A 20-year prospective study of plasma prolactin as a risk marker of breast cancer development

Structural Investigation of Human Prolactin Receptor Transmembrane Domain Homodimerization in a Membrane Environment through Multiscale Simulations

It is well established that prolactin (PRL) and its receptor (PRLR) are associated with hundreds of biological functions. They have been postulated to be linked to breast and prostate cancers, and PRLR signaling has attracted considerable medical and pharmaceutical interest in the development of compounds targeting PRLR. Dimerization of the receptor through its transmembrane (TM) domain is a key step for understanding its signaling and related issues. Our multiscale simulation results revealed that its TM domain can form dimers in a membrane environment with distinct states stabilized by different residue motifs. On the basis of the simulated data, an activation mechanism of PRL with the importance of two symmetrical tryptophan residues was proposed in detail to determine the conformational change of its receptor, which is essential for signal transduction. The better knowledge of PRLR structure and its protein-protein interaction can considerably contribute to a further understanding of PRLR signaling action and thereby help to develop some new PRLR signaling-based strategies for PRL-related diseases.

An in vivo half-life extended prolactin receptor antagonist can prevent STAT5 phosphorylation

Increasing evidence suggests that signaling through the prolactin/prolactin receptor axis is important for stimulation the growth of many cancers including glioblastoma multiforme, breast and ovarian carcinoma. Efficient inhibitors of signaling have previously been developed but their applicability as cancer drugs is limited by the short in vivo half-life. In this study, we show that a fusion protein, consisting of the prolactin receptor antagonist PrlRA and an albumin binding domain for half-life extension can be expressed as inclusion bodies in Escherichia coli and efficiently refolded and purified to homogeneity. The fusion protein was found to have strong affinity for the two intended targets: the prolactin receptor (K_D = 2.3±0.2 nM) and mouse serum albumin (K_D = 0.38±0.01 nM). Further investigation showed that it could efficiently prevent prolactin mediated phosphorylation of STAT5 at 100 nM concentration and above, similar to the PrlRA itself, suggesting a potential as drug for cancer therapy in the future. Complexion with HSA weakened the affinity for the receptor to 21±3 nM, however the ability to prevent phosphorylation of STAT5 was still prominent. Injection into rats showed a 100-fold higher concentration in blood after 24 h compared to PrlRA itself.

Prolactin modulates TNBC aggressive phenotype limiting tumorigenesis

Triple-negative breast cancer (TNBC) accounts for ~20% of all breast cancer cases. The management of TNBC represents a challenge due to its aggressive phenotype, heterogeneity and lack of targeted therapy. Loss of cell differentiation and enrichment with breast cancer stem-like cells (BCSC) are features of TNBC contributing to its aggressive nature. Here, we found that treatment of TNBC cells with PRL significantly depletes the highly tumorigenic BCSC subpopulations CD44+/CD24- and ALDH+ and differentiates them to the least tumorigenic CD44-/CD24- and ALDH- phenotype with limited tumorsphere formation and self-renewal capacities. Importantly, we found PRL to induce a heterochromatin phenotype marked by histone H3 lysine 9 trimethylation (H3K9me3) and accompanied by ultra-structural cellular architecture associated with differentiation and senescence rendering the cells refractory to growth signals. Crucially, we found PRL to mediate these effects in vivo in a pre-clinical animal xenograft of TNBC controlling tumor growth. These results reveal that the lactogenic hormone PRL may exert its anti-tumorigenic effects on TNBC through cellular reprogramming indicative of differentiation resulting in the depletion of BCSCs and restricting tumorigenesis.

Inclusion of Plasma Prolactin Levels in Current Risk Prediction Models of Premenopausal and Postmenopausal Breast Cancer

Background

Circulating plasma prolactin is associated with breast cancer risk and may improve our ability to identify high-risk women. Mammographic density is a strong risk factor for breast cancer, but the association with prolactin is unclear. We studied the association between breast cancer, established breast cancer risk factors and plasma prolactin, and improvement of risk prediction by adding prolactin.

Methods

We conducted a nested case-control study including 721 breast cancer patients and 1400 age-matched controls. Plasma prolactin levels were assayed using immunoassay and mammographic density measured by STRATUS. Odds ratios (ORs) were calculated by multivariable adjusted logistic regression, and improvement in the area under the curve for the risk of breast cancer by adding prolactin to established risk models. Statistical tests were two-sided.

Results

In multivariable adjusted analyses, prolactin was associated with risk of premenopausal (OR, top vs bottom quintile = 1.9; 1.88 (95% confidence interval [CI] = 1.08 to 3.26) but not with postmenopausal breast cancer. In postmenopausal cases prolactin increased by 10.6% per cBIRADS category (P_trend = .03). In combined analyses of prolactin and mammographic density, ORs for women in the highest vs lowest tertile of both was 3.2 (95% CI = 1.3 to 7.7) for premenopausal women and 2.44 (95% CI = 1.44 to 4.14) for postmenopausal women. Adding prolactin to current risk models improved the area under the curve of the Gail model (+2.4 units, P = .02), Tyrer-Cuzick model (+3.8, P = .02), and the CAD2Y model (+1.7, P = .008) in premenopausal women.

Conclusion

Circulating plasma prolactin and mammographic density appear independently associated with breast cancer risk among premenopausal women, and prolactin may improve risk prediction by current risk models.

Circulating Growth and Sex Hormone Levels and Breast Tissue Composition in Young Nulliparous Women

BACKGROUND

Endogenous hormones are associated with breast cancer risk, but little is known about their role on breast tissue composition, a strong risk predictor. This study aims to investigate the relationship between growth and sex hormone levels and breast tissue composition in young nulliparous women.

METHODS

A cross-sectional study of 415 young (age ∼21.5 years) nulliparous women from an English prebirth cohort underwent a MRI examination of their breasts to estimate percent-water (a proxy for mammographic percent density) and provided a blood sample to measure plasma levels of growth factors (insulin-like growth factor-I, insulin-like growth factor-II, insulin growth factor-binding protein-3, growth hormone) and, if not on hormonal contraception (n = 117) sex hormones (dehydroepiandrosterone, androstenedione, testosterone, estrone, estadiol, sex hormone-binding globulin, prolactin). Testosterone (n = 330) and sex hormone-binding globulin (n = 318) were also measured at age 15.5 years. Regression models were used to estimate the relative difference (RD) in percent-water associated with one SD increment in hormone levels.

RESULTS

Estradiol at age 21.5 and sex hormone-binding globulin at age 21.5 were positively associated with body mass index (BMI)-adjusted percent-water [RD (95% confidence interval (CI)): 3% (0%-7%) and 3% (1%-5%), respectively]. There was a positive nonlinear association between androstenedione at age 21.5 and percent-water. Insulin-like growth factor-I and growth hormone at age 21.5 were also positively associated with BMI-adjusted percent-water [RD (95% CI): 2% (0%-4%) and 4% (1%-7%), respectively].

CONCLUSIONS

The findings suggest that endogenous hormones affect breast tissue composition in young nulliparous women.

IMPACT

The well-established associations of childhood growth and development with breast cancer risk may be partly mediated by the role of endogenous hormones on breast tissue composition.

Circulating prolactin concentrations and risk of type 2 diabetes in US women

AIMS/HYPOTHESIS

Prolactin, a multifunctional hormone, is involved in regulating insulin sensitivity and glucose homeostasis in experimental studies. However, whether circulating concentrations of prolactin are associated with risk of type 2 diabetes remains uncertain.

METHODS

We analysed the prospective relationship between circulating prolactin concentrations and type 2 diabetes risk in the Nurses' Health Study (NHS) and NHSII with up to 22 years of follow-up. Total plasma prolactin was measured using immunoassay in 8615 women free of type 2 diabetes and cardiovascular disease at baseline blood collection (NHS 1989-1990; NHSII 1996-1999) and a subset of 998 NHS women providing a second blood sample during 2000-2002. Baseline bioactive prolactin was measured in a subset of 2478 women using the Nb2 bioassay. HRs were estimated using Cox regression.

RESULTS

A total of 699 incident type 2 diabetes cases were documented during 156,140 person-years of follow-up. Total plasma prolactin levels were inversely associated with type 2 diabetes risk; the multivariable HR comparing the highest with the lowest quartile was 0.73 (95% CI 0.55, 0.95; p_trend = 0.02). The associations were similar by menopausal status and other risk factors (p_interaction > 0.70). Additional adjustment for sex and growth hormones, adiponectin, and inflammatory and insulin markers did not significantly alter the results. The association of plasma bioactive prolactin with type 2 diabetes risk was non-significantly stronger than that of total prolactin (HR comparing extreme quartiles, 0.53 vs 0.81 among the subset of 2478 women, p_difference = 0.11). The inverse association of total prolactin with type 2 diabetes was significant during the first 9 years after blood draw but waned linearly with time, whereas for bioactive prolactin, the inverse relationship persisted for a longer follow-up time after blood draw.

CONCLUSIONS/INTERPRETATION

A normally high circulating total prolactin concentration was associated with a lower type 2 diabetes risk within 9-10 years of follow-up since blood draw in US women. Our findings are consistent with experimental evidence, suggesting that among healthy women, prolactin within the biologically normal range may play a protective role in the pathogenesis of type 2 diabetes.

Receptor activator of nuclear factor kB ligand, osteoprotegerin, and risk of death following a breast cancer diagnosis: results from the EPIC cohort

BACKGROUND

Receptor activator of nuclear factor kappa-B (RANK)-signaling is involved in tumor growth and spread in experimental models. Binding of RANK ligand (RANKL) to RANK activates signaling, which is inhibited by osteoprotegerin (OPG). We have previously shown that circulating soluble RANKL (sRANKL) and OPG are associated with breast cancer risk. Here we extend these findings to provide the first data on pre-diagnosis concentrations of sRANKL and OPG and risk of breast cancer-specific and overall mortality after a breast cancer diagnosis.

METHODS

Two thousand six pre- and postmenopausal women with incident invasive breast cancer (1620 (81%) with ER+ disease) participating in the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort were followed-up for mortality. Pre-diagnosis concentrations of sRANKL and OPG were quantified in baseline serum samples using an enzyme-linked immunosorbent assay and electrochemiluminescent assay, respectively. Hazard ratios (HRs) and 95% confidence intervals (CIs) for breast cancer-specific and overall mortality were calculated using Cox proportional hazards regression models.

RESULTS

Especially in women with ER+ disease, higher circulating OPG concentrations were associated with higher risk of breast cancer-specific (quintile 5 vs 1 HR 1.77 [CI 1.03, 3.04]; ptrend 0.10) and overall mortality (q5 vs 1 HR 1.39 [CI 0.94, 2.05]; ptrend 0.02). sRANKL and the sRANKL/OPG ratio were not associated with mortality following a breast cancer diagnosis.

CONCLUSIONS

High pre-diagnosis endogenous concentrations of OPG, the decoy receptor for RANKL, were associated with increased risk of death after a breast cancer diagnosis, especially in those with ER+ disease. These results need to be confirmed in well-characterized patient cohorts.

Differentiated thyroid cancer: Why does it affect predominantly women during the reproductive period and have higher incidence of mutual association with breast cancer?

Differentiated thyroid cancer (DTC) is markedly more common in women than men, and its occurrence and risk for poorer prognosis are associated with pregnancy. Further, it is known that there is a high frequency of co-occurrence of DTC and breast cancer. Although the underlying mechanisms that contribute to these phenomena are not entirely clear, 2 hypotheses are proposed here. First, human chorionic gonadotropin (hCG) produced by the placenta may be involved, since hCG has a similar function to stimulate the thyroid as thyroid-stimulating hormone (TSH), the latter of which is known to play a role in causing DTC and may promote breast cancer through the secretion of thyroid hormones (THs). Second, thyrotropin-releasing hormone (TRH), which is stimulated by suckling in the puerperal period, induces the secretion of not only TSH and thus indirectly THs, but also prolactin (PRL), which can accelerate the development of breast cancer. These hypotheses also explain the pregnancy-associated transient increase in breast cancer risk, while inhibition of estrogen by PRL may have a long-term preventive effect on breast cancer. Pregnancy-associated hyperthyroidism may also account for female preponderance of thyroid disease in general as well as tumors in organs that the thyroid hormone targets such as cardiac myxoma and diffuse-type gastric carcinoma.

Addition of a polygenic risk score, mammographic density, and endogenous hormones to existing breast cancer risk prediction models: A nested case-control study

BACKGROUND

No prior study to our knowledge has examined the joint contribution of a polygenic risk score (PRS), mammographic density (MD), and postmenopausal endogenous hormone levels-all well-confirmed risk factors for invasive breast cancer-to existing breast cancer risk prediction models.

METHODS AND FINDINGS

We conducted a nested case-control study within the prospective Nurses' Health Study and Nurses' Health Study II including 4,006 cases and 7,874 controls ages 34-70 years up to 1 June 2010. We added a breast cancer PRS using 67 single nucleotide polymorphisms, MD, and circulating testosterone, estrone sulfate, and prolactin levels to existing risk models. We calculated area under the curve (AUC), controlling for age and stratified by menopausal status, for the 5-year absolute risk of invasive breast cancer. We estimated the population distribution of 5-year predicted risks for models with and without biomarkers. For the Gail model, the AUC improved (p-values < 0.001) from 55.9 to 64.1 (8.2 units) in premenopausal women (Gail + PRS + MD), from 55.5 to 66.0 (10.5 units) in postmenopausal women not using hormone therapy (HT) (Gail + PRS + MD + all hormones), and from 58.0 to 64.9 (6.9 units) in postmenopausal women using HT (Gail + PRS + MD + prolactin). For the Rosner-Colditz model, the corresponding AUCs improved (p-values < 0.001) by 5.7, 6.2, and 6.5 units. For estrogen-receptor-positive tumors, among postmenopausal women not using HT, the AUCs improved (p-values < 0.001) by 14.3 units for the Gail model and 7.3 units for the Rosner-Colditz model. Additionally, the percentage of 50-year-old women predicted to be at more than twice 5-year average risk (≥2.27%) was 0.2% for the Gail model alone and 6.6% for the Gail + PRS + MD + all hormones model. Limitations of our study included the limited racial/ethnic diversity of our cohort, and that general population exposure distributions were unavailable for some risk factors.

CONCLUSIONS

In this study, the addition of PRS, MD, and endogenous hormones substantially improved existing breast cancer risk prediction models. Further studies will be needed to confirm these findings and to determine whether improved risk prediction models have practical value in identifying women at higher risk who would most benefit from chemoprevention, screening, and other risk-reducing strategies.

Use of antipsychotics and risk of breast cancer: a Danish nationwide case-control study

AIMS

Some antipsychotics increase prolactin levels, which might increase the risk of breast cancer. Existing evidence is conflicting and based on sparse data, especially for the increasingly used second-generation antipsychotics. We conducted a nationwide case-control study of the association between antipsychotic use and incident breast cancer.

METHODS

From the Danish Cancer Registry, we identified women with a first-time diagnosis of breast cancer 2000-2015 (n = 60 360). For each case, we age-matched 10 female population controls. Using conditional logistic regression, we calculated odds ratios (ORs) for breast cancer associated with use of antipsychotics. We stratified antipsychotics by first- and second-generation status and by ability to induce elevation of prolactin.

RESULTS

In total, 4951 cases (8.1%) and 47 643 controls (7.9%) had ever used antipsychotics. Long-term use (≥10 000 mg olanzapine equivalents) was associated with breast cancer, with an adjusted OR of 1.18 [95% confidence interval (CI), 1.06, 1.32]. A weak dose-response pattern was seen, with ORs increasing to 1.27 (95% CI 1.01, 1.59) for ≥50 000 mg olanzapine equivalents. Associations were similar for first- and second-generation antipsychotics (ORs 1.17 vs. 1.11), but also for nonprolactin inducing-antipsychotics (OR 1.17). Stratifying by oestrogen receptor status, positive associations were seen for oestrogen receptor-positive cancers (long-term use: OR 1.29; 95% CI 1.13, 1.47) while no associations were observed for oestrogen receptor-negative cancers.

CONCLUSIONS

Overall, our results do not suggest a clinically important association between antipsychotic use and risk of breast cancer. The importance of drug-induced prolactin elevation is unclear but may lead to a slightly increased risk of oestrogen receptor-positive breast cancer.

High collagen density augments mTOR-dependent cancer stem cells in ERα+ mammary carcinomas, and increases mTOR-independent lung metastases

Metastatic estrogen receptor alpha positive (ERα+) cancers account for most breast cancer mortality. Cancer stem cells (CSCs) and dense/stiff extracellular matrices are implicated in aggression and therapy resistance. We examined this interplay and response to mTOR inhibition using ERα+ adenocarcinomas from NRL-PRL females in combination with Col1a1^tmJae/+ (mCol1a1) mice, which accumulate collagen-I around growing tumors. Orthotopic transplantation of tumor cells to mCol1a1 but not wildtype hosts resulted in striking desmoplasia. Mammary tumors in mCol1a1 recipients displayed higher CSC activity and enhanced AKT-mTOR and YAP activation, and these animals developed more and larger lung metastases. Treatment with the mTOR inhibitor, rapamycin, with or without the anti-estrogen, ICI182780, rapidly diminished mammary tumors, which rapidly reversed when treatment ceased. In contrast, lung metastases, which exhibited lower proliferation and pS6RP, indicating lower mTOR activity, were unresponsive, and mCol1a1 hosts continued to sustain greater metastatic burdens. These findings shed light on the influence of desmoplastic tumor microenvironments on the CSC niche and metastatic behavior in ERα+ breast cancer. The differential mTOR dependence of local mammary tumors and pulmonary lesions has implications for success of mTOR inhibitors in advanced ERα+ disease.

Serum osteoprotegerin levels and mammographic density among high-risk women

PURPOSE

Mammographic density is a risk factor for breast cancer but the mechanism behind this association is unclear. The receptor activator of nuclear factor κB (RANK)/RANK ligand (RANKL) pathway has been implicated in the development of breast cancer. Given the role of RANK signaling in mammary epithelial cell proliferation, we hypothesized this pathway may also be associated with mammographic density. Osteoprotegerin (OPG), a decoy receptor for RANKL, is known to inhibit RANK signaling. Thus, it is of interest to evaluate whether OPG levels modify breast cancer risk through mammographic density.

METHODS

We quantified serum OPG levels in 57 premenopausal and 43 postmenopausal women using an enzyme-linked immunosorbent assay (ELISA). Cumulus was used to measure percent density, dense area, and non-dense area for each mammographic image. Subjects were classified into high versus low OPG levels based on the median serum OPG level in the entire cohort (115.1 pg/mL). Multivariate models were used to assess the relationship between serum OPG levels and the measures of mammographic density.

RESULTS

Serum OPG levels were not associated with mammographic density among premenopausal women (P ≥ 0.42). Among postmenopausal women, those with low serum OPG levels had higher mean percent mammographic density (20.9% vs. 13.7%; P = 0.04) and mean dense area (23.4 cm² vs. 15.2 cm²; P = 0.02) compared to those with high serum OPG levels after covariate adjustment.

CONCLUSIONS

These findings suggest that low OPG levels may be associated with high mammographic density, particularly in postmenopausal women. Targeting RANK signaling may represent a plausible, non-surgical prevention option for high-risk women with high mammographic density, especially those with low circulating OPG levels.

Prolactin signaling through focal adhesion complexes is amplified by stiff extracellular matrices in breast cancer cells

Estrogen receptor α positive (ERα+) breast cancer accounts for most breast cancer deaths. Both prolactin (PRL) and extracellular matrix (ECM) stiffness/density have been implicated in metastatic progression of this disease. We previously demonstrated that these factors cooperate to fuel processes involved in cancer progression. Culture of ERα+ breast cancer cells in dense/stiff 3D collagen-I matrices shifts the repertoire of PRL signals, and increases crosstalk between PRL and estrogen to promote proliferation and invasion. However, previous work did not distinguish ECM stiffness and collagen density. In order to dissect the ECM features that control PRL signals, we cultured T47D and MCF-7 cells on polyacrylamide hydrogels of varying elastic moduli (stiffness) with varying collagen-I concentrations (ligand density). Increasing stiffness from physiological to pathological significantly augmented PRL-induced phosphorylation of ERK1/2 and the SFK target, FAK-Y925, with only modest effects on pSTAT5. In contrast, higher collagen-I ligand density lowered PRL-induced pSTAT5 with no effect on pERK1/2 or pFAK-Y925. Disrupting focal adhesion signaling decreased PRL signals and PRL/estrogen-induced proliferation more efficiently in stiff, compared to compliant, extracellular environments. These data indicate that matrix stiffness shifts the balance of PRL signals from physiological (JAK2/STAT5) to pathological (FAK/SFK/ERK1/2) by increasing PRL signals through focal adhesions. Together, our studies suggest that PRL signaling to FAK and SFKs may be useful targets in clinical aggressive ERα+ breast carcinomas.

Progesterone receptors (PR) mediate STAT actions: PR and prolactin receptor signaling crosstalk in breast cancer models

Estrogen is the major mitogenic stimulus of mammary gland development during puberty wherein ER signaling acts to induce abundant PR expression. PR signaling, in contrast, is the primary driver of mammary epithelial cell proliferation in adulthood. The high circulating levels of progesterone during pregnancy signal through PR, inducing expression of the prolactin receptor (PRLR). Cooperation between PR and prolactin (PRL) signaling, via regulation of downstream components in the PRL signaling pathway including JAKs and STATs, facilitates the alveolar morphogenesis observed during pregnancy. Indeed, these pathways are fully integrated via activation of shared signaling pathways (i.e. JAKs, MAPKs) as well as by the convergence of PRs and STATs at target genes relevant to both mammary gland biology and breast cancer progression (i.e. proliferation, stem cell outgrowth, tissue cell type heterogeneity). Thus, rather than a single mediator such as ER, transcription factor cascades (ER>PR>STATs) are responsible for rapid proliferative and developmental programming in the normal mammary gland. It is not surprising that these same mediators typify uncontrolled proliferation in a majority of breast cancers, where ER and PR are most often co-expressed and may cooperate to drive malignant tumor progression. This review will primarily focus on the integration of PR and PRL signaling in breast cancer models and the importance of this cross-talk in cancer progression in the context of mammographic density. Components of these PR/PRL signaling pathways could offer alternative drug targets and logical complements to anti-ER or anti-estrogen-based endocrine therapies.

ATM Is Required for the Prolactin-Induced HSP90-Mediated Increase in Cellular Viability and Clonogenic Growth After DNA Damage

Prolactin (PRL) acts as a survival factor for breast cancer cells, but the PRL signaling pathway and the mechanism are unknown. Previously, we identified the master chaperone, heat shock protein 90 (HSP90) α, as a prolactin-Janus kinase 2 (JAK2)-signal transducer and activator of transcription 5 (STAT5) target gene involved in survival, and here we investigated the role of HSP90 in the mechanism of PRL-induced viability in response to DNA damage. The ataxia-telangiectasia mutated kinase (ATM) protein plays a critical role in the cellular response to double-strand DNA damage. We observed that PRL increased viability of breast cancer cells treated with doxorubicin or etoposide. The increase in cellular resistance is specific to the PRL receptor, because the PRL receptor antagonist, Δ1-9-G129R-hPRL, prevented the increase in viability. Two different HSP90 inhibitors, 17-allylamino-17-demethoxygeldanamycin and BIIB021, reduced the PRL-mediated increase in cell viability of doxorubicin-treated cells and led to a decrease in JAK2, ATM, and phosphorylated ATM protein levels. Inhibitors of JAK2 (G6) and ATM (KU55933) abolished the PRL-mediated increase in cell viability of DNA-damaged cells, supporting the involvement of each, as well as the crosstalk of ATM with the PRL pathway in the context of DNA damage. Drug synergism was detected between the ATM inhibitor (KU55933) and doxorubicin and between the HSP90 inhibitor (BIIB021) and doxorubicin. Short interfering RNA directed against ATM prevented the PRL-mediated increase in cell survival in two-dimensional cell culture, three-dimensional collagen gel cultures, and clonogenic cell survival, after doxorubicin treatment. Our results indicate that ATM contributes to the PRL-JAK2-STAT5-HSP90 pathway in mediating cellular resistance to DNA-damaging agents.

Antiestrogen Therapy Increases Plasticity and Cancer Stemness of Prolactin-Induced ERα+ Mammary Carcinomas

Although antiestrogen therapies are successful in many patients with estrogen receptor alpha-positive (ERα⁺) breast cancer, 25% to 40% fail to respond. Although multiple mechanisms underlie evasion of these treatments, including tumor heterogeneity and drug-resistant cancer stem cells (CSC), further investigations have been limited by the paucity of preclinical ERα⁺ tumor models. Here, we examined a mouse model of prolactin-induced aggressive ERα⁺ breast cancer, which mimics the epidemiologic link between prolactin exposure and increased risk for metastatic ERα⁺ tumors. Like a subset of ERα⁺ patient cancers, the prolactin-induced adenocarcinomas contained two major tumor subpopulations that expressed markers of normal luminal and basal epithelial cells. CSC activity was distributed equally across these two tumor subpopulations. Treatment with the selective estrogen receptor downregulator (SERD), ICI 182,780 (ICI), did not slow tumor growth, but induced adaptive responses in CSC activity, increased markers of plasticity including target gene reporters of Wnt/Notch signaling and epithelial-mesenchymal transition, and increased double-positive (K8/K5) cells. In primary tumorsphere cultures, ICI stimulated CSC self-renewal and was able to overcome the dependence of self-renewal upon Wnt or Notch signaling individually, but not together. Our findings demonstrate that treatment of aggressive mixed lineage ERα⁺ breast cancers with a SERD does not inhibit growth, but rather evokes tumor cell plasticity and regenerative CSC activity, predicting likely negative impacts on patient tumors with these characteristics.Significance: This study suggests that treatment of a subset of ERα⁺ breast cancers with antiestrogen therapies may not only fail to slow growth but also promote aggressive behavior by evoking tumor cell plasticity and regenerative CSC activity. Cancer Res; 78(7); 1672-84. ©2018 AACR.

Hyperprolactinaemia and antipsychotics

This overview explains antipsychotic-induced hyperprolactinaemia and offers guidance on the management of this common and underestimated problem in general psychiatric practice.

Hyperprolactinaemia: A guide for psychiatrists

Medications prescribed by psychiatrists are known to elevate serum prolactin levels, but hyperprolactinaemia remains underrecognised, as the adverse effects of an elevated prolactin are mostly not visible. Hyperprolactinaemia can lead to adverse health outcomes, so clinicians need not only to be alert to its symptoms, but to manage the consequences as well. In this article we provide a brief overview of prolactin physiology, regulation and function. We list various factors that can lead to elevated serum prolactin. We discuss the interpretation of blood results and the management of psychotropic-induced hyperprolactinaemia. We include a flow diagram to assist clinicians in decision-making in the clinical management of hyperprolactinaemia.

Learning Objectives

• Understand prolactin physiology and regulation

• Understand hyperprolactinaemia and its causes

• Know the consequences of hyperprolactinaemia and appropriately manage it in clinical practice

Determinants of prolactin in postmenopausal Chinese women in Singapore

PURPOSE

Mechanistic and observational data together support a role for prolactin in breast cancer development. Determinants of prolactin in Asian populations have not been meaningfully explored, despite the lower risk of breast cancer in Asian populations.

METHODS

Determinants of plasma prolactin were evaluated in 442 postmenopausal women enrolled in the Singapore Chinese Health Study, a population-based prospective cohort study. At baseline all cohort members completed an in-person interview that elicited information on diet, menstrual and reproductive history, and lifestyle factors. One year after cohort initiation we began collecting blood samples. Quantified were plasma concentrations of prolactin, estrone, estradiol, testosterone, androstenedione, and sex hormone-binding globulin (SHBG). Analysis of covariance method was used for statistical analyses with age at blood draw, time since last meal, and time at blood draw as covariates.

RESULTS

Mean prolactin levels were 25.1% lower with older age at menarche (p value = 0.001), and 27.6% higher with greater years between menarche and menopause (p value = 0.009). Prolactin levels were also positively associated with increased sleep duration (p value = 0.005). The independent determinants of prolactin were years from menarche to menopause, hours of sleep, and the plasma hormones estrone and SHBG (all p values < 0.01).

CONCLUSION

The role of prolactin in breast cancer development may involve reproductive and lifestyle factors, such as a longer duration of menstrual cycling and sleep patterns.

Depression, Antidepressant Use, and Breast Cancer Risk in Pre- and Postmenopausal Women: A Prospective Cohort Study

Background: Depression and antidepressant use is highly prevalent among U.S. women and may be related to increased breast cancer risk. However, prior studies are not in agreement regarding an increase in risk.Methods: We conducted a prospective cohort study within the Nurses' Health Study (NHS) and NHSII among females age 25 and older. Over more than 10 years of follow-up in each cohort, 4,014 incident invasive breast cancers were diagnosed. We used Cox proportional hazards regressions with updating of exposures and covariates throughout follow-up to estimate HRs and 95% confidence intervals (CIs) for associations between clinical depression and antidepressant use with invasive breast cancer risk. Analyses were repeated separately for in situ disease, as well as stratified by estrogen receptor (ER) subtype and menopausal status at diagnosis.Results: No statistically significant associations were observed between clinical depression (HR for reporting ≥3 times vs. 0, 1.13; 95% CI, 0.85-1.49) or antidepressant use (HR for reporting ≥3 times vs. 0, 0.92; 95% CI, 0.80-1.05) and invasive breast cancer risk in multivariable analyses. Likewise, we observed no significant associations between clinical depression or antidepressant use and risk of in situ, ER⁺, ER^-, premenopausal, or postmenopausal breast cancer.Conclusions: In the largest prospective study to date, we find no evidence that either depression or antidepressant use increase risk of breast cancer.Impact: The results of this study are reassuring in that neither depression nor antidepressant use appear to be related to subsequent breast cancer risk. Cancer Epidemiol Biomarkers Prev; 27(3); 306-14. ©2017 AACR.

Plasma Prolactin and Total Lipid Levels and Subsequent Risk of Breast Cancer in Pre- and Postmenopausal Women: Experience from an Indian Rural Centre

AIMS AND OBJECTIVES

1) To analyze serum lipid and prolactin levels in breast cancer patients and normal subjects; 2) to correlate those levels with risk and prognostic factors.

MATERIAL AND METHODS

The present study was performed in the Department of Surgery, MMIMSR, Mullana, Ambala, from 2013 to 2014, at a rural centre. The study group comprised 40 patients with carcinoma of the breast who underwent surgery and the control group included 10 patients who underwent surgery for reasons other than carcinoma of the breast. Apart from routine tests, special investigations like estimation of serum lipids and prolactin levels were carried out in each patient to assess the general health status and detect any potential evidence of distance metastasis.

RESULTS

Most patients were in the fourth and fifth decade of life. The mean value of serum total cholesterol in the study group (190.77 mg/dL) was higher than that of the control group (166.22 mg/dL), which was statistically significant. The mean value of LDL in the study group was 153.8 mg/dL, as compared to 118.4 mg/dL in the control group; therefore, the difference in LDL cholesterol levels between the two groups was statistically significant. The VLDL level was also higher in breast cancer patients, with a mean value of 35.25 mg/dL, as compared to 22.6 mg/dL in the control group. Serum triglycerides showed higher trends in the study group than in controls. The correlation coefficient of total lipids and prolactin was 0.428, which was significant (p value 0.002), and pointed to a positive relation between prolactin and total lipids, meaning that an elevation in total lipids would lead to an increase in prolactin levels.

CONCLUSIONS

It was observed that significantly increased prolactin levels were found among patients with breast cancer. Serum lipids in carcinoma of the breast had higher levels of VLDL and LDL cholesterol and elevated triglyceride concentrations. Serum prolactin showed a statistically significant elevation in premenopausal patients as compared to postmenopausal subjects with breast cancer. Prolactin level may be also one of the risk factors for breast cancer, which points to its diagnostic significance.

Truncating Prolactin Receptor Mutations Promote Tumor Growth in Murine Estrogen Receptor-Alpha Mammary Carcinomas

Estrogen receptor alpha-positive (ERα+) luminal tumors are the most frequent subtype of breast cancer. Stat1(-/-) mice develop mammary tumors that closely recapitulate the biological characteristics of this cancer subtype. To identify transforming events that contribute to tumorigenesis, we performed whole genome sequencing of Stat1(-/-) primary mammary tumors and matched normal tissues. This investigation identified somatic truncating mutations affecting the prolactin receptor (PRLR) in all tumor and no normal samples. Targeted sequencing confirmed the presence of these mutations in precancerous lesions, indicating that this is an early event in tumorigenesis. Functional evaluation of these heterozygous mutations in Stat1(-/-) mouse embryonic fibroblasts showed that co-expression of truncated and wild-type PRLR led to aberrant STAT3 and STAT5 activation downstream of the receptor, cellular transformation in vitro, and tumor formation in vivo. In conclusion, truncating mutations of PRLR promote tumor growth in a model of human ERα+ breast cancer and warrant further investigation.

Morbidity and mortality in patients with hyperprolactinaemia: the PROLEARS study

PURPOSE

High serum prolactin concentrations have been associated with adverse health outcomes in some but not all studies. This study aimed to examine the morbidity and all-cause mortality associated with hyperprolactinaemia.

METHODS

A population-based matched cohort study in Tayside (Scotland, UK) from 1988 to 2014 was performed. Record-linkage technology was used to identify patients with hyperprolactinaemia that were compared to an age-sex-matched cohort of patients free of hyperprolactinaemia. The number of deaths and incident admissions with diabetes mellitus, cardiovascular disease, cancer, breast cancer, bone fractures and infectious conditions were compared by the survival analysis.

RESULTS

Patients with hyperprolactinaemia related to pituitary tumours had no increased risk of diabetes, cardiovascular disease, bone fractures, all-cause cancer or breast cancer. Whilst no increased mortality was observed in patients with pituitary microadenomas (HR = 1.65, 95% CI: 0.79-3.44), other subgroups including those with pituitary macroadenomas and drug-induced and idiopathic hyperprolactinaemia demonstrated an increased risk of death. Individuals with drug-induced hyperprolactinaemia also demonstrated increased risks of diabetes, cardiovascular disease, infectious disease and bone fracture. However, these increased risks were not associated with the degree of serum prolactin elevation (P_trend > 0.3). No increased risk of cancer was observed in any subgroup.

CONCLUSIONS

No excess morbidity was observed in patients with raised prolactin due to pituitary tumours. Although the increased morbidity and mortality associated with defined patient subgroups are unlikely to be directly related to the elevation in serum prolactin, hyperprolactinaemia might act as a biomarker for the presence of some increased disease risk in these patients.

[Prolactin-secreting microadenoma in menopausal women]

Prolactin-secreting adenoma is rare in elderly women. Patient's clinical picture may be confused with that of menopause, making diagnosis sometimes difficult. We report the case of a 57-year old woman with a 2-year history of secondary amenorrhea without hot flushes associated with galactorrhea in order to highlight the peculiarities of prolactin-secreting microadenomas. Physical examination confirmed the diagnosis of galactorrhoea and biology showed hyperprolactinemia at mIU/L, FSH = 15.1 IU/L and LH = 4,1 IU/L. Pituitary MRI showed left adenoma measuring 8 mm. Patient's evolution under dopaminergic treatment was marked by the recovery, for a transitional period, of mestrual cycles and the occurrence of hot flushes, normalization of prolactin levels and reduction of adenoma size.

Prolactin Alters the Mammary Epithelial Hierarchy, Increasing Progenitors and Facilitating Ovarian Steroid Action

Hormones drive mammary development and function and play critical roles in breast cancer. Epidemiologic studies link prolactin (PRL) to increased risk for aggressive cancers that express estrogen receptor α (ERα). However, in contrast to ovarian steroids, PRL actions on the mammary gland outside of pregnancy are poorly understood. We employed the transgenic NRL-PRL model to examine the effects of PRL alone and with defined estrogen/progesterone exposure on stem/progenitor activity and regulatory networks that drive epithelial differentiation. PRL increased progenitors and modulated transcriptional programs, even without ovarian steroids, and with steroids further raised stem cell activity associated with elevated canonical Wnt signaling. However, despite facilitating some steroid actions, PRL opposed steroid-driven luminal maturation and increased CD61⁺ luminal cells. Our findings demonstrate that PRL can powerfully influence the epithelial hierarchy alone and temper the actions of ovarian steroids, which may underlie its role in the development of breast cancer.

Inhibition of 17beta-hydroxysteroid dehydrogenase type 7 modulates breast cancer protein profile and enhances apoptosis by down-regulating GRP78

17beta-hydroxysteroid dehydrogenase type 7 (17β-HSD7) promotes breast cancer cell growth via dual-catalytic activity by modulating estradiol and DHT. Here, we clarified the expression pattern of 17β-HSD7 in postmenopausal luminal A type breast cancer with The Cancer Genome Atlas (TCGA) cohort. The impact of 17β-HSD7 inhibition on the proteome of MCF-7 cells was investigated and on cell apoptosis was revealed. MCF-7 cells were treated with an efficient inhibitor of 17β-HSD7 (INH7) or with vehicle, and a differential proteomics study was performed using two-dimensional (2D) gel electrophoresis followed by mass spectrometry and ingenuity pathway analysis (IPA). Cell apoptosis was analyzed by flow cytometry, followed by reverse transcription quantitative real-time PCR (RT-qPCR) and Western blot to investigate the expression of apoptosis-related genes. Our data showed 17β-HSD7 is amplified in primary and progressive breast cancer, inhibition of 17β-HSD7 in MCF-7 cells modulated 104 proteins primarily involved in cell death/survival, cell growth and DNA processing. The expression of 78kDa glucose-regulated protein (GRP78) and anti-apoptosis factor Bcl-2 were significantly suppressed via 17β-HSD7 inhibition with INH7, consequently induced MCF-7 cell apoptosis. However, INH7 treatment of T47D, another widely used epithelial ER+ breast cancer cell line, led to an up-regulation of GRP78 expression, resulting in a limited increase in apoptosis. These results suggest cell-specific effects of INH7 in the breast cancer, which is interesting for further study. An combinatory effect on apoptosis by INH7 and Letrozole (aromatase inhibitor) was further demonstrated in MCF-7. Down-regulation of GRP78 via 17β-HSD7 inhibition enhances cell apoptosis in response to Letrozole. This study highlights GRP78 as a key regulator related to 17β-HSD7 inhibition and effect. Taken together, results from the present study suggest a hypothesis that inhibition of 17β-HSD7 would be a complementary strategy to Letrozole by suppression of GRP78 in ER+ breast cancer. However, from a research perspective, further studies have to be carried out with more breast cancer cell lines as well as in vivo model to assess the efficacy of inhibitor combination.

Added Value of Serum Hormone Measurements in Risk Prediction Models for Breast Cancer for Women Not Using Exogenous Hormones: Results from the EPIC Cohort

Purpose: Circulating hormone concentrations are associated with breast cancer risk, with well-established associations for postmenopausal women. Biomarkers may represent minimally invasive measures to improve risk prediction models.Experimental Design: We evaluated improvements in discrimination gained by adding serum biomarker concentrations to risk estimates derived from risk prediction models developed by Gail and colleagues and Pfeiffer and colleagues using a nested case-control study within the EPIC cohort, including 1,217 breast cancer cases and 1,976 matched controls. Participants were pre- or postmenopausal at blood collection. Circulating sex steroids, prolactin, insulin-like growth factor (IGF) I, IGF-binding protein 3, and sex hormone-binding globulin (SHBG) were evaluated using backward elimination separately in women pre- and postmenopausal at blood collection. Improvement in discrimination was evaluated as the change in concordance statistic (C-statistic) from a modified Gail or Pfeiffer risk score alone versus models, including the biomarkers and risk score. Internal validation with bootstrapping (1,000-fold) was used to adjust for overfitting.Results: Among women postmenopausal at blood collection, estradiol, testosterone, and SHBG were selected into the prediction models. For breast cancer overall, model discrimination after including biomarkers was 5.3 percentage points higher than the modified Gail model alone, and 3.4 percentage points higher than the Pfeiffer model alone, after accounting for overfitting. Discrimination was more markedly improved for estrogen receptor-positive disease (percentage point change in C-statistic: 7.2, Gail; 4.8, Pfeiffer). We observed no improvement in discrimination among women premenopausal at blood collection.Conclusions: Integration of hormone measurements in clinical risk prediction models may represent a strategy to improve breast cancer risk stratification. Clin Cancer Res; 23(15); 4181-9. ©2017 AACR.

Risk of breast cancer in risperidone users: A nationwide cohort study

BACKGROUND

Several antipsychotics, especially risperidone, are known to increase serum prolactin. Hyperprolactinemia has been linked to the development of mammary gland tumors in animal studies. We therefore investigated the risk of breast cancer in a nationwide cohort of women using risperidone or other antipsychotics.

METHODS

All women, 18years or older, who initiated treatment with risperidone or any other antipsychotic between 2006 and 2012 were identified in Swedish nationwide registers. Patients with two consecutive dispensations of the same antipsychotic within 3months, no previous cancer diagnosis, and no previous dispensations of paliperidone were included. The final cohort consisted of 55976 women of whom 22908, 24524, and 8544 were exposed to risperidone, other atypical antipsychotics, and typical antipsychotics, respectively. A Cox regression model was used to estimate the hazard ratio (HR) and 95% confidence interval (CI) for the association between antipsychotics and breast cancer.

RESULTS

Patients were followed prospectively, the mean follow-up time ranging from 2.4 to 2.8years between treatment groups. After adjusting for age, there was no increased risk for breast cancer among risperidone users compared to patients exposed to another atypical antipsychotic (HR 0.94, 95% CI 0.72-1.22) or a typical antipsychotic (HR 1.25, 95% CI 0.94-1.66). Analyses stratified by tumor stage, using active treatment follow-up time, or including only treatment naïve patients did not reveal any noteworthy change in the results.

CONCLUSION

Risperidone use does not confer an increased short-term risk of breast cancer compared to other antipsychotic agents.

Breast carcinoma associated with prolactinoma: A case report

We report a 28-year-old woman who presented with a 6-year history of milk-like discharge from both of her nipples and was diagnosed with prolactinoma based on computed tomography (CT) findings and serum prolactin level. Further breast examination revealed a mass located in the upper outer region of the left breast. She underwent subtotal pituitary tumor resection. Thereafter, modified radical mastectomy was performed for left breast cancer. Twelve years after treatment, prolactinoma recurrence was detected, and bromocriptine therapy was administered. No recurrence of breast cancer was discovered. Based on this case report, we stress the importance of prolactin levels due to their possible biologic effects on breast cancer induction or growth.

From Bench to Bedside: Translating the Prolactin/Vasoinhibin Axis

The prolactin/vasoinhibin axis defines an endocrine system, in which prolactin (PRL) and vasoinhibins regulate blood vessel growth and function, the secretion of other hormones, inflammatory and immune processes, coagulation, and behavior. The core element of the PRL/vasoinhibin axis is the generation of vasoinhibins, which consists in the proteolytic cleavage of their precursor molecule PRL. Vasoinhibins can interact with multiple different partners to mediate their effects in various tissues and anatomical compartments, indicating their pleiotropic nature. Based on accumulating knowledge about the PRL/vasoinhibin axis, two clinical trials were initiated, in which vasoinhibin levels are the target of therapeutic interventions. One trial investigates the effect of levosulpiride, a selective dopamine D2-receptor antagonist, on retinal alterations in patients with diabetic macular edema and retinopathy. The rationale of this trial is that the levosulpiride-induced hyperprolactinemia resulting in increased retinal vasoinhibins could lead to beneficiary outcomes in terms of a vasoinhibin-mediated antagonization of diabetes-induced retinal alterations. Another trial investigated the effect of bromocriptine, a dopamine D2-receptor agonist, for the treatment of peripartum cardiomyopathy. The rationale of treatment with bromocriptine is the inhibition of vasoinhibin generation by substrate depletion to prevent detrimental effects on the myocardial microvascularization. The trial demonstrated that bromocriptine treatment was associated with a high rate of left ventricular recovery and low morbidity and mortality. Therapeutic interventions into the PRL/vasoinhibin axis bear the risk of side effects in the areas of blood coagulation, blood pressure, and alterations of the mental state.

Histone H1 and Chromosomal Protein HMGN2 Regulate Prolactin-induced STAT5 Transcription Factor Recruitment and Function in Breast Cancer Cells

The hormone prolactin (PRL) contributes to breast cancer pathogenesis through various signaling pathways, one of the most notable being the JAK2/signal transducer and activator of transcription 5 (STAT5) pathway. PRL-induced activation of the transcription factor STAT5 results in the up-regulation of numerous genes implicated in breast cancer pathogenesis. However, the molecular mechanisms that enable STAT5 to access the promoters of these genes are not well understood. Here, we show that PRL signaling induces chromatin decompaction at promoter DNA, corresponding with STAT5 binding. The chromatin-modifying protein high mobility group nucleosomal binding domain 2 (HMGN2) specifically promotes STAT5 accessibility at promoter DNA by facilitating the dissociation of the linker histone H1 in response to PRL. Knockdown of H1 rescues the decrease in PRL-induced transcription following HMGN2 knockdown, and it does so by allowing increased STAT5 recruitment. Moreover, H1 and STAT5 are shown to function antagonistically in regulating PRL-induced transcription as well as breast cancer cell biology. While reduced STAT5 activation results in decreased PRL-induced transcription and cell proliferation, knockdown of H1 rescues both of these effects. Taken together, we elucidate a novel mechanism whereby the linker histone H1 prevents STAT5 binding at promoter DNA, and the PRL-induced dissociation of H1 mediated by HMGN2 is necessary to allow full STAT5 recruitment and promote the biological effects of PRL signaling.

What Is Breast in the Bone?

The normal developmental program that prolactin generates in the mammary gland is usurped in the cancerous process and can be used out of its normal cellular context at a site of secondary metastasis. Prolactin is a pleiotropic peptide hormone and cytokine that is secreted from the pituitary gland, as well as from normal and cancerous breast cells. Experimental and epidemiologic data suggest that prolactin is associated with mammary gland development, and also the increased risk of breast tumors and metastatic disease in postmenopausal women. Breast cancer spreads to the bone in approximately 70% of cases with advanced breast cancer. Despite treatment, new bone metastases will still occur in 30%–50% of patients. Only 20% of patients with bone metastases survive five years after the diagnosis of bone metastasis. The breast cancer cells in the bone microenvironment release soluble factors that engage osteoclasts and/or osteoblasts and result in bone breakdown. The breakdown of the bone matrix, in turn, enhances the proliferation of the cancer cells, creating a vicious cycle. Recently, it was shown that prolactin accelerated the breast cancer cell-mediated osteoclast differentiation and bone breakdown by the regulation of breast cancer-secreted proteins. Interestingly, prolactin has the potential to affect multiple proteins that are involved in both breast development and likely bone metastasis, as well. Prolactin has normal bone homeostatic roles and, combined with the natural “recycling” of proteins in different tissues that can be used for breast development and function, or in bone function, increases the impact of prolactin signaling in breast cancer bone metastases. Thus, this review will focus on the role of prolactin in breast development, bone homeostasis and in breast cancer to bone metastases, covering the molecular aspects of the vicious cycle.

The Impact of the Nurses' Health Study on Population Health: Prevention, Translation, and Control

OBJECTIVES

To summarize the overall impact of the Nurses' Health Study (NHS) over the past 40 years on the health of populations through its contributions on prevention, translation, and control.

METHODS

We performed a narrative review of the findings of the NHS, NHS II, and NHS3 between 1976 and 2016.

RESULTS

The NHS has generated significant findings about the associations between (1) smoking and type 2 diabetes, cardiovascular diseases, colorectal and pancreatic cancer, psoriasis, multiple sclerosis, and eye diseases; (2) physical activity and cardiovascular diseases, breast cancer, psoriasis, and neurodegeneration; (3) obesity and cardiovascular diseases, numerous cancer sites, psoriasis, multiple sclerosis, kidney stones, and eye diseases; (4) oral contraceptives and cardiovascular disease, melanoma, and breast, colorectal, and ovarian cancer; (5) hormone therapy and cardiovascular diseases, breast and endometrial cancer, and neurodegeneration; (6) endogenous hormones and breast cancer; (7) dietary factors and type 2 diabetes, cardiovascular diseases, breast and pancreatic cancer, non-Hodgkin's lymphoma, neurodegeneration, multiple sclerosis, kidney stones, and eye diseases; and (8) sleep and shift work and chronic diseases.

CONCLUSIONS

The NHS findings have influenced public health policy and practice both locally and globally to improve women's health.

Identification of NEK3 Kinase Threonine 165 as a Novel Regulatory Phosphorylation Site That Modulates Focal Adhesion Remodeling Necessary for Breast Cancer Cell Migration

Accumulating evidence supports a role for prolactin (PRL) in the development and progression of human breast cancer. Although PRL is an established chemoattractant for breast cancer cells, the precise molecular mechanisms of how PRL regulates breast cancer cell motility and invasion are not fully understood. PRL activates the serine/threonine kinase NEK3, which was reported to enhance breast cancer cell migration, invasion, and the actin cytoskeletal reorganization necessary for these processes. However, the specific mechanisms of NEK3 activation in response to PRL signaling have not been defined. In this report, a novel PRL-inducible regulatory phosphorylation site within the activation segment of NEK3, threonine 165 (Thr-165), was identified. Phosphorylation at NEK3 Thr-165 was found to be dependent on activation of the extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathway using both pharmacological inhibition and siRNA-mediated knockdown approaches. Strikingly, inhibition of phosphorylation at NEK3 Thr-165 by expression of a phospho-deficient mutant (NEK3-T165V) resulted in increased focal adhesion size, formation of zyxin-positive focal adhesions, and reorganization of the actin cytoskeleton into stress fibers. Concordantly, NEK3-T165V cells exhibited migratory defects. Together, these data support a modulatory role for phosphorylation at NEK3 Thr-165 in focal adhesion maturation and/or turnover to promote breast cancer cell migration.

Breast Cancer Research in the Nurses' Health Studies: Exposures Across the Life Course

OBJECTIVES

To review the contribution of the Nurses' Heath Study (NHS) and the NHS II in identifying risk and protective factors for breast cancer incidence and survival.

METHODS

We conducted a narrative review of NHS and NHS II articles on breast cancer incidence and survival published from 1976 to 2016, with a focus on exogenous and endogenous hormones; lifestyle factors, including diet, physical activity, and aspirin use; intermediate markers of risk; and genetic factors.

RESULTS

With the investigation of individual risk factors, as well as their incorporation into risk prediction models, the NHS has contributed to the identification of ways in which women may reduce breast cancer risk, including limiting alcohol consumption, reducing the duration of postmenopausal estrogen-plus-progestin use, avoiding weight gain, and increasing vegetable consumption. In addition, the NHS has helped elucidate the roles of several biomarkers and contributed to the identification of risk alleles.

CONCLUSIONS

The NHS has contributed to our understanding of lifestyle, hormonal, and genetic risk factors for breast cancer, highlighting the importance of exposures across the life course, and has helped identify lifestyle changes that may reduce risk and improve survival after a diagnosis of breast cancer.

Plasma prolactin and breast cancer risk: a meta- analysis

Breast cancer is the most common cancer among women, and its incidence is on a constant rise. Previous studies suggest that higher levels of plasma prolactin are associated with escalated risk of breast cancer, however, these results are contradictory and inconclusive. PubMed and Medline were used to search and identify published observational studies that assessed the relationship between plasma prolactin levels and the risk of breast cancer. The pooled relative risks (RRs) with 95% confidence intervals (CIs) were calculated using a fixed-effects or random-effects model. A total of 7 studies were included in our analysis. For the highest versus lowest levels of plasma prolactin, the pooled RR (95% CI) of breast cancer were 1.16 (1.04, 1.29). In subgroup analyses, we found a positive association between plasma prolactin levels and the risk of breast cancer among the patients who were postmenopausal, ER(+)/PR(+) or in situ and invasive carcinoma. However, this positive association was not detected in the premenopausal and ER(-)/PR(-) patients. In conclusion, the present study provides evidence supporting a significantly positive association between plasma prolactin levels and the risk of breast cancer.

Prolactin Signaling Stimulates Invasion via Na(+)/H(+) Exchanger NHE1 in T47D Human Breast Cancer Cells

Prolactin (PRL) and its receptor (PRLR) are implicated in breast cancer invasiveness, although their exact roles remain controversial. The Na(+)/H(+) exchanger (NHE1) plays essential roles in cancer cell motility and invasiveness, but the PRLR and NHE1 have not previously been linked. Here we show that in T47D human breast cancer cells, which express high levels of PRLR and NHE1, exposure to PRL led to the activation of Janus kinase-2 (JAK2)/signal transducer and activator of transcription-5 (STAT5), Akt, and ERK1/2 signaling and the rapid formation of peripheral membrane ruffles, known to be associated with cell motility. NHE1 was present in small ruffles prior to PRL treatment and was further recruited to the larger, more dynamic ruffles induced by PRL exposure. In PRL-induced ruffles, NHE1 colocalized with activated Akt, ERK1/2, and the ERK effector p90Ribosomal S kinase (p90RSK), known regulators of NHE1 activity. Stimulation of T47D cells with PRL augmented p90RSK activation, Ser703-phosphorylation of NHE1, NHE1-dependent intracellular pH recovery, pericellular acidification, and NHE1-dependent invasiveness. NHE1 activity and localization to ruffles were attenuated by the inhibition of Akt and/or ERK1/2. In contrast, noncancerous MCF10A breast epithelial cells expressed NHE1 and PRLR at lower levels than T47D cells, and their stimulation with PRL induced neither NHE1 activation nor NHE1-dependent invasiveness. In conclusion, we show for the first time that PRLR activation stimulates breast cancer cell invasiveness via the activation of NHE1. We propose that PRL-induced NHE1 activation and the resulting NHE1-dependent invasiveness may contribute to the metastatic behavior of human breast cancer cells.

Antidepressant use and circulating prolactin levels

PURPOSE

To determine whether antidepressants (AD), specifically selective serotonin reuptake inhibitors (SSRIs), are linked to elevated prolactin levels among the general population.

METHODS

Circulating prolactin levels were available for 4593 healthy participants in the Nurses' Health Study (NHS) and NHS2, including 267 AD users. We fit generalized linear models to calculate and compare adjusted mean prolactin levels between AD users and non-users and further among SSRI users. Multivariable logistic regression was used to estimate odds ratios (ORs) and 95 % confidence intervals (CIs) for "elevated" prolactin levels (>11 ng/mL) comparing AD users to non-users. We evaluated AD use and change in prolactin levels among 610 NHS participants with two measurements an average of 11 years apart.

RESULTS

Adjusted geometric mean prolactin levels were similar among SSRI users (13.2 ng/mL, 95 % CI 12.2-14.4), users of other classes of ADs (12.7 ng/mL, 95 % CI 11.0-14.6), and non-users (13.1 ng/mL, 95 % CI 12.8-13.4). Neither AD use (OR 1.17, 95 % CI 0.89-1.53) nor SSRI use (OR 0.95, 95 % CI 0.66-1.38) was associated with elevated prolactin levels. Change in prolactin levels was similar across women who started, stopped, consistently used, or never used ADs.

CONCLUSIONS

This study does not support the hypothesis that AD use would influence breast cancer risk via altered prolactin levels. These results provide some evidence that use of ADs to treat depression or other conditions may not substantially increase prolactin levels in the majority of women.

Targeting Prolactin Receptor (PRLR) Signaling in PRLR-Positive Breast and Prostate Cancer

In this issue of The Oncologist, Agarwal et al. report negative results from a phase I trial of LFA102. Although “negative” in terms of antitumor activity, the study provides useful pharmacokinetic and pharmacodynamic information. Future trials evaluating PRLR blockers alone and in combination with other agents may still be warranted in patients with breast and prostate cancer.

Phase I Study of the Prolactin Receptor Antagonist LFA102 in Metastatic Breast and Castration-Resistant Prostate Cancer

LESSONS LEARNED

Despite evidence for a role for prolactin signaling in breast and prostate tumorigenesis, a prolactin receptor-binding monoclonal antibody has not produced clinical efficacy.Increased serum prolactin levels may be a biomarker for prolactin receptor inhibition.Results from the pharmacokinetic and pharmacodynamics (PD) studies suggest that inappropriately long dosing intervals and insufficient exposure to LFA102 may have resulted in lack of antitumor efficacy.Based on preclinical data, combination therapy of LFA102 with those novel agents targeting hormonal pathways in metastatic castration-resistant prostate cancer and metastatic breast cancer is promising.Given the PD evidence of prolactin receptor blockade by LFA102, this drug has the potential to be used in conditions such as hyperprolactinemia that are associated with high prolactin levels.

BACKGROUND

Prolactin receptor (PRLR) signaling is implicated in breast and prostate cancer. LFA102, a humanized monoclonal antibody (mAb) that binds to and inhibits the PRLR, has exhibited promising preclinical antitumor activity.

METHODS

Patients with PRLR-positive metastatic breast cancer (MBC) or metastatic castration-resistant prostate cancer (mCRPC) received doses of LFA102 at 3-60 mg/kg intravenously once every 4 weeks. Objectives were to determine the maximum tolerated dose (MTD) and/or recommended dose for expansion (RDE) to investigate the safety/tolerability of LFA102 and to assess pharmacokinetics (PK), pharmacodynamics (PD), and antitumor activity.

RESULTS

A total of 73 patients were enrolled at 5 dose levels. The MTD was not reached because of lack of dose-limiting toxicities. The RDE was established at 60 mg/kg based on PK and PD analysis and safety data. The most common all-cause adverse events (AEs) were fatigue (44%) and nausea (33%) regardless of relationship. Grade 3/4 AEs reported to be related to LFA102 occurred in 4% of patients. LFA102 exposure increased approximately dose proportionally across the doses tested. Serum prolactin levels increased in response to LFA102 administration, suggesting its potential as a biomarker for PRLR inhibition. No antitumor activity was detected.

CONCLUSION

Treatment with LFA102 was safe and well tolerated, but did not show antitumor activity as monotherapy at the doses tested.

Prolactin Inhibits BCL6 Expression in Breast Cancer Cells through a MicroRNA-339-5p-Dependent Pathway

PURPOSE

Prolactin (PRL) plays a critical role in breast cancer progression by activating its cognate receptor and promotes the growth and differentiation of breast cancer cells. Studies have shown that B-cell lymphoma 6 (BCL6) is the target gene of microRNA-339-5p (miR-339-5p) and that BCL6 expression contributes to breast cancer progression. Herein, we identified PRL as a potent suppressor of BCL6 expression in human breast cancer cells.

METHODS

Western blotting and quantitative reverse transcription-polymerase chain reaction were used to investigate molecular mechanisms underlying miR-339-5p expression and BCL6 manipulation in MCF-7, T47D, and SKBR3 breast cancer cells. Phenotypic changes in these breast cancer cell lines were assessed by performing cell viability (MTT), colony formation, migration, and invasion assays.

RESULTS

PRL suppressed BCL6 protein and mRNA expression and upregulated miR-339-5p expression in MCF-7 and T47D breast cancer cells. Selective downregulation of miR-339-5p expression significantly reversed PRL-induced suppression of BCL6 mRNA and protein expression. Exogenous PRL stimulation significantly decreased the proliferation, colony formation, migration, and invasion of breast cancer cells, and suppression of miR-339-5p expression reversed these processes in vitro.

CONCLUSION

These results indicated that PRL inhibited BCL6 expression and regulated breast cancer progression through a miR-339-5p-dependent pathway.

Synergistic Activation of ERα by Estrogen and Prolactin in Breast Cancer Cells Requires Tyrosyl Phosphorylation of PAK1

Serine/threonine kinase PAK1 is activated by estrogen and plays an important role in breast cancer. However, the integration of PAK1 into the estrogen response is not fully understood. In this study, we investigated the mechanisms underlying the hormone-induced activation of estrogen receptor (ERα, ESR1). We show that estrogen activated PAK1 through both the ERα and GPER1 membrane receptors. Estrogen-dependent activation of PAK1 required the phosphorylation of tyrosine residues by Etk/Bmx and protein kinase A (PKA) within an assembled signaling complex comprising pTyr-PAK1, Etk/Bmx, the heterotrimer G-protein subunits Gβ1, Gγ2, and/or Gγ5, PAK-associated guanine nucleotide exchange factor (βPIX, ARHGEF7), and PKA. Moreover, the PKA RIIβ subunit is a direct target of PAK1, and thus in response to estrogen, the activated pTyr-PAK1 complex reciprocally potentiated PKA activity, suggesting a positive feedback mechanism. We also demonstrate that PKA phosphorylated Ser305-ERα in response to estrogen, but pTyr-PAK1 phosphorylated Ser305-ERα in response to prolactin (PRL), implying that maximal ERα phosphorylation is achieved when cells are exposed to both PRL and estrogen. Furthermore, S305-ERα activation led to enhanced phosphorylation of Ser118-ERα and promoted cell proliferation and tumor growth. Together, these data strongly support a critical interplay between PRL and estrogen via PAK1 and suggest that ligand-independent activation of ERα through PRL/PAK1 may impart resistance to anti-estrogen therapies. Cancer Res; 76(9); 2600-11. ©2016 AACR.

Spanish consensus on the risks and detection of antipsychotic drug-related hyperprolactinaemia

INTRODUCTION

Iatrogenic hyperprolactinaemia (IHPRL) has been more frequently related to some antipsychotic drugs that provoke an intense blockade of dopamine D2 receptors. There is a wide variation in clinical practice, and perhaps some more awareness between clinicians is needed. Due to the high frequency of chronic treatment in severe mental patients, careful attention is recommended on the physical risk. IHPRL symptoms could be underestimated without routine examination.

METHODOLOGY

An intense scientific literature search was performed in order to draw up a multidisciplinary consensus, including different specialists of psychiatry, endocrinology, oncology and internal medicine, and looking for a consensus about clinical risk and detection of IHPRL following evidence-based medicine criteria levels (EBM I- IV).

RESULTS

Short-term symptoms include amenorrhea, galactorrhoea, and sexual dysfunction with decrease of libido and erectile difficulties related to hypogonadism. Medium and long-term symptoms related to oestrogens are observed, including a decrease bone mass density, hypogonadism, early menopause, some types of cancer risk increase (breast and endometrial), cardiovascular risk increase, immune system disorders, lipids, and cognitive dysfunction. Prolactin level, gonadal hormones and vitamin D should be checked in all patients receiving antipsychotics at baseline although early symptoms (amenorrhea-galactorrhoea) may not be observed due to the risk of underestimating other delayed symptoms that may appear in the medium term. Routine examination of sexual dysfunction is recommended due to possible poor patient tolerance and low compliance. Special care is required in children and adolescents, as well as patients with PRL levels >50ng/ml (moderate hyperprolactinaemia). A possible prolactinoma should be investigated in patients with PRL levels >150ng/ml, with special attention to patients with breast/endometrial cancer history. Densitometry should be prescribed for males >50 years old, amenorrhea>6 months, or early menopause to avoid fracture risk.

Relationship between prolactin, breast cancer risk, and antipsychotics in patients with schizophrenia: a critical review

OBJECTIVE

A recent meta-analysis showed that breast cancer probably is more common in female patients with schizophrenia than in the general population (effect size = 1.25, P < 0.05). Increasing experimental and epidemiological data have alerted researchers to the influence of prolactin (PRL) in mammary carcinogenesis. We therefore investigated the possible relationship between antipsychotic-induced hyperprolactinemia (HPRL) and breast cancer risk in female patients with schizophrenia.

METHOD

A literature search (1950 until January 2015), using the MEDLINE database, was conducted for English-language published clinical trials to identify and synthesize data of the current state of knowledge concerning breast cancer risk (factors) in women with schizophrenia and its (their) relationship between HPRL and antipsychotic medication.

RESULTS

Although an increasing body of evidence supports the involvement of PRL in breast carcinogenesis, results of human prospective studies are limited, equivocal, and correlative (with risk ratios ranging from 0.70 to 1.9 for premenopausal women and from 0.76 to 2.03 for postmenopausal women). Moreover, these studies equally do not take into account the local production of PRL in breast epithelium, although amplification or overexpression of the local autocrine/paracrine PRL loop may be a more important mechanism in tumorigenesis. Until now, there is also no conclusive evidence that antipsychotic medication can increase the risk of breast malignancy and mortality.

CONCLUSION

Other breast risk factors than PRL, such as nulliparity, obesity, diabetes mellitus, and unhealthy lifestyle behaviours (alcohol dependence, smoking, low physical activity), probably are of greater relevance in individual breast cancer cases within the population of female patients with schizophrenia.

The Role of Prolactin in Bone Metastasis and Breast Cancer Cell-Mediated Osteoclast Differentiation

BACKGROUND

Metastasis to the bone is a deleterious aspect of breast cancer and is a preferred site that results in bone loss. Hormones such as prolactin (PRL) have not yet been studied for their role in modulating the secondary tumor bone microenvironment.

METHODS

We used quantitative immunohistochemistry with 134 samples of human primary breast cancer and 17 matched primary breast cancers and bone metastases. A Cox proportional hazards regression model was fitted to evaluate the associations between high prolactin receptor (PRLR) expression and time to bone metastasis, adjusting for estrogen receptor status, lymph node status, and chemotherapy status. We assessed osteoclast differentiation, osteoclast size, and measured pit formation in dentine slices. Statistical tests were two-sided.

RESULTS

High PRLR expression in the primary breast tumor was associated with a shorter time to metastasis that includes bone (PRLRAQUA Max-per 100 unit hazard ratio = 1.04, 95% confidence interval = 1.00 to 1.07, P = .03). We observed the PRLR in rare samples of bone metastases and matched primary breast cancer. PRL treatment of breast cancer cells induced osteoclast differentiation and bone lysis via secreted factors and was abrogated by a PRLR antagonist (delta1-9-G129R-hPRL). We demonstrated that sonic hedgehog is a PRL-regulated cytokine in breast cancer cells and part of the mechanism that induces osteoclast differentiation.

CONCLUSIONS

Our evidence indicates that PRL-PRLR can escalate the impact of breast cancer on bone metastasis and that the presence of the PRLR in the tumor microenvironment of breast cancer bone metastasis has the potential to modulate the microenvironment to induce lytic osteoclast formation.