A proposed unified mechanism for the reduction of human breast cancer risk by the hormones of pregnancy

Inhibition of GPR30 by estriol prevents growth stimulation of triple-negative breast cancer cells by 17β-estradiol

Background

Due to the lack of ERα, triple negative breast cancers (TNBCs) are not susceptible to endocrine therapy using antiestrogens. However, the majority of TNBCs express the membrane bound estrogen receptor GPR30. We have recently shown that knock-down of GPR30 expression prevented growth stimulation of TNBC cell lines by 17β-estradiol. Now we analyzed whether specific inhibition of GPR30 represents a new option for therapy of TNBC.

Methods

Growth of TNBC cells was assessed using Alamar-blue colorimetric assay. Activation of c-Src and EGF-receptor was assessed using Western blots. Expression of c-fos, cyclin D1 and aromatase was quantified by RT-PCR. Gα-specific signaling of GPR30 was analyzed by electrophoretic mobility shift assay.

Results

HCC1806 cells showed the highest GPR30 expression, in HCC70 cells it was clearly lower, in MDA-MB-231 cells it was lowest. 10^-8 M 17β-estradiol significantly increased proliferation of HCC1806 cells to 134 ± 12% of control (p < 0.01). Proliferation of HCC70 cells was slightly increased to 116 ± 8% of control. Estriol significantly reduced cell number of HCC1806 cells to 16 ± 12% (p < 0.01). Cell number of HCC70 cells and of MDA-MB-231 cells was reduced to 68 ± 25% and to 61 ± 10%, respectively.

Activity of Src kinase increased to 150 ± 10% (p < 0.05) by 10^-8 M 17β-estradiol treatment in HCC1806 and to 220 ± 20% in HCC70 cells (p < 0.01). Estriol treatment completely inhibited 17β-estradiol-induced p-src activation. Transactivation of EGF-receptor increased by estradiol treatment to 350% in HCC1806 and to 280% in HCC70 cells. Estriol completely suppressed EGF-receptor transactivation. c-fos expression increased to 260% and to 190%, respectively. Estriol reduced this induction to 160% (HCC1806) and below control in HCC70 cells. Cyclin D1 was induced to 290% (HCC1806) and 170% (HCC70) and completely inhibited by estriol. 17β-estradiol increased CREB-phosphorylation to 400%. Binding of phospho-CREB to a CRE of cyclin D1 was enhanced to 320%.

Conclusion

Specific pharmacological inhibition of GPR30 might become a promising targeted therapy for TNBC in future.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2407-14-935) contains supplementary material, which is available to authorized users.

The protective effect of parity in hormone receptor-positive, Ki-67 expressing breast cancer

BACKGROUND

Epidemiologic studies showed that the experience of pregnancy is associated with a reduced risk of breast cancer. We hypothesized that parity may differentially be associated with the development of invasive breast cancer by each subtype.

METHODS

We reviewed the clinical, radiological, and pathological records of women diagnosed with invasive ductal carcinoma of the breast at Samsung Medical Center between 2005 and 2009. Clinicopathologic results were assessed by χ(2) and Fisher's exact tests with a Bonferroni correction for categorical variables, and by the Kruskal-Wallis test for nonparametric continuous variables. A multinomial logistic regression model was used for multivariate analysis.

RESULTS

Among a total of 3,095 patients, 283 (9.14 %) patients were nulliparous. Older age, higher pN, and expression of HER2 were associated with parity. In the analysis between parity and molecular subtypes, parity also had a variable influence on breast cancer subtypes (p = 0.032). Intergroup analysis with multiple comparison showed that luminal B subtype was related to nulliparity compared with HER2-positive subtypes (p = 0.03).

CONCLUSIONS

The effect of parity on the development of breast cancer differed by hormone receptor and HER2 expression. It seems that parity might have a protective effect against hormone receptor-positive breast cancer, especially cancers expressing HR+ and Ki-67. Further basic research to define and understand this result is ongoing.

Free β-human chorionic gonadotropin, total human chorionic gonadotropin and maternal risk of breast cancer

BACKGROUND

We investigated whether the free β-human chorionic gonadotropin (free β-hCG) would provide additional information to that provided by total hCG alone and thus be useful in future epidemiological studies relating hCG to maternal breast cancer risk.

MATERIALS & METHODS

Cases (n = 159) and controls (n = 286) were a subset of our previous study within the Northern Sweden Maternity Cohort on total hCG during primiparous pregnancy and breast cancer risk.

RESULTS

The associations between total hCG (hazard ratio: 0.79; 95% CI: 0.49-1.27), free β-hCG (hazard ratio: 0.85; 95% CI: 0.33-2.18) and maternal risk of breast cancer were very similar in all analyses and mutual adjustment for either one had minor effects on the risk estimates.

CONCLUSION

In the absence of a reliable assay on intact hCG, total hCG alone can be used in epidemiological studies investigating hCG and breast cancer risk, as free β-hCG does not appear to provide any additional information.

Alpha fetoprotein can induce malignant transformation of liver cells and be used as a therapeutic target for hepatocellular carcinoma

Alpha-fetoprotein (AFP) is associated with the development of hepatocellular carcinoma (HCC) and widely used as a golden tumor marker for diagnosing HCC since the AFP gene is activated in the early stage of malignant transformation of liver cells. However, the molecular mechanisms responsible for the role of AFP in hepatocarcinogenesis remain poorly understood. Recently, we found that hepatitis B virus (HBV) preferentially induces the expression of AFP when triggering malignant transformation of hepatocytes, and AFP activates phosphoinositide-3-kinase (PI3K)/protein kinase B (AKT) signaling by inhibiting the activity of phosphatase and tensin homolog deleted on chromosome ten (PTEN). Our results also indicated that AFP not only impedes all-trans retinoid acid receptor-β (RAR-β) regulated expression of target genes, but also blocks the transduction of apoptotic signaling by suppressing the activity of Caspase3. Inhibited expression of AFP is able to augment HCC sensitivity to tumor necrosis factor-related apoptosis-induced ligand (TRAIL) and all-trans retinoid acid. These data indicate that AFP can drive the malignant transformation of liver cells and antagonize apoptosis induced by agents for HCC. Taken together, these findings suggest that AFP may drive the malignant transformation of liver cells and can be used as a target for therapy of HCC.

Mimicking pregnancy as a strategy for breast cancer prevention

Pregnancy and its effects on breast cancer risk have been widely investigated; there is consensus among researchers that early pregnancy confers protection against breast cancer later in life, whereas nulliparity and late-age parity have been associated with increased risk of developing breast cancer. The answer to the question of how pregnancy reduces breast cancer risk has been elusive; however, pregnancy, like breast cancer, is a similar hormone-dependent entity under direct control of estrogen, progesterone and, of particular importance, human chorionic gonadotropin (hCG). In this report, we emphasize the main changes, previously described by our laboratory, in morphology and gene expression levels of the mammary gland of Sprague-Dawley rats exposed to known cancer-preventative conditions (pregnancy, hCG and progesterone + estrogen). In addition, we postulate a protective mechanism induced by hCG that could reduce the cell's potential to be transformed by carcinogens.

Engineering of the Saccharomyces cerevisiae yeast strain with multiple chromosome-integrated genes of human alpha-fetoprotein and its high-yield secretory production, purification, structural and functional characterization

Alpha-fetoprotein (AFP) is a biological drug candidate of high medicinal potential in the treatment of autoimmune diseases, cancer, and regenerative medicine. Large-scale production of recombinant human alpha-fetoprotein (rhAFP) is desirable for structural and functional studies and applied research. In this study we cloned and expressed in the secreted form wild-type glycosylated human rhAFP and non-glycosylated mutant rhAFP(0) (N233S) in the yeast strain Saccharomyces cerevisiae with multiple chromosome-integrated synthetic human AFP genes. RhAFP and rhAFP(0) were successfully produced and purified from the culture liquids active naturally folded proteins. Elimination of the glycosylation by mutation reduced rhAFP(0) secretion about threefold as compared to the wild-type protein showing critical role of the N-linked glycan for heterologous protein folding and secretion. Structural similarity of rhAFP and rhAFP(0) with natural embryonic eAFP was confirmed by circular dichroism technique. Functional tests demonstrated similar type of tumor suppressive and immunosuppressive activity for both recombinant species rhAFP and rhAFP(0) as compared to natural eAFP. It was documented that both types of biological activities attributed to rhAFP and rhAFP(0) are due to the fast induction of apoptosis in tumor cells and mitogen-activated lymphocytes. Despite the fact that rhAFP and rhAFP(0) demonstrated slightly less effective tumor suppressive activity as compared to eAFP but rhAFP(0) had produced statistically notable increase in its ability to induce inhibition of in vitro lymphocyte proliferation as compared to the glycosylated rhAFP and eAFP. We conclude that N-linked glycosylation of rhAFP is required for efficient folding and secretion. However the presence of N-linked sugar moiety was shown to be unimportant for tumor suppressive activity but was critically important for its immunoregulative activity which demonstrates that different molecular mechanisms are involved in these two types of biological functional activities attributed to AFP.

Design and synthesis of biologically active peptides: a 'tail' of amino acids can modulate activity of synthetic cyclic peptides

In earlier work, we synthesized a cyclic 9-amino acid peptide (AFPep, cyclo[EKTOVNOGN]) and showed it to be useful for prevention and therapy of breast cancer. In an effort to explore the structure-function relationships of AFPep, we have designed analogs that bear a short 'tail' (one or two amino acids) attached to the cyclic peptide distal to its pharmacophore. Analogs that bore a tail of either one or two amino acids, either of which had a hydrophilic moiety in the side chain (e.g., cyclo[EKTOVNOGN]FS) exhibited greatly diminished biological activity (inhibition of estrogen-stimulated uterine growth) relative to AFPep. Analogs that bore a tail of either one or two amino acids which had hydrophobic (aliphatic or aromatic) side chains (e.g., cyclo[EKTOVNOGN]FI) retained (or had enhanced) growth inhibition activity. Combining in the same biological assay a hydrophilic-tailed analog with either AFPep or a hydrophobic-tailed analog resulted in decreased activity relative to that for AFPep or for the hydrophobic-tailed analog alone, suggesting that hydrophilic-tailed analogs are binding to a biologically active receptor. An analog with a disrupted pharmacophore (cyclo[EKTOVGOGN]) exhibited little or no growth inhibition activity. An analog with a hydrophilic tail and a disrupted pharmacophore (cyclo[EKTOVGOGN]FS) exhibited no growth inhibition activity of its own and did not affect the activity of a hydrophobic-tailed analog, but enhanced the growth inhibition activity of AFPep. These results are discussed in the context of a two-receptor model for binding of AFPep and ring-and-tail analogs. We suggest that tails on cyclic peptides may comprise a useful method to enhance diversity of peptide design and specificity of ligand-receptor interactions.