Proteomic comparison between different tissue preservation methods for identification of promising biomarkers of urothelial bladder cancer

Samples in biobanks are generally preserved by formalin-fixation and paraffin-embedding (FFPE) and/or optimal cutting temperature compound (OCT)-embedding and subsequently frozen. Mass spectrometry (MS)-based analysis of these samples is now available via developed protocols, however, the differences in results with respect to preservation methods needs further investigation. Here we use bladder urothelial carcinoma tissue of two different tumor stages (Ta/T1—non-muscle invasive bladder cancer (NMIBC), and T2/T3—muscle invasive bladder cancer (MIBC)) which, upon sampling, were divided and preserved by FFPE and OCT. Samples were parallel processed from the two methods and proteins were analyzed with label-free quantitative MS. Over 700 and 1200 proteins were quantified in FFPE and OCT samples, respectively. Multivariate analysis indicates that the preservation method is the main source of variation, but also tumors of different stages could be differentiated. Proteins involved in mitochondrial function were overrepresented in OCT data but missing in the FFPE data, indicating that these proteins are not well preserved by FFPE. Concordant results for proteins such as HMGCS2 (uniquely quantified in Ta/T1 tumors), and LGALS1, ANXA5 and plastin (upregulated in T2/T3 tumors) were observed in both FFPE and OCT data, which supports the use of MS technology for biobank samples and encourages the further evaluation of these proteins as biomarkers.

Authentication of In Situ Measurements for Thoracic Aortic Aneurysms in Mice

Aortic diameter is a standard parameter for defining disease severity of thoracic aortic aneurysms. In mouse studies, aortic diameters can be measured directly in situ, but this approach has the potential confounder of underestimation due to the absence of physiological arterial pressure. In the present study, we developed an in situ approach for authentic aortic measurements. Thoracic aortic aneurysms were induced by β-aminopropionitrile (BAPN, 0.5% wt/vol) administration in 4-week-old male C57BL/6J mice. Ultrasonography was performed to examine aortic dimensions, and mice with thoracic aortic dilatations were terminated subsequently. After saline perfusion through the left ventricle, periaortic tissues were removed to expose thoracic aortas. Optimal cutting temperature (OCT) compound was injected via the left ventricle to maintain aortic patency. In situ aortic images were captured pre- and post-OCT injection. In mice with severe thoracic aortic aneurysms, smaller aortic diameters were observed prior to OCT injection compared to ultrasound measurements, while aortic diameters in situ after OCT were comparable to diameters measured using ultrasound. Immunostaining for CD31 revealed that endothelial cells were preserved in the intima after OCT injection, indicating that OCT injection does not cause endothelial damage. In conclusion, in situ imaging with OCT injection provides authentic aortic measurements without overt aortic damage in mice with thoracic aortic aneurysms.

Optimal cutting temperature medium embedding and cryostat sectioning are valid for cardiac myofilament function assessment

Myocardial tissue in optimal cutting temperature (OCT) fixation and cryostat sectioning was tested as a means of storing and preparing tissue for myofilament function analysis in relation to conventional liquid nitrogen freezing and dissection. Actomyosin interaction, Ca2+ force activation, and passive compliance were tested. The study concluded that OCT storage and cryostat sectioning do not interfere with the actomyosin cross-bridge dynamics or Ca2+ activation but that absolute tension values suffer and may not be investigated by this method.

A simple method for sphingolipid analysis of tissues embedded in optimal cutting temperature compound

MS-assisted lipidomic tissue analysis is a valuable tool to assess sphingolipid metabolism dysfunction in disease. These analyses can reveal potential pharmacological targets or direct mechanistic studies to better understand the molecular underpinnings and influence of sphingolipid metabolism alterations on disease etiology. But procuring sufficient human tissues for adequately powered studies can be challenging. Therefore, biorepositories, which hold large collections of cryopreserved human tissues, are an ideal retrospective source of specimens. However, this resource has been vastly underutilized by lipid biologists, as the components of OCT compound used in cryopreservation are incompatible with MS analyses. Here, we report results indicating that OCT compound also interferes with protein quantification assays, and that the presence of OCT compound impacts the quantification of extracted sphingolipids by LC-ESI-MS/MS. We developed and validated a simple and inexpensive method that removes OCT compound from OCT compound-embedded tissues. Our results indicate that removal of OCT compound from cryopreserved tissues does not significantly affect the accuracy of sphingolipid measurements with LC-ESI-MS/MS. We used the validated method to analyze sphingolipid alterations in tumors compared with normal adjacent uninvolved lung tissues from individuals with lung cancer and to determine the long-term stability of sphingolipids in OCT compound-cryopreserved normal lung tissues. We show that lung cancer tumors have significantly altered sphingolipid profiles and that sphingolipids are stable for up to 16 years in OCT compound-cryopreserved normal lung tissues. This validated sphingolipidomic OCT compound-removal protocol should be a valuable addition to the lipid biologist’s toolbox.

SAT-553 Use of Optimal Cutting Temperature Compound (OCT)-Embedded Adrenal Tumor Tissue for Intratumoral Steroid Hormone Profiling

Background: Primary aldosteronism (PA) is the most common cause of secondary hypertension, accounting for 5-8% of all hypertension. PA is most commonly attributed to an aldosterone-producing adenoma (APA) or to bilateral hyperaldosteronism (BHA). Mutations in the inward-rectifying K+ channel (mKCNJ5), which increase autonomous aldosterone production, are most frequently detected in APAs. APAs with mKCNJ5 display aberrant expression of aldosterone synthase (CYP11B2) and 17α-hydroxylase (CYP17A1), which are involved in aldosterone and cortisol synthesis, respectively. Co-expression of these enzymes results in the production of a set of “hybrid” steroids, which have been proposed as serum biomarkers. The relative production of hybrid steroids in adrenal tumors vs. adjacent normal adrenal (NA) tissue has not been investigated. Objectives: To determine the utility of OCT-embedded adrenal tumor tissue for steroid profiling. To use immunohistochemistry (IHC)-guided OCT tumor capture for intratumoral hybrid steroid profiling in mKCNJ5 APA and NA tissue. Methods: OCT-embedded adrenal tissue from 9 patients (8 women, Age 45.9 ± 3.3 years) with APAs harboring known KCNJ5 mutations were used for the study. Where available OCT-embedded normal adrenal (NA) tissue adjacent to APAs were used as controls (n=4). IHC was performed for CYP11B2 and CYP17A1 on OCT tissue allowing guided APA capture from serial sections. Steroids were extracted from APA and adjacent NA tissue, and quantified by liquid chromatography/tandem mass spectrometry. Steroids measured were normalized to the protein content of the extracted tissue. Results: Compared to NA, APA tissue demonstrated 23-, 5.6- and 6.4-fold higher levels of aldosterone, 11-deoxycorticosterone, and 18-hydroxycorticosterone, respectively (P<0.05). In addition, the “hybrid” steroid products, 18-oxocortisol and 18-hydroxycortisol, were significantly elevated in APA vs. NA (P<0.01). Conversely, the adrenal androgens dehydroepiandrosterone and 11-hydroxyandrostenedione were lower in APA as compared with NA (P<0.05). All mKCNJ5 APAs were also found to co-express CYP11B2 and CYP17A1. Conclusion: IHC-guided mKCNJ5 APA capture and steroid extraction identified a distinct intratumoral hybrid steroid signature that associated with co-expression of CYP11B2 and CYP17A1.These findings also demonstrate that OCT-embedded tissue can be used to accurately define intra-tissue steroid profiles, which will have application for steroid-producing and steroid-responsive tumors.