Biology subjects

Riemers, F. M.

Publications and source records attributed to Riemers, F. M..

3 recordsLinked to original sources

bioRxiv2021

Circulating microRNAs as noninvasive biomarkers for canine Cushing's syndrome

Canine Cushings syndrome (hypercortisolism) can be caused by a pituitary tumor (pituitary-dependent hypercortisolism; PDH) or a cortisol-secreting adrenocortical tumor (csACT). For both cases, noninvasive biomarkers that could pre-operatively predict the risk of recurrence after surgery would greatly impact clinical decision making. The aim of this study was to determine whether circulating microRNAs (miRNAs) can be used as noninvasive biomarkers for canine Cushings syndrome. After a pilot study with 40 miRNAs in blood samples of healthy dogs (n = 3), dogs with PDH (n = 3) and dogs with a csACT (n = 4), we selected a total of 20 miRNAs for the definitive study. In the definitive study, these 20 miRNAs were analyzed in blood samples of healthy dogs (n = 6), dogs with PDH (n = 19, pre-and post-operative samples) and dogs with a csACT (n = 26, pre-operative samples). In dogs with PDH, six miRNAs (miR-122-5p, miR-126-5p, miR-141-3p, miR-222-3p, miR-375-3p and miR-483-3p) were differentially expressed compared to healthy dogs. Of one miRNA, miR-122-5p, the expression levels did not overlap between healthy dogs and dogs with PDH (p = 2.9x10-4), significantly decreased after hypophysectomy (p = 0.013), and were significantly higher (p = 0.017) in dogs with recurrence (n = 3) than in dogs without recurrence for at least one year after hypophysectomy (n = 7). In dogs with csACTs, two miRNAs (miR-483-3p and miR-223-3p) were differentially expressed compared to healthy dogs. Additionally, miR-141-3p was expressed significantly lower (p = 0.009) in dogs with csACTs that had a histopathological Utrecht score of [≥] 11 compared to those with a score of < 11. These results indicate that circulating miRNAs have the potential to be noninvasive biomarkers in dogs with Cushings syndrome that may contribute to clinical decision-making.

cancer biology↗

bioRxiv2021

Oncogenic RAS sensitizes cells to drug-induced replication stress via transcriptional silencing of P53

Cancer cells often experience high basal levels of DNA replication stress (RS), for example due to hyperactivation of oncoproteins like MYC or RAS. Therefore, cancer cells are considered to be sensitive to drugs that exacerbate the level of RS or block the intra S-phase checkpoint. Consequently, RS-inducing drugs including ATR and CHK1 inhibitors are used or evaluated as anti-cancer therapies. However, drug resistance and lack of biomarkers predicting therapeutic efficacy limit efficient use. This raises the question what determines sensitivity of individual cancer cells to RS. Here, we report that oncogenic RAS does not only enhance the sensitivity to ATR/CHK1 inhibitors by directly causing RS. Instead, we observed that HRASG12V dampens the activation of the P53-dependent transcriptional response to drug-induced RS, which in turn confers sensitivity to RS. We demonstrate that inducible expression of HRASG12V sensitized retina pigment epithelial (RPE-hTERT) as well as osteosarcoma (U2OS) cells to ATR and CHK1 inhibitors. Using RNA-sequencing of FACS-sorted cells we discovered that P53 signaling is the sole transcriptional response to RS. However, oncogenic RAS attenuates the transcription of P53 and its target genes. Accordingly, live cell imaging showed that HRASG12V exacerbates RS in S/G2-phase, which could be rescued by stabilization of P53. Thus, our results demonstrate that transcriptional control of P53 is a prime determinant in the response to ATR/CHK1 inhibitors and show that hyperactivation of the MAPK pathway impedes this response. Our findings suggest that the level of oncogenic MAPK signaling could predict sensitivity to intra-S-phase inhibition in cancers with intact P53.

cancer biology↗

bioRxiv2020

Excessive E2F transcription in single cancer cells precludes transient cell cycle exit after DNA damage.

E2F transcription factors control the expression of cell cycle genes. Cancers often demonstrate enhanced E2F target gene expression, which can be explained by increased percentages of replicating cells. However, we now demonstrate in human cancer biopsies that individual neoplastic cells display abnormally high levels of E2F-dependent transcription. To mimic this situation, we deleted the atypical E2F repressors (E2F7/8) in untransformed cells. Individual cells with elevated E2F-activity during S/G2-phase failed to exit the cell cycle after DNA damage and underwent mitosis. In contrast, wild type cells completed S-phase and then exit the cell cycle by activating the APC/CCdh1 via repression of the E2F-target Emi1. Strikingly, many arrested wildtype cells could eventually inactivate APC/CCdh1 to execute a second round of DNA replication and mitosis, thereby becoming tetraploid. Cells with elevated E2F-transcription fail to exit the cell cycle after DNA damage which potentially causes genomic instability, promotes malignant progression and reduces drug sensitivity.

cancer biology↗