Correlation of umbilical cord blood haematopoietic stem and progenitor cell levels with birth weight: implications for a prenatal influence on cancer risk

Multi-omics Analysis of Umbilical Cord Hematopoietic Stem Cells from a Multi-ethnic Cohort of Hawaii Reveals the Transgenerational Effect of Maternal Pre-Pregnancy Obesity

Background

Maternal obesity is a health concern that may predispose newborns to a high risk of medical problems later in life. To understand the transgenerational effect of maternal obesity, we conducted a multi-omics study, using DNA methylation and gene expression in the CD34+/CD38-/Lin- umbilical cord blood hematopoietic stem cells (uHSCs) and metabolomics of the cord blood, all from a multi-ethnic cohort (n=72) from Kapiolani Medical Center for Women and Children in Honolulu, Hawaii (collected between 2016 and 2018).

Results

Differential methylation (DM) analysis unveiled a global hypermethylation pattern in the maternal pre-pregnancy obese group (BH adjusted p<0.05), after adjusting for major clinical confounders. Comprehensive functional analysis showed hypermethylation in promoters of genes involved in cell cycle, protein synthesis, immune signaling, and lipid metabolism. Utilizing Shannon entropy on uHSCs methylation, we discerned notably higher quiescence of uHSCs impacted by maternal obesity. Additionally, the integration of multi-omics data-including methylation, gene expression, and metabolomics-provided further evidence of dysfunctions in adipogenesis, erythropoietin production, cell differentiation, and DNA repair, aligning with the findings at the epigenetic level. Furthermore, the CpG sites associated with maternal obesity from these pathways also predicted highly accurately (average AUC = 0.8687) between cancer vs. normal tissues in 14 cancer types in The Cancer Genome Atlas (TCGA).

Conclusions

This study revealed the significant correlation between pre-pregnancy maternal obesity and multi-omics level molecular changes in the uHSCs of offspring, particularly in DNA methylation. Moreover, these maternal obesity epigenetic markers in uHSCs may predispose offspring to higher cancer risks.

Associations of Early-Life and Adult Anthropometric Measures with the Expression of Stem Cell Markers CD44, CD24, and ALDH1A1 in Women with Benign Breast Biopsies

BACKGROUND

According to the stem cell hypothesis, breast carcinogenesis may be related to the breast stem cell pool size. However, little is known about associations of breast cancer risk factors, such as anthropometric measures, with the expression of stem cell markers in noncancerous breast tissue.

METHODS

The analysis included 414 women with biopsy-confirmed benign breast disease in the Nurses' Health Study and Nurses' Health Study II. Birthweight, weight at age 18, current weight, and current height were reported via self-administered questionnaires. IHC staining of stem cell markers (CD44, CD24, and aldehyde dehydrogenase family 1 member A1) in histopathologically normal epithelial and stromal breast tissue was quantified using an automated computational image analysis system. Linear regression was used to examine the associations of early-life and adult anthropometric measures with log-transformed stem cell marker expression, adjusting for potential confounders.

RESULTS

Birthweight [≥10.0 vs. <5.5 lbs: β (95% confidence interval) = 4.29 (1.02, 7.56); P trend = 0.001 in the stroma] and adult height [≥67.0 vs. <63.0 inch: 0.86 (0.14, 1.58); P trend = 0.02 in the epithelium and stroma combined] were positively associated with CD44 expression. Childhood body fatness was inversely associated (P trend = 0.03) whereas adult height was positively associated with CD24 expression in combined stroma and epithelium (P trend = 0.03).

CONCLUSIONS

Our data suggest that anthropometric measures, such as birthweight, adult height, and childhood body fatness, may be associated with the stem cell expression among women with benign breast disease.

IMPACT

Anthropometric measures, such as birthweight, height, and childhood body fatness, may have long-term impacts on stem cell population in the breast.

Why does hormonal contraception and menopausal hormonal treatment have such a small effect on breast cancer risk?

Oestrogen is considered by many to be a major cause of breast cancer, and yet hormonal contraception and menopausal hormonal therapy have a paradoxically small effect on breast cancer risk. Also, in the oestrogen-only arm of the Women's Health Initiative, subjects given oestrogen had a reduced risk of breast cancer compared to controls. Initiation of breast cancer likely begins early in life, in the long-lived ER-PR- breast stem cell. The main mitogen of ER+PR+ breast cancers is oestrogen derived from local breast fat and the tumour itself, rather than circulating oestrogens. Progesterone is relatively breast neutral, but progestins in the laboratory have been shown to expand malignant breast stem cell number.

Overexpression of IGF-1 During Early Development Expands the Number of Mammary Stem Cells and Primes them for Transformation

Insulin-like growth factor I (IGF-1) has been implicated in breast cancer due to its mitogenic and anti-apoptotic effects. Despite substantial research on the role of IGF-1 in tumor progression, the relationship of IGF-1 to tissue stem cells, particularly in mammary tissue, and the resulting tumor susceptibility has not been elucidated. Previous studies with the BK5.IGF-1 transgenic (Tg) mouse model reveals that IGF-1 does not act as a classical, post-carcinogen tumor promoter in the mammary gland. Pre-pubertal Tg mammary glands display increased numbers and enlarged sizes of terminal end buds, a niche for mammary stem cells (MaSCs). Here we show that MaSCs from both wild type (WT) and Tg mice expressed IGF-1R and that overexpression of Tg IGF-1 increased numbers of MaSCs by undergoing symmetric division, resulting in an expansion of the MaSC and luminal progenitor (LP) compartments in pre-pubertal female mice. This expansion was maintained post-pubertally and validated by mammosphere assays in vitro and transplantation assays in vivo. The addition of recombinant IGF-1 promoted, and IGF-1R downstream inhibitors decreased mammosphere formation. Single-cell transcriptomic profiles generated from two related platforms reveal that IGF-1 stimulated quiescent MaSCs to enter the cell cycle and increased their expression of genes involved in proliferation, plasticity, tumorigenesis, invasion, and metastasis. This study identifies a novel, pro-tumorigenic mechanism, where IGF-1 increases the number of transformation-susceptible carcinogen targets during the early stages of mammary tissue development, and “primes” their gene expression profiles for transformation.

The association of women's birth size with risk of molecular breast cancer subtypes: a cohort study

Background

Because birth size appears to be positively associated with breast cancer risk, we have studied whether this risk may differ according to molecular breast cancer subtypes.

Methods

A cohort of 22,931 women born 1920–1966 were followed up for breast cancer occurrence from 1961 to 2012, and 870 were diagnosed during follow-up. Archival diagnostic material from 537 patients was available to determine molecular breast cancer subtype, specified as Luminal A, Luminal B (human epidermal growth factor receptor 2 (HER2)-), Luminal B (HER2+), HER2 type, and Triple negative (TN) breast cancer. Information on the women’s birth weight, birth length and head circumference at birth was used to estimate hazard ratios (HR) with 95% confidence intervals (CI) for each molecular subtype, applying Cox regression, and stratified by maternal height.

Results

Birth length (per 2 cm increments) was positively associated with Luminal A (HR = 1.2, 95% CI, 1.0–1.3), Luminal B (HER2+) (HR = 1.3, 95% CI, 1.0–1.7), and TN breast cancer (HR = 1.4, 95% CI, 1.0–1.9). No clear association was found for birth weight and head circumference. The positive associations of birth length were restricted to women whose mothers were relatively tall (above population median).

Conclusion

We found a positive association of birth length with risk of Luminal A, Luminal B (HER2+) and TN breast cancer that appears to be restricted to women whose mothers were relatively tall. This may support the hypothesis that breast cancer risk is influenced by determinants of longitudinal growth and that this finding deserves further scrutiny.

Identification of Differentially Expressed Hematopoiesis-associated Genes in Term Low Birth Weight Newborns by Systems Genomics Approach

Background

Low Birth Weight (LBW) (birth weight <2.5 Kg) newborns are associated with a high risk of infection, morbidity and mortality during their perinatal period. Compromised innate immune responses and inefficient hematopoietic differentiation in term LBW newborns led us to evaluate the gene expression status of hematopoiesis.

Materials and Methods

In this study, we compared our microarray datasets of LBW-Normal Birth Weight (NBW) newborns with two reference datasets to identify hematopoietic stem cells genes, and their differential expression in the LBW newborns, by hierarchical clustering algorithm using gplots and RcolorBrewer package in R.

Results

Comparative analysis revealed 108 differentially expressed hematopoiesis genes (DEHGs), of which 79 genes were up-regulated, and 29 genes were down-regulated in LBW newborns compared to their NBW counterparts. Moreover, protein-protein interactions, functional annotation and pathway analysis demonstrated that the up-regulated genes were mainly involved in cell proliferation and differentiation, MAPK signaling and Rho GTPases signaling, and the down-regulated genes were engaged in cell proliferation and regulation, immune system regulation, hematopoietic cell lineage and JAK-STAT pathway. The binding of down-regulated genes (LYZ and GBP1) with growth factor GM-CSF using docking and MD simulation techniques, indicated that GM-CSF has the potential to alleviate the repressed hematopoiesis in the term LBW newborns.

Conclusion

Our study revealed that DEHGs belonged to erythroid and myeloid-specific lineages and may serve as potential targets for improving hematopoiesis in term LBW newborns to help build up their weak immune defense against life-threatening infections.

The association between weight at birth and breast cancer risk revisited using Mendelian randomisation

Observational studies suggest that higher birth weight (BW) is associated with increased risk of breast cancer in adult life. We conducted a two-sample Mendelian randomisation (MR) study to assess whether this association is causal. Sixty independent single nucleotide polymorphisms (SNPs) known to be associated at P < 5 × 10-8 with BW were used to construct (1) a 41-SNP instrumental variable (IV) for univariable MR after removing SNPs with pleiotropic associations with other breast cancer risk factors and (2) a 49-SNP IV for multivariable MR after filtering SNPs for data availability. BW predicted by the 41-SNP IV was not associated with overall breast cancer risk in inverse-variance weighted (IVW) univariable MR analysis of genetic association data from 122,977 breast cancer cases and 105,974 controls (odds ratio = 0.86 per 500 g higher BW; 95% confidence interval 0.73-1.01). Sensitivity analyses using four alternative methods and three alternative IVs, including an IV with 59 of the 60 BW-associated SNPs, yielded similar results. Multivariable MR adjusting for the effects of the 49-SNP IV on birth length, adult height, adult body mass index, age at menarche, and age at menopause using IVW and MR-Egger methods provided estimates consistent with univariable analyses. Results were also similar when all analyses were repeated after restricting to estrogen receptor-positive or -negative breast cancer cases. Point estimates of the odds ratios from most analyses performed indicated an inverse relationship between genetically-predicted BW and breast cancer, but we are unable to rule out an association between the non-genetically-determined component of BW and breast cancer. Thus, genetically-predicted higher BW was not associated with an increased risk of breast cancer in adult life in our MR study.

Breast cancer protection by genomic imprinting in close kin families

Human inbreeding generally reduces breast cancer risk (BCR). When the parents are biologically related, their infants have a lower birth weight due to smaller body organs. The undersized breasts, because of fewer mammary stem cells, have a lower likelihood of malignant conversion. Fetal growth is regulated by genomically imprinted genes which are in conflict; they promote growth when derived from the father and suppress growth when derived from the mother. The kinship theory explicates that the intensity of conflict between these genes affects growth and therefore the size of the newborn. In descendants of closely related parents, this gene clash is less resulting in a smaller infant. In this review, we elucidate the different mechanisms by which human inbreeding affects BCR, and why this risk is dissimilar in different inbred populations.

Roles of Endogenous Retroviruses in Early Life Events

A retrovirus that infected our ancestors 100 million years ago became a human gene that is expressed in embryos and cancers, and can be detected in the blood of pregnant women. Accumulating evidence suggests potential roles for endogenous retroviruses in early life events, which may affect adult health.

The effect of maternal and infant factors on cord blood yield

Umbilical cord blood (CB) can be used as an alternative hematopoietic stem cell source for transplantation in hematological malignancy and blood disorders. The success of transplantation is highly related to the levels of total nucleated cell and CD34⁺ cell counts. The evaluation of optimal conditions can decrease the rate of graft rejection due to low cell count and increases the quality of CB units (CBUs) in the blood bank and the success rate of engraftment. To this end, we review the maternal and infant parameters affecting the quality and quantity of CBUs.

Is birthweight associated with total and aggressive/lethal prostate cancer risks? A systematic review and meta-analysis

Background:

It has been hypothesised that intrauterine exposures are important for subsequent prostate cancer risk. Prior epidemiological studies have used birthweight as a proxy of cumulative intrauterine exposures to test this hypothesis, but results have been inconsistent partly because of limited statistical power.

Methods:

We investigated birthweight in relation to prostate cancer in the Medical Research Council (MRC) National Survey of Health and Development (NSHD) using Cox proportional hazards models. We then conducted a meta-analysis of birthweight in relation to total and aggressive/lethal prostate cancer risks, combining results from the NSHD analysis with 13 additional studies on this relationship identified from a systematic search in four major scientific literature databases through January 2015.

Results:

Random-effects models found that per kg increase in birthweight was positively associated with total (OR=1.02, 95% confidence interval (95% CI)=1.00, 1.05; I²=13%) and aggressive/lethal prostate cancer (OR=1.08, 95% CI=0.99, 1.19; I²=40%). Sensitivity analyses restricted to studies with birthweight extracted from medical records demonstrated stronger positive associations with total (OR=1.11, 95% CI=1.03, 1.19; I²=0%) and aggressive/lethal (OR=1.37, 95% CI=1.09, 1.74; I²=0%) prostate cancer. These studies heavily overlapped with those based in Nordic countries.

Conclusions:

This study provides evidence that heavier birthweight may be associated with modest increased risks of total and aggressive/lethal prostate cancer, which supports the hypothesis that intrauterine exposures may be related to subsequent prostate cancer risks.

Size at birth and risk of breast cancer: update from a prospective population-based study

Birth size variables (birth weight, birth length and head circumference) have been reported to be positively associated with adult breast cancer risk, whereas a possible association of placental weight has not been adequately studied. It has also been suggested that maternal height may modify the association of birth size with adult breast cancer risk, but this has not been studied in detail. We updated a long-term follow-up of 22,931 Norwegian women (average of 51 years of follow up during which 870 women were diagnosed with breast cancer) and assessed placental weight in relation to breast cancer risk, in addition to providing updated analyses on breast cancer risk in relation to birth weight, birth length and head circumference. Placental weight was not associated with risk for breast cancer in adulthood, but there was a positive association of breast cancer risk with birth length (HR 1.13, 95% CI 1.05-1.21, per 2 cm increment), though not with birth weight (HR 1.02, 95% CI 0.95-1.10 per 0.5 kg increment). For birth length, the graded increase in risk was particularly strong among women whose mothers were relatively tall (p for trend, 0.001), compared to the trend among women whose mothers were relatively short (p for trend, 0.221). The results showed a robust and positive association of birth length with breast cancer risk, and may be especially strong in women whose mothers were relatively tall. We found no association of placental weight with risk for breast cancer.

Infant birthweight and risk of childhood cancer: international population-based case control studies of 40 000 cases

BACKGROUND

High birthweight is an established risk factor for childhood leukaemia. Its association with other childhood cancers is less clear, with studies hampered by low case numbers.

METHODS

We used two large independent datasets to explore risk associations between birthweight and all subtypes of childhood cancer. Data for 16 554 cases and 53 716 controls were obtained by linkage of birth to cancer registration records across five US states, and 23 772 cases and 33 206 controls were obtained from the UK National Registry of Childhood Tumours. US, but not UK, data were adjusted for gestational age, birth order, plurality, and maternal age and race/ethnicity.

RESULTS

Risk associations were found between birthweight and several childhood cancers, with strikingly similar results between datasets. Total cancer risk increased linearly with each 0.5 kg increase in birthweight in both the US [odds ratio 1.06 (95% confidence interval 1.04, 1.08)] and UK [1.06 (1.05, 1.08)] datasets. Risk was strongest for leukaemia [USA: 1.10 (1.06, 1.13), UK: 1.07 (1.04, 1.10)], tumours of the central nervous system [USA: 1.05 (1.01, 1.08), UK: 1.07 (1.04, 1.10)], renal tumours [USA: 1.17 (1.10, 1.24), UK: 1.12 (1.06, 1.19)] and soft tissue sarcomas [USA: 1.12 (1.05, 1.20), UK: 1.07 (1.00, 1.13)]. In contrast, increasing birthweight decreased the risk of hepatic tumours [USA: 0.77 (0.69, 0.85), UK: 0.79 (0.71, 0.89) per 0.5 kg increase]. Associations were also observed between high birthweight and risk of neuroblastoma, lymphomas, germ cell tumours and malignant melanomas. For some cancer subtypes, risk associations with birthweight were non-linear. We observed no association between birthweight and risk of retinoblastoma or bone tumours.

CONCLUSIONS

Approximately half of all childhood cancers exhibit associations with birthweight. The apparent independence from other factors indicates the importance of intrauterine growth regulation in the aetiology of these diseases.

Human adult stem cells as the target cells for the initiation of carcinogenesis and for the generation of "cancer stem cells"

The inference to stem cells has been found in ancient myths and the concept of stem cells has existed in the fields of plant biology, developmental biology and embryology for decades. In the field of cancer research, the stem cell theory was one of the earliest hypotheses on the origin of a cancer from a single cell. However, an opposing hypothesis had it that an adult differentiated somatic cell could "de-differentiate" to become a cancer cell. Only within the last decade, via the "cloning" of Dolly, the sheep, did the field of stem cell biology really trigger an exciting revolution in biological research. The isolation of human embryonic stem cells has created a true revolution in the life sciences that has led to the hope that these human stem cells could lead to (a) basic science understanding of gene regulation during differentiation and development; (b) stem cell therapy; (c) gene therapy via stem cells; (d) the use of stem cells for drug discovery; (e) screening for toxic effects of chemicals; and (f) understand the aging and diseases of aging processes.

High Bab Birth Weight Andof Hormone-Associated Cancer in Mothers: The Cancer–Cardiovascular Disease Dichotomy and its Possible Causes

The idea of intrauterine or fetal factors being the cause of several prevalent noninfectious diseases in adults has recently gained the status of an axiom. One of the most thoroughly studied predictors is birth weight (BW). Although many published studies point at relations between BW and later adult morbidity or mortality, much less attention is paid to associations between baby BW and maternal morbidity. Available data suggest a sort of dichotomy in these relationships. Thus, cardiovascular risk is higher in mothers of babies with a reduced BW, while cancer risk, mainly of the breast and some other hormone-dependent cancers, is often higher among mothers of babies with a large BW (newborn macrosomia). This review addresses possible causes and endocrine mechanisms of this topic and suggests a ‘particular’ and ‘general’ solution for arising controversy. Emphasis is placed on a probable competition between chronic diseases (mainly, between female hormone-related cancer and cardiovascular pathology) within the concept of multiple causes of death. These associations should be remembered while studying the relation between offspring BW and maternal predisposition to hormone-associated cancers and other noncommunicable diseases.

Umbilical cord blood-derived mesenchymal stem cells consist of a unique population of progenitors co-expressing mesenchymal stem cell and neuronal markers capable of instantaneous neuronal differentiation

INTRODUCTION

Umbilical cord blood (UCB)-derived mesenchymal stem cells (MSCs) are self-renewing multipotent progenitors with the potential to differentiate into multiple lineages of mesoderm, in addition to generating ectodermal and endodermal lineages by crossing the germline barrier. In the present study we have investigated the ability of UCB-MSCs to generate neurons, since we were able to observe varying degrees of neuronal differentiation from a few batches of UCB-MSCs with very simple neuronal induction protocols whereas other batches required extensive exposure to combination of growth factors in a stepwise protocol. Our hypothesis was therefore that the human UCB-MSCs would contain multiple types of progenitors with varying neurogenic potential and that the ratio of the progenitors with high and low neurogenic potentials varies in different batches of UCB.

METHODS

In total we collected 45 UCB samples, nine of which generated MSCs that were further expanded and characterized using immunofluorescence, fluorescence-activated cell sorting and RT-PCR analysis. The neuronal differentiation potential of the UCB-MSCs was analyzed with exposure to combination of growth factors.

RESULTS

We could identify two different populations of progenitors within the UCB-MSCs. One population represented progenitors with innate neurogenic potential that initially express pluripotent stem cell markers such as Oct4, Nanog, Sox2, ABCG2 and neuro-ectodermal marker nestin and are capable of expanding and differentiating into neurons with exposure to simple neuronal induction conditions. The remaining population of cells, typically expressing MSC markers, requires extensive exposure to a combination of growth factors to transdifferentiate into neurons. Interesting to note was that both of these cell populations were positive for CD29 and CD105, indicating their MSC lineage, but showed prominent difference in their neurogenic potential.

CONCLUSION

Our results suggest that the expanded UCB-derived MSCs harbor a small unique population of cells that express pluripotent stem cell markers along with MSC markers and possess an inherent neurogenic potential. These pluripotent progenitors later generate cells expressing neural progenitor markers and are responsible for the instantaneous neuronal differentiation; the ratio of these pluripotent marker expressing cells in a batch determines the innate neurogenic potential.

Prenatal modulation of breast density and breast stem cells by insulin-like growth factor-1

Biological determinants of breast density, a strong predictor of human breast cancer risk, are postulated to be influenced by prenatal exposures to mitogens. We investigated the extent to which prenatal exposures to insulin-like growth factor-1 (IGF-1) would affect body weight, breast density, and levels of breast stem/progenitor cells in the prepubescent offspring of wild type C57BL/6J and IGF-1 deficient mice. We found that administration of IGF-1 to pregnant mice resulted in significantly heavier birth and postnatal body weights of the offspring when compared to PBS controls. Morphometric analysis of whole mount carmine alum staining of the left fourth inguinal mammary gland revealed that a prenatal dose of 5 μg IGF-1 resulted in significantly longer ductal elongation in wild type mice and significantly higher breast density in both mouse strains. Furthermore, 5 μg IGF-1 also resulted in the highest number of putative CD49f(+)CD24(+) and CD49f(+)CD24(+)CD29(+) breast stem/progenitor cells in the wild type offspring when compared to PBS controls, as assessed by flow cytometric analysis of dissociated cells from the right fourth inguinal mammary gland, while significantly higher numbers of these cell populations as well as CD24(+)CD29(+) and CD49f(+)EpCAM(+) cells were observed in IGF-1 deficient mice. These findings provide direct evidence for a prenatal modulation of breast density in the offspring by IGF-1, possibly involving populations of breast stem/progenitor cells.

Fetal growth and body size genes and risk of childhood acute lymphoblastic leukemia

Accumulating evidence suggests that childhood acute lymphoblastic leukemia (ALL) may be initiated in utero or early in the postnatal period. High birth weight (or rapid fetal growth) is associated with risk of ALL, but the mechanisms are not understood. In a population-based epidemiologic study of childhood ALL, we utilized a haplotype-based approach to assess the role of eight genes involved in fetal growth and body size regulation in 377 childhood ALL cases and 448 controls. We found significant haplotype associations with risk of childhood ALL for IGF1 among non-Hispanics and Hispanics together (p = 0.002), for IGF2 among Hispanics (p = 0.040), and for IGF2R among Hispanics and non-Hispanics (p = 0.051 and 0.009, respectively). No haplotype associations were observed for IGF1R or the studied genes involved in body size regulation, including LEP, LEPR, GHRL, and NPY. Our study is the first to identify an association between the genes involved in the IGF axis and risk of childhood ALL. These findings for childhood ALL emphasize the importance of fetal growth, when lymphoid progenitor cells are not yet fully differentiated and therefore more susceptible to malignant transformation. Additional studies are needed to confirm these findings and identify specific causal variants.

Novel measurements of mammary stem cells in human umbilical cord blood as prospective predictors of breast cancer susceptibility in later life

BACKGROUND

The size of the breast stem-cell pool could underlie the intrauterine roots of breast cancer. We studied whether breast stem cells exist in umbilical cord blood and if they correlate with hematopoietic stem-cell measurements that have been positively associated with perinatal risk factors for breast cancer.

SUBJECTS AND METHODS

We isolated mononuclear cells from umbilical cord blood of 170 singleton full-term pregnancies and determined, by reverse transcription polymerase chain reaction, the presence of genes of putative breast epithelial stem-cell/progenitor markers [including epithelial cell adhesion molecule (EpCAM), CD49f (α6-integrin), CD117 (c-kit receptor), CD24, and CD29 (β1-integrin)]. By immunocytochemistry, we colocalized protein expressions of EpCAM+CD49f+, CD49f+CD24+, and CD24+CD29+. We correlated concentrations of putative breast stem-cell/progenitor subpopulations, quantified by flow cytometry, with concentrations of hematopoietic stem cells.

RESULTS

Mammary stem-cell phenotypes were identified in umbilical cord blood. The measured EpCAM+ subpopulation was positively correlated with concentrations of CD34+ and CD34+CD38- hematopoietic stem cells (both P=0.006). Additionally, EpCAM+CD49f+ and CD49f+CD24+ subpopulations were positively correlated to the CD34+ cells (P=0.03 and 0.008, respectively).

CONCLUSION

The positive association between measurable breast and hematopoietic stem cells in human umbilical cord blood suggests plausible mechanisms for a prenatal influence on breast cancer risk.

Childhood cancer mortality and birth characteristics in Korea: a national population-based birth cohort study

To examine the relationship between birth characteristics and childhood cancer mortality, a retrospective cohort study of Korean children was conducted using data collected by the national birth register between 1995 and 2006, which were then individually linked to death data. A cohort of 6,479,406 children was followed from birth until their death or until December 31, 2006. Poisson regression analyses were used to calculate rate ratios of childhood cancer deaths according to birth characteristics. A total of 1,469 cancer deaths were noted and the childhood cancer mortality rate was found to be 3.43 per 100,000 person-years in Korea during the period of 1995-2006. The birth characteristics examined in this study (i.e. , birth weight, gestational age, multiple births, parental ages, and number of siblings) were generally found to be not significantly associated with childhood cancer mortality, and the associations did not vary meaningfully with gender nor with cancer sites. However, among children aged 5-11 yr, higher birth weight was associated with elevated childhood cancer mortality (rate ratio = 1.28, 95% confidence interval 1.04-1.58). Our results offer no overall associations between childhood cancer mortality and birth characteristics, but suggest that the association may be specific to age group.

A paradigm shift is required for the risk assessment of potential human health after exposure to low level chemical exposures: a response to the toxicity testing in the 21st century report

Chemicals are known to be associated with birth defects, cancer, cardiovascular diseases, immunological, reproductive, and neurological disorders. In response to recent reviews of limitations of current concepts and techniques for toxicity testing, this commentary challenges the paradigm that chemicals are directly responsible for DNA damage in the genomic-nuclear DNA in relevant cells of the human body. This challenge is not that mutations do not play roles in human-inherited or somatic diseases but that chemical exposures bring about disease end points by epigenetic mechanisms or by alterations in adult stem cell numbers in utero (ie, the Barker hypothesis) or postnatally, by selecting preexisting mutated cells. Classic concepts, that is, multistage, multimechanism process of carcinogenesis, stem cell theory of cancer, and newer and ignored concepts, such as cancer stem cells and cell-cell communication, will be used to support the view that the toxic effect of chemicals is mediated by nonmutagenic mechanisms at human relevant exposures.

Does ageing originate in utero?

Ageing still remains a conundrum on the cellular and molecular level, while environmental factors and interactions further increase the complexity of the ageing process. On the other hand is cancer, for which 20 years ago, it was proposed by Trichopoulos that it might have intrauterine origin. We herein discuss the idea that parameters such as the influence of insulin-like growth factor (IGF) signalling, of hormones and of the number of stem cells, as well as the effect of foetal and early life nutrition on ageing may also commence in utero and we provide epidemiological and biological data to advocate for this hypothesis. Finally, we analyse the public health implication of this hypothesis based on the World Health Organization (WHO) report that the burden of diseases, including ageing, may be due to impaired foetal development.

Breast cancer, stem cells and sex hormones: part 1. The impact of fetal life and infancy

Like other organs, the breast contains rare somatic stem cells (SCs) that are long-lived and slowly dividing. In the adult breast, they are closely regulated in areas located along the breast ducts called SC niches. Breast SCs can produce offspring that become ductal, alveoli or myoepithelial cells. In fetal life, SCs form the primitive breast ducts and up to 30 weeks of gestational age, this process appears to be largely independent of estrogen. Early life risk factors for breast cancer include birth weight, rapid growth during infancy and diet. The impact of these risk factors may be mediated through SC number. These somatic breast SCs persist into adult life and so they are exposed to oncogenic influences for much longer than the short-lived differentiated breast ductal and alveolar cells. As such, it is likely that the breast SC is a prominent target for carcinogenesis and so SC number may be an important determinant of breast cancer risk later in life.

Birth weight and mammographic density among postmenopausal women in Sweden

Birth weight is a significant predictor of breast cancer risk in adult life and mammary gland mass could be an intermediate stage in this long process. We have studied the association of birth size measurements with mammographic density, a marker of mammary gland mass. For a population-based sample of 893 postmenopausal women without previous cancer in Sweden, we retrieved information on birth size from birth records and their most recent mammography. Film mammograms of the medio-lateral oblique view were digitized and the Cumulus software was used for computer-assisted semi-automated thresholding of mammographic density. Results were analyzed using generalized linear models controlling for possible confounders. Mean percent mammographic density increased when comparing the extreme categories of birth weight (from 15.6% to 18.6%) and head circumference (from 15.5% to 20.4%), and the corresponding linear trends were statistically significant (p values 0.02 and 0.007, respectively). The associations were particularly strong when the cutoff for high versus low mammographic density was set at the relatively high value of 50%. Compared to women weighing 3001-3500 grams at birth, women with birth weights >4000g were at almost 3-fold risk of developing high mammographic density (odds ratio: 2.9, 95% confidence interval 1.1 to 7.9). No association with mammographic density was evident with respect to birth length which, however, is known to be less accurately measured. These results indicate that adult breast density, a powerful predictor of breast cancer risk, has intrauterine roots, as reflected in birth size.

Birth weight, breast cancer susceptibility loci, and breast cancer risk

BACKGROUND

There is considerable evidence that birth weight is positively associated with breast cancer risk, and seven single-nucleotide polymorphisms (SNPs) have been conclusively associated with this risk. We have hypothesized that breast cancer susceptibility loci may have a greater influence on breast cancer risk among women with higher birth weight, who are expected to have a larger pool of mammary stem cells that are susceptible to malignant transformation.

PATIENTS AND METHODS

In the context of a nationwide, population-based case-control study in Sweden, we retrieved recorded birth weight for 693 breast cancer cases and 747 control women who were also genotyped for most or all of the seven recently documented breast cancer susceptibility SNPs: rs2981582, rs12443621, rs8051542, rs3803662, rs889312, rs13281615, and rs3817198.

RESULTS

We grouped heterozygotes with homozygotes for the wild-type allele, and we found a marginally significant interaction (p~0.07) between birth weight and rs2981582 (FGFR2), the genotype repeatedly identified as the top hit in genome-wide association studies. There were similar, though not significant, patterns for the other six SNPs.

CONCLUSIONS

Although our findings require confirmation, we found suggestive evidence that genetic susceptibility modifies the positive association of birth weight with breast cancer.

Insulin-like growth factor levels in cord blood, birth weight and breast cancer risk

Breast cancer incidence and birth weight are higher among Caucasian than Asian women, and birth size has been positively associated with breast cancer risk. Pregnancy hormone levels, however, have been generally lower in Caucasian than Asian women. We studied components of the insulin-like growth factor (IGF) system in cord blood from 92 singleton babies born in Boston, USA, and 110 born in Shanghai, China, in 1994–1995. Cord blood IGF-1 was significantly higher among Caucasian compared with Chinese babies (P<10⁻⁶). The opposite was noted for IGF-2 (P∼10⁻⁴). IGF-1 was significantly positively associated with birth weight and birth length in Boston, but not Shanghai. In contrast, stronger positive, though statistically non-significant, associations of IGF-2 with birth size were only evident in Shanghai. The associations of birth weight and birth length were positive and significant in taller women (for IGF-1 in Boston P∼0.003 and 0.03, respectively; for IGF-2 in Shanghai P∼0.05 and ∼0.04, respectively), among whom maternal anthropometry does not exercise strong constraints in foetal growth. The documentation of higher cord blood levels of IGF-1, a principal growth hormone that does not cross the placenta, among Caucasian than in Asian newborns is concordant with breast cancer incidence in these populations.

Neonatal growth and breast cancer risk in adulthood

Birth size of a woman has been positively associated with her breast cancer risk, particularly before menopause, but no study has investigated neonatal growth in relation to this risk. We conducted a case-control study nested within a population-based cohort of women, born in Sweden between 1901 and 1961, covering all 405 breast cancer patients and 1081 age- and hospital-matched controls, who were born after newborn charts became available. Compared to neonates who lost <200 g after birth and grew at a rate <25 g day(-1) after reaching postnatal weight nadir (ie, the minimum, before starting to regain weight), those who either lost >/=200 g after birth or grew >/=25 g day(-1) after nadir, or both, were at an approximately 50% increased breast cancer risk. The excess risk was striking and statistically significant among women below 50 years of age, but was not evident among older women. Immediate postnatal weight loss (an indicator of water loss, likely to reflect water retention associated with pregnancy hormones) as well as neonatal weight gain rate after the nadir (known to reflect growth hormone levels) was significantly positively associated with premenopausal breast cancer risk.