Complete tumour regressions induced by vaccination with IL-12 gene-transduced tumour cells in combination with IL-15 in a melanoma model in mice

In the present study, IL-12 gene-transduced B78-H1 melanoma cells (B78/IL-12) were used in combination with IL-15 to treat melanoma-bearing mice. Genetically modified B78/IL-12 cells, when injected subcutaneously, induced strong activation of antitumour mechanisms resulting in complete loss of tumourigenicity. In a therapeutic model, intratumoural injection of irradiated B78/IL-12 cells significantly delayed tumour growth and led to the regression of melanoma in one case. Similarly, consecutive daily injections of IL-15 markedly inhibited tumour progression with occasional curative effects. When used in combination, vaccination with B78/IL-12 cells and treatment with IL-15 caused eradication of established tumours in all treated mice. The combined treatment with B78/IL-12 cells and IL-15 activated not only a local response against tumour, but also induced systemic antitumour immunity that led to a delay or inhibition of tumour development at a distant site. In vitro studies demonstrated that when used together, B78/IL-12 cells and IL-15 induced a shift from a type Th2 to a type Th1 response. Activation of the antitumour immune response in double-treated mice resulted, in part, from stimulation of IFN-gamma production and was accompanied by the development of cytotoxic effectors in the spleen. As shown in a macrophage tumouricidal assay, macrophages could also play a role in the antitumour effects. The results confirmed that vaccination with IL-12 gene-modified tumour cells is superior to the treatment with unmodified tumour cell vaccine and, additionally, showed that IL-15 is an excellent candidate for adjuvant therapy, inducing synergistically not only a delay of tumour growth but also its complete eradication.

Increased local vascular endothelial growth factor expression associated with antitumor activity of proteasome inhibitor

Inhibition of the proteasome, a multicatalytic proteinase complex, is an attractive approach to cancer therapy. Here we report that a selective inhibitor of the chymotrypsin-like activity of the proteasome, PSI (N-benzyloxycarbonyl-Ile-Glu(O-t-butyl)-Ala-leucinal) may inhibit growth of solid tumors not only through apoptosis induction, but also indirectly--through inhibition of angiogenesis. Two murine tumors: colon adenocarcinoma (C-26) and Lewis lung carcinoma (3LL) were chosen to study the antitumor effect of PSI. In an in vivo model of local tumor growth, PSI exerted significant antitumor effects against C-26 colon carcinoma, but not against 3LL lung carcinoma. Retardation of tumor growth was observed in mice treated with both 10 nmoles and 100 nmoles doses of PSI and in the latter group prolongation of the survival time of tumor-bearing mice was observed. PSI inhibited angiogenesis in the C-26 growing tumors with no such effect in 3LL tumors. Unexpectedly, that activity was associated with upregulation of vascular endothelial growth factor (VEGF) at the level of mRNA expression and protein production in C-26 tumors treated with PSI. C-26 cells treated with PSI produced increased amounts of VEGF in vitro in a dose- and time-dependent manner. We demonstrated that in C-26 colon adenocarcionoma higher VEGF production may render endothelial cells susceptible to the proapoptotic activity of PSI and is associated with inhibition of tumor growth.

Role of N-methyl-D-aspartate receptors in the neuroprotective activation of extracellular signal-regulated kinase 1/2 by cisplatin

Neurons are exposed to damaging stimuli that can trigger cell death and subsequently cause serious neurological disorders. Therefore, it is important to define defense mechanisms that can be activated in response to damage to reduce neuronal loss. Here we report that cisplatin (CPDD), a neurotoxic anticancer drug that damages DNA, triggered apoptosis and activated the extracellular signal-regulated kinase 1/2 (ERK1/2) pathway in cultured rat cortical neurons. Inhibition of ERK1/2 activation using either pharmacological inhibitors or a dominant-negative mutant of the ERK1/2 activator, mitogen-activated protein kinase kinase 1, increased the toxicity of CPDD. Interestingly, N-methyl-d-aspartate (NMDA) receptor (NMDAR) antagonists reduced the ERK1/2 activation and exacerbated apoptosis in CPDD-treated neurons. Pre-treatment with CPDD increased ERK1/2 activation triggered by exogenous NMDA, suggesting that CPDD augmented NMDAR responsiveness. CPDD-enhanced response of NMDAR and CPDD-mediated ERK1/2 activation were both decreased by inhibition of poly(ADP-ribose) polymerase (PARP). Interestingly, PARP activation did not produce ATP depletion, suggesting involvement of a non-energetic mechanism in NMDAR regulation by PARP. Finally, CPDD toxicity was reduced by brain-derived neurotrophic factor, and this protection required ERK1/2. In summary, our data identify a novel compensatory circuit in central nervous system neurons that couples the DNA injury, through PARP and NMDAR, to the defensive ERK1/2 activation.

Antitumor effects of photodynamic therapy are potentiated by 2-methoxyestradiol. A superoxide dismutase inhibitor

Photodynamic therapy (PDT), a promising therapeutic modality for the management of solid tumors, is a two-phase treatment consisting of a photosensitizer and visible light. Increasing evidence indicates that tumor cells in regions exposed to sublethal doses of PDT can respond by rescue responses that lead to insufficient cell death. We decided to examine the role of superoxide dismutases (SODs) in the effectiveness of PDT and to investigate whether 2-methoxyestradiol (2-MeOE(2)), an inhibitor of SODs, is capable of potentiating the antitumor effects of this treatment regimen. In the initial experiment we observed that PDT induced the expression of MnSOD but not Cu,Zn-SOD in cancer cells. Pretreatment of cancer cells with a cell-permeable SOD mimetic, Mn(II)-tetrakis(4-benzoic acid)porphyrin chloride, and transient transfection with the MnSOD gene resulted in a decreased effectiveness of PDT. Inhibition of SOD activity in tumor cells by preincubation with 2-MeOE(2) produced synergistic antitumor effects when combined with PDT in 3 murine and 5 human tumor cell lines. The combination treatment was also effective in vivo producing retardation of the tumor growth and prolongation of the survival of tumor-bearing mice. We conclude that inhibition of MnSOD activity by 2-MeOE(2) is an effective treatment modality capable of potentiating the antitumor effectiveness of PDT.

A single injection of immature dendritic cells is able to induce antitumour response against a murine colon adenocarcinoma with a low apoptotic index

Dendritic cells can induce an immune response as competent antigen presenting cells. It has been reported that immature bone marrow derived dendritic cells are capable of inducing an immune response against tumours displaying significant apoptosis. It is still controversial, however whether immature dendritic cells can also induce an immune response against tumours with a low apoptotic index. C-26 adenocarcinoma cells were injected into the footpad of Balb/c mice. One million immature dendritic cells cultured in vitro using GM-CSF and IL-4 were injected into the tumour-bearing footpad on day 6 after tumour cell inoculation. Tumour volume was measured starting from day 5 after tumour cell inoculation. Mice were observed daily for survival. The growing tumours were characterized by a low apoptotic index. There was a statistically significant delay in the tumour growth and a significant prolongation of the survival time in DC treated group as compared with controls (p<0.05). Immature dendritic cells injected into the site of tumour growth are able to induce a potent antitumour response which leads to the retardation of the tumour growth and the prolongation of the life survival time. Here we show that even a single injection of immature dendritic cells is able to induce a significant immune response against tumours with low apoptotic index.

Stimulation of TNF-alpha production by 2-(1-adamantylamino)-6-methylpyridine (AdAMP) - a novel immunomodulator with potential application in tumour immunotherapy

The immunomodulatory effects of a recently synthesized adamantane derivative of aminopyridine - 2-(1-adamantylamino)-6-methylpyridine (AdAMP) - were tested on normal and neoplastic cells in vitro. When incubated with TNF-alpha gene-transduced mouse melanoma cells (B78/TNF), AdAMP significantly enhanced basal production of TNF-alpha by these cells, both by "high" and "moderate" TNF-alpha-producer cells. A similar TNF-alpha production-enhancing effect was observed in cultures of human ovarian carcinoma cells (CAOV1) which spontaneously produce TNF-alpha but not in cultures of tumour cells incapable of TNF-alpha secretion. RT-PCR analysis showed that the enhancement of TNF-alpha production by AdAMP was associated with an increase in TNF-alpha mRNA expression in the treated cells. The results of an electrophoretic mobility shift assay (EMSA) showed that AdAMP significantly activated nuclear factor kappaB (NF-kappaB) in both CAOV1 and B78/TNF cells. The role of NF-kappaB in enhancement of TNF-alpha production was confirmed in experiments in which MG132, an inhibitor of NF-kappaB activation, reversed the effect of AdAMP. Unexpectedly, dexamethasone, a potent antiinflammatory agent and a strong inhibitor of TNF-alpha production in vivo, increased both spontaneous and AdAMP-augmented production of TNF-alpha in in vitro cultures of ovarian carcinoma cells and B78/TNF cells. AdAMP also enhanced TNF-alpha secretion by LPS-induced monocytes. AdAMP-induced augmentation of TNF-alpha production by B78/TNF cells was accompanied by morphological changes in the treated cells and a decrease in their adherence to fibrinogen and collagen IV. In view of these properties, AdAMP seems to be a therapeutically promising compound with potential application as an adjuvant augmenting the efficacy of cancer vaccine-based therapies or in the local treatment of certain tumours.

Augmented antitumour effects of combination therapy with TNP-470 and chemoimmunotherapy in mice

PURPOSE

To investigate antitumour efficacy of the combination of the antiangiogenic agent TNP-470 combined with chemoimmunotherapy in different tumour models in mice

MATERIALS

B6D2F1 mice and BALB/c mice were inoculated in the footpad of the right hind limb with B16F10 melanoma cells or colon adenocarcinoma cells C-26, respectively. Subsequently, they received therapy consisting of TNP-470 and/or IL-12 and tumour growth was observed. In the melanoma model this therapy regimen was combined with cisplatin in a subtherapeutic dose. The antiangiogenic action of the tested agents was evaluated using tumour-induced angiogenesis assay in vivo. In order to analyse interactions between TNP-470 (or cisplatin) and IFN-gamma on tumour cells in vitro, the following methods were used: MTT assay, Western blot analysis, and flow cytometry analysis.

RESULTS

Administration of the combined therapy with TNP-470 and IL-12 resulted in augmented antitumour activity in colon-26 and B16F10 melanoma models. Addition of cisplatin further enhanced efficacy of this combined therapy in the melanoma model. We showed that antitumour activity of this combined therapy is mediated by multiple mechanisms: not only is enhancement of the antiangiogenic activity mediated by TNP-470 and IL-12 but also by the synergistic cytostatic/cytotoxic action of IL-12-induced IFN-gamma and TNP-470 or cisplatin on tumour cells. The experiments revealed that TNP-470 together with IFN-gamma leads to the increased expression of p21 protein in cancer cells, which in turn may contribute to their cytostatic/cytotoxic action in vitro.

CONCLUSION

Our experiments show a successful TNP-470-based combination therapy and suggest that the enhancement of the antitumour activity could be explained by a concomitant effect on both endothelial and tumour cell compartments.

Synergistic interaction between highly specific cyclooxygenase-2 inhibitor, MF-tricyclic and lovastatin in murine colorectal cancer cell lines

Statins, anti-hypercholesterolemic agents, have previously been reported to induce apoptosis and exert antitumor activity when combined with other antitumor agents. The potential of lovastatin in combination with highly specific COX-2 inhibitor (MF-tricyclic) to induce anti-proliferative activity against tumour cells was evaluated using the combination index (CI) method. Murine colorectal cancer (colon-26, CMT-93), melanoma (B16F10) and human bladder carcinoma cells (T24) were tested. Exposure of colon-26 and CMT-93 cells resulted in synergistic interactions in both cell lines with CI<1 for 20-80% inhibition of cell growth in both cell lines. This synergy was not observed in the B16F10 melanoma and T24 bladder carcinoma cells. MF-tricyclic (40 microg/ml), augmented lovastatin-induced apoptosis up to 2.5-fold in colon-26 cancer cells. Combination of a specific COX-2 inhibitor, MF-tricyclic, may increase antiproliferative effects of lovastatin in colon cancer cells and this effect was due to an augmented apoptosis.

Lovastatin potentiates antitumor activity of doxorubicin in murine melanoma via an apoptosis-dependent mechanism

Lovastatin, a drug successfully used in the clinic to prevent and to treat coronary heart disease, has recently been reported to decrease the incidence of melanoma in lovastatin-treated patients. Lovastatin has also been proved to potentiate antitumor effects of both cisplatin and TNF-alpha in murine melanoma models. Recently, an augmented therapeutic effect of lovastatin and doxorubicin has been reported in 3 tumor models in mice. In our preliminary study lovastatin caused retardation of melanoma growth in mice treated with doxorubicin (Feleszko et al. J Natl Cancer Inst 1998;90:247-8). In the present report, we supplement our preliminary observations and demonstrate in 2 murine and 2 human melanoma cell lines that lovastatin effectively potentiates the cytostatic/cytotoxic activity of doxorubicin in vitro via an augmentation of apoptosis (estimated with PARP-cleavage assay, annexin V assay and TUNEL). The combined antiproliferative activity of lovastatin and doxorubicin was evaluated using the combination index (CI) method of Chou and Talalay, revealing synergistic interactions in melanoma cells exposed to lovastatin and doxorubicin. In B16F10 murine melanoma model in vivo, we have demonstrated significantly increased sensitivity to the combined treatment with both lovastatin (5 mg/kg for 14 days) and doxorubicin (4 x 1 mg/kg) as compared with either agent acting alone. Lovastatin treatment resulted also in significant reduction of the number of experimental metastasis in doxorubicin-treated mice. The results of our studies suggest that lovastatin may enhance the effectiveness of chemotherapeutic agents in the treatment of malignant melanomas.

Erythropoietin restores the antitumor effectiveness of photodynamic therapy in mice with chemotherapy-induced anemia

PURPOSE

The study was designed to examine the impact of anemia on the antitumor efficacy of photodynamic therapy (PDT) in a murine colon-26 adenocarcinoma model syngeneic with BALB/c mice.

EXPERIMENTAL DESIGN

Acute hemolytic anemia was induced by a single i.p. injection of phenylhydrazine hydrochloride (150 mg/kg). Anemia induced by i.p. administration of carboplatin (100 mg/kg) was corrected by s.c. treatment with recombinant human erythropoietin (1000 units/kg/day). The effectiveness of PDT (10 mg/kg Photofrin, 150 J/cm2 laser dose) was evaluated by measurements of the footpad edema and tumor volume. All of the RBC-related parameters were measured from the tail vein.

RESULTS

Phenylhydrazine hydrochloride injection resulted in a blunted response of normal tissues to Photofrin-mediated PDT-induced edema formation. Similarly, the antitumor response in mice with hemolytic anemia was nearly completely abrogated. The antitumor effectiveness of PDT was also significantly diminished in a more realistic clinical situation when anemia was induced by administration of carboplatin. Importantly, administration of recombinant human erythropoietin completely restored the sensitivity of the tumor to PDT in carboplatin-treated mice.

CONCLUSIONS

These results indicate that anemia can negatively influence the therapeutic effectiveness of PDT. For optimal antitumor response anemia should be corrected before PDT procedure.

Potentiating antitumor effects of a combination therapy with lovastatin and butyrate in the Lewis lung carcinoma model in mice

Lovastatin, the drug used for the treatment of hypercholesterolemia, has previously been reported to exert antitumor activity in experimental murine models. Butyrate and butyric acid derivatives are well known to induce differentiation and apoptosis of tumour cells and also have recently gained acceptance as potential anticancer agents. In this study, we examined the antitumor effects of the combination of lovastatin and butyrate or its prodrug tributyrin in vitro and in vivo against a murine Lewis lung carcinoma (3LL). This combination therapy showed synergistic antitumor activity against 3LL cells in vitro. These effects were at least in part due to apoptosis induction that occurred after 12 hr of incubation with lovastatin and butyrate and was preceded by changes in cell cycle distribution of treated cells and expression of p21, p53 and cyclin D1. Remarkably, a systemic treatment of syngeneic mice inoculated with 3LL cells with both drugs resulted in significant tumour growth retardation.

Potentiated antitumor effects of butyrate and actinomycin D in melanoma model in mice

Butyrate and butyric acid derivatives are well known to induce differentiation and apoptosis of tumor cells and have also recently gained acceptance as potential anticancer agents. In this study we observed an increased expression of mTNFalpha in tumor tissues in mice treated with butyrate prodrug tributyrin. Since in in vitro experiments we observed a potentiating effects of TNFalpha and actinomycin D on B16F10 cells and also a synergistic interaction was previously claimed between those agents, we investigated the anti-tumor activity of the combination therapy with butyrate and actinomycin D in the B16F10 melanoma model in mice. The combination of the drugs resulted in a strongly potentiated tumor growth retardation in melanoma bearing mice. However the B16F10 cells in vitro did not produce any detectable amounts of TNFalpha. The presented data strongly suggest that one of the mechanism of this successful drug combination could depend on the interaction of the actinomycin D with butyrate-induced TNFalpha produced by stromal or tumor infiltrating immune cells. The results illustrate also the possible application of this combination in cancer therapy.

Antitumor activity of tributyrin in murine melanoma model

Butyric acid has been known to inhibit growth and to induce differentiation of a variety of tumor cells. Butyrate-treated tumor cells have also been observed to undergo apoptosis. Although butyrate compounds have demonstrated antitumor activity in murine tumor models and have already been admitted to clinical trials in tumor patients, the exact mechanism of their antitumor effects has not been elucidated. The results of our study showed antitumor activity of tributyrin, a butyric acid prodrug, in murine melanoma model and are strongly suggestive that antiangiogenic effects could participate in antitumor effects of butyrate compounds in vivo.

The potentiated antileukemic effects of doxorubicin and interleukin-12 combination are not dependent on nitric oxide production

In our recent study we described a significant antileukemic efficacy of a combination therapy with interleukin-12 (IL-12) and doxorubicin (DOX) in the L1210 leukemia model. This therapeutic effect was abrogated by elimination of activated macrophages. Activated macrophages produce a variety of factors that can contribute to the elimination of tumor cells in vivo, including proteases, TNF, reactive oxygen intermediates, and nitric oxide (NO). Based on the results of previous reports, the contribution of NO in potentiated antileukemic effects of IL-12 + DOX combination seemed to be highly possible. Both DOX and IL-12 given alone increased the production of NO by peritoneal macrophages, however, macrophages derived from the mice treated with the combination of those agents produced significantly less NO than macrophages from IL-12-alone-treated mice. Production of NO by spleen macrophages after IL-12 + DOX treatment was higher than it was in controls, IL-12-alone or DOX-alone-treated groups. In serum, concentrations of NOx- in IL-12- or IL-12 + DOX-treated mice were significantly higher in comparison with controls, however not significantly different from each other. Addition of L-NAME treatment to the IL-12 + DOX therapy in leukemia-bearing mice did not significantly change the antileukemic efficacy of this therapy. Thus, our results indicate that the augmented antileukemic effects of IL-12 + DOX combination therapy in L1210 model are NO-independent. Therefore, further studies on the possible mechanisms of potentiated antileukemic activity of combination of IL-12 and DOX would be worth pursuing.