MSH3 Mismatch Repair Protein Regulates Sensitivity to Cytotoxic Drugs and a Histone Deacetylase Inhibitor in Human Colon Carcinoma Cells.

MSH3 Mismatch Repair Protein Regulates Sensitivity to Cytotoxic Drugs and a Histone Deacetylase Inhibitor in Human Colon Carcinoma Cells.

PLoS One. 2013; 8(5): e65369
Park JM, Huang S, Tougeron D, Sinicrope FA

MSH3 is a DNA mismatch repair (MMR) gene that undergoes frequent somatic mutation in colorectal cancers (CRCs) with MMR deficiency. MSH3, together with MSH2, forms the MutS? heteroduplex that interacts with interstrand cross-links induced by drugs such as cisplatin. To date, the impact of MSH3 on chemosensitivity is unknown.We utilized isogenic HCT116 (MLH1-/MSH3-) cells where MLH1 is restored by transfer of chromosome 3 (HCT116+ch3) and also MSH3 by chromosome 5 (HCT116+3+5). We generated HCT116+3+5, SW480 (MLH1+/MSH3+) and SW48 (MLH1-/MSH3+) cells with shRNA knockdown of MSH3. Cells were treated with 5-fluorouracil (5-FU), SN-38, oxaliplatin, or the histone deacetylase (HDAC) inhibitor PCI-24781 and cell viability, clonogenic survival, DNA damage and apoptosis were analyzed.MSH3-deficient vs proficient CRC cells showed increased sensitivity to the irinotecan metabolite SN-38 and to oxaliplatin, but not 5-FU, as shown in assays for apoptosis and clonogenic survival. In contrast, suppression of MLH1 attenuated the cytotoxic effect of 5-FU, but did not alter sensitivity to SN-38 or oxaliplatin. The impact of MSH3 knockdown on chemosensitivity to SN-38 and oxaliplatin was maintained independent of MLH1 status. In MSH3-deficient vs proficient cells, SN-38 and oxaliplatin induced higher levels of phosphorylated histone H2AX and Chk2, and similar results were found in MLH1-proficient SW480 cells. MSH3-deficient vs proficient cells showed increased 53BP1 nuclear foci after irradiation, suggesting that MSH3 can regulate DNA double strand break (DSB) repair. We then utilized PCI-24781 that interferes with homologous recombination (HR) indicated by a reduction in Rad51 expression. The addition of PCI-24781 to oxaliplatin enhanced cytotoxicity to a greater extent compared to either drug alone.MSH3 status can regulate the DNA damage response and extent of apoptosis induced by chemotherapy. The ability of MSH3 to regulate chemosensitivity was independent of MLH1 status. PCI-24781-mediated impairment of HR enhanced oxaliplatin sensitivity, suggesting that reduced DSB repair capacity may be contributory. HubMed – drug


How to improve the implementation of academic clinical pediatric trials involving drug therapy? A qualitative study of multiple stakeholders.

PLoS One. 2013; 8(5): e64516
Girard D, Bourdon O, Abdoul H, Prot-Labarthe S, Brion F, Tibi A, Alberti C

The need for encouraging pediatric drug research is widely recognized. However, hospital-based clinical trials of drug treatments are extremely time-consuming, and delays in trial implementation are common. The objective of this qualitative study was to collect information on the perceptions and experience of health professionals involved in hospital-based pediatric drug trials.Two independent researchers conducted in-depth semi-structured interviews with principal investigators (n?=?17), pharmacists (n?=?7), sponsor representatives (n?=?4), and drug regulatory agency representatives (n?=?3) who participated in institutionally sponsored clinical trials of experimental drugs in pediatric patients between 2002 and 2008.Dissatisfaction was reported by 67% (16/24) of principal investigators and pharmacists: all 7 pharmacists felt they were involved too late in the trial implementation process, whereas 11 (65%) principal investigators complained of an excessive regulatory burden and felt they were insufficiently involved in the basic research questions. Both groups perceived clinical trial implementation as burdensome and time-consuming. The sponsor and regulatory agency representatives reported a number of difficulties but were not dissatisfied.The heavy burden related to regulatory requirements, and suboptimal communication across disciplines involved, seem to be the main reasons for the major delays in pediatric drug trial implementation. The pharmaceutical aspects are intrinsically tied to trial methodology and implementation and must therefore be examined, in particular by involving Clinical Research Pharmacists at early stages of study conception. HubMed – drug


Atomic force microscopy images label-free, drug encapsulated nanoparticles in vivo and detects difference in tissue mechanical properties of treated and untreated: a tip for nanotoxicology.

PLoS One. 2013; 8(5): e64490
Lamprou DA, Venkatpurwar V, Kumar MN

Overcoming the intractable challenge of imaging of label-free, drug encapsulated nanoparticles in tissues in vivo would directly address associated regulatory concerns over ‘nanotoxicology’. Here we demonstrate the utility of Atomic Force Microscopy (AFM) for visualising label-free, drug encapsulated polyester particles of ?280 nm distributed within tissues following their intravenous or peroral administration to rodents. A surprising phenomenon, in which the tissues’ mechanical stiffness was directly measured (also by AFM) and related to the number of embedded nanoparticles, was utilised to generate quantitative data sets for nanoparticles localisation. By coupling the normal determination of a drug’s pharmacokinetics/pharmacodynamics with post-sacrifice measurement of nanoparticle localisation and number, we present for the first time an experimental design in which a single in vivo study relates the PK/PD of a nanomedicine to its toxicokinetics. HubMed – drug