Hereditary breast cancer next-generation sequencing panel evaluation in the south region of Brazil: A novel BRCA2 candidate pathogenic variant is reported.

BACKGROUND: In this article, we delineate a loosely selected cohort comprising patients with a history of early-onset breast cancer and/or a familial occurrence of cancer. The aim of this study was to gain insights into the presence of breast cancer-related gene variants in a population from a micro-region in southern Brazil, specifically the Metropolitan Region of Curitiba. This area exhibits a highly genetically mixed population, mirroring the general characteristics of the Brazilian people. METHODS: Comprehensive next-generation sequencing (NGS) multigene panel testing was conducted on 12 patients from the region, utilizing three different library preparation methods. RESULTS: Two pathogenic variants and one candidate pathogenic variant were identified: BRCA2 c.8878C>T, p.Gln2960Ter; CHEK2 c.1100del, p.Thr367Metfs15, and BRCA2 c.3482dup, p.Asp1161Glufs3. CONCLUSION: BRCA2 c.3482dup, a novel candidate pathogenic variant, previously unpublished, is reported. The prevalence of pathogenic variants in this small cohort is similar to that described in the literature. All different library preparation methods were equally proficient in enabling the detection of these variants.

Alantolactone Induced Apoptosis and DNA Damage of Cervical Cancer through ATM/CHK2 Signaling Pathway.

Traditional Chinese Medicine, known for its minimal side effects and significant clinical efficacy, has attracted considerable interest for its potential in cancer therapy. In particular, Inula helenium L. has demonstrated effectiveness in inhibiting a variety of cancers. This study focuses on alantolactone (ALT), a prominent compound from Inula helenium L., recognized for its anti-cancer capabilities across multiple cancer types. The primary objective of this study is to examine the influence of ALT on the proliferation, apoptosis, cell cycle, and tumor growth of cervical cancer (CC) cells, along with its associated signaling pathways. To determine protein expression alterations, Western blot analysis was conducted. Furthermore, an in vivo model was created by subcutaneously injecting HeLa cells into nude mice to assess the impact of ALT on cervical cancer. Our research thoroughly investigates the anti-tumor potential of ALT in the context of CC. ALT was found to inhibit cell proliferation and induce apoptosis in SiHa and HeLa cell lines, particularly targeting ataxia-telangiectasia mutated (ATM) proteins associated with DNA damage. The suppression of DNA damage and apoptosis induction when ATM was inhibited underscores the crucial role of the ATM/cell cycle checkpoint kinase 2 (CHK2) axis in ALT's anti-tumor effects. In vivo studies with a xenograft mouse model further validated ALT's effectiveness in reducing CC tumor growth and promoting apoptosis. This study offers new insights into how ALT combats CC, highlighting its promise as an effective anti-cervical cancer agent and providing hope for improved treatment outcomes for CC patients.

Investigation into the Neuroprotective and Therapeutic Potential of Plant-Derived Chk2 Inhibitors.

Nature provides us with a rich source of compounds with a wide range of applications, including the creation of innovative drugs. Despite advancements in chemically synthesized therapeutics, natural compounds are increasingly significant, especially in cancer treatment, a leading cause of death globally. One promising approach involves the use of natural inhibitors of checkpoint kinase 2 (Chk2), a critical regulator of DNA repair, cell cycle arrest, and apoptosis. Chk2's activation in response to DNA damage can lead to apoptosis or DNA repair, influencing glycolysis and mitochondrial function. In cancer therapy, inhibiting Chk2 can disrupt DNA repair and cell cycle progression, promoting cancer cell death and enhancing the efficacy of radiotherapy and chemotherapy. Additionally, Chk2 inhibitors can safeguard non-cancerous cells during these treatments by inhibiting p53-dependent apoptosis. Beyond oncology, Chk2 inhibition shows potential in treating hepatitis C virus (HCV) infections, as the virus relies on Chk2 for RNA replication in neurodegenerative diseases like amyotrophic lateral sclerosis (ALS), in which DNA damage plays a crucial role. Plant-derived Chk2 inhibitors, such as artemetin, rhamnetin, and curcumin, offer a promising future for treating various diseases with potentially milder side effects and broader metabolic impacts compared to conventional therapies. The review aims to underscore the immense potential of natural Chk2 inhibitors in various therapeutic contexts, particularly in oncology and the treatment of other diseases involving DNA damage and repair mechanisms. These natural Chk2 inhibitors hold significant promise for revolutionizing the landscape of cancer treatment and other diseases. Further research into these compounds could lead to the development of innovative therapies that offer hope for the future with fewer side effects and enhanced efficacy.

Post-Integrational DNA Repair of HIV-1 Is Associated with Activation of the DNA-PK and ATM Cellular Protein Kinases and Phosphorylation of Their Targets.

Integration of the DNA copy of HIV-1 genome into the cellular genome results in series of damages, repair of which is critical for successful replication of the virus. We have previously demonstrated that the ATM and DNA-PK kinases, normally responsible for repairing double-strand breaks in the cellular DNA, are required to initiate the HIV-1 DNA postintegrational repair, even though integration does not result in DNA double-strand breaks. In this study, we analyzed changes in phosphorylation status of ATM (pSer1981), DNA-PK (pSer2056), and their related kinase ATR (pSer428), as well as their targets: Chk1 (pSer345), Chk2 (pThr68), H2AX (pSer139), and p53 (pSer15) during the HIV-1 DNA postintegrational repair. We have shown that ATM and DNA-PK, but not ATR, undergo autophosphorylation during postintegrational DNA repair and phosphorylate their target proteins Chk2 and H2AX. These data indicate common signaling mechanisms between the double-strand DNA break repair and postintegrational repair of HIV-1 DNA.

A comprehensive analysis of germline predisposition to early-onset ovarian cancer.

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.

Citrinin Provoke DNA Damage and Cell-Cycle Arrest Related to Chk2 and FANCD2 Checkpoint Proteins in Hepatocellular and Adenocarcinoma Cell Lines.

Citrinin (CIT), a polyketide mycotoxin produced by Penicillium, Aspergillus, and Monascus species, is a contaminant that has been found in various food commodities and was also detected in house dust. Several studies showed that CIT can impair the kidney, liver, heart, immune, and reproductive systems in animals by mechanisms so far not completely elucidated. In this study, we investigated the CIT mode of action on two human tumor cell lines, HepG2 (hepatocellular carcinoma) and A549 (lung adenocarcinoma). Cytotoxic concentrations were determined using an MTT proliferation assay. The genotoxic effect of sub-IC50 concentrations was investigated using the alkaline comet assay and the impact on the cell cycle using flow cytometry. Additionally, the CIT effect on the total amount and phosphorylation of two cell-cycle-checkpoint proteins, the serine/threonine kinase Chk2 and Fanconi anemia (FA) group D2 (FANCD2), was determined by the cell-based ELISA. The data were analyzed using GraphPad Prism statistical software. The CIT IC50 for HepG2 was 107.3 µM, and for A549, it was >250 µM. The results showed that sensitivity to CIT is cell-type dependent and that CIT in sub-IC50 and near IC50 induces significant DNA damage and cell-cycle arrest in the G2/M phase, which is related to the increase in total and phosphorylated Chk2 and FANCD2 checkpoint proteins in HepG2 and A549 cells.

FAM122A ensures cell cycle interphase progression and checkpoint control by inhibiting B55α/PP2A through helical motifs.

The Ser/Thr protein phosphatase 2 A (PP2A) regulates the dephosphorylation of many phosphoproteins. Substrate recognition are mediated by B regulatory subunits. Here, we report the identification of a substrate conserved motif [RK]-V-x-x-[VI]-R in FAM122A, an inhibitor of B55α/PP2A. This motif is necessary for FAM122A binding to B55α, and computational structure prediction suggests the motif, which is helical, blocks substrate docking to the same site. In this model, FAM122A also spatially constrains substrate access by occluding the catalytic subunit. Consistently, FAM122A functions as a competitive inhibitor as it prevents substrate binding and dephosphorylation of CDK substrates by B55α/PP2A in cell lysates. FAM122A deficiency in human cell lines reduces the proliferation rate, cell cycle progression, and hinders G1/S and intra-S phase cell cycle checkpoints. FAM122A-KO in HEK293 cells attenuates CHK1 and CHK2 activation in response to replication stress. Overall, these data strongly suggest that FAM122A is a short helical motif (SHeM)-dependent, substrate-competitive inhibitor of B55α/PP2A that suppresses multiple functions of B55α in the DNA damage response and in timely progression through the cell cycle interphase.

Germline pathogenic variants of cancer predisposition genes in a multicentre Italian cohort of pancreatic cancer patients.

BACKGROUND AND AIM: Germline BRCA1-2 test is routinely recommended in Pancreatic Cancer (PC) patients, due to its clinical-epidemiological relevance. Data on the prevalence of germline pathogenic variants (gPV) in other cancer predisposition and DNA Damage Repair (DDR) system-related genes in unselected PC cases are sparce in Italy. We assessed this prevalence in a multicentre cohort, to derive recommendations for PC patients. METHODS: Clinical data of 1200 consecutive PC patients, of any age and stage, tested with a multigene germline panel were collected. A descriptive analysis of gPV frequency and clinical variables was performed both in 1092 patients tested for an 18 genes core-panel (CP-18 cohort) and in 869 patients screened only for CDKN2A. RESULTS: 11.5 % (126/1092) of CP-18 cohort patients harbored a gPV in ≥ 1 gene. Highest gPV frequencies were detected in ATM (3.1 %), BRCA2 (2.9 %), BRCA1 (1.6 %), CHEK2 (1.1 %). Patients harboring any CP-18 gene and BRCA1-2 gPV were younger and with a higher rate of personal (PH) or family history (FH) of cancer when compared to no gPV patients. The risk of having a gPV was ≥ 7 % in all subgroups of patients, including those aged > 73, with tumor stage I-III and negative FH/PH. CDKN2A gPV were detected in 2.6 % (23/869) of patients. CONCLUSIONS: A remarkable prevalence of gPV in cancer predisposition and DDR genes is reported in this large multicentre cohort of consecutive and unselected PC patients. Therefore, we recommend multigene germline testing (at least including BRCA1-2, ATM, CDKN2A, PALB2) for all PC patients, irrespective of age, stage, PH/FH.

Human umbilical cord mesenchymal stem cells attenuate diabetic nephropathy through the IGF1R-CHK2-p53 signalling axis in male rats with type 2 diabetes mellitus. / 人脐带间å 质干细胞通过IGF1R-CHK2-p53信号轴减轻2åž‹ç³–å°¿ç— é›„æ€§å¤§é¼ ç³–å°¿ç— è‚¾ç— .

Diabetes mellitus (DM) is a disease syndrome characterized by chronic hyperglycaemia. A long-term high-glucose environment leads to reactive oxygen species (ROS) production and nuclear DNA damage. Human umbilical cord mesenchymal stem cell (HUcMSC) infusion induces significant antidiabetic effects in type 2 diabetes mellitus (T2DM) rats. Insulin-like growth factor 1 (IGF1) receptor (IGF1R) is important in promoting glucose metabolism in diabetes; however, the mechanism by which HUcMSC can treat diabetes through IGF1R and DNA damage repair remains unclear. In this study, a DM rat model was induced with high-fat diet feeding and streptozotocin (STZ) administration and rats were infused four times with HUcMSC. Blood glucose, interleukin-6 (IL-6), IL-10, glomerular basement membrane, and renal function were examined. Proteins that interacted with IGF1R were determined through coimmunoprecipitation assays. The expression of IGF1R, phosphorylated checkpoint kinase 2 (p-CHK2), and phosphorylated protein 53 (p-p53) was examined using immunohistochemistry (IHC) and western blot analysis. Enzyme-linked immunosorbent assay (ELISA) was used to determine the serum levels of 8-hydroxydeoxyguanosine (8-OHdG). Flow cytometry experiments were used to detect the surface markers of HUcMSC. The identification of the morphology and phenotype of HUcMSC was performed by way of oil red "O" staining and Alizarin red staining. DM rats exhibited abnormal blood glucose and IL-6/10 levels and renal function changes in the glomerular basement membrane, increased the expression of IGF1 and IGF1R. IGF1R interacted with CHK2, and the expression of p-CHK2 was significantly decreased in IGF1R-knockdown cells. When cisplatin was used to induce DNA damage, the expression of p-CHK2 was higher than that in the IGF1R-knockdown group without cisplatin treatment. HUcMSC infusion ameliorated abnormalities and preserved kidney structure and function in DM rats. The expression of IGF1, IGF1R, p-CHK2, and p-p53, and the level of 8-OHdG in the DM group increased significantly compared with those in the control group, and decreased after HUcMSC treatment. Our results suggested that IGF1R could interact with CHK2 and mediate DNA damage. HUcMSC infusion protected against kidney injury in DM rats. The underlying mechanisms may include HUcMSC-mediated enhancement of diabetes treatment via the IGF1R-CHK2-p53 signalling pathway.

DSB-induced oxidative stress: Uncovering crosstalk between DNA damage response and cellular metabolism.

While that ROS causes DNA damage is well documented, there has been limited investigation into whether DNA damages and their repair processes can conversely induce oxidative stress. By generating a site-specific DNA double strand break (DSB) via I-SceI endonuclease expression in S. cerevisiae without damaging other cellular components, this study demonstrated that DNA repair does trigger oxidative stress. Deleting genes participating in the initiation of the resection step of homologous recombination (HR), like the MRX complex, resulted in stimulation of ROS. In contrast, deleting genes acting downstream of HR resection suppressed ROS levels. Additionally, blocking non-homologous end joining (NHEJ) also suppressed ROS. Further analysis identified Rad53 as a key player that relays DNA damage signals to alter redox metabolism in an HR-specific manner. These results suggest both HR and NHEJ can drive metabolism changes and oxidative stress, with NHEJ playing a more prominent role in ROS stimulation. Further analysis revealed a correlation between DSB-induced ROS increase and enhanced activity of NADPH oxidase Yno1 and various antioxidant enzymes. Deleting the antioxidant gene SOD1 induced synthetic lethality in HR-deficient mutants like mre11Δ and rad51Δ upon DSB induction. These findings uncover a significant interplay between DNA repair mechanisms and cellular metabolism, providing insights into understanding the side effects of genotoxic therapies and potentially aiding development of more effective cancer treatment strategies.

Comparing Cancer Risk Management between Females with Truncating CHEK2 1100delC versus Missense CHEK2 I157T Variants.

Breast cancer (BC) risks imparted by CHEK2 c.1100delC ("1100delC") germline pathogenic/likely pathogenic variant (GPV) are 20-30%, compared to CHEK2 c.470T>C ("I157T") GPV with <20%, leading to different breast screening recommendations through MRI. We compared cancer risk management (CRM) across these two GPVs. Study participants were adult females with an 1100delC or I157T GPV drawn from the Inherited Cancer Registry (ICARE) across the United States. Cancer history, clinical characteristics, and CRM were compared using chi-squared tests, t-tests, and logistic regression. Of 150 CHEK2 carriers, 40.7% had BC, with a mean age of 50. Comparing 1100delC and I157T GPVs, there were no differences in rates of (1) breast MRI among those with (65.2% versus 55.6% of 23 and 9; p = 0.612) and without (44.0% versus 44.8% of 50 and 29; p = 0.943) BC; (2) risk-reducing mastectomy among those with (50% versus 38.9% of 46 and 15; p = 0.501) and without (13.8% versus 6.5% of 58 and 31; p = 0.296) BC; and (3) risk-reducing salpingo-oophorectomy among those with (24.2% versus 22.2% of 45 and 18; p = 0.852) and without (17.5% versus 16.7% of 57 and 30; p = 0.918) BC. The results suggest over-screening with breast MRI among CHEK2 I157T GPV carriers and possible overuse of risk-reducing surgeries among CHEK2 carriers.

The genomic landscape of breast and non-breast cancers from individuals with germline CHEK2 deficiency.

CHEK2 is considered to be involved in homologous recombination repair (HRR). Individuals who have germline pathogenic variants (gPVs) in CHEK2 are at increased risk to develop breast cancer and likely other primary cancers. PARP inhibitors (PARPi) have been shown to be effective in the treatment of cancers that present with HRR deficiency-for example, caused by inactivation of BRCA1/2. However, clinical trials have shown little to no efficacy of PARPi in patients with CHEK2 gPVs. Here, we show that both breast and non-breast cancers from individuals who have biallelic gPVs in CHEK2 (germline CHEK2 deficiency) do not present with molecular profiles that fit with HRR deficiency. This finding provides a likely explanation why PARPi therapy is not successful in the treatment of CHEK2-deficient cancers.

Inhibition of Melanoma Cell Growth by Salvianolic Acid A through CHK2-CDC25A Pathway Modulation.

BACKGROUND: This study investigated the impact of salvianolic acids, derived from Danshen, on melanoma cell growth. Specifically, we assessed the ability of salvianolic acid A (Sal A) to modulate melanoma cell proliferation. METHODS: We used human melanoma A2058 and A375 cell lines to investigate the effects of Sal A on cell proliferation and death by measuring bromodeoxyuridine incorporation and lactate dehydrogenase release. We assessed cell viability and cycle progression using water soluble tetrazolium salt-1 (WST-1) mitochondrial staining and propidium iodide. Additionally, we used a phospho-kinase array to investigate intracellular kinase phosphorylation, specifically measuring the influence of Sal A on checkpoint kinase-2 (Chk-2) via western blot analysis. RESULTS: Sal A inhibited the growth of A2058 and A375 cells dose-responsively and induced cell cycle arrest at the G2/M phase. Notably, Sal A selectively induces Chk-2 phosphorylation without affecting Chk-1, thereby degrading Chk-2-regulated genes Cdc25A and Cdc2. However, Sal A does not affect the Chk1-Cdc25C pathway. CONCLUSIONS: Salvianolic acids, especially Sal A, effectively hinder melanoma cell growth by inducing Chk-2 phosphorylation and disrupting G2/M checkpoint regulation.

Universal genetic counseling in breast cancer patients significantly improves overall testing rates and improves completion rates in subpopulations.

PURPOSE: The NCCN guidelines recommend genetic testing in those patients at increased risk of breast cancer in order to identify candidates for increased frequency of screening or prophylactic mastectomy. However, genetic testing may now identify patients who may benefit from recently developed targeted breast cancer therapy. In order to more widely identify these patients, we implemented genetic counseling for all patients diagnosed with breast cancer. METHODS: In 2021, all patients evaluated within a Midwestern community hospital system diagnosed with breast cancer were offered genetic counseling. This group of patients was compared to a cohort of patients in 2021 who were offered genetic counseling based on NCCN guidelines. With Pearson's chi square, Fisher's Exact test, Mann-Whitney U, and multivariate regression as appropriate, individual demographic data and genetic testing completion between 2019 and 2021 were evaluated. RESULTS: A total of 973 patients were reviewed. 439 were diagnosed with breast cancer in 2019 and 534 in 2021. Demographics and stage at diagnosis (p = 0.194) were similar between years. Completion of genetic testing increased from 204 (46.5%) in 2019 to 338 (63.3%) in 2021 (p < 0.01) with the universal counseling protocol. Specifically, genetic testing completion increased significantly in older patients (p = 0.041) and patients receiving Medicare benefits (p = 0.005). The overall pathogenic variants found increased from 32 to 39 with the most common including BRCA2 (n = 11), CFTR (n = 9), CHEK2 (n = 8), BRCA1 (n = 6). CONCLUSION: Universal genetic counseling was related to a significant increase in genetic testing completion and an increase in pathogenic variants found among breast cancer patients, specifically in subpopulations which may have been previously excluded by traditional NCCN genetic testing screening guidelines.

Prevalence of pathogenic or likely pathogenic germline variants in cancer predisposition genes among selected patients with lung adenocarcinoma: The GERMLUNG study.

INTRODUCTION: Pathogenic or likely pathogenic germline variants (PGVs) in cancer predisposition genes may play a role in lung cancer (LC) susceptibility. However, determining an eligible population for genetic testing remains uncertain. This study aimed to assess the prevalence of PGVs in a selected cohort of individuals with lung adenocarcinoma. METHODS: A cross-sectional cohort study was conducted to assess the PGVs rate in lung adenocarcinoma patients with a family history of LC, young-onset presentation, history of never/light smoking, or actionable genomic alterations (AGAs). Sequencing was performed using Sophia Hereditary Cancer Solution panel F, including 144 cancer predisposition genes. Variants classified as pathogenic or likely pathogenic were included for further analysis. RESULTS: Of 201 patients, 43 (21.4 %) exhibited PGVs, among which 64.5 % were DNA damage repair genes, and 86.1 % were clinically actionable. The main PGVs were in ATM (9.3 %), TP53 (6.9 %), BRCA2 (6.9 %), and CHEK2 (6.9 %) genes. PGVs were associated with male sex (adjusted odds ratio [aOR] 2.46, 95 % CI 1.15-5.32, p = 0.021), along with a trend toward association with AGAs (aOR 6.04, 95 % CI 0.77-49.74, p = 0.094). CONCLUSIONS: In this study, a high PGVs prevalence was identified based on our selection criteria, which represents an effective strategy to identify candidates for germline genomic testing, potential screening strategies in close relatives, and personalized therapeutic modalities. Our results warrant further exploration in other populations to confirm them.

Clinical significance of LINC02532 in hepatitis B virus-associated hepatocellular carcinoma and its regulatory effect on tumor progression.

BACKGROUND AND AIM: Long non-coding RNAs (lncRNAs) play an important role in tumor progression, including in hepatocellular carcinoma (HCC) induced by hepatitis B virus (HBV). Therefore, the aim of this study was to investigate the role of LINC02532 in HCC, mainly for diagnostic prognostic value and cellular function, as well as mechanistic aspects. METHODS: Initially, GEO and VirBase databases were used to screen for aberrant lncRNAs in HBV-HCC.Then, HBV-HCC persons followed up in our center were retrospectively studied to investigate the diagnostic, prognostic value of LINC02532 in HBV-HCC. Subsequently, the role of LINC02532 in HBV-HCC was measured using cellular function assay methods and possible mechanisms were analyzed in conjunction with bioinformatic predictive science. RESULTS: LINC02532 was a lncRNA abnormally expressed in HBV-HCC. LINC02532 was significantly up-regulated in the expression level in HBV-HCC tissues compared with normal tissues from patients. Moreover, LINC02532 could distinguish HBV-HCC and predict the prognosis of HBV-HCC. In vitro experiments showed that LINC02532 could regulate miR-455-3p and promote the malignant characterization of HBV-HCC cells. CHEK2 was a target gene of miR-455-3p. CONCLUSIONS: The prognosis and diagnosis of HBV-HCC can rely on the expression of LINC02532. LINC02532 was important for further progression of HBV-HCC, by moderating miR-455-3p/CHEK2.

Multi-step control of homologous recombination via Mec1/ATR suppresses chromosomal rearrangements.

The Mec1/ATR kinase is crucial for genome stability, yet the mechanism by which it prevents gross chromosomal rearrangements (GCRs) remains unknown. Here we find that in cells with deficient Mec1 signaling, GCRs accumulate due to the deregulation of multiple steps in homologous recombination (HR). Mec1 primarily suppresses GCRs through its role in activating the canonical checkpoint kinase Rad53, which ensures the proper control of DNA end resection. Upon loss of Rad53 signaling and resection control, Mec1 becomes hyperactivated and triggers a salvage pathway in which the Sgs1 helicase is recruited to sites of DNA lesions via the 911-Dpb11 scaffolds and phosphorylated by Mec1 to favor heteroduplex rejection and limit HR-driven GCR accumulation. Fusing an ssDNA recognition domain to Sgs1 bypasses the requirement of Mec1 signaling for GCR suppression and nearly eliminates D-loop formation, thus preventing non-allelic recombination events. We propose that Mec1 regulates multiple steps of HR to prevent GCRs while ensuring balanced HR usage when needed for promoting tolerance to replication stress.

Myeloid neoplasms in individuals with breast and ovarian cancer and the association with deleterious germline variants.

Historically, the increased incidence of myeloid neoplasms observed in individuals with breast and ovarian cancer has been attributed exclusively to prior exposure to cancer-directed therapies. However, as the association between deleterious germline variants and the development of hematopoietic malignancies (HMs) becomes better established, we propose the increased incidence of myeloid neoplasms in those with breast and ovarian cancer may be at least partially related to underlying germline cancer predisposition alleles. Deleterious germline variants in BRCA1/2, ATM, CHEK2, PALB2, and other related genes prevent normal homologous recombination DNA repair of double-strand breaks, leading to reliance on less effective repair mechanisms. This results in a high lifetime risk of breast and ovarian cancer, and likely also increases the risk of subsequent therapy-related myeloid neoplasms (t-MNs). These deleterious germline variants likely increase the risk for de novo HMs as well, as evidenced by the increased incidence of HMs observed in those with deleterious germline BRCA1/2 variants even in the absence of prior cancer-directed therapy. Thus, the association between poly(ADP-ribose) polymerase (PARP) inhibitors and other solid tumor directed therapies and the development of t-MNs may be confounded by the presence of deleterious germline variants which inherently increase the risk of both de novo and t-MNs, and additional data regarding the direct toxic effects of these drugs on bone marrow function are needed.