Angiostatin and Endostatin: Angiogenesis Inhibitors in Blood and Stroma

Understanding the role of endothelial cells in brain tumor formation and metastasis: a proposition to be explored for better therapy

Glioblastoma is one of the most devastating central nervous system disorders. Being a highly vascular brain tumor, it is distinguished by aberrant vessel architecture. This lends credence to the idea that endothelial cells (ECs) linked with glioblastoma vary fundamentally from ECs seen in the healthy human brain. To effectively design an antiangiogenic treatment, it is crucial to identify the functional and phenotypic characteristics of tumor-associated ECs. The ECs associated with glioblastoma are less prone to apoptosis than control cells and are resistant to cytotoxic treatments. Additionally, ECs associated with glioblastoma migrate more quickly than control ECs and naturally produce large amounts of growth factors such as endothelin-1, interleukin-8, and vascular endothelial growth factor (VEGF). For designing innovative antiangiogenic drugs that particularly target tumor-related ECs in gliomas, it is critical to comprehend these distinctive features of ECs associated with gliomas. This review discusses the process of angiogenesis, other factors involved in the genesis of tumors, and the possibility of ECs as a potential target in combating glioblastoma. It also sheds light on the association of tumor microenvironment and ECs with immunotherapy. This review, thus gives us the hope that neuro endothelial targeting with growth factors and angiogenesis regulators combined with gene therapy would open up new doorways and change our traditional perspective of treating cancer.

Novel combination of 2-methoxyestradiol and cyclophosphamide enhances the antineoplastic and pro-apoptotic effects on S-180 ascitic tumour cells

Sarcoma 180 (S-180) tumour cell line is a stable murine tumour cell line with 98-99% stumour takes capacity in Swiss albino mouse - Mus musculus. 2 Methoxyestradiol (2ME) - a promising anti-neoplastic and anti-angiogenic agent, showed toxicity to host body in higher concentration. Cyclophosphamide (CP), the anti-neoplastic agent has long been used as a chemotherapeutic drug for treatment of different cancers. Our studies have shown that the combination effect of 2ME and CP on S-180 tumour cell line is anti-proliferative and less toxic. The treatment with lower concentrations of 2ME and CP (6.5 mg 2ME/kg body weight + 75 mg CP/kg body weight) antagonistically increased the life span of tumour bearing mice and synergistically inhibited the viable cell population. 2ME or CP treatment individually induces G2/M arrest. The combination treatment of 2ME + CP (6.5 mg 2ME/kg body weight + 75 mg CP/kg body weight) produced a significant increase of cells in the G0 which is the indication of cell arrest or apoptosis. Reduction of cell viability by 2ME + CP treatments is due to apoptotic cell death. This combination therapy produced a significant inhibitory effect of cell proliferation and augmentation of cell accumulation in the G0 phase (i.e. apoptosis). Apoptosis is validated by Fluorescence staining of control and treated S-180 tumour cells with Acridine Orange and EtBr dye. Moreover, a steady increase in the frequency of complex chromosomal aberrations (i.e. tri-, qudri-radial translocations) in tumour cells was noted in that particular concentration of combination therapy treated series along with the increase in dead cell frequency and tumour regression pattern. It is assumed that, these chromosomal abnormalities or damages recorded in higher frequency prevent the affected metaphases to enter into the next cell cycle through apoptosis or necrosis. This study introduces a novel combination, where this particular concentration of 2ME + CP (i.e. 6.5 mg 2ME/kg body weight + 75 mg CP/kg body weight) not only enhanced the life span of tumour bearing mouse and decreased the tumour volume antagonistically but also inhibited the viable cell population synergistically, which could serve as a potential effective regimen for cancer treatment.

Temporal and pharmacological characterization of angiostatin release and generation by human platelets: implications for endothelial cell migration

Platelets play an important role in thrombosis and in neo-vascularisation as they release and produce factors that both promote and suppress angiogenesis. Amongst these factors is the angiogenesis inhibitor angiostatin, which is released during thrombus formation. The impact of anti-thrombotic agents and the kinetics of platelet angiostatin release are unknown. Hence, our objectives were to characterize platelet angiostatin release temporally and pharmacologically and to determine how angiostatin release influences endothelial cell migration, an early stage of angiogenesis. We hypothesized anti-platelet agents would suppress angiostatin release but not generation by platelets. Human platelets were aggregated and temporal angiostatin release was compared to vascular endothelial growth factor (VEGF). Immuno-gold electron microscopy and immunofluorescence microscopy identified α-granules as storage organelles of platelet angiostatin. Acetylsalicylic acid, MRS2395, GPIIb/IIIa blocking peptide, and aprotinin were used to characterize platelet angiostatin release and generation. An endothelial cell migration assay was performed under hypoxic conditions to determine the effects of pharmacological platelet and angiostatin inhibition. Compared to VEGF, angiostatin generation and release from α-granules occurred later temporally during platelet aggregation. Consequently, collagen-activated platelet releasates stimulated endothelial cell migration more potently than maximally-aggregated platelets. Platelet inhibitors prostacyclin, S-nitroso-glutathione, acetylsalicylic acid, and GPIIb/IIIa blocking peptide, but not a P2Y12 inhibitor, suppressed angiostatin release but not generation. Suppression of angiostatin generation in the presence of acetylsalicylic acid enhanced platelet-stimulated endothelial migration. Hence, the temporal and pharmacological modulation of platelet angiostatin release may have significant consequences for neo-vascularization following thrombus formation.