Genomic imprinting in plants

Genomic imprinting, though most extensively studied in mammals, has long been known to perform an important role in seed development in flowering plants. In this chapter, an overview of what is known to date about genomic imprinting in flowering plants and how this knowledge came into being will be given.

Modalities of prescription of aromatase inhibitors (AI) in adjuvant therapy for postmenopausal women with HR+ breast cancer: Analysis of daily practices in France

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Background: Aromatase inhibitors (AIs) are widely used as adjuvant therapy for HR+ breast cancer. This survey is an overview of clinical daily practices in France Methods: Multicentric survey conducted in October 2008 by Internet among a sample of 293 physicians specialized in breast cancer management (oncologists, radiotherapists, surgeons) prescribing adjuvant AIs in post-menopausal patients with HR+ breast cancer Results: When started upfront, 87% of physicians expressed that the optimal duration of AIs treatment is 5 years, and 7 % more than 5 years. Nevertheless only, 33% of physicians inform their patients of a total duration of AIs therapy of 5 years, and 66% of a possible adjustment according to the evolution of the scientific knowledge during the five years. AIs are prescribed after the end of chemotherapy by 97% of physicians, after the end of radiotherapy by 83%, and during radiotherapy by 15%. When started after two years of tamoxifen, 71 % of physicians expressed that the optimal duration of AIs treatment is 3 years, 22% 5 years, and 3% more than five years. When started after five years of tamoxifen, 48% of physicians expressed that the optimal duration of AIs treatment is less than three years, 15% 3 years, 15% 5 years, and 2% more than five years. The optimal duration of treatment with aromatase inhibitors is still subject to question for 73% of the physicians interviewed Conclusions: In France, most physicians declared an optimal duration of treatment with aromatase inhibitors in adjuvant setting in HR+ breast cancer in line with guidelines and/or approved indications. However, the optimal duration of treatment is still subject to question for many physicians

No significant financial relationships to disclose.

Specimen radiography as predictor of resection margin status in non-palpable breast lesions

AIM

This study aimed to evaluate the role of specimen radiography in predicting margin status for non-palpable breast malignancies.

METHODS

We retrospectively reviewed the clinical and pathological data together with specimen radiographs of 164 women with ductal carcinoma in situ, who were referred to our centre between January 1997 and December 2000. In all cases microcalcifications were discovered on mammography. Lesions were localized preoperatively using a guide-wire. Specimen radiography findings and clinicopathological data were correlated with pathological findings.

RESULTS

Findings comprised 122 pure ductal carcinomas in situ (74%) and 42 mixed carcinomas, both infiltrating and in situ (26%). On the specimen radiographs, the lesions were close (<1mm) to one edge of the lumpectomy in 34 (21%) cases. Histologically, there were 103 positive resection margins (<1mm, 63%) and only 61 negative margins (> or =1mm, 37%). On univariate analysis, factors associated with positive resection margins were found to be distance from microcalcifications to edge of lesion on specimen radiographs, and radiological multifocality. On multivariate analysis (logistic regression), a radiological margin <5mm and multifocality were the only risk factors for close histological margins. Radiological margins were not associated with surgical findings.

CONCLUSION

Our results demonstrate that there is a correlation between specimen radiographs and histological results. The clinical relevance of this should be evaluated in a prospective study.

Genomic imprinting in plants and mammals: how life history constrains convergence

In both flowering plants and mammals, DNA methylation is involved in silencing alleles of imprinted genes, but surprising differences in imprinting control are emerging between the two taxa which may be traced to differences in their life cycles. Imprinted gene expression in plants occurs in the endosperm, a separate fertilisation product which transmits nutrients to the embryo and does not contribute a genome to the next generation. Regulation of expression of the known imprinted genes in Arabidopsis involves a cascade of gene expression beginning in the gametophyte, a haploid life phase interposed between the meiotic products and the gametes, which evolved from free-living organisms that constitute the dominant life phase of lower plants. Although the gametophytes of flowering plants are highly reduced they still express large numbers of genes, perhaps reflecting their evolutionary legacy, and which may now be recruited for control of imprinting. Strikingly, the genes at the top of the expression cascade appear to be specifically activated by demethylation, rather than targeted for silencing. Unlike in mammals, there is no evidence for global resetting of methylation in plants, and although imprinting involves the activity of a maintenance methyltransferase, de novo methyltransferases do not appear to be required. Plants do not set aside a germline; instead the cells that undergo meiosis to produce gametophytes differentiate in the adult plant during flower development. Both the late differentiation of the lineage producing germ cells, and the extent of gene expression during the haploid phase, may be incompatible with global resetting of methylation. Resetting may be unnecessary in any case because the adult plant expresses imprinted loci either biallelically or not at all, suggesting there is no chromosomal memory of parent-of-origin in the lineage that produces the gametophytes. Thus several features of the plant life cycle may account for the different strategies used by plants and animals to regulate parent-specific gene expression.

TETRASPORE encodes a kinesin required for male meiotic cytokinesis in Arabidopsis

A key step in pollen formation is the segregation of the products of male meiosis into a tetrad of microspores, each of which develops into a pollen grain. Separation of microspores does not occur in tetraspore (tes) mutants of Arabidopsis thaliana, owing to the failure of male meiotic cytokinesis. tes mutants thus generate large 'tetraspores' containing all the products of a single meiosis. Here, we report the positional cloning of the TES locus and details of the role played by the TES product in male cytokinesis. The predicted TES protein includes an N-terminal domain homologous to kinesin motors and a C-terminus with little similarity to other proteins except for a small number of plant kinesins. These include the Arabidopsis HINKEL protein and NACK1 and two from tobacco (Nishihama et al., 2002), which are involved in microtubule organization during mitotic cytokinesis. Immunocytochemistry shows that the characteristic radial arrays of microtubules associated with male meiotic cytokinesis fail to form in tes mutants. The TES protein therefore is likely to function as a microtubule-associated motor, playing a part either in the formation of the radial arrays that establish spore domains following meiosis, or in maintaining their stability.

The epigenetic basis of gender in flowering plants and mammals

What makes a sperm male or an egg female, and how can we tell? A gamete's gender could be defined in many ways, such as the sex of the individual or organ that produced it, its cellular morphology, or its behaviour at fertilization. In flowering plants and mammals, however, there is an extra dimension to the gender of a gamete--due to parental imprinting, some of the genes it contributes to the next generation will have different expression patterns depending on whether they were maternally or paternally transmitted. The non-equivalence of gamete genomes, along with natural and experimental modification of imprinting, reveal a level of sexual identity that we describe as 'epigender'. In this paper, we explore epigender in the life history of plants and animals, and its significance for reproduction and development.

Parent-of-origin effects on seed development in Arabidopsis thaliana require DNA methylation

Some genes in mammals and flowering plants are subject to parental imprinting, a process by which differential epigenetic marks are imposed on male and female gametes so that one set of alleles is silenced on chromosomes contributed by the mother while another is silenced on paternal chromosomes. Therefore, each genome contributes a different set of active alleles to the offspring, which develop abnormally if the parental genome balance is disturbed. In Arabidopsis, seeds inheriting extra maternal genomes show distinctive phenotypes such as low weight and inhibition of mitosis in the endosperm, while extra paternal genomes result in reciprocal phenotypes such as high weight and endosperm overproliferation. DNA methylation is known to be an essential component of the parental imprinting mechanism in mammals, but there is less evidence for this in plants. For the present study, seed development was examined in crosses using a transgenic Arabidopsis line with reduced DNA methylation. Crosses between hypomethylated and wild-type diploid plants produced similar seed phenotypes to crosses between plants with normal methylation but different ploidies. This is consistent with a model in which hypomethylation of one parental genome prevents silencing of alleles that would normally be active only when inherited from the other parent - thus phenocopying the effects of extra genomes. These results suggest an important role for methylation in parent-of-origin effects, and by inference parental imprinting, in plants. The phenotype of biparentally hypomethylated seeds is less extreme than the reciprocal phenotypes of uniparentally hypomethylated seeds. The observation that development is less severely affected if gametes of both sexes (rather than just one) are ‘neutralized’ with respect to parent-of-origin effects supports the hypothesis that parental imprinting is not necessary to regulate development.

Factors predicting for efficacy and safety of docetaxel in a compassionate-use cohort of 825 heavily pretreated advanced breast cancer patients

PURPOSE

To identify predictive factors for efficacy and safety in advanced breast cancer (ABC) patients treated in the French compassionate-use docetaxel program.

PATIENTS AND METHODS

A total of 825 ABC patients treated with docetaxel (100 mg/m(2) every 3 weeks) were source-reviewed and analyzed for prognostic factors associated with overall response rate (ORR), time to treatment failure (TTF), overall survival (OS), febrile neutropenia, mucositis, and severe fluid retention syndrome by univariate and multivariate analysis.

RESULTS

The ORR was 22.9% (95% confidence interval, 20.2% to 26.2%). The median TTF and OS were 4.0 and 9.8 months, respectively. By multivariate analysis, secondary anthracycline-resistant disease was significantly associated (P <. 05) with lower ORR and shorter TTF and OS, whereas anthracycline-refractory disease was associated with shorter OS. Poor performance status was associated with lower ORR, shorter TTF, and shorter OS. Liver dysfunction (transaminase levels > 1.5 times the upper limit of normal [ULN] and alkaline phosphatase [AP] level > three times ULN) and time since first relapse less than 24 months were associated with shorter TTF and OS. Other significant correlations included the following: elevated CA 15-3 serum level with lower ORR; more than two involved sites, and minor transaminase and AP level abnormalities with shorter OS; and no previous chemotherapy for ABC with shorter TTF. According to multivariate analysis, ORR, TTF, and OS were not decreased in patients with liver metastases but without liver dysfunction.

CONCLUSION

Docetaxel activity was maintained in heavily pretreated ABC patients and in those with liver metastasis; docetaxel must be used cautiously, however, in patients with liver dysfunction in whom high morbidity risk necessitates strict adherence to dose-adaptation guidelines.

Efficacy and safety of docetaxel (Taxotere) in heavily pretreated advanced breast cancer patients: the French compassionate use programme experience

The aim of this investigation was to assess retrospectively docetaxel safety and efficacy in advanced breast cancer patients in a French compassionate use programme. Patients had received > 1 prior chemotherapy regimen for advanced disease, were either anthracycline-resistant (that is progressed within 6 months after anthracycline-based chemotherapy) or had received the maximum cumulative dose. The recommended docetaxel dose was 100 mg/m2/cycle (75 mg/m2 in case of liver function impairment: transaminases > 1.5 x upper limit of normal (ULN), alkaline phosphatases > 3 x ULN). Between August 1993 and December 1995, 889 patients were treated in 67 French centres, of whom 870 were evaluable for safety and 825 were evaluable for patient and treatment characteristics and efficacy. 20.5% (of the 825 patients evaluable for baseline characteristics) had poor performance status (PS > or = 2), 49.3% liver metastasis and 9.6% biological liver dysfunction. 98.4% had been previously treated by anthracyclines, 50.8% had resistant disease and 37.1% had received > 2 prior palliative chemotherapy lines. The most frequent severe toxicity, febrile neutropenia (reported in 223/870 (25.6%) patients evaluable for safety), caused 10 deaths, 6 of these being patients with severe liver impairment before inclusion. Fluid retention syndrome and other common non-haematological toxicities were well tolerated. 3.1% (28/889) of all patients and 11.4% of those with liver dysfunction, died from treatment-related causes. The overall response rate in 825 assessable patients was 22.9% (95% confidence interval (CI): 20.2-26.2%). Median time to treatment failure was 4 months (95% CI: 3.6-4.3) and median survival was 9.8 months (95% CI: 8.8-10.7). This report on the largest series of unselected advanced breast cancer patients treated with docetaxel, supports previous phase II studies, confirming docetaxel's utility in patients relapsing after failing anthracycline-containing palliative chemotherapy.

Parent-of-origin effects on seed development in Arabidopsis thaliana

Many flowering plants are polyploid, but crosses between individuals of different ploidies produce seeds that develop abnormally and usually abort. Often, seeds from interploidy crosses develop differently depending on whether the mother or father contributes more chromosome sets, suggesting that maternal and paternal genomes are not functionally equivalent. Here we present the first cytological investigation of seed development following interploidy crosses in Arabidopsis thaliana. We find that crosses between diploid and tetraploid plants in either direction, resulting in double the normal dose of maternal or paternal genomes in the seed, produce viable seeds containing triploid embryos. However, development of the seed and in particular the endosperm is abnormal, with maternal and paternal genomic excess producing complementary phenotypes. A double dose of maternal genomes with respect to paternal contribution inhibits endosperm development and ultimately produces a smaller embryo. In contrast, a double dose of paternal genomes promotes growth of the endosperm and embryo. Reciprocal crosses between diploids and hexaploids, resulting in a triple dose of maternal or paternal genomes, produce seeds that begin development with similar but more extreme phenotypes than those with a double dose, but these invariably abort. One explanation of our observations is that seeds with maternal or paternal excess contain different doses of maternally or paternally expressed imprinted loci affecting endosperm development.

TETRASPORE is required for male meiotic cytokinesis in Arabidopsis thaliana

In flowering plants, male meiosis occurs in the microsporocyte to produce four microspores, each of which develops into a pollen grain. Here we describe four mutant alleles of TETRASPORE (TES), a gene essential for microsporocyte cytokinesis in Arabidopsis thaliana. Following failure of male meiotic cytokinesis in tes mutants, all four microspore nuclei remain within the same cytoplasm, with some completing their developmental programmes to form functional pollen nuclei. Both of the mitotic divisions seen in normal pollen development take place in tes mutants, including the asymmetric division required for the differentiation of gametes; some tes grains perform multiple asymmetric divisions in the same cytoplasm. tes pollen shows a variety of abnormalities subsequent to the cytokinetic defect, including fusion of nuclei, formation of ectopic internal walls, and disruptions to external wall patterning. In addition, ovules fertilized by tes pollen often abort, possibly because of excess paternal genomes in the endosperm. Thus tes mutants not only reveal a gene specific to male meiosis, but aid investigation of a wide range of processes in pollen development and function.

Locally advanced breast cancer: contrast-enhanced subtraction MR imaging of response to preoperative chemotherapy

PURPOSE

To determine the value of contrast material-enhanced subtraction magnetic resonance (MR) imaging in assessment of response to chemotherapy in locally advanced breast cancer.

MATERIALS AND METHODS

Eighteen women treated with chemotherapy because of locally advanced breast cancer underwent preoperative MR examination including both routine and dynamic MR sequences after injection of gadolinium tetraazacyclododecanetetraacetic acid. Any early contrast enhancement, concomitant with early vascular enhancement during the dynamic MR study, was considered pathologic.

RESULTS

Dynamic MR studies showed early contrast enhancement in all women with residual tumor except one with nodular residual tumor. Histopathologic analysis and dynamic MR images of contrast-enhanced lesions correlated well, but in one patient, intraductal extension was not seen on MR images, and in another, additional isolated tumor cells were seen in the histologic specimen. Subtraction images always facilitated visualization of vascular and pathologic contrast enhancement.

CONCLUSION

Dynamic MR contrast-enhanced subtraction studies are useful in assessment of residual tumor after chemotherapy.

Phase II trial of methotrexate-FAM (m-FAM) in adenocarcinoma of unknown primary

Nineteen patients with adenocarcinoma of unknown primary were treated with the m-FAM regimen, consisting of methotrexate 50 mg/m2 days 0, 28; 5-fluorouracil 600 mg/m2 days 1, 8, 29, 36; Adriamycin 30 mg/m2 days 1, 29; and mitomycin-C 10 mg/m2 day 1. All drugs were recycled every 56 days. No complete responses were seen. Seven patients (37%) achieved partial remission for a median duration of 11 months. An additional nine patients (47%) had stable disease for a median duration of 6 months. Median survival for responders was 16 months and was 10 months for those with stable disease. Toxicity was acceptable. This Phase II study attempted to evaluate the clinical impact of the pharmacological modulation of 5-fluorouracil with methotrexate, the goal being improvement of the results of FAM alone in adenocarcinoma of unknown primary. However, the addition of methotrexate, at least in the schedule employed in this study, did not appear superior to FAM.

Clinical and radiologic analysis of 13 cases of primary neuroectodermal tumors of bone

Radiographs and clinical charts were reviewed in a series of 13 cases of primary neuroectodermal bone tumors, involving 9 males and 4 females, aged from 3 to 32 years (average: 15 years). The average delay between the onset and diagnosis was 5 months. Fever and other systemic symptoms were present in 6 cases; in 4 cases a fracture was the mode of presentation. Seven patients had metastases (4 involving bone) at the time of presentation. Only one patient is still alive after 5 years. In the 10 patients who died as a direct result of the tumor, death occured on average 8 months following diagnosis if metastases were present initially, and 36 months after the diagnosis otherwise. Tumors predominantly involved the leg (7 cases), the pelvis (2 cases), and the humerus (2 cases), the involvement being both diaphyseal and metaphyseal. The radiologic appearance is that of an aggressive, poorly demarcated tumor, with cortical destruction, periosteal reaction and soft tissue invasion. Comparison with Ewing sarcoma shows little radiologic or clinical difference, except for a poorer prognosis in neuroectodermal bone tumors. Both bone tumors may have a similar neuroectodermal origin, with Ewing sarcoma representing the undifferentiated variety.

Cardiac metastases. Case report on an isolated cardiac metastasis of a myxoid liposarcoma

This report describes an isolated case of cardiac metastasis of a myxoid liposarcoma that was successfully resected by surgery after clinical and ultrasound diagnosis. Although cardiac metastases are rarely diagnosed during patients' lifetimes, a search should be made for such lesions whenever cardiac disorders appear suddenly in cancer patients. Echocardiography appears to be one of the best investigative techniques for such purposes. Despite generally poor therapeutic results, surgical resection occasionally permits long periods of survival.

Cis platine (CDDP) in continuous intravenous ambulatory infusion: a new method of administration

Twenty-three patients with metastatic tumors received multiple chemotherapy regimens which included CIS platine (CDDP) by continuous ambulatory infusion for 4 successive days at a rate of 25 mg/m2/day repeated every 4 weeks. Continuous infusion was provided by an external disposable pump, the "Infusor," which delivers the drug in a volume of 48 ml at a constant rate of 2 ml/hour, in conjunction with oral hydration and antiemetics. No incident detrimental to the patient was recorded. The average duration of the infusions was 23 hr. Only 22% of the patients had minor nausea and vomiting, and 1 case of functional renal insufficiency (4%) was easily corrected by simple intravenous hydration. A randomized study is ongoing to compare continuous perfusion with standard infusion for efficiency, side effects and response rate. Patients with "Infusor" are treated at home under Minitel supervision.

Phase II trial of elliptinium in advanced renal cell carcinoma

Forty patients with advanced renal cell carcinoma were treated with elliptinium by a weekly infusion of 100 mg/m2. Of 38 evaluable patients, five had an objective response (13.2%). Average response duration was 8 months (range, 5-11). The major dose-limiting toxic effect was induction of antielliptinium antibodies, with the risk of intravascular hemolysis. Elliptinium has modest activity in advanced renal cell cancer and does not produce myelosuppression.