Cell cycle checkpoints, oncogene-induced senescence and programmed cell death represent intrinsic barriers to tumorigenesis. Protein phosphatase magnesium-dependent 1 (PPM1D) is a negative regulator of the tumour suppressor p53 and has been implicated in termination of the DNA damage response. Here, we addressed the consequences of increased PPM1D activity resulting from the gain-of-function truncating mutations in exon 6 of the PPM1D. We show that while control cells permanently exit the cell cycle and reside in senescence in the presence of DNA damage caused by ionising radiation or replication stress induced by the active RAS oncogene, RPE1-hTERT and BJ-hTERT cells carrying the truncated PPM1D continue proliferation in the presence of DNA damage, form micronuclei and accumulate genomic rearrangements revealed by karyotyping. Further, we show that increased PPM1D activity promotes cell growth in the soft agar and formation of tumours in xenograft models. Finally, expression profiling of the transformed clones revealed dysregulation of several oncogenic and tumour suppressor pathways. Our data support the oncogenic potential of PPM1D in the context of exposure to ionising radiation and oncogene-induced replication stress.

• MeSH
• Cell Death genetics   MeSH
• Humans MeSH
• Mice MeSH
• Cell Transformation, Neoplastic * genetics   MeSH
• Tumor Suppressor Protein p53 genetics   metabolism   MeSH
• DNA Damage * genetics   MeSH
• Cell Proliferation genetics   MeSH
• Protein Phosphatase 2C * genetics   metabolism   MeSH
• Phosphoprotein Phosphatases genetics   metabolism   MeSH
• Cellular Senescence * genetics   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Tumor Suppressor Protein p53 MeSH
• PPM1D protein, human MeSH Browser
• Protein Phosphatase 2C * MeSH
• Phosphoprotein Phosphatases MeSH

The subset of ovarian cancer (OC) diagnosed ≤ 30yo represents a distinct subgroup exhibiting disparities from late-onset OC in many aspects, including indefinite germline cancer predisposition. We performed DNA/RNA-WES with HLA-typing, PRS assessment and survival analysis in 123 early-onset OC-patients compared to histology/stage-matched late-onset and unselected OC-patients, and population-matched controls. Only 6/123(4.9%) early-onset OC-patients carried a germline pathogenic variant (GPV) in high-penetrance OC-predisposition genes. Nevertheless, our comprehensive germline analysis of early-onset OC-patients revealed two divergent trajectories of potential germline susceptibility. Firstly, overrepresentation analysis highlighted a connection to breast cancer (BC) that was supported by the CHEK2 GPV enrichment in early-onset OC(p = 1.2 × 10-4), and the presumably BC-specific PRS313, which successfully stratified early-onset OC-patients from controls(p = 0.03). The second avenue pointed towards the impaired immune response, indicated by LY75-CD302 GPV(p = 8.3 × 10-4) and diminished HLA diversity compared with controls(p = 3 × 10-7). Furthermore, we found a significantly higher overall GPV burden in early-onset OC-patients compared to controls(p = 3.8 × 10-4). The genetic predisposition to early-onset OC appears to be a heterogeneous and complex process that goes beyond the traditional Mendelian monogenic understanding of hereditary cancer predisposition, with a significant role of the immune system. We speculate that rather a cumulative overall GPV burden than specific GPV may potentially increase OC risk, concomitantly with reduced HLA diversity.

• Keywords
• Early-onset, Germline whole exome sequencing, HLA, Mutation burden, Ovarian cancer, Polygenic risk score,
• MeSH
• Checkpoint Kinase 2 genetics   MeSH
• Adult MeSH
• Genetic Predisposition to Disease * MeSH
• Middle Aged MeSH
• Humans MeSH
• Young Adult MeSH
• Ovarian Neoplasms * genetics   MeSH
• Case-Control Studies MeSH
• Age of Onset * MeSH
• Germ-Line Mutation * MeSH
• Check Tag
• Adult MeSH
• Middle Aged MeSH
• Humans MeSH
• Young Adult MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Checkpoint Kinase 2 MeSH

Germline CHEK2 pathogenic variants confer an increased risk of female breast cancer (FBC). Here we describe a recurrent germline intronic variant c.1009-118_1009-87delinsC, which showed a splice acceptor shift in RNA analysis, introducing a premature stop codon (p.Tyr337PhefsTer37). The variant was found in 21/10,204 (0.21%) Czech FBC patients compared to 1/3250 (0.03%) controls (p = 0.04) and in 4/3639 (0.11%) FBC patients from an independent German dataset. In addition, we found this variant in 5/2966 (0.17%) Czech (but none of the 443 German) ovarian cancer patients, three of whom developed early-onset tumors. Based on these observations, we classified this variant as likely pathogenic.

• Keywords
• Breast cancer, Deep intronic CHEK2 variant, Genetic testing, NGS, RNA analysis,
• MeSH
• Checkpoint Kinase 2 * genetics   MeSH
• Adult MeSH
• Genetic Predisposition to Disease * genetics   MeSH
• Introns * genetics   MeSH
• Middle Aged MeSH
• Humans MeSH
• Breast Neoplasms * genetics   MeSH
• Ovarian Neoplasms genetics   MeSH
• RNA Precursors genetics   MeSH
• RNA Splicing * genetics   MeSH
• Germ-Line Mutation * MeSH
• Check Tag
• Adult MeSH
• Middle Aged MeSH
• Humans MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Geographicals
• Czech Republic MeSH
• Germany MeSH
• Names of Substances
• CHEK2 protein, human MeSH Browser