Up-regulation of the lymphatic marker podoplanin, a mucin-type transmembrane glycoprotein, in human squamous cell carcinomas and germ cell tumors

Podoplanin is expressed in subsets of tumors of the central nervous system

Immunohistochemical analyses with the monoclonal antibody D2-40 were performed to ascertain the expression of podoplanin (a.k.a. T1-alpha, gp36, or aggrus) in tumors of the central nervous system (CNS) and to determine the diagnostic utility of the antibody. The analyses were performed on 325 tumors of various histologic types. The chief finding was almost constant immunoreactivity in ependymal tumors (37/40, 92.5%), choroid plexus papillomas (8/8, 100%), and meningiomas (100/100, 100%). The reactivity was considered "tissue-specific," as the corresponding normal tissue of each tumor was also found to express podoplanin. In addition, expression, not committed to the lineages, was found in many other tumor types, including astrocytic tumors, medulloblastomas, and hemangioblastomas, with variable frequency and intensity. The way of expression was not fully understood, but the expression in astrocytic tumors seemed to be associated with pronounced fibrous properties or malignant phenotype, as was shown by high-frequent expression in pilocytic astrocytomas (12/12, 100%) and glioblastomas (29/35, 82.9%). The present study has shown that podoplanin is expressed in several types of CNS tumors with variable frequency and intensity. Given the widespread expression of podoplanin, the antibody D2-40 is of little use in diagnostic practice for CNS tumors.

Value of immunohistochemistry in distinguishing peritoneal mesothelioma from serous carcinoma of the ovary and peritoneum: a review and update

At present, a large number of immunohistochemical markers that can be used in the differential diagnosis between epithelioid peritoneal mesotheliomas and serous carcinomas are available. However, great differences of opinion exist regarding the individual value of some of these markers. This article provides a critical review of all of the information that is currently available on those markers that have the greatest potential for assisting in distinguishing between peritoneal mesotheliomas and serous carcinomas. The conclusion of this review indicates that the positive serous carcinoma markers, by and large, have a higher degree of sensitivity and specificity in assisting in discriminating between these malignancies than the positive mesothelioma markers. From a practical point of view, a combination of MOC-31 (or Ber-EP4), estrogen receptors, and calretinin immunostaining should allow a clear distinction to be made between epithelioid peritoneal mesotheliomas and serous carcinomas in most cases.

Overexpression of podoplanin in oral cancer and its association with poor clinical outcome

BACKGROUND

Podoplanin is a mucin-like glycoprotein that is important in lymphangiogenesis but not blood vessel formation. Recent studies suggested a potential role of podoplanin in certain tumor cells. The purpose of the current study was to determine the role of podoplanin in head and neck squamous cell carcinoma (HNSCC).

METHODS

Podoplanin expression was analyzed in 35 patients with HNSCC including 16 oral tumors and 19 hypopharyngeal tumors by immunohistochemical analysis and the association between the podoplanin expression status and patients' clinical and pathologic characteristics was evaluated. An independent set of 60 patients with oral tongue cancer was then analyzed for associations between the podoplanin expression status and patients' clinical and pathologic characteristics, including survivals.

RESULTS

Podoplanin was not expressed in normal oral epithelial cells but was detected in some hyperplastic and dysplastic lesions. High podoplanin expression was found in 20 (57%) of the 35 tumors and was more frequent in tumors with lymph node metastasis, particularly for tumors in the oral cavity. In the second set of 60 oral tongue cancers, 36 (60%) expressed high levels of podoplanin. Patients whose tumors expressed high levels of podoplanin had a statistically significantly higher rate of lymph node metastasis (P < .0001). Patients with lymph node metastasis and high-level podoplanin showed the shortest disease-specific survival (P = .0004) than other patients.

CONCLUSIONS

Podoplanin is involved in oral tumorigenesis and may serve as a predictor for lymph node metastasis and poor clinical outcome.

Isolation and characterization of lymphatic microvascular endothelial cells from human tonsils

Human lymphatic endothelial cells (LECs) have isolated prevalently from human derma and tumors. As specialized lymphatic organs within the oropharynx, palatine tonsils are easily obtained and rich in lymphatic venules. Using a two-step purification method based on the sorting of endothelial cells with Ulex Europaeus Agglutinin 1 (UEA-1)-coated beads, followed by purification with monoclonal antibody D2-40, we successfully purified LECs from human palatine tonsils. The LECs were expanded on flasks coated with collagen type 1 and fibronectin for up to 8-10 passages and then analyzed for phenotypic and functional properties. Cultured cells retained the phenotypic pattern of the lymphatic endothelium of palatine tonsils and expressed functional VEGFR-3 molecules. In fact, stimulation with VEGFR-3 ligand, the vascular endothelium grow factor C, induced a marked increase in cell proliferation. Similarly to blood endothelial cells (BECs), LECs were able to form tube-like structure when seeded in Cultrex basement membrane extract. Comparative studies performed on LECs derived from palatine tonsils and iliac lymphatic vessels (ILVs), obtained with the same procedures, showed substantial discrepancies in the expression of various lymphatic markers. This points to the existence of micro- and macrovessel-derived LECs with different phenotypes, possibly involving different biological activities and functions. Palatine tonsil- and ILV-derived LECs may, therefore, represent new models for investigating function and biochemical properties of these lymphatic endothelia.

Comparison of the diagnostic accuracy of lymphatic endothelium markers: Bayesian approach

Tumor lymphatic density is evaluated by means of specific lymphatic endothelium markers, and is a potential predictor of clinically meaningful outcomes. There are many claims on the postulated superiority of some of these markers to identify lymphatics, always in the absence of quantitative data. We therefore compared the diagnostic accuracy of the antibody against podoplanin and the commercially available D2-40, employing Bayesian statistics to account for the absence of a gold standard. We used the pan-endothelial marker CD34 to identify 23,542 distinct blood and lymphatic vessels in sections from 30 formalin-fixed, paraffin-embedded archival tissue blocks of head and neck squamous cell carcinoma specimens. We stained two adjacent sections with podoplanin and D2-40 and identified the continuum of each stained vessel in the sections with a comprehensive method. Overall, 1,864 vessels were stained with both markers, 119 only with podoplanin and 391 only with D2-40. Significantly more vessels with intraluminal red blood cells were stained with D2-40 compared to podoplanin (McNemar's P<0.0001). Both antibodies had extremely high specificity (99.7% (95% credible interval (CrI): 99.5-99.9%) and 98.8% (95% CrI: 98.3-99.5%) for podoplanin and D2-40, respectively) and very high sensitivity (92.6% (95% CrI: 86.1-97.9%) and 97.3% (95% CrI: 94.9-99.2%) for podoplanin and D2-40, respectively). Inferences were qualitatively similar when we took into account in the analyses the possibility that the two tests (antibodies) may be correlated. We calculated that 96.3% (95% CrI: 94.2-98.6%) of the vessels stained with podoplanin and 88.9% (95% CrI: 83.9-95.7%) of the vessels stained with D2-40 were truly lymphatics. These numbers were in agreement with the observed number of stained vessels without intraluminal red blood cells. Our results suggest that both antibodies are excellent lymphatic endothelium markers and that there may be little reason to prefer either of them in most settings.

Lymphatic vessel density and lymph node metastasis in prostate cancer

BACKGROUND

Few data are available examining the significance of prostatic lymphatic vessel density (LVD) to lymph node metastasis in patients with prostate cancer. The purpose of this study was to determine the distribution of lymphatic vessels in non-carcinomatous prostate tissue, and investigate the relationship between LVD and lymph node status in prostate cancer.

METHODS

LVD, identified by D2-40 immunostaining, was evaluated in non-carcinomatous prostates (n = 7) and prostate cancer (n = 37). The staining pattern of D2-40 was compared with that of another lymphatic vessel marker, vascular endothelial growth factor (VEGF) receptor-3, and a blood vessel endothelial marker, CD34, in adjacent sections.

RESULTS

The D2-40 antigen, podoplanin, was expressed exclusively in lymphatic vessels within tumor and normal tissue in all specimens. There was no overlap between cell staining for D2-40 and CD34. Peritumoral LVD and peritumoral lymphatic invasion were significantly associated with lymph node metastasis. VEGF receptor-3 was expressed in a subset of D2-40+ lymphatic vessels.

CONCLUSIONS

We have demonstrated that peritumoral lymphatic vessels are likely to serve as major conduits for nodal metastasis in prostate cancer using D2-40 to decorate lymphatic endothelium marker podoplanin. Lack of coexpression of podoplanin and VEGF receptor-3 in some lymphatic vessels suggests the heterogeneity of lymphatic endothelial cells in prostate tissue.

Accelerated lymphangiogenesis in malignant lymphoma: possible role of VEGF-A and VEGF-C

There is little information regarding the lymphangiogenesis of malignant lymphoma. In this study, we evaluated the lymphangiogenesis and angiogenesis in 44 lymph nodes of 39 malignant lymphomas and five non-reactive normal lymph nodes, based on the lymphatic vessel density (LVD) and microvessel density (MVD) calculated by the computer-assisted assessment of vessel density. The LVD of malignant lymphomas was significantly higher than that of non-reactive normal lymph nodes, irrespective of subtypes (P = 0.00077). On the contrary, there was no difference in MVD between malignant lymphomas and non-reactive normal lymph nodes, except for diffuse large B cell lymphomas, which had a significantly low value of MVD, in comparison with non-reactive normal lymph nodes (P = 0.009). We further examined the expression of vascular endothelial growth factor (VEGF)-C and VEGF-A, which function on lymphangiogenesis in lymph node samples. VEGF-C was expressed in 36 of 39 malignant lymphomas. All 39 of the malignant lymphoma samples expressed VEGF-A. Furthermore, the level of LVD and VEGF-A or VEGF-C was positively correlated. These findings suggest that lymphangiogenesis is actively developed in lymph nodes of malignant lymphomas and it may be induced by both VEGF-A and VEGF-C secreted from lymphoma cells.

Tumor lymphangiogenesis predicts melanoma metastasis to sentinel lymph nodes

Cutaneous melanoma is a common melanocytic neoplasm that can quickly metastasize to regional lymph nodes. Currently, prognosis is determined by measuring tumor thickness but more reliable markers for metastatic spread are urgently needed. We investigated whether the extent of tumor lymphangiogenesis can predict melanoma metastasis to sentinel lymph nodes. We quantified the extent of tumor lymphangiogenesis, as well as other factors, in excised primary tumors and in sentinel lymph node biopsy samples from 45 patients with primary cutaneous melanoma. The results were correlated with histological and clinical outcome. Primary melanomas from patients whose tumors had metastasized to the sentinel lymph nodes contained prominent 'hot spots' of increased lymphatic vessel density, compared to nonmetastatic tumors. Multivariate risk analysis revealed that the lymphatic vascular area of primary melanomas, an index of tumor lymphangiogenesis, was the most sensitive prognostic marker for sentinel lymph node metastasis, and was even able to more accurately predict which tumors were metastatic to sentinel lymph nodes than the currently used method of measuring tumor thickness. Highly lymphangiogenic melanomas maintained their lymphangiogenic activity after metastasis to the sentinel lymph node. The extent of tumor lymphangiogenesis is a highly sensitive (83%) and specific (89%) prognostic marker of lymph node metastasis. Assessment of lymphangiogenesis in primary melanomas may be a more effective approach than the currently used technique of measuring tumor thickness in selecting patients with early metastatic disease for aggressive therapy.