The SUMO Isopeptidase Ulp2p Is Required to Prevent Recombination-Induced Chromosome Segregation Lethality following DNA Replication Stress

SUMO conjugation is a key regulator of the cellular response to DNA replication stress, acting in part to control recombination at stalled DNA replication forks. Here we examine recombination-related phenotypes in yeast mutants defective for the SUMO de-conjugating/chain-editing enzyme Ulp2p. We find that spontaneous recombination is elevated in ulp2 strains and that recombination DNA repair is essential for ulp2 survival. In contrast to other SUMO pathway mutants, however, the frequency of spontaneous chromosome rearrangements is markedly reduced in ulp2 strains, and some types of rearrangements arising through recombination can apparently not be tolerated. In investigating the basis for this, we find DNA repair foci do not disassemble in ulp2 cells during recovery from the replication fork-blocking drug methyl methanesulfonate (MMS), corresponding with an accumulation of X-shaped recombination intermediates. ulp2 cells satisfy the DNA damage checkpoint during MMS recovery and commit to chromosome segregation with similar kinetics to wild-type cells. However, sister chromatids fail to disjoin, resulting in abortive chromosome segregation and cell lethality. This chromosome segregation defect can be rescued by overproducing the anti-recombinase Srs2p, indicating that recombination plays an underlying causal role in blocking chromatid separation. Overall, our results are consistent with a role for Ulp2p in preventing the formation of DNA lesions that must be repaired through recombination. At the same time, Ulp2p is also required to either suppress or resolve recombination-induced attachments between sister chromatids. These opposing defects may synergize to greatly increase the toxicity of DNA replication stress

Current clinical practice and outcome of neoadjuvant chemotherapy for early breast cancer: analysis of individual data from 94,638 patients treated in 55 breast cancer centers

Neoadjuvant chemotherapy (NACT) is frequently used in patients with early breast cancer. Randomized controlled trials have demonstrated similar survival after NACT or adjuvant chemotherapy (ACT). However, certain subtypes may benefit more when NACT contains regimes leading to high rates of pathologic complete response (pCR) rates. In this study we analyzed data using the OncoBox research from 94,638 patients treated in 55 breast cancer centers to describe the current clinical practice of and outcomes after NACT under routine conditions. These data were compared to patients treated with ACT. 40% of all patients received chemotherapy. The use of NACT increased over time from 5% in 2007 up to 17.3% in 2016. The proportion of patients receiving NACT varied by subtype. It was low in patients with HR-positive/HER2-negative breast cancer (5.8%). However, 31.8% of patients with triple-negative, 31.9% with HR-negative/HER2-positive, and 26.5% with HR-positive/HER2-positive breast cancer received NACT. The rates of pCR were higher in patients with HR-positive/HER2-positive, HR negative/HER2-positive and triple-negative tumors (36, 53 and 38%) compared to HR-positive/HER2-negative tumors (12%). PCR was achieved more often in HER2-positive and triple-negative tumors over time. This is the largest study on use and effects of NACT in German breast cancer centers. It demonstrates the increased use of NACT based on recommendations in current clinical guidelines. An improvement of pCR was shown in particular in HER2-positive and triple-negative breast cancer, which is consistent with data from randomized controlled trails

Vascularised Chorioallantoic Membrane (CAM) Culture System for Cryopreserved Human Ovarian Tissue as an Alternative to Xenotransplantation

Purpose: Previously there were only two effective ways to determine the quality of cryopreservation procedures for ovarian tissue after thawing: xenotransplantation and in vitro culture in a big volume of medium with permanent mechanical agitation. The Belgian group of J. Donnez has shown that the chorioallantoic membrane (CAM) culture system offers a new approach to study human ovarian tissue transplantation in its first ischemic stages, yielding information on the timing of tissue changes before neovascularization is established. The aim of this study was to compare the effectiveness after thawing of human ovarian tissue cultured in vitro in a big volume of medium with agitation with a CAM culture system. Material and Methods: Ovarian tissue fragments from 5 patients were transported within 20 min at 32-34 degrees C to the laboratory. The fragments were divided into smaller pieces (1-2 x 0.7-1 mm), frozen, thawed and randomly divided into the following two groups: Group 1: tissue cultured in vitro for 7 days in a big volume of medium with mechanical agitation; Group 2: tissue cultured in a CAM system for 5 days. The viability of the tissue from the respective method of cultivation was evaluated by immunohistochemistry (cytokeratin and Ki-67) and assessed according to the development of follicles and follicular cell proliferation. Results: 85 and 87% of the follicles were morphologically normal in group 1 and group 2, respectively. Immunohistochemical analysis showed that the proliferative characteristics of follicular cells after culture in the CAM system were significantly increased. Conclusion: Both the CAM system and in vitro culturing in a big volume of medium with permanent mechanical agitation are suitable for culturing human ovarian tissue. However, the CAM system provides more information