Insights into gemcitabine resistance and the potential for therapeutic monitoring

Introduction

Gemcitabine is an important component of pancreatic cancer clinical management. Unfortunately, acquired gemcitabine resistance is widespread and there are limitations to predicting and monitoring therapeutic outcomes.

Objective

To investigate the potential of metabolomics to differentiate pancreatic cancer cells that develops resistance or respond to gemcitabine treatment.

Results

We applied 1D ¹H and 2D ¹H–¹³C HSQC NMR methods to profile the metabolic signature of pancreatic cancer cells. ¹³C₆-glucose labeling identified 30 key metabolites uniquely altered between wild-type and gemcitabine-resistant cells upon gemcitabine treatment. Gemcitabine resistance was observed to reprogram glucose metabolism and to enhance the pyrimidine synthesis pathway. Myo-inositol, taurine, glycerophosphocholine and creatinine phosphate exhibited a “binary switch” in response to gemcitabine treatment and acquired resistance.

Conclusion

Metabolic differences between naïve and resistant pancreatic cancer cells and, accordingly, their unique responses to gemcitabine treatment were revealed, which may be useful in the clinical setting for monitoring a patient’s therapeutic response.

     

Sensitivity to house dust mite allergens and prevalence of allergy-causing house dust mite species in Pothwar,Pakistan

This study is the first report on the epidemiological status of house dust mite (HDM) allergy in Pothwar, Pakistan. Allergy data of 2087 symptomatic patients were obtained, of whom 1706 (81.7%) patients were skin-prick-test positive for HDM allergens. This percentage was significantly higher than for pollen and food allergens. In the results of this study Dermatophagoides farinae (61%) and D. pteronyssinus (29%) were the predominant species in the study area. Besides these pyroglyphids, predatory Cheyletus sp. (10%) and an oribatid mite sp. (1%) were also observed. Random and patients’ houses showed 87.4 and 87.1% positive mite infestation, respectively. Mean (±?SEM) D. farinae counts per g of dust in random samples was 235.4 ± 7.93 compared to 274.7 ± 10.78 from patients’ homes. Mean D. pteronyssinus counts from random houses compared to patients’ houses were 115.0 ± 4.57 and 124.6 ± 5.76, respectively. Mite counts depicted seasonal variation, with peaks during monsoon season. ELISA results of dust samples demonstrated that of the dust samples with?>?10 µg/g of dust, the threshold value described as a risk factor for developing asthma, 57.6% had Der f1 and 20% Der p1 allergen load. Mean Der f1 burden was significantly higher than Der p1, with maximum levels during monsoon and autumn seasons. This research established a better awareness about the epidemiological status of HDM allergy and prevalence of allergy causing HDM species in Pakistan.     

Multielement proton-induced X-ray emission analysis of betel leaves,betel nuts,and lime

Proton-induced X-ray emission (PIXE) method was employed to study the concentration of heavy elements in betel leaves, betel nuts, and mineral lime consumed in Bangladesh. The samples were collected from different parts of Bangladesh and analyzed by the thicktarget external beam technique of the PIXE method. The samples were exposed to the proton beam as 1-mm thick pellets and irradiated with 2.0-MeV protons having 20-nA beam intensity. The concentration of some 15 elements (K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Se, Br, Rb, Sr, and Pb) was measured by comparison with a calibration curve constructed from the NBS orchard leaf standard SRM 1571. The validity of the procedure has been established by comparative measurements of Cu and Zn with atomic absorption spectrophotometry. The significance of the results is discussed in view of their implications in health and disease.     

Melittin peptides exhibit different activity on different cells and model membranes

Melittin (MLT) is a lytic peptide with a broad spectrum of activity against both eukaryotic and prokaryotic cells. To understand the role of proline and the thiol group of cysteine in the cytolytic activity of MLT, native MLT and cysteine-containing analogs were prepared using solid phase peptide synthesis. The antimicrobial and cytolytic activities of the monomeric and dimeric MLT peptides against different cells and model membranes were investigated. The results indicated that the proline residue was necessary for antimicrobial activity and cytotoxicity and its absence significantly reduced lysis of model membranes and hemolysis. Although lytic activity against model membranes decreased for the MLT dimer, hemolytic activity was increased. The native peptide and the MLT-P14C monomer were mainly unstructured in buffer while the dimer adopted a helical conformation. In the presence of neutral and negatively charged vesicles, the helical content of the three peptides was significantly increased. The lytic activity, therefore, is not correlated to the secondary structure of the peptides and, more particularly, on the propensity to adopt helical conformation.     

Proline-rich antimicrobial peptides: potential therapeutics against antibiotic-resistant bacteria

The increasing resistance of pathogens to antibiotics causes a huge clinical burden that places great demands on academic researchers and the pharmaceutical industry for resolution. Antimicrobial peptides, part of native host defense, have emerged as novel potential antibiotic alternatives. Among the different classes of antimicrobial peptides, proline-rich antimicrobial peptides, predominantly sourced from insects, have been extensively investigated to study their specific modes of action. In this review, we focus on recent developments in these peptides. They show a variety of modes of actions, including mechanism shift at high concentration, non-lytic mechanisms, as well as possessing different intracellular targets and lipopolysaccharide binding activity. Furthermore, proline-rich antimicrobial peptides display the ability to not only modulate the immune system via cytokine activity or angiogenesis but also possess properties of penetrating cell membranes and crossing the blood brain barrier suggesting a role as potential novel carriers. Ongoing studies of these peptides will likely lead to the development of more potent antimicrobial peptides that may serve as important additions to the armoury of agents against bacterial infection and drug delivery.     

Active site conformational changes upon reaction intermediate biotinyl‐5'‐AMP binding in biotin protein ligase from Mycobacterium tuberculosis

Protein biotinylation, a rare form of post‐translational modification, is found in enzymes required for lipid biosynthesis. In mycobacteria, this process is essential for the formation of their complex and distinct cell wall and has become a focal point of drug discovery approaches. The enzyme responsible for this process, biotin protein ligase, substantially varies in different species in terms of overall structural organization, regulation of function and substrate specificity. To advance the understanding of the molecular mechanism of biotinylation in Mycobacterium tuberculosis we have biochemically and structurally characterized the corresponding enzyme. We report the high‐resolution crystal structures of the apo‐form and reaction intermediate biotinyl‐5'‐AMP‐bound form of M. tuberculosis biotin protein ligase. Binding of the reaction intermediate leads to clear disorder‐to‐order transitions. We show that a conserved lysine, Lys138, in the active site is essential for biotinylation.