Combined temozolomide and sunitinib treatment leads to better tumour control but increased vascular resistance in O6-methylguanine methyltransferase-methylated gliomas.

INTRODUCTION: Combined antiangiogenic and cytotoxic treatment represents an appealing treatment approach for malignant glioma. In this study we characterised the antitumoural and microvascular consequences of sunitinib (Su) and temozolomide (TMZ) therapy and verified the ideal treatment protocol, with special focus on a potential therapeutic window for combined scheduling. MATERIALS AND METHODS: O(6)-Methylguanine methyltransferase (MGMT) status was analysed by pyrosequencing. Tumour growth of subcutaneous xenografts was assessed under different treatment protocols (TMZ, SU, SU followed by TMZ, TMZ followed by SU, combined TMZ/SU). Intravital microscopy (dorsal skinfold chamber model) assessed microvascular consequences. Immunohistochemistry included tumour and endothelial cell proliferation, apoptosis and vascular pericyte coverage. Real-time polymerase chain reaction (RT-PCR) analysed the expression of angiogenesis-related pathways in response to therapy. RESULTS: Combined TMZ/SU resulted in significantly reduced tumour growth compared to either monotreatment (TMZ: 106 ± 13 mm(3); SU: 114 ± 53 mm(3); TMZ/SU: 34 ± 7 mm(3)) by additional antiangiogenic effects and synergistic induction of apoptosis versus TMZ monotreatment. Sequential treatment protocols did not show additive antitumour responses. TMZ/SU aggravated vascular resistance mechanisms characterised by significantly higher blood flow rate (TMZ: 74 ± 34 µl/s; SU: 164 ± 36 µl/s; TMZ/SU: 254 ± 95 µl/s), reduced permeability (TMZ: 1.05 ± 0.02; SU: 0.99 ± 0.07; TMZ/SU: 0.89 ± 0.05) and recovery of pericyte-endothelial interactions (TMZ: 89 ± 7%; SU: 67 ± 9%, TMZ/SU:80 ± 10%) versus either monotreatment. Vascular resistance was paralleled by an increase in Ang-1 and Tie-2 and by the downregulation of Dll4. CONCLUSION: Sequential application of TMZ and SU in the angiogenic window does not add antitumour efficacy to monotherapy. Simultaneous application yields beneficial tumour control due to additive antiangiogenic and proapoptotic effects. Combined treatment may aggravate pericyte-mediated vascular resistance mechanisms by altering Ang-1-Tie-2 and Dll4/Notch pathways.

Sequence and analysis of chromosome 1 of the plant Arabidopsis thaliana.

The genome of the flowering plant Arabidopsis thaliana has five chromosomes. Here we report the sequence of the largest, chromosome 1, in two contigs of around 14.2 and 14.6 megabases. The contigs extend from the telomeres to the centromeric borders, regions rich in transposons, retrotransposons and repetitive elements such as the 180-base-pair repeat. The chromosome represents 25% of the genome and contains about 6,850 open reading frames, 236 transfer RNAs (tRNAs) and 12 small nuclear RNAs. There are two clusters of tRNA genes at different places on the chromosome. One consists of 27 tRNA(Pro) genes and the other contains 27 tandem repeats of tRNA(Tyr)-tRNA(Tyr)-tRNA(Ser) genes. Chromosome 1 contains about 300 gene families with clustered duplications. There are also many repeat elements, representing 8% of the sequence.