Objective To study the role of protective antigen(PA)and N-terminal segment of lethal factor (LFn)in the entrance of EGFP(enhanced green fluorescent protein)into HeLa cells. Methods The DNA fragments encoding LFn and EGFP were amplified,respectively,and cloned into the plasmid pET-21 a(+)one after another to construct a recombinant plasmid pET-LFn-EGFP. The plasmid was txansformed into BL21 cells to express LFn-EGFP protein under the induction of IPTG. The protein was purified by Ni chelating chromatography. After incubation with LFn-EGFP in the presence of PA or not, the HeLa cells were analyzed by flow cytometry or laser confocal microscopy. Results The fusion protein LFn-EGFP was purified by over 90% homogeneity and retained the ability of LF to bind with PA when incubated with J774A.1 macrophage cells,and could get into HeLa cells. Conclusion The LFn-EGFP could enter the HeLa cells in a PA independent pathway. But PA could help more LFn-EGFP molecules enter into HeLa cells.

OBJECTIVETo study the relationship between sensitivity to 5-FU and the status of a panel of microsatellite loci in three human colon cancer cell lines.

METHODSCell viability in several concentrations of 5-FU was assessed by the MTT test. Expression of hMSH2 and hMLH1 in LoVo, SW480 and SW1116 cells were analyzed by immunocytochemical staining.Ten mononucleotide and dinucleotide microsatellite loci were analyzed by the PCR-SSLP-silver staining method.

RESULTSBy MTT assay, it showed that LoVo cells were more sensitive than SW480 and SW1116 cells (0.8 micromol/L,2.2 micromol/L and 1.9 micromol/L, respectively, P < 0.05). By immunocytochemical staining, hMSH2 was expressed in SW480 and SW1116 cells but not in LoVo cells, while hMLH1 was positive in all three cell lines. The PCR-SSLP-silver staining of 10 microsatellite loci revealed that LoVo cells had a different pattern of electrophoretic bands compared with SW480 and SW1116 cells, manifesting both additions and band-shifts.

CONCLUSIONTogether with hMSH2 and hMLH1, the status of a panel of microsatellite loci may be used as convenient predictors for drug-optimization or prognosis-assessment in colorectal cancer patients before chemotherapy.

Adaptor Proteins, Signal Transducing ; Antimetabolites, Antineoplastic ; pharmacology ; Base Pair Mismatch ; Carrier Proteins ; Colorectal Neoplasms ; drug therapy ; genetics ; pathology ; DNA Repair ; DNA-Binding Proteins ; Fluorouracil ; pharmacology ; Humans ; Immunohistochemistry ; Microsatellite Repeats ; MutL Protein Homolog 1 ; MutS Homolog 2 Protein ; Neoplasm Proteins ; genetics ; Nuclear Proteins ; Polymerase Chain Reaction ; Proto-Oncogene Proteins ; genetics ; Tumor Cells, Cultured