Radiation pharmacogenomics: a genome-wide association approach to identify radiation response biomarkers using human lymphoblastoid cell lines.

Radiation therapy is used to treat half of all cancer patients. Response to radiation therapy varies widely among patients. Therefore, we performed a genome-wide association study (GWAS) to identify biomarkers to help predict radiation response using 277 ethnically defined human lymphoblastoid cell lines (LCLs). Basal gene expression levels and 1.3 million genome-wide single nucleotide polymorphism (SNP) markers from both Affymetrix and Illumina platforms were assayed for all 277 human LCLs. MTS [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium] assays for radiation cytotoxicity were also performed to obtain area under the curve (AUC) as a radiation response phenotype for use in the association studies. Functional validation of candidate genes, selected from an integrated analysis that used SNP, expression, and AUC data, was performed with multiple cancer cell lines using specific siRNA knockdown, followed by MTS and colony-forming assays. A total of 27 loci, each containing at least two SNPs within 50 kb with P-values less than 10(-4) were associated with radiation AUC. A total of 270 expression probe sets were associated with radiation AUC with P < 10(-3). The integrated analysis identified 50 SNPs in 14 of the 27 loci that were associated with both AUC and the expression of 39 genes, which were also associated with radiation AUC (P < 10(-3)). Functional validation using siRNA knockdown in multiple tumor cell lines showed that C13orf34, MAD2L1, PLK4, TPD52, and DEPDC1B each significantly altered radiation sensitivity in at least two cancer cell lines. Studies performed with LCLs can help to identify novel biomarkers that might contribute to variation in response to radiation therapy and enhance our understanding of mechanisms underlying that variation.

Experimental therapy of hepatoma with artemisinin and its derivatives: in vitro and in vivo activity, chemosensitization, and mechanisms of action.

PURPOSE: ART and its derivatives, clinically used antimalarial agents, have recently shown antitumor activities. However, the mechanisms underlying these activities remain unclear. This study was designed to determine their antitumor efficacy and underlying mechanisms of action in human hepatoma cells. EXPERIMENTAL DESIGN: The in vitro cytotoxicities of ART, DHA, artemether, and artesunate were compared in human hepatoma cells, HepG2 (p53 wild-type), Huh-7 and BEL-7404 (p53 mutant), and Hep3B (p53 null), and a normal human liver cell line, 7702. Based on their activity and specificity, ART and DHA were further investigated for their in vitro and in vivo antitumor effects and their effects on the protein expression of genes associated with cell proliferation and apoptosis. RESULTS: ART and DHA exerted the greatest cytotoxicity to hepatoma cells but significantly lower cytotoxicity to normal liver cells. The compounds inhibited cell proliferation, induced G(1)-phase arrest, decreased the levels of cyclin D1, cyclin E, cyclin-dependent kinase 2, cyclin-dependent kinase 4, and E2F1, and increased the levels of Cip1/p21 and Kip1/p27. They induced apoptosis, activated caspase-3, increased the Bax/Bcl-2 ratio and poly(ADP-ribose) polymerase, and down-regulated MDM2. In mice bearing HepG2 and Hep3B xenograft tumors, ART and DHA inhibited tumor growth and modulated tumor gene expression consistent with in vitro observations. DHA increased the efficacy of the chemotherapeutic agent gemcitabine. CONCLUSIONS: ART and DHA have significant anticancer effects against human hepatoma cells, regardless of p53 status, with minimal effects on normal cells, indicating that they are promising therapeutics for human hepatoma used alone or in combination with other therapies.

FKBP5 as a selection biomarker for gemcitabine and Akt inhibitors in treatment of pancreatic cancer.

We have recently shown that the immunophilin FKBP5 (also known as FKBP51) is a scaffolding protein that can enhance PHLPP-AKT interaction and facilitate PHLPP-mediated dephosphorylation of Akt Ser473, negatively regulating Akt activation in vitro. Therefore, FKBP5 might function as a tumor suppressor, and levels of FKBP5 would affect cell response to chemotherapy. In the current study, we have taken a step forward by using a pancreatic cancer xenograft mice model to show that down regulation of FKBP5 in shFKBP5 xenograft mice promotes tumor growth and resistance to gemcitabine, a phenomenon consistent with our previous findings in pancreatic cell lines. In addition, we also found that inhibitors targeting the Akt pathway, including PI3K inhibitor, Akt inhibitor and mTOR inhibitor had a different effect on sensitization to gemcitabine and other chemotherapeutic agents in cell lines, with a specific Akt inhibitor, triciribine, having the greatest sensitization effect. We then tested the hypothesis that addition of triciribine can sensitize gemcitabine treatment, especially in shFKBP5 pancreatic cancer xenograft mice. We found that combination treatment with gemcitabine and triciribine has a better effect on tumor inhibition than either drug alone (p<0.005) and that the inhibition effect is more significant in shFKBP5 xenograft mice than wt mice (p<0.05). These effects were correlated with level of Akt 473 phosphorylation as well as proliferation rate, as indicated by Ki67 staining in xenograft tumor tissues. These results provide evidence in support of future clinical trials designed to tailor therapy based on our observations.

Iron deprivation suppresses hepatocellular carcinoma growth in experimental studies.

PURPOSE: Hepatocellular carcinoma (HCC) is the third most common cause of cancer-related death, and iron overload is a significant risk factor in the development of HCC. In this study, we investigated the potential application of depriving iron by a novel iron chelator, thiosemicarbazone-24 (TSC24), in HCC treatment. EXPERIMENTAL DESIGN: Two HCC cell lines and HFE knockout (HFE(-/-)) mice were used to determine iron chelation efficiency of TSC24. The anticancer effects of TSC24 on HCC were analyzed in vitro and in athymic xenograft mouse models. RESULTS: Treatment with TSC24 significantly decreased the cellular iron concentration in hepatoma cells and the serum iron concentration in HFE(-/-) mice by blocking iron uptake and interfering with normal regulation of iron levels. Moreover, the viability of HCC cell lines was reduced by TSC24. Confirming the mechanism of the agent, this decrease in viability could be partially rescued by addition of exogenous iron. TSC24 also suppressed tumor growth in athymic mice bearing human HCC xenografts in a concentration-dependent manner, without apparent toxicity in parallel with a decrease in the serum iron level. Further studies revealed that TSC24 efficiently triggered cell-cycle arrest and apoptosis in Hep3B and HepG2 cell lines. CONCLUSIONS: TSC24 is a potent iron chelator that suppresses human HCC tumor growth by disrupting iron homeostasis, reducing available iron, and triggering cell-cycle arrest and apoptosis, without apparent host toxicity at effective doses. Thus, TSC24 shows great potential for the treatment of HCC.