Podoplanin in cancer cells is experimentally able to attenuate prolymphangiogenic and lymphogenous metastatic potentials of lung squamoid cancer cells

Decorin suppresses tumor lymphangiogenesis: A mechanism to curtail cancer progression

The complex interplay between malignant cells and the cellular and molecular components of the tumor stroma is a key aspect of cancer growth and development. These tumor-host interactions are often affected by soluble bioactive molecules such as proteoglycans. Decorin, an archetypical small leucine-rich proteoglycan primarily expressed by stromal cells, affects cancer growth in its soluble form by interacting with several receptor tyrosine kinases (RTK). Overall, decorin leads to a context-dependent and protracted cessation of oncogenic RTK activity by attenuating their ability to drive a pro-survival program and to sustain a pro-angiogenic network. Through an unbiased transcriptomic analysis using deep RNAseq, we discovered that decorin downregulated a cluster of tumor-associated genes involved in lymphatic vessel development when systemically delivered to mice harboring breast carcinoma allografts. We found that Lyve1 and Podoplanin, two established markers of lymphatic vessels, were markedly suppressed at both the mRNA and protein levels and this suppression correlated with a significant reduction in tumor lymphatic vessels. We further discovered that soluble decorin, but not its homologous proteoglycan biglycan, inhibited lymphatic vessel sprouting in an ex vivo 3D model of lymphangiogenesis. Mechanistically, we found that decorin interacted with VEGFR3, the main lymphatic RTK, and its activity was required for the decorin-mediated block of lymphangiogenesis. Finally, we discovered that Lyve1 was in part degraded via decorin-evoked autophagy in a nutrient- and energy-independent manner. These findings implicate decorin as a new biological factor with anti-lymphangiogenic activity and provide a potential therapeutic agent for curtailing breast cancer growth and metastasis.

Relationship between podoplanin-expressing cancer-associated fibroblasts and the immune microenvironment of early lung squamous cell carcinoma

AIM

Cancer-associated fibroblasts (CAFs) expressing podoplanin (PDPN) harbor a fibrous tumor microenvironment that promotes cancer progression in lung adenocarcinoma. In this study, we investigated whether tumor-promoting PDPN⁺ CAFs contribute to the immunosuppressive microenvironment in lung squamous cell carcinoma (SqCC). M&M: The gene expression profiles of immunosuppressive cytokines were compared using The Cancer Genome Atlas (TCGA) microarray lung SqCC data (n = 484) between a PDPN-high group and a PDPN-low group. Further, using patient-derived CAFs from surgically resected lung SqCC, the PDPN⁺ fraction was sorted and gene and protein expressions were analyzed. Finally, immunohistochemical staining was conducted on 131 surgically resected lung SqCC; CD8⁺ and FOXP3⁺ tumor infiltrating lymphocytes (TILs), and CD204⁺ tumor-associated macrophages (TAMs) were evaluated in cases with PDPN⁺ and PDPN^- CAFs.

RESULTS

Analysis of TCGA database revealed that the PDPN-high group exhibited significantly higher expression of interleukin (IL)-1A, IL-1B, IL-6, IL-10, monocyte chemoattractant protein-1 (CCL2), colony stimulating factor 1 (CSF1), fibroblast growth factor 2 (FGF2), galectin 1 (LGALS1), platelet derived growth factor subunit A (PDGFA), PDGFB, and transforming growth factor-β1 (TGFB1) than those in the PDPN-low group. Among them, it was found that TGFB1 expression was higher in patient-derived PDPN⁺ CAFs. Immunohistochemical analyses revealed that more CD204⁺ TAMs infiltrated the tumor tissues in cases with PDPN⁺ CAFs than in cases with PDPN^- CAFs (P <  0.03), while CD8⁺ and FOXP3⁺ TILs did not. Furthermore, in the same tumor, CD204⁺ TAMs infiltrated more in PDPN⁺ CAF-rich areas (P =  0.005).

CONCLUSION

PDPN⁺ CAFs showed higher expression of TGFB1 and were associated with CD204⁺ TAM infiltration in stage-I lung SqCC, suggesting that PDPN⁺ CAFs were associated with the immunosuppressive tumor microenvironment.

Podoplanin is a useful prognostic marker and indicates better differentiation in lung squamous cell cancer patients? A systematic review and meta-analysis

Background

The CSC (cancer stem cell) markers often indicate poor prognosis and more cell invasion or migration of cancer patients. Podoplanin was assumed as a candidate CSC marker and predict poor prognosis among squamous cancers. Whereas, the prognostic value of podoplanin among lung squamous cancer (LUSC) patients remains controversial.

Methods

A search of databases including PubMed, Embase and Web of Science was performed. Eligible articles studying the prognostic significance of podoplanin were selected. Odds ratio and HR (hazard ratio) were used to assess the relationships between podoplanin and clinical characteristics, as well as to quantify its prognostic role. The heterogeneity was estimated by I² Statistic and P values from sensitivity analysis. Begg’s funnel plots were used to estimate possible publication bias.

Results

8 eligible studies containing 725 I-IV LUSC patients were included. Podoplanin expression showed no significant correlations with TNM stage, vascular invasion, lymphatic invasion, lymph node metastasis, pleural metastasis of tumor and gender of patients. However, podoplanin showed significant associations with better differentiation (pooled OR = 2.64, 95% CI 1.53–4.56, P = 0.0005, fixed effect) and better overall survival (HR = 2.14, 95% CI 1.45–3.15, P = 0.0001, fixed effect) and progression-free survival (HR = 1.73, 95% CI: 1.01–2.98, P = 0.05, fixed effect) of LUSC. Funnel plots illustrated no evidence of publication bias in our results.

Conclusions

Podoplanin could be a useful prognostic marker and indicates better differentiation for LUSC patients, and the value of PDPN expression as a marker for cancer stem cells in LUSC should be critically evaluated in future studies.

Podoplanin-Expressing Macrophages Promote Lymphangiogenesis and Lymphoinvasion in Breast Cancer

Among mammary tumor-infiltrating immune cells, the highest expression of podoplanin (PDPN) is found in a subset of tumor-associated macrophages (TAMs). We hereby demonstrate that PDPN is involved in the attachment of this TAM subset to lymphatic endothelial cells (LECs). Mechanistically, the binding of PDPN to LEC-derived galectin 8 (GAL8) in a glycosylation-dependent manner promotes the activation of pro-migratory integrin β1. When proximal to lymphatics, PDPN-expressing macrophages (PoEMs) stimulate local matrix remodeling and promote vessel growth and lymphoinvasion. Anti-integrin β1 blockade, macrophage-specific Pdpn knockout, or GAL8 inhibition impairs TAM adhesion to LECs, restraining lymphangiogenesis and reducing lymphatic cancer spread. In breast cancer patients, association of PoEMs with tumor lymphatic vessels correlates with incidences of lymph node and distant organ metastasis.

Evaluation of SOX2 and podoplanin expression in oral epithelial dysplasia and its correlation with malignant transformation

AIM

Oral carcinogenesis cascade is a complex process, characterized by variable numbers of genetic and epigenetic alterations of various genes with manifold roles that could serve as biological hallmarks. This study was undertaken to assess the protein expression of SOX2 and podoplanin in oral epithelial dysplasia and correlate the expression with clinicopathological parameters and risk of malignant transformation.

METHODS

SOX2 and podoplanin expression were analyzed in 60 cases of oral epithelial dysplasia. The association between SOX2 and podoplanin expression with various clinicopathological parameters and transformation to oral cancer was analyzed.

RESULTS

A higher Histoscore was seen in 55% of moderate and 30% of severe dysplasia. 25% of the cases showed a negative podoplanin expression and 30% of patients had higher podoplanin expression (score 2 and 3). Though there was significant association of both SOX2 and podoplanin expression with the degree of dysplasia, the association of their expression with transformation to oral squamous cell carcinoma did not reach statistical significance.

CONCLUSION

Alteration in SOX2 and podoplanin is likely an important event in head and neck carcinogenesis; however, their expression may be valuable only in a few cases of oral epithelial dysplasia to assess the risk of malignant transformation.

Podoplanin in Inflammation and Cancer

Podoplanin is a small cell-surface mucin-like glycoprotein that plays a crucial role in the development of the alveoli, heart, and lymphatic vascular system. Emerging evidence indicates that it is also involved in the control of mammary stem-cell activity and biogenesis of platelets in the bone marrow, and exerts an important function in the immune response. Podoplanin expression is upregulated in different cell types, including fibroblasts, macrophages, T helper cells, and epithelial cells, during inflammation and cancer, where it plays important roles. Podoplanin is implicated in chronic inflammatory diseases, such as psoriasis, multiple sclerosis, and rheumatoid arthritis, promotes inflammation-driven and cancer-associated thrombosis, and stimulates cancer cell invasion and metastasis through a variety of strategies. To accomplish its biological functions, podoplanin must interact with other proteins located in the same cell or in neighbor cells. The binding of podoplanin to its ligands leads to modulation of signaling pathways that regulate proliferation, contractility, migration, epithelial⁻mesenchymal transition, and remodeling of the extracellular matrix. In this review, we describe the diverse roles of podoplanin in inflammation and cancer, depict the protein ligands of podoplanin identified so far, and discuss the mechanistic basis for the involvement of podoplanin in all these processes.

Cancer-associated fibroblast regulation of tumor neo-angiogenesis as a therapeutic target in cancer

Adequate blood supply is essential for tumor survival, growth and metastasis. The tumor microenvironment (TME) is dynamic and complex, comprising cancer cells, cancer-associated stromal cells and their extracellular products. The TME serves an important role in tumor progression. Cancer-associated fibroblasts (CAFs) are the principal component of stromal cells within the TME, and contribute to tumor neo-angiogenesis by altering the proteome and degradome. The present paper reviews previous studies of the molecular signaling pathways by which CAFs promote tumor neo-angiogenesis and highlights therapeutic response targets. Also discussed are potential strategies for antitumor neo-angiogenesis to improve tumor treatment efficacy.

Podoplanin (PDPN) affects the invasiveness of thyroid carcinoma cells by inducing ezrin, radixin and moesin (E/R/M) phosphorylation in association with matrix metalloproteinases

Background

Podoplanin (PDPN) is a mucin-type transmembrane glycoprotein specific to the lymphatic system. PDPN expression has been found in various human tumors and is considered to be a marker of cancer. We had previously shown that PDPN expression contributes to carcinogenesis in the TPC1 papillary thyroid cancer-derived cell line by enhancing cell migration and invasiveness. The aim of this study was to determine the effect of PDPN down-regulation in another thyroid cancer-derived cell line: BcPAP.

Methods

In order to determine the effects of PDPN on malignant features of BcPAP cells (harboring the BRAFV600E mutated allele) and TPC1 cells (carrying the RET/PTC1 rearrangement), we silenced PDPN in these cells using small interfering RNA (siRNA). The efficacy of PDPN silencing was confirmed by qRT-PCR and Western blotting. Then, we tested the motility and invasiveness of these cells (using scratch test and Transwell assay), their growth capacities F(cell cycle analysis, viability, clonogenic activity) and apoptosis assays), adhesion-independent colony-formation capacities, as well as the effect of PDPN silencing on MMPs expression and activity (zymography).

Results

We found that PDPN-induced cell phenotype depended on the genetic background of thyroid tumor cells. PDPN down-regulation in BcPAP cells was negatively correlated with the migration and invasion, in contrast to TPC1 cells in which PDPN depletion resulted in enhanced migration and invasiveness. Moreover, our results suggest that in BcPAP cells, PDPN may be involved in the epithelial-mesenchymal transition (EMT) through regulating the expression of the ezrin, radixin and moesin (E/R/M) proteins, MMPs 9 and MMP2, remodeling of actin cytoskeleton and cellular protrusions. We also demonstrated that PDPN expression is associated with the MAPK signaling pathway. The inhibition of the MAPK pathway resulted in a decreased PDPN expression, increased E/R/M phosphorylation and reduced cell migration. Additionally, PDPN depleted BcPAP cells treated with inhibitors of MEK1/2 kinases (U0126) or of the BRAF V600E protein (PLX4720) had reduced motility, similar to that previously observed in TPC1 cells after PDPN knock-down.

Conclusions

Altogether, our data suggest that PDPN may play an important role in the control of invasion and migration of papillary thyroid carcinoma cells in association with the E/R/M, MMPs and MAPK kinases.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-5239-z) contains supplementary material, which is available to authorized users.

Lymphatics-associated genes are downregulated at transcription level in non-small cell lung cancer

The present study aimed to verify a possibility of ongoing lymphangiogenesis in non-small cell lung cancer (NSCLC) via examination of mRNA levels of a number of lymphangiogenesis-associated genes in tumors. It was hypothesized that transcriptional activation of these genes would occur in tumors that stimulate new lymphatic vessel formation. The study was performed on 140 pairs of fresh-frozen surgical specimens of cancer and unaffected lung tissues derived from NSCLC stage I-IIIA patients. mRNA levels were evaluated with the reverse transcription-quantitative polymerase chain reaction method and expressed as fold change differences between the tumor and normal tissues. Possible associations between expression and patient clinicopathological characteristics and survival were analyzed. In the NSCLC tissue samples, vascular endothelial growth factor (VEGF) C, VEGFD, VEGFR3, VEGFR2, VEGFR1, lymphatic vessel endothelial hyaluronan receptor 1, integrin subunit α 9, FOX2, neuropilin 2, fibroblast growth factor 2 genes were significantly downregulated (P<0.001 for all) compared with matched normal lung tissues, whereas mRNA levels for VEGFA, spleen associated tyrosine kinase, podoplanin, and prospero homeobox 1 genes were similar in both tissues. Neither lymph node status, nor disease pathological stage influenced expression, whereas more profound suppression of gene activities appeared to occur in squamous cell carcinomas compared with adenocarcinomas. The VEGFR1 mRNA expression level was significantly connected with patient survival in the univariate analysis, and was an independent prognostic factor for overall survival in the multivariate Cox's proportional hazards model (HR 2.103; 95% confidence interval: 1.005-4.401; P=0.049). The results support a hypothesis of absence of new lymphatic vessel formation inside growing NSCLC tumor mass, however do not exclude a possibility of lymphangiogenesis in narrow marginal tumor parts.

Co-expression of podoplanin and fibroblast growth factor 1 predicts poor prognosis in patients with lung squamous cell carcinoma

Podoplanin and fibroblast growth factor (FGF) 1 have been detected more frequently in lung squamous cell carcinoma (SQCC) compared with lung adenocarcinoma. Furthermore, it has been previous demonstrated that FGF1 is located on the edge of tumor nests in certain lung SQCC sections, which resembles the characteristic expression pattern of podoplanin. Podoplanin and FGF1 have roles in lymphangiogenesis and angiogenesis. Based on their consistently specific expression in lung SQCC and similar localization patterns, the present study aimed to investigate whether the expression of podoplanin in tumor cells is correlated with FGF1 expression in lung SQCC and whether their co-expression has clinicopathological significance, particularly for lymphangiogenesis/angiogenesis. The correlation between podoplanin and FGF1 expression in tumor cells of 82 lung SQCC cases was investigated by immunohistochemical staining and the association between the co-expression of podoplanin and FGF1, and clinicopathological factors such as microvessel density (MVD), was examined in these samples. In addition, the prognostic value of co-expression of podoplanin and FGF1 in tumor cells was determined, and the regulation of FGF1 expression and angiogenesis by podoplanin was examined in vitro in a human lung SQCC cell line. Immunohistochemical analysis demonstrated that there was a significant correlation between podoplanin and FGF1 expression in lung SQCC tumor cells (R=0.591; P<0.0001). Co-expression of podoplanin and FGF1 was significantly associated with larger primary tumor size, advanced TNM stage and higher intratumoral MVD. Survival analysis demonstrated that cases with podoplanin and FGF1 double-positive staining had a significantly lower survival rate compared with cases with double-negative staining. In vitro experiments revealed that podoplanin regulated FGF1 expression and affected tube formation of human umbilical vein endothelial cells. Combined, the results demonstrated that podoplanin was co-expressed with FGF1 in lung SQCC and this co-expression was correlated with poor prognosis.

Podoplanin expression is correlated with the prognosis of lung squamous cell carcinoma

Podoplanin is a 38 kDa transmembrane protein that is involved in cell migration and cancer cell invasion. Some studies have reported that podoplanin expression was correlated with poor prognosis in lung squamous cell carcinoma (SqCC). However, there have been no clinicopathological studies of podoplanin membrane expression and localization in lung SqCC. In this study, we focused on the intensity and localization of podoplanin membrane expression, and its clinicopathological significance for lung SqCC. Strong membrane expression of podoplanin was significantly associated with lymph node metastasis, lymphatic invasion, and histological differentiation. Cases with strong podoplanin expression at cell membrane showed better prognosis of lung SqCC (HR, 3.301). Peripheral localization of podoplanin was associated with tumor size, lymphatic invasion, and histological differentiation. Cases with peripheral podoplanin expression showed favorable prognosis of lung SqCC (HR, 2.830). Both strong membrane expression and peripheral expression of podoplanin were independent predictors of mortality of lung SqCC (HR, 2.869; HR, 2.443, respectively). The cases with strong or peripheral podoplanin expression showed better overall survival (P = 0.001, both). Podoplanin intensity is significantly associated with podoplanin localization (P < 0.001), and its correlation coefficient was 0.678. We concluded that podoplanin membrane expression, not only its localization, is a useful prognostic indicator of lung SqCC patients.

Isolation of individual cellular components from lung tissues of patients with lymphangioleiomyomatosis

Lymphangioleiomyomatosis (LAM) is a rare neoplastic disease entailing cystic destruction of the lungs and progressive respiratory failure. LAM lungs are histologically characterized by the proliferation of smooth muscle-like cells (LAM cells) and an abundance of lymphatic vessels. To elucidate the pathophysiological processes of LAM, cell-type-specific analyses are required. However, no method exists for isolating the individual types of cells in LAM lesions. Therefore, we established a fluorescence-activated cell sorting (FACS)-based method for the direct isolation of LAM cells and other various cellular components from LAM-affected lung tissue. We obtained LAM-affected lung tissue from resections or transplant recipients and prepared single-cell suspensions. FACS, immunohistochemical, and molecular analysis were used cooperatively to isolate HMB45-positive LAM cells with tuberous sclerosis complex (TSC) 2 loss of heterozygosity (LOH). Using a combination of antibodies against an epithelial cell adhesion molecule (EpCAM) and podoplanin, we fractionated CD45-negative lung cells into three groups: lymphatic endothelial cells (LEC) (EpCAM(-)/podoplanin(hi) subset), alveolar type II cells (EpCAM(hi)/podoplanin(-) subset), and mesenchymal cells (EpCAM(-)/podoplanin(-/low) subset). During subsequent analysis of HMB45 expression, as a LAM-specific marker, we clearly identified LAM cells in the mesenchymal cell population. We then discovered that CD90(+)/CD34(-) cells in the mesenchymal cell population are not only positive for HBM45 but also had TSC2 LOH. These isolated cells were viable and subsequently amenable to cell culture. This method enables us to isolate LAM cells and other cellular components, including LAM-associated LEC, from LAM-affected lung tissues, providing new research opportunities in this field.

Podoplanin - a small glycoprotein with many faces

Podoplanin is a small membrane glycoprotein with a large number of O-glycoside chains and therefore it belongs to mucin-type proteins. It can be found on the surface of many types of normal cells originating from various germ layers. It is present primarily on the endothelium of lymphatic vessels, type I pneumocytes and glomerular podocytes. Increased levels of podoplanin or its neo-expression have been found in numerous types of human carcinomas, but it is especially common in squamous cell carcinomas, such as cervical, larynx, oral cavity, skin and lung cancer. This small sialomucin is also seen on the surface of cancer-associated fibroblasts (CAFs) in lung adenocarcinomas, as well as in breast and pancreatic tumors. In most cancers, a high level of podoplanin expression, both in cancer cells, as well as in CAFs, is correlated with an increased incidence of metastasis to lymph nodes and shorter survival time of patients. Little is known about the biological role of podoplanin, however research carried out on mice with a knock-out gene of this glycoprotein shows that the presence of podoplanin determines normal development of lungs, the lymphatic system and heart. Podoplanin on cancer cells and CAFs seems to play an important role in the development and progression of various cancers. However, its role in these processes is both unclear and controversial. In this review, the role of podoplanin in both physiological processes and carcinogenesis is discussed.

Expression of podoplanin and vimentin is correlated with prognosis in esophageal squamous cell carcinoma

Podoplanin is a small membrane mucin, which is involved in cell migration and cancer cell invasion. However, the roles of podoplanin in esophageal squamous cell carcinoma (ESCC) are poorly understood. In the present study, 139 cases of surgically resected ESCC were analyzed and the clinicopathological significance of podoplanin membrane expression in ESCC was demonstrated. Podoplanin expression was positive in 66.2% (92/139) of ESCC samples; with weak expression in 32.4% (45/139), and strong expression in 33.8% (47/139). Membrane expression of podoplanin was significantly associated with tumor status (P=0.001), venous invasion (P=0.035) and Union for International Cancer Control stage (P=0.029). Patients who exhibited strong podoplanin expression, were shown to have a poorer prognosis [hazard ratio (HR), 3.949; 95% confidence interval (CI), 2.001–7.794]. Expression of vimentin, a mesenchymal marker, was detected in 49 cases (35.3%) and was associated with venous invasion (P=0.020). Vimentin-positive cases were also more likely to have a worse prognosis than vimentin-negative cases (HR, 2.161; 95% CI, 1.300–3.592). Podoplanin membrane expression was significantly correlated with vimentin cytoplasmic expression in ESCC (P<0.001). The present study confirmed that podo-planin and vimentin are independent predictors of mortality (HR, 3.084; 95% CI, 1.543–6.164). These results suggest that podoplanin membrane expression results in epithelial-mesenchymal transition and promotes aggressive invasion in human ESCC.

Podoplanin: a novel regulator of tumor invasion and metastasis

Podoplanin, a small mucin-type sialoglycoprotein, was recently shown to be involved in tumor progression. Podoplanin is overexpressed in cancer cells of various human malignancies, and recently, it is also detected in intratumoral stromal cells. We now appreciate that podoplanin plays a dual role in cancer: it can not only suppress tumor growth but also promote tumor progression. Researchers have identified several potential pathways invoked by podoplanin, which participate in the epithelial-to-mesenchymal transition, collective-cell migration, platelet activation and aggregation, and lymphangiogenesis, and thus regulate the tumor invasion and metastasis. Here, we discuss the current experimental and human clinical data on podoplanin to validate the multiple context-dependent functions in different microenvironments and to delineate the diverse regulatory mechanisms.

Podoplanin‑positive cancer cells at the edge of esophageal squamous cell carcinomas are involved in invasion

Podoplanin (PDPN) is a well established lymphatic endothelial marker and has frequently been observed in cancer cells at the edge of cancer masses. Previous studies investigating the association between PDPN expression and patient prognosis have had contradictory results. In the present study, it was hypothesized that the different locations of PDPN‑positive cells may explain these varying results. The present study aimed to focus on PDPN expression at the edge of esophageal cancer cell nests. In order to analyze the clinical significance of this PDPN expression, immunohistochemistry was performed using esophageal cancer tissue microarrays. PDPN expression at the edge of the cancer cell nest was found to be significantly associated with invasion (P<0.05) and poor prognosis (P<0.001) in patients with cancer. To further investigate the role of PDPN expression in cancer cells, the PDPN gene was cloned and transfected into esophageal squamous cell carcinoma (ESCC) cell lines. PDPN expression was also knocked down using small interfering RNA. PDPN‑positive cancer cells were found to exhibit invasion characteristics. Thus, PDPN expression at the edge of a cancer cell nest may indicate invasion and represent a poor prognostic factor for ESCCs.

Expression and clinical significance of matrix metalloproteinase-9 in lymphatic invasiveness and metastasis of breast cancer

BACKGROUND

Matrix metalloproteinase 9 (MMP-9) is a type-IV collagenase that is highly expressed in breast cancer, but its exact role in tumor progression and metastasis is unclear.

METHODS

MMP-9 mRNA and protein expression was examined by real-time reverse transcriptase PCR and immunohistochemical staining, respectively, in 41 breast cancer specimens with matched peritumoral benign breast epithelial tissue and suspicious metastatic axillary lymph nodes. Lymph vessels were labeled with D2-40 and lymphatic microvessel density (LMVD) was calculated. Correlation of MMP-9 protein expression with clinicopathological parameters and LMVD was also evaluated.

RESULTS

MMP-9(+) staining in breast cancer specimens (35/41, 85.4%) was higher than in matched epithelium (21/41, 51.2%; P<0.05) and lymph nodes (13/41, 31.7%; P<0.001). Higher MMP-9 mRNA expression was also detected in tumor specimens compared with matched epithelial tissues and lymph nodes (P<0.05). Elevated MMP-9 expression was correlated with lymph node metastasis and LMVD (P<0.05).

CONCLUSION

MMP-9 was overexpressed in breast cancer specimens compared with peritumoral benign breast epithelium and lymph nodes. Moreover, its expression in the matched epithelium and lymph nodes was positively associated with lymph node metastasis, and its expression in lymph nodes was positively associated with lymphangiogenesis in breast cancer. Thus, MMP-9 is a potential marker for breast cancer progression.

The role of podoplanin in the biology of differentiated thyroid cancers

Podoplanin (PDPN), a mucin-type transmembrane glycoprotein specific to the lymphatic system is expressed in a variety of human cancers, and is regarded as a factor promoting tumor progression. The purpose of this study was to elucidate the molecular role of PDPN in the biology of thyroid cancer cells. PDPN expression was evaluated in primary thyroid carcinomas and thyroid carcinoma cell lines by RT-qPCR, Western blotting, IF and IHC. To examine the role of podoplanin in determining a cell's malignant potential (cellular migration, invasion, proliferation, adhesion, motility, apoptosis), a thyroid cancer cell line with silenced PDPN expression was used. We observed that PDPN was solely expressed in the cancer cells of 40% of papillary thyroid carcinoma (PTC) tissues. Moreover, PDPN mRNA and protein were highly expressed in PTC-derived TPC1 and BcPAP cell lines but were not detected in follicular thyroid cancer derived cell lines. PDPN knock-down significantly decreased cellular invasion, and modestly reduced cell migration, while proliferation and adhesion were not affected. Our results demonstrate that PDPN mediates the invasive properties of cells derived from papillary thyroid carcinomas, suggesting that podoplanin might promote PTC progression.

Extracellular matrix protein 1 is correlated to carcinogenesis and lymphatic metastasis of human gastric cancer

Background

Tumor-induced lymphangiogenesis is a crucial step in malignant invasion and metastasis. Extracellular matrix protein 1 (ECM1) was recently reported to play a role in lymphangiogenesis. In the present work, we aimed to evaluate the role of ECM1 in gastric cancer and examined whether aberrant expression of ECM1 increased the tumorigenic and metastatic potential of human gastric cancer.

Methods

The mRNA and protein expression of ECM1 in gastric cancer specimen and the noncancerous counterparts from 77 patients were detected by real-time PCR and immunohistochemistry staining. Lymphatic microvessel density (LMVD) in the corresponding serial sections was assessed by counting the lymphatic microvessels labelled by D2-40. The correlations between ECM1 expression, LMVD, and the clinicopathological parameters were examined.

Results

ECM1 protein expression was detected in 70.1% (54/77) of gastric cancer specimen, significantly higher than that in the corresponding counterparts (P <0.01). ECM1 mRNA in tumor specimen was also dramatically amplified. Elevated LMVD and ECM1 were positively correlated (P <0.01). In addition, ECM1 protein expression was also closely associated with depth of tumor invasion and TNM stage (P <0.05, respectively).

Conclusions

ECM1 expression is aberrant elevated in tumor specimen and is closely related to the tumorigenic and metastatic potential of human gastric cancer. Thus, carrying out the protein examination may be beneficial to predict carcinogenesis and metastatic spread of human gastric cancer.

Podoplanin expression in cancer-associated fibroblasts enhances tumor progression of invasive ductal carcinoma of the pancreas

Background

Interactions between cancer cells and surrounding cancer-associated fibroblasts (CAFs) play an important role in cancer progression. Invasive ductal carcinoma (IDC) of the pancreas is characterized by abundant fibrous connective tissue called desmoplasia. Podoplanin (PDPN) is a lymphatic vessel marker (D2-40), and expression of PDPN by stromal CAFs has been reported to be a prognostic indicator in various types of cancer.

Methods

Expression of PDPN in pancreatic IDCs was assessed by immunohistochemical examination in 105 patients who underwent pancreatic resection. Primary CAFs were established from pancreatic cancer tissue obtained by surgery. Quantitative reverse transcription-polymerase chain reaction and flow cytometric analysis were performed to investigate PDPN expression in CAFs. We sorted CAFs according to PDPN expression, and analyzed the functional differences between PDPN+ CAFs and PDPN– CAFs using indirect co-culture with pancreatic cancer cell lines. We also investigated the culture conditions to regulate PDPN expression in CAFs.

Results

PDPN expression in stromal fibroblasts was associated with lymphatic vessel invasion (P = 0.0461), vascular invasion (P = 0.0101), tumor size ≥3 cm (P = 0.0038), histological grade (P = 0.0344), Union for International Cancer Control classification T stage (P = 0.029), and shorter survival time (P < 0.0001). Primary CAFs showed heterogeneous PDPN expression in vitro. Moreover, migration and invasion of pancreatic cancer cell lines (PANC-1 and SUIT-2) were associated with PDPN expression in CAFs (P < 0.01) and expression of CD10, matrix metalloproteinase (MMP) 2, and MMP3. In cultured CAFs, PDPN positivity changed over time under several conditions including co-culture with cancer cells, different culture media, and addition of growth factor.

Conclusions

PDPN-expressing CAFs enhance the progression of pancreatic IDC, and a high ratio of PDPN-expressing CAFs is an independent predictor of poor outcome. Understanding the regulation of the tumor microenvironment is an important step towards developing new therapeutic strategies.

Podoplanin promotes cell migration via the EGF-Src-Cas pathway in oral squamous cell carcinoma cell lines

Human podoplanin is a type-1 transmembrane sialomucin-like glycoprotein that is involved in cell migration, tumor cell invasion and metastasis. Our recent study of oral squamous cell carcinoma (OSCC) demonstrated that the degree of immunohistochemical expression of podoplanin was correlated with the severity of epithelial dysplasia and significantly associated with a poor pathologic grade of differentiation. Furthermore, it has been reported that Src directly associates with the epidermal growth factor receptor (EGFR) in OSCC cells upon stimulation with EGF and phosphorylates Crk-associated substrate (Cas), podoplanin acting downstream of Src and Cas to promote cell migration. However, the molecular function of podoplanin remains unclear. In this study we performed real-time RT-PCR, Western blotting and scratch assay using OSCC cell lines in order to clarify the molecular biological function of podoplanin expression associated with various growth factors including EGF and with the Src-Cas signaling pathway. Podoplanin was found to have a marked influence on cancer cell migration and the expression of matrix metalloprotease-9 (MMP-9) in the oral cavity upon stimulation with EGF. Podoplanin promotes oral cancer cell migration, and the EGF-Src-Cas pathway is one of the possible mechanisms responsible for progression of cancer in the oral cavity.

Podoplanin-mediated cell adhesion through extracellular matrix in oral squamous cell carcinoma

Podoplanin (PDPN), one of the representative mucin-like type-I transmembrane glycoproteins specific to lymphatic endothelial cells, is expressed in various cancers including squamous cell carcinoma (SCC). On the basis of our previous studies, we have developed the hypothesis that PDPN functions in association with the extracellular matrix (ECM) from the cell surface side. The aim of this study was to elucidate the molecular role of PDPN in terms of cell adhesion, proliferation, and migration in oral SCC cells. Forty-four surgical specimens of oral SCC were used for immunohistochemistry for PDPN, and the expression profiles were correlated with their clinicopathological properties. Using ZK-1, a human oral SCC cell system, and five other cell systems, we examined PDPN expression levels by immunofluorescence, western blotting, and real-time PCR. The effects of transient PDPN knockdown by siRNA in ZK-1 were determined for cellular functions in terms of cell proliferation, adhesion, migration, and invasion in association with CD44 and hyaluronan. Cases without PDPN-positive cells were histopathologically classified as less-differentiated SCC, and SCC cells without PDPN more frequently invaded lymphatics. Adhesive properties of ZK-1 were significantly inhibited by siRNA, and PDPN was shown to collaborate with CD44 in cell adhesion to tether SCC cells with hyaluronan-rich ECM of the narrow intercellular space as well as with the stromal ECM. There was no siRNA effect in migration. We have demonstrated the primary function of PDPN in cell adhesion to ECM, which is to secondarily promote oral SCC cell proliferation.

Podoplanin-positive cancer-associated fibroblasts could have prognostic value independent of cancer cell phenotype in stage I lung squamous cell carcinoma: usefulness of combining analysis of both cancer cell phenotype and cancer-associated fibroblast phenotype

BACKGROUND

The prognostic significance of the tumor microenvironment, which is created by both cancer cells and cancer-associated fibroblasts (CAFs), has been increasingly recognized. The purpose of this study was to analyze the prognostic markers of stage I squamous cell carcinoma (SqCC), with special reference to the immunophenotypes of both cancer cells and CAFs.

METHODS

A total of 142 patients with stage I SqCC were included in this study. We examined the expressions of E-cadherin, laminin-5, podoplanin, c-MET, carbonic anhydrase IX (CA-IX), CD10, and CD44 in the cancer cells and those of podoplanin, CA-IX, CD10, and CD44 in the CAFs to evaluate their prognostic value.

RESULTS

Patients with low E-cadherin expression in the cancer cells showed a significantly poorer prognosis than those with high E-cadherin expression in the cancer cells ( P , .001). On the other hand, high podoplanin expression in the CAFs was also associated with a significantly poorer prognosis ( P , .001). A multivariate analysis identified low E-cadherin expression in the cancer cells and high podoplanin expression in the CAFs as significantly independent prognostic factors for overall survival ( P 5 .013 and P 5 .0011, respectively). According to subgroup analyses combining E-cadherin expression in cancer cells and podoplanin expression in CAFs, 5-year overall survival of patients with low E-cadherin expression in the cancer cells and high podoplanin expression in the CAFs was 7.0% and showed a significantly poorer prognosis as compared with other groups ( P , .001).

CONCLUSIONS

The current study indicates that immunophenotypes of CAFs could have a prognostic value independent of those of the cancer cells in SqCC.

Significance of podoplanin expression in cancer-associated fibroblasts: a comprehensive review

Cancer-associated fibroblasts (CAFs) are well-known to be part of the tumor microenvironment. This heterogeneous population of cells of the tumor microenvironment via secretion of various growth factors and cytokines was shown to contribute to increased cancer cell proliferation rate, migration, invasiveness and other key processes such as angiogenesis and lymphangiogenesis. Recent studies identified podoplanin as a marker of CAFs in various malignancies and its expression in these cells was shown to influence cancer progression. In some studies it yielded a prognostic impact on patient survival which was strongly dependent on the entity of the tumor. This review summarizes recent findings concerning the biology of podoplanin in cancer progression with particular emphasis on its expression in CAFs.

Expression of podoplanin is a rare event in sporadic gastrointestinal stromal tumors and does not influence prognosis

Aims: Podoplanin overexpression is associated with worse prognosis in several human cancers. In gastrointestinal stromal tumors (GISTs) very few data on the expression of podoplanin exist, but it seems to be frequently overexpressed in pediatric/syndromic GISTs. We investigated podoplanin expression and its clinical relevance in a large series of sporadic GISTs. Methods: Podoplanin expression was determined immunohistochemically in 145 sporadic adult GISTs. Aneuploidies of 1p36 and 1q25 were investigated using FISH, and KIT and PDGFRA genes were investigated by sequencing. Results: Overexpression of podoplanin was observed in eight (5.6%) GISTs and no association with amplification of 1p36 or KIT or PDGFRA mutations was seen. The amount of podoplanin expression was not associated with clinical risk factors or patient survival. Conclusion: Overexpression of podoplanin is a rare event in sporadic GISTs and is not associated with amplification of 1p36 or with KIT or PDGFRA mutations, which indicates limited pathobiological or clinical relevance.

Establishment and characterization of primary cell lines of squamous cell carcinoma of the penis and its metastasis

PURPOSE

We established cell lines from penile squamous cell carcinoma and its lymph node metastasis, and investigated the role of chemokines, chemokine receptors and podoplanin in cancer progression.

MATERIALS AND METHODS

Tumor specimen of primary tumors, and lymph node and distant metastases were cultured in vitro and xenotransplanted in SCID beige mice. Specimens were analyzed by hematoxylin and eosin staining, and immunohistochemistry. Comparative screening for chemokines, chemokine receptors and podoplanin was done by polymerase chain reaction, fluorescence activated cell sorting and enzyme-linked immunosorbent assay.

RESULTS

We established 2 cell lines from a primary tumor and its corresponding lymph node metastasis, respectively. Heterotopic xenotransplantation revealed reliable tumor growth in vivo. Morphological and immunohistological analysis showed comparable features for human tumors, cell lines in vitro and xenotransplanted tumors in mice regarding the primary tumor and metastasis. Comprehensive analysis of chemokines and chemokine receptors in the metastasis derived cell line and in the cell line originating from the primary tumor revealed the most pronounced changes for CXCL14. This pattern was confirmed on the protein level. Comparative analysis of podoplanin showed marked down-regulation in the metastatic variant on the mRNA and protein levels.

CONCLUSIONS

To our knowledge we established the first pair of cell lines of a human primary penile tumor and the corresponding lymph node metastasis. These cell lines offer unique possibilities for further comparative functional investigations in in vitro and in vivo settings. They enable studies of new potential therapeutic agents and other assays to better understand the molecular mechanisms of penile cancer progression.

Expression and clinical significance of extracellular matrix protein 1 and vascular endothelial growth factor-C in lymphatic metastasis of human breast cancer

BACKGROUND

Extracellular matrix protein 1 (ECM1) and vascular endothelial growth factor-C (VEGF-C) are secretory glycoproteins that are associated with lymphangiogenesis; these proteins could, therefore, play important roles in the lymphatic dissemination of tumors. However, very little is known about their potential roles in lymphangiogenesis. The aim of this study was to investigate whether correlations exist between ECM1 and VEGF-C in human breast cancer, lymphangiogenesis, and the clinicopathological characteristics of the disease.

METHODS

ECM1 and VEGF-C mRNA and protein expression levels in 41 patients were investigated using real-time reverse transcriptase polymerase chain reaction (RT-PCR), or immunohistochemical (IHC) staining of breast cancer tissue, matched noncancerous breast epithelial tissues, and suspicious metastatic axillary lymph nodes. D2-40 labelled lymph vessels and lymphatic microvessel density (LMVD) were counted. Correlations between ECM1 or VEGF-C protein expression levels, LMVD, and clinicopathological parameters were statistically tested.

RESULTS

The rate of ECM1 positive staining in breast cancer tissues was higher (31/41, 75.6%) than that in the corresponding epithelial tissues (4/41, 9.8%, P < 0.001) and lymph nodes (13/41, 31.7%, P < 0.001). Similarly, the VEGF-C expression rate in cancer specimens was higher (33/41, 80.5%) than in epithelial tissues (19/41, 46.3%, P < 0.01) or lymph nodes (15/41, 36.6%, P < 0.01). Higher ECM1 and VEGF-C mRNA expression levels were also detected in the tumor tissues, compared to the non-cancerous tissue types or lymph nodes (P < 0.05). ECM1 protein expression was positively correlated with the estrogen receptor status (P < 0.05) and LMVD (P < 0.05). LMVD in the ECM1- and VEGF-C-positive tumor specimens was higher than that in the tissue types with negative staining (P < 0.05).

CONCLUSIONS

Both ECM1 and VEGF-C were overexpressed in breast cancer tissue samples. ECM1 expression was positively correlated with estrogen responsiveness and the metastatic properties of breast cancer. We conclude, therefore, that ECM1 and VEGF-C may have a synergistic effect on lymphangiogenesis to facilitate lymphatic metastasis of breast cancer.

High podoplanin expression in cancer cells predicts lower incidence of nodal metastasis in patients with lung squamous cell carcinoma

Podoplanin is expressed in a variety of malignant cells, and is generally regarded as a factor promoting tumor progression in conventional studies. Conversely, a recent clinicopathological study has revealed that low podoplanin in cancer cells was correlated with poor prognosis of patients with stage IB lung squamous cell carcinoma (LSCC). We here evaluated the clinicopathological relationship between cancer-cell podoplanin expression and clinicopathological parameters in 40 cases of LSCC (stage I-III). Immunohistochemical podoplanin expression significantly correlated with N classification and pathological stage, but not with other clinicopathological parameters. Notably, all 16 cases with high podoplanin expression unexceptionally exhibited pathological N0 status. Cases without nodal metastasis showed a significantly higher podoplanin-positive score. Furthermore, patients with high podoplanin expression exhibited a significantly longer survival time and disease-free time. These findings suggest that immunohistochemical analysis for podoplanin may serve as a marker of risk of nodal metastasis and prognosis in patients with LSCC.