[Experimental study of IFN-alpha and IFN-gamma on reversing ATRA-resistance in MR2 cell line].

AIM: To explore the possibility and the possible mechanism of reversing ATRA-resistance in MR2 cells by using IFN-alpha and IFN-gamma in combination with all-trans retinoic acid (ATRA). METHODS: After MR2 cells(ATRA-resistance cell line) were treated with IFN-alpha, IFN-gamma and ATRA alone or IFN-alpha and IFN-gamma in combination with ATRA respectively, the cell proliferation was tested by MTT colorimetry, the cell differentiation was tested through light microscope, by NBT test and flow cytometry (FCM). The expression of promyelocytic leukemia (PML) protein was observed by indirect immunofluorescence staining. RESULTS: Both IFN-alpha and IFN-gamma could inhibit the proliferation of MR2 cells. The effects were more obviously in both IFN-alpha+ATRA group and IFN-gamma+ATRA group. But there were no significant difference between either IFN-alpha group and IFN-gamma group or IFN-alpha+ATRA group and IFN-gamma+ATRA group (P>0.05). Both IFN could also induce the differentiation of MR2 cells. The effects of IFN-alpha+ATRA group and IFN-gamma+ATRA group were more obvious. However, the differentiation of MR2 cells induced by IFN-gamma+ATRA group was more higher than that by IFN-alpha+ATRA group (P<0.05). Both IFN could induce the expression of PML protein. CONCLUSION: The reversing effcet of IFN-gamma+ATRA group on ATRA-resistence in MR2 cells are more powerful than that of IFN-alpha+ATRA group, which may be related to the different signal transduction pathway of IFN-alpha and IFN-gamma.

[Effects of interferon-gamma combined with all-trans retinoic acid on proliferation and differentiation of leukemia cell lines NB4 and MR2].

BACKGROUND & OBJECTIVE: More than 90% patients with acute promyelocytic leukemia (APL) achieve clinical complete remission by using all-trans retinoic acid (ATRA). However, the rapid development of ATRA-resistance has become a problem in treating APL. Many researches indicate that the mechanism of ATRA-resistance is related to lack of some proteins synthesized by interferon (IFN). This study was to explore the possibility and the possible mechanism of treating ATRA-resistant APL with IFN in combination with ATRA. METHODS: Interferon-gamma (IFNgamma) alone or IFNgamma combined with ATRA was used to treat ATRA-sensitive cell line NB4 and ATRA-resistant cell line MR2. Cell proliferation was tested by MTT assay. Light microscope and NBT test were used to evaluate cell differentiation. The expression of promyelocytic leukemia (PML) protein was observed by indirect immune fluorescent method. RESULTS: On the 8th day, the growth inhibition rates of NB4 cells and MR2 cells were significantly higher in combination group than in IFNgamma group and ATRA group (95.2% vs. 68.0% and 85.0%, P<0.05; 51.5% vs. 24.1% and 4.3%, P<0.05). On the 3rd day, the positive rates of NBT in NB4 cells and MR2 cells were significantly higher in combination group than in IFNgamma group and ATRA group (93.3% vs. 19.3% and 74.7%, P<0.05; 31.5% vs. 16.8% and 5.2%, P<0.05). After treatment of IFNgamma, the fluorescent particles in NB4 and MR2 cell nuclei were obviously increased as compared with those in control group. CONCLUSION: IFNgamma and ATRA have synergistic inhibitory effect on the proliferation of NB4 cells and MR2 cells, and can partially induce the differentiation of ATRA-resistant MR2 cells.

[Induction of active antitumor immune response by myeloma idiotype protein-pulsed dendritic cells].

BACKGROUND & OBJECTIVE: Most multiple myeloma (MM) patients could not be cured by high-dose chemotherapy and bone marrow transplantation. This study was designed to investigate in vitro killing effect of tumor-specific cytotoxic T lymphocytes (CTLs) stimulated by idiotype protein (Id)-pulsed dendritic cells (DCs) on autologous MM cells. METHODS: DCs were generated from peripheral blood monocytes of 6 MM patients using interleukin-4 (IL-4) and granulocyte-macrophage colony-stimulating factor (GM-CSF). After cultured for 5 days, immature DCs were pulsed with Idû tumor necrosis factor-alpha (TNF-alpha) was added at the 7th day. Id-pulsed DCs were cocultured with autologous T cells for 3 days to induce tumor-specific CTLs. MTT assay was used to detect proliferation of autologous T cells, and evaluate killing effect of CTLs on autologous MM cells. RESULTS: Mature DCs were successfully induced. Id-pulsed DCs markedly increased proliferation of autologous T cells in a dose-dependent manner; stimulation index (SI) of Id-pulsed DCs was the highest [(39.1+/-6.0)%] when the radio of DCs to T cells was 10:1, which was significantly higher than those of unpulsed mature DCs [(19.3+/-7.7)%], Id-pulsed immature DCs [(15.9+/-6.1)%], and unpulsed immature DCs [(11.4+/-4.9)%] (P < 0.01). Id-pulsed DCs induced anti-MM activity of CTLs in a dose-dependent manner. Unpulsed mature DCs also induced cytotoxicity of CTLs against autologous MM cellsû however, when DC:T was 30:1, killing rate of MM cells was significantly higher in Id-pulsed mature DCs group than in unpulsed mature DCs group [(70.1+/-7.9)% vs. (40.8+/-7.8)%,P < 0.05]. KRN7000-pulsed mature DCs stimulated proliferation of allogeneic T cells in a dose-dependent manner; when DC:T was 1:10, SI was significantly higher in KRN7000-pulsed mature DCs group than in unpulsed mature DCs group [(38.5+/-5.7)% vs. (20.2+/-5.7)%, P < 0.05]. CONCLUSIONS: Mature DCs could be induced and Id with biological activity could be extracted from peripheral blood of MM patients. Id-pulsed DCs could induce antitumor immune response. KRN7000 could improve the immune function of in vitro cultured DCs.

[Development of MTS/pms colorimetric assay in the proliferation of leukemic cells].

In order to establish a new more rapid, safe and sensitive colorimetric assay for the proliferation of leukemic cells, MTS/pms has been developed. This automated colorimetric assay is based on the characteristic of viable and metabolically active leukemic cells to cleave MTS/pms into a water-soluble product whose optical density is determined at 492 nm by an automated microtiter-plate reader photometer. The results indicated that only active leukemic cells cleaved MTS/pms into product measured, and dead cells did not reduce MTS/pms. A linear relations hip were found between the viable cell number and optical density of MTS/pms cleaved by HL-60 and K562 cell (r = 0.963). Compared with MTT and INT assays, the reduced product of MTS/pms is water-soluble. It is concluded that MTS/pms colorimetric assay is more rapid, accurate and sensitive for the bioassay of proliferation of leukemic cells.

[The expression of glutathione s-transferase in leukemic cells and resistance to chemotherapy].

In order to study the relationship between the expression of glutathione S-transferase (GST) in leukemic cells and the chemoresistance in patients with acute leukemia, the expressions of GST activity and GST mRNA were measured according to spectrophotometric assay based on the use of 1-choloro-2, 4-dinitro benzene and in situ hybridization. The results were studied in correlation with some clinical and pathological data. Results showed that: 1. There is no significant differences between activities of the enzyme with the different leukemia types according to the FAB classification. 2. GST activity and GST mRNA expression in the patients, both untreated and relapse, were (4.5 +/- 1.0) U, 33.3% and (7.9 +/- 15) U, 66.3% respectively. 3. In 56 patients, GST activity was 1.7 +/- 0.7, 5.9 +/- 2.0 and 9.3 +/- 1.7 U and GST mRNA expression was 13.3%, 29.7% and 76.6%, respectively, in CR, PR and NR groups. The lowest values of GST activity and GST mRNA expression were observed in those patients who achieved complete remission. The highest values of GST activity and GST mRNA expression were observed in those patients with no response to treatment. It was concluded that the expression of GST in patients with acute leukemia is closely related to the chemosensitivities clinically. Determinations of GST activity and GST mRNA are useful for predicting the chemosensitivities and the prognosis of the disease.