A novel interplay between the Fanconi anemia core complex and ATR-ATRIP kinase during DNA cross-link repair.

When DNA replication is stalled at sites of DNA damage, a cascade of responses is activated in the cell to halt cell cycle progression and promote DNA repair. A pathway initiated by the kinase Ataxia teleangiectasia and Rad3 related (ATR) and its partner ATR interacting protein (ATRIP) plays an important role in this response. The Fanconi anemia (FA) pathway is also activated following genomic stress, and defects in this pathway cause a cancer-prone hematologic disorder in humans. Little is known about how these two pathways are coordinated. We report here that following cellular exposure to DNA cross-linking damage, the FA core complex enhances binding and localization of ATRIP within damaged chromatin. In cells lacking the core complex, ATR-mediated phosphorylation of two functional response targets, ATRIP and FANCI, is defective. We also provide evidence that the canonical ATR activation pathway involving RAD17 and TOPBP1 is largely dispensable for the FA pathway activation. Indeed DT40 mutant cells lacking both RAD17 and FANCD2 were synergistically more sensitive to cisplatin compared with either single mutant. Collectively, these data reveal new aspects of the interplay between regulation of ATR-ATRIP kinase and activation of the FA pathway.

Association Between Preoperative Osteopenia and Prognosis in Breast Cancer Patients.

BACKGROUND/AIM: Osteopenia, the loss of bone mineral density (BMD), was recently reported as a prognostic factor in various cancers. However, the prognostic significance of preoperative osteopenia in breast cancer remains unclear. This study aimed to clarify the clinical significance of preoperative osteopenia in breast cancer. PATIENTS AND METHODS: We retrospectively analyzed the relationship between osteopenia and clinical factors and prognosis in 532 patients with pathological Stage I-III primary breast cancer between 2009 and 2017. Osteopenia was assessed by measuring the average pixel density (Hounsfield unit) in the midvertebral core of the 11th thoracic vertebra on enhanced preoperative computed tomography. RESULTS: Osteopenia was diagnosed in 186 (35.0%) patients. The recurrence-free survival (RFS) rate was significantly worse in the osteopenia group than in the non-osteopenia group (p=0.0275), but there was no significant difference in overall survival (OS) between the two groups. When evaluated by menopausal status, RFS and OS were significantly worse in the osteopenia group than in the non-osteopenia group (p=0.0094 and p=0.0264, respectively) in premenopausal patients. However, there were no significant differences in RFS and OS between the two groups among postmenopausal patients. In premenopausal patients, osteopenia was an independent prognostic factor for RFS in a multivariate analysis (p=0.0266). CONCLUSION: Preoperative osteopenia was independently associated with recurrence of breast cancer.

Trastuzumab deruxtecan for human epidermal growth factor receptor 2-low advanced or metastatic breast cancer: recommendations from the Japanese Breast Cancer Society Clinical Practice Guidelines.

The Japanese Breast Cancer Society Clinical Practice Guidelines are published as timely guidance on clinical issues in breast cancer treatment in Japan. In the recent edition of these guidelines, we addressed a new clinical question 34 (CQ 34, systemic treatment part) "Is trastuzumab deruxtecan recommended for patients with unresectable or metastatic HER2-low breast cancer?" and a new future research question 7 (FRQ 7, pathological diagnosis part) "How is HER2-low breast cancer diagnosed for the indication of trastuzumab deruxtecan?". These questions address use of trastuzumab deruxtecan in patients with unresectable or metastatic HER2-low breast cancer who have previously received chemotherapy for metastatic disease. The strengths of evidence and recommendation were determined through a quantitative and qualitative systematic review using multiple outcomes, including efficacy and safety. We conclude that trastuzumab deruxtecan is recommended for this patient population (strength of recommendation: 1; strength of evidence: moderate; CQ34) and that HER2-low expression for the indication of trastuzumab deruxtecan should be diagnosed using companion diagnostics based on appropriate criteria (FRQ7).

Successful Prevention of Tumour Lysis Syndrome in HER2-positive Breast Cancer: Case Report and Literature Review.

BACKGROUND/AIM: Tumour lysis syndrome (TLS) is a life-threatening oncological emergency. TLS is rare and associated with a higher mortality rate in solid tumours than in haematological malignancies. Our case report and literature review aimed to identify the distinctive features and hazards of TLS in breast cancer. CASE REPORT: A 41-year-old woman complained of vomiting and epigastric pain and was diagnosed with HER2-positive, hormone-receptor-positive breast cancer with multiple liver and bone metastases and lymphangitis carcinomatosis. She had several risk factors for TLS: high tumour volume, high sensitivity to antineoplastic treatment, multiple liver metastases, high lactate dehydrogenase levels, and hyperuricaemia. To prevent TLS, she was treated with hydration and febuxostat. One day after the first course of trastuzumab and pertuzumab, she was diagnosed with disseminated intravascular coagulation (DIC). After 3 further days of observation, she was relieved of DIC and administered a reduced dose of paclitaxel without life-threatening complications. The patient achieved a partial response after four cycles of anti-HER2 therapy and chemotherapy. CONCLUSION: TLS in solid tumours is a lethal situation and can be complicated by DIC. Early recognition of patients who are at risk of TLS and initiation of therapy is essential to avoid fatal situations.

The Japanese Breast Cancer Society Clinical Practice Guidelines for systemic treatment of breast cancer, 2022 edition.

The Japanese Breast Cancer Society (JBCS) Clinical Practice Guidelines for systemic treatment of breast cancer were updated to the 2022 edition through a process started in 2018. The updated guidelines consist of 12 background questions (BQs), 33 clinical questions (CQs), and 20 future research questions (FRQs). Multiple outcomes including efficacy and safety were selected in each CQ, and then quantitative and qualitative systematic reviews were conducted to determine the strength of evidence and strength of recommendation, which was finally determined through a voting process among designated committee members. Here, we describe eight selected CQs as important updates from the previous guidelines, including novel practice-changing updates, and recommendations based on evidence that has emerged specifically from Japanese clinical trials.

ATR-ATRIP kinase complex triggers activation of the Fanconi anemia DNA repair pathway.

ATR kinase activates the S-phase checkpoint when replication forks stall at sites of DNA damage. This event also causes phosphorylation of the Fanconi anemia (FA) protein FANCI, triggering its monoubiquitination of the key DNA repair factor FANCD2 by the FA core E3 ligase complex, thereby promoting this central pathway of DNA repair which permits replication to be restarted. However, the interplay between ATR and the FA pathway has been unclear. In this study, we present evidence that their action is directly linked, gaining insights into this relationship in a DT40 mutant cell line that is conditionally deficient in the critical ATR-binding partner protein ATRIP. Using this system, we showed that ATRIP was crucial for DNA damage-induced FANCD2 monoubiquitination and FANCI phosphorylation. ATR kinase phosphorylated recombinant FANCI protein in vitro, which was facilitated by the presence of FANCD2. Mechanistic investigations revealed that the RPA region but not the TopBP1 region of ATRIP was required for FANCD2 monoubiquitination, whereas Chk1 phosphorylation relied upon both domains. Together, our findings identify ATR as the kinase responsible for activating the FA pathway of DNA repair.