Redox regulation of the stability of the SUMO protease SENP3 via interactions with CHIP and Hsp90SENP3 was recently implicated as redox sensor affecting hypoxia-inducible factor-1-dependent transcription under conditions of mild oxidative stress. In a novel mechanism, the chaperone Hsp90 selectively stabilizes oxidized SENP3 by protecting it from ubiquitination mediated by the co-chaperone CHIP.

Small ubiquitin-like modifier (SUMO) 2/3 is known to conjugate to substrates in response to a variety of cellular stresses. However, whether and how SUMO2/3-specific proteases are involved in de-conjugation under cell stress is unclear. Here, we show that low doses of hydrogen peroxide (H 2 O 2 ) induce an increase of the SENP3 protein, which removes SUMO2/3 from promyelocytic leukemia (PML). Low dose H 2 O 2 causes SENP3 to co-localize with PML bodies and reduces the number of PML bodies in a SENP3-dependent manner. Furthermore, de-conjugation of SUMO2/3 from PML is responsible for the accelerated cell proliferation caused by low dose H 2 O 2 . Knocking down PML promotes basal cell proliferation as expected. This can be reversed by reconstitution with wild-type PML but not its mutant lacking SUMOylation, indicating that only the SUMOylated PML can play an inhibitory role for cell proliferation. Thus, SENP3 appears to be a key mediator in mild oxidative stress-induced cell proliferation via regulation of the SUMOylation status of PML. Furthermore, SENP3 is over-accumulated in a variety of primary human cancers including colon adenocarcinoma in which PML is hypo-SUMOylated. These results reveal an important role of SENP3 and the SUMOylation status of PML in the regulation of cell proliferation under oxidative stress.

Intracellular reactive oxygen species (ROS) are known to regulate apoptosis. Activation of caspase-9, the initial caspase in the mitochondrial apoptotic cascade, is closely associated with ROS, but it is unclear whether ROS regulate caspase-9 via direct oxidative modification. The present study aims to elucidate the molecular mechanisms by which ROS mediate caspase-9 activation. Our results show that the cellular oxidative state facilitates caspase-9 activation. Hydrogen peroxide treatment causes the activation of caspase-9 and apoptosis, and promotes an interaction between caspase-9 and apoptotic protease-activating factor 1 (Apaf-1) via disulfide formation. In addition, in an in vitro mitochondria-free system, the thiol-oxidant diamide promotes auto-cleavage of caspase-9 and the caspase-9/ Apaf-1 interaction by facilitating the formation of disulfide-linked complexes. Finally, a point mutation at C403 of caspase-9 impairs both H 2 O 2 -promoted caspase-9 activation and interaction with Apaf-1 through the abolition of disulfide formation. The association between cytochrome c and the C403S mutant is significantly weaker than that between cytochrome c and wild-type caspase-9, indicating that oxidative modification of caspase-9 contributes to apoptosome formation under oxidative stress. Taken together, oxidative modification of caspase-9 by ROS can mediate its interaction with Apaf-1, and can thus promote its auto-cleavage and activation. This mechanism may facilitate apoptosome formation and caspase-9 activation under oxidative stress.

Introduction: cfDNA (circulating cell-free DNA), short DNA fragments shredded from dying normal and tumor cells, has been proved capable of serving as molecular biomarkers for clinical decision making, including but not limit to tumor diagnosis, treatment and monitoring. Urine, by its non-invasive nature and unique biological characteristics, is far superior comparing to other liquid biopsy specimens, such as blood and cerebrospinal fluid, and has broad clinical implications for genitourinary cancers. The challenge for urine cfDNA test, is the instability of cfDNA, caused by nuclease, high content of urea, and contamination from genomic DNA released from nucleated cells and microbials in urine. Here, we have developed a robust and user friendly urine preservative collection Kit to maintain integrity of cfDNA in urine and to facilitate transportation of urinary samples to clinical laboratory. Methods: Urine samples from 5 donors collected using the developed urine collection kit were tested after incubation under 4°C and 37°C, mimicking extreme storage or transporting environments, and were compared to untreated urine and treated urine by another commercial preserve buffer. cfDNA was extracted after incubation of 0, 4, 7 days and then quantified by ddPCR with 3 markers: EGFR as an endogenous DNA marker, PSA (synthetic oligos containing intron-deleted sequence, pre-incubation spike-in) as an exogenous DNA marker, ARv7 (synthetic oligos containing intron-deleted sequence, post-incubation spike-in) as an inner control for the extraction and detection assays. Results While untreated urine showed significant decrease after incubation under 37°C, cfDNA derived from urine stored in developed urine collection tubes remained stable till day 7. There is no significant change on normalized copies of EGFR and PSA in the treated urine samples under 4°C for up to 7 days. Conclusion: the developed Urine Collection Kit demonstrated great urine cfDNA preserving capacity under different temperatures for at least 7 days, on par with commercially available preserve buffer and even outperforming it under certain circumstances. The developed kit provides an easy-to-use solution of obtaining stable urine cfDNA for clinical use. Citation Format: Zheng Li, Haoran Tang, Tiantian Zhang, Chunxiao Liu, Shengnan Zhu, Ying Zhang, Binggang Xiang, Zhixin Zhao. Development and validation of urine cfDNA preservative kit for detection of genomic alterations in cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2236.

Introduction: By 2020 the estimated incidence of genitourinary (GU) cancers (prostate, bladder, and kidney) will be over 2 million worldwide and responsible for ∼800 000 deaths. Current diagnosis and monitoring methods of GU cancer patients are often invasive and/or lack sensitivity and specificity. The tremendous success in cell-free DNA (cfDNA) blood test provides a strong rationale for using body fluids such as blood and urine as minimally invasive “liquid biopsies” to identify DNA-based molecular biomarkers in urologic malignancies. Urinary cfDNA as a liquid biopsy holds greater potential for a more sensitive alternative to blood biopsies-based tests for clinical use in GU cancers. Urinary biomarker test offers advantages including the potential for more convenient testing, monitoring, and home use. Methods: Analytic validation was conducted using urine cfDNA samples containing different SNPs with different titrations. Urine samples were collected from two different groups, including treatment-naïve patients with pathology-confirmed bladder cancer (BLCA) and healthy donors. Both tumor and germline tissues were collected from the BLCA patients. Results: We report the development, validation, and clinical application of the urine-based next-generation sequencing for integrated genomic cfDNA profiling of bladder cancers, including genomic alterations, tumor mutation burden (TMB) and microsatellite instability (MSI). The analytic sensitivity goes down to 0.5% with 100% analytical specificity. High concordance for mutations between tumor tissue and urinary cfDNA suggests a higher sensitivity alternative for the non-invasive early detection of BLCA. In addition to the NGS-based test, we also developed a Bio-Rad digital PCR assay for orthogonal confirmation of the detected biomarkers such as FGFR3 hotspot mutations. Conclusions: Our work has demonstrated the promise of using urinary cfDNA for detecting genomic alterations at the early stage of BLCA for biomarker detections. Citation Format: Zhixin Zhao, Amy Chang, Binggang Xiang, Feng Xie, Xiaohong Wang, Kemin Zhou, Jianjun Yu, Pan Du, Shidong Jia. Urine-based molecular biomarker signatures for bladder cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3098.