Evaluation of quantified contrast-enhanced color and power Doppler ultrasonography for the assessment of vascularity and perfusion of naturally occurring tumors in dogs.

OBJECTIVE: To investigate subjective and computerized methods of evaluation of color Doppler (CD) and power Doppler (PD) ultrasonographic images (obtained before and after administration of contrast medium) for quantitative assessment of vascularity and perfusion of various naturally occurring tumors in dogs. SAMPLE POPULATION: 34 tumors in 34 dogs. PROCEDURE: Tumors in dogs were examined via CD and PD ultrasonography before and after i.v. injection of a microbubble contrast agent (pre- and postcontrast examinations, respectively). Images were digitized for subjective assessment of vessel density and vascular pattern and computer-aided assessment of parameters of vascularity (fractional area [FA]) and perfusion (color-weighted FA [CWFA] and mean color-weighted FA [CWFA] and mean color level). RESULTS: With both analysis methods, more vessels were identified in precontrast PD ultrasonographic images than in precontrast CD ultrasonographic images. Moreover, compared with values for precontrast PD ultrasonography, FA, CWFA, and mean color level were higher for postcontrast PD ultrasonography. In postcontrast images, there was a significant association between vessel densities determined through subjective and computerized assessments. Although sample size was small, vascularity of squamous cell carcinomas was significantly greater than that of other tumor types. Ten of the 19 softer than issue that sarcomas had low vessel density with minor contrast enhancement. With increasing gross tumor volume, FA and CWFA decreased for all Doppler ultrasonographic methods. CONCLUSIONS AND CLINICAL RELEVANCE: Higher values of the ultrasonographic parameters representing vascularity and perfusion of tumors in dogs were determined via PD ultrasonography after administration of contrast medium than via PD or CD ultrasonography without administration of contrast medium.

Ultrasound guided, pre-radiation oxygen measurements using polarographic oxygen needle electrodes in spontaneous canine soft tissue sarcomas.

BACKGROUND: Poor tumour oxygenation is associated with radiation resistance. The recording of pre-treatment oxygenation status has been shown to be of prognostic relevance. MATERIAL AND METHODS: Eleven dogs with spontaneously arising soft tissue sarcomas were included in this study. Oxygen partial pressure measurements (pO2) were performed with the Eppendorf method. RESULTS: The mean of median pO2 was 9.6 mmHg (range: 0.1-30 mmHg). Four of the nine dogs included in the statistical analysis showed a median pO2 < or = 2.5 mmHg. The natural logarithm of the hypoxic subvolume correlated with the hypoxic fraction < or = 2.5 mmHg (p = 0.0712) and < or 5 mmHg (p = 0.0988). Mean corpuscular hemoglobin (MCH) and mean corpuscular volume (MCV) correlated significantly to several oxygen parameters. CONCLUSION: Hypoxia exists in spontaneous canine soft tissue sarcomas and the dog can be used as a reliable model for repeated oxygenation measurements. Ultrasonography assures reliability of needle placement.

Rescue of hypoxia-inducible factor-1alpha-deficient tumor growth by wild-type cells is independent of vascular endothelial growth factor.

In tumors, rapid cell proliferation associated with deficient vascularization leads to areas of hypoxia. Tumor hypoxia has direct consequences on clinical and prognostic parameters and is a potential therapeutic target. The hypoxic response depends critically on hypoxia-inducible factor-1alpha (HIF-1alpha) in pathological (e.g., tumorigenesis) as well as physiological (e.g., development and wound healing) processes. By s.c. injection of HIF-1alpha(-/-) embryonic stem (ES) cells in nude mice, we were able to demonstrate the role of HIF-1alpha in cell differentiation of teratocarcinomas. HIF-1alpha(+/+) tumors grow fast and preferentially form neuronal tissue, whereas HIF-1alpha(-/-) tumors show delayed growth and favorably form mesenchyme-derived tissue. Mixing wild-type and HIF-1alpha(-/-) ES cells in the same tumor at a ratio as low as 1:100, we showed that HIF-1alpha(+/+) cells can rescue the growth of mixed tumors although these tumors are not significantly different phenotypically or genotypically from the original HIF-1alpha(-/-) tumors. Interestingly, these results are not restricted to teratocarcinomas: they were confirmed with mixtures of Hepa1/Hepa1C4 cells (where HIF-1beta is mutated), demonstrating that growth changes are not related to differences in differentiation observed within teratocarcinomas. We also showed that despite lower mRNA expression, vascular endothelial growth factor protein status in HIF-1alpha(-/-) and mixed tumors does not significantly differ from the HIF-1alpha(+/+) tumors. Moreover, we demonstrated that tumor vascularization remains proportional to vascular endothelial growth factor protein levels, but that hypoxic up-regulation of this growth factor is not the decisive factor influencing tumor growth. Differences in levels of apoptosis are not responsible for alteration in growth because poly(ADP-ribose) polymerase cleavage, a hallmark of the apoptotic process, was similar in HIF-1alpha(+/+), HIF-1alpha(-/-), and mixed tumors. Our data demonstrate that the HIF-1alpha-dependent response of a few cells is capable of sustaining the growth of the whole tumor, probably through the secretion of factors up-regulated under low oxygen conditions.