DNA damage assessment for precision medicine: an emerging diagnostic option

DNA damage analysis is an evolving diagnostic field, particularly for precision medicine, that opens new avenues for the use of potential biomarkers such as the phosphorylated histone 2Ax (γH2AX), 8-hydroxy-2'-deoxyguanosine (8-OHdG) or 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) (1-3). In fact, innovative diagnostic techniques have moved into the limelight that make it possible to analyze a plethora of new potential biomarkers, which requires the awareness of experts in laboratory medicine and beyond. Despite this enormous scientific progress, the number of novel biomarkers introduced into routine clinical diagnostics is still modest (4). In this focused issue, such a biomarker-based stratification of patients into cohorts with a distinct disease predisposition enabling early and targeted prevention or that benefit from a tailored therapy is discussed. Thus, Reddig et al. highlight the role of γH2AX as a promising marker for DNA double strand breaks (DSB) in the context of precision medicine in a comprehensive review (5). The authors compare γH2AX with other emerging biomarkers for genotoxicity analysis and review the different methods, characteristics, technical advances and potential clinical applications thereof. Obviously, one of the most intriguing changes has evolved in the field of precision cancer therapy. Though tumor heterogeneity is considered a major obstacle for precision medicine, much progress, nevertheless, has been achieved in treating cancer patients based on individual diagnostic profiles (6). In order to replace the traditional, uniform classification and treatment of tumor disorder, a paradigm shift seems to be taking place in which the high heterogeneity among tumors is addressed by a more comprehensive biomarker-based stratification of patients within the framework of precision medicine. Hence, Reddig et al. provide an overview of the applicability of genotoxicity methods in that context and underline the benefits of fluorescence microscopy with its superior sensitivity for γH2AX foci counting in the case of DSB assessment in a comparative analysis with other γH2AX-detecting methods (5,7). In another review, Ruhe et al. elaborate on 13 biomarkers including DNA repair response markers that have been described in the context of diagnostic tests, clinical studies or basic research of solid and hematological malignancies (8). In particular, the authors highlight markers of diffuse large B-cell lymphoma being one of the most aggressive forms of non-Hodgkin’s lymphoma diagnosed in more than 50% of lymphoma patients over the age of 65 (9). They conclude that a broad range of biomarkers would be required to enable complete and early detection of oncological illnesses, which requires a multiplex diagnostic methodology.

The need for readily accessible patient material for such diagnostic approaches is addressed by Sowa et al., who demonstrate the use of capillary peripheral blood mononuclear cells as a possible substrate for the automated detection of γH2AX foci (10). The authors underline the benefits of capillary puncture in contrast to venipuncture for the collection of blood specimens especially for pediatric and multi-morbid patients. Thus, this new approach could facilitate the planning of clinical trials or experimental settings.

As currently commonly accepted, automation and standardization are urgently required for the predominantly subjective genotoxicity tests, and the initiatives related to the later ones are discussed (5,11-13). The development of automated versions of these methodologies, especially with regard to the DSB analysis by γH2AX foci counting are major topics of this focused issue. The use of digital fluorescence and emerging Bioimage Informatics Tools are discussed in length by Schneider et al. in this context (14). The authors give an overview of open source image processing software packages such as the graphical user interfaces CellProfiler, Icy, ImageJ/Fiji and FindFoci which are widely used for γH2AX foci counting currently. Moreover, software packages such as CellProfiler and Icy that can obtain high-content information on biomarkers through multiparametric analyses, as well as R and Python are described using examples of custom-made solutions.

Apart from cancer, DNA damage analysis might be a useful diagnostic tool for metabolic illnesses. In this issue, Lippi et al. report an interesting example of physical exercise as an essential part in prevention and therapeutic management of subjects with type 1 and 2 diabetes mellitus (15). The authors investigated the burden of DNA injury after middle-distance endurance running in diabetic subjects and concluded that the extent of DNA damage in diabetics engaged in middle-distance running was not significantly different from that observed in euglycemic subjects. It is noteworthy that DNA damage analysis by γH2AX foci counting was reported as a useful marker for strenuous exercise recently (16).

Another set of biomarkers used for the assessment of oxidative stress leading to the accumulation of reactive oxygen species (ROS) is discussed by Korkmaz et al. in this focused issue (17). It is a well-known fact that ROS can result in structural cellular and/or genetic changes modulating essential triggers of tumor formation, especially at the initial steps of carcinogenesis (18). Both 8-OHdG and 8-oxodG are the most frequently observed single nucleotide-base lesions and thus potential biomarkers of oxidative DNA damage (19). Novel techniques for 8-OHdG detection in the connection with oxidatively-generated clustered DNA lesions are emerging, enabling the application of automated image analysis at a single-cell level (17,20,21).

Altogether, advances in DNA damage analysis and the emergence of corresponding novel biomarkers is a rapidly developing field with great potential for its application in precision medicine (22). Laboratory experts can expect further progress in this area in the near future and should follow the upcoming achievements closely.

Acknowledgments

Funding: None.

Footnote

Provenance and Peer Review: This article was commissioned by the editorial office, Journal of Laboratory and Precision Medicine for the series “DNA Damage Assessment for Precision Medicine”. The article did not undergo external peer review.

Conflicts of Interest: The series “DNA Damage Assessment for Precision Medicine” was commissioned by the editorial office without any funding or sponsorship. Dirk Roggenbuck served as an unpaid Guest Editor of the series and serves as an unpaid editorial board member of Journal of Laboratory and Precision Medicine from August 2017 to July 2019. Dirk Roggenbuck is a shareholder of GA Generic Assays GmbH and MEDIPAN GmbH being diagnostic manufacturers.

Ethical Statement: The author is accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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Dirk Roggenbuck