Abstract P4-22-12: Ribociclib + fulvestrant in postmenopausal women with HR+, HER2– advanced breast cancer (ABC)

Background: Endocrine therapy (ET) is the treatment backbone for hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2–) ABC, but efficacy is limited by ET resistance. The cyclin-dependent kinase (CDK) 4/6–cyclin D (CCND1)–retinoblastoma (Rb) and phosphatidylinositol 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) pathways have been implicated in ET resistance. CDK4/6 and PI3K/mTOR inhibitors act synergistically with ET in preclinical and clinical studies of HR+ breast cancer. Ribociclib (LEE011; CDK4/6 inhibitor) + fulvestrant ± alpelisib (BYL719) or buparlisib (BKM120) in HR+, HER2– ABC is being investigated in a Phase Ib/II study (NCT02088684). Here, we present results from the ribociclib + fulvestrant combination, with intermittent and continuous ribociclib dosing.

Methods: Postmenopausal patients (pts) with HR+, HER2– ABC refractory to aromatase inhibitors received ribociclib intermittently (600 mg/day, 3-weeks-on/1-week-off; Arm A) or continuously (400 mg/day; Arm B; following Arm A safety evaluation) + fulvestrant (500 mg; Cycle 1 Day 1 and 15; subsequent cycles Day 1). Primary objective: dose-limiting toxicities (DLTs) to confirm the recommended Phase II dose of ribociclib + fulvestrant. Secondary objectives: safety, pharmacokinetics, and preliminary antitumor activity (RECIST v1.1); biomarkers that may correlate with response were also assessed.

Results: As of March 10, 2016, 24 pts received ribociclib + fulvestrant (Arm A, n=13; Arm B, n=11); 4 pts in Arm B were ongoing; median duration of exposure was 7.4 (Arm A) and 4.5 (Arm B) months. Median number of prior regimens: 4 (Arm A) and 3 (Arm B). Treatment discontinuation (n; Arm A, Arm B) was due to disease progression (11, 4), physician decision (1, 2), and adverse events (AEs; 1, 1). DLTs in Cycle 1 (n; Arm A, Arm B) were Grade [G] 3 pulmonary embolism (1, 0) and G3 aspartate aminotransferase elevation (0, 1). The most common G3/4 drug-related AE (Arm A, Arm B) was neutropenia (62%, 36%); 5 pts had QTcF prolongation >60 ms (n; 4, 1).

Common all-Grade drug-related AEs (>35% pts) n (%)Arm A (n=13)Arm B (n=11)Neutropenia10 (77)7 (64)Fatigue9 (69)3 (27)Nausea6 (46)5 (46)Anemia6 (46)0 (0)Reduced appetite5 (39)1 (9)

Best overall responses (BORs; n; Arm A, Arm B): partial response (PR; 3, 1), stable disease (SD; 9, 6), and neither complete response nor progressive disease (NCRNPD; non-measurable disease; 1, 4). Overall response rate: 23% (Arm A) and 9% (Arm B); disease control rate (BOR of complete response, PR, SD, or NCRNPD): 100% in both arms. Next-generation sequencing data (n; Arm A, Arm B) were available for 16 pts (7, 9): 5 pts had CCND1 alterations (PR [1, 0], SD [2, 1], and NCRNPD [0, 1]); 11 pts had PIK3CA alterations (PR [1, 0], SD [3, 4], and NCRNPD [1, 2]); 2 of these pts had both CCND1 and PIK3CA alterations (SD [1, 0] and NCRNPD [0, 1]).

Conclusions: Ribociclib + fulvestrant has a manageable safety profile and shows preliminary clinical activity in pretreated pts with HR+, HER2– ABC. Both ribociclib intermittent and continuous dosing schedules were well tolerated. Clinical responses were observed in tumors with and without CDK4/6–cyclin D–Rb and PI3K/mTOR pathway alterations.

Citation Format: Tolaney SM, Forero-Torres A, Boni V, Bachelot T, Lu Y-S, Maur M, Fasolo A, Motta M, Pan C, Dobson J, Hewes B, Chin Lee S. Ribociclib + fulvestrant in postmenopausal women with HR+, HER2– advanced breast cancer (ABC) [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-22-12.

Integrative population pharmacokinetic and pharmacodynamic dose finding approach of the new camptothecin compound namitecan (ST1968)

AIMS

Namitecan is a new camptothecan compound undergoing early clinical development. This study was initiated to build an integrated pharmacokinetic (PK) and pharmacodynamic (PD) population model of namitecan to guide future clinical development.

METHODS

Plasma concentration-time data, neutrophils and thrombocytes were pooled from two phase 1 studies in 90 patients with advanced solid tumours, receiving namitecan as a 2 h infusion on days 1 and 8 every 3 weeks (D1,8) (n = 34), once every 3 weeks (D1) (n = 29) and on 3 consecutive days (D1-3) (n = 27). A linear three compartment PK model was coupled to a semiphysiological PD-model for neutrophils and thrombocytes. Data simulations were used to interrogate various dosing regimens and give dosing recommendations.

RESULTS

Clearance was estimated to be 0.15 l h(-1), with a long terminal half-life of 48 h. Body surface area was not associated with clearance, supporting flat-dosing of namitecan. A significant and clinically relevant association was found between namitecan area under the concentration-time curve (AUC) and the percentage drop of neutrophils (r(2) = 0.51, P < 10(-4)) or thrombocytes (r(2) = 0.49, P < 10(-4)). With a target for haematological dose-limiting toxicity of <20%, the recommended dose was defined as 12.5 mg for the D1,8 regimen, 23 mg for the once every 3 week regimen and 7 mg for the D1-3 regimen.

CONCLUSION

This is the first integrated population PK-PD analysis of the new hydrophilic topoisomerase I inhibitor namitecan, that is currently undergoing early clinical development. A distinct relationship was found between drug exposure and haematological toxicity, supporting flat-dosing once every 3 weeks as the most adequate dosing regimen.

Quiescent neuronal progenitors are activated in the juvenile guinea pig lateral striatum and give rise to transient neurons

In the adult brain, active stem cells are a subset of astrocytes residing in the subventricular zone (SVZ) and the dentate gyrus (DG) of the hippocampus. Whether quiescent neuronal progenitors occur in other brain regions is unclear. Here, we describe a novel neurogenic system in the external capsule and lateral striatum (EC-LS) of the juvenile guinea pig that is quiescent at birth but becomes active around weaning. Activation of neurogenesis in this region was accompanied by the emergence of a neurogenic-like niche in the ventral EC characterized by chains of neuroblasts, intermediate-like progenitors and glial cells expressing markers of immature astrocytes. Like neurogenic astrocytes of the SVZ and DG, these latter cells showed a slow rate of proliferation and retained BrdU labeling for up to 65 days, suggesting that they are the primary progenitors of the EC-LS neurogenic system. Injections of GFP-tagged lentiviral vectors into the SVZ and the EC-LS of newborn animals confirmed that new LS neuroblasts originate from the activation of local progenitors and further supported their astroglial nature. Newborn EC-LS neurons existed transiently and did not contribute to neuronal addition or replacement. Nevertheless, they expressed Sp8 and showed strong tropism for white matter tracts, wherein they acquired complex morphologies. For these reasons, we propose that EC-LS neuroblasts represent a novel striatal cell type, possibly related to those populations of transient interneurons that regulate the development of fiber tracts during embryonic life.

Abstract P3-15-03: Safety analysis of BOLERO-3: A phase 3 trial of daily everolimus (EVE) vs placebo (PBO), both with weekly trastuzumab (TRAS) and vinorelbine in trastuzumab-resistant, advanced breast cancer

Background: Activation of the PI3K/mTOR pathway is thought to be involved in resistance to TRAS. BOLERO-3 is a randomized phase 3, double-blind, placebo-controlled, international, clinical trial evaluating the addition of the mTOR inhibitor EVE (5 mg/day) to TRAS plus vinorelbine (25 mg/m2) in patients with HER2+ advanced breast cancer resistant to TRAS and who were previously treated with a taxane. A total of 569 adult women were randomized 1:1 to receive EVE (n = 284) or PBO (n = 285). Study treatment represented the 2nd, 3rd, or 4th line of chemotherapy-containing regimen for 83% of patients in the metastatic setting. The primary endpoint, progression-free survival based on local radiologic assessment, was significantly longer in the EVE arm versus PBO (HR = 0.78; P = .0067) at a median follow-up of 20 months.

Methods: Study drugs were continued until disease progression or unacceptable toxicity. Incidences of adverse events (AEs) were monitored continuously. Dose modifications and discontinuations were recorded.

Results: The median duration of exposure to study treatment was similar across treatment groups: 24.8 weeks for EVE, 25.1 weeks for TRAS, and 24.0 weeks for vinorelbine (EVE arm); and 22.9 weeks for PBO, 24.0 weeks for TRAS, and 23.1 weeks for vinorelbine (PBO arm). The AEs were consistent with known drug-safety profiles. Class-effect AEs with mTOR inhibitors (including stomatitis, rash, noninfectious pneumonitis, and hyperglycemia) were higher in the EVE arm and were mainly grade 1/2. Grade 3 class-effect AEs each occurred in &lt;15% of patients (stomatitis [13%], hyperglycemia [2%], and noninfectious pneumonitis [&lt;1%]). Grade 4 noninfectious pneumonitis (&lt;1%) was uncommon; there were no grade 4 events of stomatitis or hyperglycemia, and no grade 3/4 events of rash. The incidence and grade of hematologic AEs were increased in the EVE arm vs the PBO arm, including all grade neutropenia (81% vs 70%), anemia (49% vs 29%), febrile neutropenia (17% vs 4%) and thrombocytopenia (14% vs 2%); grade 3/4 hematologic AEs included neutropenia (grade 3: 35% vs 32%; grade 4: 38% vs 30%), anemia (grade 3: 17% vs 6%; grade 4: 2% vs &lt;1%), febrile neutropenia (grade 3: 11% vs 3%; grade 4: 5% vs 1%), and thrombocytopenia (grade 3: 3% vs &lt;1%; grade 4: 1% vs 0). The incidences and grades of changes in liver enzymes and hyperlipidemia were similar between arms. Serious AEs were reported in 42% of patients in the EVE arm and 20% of patients in the PBO arm (26% and 6% were attributed to study treatments, respectively). A higher percentage of patients discontinued treatment because of AEs in the EVE arm versus PBO (10% vs 5%). In all, 83% of patients required at least 1 EVE dose interruption and/or reduction; 96% of these were attributed to AEs. There were fewer deaths in the EVE arm (37%) compared with PBO (41%).

Conclusions: The safety of the combination of EVE, TRAS, and vinorelbine was considered manageable in this heavily pretreated patient population. Overall, the results from BOLERO-3 demonstrate that EVE can be combined with TRAS and chemotherapy to improve efficacy in TRAS-resistant HER2+ advanced breast cancer previously treated with a taxane.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P3-15-03.

Abstract P4-12-19: BOLERO-3: Everolimus plus trastuzumab and vinorelbine in Asian patients with HER2-positive metastatic breast cancer

Background: Resistance to trastuzumab may occur through activation of the PI3K/Akt/mTOR signaling pathway, the inhibition of which may restore trastuzumab sensitivity. BOLERO-3, a phase 3, double-blind, international trial involving 569 patients with trastuzumab-resistant, HER2-positive (HER2+), advanced breast cancer pretreated with a taxane, recently reported that adding everolimus (EVE; an mTOR inhibitor) to vinorelbine and trastuzumab significantly improved progression-free survival (PFS) vs placebo (PBO) plus vinorelbine and trastuzumab (hazard ratio [HR] = 0.78; log-rank P = .0067). As EVE pharmacokinetics and, therefore, clinical effects may be different in Asian patients, we analyzed the efficacy and safety data from BOLERO-3 for the Asian population.

Methods: Eligible women with trastuzumab-resistant, HER2+, advanced breast cancer who received prior taxane therapy were randomized (1:1) to EVE (5 mg/day) or matching PBO in combination with weekly vinorelbine (25 mg/m2) and trastuzumab (2 mg/kg after 4-mg/kg loading dose). The primary endpoint was PFS by investigator. Secondary endpoints included safety.

Results: Among 569 patients enrolled in this study, 166 (29%) patients were Asian; 88 and 78 were assigned to EVE or PBO arms, respectively. In this subpopulation, adding EVE to vinorelbine and trastuzumab prolonged median PFS compared with the PBO arm (8.3 vs 6.8 months, respectively; HR = 0.83; 95% confidence interval, 0.59 - 1.18). In general, the incidence of all grade adverse events was similar for Asian versus non-Asian patients in the EVE arm (stomatitis, 71% vs 59%; pneumonitis, 7% vs 5%; and infections, 58% vs 70%) and the PBO arm (stomatitis, 31% vs 26%; pneumonitis, 1% vs 4%; and infections, 48% vs 49%). Serious adverse events had a low incidence and included febrile neutropenia (9.1%), neutropenia (2.3%), stomatitis (2.3%), anemia (2.3%), and cataract (2.3%) as the most common among Asian patients in the EVE arm. The incidence of serious pneumonitis was low: Asian (1.1%) versus non-Asian patients (0%) in the EVE arm and 0% versus 1.5%, respectively, in the PBO arm.

Conclusions: Asian patients in the BOLERO-3 trial treated with EVE plus vinorelbine and trastuzumab showed PFS benefits similar to the overall population and had a comparable manageable safety profile. Thus, EVE in combination with vinorelbine and trastuzumab may be considered as a new therapeutic option for Asian women with trastuzumab-resistant, HER2+, advanced breast cancer progressing after taxane-based therapies.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P4-12-19.

Abstract P4-12-18: BOLERO-3: Quality-of-life maintained in patients with metastatic breast cancer treated with everolimus plus trastuzumab plus vinorelbine

Background: Activation of the PI3K/mTOR pathway is implicated in resistance to trastuzumab. Accordingly, the BOLERO-3 study evaluated the efficacy of adding everolimus (EVE), an mTOR inhibitor, to vinorelbine and trastuzumab. At the final progression-free survival (PFS) analysis, EVE significantly improved PFS vs PBO (hazard ratio [HR] = 0.78; log-rank P = .0067) but EVE-treated patients had higher rate of grade 3/4 toxicity. To further qualify the benefit:risk of adding EVE to trastuzumab-based therapy, per-protocol, patient-reported, health-related quality-of-life (HRQoL) data were analyzed.

Methods: BOLERO-3 is a randomized phase 3, double-blind, placebo-controlled, international multicenter trial. Taxane-pretreated patients (N = 569) with trastuzumab-resistant, HER2+, advanced breast cancer were randomized (1:1) to treatment with EVE or placebo (PBO) plus vinorelbine and trastuzumab. The European Organisation for Research and Treatment of Cancer (EORTC) quality-of-life questionnaire C30 (QLQ-C30) (including the breast cancer-specific BR23 module) was administered at baseline and every 6 weeks thereafter until progression. The QLQ-C30 consists of 30 items combined into 15 subscales, including Global Health Status and functional subscales, where higher scores (range, 0 to 100) indicate better HRQoL. Time to definitive deterioration (TTD) based on a 10% decrease from baseline for GHS and for the physical, emotional, and social function subscales was determined using the Kaplan-Meier method. Treatment arms were compared using a 2-sided log-rank test stratified by prior use of lapatinib.

Results: Overall, there was no significant difference in median TDD of HRQoL between treatment arms. The median TTD in global health status score was 8.3 months for EVE (95% confidence interval [CI], 6.9-11.5) vs 7.3 months for PBO (95% CI, 5.6-10.4; P = .8386). The median TTD in the physical, emotional, and social function subscale scores showed no significant difference between arms. For example, median TTD in the physical function subscale score was 12.0 months (95% CI, 8.3-14.1) for EVE vs 12.5 months (95% CI, 8.3-20.9) for PBO (P = .4251), and median TTD in the emotional function subscale score was 15.2 months (95% CI, 9.2-17.3) for EVE vs 12.5 months (95% CI, 9.7-16.4) for PBO (P = .8140).

Conclusions: These analyses demonstrate that, despite increased frequency of adverse events observed with the addition of EVE to the standard treatment of vinorelbine and trastuzumab, overall and functional HRQoL scores were not negatively impacted in patients with trastuzumab-resistant, HER2+, advanced breast cancer.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P4-12-18.

Transitory and activity-dependent expression of neurogranin in olfactory bulb tufted cells during mouse postnatal development

Neurogranin (Ng) is a brain-specific postsynaptic calmodulin-binding protein involved in synaptic activity-dependent plasticity. In the adult olfactory bulb (OB), Ng is expressed by a large population of GABAergic interneurons in the granule cell layer. We show here that, during postnatal development, Ng is also expressed by OB neurons in the superficial external plexiform layer (sEPL) and glomerular layer (GL). These Ng-positive neurons display morphological and neurochemical features of superficial and external tufted cells. Ng expression in these cells is transient during OB development: few elements express Ng at postnatal day (P) 5, increasing in number and reaching a peak at P10, then progressively decreasing. At P30, Ng is rarely detectable in these neurons. Ng expression in developing tufted cells is also modulated at the cellular level: at earlier stages, Ng labeling is distributed throughout the cell body and dendritic arborization in the GL, but, at P20, when the glomerular circuits are fully matured, Ng becomes restricted to the soma and proximal portion of tufted cell apical dendrites. We show that olfactory deprivation at early postnatal stages induces a strong increase in Ng-positive tufted cells from P10 to P20, whereas no changes have been observed following olfactory deprivation in adult mice. These findings demonstrate that Ng expression in sEPL-GL is restricted to developmental stages and indicate its activity-dependent regulation in a time window critical for glomerular circuit development, suggesting a role for Ng in maturation and dendritic remodeling of tufted cells.

Seminars in clinical pharmacology: an introduction to MET inhibitors for the medical oncologist

MET is a tyrosine kinase receptor for hepatocyte growth factor (HGF), primarily expressed on epithelial cells; the activation of MET induces several biological responses relevant for the development and growth of many human cancers. Several human malignancies present altered expression of MET and this is usually associated with poor prognosis and aggressive phenotype. The majority of MET inhibitors in clinical development target directly the receptor through the use of monoclonal antibodies (MAbs) or through small molecule inhibitors of MET kinase activity; small molecule inhibitors are very potent but less specific than MAbs. MET inhibitors are of great clinical interest because of the extensive crosstalk of the HGF/MET axis with many other signaling pathways, including growth factor-dependent pathways (like PI3K/AKT/mTOR,RAS/RAF/ERK) and vascular endothelial growth factor (VEGF) axis. In preclinical studies, the treatment with MET inhibitors could prevent or reverse resistance to inhibitors of growth factor-dependent signaling; this hypothesis is currently tested in phase III trials with anti-epidermal growth factor receptor (EGFR) inhibitors in non-small-cell lung cancer (NSCLC). Based on preclinical and preliminary clinical results, a rational strategy for the clinical development of MET antagonists should include a selection of the tumors with MET overexpression, the identification of prognostic/predictive biomarkers, the evaluation of combinations with anti-VEGF compounds.

From chemical neuroanatomy to an understanding of the olfactory system

The olfactory system is the appropriate model for studying several aspects of neuronal physiology spanning from the developmental stage to neural network remodelling in the adult brain. Both the morphological and physiological understanding of this system were strongly supported by classical histochemistry. It is emblematic the case of the Olfactory Marker Protein (OMP) staining, the first, powerful marker for fully differentiated olfactory receptor neurons and a key tool to investigate the dynamic relations between peripheral sensory epithelia and central relay regions given its presence within olfactory fibers reaching the olfactory bulb (OB). Similarly, the use of thymidine analogues was able to show neurogenesis in an adult mammalian brain far before modern virus labelling and lipophilic tracers based methods. Nowadays, a wealth of new histochemical techniques combining cell and molecular biology approaches is available, giving stance to move from the analysis of the chemically identified circuitries to functional research. The study of adult neurogenesis is indeed one of the best explanatory examples of this statement. After defining the cell types involved and the basic physiology of this phenomenon in the OB plasticity, we can now analyze the role of neurogenesis in well testable behaviours related to socio-chemical communication in rodents.

Newborn interneurons in the accessory olfactory bulb promote mate recognition in female mice

In the olfactory bulb of adult rodents, local interneurons are constantly replaced by immature precursors derived from the subventricular zone. Whether any olfactory sensory process specifically relies on this cell renewal remains largely unclear. By using the well known model of mating-induced imprinting to avoid pregnancy block, which requires accessory olfactory bulb (AOB) function, we demonstrate that this olfactory memory formation critically depends on the presence of newborn granule neurons in this brain region. We show that, in adult female mice, exposure to the male urine compounds involved in mate recognition increases the number of new granule cells surviving in the AOB. This process is modulated by male signals sensed through the vomeronasal organ and, in turn, changes the activity of the downstream amygdaloid and hypothalamic nuclei involved in the pregnancy block response. Chemical depletion of newly generated bulbar interneurons causes strong impairment in mate recognition, thus resulting in a high pregnancy failure rate to familiar mating male odors. Taken together, our results indicate that adult neurogenesis is essential for specific brain functions such as persistent odor learning and mate recognition.

Dysregulation of Semaphorin7A/β1-integrin signaling leads to defective GnRH-1 cell migration, abnormal gonadal development and altered fertility

Reproduction in mammals is dependent on the function of specific neurons that secrete gonadotropin-releasing hormone-1 (GnRH-1). These neurons originate prenatally in the nasal placode and migrate into the forebrain along the olfactory-vomeronasal nerves. Alterations in this migratory process lead to defective GnRH-1 secretion, resulting in heterogeneous genetic disorders such as idiopathic hypogonadotropic hypogonadism (IHH), and other reproductive diseases characterized by the reduction or failure of sexual competence. Combining mouse genetics with in vitro models, we demonstrate that Semaphorin 7A (Sema7A) is essential for the development of the GnRH-1 neuronal system. Loss of Sema7A signaling alters the migration of GnRH-1 neurons, resulting in significantly reduced numbers of these neurons in the adult brain as well as in reduced gonadal size and subfertility. We also show that GnRH-1 cells differentially express the Sema7 receptors β1-integrin and Plexin C1 as a function of their migratory stage, whereas the ligand is robustly expressed along developing olfactory/vomeronasal fibers. Disruption of Sema7A function in vitro inhibits β1-integrin-mediated migration. Analysis of Plexin C1(-/-) mice did not reveal any difference in the migratory process of GnRH-1 neurons, indicating that Sema7A mainly signals through β1-integrin to regulate GnRH-1 cell motility. In conclusion, we have identified Sema7A as a gene implicated in the normal development of the GnRH-1 system in mice and as a genetic marker for the elucidation of some forms of GnRH-1 deficiency in humans.

From progenitors to integrated neurons: role of neurotransmitters in adult olfactory neurogenesis

Adult neurogenesis is due to the persistence of pools of constitutive stem cells able to give rise to a progeny of proliferating progenitors. In rodents, adult neurogenic niches have been found in the subventricular zone (SVZ) along the lateral ventricles and in the subgranular zone of the dentate gyrus in the hippocampus. SVZ progenitors undergo a unique process of tangential migration from the lateral ventricle to the olfactory bulb (OB) where they differentiate mainly into GABAergic interneurons in the granule and glomerular layers. SVZ progenitor proliferation, migration and differentiation into fully integrated neurons, are strictly related processes regulated by complex interactions between cell intrinsic and extrinsic influences. Numerous observations demonstrate that neurotrasmitters are involved in all steps of the adult neurogenic process, but the understanding of their role is hampered by their intricate mechanism of action and by the highly complex network in which neurotransmitters work. By considering the three main steps of olfactory adult neurogenesis (proliferation, migration and integration), this review will discuss recent advances in the study of neurotransmitters, highlighting the regulatory mechanisms upstream and downstream their action.

Combining confocal laser scanning microscopy with serial section reconstruction in the study of adult neurogenesis

Current advances in imaging techniques have extended the possibility of visualizing small structures within large volumes of both fixed and live specimens without sectioning. These techniques have contributed valuable information to study neuronal plasticity in the adult brain. However, technical limits still hamper the use of these approaches to investigate neurogenic regions located far from the ventricular surface such as parenchymal neurogenic niches, or the scattered neuroblasts induced by brain lesions. Here, we present a method to combine confocal laser scanning microscopy (CLSM) and serial section reconstruction in order to reconstruct large volumes of brain tissue at cellular resolution. In this method a series of thick sections are imaged with CLSM and the resulting stacks of images are registered and 3D reconstructed. This approach is based on existing freeware software and can be performed on ordinary laboratory personal computers. By using this technique we have investigated the morphology and spatial organization of a group of doublecortin (DCX)+ neuroblasts located in the lateral striatum of the late post-natal guinea pig. The 3D study unraveled a complex network of long and poorly ramified cell processes, often fascicled and mostly oriented along the internal capsule fiber bundles. These data support CLSM serial section reconstruction as a reliable alternative to the whole mount approaches to analyze cyto-architectural features of adult germinative niches.

Expression and localization of the calmodulin-binding protein neurogranin in the adult mouse olfactory bulb

Neurogranin (Ng) is a brain-specific postsynaptic protein involved in activity-dependent synaptic plasticity through modulation of Ca(2+)/calmodulin (CaM)-dependent signal transduction in neurons. In this study, using biochemical and immunohistochemical approaches, we demonstrate Ng expression in the adult mouse olfactory bulb (OB), the first relay station in odor information processing. We show that Ng is principally associated with the granule cell layer (GCL), which is composed of granule cell inhibitory interneurons. This cell type is continuously renewed during adult life and plays a key role in OB circuits, integrating and modulating the activity of mitral/tufted cells. Our results indicate that Ng localizes in the soma and dendrites of a defined subpopulation of mature GABAergic granule cells, enriched in the deep portion of the GCL. Ng-immunopositive cells largely coexpress the Ca(+)/CaM-dependent kinase IV (CaMKIV), a downstream protein of CaM signaling cascade, whereas no colocalization was observed between Ng and the calcium-binding protein calretinin. Finally, we demonstrate that adult neurogenesis contributes to the Ng-expressing population, with more newly generated Ng-positive cells integrated in the deep GCL. Together, these results provide a new specific neurochemical marker to identify a subpopulation of olfactory granule cells and suggest possible functional implications for Ng in OB plasticity mechanisms.

Olfactory enrichment influences adult neurogenesis modulating GAD67 and plasticity-related molecules expression in newborn cells of the olfactory bulb

The olfactory bulb (OB) is a highly plastic region of the adult mammalian brain characterized by continuous integration of inhibitory interneurons of the granule (GC) and periglomerular cell (PGC) types. Adult-generated OB interneurons are selected to survive in an experience-dependent way but the mechanisms that mediate the effects of experience on OB neurogenesis are unknown. Here we focus on the new-generated PGC population which is composed by multiple subtypes. Using paradigms of olfactory enrichment and/or deprivation combined to BrdU injections and quantitative confocal immunohistochemical analyses, we studied the effects of olfactory experience on adult-generated PGCs at different survival time and compared PGC to GC modulation. We show that olfactory enrichment similarly influences PGCs and GCs, increasing survival of newborn cells and transiently modulating GAD67 and plasticity-related molecules expression. However, PGC maturation appears to be delayed compared to GCs, reflecting a different temporal dynamic of adult generated olfactory interneuron integration. Moreover, olfactory enrichment or deprivation do not selectively modulate the survival of specific PGC phenotypes, supporting the idea that the integration rate of distinct PGC subtypes is independent from olfactory experience.

Developmental regulation of metabotropic glutamate receptor 1 splice variants in olfactory bulb mitral cells

Alternative splicing of the metabotropic glutamate receptor 1 (mGluR1) receptor gene generates two major receptor isoforms, mGluR1a and mGluR1b, differing in intracellular function and distribution. However, little is known on the expression profiles of these variants during development. We examined the mRNA expression profile of mGluR1a/b in microdissected layers and acutely isolated mitral cells in the developing mouse olfactory bulb. This analysis showed that the two mGluR1 variants are differentially regulated within each bulb layer. During the first postnatal week, the mGluR1a isoform replaces GluR1b in the microdissected mitral cell layer (MCL) and in isolated identified mitral cells, coinciding with a developmental epoch of mitral cell dendritic reorganization. Although mGluR1a mRNA is expressed at high levels in both the adult external plexiform layer (EPL) and MCL, Western blotting analysis reveals a marked reduction of the mGluR1a protein in the MCL, where mitral cell bodies are located, and strong labeling in the EPL, which contains mitral cell dendrites. This suggests that there is increased dendritic trafficking efficiency of the receptor in adult. The temporal and spatial shift in mGluR1b/a expression suggests distinct roles of the mGluR1 isoforms, with mGluR1b potentially involved in the early mitral cell maturation and mGluR1a in dendritic and synapse function.

Integration and sensory experience-dependent survival of newly-generated neurons in the accessory olfactory bulb of female mice

Newborn neurons generated by proliferative progenitors in the adult subventricular zone (SVZ) integrate into the olfactory bulb circuitry of mammals. Survival of these newly-formed cells is regulated by the olfactory input. The presence of new neurons in the accessory olfactory bulb (AOB) has already been demonstrated in some mammalian species, albeit their neurochemical profile and functional integration into AOB circuits are still to be investigated. To unravel whether the mouse AOB represents a site of adult constitutive neurogenesis and whether this process can be modulated by extrinsic factors, we have used multiple in vivo approaches. These included fate mapping of bromodeoxyuridine-labelled cells, lineage tracing of SVZ-derived enhanced green fluorescent protein-positive engrafted cells and neurogenesis quantification in the AOB, in both sexes, as well as in females alone after exposure to male-soiled bedding or its derived volatiles. Here, we show that a subpopulation of SVZ-derived neuroblasts acquires proper neurochemical profiles of mature AOB interneurons. Moreover, 3D reconstruction of long-term survived engrafted neuroblasts in the AOB confirms these cells show features of fully integrated neurons. Finally, exposure to male-soiled bedding, but not to its volatile compounds, significantly increases the number of new neurons in the AOB, but not in the main olfactory bulb of female mice. These data show SVZ-derived neuroblasts differentiate into new functionally integrated neurons in the AOB of young and adult mice. Survival of these cells seems to be regulated by an experience-specific mechanism mediated by pheromones.

Clinical and pharmacological phase I evaluation of Exherin (ADH-1), a selective anti-N-cadherin peptide in patients with N-cadherin-expressing solid tumours

BACKGROUND

Upregulation of N-cadherin promotes dysregulated cell growth, motility, invasiveness, plus maintenance of vascular stability and is associated with cancer progression in several human tumour types. N-cadherin is expressed also on tumour cells and the anti-N-cadherin cyclic pentapeptide ADH-1, tested in the present study, can exert a direct antitumour effect.

PATIENTS AND METHODS

Adult patients with advanced solid malignancies expressing N-cadherin on tumour biopsies carried out in the previous 12 months received escalating i.v. doses of ADH-1 given weekly (initially for 3 of 4 weeks, then every week). Plasma pharmacokinetics (PK) was studied at cycle 1. Blood flow changes were assessed after first dosing in all patients treated in the initial regimen.

RESULTS

In all, 129 patients were screened, 65 (50%) were N-cadherin positive, and 30 were enrolled. The doses ranged from 150 to 2400 mg/m(2); no maximum tolerated dose was reached. Treatment was well tolerated with asthenia as the most frequent adverse event. Two patients with ovarian cancer showed prolonged disease stabilisation while one patient with fallopian tube carcinoma achieved a mixed response. PK was linear in the range of doses tested.

CONCLUSION

ADH-1 is the first anti-N-cadherin compound tested in humans. In N-cadherin-positive patients, ADH-1 showed an acceptable toxicity profile, linear PK and hints of antitumour activity in gynaecological cancers.

Semaphorin 4D regulates gonadotropin hormone-releasing hormone-1 neuronal migration through PlexinB1-Met complex

In mammals, reproduction is dependent on specific neurons secreting the neuropeptide gonadotropin hormone–releasing hormone-1 (GnRH-1). These cells originate during embryonic development in the olfactory placode and migrate into the forebrain, where they become integral members of the hypothalamic–pituitary–gonadal axis. This migratory process is regulated by a wide range of guidance cues, which allow GnRH-1 cells to travel over long distances to reach their appropriate destinations. The Semaphorin4D (Sema4D) receptor, PlexinB1, is highly expressed in the developing olfactory placode, but its function in this context is still unknown. Here, we demonstrate that PlexinB1-deficient mice exhibit a migratory defect of GnRH-1 neurons, resulting in reduction of this cell population in the adult brain. Moreover, Sema4D promotes directional migration in GnRH-1 cells by coupling PlexinB1 with activation of the Met tyrosine kinase (hepatocyte growth factor receptor). This work identifies a function for PlexinB1 during brain development and provides evidence that Sema4D controls migration of GnRH-1 neurons.

DCX and PSA-NCAM expression identifies a population of neurons preferentially distributed in associative areas of different pallial derivatives and vertebrate species

In adult rodents, doublecortin (DCX) and polysialylated neural cell adhesion molecule (PSA-NCAM) expression is mostly restricted to newly generated neurons. These molecules have also been described in prenatally generated cells of the piriform cortex and, to a lesser extent, neocortex (NC) of the rat. In addition, PSA-NCAM+ cells have been identified in several telencephalic regions of the lizard. Here, through immunohistochemistry and 3-dimensional reconstruction, we have investigated distribution, morphology, and phenotype of DCX/PSA-NCAM-expressing cells in the pallium of different mammals and in lizard. In all species, a population of nonnewly-generated pallial DCX+/PSA-NCAM+ cells shows common morphological and phenotypic characteristics, including expression of Tbr-1, a transcription factor expressed in pallial projection neurons, and preferential distribution in associative areas. In the guinea pig and rabbit, DCX+/PSA-NCAM+ elements are also abundant in the NC, particularly in areas implicated in nonspatial learning and memory networks. In reptiles, DCX+/PSA-NCAM+ cells are located in the lateral and medial cortex and dorsal ventricular ridge but not in the dorsal cortex. These data support the fact that coexpression of DCX+/PSA-NCAM+/Tbr-1+ in the adult brain identifies evolutionary conserved cell populations shared by different pallial derivatives including the mammalian NC.

BDNF/ TrkB interaction regulates migration of SVZ precursor cells via PI3-K and MAP-K signalling pathways

Neuroblasts born in the subventricular zone (SVZ) migrate along the rostral migratory stream, reaching the olfactory bulb (OB) where they differentiate into local interneurons. Several extracellular factors have been suggested to control specific steps of this process. The brain-derived neurotrophic factor (BDNF) has been demonstrated to promote morphological differentiation and survival of OB interneurons. Here we show that BDNF and its receptor TrkB are expressed in vivo throughout the migratory pathway, implying that BDNF might also mediate migratory signals. By using in vitro models we demonstrate that BDNF promotes migration of SVZ neuroblasts, acting both as inducer and attractant through TrkB activation. We show that BDNF induces cAMP response element-binding protein (CREB) activation in migrating neuroblasts via phosphatidylinositol 3-kinase (PI3-K) and mitogen-activated protein kinase (MAP-K) signalling. Pharmacological blockade of these pathways on SVZ explants significantly reduces CREB activation and impairs neuronal migration. This study identifies a function of BDNF in the SVZ system, which involves multiple protein kinase pathways leading to neuroblast migration.

Adult Neurogenesis and Local Neuronal Progenitors in the Striatum

Mechanisms underlying neurogenesis in the subventricular-zone-olfactory-bulb system and dentate gyrus of the hippocampus are beginning to be delineated and show common regulative features. In both regions neurogenesis is attributable to progenitor cells whose progeny progressively matures to functional neurons under genetic and epigenetic influence. Persistence of endogenous neuronal progenitors and integration of new neurons in preexisting circuits provide an appealing model of study to develop therapy strategies for neurodegenerative diseases. Interestingly, comparative analysis in mammals indicates that low neurogenic activity is also present in regions classically considered nonneurogenic in both normal and pathological conditions. Neurogenesis in these regions can be due to progenitors derived from the subventricular germinal zone and/or local parenchymal progenitors. Although, in vivo, the origin, identity and putative function of parenchymal progenitors are still obscure, in vitro studies suggest that many regions of the adult central nervous system potentially contain multipotent parenchymal progenitors. The aim of this review is to delineate the common regulative features underlying adult neurogenesis in the main neurogenic regions and in the striatum focusing on our recent data concerning the existence of local parenchymal progenitors in the caudate nucleus of the adult rabbit.

Spatio-temporal specification of olfactory bulb interneurons

Olfactory bulb (OB) interneurons are continuously generated throughout development and in adulthood, and are derived from different progenitor zones. Once integrated in the OB circuits, interneurons play essential roles in olfactory information processing by modulating the activity of major output neurons. These functions are performed by multiple classes of neurons that differ in their spatial distribution, morphology, neurochemical and synaptic properties. This diversity, and the continuous neurogenesis make the understanding of the specification mechanisms in the OB a challenging task. New studies suggest that both intrinsic and extrinsic cues are involved in fate determination of OB interneurons. In both development and adulthood the expression of specific transcription factors not only defines different progenitor regions but also precise interneuronal phenotypes. Here we discuss recent findings on the molecular mechanisms regulating production and diversity of OB interneurons with respect to the spatial and temporal parameters.

Generation of distinct types of periglomerular olfactory bulb interneurons during development and in adult mice: implication for intrinsic properties of the subventricular zone progenitor population

The subventricular zone (SVZ) of the lateral ventricle develops from residual progenitors of the embryonic lateral ganglionic eminence (LGE) and maintains neurogenic activity throughout life. Precursors from LGE/SVZ migrate to the olfactory bulb (OB) where they differentiate into local interneurons, principally in the granule layer and glomerular layer (GL). By in situ dye labeling, we show that neonatal and adult SVZ progenitors differentially contribute to neurochemically distinct types of periglomerular interneurons in the GL. Namely, calbindin-positive periglomerular cells are preferentially generated during early life, whereas calretinin- and tyrosine hydroxylase-expressing neurons are mainly produced at later ages. Furthermore, homochronic/heterochronic transplantation demonstrates that progenitor cells isolated from the LGE or SVZ at different stages (embryonic day 15 and postnatal days 2 and 30) engraft into the SVZ of neonatal or adult mice, migrate to the OB, and differentiate into local interneurons, including granule and periglomerular cells as well as other types of interneurons. The total number of integrated cells and the relative proportion of granule or periglomerular neurons change, according to the donor age, whereas they are weakly influenced by the recipient age. Analysis of the neurochemical phenotypes acquired by transplanted cells in the GL shows that donor cells of different ages also differentiate according to their origin, regardless of the host age. This suggests that progenitor cells at different ontogenetic stages are intrinsically directed toward specific lineages. Neurogenic processes occurring during development and in adult OB are not equivalent and produce different types of periglomerular interneurons as a consequence of intrinsic properties of the SVZ progenitors.

Hepatocyte growth factor acts as a motogen and guidance signal for gonadotropin hormone-releasing hormone-1 neuronal migration

Reproduction in mammals is under the control of the hypothalamic neuropeptide gonadotropin hormone-releasing hormone-1 (GnRH-1). GnRH-1-secreting neurons originate during embryonic development in the nasal placode and migrate into the forebrain along olfactory nerves. Gradients of secreted molecules may play a role in this migratory process. In this context, hepatocyte growth factor (HGF) is a potential candidate, because it promotes cell motility in developing brain and has been shown previously to act as a motogen on immortalized GnRH-1 neurons (GN11). In this study, the role of HGF and its receptor Met during development of the GnRH-1 system was examined. GnRH-1 cells express Met during their migration and downregulate its expression once they complete this process. Tissue-type plasminogen activator (tPA), a known HGF activator, is also detected in migratory GnRH-1 neurons. Consistent with in vivo expression, HGF is present in nasal explants, and GnRH-1 neurons express Met. HGF-neutralizing antibody was applied to explants to examine the role of the endogenous growth factor. Migration of GnRH-1 cells and olfactory axon outgrowth were significantly reduced, in line with disruption of a guidance gradient. Exogenous application of HGF to explants increased the distance that GnRH-1 cells migrated, suggesting that HGF also acts as a motogen to GnRH-1 neurons. Functional experiments, performed on organotypic slice cultures, show that creation of an opposing HGF gradient inhibits GnRH-1 neuronal migration. Finally, tPA(-/-):uPA(-/-) (urokinase-type plasminogen activator(-/-)) knock-out mice exhibit strong reduction of the GnRH-1 cell population. Together, these data indicate that HGF signaling via Met receptor influences the development of GnRH-1.

Maternal deprivation and early handling affect density of calcium binding protein-containing neurons in selected brain regions and emotional behavior in periadolescent rats

Adverse early life experiences can induce neurochemical changes that may underlie modifications in hypothalamic-pituitary-adrenal axis responsiveness, emotionality and cognition. Here, we investigated the expression of the calcium binding proteins (CBPs) calretinin, calbindin and parvalbumin, which identify subpopulations of GABAergic neurons and serve important functional roles by buffering intracellular calcium levels, following brief (early handling) and long (maternal deprivation) periods of maternal separation, as compared with non-handled controls. CBP-expressing neurons were analyzed in brain regions related to stress and anxiety. Emotionality was assessed in parallel using the social interaction test. Analyses were carried out at periadolescence, an important phase for the development of brain areas involved in stress responses. Our results indicate that density of CBP-immunoreactive neurons decreases in the paraventricular region of deprived rats but increases in the hippocampus and lateral amygdala of both early-handled and deprived rats when compared with controls. Emotionality is reduced in both early-handled and deprived animals. In conclusion, early handling and deprivation led to neurochemical and behavioral changes linked to stress-sensitive brain regions. These data suggest that the effects of early experiences on CBP containing neurons might contribute to the functional changes of neuronal circuits involved in emotional response.

An enriched phase I, pharmacokinetic and pharmacodynamic study of the N-cadherin (NCAD) cyclic competitive binder exherin (ADH-1) in patients with solid tumors

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Background: N-cad is a cell adhesion molecule expressed by vascular endothelium and tumor cells of invasive tumors. ADH-1, a cyclic pentapeptide, antagonizes N-cad, causing rapid tumor vascular disruption and apoptosis in preclinical models. We report results from a Phase I study of weekly doses of intravenous ADH-1 given to patients with N-cad+ solid tumors, to evaluate safety, PK, antitumor activity, and effect of ADH-1 on tumor vasculature assessed by DCE-MRI. Methods: ADH-1 starting dose was 150 mg/m2 administered weekly for 3 W in 28 D cycles. DCE-MRI was performed to assess changes in tumor perfusion 90 mins after the first dose of ADH-1, and repeated on D 15 if no changes were noted. Following the 3rd dose level (DL 3, 600 mg/m2 ), the schedule was amended to weekly ADH-1 without interruption, in 21 D cycles. Results: 55 pts with refractory solid tumors were screened, 56% were N-cad+ [screened/N-cad+: GYN 16/21 (Ovarian 13/17), GI 5/14, breast 2/6, renal 5/5, head & neck 2/3, others 2/6]. 13 pts (5 males, median age 53 yrs.) received 20 cycles of ADH-1 by bolus injection at 150, 300 and 600 mg/m2/weekly ×3 W Q21–28 D. No DLTs have occurred to date. No pts have experienced > grade 2 study drug related AEs. One pt, with fallopian tube ca. had a mixed response. There was a 30% reduction in retroperitoneal nodal disease at the end of cycle 3, and a 37% reduction at the end of Cy 4. However, new bone lesions were also noted at the end of cycle 4 assessment. Tumor blood flow reduction of ≥40% was noted in this patient, and she also reported pain in the region of the tumor following multiple doses of ADH-1. PK parameters are available for the first 3 DLs (150, 300, and 600 mg/m2): mean Cmax 22.1, 37.0, and 50.8μg/mL, respectively; AUCinf 24.3, 60.6, and 110.3 h·μg/mL; Vss 12.6, 15.1, and 16.3 L/m2; and T1/2 1.8, 2.7, and 2.4hr. Conclusions: ADH-1 has been well tolerated in 4 dose levels tested to date, dose escalation is proceeding. No DLTs have occurred and the MTD has not been reached. Anti-tumor activity has been noted. Updated clinical, PK and PD results will be presented.

[Table: see text]