Estrogen and progesterone interactive effects in postconfluent MCF-7 cell culture

Sustained postconfluent culture of human mammary epithelial cells enriches for luminal and c-Kit+ subtypes

BACKGROUND

A challenge in human mammary epithelial cell (HMEC) culture is sustaining the representation of competing luminal, myoepithelial, and progenitor lineages over time. As cells replicate in culture, myoepithelial cells come to dominate the composition of the culture with serial passaging. This drift in composition presents a challenge for studying luminal and progenitor cells, which are prospective cells of origin for most breast cancer subtypes.

METHODS

We demonstrate the use of postconfluent culture on HMECs. Postconfluent culture entails culturing HMECs for 2-5 weeks without passaging but maintaining frequent feedings in low-stress M87A culture medium. In contrast, standard HMEC culture entails enzymatic subculturing every 3-5 days to maintain subconfluent density.

RESULTS

When compared to standard HMEC culture, postconfluent culture yields increased proportions of luminal cells and c-Kit+ progenitor cells. Postconfluent cultures develop a distinct multilayered morphology with individual cells showing decreased physical deformability as compared to cells in standard culture. Gene expression analysis of postconfluent cells shows increased expression of lineage-specific markers and extracellular matrix components.

CONCLUSIONS

Postconfluent culture is a novel, useful strategy for altering the lineage composition of HMECs, by increasing the proportional representation of luminal and progenitor cells. We speculate that postconfluent culture creates a microenvironment with cellular composition closer to the physiological state and eases the isolation of scarce cell subtypes. As such, postconfluent culture is a valuable tool for researchers using HMECs for breast cancer research.

Breast cancer, placenta and pregnancy

BACKGROUND

Breast cancer is one of the most frequently diagnosed malignancies during pregnancy. Tumours often present characteristics of high malignancy and are hormone receptor negative/HER2 positive or triple negative. In general, pregnancy, including the postpartum period, is associated with a transiently increased risk of developing breast cancer but followed by a long-lasting protective period. Placental metastases are very rare and, thus far, breast cancer metastases in the foetal compartment have not been described. To discuss these apparently contradictory observations, this narrative review resumes immunological and hormonal alterations during pregnancy potentially affecting breast cancer risk as well as tumour growth and behaviour.

OBSERVATIONS

Upregulation of breast cancer-associated genes involved in immunological and reproductive processes has been observed in parous women and is potentially responsible for a transiently increased risk in pregnancy. In contrast, maternal immunisation and immunoglobulin production against antigens expressed on trophoblast cells, such as specific glycosylation patterns of mucin-1 or RCAS1-associated truncated glycans, seem to prevent breast cancer development in later years. Animal and human studies indicate that T cells are involved in these processes. Several placenta-derived factors, especially kisspeptin, have direct anti-tumour effects. The pregnancy-related increase of estrogen, progesterone, and other hormones influence growth and characteristics of breast cancer while the role of further placenta-secreted factors is still controversially discussed.

CONCLUSION

Several factors and cells are involved in altered breast cancer risk during and after pregnancy and have potential for developing novel treatment strategies in future.

The unique transcriptional response produced by concurrent estrogen and progesterone treatment in breast cancer cells results in upregulation of growth factor pathways and switching from a Luminal A to a Basal-like subtype

BACKGROUND

In breast cancer, progesterone receptor (PR) positivity or abundance is positively associated with survival and treatment response. It was initially believed that PR was a useful diagnostic marker of estrogen receptor activity, but increasingly PR has been recognised to play an important biological role in breast homeostasis, carcinogenesis and metastasis. Although PR expression is almost exclusively observed in estrogen receptor positive tumors, few studies have investigated the cellular mechanisms of PR action in the context of ongoing estrogen signalling.

METHODS

In this study, we contrast PR function in estrogen pretreated ZR-75-1 breast cancer cells with vehicle treated ZR-75-1 and T-47D breast cancer cells using expression microarrays and chromatin immunoprecipitation-sequencing.

RESULTS

Estrogen cotreatment caused a dramatic increase in the number of genes regulated by progesterone in ZR-75-1 cells. In T-47D cells that have naturally high levels of PR, estrogen and progesterone cotreatment resulted in a reduction in the number of regulated genes in comparison to treatment with either hormone alone. At a genome level, estrogen pretreatment of ZR-75-1 cells led to a 10-fold increase in the number of PR DNA binding sites detected using ChIP-sequencing. Time course assessment of progesterone regulated genes in the context of estrogen pretreatment highlighted a series of important regulatory pathways, including those driven by epithelial growth factor receptor (EGFR). Importantly, progesterone applied to cells pretreated with estradiol resulted in switching of the PAM50-determined intrinsic breast cancer subtype from Luminal A to Basal-like, and increased the Oncotype DX® Unscaled Recurrence Score.

CONCLUSION

Estrogen pretreatment of breast cancer cells increases PR steady state levels, resulting in an unequivocal progesterone response that upregulates key members of growth factor pathways. The transformative changes progesterone exerts on the breast cancer subtype suggest that these subtyping tools should be used with caution in premenopausal women.

Anastrozole and RU486: Effects on estrogen receptor α and Mucin 1 expression and correlation in the MCF-7 breast cancer cell line

Anastrozole and RU486 are shown to reduce hormone-responsive breast cancer progression when used as adjuvant treatments to surgical intervention, however, a high incidence of cancer recurrence remains. Estrogen receptor alpha (ERα) and Mucin 1 (MUC1), a glycoprotein, are both implicated in breast cancer progression. We assessed whether Anastrozole and RU486 treatment affects the expression of, and relationship between, ERα and MUC1 in the ERα(+) MUC1(+) MCF-7 breast cancer cell line. MCF-7 cells, treated with physiological concentrations of either Anastrozole or RU486 for 18 h or 72 h, were subjected to immunolocalization of both markers. CellProfiler software was used to quantify intensity for statistical analyses. ERα expression increased at both time periods following treatment. MUC1 expression increased with RU486-treatment at both times, whereas Anastrozole induced increased MUC1 expression at 72 h only. The biomarkers demonstrated increased point association at 72 h within treatment groups despite MUC1 diverging from correlation with ERα. We propose that tumor progression is independent of MUC1 and ERα correlation. These preliminary results indicate that withdrawal of adjuvant treatment may result in residual cell populations expressing increased ERα and MUC1. This phenotype may allow enhanced estrogenic and metastatic capacity influencing cancer recurrence, a hypothesis we are investigating further.

Estrogen receptor alpha interacts with mitochondrial protein HADHB and affects beta-oxidation activity

It is known that estrogen receptors can function as nuclear receptors and transcription factors in the nucleus and as signaling molecules in the plasma membrane. In addition, the localization of the receptors in mitochondria suggests that they may play important roles in mitochondria. In order to identify novel proteins that are involved in ERα-mediated actions of estrogens, we used a proteomic method that integrated affinity purification, two-dimensional gel electrophoresis, and mass spectrometry to isolate and identify cellular proteins that interact with ERα. One of the proteins identified was trifunctional protein β-subunit (HADHB), a mitochondrial protein that is required for β-oxidation of fatty acids in mitochondria. We have verified the interaction between ERα and HADHB by coimmunoprecipitation and established that ERα directly binds to HADHB by performing an in vitro binding assay. In addition, we have shown that ERα colocalizes with HADHB in the mitochondria by confocal microscopy, and the two proteins interact with each other within mitochondria by performing coimmunoprecipitation using purified mitochondria as starting materials. We have demonstrated that the expression of ERα affects HADHB activity, and a combination of 17β-estrodiol and tamoxifen affects the activity of HADHB prepared from human breast cancer cells that express ERα but not from the cells that are ERα deficient. Furthermore, we have demonstrated that 17β-estrodiol plus tamoxifen affects the association of ERα with HADHB in human cell extract. Our results suggest that HADHB is a functional molecular target of ERα in the mitochondria, and the interaction may play an important role in the estrogen-mediated lipid metabolism in animals and humans.

High expression of sphingosine 1-phosphate receptors, S1P1 and S1P3, sphingosine kinase 1, and extracellular signal-regulated kinase-1/2 is associated with development of tamoxifen resistance in estrogen receptor-positive breast cancer patients

Various studies in cell lines have previously demonstrated that sphingosine kinase 1 (SK1) and extracellular signal-regulated kinase 1/2 (ERK-1/2) interact in an estrogen receptor (ER)-dependent manner to influence both breast cancer cell growth and migration. A cohort of 304 ER-positive breast cancer patients was used to investigate the prognostic significance of sphingosine 1-phosphate (S1P) receptors 1, 2, and 3 (ie, S1P1, S1P2, and S1P3), SK1, and ERK-1/2 expression levels. Expression levels of both SK1 and ERK-1/2 were already available for the cohort, and S1P1, S1P2, and S1P3 levels were established by immunohistochemical analysis. High membrane S1P1 expression was associated with shorter time to recurrence (P=0.008). High cytoplasmic S1P1 and S1P3 expression levels were also associated with shorter disease-specific survival times (P=0.036 and P=0.019, respectively). Those patients with tumors that expressed high levels of both cytoplasmic SK1 and ERK-1/2 had significantly shorter recurrence times than those that expressed low levels of cytoplasmic SK1 and cytoplasmic ERK-1/2 (P=0.00008), with a difference in recurrence time of 10.5 years. Similarly, high cytoplasmic S1P1 and cytoplasmic ERK-1/2 expression levels (P=0.004) and high cytoplasmic S1P3 expression and cytoplasmic ERK-1/2 expression levels (P=0.004) were associated with shorter recurrence times. These results support a model in which the interaction between SK1, S1P1, and/or S1P3 and ERK-1/2 might drive breast cancer progression, and these findings, therefore, warrant further investigation.

Breast cancer characteristics are modified by first trimester human placenta: in vitro co-culture study

BACKGROUND

Pregnant women with breast cancer present with a more advanced disease compared with non-pregnant women. Nevertheless, breast cancer metastasis to the placenta is rare. Trophoblast/tumor implantations share the same biochemical mediators, while only the first is stringently controlled. We hypothesized that the same mechanisms that affect/restrain placental implantation may inhibit metastatic growth in the placenta. We aimed to analyze the effects of human placenta on breast cancer cells.

METHODS

First trimester human placental explants were co-cultured with MCF-7/T47D-eGFP tagged cells. Following culture, placenta/cancer cells/both were fixed, paraffin embedded and sliced for immunohistochemical analysis or sorted by their eGFP expression for future analysis. The tested parameters were: proliferation (immunohistochemistry)/cell cycle (FACS), apoptosis (immunohistochemistry/FACS), cell count/adhesion/distribution around the placenta (cell sorter, visual observation and counting), matrix metalloproteinase activity (zymogram) and estrogen receptor (ER) expression (western blotting, immunohistochemistry).

RESULTS

Reduced breast cancer cell numbers (45%↓, 48%↓ for MCF-7/T47D, respectively, P < 0.05) were observed near the placenta. The placenta elevated MCF-7 sub-G1 phase and modestly elevated apoptosis (3-17%↑ for T47D/MCF-7, respectively, P < 0.05). Our findings demonstrate breast cancer cell migration from the placenta as: (i) T47D/MCF-7 cells changed their morphology to that of motile cells; (ii) elevated MMPs activity was found in the co-culture; (iii) placental soluble factors detached breast cancer cells; and (4) the placenta reduced MCF-7/T47D cells' ER expression (a characteristic of motile cells).

CONCLUSIONS

MCF-7/T47D cells are eliminated from the placental surroundings. Analyzing the causes of these phenomena may suggest biological pathways for this event and raise new therapeutic targets.

Regulation of lysophosphatidate signaling by autotaxin and lipid phosphate phosphatases with respect to tumor progression, angiogenesis, metastasis and chemo-resistance

Evidence from clinical, animal and cell culture studies demonstrates that increased autotaxin (ATX) expression is responsible for enhancing tumor progression, cell migration, metastases, angiogenesis and chemo-resistance. These effects depend mainly on the rapid formation of lysophosphatidate (LPA) by ATX. Circulating LPA has a half-life of about 3 min in mice and it is degraded by the ecto-activities of lipid phosphate phosphatases (LPPs). These enzymes also hydrolyze extracellular sphingosine 1-phosphate (S1P), a potent signal for cell division, survival and angiogenesis. Many aggressive tumor cells express high ATX levels and low LPP activities. This favors the formation of locally high LPA and S1P concentrations. Furthermore, LPPs attenuate signaling downstream of the activation of G-protein coupled receptors and receptor tyrosine kinases. Therefore, we propose that the low expression of LPPs in many tumor cells makes them hypersensitive to growth promoting and survival signals that are provided by LPA, S1P, platelet-derived growth factor (PDGF) and epidermal growth factor (EGF). One of the key signaling pathways in this respect appears to be activation of phospholipase D (PLD) and phosphatidate (PA) production. This is required for the transactivations of the EGFR and PDGFR and also for LPA-induced cell migration. PA also increases the activities of ERK, mTOR, myc and sphingosine kinase-1 (SK-1), which provide individual signals for cells division, survival, chemo-resistance and angiogenesis. This review focuses on the balance of signaling by bioactive lipids including LPA, phosphatidylinositol 3,4,5-trisphosphate, PA and S1P versus the action of ceramides. We will discuss how these lipid mediators interact to produce an aggressive neoplastic phenotype.

Progesterone induces scolex evagination of the human parasite Taenia solium: evolutionary implications to the host-parasite relationship

Taenia solium cysticercosis is a health problem in underdeveloped and developed countries. Sex hormones are involved in cysticercosis prevalence in female and male pigs. Here, we evaluated the effects of progesterone and its antagonist RU486 on scolex evagination, which is the initial step in the development of the adult worm. Interestingly, progesterone increased T. solium scolex evagination and worm growth, in a concentration-independent pattern. Progesterone effects could be mediated by a novel T. solium progesterone receptor (TsPR), since RU486 inhibits both scolex evagination and worm development induced by progesterone. Using RT-PCR and western blot, sequences related to progesterone receptor were detected in the parasite. A phylogenetic analysis reveals that TsPR is highly related to fish and amphibian progesterone receptors, whereas it has a distant relation with birds and mammals. Conclusively, progesterone directly acts upon T. solium cysticerci, possibly through its binding to a progesterone receptor synthesized by the parasite.