Rare SNP in the HELB gene interferes with RPA interaction and cellular function of HELB

HELB is a human helicase involved in initiation of DNA replication, the replication stress response, and regulation of double-strand DNA break repair. rs75770066 is a rare SNP in the HELB gene that affects age at natural menopause. rs75770066 results in a D506G substitution in an acidic patch within the 1A domain of the helicase that is known to interact with RPA. We found that this amino acid change dramatically impairs the cellular function of HELB. D506G-HELB exhibits impaired interaction with RPA, which likely results in the effects of rs75770066 as this reduces recruitment of HELB to sites of DNA damage. Reduced recruitment of D506G-HELB to double-strand DNA breaks and the concomitant increase in homologous recombination likely alters the levels of meiotic recombination, which affects the viability of gametes. Because menopause occurs when oocyte levels drop below a minimum threshold, altered repair of meiotic double-stranded DNA breaks has the potential to directly affect the age at natural menopause.

Abstract 1010: LIG1 deletion predicts chemotherapy resistance, chromosomal instability, and poor prognosis in triple negative breast cancer

Introduction: Cytotoxic chemotherapy for sporadic Triple Negative Breast Cancer (TNBC) remains the standard of care and the recent approval for adjuvant PD1 therapy is not biomarker guided. Pathological complete response (pCR) is often not achieved and portends poor survival. Predictive markers for individual drugs have proven elusive.

Approach: Microscaled proteogenomics (MPG) was applied to snap-frozen TNBC clinical trial core needle biopsies obtained before treatment with carboplatin and docetaxel (WashU: NCT201404107 and BCM: NCT02544987). Clinical endpoints for discovery analysis were pathological complete response (pCR) and residual cancer burden (RCB). Standard non-parametric statistical tests were employed to identify proteogenomic features associated with these endpoints.

Results: Copy number aberrations (CNA) are a recurrent feature of TNBC and a potential driver of chemotherapy sensitivity. We therefore sought CNA with concordant changes at the mRNA and protein levels that also associate with pCR status. Genes located within a recurrent interstitial deletion at chromosomal location 19q13.3 were the most significantly down-regulated at mRNA and protein level in chemotherapy resistant cases. 19q13.3 encodes multiple DNA damage response (DDR) genes; however, only LIG1, a DNA ligase required for lagging strand synthesis and DNA repair, showed concordant changes at both the mRNA and protein level. In multiple independent TNBC data sets, LIG1 deletion was associated lack of pCR and poor metastasis-free survival. Additionally in the BrighTNess TNBC trial lower LIG1 mRNA levels were associated with increased chemotherapy resistance in the carboplatin containing arms (no pCR and residual cancer burden I-III; p=0.0008 and 0.003 respectively). In PDX-derived short-term cultures and PDXs treated with docetaxel or carboplatin, a specific association of carboplatin resistance with LIG1 deletion was observed. LIG1 depleted-tumors did not harbor elevated scores for homologous recombination defect signature, suggesting LIG1 loss is an orthogonal pathway for TNBC pathogenesis The high chromosomal instability index in LIG1 deletion tumors in our TNBC study was robustly reproduced in multiple datasets (including TCGA-BRCA ; Metastatic breast cancer project). LIG1 copy number deletion was also associated with poor progression free survival, and high chromosomal instability in multiple other cancers (including TCGA-​UCEC HR=2.23, TCGA-HNSC HR=1.46, TCGA-PRAD HR=2.07, TCGA- COAD HR=1.75 and TCGA-KIRP HR=4.00).

Conclusion: Deletion of LIG1 is associated with chromosomal instability in TNBC and occurs in tumors without genomic evidence for defects in homologous recombination. Other clinical features of LIG1 deleted TNBC and how LIG1 loss may cause chromosomal instability and tumorigenesis will be discussed.

Citation Format: Meenakshi Anurag, Eric Jaehnig, Jonathan Lei, Beom-Jun Kim, Anh Minh Tran Huynh, Yongchao Dou, Tanmayi Vashist, Erik Bergstrom, Xuxu Gou, Viktoriya Korchina, Donna Marie Muzny, Kristen Otte, Harshavardhan Doddapaneni, Lacey Dobrolecki, Gloria Vittone Echeverria, Bora Lim, Mothaffar Rimawi, Karsten Krug, Ian Hageman, Henry Rodriguez, Ana I. Robles, Tara Hiltke, Kent Osborne, Michael Gillette, George Miles, Steven Carr, Michael T Lewis, Bing Zhang, Foluso Ademuyiwa, Shankha Satpathy, Matthew J. Ellis. LIG1 deletion predicts chemotherapy resistance, chromosomal instability, and poor prognosis in triple negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1010.

Does initial breastfeeding lead to lower blood cholesterol in adult life? A quantitative review of the evidence

BACKGROUND

Earlier studies have suggested that infant feeding may program long-term changes in cholesterol metabolism.

OBJECTIVE

We aimed to examine whether breastfeeding is associated with lower blood cholesterol concentrations in adulthood.

DESIGN

The study consisted of a systematic review of published observational studies relating initial infant feeding status to blood cholesterol concentrations in adulthood (ie, aged >16 y). Data were available from 17 studies (17 498 subjects; 12 890 breastfed, 4608 formula-fed). Mean differences in total cholesterol concentrations (breastfed minus formula-fed) were pooled by using fixed-effect models. Effects of adjustment (for age at outcome, socioeconomic position, body mass index, and smoking status) and exclusion (of nonexclusive breast feeders) were examined.

RESULTS

Mean total blood cholesterol was lower (P = 0.037) among those ever breastfed than among those fed formula milk (mean difference: -0.04 mmol/L; 95% CI: -0.08, 0.00 mmol/L). The difference in cholesterol between infant feeding groups was larger (P = 0.005) and more consistent in 7 studies that analyzed "exclusive" feeding patterns (-0.15 mmol/L; -0.23, -0.06 mmol/L) than in 10 studies that analyzed nonexclusive feeding patterns (-0.01 mmol/L; -0.06, 0.03 mmol/L). Adjustment for potential confounders including socioeconomic position, body mass index, and smoking status in adult life had minimal effect on these estimates.

CONCLUSIONS

Initial breastfeeding (particularly when exclusive) may be associated with lower blood cholesterol concentrations in later life. Moves to reduce the cholesterol content of formula feeds below those of breast milk should be treated with caution.

Pulmonary epithelial integrity in children: relationship to ambient ozone exposure and swimming pool attendance

Airway irritants such as ozone are known to impair lung function and induce airway inflammation. Clara cell protein (CC16) is a small anti-inflammatory protein secreted by the nonciliated bronchiolar Clara cells. CC16 in serum has been proposed as a noninvasive and sensitive marker of lung epithelial injury. In this study, we used lung function and serum CC16 concentration to examine the pulmonary responses to ambient O3 exposure and swimming pool attendance. The measurements were made on 57 children 10-11 years of age before and after outdoor exercise for 2 hr. Individual O3 exposure was estimated as the total exposure dose between 0700 hr until the second blood sample was obtained (mean O3 concentration/m3 times symbol hours). The maximal 1-hr value was 118 microg/m3 (59 ppb), and the individual exposure dose ranged between 352 and 914 microg/m3hr. These O3 levels did not cause any significant changes in mean serum CC16 concentrations before or after outdoor exercise, nor was any decrease in lung function detected. However, children who regularly visited chlorinated indoor swimming pools had significantly lower CC16 levels in serum than did nonswimming children both before and after exercise (respectively, 57 +/- 2.4 and 53 +/- 1.7 microg/L vs. 8.2 +/- 2.8 and 8.0 +/- 2.6 microg/L; p < 0.002). These results indicate that repeated exposure to chlorination by-products in the air of indoor swimming pools has adverse effects on the Clara cell function in children. A possible relation between such damage to Clara cells and pulmonary morbidity (e.g., asthma) should be further investigated.

An international study of the exposure of children to traffic

OBJECTIVES

To examine the extent of international differences in children's exposure to traffic as pedestrians or bicyclists.

DESIGN

Children's travel patterns were surveyed using a parent-child administered questionnaire. Children were sampled via primary schools, using a probability cluster sampling design.

SETTING

Six cities in five countries: Melbourne and Perth (Australia), Montreal (Canada), Auckland (New Zealand), Umeå (Sweden), and Baltimore (USA).

SUBJECTS

Children aged 6 and 9 years.

MAIN OUTCOME MEASURES

Modes of travel on the school-home journey, total daily time spent walking, and the average daily number of roads crossed.

MAIN FINDINGS

Responses were obtained from the parents of 13423 children. There are distinct patterns of children's travel in the six cities studied. Children's travel in the three Australasian cities, Melbourne, Perth and Auckland, is characterised by high car use, low levels of bicycling, and a steep decline in walking with increasing car ownership. In these cities, over a third of the children sampled spent less than five minutes walking per day. In Montreal, walking and public transport were the most common modes of travel. In Umeå, walking and bicycling predominated, with very low use of motorised transport. In comparison with children in the Australasian and North American cities, children in Umeå spend more time walking, with 87% of children walking for more than five minutes per day.

CONCLUSIONS

There are large international differences in the extent to which children walk and cycle. These findings would suggest that differences in 'exposure to risk' may be an important contributor to international differences in pedestrian injury rates. There are also substantial differences in pedestrian exposure to risk by levels of car ownership-differences that may explain socioeconomic differentials in pedestrian injury rates.

Intrathecal baclofen--a multicentre clinical comparison of the Medtronics Programmable, Cordis Secor and Constant Infusion Infusaid drug delivery systems

A retrospective review was carried out of 34 consecutive traumatic spinal cord damaged patients who have had the Medtronics Programmable, Cordis Secor or Constant Infusion Infusaid intrathecal baclofen drug delivery systems inserted between July 1987 and 1992. The results indicate that whilst this treatment has many benefits there is a significant risk of complications, some potentially fatal. It should only be provided by a skilled and experienced team. The Medtronics Programmable pump is an excellent pump. It is of particular benefit where the therapeutic window is small or fine-tuning required. The Constant Infusion Infusaid is adequate if less precise control and continuous infusion is sufficient. It is of particular benefit in financially disadvantaged countries. The Cordis Secor device is helpful when unpredictable intermittent relief of spasticity is required but is otherwise limited by its complication rate.

Increased hypoxic ventilatory sensitivity during exercise in man: are neural afferents necessary?

1. The acute ventilatory response to 3 min periods of hypoxia (AHR) was examined in nine patients with clinically complete spinal cord transection (T4-T7) during (a) rest and (b) electrically induced leg exercise (EEL). 2. EEL was produced by surface electrode stimulation of the quadriceps muscles so as to cause the legs to extend at the knee against gravity. End-tidal PCO2 was held constant 1-2 mmHg above resting values throughout both protocols. 3. On exercise, the average increase in metabolic CO2 production (VCO2 +/- S.E.M.) was 41 +/- 5 ml min-1. Venous lactate levels did not rise with exercise. 4. Baseline euoxic ventilation did not increase significantly with EEL, but there was a consistent and highly significant increase in the ventilatory response to hypoxia during EEL (mean delta AHR +/- S.E.M. of 1.6 +/- 0.21 min-1). 5. We conclude that an increase in hypoxic sensitivity during exercise can occur in the absence of volitional control of exercise and in the absence of afferent neural input from the limbs.

Long-term spinal cord injury: functional changes over time

Functional changes were assessed in a group of 279 individuals with long-term spinal cord injuries. All had sustained their initial injuries 20 to 47 years ago and all had received initial and postinjury follow-up care at one of two British spinal cord injury treatment centers. Twenty-two percent reported that the need for physical assistance from others had increased over the years. Most (45%) needed additional help with transfers; others needed more assistance with dressing, mobility, and toileting. When compared to those whose need for help had not increased, significant differences were found by age: as a group, and when separated by level and severity of injury, those needing more help were older, and those with cervical injuries needed help at younger ages than their counterparts with lower level injuries. Those needing more help also had significantly more reports of shoulder pain, fatigue and weakness, weight gain, and postural changes. They used more attendant care, and perceived their quality of life to be lower than those whose level of function had not changed over time.

PRIMARY CULTURES OF EPITHELIAL CELLS FROM RAINBOW TROUT GILLS

A method for obtaining primary cultures of epithelial cells from rainbow trout gills is described. The yield of cells from approximately 1.5 g wet mass of tissue was 218×106+/−12×106 cells with a viability defined by eosin exclusion of 80+/−6 %. Cells were seeded in culture dishes and grown in Leibowitz L-15 medium supplemented with 5 % foetal bovine serum. Attachment efficiency after 24 h was 35+/−6 %. The cells appeared confluent 10–12 days after seeding and exhibited surface structures similar to those seen on respiratory epithelial cells of trout gills in vivo. Growth rate, [3H]thymidine incorporation and attachment efficiency were used to evaluate culture conditions. Epidermal growth factor, insulin, transferrin, hydrocortisone, laminin and collagen did not improve growth and attachment. Similarly, coating the culture dishes with rat tail collagen, trout skin extract, laminin or a mixture of human basement membrane proteins (Matrigel) failed to improve attachment. It is concluded that the cells in culture are respiratory epithelial cells and that this culture system could provide a valuable new approach for studying the physiology of these cells.