OT3-01-01: Randomized Phase II Study of Fulvestrant Versus Fulvestrant Plus Bortezomib in Postmenopausal Women with Estrogen Receptor (ER) Positive, Aromatase-Inhibitor (AI) Resistant Metastatic Breast Cancer (MBC): New York Cancer Consortium Trial P8457

Background: Bortezomib ia proteasome inhibitor that enhances fulvestrant-mediated aggregation of the ER in the cytoplasm without blocking ER degradation in the nucleus in ER+ human breast cancer cell lines, thereby promoting cytoplasmic ER aggresomes which activate a sustained unfolded protein response leading to apoptotic cell death; the combination also induces tumor regression in a tamoxifen resistant T47D-cyclin D1 xenograft model more effectively than either agent alone (Clin Cancer Res 2011; 17: 2292–2300).

Hypothesis: We hpothesize that the combination of fulvestrant and bortezomib will be more effective than fulvestrant alone in ER+, AI-resistant MBC.

Trial design: This is an open-label randomized phase II design in which patients with MBC are randomized to receive fulvestrant alone (500 mg IM day −14, day +1, and day +14 during cycle 1, then 500 mg every 4 weeks on day +1 during cycle 2 and thereafter) or in combination with bortezomib (1.6 mg/m2 IV days +1, +8, +15 every cycle). Stratification factors for randomization include performance status (ECOG 0 vs. 1–2), measurable disease (yes vs. no), and prior chemotherapy for MBC (yes vs. no). Patients who progress on fulvestrant alone may cross over to the combination.

Eligibility criteria: Postmenopausal women with ER+, Her2-negative, MBC who have progressive disease during AI therapy for metastatic disease, or relapse while receiving adjuvant AI therapy. Up to one prior chemotherapy regimen for metastatic disease is permitted.

Specific aims: Primary Objective: To determine if the addition of bortezomib to fulvestrant significantly improves median progression-free survival (PFS), defined as the time from cycle 1, day 1 of therapy until disease progression or death from any cause.

Secondary Objectives: To determine: (1) adverse event rates in both arms, (2) the clinical benefit rate (CBR — objective response [by RECIST 1.1] and/or progression free at 24 weeks), (3) the objective response and CBR after crossover from fulvestrant to fulvestrant plus bortezomib.

Translational Objectives: To perform an exploratory analysis of the effects of the combination on intratumoral nuclear/cytoplasmic ER ratio, unfolded protein response (BiP), apoptotis (cleaved caspase 3, Bc1-2 phospho JNK.)

Statistical methods: he median PFS for patients receiving fulvestrant alone is expected to be approximately 5.4 months based upon patients with AI-resistant disease enrolled on the CONFIRM trial ( J Clin Oncol 2010; 28: 4594–4600). The trial is designed to detect a 70% improved in median PFS to 9.0 months (alpha=0.10, beta =0.10), which will require 59 eligible patients in each arm.

Present accrual and target accrual: 24/118

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr OT3-01-01.

Estrogen carcinogenesis in breast cancer

Many studies have reported a correlation between elevated estrogen blood levels and breast cancer and this observation has raised controversy concerning the long-term use of hormonal replacement therapy. This review will not address further this controversial topic; but rather, this review focuses on the role of estrogen signaling in first, the normal development of the breast and second, how alterations of this signaling pathway contribute to breast cancer.

Hormonal modulation in the treatment of breast cancer

This article explores the history of endocrine therapy for the treatment of breast cancer, the clinical evidence behind the current standards of care, and controversies that may change these standards in the future.

Skp2B overexpression alters a prohibitin-p53 axis and the transcription of PAPP-A, the protease of insulin-like growth factor binding protein 4

Background

We previously reported that the degradation of prohibitin by the SCF^Skp2B ubiquitin ligase results in a defect in the activity of p53. We also reported that MMTV-Skp2B transgenic mice develop mammary gland tumors that are characterized by an increased proteolytic cleavage of the insulin-like growth factor binding protein 4 (IGFBP-4), an inhibitor of IGF signaling. However, whether a link exists between a defect in p53 activity and proteolysis of IGFBP-4 was not established.

Methods and Results

We analyzed the levels of pregnancy-associated plasma protein A (PAPP-A), the protease of IGFBP-4, in MMTV-Skp2B transgenic mice and found that PAPP-A levels are elevated. Further, we found a p53 binding site in intron 1 of the PAPP-A gene and that both wild type and mutant p53 bind to this site. However, binding of wild type p53 results in the transcriptional repression of PAPP-A, while binding of mutant p53 results in the transcriptional activation of PAPP-A. Since MMTV-Skp2B mice express wild type p53 and yet show elevated levels of PAPP-A, at first, these observations appeared contradictory. However, further analysis revealed that the defect in p53 activity in Skp2B overexpressing cells does not only abolish the activity of wild type of p53 but actually mimics that of mutant p53. Our results suggest that in absence of prohibitin, the half-life of p53 is increased and like mutant p53, the conformation of p53 is denatured.

Conclusions

These observations revealed a novel function of prohibitin as a chaperone of p53. Further, they suggest that binding of denatured p53 in intron 1 causes an enhancer effect and increases the transcription of PAPP-A. Therefore, these findings indicate that the defect in p53 function and the increased proteolysis of IGFBP-4, we had observed, represent two components of the same pathway, which contributes to the oncogenic function of Skp2B.

Estrogen receptor mediates a distinct mitochondrial unfolded protein response

Unfolded protein responses (UPRs) of the endoplasmic reticulum and mitochondrial matrix have been described. Here, we show that the accumulation of proteins in the inter-membrane space (IMS) of mitochondria in the breast cancer cell line MCF-7 activates a distinct UPR. Upon IMS stress, overproduction of reactive oxygen species (ROS) and phosphorylation of AKT triggers estrogen receptor (ER) activity, which further upregulates the transcription of the mitochondrial regulator NRF1 and the IMS protease OMI (officially known as HTRA2). Moreover, we demonstrate that the IMS stress-induced UPR culminates in increased proteasome activity. Given our previous report on a proteasome- and OMI-dependent checkpoint that limits the import of IMS proteins, the findings presented in this study suggest that this newly discovered UPR acts as a cytoprotective response to overcome IMS stress.

Abstract 2096: Estrogen receptor alpha activation mediates a novel mitochondrial unfolded protein response

Unfolded protein responses (UPR) of the endoplasmic-reticulum and of the matrix of the mitochondria have been described. Our data indicates that accumulation of proteins in the inter-membrane space of the mitochondria (IMS) activates a distinct UPR from that induced by stress in the mitochondrial matrix. We show that upon IMS-stress, cells activate the Estrogen Receptor (ERα) in a ligand independent fashion through ROS overproduction and AKT phosphorylation. ERα activation further triggers the induction of the mitochondrial regulator NRF-1 and the IMS protease Omi. In addition, IMS stress leads to an acceleration in the trypsin-like activity of the proteasome. Since we reported a proteasome and Omi-dependent checkpoint that limits the import of IMS proteins, these results suggest that this novel UPR acts as cyto-protective responses to overcome IMS-stress. Indeed, we show that whereas ERα is required for activation of these cyto-protective responses, its ligand-independent activation is necessary to prevent IMS stress-induced collapse in the mitochondrial potential. Notably, our result show that upon mitochondrial dysfunction, cells trigger the retrograde pathway involving the activation of ERα to facilitate the recovery of the physiological functions of the mitochondria and maintain their integrity.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2096. doi:10.1158/1538-7445.AM2011-2096

Bortezomib enhances the efficacy of fulvestrant by amplifying the aggregation of the estrogen receptor, which leads to a proapoptotic unfolded protein response

PURPOSE

Fulvestrant is known to promote the degradation of the estrogen receptor (ER) in the nucleus. However, fulvestrant also promotes the aggregation of the newly synthesized ER in the cytoplasm. Accumulation of protein aggregates leads to cell death but this effect is limited as a result of their elimination by the proteasome. We tested whether combining fulvestrant with the proteasome inhibitor, bortezomib, could enhance the accumulation of ER aggregates and cause apoptotic cell death.

EXPERIMENTAL DESIGN

The rate of aggregation of the ER was monitored in ER(+) breast cancer cells lines, T47D, ZR-75.1, BT474, MDA-MB-361, MCF-7, fulvestrant resistance MCF-7, and tamoxifen-resistant T47D-cyclin D1 cells. Activation of the unfolded protein response, apoptosis, and metabolic rate were also monitored in these cell lines following treatment with fulvestrant, bortezomib, or bortezomib in combination with fulvestrant.

RESULTS

We found that bortezomib enhances the fulvestrant-mediated aggregation of the ER in the cytoplasm without blocking the degradation of the ER in the nucleus. Further, these aggregates activate a sustained unfolded protein response leading to apoptotic cell death. Further, we show that the combination induced tumor regression in a breast cancer mouse model of tamoxifen resistance.

CONCLUSIONS

Adding bortezomib to fulvestrant enhances its efficacy by taking advantage of the unique ability of fulvestrant to promote cytoplasmic aggregates of the ER. As this effect of fulvestrant is independent of the transcriptional activity of the ER, these results suggest that this novel combination may be effective in breast cancers that are ER(+) but estrogen independent.

Limb-bone histology of temnospondyls: implications for understanding the diversification of palaeoecologies and patterns of locomotion of Permo-Triassic tetrapods

The locomotion of early tetrapods has long been a subject of great interest in the evolutionary history of vertebrates. However, we still do not have a precise understanding of the evolutionary radiation of their locomotory strategies. We present here the first palaeohistological study based on theoretical biomechanical considerations among a highly diversified group of early tetrapods, the temnospondyls. Based on the quantification of microanatomical and histological parameters in the humerus and femur of nine genera, this multivariate analysis provides new insights concerning the adaptations of temnospondyls to their palaeoenvironments during the Early Permian, and clearly after the Permo-Triassic crisis. This study therefore presents a methodology that, if based on a bigger sample, could contribute towards a characterization of the behaviour of species during great evolutionary events.

Skp2B attenuates p53 function by inhibiting prohibitin

The F-box protein Skp2 and its isoform Skp2B are both overexpressed in breast cancers. Skp2 alters the activity of p53 by inhibiting its interaction with p300 and by promoting p300 degradation. Here, we report that Skp2B also attenuates the activity of p53; however, this effect is independent of p300, suggesting that another mechanism might be involved. Prohibitin, a protein reported to activate p53, was isolated in a two-hybrid screen with the carboxy-terminal domain unique to Skp2B. We observed that prohibitin is a new substrate of Skp2B and that the degradation of prohibitin is responsible for the attenuated activity of p53 in cells overexpressing Skp2B. Furthermore, we show that the activity of p53 is reduced in the mammary glands of Skp2B transgenic mice. This study indicates that both Skp2 and Skp2B attenuate p53 activity through different pathways, suggesting that amplification of the Skp2 locus represents a powerful mechanism to attenuate p53 function in cancer.

Correlation of Oncotype DX Recurrence Score with Cyclin D1 and ErbB2

Background: The Oncotype DX assay predicts the risk of recurrence in patients with stage I-II ER+, node negative breast cancer treated with tamoxifen. It is not understood if the Oncotype DX assay predicts the natural aggressiveness of an individual breast cancer or if it identifies a subtype of tamoxifen resistant breast cancer. In clinical practice, a high recurrence score (RS) on Oncotype DX is interpreted as a more aggressive tumor and is used to justify the use of chemotherapy. However, if the RS was actually predictive of tamoxifen resistance, patients may benefit from the use of an aromatase inhibitor, and chemotherapy may be unnecessary. Cyclin D1 and ErbB2 are two biomarkers shown to predict tamoxifen resistance.Cyclin D1 is overexpressed in approximately 35% of breast cancers. The Austrian Breast and Colorectal Cancer Study Group assessed expression of Cyclin D1 in patients taking tamoxifen within the ABCSG trial 05 and ABCSG trial 06. In both trials, Cyclin D1 overexpression correlated with a lower relapse free survival and overall survival compared to patients without Cyclin D1 overexpression.Erb2 is overexpressed in 15-30% of breast cancers. In the Gruppo Universitario Napoletano 1 trial, ER+ patients with early stage node negative breast cancer who overexpressed ErbB2 had no improvement in progression free survival and overall survival with 2 years of adjuvant tamoxifen therapy. Additional retrospective studies have supported initial reports of an association between overexpression of ErbB2 and tamoxifen resistance.Methods: 69 patients who had the Oncotype DX assay performed and had unstained pathology slides available were assessed for ErbB2 and Cyclin D1 expression. ErbB2 overexpression status was also obtained in another 74 patients who had the Oncotype DX assay performed. ErbB2 overexpression was determined from a review of medical records where ErbB2 was defined as being positive if immunohistochemical (IHC) staining intensity was 3+ with >90% of cells expressing ErbB2 or FISH revealed an amplification of >2.0. IHC analysis of Cyclin D1 was performed according to standard protocol and using commercially available antibodies. Scoring of slides for Cyclin D1 staining were performed by blinded pathologists who assessed both extent and intensity of nuclear staining for Cyclin D1.Results: The median Oncotype Dx RS within ErbB2+ patients was significantly higher than ErbB2- patients (36.5 vs. 18 p<0.0001), and approximately 50% of patients within each RS grouping (high, intermediate, and low) overexpressed cyclin D1.Conclusion: ErbB2 overexpression among high RS patients suggests the Oncotype DX assay may predict tamoxifen resistance and other markers for tamoxifen resistance need to be correlated with the RS. Although preliminary analysis of the IHC staining for Cyclin D1 does not correlate with a high RS, high Cyclin D1 expression among patients within the low RS subgroup is concerning since this subgroup may have an increased likelihood of disease relapse when treated with adjuvant tamoxifen alone.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 3035.

Bortezomib Enhances the Efficacy of Fulvestrant by Promoting the Aggregation of the Estrogen Receptor in the Cytoplasm

Background: Aromatase inhibitors (AIs) are standard treatment for Estrogen Receptor (ER)+ breast cancers in post-menopausal women where the main source of estradiol comes from adipose tissue when the aromatase enzyme converts androgens to estrogens. However, in premenopausal women, functioning ovaries flood the body with estrogens, and aromatase inhibitors used alone offer no therapeutic benefit. In addition to tamoxifen and aromatase inhibitors, estrogen receptor down-regulators, are a third type of anti-estrogen. The first of this class to be FDA approved is Fulvestrant, which acts by promoting the proteosomal degradation of the ER. Like tamoxifen, fulvestrant binds directly to the ER but while tamoxifen has both antagonist and agonist effects on the ER, fulvestrant is a pure antagonist. Other important advantages of fulvestrant over tamoxifen are that 1) fulvestrant prevents the ER from binding DNA, 2) fulvestrant is not linked to increased risk of endometrial cancer, 3) fulvestrant promotes permanent degradation of the ER.The molecular machinery leading to the degradation of the ER in the nucleus following fulvestrant treatment is well described and correlates with its ubiquitination in the nucleus. A less well-recognized mechanism, is fulvestrant’s ability to promote the aggregation of the newly synthesized ER in the cytoplasm. Understanding that protein aggregates are toxic when not eliminated by the proteasome, we took advantage of this effect of fulvestrant to ask whether combining fulvestrant with the proteasome inhibitor Bortezomib could enhance the efficacy of Fulvestrant.Results: We found that bortezomib enhances the aggregation of the ER in the cytoplasm following treatment with fulvestrant. Further, these aggregates were found to be insoluble and to activate the unfolded protein response (UPR), a stress response that leads to cell death. Further, bortezomib is able to prevent the activation of cytoprotective responses linked to the acquisition of fulvestrant resistance. Furthermore, in a breast cancer mouse model of tamoxifen resistance, the combination induced tumor regression.Conclusion: We conclude that adding bortezomib to fulvestrant enhances its efficacy by taking advantage of a previously poorly recognized mechanism–fulvestrant’s induction of ER aggregation in the cytoplasm. Further, our data suggest that this strategy will block the ability of cells to acquired resistance to fulvestrant. Our group has developed a clinical trial that will test this combination.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 5142.

Wound Fluid Induces Cancer Cell Growth: A Mechanism for Recurrence?

Background: The process of wound healing after surgical resection of breast cancer may contribute to the development of local recurrence and possibly even metastases. Local recurrence after lumpectomy or mastectomy occurs most frequently near the surgical scar, leading to the hypothesis that the wound itself may promote the growth of residual disease. Some studies even suggest that removal of the primary tumor can accelerate progression of occult metastases. Two studies have shown that wound fluid can stimulate the growth of cancer cells and that differing cancer cell lines may be stimulated by differing wound fluid. A major criticism of these studies is that the activity of the wound fluid was compared to either the patient serum, which is likely less inflammatory than the wound fluid, or to serum free media. Thus, these studies did not define whether the inflammatory component of wound fluid alone is sufficient to stimulate cancer cell growth or whether the ability was specific to breast derived wound fluid. In this pilot study wound fluid was collected from 10 patients who had undergone unilateral mastectomy with abdominal flap reconstruction or bilateral mastectomy where one breast had known cancer and the contralateral did not. In the unilateral mastectomy patients, the fluid from the involved breast was compared to the fluid from the abdominal drain. In the bilateral mastectomy patients the fluid from the breast with cancer was compared with the fluid from the prophylactically removed breast. The effect of wound fluid on the growth of breast cancer cells was analyzed for each patient.Methods: Fluid from each breast and abdominal drain were collected 24 and 48 hours after surgery and their ability to promote growth of 6 different breast cancer cell lines was tested. In addition, the ability of the 48 hour wound fluid to stimulate colony formation of HBL-100 cells (ER-) on matrigel was established. The cytokine profile of the different wound fluid was also analyzed.Results: We found that when the ER – cells were cultured on matrigel, the breast derived fluid led to growth of invasive, branching colonies, while abdominal fluid from the same patient led to small round colonies. Further, we found that wound fluid derived from the breast where a tumor was present led to the formation of more invasive colonies than the wound fluid derived from the normal breast. Thus, we speculate that in addition to the normal cytokines and matrix metalloproteases associated with inflammation, breast wound fluid may contain additional proteins from the tumor bed microenvironment. In support of this model, we found that the protein composition of wound fluid varies from one site to another in the same patient.Conclusion: The biological activity and protein composition of wound fluid from the breast and abdomen is drastically different—such that breast wound fluid promotes growth and invasion of breast cancer cells. Thus, we hypothesize that residual disease may be stimulated to grow during the window of time after surgery when the wound fluid is produced. This transient stimulation may result in local recurrence if the nature of the residual disease is a foci cancer or acceleration of metastasis if the residual disease is disseminated into the surrounding lymph nodes or blood vessels.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 3146.

[Induced pluripotent stem cells (iPS cells)]

There is less than three years, the reprogramming of adult cells in induced pluripotent stem cells (iPS cells) has been added to the techniques producing natural or manufactured embryonic cells. Easier to obtain than these last, the human iPS cells are ethically irreproachable. They allow the study of many disorders at the cellular level and put at the disposal of pharmacologists a material of an exceptional interest. The improvement of the quality of their reprogramming is the object of active search all over the world. It is not utopian to hope that the iPS cells will quickly take a choice place in human cellular therapy.

How does increasingly plainer cigarette packaging influence adult smokers' perceptions about brand image? An experimental study

Background:

Cigarette packaging is a key marketing strategy for promoting brand image. Plain packaging has been proposed to limit brand image, but tobacco companies would resist removal of branding design elements.

Method:

A 3 (brand types) × 4 (degree of plain packaging) between-subject experimental design was used, using an internet online method, to expose 813 adult Australian smokers to one randomly selected cigarette pack, after which respondents completed ratings of the pack.

Results:

Compared with current cigarette packs with full branding, cigarette packs that displayed progressively fewer branding design elements were perceived increasingly unfavourably in terms of smokers’ appraisals of the packs, the smokers who might smoke such packs, and the inferred experience of smoking a cigarette from these packs. For example, cardboard brown packs with the number of enclosed cigarettes displayed on the front of the pack and featuring only the brand name in small standard font at the bottom of the pack face were rated as significantly less attractive and popular than original branded packs. Smokers of these plain packs were rated as significantly less trendy/stylish, less sociable/outgoing and less mature than smokers of the original pack. Compared with original packs, smokers inferred that cigarettes from these plain packs would be less rich in tobacco, less satisfying and of lower quality tobacco.

Conclusion:

Plain packaging policies that remove most brand design elements are likely to be most successful in removing cigarette brand image associations.

Mitochondrial protein quality control by the proteasome involves ubiquitination and the protease Omi

We report here that blocking the activity of the 26 S proteasome results in drastic changes in the morphology of the mitochondria and accumulation of intermembrane space (IMS) proteins. Using endonuclease G (endoG) as a model IMS protein, we found that accumulation of wild-type but to a greater extent mutant endoG leads to changes in the morphology of the mitochondria similar to those observed following proteasomal inhibition. Further, we show that wild-type but to a greater extent mutant endoG is a substrate for ubiquitination, suggesting the presence of a protein quality control. Conversely, we also report that wild-type but not mutant endoG is a substrate for the mitochondrial protease Omi but only upon inhibition of the proteasome. These findings suggest that although elimination of mutant IMS proteins is strictly dependent on ubiquitination, elimination of excess or spontaneously misfolded wild-type IMS proteins is monitored by ubiquitination and as a second checkpoint by Omi cleavage when the proteasome function is deficient. One implication of our finding is that in the context of attenuated proteasomal function, accumulation of IMS proteins would contribute to the collapse of the mitochondrial network such as that observed in neurodegenerative diseases. Another implication is that such collapse could be accelerated either by mutations in IMS proteins or by mutations in Omi itself.

Arctiin induces cell growth inhibition through the down-regulation of cyclin D1 expression

Arctiin is a major lignan constituent of Arctium lappa and has anti-cancer properties in animal models. It was recently reported that arctiin induces growth inhibition in human prostate cancer PC-3 cells. However, the growth inhibitory mechanism of arctiin remains unknown. Herein we report that arctiin induces growth inhibition and dephosphorylates the tumor-suppressor retinoblastoma protein in human immortalized keratinocyte HaCaT cells. We also show that the growth inhibition caused by arctiin is associated with the down-regulation of cyclin D1 protein expression. Furthermore, the arctiin-induced suppression of cyclin D1 protein expression occurs in various types of human tumor cells, including osteosarcoma, lung, colorectal, cervical and breast cancer, melanoma, transformed renal cells and prostate cancer. Depletion of the cyclin D1 protein using small interfering RNA-rendered human breast cancer MCF-7 cells insensitive to the growth inhibitory effects of arctiin, implicates cyclin D1 as an important target of arctiin. Taken together, these results suggest that arctiin down-regulates cyclin D1 protein expression and that this at least partially contributes to the anti-proliferative effect of arctiin.

Targeting the cytoplasmic and nuclear functions of signal transducers and activators of transcription 3 for cancer therapy

Signal transducers and activators of transcription (STAT) are a highly conserved family of transcription factors that are activated by phosphorylation in the cytoplasm, after which they translocate to the nucleus to regulate gene expression. Among the seven STATs, STAT3 is of particular interest due to its constitutive phosphorylation in a large proportion of human cancers and its ability to induce neoplastic transformation. Inhibition of STAT3 can reverse tumor growth in experimental systems while having few effects in normal cells. These findings have implicated STAT3 as a potentially important target for therapeutic intervention. In addition to its well-described role as a transcription factor, STAT3 has been found recently to have important effects in the cytoplasm. Collectively, these functions of STAT3 directly contribute to tumorigenesis, invasion, and metastasis. Given the potential importance of STAT3 as a target for cancer therapy, molecules have been developed that can block STAT3 function at a variety of steps. These drugs show promise as anticancer agents in model systems of a variety of common human cancers. Thus, elucidating the functions of STAT3 and developing agents to inhibit this protein remain important scientific and clinical challenges.

Skp2B stimulates mammary gland development by inhibiting REA, the repressor of the estrogen receptor

Skp2B, an F-box protein of unknown function, is frequently overexpressed in breast cancer. In order to determine the function of Skp2B and whether it has a role in breast cancer, we performed a two-hybrid screen and established transgenic mice expressing Skp2B in the mammary glands. We found that Skp2B interacts with the repressor of estrogen receptor activity (REA) and that overexpression of Skp2B leads to a reduction in REA levels. In the mammary glands of MMTV-Skp2B mice, REA levels are also low. Our results show that in virgin transgenic females, Skp2B induces lobuloalveolar development and differentiation of the mammary glands normally observed during pregnancy. As this phenotype is identical to what was observed for REA heterozygote mice, our observations suggest that the Skp2B-REA interaction is physiologically relevant. However, in contrast to REA(+/-) mice, MMTV-Skp2B mice develop mammary tumors, suggesting that Skp2B affects additional proteins. These results indicate that the observed expression of Skp2B in breast cancer does contribute to tumorigenesis at least in part by modulating the activity of the estrogen receptor.

Aspects pédiatriques de la maladie de Fabry

Fabry's disease is a rare X-linked inborn error of glycosphingolipid metabolism characterised by an abnormal lipid storage due to a defect of lysozomal alphagalactosidase. The consequence is a storage of glycosphingolipides in all tissues. This storage in vessels's endothelial cells is responsible, in males, for severe ischemic lesions leading to progressive kidney failure, cardiac and cerebral dysfunctions. Similarly, it involves ocular tissues, mainly the cornea, the conjunctiva and the lens. The corneal storage, known as cornea verticillata, is a clinical marker easy to recognize by slit lamp examination of the affected males and carrier females. The enzymatic activity of alphagalactosidase is reduced in tears. Characteristic lamellar bodies can be observed by electron microscopy study of a conjunctival biopsy. Until recently, treatment was limited to symptomatic management of pain, and end-stage complications of renal failure, cardiac or brain disease. Recent studies have demonstrated that enzyme replacement therapy by genetic engineering is now shown to be promising for affected patients.

Cyclin D1 Overexpression and Response to Bortezomib Treatment in a Breast Cancer Model

BACKGROUND

Cyclin D1 is frequently overexpressed in breast cancer, and its overexpression is, surprisingly, associated with improved survival. One potential mechanism for this association involves signal transducer and activator of transcription 3 (STAT3).

METHODS

Cyclin D1 and STAT3 expression were assessed in human tumors using microarray analysis and in breast cancer cell lines HBL100, T47D, MCF7, MDA-MB-453, and BT20 and in HBL100 and T47D cells stably overexpressing cyclin D1 using immunoblot analysis. Cyclin D1 protein was stabilized by treatment with the proteasome inhibitor bortezomib, and the effects on STAT3 expression in vitro was determined by using immunoblotting and on xenograft tumor growth and apoptosis in vivo was determined by using terminal deoxyuridine nick-end labeling assays. All statistical tests were two-sided.

RESULTS

Tumors with high cyclin D1 expression (n = 17) had low STAT3 expression (mean = 274 arbitrary units), and those with low cyclin D1 expression (n = 31) had high STAT3 expression (mean = 882 arbitrary units) (P<.001). In HBL100 and T47D parental and cyclin D1-overexpressing cells, cyclin D1 overexpression was also inversely associated with STAT3 expression, and cyclin D1 directly reduced the expression of STAT3. Stabilization of cyclin D1 protein by bortezomib treatment further amplified the cyclin D1-dependent repression of STAT3 in vitro and slowed tumor growth in vivo (week 7: untreated mean = 185.7 mm3 versus treated mean = 136.2 mm3, difference = 49.5 mm3, 95% confidence interval [CI] = 18 to 81 mm3, P = .007; week 8: untreated mean = 240.2 mm3 versus treated mean = 157.3 mm3, difference = 82.9 mm3, 95% CI = 9.1 to 156.7 mm3, P = .0014; and week 9: untreated mean = 256.4 mm3 versus treated mean = 170.2 mm3, difference = 86.2 mm3, 95% CI = 22.8 to 149.6 mm3, P = .006) and increased apoptosis (untreated mean = 19% versus treated mean = 54%, difference = 35%, 95% CI = 24.7% to 45.4%; P = .013) of xenograft tumors.

CONCLUSIONS

Cyclin D1 repression of STAT3 expression may explain the association between cyclin D1 overexpression and improved outcome in breast cancer. In addition, bortezomib can amplify the proapoptotic function of cyclin D1, raising the possibility that cyclin D1 levels may be a marker for predicting the response to this novel drug.

Vesicular roundness and compound release in PC-12 cells

The principal goals of this study were to establish a quantitative morphological analysis of spatial and regional properties of dense core vesicles, and to use this analysis to assess whether homotypic fusion is prominent in chronically treated PC-12 cells at elevated release levels. Simple computerized image processing of electron-micrographs provided the binary images of vesicular dense cores, whilst the artificial intelligence methods were needed to determine the vesicular membranes. As in the past, the presence of large, highly irregular vesicles, provided the morphological evidence of fused vesicles, but the irregularity of vesicular shape was assessed quantitatively-from its roundness. Free space of each vesicle was determined from the distance to its nearest-neighbor, or from the size of its Voronoi polygon. Within a Voronoi polygon, each point is closer to that vesicle than to any other vesicle. Large vesicles were not less round and did not have larger free space, as expected if they result from fusion of several smaller vesicles. In conclusion, we present a novel and rigorous morphological analysis of spatial and regional properties of dense core vesicles. The results demonstrate that the homotypic fusion is not prominent in PC-12 cells, before or following a chronic treatment that enhances release.

Differential expression of the F-box proteins Skp2 and Skp2B in breast cancer

Skp2 is an F-box protein involved in the ubiquitination and subsequent degradation of the cyclin-dependent kinase (Cdk) inhibitor p27. Skp2 has been reported to be overexpressed in a variety of cancer types and to correlate with poor prognosis. We have identified a novel isoform of Skp2 we named Skp2B, which differs from Skp2 only in the C-terminal domain and unlike Skp2 localizes to the cytoplasm. Here, we describe the relative expression of both Skp2 and Skp2B in breast cancer cell lines and in primary breast cancers using quantitative real time RT-PCR. We show that Skp2B mRNA is expressed 10-fold less than Skp2 mRNA in the immortalized but non-transformed breast cell line, 184B5. However, Skp2B is overexpressed as frequently as Skp2, and to higher levels than Skp2 in breast cancer cell lines and primary cancers. Further, we show that cytoplasmic staining is frequent in primary breast cancers. In addition, we found that xenografts expressing Skp2B grow faster than xenografts expressing low levels of Skp2B, and that this effect is independent of p27 degradation. These findings therefore suggest that Skp2B overexpression is also observed in breast cancers and identify Skp2B as a putative oncogene.

Cyclin-dependent kinase inhibition by the KLF6 tumor suppressor protein through interaction with cyclin D1

Kruppel-like factor 6 (KLF6) is a tumor suppressor gene inactivated in prostate and colon cancers, as well as in astrocytic gliomas. Here, we establish that KLF6 mediates growth inhibition through an interaction with cyclin D1, leading to reduced phosphorylation of the retinoblastoma protein (Rb) at Ser(795). Furthermore, introduction of KLF6 disrupts cyclin D1-cyclin-dependent kinase (cdk) 4 complexes and forces the redistribution of p21(Cip/Kip) onto cdk2, which promotes G(1) cell cycle arrest. Our data suggest that KLF6 converges with the Rb pathway to inhibit cyclin D1/cdk4 activity, resulting in growth suppression.

Alternative mammary oncogenic pathways are induced by D-type cyclins; MMTV-cyclin D3 transgenic mice develop squamous cell carcinoma

The three human D-type cyclins, cyclin D1, D2 and D3 share the ability to bind to and activate cdk4 and 6. MMTV-cyclin D1 transgenic mice develop mainly adenocarcinoma, while MMTV-cyclin D2 mice show a lack of alveologenesis during pregnancy and only develop carcinoma at low frequency. The effect of cyclin D3 overexpression in mammary glands remains hitherto unknown. We generated MMTV-cyclin D3 transgenic mice and report here that they develop exclusively squamous cell carcinoma. We show that although cyclin D3 transgene expression was detected early in puberty, postnatal development and mammary gland proliferation were normal in virgin animals. In contrast, multiparous mice develop multiple foci of abnormal growth that correspond to various stages of squamous metaplasia. Therefore, our results support a role for cyclin D3 in squamous differentiation. In addition, we found that p16 expression during involution is abolished, while p27 expression increased in MMTV-cyclin D3 mice, two modifications that have been reported in the other MMTV-D-type cyclin transgenic models. Our observations indicate that despite biochemical redundancy in vitro and in vivo, D-type cyclins promote distinct oncogenic pathways.

Cyclin d1 overexpression sensitizes breast cancer cells to fenretinide

PURPOSE

Fenretinide has shown promise in the chemoprevention of breast cancer, a tumor type in which the oncogene cyclin D1 is overexpressed frequently. We aimed at determining the effect of cyclin D1 level on the response to fenretinide treatment.

EXPERIMENTAL DESIGN

Stable clones of T47-D cells were created to overexpress cyclin D1 or a mutant of cyclin D1, injected in nude mice for xenograft formation, and the rate of tumor growth and tumor regression determined.

RESULTS

We show here that cells overexpressing cyclin D1 are significantly more sensitive to fenretinide than genetically matched cells that express low levels of cyclin D1, and that fenretinide prevents tumor formation arising from cyclin D1-overexpressing cells. Furthermore, we show that fenretinide is also able to promote the regression of cyclin D1-positive tumors. We also show that cells expressing a mutant of cyclin D1 that cannot bind to cdk4 are also more sensitive to fenretinide.

CONCLUSIONS

These results suggest that fenretinide may be particularly useful in the treatment of cyclin D1-positive breast cancers, and that the interaction between cyclin D1 and fenretinide is independent of cyclin D1 binding to cdk4.

MR temperature measurement in liver tissue at 0.23 T with a steady-state free precession sequence

MRI can be used for monitoring temperature during a thermocoagulation treatment of tumors. The aim of this study was to demonstrate the suitability of a 3D steady-state free precession sequence (3D Fast Imaging with Steady-State Precession, 3D TrueFISP) for MR temperature measurement at 0.23 T, and to compare it to the spin-echo (SE) and spoiled 3D gradient-echo (3D GRE) sequences. The optimal flip angle for the TrueFISP sequence was calculated for the best temperature sensitivity in the image signal from liver tissue, and verified from the images acquired during the thermocoagulation of excised pig liver. Factors influencing the accuracy of the measured temperatures are discussed. The TrueFISP results are compared to the calculated values of optimized SE and 3D GRE sequences. The accuracy of TrueFISP in the liver at 0.23 T, in imaging conditions used during thermocoagulation procedures, is estimated to be +/-3.3 degrees C for a voxel of 2.5 x 2.5 x 6 mm(3) and acquisition time of 18 s. For the SE and GRE sequences, with similar resolution and somewhat longer imaging time, the uncertainty in the temperature is estimated to be larger by a factor of 2 and 1.2, respectively.

Retinoic acid-mediated growth arrest requires ubiquitylation and degradation of the F-box protein Skp2

The mechanism by which all-trans retinoic acid (ATRA) leads to a G(1) arrest of the cell cycle remains unclear. We show here that the decrease in D-type cyclin levels observed following ATRA treatment correlates with an increase in the rate of cyclin D1 ubiquitylation in both T-47D and MCF-7 breast cancer cell lines. However, MCF-7 cells are more resistant to ATRA than T-47D cells indicating that cyclin D1 degradation is not sufficient for ATRA-mediated arrest. We found a striking difference between these cells in that while ATRA induces an elevation in the cdk inhibitor p27 in T-47D cells, this is not observed in the ATRA-resistant MCF-7 cells. Furthermore, we demonstrate that ATRA promotes the ubiquitylation of Skp2, an F-box protein that targets p27 for degradation. Moreover, overexpression of Skp2 in T-47D cells prevents accumulation of p27 and promotes resistance to ATRA. In addition, overexpression of cyclin D1 in T-47D cells also promotes ATRA resistance. We found that the mechanism of ATRA-induced ubiquitylation of cyclin D1 and Skp2 is independent of CUL-1 expression and that ATRA can rescue cyclin D1 degradation in the uterine cell line SK-UT-1, where D-type cyclins are stabilized due to a specific defect in proteolysis. These data suggest that ATRA induces a novel pathway of ubiquitylation and that the degradation of the F-box protein Skp2 is the mechanism underlying p27 accumulation and cyclin E-cdk2 inactivation following ATRA treatment.

MR monitoring of tumour thermal therapy

Thermal therapy of tumour including hyperthermia and thermal ablation by heat or cold delivery requires on line monitoring. Due to its temperature sensitivity, Magnetic Resonance Imaging (MRI) allows thermal mapping at the time of the treatment. The different techniques of MR temperature monitoring based on water proton resonance frequency (PRF), longitudinal relaxation time T1, diffusion coefficient and MR Spectroscopic Imaging (MRSI) are reviewed and debated. The PRF method appears the most widely used and the most efficient at high magnetic field in spite of important drawbacks. The T1 method is the easiest method of visualisation of qualitative temperature distribution and quantitative measurement seems possible in the tissue surrounding the tumour up to a temperature of 45-65 degrees C. Despite its high temperature sensitivity, application of the diffusion method in vivo is restricted due to its high motion sensitivity. The recent MRSI technique seems very promising provided acquisition times can be reduced. Results from the literature indicate that MR temperature monitoring in vivo can be achieved in vivo with a precision of about 3 degrees C in 13 s for a voxel of 16 mm3 (1.5 x 1.5 x 7 mm) in 1.5 T scanners.

A splice variant of Skp2 is retained in the cytoplasm and fails to direct cyclin D1 ubiquitination in the uterine cancer cell line SK-UT

Cyclin D1 is an important regulator of the transition from G1 into S phase of the cell cycle. The level to which cyclin D1 accumulates is tightly regulated. One mechanism contributing to the control of cyclin D1 levels is the regulation of its ubiquitination. SK-UT-1B cells are deficient in the degradation of D-type cyclins. We show here that p27, a substrate of the SCF(Skp2) ubiquitin ligase complex, is coordinately stabilized in SK-UT-1B cells. Further, we show that expression of Skp2 in SK-UT-1B cells rescues the cyclin D1 and p27 degradation defect observed in this cell line. These results therefore indicate that the SCF(Skp2) ubiquitin ligase complex affects the ubiquitination of cyclin D1. In addition, we show that SK-UT-1B cells express a novel splice variant of Skp2 that localizes to the cytoplasm and that cyclin D1 ubiquitination takes place in the nucleus. We propose that the translocation of Skp2 into the nucleus is required for the ubiquitination of cyclin D1 and that the absence of the SCF(Skp2) complex in the nucleus of SK-UT-1B cells is the mechanism underlying the ubiquitination defect observed in this cell line. Finally, our data indicates that differential splicing of F-box proteins may represent an additional level of regulation of the F-box mediated ubiquitination pathway.

MR monitoring of laser-induced lesions of the liver in vivo in a low-field open magnet: temperature mapping and lesion size prediction

The aims of this study were, firstly, to monitor temperature with magnetic resonance (MR) during laser ablations performed in pig livers in vivo in a low-field open scanner (0.23T) and, secondly, to study the feasibility of lesion size prediction. Spin-echo (SE) images of 29 sec acquired during laser applications allowed calculation of temperature maps using T1 and M(0) temperature sensitivity. Temperature was also measured with thermocouples. Images of prediction of tissue damage were calculated using temperature maps and Arrhenius model. T2W sequences were acquired after the ablations. Animals were sacrificed immediately. Lesions were photographed macroscopically. Lesion surfaces were measured and compared in T2W images, temperature images, damage prediction images, and macroscopic pictures. A correlation exists between temperature measured with MR and with thermocouples (rho = 0.878; P < 0.001, Spearman test). Mean surface of predicted damaged tissue is consistent with mean early necrosis measured in macroscopic pictures. Early T2W images underestimate mean necrosis size. J. Magn. Reson. Imaging 2001;13:42-49.

MR monitoring of laser-induced lesions of the liver in vivo in a low-field open magnet: temperature mapping and lesion size prediction

The aims of this study were, firstly, to monitor temperature with magnetic resonance (MR) during laser ablations performed in pig livers in vivo in a low-field open scanner (0.23T) and, secondly, to study the feasibility of lesion size prediction. Spin-echo (SE) images of 29 sec acquired during laser applications allowed calculation of temperature maps using T1 and M(0) temperature sensitivity. Temperature was also measured with thermocouples. Images of prediction of tissue damage were calculated using temperature maps and Arrhenius model. T2W sequences were acquired after the ablations. Animals were sacrificed immediately. Lesions were photographed macroscopically. Lesion surfaces were measured and compared in T2W images, temperature images, damage prediction images, and macroscopic pictures. A correlation exists between temperature measured with MR and with thermocouples (rho = 0.878; P < 0.001, Spearman test). Mean surface of predicted damaged tissue is consistent with mean early necrosis measured in macroscopic pictures. Early T2W images underestimate mean necrosis size. J. Magn. Reson. Imaging 2001;13:42-49.

Ubiquitination of free cyclin D1 is independent of phosphorylation on threonine 286

Cyclin D1 binds and regulates the activity of cyclin-dependent kinases (CDKs) 4 and 6. Phosphorylation of the retinoblastoma protein by cyclin D1.CDK4/6 complexes during the G(1) phase of the cell cycle promotes entry into S phase. Cyclin D1 protein is ubiquitinated and degraded by the 26 S proteasome. Previous studies have demonstrated that cyclin D1 ubiquitination is dependent on its phosphorylation by glycogen synthase kinase 3beta (GSK-3beta) on threonine 286 and that this phosphorylation event is greatly enhanced by binding to CDK4 (Diehl, J. A., Cheng, M. G., Roussel, M. F., and Sherr, C. J. (1998) Genes Dev. 12, 3499-3511). We now report an additional pathway for the ubiquitination of free cyclin D1 (unbound to CDKs). We show that, when unbound to CDK4, a cyclin D1-T286A mutant is ubiquitinated. Further, we show that a mutant of cyclin D1 that cannot bind to CDK4 (cyclin D1-KE) is also ubiquitinated in vivo. Our results demonstrate that free cyclin D1 is ubiquitinated independently of its phosphorylation on threonine 286 by GSK-3beta, suggesting that, as has been shown for cyclin E, distinct pathways of ubiquitination lead to the degradation of free and CDK-bound cyclin D1. The pathway responsible for ubiquitination of free cyclin D1 may be important in limiting the effects of cyclin D1 overexpression in a variety of cancers.

Inhibitory effect of p21 in MCF-7 cells is overcome by its coordinated stabilization with D-type cyclins

Coordinated accumulation of cyclin D1 and D3 is observed in 15% of primary breast cancers and in the breast cancer cell line MCF-7 this simultaneous overexpression is due to a defect in their ubiquitin-mediated proteolysis. The F-box protein Skp2 is a component of an SCF ubiquitin ligase complex and can associate with cyclin D1 and the cdk inhibitor p21 (Zhong-Kang et al., 1998). We extend this observation and show that cyclin D3 can also associate with Skp2 suggesting that cyclins D1, D3 and p21 may share the same SCF complex. In agreement with this hypothesis we report here that in primary breast cancers and in MCF-7 cells where cyclins D1 and D3 are elevated the level of p21 is also elevated. Further, we demonstrate that the turnover of p21 protein is reduced in MCF-7 cells. We show that p21 is active as a cdk inhibitor in this cell line but that the presence of elevated levels of cyclin D3 titrates p21 away from cyclin D1-cdk4/6 complexes and cdk2 complexes resulting in increased kinase activities. Our results suggest that a defect in the SCF complex may occur in 15-20% of breast cancers and that the resulting coordinated elevation of cyclins D1 and D3 overcomes the inhibition of cell cycle progression by p21. We propose that in the context of cyclins D1 and D3 overexpression, p21 may promote cell cycle progression.

Cyclin D1 and D3 associate with the SCF complex and are coordinately elevated in breast cancer

D-type cyclins are important cell cycle regulators that promote cellular proliferation in response to growth factors by inactivation of the retinoblastoma protein (Rb). Cyclin D1 has been shown to be overexpressed in several cancer types and to act as an oncogene in breast cancers. As D-type cyclins are rate limiting for progression into S phase, the level at which they accumulate must be carefully regulated. Several mechanisms leading to overexpression of cyclin D1 have been reported including amplification, translocation and stabilization of the mRNA. Here, we present data showing elevated cyclin D1 protein in breast cancer samples in the absence of elevated mRNA level. Further, we found that in these cases, cyclin D3 protein also accumulates and that the coordinate increase in cyclin D1 and D3 occurs in 15% (7/47) of breast cancers. In addition we show that blocking the activity of the 26S proteosome results in the accumulation of cyclin D1 and D3, that both D-type cyclins are ubiquitinated and associate with Cul-1, a component of the SCF ubiquitin ligase complex. Finally, we show that the coordinated elevation of cyclin D1 and D3 is also observed in the breast cell line MCF-7 and demonstrate that the degradation of cyclin D1 and D3 is deficient in this cell line. These results indicate that cyclin D1 and cyclin D3 share a common mechanism of degradation and we propose that the coordinate increase of D-type cyclins observed in primary breast cancers reflects a defect in their proteolysis.

DNA damage inhibits proteolysis of the B-type cyclin Clb5 in S. cerevisiae

Cell cycle progression is mediated by waves of specific cyclin dependent kinases (CDKs) in all eukaryotes. Cyclins are degraded by the ubiquitin pathway of proteolysis. The recent identification of several components of the cyclin proteolysis machinery has highlighted both the importance of proteolysis at multiple transition points in the cell cycle and the involvement of other substrates degraded by the same machinery. In this study, we have investigated the effects of DNA damage on the cyclin proteolytic machinery in Saccharomyces cerevisiae. We find that the half-life of the B-type cyclin Clb5 is markedly increased following DNA damage while that of G1 cyclins is not. This effect is independent of cell cycle phase. Clb5 turnover requires p34CDC28 activity. Stabilisation of Clb5 correlates with an increase in tyrosine phosphorylation of p34CDC28, but stabilisation does not require this tyrosine phosphorylation. The stabilisation is independent of the checkpoint genes Mec1 and Rad53. These observations establish a new link between the regulation of proteolysis and DNA damage.

Fluorescence-assisted mismatch analysis (FAMA) for exhaustive screening of the alpha-galactosidase A gene and detection of carriers in Fabry disease

We used the fluorescence-assisted mismatch analysis (FAMA) method to screen rapidly the alpha-galactosidase A gene in patients with Fabry disease in order to identify unknown mutations and help define genotype-phenotype correlations in this X-linked lysosomal storage disorder. Chemical cleavage at mismatches on heteroduplex DNA end-labeled with strand-specific fluorescent dyes, reliably detects sequence changes in DNA fragments of up to 1.5 kb and locates them precisely. Exhaustive scanning of the alpha-galactosidase gene was accomplished on four polymerase chain reaction-generated amplicons, covering all seven exons, the exon-intron boundaries, and 700 bp of 5'-flanking sequence. Mutations were identified in each of the 15 patients studied from nine unrelated kindreds. Among the seven previously undescribed sequence changes, three are obviously pathogenic because they lead to premature protein termination. The other four, a splicesite mutation and three missense mutations, were the only changes found upon complete scanning of the gene and its promoter. In addition, FAMA also detects female heterozygous carriers more dependably than direct sequencing, and thus provides a valuable diagnostic test. In Fabry disease, this molecular criterion is especially important for genetic counseling since heterozygotes can be asymptomatic and their enzymatic values within the normal range.