. There are four defined chemokine subfamilies based on their primary structure, CXC, CC, C and CX3C. Members of the CC chemokine subfamily, such as monocyte chemoattractant protein 1 (MCP-1), are chemotactic for monocytes and other leukocyte subsets. The studies described below focus on the expression of MCP-1 in vitro and in vivo in an osseous environment. These studies indicate that MCP-1 is typically not expressed in normal bone or by normal osteoblasts in vitro. Upon stimulation by inflammatory mediators, MCP-1 is up-regulated. This expression is temporally and spatially associated with the recruitment of monocytes in both osseous inflammation and during developmentally regulated bone remodelling. Furthermore, exogenous MCP-1 applied to inflamed bone enhances the recruitment of monocytes. Because monocytes produce factors that influence osseous metabolism, including but not limited to prostglandins, platelet-derived growth factor, interleukin-1 or tumor necrosis factor, chemokines that initiate their recruitment are likely to be highly important.

Animals↗

PubMed1999

Periodontal pathogens stimulate CC-chemokine production by mononuclear and bone-derived cells.

BACKGROUND: Chemokines are chemotactic cytokines that stimulate recruitment of leukocytes. Monocyte chemoattractant protein-1, macrophage inflammatory protein-1alpha, and RANTES (regulated on activation, normal T cell expressed, and secreted) are 3 well-characterized CC-chemokines that regulate mononuclear cell recruitment. The recruitment of inflammatory cells is of particular importance in the oral cavity because of the likelihood that cells will be challenged with bacteria either during acute infection or following surgical procedures. Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans are putative periodontal pathogens that may be harbored in subgingival and supragingival plaque. The capacity of the host to respond to these bacteria by the elaboration of chemoattractants may represent an important defense mechanism. METHODS: In the present study, we examined CC-chemokine production by human mononuclear cells and bone-derived cells in response to P. gingivalis, A. actinomycetemcomitans and lipopolysaccharides (LPS) stimulation in vitro. The chemokines produced were measured by ELISA. RESULTS: The results demonstrate that P. gingivalis and A. actinomycetemcomitans induce high levels of MIP-1alpha in mononuclear cells. P. gingivalis and A. actinomycetemcomitans stimulated high levels of MCP-1 in bone-derived cells and induced moderate levels of RANTES production in both mononuclear and osteoblastic cells. In mononuclear cells, LPS induced high levels of MIP-1alpha and RANTES and moderate levels of MCP-1; in osteoblasts LPS only induced MCP-1. CONCLUSIONS: The capacity of bacteria to induce a given chemokine depends upon the cell type stimulated. That different cell types would exhibit differences in the CC-chemokines produced under the same stimulus provides a mechanism to explain tissue-specific recruitment of leukocytes.

Adult↗

PubMed1998

A complex element regulates IFN-gamma-stimulated monocyte chemoattractant protein-1 gene transcription.

Monocyte chemoattractant protein-1 (MCP-1) is induced in chronic osseous inflammation, and is temporally and spatially correlated with monocyte recruitment. We investigated the mechanism of MCP-1 regulation in a human osteoblastic cell line in response to IFN-gamma, a potent mediator of the immune inflammatory response. Nuclear run-on and stability studies demonstrated that IFN-gamma stimulated MCP-1 transcription and did not enhance mRNA stabilization. Using MCP-1 promoter/reporter gene constructs, we determined that IFN-gamma-enhanced MCP-1 transcription is regulated by a 29-bp element located at -227 relative to the ATG start codon. This element contains a 13-bp CT-rich sequence (GCTTCCCTTTCCT) adjacent to a IFN-gamma activation site (GAS). Since deletion of the CT sequence enhanced both the magnitude and duration of IFN-gamma-stimulated, GAS-mediated transcription, we have termed it the IFN response-inhibitory sequence (IRIS). The combined IRIS/GAS sequence is highly conserved in mouse, rat, and bovine MCP-1 genes. In gel-shift assays, nuclear extracts from IFN-gamma-stimulated osteoblastic cells formed two specific inducible bands with labeled IRIS/GAS DNA. Both bands were supershifted by anti-STAT1 Abs, but not by Abs to STAT2, p48(ISGF-3y), IFN-regulatory factor-1, or IFN-regulatory factor-2. Formation of one of the bands required the presence of the IRIS moiety. IRIS/GAS DNA also formed a number of specific complexes with constitutively expressed factors, none of which were affected by the above Abs. These studies establish a mechanism for IFN-gamma-stimulated MCP-1 expression and identify a complex element that regulates MCP-1 gene transcription.

Base Sequence↗

PubMed1998

Pulse application of platelet-derived growth factor enhances formation of a mineralizing matrix while continuous application is inhibitory.

Platelet-derived growth factor (PDGF) stimulates chemotaxis and proliferation of osteoblasts, and induces bone formation in vivo. To determine how PDGF might regulate these cells, the effect of PDGF on long-term mineralizing cultures of fetal rat osteoblastic cells was examined. Although PDGF increased cell proliferation in these cultures, continuous treatment with PDGF caused a dose-dependent decrease in mineralized nodule formation. When cells were treated with multiple, brief (1 day) exposures to PDGF at the osteoblast differentiation stage, there was a significant 50% increase in mineralized nodule area. Based on modulation of alkaline phosphatase activity it appears that longer-term exposure to PDGF reduces mineralized nodule formation largely by inhibiting differentiated osteoblast function, while short-term exposure enhances proliferation without inhibiting the differentiated phenotype. Thus, the ultimate affect of PDGF on bone formation is likely to reflect two processes: a positive effect through enhancing cell number or a negative effect by inhibiting differentiated function. The inhibitory effect of PDGF on formation of a mineralized matrix is unlikely to be simply a result of enhanced proliferation of "fibroblastic" cells since cultures treated with PDGF for 3 days and then transferred to new plastic dishes exhibited a 70% increase in mineralized nodule area compared to controls. These results would predict that multiple, brief exposures to PDGF would enhance bone formation in vivo, while prolonged exposure to PDGF, which is likely to occur in chronic inflammation, would inhibit differentiated osteoblast function and limit bone regeneration.

Animals↗

PubMed1998

IL-1 and TNF antagonists inhibit the inflammatory response and bone loss in experimental periodontitis.

Periodontal disease is the most frequent cause of tooth loss in humans and is the most prevalent disease associated with bone loss, including osteoporosis. Periodontal destruction is initiated by bacteria that colonize the tooth surface, leading to inflammation and bone resorption. To assess the roles of IL-1 and TNF in this process, studies were conducted in a Macaca fascicularis primate model of experimental periodontitis. Function-blocking soluble receptors to IL-1 and TNF were applied by local injection to sites with induced periodontal destruction and compared with similar sites injected with vehicle alone. The results indicate that injection of soluble receptors to IL-1 and TNF inhibited by approximately 80% the recruitment of inflammatory cells in close proximity to bone. The formation of osteoclasts was reduced by 67% at the experimental sites compared with that at the control sites, and the amount of bone loss was reduced by 60%. All results were statistically significant (p < 0.01). These findings indicate that a significant component of the pathologic process of periodontitis is due to IL-1/TNF activity, since inhibiting IL-1/TNF reduces both inflammatory cell recruitment and bone loss. The data also suggest that inflammation associated with gingivitis is actively protective, since blocking further up-regulation of the host response with IL-1/TNF inhibitors does not cause periodontal damage. Furthermore, these results coupled with recent evidence that IL-1 and TNF participate in endocrine-associated osteoporosis suggest that multiple pathologies involving excessive loss of bone may operate through a common mechanism involving IL-1 and/or TNF.

Animals↗

PubMed1998

Inflammation-associated lysyl oxidase protein expression in vivo, and modulation by FGF-2 plus IGF-1.

Lysyl oxidase is the extracellular enzyme that catalyzes oxidative deamination of peptidyl-lysine residues in elastin precursors, and lysine and hydroxylysine residues in collagen precursors to form peptidyl-aldehydes. These aldehydes then spontaneously condense to crosslink collagen and elastin and thereby allow the formation of a mature and functional extracellular matrix. In the present study, cryosections made from aseptic immune-induced periapical lesions experimentally generated in laboratory rats were examined by immunohistochemistry to investigate whether lysyl oxidase protein expression is altered in inflamed oral tissues. Periapical lesions are experimentally induced endodontic lesions of tooth roots. In addition, the effect of administration of a mixture of fibroblast growth factor (FGF)-2 and insulin-like growth factor (IGF)-1 into these lesions on lysyl oxidase expression was determined. Lysyl oxidase expression was found to be increased in non-mineralized connective tissue adjacent to inflamed lesions. Morphometric analyses indicated that maximum lysyl oxidase expression occurred at a discrete distance from the lesion not exceeding 350 microm from the inflammatory cells. Staining was associated with mesenchymal cells with a fibroblastic morphology. No lysyl oxidase staining was found near teeth where no lesion was induced. Application of a mixture of FGF-2 and IGF-1 resulted in a further twofold increase in lysyl oxidase expression. These results provide a new in vivo model to study lysyl oxidase regulation, and suggest that inflammatory cells may control lysyl oxidase expression in oral tissues, possibly by a mechanism involving secretion of cytokines and other factors, probably contributing to the regulation of extracellular matrix accumulation.

Animals↗

PubMed1998

Endodontic pathogens stimulate monocyte chemoattractant protein-1 and interleukin-8 in mononuclear cells.

Microbial infection of the dental pulp leads to the recruitment of leukocytes and the formation of lesions of endodontic origin. The chemokines interleukin-8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1) are relatively specific chemoattractants for neutrophils and monocytes, respectively. In the present studies, peripheral blood mononuclear cells were stimulated by Streptococcus mutants, Porphyromonas endodontalis, and Peptostreptococcus anaerobius, which are associated with lesions of endodontic origin. Each of these bacteria induced a dose-dependent increase in IL-8 and MCP-1, determined by ELISA. The levels induced are physiologically relevant. However, low doses of P. endodontalis were less effective in inducing IL-8 or MCP-1 expression, compared with S. mutants or P. anaerobius. Thus, these bacteria can induce significant levels of the chemokines IL-8 and MCP-1, which could contribute to the recruitment of neutrophils or monocytes in vivo. The expression of these mediators may contribute to the development of endodontic infections, particularly with regard to inflammatory leukocyte recruitment.

Animals↗

PubMed1998

PDGF-alpha receptor subunit expression down-regulated by IL-1beta in human periodontal ligament cells.

The responses of cells to the distinct PDGF isoforms have been correlated directly to the relative numbers of specific PDGF receptor subunits on the cell surface. The modulation of PDGF-alpha receptor subunits, the major subunit expressed in human periodontal ligament (PDL) cells, by cytokines present in the periodontal wound site, such as interleukin-1 (IL-1), may be an important factor influencing regenerative outcomes. The purpose of the present study was to examine the effects of IL-1 beta on PDGF-alpha receptor subunit expression in human PDL cells. Primary cultures of human PDL cells were treated with IL-1 beta over a range of concentrations. We assessed PDGF-alpha receptor subunits by examining the mitogenic responses of cells to PDGF-AA, specific binding of 125I-labeled PDGF-AA, immunofluorescent analysis of PDGF-alpha receptor subunits, and PDGF-alpha receptor subunit mRNA levels using Northern blot analysis. The results demonstrate a significant concentration-dependent decrease in 3H-thymidine incorporation in response to PDGF-AA following IL-1 beta treatment (p < 0.001). This decreased response correlated directly with IL-1-induced decreases in 125I-labeled PDGF-AA binding (p < 0.01), the numbers of immunolabeled PDGF-alpha receptor subunits, and in PDGF-alpha receptor subunit mRNA levels. However, when combined with TGF-beta, IL-1 beta did not show additional down-regulation in proliferative response to PDGF-AA or PDGF-alpha receptor subunits beyond that achieved with these factors individually. These experiments identify IL-1 beta, along with TGF-beta, as significant inhibitors of PDGF stimulation in human PDL cells, acting through the down-regulation of PDGF-alpha receptor subunit expression.

Analysis of Variance↗

PubMed1998

Interleukin-1 and tumor necrosis factor antagonists inhibit the progression of inflammatory cell infiltration toward alveolar bone in experimental periodontitis.

Periodontal disease is a significant cause of tooth loss in humans and is one of the most prevalent diseases associated with bone loss. Following bacterial colonization, the gingiva becomes inflamed and, in some cases, progresses to destruction of alveolar bone. To investigate the temporal movement of inflammatory cells toward alveolar bone and the role of interleukin-1 (IL-1) and tumor necrosis factor (TNF) in this process, studies were carried out in a Macaca fascicularis primate model of experimental periodontitis. IL-1 and TNF activity was inhibited by local application of soluble receptors to IL-1 and TNF by injection into interdental papillae. The results indicate that following induction of experimental periodontitis, the front of inflammatory cells progresses toward alveolar bone and is associated with osteoclast formation. These processes are inhibited by blockers to IL-1 and TNF. These studies suggest that the conversion from gingivitis to periodontitis is directly associated with the movement of an inflammatory infiltrate toward alveolar bone, and that this activity is at least partially dependent upon IL-1 and/ or TNF.

Alveolar Bone Loss↗

PubMed1997

Antibody to Mac-1 or monocyte chemoattractant protein-1 inhibits monocyte recruitment and promotes tumor growth.

Human tumors are frequently infiltrated by numerous monocytes/macrophages, which can be found within the tumor mass (intratumoral) or surrounding the tumor (peritumoral). The functional role that these monocytes/macrophages play in tumor growth is controversial. To address this issue we inhibited intratumoral monocyte/macrophage recruitment with mAbs that either blocked integrin function or neutralized a tumor-produced chemotactic protein. Both treatments significantly increased tumor formation and accelerated tumor growth. Surprisingly, the same results were obtained when recruitment of peritumoral or intratumoral monocytes/macrophages was blocked. Our findings are contrary to one of the purported roles of monocytes/macrophages, particularly in the peritumoral area, since we found no evidence for monocyte/macrophage-supported tumor growth. These results provide direct evidence that intratumoral as well as peritumoral monocytes/macrophages act to limit tumor size in the early stages following tumor inoculation and provide a mechanism that accounts for monocyte/macrophage recruitment to human tumors.

Animals↗

PubMed1997

Moloney murine leukemia virus long terminal repeat activates monocyte chemotactic protein-1 protein expression and chemotactic activity.

Moloney murine leukemia virus (Mo-MuLV) is a thymotropic and leukemogenic retrovirus which causes T lymphomas. Recently, Mo-MuLV has been shown to trans-activate cellular genes. Monocyte chemoattractant protein-1 (MCP-1) is a chemokine which can promote the migration and diapedesis of monocytes and lymphocytes, as well as inducing metastasis of lymphomas. Here we demonstrate that introduction of Mo-MuLV or the MuLV LTR alone, transiently or stably, into Balb/c-3T3 cells or HeLa cells resulted in 9-11 fold increases in MCP-1 transcripts. This trans-activation of the MCP-1 gene by the Mo-MuLV LTR is independent of the physical location of the MCP-1 gene or of the LTR, occurring whether the LTR or the MCP-1 gene is integrated in the genome or transiently expressed. Immunoblot analysis using an anti-MCP-1 polyclonal antibody showed that the expression of the MuLV LTR in HeLa cells also induced the appearance of the MCP-1 protein. Boyden Chamber analysis demonstrated that the MCP-1 chemotactic activity produced by HeLa cells with an integrated MuLV LTR was elevated by 11 fold and that neutralizing antibody to human MCP-1 abrogated monocyte migration in response to MuLV LTR expression. Promoter deletional analysis showed the LTR responsive cis-acting element in the MCP-1 promoter is located between -141 and -88. Deletion of this region abolished the trans-activation of MCP-1 by the LTR. These LTR-mediated activations of a chemotactic and inflammatory cytokine may be relevant as mechanisms whereby retroviruses which do not contain oncogenes can induce neoplasia.

Animals↗

PubMed1997

Monocyte chemoattractant protein-1 induces monocyte recruitment that is associated with an increase in numbers of osteoblasts.

Monocyte chemoattractant protein-1 (MCP-1) is a member of the chemokine family of cytokines. The principal function of MCP-1 is thought to be the stimulation of monocyte recruitment. Monocyte products are potential regulators of bone cell activity. Growth factors produced by monocytes may stimulate bone formation, while cytokines such as IL-1 and IL-6 can induce bone resorption. To determine whether MCP-1 enhances recruitment of monocytes during bone healing, studies were carried out in which MCP-1 was applied to osseous sites in vivo. Changes in monocyte number were determined by immunohistochemistry using the antibody ED-1 specific for peripheral monocytic cells. The effect of MCP-1 on osteoblast number was determined by counting the number of alkaline phosphatase positive cells in close proximity to bone. For comparison, osteoblast number was also determined following stimulation with platelet-derived growth factor (PDGF)-BB plus IGF-1 in vivo. Results indicate that MCP-1 stimulated a large increase in monocyte recruitment compared to vehicle alone. An increase in monocytes induced by MCP-1 was associated with an increase in the number of osteoblasts lining the bone surface, although not to the same magnitude as a positive control, PDGF-BB, and IGF-1. These results indicate that MCP-1 induces the recruitment of monocytes to bone and suggest that the recruitment is associated with an increase in osteoblast number. This is likely to occur via indirect mechanisms, because MCP-1 did not directly enhance DNA synthesis in osteoblastic cells in vitro. Thus, activated mononuclear phagocytes may play an important role in osseous wound healing by stimulating proliferation of osteoblastic cells, presumably through the elaboration of growth factors.

Alkaline Phosphatase↗

PubMed1997

Temporal expression of PDGF receptors and PDGF regulatory effects on osteoblastic cells in mineralizing cultures.

Platelet-derived growth factor (PDGF) is mitogenic and chemotactic for osteoblastic cells in vitro. It is expressed during osseous wound healing and stimulates formation of new bone in vivo. PDGF stimulates cells by binding to specific cell surface receptors. The purpose of this study was to examine the effects of PDGF on osteoblastic proliferation and differentiation in long-term mineralizing cultures. Utilizing Northern blot analysis, we found that continuous PDGF treatment increased histone expression, indicative of enhanced proliferation, but suppressed osteoblast differentiation, demonstrated by inhibition of alkaline phosphatase, type I collagen, and osteocalcin expression. The inhibitory effect of PDGF on the differentiated function of osteoblasts was further established by findings that PDGF significantly inhibited nodule formation. The expression of PDGF receptors varied at different stages of culture. PDGF receptor mRNA expression increased when the cells had achieved a mature phenotype, during the stage of matrix maturation, and then decreased. However, as demonstrated by thymidine incorporation assays, the capacity of PDGF to stimulate DNA synthesis actually decreased during osteoblast maturation, as receptor expression increased. To investigate this apparent contradiction, tyrosyl phosphorylation and immunoblot assays were performed to assess changes in PDGF activation of their cognate receptors. The pattern of PDGF-induced tyrosyl phosphorylation remained relatively constant. This suggests that the diminished mitogenic activity of PDGF that occurs after osteoblast differentiation is regulated at a postreceptor level.

Animals↗

PubMed1997

Leukocyte adhesion molecules.

Recruitment of leukocytes is critical to many of the processes studied in oral biology. With the development of new tools such as monoclonal antibody production and transgenic mice, the specific adhesion molecules thought to be important in leukocyte recruitment have been identified and their function examined. These molecules can be divided into three major classes: selectins, members of the immunoglobulin superfamily, and integrins. They mediate interactions between leukocytes and endothelial cells, facilitating the initial process of leukocyte rolling, firm attachment to endothelium, transendothelial migration, diapedesis, and migration along connective tissue. The goal of this paper is to provide an understanding of which molecules are involved in the above processes by discussing their cellular distribution, counter-receptors, and physiologic function.

Animals↗

PubMed1997

The use of biologic response modifiers in human clinical trials.

To optimize regeneration of the periodontium, new cementum, periodontal ligament, and bone must be formed. Conventional periodontal surgery decreases the likelihood of continued progressive periodontal disease however, it does not lead to significant periodontal regeneration. In vitro studies have identified a class of biologic response modifiers loosely referred to as growth factors, which stimulate the cellular events of tissue regeneration. The most promising are mitogenic and differentiation factors. Based on promising results from animal studies, the application of growth factors to predictably stimulate periodontal regeneration is entering human clinical trials. This manuscript deals with several important considerations in testing biologic response modifiers in humans. Suggestions are made regarding the following parameters: 1) selection of the unit of measurement; 2) patient and lesion selection; 3) identification of controls; 4) selection of outcome parameters; 5) statistical approach; and 6) considerations in treatment regimens.

Animals↗

PubMed1997

Cells with osteoblastic phenotypes can be explanted from human gingiva and periodontal ligament.

Considerable phenotypic heterogeneity has been reported in gingival fibroblasts. Similarly, cells from the periodontal ligament (PDL) can be isolated with different phenotypes. Although it has been suggested that cells from the gingiva do not contribute to the formation of hard tissue, it is theoretically possible that under appropriate stimuli, immature mesenchymal cells in gingiva could differentiate along an osteoblastic pathway. Differentiation of immature mesenchymal cells into osteoblasts following stimulation with osteoinductive factors has been demonstrated in muscle. We undertook experiments to establish whether cells with osteoblastic characteristics could be identified from human gingiva as well as from human periodontal ligament. Some cell populations from each of these tissues were found to have high basal alkaline phosphatase activity, to release osteocalcin in response to 1,25(OH)2 VitD3, and to form a mineralized matrix. Thus, cells can be isolated from the gingiva and PDL that exhibit phenotypic markers, which taken together are characteristic of osteoblastic cells. Other cell populations derived from the PDL and gingival connective tissue were isolated that had fibroblastic characteristics. These studies support the concept that gingival tissue can give rise to cells which may differentiate along either a fibroblastic or an osteoblastic pathway.

Adult↗

PubMed1997

The pattern of monocyte recruitment in tumors is modulated by MCP-1 expression and influences the rate of tumor growth.

Macrophage infiltration is an important aspect of the host response to tumor growth. Tumor-associated macrophages often exhibit intratumoral or peritumoral infiltration patterns. However, the mechanism that mediates distinctive patterns of macrophage infiltration and their impact on tumor growth is not known. We studied macrophage infiltration and the effect of this infiltration on tumor growth in mice inoculated with four human tumor cell lines. We report here that tumor cells producing high levels of monocyte chemoattractant protein-1 (MCP-1) had earlier recruitment of intratumoral macrophages than did lower producers and nonproducers. These MCP-1 high producers also had a lower tumor take rate than tumors that produced little or no MCP-1. The importance of early recruitment of monocytes was further demonstrated by introduction of fMLP (a chemotactic peptide) to the tumor sites. Administration of fMLP abolished the tumor formation when applied at the time of tumor-cell inoculation. When injection of fMLP was delayed, tumor growth was slowed but not eliminated. We also demonstrated that all MCP-1-producing tumors exhibited both intratumoral and peritumoral macrophage patterns, whereas MCP-1 nonproducers exhibited a peritumoral macrophage pattern only. The number of intratumoral macrophages was negatively correlated with tumor size. Collectively, our results suggest that (a) early recruitment of monocytes inhibits tumor growth; and (b) early intratumoral macrophage infiltration in vivo corresponds to the level of MCP-1 produced by tumors in vitro. In contrast, recruitment of neutrophils was not negatively correlated with tumor growth. Thus, early recruitment of macrophages may be beneficial to cancer patients.

Animals↗