Altered actin and immunoglobulin Cμ expression in nitrogen mustard-resistant human Burkitt lymphoma cells
✍ Scribed by K. B. Tan; Lisa Grillone; Rebecca Boyce; Stanley T. Crooke
- Publisher
- John Wiley and Sons
- Year
- 1989
- Tongue
- English
- Weight
- 565 KB
- Volume
- 40
- Category
- Article
- ISSN
- 0730-2312
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✦ Synopsis
Raji-HN2 is a B cell lymphoma (Burkitt lymphoma) line that was made resistant to nitrogen mustard. The drug-resistant phenotype was accompanied by changes in gene expression. The expression of four unrelated genes was examined by Northern blot analysis. Raji-HN2 cells were found to contain about twice the number of actin mRNA found in Raji cells. Both cell lines were found to contain equivalent amounts of /32-microglobulin, c-myc oncogene, and immunoglobulin Cp mRNAs. The Cp mRNA was, however, larger in size in Raji-HN2 cells. Alterations in actin and C p mRNAs in Raji-HN2 cells were not due to gene amplification or rearrangement because Southern blot analysis revealed no changes in the genomic organization of these genes. The increased actin mRNA content was correlated with an increased actin content of Raji-HN2 cells. The F-actin (stained with 7-nitrobenz-2-oxa-1,3diazolylphallacidin) content of single cells was quantitated in a meridian interactive laser cytometer. Raji-HN2 cells contained about twice the amount of F-actin present in the parental Raji cells. Similar results were obtained when large populations, 106 cells each, were examined in a flow cytometer. Key words: drug resktamq c-myc oncogew, (Btmicroglobulin, meridian laser cytometer Tumor cells often acquire resistance to drugs that are used in cancer chemotherapy [ 11. Numerous tissue culture cell lines have been developed to study the mechanism(s) of drug resistance in vitro. One such cell line, Raji-HN2, a Burkitt lymphoma cell line made resistant to nitrogen mustard (HN2), was developed to study the mechanism of resistance to alkylating agents [2]. HN2 is a bifunctional alkylating agent that interacts with DNA to form interstrand crosslinks which, if not removed, lead to cell death [3]. We reported that HN2 induced fewer cross-links in the DNA of Raji-HN2 than that of the parental Raji cells [4]. The reduced HN2-induced DNA cross-linking may be due to efficient repair of the DNA damage in Raji-HN2 cells. These cells have altered Abbreviations used: HN2, nitrogen mustard [2chlorc+N-(2chloroethyl)-N-methylethanamide]; N B D phallacidm, 7-nitrobenz-2-oxa-l,3diamlylphallacidm; 1 xSSPE, 0.18 M NaCI, 10 mM NaP04, pH 7.7,l mM EDTA.