The VAD Scheme versus Thalidomide plus VAD for Reduction of Vascular Endothelial Growth Factor in Multiple Myeloma: A Meta-Analysis

Thalidomide Reduces Vascular Endothelial Growth Factor Immunostaining in Canine Splenic Hemangiosarcoma

Hemangiosarcomas (HSA) are common neoplasms of dogs that often metastasize and are typically fatal. Recently it was demonstrated that thalidomide extends the survival time of dogs with HSA, potentially due to thalidomide-induced inhibition of vascular endothelial growth factor (VEGF) production by the neoplastic cells. To investigate this, immunostaining was used to evaluate VEGF within HSA metastases that developed after thalidomide treatment. The immunostaining was then compared to VEGF immunostaining in primary tumors from the same dogs prior to treatment with thalidomide and in metastatic tumors from untreated dogs with splenic HSA. Immunostaining was scored from 1 to 4 for each sample. Immunostaining in the metastatic lesions that had been treated with thalidomide had a mean immunostaining score of 1.4 which was significantly lower than the mean score in the corresponding primary splenic HSA (3.8, p = 0.02) and in metastases from untreated dogs (3.5, p = 0.02). This supports the hypothesis that thalidomide prolongs survival time in dogs with HSA due to inhibition of VEGF production by the neoplastic cells. As VEGF remained visible within HSAs exposed to thalidomide, additional treatments to inhibit VEGF production may further prolong survival times of dogs with these common canine neoplasms.

Tumor vasculature remolding by thalidomide increases delivery and efficacy of cisplatin

Background

A promising strategy to overcome the chemoresistance is the tumor blood vessel normalization, which restores the physiological perfusion and oxygenation of tumor vasculature. Thalidomide (Thal) has been shown to increase the anti-tumor effect of chemotherapy agents in solid tumors. However, it is not yet known whether the synergistic effect of Thal combined with other cytotoxic drugs is attributable to tumor vascular normalization.

Methods

We used two homograft mice models (4 T1 breast tumor model and CT26 colorectal tumor model) to investigate the effect of Thal on tumor growth, microvessel density, vascular physiology, vascular maturity and function, drug delivery and chemosensitivity. Immunofluorescence, immunohistochemistry and scanning electron microscopy were performed to determine the vessel changes. Protein array assay, qPCR and western blotting were used to detect the molecular mechanism by which Thal regulates tumor vascular.

Results

Here we report that Thal potently suppressed tumor growth, angiogenesis, hypoxia, and vascular permeability in animal models. Thal also induced a regular monolayer of endothelial cells in tumor vessels, inhibiting vascular instability, and normalized tumor vessels by increasing vascular maturity, pericyte coverage and endothelial junctions. The tumor vessel stabilization effect of Thal resulted in a decrease in tumor vessel tortuosity and leakage, and increased vessel thickness and tumor perfusion. Eventually, the delivery of cisplatin was highly enhanced through the normalized tumor vasculature, thus resulting in profound anti-tumor and anti-metastatic effects. Mechanistically, the effects of Thal on tumor vessels were caused in part by its capability to correct the imbalance between pro-angiogenic factors and anti-angiogenic factors.

Conclusions

Our findings provide direct evidence that Thal remodels the abnormal tumor vessel system into a normalized vasculature. Our results may lay solid foundation for the development of Thal as a novel candidate agent to maximize the therapeutic efficacy of chemotherapeutic drugs for solid tumors.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1366-x) contains supplementary material, which is available to authorized users.