Polarization-gated Spectroscopy Research Articles

Early increase in blood supply (EIBS) is associated with tumor risk in the Azoxymethane model of colon cancer

BackgroundThe present study aimed to investigate the role of blood supply in early tumorigenesis in colorectal cancer. We leveraged the renin angiotensin system (RAS) to alter colonic blood supply and determine the effect on tumor initiation and progression.MethodsTo test the effect of blood supply on tumorigenesis, 53 male A/J mice were randomly assigned to one of three RAS modulation groups and one of two AOM treatments. The RAS modulation groups were I) water (RAS-unmodulated) as a control group, II) angiotensin-II and III) the angiotensin receptor blocker, Losartan. The mice in each group were then randomly split into either the saline control condition or the AOM-treated condition in which tumors were induced with a standard protocol of serial azoxymethane (AOM) injections. To monitor microvascular changes in the rectal mucosa during the study, we used confocal laser endomicroscopy (CLE) with FITC-Dextran for in-vivo imaging of vessels and polarization-gated spectroscopy (PGS) to quantify rectal hemoglobin concentration ([Hb]) and blood vessel radius (BVR).ResultsAt 12 weeks post-AOM injections and before tumor formation, CLE images revealed many traditional hallmarks of angiogenesis including vessel dilation, loss of co-planarity, irregularity, and vessel sprouting in the pericryptal capillaries of the rectal mucosa in AOM-Water tumor bearing mice. PGS measurements at the same time-point showed increased rectal [Hb] and decreased BVR. At later time points, CLE images showed pronounced angiogenic features including irregular networks throughout the colon. Notably, the AOM-Losartan mice had significantly lower tumor multiplicity and did not exhibit the same angiogenic features observed with CLE, or the increase in [Hb] or decrease in BVR measured with PGS. The AOM-AngII mice did not have any significant trends.ConclusionIn-vivo PGS measurements of rectal colonic blood supply as well as CLE imaging revealed angiogenic disruptions to the capillary network prior to tumor formation. Losartan demonstrated an effective way to mitigate the changes to blood supply during tumorigenesis and reduce tumor multiplicity. These effects can be used in future studies to understand the early vessel changes observed.

Su2032 Differential Early Metabolic Changes in Colon Carcinogenesis for Health Disparities: Physiological and Molecular Evidence

Background: Epidemiologic data unequivocally demonstrate a 23% higher incidence in colonic neoplasia in blacks with concomitant 50% increase in colorectal (CRC) mortality compared to whites. However, the biological basis for this has been largely unexplored. The role of early metabolic alterations such as the Warburg effect is clearly appreciated in established cancers however it is not known in early neoplasia. Given that metabolic CRC risk factors (i.e. diabetes, obesity) disproportionately impact blacks, we used polarizationgated spectroscopy (PGS) to examine the microvascular blood flow as a surrogate of metabolic dysregulation in early neoplastic transformation. To explore potential molecular correlates behind PGS, we chose to investigate two master regulators of early CRC, Sirt 6 and Hif-1α, which couple metabolic dysregulation (Sebastian et al., Cell 2012). Methods: For this study we used a fiberoptic PGS probe to measure oxyhemoglobin (OHb) and deoxyhemoglobin (DHb) within rectal microvasculature in 80 prospectively recruited black patients. We compared results to a previous cohort of ~120 white patients in the superficial mucosa (~150μm). We assessed Sirt 6 and Hif-1α expression from rectal biopsies of 80 patients by RT-PCR. Field carcinogenesis was defined as presence of molecular changes in advanced adenomas (AAs) evident elsewhere in the colon. Results: In blacks, there was a striking induction in DHb (220% of control) with OHb being more muted (150% of control). Thus, from a diagnostic perspective, DHb appears to be a stronger marker than OHb. This was in contradistinction to whites, where only OHb was statistically significant with diagnostic potential. The molecular basis of this finding was supported by metabolic regulators, Sirt 6 and Hif-1α, in blacks. The reduced expression of Sirt6 mRNA (Figure 1) appears to give a marked induction of Hif-1α mRNA(Figure 2). Conclusions: We demonstrate herein, for the first time, that there differential metabolic changes in blacks than whites. This was supported physiologically with differential diagnostic effects of DHb versus OHb which implies altered oxygen extraction consonant with Warburg effect. The molecular underpinnings may be related to the key metabolic sensor, Sirt 6 through control of Hif-1α. This work provides potentially important insights into the pathogenesis of CRC disparities and demonstrates the power of optical spectroscopy provide physiological common denominator of the myriad of complex molecular alterations in early carcinogenesis.

Polarization-gated Spectroscopy (PGS) to Detect Tissue Microstructural Alterations in Esophageal Field Carcinogenesis

Polarization-gated Spectroscopy (PGS) to Detect Tissue Microstructural Alterations in Esophageal Field Carcinogenesis

Tu1965 Polarization Gating Spectroscopy to Detect Pancreas Cancer - Final Results of the Pilot Study

BACKGROUND/AIMS: Three-dimensional endomicroscopy using optical coherence tomography (3D-OCT) provides cross sectional and volumetric images of tissue microstructure without requiring extrinsic contrast agents. We recently described "buried" Barrett's esophagus (BE) glands and ability to predict the efficacy of radio frequency ablation (RFA) using this uniquely suited imaging modality. In this study, we demonstrate a processing method that provides enhanced contrast to 3D-OCT images by analysing the variations in the intensity profile of the structural images. The processed 3D-OCT images improve the identification and classification of subsurface tissue architectures. METHODS: The study was performed at the VA Boston Healthcare System (VABHS) with the study protocol approved by the VABHS, Harvard Medical School and M.I.T. The analysis method calculates the normalized gradient of the local intensity profile of 3D-OCT images and overlays the processing result onto the original intensity image in a Hue-Saturation-Value (HSV) color space. Images acquired from upper esophagus of normal and BE patients undergoing endoscopic surveillance are analysed with the new processing method. RESULTS: 3D-OCT intensity images (Fig. 1(A, C), and the overlay images derived from the intensity analysis (Fig. 1(B, D)) from endoscopically normal-appearing (A and B) and Barrett's (C and D) esophagus demonstrate the ability of the new analysis method to enhance the contrast of the 3D-OCT images. Consistent with characteristic features of normal esophagus, intensity image in Fig. 1(A) shows squamous epithelium (SE) and lamina propria/muscularis mucosa (LP/MM) layers. These two layers are better delineated in the enhanced HSV image shown in Fig. 1(B), where the SE layer appears with the tones blue and the LP/MM layers appears with the tones of green and red. Application of this method for 3D-OCT images taken from the BE patient showed disruption of this layered architecture (Fig. 1(D)). Moreover, images taken from BE patients immediately after RFA showed enhanced contrast for the residual burned tissue and the underlying subsurface structures, showing that the enhanced contrast might also be useful in assessing RFA treatment response and efficacy. CONCLUSIONS: This study demonstrates that by analysing the variations of the local intensity profile it is possible to enhance the contrast of conventional 3D-OCT images without the use of extrinsic contrast agents. The application of this method should aid the identification of fine subsurface structures and possibly improve the diagnostic capability of the 3D-OCT. ACKNOWLEDGEMENT: NIH 5R01-CA075289-14, K99-EB010071-01A1, AFOSR FA9550-07-1-0101, and FA9550-10-1-0551.

722 Polarization Gating Spectroscopy of Apparently Normal Duodenal Mucosa to Detect Pancreatic Cancer

722 Polarization Gating Spectroscopy of Apparently Normal Duodenal Mucosa to Detect Pancreatic Cancer

In vivo measurement of the shape of the tissue-refractive-index correlation function and its applicationto detection of colorectal field carcinogenesis

Polarization-gated spectroscopy is an established method to depth-selectively interrogate the structural properties of biological tissue. We employ this method in vivo in the azoxymethane (AOM)-treated rat model to monitor the morphological changes that occur in the field of a tumor during early carcinogenesis. The results demonstrate a statistically significant change in the shape of the refractive-index correlation function for AOM-treated rats versus saline-treated controls. Since refractive index is linearly proportional to mass density, these refractive-index changes can be directly linked to alterations in the spatial distribution patterns of macromolecular density. Furthermore, we found that alterations in the shape of the refractive-index correlation function shape were an indicator of both present and future risk of tumor development. These results suggest that noninvasive measurement of the shape of the refractive-index correlation function could be a promising marker of early cancer development.

Analysis of pressure, angle and temporal effects on tissue optical properties from polarization-gated spectroscopic probe measurements

Noninvasive optical techniques for tissue characterization, in particular, light scattering properties and blood supply quantification of mucosa, is useful in a wide variety of applications. However, fiber-optic probes that require contact with the tissue surface can present a challenging problem in the variability of in vivo measurements due the nature of interactions, for example affects due to variations in pressure applied to the probe tip. We present an in vivo evaluation of pressure, angle, and temporal effects on tissue properties for polarization-gated spectroscopy at superficial depths (within 100 to 200 microns of tissue surface) for oral mucosa.

Optical Measurement of Rectal Microvasculature as an Adjunct to Flexible Sigmoidosocopy: Gender-Specific Implications

Flexible sigmoidoscopy is a robust, clinically validated, and widely available colorectal cancer screening technique that is currently sanctioned by major guideline organizations. Given that endoscopic visualization is generally limited to the distal third of the colon and women tend to have a proclivity for proximal lesions, the flexible sigmoidoscopy performance is markedly inferior in women than in men. Our group has shown that by using a novel light-scattering approach, we were able to detect an early increase in blood supply (EIBS) in the distal colonic mucosa, which served as a marker of field carcinogenesis and, hence, proximal neoplasia. Therefore, we sought to ascertain whether rectal EIBS would improve flexible sigmoidoscopy, especially in women. A polarization-gated spectroscopy fiber-optic probe was used to assess EIBS in the endoscopically normal rectum (n = 366). When compared with gender-matched neoplasia-free controls, females with advanced proximal neoplasia (n = 10) had a robust (60%; P = 0.002) increase in rectal mucosal oxyhemoglobin content whereas the effect size in males was less marked (33%; P = 0.052). In women, addition of rectal oxyhemoglobin tripled the sensitivity for advanced neoplasia over flexible sigmoidoscopy alone. Indeed, the performance characteristics seemed to be excellent (sensitivity, 100%; specificity, 76.8%; positive predictive value, 32.6%; and negative predictive value, 100%). A variety of nonneoplastic factors were assessed and did not confound the relationship between rectal EIBS and advanced neoplasia. Therefore, using rectal EIBS in combination with flexible sigmoidoscopy mitigated the gender gap and may allow flexible sigmoidoscopy to be considered as a viable colorectal cancer screening test in women.

Rectal Mucosal Microvascular Blood Supply Increase Is Associated with Colonic Neoplasia

Endoscopic examination has proven effective in both detecting and preventing colorectal cancer; however, only about a quarter of eligible patients undergo screening. Even if the compliance rate increased, limited endoscopic capacity and cost would be prohibitive. There is a need for an accurate method to target colonoscopy to those most at risk of harboring colonic neoplasia. Exploiting field carcinogenesis seems to be a promising avenue. Our group recently reported that an early increase in blood supply (EIBS) is a reliable marker of field carcinogenesis in experimental models. We now investigate whether in situ detection of EIBS in the rectum can predict neoplasia elsewhere in the colon. We developed a novel polarization-gated spectroscopy fiber-optic probe that allows depth-selective interrogation of microvascular blood content. Using the probe, we examined the blood content in vivo from the rectal mucosa of 216 patients undergoing screening colonoscopy. Microvascular blood content was increased by approximately 50% in the endoscopically normal rectal mucosa of patients harboring advanced adenomas when compared with neoplasia-free patients irrespective of lesion location. Demographic factors and nonneoplastic lesions did not confound this observation. Logistic regression using mucosal oxyhemoglobin concentration and patient age resulted in a sensitivity of 83%, a specificity of 82%, and an area under the receiver operating characteristic curve of 0.88 for the detection of advanced adenomas. Increased microvascular blood supply in the normal rectal mucosa is associated with the presence of clinically significant neoplasia elsewhere in the colon, supporting the development of rectal EIBS as a colon cancer risk-stratification tool.

Resonance energy transfer and ligand binding studies on pH-induced folded states of human serum albumin

Human serum albumin (HSA) is a very important transporter protein in the circulatory system. It is a multi-domain binding protein, which binds a wide variety of ligands in its multiple binding sites and aids in transport, distribution and metabolism of many endogenous and exogenous ligands. With change in pH, HSA is known to undergo conformational transformation, which is very essential for picking up and releasing them at sites of differing pH inside physiological system. Hence, the characterization of ligand binding to these pH-induced conformers is extremely important. We have explored binding interaction of a ligand protoporphyrin IX (PPIX), which is demonstrated (X-ray crystallography) to reside in domain-IB at the various pH-induced folded states of HSA. The ligand PPIX is found to remain attached to all the HSA conformers which offers an opportunity to use Förster’s resonance energy transfer (FRET) between an intrinsic donor fluorophore (Trp214) located in domain-IIA to the acceptor ligand PPIX to characterize the inter-domain separation between IB and IIA. Additionally FRET between an extrinsic fluorophore 2- p-toluidinylnaphthalene-6-sulfonate (TNS) located in domain-IIIA and PPIX is also undertaken to quantify the inter-domain separation between IB and IIIA. Circular dichroism (CD) and dynamic light scattering (DLS) studies have been done in conjunction with picosecond time resolved fluorescence and polarization-gated spectroscopy to determine, respectively, the secondary and tertiary structures of various pH-induced folded states of the protein. Severe structural perturbation including swelling of the protein is observed in the low pH-induced conformer of HSA as evidenced from all the techniques used.