Risk Reduction of Breast Cancer by Childbirth, Breastfeeding, and Their Interaction in Korean Women: Heterogeneous Effects Across Menopausal Status, Hormone Receptor Status, and Pathological Subtypes

Association of reproductive risk factors and breast cancer molecular subtypes: a systematic review and meta-analysis

BACKGROUND

Associations between reproductive factors and breast cancer (BC) risk vary by molecular subtype (i.e., luminal A, luminal B, HER2, and triple negative/basal-like [TNBC]). In this systematic review and meta-analysis, we summarized the associations between reproductive factors and BC subtypes.

METHODS

Studies from 2000 to 2021 were included if BC subtype was examined in relation to one of 11 reproductive risk factors: age at menarche, age at menopause, age at first birth, menopausal status, parity, breastfeeding, oral contraceptive (OC) use, hormone replacement therapy (HRT), pregnancy, years since last birth and abortion. For each reproductive risk factor, BC subtype, and study design (case-control/cohort or case-case), random-effects models were used to estimate pooled relative risks and 95% confidence intervals.

RESULTS

A total of 75 studies met the inclusion criteria for systematic review. Among the case-control/cohort studies, later age at menarche and breastfeeding were consistently associated with decreased risk of BC across all subtypes, while later age at menopause, later age of first childbirth, and nulliparity/low parity were associated with increased risk of luminal A, luminal B, and HER2 subtypes. In the case-only analysis, compared to luminal A, postmenopausal status increased the risk of HER2 and TNBC. Associations were less consistent across subtypes for OC and HRT use.

CONCLUSION

Identifying common risk factors across BC subtypes can enhance the tailoring of prevention strategies, and risk stratification models can benefit from subtype specificity. Adding breastfeeding status to current BC risk prediction models can enhance predictive ability, given the consistency of the associations across subtypes.

Novel insights linking BRCA1-IRIS role in mammary gland development to formation of aggressive PABCs: the case for longer breastfeeding

Pregnancy-associated breast cancer (PABC) is diagnosed during or shortly after pregnancy. Although rare, PABC is a serious occurrence often of the triple negative (TNBC) subtype. Here we show progesterone, prolactin, and RANKL upregulate BRCA1-IRIS (IRIS) in separate and overlapping subpopulations of human mammary epithelial cell lines, which exacerbates the proliferation, survival, and the TNBC-like phenotype in them. Conversely, vitamin D₃ reduces IRIS expression in TNBC cell lines, which attenuates growth, survival, and the TNBC-like phenotype in them. In the mouse, Brca1-Iris (Iris, mouse IRIS homolog) is expressed at low-level in nulliparous mice, increases ~10-fold in pregnant/lactating mice, to completely disappear in involuting mice, and reappears at low-level in regressed glands. Mice underwent 3 constitutive pregnancies followed by a forced involution (after 5 days of lactation) contained ~10-fold higher Iris in their mammary glands compared to those underwent physiological involution (after 21 days of lactation). While protein extracts from lactating glands promote proliferation in IRIS^low and IRIS overexpressing (IRISOE) cells, extracts from involuting glands promote apoptosis in IRIS^low, and aneuploidy in IRISOE cells. In a cohort of breast cancer patients, lack of breastfeeding was associated with formation of chemotherapy resistant, metastatic IRISOE breast cancers. We propose that terminal differentiation triggered by long-term breastfeeding reduces IRIS expression in mammary cells allowing their elimination by the inflammatory microenvironment during physiological involution. No/short-term breastfeeding retains in the mammary gland IRISOE cells that thrive in the inflammatory microenvironment during forced involution to become precursors for aggressive breast cancers shortly after pregnancy.

PI3K/AKT/mTOR Signaling Pathway in Breast Cancer: From Molecular Landscape to Clinical Aspects

Breast cancer is a serious health problem worldwide, representing the second cause of death through malignancies among women in developed countries. Population, endogenous and exogenous hormones, and physiological, genetic and breast-related factors are involved in breast cancer pathogenesis. The phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) is a signaling pathway involved in cell proliferation, survival, invasion, migration, apoptosis, glucose metabolism and DNA repair. In breast tumors, PIK3CA somatic mutations have been reported, located in exon 9 and exon 20. Up to 40% of PIK3CA mutations are estrogen receptor (ER) positive and human epidermal growth factor receptor 2 (HER2) -negative in primary and metastatic breast cancer. HER2 is overexpressed in 20-30% of breast cancers. HER1, HER2, HER3 and HER4 are membrane receptor tyrosine kinases involved in HER signaling to which various ligands can be attached, leading to PI3K/AKT activation. Currently, clinical studies evaluate inhibitors of the PI3K/AKT/mTOR axis. The main purpose of this review is to present general aspects of breast cancer, the components of the AKT signaling pathway, the factors that activate this protein kinase B, PI3K/AKT-breast cancer mutations, PI3K/AKT/mTOR-inhibitors, and the relationship between everolimus, temsirolimus and endocrine therapy.

Combination of circulating miR-145-5p/miR-191-5p as biomarker for breast cancer detection

Background

Breast cancer (BC) is the most common cancer among women worldwide. At present, there is a need to search for new, accurate, reliable, minimally invasive and cheap biomarkers in addition to existing methods for the diagnosis and prognosis of BC. The main goal of this study was to test the diagnostic value of six circulating miRNAs in Kazakh women.

Materials and methods

TaqMan-based miRNA profiling was conducted using plasma specimens from 35 BC women patients and 33 healthy women samples (control group).

Results

The level of all seven miRNAs (including endogenous control) normalized by synthetic cel-miR-39 were significantly elevated in the group of BC patients. Normalization using miR-222-3p as endogenous control reduced differences in level of miRNAs between groups; as a result, only three miRNAs were significantly upregulated in the group of BC patients—miR-145-5p (P = 6.5e−12), miR-191-5p (P = 3.7e−10) and miR-21-5p (P = 0.0034). Moreover, ROC analysis showed that the use of miR-145-5p and miR-191-5p, both individually (AUC = 0.931 and 0.904, respectively) or in combination (AUC = 0.984), allows to accurately differentiate BC patients from healthy individuals.

Conclusions

Two plasma miRNAs—miR-145-5p and miR-191-5p—are potential biomarkers for diagnosis of BC in the Kazakh population. The findings need to be further substantiated using a more representative sample.

Maternal Personality and Psychosocial Variables Associated with Initiation Compared to Maintenance of Breastfeeding: A Study in Low Obstetric Risk Women

INTRODUCTION

The benefits of breastfeeding are well known for mother and child. Research about the predictive factors related to the initiation and maintenance of breastfeeding is of great interest to public health.

AIM

To analyze the factors associated with the timely initiation of breastfeeding at immediate postpartum and the variables that facilitate their maintenance 4 months after birth.

MATERIALS AND METHODS

A longitudinal prospective design was used, including four stages: first trimester of pregnancy (personality), third trimester (childbirth expectations, breastfeeding intention, pregnancy worries, and coping strategies), immediately after childbirth (initiation of breastfeeding and childbirth satisfaction), and 4 months after birth (continuation of breastfeeding).

RESULTS

A sample of 116 women took part in the study from the first trimester to 4 months after birth. Timely initiation of breastfeeding is associated with vaginal birth (p < 0.000) and with variables related to the absence of stress factors: fewer worries regarding childbirth (p = 0.009), higher satisfaction during birth in relation to holding the baby (p > 0.000), and the meeting of expectations (p = 0.017). These associations disappear when the type of birth is introduced. Maintenance of breastfeeding is associated with maternal personality and psychosocial variables: openness to experience (p = 0.007), increased worries about coping with the baby (p = 0.046), relationship with partner (p = 0.047), and overt emotional expression (p = 0.040).

CONCLUSION

Different factors are associated with initiation and maintenance of breastfeeding. Specific prevention strategies are needed, aimed toward health care staff for improving breastfeeding initiation and to empower women during the entire pregnancy for breastfeeding maintenance.