Murine double minute-2 (MDM2) is an E3-ubiquitin ligase and the main negative regulator of tumor suppressor gene p53. MDM2 has also a non-redundant function as a modulator of NF-kB signaling. As such it promotes proliferation and inflammation. MDM2 is highly expressed in the unchallenged tubular epithelial cells and we hypothesized that MDM2 is necessary for their survival and homeostasis. MDM2 knockdown by siRNA or by genetic depletion resulted in demise of tubular cells in vitro. This phenotype was completely rescued by concomitant knockdown of p53, thus suggesting p53 dependency. In vivo experiments in the zebrafish model demonstrated that the tubulus cells of the larvae undergo cell death after the knockdown of mdm2. Doxycycline-induced deletion of MDM2 in tubular cell-specific MDM2-knockout mice Pax8rtTa-cre; MDM2f/f caused acute kidney injury with increased plasma creatinine and blood urea nitrogen and sharp decline of glomerular filtration rate. Histological analysis showed massive swelling of renal tubular cells and later their loss and extensive tubular dilation, markedly in proximal tubules. Ultrastructural changes of tubular epithelial cells included swelling of the cytoplasm and mitochondria with the loss of cristae and their transformation in the vacuoles. The pathological phenotype of the tubular cell-specific MDM2-knockout mouse model was completely rescued by co-deletion of p53. Tubular epithelium compensates only partially for the cell loss caused by MDM2 depletion by proliferation of surviving tubular cells, with incomplete MDM2 deletion, but rather mesenchymal healing occurs. We conclude that MDM2 is a non-redundant survival factor for proximal tubular cells by protecting them from spontaneous p53 overexpression-related cell death.

Oncologic patients are regarded as the population most at risk of developing a severe course of COVID‐19 due to the fact that malignant diseases and chemotherapy often weaken the immune system. In the face of the ongoing SARS‐CoV‐2 pandemic, how particular patients deal with this infection remains an important question. In the period between the 15 and 26 April 2020, a total of 1227 patients were tested in one of seven oncologic outpatient clinics for SARS‐CoV‐2, regardless of symptoms, employing RT‐qPCR. Of 1227 patients, 78 (6.4%) were tested positive of SARS‐CoV‐2. Only one of the patients who tested positive developed a severe form of COVID‐19 with pneumonia (CURB‐65 score of 2), and two patients showed mild symptoms. Fourteen of 75 asymptomatic but positively tested patients received chemotherapy or chemo‐immunotherapy according to their regular therapy algorithm (±4 weeks of SARS‐CoV‐2 test), and 48 of 78 (61.5%) positive‐tested patients received glucocorticoids as co‐medication. None of the asymptomatic infected patients showed unexpected complications due to the SARS‐CoV‐2 infection during the cancer treatment. These data clearly contrast the view that patients with an oncologic disease are particularly vulnerable to SARS‐CoV‐2 and suggest that compromising therapies could be continued or started despite the ongoing pandemic. Moreover the relatively low appearance of symptoms due to COVID‐19 among patients on chemotherapy and other immunosuppressive co‐medication like glucocorticoids indicate that suppressing the response capacity of the immune system reduces disease severity.

SARS-CoV-2 antibody development and immunity will be crucial for the further course of the pandemic. Until now, it has been assumed that patients who were infected with SARS-CoV-2 develop antibodies as it is the case with other coronaviruses, like MERS-CoV and SARS-CoV. In the present study, we analyzed the antibody development of 77 oncology patients 26 days after positive RT-qPCR testing for SARS-CoV-2. RT-qPCR and anti-SARS-CoV2-antibody methods from BGI (MGIEasy Magnetic Beads Virus DNA/RNA Extraction Kit) and Roche (Elecsys Anti-SARS-CoV-2 immunoassay) were used, respectively, according to the manufacturers’ specifications.Surprisingly, in only 6 of 77 individuals with a confirmed history of COVID-19 antibody development was detected. Despite of multiple testing, the remaining patients did not show measurable antibody concentrations in subsequent tests. These results undermine the previous hypothesis that SARS-CoV-2 infections are regularly associated with antibody development and cast doubt on the provided immunity to COVID-19. Understanding the adaptive and humoral response to SARS-CoV-2 will play a key-roll in vaccine development and gaining further knowledge on the pathogenesis.

No abstract

No abstract