Interferon (IFN) treatment of target cells can alter their susceptibility to natural resistance (NR), evidenced as in vitro 'natural killer' (NK) cell-mediated lysis or as in vivo rapid cell clearance. This paper reports the consequence of direct in vitro treatment with IFN-alpha/beta or IFN-gamma on acute rejection of leukemia cells in lethally irradiated hosts. This type of rejection has the characteristics of NR, although it is specific and genetically regulated. The data were obtained injecting intravenously FLC (FLC-745 and FLC-3C18 clones; H-2d) and EL-4 (H-2b) leukemia lines in lethally irradiated syngeneic mice and evaluating proliferation 4 days later by 125IUdR uptake. Overnight pretreatment with 100 U/ml of IFN-gamma protected tumor cells from NR-induced rejection in mice. This was evident by higher 125IUdR incorporation in spleens of mice inoculated with IFN-gamma pretreated leukemia cells, as compared to that detected in the spleens of hosts injected with untreated cells, in mice with high levels of NR, but not in hosts depressed for NR. Treatment with 1,000 U/ml of IFN-alpha/beta induced protection only of FLC-745 cells, injected in Poly I:C stimulated hosts. On the other hand, a lower 125IUdR uptake after IFN-alpha/beta incubation, as compared with control cells, was evidenced with FLC-745 and EL-4 lines inoculated in mice with normal or depressed NR. The IFN-induced alterations of leukemia cells to in vivo NR susceptibility were not associated with substantial changes of binding ability to NR effectors or of MHC-antigen expression.

Animals↗

PubMedDate not supplied

Differential effects of recombinant interferon-alpha and 5-fluorouracil against colon cancer cells or against peripheral blood mononuclear cells.

Comparative studies on the suppressive effects of recombinant interferon-alpha (IFN-alpha), 5-fluorouracil (5-FU), or IFN-alpha + 5-FU have been performed in vitro on colon carcinoma cells (HT-29 cell line) and PHA-stimulated mononuclear cells (MNC) of peripheral blood obtained from healthy donors. IFN-alpha was used at 500 U/ml against HT-29 cells and at 1000 U/ml against MNC on day 1 of culture; 5-FU was used at 250 microM against HT-29 and at 1400 microM against MNC on day 2 of culture. The results show that: (a) IFN-alpha inhibited MNC and HT-29 cells by 13.4% and 32.9%, respectively; (b) 5-FU inhibited MNC and HT-29 cells by 54.7% and 87.0%, respectively; (c) IFN-alpha + 5-FU resulted in a stronger inhibition of HT-29 cells (i.e., 96.1%). In contrast, that combination was significantly less suppressive than 5-FU alone when MNC were used as targets (i.e., 35.9% inhibition). Natural cell-mediated cytotoxic activity relative to 10(6) MNC was not markedly altered by all agents alone or in combination. Moreover, treatment with IFN-alpha, 5-FU or IFN-alpha + 5-FU resulted in a marked increase in the number of HT-29 cells positive for the CEA surface antigen. These data seem to provide further rational support of the clinical use of IFN-alpha + 5-FU in colorectal cancer, based on the differential toxicity of this drug combination on tumor versus normal immunocompetent cells.

Antineoplastic Combined Chemotherapy Protocols↗

PubMedDate not supplied

Effect of 4-hydroxynonenal, a product of lipid peroxidation, on NK susceptibility of human K562 target cells.

4-Hydroxynonenal (HNE) is one of the major breakdown products generated by lipid peroxidation of cellular membranes. The level of lipid peroxidation and the concentration of its products are inversely related to the rate of cell proliferation and directly related to the level of cell differentiation. It has been reported that HNE inhibits DNA synthesis, ornithine decarboxylase (ODC) activity and c-myc expression in different leukemic cells lines. It has also been demonstrated that HNE inhibits proliferation and induces differentiation in HL60 cell line. In the present study the effects of HNE, at concentrations close to those found in the normal tissues, on the NK susceptibility of human K562 target cells were analyzed. Repeated treatments at 45 minutes intervals with 1 microM HNE were performed to maintain the cells in the presence of the aldehyde for 12 hours. The effect of HNE was compared with that obtained in Haemin-treated cells. HNE causes a strong inhibition of cells growth (53% vs. 34% with Haemin) without affecting cell viability. We further investigated the NK susceptibility of K562 cell line upon in vitro treatment with HNE. Cytotoxic activity of mononuclear cells (MNC) from peripheral blood of healthy donors was determined by 4 hours Cr51-release assay. The results obtained, expressed in terms of percentage of specific lysis at different E:T ratios and in terms of KC (10(6)) at the E:T ratio of 50:1, show that HNE treatment of K562 cells leads to a marked reduction of susceptibility to NK cells; this decrease is very close to that found in the K562 cells treated with Haemin used as inducer. Similar results were obtained using MNC pre-treated with beta-interferon (IFN) as effector cells. MNC show a reduced capacity to lyse HNE-treated cells also under the enhancing cytolytic effect of IFN. These results are in line with data obtained with several common inducers of differentiation such as DMSO, retinoic acid or others.

Aldehydes↗

PubMedDate not supplied

2'-2'-difluorodeoxycytidine: in vitro effects on cell-mediated immune response.

Little or no data are available on the immunotoxicity of the new deoxycytidine analogue, gemcitabine (2'-2'-Difluorodeoxycytidine, dFdC). The drug was tested on natural killer (NK), interleukin 2-activated killer (LAK) and antigen-dependent cytotoxic effector cells (CTL) activity. NK cells were treated for 16 hours and then tested against K562 cell line. LAK cells were pretreated for 16 hours before or after IL2 stimulation, and tested against DAUDI cells on day 4. CTL were pretreated for 16 hours on day-1 or on day 4 of coculture, and then tested against MT-2 on day 5. Cytotoxic activity was evaluated by a 4 hours 51Cr-release assay. The results indicate that dFdC inhibits markedly LAK or CTL generation, but does so less efficiently on "mature" LAK or CTL lymphocyte function and only slightly on NK cell activity. Therefore dFdC can be considered immunotoxic for either natural or antigen-dependent cell-mediated immunity.

Antimetabolites, Antineoplastic↗