Breast cancer, stem cells and sex hormones. Part 3: The impact of the menopause and hormone replacement

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.

Invasive ductal carcinoma and small lymphocytic lymphoma/chronic lymphocytic leukemia manifesting as a collision breast tumor: A case report and literature review

Collision breast tumors, consisting of breast cancer (BC) and non-Hodgkin’s lymphoma (NHL), are extremely rare. Here we report the case of a 64-year-old woman with a collision tumor in her left breast mass that was composed of invasive ductal carcinoma and small lymphocytic lymphoma/chronic lymphocytic leukemia. In addition, we reviewed the published comparable English-language literature. Collision breast tumor composed of BC and NHL is extremely rare. For that reason, there is a lack of consensus about the underlying mechanism, and diagnosing it without delay remains a complex clinical challenge. We found that post-menopausal, age-related estrogen levels changes and Epstein-Barr virus infection are possible pathogenic factors. However, the symptoms are almost identical, and it is difficult to distinguish a simple breast tumor from a breast collision tumor. In this study, we reviewed the clinical features of all patients with BC and NHL colliding breast tumors; this information might enable early identification and prevention of misdiagnosis.

Hormone Therapy and Breast Cancer: Emerging Steroid Receptor Mechanisms

Although hormone therapy is widely used by millions of women to relieve symptoms of menopause, it has been associated with several side-effects such as coronary heart disease, stroke and increased invasive breast cancer risk. These side-effects have caused many women to seek alternatives to conventional hormone therapy, including the controversial custom-compounded bioidentical hormone therapy suggested to not increase breast cancer risk. Historically estrogens and the estrogen receptor were considered the principal factors promoting breast cancer development and progression, however, a role for other members of the steroid receptor family in breast cancer pathogenesis is now evident, with emerging studies revealing an interplay between some steroid receptors. In this review, we discuss examples of hormone therapy used for the relief of menopausal symptoms, highlighting the distinction between conventional hormone therapy and custom-compounded bioidentical hormone therapy. Moreover, we highlight the fact that not all hormones have been evaluated for an association with increased breast cancer risk. We also summarize the current knowledge regarding the role of steroid receptors in mediating the carcinogenic effects of hormones used in menopausal hormone therapy, with special emphasis on the influence of the interplay or crosstalk between steroid receptors. Unraveling the intertwined nature of steroid hormone receptor signaling pathways in breast cancer biology is of utmost importance, considering that breast cancer is the most prevalent cancer among women worldwide. Moreover, understanding these mechanisms may reveal novel prevention or treatment options, and lead to the development of new hormone therapies that does not cause increased breast cancer risk.

Risk assessment model for invasive breast cancer in Hong Kong women

No risk assessment tool is available for identifying high risk population of breast cancer (BCa) in Hong Kong. A case-control study including 918 BCa cases and 923 controls was used to develop the risk assessment model among Hong Kong Chinese women.Each participant received an in-depth interview to obtain their lifestyle and environmental risk factors. Least absolute shrinkage and selection operator (LASSO) selection model was used to select the optimal risk factors (LASSO-model). A risk score system was constructed to evaluate the cumulative effects of selected factors. Bootstrap simulation was used to test the internal validation of the model. Model performance was evaluated by receiver-operator characteristic curves and the area under the curve (AUC).Age, number of parity, number of BCa cases in 1st-degree relatives, exposure to light at night, and sleep quality were the common risk factors for all women. Alcohol drinking was included for premenopausal women; body mass index, age at menarche, age at 1st give birth, breast feeding, using of oral contraceptive, hormone replacement treatment, and history of benign breast diseases were included for postmenopausal women. The AUCs were 0.640 (95% CI, 0.598-0.681) and 0.655 (95% CI, 0.621-0.653) for pre- and postmenopausal women, respectively. Further subgroup evaluation revealed that the model performance was better for women aged 50 to 70 years or ER-positive.This BCa risk assessment tool in Hong Kong Chinese women based on LASSO selection is promising, which shows a slightly higher discriminative accuracy than those developed in other populations.

Breastfeeding status and maternal cardiovascular variables across the postpartum

BACKGROUND

There have been recent reports that lactational history is associated with long-term women's health benefits. Most of these studies are epidemiological. If particular cardiometabolic changes that occur during lactation ultimately influence women's health later is unknown.

METHODS

Seventy-one healthy women participated in a prospective postpartum study that provided an opportunity to study anthropometric, endocrine, immune, and behavioral variables across time. Variables studied were heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), C-reactive protein, body mass index (BMI), perceived stress, and hormones. A cohort of women without a change in breastfeeding (N=22) or formula feeding (N=23) group membership for 5 months was used for analysis of effects of feeding status. The data were analyzed using factorial repeated measures analysis of variance and analysis of covariance.

RESULTS

SBP and HR declined across the postpartum and were significantly lower in breastfeeding compared to formula feeding mothers (p<0.05). These differences remained statistically significant when BMI was added to the model. Other covariates of income, stress, marital status, and ethnicity were not significantly associated with these variables over time. DBP was also lower, but the significance was reduced by the addition of BMI as a covariate. Stress also was lower in breastfeeders, but this effect was reduced by the addition of income as a covariate.

CONCLUSIONS

These data suggest that there are important physiological differences in women during months of breastfeeding. These may have roles in influencing or programming later risks for a number of midlife diseases.

Menopausal status, adipose tissue, and breast cancer risk: impact of estrogen replacement therapy

The seeds of breast cancer are likely sown in the first two or three decades of life. Rapid weight gain and height in infancy predict breast cancer risk in later life. The age at first pregnancy is also a strong predictor for breast cancer; the earlier the first full-term pregnancy, then the lower the risk of breast cancer in later life. It has been postulated that the breast stem cell number may be the factor linking these observations together. Menopause, per se, is associated with an increase in central adiposity, which is reversed by hormone replacement usage. Breast and nonbreast fat both produce estrogens and cytokines that may promote the growth of small breast cancers making them appear earlier. Obesity also is associated with metabolic syndrome, which is a risk factor for breast cancer. The breast cancer stem cells make up only around 1%-2% of the tumor mass and, yet, are the likely driver for much of a breast cancer's behavior. Future research into breast cancer biology, especially into the cancer stem cells is likely to translate into novel methods of treatment and prevention of this common cancer.

Progesterone--promoter or inhibitor of breast cancer

Based on the results of a French cohort of postmenopausal women, it has been claimed that micronized progesterone does not enhance breast cancer risk. The impact of reproductive factors on breast cancer risk and a high prevalence of occult breast carcinomas at the time of menopause suggest an involvement of endogenous progesterone in the development of breast cancer. High mammographic density in the luteal phase and during treatment with estrogen/progestogen combinations reflect a change in the composition of mammary stroma and an increased water accumulation in the extracellular matrix which is caused by hygroscopic hyaluronan-proteoglycan aggregates. Proteoglycans are also involved in the regulation of proliferation, migration, and differentiation of epithelial cells and angiogenesis, and may influence malignant transformation of breast cells and progression of tumors. Reports on a lack of effect of estrogen/progesterone therapy on breast cancer risk may be rooted in a selective prescription to overweight women and/or to the very low progesterone serum levels after oral administration owing to a strong inactivation rate. The contradictory results concerning the proliferative effect of progesterone may be associated with a different local metabolism in normal compared to malignant breast tissue. Similar to other progestogens, hormone replacement therapy with progesterone seems to promote the development of breast cancer, provided that the progesterone serum levels have reached the threshold for endometrial protection.

Breast-cancer stem cells-beyond semantics

Intratumoral heterogeneity in breast cancer is well documented. Although the mechanisms leading to this heterogeneity are not understood, a subpopulation of cancer cells, cancer stem cells (CSCs), that have some phenotypic similarities with adult tissue stem cells, has been suggested to contribute to tumour heterogeneity. It has been postulated that these CSCs are dormant, and by virtue of their low proliferative activity and ability to exclude intracellular toxins, are resistant to chemotherapy and radiation therapy. These cells were initially isolated based on the presence of markers such as CD44, CD24, and ALDH1, with further characterisation using mammosphere assay and transplantation into immunodeficient mice. The CSC hypothesis raises several theoretical and practical questions. Does cancer arise in normal mammary stem cells or do some malignant cells acquire a CSC phenotype through clonal evolution? Are CSCs in different molecular (intrinsic) subtypes of breast cancer similar, or do they have distinct properties based on the subtype? Does the CSC phenotype reflect plasticity or the dynamic nature of a few cancer cells? How do these cells acquire invasive behaviour, as they go through epithelial-to-mesenchymal transition and then revert to epithelial phenotype at sites of metastasis in response to tumour microenvironmental and metastasis site-specific cues? It is increasingly recognised that the methods and assays used for identifying CSCs have substantial limitations; does this negate the entire concept? In this Personal View, we argue that the CSC phenotype represents an aggressive clone that survives in an adverse environment through constant evolution and integration of various hallmarks of cancer. This evolution could involve acquiring mutations that permit asymmetric and symmetric division, converting the host immune attack to its own advantage, and plasticity to adapt to sites of metastasis through reversible change in adhesion molecules. We also argue that the cell-type origin of cancer could affect the rate at which CSCs develop in a tumour, with an eventual effect on disease outcome.

Biomarkers for breast cancer stem cells: the challenges ahead

Recent studies suggest that a subset of cancer cells with the ability for self-renewal and differentiation into different cell lineages is responsible for tumor progression, metastasis and resistance therapy. These cells, designated as tumor-initiating cells, tumor-propagating cells or cancer stem cells, are of great interest for cancer prognostication and therapeutics. Numerous cell surface and intracellular markers exhibiting cancer stem cell characteristics have been identified in breast cancer, presenting a promise to use them as biomarkers. However, there is a great need for the improvement of experimental methods to detect them in clinical samples, and validate their utility as predictors of the disease outcome, propensity for metastasis and response to treatment. In this article, we present an overview of the current status of breast cancer stem cells, with a focus on biomarkers. We also discuss the technical challenges on the road to defining breast cancer stem cells as biomarkers.