Potentiation of antitumor effects of tumor necrosis factor alpha and interferon gamma by macrophage-colony-stimulating factor in a MmB16 melanoma model in mice

Unexpected therapeutic effects of cisplatin

Cisplatin is a widely used chemotherapeutic agent that is clinically approved to fight both carcinomas and sarcomas. It has relatively high efficiency in treating ovarian cancers and metastatic testicular cancers. It is generally accepted that the major mechanism of cisplatin anti-cancer action is DNA damage. However, cisplatin is also effective in metastatic cancers and should, therefore, affect slow-cycling cancer stem cells in some way. In this review, we focused on the alternative effects of cisplatin that can support a good therapeutic response. First, attention was paid to the effects of cisplatin at the cellular level such as changes in intracellular pH and cellular mechanical properties. Alternative cellular targets of cisplatin, and the effects of cisplatin on cancer cell metabolism and ER stress were also discussed. Furthermore, the impacts of cisplatin on the tumor microenvironment and in the whole organism context were reviewed. In this review, we try to reveal possible causes of the unexpected effectiveness of this anti-cancer drug.

The Melding of Drug Screening Platforms for Melanoma

The global incidence of cancer is rising rapidly and continues to be one of the leading causes of death in the world. Melanoma deserves special attention since it represents one of the fastest growing types of cancer, with advanced metastatic forms presenting high mortality rates due to the development of drug resistance. The aim of this review is to evaluate how the screening of drugs and compounds for melanoma has been performed over the last seven decades. Thus, we performed literature searches to identify melanoma drug screening methods commonly used by research groups during this timeframe. In vitro and in vivo tests are essential for the development of new drugs; however, incorporation of in silico analyses increases the possibility of finding more suitable candidates for subsequent tests. In silico techniques, such as molecular docking, represent an important and necessary first step in the screening process. However, these techniques have not been widely used by research groups to date. Our research has shown that the vast majority of research groups still perform in vitro and in vivo tests, with emphasis on the use of in vitro enzymatic tests on melanoma cell lines such as SKMEL and in vivo tests using the B16 mouse model. We believe that the union of these three approaches (in silico, in vitro, and in vivo) is essential for improving the discovery and development of new molecules with potential antimelanoma action. This workflow would provide greater confidence and safety for preclinical trials, which will translate to more successful clinical trials and improve the translatability of new melanoma treatments into clinical practice while minimizing the unnecessary use of laboratory animals under the principles of the 3R's.

Cancer immunotherapy: potential involvement of mediators

The description of a cell-free soluble anti-tumour factor by Carswell et al. in 1975 (Proc Natl Acad Sci USA, 72: 3666–3670) was followed by a long series of experimental and clinical investigations into the role of cell-free mediators in cancer immunotherapy. These investigations included research on the effects of macrophage–derived eicosanoids (cycloxygenase and lipoxygenase derivates of arachidonic acid) and of monokines such as tumour necrosis factor-α, interleukin-1 and granulocyte–monocyte–macrophage–colony stimulating factor) and of lymphocyte products: interleukins and interferons. The investigations yielded information on the effects of various factors on macrophage and T-cell activation in vitro, determination of direct anti-tumour properties on animal and human tumour cells in vitro and on therapeutic effectiveness in tumour-bearing individuals either alone or in combination with other therapeutic factors and their production by tumour cells. During recent years much effort has been dedicated towards the use of the tumour cells transfected with cytokine genes in the preparation of cancer vaccines. Cycloxygenase products (prostaglandins) were usually assumed to inhibit expression of anti-tumour activity by macrophages and an increase in their production in cancer patients was considered as a poor prognostic index. Lipoxygenase (leukotrienes) products were assumed to exhibit antitumour activity and to induce production of IL-1 by macrophages. Interleukins 2, 4, 6, 7, 12 and the interferons were extensively tested for their therapeutic effectiveness in experimental tumour models and in cancer clinical trials. The general conclusion on the use of cell-free mediators for cancer immunotherapy is that much still has to be done in order to assure effective and reproducible therapeutic effectiveness for routine use in the treatment of human neoplasia.

Functional Analysis of Cultured Neural Cells for Evaluating Cold/Cool- and Hot/Warm-Natured Chinese Herbs

Recently, modern scientific research has been required to understand pharmacological basis of traditional Chinese medicine (TCM) theory based on the ancient clinical experience, and to investigate the molecular mechanisms of action of Chinese herbs. Here, 20 Chinese herbs, classified into 4 properties (hot, warm, cold and cool) of TCM, were analyzed for their ability to exhibit antioxidant action, to enhance glucose uptake by murine microglia N9 cells, and to influence neurotransmitter norepinephrine (NE) release from rat pheochromocytoma PC12 cells. We found a generally protective effect of both hot/warm-natured and cold/cool-natured herbs against H 2 O 2-induced N9 cell death, partially by elevating superoxide dismutase (SOD) activity. Glucose uptake was elevated after treatment with some hot/warm-natured herbs. In addition, most herbs with hot/warm nature tended to stimulate NE release, while such stimulatory effect was not observed in the herbs with cold/cool nature. Two cold/cool-natured herbs, Rhizoma coptidis and Radix scutellariae, even significantly suppressed the release. These results suggest that the distinct abilities of Chinese herbs to regulate neural cell functions appear to be correlated with their natures identified in traditional TCM theory, and may be a useful guide for their utility in neural degenerative diseases.

Cytotoxic activity of flavonoids from the flowers of Chrysanthemum morifolium on human colon cancer Colon205 cells

A new p-hydroxyphenylacetyl flavonoid, diosmetin 7-(6''-O-p-hydroxyphenylacetyl)-O-beta-d-glucopyranoside (1), was isolated from the flowers of Chrysanthemum morifolium Ramat. 'huaiju' cv. nov. (Compositae), together with five known flavonoids, luteolin (2), diosmetin (3), diosmetin 7-O-beta-d-glucopyranoside (4), diosmin (5), and scolimoside (6), and four known caffeoylquinic acid derivatives, macranthoin F (7), 3,5-dicaffeoylquinic acid (8), 1,3-dicaffeoyl-epi-quinic acid (9), and chlorogenic acid (10). The structure of 1 was elucidated by UV, IR, ESI-TOF-MS, 1D, and 2D NMR spectroscopic methods. Cytotoxic activity of compounds 1-5 against human colon cancer cell Colon205 was investigated using MTT assays. Compounds 2 and 3 showed significant cytotoxicities against Colon205, with their IC(50) values being 96.9 and 82.9 microM, respectively. However, compounds 1, 4, and 5 showed little cytotoxic activity.

A novel triterpenoid isolated from the root bark of Ailanthus excelsa Roxb (Tree of Heaven), AECHL-1 as a potential anti-cancer agent

Background

We report here the isolation and characterization of a new compound Ailanthus excelsa chloroform extract-1 (AECHL-1) (C₂₉H₃₆O₁₀; molecular weight 543.8) from the root bark of Ailanthus excelsa Roxb. The compound possesses anti-cancer activity against a variety of cancer cell lines of different origin.

Principal Findings

AECHL-1 treatment for 12 to 48 hr inhibited cell proliferation and induced death in B16F10, MDA-MB-231, MCF-7, and PC3 cells with minimum growth inhibition in normal HEK 293. The antitumor effect of AECHL-1 was comparable with that of the conventional antitumor drugs paclitaxel and cisplatin. AECHL-1-induced growth inhibition was associated with S/G₂-M arrests in MDA-MB-231, MCF-7, and PC3 cells and a G₁ arrest in B16F10 cells. We observed microtubule disruption in MCF-7 cells treated with AECHL-1 in vitro. Compared with control, subcutaneous injection of AECHL-1 to the sites of tumor of mouse melanoma B16F10 implanted in C57BL/6 mice and human breast cancer MCF-7 cells in athymic nude mice resulted in significant decrease in tumor volume. In B16F10 tumors, AECHL-1 at 50 µg/mouse/day dose for 15 days resulted in increased expression of tumor suppressor proteins P53/p21, reduction in the expression of the oncogene c-Myc, and downregulation of cyclin D1 and cdk4. Additionally, AECHL-1 treatment resulted in the phosphorylation of p53 at serine 15 in B16F10 tumors, which seems to exhibit p53-dependent growth inhibitory responses.

Conclusions

The present data demonstrate the activity of a triterpenoid AECHL-1 which possess a broad spectrum of activity against cancer cells. We propose here that AECHL-1 is a futuristic anti-cancer drug whose therapeutic potential needs to be widely explored for chemotherapy against cancer.

The prince and the pauper. A tale of anticancer targeted agents

Cancer rates are set to increase at an alarming rate, from 10 million new cases globally in 2000 to 15 million in 2020. Regarding the pharmacological treatment of cancer, we currently are in the interphase of two treatment eras. The so-called pregenomic therapy which names the traditional cancer drugs, mainly cytotoxic drug types, and post-genomic era-type drugs referring to rationally-based designed. Although there are successful examples of this newer drug discovery approach, most target-specific agents only provide small gains in symptom control and/or survival, whereas others have consistently failed in the clinical testing. There is however, a characteristic shared by these agents: -their high cost-. This is expected as drug discovery and development is generally carried out within the commercial rather than the academic realm. Given the extraordinarily high therapeutic drug discovery-associated costs and risks, it is highly unlikely that any single public-sector research group will see a novel chemical "probe" become a "drug". An alternative drug development strategy is the exploitation of established drugs that have already been approved for treatment of non-cancerous diseases and whose cancer target has already been discovered. This strategy is also denominated drug repositioning, drug repurposing, or indication switch. Although traditionally development of these drugs was unlikely to be pursued by Big Pharma due to their limited commercial value, biopharmaceutical companies attempting to increase productivity at present are pursuing drug repositioning. More and more companies are scanning the existing pharmacopoeia for repositioning candidates, and the number of repositioning success stories is increasing. Here we provide noteworthy examples of known drugs whose potential anticancer activities have been highlighted, to encourage further research on these known drugs as a means to foster their translation into clinical trials utilizing the more limited public-sector resources. If these drug types eventually result in being effective, it follows that they could be much more affordable for patients with cancer; therefore, their contribution in terms of reducing cancer mortality at the global level would be greater.

Silymarin enhanced cytotoxic effect of anti-Fas agonistic antibody CH11 on A375-S2 cells

Silymarin is a polyphenolic flavonoid from milk thistle (Silybum marianum), which has anti-inflammatory, cytoprotective as well as antioxidant effects. Our previous study demonstrated that silymarin has anti-apoptotic effect against UV irradiation. In this study, we assessed the effect of silymarin on anti-Fas agonistic antibody CH11-treated human malignant melanoma, A375-S2 cells. Pretreatment with silymarin (3 x 10(- 4) mol/L) significantly induced cell apoptosis in CH11-treated A375-S2 cells. Mitochondrial transmembrane potential (DeltaPsi(m)) was also down-regulated by silymarin pretreatment. Caspase-8, -9, -3 and pan-caspase inhibitors partially reversed silymarin-induced apoptosis of CH11-treated cells. The expression of Fas-associated proteins with death domain (FADD), a downstream molecule of the death receptor pathway, was increased by silymarin pretreatment, followed by cleavage of procaspase-8, whose activation induced cell apoptosis. Moreover, cleavage of procaspase-3 and digestion of its substrate, the inhibitor of caspase-activated DNase (ICAD), were also increased by silymarin pretreatment. These results suggested that silymarin could also exaggerate the apoptotic effect of anti-Fas agonistic antibody CH11 on A375-S2 cells.

P53-mediated cell cycle arrest and apoptosis through a caspase-3- independent, but caspase-9-dependent pathway in oridonin-treated MCF-7 human breast cancer cells

AIM

To study the caspase-3-independent mechanisms in oridonin-induced MCF-7 human breast cancer cell apoptosis in vitro.

METHODS

The viability of oridonin-treated MCF-7 cells was measured by MTT (thiazole blue) assay. Apoptotic cells with condensed nuclei were visualized by phase contrast microscopy. Nucleosomal DNA fragmentation was assayed by agarose gel electrophoresis. The apoptotic ratio was determined by lactate dehydrogenase assay. Cell cycle alternation and mitochondrial membrane potential were measured by flow cytometric analysis. Bax, Bcl-2, caspase-3, caspase-9, heat shock protein (Hsp)90, p53, p-p53, p21, Poly (ADP-ribose) polymerase (PARP), and the inhibitor of caspase-activated DNase (ICAD) protein expressions were detected by Western blot analysis.

RESULTS

Oridonin inhibited cell growth in a time- and dose-dependent manner. Cell cycle was altered through the upregulation of p53 and p21 protein expressions. Pancaspase inhibitor Z-VAD-fmk and calpain inhibitor II both decreased cell death ratio. Nucleosomal DNA fragmentation and the downregulation of DeltaPhimit were detected in oridonin-induced MCF-7 cell apoptosis, which was involved in a postmitochondrial caspase-9-dependent pathway. Decreased Bcl-2 and Hsp90 expression levels and increased Bax and p21 expression levels were positively correlated with elevated levels of phosphorylated p53 phosphorylation. Moreover, PARP was partially cleaved by calpain rather than by caspase-3.

CONCLUSION

DNA damage provoked alternations in the mitochondrial and caspase-9 pathways as well as p53-mediated cell cycle arrest, but was not related to caspase-3 activity in oridonin-induced MCF-7 cells.

Activation of extracellular signal-regulated kinase during silibinin-protected, isoproterenol-induced apoptosis in rat cardiac myocytes is tyrosine kinase pathway-mediated and protein kinase C-dependent

AIM

To investigate the mechanism of silibinin-protected isoproterenol-induced apoptosis in rat cardiac myocytes.

METHODS

The viability of rat cardiac myocytes was measured by MTT method. The apoptotic ratio was measured by terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling. Protein kinase C (PKC) activity assay was carried out according to the instructions of the PepTag non-radioactive protein kinase C assay kit. Western blot analysis was used to evaluate the level of Ras, Raf-1 and mitogen-activated protein kinase (MAPK) expression.

RESULTS

The protective effects of silibinin were significantly suppressed by inhibitors, including genistein, manumycin A and GW5074 [inhibitors for protein tyrosine kinases (PTK), Ras and Raf-1, respectively]. The exposure of rat cardiac myocytes to isoproterenol alone caused decreased PKC activity, which was prevented by pretreatment with silibinin dose-dependently. Simultaneously, the increased expression of Ras and Raf-1 activated by silibinin were blocked by the PKC inhibitor, stauroporine. In addition, the extracellularly responsive kinase (ERK) inhibitor, PD98059, suppressed silibinin-protected apoptosis, whereas the p38 MAPK inhibitor, SB203580, protected cardiac myocytes from isoproterenol-induced injury, and the c-Jun N-terminal kinase (JNK) inhibitor, SP600125 had no protective effects. Furthermore, Western blot analysis showed that the expression of phosphorylated ERK was increased by silibinin, the expression of phosphorylated p38 MAPK was decreased and total ERK, p38, JNK and phosphorylated JNK MAPK did not change after treatment with both isoproterenol and silibinin. Furthermore, pretreatment of cardiac myocyte with PKC, Ras and Raf inhibitors significantly blocked ERK phosphorylation.

CONCLUSION

Silibinin is suggested to protect isoproterenol-induced rat cardiac myocyte apoptosis by activating the tyrosine kinase pathway, PKC and MAPK pathways.

Activation of the SIRT1 pathway and modulation of the cell cycle were involved in silymarin's protection against UV-induced A375-S2 cell apoptosis

Silymarin, derived from the milk thistle plant, Silybum marianum, has been traditionally used in the treatment of liver disease. Our previous study demonstrated that silymarin has an anti-apoptotic effect against UV irradiation. In this study, SIRT1, a human deacetylase that was reported to promote cell survival, was activated by silymarin (5 x 10(- 4) mol/L) in UV-irradiated human malignant melanoma, A375-S2 cells, followed by down-regulated expression of Bax and decreased release of cytochrome c. Cleavage of procaspase-3 and digestion of its substrates, the inhibitor of caspase-activated DNase (ICAD) and poly(ADP-ribose) polymerase (PARP), were also reduced. Consistent with its protective effect on UV-induced apoptosis, silymarin (5 x 10(- 4) mol/L) also increased G(2)/M phase arrest, possibly providing a prolonged time for efficient DNA repair. Consequently, that silymarin protected A375-S2 cell against UV-induced apoptosis was partially through SIRT1 pathway and modulation of the cell cycle distribution.

Silibinin protects against isoproterenol-induced rat cardiac myocyte injury through mitochondrial pathway after up-regulation of SIRT1

Terminally differentiated adult injured cardiac myocytes have been used for various animal models of heart failure. It has recently been shown that isoproterenol induces injury in rat neonatal cardiac myocytes via a beta-adrenergic pathway, suggesting that it might be one of the factors involved in myocardial cell injury in heart failure in vivo. In the study, silibinin, a plant flavanoid from milk thistle was first evaluated for its protective effect against beta-adrenergic agonist isoproterenol-induced injury in cultured rat neonatal cardiac myocytes. The viability, activation of lactate dehydrogenase (LDH), and content of maleic dialdehyde (MDA) were chosen for measuring the degree of cardiac myocytes injury. As a result, silibinin protected isoproterenol-treated rat cardiac myocytes from death and significantly decreased LDH release and MDA production. Silibinin increased superoxide dismutase activity, decreased [Ca(2+)](i), and increased mitochondrial membrane potential (DeltaPsi). Furthermore, the release of pro-apoptotic cytochrome c from mitochondria was reduced by silibinin. Silibinin increased the expression of anti-apoptotic Bcl-2 family protein Bcl-2, and up-regulation of SIRT1 inhibited the translocation of Bax from cytoplasm to mitochondria, which caused mitochondrial dysfunction and cell injury. These results demonstrate that silibinin protects against isoproterenol-induced cardiac myocytes injury through resuming mitochondrial function and regulating the expression of SIRT1 and Bcl-2 family members.

Surface Modification of RGD-Liposomes for Selective Drug Delivery to Monocytes/Neutrophils in Brain

In the present study, RGD peptide was coupled with ferulic acid (FA) liposomes for binding to monocytes and neutrophils in peripheral blood for brain targeting in response to leukocyte recruitment. Cholesterol (Ch) was esterified with succinic anhydride to introduce a carboxylic end group (Ch-COOH). Soybean phosphatidylcholine, cholesterol and Ch-COOH were in a molar ratio of 1 : 0.23 : 0.05. FA was loaded into liposomes with 80.2+/-5.2% entrapment efficiency (EE) using a calcium acetate gradient method since it was difficult to load FA by other methods. RGD peptide was a novel compound coupled with Ch-COOH via carbodiimide and N-hydroxysulfosuccinimide. The results of the in vitro flow cytometric study showed that RGD conjugation liposomes (RGD-liposomes) could bind to monocytes/neutrophils efficiently. The rats were subjected to intrastriatal microinjections of 100 microl of human recombinant IL-1beta to produce brain inflammation and subsequently sacrificed after 15, 30, 60 and 120 min of administration of three formulations (FA solution, FA liposome, RGD-coated FA liposome). The body distribution results showed that RGD-liposomes could be directed to the target site, i.e. the brain, by cell selectivity in case of an inflammatory response. For RGD coated liposomes, the concentration of FA in brain was 6-fold higher than that of FA solution and 3-fold higher than that of uncoated liposomes. MTT assay and flow cytometry were used in the pharmacodynamic studies where it was found that FA liposomes exhibited greater antioxidant activity to FA solution on U937 cell.

Tumour-associated macrophages and melanoma tumourigenesis: integrating the complexity

When the body discovers a tumour cell (foreign antigen), several kinds of mechanisms and cells operate in what is called an immune response. The latter has evolved into two mechanisms: non-specific immunity and specific immunity, which are closely linked to and influence each other. The former represents the first line of defence against neoplastic cells. The adaptive (specific) immunity is orchestrated by antigen-specific T and B lymphocytes. The effector cells of innate immunity include granulocytes, macrophages and natural killer cells. Among these cells, macrophages represent the most important part of innate immunity against tumours. Tumour-associated macrophages (TAMs) are important antigen-presenting cells and as such an understanding of their interactions with tumour cells gives insights into novel therapeutic strategies. In tumours, the effect of TAMs is the outcome of their two concomitantly competing interactions: tumour growth reduction and tumour growth promotion. The macrophage (TAMs) content of melanoma ranges from 0 to 30% and their density increases with increasing tumour thickness. The melanoma cells and TAMs seem to interact with each other through the release of soluble factors that either prevent or enhance tumour growth. For instance, syngeneic macrophages from tumour-bearing mice can inhibit melanoma growth in the nude mice more than the control macrophages. Alternatively, metastatic B16 melanoma cells can produce some macrophage cytotoxic substances that help tumour cells not only escape the host immunosurveillance system but also prevent distant metastasis. Together, these observations suggest opposing effects for these soluble factors in melanoma. To date, little is available in the literature about the interactions between TAMs and melanoma cells. This viewpoint not only tries to examine these interactions but also provides relevant speculations.

The roles of Akt and MAPK family members in silymarin's protection against UV-induced A375-S2 cell apoptosis

Silymarin is a polyphenolic flavonoid derived from milk thistle (Silybum marianum) and has anti-inflammatory, cytoprotective as well as anticarcinogenic effects [Manna, S.K., Mukhopadlhyay, A., Van, N.T., Aggarwal, B., Silymarin suppresses TNF-induced activation of NF-kappaB, c-Jun N-terminal kinase, and apoptosis. J. Immunol. 1999; 163, 6800-6809.]. In this study, we assessed the effect of silymarin on ultraviolet light (UV)-induced cell apoptosis in human malignant melanoma, A375-S2 cells. Silymarin pre-treatment reversed the effect of UV irradiation on the expression of phosphorylated Akt and phosphorylated p53 (regulated by Akt activation), followed by down-regulation of Bax and up-regulated expressions of Bcl-2 and Bcl-xL proteins in UV-irradiated A375-S2 cells. Akt inhibitor decreased the viability of UV-irradiated cells which was treated with silymarin. In addition, the effect of UV irradiation on the phosphorylation of mitogen-activated protein kinase (MAPK) family members [extracellular signal-regulated kinase (ERK), p38 and c-Jun N-terminal kinase (JNK)] was also reversed by silymarin. Moreover, ERK inhibitor (PD98059) and p38 inhibitor (SB203580) augmented UV-induced apoptosis in silymarin treated A375-S2 cells. Consequently, silymarin partially reduced UV-induced apoptosis by activating the Akt pathway, and silymarin's protective effect was also exerted by MAPK family members.

Shikonin regulates HeLa cell death via caspase-3 activation and blockage of DNA synthesis

Shikonin, isolated from the plant Lithospermum erythrorhizon Sieb. ET Zucc, inhibited tumor cell growth and induced cell death in various tumor cells, with 50% growth inhibition of human cervical cancer cells, HeLa, at 18.9 +/- 1.1 mumol L-1. Treated with 40 mumol L-1 shikonin, HeLa cells underwent marked apoptotic morphological changes such as a round shape, membrane blebbing and apoptotic bodies derived from the fragmented nuclei. Another hallmark of apoptosis, DNA fragmentation, was observed by gel electrophoresis. Shikonin (10 mumol L-1) significantly blocked the transition from G1 to S phase in the HeLa cell cycle. Pan-caspase inhibitor (Z-VAD-FMK), caspase-3 inhibitor (Z-DEVD-FMK) or caspase-8 inhibitor (Z-IETD-FMK) effectively inhibited shikonin-induced cell death, while caspase-1 inhibitor (Ac-YVAD-CMK) and caspase-9 inhibitor (Z-LEHD-FMK) failed to affect cell death. Caspase-3 activity significantly increased within 12 h after shikonin treatment. Reduced expression of inhibitor of caspase-activated deoxyribonuclease (ICAD) after exposure to shikonin for 12 h suggests the resultant activation of caspase-activated deoxyribonuclease (CAD), leading to apoptosis.

Natural mechanisms protecting against cancer

Carcinogenesis is a multistage process. At each step of this process, there are natural mechanisms protecting against development of cancer. The majority of cancers in humans is induced by carcinogenic factors present in our environment including our food. However, some natural substances present in our diet or synthesized in our cells are able to block, trap or decompose reactive oxygen species (ROS) participating in carcinogenesis. Carcinogens can also be removed from our cells. If DNA damage occurs, it is repaired in most of the cases. Unrepaired DNA alterations can be fixed as mutations in proliferating cells only and mutations of very few strategic genes can induce tumor formation, the most relevant are those activating proto-oncogenes and inactivating tumor suppressor genes. A series of mutations and/or epigenetic changes is required to drive transformation of a normal cell into malignant tumor. The apparently unrestricted growth has to be accompanied by a mechanism preserving telomeres which otherwise shorten with succeeding cell divisions leading to growth arrest. Tumor can not develop beyond the size of 1-2mm in diameter without the induction of angiogenesis which is regulated by natural inhibitors. To invade the surrounding tissues epithelial tumor cells have to lose some adhesion molecules keeping them attached to each other and to produce enzymes able to dissolve the elements of the basement membrane. On the other hand, acquisition of other adhesion molecules enables interaction of circulating tumor cells with endothelial cells facilitating extravasation and metastasis. One of the last barriers protecting against cancer is the activity of the immune system. Both innate and adaptive immunity participates in anti-tumor effects including the activity of natural killer (NK) cells, natural killer T cells, macrophages, neutrophils and eosinophils, complement, various cytokines, specific antibodies, and specific T cytotoxic cells. Upon activation neutrophils and macrophages are able to kill tumor cells but they can also release ROS, angiogenic and immunosuppressive substances. Many cytokines belonging to different families display anti-tumor activity but their role in natural anti-tumor defense remains largely to be established.

Effect of honey bee venom on proliferation of K1735M2 mouse melanoma cells in-vitro and growth of murine B16 melanomas in-vivo

Bee venom has been reported to exhibit antitumour activity in-vitro and in-vivo. Apoptosis, necrosis and lysis of tumour cells were suggested as possible mechanisms by which bee venom inhibited tumour growth. The aim of this study was to investigate potential mechanisms by which bee venom inhibits K1735M2 mouse melanoma cells in-vitro and B16 melanoma, a transplantable solid melanoma in C57BL/6 mice, in-vivo. The proliferation of K1735M2 cells in-vitro was inhibited by bee venom in a concentration- and time-dependent manner. The inhibition was indicated by the arrest of the cell cycle at the G1 stage, as detected by flow cytometric measurements. The bee venom induced apoptosis-like cell death as identified by histological observations and by DNA fragmentation. In the in-vivo experiments, the bee venom (1.0, 3.0, 9.0 mg kg-1 of body weight, on days 1-12) was injected intraperitoneally into mice 24 h after the mice were inoculated with B16 cells. Inhibition of the solid tumour was observed. Apoptosis of the K1735M2 cells was suggested as the possible mechanism by which bee venom inhibited cell proliferation and induced K1735M2 cell differentiation in-vitro. The in-vivo experiment indicated that bee venom could be used as a chemotherapeutic agent against malignant tumours.

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.

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.

Recombinant yellow fever viruses are effective therapeutic vaccines for treatment of murine experimental solid tumors and pulmonary metastases

We have genetically engineered an attenuated yellow fever (YF) virus to carry and express foreign antigenic sequences and evaluated the potential of this type of recombinant virus to serve as a safe and effective tumor vaccine. Live-attenuated YF vaccine is one of the most effective viral vaccines available today. Important advantages include its ability to induce long-lasting immunity, its safety, its affordability, and its documented efficacy. In this study, recombinant live-attenuated (strain 17D) YF viruses were constructed to express a cytotoxic T-lymphocyte epitope derived from chicken ovalbumin (SIINFEKL). These recombinant viruses replicated comparably to the 17D vaccine strain in cell culture and stably expressed the ovalbumin antigen, and infected cells presented the antigen in the context of major histocompatibility complex class I. Inoculation of mice with recombinant YF virus elicited SIINFEKL-specific CD8(+) lymphocytes and induced protective immunity against challenge with lethal doses of malignant melanoma cells expressing ovalbumin. Furthermore, active immunotherapy with recombinant YF viruses induced regression of established solid tumors and pulmonary metastases. Thus, recombinant YF viruses are attractive viral vaccine vector candidates for the development of therapeutic anticancer vaccines.

Lack of mda-6/WAF1/CIP1-mediated inhibition of cyclin-dependent kinases in interferon-alpha resistant murine B16 melanoma cells

Previously we demonstrated that IFN-alpha augments mda-6/WAF1 and inhibits cyclin-dependent kinases in a p53-independent fashion in B 16 murine melanoma cells. On the other hand, IFN-gamma activates p53 expression without affecting the mda-6/WAF1 system. Combination of the two IFNs is additive. B16 cells acquire IFN-alpha resistant but IFN-gamma sensitive phenotype after long term IFN-alpha treatment (B16alpha cells). Here we demonstrate the absence of mda-6/WAF1-associated repression of cyclin-dependent kinases, but the existence of p53-dependent c-myc inhibition in IFN-gamma-treated B16alpha cells. Clearly, selective desensitization of IFN-alpha related growth regulation does not influence the IFN-gamma associated pathway. Our results further support the coexistence of distinct growth regulatory mechanisms in B16 cells that can be activated by different IFN-types independently of each other.

Interferon regulates expression of mda-6/WAF1/CIP1 and cyclin-dependent kinases independently from p53 in B16 murine melanoma cells

Interferons (IFNs) induce growth arrest and terminal differentiation through regulation of proliferative genes in a variety of cell types including tumor cells. Growth of melanoma cells is believed to be controlled by the cyclin-dependent kinase inhibitor, mda-6/WAF1/CIP1 gene. IFNs affect the expression of WAF1 in several cell types, including human melanomas. In our earlier reports we demonstrated the antitumor and anticellular activities of different IFN-types on B16 murine melanoma cells. The present study aimed to demonstrate the involvement of mda-6/WAF1 and related cyclin-dependent kinases in antitumor action of different IFN-types in B16 melanoma cells. IFN-alpha has been proven to be a potent inducer of mda-6/WAF1, also inhibiting cyclin-dependent kinases, such as cdc2- and cdk2-kinase. This induction is p53-independent. However, IFN-gamma affects B16 cells differently, it induces p53 activity without inducing WAF1. The combination of IFN-alpha plus IFN-gamma is additive rather than synergistic. Our data demonstrate differential effects of different IFNs on murine B16 melanoma cells which may have relevance in nonsurgical treatment of melanomas.

In vivo anti-tumor efficacy of polyethylene glycol-modified tumor necrosis factor-alpha against tumor necrosis factor-resistant tumors

We previously reported that the optimally PEGylated tumor necrosis factor-alpha (MPEG-TNF-alpha), in which 56% of the TNF-alpha-lysine amino groups were coupled with polyethylene glycol (PEG), had about 100-fold greater anti-tumor effect than native TNF-alpha. Here, we assessed the usefulness of MPEG-TNF-alpha as a systemic anti-tumor therapeutic drug, using B16-BL6 melanoma and colon-26 adenocarcinoma, which have been reported to be resistant to TNF-alpha in vivo, as compared with Meth-A fibrosarcoma. MPEG-TNF-alpha markedly inhibited the growth of both tumors without causing any TNF-alpha-mediated side-effects, whereas native TNF-alpha had no anti-tumor effects and caused adverse side-effects. In addition, MPEG-TNF-alpha drastically inhibited the metastatic colony formation of B16-BL6 melanoma. MPEG-TNF-alpha may, thus, be a potential systemic anti-tumor therapeutic agent.

Potentiation of the anti-tumor effect of actinomycin D by tumor necrosis factor alpha in mice: correlation between in vitro and in vivo results

The anti-tumor effects of actinomycin D (Act D) and recombinant human tumor necrosis factor (TNF)-alpha have been studied on 4 established murine tumor cell lines: MmB16 melanoma, Lewis lung (LL/2) carcinoma, L1 sarcoma and L1210 leukemia. During short-term incubation (24 hr) Act D produced dose-dependent cytostatic/cytotoxic effects against MmB16, LL/2 and L1 tumor cells but did not reduce the viability of these cells even at high concentration (10 micrograms/ml), below a threshold of 30-60%. However, L1210 leukemic cells were highly susceptible to Act D, and no viable cells were detected in cultures incubated with 1 microgram/ml of Act D. TNF-alpha alone, when used under the same culture conditions, had only a negligible effect on all cell lines tested. However, the combination of this cytokine with Act D produced synergistic cytotoxic effects against MmB16, LL/2 and L1 cells but not against L1210 leukemia cells. In an in vivo model of regional therapy in which tumor-bearing mice were treated with Act D and TNF-alpha, a correlation with in vitro results was observed. In mice bearing MmB16 melanoma, LL/2 carcinoma and L1 sarcoma, the most potent anti-tumor effects were observed in mice treated with Act D and TNF-alpha together. This treatment led to a delay of tumor growth and induced complete tumor regression in some cases. On the contrary, TNF-alpha did not enhance the effect of Act D in mice injected with L1210 leukemia cells. Our results show that TNF-alpha can potentiate the anti-tumor effects of Act D against tumors weakly susceptible to Act D and may be a useful adjuvant to chemotherapy in the local treatment of neoplasia.

Granulocyte-macrophage colony-stimulating factor accelerates growth of Lewis lung carcinoma in mice

Granulocyte-macrophage colony-stimulating factor (GM-CSF) has not been found to exert any influence on the proliferation of Lewis lung carcinoma (LLC) cells in vitro. Nevertheless, when administered intraperitoneally, GM-CSF accelerated the growth of subcutaneously growing LLC in mice.