Overcoming tumor necrosis factor-alpha resistance of human renal and ovarian carcinoma cells by combination treatment with buthionine sulfoximine and tumor necrosis factor-alpha. Role of tumor necrosis factor-alpha mRNA down-regulation in tumor cell sensitization

Increased intracellular doxorubicin by anti-FAS monoclonal antibody: a mechanism that enhances the cytotoxicity in renal cell carcinoma cells

OBJECTIVES

To investigate the effect of anti-Fas monoclonal antibody (mAb) on the intracellular concentration of doxorubicin in renal cell carcinoma (RCC) cells. Little is known about the influence of anti-Fas mAb on the intracellular concentration of chemotherapeutic agents.

METHODS

The concentration of intracellular doxorubicin was determined by high-performance liquid chromatography. The mRNA and protein levels of multidrug resistance-associated protein gene were evaluated by reverse transcriptase-polymerase chain reaction and immunocytochemistry, respectively.

RESULTS

An increased concentration of doxorubicin inside the cells was found: 2.4-fold in ACHN cells (a human RCC cell line) after treatment with doxorubicin combined with anti-Fas mAb compared with doxorubicin alone. Of the five cases of freshly derived RCC cells treated with doxorubicin and anti-Fas mAb, the intracellular concentration of doxorubicin was increased 2.3 and 2.7-fold in two of them, respectively. Furthermore, both the mRNA and the protein levels of the multidrug resistance-associated protein gene were downregulated after treatment of ACHN cells with anti-Fas mAb. Treatment of ACHN cells with a combination of anti-Fas mAb and doxorubicin resulted in a potentiation of the doxorubicin-mediated cytotoxicity.

CONCLUSIONS

The increased intracellular concentration of doxorubicin by anti-Fas mAb might be one of the mechanisms responsible for the enhancement of doxorubicin-mediated cytotoxicity in RCC cells.

The significance of dihydropyrimidine dehydrogenase (DPD) activity in bladder cancer

Dihydropyrimidine dehydrogenase (DPD) is the rate-limiting enzyme in the pathway of uracil and thymine catabolism. DPD is also the principal enzyme involved in the degradation of 5-fluorouracil (5-FU), which is one of the anticancer chemotherapeutic agents currently used in the treatment of bladder cancer. Little is known about the significance of DPD activity in human cancers. We investigated the activity of DPD in 74 bladder cancers and the relationship between the DPD activity and the sensitivity to 5-FU. The levels of DPD activity in bladder cancer and normal bladder tissues were determined by the 5-FU degradation assay. The sensitivity to 5-FU was assessed by the microculture tetrazolium dye (dimethylthiazolyl-2-5-diphenyltetrazolium bromide; MTT) assay. The activity of DPD was approximately 2-fold higher in bladder cancer tissues compared with normal bladder tissues. DPD activity in invasive bladder cancers was approximately 2-fold higher than that in superficial cancers. In addition, the levels of DPD activity in grade 2 and grade 3 bladder cancers were approximately 3-fold and 4-fold higher than that in grade 1 cancers, respectively. Patients with superficial bladder cancer with a low DPD activity had a slightly longer postoperative tumour-free period than those with a high DPD activity over a 2-year follow-up period, but this was not significant. There was an inverse correlation between DPD activity in bladder cancer cells and their sensitivity to 5-FU. Furthermore, 5-chloro-2,4-dihydroxypyridine (CDHP), a potent DPD inhibitor, enhanced the sensitivity to 5-FU. The present study has demonstrated that the level of DPD activity correlated with the progression of the stage and an increase in the grade of the bladder cancer. These results suggest that an elevated DPD activity might be associated with the malignant potential of the bladder cancer. In addition, it might be possible to overcome 5-FU insensitivity by using DPD inhibitors in the treatment protocols of 5-FU-based chemotherapy for bladder cancers.

Cis-platinum-induced immunosuppression: relationship to melatonin in human peripheral blood mononuclear cells

OBJECTIVES

The purpose of this study was to investigate the immunomodulatory effect of melatonin (MLT) on human peripheral blood mononuclear cells (PBMC) and to address its effects on Cis-platinum (CDDP)-induced cytotoxicity.

METHODS AND RESULTS

The obtained data from this study revealed that treatment of cells with MLT (100 microg/ml) for 24 h enhanced cell viability. When cells were exposed to CDDP (5 microg/ml), cell proliferation in response to phytohaemagglutinin (PHA) stimulation was reduced by 49.63% compared to control cells as detected by 3[H]-thymidine uptake. Furthermore, Cis-platinum significantly depleted intracellular glutathione (GSH) levels by approximately 47% below that of untreated cells and led to apoptotic changes in the target cells as evidenced by DNA fragmentation (45% compared to 5% in control cells as measured by diphenylamine assay). DNA fragmentation was also confirmed by agarose gel electrophoresis. However, MLT enhanced cell proliferation by approximately 8.63% above the control values, and counteracted the antiproliferative effect of CDDP. The GSH levels were significantly increased in response to MLT (71% above control values) and it protected the cells against GSH depletion induced by CDDP. Moreover, DNA fragmentation and laddering produced by CDDP were significantly reduced or even disappeared when the cells were pretreated with MLT or the latter was simultaneously added with CDDP.

CONCLUSIONS

The findings from this study indicated that melatonin is a potent immunomodulatory hormone that protects PBMC against cis-platinum-induced immunosuppressive effects. These effects might improve the patients' response to cis-platinum therapy and, therefore, their survival rates.

N-acetyl-L-cysteine Exhibits Antitumoral Activity by Increasing Tumor Necrosis Factor α-Dependent T-Cell Cytotoxicity

Because of its anticarcinogenic and antimutagenic properties, N-acetyl-L-cysteine (NAC) has been proposed for cancer treatment. Here we present a mechanism of action for NAC in cancer. Our data show that NAC (1) induces an early and sustained increase of membrane tumor necrosis factor α (TNFα) expression on human stimulated-peripheral blood (PB) T cells and (2) increases membrane TNF-RI and TNF-RII on tumoral cell lines and on T cells after stimulation. These effects result from an early inhibition of both TNFα and TNF-R shedding, as well as a later increase of the respective mRNA expression. Consequently, NAC confers cytotoxic properties to human PB T cells through a membrane TNFα-dependent pathway. In vivo, NAC given orally inhibits tumor appearance in more than a third (18 out of 50) B6D2F1 mice injected with L1210 lymphoma cells. Spleen cells from protected mice killed L1210 lymphoma cells in vitro in a membrane TNFα-dependent manner. Furthemore these mice were resistant to a second inoculation of L1210 cells without further treatment with NAC. Thus, NAC exhibits a potent antitumoral activity by modulating TNFα and TNF-R processing without showing any in vitro and in vivo toxicity.

N-acetyl-L-cysteine Exhibits Antitumoral Activity by Increasing Tumor Necrosis Factor α-Dependent T-Cell Cytotoxicity

Because of its anticarcinogenic and antimutagenic properties, N-acetyl-L-cysteine (NAC) has been proposed for cancer treatment. Here we present a mechanism of action for NAC in cancer. Our data show that NAC (1) induces an early and sustained increase of membrane tumor necrosis factor α (TNFα) expression on human stimulated-peripheral blood (PB) T cells and (2) increases membrane TNF-RI and TNF-RII on tumoral cell lines and on T cells after stimulation. These effects result from an early inhibition of both TNFα and TNF-R shedding, as well as a later increase of the respective mRNA expression. Consequently, NAC confers cytotoxic properties to human PB T cells through a membrane TNFα-dependent pathway. In vivo, NAC given orally inhibits tumor appearance in more than a third (18 out of 50) B6D2F1 mice injected with L1210 lymphoma cells. Spleen cells from protected mice killed L1210 lymphoma cells in vitro in a membrane TNFα-dependent manner. Furthemore these mice were resistant to a second inoculation of L1210 cells without further treatment with NAC. Thus, NAC exhibits a potent antitumoral activity by modulating TNFα and TNF-R processing without showing any in vitro and in vivo toxicity.

Doxorubicin sensitizes human bladder carcinoma cells to Fas-mediated cytotoxicity

BACKGROUND

The resistance of bladder carcinoma to anticancer chemotherapeutic agents remains a major problem. Hence, several immunotherapeutic approaches have been developed to treat the drug-resistant cancer cells. Fas antigen (Fas) and Fas ligand participate in cytotoxicity mediated by T lymphocytes and natural killer cells. Like Fas ligand, anti-Fas monoclonal antibody (MoAb) induces apoptosis of the cells expressing Fas. This study examined whether bladder carcinoma cells are sensitive to cytotoxicity mediated by anti-Fas MoAb and whether anticancer agents synergize with anti-Fas MoAb in cytotoxicity.

METHODS

Cytotoxicity was determined by a 1-day microculture tetrazolium dye assay. Synergy was assessed by isobolographic analysis.

RESULTS

The T24 human bladder carcinoma cell line constitutively expressed the Fas on the cell surface; however, T24 line was resistant to anti-Fas MoAb. Treatment of T24 cells with anti-Fas MoAb in combination with mitomycin C, methotrexate, or 5-fluorouracil did not overcome their resistance to these agents. However, treatment of T24 cells with a combination of anti-Fas MoAb and doxorubicin resulted in a synergistic cytotoxic effect. In addition, the doxorubicin-resistant T24 cells were sensitive to treatment with a combination of anti-Fas MoAb and doxorubicin. Synergy was also achieved in three other bladder carcinoma cell lines and four freshly derived human bladder carcinoma cells. Treatment with anti-Fas MoAb in combination with epirubicin or pirarubicin also resulted in a synergistic cytotoxic effect on T24 cells. The mechanisms of synergy were examined. Anti-Fas MoAb did not affect the intracellular accumulation of doxorubicin, the expression of P-glycoprotein, or the expression of the antioxidant glutathione S-transferase-pi mRNA. However, treatment with doxorubicin enhanced the expression of Fas on T24 cells.

CONCLUSIONS

This study demonstrated that treatment of bladder carcinoma cells with doxorubicin sensitized the cells to lysis by anti-Fas MoAb. The synergistic effect obtained with established doxorubicin-resistant bladder carcinoma cells and freshly isolated bladder carcinoma cells suggests that drug-resistant bladder carcinoma cells can be sensitized by doxorubicin to Fas- and Fas ligant-mediated cytotoxicity by lymphocytes. Furthermore, the sensitization required low concentrations of doxorubicin, thus supporting the in vivo application of a combination of chemotherapy and immunotherapy in the treatment of drug-resistant and/or immunotherapy-resistant bladder carcinoma.

Thiols prevent Fas (CD95)-mediated T cell apoptosis by down-regulating membrane Fas expression

Thiol antioxidants have been shown to protect cells against apoptosis. Based on the role of Fas in T cell apoptosis, we investigated the effect of thiols on Fas expression. We report that the thiol N-acetyl-L-cysteine (NAC) prevents the induction of Fas on human peripheral blood T cells in a dose-dependent manner. It also down-regulates in a time- and dose-dependent manner Fas expression on Fas-expressing T cells. Although these effects were not mediated through de novo glutathione synthesis, only compounds with a free thiol group decreased membrane Fas expression. The decrease of Fas expression induced by NAC was not associated with a modulation of Fas mRNA transcription nor with an internalization, suggesting that NAC may affect the processing of Fas. Indeed, a soluble immunoreactive form of Fas was detected by ELISA and by Western blotting in the supernatants of Fas-expressing T cells treated with NAC. As a functional consequence, NAC partly protected Jurkat cells against Fas-mediated apoptotic cell death. Thus, this study shows that, by regulating Fas expression, the cytoprotective properties of NAC can be extended to Fas-mediated cell death.

The role of tumor necrosis factor receptors in tumor necrosis factor-alpha-mediated cytolysis of ovarian cancer cell lines

OBJECTIVE

Our purpose was to define the expression of tumor necrosis factor receptors on ovarian cancer cells and determine what role these receptors play in tumor necrosis factor-alpha-mediated cytolysis.

STUDY DESIGN

Cell surface expression of tumor necrosis factor-alpha receptors was determined on ovarian cancer cell lines Caov-3, SK-OV-3, NIH:OVCAR-3, and A2780 by a tumor necrosis factor-alpha-binding assay that used iodine 125-labeled tumor necrosis factor-alpha. Monoclonal antibodies specific for the 55 to 60 kd (TR60) and 75 to 80 kd (TR80) tumor necrosis factor receptors were used to determine the relative density of each receptor type. To elucidate which receptor(s) was responsible for mediating the signal for cytolysis, 24-hour MTT cytolytic assays that used tumor necrosis factor-alpha and emetine were performed in the presence or absence of receptor-specific monoclonal antibodies.

RESULTS

The four ovarian cell lines expressed a similar number of surface receptors, 4500 to 7000 per cell, had similar dissociation constants, 0.3 to 0.6 nmol/L, and expressed predominately the TR60 receptor subtype. Receptor function studies showed that the presence of the monoclonal antibody to the TR60 receptor completely inhibited tumor necrosis factor-alpha-mediated cytolysis, whereas the monoclonal antibody to the TR80 receptor only partially blocked cytolysis.

CONCLUSIONS

Ovarian cancer cell lines express both tumor necrosis factor receptors, with the TR60 receptor being the dominant subtype. Tumor necrosis factor-alpha-mediated cytolysis appears to be dependent on the presence of a functional TR60 receptor. The TR80 receptor does not appear requisite for cytolysis; however, a complementary role cannot be excluded. Manipulation of tumor necrosis factor receptor subtypes on ovarian cancer cells may enhance the cytotoxic effects, thus improving the therapeutic efficacy of tumor necrosis factor-alpha.

Enhancement of sensitivity of urinary bladder tumor cells to cisplatin by c-myc antisense oligonucleotide

BACKGROUND

Tumor cells have different degrees of sensitivity and resistance to anticancer agents. The acquisition of drug resistance is a major concern in cancer treatment. Because the c-myc oncogene has been implicated in the poor prognosis of some human tumors including urinary bladder tumor (UBT), the resistance of such tumors to anticancer drugs may correlate with c-myc expression. The present study tested this hypothesis by examining the effect of c-myc antisense oligonucleotide treatment on the sensitivity of human UBT cells to anticancer chemotherapeutic agents.

METHODS

Cytotoxicity determined by a 1-day microculture tetrazolium dye assay. C-myc mRNA was examined by Northern blot analysis.

RESULTS

The T24 human UBT cell line constitutively expresses c-myc mRNA. Treatment of T24 cells with the c-myc antisense oligonucleotide resulted in a significant inhibition of the expression of c-myc mRNA. Treatment of T24 cells with the c-myc antisense oligonucleotide in combination with mitomycin C, Adriamycin, or 5-fluorouracil (5-FU) did not overcome their resistance to these anticancer chemotherapeutic agents. However, combination treatment with the c-myc antisense oligonucleotide and CDDP resulted in a synergistic cytotoxic effect on T24 cells and two freshly derived UBT cells. Further, treatment of CDDP-resistant T24 cells (T24/CDDP) with c-myc antisense oligonucleotide and CDDP reversed the resistance. Pretreatment of T24 cells with either agent and then treatment with the second agent resulted in the same cytotoxic activity as achieved in the presence of the two agents. The combination of c-myc antisense oligonucleotide and carboplatin also resulted in a synergistic cytotoxic effect on T24 cells, and the combination of c-myc antisense oligonucleotide and trans-diamminedichloro-platinum resulted in an additive cytotoxic effect. Incubation of T24 or T24/CDDP cells with the c-myc antisense oligonucleotide increased the intracellular accumulation of CDDP, but not the accumulation of 5-FU.

CONCLUSIONS

This study demonstrates that combination treatment with c-myc antisense oligonucleotide and CDDP can overcome the CDDP-resistance of UBT cells and that the increased intracellular accumulation of CDDP by c-myc antisense oligonucleotide may play a role in the enhanced cytotoxicity obtained. The synergistic effect obtained with established UBT cells and freshly isolated UBT cells suggests that combination treatment with c-myc antisense oligonucleotide and CDDP may have clinical application in the therapy of CDDP-resistant UBT.

Overcoming TNF-alpha and drug resistance of human renal cell carcinoma cells by treatment with pentoxifylline in combination with TNF-alpha or drugs: the role of TNF-alpha mRNA downregulation in tumor cell sensitization

Previous studies have demonstrated that one of the possible mechanisms responsible for the resistance of tumor cells to tumor necrosis factor-alpha (TNF-alpha) is the expression of TNF-alpha mRNA and/or protein. Pentoxifylline (PTX) suppressed TNF-alpha gene transcription and downregulates the expression of TNF-alpha mRNA and the secretion of TNF-alpha protein in macrophages and monocytes. This study investigates whether PTX downregulates the expression of TNF-alpha mRNA and/or protein in renal cell carcinoma (RCC) cells and whether PTX enhances the sensitivity of TNF-alpha-resistant RCC cells to TNF-alpha. Further, we explored whether PTX enhances the sensitivity of RCC cells to agents other than TNF-alpha by downregulation of the expression of TNF-alpha mRNA and protein. The R4 human RCC cell line constitutively expressed TNF-alpha mRNA and protein and was resistant to TNF-alpha. When R4 cells were incubated with PTX, the level of TNF-alpha mRNA and protein was markedly reduced. Pentoxifylline and TNF-alpha together overcame the resistance of R4 cells to TNF-alpha. The R11 human RCC cell line did not constitutively express TNF-alpha mRNA or protein, and was resistant to TNF-alpha. The expression of TNF-alpha mRNA in R11 cells, but not the production of TNF-alpha protein, was induced by TNF-alpha. When PTX was used in combination with TNF-alpha, the level of TNF-alpha mRNA induced by TNF-alpha was markedly reduced. The combination of PTX and TNF-alpha overcame the resistance of R11 cells to TNF-alpha. Pentoxifylline also enhanced the sensitivity of R4 cells to interferon-alpha. Pentoxifylline and anti-TNF-alpha monoclonal antibody augmented the sensitivity of R4 cells to cis-diamminedichloroplatinum (II) (CDDP). This study demonstrated that PTX, in combination with TNF-alpha, IFN-alpha or CDDP, overcame the drug resistance to RCC cells and that downregulation of TNF-alpha mRNA by PTX may be related to the cytotoxicity enhanced by the combination. The implications of these findings for clinical therapy are discussed.

Cytotoxic effect of diphtheria toxin used alone or in combination with other agents on human renal cell carcinoma cell lines

Treatment of renal cell carcinoma (RCC) by conventional chemotherapy and immunotherapy has resulted in minimal remissions. Alternative forms of therapy are therefore being sought. The present study investigated the sensitivity of RCC cell lines to several toxins used alone and in combination with other agents. RCC lines were relatively sensitive to the direct cytotoxic effect of diphtheria toxin (DTX), Pseudomonas aeruginosa exotoxin A (PEA) and ricin. Furthermore, DTX in combination with tumor necrosis factor-alpha (TNF-alpha) resulted in synergistic cytotoxic activity. The mechanism of synergy was examined. A possible mechanism of resistance to TNF-alpha in tumor cells is the expression of TNF-alpha mRNA or protein. R11 cells did not constitutively express mRNA for TNF-alpha, however, treatment of R11 cells with TNF-alpha induced the expression of TNF-alpha mRNA. When DTX was used in combination with TNF-alpha, the level of TNF-alpha mRNA induced by TNF-alpha was markedly reduced. These studies suggest that DTX in combination with TNF-alpha can overcome the resistance of RCC lines and that the marked downregulation of TNF-alpha mRNA by DTX may play a role in the enhanced cytotoxicity seen with the combination of DTX and TNF-alpha. Furthermore, the combination treatment might also potentiate the antitumor host responses. The implications of these findings in clinical therapy are discussed.

Pentoxifylline enhances sensitivity of a human ovarian cancer cell line (OVC-8) to TNF-alpha

The OVC-8 human ovarian cancer cell line constitutively expresses tumor necrosis factor alpha (TNF-alpha) mRNA and protein and is resistant to TNF-alpha. When OVC-8 cells are treated with pentoxifylline (PTX), the level of mRNA for TNF-alpha is markedly reduced. Combination treatment of OVC-8 cells with PTX and TNF-alpha overcomes the resistance. PTX-treatment has no effect on the expression of TNF-alpha mRNA in C30 cells, which do not constitutively express TNF-alpha mRNA. The combination of PTX and TNF-alpha do not overcome the resistance of C30 cells to TNF-alpha. PTX or anti-TNF-alpha monoclonal antibody has no effect on the growth of OVC-8 cells, suggesting that the growth of OVC-8 cells does not depend upon an autocrine action of TNF-alpha. The synergistic cytotoxic effect obtained with ovarian cancer cells suggests that the combination of PTX and TNF-alpha could be applied clinically in the therapy of TNF-alpha-producing ovarian cancer.