Inhibitory effect of Lovastatin on spontaneous metastases derived from a rat lymphoma.

The HMGCoA reductase inhibitor Lovastatin (LOV) has previously shown to abrogate p21ras farnesylation, which is associated with invasive and metastatic abilities in many tumor models. Considering the scarcity of therapeutic resources against metastasis, our objective was to study LOV as an antimetastatic agent on L-TACB rat lymphoma, which as a syngeneic tumor model resembles more closely the situation in human cancer. We also aimed to analyze the effect of LOV on chemoinvasion, motility, metalloproteases secretion, angiogenic capacity, and adhesion to the reconstituted basement membrane Matrigel. Our results showed that LOV caused no effect on cell motility, metalloprotease secretion and neovascularization. Conversely, LOV produced a significant inhibition of invasiveness, which could be a consequence of an impaired cell adhesion to the basement membrane observed. These effects could explain, at least in part, the inhibitory action of LOV on L-TACB rat lymphoma metastases.

Mechanism of antimetastatic immunopotentiation by low-dose cyclophosphamide.

We have previously reported the antimetastatic effect of a single low-dose of cyclophosphamide (Cy) on L-TACB rat lymphoma. The phenomenon could be adoptively transferred in immunocompetent rats and is abolished in nude mice, facts for which an immunomodulatory explanation was proposed. The aim of this paper was to identify the mechanism(s) by which spleen cells from Cy-treated tumour-bearing rats could exert this antimetastatic activity. Conditioned media obtained by incubation of spleen cells from Cy-treated and non-treated tumour-bearing rats, under specific or non-specific stimulation, were assayed to evaluate their effect on lymphocyte proliferation. The production of transforming growth factor beta (TGF-beta), interleukin-10 (IL-10) and nitric oxide (NO) by conditioned media was also studied. The restoration of spleen lymphoproliferative responses to normal levels when exposed to media conditioned by splenocytes from Cy-treated tumour-bearing rats, together with a decreased production of suppressive cytokines TGF-beta, IL-10 and NO, suggest an enhancement of host antimetastatic immunity triggered by single low-dose Cy treatment.

Down regulation of T-cell-derived IL-10 production by low-dose cyclophosphamide treatment in tumor-bearing rats restores in vitro normal lymphoproliferative response.

In previous reports, we demonstrated an inhibitory effect of a single low-dose of cyclophosphamide (Cy) on spontaneous and experimental metastasis of a rat lymphoma (L-TACB). This antimetastatic effect could be adoptively transferred by immune spleen cells from Cy-treated tumor-bearing rats and it was abrogated by the use of immunosuppressed hosts, suggesting an immunomodulatory effect. Subsequently, we found that increased levels of TGF-beta, IL-10 and NO were involved in tumor-induced immunosuppression by inhibiting lymphocyte proliferation. The treatment of tumor-bearing rats with low-dose Cy reduced the splenic production of these suppressive cytokines, restoring the lymphoproliferative capacity otherwise diminished during tumor growth. Here, we investigated the changes of the cytokines modulated by the Cy therapy that are responsible for the restoration of the lymphoproliferative response and determined the spleen cell type producing TGF-beta, IL-10 and NO in our experimental model. Our current results show that IL-10 and NO are produced exclusively by T lymphocytes and macrophages, respectively, whereas TGF-beta is produced by both cell types. The high level of IL-10 produced by T-cells from tumor-bearing rats is responsible for the inhibition of lymphocyte proliferation. Moreover, our results suggest that the shift from immunosuppression to immunopotentiation induced by treatment of tumor-bearing rats with a single low-dose of Cy is mediated by a reduction in T-cell derived IL-10 production, which would account, to some extent, for the antimetastatic effect of Cy treatment.

Lovastatin inhibits tumor growth and metastasis development of a rat fibrosarcoma.

HMG-CoA (3-hydroxy-3-methylglutaryl coenzyme A) reductase, the rate limiting enzyme in cholesterol synthesis, catalyses mevalonate production and, hence, influence the synthesis of isoprenoid metabolites. It has already been demonstrated that products of the mevalonate pathway play an important role in the progress of the cell cycle and cell survival. Lovastatin (LOV) competitively inhibits HMG-CoA reductase, blocking the synthesis of mevalonic acid and the generation of non-sterol isoprenoids, such as farnesyl residues. The posttranslational farnesylation of p21ras protein is essential for its binding to the membrane and, therefore, for its transforming activity. Considering that p21ras protein was reported to have a significant rol in metastatic behavior of tumor cells, we decided to study LOV as an antimetastatic agent on a rat fibrosarcoma. We demonstrated that a short treatment with LOV diminished primary tumor growth and the number and size of lung experimental metastasis.

Angiogenesis induced by tumor-host interaction in the rat.

There is a clear-cut cause-effect relationship between vascularization of a given tumor and its capacity to disseminate and metastasize. Hence, it is very important to study the contribution of the two main factors determining the generation of new blood vessels namely the tumor and the host where it grows. The influence of the tumor-host interaction on the induction of angiogenesis was studied in a tumor model-system composed by two lines of rats selected for resistance or susceptibility to a sarcoma (S-E100) and two transplantable tumors: Sarcoma E 100 and Lymphoma TACB. One line is resistant to the sarcoma but susceptible to the lymphoma while the other line behaves in the opposite way. Studying the angiogenesis generated by the s.c. implantation of each tumor in two different hosts we found that the same tumor induced different angiogenic responses according to the host in which it is growing and that the same host shows a different response according to the tumor with which it is challenged, suggesting that tumor-host interactions determine the intensity of the neovascularization process.

[Preclinical and clinical results with the epidermal growth factor receptor inhibitor Gefitinib (ZD1839, Iressa)]. / Risultati preclinici e clinici con Gefitinib (ZD1839, Iressa) inibitore del recettore per il fattore di crescita epidermoidale.

Since epidermal growth factor receptor (EGFR) is involved in tumor proliferation and angiogenesis, and in the mechanisms of resistance to chemo- and hormono-therapy, it represents a unique promising target for anticancer treatment. Gefinitib (Iressa, ZD1839), an inhibitor of the EGFR tyrosine kinase activity able to bind the intracellular domain of the receptor, is at present in clinical development. In preclinical models Gefitinib induced a dose-dependent response rate in tumor xenografts obtained from different human cancer cells lines. The expression of EGFR in the prior tumor did not appear to be a predictive marker for Gefitinib sensitivity. Furthermore, long-term drug use was well tolerated in mice without inducing resistance. However, tumors started to grow again after treatment interruption. Laboratory findings and in vivo data have prompted the evaluation of Gefitinib administered as a single oral daily dose alone or in combination with conventional anticancer treatment.

Regulatory T cells but not NKT I cells are modulated by a single low-dose cyclophosphamide in a B cell lymphoma tumor-model.

AIM: Experimental and clinical studies showed that the administration of cyclophosphamide (Cy) in low doses leads to an enhancement of the antitumor immune response. Our objective was to study the modulation, if any, by low dose Cy, of T regulatory (Treg) and natural killer T (NKT) I cells, two cell populations of the innate immune response with opposing effects on the tumors, in a rat B cell lymphoma model. METHODS: Inbred e rats were challenged s.c. with L-TACB lymphoma and on day 14 animals were distributed in two groups. Treated: injected i.p. with cyclophosphamide (10mg/kg of body weight) and CONTROL: injected i.p. with saline. Blood samples were taken from days 0 to 21 and the percentage of T regulatory and natural killer T I cells were determined by flow cytometry. RESULTS: We found that the increase of natural and inducible T regulatory cells of peripheral blood achieved during tumor growth was significantly downregulated by cyclophosphamide. On the contrary, natural killer T I cells were not modulated by the treatment. CONCLUSION: The antimetastatic effect of a single low dose of Cy would be due, at least in part, to downregulation of natural and inducible T regulatory cells.

Inhibition of ras oncogene: a novel approach to antineoplastic therapy.

The most frequently detected oncogene alterations, both in animal and human cancers, are the mutations in the ras oncogene family. These oncogenes are mutated or overexpressed in many human tumors, with a high incidence in tumors of the pancreas, thyroid, colon, lung and certain types of leukemia. Ras is a small guanine nucleotide binding protein that transduces biological information from the cell surface to cytoplasmic components within cells. The signal is transduced to the cell nucleus through second messengers, and it ultimately induces cell division. Oncogenic forms of p21(ras) lead to unregulated, sustained signaling through downstream effectors. The ras family of oncogenes is involved in the development of both primary tumors and metastases making it a good therapeutic target. Several therapeutic approaches to cancer have been developed pointing to reducing the altered gene product or to eliminating its biological function: (1) gene therapy with ribozymes, which are able to break down specific RNA sequences, or with antisense oligonucleotides, (2) immunotherapy through passive or active immunization protocols, and (3) inhibition of p21(ras) farnesylation either by inhibition of farnesyl transferase or synthesis inhibition of farnesyl moieties.

Modulation of the antimetastatic effect of a single low dose of cyclophosphamide on rat lymphoma.

The aim of this paper was to identify the mechanism/s responsible of the antimetastatic effect of a single low dose of cyclophosphamide (Cy), previously demonstrated by us in the rat lymphoma LTACB. No direct cytotoxic antimetastatic activity of Cy could be proved. In vitro treatment of L-TACB cells with mafosfamide did not alter their invasiveness or their motility. The adoptive transfer of splenocytes from Cy-treated tumor-bearing rats, together with L-TACB cells inhibited their metastatic growth. The single low dose Cy treatment of T-immunodeficient nude mice did not show the antimetastatic effect on L-TACB observed in immunocompetent mice. An inhibition of the metastatic ability due to immunomodulation by Cy is proposed.

Metronomic therapy with cyclophosphamide induces rat lymphoma and sarcoma regression, and is devoid of toxicity.

BACKGROUND: Our aim was to investigate the clinical efficacy and toxicity of metronomic administration of low-dose cyclophosphamide (Cy) in lymphoma and sarcoma rat tumour models. METHODS: Adult inbred rats were challenged with lymphoma TACB and sarcoma E100 s.c. on day 0. Animals were divided into two groups: group I, control, injected with saline three times a week; and group II, treated with Cy 10 mg/kg three times a week, from day 10 until the tumour was non-palpable, or 5 mg/kg three times a week from day 7. Tumours were measured and animals were weighed twice weekly. Periodic blood samples were taken for determination of urea, creatinine, serum glutamic-oxaloacetic transaminase, lactate dehydrogenase and haematological parameters. RESULTS: The administration of low-dose Cy eradicated established rat lymphomas and sarcomas; there was neither metastatic growth nor recurrence at primary sites for 100% of the lymphomas and 83% of the sarcomas. In addition, the treatment did not cause weight loss, and was devoid of haematological, cardiac, hepatic and renal toxicity. CONCLUSIONS: Metronomic administration of Cy at low doses on a thrice weekly schedule to already grown rat lymphomas and sarcomas demonstrated itself to be a successful antitumour therapy that did not cause weight loss and was devoid of haematological, cardiac, hepatic and renal toxicity.