In Vivo 3D MRI Measurement of Tumour Volume in an Orthotopic Mouse Model of Prostate Cancer

Trends in Subcutaneous Tumour Height and Impact on Measurement Accuracy

Tumour volume is typically calculated using only length and width measurements, using width as a proxy for height in a 1:1 ratio. When tracking tumour growth over time, important morphological information and measurement accuracy is lost by ignoring height, which we show is a unique variable. Lengths, widths, and heights of 9522 subcutaneous tumours in mice were measured using 3D and thermal imaging. The average height:width ratio was found to be 1:3 proving that using width as a proxy for height overestimates tumour volume. Comparing volumes calculated with and without tumour height to the true volumes of excised tumours indeed showed that using the volume formula including height produced volumes 36X more accurate (based off of percentage difference). Monitoring the height:width relationship (prominence) across tumour growth curves indicated that prominence varied, and that height could change independent of width. Twelve cell lines were investigated individually; the scale of tumour prominence was cell line-dependent with relatively less prominent tumours (MC38, BL2, LL/2) and more prominent tumours (RENCA, HCT116) detected. Prominence trends across the growth cycle were also dependent on cell line; prominence was correlated with tumour growth in some cell lines (4T1, CT26, LNCaP), but not others (MC38, TC-1, LL/2). When pooled, invasive cell lines produced tumours that were significantly less prominent at volumes >1200 mm³ compared to non-invasive cell lines (P < .001). Modelling was used to show the impact of the increased accuracy gained by including height in volume calculations on several efficacy study outcomes. Variations in measurement accuracy contribute to experimental variation and irreproducibility of data, therefore we strongly advise researchers to measure height to improve accuracy in tumour studies.

In Silico Modeling Demonstrates that User Variability During Tumor Measurement Can Affect In Vivo Therapeutic Efficacy Outcomes

User measurement bias during subcutaneous tumor measurement is a source of variation in preclinical in vivo studies. We investigated whether this user variability could impact efficacy study outcomes, in the form of the false negative result rate when comparing treated and control groups. Two tumor measurement methods were compared; calipers which rely on manual measurement, and an automatic 3D and thermal imaging device. Tumor growth curve data were used to create an in silico efficacy study with control and treated groups. Before applying user variability, treatment group tumor volumes were statistically different to the control group. Utilizing data collected from 15 different users across 9 in vivo studies, user measurement variability was computed for both methods and simulation was used to investigate its impact on the in silico study outcome. User variability produced a false negative result in 0.7% to 18.5% of simulated studies when using calipers, depending on treatment efficacy. When using an imaging device with lower user variability this was reduced to 0.0% to 2.6%, demonstrating that user variability impacts study outcomes and the ability to detect treatment effect. Reducing variability in efficacy studies can increase confidence in efficacy study outcomes without altering group sizes. By using a measurement device with lower user variability, the chance of missing a therapeutic effect can be reduced and time and resources spent pursuing false results could be saved. This improvement in data quality is of particular interest in discovery and dosing studies, where being able to detect small differences between groups is crucial.

Oberley-Deegan R. CT vs. bioluminescence: A comparison of imaging techniques for orthotopic prostate tumors in mice

Prostate cancer is one of the most diagnosed cancers in men in the United States. In mouse models, orthotopic tumors are favored for their biological relevance and simulation of growth in a microenvironment akin to that found in humans. However, to monitor the disease course, animal models require consistent and noninvasive surveillance. In vivo bioluminescent imaging has become a mainstay imaging modality due to its flexibility and ease of use. However, with some orthotopic prostate tumor models, bioluminescence fails to describe disease progression due to optical scattering and signal attenuation. CT scanning, in addition to its utility in human cancer diagnosis and surveillance, can be applied to mouse models with improved results. However, CT imaging has poor definition when imaging soft tissues and is not routinely used in prostate cancer models. Using an orthotopic prostate cancer model, our results demonstrate that, when compared to bioluminescent imaging, CT imaging correlates more closely to orthotopic prostate tumor growth in mice. Based on the data from this study, we conclude that CT imaging can be used as an alternative to the more commonly used bioluminescent imaging for measuring orthotopic prostate cancer growth over time.

Establishment of an orthotopic prostate cancer xenograft mouse model using microscope-guided orthotopic injection of LNCaP cells into the dorsal lobe of the mouse prostate

Background

Orthotopic LNCaP xenograft mouse models closely mimic the progression of androgen-dependent prostate cancer in humans; however, orthotopic injection of LNCaP cells into the mouse prostate remains a challenge.

Methods

Under the guidance of a stereoscopic microscope, the anatomy of the individual prostate lobes in male Balb/c athymic nude mice was investigated, and LNCaP cells were inoculated into the mouse dorsal prostate (DP) to generate orthotopic tumors that mimicked the pathophysiological process of prostate cancer in humans. Real-time ultrasound imaging was used to monitor orthotopic prostate tumorigenesis, contrast-enhanced ultrasonography (CEUS) was used to characterize tumor angiogenesis, and macroscopic and microscopic characteristics of tumors were described.

Results

The DP had a trigonal bipyramid-shape and were located at the base of the seminal vesicles. After orthotopic inoculation, gray scale ultrasound imaging showed progressive changes in tumor echotexture, shape and location, and tumors tended to protrude into the bladder. After 8 weeks, the tumor take rate was 65% (n = 13/20 mice). On CEUS, signal intensity increased rapidly, peaked, and decreased gradually. Observations of gross specimens showed orthotopic prostate tumors were well circumscribed, round, dark brown, and soft, with a smooth outer surface and a glossy appearance. Microscopically, tumor cells were arranged in acini encircled by fibrous septa with variably thickened walls, mimicking human adenocarcinoma.

Conclusions

This study describes a successful approach to establishing an orthotopic LNCaP xenograft Balb/c athymic nude mouse model. The model requires a thorough understanding of mouse prostate anatomy and proper technique. The model represents a valuable tool for the in vivo study of the biological processes involved in angiogenesis in prostate cancer and preclinical evaluations of novel anti-angiogenic therapies.

Three-dimensional measurement and analysis of benign prostatic hyperplasia

Background

The volume and thickness of intravesical prostatic protrusion and other characteristics of benign prostatic hyperplasia have not been investigated. We determine the effects of age and prostate volume on anatomical features of benign prostatic hyperplasia using three-dimensional measurement in this study.

Methods

This retrospective study included a total of 98 patients with benign prostatic hyperplasia. Three-dimensional models of prostate, central gland, peripheral zone, intravesical prostatic protrusion, prostatic urethra and bladder were reconstructed according to pelvic T2-weighted magnetic resonance imaging of these patients. The models were used to measure the intravesical prostatic protrusion volume, intravesical prostatic protrusion thickness, intravesical prostatic protrusion index, intravesical prostatic protrusion, prostate volume, peripheral zone volume, peripheral zone thickness, peripheral zone index, prostatic urethra thickness, the angle and distance of distal prostatic urethra with regard to coronal plane and sagittal plane and so on.

Results

Intravesical prostatic protrusion volume, intravesical prostatic protrusion thickness and peripheral zone volume of prostate volume >80 mL group were significantly higher than these in prostate volume <80 mL group (P<0.001, 0.01, 0.01, respectively). These parameters significantly increased with age (P<0.001, 0.01, 0.05, respectively). Peripheral zone index was significantly lower of prostate volume >80 mL group than these in prostate volume <80 mL group (P<0.05). Peripheral zone index significantly decreased with age (P<0.01). Intravesical prostatic protrusion index had no significant difference in all age groups. Peripheral zone thickness and prostatic urethra thickness had no significant difference in all groups. The distance and angle of distal prostatic urethra prostatic urethra with regard to coronal plane were significantly higher than these with regard to sagittal plane (both P<0.001).

Conclusions

The rearward slope of the prostatic urethra is greater than the left or right offset during the process of benign prostatic hyperplasia. Three-dimensional measurement provides good supports for further clinical and scientific research.

Macrophage accumulation within coronary arterial wall in diabetic patients with acute coronary syndrome: a study with in-vivo intravascular imaging modalities

Background and aims

Macrophage accumulation in arteriosclerotic plaque of coronary arteries is involved in plaque destabilization. Atherosclerosis has been known to be progressive in patients with type 2 diabetes mellitus (DM). This study compared the features of 3-dimensional (3D) spatial distribution of macrophage accumulation within coronary artery wall between acute coronary syndrome (ACS) patients with DM (n = 20) and those without (non-DM, n = 20) by using intravascular ultrasound (IVUS) and optical coherence tomography (OCT).

Methods

The OCT-derived macrophage accumulation was measured within the proximal left anterior-descending artery. This measurement was performed for the whole vessel segment of interest, higher shear stress region (flow divider side) and lower shear stress region (the opposite side).

Results

Normalized macrophage accumulation per unit length of the whole segment of interest was significantly larger in ACS patients with DM than without. In non-DM patients, macrophage density per IVUS-derived plaque volume was significantly higher in high shear stress region compared to low shear stress region, however, there was no significant difference between the two regions in DM patients. The macrophage density in the low shear stress region was significantly higher in the DM group than in the non-DM group. A multivariate analysis showed that the presence of DM was a major determinant for macrophage distribution.

Conclusions

Macrophage accumulation was more abundant and homogeneous within coronary arterial wall in DM patients with ACS compared to non-DM patients, suggesting that plaque destabilization may occur more widely throughout coronary wall in DM patients.