Dynamic contrast-enhanced magnetic resonance imaging of the metastatic potential of tumors: a preclinical study of cervical carcinoma and melanoma xenografts.

BACKGROUND: Gadolinium diethylene-triamine penta-acetic acid (Gd-DTPA)-based dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) has been suggested to be a useful non-invasive method for providing biomarkers for personalized cancer treatment. In this preclinical study, we investigated whether Gd-DTPA-based DCE-MRI may have the potential to differentiate between poorly and highly metastatic tumors. MATERIAL AND METHODS: CK-160 cervical carcinoma and V-27 melanoma xenografts were used as tumor models. Fifty-six tumors were imaged, and parametric images of K(trans) (the volume transfer constant of Gd-DTPA) and v(e) (the fractional distribution volume of Gd-DTPA) were produced by pharmacokinetic analysis of the DCE-MRI series. The host mice were examined for lymph node metastases immediately after the DCE-MRI. RESULTS: Highly metastatic tumors showed lower values for median K(trans) than poorly metastatic tumors (p = 0.00033, CK-160; p < 0.00001, V-27). Median v(e) was lower for highly than for poorly metastatic V-27 tumors (p = 0.047), but did not differ significantly between metastatic and non-metastatic CK-160 tumors (p > 0.05). CONCLUSION: This study supports the clinical attempts to establish DCE-MRI as a method for providing biomarkers for tumor aggressiveness and suggests that tumors showing low K(trans) and low ve values may have high probability of lymphogenous metastatic dissemination.

Interstitial fluid pressure and associated lymph node metastasis revealed in tumors by dynamic contrast-enhanced MRI.

Elevated interstitial fluid pressure (IFP) in tumors can cause metastatic dissemination and treatment resistance, but its study poses a challenge because of a paucity of noninvasive imaging strategies. In this study, we address this issue by reporting the development of a noninvasive tool to assess tumor IFP and interstitial hypertension-induced lymph node metastasis. Using mouse xenograft models of several types of human cancer, we used gadolinium diethylene-triamine penta-acetic acid (Gd-DTPA) as a contrast agent for dynamic contrast-enhanced MRI (DCE-MRI). Immediately after Gd-DTPA administration, a high-signal-intensity rim was observed in the tumor periphery, which moved outward with time. Assuming the velocity of Gd-DTPA to be equal to the fluid flow velocity, we used a simple model of peritumoral interstitial fluid flow to calculate the fluid flow velocity at the tumor surface (v(0)) based on the rim movement. Significant positive correlations were found between v(0) and IFP in all tumor xenografts. Moreover, the primary tumors of metastasis-positive mice displayed higher IFP and v(0) than the primary tumors of metastasis-negative mice. Findings were confirmed in cervical cancer patients with pelvic lymph node metastases, where we found v(0) to be higher compared with patients without lymph node involvement (P < 0.00001). Together, these findings establish that Gd-DTPA-based DCE-MRI can noninvasively visualize tumor IFP, and they reveal the potential for v(0) determined by this method to serve as a novel general biomarker of tumor aggressiveness.

Dynamic contrast-enhanced magnetic resonance imaging of the metastatic potential of melanoma xenografts.

PURPOSE: Gadolinium diethylene-triamine penta-acetic acid (Gd-DTPA)-based dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) has been suggested as a useful noninvasive method for characterizing the physiologic microenvironment of tumors. In the present study, we investigated whether Gd-DTPA-based DCE-MRI has the potential to provide biomarkers for hypoxia-associated metastatic dissemination. METHODS AND MATERIALS: C-10 and D-12 melanoma xenografts were used as experimental tumor models. Pimonidazole was used as a hypoxia marker. A total of 60 tumors were imaged, and parametric images of K(trans) (volume transfer constant of Gd-DTPA) and v(e) (fractional distribution volume of Gd-DTPA) were produced by pharmacokinetic analysis of the DCE-MRI series. The host mice were killed immediately after DCE-MRI, and the primary tumor and the lungs were resected and prepared for histologic assessment of the fraction of pimonidazole-positive hypoxic tissue and the presence of lung metastases, respectively. RESULTS: Metastases were found in 11 of 26 mice with C-10 tumors and 14 of 34 mice with D-12 tumors. The primary tumors of the metastatic-positive mice had a greater fraction of hypoxic tissue (p = 0.00031, C-10; p < 0.00001, D-12), a lower median K(trans) (p = 0.0011, C-10; p < 0.00001, D-12), and a lower median v(e) (p = 0.014, C-10; p = 0.016, D-12) than the primary tumors of the metastatic-negative mice. CONCLUSIONS: These findings support the clinical attempts to establish DCE-MRI as a method for providing biomarkers for tumor aggressiveness and suggests that primary tumors characterized by low K(trans) and low v(e) values could have a high probability of hypoxia-associated metastatic spread.

Direct measurement of the interaction force between immunostimulatory CpG-DNA and TLR9 fusion protein.

The specific interaction between human Toll-like receptor 9 (TLR9)-ectodomain (ECD)-fusion protein and immunostimulatory CpG-DNA was measured using force spectroscopy. Flexible tethers were used between receptors and surface as well as between DNA and atomic force microscope tip to make efficient recognition studies possible. The molecular recognition forces detected are in the range of 50 to 150 ± 20 pN at the used force-loading rates, and the molecular interaction probability was much reduced when the receptors were blocked with free CpG-DNA. A linear increase of the unbinding force with the logarithm of the loading rate was found over the range 0.1 to 30 nN/s. This indicates a single potential barrier characterizing the energy landscape and no intermediate state for the unbinding pathway of CpG-DNA from the TLR9-ECD. Two important kinetic parameters for CpG-DNA interaction with TLR9-ECD were determined from the force-loading rate dependency: an off-rate of k(off) = 0.14 ± 0.10 s(-1) and a binding interaction length of x(ß) = 0.30 ± 0.03 nm, which are consistent with literature values. Various models for the molecular interaction of this innate immune receptor binding to CpG-DNA are discussed.

pO2 fluctuation pattern and cycling hypoxia in human cervical carcinoma and melanoma xenografts.

PURPOSE: Blood perfusion in tumors is spatially and temporally heterogeneous, resulting in local fluctuations in tissue oxygen tension (pO(2)) and tissue regions showing cycling hypoxia. In this study, we investigated whether the pO(2) fluctuation pattern and the extent of cycling hypoxia differ between tumor types showing high (e.g., cervical carcinoma xenograft) and low (e.g., melanoma xenograft) fractions of connective tissue-associated blood vessels. METHODS AND MATERIALS: Two cervical carcinoma lines (CK-160 and TS-415) and two melanoma lines (A-07 and R-18) transplanted into BALB/c nu/nu mice were included in the study. Tissue pO(2) was measured simultaneously in two positions in each tumor by using a two-channel OxyLite fiber-optic oxygen-sensing device. The extent of acute and chronic hypoxia was assessed by combining a radiobiological and a pimonidazole-based immunohistochemical assay of tumor hypoxia. RESULTS: The proportion of tumor regions showing pO(2) fluctuations, the pO(2) fluctuation frequency in these regions, and the relative amplitude of the pO(2) fluctuations were significantly higher in the melanoma xenografts than in the cervical carcinoma xenografts. Cervical carcinoma and melanoma xenografts did not differ significantly in the fraction of acutely hypoxic cells or the fraction of chronically hypoxic cells. However, the ratio between fraction of acutely hypoxic cells and fraction of chronically hypoxic cells was significantly higher in melanoma than in cervical carcinoma xenografts. CONCLUSIONS: Temporal heterogeneity in blood flow and tissue pO(2) in tumors may depend on tumor histology. Connective tissue surrounding microvessels may stabilize blood flow and pO(2) and, thus, protect tumor tissue from cycling hypoxia.

Assessment of hypoxia and radiation response in intramuscular experimental tumors by dynamic contrast-enhanced magnetic resonance imaging.

BACKGROUND AND PURPOSE: Studies of intradermal melanoma xenografts have suggested that dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) may be a useful method for assessing the extent of hypoxia in tumors. Because the microvascular network of tumors is influenced significantly by the site of growth, we challenged this possibility in the present work by studying relationships between DCE-MRI-derived parameters and hypoxia in intramuscular melanoma xenografts. MATERIALS AND METHODS: Intramuscular R-18, U-25, and V-27 tumors were subjected to DCE-MRI and measurement of the fraction of radiobiologically hypoxic cells (HF(Rad)). Parametric images of K(trans) and v(e) were produced by pharmacokinetic analysis, and K(trans) and v(e) were related to HF(Rad) in individual tumors. RESULTS: K(trans) decreased with increasing HF(Rad). The correlations between K(trans) and HF(Rad) were similar for the three tumor lines and were highly significant (P<0.00001). There was no correlation between v(e) and HF(Rad). However, v(e) decreased significantly with increasing cell survival after single dose irradiation. CONCLUSION: Intramuscular melanoma xenografts show similar inverse correlations between K(trans) and HF(Rad) as intradermal tumors, which support the current clinical attempts to establish DCE-MRI as a method for detecting hypoxia and defining therapeutic targets in tumors.

Assessment of tumor radioresponsiveness and metastatic potential by dynamic contrast-enhanced magnetic resonance imaging.

PURPOSE: It has been suggested that gadolinium diethylene-triamine penta-acetic acid (Gd-DTPA)-based dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) may provide clinically useful biomarkers for personalized cancer treatment. In this preclinical study, we investigated the potential of DCE-MRI as a noninvasive method for assessing the radioresponsiveness and metastatic potential of tumors. METHODS AND MATERIALS: R-18 melanoma xenografts growing in BALB/c nu/nu mice were used as experimental tumor models. Fifty tumors were subjected to DCE-MRI, and parametric images of Ktrans (the volume transfer constant of Gd-DTPA) and ve (the fractional distribution volume of Gd-DTPA) were produced by pharmacokinetic analysis of the DCE-MRI series. The tumors were irradiated after the DCE-MRI, either with a single dose of 10 Gy for detection of radiobiological hypoxia (30 tumors) or with five fractions of 4 Gy in 48 h for assessment of radioresponsiveness (20 tumors). The host mice were then euthanized and examined for lymph node metastases, and the primary tumors were resected for measurement of cell survival in vitro. RESULTS: Tumors with hypoxic cells showed significantly lower Ktrans values than tumors without significant hypoxia (p<0.0001, n=30), and Ktrans decreased with increasing cell surviving fraction for tumors given fractionated radiation treatment (p<0.0001, n=20). Tumors in metastasis-positive mice had significantly lower Ktrans values than tumors in metastasis-negative mice (p<0.0001, n=50). Significant correlations between ve and tumor hypoxia, radioresponsiveness, or metastatic potential could not be detected. CONCLUSIONS: R-18 tumors with low Ktrans values are likely to be resistant to radiation treatment and have a high probability of developing lymph node metastases. The general validity of these observations should be investigated further by studying preclinical tumor models with biological properties different from those of the R-18 tumors.

Differentiation between hypoxic and non-hypoxic experimental tumors by dynamic contrast-enhanced magnetic resonance imaging.

BACKGROUND AND PURPOSE: Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) has been suggested to be a useful method for detecting tumor hypoxia. In this study, we investigated whether DCE-MRI can differentiate between hypoxic and non-hypoxic experimental tumors. MATERIALS AND METHODS: Three tumor models with hypoxic tissue and three tumor models without hypoxic tissue were subjected to DCE-MRI. Parametric images of K(trans) (the volume transfer constant of Gd-DTPA) and v(e) (the fractional distribution volume of Gd-DTPA) were produced by pharmacokinetic analysis of the DCE-MRI series. Tumor oxygenation status was assessed by using a radiobiological assay and a pimonidazole-based immunohistochemical assay. Tumor response to fractionated irradiation (six fractions of 2Gy in 60h) was measured in vitro by using a clonogenic assay. RESULTS: Tumors with hypoxic regions were more resistant to radiation treatment than were tumors without hypoxia. K(trans) was significantly higher for radiation sensitive tumors without hypoxia than for radiation resistant tumors with hypoxic regions, whereas v(e) did not differ significantly between non-hypoxic and hypoxic tumors. CONCLUSION: This study supports the clinical attempts to establish DCE-MRI as a noninvasive method for providing useful biomarkers for personalized radiation therapy.

Dose levels from thoracic and pelvic examinations in two pediatric radiological departments in Norway - a comparison study of dose-area product and radiographic technique.

BACKGROUND: pediatric doses expressed in dose-area product (DAP) can be retrieved from only a few publications; most of which correlate DAP to patient size or large age spans. In clinical practice age is often the only available parameter describing the patient, and thus, evaluation of dose levels in pediatric radiology on the basis of DAP related to age alone would be useful in optimization work. PURPOSE: to provide comparable data on age-related DAP from thoracic and pelvic radiological examinations of children, and evaluate the usefulness of comparing age-related DAP and radiographic technique between systems to identify areas with potential for optimization. MATERIAL AND METHODS: DAP, age, and radiographic technique were registered for 575 thoracic examinations and 371 pelvic examinations of children from newborn up to 14 years of age in groups with an age span of 1 year, performed with two digital flat-panel systems and one computed radiography system. RESULTS: DAP varies from 2.2 to 54.0 mGycm(2) for thoracic examinations, and from 4.6 to 532.5 mGycm(2) for pelvic examinations. There are significant differences in DAP between systems and departments due to differences in technique, equipment, and staff. CONCLUSION: this study provides comparable data on age-related DAP from thoracic and pelvic radiological examinations of children, which could be used as an input to estimate diagnostic reference levels. The comparison between systems of DAP and radiographic technique has proven useful in identifying areas where there may be a potential for optimization.