Curcumin induces apoptosis and inhibits growth of human Burkitt's lymphoma in xenograft mouse model.

Curcumin, a natural compound extracted from rhizomes of curcuma Curcuma species, has been shown to possess potent anti-inflammatory, anti-tumor and anti-oxidative properties. However, the mechanism of action of the compound remains poorly understood. In this report, we have analyzed the effects of curcumin on the cell proliferation of Burkitt's lymphoma Raji cells. The results demonstrated that curcumin could effectively inhibit the growth of Raji cells in a dose- and time-dependent manner. Further studies indicated that curcumin treatment resulted in apoptosis of cells. Biochemical analysis showed that the expression of Bax, Bid and cytochrome C were up-regulated, while the expression of oncogene c-Myc was down regulated after curcumin treatment. Furthermore, poly (ADP-ribose) polymerase (PARP) cleavage was induced by the compound. Interestingly, the antiapoptotic Bcl-2 expression was not significantly changed in Raji cells after curcumin treatment. These results suggested that the mechanism of action of curcumin was to induce mitochondrial damage and therefore led to Raji cell apoptosis. We further investigated the in vivo effects of curcumin on the growth of xenograft tumors in nude mice. The results showed that curcumin could effectively inhibit tumor growth in the xenograft mouse model. The overall results showed that curcumin could suppress the growth of Burkitt's lymphoma cells in both in vitro and in vitro systems.

[Studies on fermentation conditions and purification of mutant human interleukin-2 expressed in Pichia pastoris].

Interleukin-2 (IL-2) was initially isolated as a T cell growth factor and had been shown to direct the expansion and differentiation of several hematopoietic cell types. Clinical studies using IL-2 in the treatment of AIDS have been encouraging, due to its critical role as a proliferative signal for activated T-lymphocytes. IL-2 has also undergone trials in the treatment of several types of cancer, based on its stimulation of cytotoxic, antitumor cells. Today, human IL-2 is produced completely by genetically engineered method, and it has been proved that genetically engineered recombinant human IL-2 has almost the same function and clinical effect as wild IL-2. In the former study, recombinant human IL-2 usually comes from E. coli, in this paper the mutant IL-2 was successfully expressed and purified in Pichia pastoris for the first time. As a eukaryote, Pichia pastoris has many of the advantages of higher eukaryotic expression systems such as protein processing, protein folding, and posttranslational modification, while being as easy to manipulate as E. coli or Saccharomyces cerevisiae. It is faster, easier, and less expensive to use than other eukaryotic expression systems such as baculovirus or mammalian tissue culture, and generally gives higher expression level. Expression conditions of human mutant interleukin-2(the codon for cysteine-125 of human IL-2 with alanine; the codon for leucine-18 with methionine; the codon for leucine-19 with serine) in the recombinant Pichia pastoris strain were optimized via test of some factors such as the rate of aeration, the inductive duration, the initial pH and the concentration of methanol. The results from tests showed that the most important parameter for efficient expression of interleukin-2 in recombinant Pichia pastoris strain is adequate aeration during methanol induction, and the optimum inductive condition for interleukin-2 expression was: more than 80% aeration, 2 days for induction, the initial pH of 6.0, the final methanol concentration of 1.0%. With this condition, the expressed IL-2 was secreted into fermentation broth and reached a yield of 30%, approximately 200 mg/L. Expressed interleutin-2 (MvIL-2) was isolated and purified by centrifugation, millipore filtration to concentration, Econo-PacS strongly acidic cation exchanger cartridge and molecular sieve chromatography and the yield of MvIL-2 was 27%. MvIL-2 was purified to electrophoretic purity by SDS-PAGE and only one peak being loaded on HPLC. Purified MvIL-2 protein had stimulating activity similar to the wild type of IL-2 as assayed by IL-2-dependent CTLL-2 cells. However, the stability of MvIL-2 was superior than that of IL-2 at different temperatures. The activity of obtained MvIL-2 was 4 - 5 times of the wild type of IL-2, So MvIL-2 had an advantage over wild type of rhIL-2 in storage stability and activity.