Targeting ß-catenin overcomes MEK inhibition resistance in colon cancer with KRAS and PIK3CA mutations.

BACKGROUND: Mitogen-activated protein kinases (MEK 1/2) are central components of the RAS signalling pathway and are attractive targets for cancer therapy. These agents continue to be investigated in KRAS mutant colon cancer but are met with significant resistance. Clinical investigations have demonstrated that these strategies are not well tolerated by patients. METHODS: We investigated a biomarker of response for MEK inhibition in KRAS mutant colon cancers by LC-MS/MS analysis. We tested the MEK inhibitor in PIK3CA wild(wt) and mutant(mt) colon cancer cells. In addition, we tested the combinational effects of MEK and TNKS inhibitor in vitro and in vivo. RESULTS: We identified ß-catenin, a key mediator of the WNT pathway, in response to MEK inhibitor. MEK inhibition led to a decrease in ß-catenin in PIK3CA wt colon cancer cells but not in mt. Tumour regression was promoted by combination of MEK inhibition and NVP-TNS656, which targets the WNT pathway. Furthermore, inhibition of MEK promoted tumour regression in colon cancer patient-derived xenograft models expressing PIK3CA wt. CONCLUSIONS: We propose that inhibition of the WNT pathway, particularly ß-catenin, may bypass resistance to MEK inhibition in human PIK3CA mt colon cancer. Therefore, we suggest that ß-catenin is a potential predictive marker of MEK inhibitor resistance.

Time-dependent proteomic and genomic alterations in Toll-like receptor-4-activated human chondrocytes: increased expression of lamin A/C and annexins.

Activation of Toll-like receptor-4 (TLR-4) in articular chondrocytes increases the catabolic compartment and leads to matrix degradation during the development of osteoarthritis. In this study, we determined the proteomic and genomic alterations in human chondrocytes during lipopolysaccharide (LPS)-induced inflammation to elucidate the underlying mechanisms and consequences of TLR-4 activation. Human chondrocytes were cultured with LPS for 12, 24, and 36 h to induce TLR-4 activation. The TLR-4-induced inflammatory response was confirmed by real-time PCR analysis of increased interleukin-1 beta (IL-1ß), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF-α) expression levels. In TLR-4-activated chondrocytes, proteomic changes were determined by two-dimensional electrophoresis and matrix-assisted laser desorption/ionization-mass spectroscopy analysis, and genomic changes were determined by microarray and gene ontology analyses. Proteomics analysis identified 26 proteins with significantly altered expression levels; these proteins were related to the cytoskeleton and oxidative stress responses. Gene ontology analysis indicated that LPS treatment altered specific functional pathways including 'chemotaxis', 'hematopoietic organ development', 'positive regulation of cell proliferation', and 'regulation of cytokine biosynthetic process'. Nine of the 26 identified proteins displayed the same increased expression patterns in both proteomics and genomics analyses. Western blot analysis confirmed the LPS-induced increases in expression levels of lamin A/C and annexins 4/5/6. In conclusion, this study identified the time-dependent genomic, proteomic, and functional pathway alterations that occur in chondrocytes during LPS-induced TLR-4 activation. These results provide valuable new insights into the underlying mechanisms that control the development and progression of osteoarthritis.

A novel small-molecule IAP antagonist, AZD5582, draws Mcl-1 down-regulation for induction of apoptosis through targeting of cIAP1 and XIAP in human pancreatic cancer.

Inhibitor of apoptosis proteins (IAPs) plays an important role in controlling cancer cell survival. IAPs have therefore attracted considerable attention as potential targets in anticancer therapy. In this study, we investigated the anti-tumor effect of AZD5582, a novel small-molecule IAP inhibitor, in human pancreatic cancer cells. Treating human pancreatic cancer cells with AZD5582 differentially induced apoptosis, dependent on the expression of p-Akt and p-XIAP. Moreover, the knockdown of endogenous Akt or XIAP via RNA interference in pancreatic cancer cells, which are resistant to AZD5582, resulted in increased sensitivity to AZD5582, whereas ectopically expressing Akt or XIAP led to resistance to AZD5582. Additionally, AZD5582 targeted cIAP1 to induce TNF-α-induced apoptosis. More importantly, AZD5582 induced a decrease of Mcl-1 protein, a member of the Bcl-2 family, but not that of Bcl-2 and Bcl-xL. Interestingly, ectopically expressing XIAP and cIAP1 inhibited the AZD5582-induced decrease of Mcl-1 protein, which suggests that AZD5582 elicits Mcl-1 decrease for apoptosis induction by targeting of XIAP and cIAP1. Taken together, these results indicate that sensitivity to AZD5582 is determined by p-Akt-inducible XIAP phosphorylation and by targeting cIAP1. Furthermore, Mcl-1 in pancreatic cancer may act as a potent marker to analyze the therapeutic effects of AZD5582.

Cellular inhibitor of apoptosis protein 1 (cIAP1) stability contributes to YM155 resistance in human gastric cancer cells.

YM155, which blocks the expression of survivin, a member of the inhibitor of apoptosis (IAP) family, induces cell death in a variety of cancer types, including prostate, bladder, breast, leukemia, and non-small lung cancer. However, the mechanism underlying gastric cancer susceptibility and resistance to YM155 is yet to be specified. Here, we demonstrate that cIAP1 stability dictates resistance to YM155 in human gastric cancer cells. Treatment of human gastric cancer cells with YM155 differentially induced cell death dependent on the stability of cIAP1 as well as survivin. Transfection with cIAP1 expression plasmids decreased cell sensitivity to YM155, whereas knockdown of endogenous cIAP1 using RNA interference enhanced sensitivity to YM155. In addition, double knockdown of survivin and cIAP1 significantly induced cell death in the YM155-resistant cell line, MKN45. We also showed that YM155 induced autoubiquitination and proteasome-dependent degradation of cIAP1. Surprisingly, survivin affected the stability of cIAP1 through binding, contributing to cell sensitivity to YM155. Thus, our findings reveal that YM155 sensitizes human gastric cancer cells to apoptotic cell death by degrading cIAP1, and furthermore, cIAP1 in gastric cancer cells may act as a PD marker for YM155 treatment.

NVP-BEZ235, a dual PI3K/mTOR inhibitor, induces cell death through alternate routes in prostate cancer cells depending on the PTEN genotype.

Deregulation of the PI3K-AKT/mTOR pathway due to mutation of the tumor suppressor gene PTEN frequently occurs in human prostate cancer and is therefore considered to be an attractive therapeutic target. Here, we investigated how the PTEN genotype affected the antitumor effect of NVP-BEZ235 in human prostate cancer cells. In this setting, NVP-BEZ235 induced cell death in a PTEN-independent manner. NVP-BEZ235 selectively induced apoptotic cell death in the prostate cancer cell line DU145, which harbors wild-type PTEN; however, in the PC3 cell line, which is PTEN-null, treatment with NVP-BEZ235 resulted in autophagic cell death. Consistently, NVP-BEZ235 treatment did not result in the cleavage of caspase-3; instead, it resulted in the conversion of LC3-I to LC3-II, indicating autophagic cell death; these results suggest that an alternate mechanism of cell death is induced by NVP-BEZ235 in PTEN-null prostate cancer cells. Based on our findings, we conclude that the PTEN/PI3K/Akt pathway is critical for prostate cancer survival, and targeting PI3K signaling by NVP-BEZ235 may be beneficial in the treatment of prostate cancer, independent of the PTEN genotype.

Antitumor activity of sorafenib-incorporated nanoparticles of dextran/poly(dl-lactide-co-glycolide) block copolymer.

Sorafenib-incoporated nanoparticles were prepared using a block copolymer that is composed of dextran and poly(DL-lactide-co-glycolide) [DexbLG] for antitumor drug delivery. Sorafenib-incorporated nanoparticles were prepared by a nanoprecipitation-dialysis method. Sorafenib-incorporated DexbLG nanoparticles were uniformly distributed in an aqueous solution regardless of the content of sorafenib. Transmission electron microscopy of the sorafenib-incorporated DexbLG nanoparticles revealed a spherical shape with a diameter < 300 nm. Sorafenib-incorporated DexbLG nanoparticles at a polymer/drug weight ratio of 40:5 showed a relatively uniform size and morphology. Higher initial drug feeding was associated with increased drug content in nanoparticles and in nanoparticle size. A drug release study revealed a decreased drug release rate with increasing drug content. In an in vitro anti-proliferation assay using human cholangiocarcinoma cells, sorafenib-incorporated DexbLG nanoparticles showed a similar antitumor activity as sorafenib. Sorafenib-incorporated DexbLG nanoparticles are promising candidates as vehicles for antitumor drug targeting.

Self-assembled nanoparticles of hyaluronic acid/poly(DL-lactide-co-glycolide) block copolymer.

We synthesized block copolymer composed of hyaluronic acid (HA) and poly(DL-lactide-co-glycolide) (PLGA) (HAbLG) for antitumor targeting. (1)H NMR was employed to confirm synthesis of block copolymer. At (1)H NMR study, HabLG nanoparticles showed HA intrinsic peaks only at D(2)O, indicating that they contained HA as a hydrophilic outer-shell and PLGA as a inner-core. Anti-tumor activity was studied using CD44-overexpressing HCT-116 human colon carcinoma cells. Addition of doxorubicin (DOX)-incorporated nanoparticles to tumor cells resulted in the expression of a strong red fluorescence color while they expressed very weak fluorescence when CD44 receptor was blocked with free HA. Flow cytometry data also showed similar results, indicating that the fluorescence intensity of tumor cells treated with nanoparticles was significantly decreased when CD44 receptor was blocked. These results indicate that HAbLG nanoparticles were able to target CD44-overexpressing tumor cells via receptor-mediated endocytosis.

Doxorubicin-incorporated polymeric micelles composed of dextran-b-poly(DL-lactide-co-glycolide) copolymer.

BACKGROUND: Polymeric micelles using amphiphilic macromolecules are promising vehicles for antitumor targeting. In this study, we prepared anticancer agent-incorporated polymeric micelles using novel block copolymer. METHODS: We synthesized a block copolymer composed of dextran and poly (DL-lactide-co-glycolide) (DexbLG) for antitumor drug delivery. Doxorubicin was selected as the anticancer drug, and was incorporated into polymeric micelles by dialysis. Polymeric micelles were observed by transmission electron microscopy to be spherical and smaller than 100 nm, with a narrow size distribution. The particle size of doxorubicin-incorporated polymeric micelles increased with increasing drug content. Higher initial drug feeding also increased the drug content. RESULTS: During the drug-release study, an initial burst release of doxorubicin was observed for 10 hours, and doxorubicin was continuously released over 4 days. To investigate the in vitro anticancer effects of the polymeric micelles, doxorubicin-resistant HuCC-T1 cells were treated with a very high concentration of doxorubicin. In an antiproliferation study, the polymeric micelles showed higher cytotoxicity to doxorubicin-resistant HuCC-T1 cells than free doxorubicin, indicating that the polymeric micelles were effectively engulfed by tumor cells, while free doxorubicin hardly penetrated the tumor cell membrane. On confocal laser scanning microscopy, free doxorubicin expressed very weak fluorescence intensity, while the polymeric micelles expressed strong red fluorescence. Furthermore, in flow cytometric analysis, fluorescence intensity of polymeric micelles was almost twice as high than with free doxorubicin. CONCLUSION: DexbLG polymeric micelles incorporating doxorubicin are promising vehicles for antitumor drug targeting.

Glutathione peroxidase 1 protects mitochondria against hypoxia/reoxygenation damage in mouse hearts.

Glutathione peroxidase 1 (GPx1) plays an important role in preventing cardiac dysfunction following ischemia-reperfusion injury. However, its role in protecting cardiac mitochondria against reoxygenation-induced reactive oxygen species (ROS) generation in vivo is unclear. We examined the role of GPx1 in protecting cardiac mitochondria against hypoxia-reoxygenation (HR) damage by testing for alterations in cardiac mitochondrial function. We used a two-dimensional gel electrophoresis proteomics analysis to examine the effects of reoxygenation on cardiac protein in wild-type (GPx1(+/+)) and GPx1 knockout (GPx1(-/-)) mouse hearts. We identified 42 protein spots showing differential expression in the two groups. Sixteen of the proteins identified were located in mitochondria and were involved in a number of key metabolic pathways. To verify our proteomics findings functionally, we performed NADH autofluorescence measurements and ATP production assays. The reduced expression of oxidative phosphorylation proteins in GPx1(-/-) mice following HR treatment resulted in loss of the mitochondrial membrane potential and decreased mitochondrial respiration. Mitochondrial ROS production and oxidative mtDNA damage were increased markedly during reoxygenation in GPx1(-/-) hearts. We also found morphological abnormalities in cardiac mitochondria and myocytes in HR-treated GPx1(-/-). This is the first report of the role of GPx1 in protecting cardiac mitochondria against reoxygenation damage in vivo. These findings will help clarify the mechanisms of HR injury and will aid in the development of antioxidant therapies to prevent cardiac mitochondrial dysfunction associated with reoxygenation.