Time-serial Assessment of Drug Combination Interventions in a Mouse Model of Colorectal Carcinogenesis Using Optical Coherence Tomography.

Optical coherence tomography (OCT) is a high-resolution, nondestructive imaging modality that enables time-serial assessment of adenoma development in the mouse model of colorectal cancer. In this study, OCT was utilized to evaluate the effectiveness of interventions with the experimental antitumor agent α-difluoromethylornithine (DFMO) and a nonsteroidal anti-inflammatory drug sulindac during early [chemoprevention (CP)] and late stages [chemotherapy (CT)] of colon tumorigenesis. Biological endpoints for drug interventions included OCT-generated tumor number and tumor burden. Immunochistochemistry was used to evaluate biochemical endpoints [Ki-67, cleaved caspase-3, cyclooxygenase (COX)-2, ß-catenin]. K-Ras codon 12 mutations were studied with polymerase chain reaction-based technique. We demonstrated that OCT imaging significantly correlated with histological analysis of both tumor number and tumor burden for all experimental groups (P < 0.0001), but allows more accurate and full characterization of tumor number and burden growth rate because of its time-serial, nondestructive nature. DFMO alone or in combination with sulindac suppressed both the tumor number and tumor burden growth rate in the CP setting because of DFMO-mediated decrease in cell proliferation (Ki-67, P < 0.001) and K-RAS mutations frequency (P = 0.04). In the CT setting, sulindac alone and DFMO/sulindac combination were effective in reducing tumor number, but not tumor burden growth rate. A decrease in COX-2 staining in DFMO/sulindac CT groups (COX-2, P < 0.01) confirmed the treatment effect. Use of nondestructive OCT enabled repeated, quantitative evaluation of tumor number and burden, allowing changes in these parameters to be measured during CP and as a result of CT. In conclusion, OCT is a robust minimally invasive method for monitoring colorectal cancer disease and effectiveness of therapies in mouse models.

Dual optical modality endoscopic imaging of cancer development in the mouse colon.

BACKGROUND AND OBJECTIVE: We utilize a miniature, dual-modality endoscope that combines fluorescence-based surface magnifying chromoendoscopy (SMC) and optical coherence tomography (OCT) to follow the anatomical changes that occur during adenoma development in the mouse colon. MATERIALS AND METHODS: Twenty-five mice were treated with the carcinogen azoxymethane (AOM) to induce tumor development in the distal colon, or were treated with saline as control, and were imaged over six months. OCT detects adenoma number with high sensitivity and specificity and can measure lesion size. In methylene blue-lavaged colons, SMC detects changes in the colonic crypts. SMC images of control mouse colons exhibit reticulated patterns of crypts of equal size, forming either a dot or honeycomb pattern. RESULTS: Images of AOM-treated colons show mild crypt irregularities even in grossly normal tissue. Images of small to medium adenoma exhibit larger crypts, more intense signal, and irregular spacing whereas those of large adenoma have heterogeneous, intense signal and loss of crypt structure. CONCLUSIONS: The combination of OCT and SMC permits the detection of neoplastic events from the earliest stages of crypt irregularities before gross tissue changes are noted, through to measuring the growth of protruding adenoma.

In vivo molecular mapping of the tumor microenvironment in an azoxymethane-treated mouse model of colon carcinogenesis.

BACKGROUND AND OBJECTIVE: Development of miniaturized imaging systems with molecular probes enables examination of molecular changes leading to initiation and progression of colorectal cancer in an azoxymethane (AOM)-induced mouse model of the disease. Through improved and novel studies of animal disease models, more effective diagnostic and treatment strategies may be developed for clinical translation. We introduce use of a miniaturized multimodal endoscope with lavage-delivered fluorescent probes to examine dynamic microenvironment changes in an AOM-treated mouse model. STUDY DESIGN/MATERIALS AND METHODS: The endoscope is equipped with optical coherence tomography (OCT) and laser induced fluorescence (LIF) imaging modalities. It is used with Cy5.5-conjugated antibodies to create time-resolved molecular maps of colon carcinogenesis. We monitored in vivo changes in molecular expression over a five month period for four biomarkers: epithelial growth factor receptor (EGFR), transferrin receptor (TfR), transforming growth factor beta 1 (TGFß1), and chemokine (C-X-C motif) receptor 2 (CXCR2). In vivo OCT and LIF images were compared over multiple time points to correlate increases in biomarker expression with adenoma development. RESULTS: This system is uniquely capable of tracking in vivo changes in molecular expression over time. Increased expression of the biomarker panel corresponded to sites of disease and offered predictive utility in highlighting sites of disease prior to detectable structural changes. Biomarker expression also tended to increase with higher tumor burden and growth rate in the colon. CONCLUSION: We can use miniaturized dual modality endoscopes with fluorescent probes to study the tumor microenvironment in developmental animal models of cancer and supplement findings from biopsy and tissue harvesting.

Diagnostic potential of multimodal imaging of ovarian tissue using optical coherence tomography and second-harmonic generation microscopy.

Ovarian cancer is particularly deadly because it is usually diagnosed after it has metastasized. We have previously identified features of ovarian cancer using optical coherence tomography (OCT) and second-harmonic generation (SHG) microscopy (targeting collagen). OCT provides an image of the ovarian microstructure while SHG provides a high-resolution map of collagen fiber bundle arrangement. Here we investigated the diagnostic potential of dual-modality OCT and SHG imaging. We conducted a fully crossed, multi-reader, multi-case study using seven human observers. Each observer classified 44 ex vivo mouse ovaries (16 normal and 28 abnormal) as normal or abnormal from OCT, SHG, and simultaneously viewed, co-registered OCT and SHG images and provided a confidence rating on a six-point scale. We determined the average receiver operating characteristic (ROC) curves, area under the ROC curves (AUC), and other quantitative figures of merit. The results show that OCT has diagnostic potential with an average AUC of 0.91 ± 0.06. The average AUC for SHG was less promising at 0.71 ± 0.13. The average AUC for simultaneous OCT and SHG was not significantly different from OCT alone, possibly due to the limited SHG field of view. The high performance of OCT and co-registered OCT and SHG warrants further investigation.

Feasibility of optical coherence tomography imaging to characterize renal neoplasms: limitations in resolution and depth of penetration.

UNLABELLED: What's known on the subject? and What does the study add? Optical coherence tomography has been used for the diagnosis of retinal disease and has been used experimentally for imaging of vascular plaques, gastrointestinal pathology, bladder cancer, prostate cancer, and recently to examine benign kidney microanatomy. It has not been previously used to image kidney cancer. This study presents the first data on the utility of OCT in the imaging for renal neoplasms. It found that OCT was most successful in distinguishing AML and TCC from normal parenchyma. OCT had more limited success at differentiating oncocytoma. Clear cell tumors and other renal cancer subtypes had a more heterogenous appearance, precluding reliable identification using OCT. The study shows that higher resolution versions of OCT, such as OCM, will be needed to allow optical coherence imaging to reach clinical utility in the assessment of renal neoplasms. OBJECTIVES: • To determine the appearance of normal and neoplastic renal tissue when imaged with optical coherence tomography (OCT). • To preliminarily assess the feasibility of using OCT to differentiate normal and neoplastic renal tissue. PATIENTS AND METHODS: • After radical or partial nephrectomy in 20 subjects, normal renal parenchyma and neoplastic tissue samples were obtained. • The tissue was evaluated with light microscopy and using a bench-top laboratory OCT system with a lateral resolution of 10 µm. • OCT images were compared with histological slides to evaluate the ability of OCT to differentiate renal neoplasms. RESULTS: • Pathological subtypes included eight clear-cell, three papillary and two chromophobe renal carcinomas; two oncocytomas; one angiomyolipoma (AML); two transitional cell carcinomas (TCCs); and one haematoma. • Using OCT, benign renal parenchyma showed recognizable glomeruli and tubules. • TCC had a distinctive appearance on OCT whereas AML showed a unique identifiable signature because of its fat content. Oncocytomas had a lobulated appearance, which appeared subtly different from renal carcinoma. • Renal carcinoma lacked recognizable anatomical elements and had a heterogeneous appearance making differentiation from normal parenchyma at times difficult. • Subtypes of renal cancer appeared to vary on OCT imaging although discrimination was unreliable. CONCLUSIONS: • OCT imaging for renal neoplasms was most successful in distinguishing AML and TCC from normal parenchyma and malignant tumours. Oncocytoma differed subtly from renal carcinoma, making distinction more challenging. • Clear-cell tumours and other renal carcinoma subtypes had a heterogeneous appearance on OCT, which precluded reliable differentiation from normal parenchyma and between renal carcinoma subtypes. • Higher resolution versions of optical coherence imaging, such as optical coherence microscopy, will be necessary to achieve clinical utility.