Expression of galectin-3 in pancreatic ductal adenocarcinoma

Interplay in galectin expression predicts patient outcomes in a spatially restricted manner in PDAC

BACKGROUND

Galectins (Gal's) are a family of carbohydrate-binding proteins that are known to support the tumour microenvironment through their immunosuppressive activity and ability to promote metastasis. As such they are attractive therapeutic targets, but little is known about the cellular expression pattern of galectins within the tumour and its neighbouring stromal microenvironment. Here we investigated the cellular expression pattern of Gals within pancreatic ductal adenocarcinoma (PDAC).

METHODS

Galectin gene and protein expression were analysed by scRNAseq (n=4) and immunofluorescence imaging (n=19) in fibroblasts and epithelial cells of pancreatic biopsies from PDAC patients. Galectin surface expression was also assessed on tumour adjacent normal fibroblasts and cancer associated primary fibroblasts from PDAC biopsies using flow cytometry.

RESULTS

scRNAseq revealed higher Gal-1 expression in fibroblasts and higher Gal-3 and -4 expression in epithelial cells. Both podoplanin (PDPN+, stromal/fibroblast) cells and EpCAM+ epithelial cells expressed Gal-1 protein, with highest expression seen in the stromal compartment. By contrast, significantly more Gal-3 and -4 protein was expressed in ductal cells expressing either EpCAM or PDPN, when compared to the stroma. Ductal Gal-4 cellular expression negatively correlated with ductal Gal-1, but not Gal-3 expression. Higher ductal cellular expression of Gal-1 correlated with smaller tumour size and better patient survival.

CONCLUSIONS

In summary, the intricate interplay and cell-specific expression patterns of galectins within the PDAC tissue, particularly the inverse correlation between Gal-1 and Gal-4 in ducts and its significant association with patient survival, highlights the complex molecular landscape underlying PDAC and provides valuable insights for future therapeutic interventions.

Unveiling the potential of galectin-3 as a diagnostic biomarker for pancreatic cancer: a review

Early detection of pancreatic cancer is crucial for improving patient outcomes, and identifying reliable biomarkers is a critical research area in this field. Galectin-3 (Gal-3) is a promising candidate for utilisation as a diagnostic biomarker in early-stage pancreatic cancer. This review aims to explore the potential of Gal-3 in pancreatic cancer diagnosis and its implications for precision medicine. Rigorous validation studies are essential to establish the clinical utility of Gal-3, including large-scale investigations to assess its sensitivity, specificity, and predictive value. Combining Gal-3 with existing biomarkers and advanced imaging techniques may enhance the accuracy of early detection. Moreover, Gal-3 holds promise for risk stratification, enabling the identification of high-risk individuals who could benefit from intensified surveillance and early interventions. However, challenges in standardised testing protocols, establishing reference ranges, assay reliability, workflow integration, cost-effectiveness, and healthcare provider education must be addressed for successful implementation. Despite these challenges, Gal-3 presents significant implications for precision medicine in pancreatic cancer management. By unravelling its potential and overcoming the hurdles, Gal-3 could revolutionise early detection, risk stratification, and personalised approaches in pancreatic cancer care. Collaborative efforts and continued research will be crucial in harnessing the full potential of Gal-3 as a diagnostic biomarker for early-stage pancreatic cancer.

Human umbilical cord mesenchymal stem cell-derived exosomes carrying hsa-miRNA-128-3p suppress pancreatic ductal cell carcinoma by inhibiting Galectin-3

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is one of the most fatal malignant tumors of the digestive system. Many patients are diagnosed at an advanced stage and lose eligibility for surgery. Moreover, there are few effective methods for treating pancreatic ductal cell carcinoma. Increasing attention has been given to microRNAs (miRNAs) and their regulatory roles in tumor progression. In this study, we investigated the effects of exosomes extracted from human umbilical cord mesenchymal stem cells (HUCMSCs) carrying hsa-miRNA-128-3p on pancreatic cancer cells.

METHODS

Based on existing experimental and database information, we selected Galectin-3, which is associated with pancreatic cancer, and the corresponding upstream hsa-miRNA-128-3p. We extracted HUCMSCs from a fresh umbilical cord, hsa-miRNA-128-3p was transfected into HUCMSCs, and exosomes containing hsa-miRNA-128-3p were extracted and collected. The effect of exosomes rich in hsa-miRNA-128-3p on pancreatic cancer cells was analyzed.

RESULTS

The expression of Galectin-3 in normal pancreatic duct epithelial cells was significantly lower than that in PDAC cell lines. We successfully extracted HUCMSCs from the umbilical cord and transfected hsa-miRNA-128-3p into HUCMSCs. Then we demonstrated that HUCMSC-derived exosomes with hsa-miRNA-128-3p could suppress the proliferation, invasion, and migration of PANC-1 cells in vitro by targeting Galectin-3.

CONCLUSION

Hsa-miRNA-128-3p could be considered as a potential therapy for pancreatic cancer. We provided a new idea for targeted therapy of PDAC.

Galectin-3 Released by Pancreatic Ductal Adenocarcinoma Suppresses γδ T Cell Proliferation but Not Their Cytotoxicity

Pancreatic ductal adenocarcinoma (PDAC) is characterized by an immunosuppressive tumor microenvironment with a dense desmoplastic stroma. The expression of β-galactoside-binding protein galectin-3 is regarded as an intrinsic tumor escape mechanism for inhibition of tumor-infiltrating T cell function. In this study, we demonstrated that galectin-3 is expressed by PDAC and by γδ or αβ T cells but is only released in small amounts by either cell population. Interestingly, large amounts of galectin-3 were released during the co-culture of allogeneic in vitro expanded or allogeneic or autologous resting T cells with PDAC cells. By focusing on the co-culture of tumor cells and γδ T cells, we observed that knockdown of galectin-3 in tumor cells identified these cells as the source of secreted galectin-3. Galectin-3 released by tumor cells or addition of physiological concentrations of recombinant galectin-3 did neither further inhibit the impaired γδ T cell cytotoxicity against PDAC cells nor did it induce cell death of in vitro expanded γδ T cells. Initial proliferation of resting peripheral blood and tumor-infiltrating Vδ2-expressing γδ T cells was impaired by galectin-3 in a cell-cell-contact dependent manner. The interaction of galectin-3 with α3β1 integrin expressed by Vδ2 γδ T cells was involved in the inhibition of γδ T cell proliferation. The addition of bispecific antibodies targeting γδ T cells to PDAC cells enhanced their cytotoxic activity independent of the galectin-3 release. These results are of high relevance in the context of an in vivo application of bispecific antibodies which can enhance cytotoxic activity of γδ T cells against tumor cells but probably not their proliferation when galectin-3 is present. In contrast, adoptive transfer of in vitro expanded γδ T cells together with bispecific antibodies will enhance γδ T cell cytotoxicity and overcomes the immunosuppressive function of galectin-3.

Prognostic and diagnostic significance of galectins in pancreatic cancer: a systematic review and meta-analysis

Background

Galectins constitute a family of β-galactoside-binding proteins, which influence various hallmarks of pancreatic cancer, including cell proliferation, invasion and migration; immune escape; and angiogenesis. Although many studies have concentrated on the role of galectins in pancreatic cancer, the results remain controversial. Hence, we performed a comprehensive meta-analysis to clarify the precise diagnostic and prognostic value of galectins in pancreatic cancer.

Methods

PubMed/MEDLINE, EMBASE and Web of Science were used to search related published literature up to July 2019. Pooled hazard ratios (HRs), diagnostic accuracy variables and related 95% confidence intervals (CIs) were calculated using STATA 14.0 software.

Results

Eleven studies including 1227 participants met our inclusion criteria. High expression of galectin family was not correlated with overall survival (OS) in pancreatic cancer (HR, 1.19; 95% CI 0.67-2.11). According to subgroup analysis, high levels of galectin-1 were significantly correlated with worse OS in pancreatic cancer (HR, 4.77; 95% CI 2.47-9.21), while high levels of tandem-repeat galectins (galectin-4 or galectin-9) predicted both better OS (HR, 0.63; 95% CI 0.46-0.86) and disease-free survival (DFS) (HR, 0.63; 95% CI 0.48-0.83). The expression levels of galectin-3 did not directly correlate with prognosis (HR, 0.99; 95% CI 0.40-2.46). The pooled sensitivity, specificity, positive likelihood ratio, and negative likelihood ratios of galectin-3 were 0.64 (95% CI 0.41-0.82), 0.76 (95% CI 0.59-0.88), 2.70 (95% CI 1.21-6.1), and 0.47 (95% CI 0.23-0.98), respectively. The area under the curve (AUC) of galectin-3 was 0.77.

Conclusion

Taken together, our results suggest that high expression of galectin-1 and low levels of galectin-4 or galectin-9 are predictors of worse prognosis in pancreatic cancer patients. The expression of galectin-3 was not directly related to OS and other clinical characteristics. Although galectin-3 exhibited some diagnostic value in patients with pancreatic cancer in this meta-analysis, clinical application prospects remain to be validated. Further studies are warranted to confirm and strengthen these findings.

Hypoxia‑induced galectin‑3 enhances RhoA function to activate the motility of tumor cells in non‑small cell lung cancer

Galectin-3 plays crucial roles in tumor progression. However, in non-small cell lung cancer (NSCLC), it remains unclear whether the hypoxic tumor microenvironment enhances galectin-3-induced cell motility. We investigated galectin-3 expression in NSCLC cells under hypoxia, and the possible molecular mechanisms by which galectin-3 influences tumor aggressiveness. Galectin-3 levels in NSCLC cell lines under hypoxia were assessed using reverse transcription PCR and western blotting. To clarify the role of endogenous galectin-3, the effect of galectin-3 knockdown in NSCLC cells was investigated using scratch and invasion assays. The expression and clinicopathological significance of galectin-3 in 57 patients with pN0M0 invasive pulmonary adenocarcinoma were investigated by immunohistochemistry. Both mRNA and protein levels of galectin-3 in the NSCLC cell lines A549 and LK-2 were upregulated by hypoxia. As revealed by scratch and invasion assays, the cell migratory and invasive activities were significantly increased under hypoxia, but were reduced by galectin-3 knockdown. Notably, addition of galectin-3 to the media did not improve the cell motility impaired by galectin-3 knockdown. To clarify the role of endogenous galectin-3 in the enhancement of tumor cell motility under hypoxia, we focused on the function of RhoA. RhoA level in the plasma membrane, but not in the cytoplasm, was increased under hypoxia and decreased by galectin-3 knockdown. RhoA activity was significantly enhanced under hypoxia and effectively inhibited by galectin-3 knockdown. In patients with pN0M0 invasive pulmonary adenocarcinoma, higher galectin-3 expression on tumor cells was significantly associated with tumor cell invasion into microvessels and tumor recurrence after surgery. These data demonstrate that in NSCLC cells under hypoxia, upregulated galectin-3 levels increase the localization of RhoA to the plasma membrane, thus enhancing RhoA activity, which is associated with aggressive cell motility. In pN0M0 invasive pulmonary adenocarcinoma, galectin-3 is a potential biomarker for predicting tumor recurrence after radical surgery.

Role of galectins in lung cancer

Lung cancer is the leading cause of cancer-associated mortality worldwide and is also associated with a poor prognosis. As in numerous other types of cancer, galectins have been demonstrated to be involved in the progression of lung cancer. Galectins belong to a superfamily of lectins, which are carbohydrate-binding proteins. There are at least 15 members in the galectin family, however, only galectin-1, −2, −3, −4, −7, −8, −9, −10, −12, and −13 are found in humans. Galectins are able to mediate interactions between cells, including homotypic and heterotypic interactions; they also facilitate the bindings between cells and extracellular matrix components. These cell-cell and cell-matrix interactions, as well as the galectin signaling on the cell surface, are able to modulate signaling pathways and thereby influence cellular functions and behaviors. Galectin-1, −3, −4, −7, −8 and −9 are associated with lung cancer. These galectins are associated with tumor invasion, migration, metastasis and progression, and may serve important roles in the tumor microenvironment of lung cancer. The majority of galectins are associated with the progression of lung cancer, with the exception of galectin-9, which is associated with enhanced anticancer immunity. Therefore, galectins may be potential targets for developing novel lung cancer therapies.

Synthesis and functionalization of protease-activated nanoparticles with tissue plasminogen activator peptides as targeting moiety and diagnostic tool for pancreatic cancer

Background

Functionalized nanoparticles (NPs) are one promising tool for detecting specific molecular targets and combine molecular biology and nanotechnology aiming at modern imaging. We aimed at ligand-directed delivery with a suitable target-biomarker to detect early pancreatic ductal adenocarcinoma (PDAC). Promising targets are galectins (Gal), due to their strong expression in and on PDAC-cells and occurrence at early stages in cancer precursor lesions, but not in adjacent normal tissues.

Results

Molecular probes (10-29 AA long peptides) derived from human tissue plasminogen activator (t-PA) were selected as binding partners to galectins. Affinity constants between the synthesized t-PA peptides and Gal were determined by microscale thermophoresis. The 29 AA-long t-PA-peptide-1 with a lactose-functionalized serine revealed the strongest binding properties to Gal-1 which was 25-fold higher in comparison with the native t-PA protein and showed additional strong binding to Gal-3 and Gal-4, both also over-expressed in PDAC. t-PA-peptide-1 was selected as vector moiety and linked covalently onto the surface of biodegradable iron oxide nanoparticles (NPs). In particular, CAN-doped maghemite NPs (CAN-Mag), promising as contrast agent for magnetic resonance imaging (MRI), were selected as magnetic core and coated with different biocompatible polymers, such as chitosan (CAN-Mag-Chitosan NPs) or polylactic co glycolic acid (PLGA) obtaining polymeric nanoparticles (CAN-Mag@PNPs), already approved for drug delivery applications. The binding efficacy of t-PA-vectorized NPs determined by exposure to different pancreatic cell lines was up to 90%, as assessed by flow cytometry. The in vivo targeting and imaging efficacy of the vectorized NPs were evaluated by applying murine pancreatic tumor models and assessed by 1.5 T magnetic resonance imaging (MRI). The t-PA-vectorized NPs as well as the protease-activated NPs with outer shell decoration (CAN-Mag@PNPs-PEG-REGAcp-PEG/tPA-pep1_Lac) showed clearly detectable drop of subcutaneous and orthotopic tumor staining-intensity indicating a considerable uptake of the injected NPs. Post mortem NP deposition in tumors and organs was confirmed by Fe staining of histopathology tissue sections.

Conclusions

The targeted NPs indicate a fast and enhanced deposition of NPs in the murine tumor models. The CAN-Mag@PNPs-PEG-REGAcp-PEG/tPA-pep1_Lac interlocking steps strategy of NPs delivery and deposition in pancreatic tumor is promising.

Secretome protein signature of human pancreatic cancer stem-like cells

Emerging research has demonstrated that pancreatic ductal adenocarcinoma (PDAC) contains a sub-population of cancer stem cells (CSCs) characterized by self-renewal, anchorage-independent-growth, long-term proliferation and chemoresistance. The secretome analysis of pancreatic CSCs has not yet been performed, although it may provide insight into tumour/microenvironment interactions and intracellular processes, as well as to identify potential biomarkers. To characterize the secreted proteins of pancreatic CSCs, we performed an iTRAQ-based proteomic analysis to compare the secretomes of Panc1 cancer stem-like cells (Panc1 CSCs) and parental cell line. A total of 72 proteins were found up-/down-regulated in the conditioned medium of Panc1 CSCs. The pathway analysis revealed modulation of vital physiological pathways including glycolysis, gluconeogenesis and pentose phosphate. Through ELISA immunoassays we analysed the presence of the three proteins most highly secreted by Panc1 CSCs (ceruloplasmin, galectin-3, and MARCKS) in sera of PDAC patient. ROC curve analysis suggests ceruloplasmin as promising marker for patients negative for CA19-9. Overall, our study provides a systemic secretome analysis of pancreatic CSCs revealing a number of secreted proteins which participate in pathological conditions including cancer differentiation, invasion and metastasis. They may serve as a valuable pool of proteins from which biomarkers and therapeutic targets can be identified.

BIOLOGICAL SIGNIFICANCE

The secretome of CSCs is a rich reservoir of biomarkers of cancer progression and molecular therapeutic targets, and thus is a topic of great interest for cancer research. The secretome analysis of pancreatic CSCs has not yet been performed. Recently, our group has demonstrated that Panc-1 CSCs isolated from parental cell line by using the CSC selective medium, represent a model of great importance to deepen the understanding of the biology of pancreatic adenocarcinoma. To our knowledge, this is the first proteomic study of pancreatic CSC secretome. We performed an iTRAQ-based analysis to compare the secretomes of Panc1 CSCs and Panc1 parental cell line and identified a total of 43 proteins secreted at higher level by pancreatic cancer stem cells. We found modulation of different vital physiological pathways (such as glycolysis and gluconeogenesis, pentose phosphate pathway) and the involvement of CSC secreted proteins (for example 72kDa type IV collagenase, galectin-3, alpha-actinin-4, and MARCKS) in pathological conditions including cancer differentiation, invasion and metastasis. By ELISA verification we found that MARCKS and ceruloplasmin discriminate between controls and PDAC patients; in addition ROC curve analyses indicate that MARCKS does not have diagnostic accuracy, while ceruloplasmin could be a promising marker only for patients negative for CA19-9. We think that the findings reported in our manuscript advance the understanding of the pathways implicated in tumourigenesis, metastasis and chemoresistance of pancreatic cancer, and also identify a pool of proteins from which novel candidate diagnostic and therapeutic biomarkers could be discovered.

Galectin expression in cancer diagnosis and prognosis: A systematic review

Galectins are a family of proteins that bind to specific glycans thereby deciphering the information captured within the glycome. In the last two decades, several galectin family members have emerged as versatile modulators of tumor progression. This has initiated the development and preclinical assessment of galectin-targeting compounds. With the first compounds now entering clinical trials it is pivotal to gain insight in the diagnostic and prognostic value of galectins in cancer as this will allow a more rational selection of the patients that might benefit most from galectin-targeted therapies. Here, we present a systematic review of galectin expression in human cancer patients. Malignant transformation is frequently associated with altered galectin expression, most notably of galectin-1 and galectin-3. In most cancers, increased galectin-1 expression is associated with poor prognosis while elevated galectin-9 expression is emerging as a marker of favorable disease outcome. The prognostic value of galectin-3 appears to be tumor type dependent and the other galectins require further investigation. Regarding the latter, additional studies using larger patient cohorts are essential to fully unravel the diagnostic and prognostic value of galectin expression. Furthermore, to better compare different findings, consensus should be reached on how to assess galectin expression, not only with regard to localization within the tissue and within cellular compartments but also regarding alternative splicing and genomic variations. Finally, linking galectin expression and function to aberrant glycosylation in cancer cells will improve our understanding of how these versatile proteins can be exploited for diagnostic, prognostic and even therapeutic purposes in cancer patients.

Galectin-3 in cancer

Galectin-3 (Gal-3) plays important roles in cell proliferation, adhesion, differentiation, angiogenesis and apoptosis in normal and pathologic tissues. Accumulated evidences indicate that Gal-3 is closely involved in tumor cell transformation, migration, invasion and metastasis. In this review, the associations of the expression and localization of Gal-3 as well as its potential action mechanism in tumorigenesis in a variety of cancers were summarized and concluded. Gal-3 is gaining its attraction as a potential new biomarker for the diagnosis, treatment and prognosis of certain tumors.

Mucins in pancreatic cancer and its microenvironment

Pancreatic cancer remains a lethal malignancy with poor prognosis owing to therapeutic resistance, frequent recurrence and the absence of treatment strategies that specifically target the tumour and its supporting stroma. Deregulated cell-surface proteins drive neoplastic transformations and are envisioned to mediate crosstalk between the tumour and its microenvironment. Emerging studies have elaborated on the role of mucins in diverse biological functions, including enhanced tumorigenicity, invasiveness, metastasis and drug resistance through their characteristic O-linked and N-linked oligosaccharides (glycans), extended structures and unique domains. Multiple mucin domains differentially interact and regulate different components of the tumour microenvironment. This Review discusses: the expression pattern of various mucins in the pancreas under healthy, inflammatory, and cancerous conditions; the context-dependent attributes of mucins that differ under healthy and pathological conditions; the contribution of the tumour microenvironment in pancreatic cancer development and/or progression; diagnostic and/or prognostic efficacy of mucins; and mucin-based therapeutic strategies. Overall, this information should help to delineate the intricacies of pancreatic cancer by exploring the family of mucins, which, through various mechanisms in both tumour cells and the microenvironment, worsen disease outcome.

Epithelial-to-mesenchymal transition in pancreatic ductal adenocarcinoma and pancreatic tumor cell lines: the role of neutrophils and neutrophil-derived elastase

Pancreatic ductal adenocarcinoma (PDAC) is frequently associated with fibrosis and a prominent inflammatory infiltrate in the desmoplastic stroma. Moreover, in PDAC, an epithelial-to-mesenchymal transition (EMT) is observed. To explore a possible connection between the infiltrating cells, particularly the polymorphonuclear neutrophils (PMN) and the tumor cell transition, biopsies of patients with PDAC (n = 115) were analysed with regard to PMN infiltration and nuclear expression of β-catenin and of ZEB1, well-established indicators of EMT. In biopsies with a dense PMN infiltrate, a nuclear accumulation of β-catenin and of ZEB1 was observed. To address the question whether PMN could induce EMT, they were isolated from healthy donors and were cocultivated with pancreatic tumor cells grown as monolayers. Rapid dyshesion of the tumor cells was seen, most likely due to an elastase-mediated degradation of E-cadherin. In parallel, the transcription factor TWIST was upregulated, β-catenin translocated into the nucleus, ZEB1 appeared in the nucleus, and keratins were downregulated. EMT was also induced when the tumor cells were grown under conditions preventing attachment to the culture plates. Here, also in the absence of elastase, E-cadherin was downmodulated. PMN as well as prevention of adhesion induced EMT also in liver cancer cell line. In conclusion, PMN via elastase induce EMT in vitro, most likely due to the loss of cell-to-cell contact. Because in pancreatic cancers the transition to a mesenchymal phenotype coincides with the PMN infiltrate, a contribution of the inflammatory response to the induction of EMT and—by implication—to tumor progression is possible.

Polymorphonuclear neutrophils promote dyshesion of tumor cells and elastase-mediated degradation of E-cadherin in pancreatic tumors

Pancreatic ductal adenocarcinoma (PDAC) presenting with a micropapillary growth pattern is frequently associated with a prominent neutrophil infiltration into the tumor. The relevance of neutrophil infiltrates for tumor progression, however, is still debated. To gain insight into the role of polymorphonuclear neutrophils (PMNs) in PDAC, we assessed their effect on pancreatic tumor cells grown in vitro as monolayers. Time-lapse video microscopy showed a PMN-induced dyshesion of the tumor cells, and subsequent experiments revealed that this dyshesion was due to PMN elastase-mediated degradation of E-cadherin, an adhesion molecule that mediates the intercellular contact of the tumor cells. E-cadherin degradation by elastase or--(for comparison) down-modulation by specific siRNA, significantly increased the migratory capacity of the pancreatic tumor cells, leading to the hypothesis that PMNs could contribute to the invasive tumor growth. To address this issue, biopsies of patients with PDAC (n = 112) were analyzed. We found that E-cadherin expression correlated negatively with PMN infiltration, compatible with the notion that E-cadherin is cleaved by PMN-derived elastase, which in turn could result in the dispersal of the tumor cells, enhanced migratory capacity and thus invasive tumor growth.

Polymorphonuclear Neutrophils in Osteomyelitis: Link to Osteoclast Generation and Bone Resorption

Chronic and persistent inflammatory processes in bones may lead to severe erosions with consequent functional impairment sometimes requiring amputation of the limb. To explore the relationship between inflammation and bone erosion, biopsies of patients with osteomyelitis due to arterial occlusive disease or to diabetes mellitus were examined (n=31). Histologically, inflammation and bone erosion were confirmed. In the eroded bones the number of osteoclasts correlated with the abundance of infiltrated polymorphonuclear neutrophils (PMN), which were highly activated as shown by expression of MHC class II. For functional characterisation of the infiltrating PMN, patients with implant-associated osteomyelitis, a condition associated with persistent bacterial infection and bone destruction, were recruited. The cells were recovered from infected sites and examined ex vivo. These PMN expressed MHC class II and produced interleukin (IL)-8, a further indication of PMN activation. To assess a possible link between infiltrating PMN and bone erosion, we tested the effect of IL-8 on osteoclast generation in vitro. CD14+ monocytes derived from the peripheral blood of healthy individuals were cultivated with monocyte colony stimulating factor (M-CSF) and IL-8. Within 3 days, a translocation of the transcription factor NFATcl into the nucleus was seen, and by 10 to 20 days multinucleated cells with typical osteoclast morphology appeared that expressed tartrate-resistant acid phosphatase (TRAP) and cathepsin K. Moreover, the cells were able to resorb bone, proving that IL-8 was able to induce the differentiation of monocytes to osteoclasts. Because IL-8 is a major cytokine produced by activated PMN, we propose that in the course of persistent infection infiltrating PMN contribute to induction of osteoclast formation, thus providing a link between inflammation and bone erosion.