Expression and localization of VEGF-C and VEGFR-3 in glioblastomas and haemangioblastomas

Abstract

Primary human brain tumours account for approximately 2% of all cancers. High levels of expression of vascular endothelial growth factor-A (VEGF-A), a potent angiogenic factor, are linked to poor prognosis. In contrast, the potential role in human brain tumour biology of newer VEGF family members, VEGF-C and VEGF-D, both of which are lymphangiogenic factors, is poorly understood. In the present study, the expression of all VEGFs (VEGF-A, -B, -C, and -D) and their receptors (VEGFR-1, -2, and -3) has been assessed in 39 primary human brain tumours. The well-established findings were confirmed with VEGF-A. Surprisingly, however, VEGF-C and VEGF-D, as well as VEGFR-3, were expressed in some tumour types such as haemangioblastomas and glioblastomas, despite their lack of lymphatic vessels. VEGF-C and VEGFR-3 transcripts were localized to the tumour palisade around necrotic areas in glioblastomas and were evenly distributed throughout haemangioblastomas. VEGF-C protein was localized by immunohistochemistry to the palisade layer in glioblastomas. More than 50% of VEGF-C-positive cells also expressed the intermediate-stage inflammatory macrophage marker CD163; however, a significant proportion of VEGF-C-positive cells were CD163-negative. These data demonstrate the presence of molecules, primarily described as regulators of lymphangiogenesis, in normal human brain and brain tumours that are devoid of lymphatics. Their localization in macrophages points to a role in tumour-associated inflammation.

Vascular Endothelial Growth Factor-C and C-C Chemokine Receptor 7 in Tumor Cell–Lymphatic Cross-talk Promote Invasive Phenotype

“…For example, Hoshida and colleagues (15) showed, using intravital microscopy, that VEGF-C increases invasion of tumor cells into draining lymphatic vessels. Furthermore, several recent studies have shown that both VEGFR-3 and VEGF-C are expressed by metastatic tumor cells (16)(17)(18)(19)(20)(21), suggesting autocrine stimulation mechanisms that may include tumor cell proliferation (19,22) and invasiveness (21,23,24) of tumor cells, directly or indirectly by increasing flow into hyperplastic peritumoral lymphatics (11,15). These findings suggest that VEGF-C may act in multiple ways to promote lymphatic invasion.…”

“…We next examined whether VEGF-C had autocrine effects on the tumor cells because others have reported correlations between tumor VEGFR-3 and metastasis (17,18,20,23,40), although expression of VEGFR-3 in some tumor cell lines has been debated. We saw no expression in any cell line when cultured in two-dimensional conditions.…”

“…Activation of lymphatic VEGFR-3 is required for lymphangiogenesis (1,4,48), and although tumor-secreted VEGF-C is correlated with incidence of lymph node metastasis (3,7,8,49), the requirement of lymphangiogenesis for lymphatic escape of tumors has not been directly shown (11,14). Recently, it has become evident that many tumors may also express VEGFR-3 (11,(15)(16)(17)(18)(19)(20)(21)(22)(23)(24), suggesting the presence of an autocrine mechanism that might promote invasion. Furthermore, the most widely correlated factor with lymph node metastasis in human tumors has been CCR7 (28-33), a receptor required for lymphatic homing of dendritic cells (25)(26)(27).…”

Role of Lymphatic Vessels in Tumor Immunity: Passive Conduits or Active Participants?

“…VEGF-C can also attract macrophages [124] that can alter the tumor microenvironment to promote invasion. Furthermore, some tumor cells also express VEGFR-3 and thus may benefit from autocrine signaling of VEGF-C or -D [121,[125][126][127][128][129]. Such autocrine signaling could help tumor cells home to lymphatics by guiding them in the direction of flow [42].…”

Recurrence of Intracranial Tumors following Adoptive T Cell Therapy Can Be Prevented by Direct and Indirect Killing Aided by High Levels of Tumor Antigen Cross-Presented on Stromal Cells

“…For example, gliomas do not induce lymphangiogenesis (48), and microglia associated with gliomas are particularly active at secreting TGF-␤ that contributes to invasiveness (49). Gliomas are also comprised of different stromal elements than peripheral tumors.…”