N2 laser excited autofluorescence spectroscopy of formalin-fixed human breast tissue

Detecting salivary host and microbiome RNA signature for aiding diagnosis of oral and throat cancer

OBJECTIVE

Oral squamous cell carcinoma (OSCC) and oropharyngeal squamous cell carcinoma (OPSCC) can go undetected resulting in late detection and poor outcomes. We describe the development and validation of CancerDetect for Oral & Throat cancer™ (CDOT), to detect markers of OSCC and/or OPSCC within a high-risk population.

MATERIAL AND METHODS

We collected saliva samples from 1,175 individuals who were 50 years or older, or adults with a tobacco use history. 945 of those were used to train a classifier using machine learning methods, resulting in a salivary microbial and human metatranscriptomic signature. The classifier was then independently validated on the 230 remaining samples prospectively collected and unseen by the classifier, consisting of 20 OSCC (all stages), 76 OPSCC (all stages), and 134 negatives (including 14 pre-malignant).

RESULTS

On the validation cohort, the specificity of the CDOT test was 94 %, sensitivity was 90 % for participants with OSCC, and 84.2 % for participants with OPSCC. Similar classification results were observed among people in early stage (stages I & II) vs late stage (stages III & IV).

CONCLUSIONS

CDOT is a non-invasive test that can be easily administered in dentist offices, primary care centres and specialised cancer clinics for early detection of OPSCC and OSCC. This test, having received FDA's breakthrough designation for accelerated review, has the potential to enable early diagnosis, saving lives and significantly reducing healthcare expenditure.

Formalin fixation and paraffin embedding interfere with the preservation of optical metabolic assessments based on endogenous NAD(P)H and FAD two-photon excited fluorescence

Endogenous NAD(P)H and FAD two-photon excited fluorescence (TPEF) images provide functional metabolic information with high spatial resolution for a wide range of living specimens. Preservation of metabolic function optical metrics upon fixation would facilitate studies which assess the impact of metabolic changes in the context of numerous diseases. However, robust assessments of the impact of formalin fixation, paraffin embedding, and sectioning on the preservation of optical metabolic readouts are lacking. Here, we evaluate intensity and lifetime images at excitation/emission settings optimized for NAD(P)H and FAD TPEF detection from freshly excised murine oral epithelia and corresponding bulk and sectioned fixed tissues. We find that fixation impacts the overall intensity as well as the intensity fluctuations of the images acquired. Accordingly, the depth-dependent variations of the optical redox ratio (defined as FAD/(NAD(P)H + FAD)) across squamous epithelia are not preserved following fixation. This is consistent with significant changes in the 755 nm excited spectra, which reveal broadening upon fixation and additional distortions upon paraffin embedding and sectioning. Analysis of fluorescence lifetime images acquired for excitation/emission settings optimized for NAD(P)H TPEF detection indicate that fixation alters the long lifetime of the observed fluorescence and the long lifetime intensity fraction. These parameters as well as the short TPEF lifetime are significantly modified upon embedding and sectioning. Thus, our studies highlight that the autofluorescence products formed during formalin fixation, paraffin embedding and sectioning overlap highly with NAD(P)H and FAD emission and limit the potential to utilize such tissues to assess metabolic activity.

Formalin fixation and paraffin embedding interfere with preservation of optical metabolic assessments based on endogenous NAD(P)H and FAD two photon excited fluorescence

Endogenous NAD(P)H and FAD two-photon excited fluorescence (TPEF) images provide functional metabolic information with high spatial resolution for a wide range of living specimens. Preservation of metabolic function optical metrics upon fixation would facilitate studies which assess the impact of metabolic changes in the context of numerous diseases. However, robust assessments of the impact of formalin fixation, paraffin embedding, and sectioning on the preservation of optical metabolic readouts are lacking. Here, we evaluate intensity and lifetime images at excitation/emission settings optimized for NAD(P)H and FAD TPEF detection from freshly excised murine oral epithelia and corresponding bulk and sectioned fixed tissues. We find that fixation impacts the overall intensity as well as the intensity fluctuations of the images acquired. Accordingly, the depth-dependent variations of the optical redox ratio (defined as FAD/(NAD(P)H + FAD)) across squamous epithelia are not preserved following fixation. This is consistent with significant changes in the 755 nm excited spectra, which reveal broadening upon fixation and additional distortions upon paraffin embedding and sectioning. Analysis of fluorescence lifetime images acquired for excitation/emission settings optimized for NAD(P)H TPEF detection indicate that fixation alters the long lifetime of the observed fluorescence and the long lifetime intensity fraction. These parameters as well as the short TPEF lifetime are significantly modified upon embedding and sectioning. Thus, our studies highlight that the autofluorescence products formed during formalin fixation, paraffin embedding and sectioning overlap highly with NAD(P)H and FAD emission and limit the potential to utilize such tissues to assess metabolic activity.

Optical characterization of the liver tissue affected by fibrolamellar hepatocellular carcinoma based on internal filters of laser-induced fluorescence

Laser-induced fluorescence (LIF) spectroscopy has recently gained regards for diagnosis of the cancer in various tissues of the human body. This method in its conventional form, when used for assay of highly scattering media, encounters a lot of noise due to multiple scattering and inner filter effects which overshadows the sensitivity and specificity of the method. Here, angular dependence of the LIF spectral shift due to the reabsorption events have been investigated for characterization of the bio-tissues. The aim was to determine the tissue morphological changeovers due to the cancer progression. The assessment of a rare type of the liver cancer i. e. fibrolamellar hepatocellular carcinoma revealed the significant difference in optical anisotropy of the parenchyma and liver tumor. As a result, utilizing LIF spectroscopy as a fast, highly sensitive and easy-to-use method one can evaluate the optical anisotropy for diagnosing tissues during the cancer progression.

Optical Redox Imaging of Fixed Unstained Muscle Slides Reveals Useful Biological Information

PURPOSE

Optical redox imaging (ORI) technique images cellular autofluorescence of nicotinamide adenine dinucleotide (NADH) and oxidized flavoproteins (Fp containing FAD, i.e., flavin adenine dinucleotide). ORI has found wide applications in the study of cellular energetics and metabolism and may potentially assist in disease diagnosis and prognosis. Fixed tissues have been reported to exhibit autofluorescence with similar spectral characteristics to those of NADH and Fp. However, few studies report on quantitative ORI of formalin-fixed paraffin-embedded (FFPE) unstained tissue slides for disease biomarkers. We investigate whether ORI of FFPE unstained skeletal muscle slides may provide relevant quantitative biological information.

PROCEDURES

Living mouse muscle fibers and frozen and FFPE mouse muscle slides were subjected to ORI. Living mouse muscle fibers were imaged ex vivo before and after paraformaldehyde fixation. FFPE muscle slides of three mouse groups (young, mid-age, and muscle-specific overexpression of nicotinamide phosphoribosyltransferase (Nampt) transgenic mid-age) were imaged and compared to detect age-related redox differences.

RESULTS

We observed that living muscle fiber and frozen and FFPE slides all had strong autofluorescence signals in the NADH and Fp channels. Paraformaldehyde fixation resulted in a significant increase in the redox ratio Fp/(NADH + Fp) of muscle fibers. Quantitative image analysis on FFPE unstained slides showed that mid-age gastrocnemius muscles had stronger NADH and Fp signals than young muscles. Gastrocnemius muscles from mid-age Nampt mice had lower NADH compared to age-matched controls, but had higher Fp than young controls. Soleus muscles had the same trend of change and appeared to be more oxidative than gastrocnemius muscles. Differential NADH and Fp signals were found between gastrocnemius and soleus muscles within both mid-aged control and Nampt groups.

CONCLUSION

Aging effect on redox status quantified by ORI of FFPE unstained muscle slides was reported for the first time. Quantitative information from ORI of FFPE unstained slides may be useful for biomedical applications.

Optical redox imaging indices discriminate human breast cancer from normal tissues

Our long-term goal was to investigate the potential of incorporating redox imaging technique as a breast cancer (BC) diagnosis component to increase the positive predictive value of suspicious imaging finding and to reduce unnecessary biopsies and overdiagnosis. We previously found that precancer and cancer tissues in animal models displayed abnormal mitochondrial redox state. We also revealed abnormal mitochondrial redox state in cancerous specimens from three BC patients. Here, we extend our study to include biopsies of 16 patients. Tissue aliquots were collected from both apparently normal and cancerous tissues from the affected cancer-bearing breasts shortly after surgical resection. All specimens were snap-frozen and scanned with the Chance redox scanner, i.e., the three-dimensional cryogenic NADH/Fp (reduced nicotinamide adenine dinucleotide/oxidized flavoproteins) fluorescence imager. We found both Fp and NADH in the cancerous tissues roughly tripled that in the normal tissues ( p < 0.05 ). The redox ratio Fp/(NADH + Fp) was ? 27 % higher in the cancerous tissues ( p < 0.05 ). Additionally, Fp, or NADH, or the redox ratio alone could predict cancer with reasonable sensitivity and specificity. Our findings suggest that the optical redox imaging technique can provide parameters independent of clinical factors for discriminating cancer from noncancer breast tissues in human patients.

Differential diagnosis of breast cancer using quantitative, label-free and molecular vibrational imaging

We present a label-free, chemically-selective, quantitative imaging strategy to identify breast cancer and differentiate its subtypes using coherent anti-Stokes Raman scattering (CARS) microscopy. Human normal breast tissue, benign proliferative, as well as in situ and invasive carcinomas, were imaged ex vivo. Simply by visualizing cellular and tissue features appearing on CARS images, cancerous lesions can be readily separated from normal tissue and benign proliferative lesion. To further distinguish cancer subtypes, quantitative disease-related features, describing the geometry and distribution of cancer cell nuclei, were extracted and applied to a computerized classification system. The results show that in situ carcinoma was successfully distinguished from invasive carcinoma, while invasive ductal carcinoma (IDC) and invasive lobular carcinoma were also distinguished from each other. Furthermore, 80% of intermediate-grade IDC and 85% of high-grade IDC were correctly distinguished from each other. The proposed quantitative CARS imaging method has the potential to enable rapid diagnosis of breast cancer.

Autofluorescent cells in rat brain can be convincing impostors in green fluorescent reporter studies

Cell transplant and gene therapies are promising approaches to many disorders of the nervous system. In studies involving cell transplants to the brain or nervous system, expression of green fluorescent protein (GFP) is commonly used to label cells, allowing their identification and histological assessment even after long post-operative survival times. Techniques employing viral tracing or reporter genes also commonly use GFP to label cells. Here, we document the presence of a subpopulation of green autofluorescent cells in the cortex and hippocampus of formaldehyde fixed, cryosectioned rat brains aged 3-9 months. Using standard microscopic fluorescence imaging techniques, we acquired clear images of green autofluorescent cells, complete with extensive processes, which appear to be well integrated into the host tissue. Treatment of brain sections with sodium borohydride followed by cupric sulfate in ammonium acetate buffer reduced background and cellular autofluorescence throughout sections but, especially in hippocampus, did not eliminate considerable green fluorescence in a subset of neurons. This autofluorescence was weak and would therefore pose a problem only when cells weakly express GFP or when few labeled cells survive. We suggest that investigators be aware of the potential for false positives, especially if the cells expressing GFP are expected to migrate widely from the transplant site. Parallel sections from naïve brains should regularly be processed and imaged alongside experimental brain sections, and anti-GFP immunohistochemistry should be performed to ensure that true GFP+ signals are imaged instead of endogenous autofluorescent neurons.

Autofluorescence of breast tissues: evaluation of discriminating algorithms for diagnosis of normal, benign, and malignant conditions

OBJECTIVE

We evaluated different discriminating algorithms for classifying laser-induced fluorescence spectra of normal, benign, and malignant breast tissues that were obtained with 325-nm excitation.

BACKGROUND DATA

Mammography and histopathology are the conventional gold standard methods of screening and diagnosis of breast cancers, respectively. The former is prone to a high rate of false-positive results and poses the risk of repeated exposure to ionizing radiation, whereas the latter suffers from subjective interpretations of morphological features. Thus the development of a more reliable detection and screening methodology is of great interest to those practicing breast cancer management. Several studies have demonstrated the efficacy of optical spectroscopy in diagnosing cancer and other biomedical applications.

MATERIALS AND METHODS

Autofluorescence spectra of normal, benign, and malignant breast tissues, with 325-nm excitation, were recorded. The data were subjected to diverse discriminating algorithms ranging from intensities and ratios of curve-resolved bands to principal components analysis (PCA)-derived parameters.

RESULTS

Intensity plots of collagen and NADPH, two known fluorescent biomarkers, yielded accurate classification of the different tissue types. PCA was carried out on both unsupervised and supervised methods, and both approaches yielded accurate classification. In the case of the supervised classification, the developed standard sets were verified and evaluated. The limit test approach provided unambiguous and objective classification, and this method also has the advantage of being user-friendly, so untrained personnel can directly compare unknown spectra against standard sets to make diagnoses instantly, objectively, and unambiguously.

CONCLUSION

The results obtained in this study further support the efficacy of 325-nm-induced autofluorescence, and demonstrate the suitability of limit test analysis as a means of objectively and unambiguously classifying breast tissues.

Protein profile study of breast-tissue homogenates by HPLC-LIF

Proteomics is a promising approach for molecular understanding of neoplastic processes including response to treatment. Widely used 2D-gel electrophoresis/Liquid chromatography coupled with mass spectrometry (LC-MS) are time consuming and not cost effective. We have developed a high-sensitivity (femto/subfemtomoles of protein/20 mul) High Performance Liquid Chromatography-Laser Induced Fluorescence HPLC-LIF instrument for studying protein profiles of biological samples. In this study, we have explored the feasibility of classifying breast tissues by multivariate analysis of chromatographic data. We have analyzed 13 normal, 17 malignant, 5 benign and 4 post-treatment breast-tissue homogenates. Data was analyzed by Principal Component Analysis PCA in both unsupervised and supervised modes on derivative and baseline-corrected chromatograms. Our findings suggest that PCA of derivative chromatograms gives better classification. Thus, the HPLC-LIF instrument is not only suitable for generation of chromatographic data using femto/subfemto moles of proteins but the data can also be used for objective diagnosis via multivariate analysis. Prospectively, identified fractions can be collected and analyzed by biochemical and/or MS methods.

Autofluorescence characteristics in human gastric cancer and precancerous tissues

AIM: To analyze the autofluorescence differences between the benign and malignant gastric mucosa.

METHODS: The specimens of gastric cancer and low-grade intraepithelial neoplasia were collected to make frozen sections. The autofluorescence intensity was observed and measured by laser confocal microscopy.

RESULTS: The autofluorescence was mainly located in gastric mucosa and submucosa. In comparison with that in nomal gastric mucosa, the green-red fluorescence intensity in gastric cancer and low-grade intraepithelial neoplasia decreased significantly (1.57 ± 0.69, 2.06 ± 0.51 vs 3.75 ± 1.41; P < 0.01, 0.05). The fluorescence intensity of green wavelength in normal gastric mucosa was significantly higher than that in gastric cancer mucosa, while it was significantly different from that in low-grade intraepithelial neoplasia mucosa.

CONCLUSION: The change of green fluorescence in gastric cancer mucosa may be a marker of malignant lesion.

Three-dimensional investigation and scoring of extracellular matrix remodeling during lung fibrosis using multiphoton microscopy

The organization of collagen during fibrotic processes is poorly characterized because of the lack of appropriate methodologies. Here we show that multimodal multiphoton microscopy provides novel insights into lung fibrosis. We characterize normal and fibrotic pulmonary tissue in the bleomycin model, and show that second-harmonic generation by fibrillar collagen reveals the micrometer-scale three-dimensional spatial distribution of the fibrosis. We find that combined two-photon excited fluorescence and second-harmonic imaging of unstained lung tissue allows separating the inflammatory and fibrotic steps in this pathology, underlining characteristic features of fibroblastic foci in human Idiopathic Pulmonary Fibrosis samples. Finally, we propose phenomenological scores of lung fibrosis and we show that they unambiguously sort out control and treated mice, with a better sensitivity and reproducibility in the subpleural region. These results should be readily generalized to other organs, as an accurate method to assess extracellular matrix remodeling during fibrosis.

Blue-Violet Excited Autofluorescence Spectroscopy and Imaging of Normal and Cancerous Human Bronchial Tissue after Formalin Fixation

Autofluorescence (AF) imaging is a powerful tool for the detection of (pre-)neoplastic lesions in the bronchi. Several endoscopic imaging systems exploit the spectral and intensity contrast of AF between healthy and (pre-)neoplastic bronchial tissues, yet, the mechanisms underlying these contrasts are poorly understood. In this report, the effect of formalin fixation on the human bronchi AF, hence on the contrast, was studied by spectrofluorometric point measurements and DAFE (Diagnostic AutoFluorescence Endoscopy) broad field imaging. Generally, formalin-fixed samples have higher AF intensity than in vivo, whereas the emission spectral shape is similar. Additionally, the spectrofluorometric data showed a moderate decrease of the AF intensity on (pre-)neoplastic lesions relative to the healthy bronchial samples. However, this decrease was lower than that reported from in vivo measurements. Neither spectral measurements nor imaging revealed spectral contrast between healthy bronchial tissue and (pre-)neoplastic lesions in formalin. These results indicate that epithelial thickening and blood supply in the adjacent lamina propria are likely to play a key role in the generation of the AF contrast in bronchial tissues. Our results show that the AF contrast in bronchial tissues was significantly affected by standard, 10% buffered, formalin fixation. Therefore, these samples are not suited to AF contrast studies.

Multi-class classification algorithm for optical diagnosis of oral cancer

We report development of a direct multi-class spectroscopic diagnostic algorithm for discrimination of high-grade cancerous tissue sites from low-grade as well as precancerous and normal squamous tissue sites of human oral cavity. The algorithm was developed making use of the recently formulated theory of total principal component regression (TPCR). The in vivo autofluorescence spectral data acquired from patients screened for neoplasm of oral cavity at the Government Cancer Hospital, Indore, was used to train and validate the algorithm. The diagnostic algorithm based on TPCR was found to provide satisfactory performance in classifying the tissue sites in four different classes - high-grade squamous cell carcinoma, low-grade squamous cell carcinoma, leukoplakia, and normal squamous tissue. The classification accuracy for these four classes was observed to be approximately 94%, 100%, 100% and 91% for the training data set (based on leave-one-out cross-validation), and was approximately 90%, 90%, 85% and 88%, respectively for the corresponding classes for the independent validation data set.