Synergistic antiproliferative effects of interleukin-1 alpha and doxorubicin against the human ovarian carcinoma cell line (NIH:OVCAR-3)

Cytokine-mediated reversal of multidrug resistance

The occurrence of the multidrug resistance phenotype still represents a limiting factor for successful cancer chemotherapy. Numerous efforts have been made to develop strategies for reversal and/or modulation of this major therapy obstacle through targeting at different levels of intervention. The phenomenon of MDR is often associated with overexpression of resistance-associated genes. Since the classical type of MDR in human cancers is mainly mediated by the P-glycoprotein encoded by the multidrug resistance gene 1, mdr1, the majority of reversal approaches target the expression and/or function of the mdr1 gene/P-glycoprotein. Due to the fact that the multidrug phenotype always represents the net effect of a panel of resistance-associated genes/gene products, other resistance genes, e.g. those encoding the multidrug resistance-associated protein MRP or the lung resistance protein LRP, were included in the studies. Cytokines such as tumor necrosis factor alpha and interleukin-2 have been shown to modulate the MDR phenotype in different experimental settings in vitro and in vivo. Several studies have been performed to evaluate their potential as chemosensitizers of tumor cells in the context of a combined application of MDR-associated anticancer drugs like doxorubicin and vincristine with cytokines. Moreover, the capability of cytokines to modulate the expression of MDR-associated genes was demonstrated, either by external addition or by transduction of the respective cytokine gene. Knowledge of the combination effects of cytokines and cytostatics and its link to their MDR-modulating capacity may contribute to a more efficient and to a more individualized immuno-chemotherapy of human malignancies.

A Novel Group of Genes Regulates Susceptibility to Antineoplastic Drugs in Highly Tumorigenic Breast Cancer Cells

Doxorubicin is an anthracycline antibiotic used for cancer chemotherapy. The utility of doxorubicin is limited by its inability to kill all of the cells within a tumor and by resistant cells emerging from the treated population. We have screened for genes that regulate doxorubicin susceptibility in highly tumorigenic breast cancer cells by cDNA microarray and RNA interference (RNAi) analysis, and we have identified genes associated with both proliferation and cell cycle arrest after doxorubicin treatment. We confirmed that MDA-MB-231 cells treated with doxorubicin induce the expression of carbonic anhydrase II (CAII), inhibitor of differentiation/DNA binding 2 (Id2), activating transcription factor 3 (Atf3), and the phosphatidylinositol 3-kinase 55-kDa regulatory subunit p55PIK. These genes were induced at different times and with varying specificities to different chemotherapeutic drugs. In addition to being induced at the transcriptional level, the CAII and clusterin proteins were elevated after doxorubicin treatment. CAII, Id2, p55PIK, and clusterin were not altered by doxorubicin in MCF-7 cells, a weakly tumorigenic cell line used in previous studies of doxorubicin-regulated gene expression. By inhibiting gene expression using RNAi, we found that CAII and clusterin increase cell survival after doxorubicin treatment, whereas Id2 increases susceptibility to doxorubicin. Our results support a model in which highly tumorigenic breast cancer cells induce a transcriptional response to doxorubicin that is distinct from less malignant cells. The induced genes regulate drug susceptibility positively and negatively and may be novel targets for therapeutic intervention.

Sensitization by interleukin-1alpha of carboplatinum anti-tumor activity against human ovarian (NIH:OVCAR-3) carcinoma cells in vitro and in vivo

Cytokines are directly cytotoxic to tumor cells in vitro and in vivo, and interleukin-1alpha (IL-1alpha) potentiates the cytotoxicity of a number of clinically active drugs in several human tumor cells, including carcinomas of the breast and ovary. In this study, we found that IL-1alpha potentiated the cytotoxicity of carboplatin in human ovarian NIH:OVCAR-3 cancer cells during simultaneous drug exposure in vitro. Human ovarian carcinoma NIH:OVCAR-3 cells are resistant to clinically relevant concentrations of chemotherapeutic agents, including cisplatin. Both carboplatin and IL-1alpha as single agents inhibited the growth of NIH:OVCAR-3 cells grown as xenograft in nude mice; however, carboplatin was more effective in delaying tumor growth, and this inhibition was dose-dependent. Treatment with IL-1alpha followed by carboplatin caused a significant delay in tumor growth, resulting in a significant enhancement (4-fold) of the anti-tumor effect of carboplatin. In vitro potentiation of carboplatin cytotoxicity by IL-1alpha did not involve formation of nitric oxide as IL-1 or combinations of IL-1 with carboplatin failed to modulate basal nitric oxide production in OVCAR-3 cells. Potentiation of the anti-tumor activity of carboplatin by IL-1alpha was due to a significant (3- to 4-fold) increase in the accumulation of total Pt in IL-1-treated tumor xenograft, resulting in a 2-fold increase in DNA-Pt adduct formation in these tumors. In contrast, IL-1alpha had no significant effect on DNA-Pt adduct formation in the kidney. The potent synergy of IL-1alpha and carboplatin in vitro and in vivo against ovarian carcinoma cells suggests that combinations of carboplatinum and interleukin-1alpha may be effective against this disease in the clinic.

Modulation of mdr1 expression by cytokines in human colon carcinoma cells: an approach for reversal of multidrug resistance

Reversal of multidrug resistance (MDR) may offer a means of increasing the effectiveness of tumour chemotherapy. A variety of recent evidence indicates that cytokines may be particularly useful in this endeavour. To investigate the molecular mechanism by which cytokines may sensitise multidrug-resistant colon carcinoma cells, HCT15 and HCT116, to treatment with MDR-related drugs, we evaluated the effects of the human cytokines tumour necrosis factor alpha (TNF alpha), interleukin 2 (IL-2) and interferon gamma (IFN gamma) on mdr1 gene expression at the mRNA level by reverse transcription-polymerase chain reaction (RT-PCR) and at the protein level with monoclonal antibodies by immuno flow cytometry. P-glycoprotein function was examined after accumulation of the fluorescent drug, doxorubicin, by flow cytometry. Chemosensitivity to doxorubicin and vincristine was analysed using the XTT assay. All three cytokines were found to modulate the MDR characteristics on mdr1 expression levels, P-glycoprotein function and measured chemosensitivity to MDR-associated anti-cancer drugs. This cytokine-induced reversal of MDR was strongly time dependent, with maximal effects after 48 and 72 h of cytokine treatment. If similar modulation of MDR phenotype can be obtained in in vivo models, it may be possible to verify the time course for modulation by cytokine treatment and to design appropriate clinical trials of this strategy for MDR reversal.