Abstract:Despite major improvements in the surgical management the prognosis for patients bearing malignant gliomas is still dismal. Malignant gliomas are notoriously resistant to treatment and the survival time of patients is between 3-8 years for low-grade and anaplastic gliomas and 6 -12 month for glioblastoma. Increasing malignancy of gliomas correlates with an increase in cellularity and a poorly organized tumour vasculature leading to insufficient blood supply, hypoxic areas and ultimately to the formation of necrosis, a characteristic of glioblastoma. Hypoxic/necrotic tumours are more resistant to chemotherapy and radiation. Hypoxia induces either directly or indirectly (through the activation of transcription factors) changes in the biology of a tumour and its microenvironment leading to increased aggressiveness and tumour resistance to chemotherapy and radiation. This review is focused on hypoxia-induced molecular changes affecting glioma biology and therapy.3

Background:Glioblastoma (GBM), being a highly vascularised and locally invasive tumour, is an attractive target for anti-angiogenic and anti-invasive therapies. The GBM/endothelial cell response to gossypol/temozolomide (TMZ) treatment was investigated with a particular aim to assess treatment effects on cancer hallmarks.Methods:Cell viability, endothelial tube formation and GBM tumour cell invasion were variously assessed following combined treatment in vitro. The U87MG-luc2 subcutaneous xenograft model was used to investigate therapeutic response in vivo. Viable tumour response to treatment was interrogated using immunohistochemistry. Combined treatment protocols were also tested in primary GBM patient-derived cultures.Results:An endothelial/GBM cell viability inhibitory effect, as well as an anti-angiogenic and anti-invasive response, to combined treatment have been demonstrated in vitro. A significantly greater anti-proliferative (P=0.020, P=0.030), anti-angiogenic (P=0.040, P<0.0001) and pro-apoptotic (P=0.0083, P=0.0149) response was observed when combined treatment was compared with single gossypol/TMZ treatment response, respectively. GBM cell line and patient-specific response to gossypol/TMZ treatment was observed.Conclusions:Our results indicate that response to a combined gossypol/TMZ treatment is related to inhibition of tumour-associated angiogenesis, invasion and proliferation and warrants further investigation as a novel targeted GBM treatment strategy.

The tricyclic antidepressants have previously been shown to exert activity against glioma cells in vitro. Initial studies in cell lines suggested that this might extend to melanoma cells. We have therefore conducted a study in primary cell cultures from metastatic cutaneous melanoma deposits using a well established ATP-based tumour chemosensitivity assay to confirm and extend these findings. Two cell lines and eight primary cell cultures from metastatic melanoma deposits were exposed to three tricyclic drugs, amitriptyline, nortriptyline and clomipramine, at concentrations ranging from 200 to 6.25 µmol/l in the ATP-based tumour chemosensitivity assay. All three drugs showed activity, although nortriptyline was more active than clomipramine or amitriptyline in both cell lines and primary cell cultures, with an IC50 of 9, 27 and 33 µmol/l, respectively. Tricyclic agents show activity against melanoma in vitro. This could be related to the lysosomal effects based on their cationic amphiphilic properties, or effects at the mitochondrial membrane.

The main problem in the treatment of malignant astrocytomas is their invasive behaviour. Successful resection of the main tumour mass cannot prevent recurrence due to single cells invading the surrounding brain parenchyma at the time of diagnosis. The classical combination therapy, PCV (Procarbazine, CCNU and Vincristine) used for over 30 years; has shown its clinical effectiveness in the treatment of malignant astrocytomas and glioblastomas is still doubtful. Using an in vitro three dimensional invasion model, we tested the effect of the tyrosine kinase inhibitor imatinib and the microtubule inhibitor docetaxel on the invasion activity of a panel of astrocytic tumour cell lines, including two established glioma cell lines, IPSB-18 and SNB-19, and two primary cell lines, originating from glioblastomas, CLOM002 and UPHHJA, and in normal astrocytes. A dose response curve for each drug alone and in combination was determined. The half maximal inhibitory concentration (IC(50)) concentration of imatinib was between 15.7 and 18.7 μM, which did not affect invasion activity of the cell lines. The IC(50) concentration of docetaxel was between 0.7 and 19.8 nM, and at 14.9 nM docetaxel had a slight transient inhibitory effect on invasion activity of all tested cells. The combination of imatinib at 13.5 μM and docetaxel at 14.9 nM, however, synergistically inhibited cell growth and invasion activity and could not be reversed by drug removal. A combination treatment with tyrosine kinase inhibitors and cytotoxic drugs shows promise in tackling both glioma proliferation and invasion, and could present a new treatment regimen for malignant astrocytomas.