Vasculogenic mimicry has no prognostic significance in pT3 and pT4 cutaneous melanoma

Hypomethylation-associated LINC00987 downregulation induced lung adenocarcinoma progression by inhibiting the phosphorylation-mediated degradation of SND1

DNA methylation, an epigenetic regulatory mechanism dictating gene transcription, plays a critical role in the occurrence and development of cancer. However, the molecular underpinnings of LINC00987 methylation in the regulation of lung adenocarcinoma (LUAD) remain elusive. This study investigated LINC00987 expression in LUAD patients through analysis of The Cancer Genome Atlas data sets. Quantitative real-time polymerase chain reaction (RT-qPCR) and fluorescence in situ hybridization assays were used to assess LINC00987 expression in LUAD. The bisulfite genomic sequence PCR (BSP) assay was used to determine the methylation levels of the LINC00987 promoter. The interaction between LINC00987 and SND1 was elucidated via immunoprecipitation and RNA pull-down assays. The functional significance of LINC00987 and SND1 in Calu-3 and NCI-H1688 cells was evaluated in vitro through CCK-8, EdU, Transwell, flow cytometry, and vasculogenic mimicry (VM) tube formation assays. LINC00987 expression decreased in LUAD concomitant with hypermethylation of the promoter region, while hypomethylation of the LINC00987 promoter in LUAD tissues correlated with tumor progression. Treatment with 5-Aza-CdR augmented LINC00987 expression and inhibited tumor growth. Mechanistically, LINC00987 overexpression impeded LUAD progression and VM through direct binding with SND1, thereby facilitating its phosphorylation and subsequent degradation. Additionally, overexpression of SND1 counteracted the adverse effects of LINC00987 downregulation on cell proliferation, apoptosis, cell migration, invasion, and VM in LUAD in vitro. In conclusion, this pioneering study focuses on the expression and function of LINC00987 and reveals that hypermethylation of the LINC00987 gene may contribute to LUAD progression. LINC00987 has emerged as a potential tumor suppressor gene in tumorigenesis through its binding with SND1 to facilitate its phosphorylation and subsequent degradation.

Vasculogenic Mimicry: A Promising Prognosticator in Head and Neck Squamous Cell Carcinoma and Esophageal Cancer? A Systematic Review and Meta-Analysis

Vasculogenic mimicry (VM) is an intratumoral microcirculation pattern formed by aggressive cancer cells, which mediates tumor growth. In this study, we compiled the evidence from studies evaluating whether positive VM status can serve as a prognostic factor to patients with squamous cell carcinoma of the head and neck (HNSCC) or esophagus (ESCC). Comprehensive systematic searches were conducted using Cochrane Library, Ovid Medline, PubMed, and Scopus databases. We appraised the quality of studies and the potential for bias, and performed random-effect meta-analysis to assess the prognostic impact of VM on the overall survival (OS). Seven studies with 990 patients were eligible, where VM was detected in 34.24% of patients. Positive-VM was strongly associated with poor OS (hazard ratio = 0.50; 95% confidence interval: 0.38-0.64), which remained consistent following the subgroup analysis of the studies. Furthermore, VM was associated with more metastasis to local lymph nodes and more advanced stages of HNSCC and ESCC. In conclusion, this study provides clear evidence showing that VM could serve as a promising prognosticator for patients with either HNSCC or ESCC. Further studies are warranted to assess how VM can be implemented as a reliable staging element in clinical practice and whether it could provide a new target for therapeutic intervention.

The role of vascular mimicry as a biomarker in malignant melanoma: a systematic review and meta-analysis

BACKGROUND

Vasculogenic mimicry (VM) a microvascular system consisting of non-endothelial cells that is newly formed by aggressive tumors, has been proposed as an important therapeutic target in malignant melanoma (MM). We performed a systematic literature review to evaluate the diagnostic and prognostic accuracy of VM status for overall survival of MM patients.

METHODS

The quality of the included studies was evaluated using the QUADAS-2 tool. Diagnostic capacity of VM variables, including sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio (DOR), and the area under summary receiver operating characteristic (SROC), were pooled using Meta-DiSc software.

RESULTS

A retrospective observational study was conducted based on twelve clinical studies including 978 clinically confirmed melanoma patients with proportion (P). VM+ melanoma cells were associated with poor prognosis in 38% of MM group (P = 0.35, 95% confidence intervals (CI): 0.27-0.42, p < 0.001). The pooled sensitivity and specificity were 0.82 (95% CI: 0.79-0.84) and 0.69 (95% CI: 0.66-0.71), respectively. Furthermore, the pooled PLR, NLR, and DOR were 2.56 (95% CI: 1.94-3.93), 0.17 (95% CI: 0.07-0.42), and 17.75 (95% CI: 5.30-59.44), respectively. Furthermore, the AUC of SROC was 0.63, indicating high reliability of VM status as a biomarker. Importantly, subgroup results suggested that VM+ status is a significantly accurate prognostic biomarker when diagnosed by the CD31-/PAS+ staining methods in Asian MM samples (p < 0.001).

CONCLUSIONS

Our findings support the potential of VM status of tumors as a promising prognostic biomarker and emphasize an effective adjuvant therapeutic strategy in the prognosis of Asian MM patients.

Molecular Mechanisms and Anticancer Therapeutic Strategies in Vasculogenic Mimicry

Vasculogenic mimicry (VM) is a vascular formation mechanism used by aggressive tumor cells. VM provides an alternative pathway for adequate blood perfusion and challenges the traditional angiogenesis mechanism that depends only on endothelial cells (ECs), as VM-forming tumor cells express a mixed endothelial/tumor phenotype. VM is closely correlated with tumor invasion, migration, and progression. Hence, anticancer therapeutic strategies targeting VM biogenesis are essential. It is widely acknowledged that the VM formation mechanism involves multiple pathways. The purpose of this review is to describe the potential molecular mechanisms related to different pathways and discuss the involvement of microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs) in VM formation. Moreover, we discuss the significance of VM in clinical practice and present new anticancer therapeutic strategies that target VM.

Overview of advances in vasculogenic mimicry - a potential target for tumor therapy

Vasculogenic mimicry (VM) describes the process utilized by highly aggressive cancer cells to generate vascular-like structures without the presence of endothelial cells. VM has been vividly described in various tumors and participates in cancer progression dissemination and metastasis. Diverse molecular mechanisms and signaling pathways are involved in VM formation. Furthermore, the patterning characteristics of VM, detected with molecular imaging, are being investigated for use as a tool to aid clinical practice. This review explores the most recent studies investigating the role of VM in tumor induction. Indeed, the recognition of these advances will increasingly affect the development of novel therapeutic target strategies for VM in human cancer.

Association of Vasculogenic Mimicry Formation and CD133 Expression with Poor Prognosis in Ovarian Cancer

AIMS

This study was conducted to investigate the association of vasculogenic mimicry (VM) formation and CD133 expression with the clinical outcomes of patients with ovarian cancer.

METHODS

This retrospective study was performed in 120 ovarian carcinoma samples. VM formation and CD133 expression was identified with CD31/periodic acid-Schiff double-staining and CD133 immunohistochemical staining. Collected clinical and pathological data included age at diagnosis, histologic type, tumor grade, tumor stage, lymph node metastases and response to chemotherapy. The overall survival time was calculated.

RESULTS

VM was identified in 52 (43%) of 120 ovarian carcinoma tissues and CD133 expression was found in 56 (47%) cases. Both VM formation and CD133 expression were associated with advanced tumor stage, high-grade carcinoma and non-response to chemotherapy (p < 0.05). They were also associated with shorter overall survival time (p < 0.05) by log-rank test. Combined marker of VM formation and CD133 expression was associated with high-grade ovarian carcinoma, late-stage disease, non-response to chemotherapy and shorter overall survival time (p < 0.05).

CONCLUSIONS

VM formation and CD133 expression can provide additional prognostic information for patients with ovarian cancer. Combined marker of VM formation and CD133 expression may be a potent predictor for poor prognosis for patients with ovarian cancer.

Advanced research on vasculogenic mimicry in cancer

Vasculogenic mimicry (VM) is a brand-new tumour vascular paradigm independent of angiogenesis that describes the specific capacity of aggressive cancer cells to form vessel-like networks that provide adequate blood supply for tumour growth. A variety of molecule mechanisms and signal pathways participate in VM induction. Additionally, cancer stem cell and epithelial-mesenchymal transitions are also shown to be implicated in VM formation. As a unique perfusion way, VM is associated with tumour invasion, metastasis and poor cancer patient prognosis. Due to VM's important effects on tumour progression, more VM-related strategies are being utilized for anticancer treatment. Here, with regard to the above aspects, we make a review of advanced research on VM in cancer.

Mechanisms of tumour vascularization in cutaneous malignant melanoma: clinical implications

Malignant melanoma represents < 10% of all skin cancers but is responsible for the majority of skin-cancer-related deaths. Metastatic melanoma has historically been considered as one of the most therapeutically challenging malignancies. Fortunately, for the first time after decades of basic research and clinical investigation, new drugs have produced major clinical responses. Angiogenesis has been considered an important target for cancer treatment. Initial efforts have focused primarily on targeting endothelial and tumour-related vascular endothelial growth factor signalling. Here, we review different mechanisms of tumour vascularization described in melanoma and discuss the potential clinical implications.

Tumour vasculogenic mimicry is associated with poor prognosis of human cancer patients: a systemic review and meta-analysis

BACKGROUND

Vasculogenic mimicry (VM) has been reported in various malignant tumours and is known to play an important role in cancer progression and metastasis. However, the impact of VM on the overall survival of human cancer patients remains controversial. The goal of this study was to evaluate whether VM is associated with 5-year survival of human cancer patients.

METHODS

Twenty-two eligible clinical studies with data on both tumour cell-dominant VM and the 5-year survival of 3062 patients involved in 15 types of cancers were pooled in the meta-analysis.

RESULTS

The 5-year overall survival of VM-positive and -negative cancer patients was 31% and 56%, respectively. The relative risk (RR) of the 5-year survival of VM-positive patients was significantly higher than that of VM-negative cases (RR=1.531; 95% confidence interval (CI): 1.357-1.726; P<0.001). Notably, metastatic melanoma patients demonstrated a higher VM rate (45.3%) than patients with primary melanoma (23.1%) and showed worse 5-year survival, suggesting that VM contributes to tumour metastasis and poor prognosis in cancer patients. Subgroup analysis indicated that a poor 5-year survival was significantly associated with eight types of VM-positive malignant tumours, such as lung, colon, liver cancers, sarcomas and melanoma; but was not associated with the seven other types of cancers, such as prostate cancer. Heterogeneity and publication biases were found among the 22 studies, mainly due to the divergent characteristics of cancers and extremely low survival rate in six types of malignant tumours.

CONCLUSION

VM-positive cancer patients show a poor 5-year overall survival compared with VM-negative malignant tumour cases, particularly in metastatic cancer.

Clinical significance of vasculogenic mimicry in human gliomas

Vasculogenic mimicry (VM) is known as non-endothelial tumor cell-lined microvascular channels in aggressive tumors. We have previously found the presence of VM in high-grade gliomas. In this study, we aimed to identify VM patterns in gliomas and to explore their clinical significance. Tumor samples as well as their detailed clinical/prognostic data were collected from 101 patients. Vasculogenic mimicry in the glioma samples was determined by dual staining for endothelial marker CD34 and periodic acid–Schiff (PAS). Tumor samples were also immunohistochemically stained for Ki-67, VEGF, COX-2 and MMP-9. The association between VM and the clinical characteristics of the patients were analyzed. A Kaplan–Meier survival analysis and log-rank tests were performed to compare survival times of the patients. Vasculogenic mimicry was present in 13 out of 101 samples. The higher grade gliomas had a higher incidence of VM than that of lower grade gliomas (P = 0.006). Vasculogenic mimicry channels were associated with the expression of COX-2 and MMP-9 (P < 0.05). While there was no association between the existence of VM and the sex, age and preoperative epilepsy of the patients, or expression of Ki-67 and VEGF. However, patients with VM-positive gliomas survived a shorter period of time than those with VM negative gliomas (P = 0.027). Interestingly, in high-grade gliomas, the level of microvascular density was lower in VM positive tumors than those VM negative tumors (P = 0.039). Our results suggest that VM channels in gliomas correlate with increasing malignancy and higher aggressiveness, and may provide a complementation to the tumor’s blood supply, especially in less vascularized regions, which may aid in the identification of glioma patients with a poorer prognosis.

Melanoma cells produce multiple laminin isoforms and strongly migrate on α5 laminin(s) via several integrin receptors

Melanoma cells express and interact with laminins (LMs) and other basement membrane components during invasion and metastasis. In the present study we have investigated the production and migration-promoting activity of laminin isoforms in melanoma. Immunohistochemistry of melanoma specimens and immunoprecipitation/western blotting of melanoma cell lines indicated expression of laminin-111/121, laminin-211, laminin-411/421, and laminin-511/521. Laminin-332 was not detected. In functional assays, laminin-111, laminin-332, and laminin-511, but not laminin-211 and laminin-411, strongly promoted haptotactic cell migration either constitutively or following stimulation with insulin-like growth factors. Both placenta and recombinant laminin-511 preparations were highly active, and the isolated recombinant IVa domain of LMα5 also promoted cell migration. Function-blocking antibodies in cell migration assays revealed α6β1 integrin as the major receptor for laminin-111, and both α3β1 and α6β1 integrins for laminin-332 and laminin-511. In contrast, isolated LMα5 IVa domain-promoted melanoma cell migration was largely mediated via αVβ3 integrin and inhibited by RGD peptides. Given the ubiquitous expression of α5 laminins in melanoma cells and in melanoma-target tissues/anatomical structures, as well as the strong migration-promoting activity of these laminin isoforms, the α5 laminins emerge as putative primary extracellular matrix mediators of melanoma invasion and metastasis via α3β1 and other integrin receptors.

Prognostic significance and mechanisms of patterned matrix vasculogenic mimicry in hepatocellular carcinoma

Vasculogenic mimicry (VM), including tubular VM and patterned matrix VM, has been generally recognized as a new pattern of tumor neovascularization. Pilot studies of tubular VM showed that it was present in hepatocellular carcinoma (HCC) and associated with poor clinical prognosis. However, whether patterned matrix VM is clinically significant in HCC is unknown. To elucidate the effects of patterned matrix VM on prognosis of HCC and the mechanisms involved in VM formation, we examined 151 cases of surgically resected human HCC by immunohistochemistry and transmission electron microscopy and conducted hypoxic experiments on human HCC cell line MHCC97-H. We observed 31 of 151 (20.5%) cases exhibited evidence of patterned matrix VM. The expression of patterned matrix VM was associated with larger tumors (P = 0.042), vascular invasion (P = 0.016), high-grade HCC (P = 0.022), and late-stage HCC (P = 0.013). Kaplan-Meier survival analysis revealed that cases of the VM group had lower overall survival (OS) rate (P < 0.001) and disease-free survival (DFS) rate (P = 0.002) than that of the non-VM group. Univariate and multivariate analysis indicated that the presence of patterned matrix VM was independent adverse prognostic factor for both OS (P = 0.004) and DFS (P = 0.011). Expression of hypoxia-inducible factor 1 alpha (HIF-1alpha), matrix metalloproteinase (MMP)-2, and MMP-9 were higher in the VM group than in the non-VM group (P = 0.001, P = 0.030, P = 0.007, respectively). After VM formation was induced by hypoxia, up-regulated expression of HIF-1α, MMP-2, and MMP-9 was also detected in cells cultured under hypoxia condition. Our results indicate that patterned matrix VM exists in HCC, and it might serve as an unfavorable prognostic factor for HCC patients. It is possible that hypoxia via induction of expression of HIF-1alpha, MMP-2, and MMP-9 may enhance VM formation in HCC.

Prognostic significance of melanoma differentiation and trans-differentiation

Cutaneous malignant melanomas share a number of molecular attributes such as limitless replicative potential that define capabilities acquired by most malignancies. Accordingly, much effort has been focused on evaluating and validating protein markers related to these capabilities to function as melanoma prognostic markers. However, a few studies have also highlighted the prognostic value of markers that define melanocytic differentiation and the plasticity of melanoma cells to trans-differentiate along several other cellular pathways. Here, we provide a comprehensive review and evaluation of the prognostic significance of melanocyte-lineage markers such as MITF and melanogenic proteins, as well as markers of vascular epithelial and neuronal differentiation.

Prognostic Relevance of CD105-Assessed Microvessel Density in Laryngeal Carcinoma

OBJECTIVE: To examine immunohistochemical expression of CD105 among patients with laryngeal cancer and investigate the prognostic significance of CD105-assessed microvessel density (MVD).

STUDY DESIGN: Cross-sectional study.

SETTING: University hospital.

SUBJECTS AND METHODS: The study comprised 80 patients with laryngeal squamous cell carcinoma who underwent complete excision. Clinicopathological data were collected retrospectively. Immunohistochemical analysis was performed with CD105 (endoglin) antibody. Positive-stained microvessels for CD105 were counted on hot spots of tumors at ×200 magnification.

RESULTS: Average CD105-assessed MVD in considered laryngeal squamous cell carcinomas (SCCs) was 12.9 (SD 3.84). High expression of CD105 correlated significantly with advanced T (tumor) classification ( P = 0.008), advanced TNM (tumor, node, metastasis) stage ( P = 0.001), tumor recurrence ( P = 0.001), and age ≥65 years ( P = 0.026). The multivariate logistic regression showed that a high CD105+ MVD (odds ratio [OR] 4.27; P = 0.019) and advanced TNM stage (OR 3.72; P = 0.047) were independent markers of tumor recurrence. High MVD, advanced clinical stage, the presence of lymph node metastasis at the time of diagnosis, and age <66 years were associated with worse disease-free survival. Cox regression analysis revealed that expression of CD105 ( P = 0.016) and advanced clinical stage ( P = 0.05) were the independent factors for disease-free survival.

CONCLUSION: The present results suggest that MVD evaluation with CD105 is a promising prognostic factor for the outcome of patients with laryngeal SCC. CD105-assessed MVD could help to identify patients with more aggressive disease and increased risk of developing malignancy recurrence after treatment.

Novel therapeutics for the treatment of metastatic melanoma

Metastatic malignant melanoma is an incurable disease with a median survival of 8.5 months and a probability of surviving 5 years after the diagnosis of less than 5%. To date, no systemic therapy has meaningfully changed these survival end points. Currently, in the USA the FDA has approved three agents for the treatment of metastatic melanoma: hydroxyurea, dacarbazine and interleukin-2. None of these have demonstrated a meaningfully prolonged survival of patients with metastatic melanoma. Therefore, a number of innovative therapeutic strategies have been pursued to improve outcomes, including immune therapy, tyrosine kinase inhibitors and angiogenesis inhibitors. Herein, we review some of the recent advances in novel therapeutic developments for the treatment of metastatic melanoma.

A pilot study of vasculogenic mimicry immunohistochemical expression in hepatocellular carcinoma

CONTEXT

The "de novo" formation of fluid-conducting patterns by tumor cells, termed vasculogenic mimicry (VM), is associated with increased mortality in many different solid tumors.

OBJECTIVE

To identify VM patterns in hepatocellular carcinoma (HCC) and to determine whether these patterns were associated with more rapid tumor recurrence after orthotopic liver transplantation.

DESIGN

Subjects included 20 patients who underwent orthotopic liver transplantation and were found to have HCC in the liver explant. Samples from 5 normal postmortem livers and 5 explanted livers with hepatitis C virus cirrhosis without HCC served as control tissues. Patterned matrix VM expression in HCC was identified by the presence of laminin-positive loops surrounding packets of tumor cells. Time to HCC recurrence after orthotopic liver transplantation was compared between patients with and without patterned VM expression. The relationships among VM in HCC, cause of chronic liver disease, serum alpha-fetoprotein level at the time of diagnosis, tissue expression by epidermal growth factor receptor, and endothelial markers including vascular endothelial growth factor and CD31 were assessed.

RESULTS

Patterned matrix VM was identified in 11 of 20 primary HCC tissue samples. Vasculogenic mimicry was absent in all 10 control cases and was not identified in any area of dysplasia. The expression of VM in HCC lesions in liver explants was associated with more rapid posttransplant recurrence (P = .01). Vasculogenic mimicry was not associated with the cause of liver disease, serum alpha-fetoprotein level at time of diagnosis, or expression of epidermal growth factor receptor, vascular endothelial growth factor, or CD31.

CONCLUSIONS

Vasculogenic mimicry of the patterned matrix type is present in hepatocellular carcinoma and is associated with tumor recurrence after orthotopic liver transplantation. Vasculogenic mimicry lesions are not associated with endothelial markers in HCC.

A phase II study of ABT-510 (thrombospondin-1 analog) for the treatment of metastatic melanoma

OBJECTIVES

Thrombospondins are natural inhibitors of angiogenesis, tumor metastases, and tumor growth (melanoma). ABT-510 is a synthetic analog of thrombospondin-1, well tolerated in phase I studies. We conducted a phase II trial evaluating the clinical efficacy of ABT-510 and its effects on biomarkers of angiogenesis and immunity in patients with metastatic melanoma (MM).

PATIENTS AND METHODS

A 2-stage phase II clinical trial was conducted to assess the clinical efficacy, safety, and pharmacodynamic effects (angiogenesis and immunity) of ABT-510 in patients with stage IV melanoma. The primary endpoint was 18-week treatment failure rate. Patients self-administered 100 mg of ABT-510 subcutaneously twice daily. Blood samples were collected at baseline and every 3 weeks while on therapy. Eligible patients demonstrated measurable disease, good performance status and no evidence of intracranial metastases. Correlative laboratory studies evaluated biomarkers of angiogenesis and immunity.

RESULTS

Twenty-one patients were enrolled. Most patients were stage M1c (71%) and all had prior therapy for MM. Only 3 of the first 20 patients enrolled were progression free and on treatment at 18 weeks resulting in early termination of the study. Decreases in peripheral blood VEGF-A levels and VEGF-C levels, and CD146 and CD34/133 counts relative to pretreatment were detected. Limited changes in antitumor T cell immunity were observed.

CONCLUSIONS

ABT-510 therapy administered at 100 mg twice/day in patients with MM did not demonstrate definite clinical efficacy. Further dose escalation or combination with cytotoxic therapy may be more effective therapeutically.

Endoglin (CD105) as a prognostic factor in head and neck squamous cell carcinoma

Endoglin (CD105) is a proliferation-associated protein abundantly expressed in angiogenic endothelial cells. Recent studies revealed that CD105 is intensively expressed in tumor vasculature, whereas intratumoral microvessel density (MVD) determined with the use of antibodies to CD105 has been found to be an important prognostic indicator for the outcome in a number of malignancies. In the current study, we investigated endoglin expression and evaluated MVD in 108 patients with head and neck squamous cell carcinoma. Endoglin was intensively expressed in intratumoral blood vessels, whilst lymphatics were rarely positive for CD105. High microvessel density was associated with a more aggressive tumor phenotype, including advanced clinical stage (p = 0.008) and the presence of lymph node metastasis at the time of diagnosis (p = 0.02). When microvessel counts were assessed for their prognostic values (high vs low MVD), there was a statistically significant difference in the overall survival among patients with tumors of the oral cavity and larynx (p < 0.001) and in the disease-free survival among patients with tumors of the lower lip (p = 0.01). The prognostic impact of microvessel density was not dependent on clinical stage or lymph node status. The results of the current study suggest that CD105 is a promising target for tumor imaging and prognosis.

Differential expression of angioregulatory matricellular proteins in posterior uveal melanoma

Metastases from uveal melanoma, the most common primary malignant eye tumour in adults, develop solely via their vascular bed due to the absence of intraocular lymphatics. The present study investigated the expression in this tumour of three matricellular proteins--Secreted Protein Acidic and Rich in Cysteine (SPARC), thrombospondin 1 (TSP1) and thrombospondin 2 (TSP2)--with putative contrasting roles in the regulation of angiogenesis. Immunohistochemical analysis of the three proteins was carried out in paraffin-embedded specimens from 27 posterior uveal melanomas and was corroborated with Western blot analysis of fresh-frozen samples from seven of the tumours. SPARC immunoreactivity was detected in all specimens and defined two categories of tumour: SPARC-rich (21 of 27 specimens) and SPARC-patchy (six of 27 specimens) uveal melanomas. SPARC-rich tumours had a significantly higher proportion of specimen area occupied by blood vessels (P=0.04) and showed a positive association with the presence of epithelioid-type tumoral cells (P=0.101). TSP1 was not detected by either of the methods in any of the tumours analysed. Some immunopositivity for TSP2 was detected in tumour cells in approximately 40% of specimens, but was not associated with survival, tumour vascularity or any other histopathological indices of survival. The pattern of expression of these matricellular proteins in uveal melanoma is consistent with a cooperative mechanism for establishing an enhanced environment favourable to angiogenesis. Interventions inducing TSP1 expression and/or inhibiting SPARC expression may be candidates for therapies directed towards the inhibition of angiogenesis in posterior uveal melanoma.

Distinguishing fibrovascular septa from vasculogenic mimicry patterns

CONTEXT

Molecular analyses indicate that periodic acid-Schiff (PAS)-positive (laminin-rich) patterns in melanomas are generated by invasive tumor cells by vasculogenic mimicry. Some observers, however, consider these patterns to be fibrovascular septa, generated by a stromal host response.

OBJECTIVE

To delineate differences between vasculogenic mimicry patterns and fibrovascular septa in primary uveal melanomas.

DESIGN

Frequency distributions, associations with outcome, and thicknesses of trichrome-positive and PAS-positive looping patterns were determined in 234 primary uveal melanomas. Sequential sections of 13 additional primary uveal melanomas that contained PAS-positive/trichrome-negative looping patterns were stained for type I and type IV collagens, laminin, and fibronectin. Real-time quantitative polymerase chain reaction was performed on RNA from cultured uveal melanoma cells for the expression of COL1A1, COL4A2, and fibronectin.

RESULTS

Trichrome-positive loops were encountered less frequently than PAS-positive loops (10% vs 56%, respectively). Death from metastatic melanoma was strongly associated with PAS-positive (P < .001) but not with trichrome-positive (P = .57) loops. Trichrome-positive loops were significantly thicker than PAS-positive loops (P < .001). The PAS-positive patterns stained positive for laminin, type I and type IV collagens, and fibronectin. Type I collagen was detected within melanoma cells and focally within some PAS-positive patterns. Real-time quantitative polymerase chain reaction revealed 3-fold, 25-fold, and 97-fold increases, respectively, in expression of COL4A2, fibronectin, and COL1A1 by invasive pattern-forming primary melanoma cells compared with poorly invasive non-pattern-forming cells.

CONCLUSIONS

Fibrovascular septa are rare and prognostically insignificant in uveal melanomas, whereas vasculogenic mimicry patterns are associated with increased mortality. Type I collagen, seen focally in some vasculogenic mimicry patterns, may be synthesized by tumor cells, independent of a host stromal response.

Vasculogenic mimicry

The term vasculogenic mimicry describes the formation of fluid-conducting channels by highly invasive and genetically dysregulated tumor cells. Two distinctive types of vasculogenic mimicry have been described. Vasculogenic mimicry of the tubular type may be confused morphologically with endothelial cell-lined blood vessels. Vasculogenic mimicry of the patterned matrix type in no way resembles blood vessels morphologically or topologically. Matrix proteins such as laminin, heparan sulfate proteoglycan, and collagens IV and VI have been identified in these patterns. The patterned matrix anastomoses with blood vessels, and systemically injected tracers co-localize to these patterns. Vasculogenic mimicry of the patterned matrix type has been identified in uveal, cutaneous and mucous membrane melanomas, inflammatory and ductal breast carcinoma, ovarian and prostatic carcinoma, and soft tissue sarcomas, including synovial sarcoma rhabdomyosarcoma, osteosarcoma, and pheochromocytoma. Because the microcirculation of many tumors may be heterogeneous -- including incorporated or co-opted vessels, angiogenic vessels, mosaic vessels, and vasculogenic mimicry of the tubular and patterned matrix types -- therapeutic regimens that target angiogenesis alone may be ineffective against highly invasive tumors that contain patterned matrices. Vasculogenic mimicry provides an opportunity to investigate the interrelationships between the genetically dysregulated invasive tumor cell, the microenvironment, and the malignant switch.