Targeting of heme oxygenase-1 as a novel immune regulator of neuroblastoma.

Heme oxygenase (HO)-1 catalyzes the degradation of cytotoxic heme into biliverdin and blocks antitumor immune responses, thus protecting cancer against host defense. Whether this scenario also applies to neuroblastoma (NB), the most common extracranial solid childhood tumor, is not known. Here, we demonstrate for the first time a prognostic relevance of HO-1 expression in samples from NB patients and show that targeting of HO-1 prevents both cancer resistance against cellular stress and immune escape in the syngeneic NXS2 A/J mouse model of NB. High HO-1 RNA expression in NB tissues emerged as unfavorable prognostic marker, in particular for patients older than 18 months as indicated by univariate as well as multivariate survival probability analyses including disease stage and MYCN status. On the basis of this observation we aimed to target HO-1 by systemic as well as tumor-specific zinc protoporphyrin-mediated HO-1 suppression in a syngeneic immunocompetent NB mouse model. This resulted in 50% reduction of primary tumor growth and a suppression of spontaneous liver metastases. Importantly, HO-1 inhibition abrogated immune cell paralysis affecting CD4 and CD8 T-effector cells. This in turn reverted HO-1-dependent immune escape mechanisms in NB by increasing NB apoptosis and improved DC maturation. In summary, HO-1 emerges as a novel immune regulator in NB and emerges as a promising target for the development of therapeutic approaches.

B cell development undergoes profound modifications and adaptations during pregnancy in mice.

Pregnancy hides an immunological riddle combining two antagonistic characteristics of immunology: the existence of a tolerance that allows the gestation of a semiallogeneic fetus and proper protection against pathogens threatening the health of the immunocompromised mother. Despite the fundamental role that B cells play in orchestrating an immune response, their behavior in the context of pregnancy has been barely investigated. Here we demonstrate that numbers of pre/pro and immature B cells were progressively diminished in the bone marrow (BM) of pregnant mice, leading to a reduced influx of B cells in blood and spleen. Correspondingly, lower levels of B cell-activating factor of the TNF family were observed in serum of pregnant mice. In contrast to immature B cells, mature B cells were accumulated in the BM during pregnancy. Accordingly, higher numbers of mature B cells were observed in the lymph nodes draining the uterus as well as in the peritoneal cavity of pregnant mice, both tissues in close contact with the fetuses. Despite an increase in spleen size, pregnant mice showed lower numbers of splenic B cells, which was mirrored by lower numbers of immature and FO B cells. However, marginal zone B cells in the spleen increased during pregnancy. Additionally, serum IgM, IgA, and IgG3 titers were elevated in pregnant mice. Collectively, our data show how the B cell compartment adapts to the presence of the semiallogeneic fetus during gravidity.

Regulatory B10 cells restore pregnancy tolerance in a mouse model.

During mammalian pregnancy, the immune system defies a double challenge: to tolerate the foreign growing fetus and to fight off infections that could affect both mother and fetus. Minimal disturbances to the fine equilibrium between immune activation and tolerance would compromise fetal survival. Here, we show that regulatory B10 cells are important for pregnancy tolerance in mice. The frequency of these cells increases during normal murine pregnancies, while mice presenting spontaneous abortion do not show elevated levels of regulatory B10 cells. When B10 cells are transferred to the abortion-prone mice, dendritic cells are kept in an immature state, and regulatory T cells increase, thus avoiding immunological rejection of the fetuses. In vitro, we could identify IL-10 secreted by B10 cells as the main mediator of these salutary effects. Our data add an important piece of information to the complex immune crosstalk during pregnancy. This study opens novel lines of work to better understand how to help women who have trouble in maintaining a pregnancy.

Neuroblastoma triggers an immunoevasive program involving galectin-1-dependent modulation of T cell and dendritic cell compartments.

The immunosuppressive strategies devised by neuroblastoma (NB), the most common solid extracranial childhood cancer, are poorly understood. Here, we identified an immunoevasive program triggered by NB through secretion of galectin-1 (Gal-1), a multifunctional glycan-binding protein. Human and mouse NB cells express and secrete Gal-1, which negatively regulates T cell and dendritic cell function. When injected subcutaneously in syngeneic A/J mice, knockdown transfectants expressing low amounts of Gal-1 (NXS2/L) showed reduction of primary tumor growth by 83-90% and prevented spontaneous liver metastases in contrast to NXS2 cell variants (NXS2/H, NXS2 wildtype) expressing high amounts of Gal-1. Splenocytes from mice receiving Gal-1 knockdown NXS2/L cells secreted higher amounts of IFN-γ and displayed enhanced cytotoxic T-cell function compared to NXS2/H or NXS2 controls. Immunohistochemical analysis revealed a six- to tenfold increase in the frequency of CD4+ and CD8+ T cells infiltrating tumors from mice receiving knockdown transfectants. This effect was confirmed by in vitro migration assays. Finally, supernatants of NXS2/H or NXS2 cells suppressed dendritic cell (DC) maturation and induce T cell apoptosis, whereas these effects were only marginal on DCs and T cells exposed to supernatants from NXS2/L cells. These results demonstrate a novel immunoinhibitory role of the Gal-1-glycan axis in NB, highlighting an alternative target for novel immunotherapeutic modalities.

[The role of estrogen receptor alpha in breast cancer cell proliferation mediated by progestins]. / El receptor de estrógenos alfa como mediador del efecto proliferativo de progestágenos en cáncer de mama.

In C4-HD murine mammary carcinomas and in human breast cancer T47D cells, we showed that medroxyprogesterone acetate (MPA) induces a nuclear physical association between estrogen receptor alpha (ERa) and progesterone receptors (PR). The blockade of ERa inhibits cell proliferation mediated by progestins. We hypothesized that this nuclear association between ERa/PR is necessary to trigger progestin-induced cell proliferation and tumor growth. We demonstrated that fulvestrant (FUL, ICI182.780) induced complete regression of C4-HD tumors growing with progestins. MPA treatment induced an early increase in both CCND1 and MYC expression in T47D cells. The blockade of ERa prevented the MPA-dependent transcription of both genes. Specific binding of PR/ERa was observed at the same MPA-sensitive regions at the CCND1 and MYC gene promoters after chromatin immunoprecipitation (ChIP) analysis. ICI inhibited binding of ERa to both gene regulatory sequences while PR binding was unaffected. The nuclear colocalization between both receptors in T47D cells was confirmed by: confocal microscopy, Duolink assays and co-immunoprecipitation assays. In breast cancer samples we also observed a nuclear interaction between both steroid receptors. Our results indicate that the presence of ERa interacting with activated PR at the CCND1 and MYC promoters is required to trigger progestin-induced gene transcription and cell proliferation in breast cancer cells.

Classical membrane progesterone receptors in murine mammary carcinomas: agonistic effects of progestins and RU-486 mediating rapid non-genomic effects.

In this article, we demonstrate the expression of functional progesterone binding sites at the cell membrane in murine mammary carcinomas that are stimulated by progestins and inhibited by antiprogestins. Using confocal immunofluorescence, ligand binding and cell compartment-specific western blots, we were able to identify the presence of the classical progesterone receptors. Medroxyprogesterone acetate (MPA) and RU-486 (1 × 10(-11) and 1 × 10(-8) M) behaved as agonists activating extracellular signal-regulated kinases (ERKs) and progestin-regulated proteins, except for Cyclin D1 and Tissue factor which failed to increase with 1 × 10(-8) M RU-486, an experimental condition that allows PR to bind DNA. These results predicted a full agonist effect at low concentrations of RU-486. Accordingly, at concentrations lower than 1 × 10(-11) M, RU-486 increased cell proliferation in vitro. This effect was abolished by incubation with the ERK kinase inhibitor PD 98059 or by OH-tamoxifen. In vivo, at a daily dose of 1.2 µg/kg body weight RU-486 increased tumor growth, whereas at 12 mg/kg induces tumor regression. Our results indicate that low concentrations of MPA and RU-486 induce similar agonistic non-genomic effects, whereas RU-486 at higher concentrations may inhibit cell proliferation by genomic-induced effects. This suggests that RU-486 should be therapeutically administered at doses high enough to guarantee its genomic inhibitory effect.

Inhibition of mammary tumor growth by estrogens: is there a specific role for estrogen receptors alpha and beta?

To evaluate the extent to which each estrogen receptor (ER) subtype contributes to the stimulation or to the inhibition of mammary tumor growth, we evaluated the effects of specific agonists in MC4-L2 cells, which are stimulated by 17ß-estradiol (E(2)), and in mammary carcinomas of the MPA mouse breast cancer model, which are inhibited by E(2). Both express ERα and ERß. In MC4-L2 cells, 4,4',4"-(4-propyl-(1H)-pyrazole-1,3,5-triyl)trisphenol (PPT; ERα agonist) and (4-hydroxy-phenyl)-propionitrile (DPN; ERß agonist) stimulated cell proliferation, whereas the opposite occurred in C4-HI primary cultures. The inhibitory effect was associated with a decrease in ERα and cyclin D1 expression and an increase in progesterone receptor (PR) expression as well as in the Bax/Bcl-xl ratio. In vivo, mice carrying C4-HI or 32-2-HI tumors were treated with E(2), PPT or DPN (3 mg/kg/day) or with vehicle. PPT and DPN inhibited tumor size, as did E(2), during the first 72 h. After a few days, DPN-treated tumors started to grow again, while PPT-treated tumors remained quiescent for a longer period of time. A pronounced decrease in the mitotic index and an increase in the apoptotic index was associated with tumor regression. All treated tumors showed: (a) an increase in integrin α6 and Bax expression, (b) an increased stromal laminin redistribution, and (c) a decrease in ERα, Bcl-xl and Bcl-2 expression (P < 0.001). Apoptosis-inducing factor (Aif) expression was increased in DPN-treated tumors, while active caspase 9 was up-regulated in PPT-treated mice, demonstrating the involvement of the intrinsic apoptotic pathway in estrogen-induced regression in this model. In conclusion, our data indicate that although there may be some preferences for activation pathways by the different agonists, the stimulatory or inhibitory effects triggered by estrogens are cell-context dependent rather than ER isoform dependent.

The MPA mouse breast cancer model: evidence for a role of progesterone receptors in breast cancer.

More than 60% of all breast neoplasias are ductal carcinomas expressing estrogen (ER) and progesterone receptors (PR). By contrast, most of the spontaneous, chemically or mouse mammary tumor virus induced tumors, as well as tumors arising in genetically modified mice do not express hormone receptors. We developed a model of breast cancer in which the administration of medroxyprogesterone acetate to BALB/c female mice induces mammary ductal carcinomas with a mean latency of 52 weeks and an incidence of about 80%. These tumors are hormone-dependent (HD), metastatic, express both ER and PR, and are maintained by syngeneic transplants. The model has been further refined to include mammary carcinomas that evolve through different stages of hormone dependence, as well as several hormone-responsive cell lines. In this review, we describe the main features of this tumor model, highlighting the role of PR as a trigger of key signaling pathways mediating tumor growth. In addition, we discuss the relevance of this model in comparison with other presently used breast cancer models pointing out its advantages and limitations and how, this model may be suitable to unravel key questions in breast cancer.

Novel human breast cancer cell lines IBH-4, IBH-6, and IBH-7 growing in nude mice.

Breast cancer is the most frequent cancer in women. However, in vivo hormone receptor positive and metastatic models are scarce. The aim of the present manuscript was to assess if the novel steroid receptor positive human cell lines IBH-4, IBH-6, and IBH-7 developed in our laboratory from primary infiltrant ductal carcinomas are good models to study in vivo human breast cancer. Cell lines or tumors were inoculated to nude mice in the presence or absence of hormone supplementation. Growth was analyzed by ANOVA followed by Tukey-Kramer's test. Steroid hormone expression was assessed by immunohistochemistry and Western blotting. The histology of the tumors was analyzed. IBH-4 and IBH-6 cells were inoculated to nude mice and 100% of the injected mice developed tumors in the presence or absence of hormone treatment, although tamoxifen inhibited growth. IBH-4 and IBH-6 cell lines in vivo gave rise to poorly differentiated carcinomas with areas of solid growth and sarcomatoid areas showing no morphological signs of epithelial differentiation. Distinct features of malignancy were observed. IBH-7 tumors in animals receiving estradiol were semi-differentiated adenocarcinomas. IBH-7 cells grew only in the presence of estradiol, but even with hormone addition, the tumor take was 20%. These tumors metastasized to the uterus and lung and vascular tumor emboli were evident. IBH-7 tumors were invasive and able to break through the peritoneum. As a conclusion, IBH-4 and IBH-6 are good models for studying tumor progression, whereas IBH-7 is a good model for tumor take, being metastatic and strictly estrogen-dependent.

Antisense oligonucleotides targeting the progesterone receptor inhibit hormone-independent breast cancer growth in mice.

INTRODUCTION: Previous data from our laboratory suggested that progesterone receptors (PRs) are involved in progestin-independent growth of mammary carcinomas. To investigate this possibility further, we studied the effects of PR antisense oligodeoxynucleotides (asPR) on in vivo tumor growth. METHOD: BALB/c mice with subcutaneous 25 mm2 mammary carcinomas expressing estrogen receptor-alpha and PR were either injected intraperitoneally with 1 mg asPR every 24 or 12 hours for 5-10 days, or subcutaneously with RU 486 (6.5 mg/kg body weight) every 24 hours. Control mice received vehicle or scPR. RESULTS: Significant inhibition of tumor growth as well as a significant decrease in bromodeoxyuridine uptake was observed in asPR-treated mice, which correlated with histological signs of regression and increased apoptosis. Mice treated with RU 486 experienced almost complete tumor regression. No differences were detected between vehicle-treated and scPR-treated mice. Anti-progestin-treated and asPR-treated mice were in a continuous estrous/meta-estrous state. Decreased phosphorylated extracellular signal-regulated kinase (ERK)1 and ERK2 levels and estrogen receptor-alpha expression were observed as late events in RU 486-treated and asPR-treated mice with regressing tumors. CONCLUSION: We demonstrate, for the first time, inhibition of tumor growth in vivo using asPR. Our results provide further evidence for a critical and hierarchical role of the PR pathway in mammary carcinomas.

Sources of myofibroblasts in kidney fibrosis: all answers are correct, however to different extent!

Most inflammatory kidney diseases have the final outcome of fibrosis with the loss of kidney architecture and progressive loss of kidney function. Excess matrix deposition is observed, which may be an inadequate attempt to limit organ damage. The primary sources of matrix synthesis are resident cells that may acquire different activated phenotypes and likely orchestrate matrix deposition. Over the last decades, intense efforts were undertaken to define the origin of myofibroblasts, resulting in four different controversially discussed hypotheses: bone marrow recruitment, vascular pericyte-derived myofibroblasts, epithelial-to-mesenchymal transition (EMT), and endothelial-to-mesenchymal transition (EndMT). In a recent article, LeBleu et al. (Nat Med 19(8):1047-1053, 2013) address this issue and come to the conclusion that most of the different hypotheses are likely true, however to different extents. To arrive at this conclusion, the authors have performed genetic cell tracking and quantification by cell labeling in newly generated knockout mouse models. Quantitative analyses have been made and yield the following estimates: 50% of the myofibroblasts are derived through proliferation from resident fibroblasts, 35% differentiate from bone marrow-derived cells, 10% arise from EndMT, and 5% through EMT.

B-1a B cells regulate T cell differentiation associated with pregnancy disturbances.

DURING PREGNANCY, THE MATERNAL IMMUNE SYSTEM FACES A DOUBLE DILEMMA: tolerate the growing semi-allogeneic fetus and at the same time protect the mother and the progeny against pathogens. This requires a fine and extremely regulated equilibrium between immune activation and tolerance. As professional antigen presenting cells, B cells and in particular B-1a B cells, can activate or tolerize T cells and thus participate in the generation or regulation of the immune response. B-1a B cells were involved in the humoral immune response leading to pre-eclampsia, one of the main medical complications during pregnancy. Here we demonstrated that B-1a B cells are additionally involved in cellular immune mechanisms associated with pregnancy complications. Using a mouse model of pregnancy disturbances, we showed that B-1a B cells from animals suffering pregnancy disturbances but not from those developing normal pregnancies induce the differentiation of naïve T cells into Th17 and Th1 cells. This differential role of B-1a B cells during pregnancy seems to be associated with the co-stimulatory molecule CD86 as normal pregnant mice showed lower percentages of CD86 expressing B-1a B cells as compared to pregnant mice developing pregnancy disturbances or to non-pregnant animals. Our data bring to light a new and not explored role of B-1a B cells in the context of pregnancy.

Salmonella SL7207 application is the most effective DNA vaccine delivery method for successful tumor eradication in a murine model for neuroblastoma.

Attenuated Salmonella is an approved oral life vaccine that is currently entering pre-clinical cancer vaccination studies as a promising DNA carrier. In a syngeneic mouse model for neuroblastoma, oral gavage of Salmonella typhimurium (SL7207) carrying recent generated survivin DNA vaccines induced a stronger cellular anti-NB immune response than gene gun application or injection of lentivirally transduced bone marrow-derived DCs. The level of Salmonella-associated side effects was not significant as indicated by unaffected survivin-mediated hematopoiesis and wound healing. We believe that our findings provide an important baseline to translate Salmonella-based DNA vaccination into a clinical application for neuroblastoma.

Estrogen receptor alpha mediates progestin-induced mammary tumor growth by interacting with progesterone receptors at the cyclin D1/MYC promoters.

Synthetic progesterone used in contraception drugs (progestins) can promote breast cancer growth, but the mechanisms involved are unknown. Moreover, it remains unclear whether cytoplasmic interactions between the progesterone receptor (PR) and estrogen receptor alpha (ERα) are required for PR activation. In this study, we used a murine progestin-dependent tumor to investigate the role of ERα in progestin-induced tumor cell proliferation. We found that treatment with the progestin medroxyprogesterone acetate (MPA) induced the expression and activation of ERα, as well as rapid nuclear colocalization of activated ERα with PR. Treatment with the pure antiestrogen fulvestrant to block ERα disrupted the interaction of ERα and PR in vitro and induced the regression of MPA-dependent tumor growth in vivo. ERα blockade also prevented an MPA-induced increase in CYCLIN D1 (CCND1) and MYC expression. Chromatin immunoprecipitation studies showed that MPA triggered binding of ERα and PR to the CCND1 and MYC promoters. Interestingly, blockade or RNAi-mediated silencing of ERα inhibited ERα, but not PR binding to both regulatory sequences, indicating that an interaction between ERα and PR at these sites is necessary for MPA-induced gene expression and cell proliferation. We confirmed that nuclear colocalization of both receptors also occurred in human breast cancer samples. Together, our findings argued that ERα-PR association on target gene promoters is essential for progestin-induced cell proliferation.

Estrogen or antiprogestin treatment induces complete regression of pulmonary and axillary metastases in an experimental model of breast cancer progression.

In this paper we demonstrate, using the C7-2-HI metastatic transplantable ductal mammary tumor, that endocrine therapy can induce complete regression of spontaneous lymph node and lung metastases in a mouse model of breast cancer progression. This tumor expresses high levels of estrogen and progesterone receptors and shows a high incidence of early axillary lymph nodes and lung metastases; using this model we had previously shown complete tumor regression of subcutaneous implants. Interestingly, although the metastases showed a more differentiated histology as compared with the primary growth, they underwent complete regression when treated with estrogens or antiprogestins. This phenomenon was associated with sustained cytostasis and apoptosis accompanied by increases in p21 and p27 expression and early tissue remodeling. These results highlight the essential role of PR in regulating cell proliferation in this model as well as its possible use as therapeutic target.

Inmunohistoquímica y expresión de receptores de estrógenos y progesterona en neoplasias mamarias malignas caninas en distintos estadios clínicos / Immunohistochemistry and expression of estrogen and progesterone receptors in canine malignant mammary tumors in different clinical stages

La técnica de inmunohistoquímica descrita por Walker y col. (1998) y Mote y col. (2001) es de utilidad para la determinación de receptores de estrógenos y de progesterona en tumores mamarios de la hembra canina. Existe bastante controversia respecto al porcentaje de receptores de estrógenos y de progesterona, con valor pronóstico o predictivo en tumores malignos caninos debido, muy probablemente, a la falta de uniformidad en criterios de inclusión de los casos en los estudios realizados. El presente trabajo se realizó en una población de 51 perras. Los tumores fueron escindidos quirúrgicamente mediante mastectomía de las glándulas afectadas. Para la determinación de receptores hormonales, se analizó la muestra con mayores características histológicas de malignidad de cada animal. Se contabilizó el porcentaje de células tumorales positivas para cada uno de los receptores (receptor de estrógeno alfa, receptor de estrógeno beta y receptores de progesterona) en los distintos estadios clínicos (I, II, II, IV). Se consideró positivo todo corte ³ 20% de células tumorales positivas para cada uno de los receptores. Se realizó una estadística descriptiva (media y error estándar) con los animales positivos para cada uno de los receptores en los distintos estadios clínicos. En línea con reportes de otros autores, más de la mitad de caninos portadores de tumores mamarios malignos expresaron receptores de estrógenos y de progesterona. Conociendo que el comportamiento biológico de una neoplasia varía con el estadio clínico del paciente, resulta interesante estudiar la expresión de los receptores en cada uno de éstos, en animales con neoplasias mamarias malignas. Adicionalmente, a este objetivo incluye la puesta a punto la de técnica de inmunohistoquímica para la determinación de receptores hormonales en la especie.

receptors in canine mammary tumors. There is considerable controversy regarding the percentage of estrogen and progesterone receptors that having prognostic or predictive value in malignant tumors in dogs because, most likely, the lack of uniform criteria for inclusion of cases. This study was conducted in a population of 51 female dogs. The tumors were surgically treated by mastectomy of the affected glands. For the determination of hormone receptors, the sample analyzed was showed higher histological malignancy features of each animal. It was counted the percentage of tumor cells positive for each of the receptors (estrogen receptor alpha, estrogen receptor beta and progesterone receptor) in animals in various clinical stages (I, II, III, IV). It was considered positive cut-off ³ 20% tumor cells positive for each of the recipients. It was conducted a descriptive statistics (mean and standard error) which positive animals for each of the receptors in different clinical stages. In line with reports of other authors, more than half of canine carriers of malignant mammary tumors expressed estrogen and progesterone receptors. Knowing that the biological behavior of cancer varies with the clinical stage of the animal, objective was to study the expression of receptors in each of the clinical stages in animals with malignant mammary tumors. Additionally, this includes the preparation of the immunohistochemical technique for the determination of hormone receptors in this species.

Isolation of a stromal cell line from an early passage of a mouse mammary tumor line: a model for stromal parenchymal interactions.

We have developed a murine mammary tumor cell line, MC4-L4, and after 15 passages, a spindle-shaped population became evident. The cuboidal cells, MC4-L4E, cloned by limit dilution, proved to be epithelial tumor cells. When inoculated in syngeneic mice, they gave rise to invasive metastatic carcinomas expressing estrogen and progesterone receptors. These tumors regressed after anti-progestin treatment and stopped growing after 17-beta-estradiol administration. In vitro, they were insensitive to medroxyprogesterone acetate (MPA), 17-beta-estradiol, and EGF and were inhibited by TGFbeta1. They expressed mutated p53 and estrogen receptors alpha; progesterone receptors were undetectable. Cells were polyploid and shared the same four common marker chromosomes present in the parental tumor in addition to an exclusive marker. Spindle-shaped cells, MC4-L4F, were selected by differential attachment and detachment and proved to be non-epithelial non-tumorigenic cells. They were cytokeratin negative, showed mesenchymal features by electron microscopy, differentiated to adipocytes when treated with an adipogenic cocktail, were stimulated by TGFbeta1 and EGF, showed a wild-type p53, and did not exhibit the marker chromosomes of the parental tumor. Although they expressed estrogen receptors alpha, they were insensitive to 17-beta-estradiol in proliferation assays. Co-cultures of both cell types had a synergic effect on progesterone receptors expression and on cell proliferation, being the epithelial cells, the most responsive ones, and 17-beta-estradiol increased cell proliferation only in co-cultures. Cytogenetic studies and data on p53 mutations rule out the possibility of an epithelial mesenchymal transition. Their unique characteristics make them an excellent model to be used in studies of epithelial-stromal interactions in the context of hormone responsiveness in hormone related tumors.

Regresión de cáncer de mama después del tratamiento hormonal en un modelo murino / Mammary cancer regression after hormonal treatment in a murine model

Carcinomas mamarios murinos, originalmente inducidos por acetato de medroxiprogesterona, con crecimiento autónomo y receptores de estrógenos y progesterona regresionan con estradiol (E2) o con antiprogestágenos. Con el objeto de analizar los mecanismos de la regresión tumoral, estudiamos las características morfológicas y la participación de los reguladores del ciclo celular tales como p21, p27, p53 y MDM2 mediante inmunohistoquímica utilizando dos tumores sensibles al E2 o a los antiprogestágenos y uno sensible al E2 y antiprogestágenos resistente. La regresión se asocia a disminución del parénquima tumoral con aumento del estroma, a un efecto antiproliferativo y proapoptótico y a la inducción de proteínas inhibitorias del ciclo celular tales como p21 y p27. Sin embargo el patrón de expresión de los reguladores del ciclo celular varió. En los tumores sensibles a ambos tratamientos aumentó p21 y p27, los valores basales de p53 fueron altos y los de MDM2 bajos. En el tumor sensible sólo a E2 aumentó únicamente p27 y p21 permaneció en valores bajos acompañados por altos niveles basales de p53 y MDM2. Estos hallazgos sugieren que p21 podría ser esencial para la acción de los antiprogestágenos y que alteraciones en la vía p21/p53 podrían participar en la resistencia al tratamiento hormonal. (AU)

Regresión de cáncer de mama después del tratamiento hormonal en un modelo murino / Mammary cancer regression after hormonal treatment in a murine model

Carcinomas mamarios murinos, originalmente inducidos por acetato de medroxiprogesterona, con crecimiento autónomo y receptores de estrógenos y progesterona regresionan con estradiol (E2) o con antiprogestágenos. Con el objeto de analizar los mecanismos de la regresión tumoral, estudiamos las características morfológicas y la participación de los reguladores del ciclo celular tales como p21, p27, p53 y MDM2 mediante inmunohistoquímica utilizando dos tumores sensibles al E2 o a los antiprogestágenos y uno sensible al E2 y antiprogestágenos resistente. La regresión se asocia a disminución del parénquima tumoral con aumento del estroma, a un efecto antiproliferativo y proapoptótico y a la inducción de proteínas inhibitorias del ciclo celular tales como p21 y p27. Sin embargo el patrón de expresión de los reguladores del ciclo celular varió. En los tumores sensibles a ambos tratamientos aumentó p21 y p27, los valores basales de p53 fueron altos y los de MDM2 bajos. En el tumor sensible sólo a E2 aumentó únicamente p27 y p21 permaneció en valores bajos acompañados por altos niveles basales de p53 y MDM2. Estos hallazgos sugieren que p21 podría ser esencial para la acción de los antiprogestágenos y que alteraciones en la vía p21/p53 podrían participar en la resistencia al tratamiento hormonal.