Journal of Pathology Informatics

TECHNICAL NOTE
Year
: 2016  |  Volume : 7  |  Issue : 1  |  Page : 3-

Oxygen supply maps for hypoxic microenvironment visualization in prostate cancer


Niels J Rupp1, Peter J Schuffler2, Qing Zhong1, Florian Falkner3, Markus Rechsteiner1, Jan H Ruschoff1, Christian Fankhauser1, Matthias Drach1, Remo Largo4, Mathias Tremp5, Cedric Poyet4, Tullio Sulser4, Glen Kristiansen6, Holger Moch1, Joachim Buhmann2, Michael Muntener7, Peter J Wild1,  
1 Institute of Surgical Pathology, University Hospital Zurich, Schmelzbergstrasse 12, 8091 Zurich, Switzerland
2 Department of Computer Science, ETH Zurich, Universitaetstr 6, 8092 Zurich, Switzerland
3 Institute of Pathology, Cantonal Hospital Winterthur, Brauerstrasse 15, 8401 Winterthur, Switzerland
4 Department of Urology, University Hospital Zurich, Rämistrasse 100, 8091 Zurich, Switzerland
5 5Department of Plastic, Reconstructive and Aesthetic Surgery, University Hospital Basel, Spitalstrasse 21, 4031 Basel, Switzerland
6 Institute of Pathology, University Hospital Bonn, Sigmund-Freud-Strasse 25, 53127 Bonn, Germany
7 Department of Urology, City Hospital Triemli, Birmensdorferstrasse 497, 8063 Zurich, Switzerland

Correspondence Address:
Mathias Tremp
5Department of Plastic, Reconstructive and Aesthetic Surgery, University Hospital Basel, Spitalstrasse 21, 4031 Basel,
Switzerland
Peter J Schuffler
Department of Computer Science, ETH Zurich, Universitaetstr 6, 8092 Zurich
Switzerland

Abstract

Background: Intratumoral hypoxia plays an important role with regard to tumor biology and susceptibility to radio. and chemotherapy. For further investigation of hypoxia.related changes, areas of certain hypoxia must be reliably detected within cancer tissues. Pimonidazole, a 2.nitroimindazole, accumulates in hypoxic tissue and can be easily visualized using immunohistochemistry. Materials and Methods: To improve detection of highly hypoxic versus normoxic areas in prostate cancer, immunoreactivity of pimonidazole and a combination of known hypoxia.related proteins was used to create computational oxygen supply maps of prostate cancer. Pimonidazole was intravenously administered before radical prostatectomy in n = 15 patients, using the da Vinci robot.assisted surgical system. Prostatectomy specimens were immediately transferred into buffered formaldehyde, fixed overnight, and completely embedded in paraffin. Pimonidazole accumulation and hypoxia.related protein expression were visualized by immunohistochemistry. Oxygen supply maps were created using the normalized information from pimonidazole and hypoxia.related proteins. Results: Based on pimonidazole staining and other hypoxia.related proteins (osteopontin, hypoxia.inducible factor 1.alpha, and glucose transporter member 1) oxygen supply maps in prostate cancer were created. Overall, oxygen supply maps consisting of information from all hypoxia.related proteins showed high correlation and mutual information to the golden standard of pimonidazole. Here, we describe an improved computer.based ex vivo model for an accurate detection of oxygen supply in human prostate cancer tissue. Conclusions: This platform can be used for precise colocalization of novel candidate hypoxia.related proteins in a representative number of prostate cancer cases, and improve issues of single marker correlations. Furthermore, this study provides a source for further in situ tests and biochemical investigations



How to cite this article:
Rupp NJ, Schuffler PJ, Zhong Q, Falkner F, Rechsteiner M, Ruschoff JH, Fankhauser C, Drach M, Largo R, Tremp M, Poyet C, Sulser T, Kristiansen G, Moch H, Buhmann J, Muntener M, Wild PJ. Oxygen supply maps for hypoxic microenvironment visualization in prostate cancer.J Pathol Inform 2016;7:3-3


How to cite this URL:
Rupp NJ, Schuffler PJ, Zhong Q, Falkner F, Rechsteiner M, Ruschoff JH, Fankhauser C, Drach M, Largo R, Tremp M, Poyet C, Sulser T, Kristiansen G, Moch H, Buhmann J, Muntener M, Wild PJ. Oxygen supply maps for hypoxic microenvironment visualization in prostate cancer. J Pathol Inform [serial online] 2016 [cited 2021 Jun 12 ];7:3-3
Available from: https://www.jpathinformatics.org/text.asp?2016/7/1/3/175376


Full Text

 Introduction



Tumor hypoxia has been shown to drive malignant progression,[1] induce genetic instability,[2] and gene amplification,[3] as well as impair DNA repair mechanisms.[4] In particular, in prostate cancer, hypoxia was identified in vivo[5] and showed a significant association with advanced tumor stage [6] and aggressive disease.[7] Other studies showed an increased resistance to androgen deprivation and radio- and chemotherapy [8],[9],[10] of tumors with large hypoxic regions. To create optical oxygen supply maps, we used a human ex vivo model, based on the compound pimonidazole.[11] Pimonidazole (hypoxyprobe™ -1; Chemicon International, Inc., Billerica, MA, USA), a 2-nitroimidazole, accumulates in vivo in hypoxic tissue (pO2 ≤ 10 mmHg at 37°C) and can be easily visualized in surgical specimens (ex vivo) by immunohistochemical analysis.[12] Pimonidazole is generally used in animal models, pimonidazole-based hypoxia labeling in human tissue samples is rarely performed because of ethical, pharmacological, and legal restrictions. To overcome these limitations, correlations between pimonidazole labeling and superimpositions with other known hypoxia-related proteins, including osteopontin (OPN),[13],[14] hypoxia-inducible factor 1-alpha (HIF1A),[15],[16] and glucose transporter member 1 (GLUT1),[17],[18] were investigated. Here, we describe a new method to reliably detect hypoxic tumor regions that does not employ invasive techniques, to further investigate hypoxia and hypoxia-related markers in prostatectomy specimens.

 Procedure



To verify that pimonidazole serves as a robust marker for hypoxia in prostate cancer cells, we incubated LNCaP cells (American Type Culture Collection, Manassas, VA, USA) under normoxic and hypoxic conditions, with or without pimonidazole. In accordance with the findings of previous studies,[11],[12] we confirmed pimonidazole as a direct marker for hypoxia. Immunocytochemical staining of pimonidazole revealed a clear positivity in LNCaP cells under hypoxic conditions while cells cultured under normoxic conditions were negative for pimonidazole [Figure 1]a.{Figure 1}

After in vivo administration of pimonidazole, following radical prostatectomy, a total of 15 prostatectomy specimens [for cohort information see Supplementary [Table 1] were subjected to immunohistochemical staining for pimonidazole, OPN, GLUT1, and HIF1A [Figure 1]b. Pimonidazole, GLUT1, and OPN showed a medium to strong cytoplasmic overall staining intensity, particularly of cancer tissues. Qualitative analysis of pimonidazole staining showed partial spatial overlapping of all hypoxia markers. A study in advanced head and neck squamous cell carcinoma described the rationale for colocalization of different hypoxia-related proteins with pimonidazole:[19] Individual hypoxia markers were higher expressed in pimonidazole-positive areas. However, the overall single correlation was poor. To this end, we targeted this issue by pooling all available information from hypoxia-related proteins to construct oxygen supply maps.{Table 1}

The staining images for the known hypoxia-related proteins OPN (O), GLUT1 (G), and HIF1A (H) of each case were automatically color corrected, aligned, superimposed, and normalized for the generation of a pseudo-colored oxygen supply map [Figure 1]c, OHG]. First, the original images were white-balanced to remove the grayish background. Second, the tissue regions were automatically identified and rotated, translated, cropped, and rescaled for rough alignment of the tissues to the middle slice. The background was then deleted to remove background artifacts which could disturb the following alignment process. Third, for pixel-wise matching and to conform to morphological changes of the tissues in consecutive slices, we incorporated a nonlinear SIFT flow algorithm [20] (see online methods for detailed description of all steps). Furthermore, an analogous oxygen supply map based on pimonidazole staining was created [Figure 1]c, pimonidazole]. These maps were then normalized by histogram equalization and compared for each case using a dot-wise correlation of both images, which yielded high Spearman correlation coefficients [Figure 1]e and Supplementary [Figure 1]a,[Figure 1]b,[Figure 1]c,[Figure 1]d,[Figure 1]e,[Figure 1]f,[Figure 1]g,[Figure 1]h,[Figure 1]i,[Figure 1]j,[Figure 1]k,[Figure 1]l,[Figure 1]m,[Figure 1]n,[Figure 1]o and mutual information (MI) [Figure 1]f. MI between two images X and Y has been calculated as [Inside:1] where P(x) is the probability of intensity x in the normalized histogram of X and P(x, y) is the probability of x and y in the normalized joint histogram of X and Y. All image processing steps were implemented in MATLAB 2014a, automatically performed and visually approved. A most simple combinatorial information of O, H, and G overlay maps were generated as the mean of individual intensity maps (more sophisticated combinations have not been considered in this study). Pimonidazole compared with an overlay of all three hypoxia markers (OHG) was highly correlative [Spearman correlation coefficient, r = 0.93, MI = 2.45; [Figure 1]d. Comparison of pimonidazole with single markers (O, H, G) and combinatory overlays (OH, OG, HG) also showed high correlation coefficients [Figure 1]e. Only two cases revealed lower correlation coefficients [Supplementary [Table 2]; B12-4671, B12-6064] because of crush artifacts. MI increases significantly in overlay images when combined with two or three markers [Figure 1]f. As previously shown,[11] scant correlations with microvessel density and pimonidazole could be observed in representative overlays of pimonidazole with CD34 immunoreactivity (n = 2, data not shown).{Table 2}

 Conclusion



Here, we introduce a computer-assisted approach to detect oxygen gradients in human prostate cancer tissues by colocalization of the expression of validated hypoxia-related markers compared to intravenously administered pimonidazole. The generated oxygen supply maps can be used to precisely colocalize potential hypoxia-related proteins in a quantitative and pictorial manner and will render compounds, such as pimonidazole, unnecessary in human patients.

Financial Support and Sponsorship

Nil.

Conflicts of Interest

There are no conflicts of interest.

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