Extended enzymatic stability of reconstituted lyophilized PEG-asparaginase in vials.

Asparaginase (ASNase) use as a tumour-inhibitor drug has changed completely the natural course of paediatric acute lymphoblastic leukaemia (ALL) in such a way that it represents a paradigm shift in ALL management. ASNase treatment emergence has significantly improved pathologic responses and increased survival rates of ALL patients. Although different ASNase forms are currently available, only the pegylated form (PEG-ASNase) is recommended by relevant clinic guides. PEG-ASNase form shows longer elimination half-life, reducing the number of administrations, along with an enhanced safety profile. In spite of all of these advantages, PEG-ASNase elevated cost limits enormously its use. PEG-ASNase is commercialised as a lyophilised powder which according to the manufacturer it is stable for 24 hours once reconstituted, as a result, the leftover is usually discarded. In this study we analysed the enzymatic stability of reconstituted PEG-ASNase after conservation in three different temperature conditions for 5 and 14 days, aiming to take advantage of the remaining leftover for the subsequent administration. Our results have shown that PEG-ASNase is stable at 4°C, -20°C and -80°C for at least 14 days, retaining the 95% from the initial enzymatic activity in all three storage temperatures. According to our results, it is feasible to reuse the remaining content of PEG-ASNase vial after reconstitution, which means a 50% reduction of its cost for paediatric patient treatment and, consequently, removes the main barrier to use this drug in a wider population.

Extended Stability of Reconstituted Lyophilized Erwinia L-asparaginase in Vials.

BACKGROUND/AIM: L-Asparaginase (L-ASNase) is used as a tumor-inhibitory drug on paediatric acute lymphoblastic leukemia (ALL). ERW-ASNase is commercialised as a lyophilized powder stable only for 8 hours once reconstituted and, consequently, the leftover is usually discarded. The aim of this study will be to analyse the stability of the reconstituted lyophilised ERW-ASNase. MATERIALS AND METHODS: In the present study, we analysed the enzymatic stability of reconstituted ERW-ASNase after conservation in three different temperature conditions for 2 and 5 days. RESULTS: Our results show that ERW-ASNase is stable at 4°C, -20°C and -80°C for up to 5 days, retaining 95% of the initial enzymatic activity in all three storage temperatures tested. CONCLUSION: It is feasible to reuse the remaining content of ERW-ASNase vial after reconstitution, which allows the optimization of the content of ERW-ASNase vials use and reduces the cost of this formulation usage, making it more accessible.

A proteomic approach to identify endosomal cargoes controlling cancer invasiveness.

We have previously shown that Rab17, a small GTPase associated with epithelial polarity, is specifically suppressed by ERK2 (also known as MAPK1) signalling to promote an invasive phenotype. However, the mechanisms through which Rab17 loss permits invasiveness, and the endosomal cargoes that are responsible for mediating this, are unknown. Using quantitative mass spectrometry-based proteomics, we have found that knockdown of Rab17 leads to a highly selective reduction in the cellular levels of a v-SNARE (Vamp8). Moreover, proteomics and immunofluorescence indicate that Vamp8 is associated with Rab17 at late endosomes. Reduced levels of Vamp8 promote transition between ductal carcinoma in situ (DCIS) and a more invasive phenotype. We developed an unbiased proteomic approach to elucidate the complement of receptors that redistributes between endosomes and the plasma membrane, and have pin-pointed neuropilin-2 (NRP2) as a key pro-invasive cargo of Rab17- and Vamp8-regulated trafficking. Indeed, reduced Rab17 or Vamp8 levels lead to increased mobilisation of NRP2-containing late endosomes and upregulated cell surface expression of NRP2. Finally, we show that NRP2 is required for the basement membrane disruption that accompanies the transition between DCIS and a more invasive phenotype.

FAK acts as a suppressor of RTK-MAP kinase signalling in Drosophila melanogaster epithelia and human cancer cells.

Receptor Tyrosine Kinases (RTKs) and Focal Adhesion Kinase (FAK) regulate multiple signalling pathways, including mitogen-activated protein (MAP) kinase pathway. FAK interacts with several RTKs but little is known about how FAK regulates their downstream signalling. Here we investigated how FAK regulates signalling resulting from the overexpression of the RTKs RET and EGFR. FAK suppressed RTKs signalling in Drosophila melanogaster epithelia by impairing MAPK pathway. This regulation was also observed in MDA-MB-231 human breast cancer cells, suggesting it is a conserved phenomenon in humans. Mechanistically, FAK reduced receptor recycling into the plasma membrane, which resulted in lower MAPK activation. Conversely, increasing the membrane pool of the receptor increased MAPK pathway signalling. FAK is widely considered as a therapeutic target in cancer biology; however, it also has tumour suppressor properties in some contexts. Therefore, the FAK-mediated negative regulation of RTK/MAPK signalling described here may have potential implications in the designing of therapy strategies for RTK-driven tumours.

Chromogranins A and B are key proteins in amine accumulation, but the catecholamine secretory pathway is conserved without them.

Chromogranins are the main soluble proteins in the large dense core secretory vesicles (LDCVs) found in aminergic neurons and chromaffin cells. We recently demonstrated that chromogranins A and B each regulate the concentration of adrenaline in chromaffin granules and its exocytosis. Here we have further studied the role played by these proteins by generating mice lacking both chromogranins. Surprisingly, these animals are both viable and fertile. Although chromogranins are thought to be essential for their biogenesis, LDCVs were evident in these mice. These vesicles do have a somewhat atypical appearance and larger size. Despite their increased size, single-cell amperometry recordings from chromaffin cells showed that the amine content in these vesicles is reduced by half. These data demonstrate that although chromogranins regulate the amine concentration in LDCVs, they are not completely essential, and other proteins unrelated to neurosecretion, such as fibrinogen, might compensate for their loss to ensure that vesicles are generated and the secretory pathway conserved.

Chromogranins A and B as regulators of vesicle cargo and exocytosis.

Chromogranins (Cgs) are acidic proteins that have been implicated in several physiological processes such as vesicle sorting, the production of bioactive peptides and the accumulation of soluble species inside large dense core vesicles (LDCV). They constitute the main protein component in the vesicular matrix of LDCV. This latter characteristic of Cgs accounts for the ability of vesicles to concentrate catecholamines and Ca(2+). It is likely that Cgs are behind the delay in the neurotransmitter exit towards the extracellular milieu after vesicle fusion, due to their low affinity and high capacity to bind solutes present inside LDCV. The recent availability of mouse strains lacking Cgs, combined with the arrival of several techniques for the direct monitoring of exocytosis, have helped to expand our knowledge about the mechanisms used by granins to concentrate catecholamines and Ca(2+) in LDCV, and how they affect the kinetics of exocytosis. We will discuss the roles of Cgs A and B in maintaining the intravesicular environment of secretory vesicles and in exocytosis, bringing together the most recent findings from adrenal chromaffin cells.

Chromogranins as regulators of exocytosis.

Chromogranins (Cgs) constitute the main protein component in the vesicular matrix of large dense core vesicles (LDCV). These acidic proteins have been implicated in several physiological processes such as vesicle sorting, the generation of bioactive peptides and the accumulation of soluble species inside LDCV. This latter feature of Cgs accounts for the ability of vesicles to concentrate catecholamines and Ca(2+). Indeed, the low affinity and high capacity of Cgs to bind solutes at the low pH of the LDCV lumen seems to be behind the delay in the neurotransmitter exit towards the extracellular milieu after vesicle fusion. The availability of new mouse strains lacking Cgs in combination with the arrival of several techniques for the direct monitoring of exocytosis (like amperometry, patch-amperometry and intracellular electrochemistry), have helped advance our understanding of how these granins concentrate catecholamines and Ca(2+) in LDCV, and how they influence the kinetics of exocytosis. In this review, we will discuss the roles of Cgs A and B in maintaining the intravesicular environment of secretory vesicles and in exocytosis, bringing together the most recent findings from adrenal chromaffin cells.

Chromogranin B gene ablation reduces the catecholamine cargo and decelerates exocytosis in chromaffin secretory vesicles.

Chromogranins/secretogranins (Cgs) are the major soluble proteins of large dense-core secretory vesicles (LDCVs). We have recently reported that the absence of chromogranin A (CgA) caused important changes in the accumulation and in the exocytosis of catecholamines (CAs) using a CgA-knock-out (CgA-KO) mouse. Here, we have analyzed a CgB-KO mouse strain that can be maintained in homozygosis. These mice have 36% less adrenomedullary epinephrine when compared to Chgb(+/+) [wild type (WT)], whereas the norepinephrine content was similar. The total evoked release of CA was 33% lower than WT mice. This decrease was not due to a lower frequency of exocytotic events but to less secretion per quantum (approximately 30%) measured by amperometry; amperometric spikes exhibited a slower ascending but a normal decaying phase. Cell incubation with L-DOPA increased the vesicle CA content of WT but not of the CgB-KO cells. Intracellular electrochemistry, using patch amperometry, showed that L-DOPA overload produced a significantly larger increase in cytosolic CAs in cells from the KO animals than chromaffin cells from the WT. These data indicate that the mechanisms for vesicular accumulation of CAs in the CgB-KO cells were saturated, while there was ample capacity for further accumulation in WT cells. Protein analysis of LDCVs showed the overexpression of CgA as well as other proteins apparently unrelated to the secretory process. We conclude that CgB, like CgA, is a highly efficient system directly involved in monoamine accumulation and in the kinetics of exocytosis from LDCVs.