Epigenetic impact of hypothyroidism on the functional differentiation of the mammary gland in rats.

Mammary gland (MG) lactogenic differentiation involves epigenetic mechanisms. We have previously shown that hypothyroidism (HypoT) alters the MG transcriptome in lactation. However, the role of thyroid hormones (T3 and T4 a. k.a. THs) in epigenetic differentiation of MG is still unknown. We used a model of post-lactating HypoT rats to study in MG: a) Methylation and expression level of Gata3, Elf5, Stat6, Stat5a, Stat5b; b) Expression of Lalba, IL-4Rα and Ncoa1 mRNA; c) Histone H3 acetylation and d) Estrogen and progesterone concentration in serum. HypoT increases the estrogen serum level, decreases the progesterone level, promotes methylation of Stat5a, Stat5b and Stat6, decreasing their mRNA level and of its target genes (Lalba and IL-4Rα) and increases the Ncoa1 mRNA expression and histone H3 acetylation level. Our results proved that HypoT alters the post-lactation MG epigenome and could compromise mammary functional differentiation.

Inpatient and outpatient treatment by specialist infant nutrition centres in Argentina effectively reduced child malnourishment.

AIM: We evaluated the impact of inpatient and outpatient treatment provided by an infant nutrition foundation in Las Heras, Mendoza, Argentina and identified the factors that influenced nutritional recovery. METHODS: This 2010-2018 retrospective study was based on 300 children up to 5 years of age with primary malnutrition, who were treated by an inpatient recovery centre, then an outpatient prevention centre. We analysed the children's height, weight, psychomotor development and living conditions when they were admitted, discharged and had received 1 year of outpatient treatment. There were full data on 241 children and just admission and discharge data for 59. RESULTS: The children's mean age on admission and weight were 14.8 ± 12.4 months and 6.9 ± 2.3 kg and they stayed in hospital for a mean of 59.5 ± 49.7 days. We observed a significant increase in the weight-for-age, height-for-age and weight-for-height z-scores when all three time points were compared (p < 0.001). Psychomotor development improved considerably in all patients after treatment. The factors that negatively influenced nutritional recovery were higher age at admission, suboptimal breastfeeding practices, low birth weight, longer hospital stays, younger maternal age and overcrowded housing. CONCLUSION: Combining inpatient recovery and outpatient preventive treatment was effective for undernourished children in Argentina.

Protective effects of Yerba mate (IIex paraguariensis) on prostate cancer development.

OBJECTIVES: Prostate cancer (PCa) is the most common adenocarcinoma in men >50 y of age. It has a long latency period, which provides time for preventive strategies like incorporating healthy eating habits. Yerba mate (YM) intake has been associated with numerous health benefits. Since YM is one of the most popular infusions in Argentina, the of this study was to examine the influence of YM on PCa development. METHODS: We carried out an in vivo model of PCa through subcutaneous inoculation of transgenic adenocarcinoma of the mouse prostate-C1 cells in C57BL/6 mice. Subsequently, the animals were divided into two groups: mate (25 mg/mL of YM in drinking water, n = 15), and control (only drinking water, n = 15). We also developed an in vitro model to study the direct effects of YM on three human PCa cell lines: lymph node carcinoma of the prostate (LNCaP), PC-3, and DU-145. RESULTS: Our in vivo model showed that YM intake slightly reduced body weight, increased the latency of tumor appearance (P <0.01), and diminished the tumor volume (P <0.05) compared with the control group. In agreement, the expression of proliferating cell nuclear antigen, and nuclear estrogen receptor α were lower in the tumors of the mate animals (P <0.05). In vitro, YM decreased the viability, proliferation, and adhesion of the three tumor cell lines (P < 0.001) and retarded the migration of LNCaP (P <0.05) and DU-145 (P <0.005), without modifying the migration of PC-3 cells. CONCLUSIONS: YM showed anticancer effects in vitro and in vivo and were more effective on the androgen-sensitive cell line (LNCaP).

Long-term impact of hypothyroidism during gestation and lactation on the mammary gland.

The functional differentiation of the mammary gland (MG) is fundamental for the prevention of mammary pathologies. This process occurs throughout pregnancy and lactation, making these stages key events for the study of pathologies associated with development and differentiation. Many studies have investigated the link between mammary pathologies and thyroid diseases, but most have ignored the role of thyroid hormone (TH) in the functional differentiation of the MG. In this work, we show the long-term impact of hypothyroidism in an animal model whose lactogenic differentiation occurred at low TH levels. We evaluated the ability of the MG to respond to hormonal control and regulate cell cycle progression. We found that a deficit in TH throughout pregnancy and lactation induces a long-term decrease in Rb phosphorylation, increases p53, p21, Cyclin D1 and Ki67 expression, reduces progesterone receptor expression, and induces nonmalignant lesions in mammary tissue. This paper shows the importance of TH level control during mammary differentiation and its long-term impact on mammary function.

Renal peritumoral adipose tissue undergoes a browning process and stimulates the expression of epithelial-mesenchymal transition markers in human renal cells.

Tumor cells can interact with neighboring adipose cells and adipocyte dedifferentiation appears to be an important aspect of tumorigenesis. We evaluated the size of adipocytes in human adipose explants from normal (hRAN) and kidney cancer (hRAT); changes in the expression of WAT and BAT/beige markers in hRAN and hRAT; the expression of epithelial-mesenchymal transition (EMT) cell markers in human kidney tumor (786-O, ACHN and Caki-1); and non-tumor (HK-2) epithelial cell lines incubated with the conditioned media (CMs) of hRAN and hRAT. We observed that hRAT adipocytes showed a significantly minor size compared to hRAN adipocytes. Also, we observed that both Prdm16 and Tbx1 mRNA and the expression of UCP1, TBX1, PPARγ, PCG1α, c/EBPα LAP and c/EBPα LIP was significantly higher in hRAT than hRAN. Finally, we found an increase in vimentin and N-cadherin expression in HK-2 cells incubated for 24 h with hRAT-CMs compared to hRAN- and control-CMs. Furthermore, desmin and N-cadherin expression also increased significantly in 786-O when these cells were incubated with hRAT-CMs compared to the value observed with hRAN- and control-CMs. We observed a significant decrease in E-cadherin expression in the ACHN cell line incubated with hRAT-CMs versus hRAN- and control-CMs. However, we did not observe changes in E-cadherin expression in HK-2, 786-O or Caki-1. The results obtained, together with the results previously published by our group, allow us to conclude that perirenal white adipose tissue browning contributes to tumor development in kidney cancer. In addition, hRAT-CMs increases the expression of mesenchymal markers in renal epithelial cells, which could indicate a regulation of EMT due to this adipose tissue.

Effects of thyroxine on apoptosis and proliferation of mammary tumors.

Hypothyroidism is a protective factor against breast cancer but long-term exposure or overdoses of thyroid replacement therapy with thyroxine (T4) may increase breast cancer risk. OBJECTIVE: to study, in vivo and in vitro, the effects of T4 on the proliferation and apoptosis of mammary tumors of hypo- and euthyroid rats, and the possible mechanisms involved in these effects. MATERIAL AND METHODS: Female Sprague-Dawley rats were treated with a single dose of dimethylbenzathracene (15 mg/rat) at 55 days of age and were divided into three groups: hypothyroidism (HypoT; 0.01% 6-N-propyl-2-thiouracil -PTU- in drinking water, n = 20), hypothyroidism treated with T4 (HypoT + T4; 0.01% PTU in drinking water and 0.25 mg/kg/day T4 via sc; n = 20) and EUT (untreated control, n = 20). At sacrifice, tumor explants from HypoT and EUT rats were obtained and treated either with 10-10 M T4 in DMEM/F12 without phenol red with 1% Charcoalized Fetal Bovine Serum or DMEM/F12 only for 15 min to evaluate intracellular signaling pathways associated with T4, and 24 h to evaluate changes in the expression of hormone receptors and proteins related to apoptosis and proliferation by immunohistochemistry and Western Blot. RESULTS: In vivo, hypothyroidism retards mammary carcinogenesis but its treatment with T4 reverted the protective effects. In vitro, the proliferative and anti-apoptosis mechanisms of T4 were different regarding the thyroid status. In EUT tumors, the main signaling pathway involved was the cross-talk with other receptors, such as ERα, PgR, and HER2. In HypoT tumors, the non-genomic signaling pathway of T4 was the chief mechanism involved since αvß3 integrin, HER2, ß-catenin and, downstream, PI3K/AKT and ERK signaling pathways were activated. CONCLUSION: T4 can regulate mammary carcinogenesis by mainly activating its non-genomic signaling pathway and by interacting with other hormone or growth factor pathways endorsing that overdoses of thyroid replacement therapy with T4 can increase the risk of breast cancer.

Changes in prolactin receptor location in prostate tumors. / Cambios en la localización del receptor prolactina en tumores prostáticos.

INTRODUCTION: Prolactin (PRL) binds its receptor (PRLR) and stimulates cell proliferation, differentiation and survival in prostate cancer (PCa) cell lines via STAT5a, MAPK and AKT. OBJECTIVE: To evaluate the expression of PRL and PRLR in normal and tumor prostate tissues with different Gleason patterns. METHODS: Samples of normal, benign prostatic hyperplasia and PCa with different Gleason patterns were selected from radical prostatectomy. The intensity, location and percentage of stained cells for PRL and PRLR were evaluated by Immunohistochemistry. Co-localization was observed by confocal microscopy. RESULTS: PRL was expressed diffusely and with a mild intensity in the cytoplasm of normal and tumor prostate luminal cells. Its expression only augmented in the Gleason 3 pattern (p< 0.0001). The immunostaining intensity and the percentage of positive cells for PRLR did not vary between normal and tumor tissues. However, the location of the PRLR was modified by the tumorigenic process.In non-tumor tissues, PRLR expression was mostly in plasma membrane in the apical zone of epithelial cells. In tumor tissues, it was expressed in intracellular vesicles.The co-localization of PRL and PRLR was demonstrated in normal and tumor tissues suggesting that PRL could be acting in an autocrine and paracrine manner. CONCLUSION: PRL and its receptor were present in the cytoplasm of the epithelial cells of the normal and tumor prostate gland. In tumor tissues, the change in the location and appearance of cryptic PRLRs that store PRL may keep active the different signaling pathways related to cell proliferation and survival.

INTRODUCCIÓN: La prolactina (PRL) se une a su receptor (PRLR) y estimula la proliferación celular, la diferenciación y la supervivencia de la líneas celulares de cáncer de próstata vía STAT5a, MAPK y AKT.OBJETIVO: Evaluar la expresión de la PRL y PRLR en tejido normal y tejido de cáncer de próstata con varios patrones de Gleason.MÉTODOS: Se seleccionaron muestras de tejido benigno, hiperplasia y cáncer de próstata con diferentes patrones de Gleason de prostatectomías radicales. La intensidad, localización y porcentaje de células teñidas por PRL y PRLR fueron evaluadas por immunohistoquimica. La co-localización se observó con microscopio confocal.RESULTADOS: PRL se presentó de forma difusa y con intensidad media en el citoplasma de células luminales normales y de tumor prostático. La expresión solamente aumentó en patrón Gleason 3 (p<0,0001). La intensidad de la tinción immunohistoquímica y el porcentaje de células positivas para PRLR no varió entre células normales y tejidos tumorales. Pero, la localización del PRLR fue modificada por el proceso generador del tumor. En tejidos no-tumorales, la expresión de PRLR fue sobre todo en la membrana plasmática en la zona apical de las células epiteliales. En tejidos tumorales, se presentó en las vesículas intracelulares. La co-localizacion de la PRL y PRLR se demostró en tejido normal y tumoral sugeriendo que la PRL funciona con un efecto autocrino y paracrino.CONCLUSIÓN: La PRL y su receptor estuvieron presentes en el citoplasma de células epiteliales de tejido normal y glándula prostática tumoral. En tejidos tumorales, el cambio de localización y la apariencia cripticas del PRLR que guarda la PRL debe mantener activos los diferentes caminos de señalización relacionados con la proliferación celular y la supervivencia.

SPINK7 expression changes accompanied by HER2, P53 and RB1 can be relevant in predicting oral squamous cell carcinoma at a molecular level.

The oral squamous cell carcinoma (OSCC), which has a high morbidity rate, affects patients worldwide. Changes in SPINK7 in precancerous lesions could promote oncogenesis. Our aim was to evaluate SPINK7 as a potential molecular biomarker which predicts OSCC stages, compared to: HER2, TP53, RB1, NFKB and CYP4B1. This study used oral biopsies from three patient groups: dysplasia (n = 33), less invasive (n = 28) and highly invasive OSCC (n = 18). The control group consisted of clinically suspicious cases later to be confirmed as normal mucosa (n = 20). Gene levels of SPINK7, P53, RB, NFKB and CYP4B1 were quantified by qPCR. SPINK7 levels were correlated with a cohort of 330 patients from the TCGA. Also, SPINK7, HER2, TP53, and RB1, were evaluated by immunohistofluorescence. One-way Kruskal-Wallis test and Dunn's post-hoc with a p < 0.05 significance was used to analyze data. In OSCC, the SPINK7 expression had down regulated while P53, RB, NFKB and CYP4B1 had up regulated (p < 0.001). SPINK7 had also diminished in TCGA patients (p = 2.10e-6). In less invasive OSCC, SPINK7 and HER2 proteins had decreased while TP53 and RB1 had increased with respect to the other groups (p < 0.05). The changes of SPINK7 accompanied by HER2, P53 and RB1 can be used to classify the molecular stage of OSCC lesions allowing a diagnosis at molecular and histopathological levels.

The epigenetic role of breastfeeding in mammary differentiation.

Maternal milk consumption can cause changes in the mammary epithelium of the offspring that result in the expression of molecules involved in the induction of differentiation, reducing the risk of developing mammary cancer later in life. We previously showed that animals that maintained a higher intake of maternal milk had a lower incidence of mammary cancer. In the present study, we evaluated one of the possible mechanisms by which the consumption of maternal milk could modify the susceptibility to mammary carcinogenesis. We used Sprague Dawley rats reared in litters of 3 (L3), 8 (L8), or 12 (L12) pups per mother in order to generate a differential consumption of milk. Whole mounts of mammary glands were performed to analyze the changes in morphology. Using real-time polymerase chain reaction (PCR), we analyzed the expression of mammary Pinc, Tbx3, Stat6, and Gata3 genes. We use the real-time methylation-specific polymerase chain reaction method to assess the methylation status of Stat6 and Gata3 CpG sites. Our findings show an increase in the size of the epithelial tree and a smaller number of ducts called terminal end buds in L3 vs. L12. We observed an increased expression of mRNA of Stat6, Gata3, Tbx3, and a lower expression of Pinc in L3 with respect to L12. Stat6 and Gata3 are more methylated in the CpG islands of the promoter analyzed in L12 vs. L3. In conclusion, the increased consumption of maternal milk during the postnatal stage generates epigenetic and morphological changes associated with the differentiation of the mammary gland.

Human renal adipose tissue from normal and tumor kidney: its influence on renal cell carcinoma.

Tumor cells can interact with neighboring adipose tissue. We evaluated components present in human adipose explants from normal (hRAN) and kidney cancer (hRAT) tissue, and we evaluated the effects of conditioned media (CMs) from hRAN and hRAT on proliferation, adhesion and migration of tumor and non-tumor human renal epithelial cell lines. In addition, we evaluated the expression of AdipoR1, ObR, CD44, vimentin, pERK and pPI3K on cell lines incubated with CMs. hRAN were obtained from healthy operated donors, and hRAT from patients who underwent a nephrectomy. hRAT showed increased levels of versican, leptin and ObR; and decreased levels of perilipin, adiponectin and AdipoR1, compared to hRAN. Cell lines showed a significant decrease in cell adhesion and increase in cell migration after incubation with hRAT-CMs vs. hRAN- or control-CMs. Surprisingly, HK-2, 786-O and ACHN cells showed a significant decrease in cell migration after incubation with hRAN-CMs vs. control-CMs. No difference in proliferation of cell lines was found after 24 or 48 h of treatment with CMs. AdipoR1 in ACHN and Caki-1 cells decreased significantly after incubation with hRAT-CMs vs. hRAN-CMs and control-CMs. ObR and CD44 increased in tumor line cells, and vimentin increased in non-tumor cells, after incubation with hRAT-CMs vs. hRAN-CMs and control-CMs. We observed an increase in the expression of pERK and pPI3K in HK-2, 786-O and ACHN, incubated with hRAT-CMs. In conclusion, results showed that adipose microenvironment can regulate the behavior of tumor and non tumor human renal epithelial cells.

Estradiol and progesterone regulate proliferation and apoptosis in colon cancer.

Epidemiological studies describe estrogens as protectors in the development of colon cancer in postmenopausal women treated with hormone replacement therapy. However, the role of progesterone in colon cancer has been minimally studied and the results are controversial. For the above, the objective of this work was to determine the hormonal regulation exerted by natural ovarian steroids on proliferation and apoptosis in an experimental model of colon cancer in ovariectomized rats treated with 17-beta estradiol and progesterone. Sprague-Dawley rats were exposed to the carcinogen 1,2-dimethylhydrazine to induce colon tumors. Thirty days later, the rats were ovariectomized and treated with estradiol (60 µg/kg), progesterone (10 mg/kg), estradiol plus progesterone (60 µg/kg and 10 mg/kg) or vehicle. We observed no significant differences in colon cancer incidence and tumor multiplicity between the groups. Nevertheless, we observed a decrease in PCNA expression and a greater number of apoptotic index, higher expression of caspase 3, cleaved PARP and cleaved caspase 8 in tumors, confirming the activation of the extrinsic pathway of apoptosis by the combined treatment. In addition, we observed a higher expression of estrogen receptor beta in these tumors. We conclude that the action of both hormones, estradiol and progesterone, is necessary to reduce proliferation and increase apoptosis in colon tumors, probably through estrogen receptor beta activation.

Comparative proteomics of soluble factors secreted by human breast adipose tissue from tumor and normal breast.

Tumor progression depends on the tumor-stroma interaction. In the breast, adipose tissue is the predominant stromal type. We have previously demonstrated that conditioned media (CMs) from explants of human adipose tissue of tumor breasts (hATT) increase proliferation and migration of breast cancer epithelial cells when compared to human adipose tissue from normal breasts (hATN). In this work, we aim to identify specific proteins and molecular/biological pathways associated with the secretion profile of hATT and hATN explants. hATT-CMs and hATN-CMs were separated by SDS-PAGE and analyzed by means of two-dimensional nano-liquid chromatography-mass spectrometry. The data was analyzed using ProteoIQ and FunRich software. In addition, 42 cytokines from hATT-CMs and hATN-CMs were assayed by a protein antibody assay. Compared to hATN-CMs, hATT-CMs showed greater protein diversity. We found that hATT-CMs presented a greater amount of proteins related to complement system activity, metabolism and immune system, as well as proteins involved in a variety of biological processes such as signal transduction and cell communication. Specifically, apolipoprotein AI and AII, complement component 3, and vimentin and desmin were significantly increased in hATT-CMs versus hATN-CMs. Moreover, a multivariate discriminant analysis of the cytokines detected by the array showed that IL-6, MCP-2 and GRO cytokines were sufficient and necessary to differentiate hATT-CMs from hATN-CMs. This analysis also showed that the levels of these three cytokines, taken together, correlated with stage and histological grade of the tumor in the hATT-CMs group, and with body mass index in the hATN-CMs group.

Human renal adipose tissue induces the invasion and progression of renal cell carcinoma.

We evaluated the effects of conditioned media (CMs) of human adipose tissue from renal cell carcinoma located near the tumor (hRATnT) or farther away from the tumor (hRATfT), on proliferation, adhesion and migration of tumor (786-O and ACHN) and non-tumor (HK-2) human renal epithelial cell lines. Human adipose tissues were obtained from patients with renal cell carcinoma (RCC) and CMs from hRATnT and hRATfT incubation. Proliferation, adhesion and migration were quantified in 786-O, ACHN and HK-2 cell lines incubated with hRATnT-, hRATfT- or control-CMs. We evaluated versican, adiponectin and leptin expression in CMs from hRATnT and hRATfT. We evaluated AdipoR1/2, ObR, pERK, pAkt y pPI3K expression on cell lines incubated with CMs. No differences in proliferation of cell lines was found after 24 h of treatment with CMs. All cell lines showed a significant decrease in cell adhesion and increase in cell migration after incubation with hRATnT-CMs vs. hRATfT- or control-CMs. hRATnT-CMs showed increased levels of versican and leptin, compared to hRATfT-CMs. AdipoR2 in 786-O and ACHN cells decreased significantly after incubation with hRATfT- and hRATnT-CMs vs. control-CMs. We observed a decrease in the expression of pAkt in HK-2, 786-O and ACHN incubated with hRATnT-CMs. This result could partially explain the observed changes in migration and cell adhesion. We conclude that hRATnT released factors, such as leptin and versican, could enhance the invasive potential of renal epithelial cell lines and could modulate the progression of the disease.

Human breast adipose tissue: characterization of factors that change during tumor progression in human breast cancer.

BACKGROUND: Adipose microenvironment is involved in signaling pathways that influence breast cancer. We aim to characterize factors that are modified: 1) in tumor and non tumor human breast epithelial cell lines when incubated with conditioned media (CMs) from human breast cancer adipose tissue explants (hATT) or normal breast adipose tissue explants (hATN); 2) in hATN-CMs vs hATT-CMs; 3) in the tumor associated adipocytes vs. non tumor associated adipocytes. METHODS: We used hATN or hATT- CMs on tumor and non-tumor breast cancer cell lines. We evaluated changes in versican, CD44, ADAMTS1 and Adipo R1 expression on cell lines or in the different CMs. In addition we evaluated changes in the morphology and expression of these factors in slices of the different adipose tissues. The statistical significance between different experimental conditions was evaluated by one-way ANOVA. Tukey's post-hoc tests were performed within each individual treatment. RESULTS: hATT-CMs increase versican, CD44, ADAMTS1 and Adipo R1 expression in breast cancer epithelial cells. Furthermore, hATT-CMs present higher levels of versican expression compared to hATN-CMs. In addition, we observed a loss of effect in cellular migration when we pre-incubated hATT-CMs with chondroitinase ABC, which cleaves GAGs chains bound to the versican core protein, thus losing the ability to bind to CD44. Adipocytes associated with the invasive front are reduced in size compared to adipocytes that are farther away. Also, hATT adipocytes express significantly higher amounts of versican, CD44 and Adipo R1, and significantly lower amounts of adiponectin and perilipin, unlike hATN adipocytes. CONCLUSIONS: We conclude that hATT secrete a different set of proteins compared to hATN. Furthermore, versican, a proteoglycan that is overexpressed in hATT-CMs compared to hATN-CMs, might be involved in the tumorogenic behavior observed in both cell lines employed. In addition, we may conclude that adipocytes from the tumor microenvironment show a less differentiated state than adipocytes from normal microenvironment. This would indicate a loss of normal functions in mature adipocytes (such as energy storage), in support of others that might favor tumor growth.

Hypothyroidism advances mammary involution in lactating rats through inhibition of PRL signaling and induction of LIF/STAT3 mRNAs.

Thyroid diseases have deleterious effects on lactation, litter growth and survival, and hinder the suckling-induced hormone release, leading in the case of hyperthyroidism, to premature mammary involution. To determine the effects of hypothyroidism (HypoT) on late lactation, we analyzed the effect of chronic 6-propyl-2-thiouracil (PTU)-induced HypoT on mammary histology and the expression of members of the JAK/STAT/SOCS signaling pathway, milk proteins, prolactin (PRLR), estrogen (ER), progesterone (PR) and thyroid hormone (TR) receptors, markers of involution (such as stat3, lif, bcl2, BAX and PARP) on lactation (L) day 21. HypoT mothers showed increased histological markers of involution compared with control rats, such as adipose/epithelial ratio, inactive alveoli, picnotic nuclei and numerous detached apoptotic cells within the alveolar lumina. We also found decreased PRLR, ß-casein and α-lactoalbumin mRNAs, but increased SOCS1, SOCS3, STAT3 and LIF mRNAs, suggesting a decrease in PRL signaling and induction of involution markers. Furthermore, Caspase-3 and 8 and PARP labeled cells and the expression of structural proteins such as ß-Actin, α-Tubulin and Lamin B were increased, indicating the activation of apoptotic pathways and tissue remodelation. HypoT also increased PRA (mRNA and protein) and erß and decreased erα mRNAs, and increased strongly TRα1, TRß1, PRA and ERα protein levels. These results show that lactating HypoT rats have premature mammary involution, most probably induced by the inhibition of prolactin signaling along with the activation of the LIF-STAT3 pathway.

Effects of parity and serum prolactin levels on the incidence and regression of DMBA-induced tumors in OFA hr/hr rats.

Prolactin (PRL) is a key player in the development of mammary cancer. We studied the effects of parity or hyperprolactinemia on mammary carcinogenesis in OFA hr/hr treated with 7,12-dimethylbenzanthracene. They were divided into three groups: nulliparous (Null), primiparous (PL, after pregnancy and lactation), and hyperprolactinemic rats (I, implanted in the arcuate nucleus with 17ß-estradiol). The tumor incidence was similar in the three groups. However, a higher percentage of regressing tumors was evident in the PL group. Serum PRL, mammary development, and mammary ß-casein content were higher in I rats compared to Null. The expression of hormone receptors was similar in the different groups. However, mammary tissue from PL rats bearing tumors had increased expression of PRL and estrogen alpha receptors compared to rats free of tumors. Our results suggest that serum PRL levels do not have relevance on the incidence of tumors, probably because the low levels of PRL in OFA rats are not further decreased by PL like in other strains. However, supraphysiological levels of PRL affect carcinogenesis. PL induces regression of the tumors due to the differentiation produced on the mammary cells. Alterations in the expression of hormonal receptors may be involved in progression and regression of tumors.

Experimental hypothyroidism increases apoptosis in dimethylbenzanthracene-induced mammary tumors.

Epidemiological and in vitro data have not provided conclusive evidence concerning the involvement of thyroid hormones (THs) on mammary carcinogenesis. We used an in vivo model to assess the relationship between THs, adipose tissue and breast cancer development. Female Sprague­Dawley rats were treated with a dose of 7,12-dimethylbenz(a)anthracene (15 mg/rat) at 55 days of age and were then divided into four experimental groups: hypothyroid rats (HypoT, 0.01% 6-N-propyl-2-thiouracil in drinking water), untreated control (EUT); hyperthyroid rats (HyperT, 0.25 mg/kg/day T4 s.c.) and vehicle-treated control rats. The latency of tumor appearance and the incidence and progression of tumors were determined. At sacrifice, blood samples were collected for hormone determinations and samples of tumor and mammary glands were obtained for immunohistological studies. HypoT rats had retarded growth and an increase in mammary fat. The latency was longer (p<0.0001), the incidence rate was lower (p<0.05) and tumor growth was slower in HypoT rats compared to EUT and HyperT rats. Mitotic index and PCNA immunostaining were similar in all groups. HypoT rats showed increased apoptosis (p<0.05) as evaluated by the apoptotic index and TUNEL staining. No differences in serum prolactin and progesterone were observed. However, circulating estradiol (E2) was significantly lower in HypoT and HyperT rats. Serum leptin levels were reduced in HypoT rats even though the abdominal fat mass was similar in all groups. To note, the leptin level was higher in HypoT rats that developed mammary tumors than the level in non-tumoral HypoT rats. In conclusion, hypothyroidism altered animal growth, breast morphology, body composition, leptin secretion and serum E2 enhancing apoptosis and, consequently, retarding mammary carcinogenesis in rats.

The inhibitory effect of progesterone on lactogenesis during pregnancy is already evident by mid- to late gestation in rodents.

Lactogenesis is a very complex process highly dependent on hormonal regulation. In the present study the time-course of the inhibitory actions of progesterone on prolactin secretion, mammary gland morphology and lactogenesis from mid- to late gestation in rodents was investigated. Groups of pregnant rats were luteectomised or administered with mifepristone on Day 10, 13, 15 or 17 of gestation and decapitated 28 or 48h later. Whole-blood samples and the inguinal mammary glands were taken for determinations of hormone levels and for measurement of mammary content of casein and lactose and for tissue morphology analyses, respectively. Luteectomy or mifepristone evoked prolactin increases only after Day 17 of gestation. Mammary content of casein was increased by both treatments regardless of timing or duration. Mifepristone was less effective than luteectomy in inducing lactose production and the effect was only observed after Day 15 of gestation. Analysis of mammary gland morphology confirmed the observed effect of progesterone on lactogenesis. Both treatments triggered remarkable secretory activity in the mammary gland, even without a parallel epithelial proliferation, demonstrating that the mammary epithelium is able to synthesise milk compounds long before its full lobulo-alveolar development is achieved, provided that progesterone action is abolished. Thus, the present study demonstrates that progesterone is a potent hormonal switch for the prolactin and prolactin-like effects on mammary gland development and its milk-synthesising capacity during pregnancy, and that its inhibitory action is already evident by mid-pregnancy in rodents.

Expression of NHERF1 in colonic tumors induced by 1,2-dimethylhydrazine in rats is independent of plasma ovarian steroids.

In normal embryonic fibroblasts, the Na(+)/H(+) exchanger regulator factor 1 (NHERF1) stabilizes E-cadherin/ß-catenin binding and the lack of NHERF1 expression promotes cell transformation thus acting as a tumor suppressor gene. We here tested the hypothesis that NHERF1 could act as a tumor suppressor gene in colon cancer as a mediator of estrogens' protective actions in colon carcinogenesis. We studied the expression and localization of NHERF1 and ß-catenin by immunohistochemistry in colonic tumors induced by 1,2 dimethylhidrazine (DMH) in Sprague-Dawley rats. One group of the rats treated with the carcinogen was ovariectomized (OVX) in the middle of the tumor induction, simulating a human menopausal condition. We observed a protective role of estrogens in colon cancer, as non-ovariectomized rats (DMH) had a reduced tumor area compared with the ovariectomized group (DMH + OVX; mean ± SE) 28.98 ± 4.65 vs. 67.58 ± 8.69 (p < 0.00380). Despite the lack of plasma estrogen stimulation, we found abundant expression of NHERF1 in colon tumors from ovariectomized rats. NHERF1 was mainly localized in the cytoplasm of the adenocarcinoma cells and lost the apical localization previously reported in normal colon tissue. We also detected expression of NHERF1 by western blot in the SW48, CACO-2, and HT29 colon cancer cell lines. Non-estrogenic factors in plasma or the tumor microenvironment may regulate NHERF1 expression in transformed colon epithelial cells. Further studies are required to understand the regulation of NHERF1 expression in colon cancer tissue.

Regulation of prolactin secretion during the estrus in rats: possible role of glucocorticoids.

Mifepristone (MIF) administration to cycling rats at proestrus induces hypersecretion of prolactin (PRL) at the following estrus. We aimed to assess whether this effect is due to the antiprogesterone or antiglucocorticoid action of MIF and to help underscore the nature of the circulating hormone(s) regulating PRL secretion at estrus. Female cycling rats in proestrus were treated with vehicle; the progesterone (Pg) and glucocorticoid receptor antagonists, MIF (5 mg/kg) or ORG-33628 (5 mg/kg); the glucocorticoid agonist dexamethasone (DEX; 27 mg/kg)±MIF; or the inhibitor of steroid synthesis aminoglutethimide (AG; 150 mg/kg)±MIF. The animals' blood was sampled the same day at 1800 h and at 1800 h of the following day to assess for circulating PRL and Pg levels. To distinguish antiglucocorticoid from antiprogesterone effects of MIF, we administered a highly specific neutralizing antibody against Pg. None of the antagonists modified serum PRL values at proestrus but increased PRL levels at estrus. DEX decreased the secretion of PRL at proestrus, yet the effect was entirely blocked by MIF. Furthermore, DEX decreased PRL at estrus in a MIF-reversible manner, suggesting that adrenal corticoids during proestrous may regulate PRL secretion at estrus. AG increased PRL secretion at estrus, whereas its association with MIF produced an even higher response. PRL concentration at estrus was not modified by the antiprogesterone antibody, suggesting that the effect of MIF is a consequence of its antiglucocorticoid effect and not due to its antiprogesterone properties. In conclusion, PRL secretion in the afternoon of the estrus is most likely regulated by glucocorticoids through an inhibitory action.