Anti-angiogenesis: making the tumor vulnerable to the immune system

Ongoing angiogenesis has been shown to possess immune suppressive activity through several mechanisms. One of these mechanisms is the suppression of adhesion receptors, such as intercellular adhesion molecule-1, vascular cell adhesion molecule-1 and E-selectin—adhesion molecules involved in leukocyte interactions—on the vascular endothelium. This phenomenon, when happening to the tumor endothelium, supports tumor growth due to escape from immunity. Since angiogenesis has this immune suppressive effect, it has been hypothesized that inhibition of angiogenesis may circumvent this problem. In vitro and in vivo data now show that several angiogenesis inhibitors are able to normalize endothelial adhesion molecule expression in tumor blood vessels, restore leukocyte vessel wall interactions, and enhance the inflammatory infiltrate in tumors. It is suggested that such angiogenesis inhibitors can make tumors more vulnerable for the immune system and may therefore be applied to facilitate immunotherapy approaches for the treatment of cancer

Histamine, a vasoactive agent with vascular disrupting potential, improves tumour response by enhancing local drug delivery

Tumour necrosis factor (TNF)-based isolated limb perfusion (ILP) is an approved and registered treatment for sarcomas confined to the limbs in Europe since 1998, with limb salvage indexes of 76%. TNF improves drug distribution in solid tumours and secondarily destroys the tumour-associated vasculature (TAV). Here we explore the synergistic antitumour effect of another vasoactive agent, histamine (Hi), in doxorubicin (DXR)-based ILP and evaluate its antivascular effects on TAV. We used our well-established rat ILP model for in vivo studies looking at tumour response, drug distribution and effects on tumour vessels. In vitro studies explored drug interactions at cellular level on tumour cells (BN-175) and Human umbilical vein endothelial cells (HUVEC). There was a 17% partial response and a 50% arrest in tumour growth when Hi was combined to DXR, without important side effects, against 100% progressive disease with DXR alone and 29% arrest in tumour growth for Hi alone. Histology documented an increased DXR leakage in tumour tissue combined to a destruction of the TAV, when Hi was added to the ILP. In vitro no synergy between the drugs was observed. In conclusion, Hi is a vasoactive drug, targeting primarily the TAV and synergises with different chemotherapeutic agents

Degree of tumour vascularity correlates with drug accumulation and tumour response upon TNF-α-based isolated hepatic perfusion

Isolated hepatic perfusion (IHP) with melphalan with or without tumour necrosis factor alpha (TNF-α) is currently performed in clinical trials in patients with hepatic metastases. Previous studies led to the hypothesis that the use of TNF-α in isolated limb perfusion causes specific destruction of tumour endothelial cells and thereby induces an increased permeability of tumour vasculature. However, whether TNF-α contributes to the therapeutic efficacy in IHP still remains unclear. In an in vivo rat liver metastas

Progressive loss of endothelial P-selectin expression with increasing malignancy in colorectal cancer.

Contains fulltext : 47950.pdf (publisher's version ) (Closed access)Adhesion of inflammatory cells to vascular endothelium is mediated by specific cell adhesion receptors on both leukocytes and endothelial cells. One of the adhesion molecules on the endothelium is P-selectin. Decreased vascular P-selectin expression has been associated with tumor progression in melanoma patients. We now report on the expression of endothelial P-selectin in colorectal cancer (CRC). We studied a colorectal tissue specimen series ranging from normal colorectal tissue via unmetastasized primary tumors to tumors with the same depth of invasion at the primary site but with liver metastases. Moreover, P-selectin expression levels in liver metastases were determined. The number of P-selectin positive vessels as a fraction of the total number of vessels, both intra- and peritumorally, was determined by staining for CD62P and CD34, respectively. Furthermore, by immunostaining for leukocytes (CD45) and macrophages (CD68), it was evaluated whether levels of P-selectin expression influenced infiltrate density and composition. The results showed that levels of peritumoral P-selectin expression were reciprocal to the degree of progression in CRC. This relation was even more pronounced intratumorally: in metastasized primary tumors and in the metastatic lesions, P-selectin expression was virtually absent. This distribution pattern was reflected in the numbers of leukocytes that accumulated in the various tissues, since in the primary tumors with metastases, and in the metastatic lesions, hardly any infiltrating cells were observed. In these lesions, leukocytes were present in the peritumoral zone, but seemed unable to enter the tumor tissue. In primary tumors without metastasis, the intratumoral leukocyte infiltration density was significantly higher. Recruitment levels of macrophages remained constant throughout the different tissues. We suggest that downregulation of endothelial P-selectin expression is a mechanism by which CRC lesions evade inflammatory regression and, thereby, progress to a more advanced stage of malignancy