Christine Ellingsen

Dynamic contrast-enhanced magnetic resonance imaging of tumors: preclinical validation of parametric images.

Abstract Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) has been suggested to be a valuable method for characterizing the physiological microenvironment of tumors and thus a promising method for individualizing cancer treatment. The aim of this study was to test the hypothesis that valid parametric images of the tumor microenvironment can be obtained by pharmacokinetic analysis of DCE-MRI series. Cells of four human melanoma xenograft lines (A-07, D-12, R-18 and T-22) were used as preclinical models of human cancer. DCE-MRI was performed at 1.5 T at a spatial resolution of 0.23 × 0.47 × 2.0 mm3 and a time resolution of 14 s. Gadolinium diethylene-triamine penta-acetic acid (Gd-DTPA) was used as contrast agent. The DCE-MRI data were analyzed on a voxel-by-voxel basis by using a pharmacokinetic model recommended for analysis of clinical DCE-MRI series. Parametric DCE-MR images were compared with tumor blood perfusion measured by the 86Rb uptake method, and fractional volume of the extravascular extracellular space assessed by analysis of histological preparations. Parametric images reflecting tumor blood perfusion and fractional volume of the extravascular extracellular space were obtained. The numerical values of the DCE-MRI-derived parameters were not significantly different from the absolute values of tumor blood perfusion or fractional volume of the extravascular extracellular space in any of the tumor lines. This study shows that DCE-MRI can provide valid quantitative parametric images of the tumor microenvironment in preclinical cancer models and thus supports the suggestion that DCE-MRI may be developed to be a clinically useful method for individualization of microenvironment-based cancer treatment, a possibility that merits increased clinical interest.

DCE-MRI of the hypoxic fraction, radioresponsiveness, and metastatic propensity of cervical carcinoma xenografts

BACKGROUND AND PURPOSE Locoregional treatment failure and poor survival rates are associated with extensive hypoxia in the primary tumor in advanced cervical carcinoma. The potential of gadolinium diethylene-triamine penta-acetic acid (Gd-DTPA)-based dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) in assessing the hypoxic fraction, radioresponsiveness, and metastatic propensity of cervical carcinomas was investigated in this preclinical study. MATERIALS AND METHODS CK-160 and TS-415 cervical carcinoma xenografts were used as tumor models. DCE-MRI was carried out at 1.5 T, and parametric images of K(trans) and v(e) were produced by pharmacokinetic analysis of the DCE-MRI series. Pimonidazole was used as a hypoxia marker. Tumor radioresponsiveness was determined by irradiating tumors with five fractions of 4 Gy in 48 h and measuring cell survival in vitro. Metastatic propensity was determined by examining host mice for tumor growth in lymph nodes. RESULTS Low values of K(trans) were associated with extensive hypoxia and radiation resistance in tumors of both lines and with high incidence of metastases in CK-160 tumors. Associations between ve and hypoxia, radioresponsiveness, or metastatic propensity were not found in any of the tumor lines. CONCLUSION K(trans) is a potentially useful biomarker of tumor hypoxia, radiation resistance, and metastatic growth in advanced cervical carcinoma.

Assessment of Hypoxia in Human Cervical Carcinoma Xenografts by Dynamic Contrast-Enhanced Magnetic Resonance Imaging

PURPOSE Patients with advanced cervical cancer and highly hypoxic primary tumors show increased frequency of locoregional treatment failure and poor disease-free and overall survival rates. The potential usefulness of gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA)-based dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) in assessing tumor hypoxia noninvasively was investigated in the present preclinical study. METHODS AND MATERIALS CK-160 and TS-415 human cervical carcinoma xenografts transplanted intramuscularly (i.m.) or subcutaneously (s.c.) in BALB/c nu/nu mice were subjected to DCE-MRI and measurement of fraction of radiobiologically hypoxic cells. Tumor images of K(trans) (the volume transfer constant of Gd-DTPA) and v(e) (the extracellular volume fraction of the imaged tissue) were produced by pharmacokinetic analysis of the DCE-MRI data. Fraction of radiobiologically hypoxic cells was measured by using the paired survival curve method. RESULTS Fraction of radiobiologically hypoxic cells differed significantly among the four tumor groups. The mean values +/- SE were determined to be 44% +/- 7% (i.m. CK-160), 77% +/- 10% (s.c. CK-160), 23% +/- 5% (i.m. TS-415), and 52% +/- 6% (s.c. TS-415). The four tumor groups differed significantly also in K(trans), and there was an unambiguous inverse relationship between K(trans) and fraction of radiobiologically hypoxic cells. On the other hand, significant differences among the groups in v(e) could not be detected. CONCLUSIONS The study supports the clinical development of DCE-MRI as a method for assessing the extent of hypoxia in carcinoma of the cervix.

Microenvironment-associated lymph node metastasis of human cervical carcinoma xenografts

Abstract Background. The prognosis is particularly poor for patients with advanced squamous cell carcinoma of the uterine cervix when the primary tumor has developed severe physiological abnormalities. The impact of the physiological microenvironment of the primary tumor on lymph node metastasis was investigated in this preclinical study. Material and methods. Xenografted tumors of two human cervical carcinoma lines (CK-160 and TS-415) transplanted into BALB/c nu/nu mice were included in the study. The fraction of radiobiologically hypoxic cells (HFRad), interstitial fluid pressure (IFP), and extracellular pH (pHe) were measured in 22 CK-160 tumors and 16 TS-415 tumors and related to the metastatic status of the host mice. Results. In CK-160, HFRad was significantly higher in the metastatic than in the nonmetastatic tumors, whereas the metastatic and nonmetastatic tumors did not differ significantly in IFP or pHe. In TS-415, IFP was significantly higher in the tumors that metastasized than in those that did not metastasize, whereas the tumors of the metastasis-positive and metastasis-negative mice did not differ significantly in HFRad or pHe. Conclusion. Lymph node metastasis is associated with abnormalities in the physiological microenvironment of the primary tumor in cervical carcinoma xenografts, and tumor line-specific mechanisms are probably involved.

Connective tissue of cervical carcinoma xenografts: Associations with tumor hypoxia and interstitial fluid pressure and its assessment by DCE-MRI and DW-MRI

Abstract Background. A high fraction of stroma in malignant tissues is associated with tumor progression, metastasis, and poor prognosis. Possible correlations between the stromal and physiologic microenvironments of tumors and the potential of dynamic contrast-enhanced (DCE) and diffusion-weighted (DW) magnetic resonance imaging (MRI) in quantification of the stromal microenvironment were investigated in this study. Material and methods. CK-160 cervical carcinoma xenografts were used as preclinical tumor model. A total of 43 tumors were included in the study, and of these tumors, 17 were used to search for correlations between the stromal and physiologic microenvironments, 11 were subjected to DCE-MRI, and 15 were subjected to DW-MRI. DCE-MRI and DW-MRI were carried out at 1.5 T with a clinical MR scanner and a slotted tube resonator transceiver coil constructed for mice. Fraction of connective tissue (CTFCol) and fraction of hypoxic tissue (HFPim) were determined by immunohistochemistry. A Millar SPC 320 catheter was used to measure tumor interstitial fluid pressure (IFP). Results. CTFCol showed a positive correlation to IFP and an inverse correlation to HFPim. The apparent diffusion coefficient assessed by DW-MRI was inversely correlated to CTFCol, whereas no correlation was found between DCE-MRI-derived parameters and CTFCol. Conclusion. DW-MRI is a potentially useful method for characterizing the stromal microenvironment of tumors.

Dynamic contrast-enhanced magnetic resonance imaging of human cervical carcinoma xenografts: Pharmacokinetic analysis and correlation to tumor histomorphology

BACKGROUND AND PURPOSE Biomarkers that can predict the outcome of treatment accurately are needed for treatment individualization in advanced carcinoma of the uterine cervix. The potential of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) was investigated in the present preclinical study. MATERIALS AND METHODS CK-160 and TS-415 human cervical carcinoma xenografts were subjected to DCE-MRI at 1.5T using a spatial resolution of 0.23×0.47×2.0mm(3). Parametric images of K(trans) (the volume transfer constant of Gd-DTPA) and v(e) (the extravascular extracellular volume fraction) were produced by pharmacokinetic analysis of the DCE-MRI data and compared with the histomorphology of the imaged tissue. RESULTS Analysis of small homogeneous tumor regions showed that K(trans), but not v(e), differed significantly between parenchymal tissue, connective tissue, and necrotic tissue, consistent with the vascularity of these compartments. However, strong correlations between K(trans) and the fractional volume of the compartments could not be detected for larger tumor regions, primarily because the majority of the voxels represented a chaotic mixture of parenchymal, connective, and necrotic tissue. CONCLUSION The potential of DCE-MRI in providing detailed information on the histomorphology of cervical carcinoma is limited, mainly because the tumor tissue shows significant morphological heterogeneity at the subvoxel level.

Peritumoral interstitial fluid flow velocity predicts survival in cervical carcinoma

BACKGROUND AND PURPOSE High tumor interstitial fluid pressure (IFP) is associated with poor outcome in locally advanced carcinoma of the uterine cervix. We have recently developed a noninvasive assay of the IFP of tumors, and in this assay, the outward interstitial fluid flow velocity at the tumor surface (v0) is measured by Gd-DTPA-based DCE-MRI and used as a parameter for IFP. Here, we investigated the independent prognostic significance of v0 in cervical cancer patients given cisplatin-based concurrent chemoradiotherapy with curative intent. PATIENTS The study involved 62 evaluable patients from a cohort of 74 consecutive patients (Stage IB through IIIB) with a median follow-up of 5.5 years. RESULTS The actuarial disease-free survival (DFS) and overall survival (OS) at 5 years were 67% and 76%, respectively. Significant associations were found between v0 dichotomized about the median value and DFS and OS, both in the total patient cohort and a subcohort of 40 Stage IIB patients. Multivariate analysis involving stage, tumor volume, lymph node status, and v0 revealed that only v0 provided independent prognostic information about DFS and OS. CONCLUSION This investigation demonstrates a strong, independent prognostic impact of the pretreatment peritumoral fluid flow velocity in cervical cancer.

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

Abstract 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 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 host mice were examined for lymph node metastases immediately after the DCE-MRI. Results. Highly metastatic tumors showed lower values for median Ktrans than poorly metastatic tumors (p = 0.00033, CK-160; p < 0.00001, V-27). Median ve 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 Ktrans and low ve values may have high probability of lymphogenous metastatic dissemination.

Preclinical evaluation of Gd-DTPA and gadomelitol as contrast agents in DCE-MRI of cervical carcinoma interstitial fluid pressure

BackgroundHigh interstitial fluid pressure (IFP) in the primary tumor is associated with poor disease-free survival in locally advanced cervical carcinoma. A noninvasive assay is needed to identify cervical cancer patients with highly elevated tumor IFP because these patients may benefit from particularly aggressive treatment. It has been suggested that dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) with gadolinium diethylene-triamine penta-acetic acid (Gd-DTPA) as contrast agent may provide useful information on the IFP of cervical carcinomas. In this preclinical study, we investigated whether DCE-MRI with contrast agents with higher molecular weights (MW) than Gd-DTPA would be superior to Gd-DTPA-based DCE-MRI.MethodsCK-160 human cervical carcinoma xenografts were subjected to DCE-MRI with Gd-DTPA (MW of 0.55 kDa) or gadomelitol (MW of 6.5 kDa) as contrast agent before tumor IFP was measured invasively with a Millar SPC 320 catheter. The DCE-MRI was carried out at a spatial resolution of 0.23 × 0.23 × 2.0 mm3 and a time resolution of 14 s by using a 1.5-T whole-body scanner and a slotted tube resonator transceiver coil constructed for mice. Parametric images were derived from the DCE-MRI recordings by using the Tofts iso-directional transport model and the Patlak uni-directional transport model.ResultsWhen gadomelitol was used as contrast agent, significant positive correlations were found between the parameters of both pharmacokinetic models and tumor IFP. On the other hand, significant correlations between DCE-MRI-derived parameters and IFP could not be detected with Gd-DTPA as contrast agent.ConclusionGadomelitol is a superior contrast agent to Gd-DTPA in DCE-MRI of the IFP of CK-160 cervical carcinoma xenografts. Clinical studies attempting to develop DCE-MRI-based assays of the IFP of cervical carcinomas should involve contrast agents with higher MW than Gd-DTPA.

Hypoxia biomarkers in squamous cell carcinoma of the uterine cervix

BackgroundThere is significant evidence that severe tumor hypoxia may cause resistance to chemoradiotherapy and promote metastatic spread in locally advanced carcinoma of the uterine cervix. Some clinical investigations have suggested that high expression of hypoxia-inducible factor-1α (HIF-1α) and/or its target gene carbonic anhydrase IX (CAIX) may be useful biomarkers of tumor hypoxia and poor outcome in cervical cancer. Here, we challenged this view by investigating possible associations between HIF-1α expression, CAIX expression, fraction of hypoxic tissue, and lymph node metastasis in experimental human tumors.MethodsTumors of two cervical carcinoma xenograft lines (CK-160 and TS-415) were included in the study. Pimonidazole was used as a hypoxia marker, and tumor hypoxia, HIF-1α expression, and CAIX expression were detected by immunohistochemistry. Metastatic status was assessed by examining external lymph nodes in the inguinal, axillary, interscapular, and submandibular regions and internal lymph nodes in the abdomen and mediastinum.ResultsTissue regions staining positive for pimonidazole, HIF-1α, or CAIX were poorly colocalized, both in CK-160 and TS-415 tumors. The expression of HIF-1α or CAIX did not correlate with the fraction of hypoxic tissue in any of the two tumor lines. Furthermore, clinically relevant associations between HIF-1α or CAIX expression and lymph node metastasis were not found.ConclusionBecause significant associations between HIF-1α expression, CAIX expression, fraction of hypoxic tissue, and incidence of lymph node metastases could not be detected in any of two preclinical models of human cervical cancer, it is not realistic to believe that high expression of HIF-1α or CAIX can be useful biomarkers of tumor hypoxia and poor outcome in a highly heterogeneous disease like cervical carcinoma.