Photodynamic therapy is a promising antitumor treatment modality approved for the management of both early and advanced tumors. The mechanisms of its antitumor action include generation of singlet oxygen and reactive oxygen species that directly damage tumor cells and tumor vasculature. A number of mechanisms seem to be involved in the protective responses to PDT that include activation of transcription factors, heat shock proteins, antioxidant enzymes and antiapoptotic pathways. Elucidation of these mechanisms might result in the design of more effective combination strategies to improve the antitumor efficacy of PDT. Using DNA microarray analysis to identify stress-related genes induced by Photofrin-mediated PDT in colon adenocarcinoma C-26 cells, we observed a marked induction of heme oxygenase-1 (HO-1). Induction of HO-1 with hemin or stable transfection of C-26 with a plasmid vector encoding HO-1 increased resistance of tumor cells to PDT-mediated cytotoxicity. On the other hand, zinc (II) protoporphyrin IX, an HO-1 inhibitor, markedly augmented PDT-mediated cytotoxicity towards C-26 and human ovarian carcinoma MDAH2774 cells. Neither bilirubin, biliverdin nor carbon monoxide, direct products of HO-1 catalysed heme degradation, was responsible for cytoprotection. Importantly, desferrioxamine, a potent iron chelator significantly potentiated cytotoxic effects of PDT. Altogether our results indicate that HO-1 is involved in an important protective mechanism against PDT-mediated phototoxicity and administration of HO-1 inhibitors might be an effective way to potentiate antitumor effectiveness of PDT.

Photodynamic therapy (PDT) is a clinically approved and rapidly developing cancer treatment regimen. It is a minimally invasive two-stage procedure that requires administration of a photosensitizing agent followed by illumination of the tumor with visible light usually generated by laser sources. A third component of PDT is molecular oxygen which is required for the most effective antitumor effects. In the presence of the latter, light of an appropriate wavelength excites the photosensitizer thereby producing cytotoxic intermediates that damage cellular structures. PDT has been approved in many countries for the treatment of lung, esophageal, bladder, skin and head and neck cancers. The antitumor effects of this treatment result from the combination of direct tumor cell photodamage, destruction of tumor vasculature and activation of an immune response. The mechanisms of the direct photodamage of tumor cells, the signaling pathways that lead to apoptosis or survival of sublethaly damaged cells, and potential novel strategies of improving the antitumor efficacy of PDT are discussed.

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A soluble complement inhibitor factor H (FH) and its splice variant factor H-like protein (FHL) have been recently discovered to play a major role in malignant cell escape from complement-mediated cytotoxicity in lung-, ovarian-and glia-derived neoplasms. The role of FH in colon cancer has not yet been examined. Here, we studied immunocytochemically FH/FHL expression in tumor samples derived from 40 patients, with both primary colon adenocarcinoma and metastatic foci in the liver. FH/FHL immunoreactivity was present in stroma of both primary and metastatic tumors, in virtually all patients. The cellular immunoreactivity was observed infrequently. Importantly, when analyzed quantitatively, FH/FHL immunoreactivity was significantly increased in liver metastases when compared with the primary sites. In addition, we have analyzed FH and FHL expression in 5 colon cancer cell lines: SW480, SW620, HCT116, HT-29 and Lovo. FH mRNA and FH secretion were observed in SW620 and HT-29 cells, whereas FHL was produced only by HT-29 cell-line. By confocal and electron microscopy, FH immunoreactivity was associated with the plasma membrane and intracellular vesicular structures. Finally, we have analyzed the role of FH in the susceptibility of SW620 colon cancer cells to complement-mediated damage. When FH function was blocked, using specific antibody, the cells became more susceptible to lysis. Taken together, our results suggest an important role of FH/FHL in colon cancer cells defense against complement-mediated cytotoxicity, and in metastatic process. ' 2008 Wiley-Liss, Inc.Key words: factor H; colon cancer; metastasis; immunotherapy; complement Although recent years have brought many advances in clinical oncology, colon cancer is still a serious problem. Surgical resection remains as the most efficient treatment, but its results are often not satisfactory. Sixty percent of patients with colon cancer develop liver metastases, which, for a third of those, is the main and only metastatic site. About 25% of the patients have potentially resectable hepatic metastases, but at least half of them have recurrence after surgery. 1 Unfortunately, for a large group of patients, radical surgery is impossible. For about 60% of such patients, advanced chemo-and radiotherapy allows for a 5-year survival, however a major objection to this kind of treatment is severe side effects. 2 To improve disease-free survival, overall survival and to prevent formation of metastases, new strategies for effective treatment should be considered.

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Advanced melanoma is a highly malignant tumor with an increasing incidence that has a poor prognosis due to resistance to common therapeutic strategies. We have demonstrated previously that cyclosporine A (CsA) induces apoptosis of rat glioma cells, reactive astrocytes, and fibroblasts. In our present study, we investigated effects of CsA and its nonimmunosuppressive derivative NIM811 on survival of human and murine melanoma cells. We demonstrated that CsA and NIM811 affect survival of human and murine melanoma cells and induce morphological changes, alterations in nuclear morphology and an internucleosomal DNA fragmentation, consistent with an apoptotic type of death. Western blot analysis showed an activation of caspases 9, 7, 3 and PARP cleavage detectable at 24 hr after exposure of human melanoma cells to the drugs. CsA and NIM811 induced a significant increase in subG1 population of murine B16F10 melanoma cells indicative of apoptotic DNA fragmentation. Studies in murine model of melanoma showed that NIM811, but not CsA, retards tumor progression and significantly decreases tumor volume after intratumoral application. Our findings indicate that CsA and its derivatives may be new candidates for the treatment of melanoma patients. ' 2005 Wiley-Liss, Inc.

The aim of the present study was to examine the potential antitumor activity of lovastatin and other statins together with pamidronate, a second generation bisphosphonate (BP), against tumor cell lines. Cytostatic/cytotoxic effects were measured using crystal violet assay. Regulation of the cell cycle and induction of apoptosis were evaluated using flow cytometry and Western blotting, migration of tumor cells was measured in a scratch wound assay and their invasiveness was measured with a Matrigel-invasion assay. Antitumor effects of the combination treatment were evaluated in a murine PANC 02 pancreatic adenocarcinoma model. Combination of pamidronate and lovastatin produced potentiated cytostatic/ cytotoxic effects against breast and pancreatic cancer cell lines. The combination was also effective in inhibition of tumor cell adhesion to collagen IV and fibronectin and interfered with migration and invasiveness of tumor cells. Neither pamidronate nor lovastatin alone affected tumor growth in mice but the combination treatment resulted in retardation of tumor growth and prolongation of mouse survival. The combination of statins and pamidronate, a second generation bisphosphonate, demonstrates promising antitumor effects at doses readily achievable in patients. This combination holds promise for future clinical studies.

Abstract. Cisplatin, a widely used chemotherapeutic is approved for the management of various solid tumors. Administration of cisplatin is associated with induction of significant toxicities that include neurotoxicity and nephrotoxicity, the latter leading to severe and debilitating anemia. Since erythropoietin, a hematopoietic growth factor that corrects chemotherapy-induced anemia, reduces transfusion requirements and seems to improve the patient's quality of life, has been shown to exert cytoprotective effects we decided to investigate its direct influence on cisplatin-induced neurotoxicity against primary cortical neurons isolated from rats. We observed that pre-treatment of neurons with erythropoietin significantly protects these cells from cisplatin-induced cytotoxicity. These effects correlated with amelioration of cisplatin-mediated activation of ERK1/2 kinases and decreased cleavage of caspase 3. Similarly to erythropoietin, a selective ERK1/2 inhibitor significantly reduced cisplatin-induced cytotoxicity against neuronal cells. Importantly, using the same experimental setting we did not observe any protection from cisplatin cytotoxicity against four established tumor cell lines. Altogether our studies confirm that erythropoietin might be an effective cytoprotective agent that reduces cisplatininduced neurotoxicity.