Upregulation of CXCR4 is functionally crucial for maintenance of stemness in drug-resistant non-small cell lung cancer cells

The hypothesis of cancer stem cells has been proposed to explain the therapeutic failure in a variety of cancers including lung cancers. Previously, we demonstrated acquisition of epithelial-mesenchymal transition, a feature highly reminiscent of cancer stem-like cells, in gefitinib-resistant A549 cells (A549/GR). Here, we show that A549/GR cells contain a high proportion of CXCR4+ cells that are responsible for having high potential of self-renewal activity in vitro and tumorigenicity in vivo. A549/GR cells exhibited strong sphere-forming activity and high CXCR4 expression and SDF-1α secretion compared with parent cells. Pharmacological inhibition (AMD3100) and/or siRNA transfection targeting CXCR4 significantly suppressed sphere-forming activity in A549 and A549/GR cells, and in various non-small cell lung cancer (NSCLC) cell lines. A549/GR cells showed enhanced Akt, mTOR and STAT3 (Y705) phosphorylation. Pharmacological inhibition of phosphatidyl inositol 3-kinase or transfection with wild-type PTEN suppressed phosphorylation of Akt, mTOR and STAT3 (Y705), sphere formation, and CXCR4 expression in A549/GR cells, whereas mutant PTEN enhanced these events. Inhibition of STAT3 by WP1066 or siSTAT3 significantly suppressed the sphere formation, but not CXCR4 expression, indicating that STAT3 is a downstream effector of CXCR4-mediated signaling. FACS-sorted CXCR4+ A549/GR cells formed many large spheres, had self-renewal capacity, demonstrated radiation resistance in vitro and exhibited stronger tumorigenic potential in vivo than CXCR4- cells. Lentiviral-transduction of CXCR4 enhanced sphere formation and tumorigenicity in H460 and A549 cells, whereas introduction of siCXCR4 suppressed these activities in A549/GR cells. Our data indicate that CXCR4+ NSCLC cells are strong candidates for tumorigenic stem-like cancer cells that maintain stemness through a CXCR4-medated STAT3 pathway and provide a potential therapeutic target for eliminating these malignant cells in NSCLC.

CD19 signalling improves the Epstein-Barr virus-induced immortalization of human B cell

Epstein-Barr virus (EBV) infection in vitro immortalizes primary B cells and generates B lymphoblastoid cell lines (LCLs). These EBV-LCLs have been used for several purposes in immunological and genetic studies, but some trials involving these transformations fail for unknown reasons, and several EBV-LCLs do not grow in normal culture. In this study, we improved the immortalization method by CD19 and B-cell receptor (BCR) co-ligation. This method shortens the time required for the immortalization and generation of EBV-LCLs but does not alter the cell phenotype of the LCLs nor the expression of the EBV genes. In particular, the CD19 and BCR co-ligation method was found to be the most effective method examined. EBV-infected B cells induced by CD19 and/or BCR ligation expressed the intracellular latent membrane protein LMP-1 earlier than EBV-infected B cells, and the expression of intracellular LMP-1 was found to be closely related to the time of immortalization. These results suggest that the modified method, using CD19 and/or BCR ligation, may efficiently generate EBV-LCLs, by expressing intracellular LMP-1 at an early stage.

Biosynthesis and local sequence specific degradation of poly(3-hydroxyvalerate-co-4-hydroxybutyrate) in Hydrogenophaga pseudoflava

A novel copolymer that consisted of 3-hydroxyvalerate and 4-hydroxybutyrate, P(3HV-co-4HB), was synthesized in Hydrogenophaga pseudoflava by growing it in media containing gamma-valerolactone and gamma-butyrolactone as a carbon source. The monomer ratio in the copolymer was changed by altering the feed ratio of the two lactones. The cultivation technique was composed of three steps: the first-step for high cell production in Luria-Bertani medium, the second-step for intracellular degrading removal of poly(3-hydroxybutyrate) (P(3HB)), which was formed in the first step, by culturing the cells in carbon-source-free medium, and the final step for accumulation of P(3HV-co-4HB) in a mixed lactone medium. All the P(3HV-co-4HB) copolymers contained less than 1 mol % of 3HB unit. These copolymers were characterized by NMR spectroscopy, differential scanning calorimetry, wide-angle X-ray diffraction, and first-order kinetic analysis of intracellular degradation. The copolymer with an approximately equal ratio of the comonomers was found amorphous. The NMR microstructural analysis showed that the copolymers contained appreciable amounts of 3HV-rich or 4HB-rich chains. The (13)C NMR splitting patterns associated with the four carbons in the 4HB unit of P(3HV-co-4HB) bear close resemblance to those observed in the 4HB unit of P(3HB-co-4HB). The signals arising from the carbons in the 3HV unit of P(3HV-co-4HB) split in a manner similar to those in the 3HB unit of P(3HB-co-4HB). Thus the sequences were assigned by comparing the NMR splittings for P(3HV-co-4HB) with those for P(3HB-co-4HB) and P(3HB-co-3HV). The sequence assignment was further checked by comparing the signal intensities before and after degradation of the copolymers. This was considered reasonable because the H. pseudoflava intracellular PHA depolymerase is more specific to the 3HV unit than to the 4HB unit, which was also confirmed by the higher degradation rate constant for the 3HV unit in the first-order kinetic analysis.

Functional characterization of TEL/AML1 fusion protein in the regulation of human CR1 gene promoter

The TEL/AML1 fusion gene occurs in childhood B-cell acute lymphoblastic leukemia (ALL) as a result of the translocation of human chromosome 12;21. Using reporter gene assays, we have functionally characterized TEL, AML1 and TEL/AML1 fusion proteins in the regulation of the human CR1 gene. Analysis of transcription activities showed that AML1 increased the CR1 promoter activity and that TEL repressed the basal activity of the promoter. Increased activities of the CR1 promoter by AML1 protein were reduced by the TEL protein in a concentration-dependent manner. When TEL/AML1 and AML1 proteins are present in cells at the same time, the TEL/AML1 protein inhibits the transactivation activities of AML1 protein on the human CR1 promoter even though TEL/AML1 retains the transactivation domain of AML1. A mutation analysis of the human CR1 promoter revealed that the binding sites for TEL and AML1 are necessary for the action of TEL and TEL/AML1, respectively. Thus, production of the TEL/AML1 protein by translocation of human chromosome 12;21 may contribute to leukemogenesis by the specific inhibition of AML1-dependent activation of myeloid promoters.

AML1, the target of chromosomal rearrangements in human leukemia, regulates the expression of human complement receptor type 1 (CR1) gene

The human CR1 gene is expressed specifically in hematopoietic cells. It is suggested that some cell-type specific factors which involve in gene-specific activation or repression exist in cells according to the result that the gene expression varies differently depend on differentiation stage. Here, we demonstrate that the integrity of a polyomavirus enhancer core sequence, 5'-TGTGGT-3', is critical to the human CR1 promoter activity. AML1 is a site-specific DNA-binding protein that recognizes the enhancer core motif TGTGGT. We show that the AML1 binds specifically to this site and activates the human CR1 promoter. Furthermore, we demonstrate that the Ets binding site (GGAA) located 2 bp upstream of the AML1 site is also involved in the regulation of the human CR1 promoter activity. Point mutations of either the AML1 or the Ets binding site that abolish the binding of the respective factors result in significant decreases of the human CR1 promoter activity. These results suggest that AML1 and Ets proteins direct the expression of the human CR1 promoter.

Expression of yeast O6-methylguanine-DNA methyltransferase (MGMT) gene

We cloned the full genomic DNA of yeast (Saccharomyces cerevisiae) O6-methylguanine-DNA methyltransferase (MGMT) gene and examined its expression. The expression of yeast MGMT gene is decreased when cells reach stationary phase and cannot be induced by the pretreatment with alkylating agents, methylmethanesulfonate (MMS) or N-methyl-N'-nitroso-N-nitrosoguanidine (MNNG). The transcription initiation site was determined by primer extension analysis. This analysis showed that the authentic start codon is the ATG at position +32 from transcription initiation site.

Oxidation of the angiotensin II receptor antagonist losartan (DuP 753) in human liver microsomes. Role of cytochrome P4503A(4) in formation of the active metabolite EXP3174

The oxidative metabolism of losartan (DuP 753), a novel angiotensin II receptor antagonist, by human liver microsomes and purified cytochrome P450 (P450) enzymes, was studied. The primary route of metabolism of losartan is by oxidation of the C5-hydroxymethyl to the carboxylic acid (EXP3174), which is an active metabolite of losartan. When microsomes prepared from different human liver samples were compared, EXP3174 formation activity was well correlated (r2 = 0.93) with nifedipine oxidation (a marker of P4503A4), but not with markers for other human liver P450s. Microsomal oxidation of losartan to EXP3174 was markedly inhibited by gestodene and ketoconazole, selective inhibitors of P4503A enzymes, but not by any of several other P450 inhibitors. Antibodies raised against P4503A4 could inhibit most of the oxidation of losartan to EXP3174 in a microsomal sample having high catalytic activity, but antibodies recognizing other P450s had no effect. The oxidation of losartan to EXP3174 was catalyzed by purified human liver microsomal P4503A4 and by purified bacterial recombinant P4503A4. These results provide evidence that P4503A4 (and possibly other P4503A enzymes) play a major role in the formation of an active metabolite EXP3174.