DONSON is pivotal for genome stability and integrity, but its role in cancer development and progression is still underinvestigated. It is an essential replisome component, responsible for replication fork stabilization during the S-phase.3,4 In addition, DONSON plays a critical role in cell-cycle regulation and the DNA damage response pathway (DDR) signaling cascade.5 Chemotherapeutic agents are an important backbone in the therapy of multiple cancers and preferentially attack tumor cells with an increased cell division rate as well as limited DNA damage repair capacity. As DONSON plays a pivotal role in both cellular processes, DNA replication, and maintaining genome stability, it could be an attractive therapeutic target for future therapies. Thus, as DONSON seems to mediate tumor-independent oncogenic properties, we believe that our study could be a starting point for further basic and oncological research on DONSON.
DONSON overexpression was associated with poor survival in 9 of the 30 examined tumor entities. Especially in clear cell renal cell carcinoma (ccRCC), adrenocortical carcinoma, and mesothelioma, DONSON was strongly associated with an unfavorable OS. Further, it has to be mentioned that DONSON overexpression was also associated with unfavorable OS in other frequently occurring tumor entities, such as lung adenocarcinoma or uterine corpus endometrial carcinoma, which is of particular interest as most of these tumors do not share similar phenotypes or phylogenetic features. Of note, although DONSON seems to mediate tumor-independent oncogenic properties, its role in cancer is still widely underinvestigated.
In multivariate Cox regression analyses, we found DONSON to be among the strongest independent predictors of unfavorable OS in the ccRCC cohort (N=533). This prompted us to further explore the role of DONSON in this particular cancer entity. With about 75% ccRCC is the most prevalent histopathological subgroup of renal cell carcinoma (RCC). In the past years, substantial progress has been made in the therapeutic landscape of metastatic ccRCC.6 However, a considerable patient subgroup does not benefit from these novel treatment regimes, which further underlines the indisputable need to further characterize this particular tumor entity.
Notably, DONSON mRNA expression was strongly associated with advanced pathological T-stages, lymphonodal, and distant metastatic spread, known as the critical steps during RCC progression. Concordantly, we were able to validate these results in two further independent cohorts by qPCR on an RCC cDNA cohort as well as by immunohistochemical staining against DONSON on a large RCC tissue microarray. Thus, we could demonstrate that DONSON is an independent predictor of unfavorable survival on both transcriptional and translational levels in three different cohorts, highlighting DONSON as a promising and robust biomarker for risk stratification. To further evaluate the functional role of DONSON, we induced antisense oligonucleotide-mediated knockdowns in established RCC cell culture models (ACHN, Caki1, 769p). Consecutive functional analyses demonstrated that DONSON depletion had an inhibitory effect on the proliferation of Caki1 and 769p in a time-dependent manner over 96 hours post-transfection. Migration capacities were also significantly attenuated by DONSON-depletion. In accordance with our presented data is that similar effects were observed in other RCC cell lines following DONSON-depletion.7 In 786O and A498, the tumor-suppressive miR-101-5p, which negatively regulated DONSON expression, as well as siRNA-mediated DONSON knockdown, also caused cell cycle arrest, apoptosis, and impaired motility.
In total, we were able to associate the widely unknown gene DONSON with poor overall survival in various solid tumors. In particular, we identify DONSON as an interesting biomarker for risk stratification in ccRCC in three independent cohorts and provide further evidence that DONSON is linked to a malignant phenotype in the RCC cell culture model.
Written by: Niklas Klümper, Iulia Blajan, Doris Schmidt, Glen Kristiansen, Marieta Toma, Michael Hölzel, Manuel Ritter, Jörg Ellinger
Department of Urology, University Hospital Bonn, Bonn, Germany; Center for Integrated Oncology, University Hospital Bonn, Bonn, Germany; Institute of Experimental Oncology, University Hospital Bonn, Bonn, Germany. Electronic address: ., Department of Urology, University Hospital Bonn, Bonn, Germany; Center for Integrated Oncology, University Hospital Bonn, Bonn, Germany., Center for Integrated Oncology, University Hospital Bonn, Bonn, Germany; Institute for Pathology, University Hospital Bonn, Bonn, Germany., Center for Integrated Oncology, University Hospital Bonn, Bonn, Germany; Institute of Experimental Oncology, University Hospital Bonn, Bonn, Germany.
- Klümper N, Blajan I, Schmidt D, Kristiansen G, Toma M, Hölzel M, et al. Downstream neighbor of SON (DONSON) is associated with unfavorable survival across diverse cancers with oncogenic properties in clear cell renal cell carcinoma. Transl Oncol. 2020 Aug 14;13(11):100844.
- The Cancer Genome Atlas Research Network, Weinstein JN, Collisson EA, Mills GB, Shaw KRM, Ozenberger BA, et al. The Cancer Genome Atlas Pan-Cancer analysis project. Nat Genet. 2013 Sep 26;45:1113–20.
- Reynolds JJ, Bicknell LS, Carroll P, Higgs MR, Shaheen R, Murray JE, et al. Mutations in DONSON disrupt replication fork stability and cause microcephalic dwarfism. Nat Genet. 2017 Apr;49(4):537–49.
- Zhang J, Bellani MA, James RC, Pokharel D, Zhang Y, Reynolds JJ, et al. DONSON and FANCM associate with different replisomes distinguished by replication timing and chromatin domain. Nat Commun. 2020 Aug 7;11(1):3951.
- Fuchs F, Pau G, Kranz D, Sklyar O, Budjan C, Steinbrink S, et al. Clustering phenotype populations by genome-wide RNAi and multiparametric imaging. Mol Syst Biol. 2010 Jun 8;6:370.
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- Yamada Y, Nohata N, Uchida A, Kato M, Arai T, Moriya S, et al. Replisome genes regulation by antitumor miR-101-5p in clear cell renal cell carcinoma. Cancer Sci. 2020 Jan 23