Inhibition of carbonic anhydrase IX (CA9) sensitizes renal cell carcinoma to ionizing radiation.

While normal kidneys are relatively sensitive to ionizing radiation (IR), renal cell carcinoma (RCC) is considered radioresistant. Carbonic anhydrase IX (CA9), an enzyme that maintains intracellular pH by carbon dioxide dissolution, is upregulated in the majority of RCC, but not in normal kidneys. Since regulation of intracellular pH may enhance radiation effects, we hypothesized that inhibition of CA9 may radiosensitize RCC. Clonogenic survival assay of human clear cell RCC 786-O and murine RCC RAG cells in the presence of a pharmacological CA9 inhibitor or with shRNA-mediated knockdown of CA9 was performed to investigate the response to IR in vitro (single dose or fractionated) and in vivo. Extracellular pH changes were measured in vitro. Treatment with AEBS [4-(2-aminoethyl)benzene sulfonamide], a sulfonamide, was used as a pharmacological inhibitor of the enzymatic activity of CA9. Nude mice bearing subcutaneous xenografts of 786-O cells stably expressing CA9 shRNA or scrambled control were irradiated (6 Gy). Tumor growth was followed longitudinally in the 786-O-bearing mice receiving AEBS (50-200 µg/ml drinking water) or control (vehicle only) which were irradiated (6 Gy) and compared with mice receiving either IR or AEBS alone. In vitro inhibition of CA9 activity or expression significantly sensitized RCC cells to the effects of IR (p<0.05), an effect even more significant when hypofractionated IR was applied. In vivo irradiated xenografts from RCC cells transfected with CA9 shRNA were significantly smaller compared to irradiated xenografts from the scrambled shRNA controls (p<0.05). RCC xenografts from mice treated with AEBS in combination with IR grew significantly slower than all controls (p<0.05). Inhibition of CA9 expression or activity resulted in radiation sensitization of RCC in a preclinical mouse model.

Modeling changes in the hemoglobin concentration of skin with total diffuse reflectance spectroscopy.

The ability to monitor changes in the concentration of hemoglobin in the blood of the skin in real time is a key component to personalized patient care. Since hemoglobin has a unique absorption spectrum in the visible light range, diffuse reflectance spectroscopy is the most common approach. Although the collection of the diffuse reflectance spectrum with an integrating sphere (IS) has several calibration challenges, this collection method is sufficiently user-friendly that it may be worth overcoming the initial difficulty. Once the spectrum is obtained, it is commonly interpreted with a log-inverse-reflectance (LIR) or "absorbance" analysis that can only accurately monitor changes in the hemoglobin concentration when there are no changes to the nonhemoglobin chromophore concentrations which is not always the case. We address the difficulties associated with collection of the diffuse reflectance spectrum with an IS and propose a model capable of retrieving relative changes in hemoglobin concentration from the visible light spectrum. The model is capable of accounting for concentration changes in the nonhemoglobin chromophores and is first characterized with theoretical spectra and liquid phantoms. The model is then used in comparison with a common LIR analysis on temporal measurements from blanched and reddened human skin.

Inexpensive diffuse reflectance spectroscopy system for measuring changes in tissue optical properties.

The measurement of changes in blood volume in tissue is important for monitoring the effects of a wide range of therapeutic interventions, from radiation therapy to skin-flap transplants. Many systems available for purchase are either expensive or difficult to use, limiting their utility in the clinical setting. A low-cost system, capable of measuring changes in tissue blood volume via diffuse reflectance spectroscopy is presented. The system consists of an integrating sphere coupled via optical fibers to a broadband light source and a spectrometer. Validation data are presented to illustrate the accuracy and reproducibility of the system. The validity and utility of this in vivo system were demonstrated in a skin blanching/reddening experiment using epinephrine and lidocaine, and in a study measuring the severity of radiation-induced erythema during radiation therapy.

Optimal time delay between epinephrine injection and incision to minimize bleeding.

BACKGROUND: The time until maximal cutaneous vasoconstriction after injection of lidocaine with epinephrine is often given in textbooks and multiple choice examinations as 7 to 10 minutes. However, in our experience, there is significantly less cutaneous bleeding if one waits considerably longer than 7 to 10 minutes after injection of local anesthesia with epinephrine for most procedures on human skin. METHODS: This was a prospective, randomized, triple-blind study where 12 volunteers were injected simultaneously in each arm with either 1% lidocaine with epinephrine (study group) or 1% plain lidocaine (control group), after which the relative hemoglobin concentration of the underlying skin and soft tissues was measured over time using spectroscopy. RESULTS: In the epinephrine group, the mean time at which the lowest cutaneous hemoglobin level was obtained was 25.9 minutes (95 percent CI, 25.9 ± 5.1 minutes). This was significantly longer than the historical literature values of 7 to 10 minutes for maximum vasoconstriction after injection. Mean hemoglobin index values at every time measurement after postinjection minute 1 were significantly different between the study group and the control group, with use of a two-tailed paired t test (p < 0.01). CONCLUSIONS: If optimal visualization is desired, the ideal time for the surgeon to begin the incision should be 25 minutes after injection of local anesthetic with epinephrine. It takes considerably longer than 7 to 10 minutes for a new local equilibrium to be obtained in relation to hemoglobin quantity.

Integrating spheres for improved skin photodynamic therapy.

The prescribed radiant exposures for photodynamic therapy (PDT) of superficial skin cancers are chosen empirically to maximize the success of the treatment while minimizing adverse reactions for the majority of patients. They do not take into account the wide range of tissue optical properties for human skin, contributing to relatively low treatment success rates. Additionally, treatment times can be unnecessarily long for large treatment areas if the laser power is not sufficient. Both of these concerns can be addressed by the incorporation of an integrating sphere into the irradiation apparatus. The light fluence rate can be increased by as much as 100%, depending on the tissue optical properties. This improvement can be determined in advance of treatment by measuring the reflectance from the tissue through a side port on the integrating sphere, allowing for patient-specific treatment times. The sphere is also effective at improving beam flatness, and reducing the penumbra, creating a more uniform light field. The side port reflectance measurements are also related to the tissue transport albedo, enabling an approximation of the penetration depth, which is useful for real-time light dosimetry.

Entrance skin dose measured with MOSFETs in children undergoing interventional radiology procedures.

BACKGROUND: Interventional procedures frequently employ fluoroscopy or digital subtraction angiography (DSA). Few studies have documented radiation doses received by children during these procedures. OBJECTIVE: To measure skin entrance dose received during common pediatric interventional procedures. MATERIALS AND METHODS: MOSFET dosimeters were placed to record skin doses in 143 children undergoing any of five procedures: 30 PICC insertions, 34 CVL/port insertions, 30 G/GJ tube insertions, 25 sclerotherapy/vascular anomaly procedures, 24 cerebral angiography procedures. The highest recorded dose (HRD) from the five MOSFET probes was assumed to be the peak skin dose per child. HRD values were averaged for children within each group and correlated with patient weight, fluoroscopy time and number of DSA frames. RESULTS: Average HRD was 1.8 mGy for PICC insertions, 1.4 mGy for CVL/port insertions, 3.9 mGy for G/GJ tube insertions, 39.1 mGy for sclerotherapy/vascular anomaly procedures, and 149.9 and 101.6 mGy for frontal and lateral portions of cerebral angiography procedures. These entrance doses corresponded to effective dose estimates in the range 0.4-3 mSv. There were only modest correlations between peak skin dose and fluoroscopy time, patient weight and DSA frames (r (2)<0.4, P < 0.01). CONCLUSION: Pediatric interventional procedures are associated with a wide range of doses; those at the higher end require careful monitoring.