Rational development of synergistic combinations of chemotherapy and molecular targeted agents for colorectal cancer treatment.

BACKGROUND: The irinotecan-induced phosphokinome changes in colorectal cancer (CRC) cells were used to guide the selection of targeted agents to be tested in combination with irinotecan. METHODS: Phosphokinome profiling with peptide arrays of tumour samples from nude mice xenografted with HT29 cells and treated or not with an effective dose of irinotecan was used to identify signalling pathways activated by irinotecan treatment. Then, drugs targeting these pathways were combined in vitro with irinotecan to test potential synergistic effect. The interactions between these drug combinations were assessed by a dose matrix approach. Confirmation of the most potential combination has been confirmed in vivo in xenografted mice. RESULTS: Irinotecan induced in vivo the activation of AKT and MEK1 phosphorylation. The dose matrix approach showed that BKM120 (PI3K inhibitor) and MEK162 (MEK inhibitor) are synergistic in vitro and in vivo with a cytostatic and cytotoxic effect, while combination of BKM120 and irinotecan or MEK162 and irinotecan are only additive or even antagonistic. However, the triple combination of SN38, BKM120 and MEK162 showed a better synergistic effect that BKM120 and MEK162, indicating that the cells need to inhibit both AKT and ERK pathways to become more sensitive to irinotecan-based chemotherapies. CONCLUSION: Analysis of chemotherapy-induced phosphokinome changes helps to elucidate the mechanisms of drug resistance and to guide the selection of targets for combination therapies with synergistic activity.

Mesenchymal stem cells seeded on a human amniotic membrane improve liver regeneration and mouse survival after extended hepatectomy.

Liver failure remains the leading cause of post-operative mortality after hepatectomy. This study investigated the effect of treatment with allogenic mesenchymal stem cells (MSCs) on survival and liver regeneration 48 hr and 7 days after 80% hepatectomy in C57Bl/6 mice. To optimize their biodistribution, MSCs were grown on acellular human amniotic membranes (HAM) and applied as a patch on the remnant liver. This approach was compared with MSC infusion and HAM patch alone. Hepatectomized mice without any treatment were used as control group. Survival rate was calculated and biological and histopathological parameters were analysed to monitor liver function and regeneration. MSCs grown on HAM retained their ability to proliferate, to differentiate into osteoblasts and adipocytes and to respond to pro-inflammatory stimuli. Extended hepatectomy (80%) led to liver failure that resulted in death within 72 hr in 76% of mice. MSC infusion showed an early but transitory positive effect on survival. MSC/HAM patches stimulated regeneration and significantly improved survival rate (54% vs. 24% in the control group at 7 days). They also decreased the severity of hepatectomy-induced steatosis, suggesting a modulation of lipid metabolism in hepatocytes. MSCs were still present on HAM at Days 2 and 7 posthepatectomy. In conclusion, engineered tissue constructs that combine MSCs and HAM improve survival and liver regeneration after 80% hepatectomy in mice. These encouraging results pave the way to potential clinical application.

BAG6/BAT3 modulates autophagy by affecting EP300/p300 intracellular localization.

We recently reported that BAG6/BAT3 (BCL2-associated athanogene 6) is essential for basal and starvation-induced autophagy in E18.5 bag6(-/-) mouse embryos and in mouse embryonic fibroblasts (MEFs) through the modulation of the EP300/p300-dependent acetylation of TRP53 and autophagy-related (ATG) proteins. We observed that BAG6 increases TRP53 acetylation during starvation and pro-autophagic TRP53-target gene expression. BAG6 also decreases the EP300 dependent-acetylation of ATG5, ATG7, and LC3-I, posttranslational modifications that inhibit autophagy. In addition, in the absence of BAG6 or when using a mutant of BAG6 exclusively located in the cytoplasm, autophagy is inhibited, ATG7 is hyperacetylated, TRP53 acetylation is abrogated, and EP300 accumulates in the cytoplasm indicating that BAG6 is involved in the regulation of the nuclear localization of EP300. We also reported that the interaction between BAG6 and EP300 occurs in the cytoplasm rather than the nucleus. Moreover, during starvation, EP300 is transported to the nucleus in a BAG6-dependent manner. We concluded that BAG6 regulates autophagy by controlling the localization of EP300 and its accessibility to nuclear (TRP53) and cytoplasmic (ATGs) substrates.

BAT3 modulates p300-dependent acetylation of p53 and autophagy-related protein 7 (ATG7) during autophagy.

Autophagy is regulated by posttranslational modifications, including acetylation. Here we show that HLA-B-associated transcript 3 (BAT3) is essential for basal and starvation-induced autophagy in embryonic day 18.5 BAT3(-/-) mouse embryos and in mouse embryonic fibroblasts (MEFs) through the modulation of p300-dependent acetylation of p53 and ATG7. Specifically, BAT3 increases p53 acetylation and proautophagic p53 target gene expression, while limiting p300-dependent acetylation of ATG7, a mechanism known to inhibit autophagy. In the absence of BAT3 or when BAT3 is located exclusively in the cytosol, autophagy is abrogated, ATG7 is hyperacetylated, p53 acetylation is abolished, and p300 accumulates in the cytosol, indicating that BAT3 regulates the nuclear localization of p300. In addition, the interaction between BAT3 and p300 is stronger in the cytosol than in the nucleus and, during starvation, the level of p300 decreases in the cytosol but increases in the nucleus only in the presence of BAT3. We conclude that BAT3 tightly controls autophagy by modulating p300 intracellular localization, affecting the accessibility of p300 to its substrates, p53 and ATG7.

Dystrophic neurites of senile plaques in Alzheimer's disease are deficient in cytochrome c oxidase.

Double-labeling immunofluorescence and confocal microscopy have been used to learn about the local relationship between amyloid, mitochondria, and cytochrome c oxidase (COX) in dystrophic neurites of senile plaques in the frontal cortex in Alzheimer's disease (AD). Dystrophic neurites surrounding amyloid plaques are filled with mitochondrial porin-immunoreactive structures. In contrast with tangle-bearing and non-tangle-bearing neurons, which express mitochondrial porin and COX subunit 4, porin-immunoreactive neurites of senile plaques lack COX subunit 4. Parallel western blot studies in mitochondria-enriched fractions of the frontal cortex in the same cases disclosed reduced expression levels of COX, but not of prohibitin, in AD stages VB/C of Braak. Co-localization of porin and lysosomal associated protein 1, as revealed by double-labeling immunofluorescence and confocal microscopy, suggests that mitochondria may be engulfed by lysosomes in dystrophic neurites. These findings support a local link between amyloid deposition, abnormal mitochondria and impaired respiratory chain function (resulting from decrease of COX expression) in dystrophic neurites of senile plaques in AD.

Increased expression of water channel aquaporin 1 and aquaporin 4 in Creutzfeldt-Jakob disease and in bovine spongiform encephalopathy-infected bovine-PrP transgenic mice.

Spongiform change is a cardinal feature in transmissible spongiform encephalopathies, including Creutzfeldt-Jakob disease (CJD) and bovine spongiform encephalopathy (BSE). It is characterized by swelling of the neuronal processes and vacuolization of the neuropil, leading to increased intraneuronal water content. The present study examines, by gel electrophoresis and Western blotting, the expression levels of the water channels aquaporin 1 (AQP1) and aquaporin 4 (AQP4) in the frontal cortex (area 8) homogenates of sporadic CJD cases (six men, four women; seven cases with methionine/methionine at codon 129 and PrP type 1; two cases with valine/valine at codon 129 and PrP type 2, and one case methionine/valine at codon 129 and PrP type 1) compared with age-matched controls, and cases with Alzheimer's disease (AD, stage VI of Braak and Braak) and diffuse Lewy body disease (DLB). AQP1 and AQP4 protein levels were also studied in the cerebral cortex of BSE-infected bovine-PrP transgenic mice (BoPrP-Tg110 mice) examined at 60, 150, 210 and 270 days post-inoculation (dpi) compared with healthy brain-inoculated control mice. Quantitative densitometry of AQP bands normalized for beta-actin was analyzed using Statgraphics plus 5.0 software from ANOVA and LSD statistical tests. Significant increased expression levels of AQP1 (as revealed with two different antibodies) and AQP4 were seen in CJD, but not in advanced AD and DLB cases when compared with controls. Immunohistochemistry revealed that AQP1 and AQP4 were expressed in astrocytes in diseased cases. No modifications in the expression levels of AQP1 and AQP4 were observed in BSE-infected bovine-PrP transgenic mice at 60, 150 and 210 dpi. However, a significant increase in the expression levels of AQP1 and AQP4 was found in mice at 270 dpi, the time corresponding with the appearance of PrP(res) immunoreactivity in Western blots and typical spongiform lesions in the brain. Together, these findings show increased expression of water channels in the brain in human and animal prion diseases. These modifications may have implications in the regulation of water transport in astrocytes and may account for an imbalance in water and ion homeostasis in prion diseases.