Tumor and lymph node lymphangiogenesis--impact on cancer metastasis

The extent of lymph node (LN) metastasis is a major determinant for the staging and the prognosis of most human malignancies and often guides therapeutic decisions. Although the clinical significance of LN involvement is well documented, little has been known about the molecular mechanisms that promote tumor spread via lymphatic vessels to sentinel and distal LN and beyond. However, recent discoveries have identified novel lymphatic-specific markers, and the newly discovered lymphangiogenesis factors vascular endothelial growth factor-C (VEGF-C) and VEGF-D were found to promote tumor-associated lymphatic vessel growth in mouse tumor models, leading to enhanced tumor spread to sentinel LN. Our recent findings indicate that VEGF-A also acts as a potent tumor lymphangiogenesis factor that promotes lymphatic tumor spread. VEGF-A overexpressing primary tumors induced sentinel LN lymphangiogenesis even before metastasizing and maintained their lymphangiogenic activity after metastasis to draining LN. Our recent studies showed that primary human melanomas that later metastasized were characterized by increased lymphangiogenesis and that the degree of tumor lymphangiogenesis can serve as a novel predictor of LN metastasis and overall patient survival, independently of tumor thickness. Tumor lymphangiogenesis also significantly predicted the presence of sentinel LN metastases at the time of surgical excision of the primary melanoma. Together, these findings suggest that tumor lymphangiogenesis actively contributes to cancer dissemination, that blockade of lymphatic vessel growth might inhibit tumor metastasis to LN, and that the extent of tumor-associated lymphangiogenesis could serve as a novel, prognostic parameter for the metastatic risk of human cancers.     

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.     

血管内皮生长因子C及其受体3在人恶性黑色素瘤组织内的表达及意义

目的 观察人恶性黑色素瘤组织内血管内皮生长因子C(VEGF-C)及其受体3(VEGFR-3)的表达,探讨VEGF-C和VEGFR-3在恶性黑色素瘤淋巴管生成及淋巴道转移中的作用.方法 取人恶性黑色素瘤组织48例(石蜡标本30例,术后新鲜组织18例),应用免疫组织化学和RT-PCR技术,观察VEGF-C和VEGFR-3蛋白及mRNA在恶性黑色素瘤组织内的表达情况.以淋巴管内皮透明质酸受体(LYVE-1)标记淋巴管,计数恶性黑色素瘤组织淋巴管数密度.结果 VEGF-C和VEGFR-3蛋白主要表达于恶性黑色素瘤细胞胞浆内,在肿瘤周围的血管和淋巴管内皮上也可见VEGFR-3蛋白表达,VEGF-C和VEGFR-3蛋白在淋巴结转移组恶性黑色素瘤组织内的表达水平明显高于无淋巴结转移组(P<0.05).在18例新鲜恶性黑色素瘤中,淋巴结转移组VEGF-C和VEGFR-3mRNA的表达明显高于无淋巴结转移组(P<0.01).LYVE-1表达于肿瘤间质内的淋巴管内皮细胞,淋巴结转移组恶性黑色素瘤组织中的淋巴管数密度(LMVD)为9.845±2.454,无淋巴结转移组恶性黑色素瘤组织中的淋巴管数密度为6.534±2.193,淋巴结转移组恶性黑色素瘤组织内的淋巴管数密度明显高于无淋巴结转移组(P<0.01).结论恶性黑色素瘤组织内VEGF-C表达明显增高,并通过上调其受体VEGFR-3的表达促进恶性黑色素瘤组织内淋巴管的生成,从而促进恶性黑色素瘤的淋巴道转移.     

Tumour lymphangiogenesis is a possible predictor of sentinel lymph node status in cutaneous melanoma: a case-control study

BACKGROUND: Cutaneous melanoma spreads preferentially through the lymphatic route and sentinel lymph node (SLN) status is regarded as the most important predictor of survival. AIMS: To evaluate whether tumour lymphangiogenesis and the expression of vascular endothelial growth factor C (VEGF-C) is related to the risk of SLN metastasis and to clinical outcome in a case-control series of patients with melanoma. METHODS: Forty five invasive melanoma specimens (15 cases and 30 matched controls) were investigated by immunostaining for the lymphatic endothelial marker D2-40 and for VEGF-C. Lymphangiogenesis was measured using computer assisted morphometric analysis. RESULTS: Peritumorous lymphatic vessels were more numerous, had larger average size, and greater relative area than intratumorous lymphatics. The number and area of peritumorous and intratumorous lymphatics was significantly higher in melanomas associated with SLN metastasis than in non-metastatic melanomas. No significant difference in VEGF-C expression by neoplastic cells was shown between metastatic and non-metastatic melanomas. Using logistic regression analysis, intratumorous lymphatic vessel (LV) area was the most significant predictor of SLN metastasis (p = 0.04). Using multivariate analysis, peritumorous LV density was an independent variable affecting overall survival, whereas the intratumorous LV area approached significance (p = 0.07). CONCLUSIONS: This study provides evidence that the presence of high peritumorous and intratumorous lymphatic microvessel density is associated with SLN metastasis and shorter survival. The intratumorous lymphatic vessel area is the most significant factor predicting SLN metastasis. The tumour associated lymphatic network constitutes a potential criterion in the selection of high risk patients for complementary treatment and a new target for antimelanoma therapeutic strategies.     

VEGF-C在卵巢癌局部淋巴结内淋巴管生成中的作用

目的观察血管内皮生长因子-C(VEGF-C)在卵巢癌组织内的表达,分析其与卵巢癌局部淋巴结内淋巴管生成之间的关系。方法取卵巢癌64例,其中,有淋巴结转移40例,无淋巴结转移24例。应用免疫组化法和Western blot技术观察VEGF-C在卵巢癌组织内的表达。以D2-40作为淋巴管内皮特异性标记物,检测卵巢癌局部淋巴结内淋巴管生成情况。结果 VEGF-C主要表达于卵巢癌细胞浆和胞膜以及癌组织周围浸润的炎性细胞,在有淋巴结转移组的表达率明显高于其在无淋巴结转移组的表达率。Western blot检测结果表明,VEGF-C蛋白在有淋巴结转移的卵巢癌组织中的表达量高于其在无淋巴结转移的卵巢癌组织内的表达量。D2-40表达于卵巢癌局部淋巴结内的淋巴管内皮细胞,在有转移的淋巴结内可见大量新生的淋巴管,淋巴管腔内存在入侵的肿瘤细胞,在无转移的淋巴结内观察到新生的淋巴管。在无淋巴结转移组病例中,卵巢癌组织VEGF-C阳性者局部淋巴结内淋巴管密度明显高于VEGF-C阴性者淋巴结内的淋巴管密度。结论 VEGF-C的表达与卵巢癌淋巴结转移密切相关,卵巢癌在发生局部淋巴结转移之前存在淋巴结内淋巴管生成的现象,卵巢癌组织内VEGF-C的表达在卵巢癌局部淋巴结内的淋巴管生成中可能发挥重要作用。     

VEGF-C表达与胰腺癌淋巴结转移及预后的关系

目的 观察血管内皮生长因子(VEGF)-C在胰腺癌组织内的表达情况,分析VEGF-C的表达与胰腺癌淋巴结转移和预后之间的关系。方法 取胰腺癌病例52例,其中,伴淋巴结转移组36例,无淋巴结转移组16例。应用免疫组化法和Western blot技术观察VEGF-C在胰腺癌组织内的表达。以D2-40作为淋巴管内皮特异性标记物,观察胰腺癌组织内淋巴管生成的情况。采用Kaplan-Meier法绘制生存曲线判断VEGF-C的表达对胰腺癌预后的影响。结果 Western blot和免疫组化法检测结果表明,VEGF-C主要表达于胰腺癌细胞浆内,淋巴结转移组阳性表达量明显高于无淋巴结转移组(p<0.05)。D2-40表达于胰腺癌组织内淋巴管内皮细胞,VEGF-C阳性组淋巴管数密度明显高于VEGF-C阴性组(p<0.05),表明VEGF-C的表达与胰腺癌淋巴管生成密切相关。Kaplan-Meier生存分析表明VEGF-C表达阴性患者的生存率均高于VEGF-C表达阳性患者,VEGF-C的表达影响患者的预后。结论 VEGF-C在胰腺癌的淋巴管生成和淋巴结转移过程中发挥重要作用,VEGF-C的表达是影响胰腺癌患者预后的主要因素之一。     

Inhibition of VEGFR-3 activation in tumor-draining lymph nodes suppresses the outgrowth of lymph node metastases in the MT-450 syngeneic rat breast cancer model

For many types of human cancer, the expression of vascular endothelial growth factor-C (VEGF-C) correlates with enhanced tumor-associated lymphatic vessel density, metastasis formation and poor prognosis. In experimental animals, VEGF-C produced by primary tumors can induce lymphangiogenesis within and/or at the periphery of the tumor, and promotes metastasis formation. Tumor-induced lymphangiogenesis is therefore thought to expedite entry of tumor cells into the lymphatic vasculature and their trafficking to regional lymph nodes, thereby fostering metastatic dissemination. Tumour-produced VEGF-C can also drain to the regional lymph nodes and induce lymphangiogenesis there. Whether this activity promotes metastasis formation remains unclear. To address this issue we manipulated VEGF-C activity and VEGFR-3 activation in the lymph nodes draining syngeneic rat breast cancers using intra-dermal delivery of either recombinant VEGF-C or VEGFR-3 blocking antibodies to induce or suppress lymph node lymphangiogenesis, respectively. Recombinant VEGF-C induced lymph node lymphangiogenesis, but was not sufficient to promote metastasis formation by poorly metastatic NM-081 breast tumours. Conversely, inhibition of lymph node lymphangiogeneis induced by highly metastatic MT-450 breast tumours suppressed the outgrowth of lymph node metastases, but not the initial colonization of the lymph nodes. Lung metastasis was also not affected. We conclude that tumor-derived VEGF-C draining to regional lymph nodes promotes the outgrowth of lymph node metastases. VEGF-C may induce lung metastasis independently of its effects on lymph node metastasis.     

The use of LYVE-1 antibody for detecting lymphatic involvement in patients with malignant melanoma of known sentinel node status

BACKGROUND: Sentinel node (SN) status is the most important prognostic indicator in patients with cutaneous melanoma without clinically evident metastatic spread, but the procedure is associated with considerable morbidity. The LYVE-1 lymphatic marker offers the possibility of studying lymphangiogenesis and tumour metastasis within the primary excision. AIMS: To establish whether lymphatic vessel numbers/distribution within the primary tumour correlated with SN status. To assess whether tumour cells were easily demonstrable within lymphatics and could be used as a surrogate for SN status. METHODS: Double immunostaining for LYVE-1 and S100 in cutaneous biopsies from 18 SN+ patients with no lymphatic/vascular involvement on routine histology and 18 SN- patients matched for tumour thickness and ulceration.RESULTS: Lymphatic vessels were detected in all cases. Vessels within the tumour mass were suggestive of active lymphangiogenesis; those outside were mainly mature vessels with well defined walls. Tumour cells within lymphatics were detected in one of 18 SN- and five of 18 SN+ patients. Lymphatics containing tumour cells were all outside the tumour mass in well formed vessels, suggesting melanoma cell invasion into preformed lymphatics. There was no significant difference in lymphatic counts between SN+ and SN- patients. Although peritumorous lymphatic counts were higher in ulcerated than non-ulcerated melanomas, they did not vary with Breslow thickness. CONCLUSION: LYVE-1 staining can reliably demonstrate lymphatic vessel distribution, but lymphatic counts cannot predict melanoma metastatic potential and cannot substitute for SN biopsy. LYVE-1 immunostaining can detect melanoma cells within lymphatics, but is unreliable in predicting melanoma metastasis, failing to detect metastatic spread in more than two thirds of patients with regional node metastasis.     

Lymphangiogenesis and lymphatic metastasis in breast cancer

Lymphatic metastasis is the main prognostic factor for survival of patients with breast cancer and other epithelial malignancies. Mounting clinical and experimental data suggest that migration of tumor cells into the lymph nodes is greatly facilitated by lymphangiogenesis, a process that generates new lymphatic vessels from pre-existing lymphatics with the aid of circulating lymphatic endothelial progenitor cells. The key protein that induces lymphangiogenesis is vascular endothelial growth factor receptor-3 (VEGFR-3), which is activated by vascular endothelial growth factor-C and -D (VEGF-C and VEGF-D). These lymphangiogenic factors are commonly expressed in malignant, tumor-infiltrating and stromal cells, creating a favorable environment for generation of new lymphatic vessels. Clinical evidence demonstrates that increased lymphatic vessel density in and around tumors is associated with lymphatic metastasis and reduced patient survival. Recent evidence shows that breast cancers induce remodeling of the local lymphatic vessels and the regional lymphatic network in the sentinel and distal lymph nodes. These changes include an increase in number and diameter of tumor-draining lymphatic vessels. Consequently, lymph flow away from the tumor is increased, which significantly increases tumor cell metastasis to draining lymph nodes and may contribute to systemic spread. Collectively, recent advances in the biology of tumor-induced lymphangiogenesis suggest that chemical inhibitors of this process may be an attractive target for inhibiting tumor metastasis and cancer-related death. Nevertheless, this is a relatively new field of study and much remains to be established before the concept of tumor-induced lymphangiogenesis is accepted as a viable anti-metastatic target. This review summarizes the current concepts related to breast cancer lymphangiogenesis and lymphatic metastasis while highlighting controversies and unanswered questions.     

Intratumoral Lymphatics and Lymphatic Vessel Invasion Detected by D2‐40 Are Essential for Lymph Node Metastasis in Bladder Transitional Cell Carcinoma

Bladder cancer is frequently associated with regional lymph node metastasis at the time of diagnosis or after initial treatment, and lymph node metastasis is crucial for clinical therapeutic strategies. Lymphangiogenesis, detected by antibodies specific for lymphatic endothelial cells, is correlated with cancer spread, but the mechanisms that underlie lymphatic spread and the role of lymphangiogenesis in cancer metastasis has been less clear. The aim of this study was to investigate the association of vascular endothelial growth factor (VEGF)‐D expression, intratumoral lymphatics, and lymphatic invasion associated with lymph node metastasis as well as the prognostic analysis in patients with bladder transitional cell carcinoma (TCC). The VEGF‐D expression was evaluated by immunohistochemistry in 72 specimens, and tumoral lymphatic vessels were measured by D2‐40. Counts of lymph vessels were taken in intratumoral and peritumoral areas. Survival analyses and their independent roles were investigated using univariate and multivariate analysis models. The high expression of VEGF‐D was closely associated with the intratumoral lymphatic vessels, tumoral lymphatic invasion, and lymph node metastasis as well as a shorter overall survival. Higher lymphatic vessel density, intratumoral lymphatics, and lymphatic invasion showed a significant association with lymph node metastasis. Univariate analysis indicated that VEGF‐D, intratumoral lymphatics, and lymphatic invasion were associated with overall survival, but they were not independent prognostic factors for bladder TCC in multivariate analysis. We conclude that VEGF‐D plays an essential role in tumoral lymphangiogenesis. Intratumoral lymphatics and lymphatic invasion are important predictive factors of pelvic lymph node metastasis in patients with bladder cancer. Anat Rec, 2010. © 2010 Wiley‐Liss, Inc.     

Lymphatic spread is related to VEGF-C expression and D2-40-positive myofibroblasts in intrahepatic cholangiocarcinoma.

Lymph node metastasis via lymphatic vessels is related with an adverse outcome in many tumors. It is unclear whether lymphatic spread needs the development of the new lymphatic vessels or the expression of lymphangiogenetic factor in intrahepatic cholangiocarcinoma. The aim of this study was to assess the role of lymphangiogenesis, vascular endothelial growth factor-C (VEGF-C) expression, and D2-40-positive myofibroblastic cells for lymphatic spread and patient outcome in 88 cases of intrahepatic cholangiocarcinoma. We also assessed VEGF-C expression in 15 cases of metastatic lymph nodes. There was a significant correlation between lower lymphatic vessel density in the tumor center and positive lymphatic invasion (P=0.0100). Poorly differentiated cholangiocarcinoma showed higher lymphatic vessel density in the tumor periphery and in the peritumoral area (P=0.0315 and P=0.0360, respectively). Lymphatic invasion was observed higher in the peritumoral area (63%, 24/38) and in the tumor periphery (79%, 30/38) than in the tumor center (27%, 9/38). There was no significant correlation between the proliferative lymphatic vessels and pathologic features; however, lymphatic invasion was significantly associated with VEGF-C expression (P=0.0006), and the VEGF-C expression was seen in 12 of 15 cases (80%) of metastatic lymph node. Nodal metastasis was correlated with D2-40-positive myofibroblasts (P=0.0161). VEGF-C expression was an independent prognostic factor by multivariate survival analysis (P=0.0131). Our findings suggest that VEGF-C has an important role in lymphatic invasion via the preexisting lymphatic vessels in the tumor margin, and that lymphangiogenesis does not play a direct role in lymphatic metastasis. D2-40-positive myofibroblasts may contribute to lymphatic metastasis.     

Tumor-induced sentinel lymph node lymphangiogenesis and increased lymph flow precede melanoma metastasis

Lymphangiogenesis is associated with human and murine cancer metastasis, suggesting that lymphatic vessels are important for tumor dissemination. Lymphatic vessel alterations were examined using B16-F10 melanoma cells implanted in syngeneic C57Bl/6 mice, which form tumors metastasizing to draining lymph nodes and subsequently to the lungs. Footpad tumors showed no lymphatic or blood vessel growth; however, the tumor-draining popliteal lymph node featured greatly increased lymphatic sinuses. Lymph node lymphangiogenesis began before melanoma cells reached draining lymph nodes, indicating that primary tumors induce these alterations at a distance. Lymph flow imaging revealed that nanoparticle transit was greatly increased through tumor-draining relative to nondraining lymph nodes. Lymph node lymphatic sinuses and lymph flow were increased in mice implanted with unmarked or with foreign antigen-expressing melanomas, indicating that these effects are not due to foreign antigen expression. However, tumor-derived immune signaling could promote lymph node alterations, as macrophages infiltrated footpad tumors, whereas lymphocytes accumulated in tumor-draining lymph nodes. B lymphocytes are required for lymphangiogenesis and increased lymph flow through tumor-draining lymph nodes, as these alterations were not observed in mice deficient for B cells. Lymph node lymphangiogenesis and increased lymph flow through tumor-draining lymph nodes may actively promote metastasis via the lymphatics.     

Smad4的表达与卵巢癌淋巴管生成及淋巴结转移之间的关系

目的观察Smad4和血管内皮生长因子(VEGF)-C在卵巢癌组织内的表达情况,分析Smad4和VEGF-C的表达与卵巢癌淋巴管生成及淋巴结转移之间的关系。方法取卵巢癌病例60例,其中,淋巴结转移组36例,无淋巴结转移组24例。应用免疫组化法和Westernblot技术观察Smad4和VEGF-C在卵巢癌组织内的表达。以D2-40作为淋巴管内皮特异性标记物,检测卵巢癌组织内淋巴管生成情况。结果 Smad4表达于卵巢癌细胞胞浆和胞核内,其在无淋巴结转移组的表达率明显高于其在有淋巴结转移组的表达率。Smad4表达阳性组的淋巴管数密度(LVD)明显低于Smad4表达阴性组的LVD。VEGF-C主要表达于卵巢癌细胞胞浆内,其在淋巴结转移组的表达率明显高于其在无淋巴结转移组的表达率。Smad4的表达与VEGF-C的表达呈显著的负相关性。Western blot检测结果表明,VEGF-C蛋白在有淋巴结转移卵巢癌组织中的表达量高于其在无淋巴结转移卵巢癌组织内的表达量,而Smad4在有淋巴结转移卵巢癌组织内的表达量明显低于其在无淋巴结转移组的表达量。结论 Smad4与VEGF-C的表达呈负相关,Smad4可能通过调节VEGF-C蛋白的表达而抑制卵巢癌淋巴管生成和淋巴道转移。     

Photodynamic ablation of lymphatic vessels and intralymphatic cancer cells prevents metastasis

The dissemination of tumor cells to sites far from the primary tumor (metastasis) is the principal cause of death in cancer patients. Tumor-associated lymphatic vessels are a key conduit for metastatic tumor cells, which typically first colonize the lymph nodes. Although the primary tumor and affected lymph nodes can be removed during surgery, tumor cells inside lymphatic vessels are left behind. Here, we show that in-transit tumor cells inside lymphatic vessels in mice bearing mouse melanomas or human lung tumors give rise to metastases. Using photodynamic therapy with the benzoporphyrin derivative verteporfin, we selectively destroyed lymphatic vessels in mice and pigs. Destruction of tumor-associated lymphatic vessels also eradicated intralymphatic tumor cells and prevented metastasis of mouse melanoma cells and subsequent relapse. Photodynamic therapy, when combined with anti-lymphangiogenic therapy, prevented further tumor invasion of lymphatic vessels. These findings highlight the potential of targeting in-transit tumor cells in patients.     

The role of VEGF-C staining in predicting regional metastasis in melanoma

Sentinel lymph node status is the most important prognostic factor in primary melanoma. The number of melanoma-associated lymphatic vessels has been associated with sentinel lymph node status and survival. Vascular endothelial growth factor-C (VEGF-C) is found to promote tumour-associated lymphatic vessel growth. In many human neoplasms, VEGF-C expression in neoplastic cells or tumour-associated macrophages (TAMs) has been linked to lymphatic dissemination of tumour cells. Recent studies have suggested a correlation between VEGF-C expression in primary melanoma and the presence of lymph node metastasis. We performed VEGF-C immunohistochemical staining on melanoma tissues of 113 patients with known sentinel lymph node status. We showed that both high VEGF-C expression in melanoma cells and TAMs are positively associated with the presence of a positive sentinel lymph node. No correlation with Breslow thickness, Clark invasion level or ulceration could be detected. VEGF-C expression in melanoma cells was predictive of a shorter overall and disease-free survival, without being an independent predictor of survival. Our results confirm that VEGF-C expression in primary cutaneous melanoma plays a role in the lymphatic spread of the tumour.     

Signaling for lymphangiogenesis via VEGFR-3 is required for the early events of metastasis

Metastasis to regional lymph nodes is an important and early event in many tumors. Vascular endothelial growth factor-C (VEGF-C), VEGF-D and their receptor VEGFR-3, play a role in tumor spread via the lymphatics, although the timing of their involvement is not understood. In contrast, VEGFR-2, activated by VEGF-A, VEGF-C and VEGF-D, is a mediator of angiogenesis and drives primary tumor growth. We demonstrate the critical role for VEGFR-3, but not VEGFR-2, in the early events of metastasis. In a tumor model exhibiting both VEGF-D-dependent angiogenesis and lymphangiogenesis, an antibody to VEGFR-2 (DC101) was capable of inhibiting angiogenesis (79 % reduction in PECAM + blood vessels) and growth (93 % reduction in tumor volume). However, unlike an anti-VEGFR-3 Mab (mF4-31C1), DC101 was not capable of eliminating either tumor lymphangiogenesis or lymphogenous metastasis (60 % reduction of lymph node metastasis by DC101 vs 95 % by mF4-31C1). Early excision of the primary tumors demonstrated that VEGF-D-mediated tumor spread precedes angiogenesis-induced growth. Small but highly metastatic primary human breast cancers had significantly higher lymphatic vessel density (23.1 vessels/mm²) than size-matched (11.7) or larger non-metastatic tumors (12.4) thus supporting the importance of lymphatic vessels, as opposed to angiogenesis-mediated primary tumor growth, for nodal metastasis. These results suggest that lymphangiogenesis via VEGF-D is more critical than angiogenesis for nodal metastasis.     

The extent of retraction clefts correlates with lymphatic vessel density and VEGF-C expression and predicts nodal metastasis and poor prognosis in early-stage breast carcinoma

Although the earliest feature of disseminated disease in breast cancer is regional lymph node involvement, little is known about the mechanisms whereby cancer cells interact with lymphatic endothelial cells and enter the lymphatic system. We have previously reported that the extensive presence of retraction clefts in breast carcinomas highly significantly correlates with lymphatic tumor spread and predicts poor outcome, suggesting that retraction clefts are not just fixation artifacts, but real potential spaces that are exaggerated by tissue processing and may reflect an early stage of lymphatic invasion. In this study, we examined the correlation between the extent of retraction clefts and lymphangiogenesis, as assessed by lymphatic vessel density and vascular endothelial growth factor-C (VEGF-C) expression in a series of 256 early-stage breast carcinomas. The presence and extent of retraction clefts around tumor cell nests was determined by review of all hematoxylin- and eosin-stained tumor sections. Lymphatic vessels were detected by podoplanin immunohistochemistry and lymphatic vessel density was measured using the hot-spot method. The expression of VEGF-C in the tumor cells was determined by immunohistochemistry and analyzed semiquantitatively on a four-tiered scale. High levels of retraction clefts, peritumor lymphatic vessel density and VEGF-C expression at the invasive edge in breast carcinomas significantly correlated with tumor size, histological grade, lymphatic invasion and nodal metastasis. Breast carcinomas showing extensive retraction clefts (>20% of tumor volume) were found to have significantly higher lymphatic vessel density and VEGF-C expression levels compared to tumors without this feature. High retraction clefts, peritumor lymphatic vessel density and VEGF-C expression predicted poor outcome in breast carcinomas. Our results support the hypothesis that retraction clefts are real potential spaces that may represent 'pre-lymphatic spaces' facilitating initial lymphatic invasion and that growth factors secreted by the tumor cells may stimulate tumor-associated lymphangiogenesis by promoting the endothelialization of these 'pre-lymphatic channels'.     

Angiogenic and lymphangiogenic microvessel density in breast carcinoma: correlation with clinicopathologic parameters and VEGF-family gene expression.

Angiogenesis and lymphangiogenesis are essential for breast cancer progression and are regulated by vascular endothelial growth factors (VEGF). To determine clinical and molecular correlates of these processes, we measured blood and lymphatic vascular microvessel density in 29 invasive carcinomas (22 ductal, six lobular, one papillary), using the vascular marker CD31 and the novel lymphatic marker D2-40. Microvessel density was assessed microscopically and by image cytometry, and was compared with tumor histology, grade, stage, lymph node metastasis, hormone receptors, HER2/neu status, and expression of VEGF, VEGF-C and VEGF-D by immunohistochemistry or quantitative RT-PCR. Strong correlation was observed between visual and image cytometric microvessel density using D2-40 but not CD31 (P=0.016 and 0.1521, respectively). Image cytometric CD31 microvessel density correlated with tumor size, grade, stage and lymph node metastasis (P=0.0001, 0.0107, 0.0035 and 0.0395, respectively). D2-40 microvessel density correlated with tumor stage (P=0.0123 by image cytometry) and lymph node metastasis (P=0.0558 by microscopy). Immunohistochemical VEGF signal in peritumoral blood vessels correlated with image cytometric CD31 and D2-40 microvessel density (P=0.022 and 0.0012, respectively), consistent with the role of VEGF in blood and lymphatic vascular growth. Intratumoral VEGF-C and VEGF-D expression by quantitative RT-PCR correlated with D2-40 (P=0.0291 by image cytometry) but not with CD31 microvessel density, which could suggest a selective role of VEGF-C and VEGF-D in lymphangiogenesis. CD31 and D2-40 microvessel density correlated significantly with several prognostic factors, including lymph node metastasis. Thus, measurements of angiogenesis and lymphangiogenesis may have utility for breast cancer pathology, particularly for estimation of metastatic risk.