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| Group Rolf
Jaggi Molecular Diagnosis of Breast Cancer |
Department of Clinical Research
(DKF) University of Bern Murtenstrasse 35, CH-3010 Bern phone ++41 31 632 32 00 FAX ++41 31 632 32 97 |
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back to Homepage R. Jaggi |
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| Group Rolf
Jaggi Molecular Diagnosis of Breast Cancer |
Department of Clinical Research
(DKF) University of Bern Murtenstrasse 35, CH-3010 Bern phone ++41 31 632 32 00 FAX ++41 31 632 32 97 |
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back to Homepage R. Jaggi |
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Research papers of the groupPopular publications
2002-2008
2001-1995
Mouse mammary gland involution is asssociated with cytochrome c release and caspase activation Marti A., Ritter P.M., Lazar H., Baltzer A., Jäger R., Declerq W., Vandenabeele, P. and Jaggi R. (pdf file of full paper: pdf/MOD (Marti_2001).pdf) [720kb] AbstractAt weaning, milk producing mammary epithelial cells undergo apoptosis and are removed by phagocytosis. Here, we show that mouse mammary gland involution is associated with mitochondrial cytochrome c release and processing of numerous caspases including caspase-1, -3, -7, -8 and -9. Induction of caspase-3-like activity paralleled cleavage of poly-(ADP-ribose) polymerase. Dexamethasone inhibited processing of caspase-3, -7 and -8 and apoptosis, but had no effect on caspase-1 accumulation and cytochrome c release. In Bcl-2 transgenic animals cytochrome c release, caspase activation and apoptosis were impaired. Thus, the pro-apoptotic signaling pathway in mammary epithelial cells during involution involves release of cytochrome c and activation of caspases. It is inhibited by Bcl-2 at the mitochondrial level and by dexamethasone at a post-mitochondrial level.
Int. J. Cancer (2000) 91:529-537. The role of FasL expression in promoting escape from immune rejection in an in vivo spontaneous tumor model Céfai D., Favre L., Buri C., Wattendorf E., Marti A., Jaggi R., and Gimmi C. AbstractTumors escape immune-mediated rejection by a variety of mechanisms that are not fully understood. Their relevance in in vivo situations suffers from the lack of suitable models of tumor escape, in particular after antigen-specific immunotherapy (ASI). In a rat neu (rNeu) transgenic mouse model (rNeu-TG) of spontaneous breast tumor formation and after an efficient cell-based ASI protocol with rNeu-expressing allogeneic fibroblasts, we showed that rNeu-TG mice developed late escape tumors despite the presence of a persistent rNeu-specific immune response. These escape tumors differed from spontaneous tumors, as a challenge with escape tumor cells was not rejected in vaccinated tumor-free mice in contrast to injected spontaneous tumor cells. Immunohistochemical analysis indicated that escape tumors retained normal levels of rNeu or MHC class I but significantly upregulated Fas ligand (CD95, APO-1). Furthermore, we demonstrated that FasL-expressing tumor cells promoted the in vivo apoptosis of infiltrating T lymphocytes in vaccinated mice. Our data thus provide the first evidence that spontaneous breast tumors upregulate FasL expression in response to an immunologic pressure after vaccination and that FasL plays a pivotal role in tumor immune escape.
Proliferation, differentiation and apoptosis of transplanted mammary epithelium Jaggi R., Vallan C., Feng Z., Lazar H., Ritter P.M., Baltzer A. and Marti A. AbstractRepeated cycles of proliferation, differentiation and involution of epithelial structures characterize the development of the mammary gland. In this study we investigated whether transplanted mammary epithelial cells which repopulate the fat pad during puberty, terminally differentiate during pregnancy and undergo apoptotic cell death during involution. Repopulated glands were generated by removing the mammary anlage from prepubertal mice and transplanting mammary epithelial cells (organoids) derived of midpregnant syngeneic mice into the remaining cleared fat pads. The implanted organoids formed an extensive lobulo-alveolar network during puberty and pregnancy resembling the epithelium of contralateral matched glands of the same animals. At parturition, repopulated epithelial cells differentiated and expressed milk protein genes. Repopulated glands underwent an involution process that was accompanied by programmed cell death and activation of caspase-3 like proteases. Therefore, repopulation of mammary glands represents a simple experimental model for studying the mechanisms of apoptosis in a single organ of an intact animal.
(submitted). Induction of caspase expression and activity in the peritumorous tissue of pancreatic cancer Graber H.U., Hulliger K. Büchler M. W., KrajewskiS., Reed J.C., Jaggi R. (pdf-file of full paper on request) AbstractPancreatic cancer is one of the most aggressive human malignancies and is resistant to chemo- and radiotherapy. As the main effect of these treatments is induction of apoptosis, it is very probable that in this neoplasm one or more steps of the complex cell death mechanism are disturbed. Especially, it is not clear how caspases are involved in the observed resistance. Caspases are cysteine proteases and play a major role in the transduction of the apoptotic signal and are key molecules in the execution of apoptosis. Using real-time quantitative RT-PCR we studied the expression of caspase-9 in specimens from 37 pancreatic cancers and in 14 normal pancreata. By comparison with normal pancreas, quantitative RT-PCR demonstrated a 3.5-fold increase of expression caspase-9 mRNA in the tumor samples (P < 0.001). Elevated levels were found in 24 cancer specimens. No association was detected between caspase-9 expression and patients’ age, sex or tumor stage. However, patients whose cancers showed caspase-9 mRNA levels found in normal pancreata had a three-times higher chance to survive than those with high expression levels (P = 0.038). Immunohistochemistry and in situ hybridization revealed that caspase-9 expression in the tumor cells was normally low to moderate. In contrast, in peritumorous regions with chronic inflammation, there was high expression in pancreas specific cells explaining the increased caspase-9 levels observed in the tumor samples. Immunohistochemistry using consecutive sections and antibodies against caspase-3 and -8 revealed staining patterns that were very similar to the one for caspase-9. Most interestingly, immunostaining for active caspase-3, a main executioner of the apoptotic pathway, showed reactivity in the peritumorous tissue, but never in neoplastic cells. The same pattern was observed for apoptotic cells as analyzed by the TUNEL assay.
Cancer Res. (2000) 60:4386-4390. Caspase-3 is essential for efficient apoptosis of breast cancer cells Blanc C., Deveraux Q.L., Krajewski S., JänickeR.U., Porter A.G., Reed J.C., Jaggi R. and Marti A. (pdf file of full paper: Blanc_et_al.pdf) [830 kb] AbstractIn this study we sought to investigate in more detail the role of caspase-3 in apoptotic processes in cultured cells and in cell-free extracts of breast cancer cells. We present evidence that apoptosis of caspase-3-deficient MCF-7 breast cancer cells is defective in response to cisplatin treatment, as determined by chromatin condensation, nuclear fragmentation, DNA-fragmentation and release of cytochrome c from mitochondria. Reconstitution of MCF-7 cells by stable transfection of a CASP-3 cDNA restores all these defects and results in an extensive apoptosis after cisplatin treatment. We further show that in extracts from caspase-3 deficient MCF-7 cells, procaspase-9 processing is strongly impaired after stimulation with either cytochrome c or recombinant caspase-8. Reconstitution of MCF-7 cell extracts with procaspase-3 corrects this defect, resulting in an efficient and complete processing of procaspase-9. Together, our data define caspase-3 as an important integrator of the apoptotic process in MCF-7 breast cancer cells and reveal an essential function of caspase-3 for procaspase-9 processing.
Adv. exp. Med. Biol. (2000) 480:195-201. Caspases: decoders of apoptotic signals during mammary epithelial cell death Marti A., Graber H., Ritter P.M., Lazar H., Baltzer A., Srinivasan A. and Jaggi R. (download full paper: pdf/Advances.pdf) [960 kb] AbstractAt weaning most of the alveolar epithelial cells in the mammary gland die by apoptosis and are removed by phagocytosis. Caspases are a family of aspartate specific cysteine proteases. Activation of caspases is generally thought to represent a major and irreversible event in the apoptotic process. We analyzed caspase expression and activation during mammary gland involution. A quantitative RT-PCR based approach revealed that levels of mRNA expression of several caspases are induced during involution. Using an antibody that specifically recognizes activated caspases we measured a transient induction of caspase activity in situ and found a maximal activation at days two and three of involution. These data were corroborated by monitoring caspase-3 like activity in mammary extracts with a synthetic DEVD-afc peptide as caspase-3 substrate. Using Fas-deficient mice we present evidence that the Fas signaling pathway is not essential for caspase activation and apoptosis during mammary gland involution. In summary, signaling pathways during involution seem to involve activation of caspases as intraepithelial triggers of mammary epithelial cell apoptosis.
Pathology (2000) 32:186-190.The TUNEL assay in the diagnosis of graft-versus-host disease: caveats for interpretationJerome K., Vallan C., and Jaggi R. (download full paper: pdf/Vallan_2000.pdf) [1.1 MB] AbstractSummary Acute graft-versus-host disease (GVHD) is a significant cause of morbidity and mortality following bone marrow transplantation, and early detection is important to allow effective therapy. Since the presence of apoptotic keratino-cytes (dyskeratotic bodies) has been suggested as a useful diagnostic criterion for GVHD, attention has focused on the use of the TUNEL assay to detect apoptosis in clinical specimens. We reviewed clinical specimens upon which TUNEL had been performed for possible artifacts that might interfere with accurate evaluation for GVHD. Several distinct types of artifact were found and could be re-created in experimental systems. Artifacts in TUNEL staining generally resulted from the lack of specificity of this reaction for apoptotic cell death. Artifacts were found resulting from inadequate fixation, over-exposure of the TUNEL reaction, and proximity to the section edge. In addition, a novel artifact, apparently resulting from DNA shearing during the sectioning process, was noted and confirmed using confocal micros-copy of experimental specimens. The TUNEL assay must therefore must be interpreted with caution in the clinical setting. In our laboratory, we consider TUNEL-positive cells as apoptotic only when accompanied by apoptotic morphol-ogy. Although these criteria clearly miss some cells in the early stages of apoptosis, they provide the highest specificity for apoptotic cell death.
Eur. J. Cell Biology (2000) 79:358-364.Nuclear association and processing of procaspase-9 by a caspase-3-like activity in mammary epithelial cellsRitter P.M., Marti A., Blanc C., Baltzer A., Krajewski S., Reed J.C., and Jaggi R.(download full paper: AbstractCaspases are aspartate-specific proteases that are specifically activated by numerous death stimuli. Caspase activation is thought to play a major role for the execution of apoptosis. Inactive caspase-9 zymogen is known to be localized within the mitochondrial intermembrane space where it is involved in monitoring mitochondrial damage associated cytochrome c release and subsequent activation of procaspase-3. Here we show that in mammary epithelial cell lines a significant fraction of caspase-9 proform is associated with discrete structures in the nucleus. Stimulation of cells with chemotherapeutic agents leads to the processing of nuclear procaspase-9 and to the accumulation of nuclear and cytoplasmic caspase activity. Using cell-free extracts from caspase-3 deficient MCF-7 cells we show that caspase-8 mediated processing of nuclear procaspase-9 requires caspase-3. In caspase-3 expressing breast cancer cells, cytochrome c induced processing of nuclear procaspase-9 is blocked by the caspase inhibitors z-VAD and DEVD but not by YVAD. Purified active caspase-3 is sufficient to cleave nuclear caspase-9 zymogen. These results suggest that, in addition to the mitochondrial localization, caspase-9 proform is found within the nucleus and its processing can be regulated by caspase-3.
Int. J. Cancer (2000) 85:578-583.Overexpression of ErbB-2/Neu inhibits mouse mammary epithelial cell differentiation and developmental apoptosisLazar H., Baltzer A., Gimmi C., Marti A., and Jaggi R.(download full paper: AbstractThe erbB-2/neu oncogene is frequently overexpressed in many different tumors in humans including breast and ovary. The oncogene encodes a receptor tyrosine kinase closely related to the epidermal growth factor receptor. We studied effects on differentiation and cell death of ErbB-2/Neu during mammary gland development in transgenic mice expressing an activated, oncogenic rat erbB-2/neu gene controlled by the mammary gland specific promoter from mouse mammary tumor virus (MMTV-LTR). Transgenic animals develop mammary cancer after repeated pregnancies and lactation. We present evidence that overexpression of ErbB-2/Neu in these mice is restricted to tumor cells. Tumor cells fail to differentiate and express milk proteins such as b -casein and whey acidic protein (WAP) during lactation. Epithelial cell apoptosis during normal involution is characterized by non-random DNA degradation into oligonucleosomal fragments. Tumor cells were mostly refractory to this developmentally controlled programmed cell death. Distinct areas within tumors, however, showed spontaneous cell death as measured by in situ TUNEL staining that co-localized with caspase-3 like activity. Our results indicate that the control of developmental cell death during involution is disturbed in erbB-2/neu induced tumors although cell death and caspase activation can take place.
Cell Death Differ. (1999) 6:1190-1201.Physiological apoptosis in hormone dependent tissues: involvement of caspasesA. Marti, R. Jaggi, C. Vallan, P. Ritter, A. Baltzer, A. M. Dharmarajan and R. R. Friisdownload full paper: AbstractPhysiological apoptosis in mammals is a type of programmed cell death, an important element in the developmental repertoire ensuring tissue homeostasis and proper disposal of cells that are no longer needed, such as milk-producing epithelial cells in the mammary gland after lactation, luteal cells in the post partum Corpus luteum or secretory cells in the prostate after castration. Although incompletely described, apoptosis in hormone-dependent tissues is apparently initiated and executed using common biochemical strategies. These include survival pathways governed by local and systemic factors and hormones, diverse regulatory pathways and caspase-dependent execution pathways. Using an antibody that recognizes processed effector caspases as well as a fluorogenic caspase substrate, we present for the first time evidence that caspases are activated in the mammary gland, in the prostate and in the ovary at the time when apoptosis occurs. Most likely phagocytosis of apoptotic cells by neighboring cells may represent an important step, since only a modest involvement of professional phagocytes is apparent. Here, we will summarize and discuss recent data, and will attempt to draw a generalized picture of how physiological apoptosis may occur in these organs.
Mammary Gland Biology and Neoplasia (1999) 4:145-152.Transcription factor activities and gene expression during mouse mammary gland involutionA. Marti, H. Lazar, P. Ritter and R. Jaggidownload full paper: pdf/Marti_1999_MB&N.pdf [630 kb] Abstract Mammary epithelial differentiation and milk production during lactation is a consequence of the suckling stimulus and the presence of lactogenic hormones (e.g. glucocorticoids, insulin and prolactin). After weaning lactogenic hormone levels drop and the gland undergoes involution, a process that is mainly characterized by three events: (i) downregulation of milk protein gene expression, (ii) loss of epithelial cells by apoptosis and, (iii) tissue remodeling and preparation of the gland for a new pregnancy. Each of these processes is likely to depend on the activity of specific sets of transcription factors in the mammary epithelium and stroma. This ensues the timely and spatially coordinated expression of critical gene products such as mediators of apoptosis (e.g. caspase-1) and regulators of tissue remodeling events (e.g. matrix metalloproteinases). Here we describe changes of signal transduction events such as protein kinase A activation, JNK activation and changes in the activity of several transcription factors like Stat5, Stat3, NF1, Oct-1, and AP-1. We discuss their possible role in regulating and coordinating mammary gland involution with emphasis on the apoptotic process of involution.
Oncogene (1998) 17:2590-2600.Apoptosis during castration-induced regression of the prostate is Fos dependentZ. Feng, H.J. Joos, C. Vallan, R. Mühlbauer, H.J. Altermatt and R. JaggiAbstractApoptotic cell death was shown to be accompanied or preceded by an elevated expression of the c-fos protooncogene and DNA binding activity of transcription factor AP-1. We used Fos-deficient mice to study the role of c-Fos during programmed cell death in the prostate. In normal mice apoptosis is induced in the prostate within 2 to 4 days after castration. Histological features of reduced secretory activity and morphological signs of programmed cell death become obvious. No apparent decrease in secretory activity and no epithelial cell death were observed in Fos-deficient animals after castration. Fragmentation of nuclear DNA was measured by in situ terminal transferase reaction. DNA fragmentation was observed in the prostate epithelium of wildtype mice after castration whereas no similar fragmentation was found in Fos-deficient animals. After castration an AP-1 complex accumulated in the prostate of Fos deficient mice which mainly consists of FosB, Fra-2 and JunD whereas in wildtype animals the AP-1 complex in addition contained c-Fos. Our data strongly suggest that c-Fos is required for programmed cell death of prostate epithelial cells.
Cell. Mol. Life Sci. (1998) 54:129-138.EGF-induced programmed cell death of human mammary carcinoma MDA-MB-468 cells is preceded by an activation of AP-1P. Schaerli and R. JaggiAbstractMDA-MB-468 is a human mammary adenocarcinoma cell line which overexpresses the epidermal growth factor (EGF) receptor and undergoes programmed cell death/apoptosis in response to EGF treatment. Programmed cell death was shown to be greatly enhanced when cells were growth-arrested prior to EGF treatment. Apoptosis was characterized by an initial rounding up and detachment of the cells from their substrate starting at about 12 h after EGF treatment, followed by chromatin condensation, nuclear fragmentation and oligonucleosomal fragmentation of the DNA at about 24 h to 48 h. Cell death was dependent on de novo protein synthesis. We found a rapid induction of c-fos, fosB, c-jun and junB at the mRNA level after about 30 min of EGF treatment and a more delayed upregulation of fra-1. The junD gene was expressed in the absence of EGF and it was moderately induced within 30 minutes of growth factor addition. The increase of the different fos and jun mRNAs were paralleled by an increase of activator protein-1 (AP-1) DNA binding activity. A characterization of the AP-1 complex revealed similar levels of several Fos and Jun proteins. Based on the kinetics of AP-1 accumulation and cell death, it seems likely that AP-1 contributes to the apoptotic cell death of EGF receptor-overexpressing MDA-MB-468 cells.
Eur. J. Cell Biol. (1997) 53:158-165.Milk accumulation triggers apoptosis of mammary epithelial cellsAndreas Marti, Zhiwei Feng, Hans Jörg Altermatt and Rolf JaggiAbstractContinuous milk production is a consequence of a complex interplay of lactogenic hormones and it depends on the suckling stimulus during lactation. Involution is associated with a massive engorgement of the gland with milk followed by apoptosis of secretory epithelial cells and a restructuring of the gland. Sealing of a single gland during lactation is sufficient to induce an initial engorgement and a subsequent collapse of alveolar structures and massive epithelial cell death while the other glands of the same animal remain morphologically and functionally in a lactating state. Many markers of involution such as sulfated glycoprotein-2, protein kinase A, transcription factor AP-1 and most notably stromelysin are induced in sealed glands. These findings suggest a cell death pathway which is independent of the systemic levels of lactogenic hormones but which is triggered by an accumulation of apoptosis-inducing factors in the milk, in the lobulo-alveolar structures or by a physical distortion of secretory epithelial cells generated by the engorgement.
J. Dairy Sci. (1996) 79:1074-1084.Regulation of a physiological apoptosis: mouse mammary involutionR. Jaggi, A. Marti, K Guo, Z. Feng and R. R. FriisAbstractContinuous milk production during lactation is dependent on a complex interplay of lactogenic hormones and the suckling stimulus exerted by the young. Involution can be initiated at any stage of lactation in the mouse mammary gland by removing the pups after which it remains reversible for about 30 to 36 hours. Involution in the mouse mammary gland is characterized by a massive loss of secretory epithelial cells due to programmed cell death. Here we show that the nuclear activation of protein kinase A and transcription factor AP-1 precede the irreversible phase of involution which is characterized by an internucleosomal DNA fragmentation. Activation of AP-1 and fragmentation of chromosomal DNA can be prevented by lactogenic hormone treatment in explant cultures derived from mammary tissue at lactation. The elevated level of AP-1 coincides with an epithelial expression of sulfated glycoprotein 2, a potential target gene of AP 1. Programmed cell death in the mammary gland is shown to be associated with the expression of the growth arrest gene, gas-1, and the integrin associated gene IAP which codes for a putative integrin-dependent Ca2+ channel. Their potential roles during involution is discussed.
J. Cell Biol. (1995) 131:1095-1103.Glucocorticoid and progesterone inhibit involution and programmed cell death in the mouse mammary glandZ. Feng, A. Marti, B. Jehn, H. J. Altermatt, G. Chicaiza and R. JaggiAbstractMilk production during lactation is a consequence of the suckling stimulus and the presence of glucocorticoids, prolactin and insulin. After weaning the glucocorticoid hormone level drops, secretory mammary epithelial cells die by programmed cell death and the gland is prepared for a new pregnancy. We studied the role of steroid hormones and prolactin on the mammary gland structure, milk protein synthesis and on programmed cell death. Slow-release plastic pellets containing individual hormones were implanted into a single mammary gland at lactation. At the same time the pups were removed and the consequences of the release of hormones were investigated histologically and biochemically. We found a local inhibition of involution in the vicinity of deoxycorticosterone- and progesterone-release pellets while prolactin-release pellets were ineffective. Dexamethasone, a very stable and potent glucocorticoid hormone analog, inhibited involution and programmed cell death in all the mammary glands. It led to an accumulation of milk in the glands and was accompanied by an induction of protein kinase A, AP 1 DNA binding activity and elevated c fos, junB and junD mRNA levels. Several potential target genes of AP-1 such as stromelysin-1, c jun and SGP-2 which are induced during normal involution were strongly inhibited in dexamethasone-treated animals. Our results suggest that the cross-talk between steroid hormone receptors and AP-1 previously described in cells in culture leads to an impairment of AP-1 activity and to an inhibition of involution in the mammary gland implying that programmed cell death in the post-lactational mammary gland depends on functional AP1.
Cell Death Diff. (1995) 2:277-283.Expression and activity of cell cycle regulators during proliferation and programmed cell death in the mammary glandA. Marti, Z. Feng, B. Jehn, V. Djonov, G. Chicaiza, H.J. Altermatt and R. JaggiAbstractIn the mammary gland distinct phases of proliferation, differentiation and programmed cell death of epithelial cells occur at defined stages of development. Here we show that the expression and activity of cell cycle regulators during normal and preneoplastic proliferation and programmed cell death are remarkably similar. In all cases we found elevated levels of a protein kinase A activity and of transcription factor AP-1, cFos and JunD being the major components of the AP-1 DNA binding complex. A correlation between cFos and JunD expression and chromosomal DNA fragmentation during programmed cell death was observed. Several genes associated with G1 including cyclin D1, D2 and D3 and c-fos, c jun, junB, junD, c myc and p53 are induced in proliferating and in apoptotic mouse mammary tissue. Whereas the expression of these genes correlated with active proliferation of epithelial cells in terminal end buds during puberty, very little proliferation or DNA synthesis but instead extensive apoptosis of epithelial cells was observed during involution. Our results suggest that a G1-like state is associated with programmed cell death of mammary epithelial cells in vivo and that apoptosis occurs without S-phase induction.
Int. J. Oncol. (1994) 5:967-972.JunD activates transcription through multiple GREs in the absence of active glucocorticoid receptorMarti A., Martin F., and Jaggi R.AbstractTranscription factor AP-1 and the glucocorticoid receptor activate gene expression through interaction with specific DNA elements located in the promoter/enhancer region of responsive genes. Recently, it was reported that AP-1 and the glucocorticoid receptor are able to mutually repress each others transcriptional activity. Both, Fos and Jun consist of small families of genes coding for structurally related proteins. The inhibition of the glucocorticoid receptor activity by AP-1 was shown for c-Fos and c-Jun. We extended these studies by investigating the effects of JunD, JunB and FosB on the activity of the glucocorticoid receptor. Transient transfection of NIH 3T3 cells with a glucocorticoid hormone dependent CAT construct containing four glucocorticoid response elements (GREs) upstream of a minimal thymidine kinase promoter (p4GRE(-37)Tk-CAT) resulted in a strong activation of CAT reporter gene expression after stimulation with dexamethasone. In this paper we present evidence that co-transfection of a JunD expression vector and a glucocorticoid hormone-dependent gene construct containing 4 GREs results in a strong promoter activation by a hormone-independent mechanism. Constructs containing a single GRE (p1GRE(-37)Tk-CAT) or a minimal construct (p( 37)Tk-CAT) were not affected by overexpressed JunD and other members of the Fos and Jun families. The effect seems to be restricted to JunD (and to some extent FosB) whereas c Fos, c-Jun or JunB do not mediate a significant stimulation of the p4GRE( 37)Tk CAT construct in similar transfection assays. The JunD mediated activation of the p4GRE(-37)Tk-CAT is independent of the normal glucocorticoid response since a similar activation is observed in CV-1 cells deficient in functional glucocorticoid receptor. Finally, we show that in NIH 3T3 cells the JunD mediated transactivation through TRE elements is inhibited by dexamethasone.
Oncogene (1994) 9:1213-1223.Protein kinase A and AP 1 (cFos/JunD) are induced during apoptosis of mouse mammary epithelial cellsA. Marti, B. Jehn, E. Costello, N. Keon, G. Ke, F. Martin and R. JaggiSummaryAt weaning the mammary gland undergoes a reductive remodelling process (involution) which is associated with the cessation of milk protein gene expression and programmed cell death of milk-producing epithelial cells. Elevated nuclear protein kinase A (PKA) activity was observed from one day post-lactation, paralleled by increased c fos, junB, junD and to a lesser extent c jun mRNA levels. AP 1 DNA binding activity was transiently induced and the AP-1 complex was shown to consist principally of cFos/JunD. Oct 1 DNA binding activity and Oct 1 protein were gradually lost from the gland over the first four days of involution, whereas Oct 1 mRNA levels remained unchanged. Comparing nuclear extracts from normal mammary glands with nuclear extracts from glands which had been cleared of all epithelial cells three weeks after birth, revealed that PKA activation, AP 1 induction and Oct 1 inactivation all are dependent on the presence of the epithelial compartment. The increased Fos/Jun expression and the inactivation of Oct 1 may be consequences of the increased PKA activity. A similar induction of AP 1 (cFos/JunD) was also observed in the involuting rat ventral prostate pointing to a possible role for AP 1 in programmed cell death.
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