Dynamic genomic changes in methotrexate-resistant human cancer cell lines beyond DHFR amplification suggest potential new targets for preventing drug resistance.

BACKGROUND: Although DHFR gene amplification has long been known as a major mechanism for methotrexate (MTX) resistance in cancer, the early changes and detailed development of the resistance are not yet fully understood. METHODS: We performed genomic, transcriptional and proteomic analyses of human colon cancer cells with sequentially increasing levels of MTX-resistance. RESULTS: The genomic amplification evolved in three phases (pre-amplification, homogenously staining region (HSR) and extrachromosomal DNA (ecDNA)). We confirm that genomic amplification and increased expression of DHFR, with formation of HSRs and especially ecDNAs, is the major driver of resistance. However, DHFR did not play a detectable role in the early phase. In the late phase (ecDNA), increase in FAM151B protein level may also have an important role by decreasing sensitivity to MTX. In addition, although MSH3 and ZFYVE16 may be subject to different posttranscriptional regulations and therefore protein expressions are decreased in ecDNA stages compared to HSR stages, they still play important roles in MTX resistance. CONCLUSION: The study provides a detailed evolutionary trajectory of MTX-resistance and identifies new targets, especially ecDNAs, which could help to prevent drug resistance. It also presents a proof-of-principal approach which could be applied to other cancer drug resistance studies.

[Preparation and characterization of visible-light response activated carbon with antibacterial behavior].

A visible-light response activated carbon with antibacterial activity was prepared by calcinations of the mixture of TiO2 precursor obtained by acid catalyzed hydrolysis method and commercial granular activated carbon (GAC) in NH3/N2 atmosphere. The antibacterial activity of the prepared activated carbon towards E. coil was investigated under the visible-light irradiation. X-ray diffraction (XRD), Scanning electron spectroscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and N2 adsorption analyser were used to characterize the crystal phase structure, surface morphology, spectral characteristics and pore properties. The results show there is no influence for crystal phase structure of TiO2 supported AC. The crystal size of TiO2 is 9.8 nm. Non-crystal phase layer and strong adsorption force of carrier can inhibit the grain growth of TiO2, and AC combines with TiO2 in Ti-O-C so that TiO2 formestight film on AC. The sample calcinated at 500 degrees C for 5 h exhibits the highest bactericidal performance, and the bactericidal rate reached up to 67% after 4 h irradiation, which was better than that of nature light (39%) in the same condition.