Mechanisms underlying apoptosis induced by combination of 5-fluorouracil and interferon-gamma

Can immunotherapy reinforce chemotherapy efficacy? a new perspective on colorectal cancer treatment

As one of the main threats to human life (the fourth most dangerous and prevalent cancer), colorectal cancer affects many people yearly, decreases patients' quality of life, and causes irreparable financial and social damages. In addition, this type of cancer can metastasize and involve the liver in advanced stages. However, current treatments can't completely eradicate this disease. Chemotherapy and subsequent surgery can be mentioned among the current main treatments for this disease. Chemotherapy has many side effects, and regarding the treatment of this type of tumor, chemotherapy can lead to liver damage, such as steatohepatitis, steatosis, and sinus damage. These damages can eventually lead to liver failure and loss of its functions. Therefore, it seems that other treatments can be used in addition to chemotherapy to increase its efficiency and reduce its side effects. Biological therapies and immunotherapy are one of the leading suggestions for combined treatment. Antibodies (immune checkpoint blockers) and cell therapy (DC and CAR-T cells) are among the immune system-based treatments used to treat tumors. Immunotherapy targets various aspects of the tumor that may lead to 1) the recruitment of immune cells, 2) increasing the immunogenicity of tumor cells, and 3) leading to the elimination of inhibitory mechanisms established by the tumor. Therefore, immunotherapy can be used as a complementary treatment along with chemotherapy. This review will discuss different chemotherapy and immunotherapy methods for colorectal cancer. Then we will talk about the studies that have dealt with combined treatment.

Liposomal simvastatin sensitizes C26 murine colon carcinoma to the antitumor effects of liposomal 5-fluorouracil in vivo

5-Fluorouracil-based therapy remains the main approach in colorectal cancer, even though there are still some drawbacks, such as chemoresistance. In this study we combined 5-fluorouracil encapsulated in long-circulating liposomes with simvastatin, also encapsulated in long-circulating liposomes, that was previously proved to exert antitumor actions on the same tumor model. The production of angiogenic/inflammatory proteins was assessed by protein array and the production of markers for tumor aggressiveness (Bcl-2, Bax, and nuclear factor [NF]-κB) were determined by western blot analysis. Intratumor oxidative stress was evaluated through measurement of malondialdehyde level by HPLC, and through spectrophotometric analysis of catalytic activity of catalase and of total antioxidant capacity. Immunohistochemical analysis of tumors for CD31 expression was assessed. Intratumor activity of MMP-2 by gelatin zymography was also carried out. Our results revealed that combined therapies based on liposomal formulations exerted enhanced antitumor activities compared with combined treatment with free drugs. Sequential treatment with liposomal simvastatin and liposomal 5-fluorouracil showed the strongest antitumor activity in C26 colon carcinoma in vivo, mainly through inhibition of tumor angiogenesis. Important markers for cancer progression (Bcl-2, Bax, NF-κB, and intratumor antioxidants) showed that liposomal simvastatin might sensitize C26 cells to liposomal 5-fluorouracil treatment in both regimens tested. The outcome of simultaneous treatment with liposomal formulations was superior to sequential treatment with both liposomal types as the invasive capacity of C26 tumors was strongly increased after the latest treatment. The antitumor efficacy of combined therapy in C26 colon carcinoma might be linked to the restorative effects on proteins balance involved in tumor angiogenesis.

Interferon-alpha and interferon-gamma modulate Fas-mediated apoptosis in mitomycin-C-resistant human Tenon's fibroblasts

BACKGROUND

The aim of the study was to investigate, using a native mitomycin-C-resistant human Tenon's fibroblast cell line, the possibility that interferon-alpha and gamma could be used with Fas agonists as an alternative anti-fibrotic strategy to mitomycin-C in trabeculectomy.

METHODS

A clinically resistant and in vitro verified mitomycin-C-resistant human Tenon's fibroblast cell line was pretreated with interferon-alpha and interferon-gamma for 48 h before stimulation with an agonistic Fas antibody (CH11) for 2 days to induce cell death. Cell death assays were undertaken. Changes in apoptosis-related proteins were determined by flow cytometry and Western blot.

RESULTS

Pretreatment with interferon-alpha or interferon-gamma for 48 h increased Fas, Fas-associated protein with death domain and caspase-8 expression. Protein expression was further increased by combined exposure to interferon-alpha and gamma. Pretreatment with cytokines had no effect on Fas-L and Bcl-2. Interferon-alpha alone did not change the rate of induced cell death. A combination of interferon-alpha and gamma synergistically increased the sensitivity of mitomycin-C-resistant human Tenon's fibroblast cell line to induced cell death. An antagonistic anti-Fas antibody (ZB4) completely blocked induced cell death. Broad caspase inhibitors specific for caspases-8 and -3 reduced induced deaths in interferon pretreated mitomycin-C-resistant human Tenon's fibroblast cell line in a dose-dependent manner.

CONCLUSIONS

Interferon-alpha and interferon-gamma render mitomycin-C-resistant human Tenon's fibroblast cell line sensitive to Fas-mediated apoptosis. The mechanism involves increased death-inducing signalling complex formation by upregulation of Fas, Fas-associated protein with death domain and caspase-8 expression.

Bax expression is a candidate prognostic and predictive marker of colorectal cancer

OBJECTIVE

Since the anti-tumor activity of 5-fluorouracil (5-FU) is due to induction of apoptosis, we assessed the value of expression of key apoptotic molecules (Bax, Bcl-2 and p53) in predicting the efficacy of 5-FU therapy for colorectal adenocarcinomas (CRCs).

METHODS

Archival tissues of CRCs from 56 patients who received a complete regimen of 5-FU-based chemotherapy after surgery, and 56 patients matched for age, gender, ethnicity, tumor stage, tumor location, and tumor differentiation who had undergone only surgery (without any pre- or post-surgery therapy), were evaluated for immunophenotypic expression of Bax, Bcl-2, and p53. Also, these CRCs were evaluated for Bax mutations. The predictive capacity or prognostic value of these markers was assessed by estimating overall survival.

RESULTS

The majority of low Bax expressing CRCs have exhibited mutations at the G (8) tract. There was no significant difference in overall survival rates between the categories of surgery alone and 5-FU-treated patients. However, a better survival was observed for patients who received chemotherapy when their CRCs had low Bax/Bcl2 ratio (HR, 1.55; 95% CI: 1.46-31.00). Patients who received surgery alone and whose CRCs lacked Bax expression had 5.33 times higher mortality than those with high Bax expression (95% CI: 1.78-15.94), when controlled for tumor stage and other confounders. Bcl-2 and nuclear p53 accumulation had no predictive value in either patient group.

CONCLUSION

These findings are the first to demonstrate that high Bax expression is a good prognosticator for patients who underwent surgery alone, and that patient with low Bax/Bcl-2 expression ratio benefit from 5-FU-based adjuvant therapies.

Caspase inhibitor ZVAD-fmk facilitates engraftment of donor hematopoietic stem cells in intra-bone marrow-bone marrow transplantation

When bone marrow transplantation (BMT) is carried out, survival of the donor hematopoietic stem cells is crucial to maintain donor hematopoiesis in the recipients. We have shown that intra-bone marrow-bone marrow transplantation (IBM-BMT) can induce the rapid recovery of donor hematopoiesis and allow a reduction in radiation doses as a pretreatment for BMT. If IBM-BMT methodology can be further improved, BMT could be carried out more safely and more easily. In this experiment, we attempted to suppress apoptosis of donor hematopoietic cells using a caspase inhibitor, ZVAD-fmk, upon IBM-BMT in mouse allogeneic IBM-BMT. IBM-BMT with ZVAD-fmk induced superior engraftment of donor hematopoietic cells and greater numbers of day-12 colony-forming units of spleen (CFU-S) than IBM-BMT without ZVAD-fmk upon allogeneic BMT (C57BL/6 into BALB/c mice). ZVAD-fmk slightly suppressed apoptosis of whole BMCs, whereas it significantly suppressed apoptosis of c-kit+/Sca-1+/lineage(-) cells (KSL cells) in vitro. These results suggest that ZVAD-fmk can suppress apoptosis of hematopoietic stem cells and/or immature progenitor cells of the donor bone marrow cells, thereby accelerating the donor hematopoiesis.

Interferons α and γ induce p53-dependent and p53-independent apoptosis, respectively

Type I interferon (IFN) enhances the transcription of the tumor suppressor gene p53. To elucidate the molecular mechanism mediating IFN-induced apoptosis, we analysed programmed cell death in response to type I (IFNalpha) or type II (IFNgamma) treatment in relation to p53 status. In two cell lines (MCF-7, SKNSH), IFNalpha, but not IFNgamma, enhanced apoptosis in a p53-dependent manner. Furthermore, only IFNalpha upregulated p53 as well as p53 target genes (Noxa, Mdm2 and CD95). The apoptotic response to IFNalpha decreased in the presence of ZB4, an anti-CD95 antibody, suggesting that CD95 is involved in this process. When p53 was inactivated by the E6 viral protein or the expression of a p53 mutant, IFNalpha-induced apoptosis and p53 target genes upregulation were abrogated. Altogether these results demonstrate that p53 plays a pivotal role in the IFNalpha-induced apoptotic response. IFNalpha-induced PML was unable to recruit p53 into nuclear bodies and its downregulation by siRNA did not alter CD95 expression. In contrast, IFNgamma-induced apoptosis is p53-independent. CD95 and IFN-regulatory factor 1 (IRF1) are directly upregulated by this cytokine. Apoptotic response to IFNgamma is decreased in the presence of ZB4 and strongly diminished by IRF1 siRNA, implicating both CD95 and IRF1 in IFNgamma-induced apoptotic response. Taken together, these results show that in two different cell lines, IFNalpha and IFNgamma, induce p53-dependent -independent apoptosis, respectively.

Interferon-gamma induces caspase-8 in neuroblastomas without affecting methylation of caspase-8 promoter

BACKGROUND

The expression of caspase-8, a cysteine protease that is crucial for the apoptotic cascade, is absent in a high percentage of neuroblastomas, the most frequent extracranial solid tumor of infants and children. Resistance of neuroblastomas to death-receptor (eg, tumor necrosis factor alpha (TNF-alpha) receptor)--mediated apoptosis is thought to be caused by loss of caspase-8 expression. Gene silencing by hypermethylation of caspase-8 promoter has been proposed for the loss of caspase-8 expression in neuroblastoma cells.

METHODS

To further evaluate the role of caspase-8 in neuroblastoma, we assessed the induction of caspase-8 expression in neuroblastoma cells by treating the cells with a physiologic agent such as interferon-gamma.

RESULTS

The authors found that interferon-gamma induces caspase-8 expression in neuroblastoma cells irrespective of the gene silenced by hypermethylation of caspase-8 promoter. The authors show that interferon-gamma also regulates other apoptosis related gene expression. Moreover, they show that interferon-gamma treatment in combination with TNF-alpha decreases neuroblastoma cell proliferation.

CONCLUSIONS

Interferon-gamma induces procaspase-8 expression in neuroblastoma cells, and this induction is not dependent on demethylation of the caspase-8 promoter. Therapies aimed at inducing caspase-8 expression by adjunctive treatment, such as interferon-gamma, may increase the effectiveness of current chemotherapeutic regimens.

Interferon-Gamma and TRAIL in Human Breast Tumor Cells

Induction of apoptosis in tumor cells by death receptor activation is a novel therapeutic strategy. However, in systemic antitumor treatments, severe toxic effects have been observed with tumor necrosis factor-alpha (TNF-alpha) and CD95 ligand. TNF-alpha causes a lethal inflammatory response and CD95L produces lethal liver damage. Preclinical studies in mice and nonhuman primates showed no systemic cytotoxicity upon injection of recombinant TNF-related apoptosis-inducing ligand (TRAIL) at doses that effectively suppressed solid tumors such as colon and mammary carcinomas. Although unwanted effects of some TRAIL preparations have been reported in normal cells, these data suggest that TRAIL could be a suitable approach in cancer therapy. However, several mechanisms of resistance to TRAIL-mediated apoptosis have been described in tumor cells such as lack of TRAIL apoptotic receptors, enhanced expression of TRAIL-decoy receptors, and expression of apoptosis inhibitors. In combination regimes, interferon-gamma (IFN-gamma) could provide a promising antitumor therapeutic approach as it has been described to enhance cellular susceptibility to apoptosis in a variety of tumor cells. The mechanism by which IFN-gamma promotes cell death seems to be via the regulation of the expression of different proteins involved in apoptosis. Altogether, these data suggest a combination strategy to selectively kill tumor cells that need to be further explored.

Influence of interferon-gamma on radiation-induced apoptosis in normal and ataxia-telangiectasia fibroblast cell lines

Combination of interferon-gamma (IFN-gamma) with radiation, or chemotherapeutic agents, produces different kind of modulatory effects, depending on the cell types and experimental conditions. The objective of the present study was verify the influence of IFN-gamma on the induction of apoptosis by gamma-radiation. Experiments were carried out on human fibroblast cell lines: VH-25 (primary), MRC-5, and AT-5BIVA (SV40-transformed). Exponentially growing cells were irradiated and exposed to IFN-gamma (1,000, 2,000, and 3,000 UI/mL) until in situ cell staining performed at 6, 24, and 48 h. Induction of apoptosis by ionising radiation was not verified in primary VH-25 cells. A significant increase in the frequencies of apoptotic cells was observed in SV-40-transformed cells lines, MRC-5, and AT-5BIVA fibroblasts, which were irradiated with 1.0 Gy, but the frequencies of necrotic cells were similar to the control levels. In MRC-5 cells, combined treatments with radiation and IFN-gamma induced a statistically significant reduction in the frequencies of apoptotic cells detected at 24 and 48 h after cell irradiation, while for AT cells the interaction effect (reduction of apoptosis frequency) was significant even at earlier time collection (6 h) after gamma-irradiation, and higher when compared to MRC-5 cells. The present study demonstrated that IFN-gamma showed an anti-apoptotic activity in SV40-transformed fibroblasts, normal and AT cells, which were irradiated with gamma-rays, thus indicating a mechanism dependent on the cellular type.

Spontaneous and inducible apoptosis in oesophageal adenocarcinoma

The use of neoadjuvant chemoradiotherapy prior to surgery in the treatment of oesophageal adenocarcinoma has increased in recent years, and up to 25% of patients will have a complete pathological response to the neoadjuvant therapy. Many patients will not respond, however, and the knowledge of molecular factors predicting response or resistance to chemoradiotherapy is required to enhance treatment results. An understanding of apoptosis and cell proliferation may be relevant and this study focused on apoptotic indices and cell-cycle related (Ki-67, p53 and bcl-2) protein expression in a cohort of 42 patients with primary oesophageal adenocarcinoma. We documented that apoptosis occurs among viable (proliferating) tumour cells in all adenocarcinoma cases examined in this study. Pre-operative chemoradiotherapy significantly increased apoptosis and significantly decreased cell proliferation (estimated by Ki-67 expression). Immunohistochemically detected p53 and bcl-2 gene products had no regulatory role in the apoptotic process. The cumulative expression of p53 protein is significantly associated with increasing proliferation activity. Evaluation of apoptosis in pre-treatment specimens may have potential utility in predicting the efficacy of treatment. Assessment of the tumours proliferation activity by Ki-67 expression might identify patients who are at risk of developing metastatic disease.

Potentiatied antitumor effectiveness of combined chemo-immunotherapy with interleukin-12 and 5-fluorouracil of L1210 leukemia in vivo

In this study we investigated the efficacy of a combination of IL-12 and 5-FU, a chemotherapeutic exerting several immunomodulatory effects, in murine L1210 leukemia. Mice inoculated with 1 x 10(5) leukemia cells were treated with a single dose of 5-FU (50 mg/kg) and seven daily doses of IL-12 (100 ng/dose), and were observed for survival. Treatment with IL-12 or 5-FU given alone produced moderate anti-leukemic effects. However, combination of both drugs resulted in a significant prolongation of mouse survival time. Importantly, there were 70% of long-term (>60 days) survivors among mice treated with both agents simultaneously. Moreover, we observed 100% of long-term survivors when mice were treated with a minimally increased dose of IL-12 (170 ng) in combination with 5-FU (50 mg/kg). The antileukemic effects were completely abrogated in scid/scid mice and in mice depleted of peritoneal macrophages and significantly decreased after administration of anti-CD3+, anti-CD4+ or anti-CD8+ monoclonal antibodies. Administration of anti-NK1.1 antibodies did not decrease the antileukemic effects indicating that NK cells are not important effectors of this treatment regimen. Collectively, these results indicate that the combination of IL-12 and 5-FU is inducing strong antileukemic responses that are dependent on the presence and activity of macrophages and T lymphocytes and warrant further studies of combined chemo-immunotherapy with IL-12.

Interferon-gamma sensitizes human myeloid leukemia cells to death receptor-mediated apoptosis by a pleiotropic mechanism

The role of interferon (IFN)-gamma as a sensitizing agent in apoptosis induced by ligation of death receptors has been evaluated in human myeloid leukemia cells. Incubation of U937 cells with IFN-gamma sensitized these cells to apoptosis induced by tumor necrosis factor-alpha, agonistic CD95 antibody, and tumor necrosis factor-related apoptosis-inducing ligand. Other human myeloid leukemic cells were also sensitized by IFN-gamma to death receptor-mediated apoptosis. Treatment of U937 cells with IFN-gamma up-regulated the expression of caspase-8 and potently synergized with death receptor ligation in the processing of caspase-8 and BID cleavage. Concomitantly, a marked down-regulation of BCL-2 protein was also observed in cells incubated with IFN-gamma. Furthermore, the caspase-dependent generation of a 23-kDa fragment of BCL-2 protein, the release of cytochrome c from mitochondria and the activation of caspase-9 were also enhanced upon death receptor ligation in IFN-gamma-treated cells. Ectopically expressed Bcl-2 protein inhibited IFN-gamma-induced sensitization to apoptosis. In summary, these results indicate that IFN-gamma sensitizes human myeloid leukemic cells to a death receptor-induced, mitochondria-mediated pathway of apoptosis.

Antioxidants enhance the susceptibility of colon carcinoma cells to 5-fluorouracil by augmenting the induction of the bax protein

5 Fluorouracil (5 FU), the most effective systemic chemotherapeutic agent in the management of advanced colorectal carcinoma acts by inducing apoptosis. Response rates, approximately 20% is improved by folinic acid. This study investigates similar modulation of 5 FU-induced apoptosis by oxidant quenching. A five-fold reduction of intracellular oxidant levels by antioxidants N-acetylcysteine and vitamin E did not induce apoptosis, it however augmented pro-apoptotic bax protein expression, and apoptotic response to a non-toxic dose of 5 FU in the colorectal cancer cell lines colo 201 and colo 205. This suggests that reduction of intracellular levels of reactive oxygen species enhance susceptibility to 5 FU (apoptotic stimuli) by augmentation of bax expression.

Bcl-2/Bax protein ratio predicts 5-fluorouracil sensitivity independently of p53 status

p53 tumour-suppressor gene is involved in cell growth control, arrest and apoptosis. Nevertheless cell cycle arrest and apoptosis induction can be observed in p53-defective cells after exposure to DNA-damaging agents such as 5-fluorouracil (5-FU) suggesting the importance of alternative pathways via p53-independent mechanisms. In order to establish relationship between p53 status, cell cycle arrest, Bcl-2/Bax regulation and 5-FU sensitivity, we examined p53 mRNA and protein expression and p53 protein functionality in wild-type (wt) and mutant (mt) p53 cell lines. p53 mRNA and p53 protein expression were determined before and after exposure to equitoxic 5-FU concentration in six human carcinoma cell lines differing in p53 status and displaying marked differences in 5-FU sensitivity, with IC(50)values ranging from 0.2-22.6 mM. 5-FU induced a rise in p53 mRNA expression in mt p53 cell lines and in human papilloma virus positive wt p53 cell line, whereas significant decrease in p53 mRNA expression was found in wt p53 cell line. Whatever p53 status, 5-FU altered p53 transcriptional and translational regulation leading to up-regulation of p53 protein. In relation with p53 functionality, but independently of p53 mutational status, after exposure to 5-FU equitoxic concentration, all cell lines were able to arrest in G1. No relationship was evidenced between G1 accumulation ability and 5-FU sensitivity. Moreover, after 5-FU exposure, Bax and Bcl-2 proteins regulation was under p53 protein control and a statistically significant relationship (r = 0.880, P = 0.0097) was observed between Bcl-2/Bax ratio and 5-FU sensitivity. In conclusion, whatever p53 status, Bcl-2 or Bax induction and Bcl-2/Bax protein ratio were correlated to 5-FU sensitivity.

Direct growth suppressive activity of interferon-alpha and -gamma on human gastric cancer cells

BACKGROUND AND OBJECTIVES

Interferons (IFNs) exhibit anti-tumor activities through either immune modulation or direct anti-tumor effects. We have investigated the activity and mechanisms of IFN-alpha and IFN-gamma on the growth of TSGH9201, TMK-1 and AGS gastric cancer cells in vitro.

METHODS

Activities of IFNs on cell growth were analyzed by measuring total cellular DNA. Effects of IFNs on apoptosis was evaluated by formation of in situ DNA breakage and DNA ladders. Effects of IFNs on cells cycle phase distribution were analyzed using flow cytometry. Levels of Bcl-2 family proteins after treatment with IFNs were analyzed using Western blot.

RESULTS

Both IFN-alpha and IFN-gamma were active in suppressing the growth of TSGH9201 and TMK-1 cells, while AGS cells were resistant to treatment with IFNs. The IC(50)s of IFN-alpha for TSGH9201 and TMK-1 cells were 300 and 500 U/ml, respectively, and the IC(50)s of IFN-gamma were 40 and 2.0 U/ml, respectively. Both IFN-alpha- and IFN-gamma-induced cell cycle arrest in sensitive cells. IFN-gamma also increased cellular apoptosis, demonstrated by increasing in situ DNA damage and DNA fragmentation. IFN-gamma increased BAK protein levels and decreased Bcl-2 and Bcl-X(S) protein levels in TSGH9201 cells.

CONCLUSIONS

IFN-alpha suppressed growth of gastric cancer cells through induction of cell cycle arrest. IFN-gamma suppressed cell growth through induction of both cell cycle arrest and apoptosis. IFN-gamma-mediated apoptosis was associated with the alteration in protein levels of Bcl-2, Bcl-X(S) and BAK.

Synergistic induction of apoptosis in murine hepatoma Hepa1-6 cells by IFN-gamma and TNF-alpha

In this study, we examined the susceptibility of murine hepatoma Hepa1-6 cells to undergo IFN-gamma- and/or TNF-alpha-induced apoptosis. IFN-gamma or TNF-alpha alone had no demonstrable cytotoxic effects, whereas IFN-gamma and TNF-alpha in combination induced apoptosis drastically in Hepa1-6 cells. During this apoptosis, an increase in caspase-3- and -8-like protease activities and activation of caspase-3, identified by the appearance of its p17 fragment, were observed. Moreover, the cytotoxic induction and caspase-3 activation were effectively inhibited by Z-Asp-CH(2)-DCB (Z-Asp), a caspase inhibitor. Further, an elevation of cytochrome c in the cytosol, in a parallel to activation of caspase-3, was observed in a time-dependent manner. Concurrently, up-regulation of caspase-11 gene expression and processing of procaspase-11 were detected during this apoptosis. These results suggest that the caspase-3 activation, the release of cytochrome c from mitochondria, and increased caspase-11 gene expression involve in synergistic induction of apoptosis in Hepa1-6 cells by IFN-gamma and TNF-alpha.

Morphological change, loss of deltapsi(m) and activation of caspases upon apoptosis of colorectal adenocarcinoma induced by 5-FU

Apoptosis is clearly distinguished from necrosis, morphologically and chemically. Morphologically, apoptosis is characterized by a condensed nucleus and the disappearance of microvilli without disruption of the cytoplasm. In this report, we demonstrate that 5-fluorouracil (5-FU)-induced early apoptotic cells are characterized by (i) ultracondensed mitochondria, (ii) no change in the microvilli or nucleus, (iii) a high mitochondrial transmembrane potential (Deltapsi(m)), and (iv) being annexin V(negative). The early apoptotic cells also show the active forms of caspase 8 and caspase 9. They rapidly lose Deltapsi(m) after further incubation. Therefore, we conclude that the ultracondensation of mitochondria precedes the loss of Deltapsi(m) and the exposure of phosphatidylserine to the outer leaflet of the cell membrane.

Distinct effect of retroviral-mediated IFN-alpha gene transfer on human erythroleukemic and CD34+ cell growth and differentiation

Human interferon-alpha (IFN-alpha) has been used in the management of leukemia, but its diverse adverse effects may influence the ability of IFN-alpha to treat this disease. We constructed two retroviral vectors, LSN-IFN-alpha and LNC-IFN-alpha, in which IFN-alpha cDNA was driven by viral LTR and CMV promoters, respectively. After transduction into the PA317 and PG13 retroviral packaging cells, high titers of retrovirus were produced and were used to infect K562 and human BM CD34+ hematopoietic cells. The IFN-alpha gene expression in transduced K562 cells was confirmed by Northern blot, RT-PCR, RIA, and biologic assay. Cell proliferation and cell viability in IFN-alpha-transduced K562 cells were significantly suppressed as compared with control K562 cells. Although the IFN-alpha expression in K562 cells did not affect BCR/ABL expression, it apparently upregulated the production of adhesion molecules (VLA-4 and Mac-1). We evaluated the effect of IFN-alpha gene transfer on human CD34+ cells infected with LSN-IFN-alpha retrovirus with the aid of fibronectin (FN) fragment CH-296 and growth factors. RIA showed that IFN-alpha-transduced CD34+ cells produced 72.2+/-15 U/ml of IFN-alpha compared with 4.3+/-1.2 U/ml in control CD34+ cells. Methylcellulose clonogenic assay indicated that IFN-alpha-transduced CD34+ cells produced similar numbers of burst-forming units-erythrocytes (BFU-E)/colony-forming units-GM (CFU-GM) colonies as compared with control CD34+ cells. Selected colonies expressed IFN-alpha and neo(r) mRNA, as measured by RT-PCR. These studies indicate that retrovirus-mediated IFN-alpha gene transfer may provide a useful tool for studying the effect of IFN-alpha gene transfer on leukemic cells and long-lived CD34+ cells.

Synergistic action of apoptosis induced by eicosapentaenoic acid and TNP-470 on human breast cancer cells

The effects of eicosapentaenoic acid (EPA) and an angiogenesis inhibitor (TNP-470) on the suppression of breast cancer cell growth were examined in five human breast cancer cell lines (MDA-MB-231, T-47D, MCF-7, KPL-1, and MKL-F). In all five cell lines, EPA and TNP-470 alone both showed tumor growth inhibition in a time- and dose-dependent manner, and in combination, a synergistic effect was seen at high concentrations. EPA plus TNP-470 treatment evoked apoptosis as confirmed by the appearance of sub G1 populations, by DNA fragmentation, and by cell morphology. With the combination, the expression of Bax and Bcl-xS, the apoptosis-enhancing proteins, was more up-regulated and that of Bcl-2 and Bcl-xL, the apoptosis-suppressing proteins, was more down-regulated compared to the use of EPA or TNP-470 alone, suggesting that their synergistic effect was due to an acceleration of apoptosis.

The inhibitory action of BOF-A2, a 5-fluorouracil derivative, on squamous cell carcinoma

Inactivation of antineoplastics is a serious problem in cancer therapy, and prevention of the inactivation is a surpassing strategy for enhancement of their therapeutic effects. BOF-A2, which contains both EM-FU, a masked form of 5-fluorouracil (5-FU), and CNDP, an inhibitor of 5-FU degradation, was developed with this aim. We compared the antitumor effects of BOF-A2 and 5-FU in human squamous cell carcinoma cells transplanted to nu/nu mice. Each drug (0.9-7.0 mg/kg of 5-FU and 3.8-30 mg/kg of BOF-A2) was orally administered every day to 5 mice in each dosage group for 4 weeks. Although the maximal tumor growth inhibition by 5-FU (3.5 mg/kg per day) was about 50% of the control value, 15 mg/kg per day of BOF-A2, which is equimolar to 3.5 mg/kg per day of 5-FU, almost completely inhibited the tumor growth. The flow-cytometric analysis revealed that BOF-A2 (15 mg/kg per day) induced more prominent S-phase-accumulation (63 +/- 6%) of tumor cells than did 3.5 mg/kg per day of 5-FU (43 +/- 18%), and immunohistochemical stainings indicated that the decrease of proliferating cell nuclear antigen expression was more prominent in tumor cells in the BOF-A2-treated mice than in the 5-FU-treated mice. Correspondingly, the DNA synthesis was markedly suppressed in tumor cells obtained from BOF-A2-treated mice. Compared with 5-FU, BOF-A2 more strongly induced apoptosis; apoptotic cells detected by nick-end labeling techniques were about 20% of the tumor cells in 5-FU (3.5 mg/kg per day)-treated mice, and nearly 50% in BOF-A2 (15 mg/kg per day)-administered mice. The expressions of involucrin, cytokeratin 10 and protein kinase C eta, which are associated with squamous cell differentiation, were not increased by BOF-A2 or 5-FU, although the expression of transglutaminase was slightly augmented by both drugs. These results indicate that compared with 5-FU, BOF-A2 more strongly suppresses the growth of squamous cell carcinoma by inhibiting DNA synthesis and inducing apoptosis but not cell differentiation.