NOTE The report of the Committee without its annexes appears as Official Records of the General Assembly, Sixty-third Session, Supplement No. 46. The designations employed and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of the Secretariat of the United Nations concerning the legal status of any country, territory, city or area, or of its authorities, or concerning the delimitation of its frontiers or boundaries. The country names used in this document are, in most cases, those that were in use at the time the data were collected or the text prepared. In other cases, however, the names have been updated, where this was possible and appropriate, to reflect political changes. Scientific Annexes Annex A. Medical radiation exposures Annex B. Exposures of the public and workers from various sources of radiation INTROdUCTION 1. In the course of the research and development for and the application of atomic energy and nuclear technologies, a number of radiation accidents have occurred. Some of these accidents have resulted in significant health effects and occasionally in fatal outcomes. The application of technologies that make use of radiation is increasingly widespread around the world. Millions of people have occupations related to the use of radiation, and hundreds of millions of individuals benefit from these uses. Facilities using intense radiation sources for energy production and for purposes such as radiotherapy, sterilization of products, preservation of foodstuffs and gamma radiography require special care in the design and operation of equipment to avoid radiation injury to workers or to the public. Experience has shown that such technology is generally used safely, but on occasion controls have been circumvented and serious radiation accidents have ensued. 2. Reviews of radiation exposures from accidents have been presented in previous UNSCEAR reports. The last report containing an exclusive chapter on exposures from accidents was the UNSCEAR 1993 Report [U6]. 3. This annex is aimed at providing a sound basis for conclusions regarding the number of significant radiation accidents that have occurred, the corresponding levels of radiation exposures and numbers of deaths and injuries, and the general trends for various practices. Its conclusions are to be seen in the context of the Committee's overall evaluations of the levels and effects of exposure to ionizing radiation. 4. The Committee's evaluations of public, occupational and medical diagnostic exposures are mostly concerned with chronic exposures of …

sources and effects of ionizing radiation

DNA damage is a relatively common event in the life of a cell and may lead to mutation, cancer, and cellular or organismic death. Damage to DNA induces several cellular responses that enable the cell either to eliminate or cope with the damage or to activate a programmed cell death process, presumably to eliminate cells with potentially catastrophic mutations. These DNA damage response reactions include: (a) removal of DNA damage and restoration of the continuity of the DNA duplex; (b) activation of a DNA damage checkpoint, which arrests cell cycle progression so as to allow for repair and prevention of the transmission of damaged or incompletely replicated chromosomes; (c) transcriptional response, which causes changes in the transcription profile that may be beneficial to the cell; and (d) apoptosis, which eliminates heavily damaged or seriously deregulated cells. DNA repair mechanisms include direct repair, base excision repair, nucleotide excision repair, double-strand break repair, and cross-link repair. The DNA damage checkpoints employ damage sensor proteins, such as ATM, ATR, the Rad17-RFC complex, and the 9-1-1 complex, to detect DNA damage and to initiate signal transduction cascades that employ Chk1 and Chk2 Ser/Thr kinases and Cdc25 phosphatases. The signal transducers activate p53 and inactivate cyclin-dependent kinases to inhibit cell cycle progression from G1 to S (the G1/S checkpoint), DNA replication (the intra-S checkpoint), or G2 to mitosis (the G2/M checkpoint). In this review the molecular mechanisms of DNA repair and the DNA damage checkpoints in mammalian cells are analyzed.

Molecular Mechanisms of Mammalian DNA Repair and the DNA Damage Checkpoints

All life on earth must cope with constant exposure to DNA-damaging agents such as the Sun's radiation. Highly conserved DNA-repair and cell-cycle checkpoint pathways allow cells to deal with both endogenous and exogenous sources of DNA damage. How much an individual is exposed to these agents and how their cells respond to DNA damage are critical determinants of whether that individual will develop cancer. These cellular responses are also important for determining toxicities and responses to current cancer therapies, most of which target the DNA.

Cell-cycle checkpoints and cancer

To ensure the high-fidelity transmission of genetic information, cells have evolved mechanisms to monitor genome integrity. Cells respond to DNA damage by activating a complex DNA-damage-response pathway that includes cell-cycle arrest, the transcriptional and post-transcriptional activation of a subset of genes including those associated with DNA repair, and, under some circumstances, the triggering of programmed cell death. An inability to respond properly to, or to repair, DNA damage leads to genetic instability, which in turn may enhance the rate of cancer development. Indeed, it is becoming increasingly clear that deficiencies in DNA-damage signaling and repair pathways are fundamental to the etiology of most, if not all, human cancers. Here we describe recent progress in our understanding of how cells detect and signal the presence and repair of one particularly important form of DNA damage induced by ionizing radiation-the DNA double-strand break (DSB). Moreover, we discuss how tumor suppressor proteins such as p53, ATM, Brca1 and Brca2 have been linked to such pathways, and how accumulating evidence is connecting deficiencies in cellular responses to DNA DSBs with tumorigenesis.

DNA double-strand breaks: signaling, repair and the cancer connection.

The budding yeast Saccharomyces cerevisiae has been the principal organism used in experiments to examine genetic recombination in eukaryotes. Studies over the past decade have shown that meiotic recombination and probably most mitotic recombination arise from the repair of double-strand breaks (DSBs). There are multiple pathways by which such DSBs can be repaired, including several homologous recombination pathways and still other nonhomologous mechanisms. Our understanding has also been greatly enriched by the characterization of many proteins involved in recombination and by insights that link aspects of DNA repair to chromosome replication. New molecular models of DSB-induced gene conversion are presented. This review encompasses these different aspects of DSB-induced recombination in Saccharomyces and attempts to relate genetic, molecular biological, and biochemical studies of the processes of DNA repair and recombination.

/pdf/multiple-pathways-of-recombination-induced-by-double-strand-1c7668ukfa.pdf

Multiple Pathways of Recombination Induced by Double-Strand Breaks in Saccharomyces cerevisiae

http://genome.imb-jena.de/publications/download/free/Varon_1998.pdf

Nibrin, a Novel DNA Double-Strand Break Repair Protein, Is Mutated in Nijmegen Breakage Syndrome

Genomic organization of a 225-kb region in Xq28 containing the gene for X-linked myotubular myopathy (MTM1) and a related gene (MTMR1).


 HER2 mutations are potent oncogenic drivers in various cancer indications. In NSCLC, about 2% of patients carry either a HER2 exon20 insertion mutation or a HER2 point mutation. With the recent approval of fam-trastuzumab deruxtecan-nxki, the first targeted treatment option became available for HER2 mutant NSCLC patients. However, there remains a high unmet need for more effective and better tolerated therapies with the potential to improve response rates and response durability.
 BAY 2927088 is a reversible small molecule inhibitor that is currently being evaluated in a first-in-human, phase I clinical trial in patients with EGFR mutant NSCLC (NCT05099172).
 Here, we present the preclinical activity profile of BAY 2927088 in HER2 mutant NSCLC. BAY 2927088 shows strong antiproliferative activity in an isogenic Ba/F3 cell line panel of HER2 exon20 insertion mutations as well as HER2 point mutations. BAY 2927088 is highly potent on the most frequent HER2 exon20 insertion mutations A775insYVMA and G776del insVC, as well as in the HER2 point mutations S310F, S335C, and L755S, among others. In addition, the compound was active in a subset of endogenously HER2 mutant cancer cell lines. The in vitro activity of BAY 2927088 was validated in vivo in a patient-derived xenograft model carrying the HER2 exon20 insertion mutation A775insYVMA.
 The strong preclinical activity of BAY 2927088 in HER2 mutant NSCLC supports clinical evaluation in this indication and might offer a novel targeted therapy option for NSCLC patients that carry HER2 mutations.
 Citation Format: Franziska Siegel, Gizem Karsli-Uzunbas, Kristyna Kotynkova, Quinn McVeigh, Stephan Siegel, Daniel Korr, Volker Schulze, Markus Berger, Georg Beckmann, Andrew Cherniack, Matthew Meyerson, Heidi Greulich. Preclinical activity of BAY 2927088 in HER2 mutant non-small cell lung cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4035.

Georg Beckmann

Papers

Nibrin, a Novel DNA Double-Strand Break Repair Protein, Is Mutated in Nijmegen Breakage Syndrome

Genomic organization of a 225-kb region in Xq28 containing the gene for X-linked myotubular myopathy (MTM1) and a related gene (MTMR1).

Abstract 4035: Preclinical activity of BAY 2927088 in HER2 mutant non-small cell lung cancer