Differential expression of matrilysin-1 (MMP-7), 92 kD gelatinase (MMP-9), and metalloelastase (MMP-12) in oral verrucous and squamous cell cancer

Squamous cell carcinoma (SCC) of the oral cavity is a highly invasive tumour of stratified squamous epithelium that spreads through degradation of the basement membrane (BM) and extracellular matrix (ECM). There are currently no reliable tissue or serum markers to predict whether the tumour has metastasized at the time of diagnosis. Verrucous carcinoma (VC) of the oral cavity is a rare low-grade variant of oral SCC that penetrates into the subepithelial connective tissue. Many matrix metalloproteinases (MMPs), such as MMP-1, -2, -7, -9, -13, and -14, as well as integrin receptors have been implicated in cancer invasion. Integrin alphavbeta6 is induced in SCC and appears to be involved in up-regulation of MMP-9 expression by oral keratinocytes and promotion of their migration. The aim of this study was to investigate whether the pattern of MMP expression or that of alphavbeta6 integrin contributes to the differences in the biological behaviour of oral SCC and VC. The results show that the less aggressive nature of oral VC may be connected to its MMP expression profile. Typically, VCs were devoid of epithelial MMP-3, -7, -9, -12 and -13 expression, compared with SCCs. MMP-19 was expressed by epithelial keratinocytes in hyperproliferative areas of verrucous hyperplasia, VC, and SCC, but was absent in the invasive cancer cell nests of SCC. MMP-26 was expressed by hyperproliferative keratinocytes in VC as well as by invasive cancer cells in SCCs. MMP-10 was expressed widely in the epithelium of all SCC specimens. alphavbeta6 integrin expression was also detected in some cases of epithelial hyperplasia but was significantly more abundant in cancers at the invasive front. The absence of MMP-7, -9 and -12 from epithelial cells may serve as a good prognostic marker of non-invasive oral carcinoma. Blocking the activity of invasion-specific MMPs or alphavbeta6 integrin might offer novel therapeutic modalities in early-stage oral carcinoma.     

Substrate-adsorbed collagen and cell secreted fibronectin concertedly induce cell migration on poly(lactide–glycolide) substrates

Limited epithelial cell migration on synthetic polymeric biomaterials, such as polyesters, presents a serious challenge to their use as scaffolds for artificial skin analogs. The mechanisms by which a physiologic matrix interface on such polymers may regulate and promote cell migration under ‘activated conditions’ were the focus of this study. We have quantified the migration behavior of epidermal growth factor (EGF) stimulated epidermal keratinocytes on 50 : 50 poly- , (lactide–glycolide) (PLGA) substrates, following exogenous and cell-derived substrate conditioning based on the model matrix proteins, collagen and fibronectin. We report that ‘non-conditioned’ PLGA substrates elicited poor levels of keratinocyte migration. However, keratinocyte migration was significantly enhanced upon the adsorption of type I collagen, and was only weakly enhanced with fibronectin adsorption. Molecular analysis of the mechanism of enhanced migration on collagen-PLGA substrates showed that keratinocyte migration was sensitive to cell-derived fibronectin conditioning, but not to cell-secreted collagen conditioning. Fibronectin control of cell migration on collagen-PLGA was found to be both stoichiometric and biologically specific, mediated via adhesion involving keratinocyte αv integrin receptors. Based on our results, we propose a unique paradigm for induction of cell migration on a non-physiologic synthetic polymer using concerted interactions between primary, polymer-instructed matrix remodeling and secondary, cell-derived matrix remodeling.     

淋巴细胞趋化因子增强肝癌树突状细胞融合瘤苗体外免疫作用

目的：观察淋巴细胞趋化因子(lymphotactin, Lptn)基因修饰的肝癌树突状细胞(dendritic cells, DC)融合瘤苗的体外生物学特征和免疫作用。方法： 以重组Lptn基因修饰小鼠骨髓来源的DC，在聚乙二醇(polyethylene glycol，PEG)作用下与H22小鼠肝癌细胞融合，分别以RT-PCR及ELISA方法检测Lptn mRNA及蛋白水平表达，流式细胞仪分析细胞表面免疫分子表达。MTT法检测Lptn基因修饰的肝癌树突状细胞融合瘤苗(DCLptn/H22)对同种异体T淋巴细胞的体外刺激作用。LDH法检测DCLptn/H22融合瘤苗诱导产生的杀伤性T淋巴细胞活性。结果： Lptn基因修饰的DC能分泌较高浓度的淋巴细胞趋化因子，并且具有明显的趋化淋巴细胞功能。DCLptn/H22不但增强融合瘤苗刺激同种异体T淋巴细胞增殖, 而且能增强杀伤性T淋巴细胞活性。结论： 淋巴细胞趋化因子基因修饰能增强融合瘤苗体外免疫刺激作用。     

Tissue transglutaminase mediates the pro‐malignant effects of oncostatin M receptor over‐expression in cervical squamous cell carcinoma

Oncostatin M receptor (OSMR) is commonly over‐expressed in advanced cervical squamous cell carcinoma (SCC), producing a significantly worse clinical outcome. Cervical SCC cells that over‐express OSMR show enhanced responsiveness to the major ligand OSM, which induces multiple pro‐malignant effects, including increased cell migration and invasiveness. Here, we show that tissue transglutaminase (TGM2) is an important mediator of the ligand‐dependent phenotypic effects of OSMR over‐expression in SCC cells. TGM2 expression correlated with disease progression and with OSMR levels in clinical samples of cervical and oral SCC. TGM2 depletion in cervical SCC cells abrogated OSM‐induced migration on fibronectin‐coated surfaces and invasiveness through extracellular matrix, while ectopic expression of TGM2 increased cell motility and invasiveness. Confocal microscopy and co‐immunoprecipitation assays showed that TGM2 interacted with integrin–α5β1 in the presence of fibronectin in cervical SCC cells, with OSM treatment strengthening the interaction. Importantly, integrin–α5β1 and fibronectin were also over‐expressed in cervical and oral SCC, where levels correlated with those of OSMR and TGM2. This combined tissue and in vitro study demonstrates for the first time that stimulation of over‐expressed OSMR in cervical SCC cells activates TGM2/integrin‐α5β1 interactions and induces pro‐malignant changes. We conclude that an OSMR/TGM2/integrin‐α5β1/fibronectin pathway is of biological significance in cervical SCC and a candidate for therapeutic targeting. Copyright © 2013 Pathological Society of Great Britain and Ireland. © 2013 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.     

Phosphodiesterase type III inhibitor, cilostazol, inhibits colon cancer cell motility

Metastasis of cancer cells is initiated by the cellular migration into extracellular matrix and surrounding vessels. We previously showed that elevation of cAMP levels in cancer cells suppressed trans-cellular migration in vitro. Drugs that can elevate cAMP levels in cancer cells effectively may be applied to prevent metastasis in cancer patients. Cilostazol, an oral anti-platelet drug, is a specific cAMP phosphodiesterase type III inhibitor and has been clinically used to treat thrombosis patients. In chemotaxis assay, cellular migration of human colon cancer cells, DLD-1, was induced by 10 μg/ml of soluble fibronectin or 10% of fetal bovine serum (FBS). Treatment with cilostazol (50 μM) suppressed 92.3% or 84.6% of the migration in control cells, respectively. When DLD-1 cells were stimulated by soluble fibronectin in phagokinetic assay, migration assessed by the area of gold particle phagocytosis track was induced and cilostazol also decreased 67.3% of the cellular migration in control cells. Furthermore, in the trans-cellular migration assay, cilostazol suppressed cancer cell invasion induced by FBS. Thus, cilostazol can suppress colon cancer cell motility and might be effective as an anti-metastasis drug for cancer patients. This revised version was published online in July 2006 with corrections to the Cover Date.     

Substrate-adsorbed collagen and cell secreted fibronectin concertedly induce cell migration on poly(lactide-glycolide) substrates

Limited epithelial cell migration on synthetic polymeric biomaterials, such as polyesters, presents a serious challenge to their use as scaffolds for artificial skin analogs. The mechanisms by which a physiologic matrix interface on such polymers may regulate and promote cell migration under 'activated conditions' were the focus of this study. We have quantified the migration behavior of epidermal growth factor (EGF) stimulated epidermal keratinocytes on 50:50 poly-D,L(lactide-glycolide) (PLGA) substrates, following exogenous and cell-derived substrate conditioning based on the model matrix proteins, collagen and fibronectin. We report that 'non-conditioned' PLGA substrates elicited poor levels of keratinocyte migration. However, keratinocyte migration was significantly enhanced upon the adsorption of type I collagen, and was only weakly enhanced with fibronectin adsorption. Molecular analysis of the mechanism of enhanced migration on collagen-PLGA substrates showed that keratinocyte migration was sensitive to cell-derived fibronectin conditioning, but not to cell-secreted collagen conditioning. Fibronectin control of cell migration on collagen-PLGA was found to be both stoichiometric and biologically specific, mediated via adhesion involving keratinocyte alpha v integrin receptors. Based on our results, we propose a unique paradigm for induction of cell migration on a non-physiologic synthetic polymer using concerted interactions between primary, polymer-instructed matrix remodeling and secondary, cell-derived matrix remodeling.     

Loss of membrane-bound serine protease inhibitor HAI-1 induces oral squamous cell carcinoma cells' invasiveness

A loss of balance between cell membrane‐associated proteases and their inhibitors may underlie cancer invasion and metastasis. We analysed the roles of a membrane‐ associated serine protease inhibitor, HAI‐1, in oral squamous cell carcinoma (OSCC). While membranous HAI‐1 was widely observed in cancer cells of human OSCC tissues, this was significantly reduced at the infiltrative invasion front. In vitro, HAI‐1 was detected in all eight OSCC cell lines examined, in which its cognate membrane protease, matriptase was also expressed. HAI‐1 expression knock‐down (KD) in OSCC lines, SAS and HSC‐3, reduced the growth of both lines in vitro but significantly enhanced SAS tumourigenicity in vivo, which was accompanied by histological changes suggestive of the epithelial‐mesenchymal transition. Both HAI‐1‐KD lines also exhibited significantly enhanced migratory capability, and membrane‐associated but not truncated HAI‐1 was required to rescue this phenotype. Other OSCC lines (HSC‐2, Sa3, Ca9‐22) also showed enhanced migration in response to HAI‐1 KD. The enhanced migration is partly attributed to dysregulation of matriptase, as simultaneous matriptase KD alleviated the migration of HAI‐1‐KD cells. HAI‐1 deficiency also altered the expression of CD24, S100A4, CCND2 and DUSP6, all of which are involved in tumour progression. While matriptase was involved in the increased CD24 expression associated with HAI‐1 deficiency, the protease appeared to be not responsible for the altered expression of other genes. Therefore, a matriptase‐independent mechanism for the invasiveness associated with HAI‐1 KD is also present. Together, these observations suggest that HAI‐1 has a crucial suppressive role in OSCC cell invasiveness. Copyright © 2012 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Expression of protein arginine methyltransferase‐5 in oral squamous cell carcinoma and its significance in epithelial‐to‐mesenchymal transition

Protein arginine methyltransferases (PRMT) 5, a member of type II arginine methyltransferases, catalyzes the symmetrical dimethylation of arginine residues on histone and non‐histone substrates. Although the overexpression of PRMT5 has been reported in various cancers, its role in oral squamous cell carcinoma (OSCC) has not been elucidated. In the present study, we immunohistochemically examined the expression of PRMT5 in surgically resected oral epithelial dysplasia (OED, n = 8), oral intraepithelial neoplasia (OIN)/carcinoma in situ (CIS) (n = 11) and OSCC (n = 52) with or without contiguous OED lesions. In the normal epithelium, PRMT5 was weakly expressed in the cytoplasm of basal layer cells. In OED, OIN/CIS, and OSCC, its expression consistently and uniformly increased in the cytoplasm of dysplastic and cancer cells. Moreover, nuclear and cytoplasmic localization was detected in the invasive front of cancer cells, particularly in cases showing poor differentiation or aggressive invasion patterns. The concomitant nuclear and cytoplasmic expression of PRMT5 correlated with the loss of E‐cadherin and cytokeratin 17, and the upregulation of vimentin, features that are both indicative of epithelial‐to‐mesenchymal transition. PRMT5 may play a role from early oncogenesis through to the progression of OSCC, particularly in the aggressive mode of stromal invasion.     

Arylsulfatase B regulates colonic epithelial cell migration by effects on MMP9 expression and RhoA activation

Arylsulfatase B (ASB; N-acetylgalactosamine-4-sulfatase; 4-sulfatase; ARSB) is the enzyme that removes 4-sulfate groups from N-acetylgalactosamine 4-sulfate, which combines with glucuronate to form the disaccharide unit of chondroitin-4-sulfate (C4S). In this study, we report how variation in expression of ASB affected the migration of human colonic epithelial cells. In the T84 cell line, derived from lung metastasis of malignant colonic epithelial cells, the activity of ASB, as well as steroid sulfatase, arylsulfatase A, and galactose-6-sulfatase, were significantly less than in normal, primary colonic epithelial cells and in the NCM460 cell line which was derived from normal colonocytes. In the T84 cells, matrix metalloproteinase 9 (MMP9), activated RhoA, and cell migration, as well as C4S content, were significantly more than in the NCM460 cells. Silencing and overexpression of ASB had inverse effects on MMP9, activated RhoA, and cell migration, as well as the C4S content, in the NCM460 and T84 cells. When ASB expression was silenced by siRNA in the NCM460 cells, MMP9 secretion increased to over 3 times the basal level, activated RhoA increased ~85%, and cell migration increased ~52%. Following overexpression of ASB, MMP9 declined 51%, activated RhoA declined ~51%, and cell migration decreased ~37%. These findings demonstrate marked effects of ASB expression on the migratory activity of colonic epithelial cells, activated RhoA, and MMP9, and suggest a potential vital role of ASB, due to its impact on chondroitin sulfation, on determination of the invasive phenotype of colonic epithelial cells.     

Distinct signatures of B-cell homeostatic and activation-dependent chemokine receptors in the development and progression of extragastric MALT lymphomas

Chemokine receptors mediate migration and activation of lymphocytes through binding of their ligands. Recent studies have revealed important contributions of chemokine receptors to the development, progression, and dissemination of haematopoietic neoplasms. Because the chemokine receptor expression profile in extragastric MALT lymphoma is unknown, we performed a comprehensive study on tissue samples of parotid glands, parotid glands affected by Sjögren syndrome, extragastric MALT lymphoma, and extranodal diffuse large B‐cell lymphoma (eDLBCL) originating from MALT lymphoma (transformed MALT lymphoma). By investigating the expression of 19 chemokine receptors by real‐time PCR using a semi‐quantitative approach and of four chemokine receptors (CCR1, CCR5, CXCR6, and XCR1) by immunohistochemistry, we show that the chemokine receptor expression profiles of extragastric MALT lymphomas differ substantially from those of extranodal DBLCL, with lower expression of CCR1, CCR8, and CXCR3, and the absence of expression of CX3CR1 and XCR1 in eDLBCL. Expression of CCR6, CCR7, CXCR3, CXCR4, and CXCR5, responsible for B‐cell homing to secondary lymphoid tissue, was detected in both B‐cell malignancies. Expression of CCR4 was just detected in trisomy 3‐positive MALT lymphoma cases. Comparing gastric with extragastric MALT lymphomas, up‐regulation of CXCR1 and CXCR2 accompanied by down‐regulation of CCR8 and CX3CR1 and loss of XCR1 expression in extragastric MALT lymphomas appear to be key determinants for the site of origin of MALT lymphomagenesis. Our results support a model of stepwise progression of extragastric MALT lymphoma from a non‐neoplastic event to Sjögren syndrome, to MALT lymphoma, and finally to overt eDLBCL, guided by differentially expressed B‐cell homeostatic and activation‐dependent chemokine receptors and their ligands. Copyright © 2008 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Interleukin‐17 regulates matrix metalloproteinase activity in human pulmonary tuberculosis

Tuberculosis (TB) is characterized by extensive pulmonary matrix breakdown. Interleukin‐17 (IL‐17) is key in host defence in TB but its role in TB‐driven tissue damage is unknown. We investigated the hypothesis that respiratory stromal cell matrix metalloproteinase (MMP) production in TB is regulated by T‐helper 17 (T_H‐17) cytokines. Biopsies of patients with pulmonary TB were analysed by immunohistochemistry (IHC), and patient bronchoalveolar lavage fluid (BALF) MMP and cytokine concentrations were measured by Luminex assays. Primary human airway epithelial cells were stimulated with conditioned medium from human monocytes infected with Mycobacterium tuberculosis (Mtb) and T_H‐17 cytokines. MMP secretion, activity, and gene expression were determined by ELISA, Luminex assay, zymography, RT‐qPCR, and dual luciferase reporter assays. Signalling pathways were examined using phospho‐western analysis and siRNA. IL‐17 is expressed in TB patient granulomas and MMP‐3 is expressed in adjacent pulmonary epithelial cells. IL‐17 had a divergent, concentration‐dependent effect on MMP secretion, increasing epithelial secretion of MMP‐3 (p < 0.001) over 72 h, whilst decreasing that of MMP‐9 (p < 0.0001); mRNA levels were similarly affected. Both IL‐17 and IL‐22 increased fibroblast Mtb‐dependent MMP‐3 secretion but IL‐22 did not modulate epithelial MMP‐3 expression. Both IL‐17 and IL‐22, but not IL‐23, were significantly up‐regulated in BALF from TB patients. IL‐17‐driven MMP‐3 was dependent on p38 MAP kinase and the PI3K p110α subunit. In summary, IL‐17 drives airway stromal cell‐derived MMP‐3, a mediator of tissue destruction in TB, alone and with monocyte‐dependent networks in TB. This is regulated by p38 MAP kinase and PI3K pathways. © 2017 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.     

Microanatomy of the Palatal Mucosa of the Semiaquatic Malayan Box Turtle,Cuora amboinensis,and Functional Implications

Scanning Electron Microscopy (SEM) revealed that the palate of Cuora amboinensis has a flat surface with keratinized and non‐keratinized regions. Keratinization is reflected in disc‐shaped keratinized dead cells with rough microplicae on the surface, and is concentrated close to the rhamphotheca. The surface of the non‐keratinized hexagonal epithelial cells is dotted with microvilli and sometimes with cilia. Taste buds are present both in lightly keratinized and non‐keratinized regions and exhibit a crater‐like shape. Light microscopy shows the different tissue layers of the oral mucosa and the different epithelial structures. In keratinized regions, keratinocytes mature from basal to superficial, where they build up keratin layers of varying thickness. In non‐keratinized regions, the epithelial cells are arranged in a stratified fashion, and cuboidal to cylindric cells form a superficial layer. Goblet cells appear to be diffusely distributed, but are often organized in goblet cell fields which can be folded into crypts. Taste buds consist of slender epithelial cells, exhibit the typical barrel‐like shape and are specially concentrated in the anterior, praechoanal palate. This anterior concentration of taste buds is shown by kinematographic analysis to correlate with the food prehension mode in Cuora amboinensis. The lamina propria of the palatal mucosa consists of loose connective tissue with inflammatory cells between capillaries. All these structures of the oral mucosa act as a functional entity and help determine how successfully an organism adapts ecologically to the environment. Anat Rec, 291:876‐885, 2008. © 2008 Wiley‐Liss, Inc.     

Homophilic complex formation is prerequisite for MT1-MMP to degrade type-I collagen on the cell surface

Introduction MT1‐MMP degrades a wide variety of extra‐cellular matrix macromolecules and some cell‐surface proteins such as CD44, transglutaminase and α_v‐integrin, and activates zymogen of MMP‐2 and MMP‐13. Among these activities, the collagenolytic activity is one of the most important functions of the enzyme in biology, as the phenotypes of MT1‐MMP gene knockout mice, such as abnormal skeletal development and various connective tissue abnormalities, are thought to be attributed to the lack of cellular collagenase activity. We have previously shown that MT1‐MMP forms homophilic complex through its haemopexin (HPX) domain facilitating the activation of proMMP‐2 ( Itoh et al. 2001 ). In this report, we present data that collagen‐degrading activity of MT1‐MMP also requires homophilic complex formation. Methods COS7 cells were cultured on type‐I collagen film and transfected with MT1‐MMP and its mutant gene to look at collagen degradation activity of these gene products. Results Co‐expression of the catalytic domain‐deleted mutant of MT1‐MMP (MT1δCat) with the wild‐type enzyme inhibited its homophilic complex formation as well as its ability to activate proMMP‐2 on the cell surface, and MT1δCat also inhibited cell‐surface collagenolytic activity of the wild‐type MT1‐MMP. A chimeric MT1‐MMP mutant (MT‐MMP13) whose catalytic domain, hinge region and HPX domain were replaced with those derived from collagenase‐3 (MMP‐13) did not degrade collagen though MT‐MMP13 was expressed and maintained its proteolytic activity against gelatin on the cell surface. When an interface for homophilic complex formation, the HPX domain derived from MT1‐MMP, was further added to the chimeric enzyme (MT‐MMP13‐HPX_mt1), it degraded collagen. Co‐expression of MT1dCat and MT‐MMP13‐HPX_mt1 also inhibited the collagenolytic activity. Discussion Homphilic complex formation is prerequisite for the expression of collagenase activity on the cell surface. Presumably, each MT1‐MMP in the complex has different roles; one unwinds triple‐helical structure of collagen locally and the other cuts peptide bond.     

MHC antigen expression in human oral squamous carcinoma cell lines.

This study quantified the constitutive and interferon-gamma (IFN-gamma) stimulated expression of MHC class I (HLA-ABC and beta 2 microglobulin) and class II antigens (HLA-DR, -DP, -DQ) on normal and malignant oral keratinocytes using radioimmunoassay and immunocytochemical techniques. Normal keratinocytes and three of four malignant cell lines (H103, H157, H314) expressed MHC class I antigens constitutively; IFN-gamma increased MHC class I expression with significant changes in normals, H157 and H314. Normal keratinocytes expressed significantly more constitutive MHC class I antigens than H103 and H157 and significantly more IFN-gamma stimulated MHC class I antigens than H103, H157 and H314. MHC class II antigens predominantly were not expressed constitutively on normals, H103 and H157 but, in H314, HLA-DR, -DP and -DQ antigens were demonstrated on 35, 11 and 5 per cent of cells, respectively, and resulted in a non-coordinated pattern of expression (HLA-DR greater than -DP = -DQ). IFN-gamma induced HLA-DR on normals, H103 and H157, whilst HLA-DP and -DQ remained undetectable. In H314, IFN-gamma enhanced HLA-DR, -DP and -DQ (significant increase of HLA-DQ) but the interrelationship between these antigens was maintained (HLA-DR greater than -DP = -DQ). Normal keratinocytes expressed significantly more IFN-gamma stimulated HLA-DR than H103 and H157 but significantly less HLA-DR than H314 under similar experimental conditions. One oral malignant cell line (H191) did not express MHC class I and MHC class II antigens either constitutively or in response to IFN-gamma. The results demonstrate aberrant patterns of MHC expression (absence, enhanced, diminished) in the different malignant oral keratinocyte cell lines.     

Adherence of group A streptococci to fibronectin on oral epithelial cells.

The possibility that fibronectin on the surface of oropharyngeal cells may serve as a receptor for the binding of group A streptococci (Streptococcus pyogenes) was investigated. Purified human plasma fibronectin inhibited the adherence of group A streptococci to oral epithelial cells in a dose-dependent manner. The relative amounts of fibronectin available on oral epithelial cells correlated closely with the ability of these cells to bind streptococci. Group A streptococci agglutinated latex beads containing covalently linked fibronectin on their surface, and this agglutination could be inhibited by lipoteichoic acid, the adhesion that mediates attachment of group A streptococci to epithelial cells. Gelatin and the alpha 1 chain of type I collagen partially inhibited both the adherence of streptococci to oral epithelial cells and the binding of radiolabeled fibronectin to streptococci; however, the purified fibronectin-binding peptide of collagen, alpha 1 (I)CB7, inhibited neither. The binding of radiolabeled fibronectin to streptococci was inhibited by lipoteichoic acid. These results suggest that fibronectin on oral epithelial cells serves as a lipoteichoic acid-sensitive receptor for group A streptococci.     

Lymphotactin: a key regulator of lymphocyte trafficking during acute graft rejection.

The attraction of leucocytes to allografts is essential for rejection. The process is controlled by chemokines. In order to clarify the role of lymphotactin (a cytokine that represents a novel branch of the chemokine superfamily) in regulating leucocyte trafficking during graft rejection, we used rat renal transplantation models to examine its gene expression and the distribution of lymphotactin-expressing cells in renal grafts. Lymphotactin mRNA was upregulated strongly in acutely rejecting renal allografts. The mRNA was undetectable in isografts, chronically rejecting renal allografts or normal kidney. Once lymphotactin was expressed, large numbers of infiltrating lymphocytes were seen. Moreover extended studies demonstrated that in cultured rat spleen cells the expression of lymphotactin mRNA was markedly induced by phytohaemagglutinin (PHA) or phorbol myristate acetate (PMA), and such induction was inhibited by the immunosuppressive drugs FK506 and cyclosporin. Collectively, these observations provide new evidence demonstrating that lymphotactin is a key regulator of lymphocyte motility and adhesiveness during acute allograft rejection. FK506 and cyclosporin inhibition of lymphotactin expression is likely to represent an important molecular mechanism of the action of the drugs.