Abstract S6-10: Identification of a Novel Tumor Suppressor Network Reveals a Role for Proto-Oncogenic Receptor Tyrosine Kinases in Triple-Negative Breast Cancer

Breast cancer is a collection of diseases with distinct clinical behaviors and underlying genetic causes. Triple-negative breast cancer (TNBC) is a common subtype of breast cancer that confers a particularly poor prognosis and is refractory to current targeted therapies. Unfortunately, the molecular determinants driving this aggressive malignancy are poorly understood. Using an unbiased genetic screen, we have identified a novel tumor suppressor network that governs proliferation and transformation of TNBCs in vitro and in vivo. We define SECT21 as a core component in this network and a commonly inactivated tumor suppressor in TNBC. SECT21 is a potent suppressor of human mammary epithelial cell proliferation and transformation. SECT21 function is frequently compromised in human TNBCs by inactivating mutations, deletion, or loss of protein expression. Mechanistically, SECT21 is a tyrosine phosphatase that suppresses cellular transformation by interacting with and inhibiting several oncogenic receptor tyrosine kinases including HER2, EGFR, and PDGFR. Notably, the tumorigenic and metastatic potential of SECT21-deficient TNBCs is severely impaired by restoring SECT21 function or by inhibiting kinase targets of SECT21, suggesting that TNBCs are dependent on the proto-oncogenic tyrosine kinases constrained by SECT21. Collectively, these data identify SECT21 as a commonly inactivated tumor suppressor and provide a rationale for combinatorially targeting tyrosine kinases in TNBC and other cancers based on their profile of tyrosine phosphatase activity.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr S6-10.

Pollen limitation of female reproductive success at fine spatial scale in a gynodioecious and wind-pollinated species, Beta vulgaris ssp. maritima

In sexually polymorphic plants, the spatial distribution of sexes is usually not random. Local variation in phenotype frequencies is expected to affect individual fitness of the different phenotypes. For gynodioecious species, with co-occurrence of hermaphrodites and females, if sexual phenotypes are structured in space and pollen flow is spatially restricted, local pollen availability should vary among patches. Female fitness may thus be low when hermaphrodites are locally rare. To test this hypothesis, we analysed how the reproductive output of females varied among patches within two natural study sites of the gynodioecious wind-pollinated Beta vulgaris ssp. maritima. Plants growing in female-biased areas and experiencing pollen limitation were found to have low fruit and seed sets but did not reallocate resources towards better offspring. Our results show that fine-scale processes influence individual fitness and the evolution of sex ratio in sexually polymorphic plants.

[Imaging of non-traumatic and non-tumoral cord lesions]

There is a wide range of spinal cord pathologies (vascular, inflammatory, infectious, metabolic, degenerative). They present clinically as acute partial or complete cord syndromes, or chronic myelopathies (more than 4 weeks in duration). MRI examination should be undertaken with a very strict protocol. Spinal cord lesions should be evaluated with regards to their T1W and T2W signal characteristics, involvement of grey and/or white matter, axial and sagittal extension, cord volume changes, contrast uptake and associated lesions (perimedullary, radicular or brain). The correlation of MR imaging features with clinical and biological data (blood and CSF) should suggest a differential diagnosis.

[Behavioral disorders in Parkinson's disease: from pathophysiology to the mastery of dopaminergic treatment]

INTRODUCTION

Behavioral changes in Parkinson's disease are complex and their pathophysiology is not yet fully understood. The dopaminergic system seems to play a major role and most of the behavioral disorders in Parkinson's disease can be classified into either hypodopaminergic if related to the disease itself or hyperdopaminergic if related to dopaminergic treatment.

STATE OF THE ART

Subthalamic stimulation, which enables withdrawal of dopaminergic medication at an advanced stage in the disease, provides a model for the study of certain nonmotor, dopamine-sensitive symptoms. Such a study has shown that apathy, which is the most frequent behavioral problem in Parkinson's disease, is part of a much broader hypodopaminergic behavioral syndrome which also includes anxiety and depression. Nonmotor fluctuations--essential fluctuations in the patient's psychological state--are an expression of mesolimbic denervation, as shown in positron emission tomography. Drug-induced sensitization of the denervated mesolimbic system accounts for hyperdopaminergic behavioral problems that encompass impulse control disorders that can be alternatively classified as behavioral addictions. The association of impulse control disorders and addiction to the dopaminergic medication has been called dopamine dysregulation syndrome. While L-dopa is the most effective treatment for motor symptoms, dopamine agonists are more effective in improving the nonmotor levodopa-sensitive symptoms. On the other hand, L-dopa induces more motor complications and dopamine agonist more behavioral side effects. There is increasing data and awareness that patients' quality of life appears to be dictated by hypo- and hyperdopaminergic psychological symptoms stemming from mesolimbic denervation and dopaminergic treatment rather than by motor symptoms and motor complications related to nigrostriatal denervation and dopaminergic treatment.

PERSPECTIVES

Better management requires knowledge of the clinical syndromes of hyper- and hypodopaminergic behaviors and nonmotor fluctuations, a better understanding of their underlying mechanisms and the development of new evaluation tools for these nonmotor symptoms.

CONCLUSIONS

The neurologist who strives to gain mastery of dopaminergic treatment needs to fine tune the dosage of levodopa and dopamine agonists on an individual basis, depending on the presence of motor and nonmotor signs respectively.

Unrecognized dural puncture during epidural analgesia in obstetrics later confirmed by brain imaging

Accidental dural puncture is a well-recognized complication of obstetric epidurals that can potentially incapacitate the patient. Unrecognized dural puncture during epidural administration can lead to a delay in therapeutic intervention resulting in potentially serious complications. We report a case of a parturient who developed disabling intracranial hypotension and diplopia following accidental dural puncture during apparently uneventful epidural catheter insertion. Magnetic resonance neuroimaging was performed to confirm the diagnosis, and direct clinical management. We also discuss the role of neuroimaging in the investigation of postpartum headache.

Treatment of proximal femur infections with antibiotic-loaded cement spacers

In case of periprosthetic hip infections the implantation of antibiotic-loaded PMMA spacers is accepted for an adequate treatment option. Although their indication for the treatment of destructive, bacterial infections of the proximal femur would make sense, literature data are scarce. Hence, the aim of this study was to evaluate the efficacy of antibiotic-impregnated spacers in the treatment of proximal femur infections. In 10 consecutive patients (5 M/ 5 F, mean age 66 y.) with bacterial proximal femur infections, a femoral head/neck resection was prospectively performed with a subsequent implantation of an antibiotic-loaded spacer. The joint-specific outcome was evaluated by the Merle d'Aubigne and the Mayo hip score, the general outcome by SF-36. The time periods were divided into "infection situation", "between stages" and meanly 1 year "after prosthesis implantation". The spacers were meanly implanted over 90 [155-744] days. In all cases an infection eradication could be achieved. After infection eradication, a prosthesis implantation was performed in 8 cases. The general scores showed significant increases at each time period. With regard to the dimension "pain", both scores demonstrated a significant increase between "infection situation" and "between stages", but no significance between "between stages" and "after prosthesis implantation". Spacers could be indicated in the treatment of proximal femur infections. Besides an infection eradication, a pain reduction is also possible.

Clinical and molecular features of mitochondrial DNA depletion due to mutations in deoxyguanosine kinase

Published mutations in deoxyguanosine kinase (DGUOK) cause mitochondrial DNA depletion and a clinical phenotype that consists of neonatal liver failure, nystagmus and hypotonia. In this series, we have identified 15 different mutations in the DGUOK gene from 9 kindreds. Among them, 12 have not previously been reported. Nonsense, splice site, or frame-shift mutations that produce truncated proteins predominate over missense mutations. All patients who harbor null mutations had early onset liver failure and significant neurological disease. These patients have all died before 2-years of age. Conversely, two patients carrying missense mutations had isolated liver disease and are alive in their 4th year of life without liver transplant. Five subjects were detected by newborn screening, with elevated tyrosine or phenylalanine. Consequently, this disease should be considered if elevated tyrosine is identified by newborn screening. Mitochondrial DNA content was below 10% of controls in liver in all but one case and modestly reduced in blood cells. With this paper a total of 39 different mutations in DGUOK have been identified. The most frequent mutation, c.763_c.766dupGATT, occurs in 8 unrelated kindreds. 70% of mutations occur in only one kindred, suggesting full sequencing of this gene is required for diagnosis. The presentation of one case with apparent viral hepatitis, without neurological disease, suggests that this disease should be considered in patients with infantile liver failure regardless of the presence of neurological features or apparent infectious etiology.