Zinc protoporphyrin IX, a heme oxygenase-1 inhibitor, demonstrates potent antitumor effects but is unable to potentiate antitumor effects of chemotherapeutics in mice

<p>Abstract</p> <p>Background</p> <p>HO-1 participates in the degradation of heme. Its products can exert unique cytoprotective effects. Numerous tumors express high levels of HO-1 indicating that this enzyme might be a potential therapeutic target. In this study we decided to evaluate potential cytostatic/cytotoxic effects of zinc protoporphyrin IX (Zn(II)PPIX), a selective HO-1 inhibitor and to evaluate its antitumor activity in combination with chemotherapeutics.</p> <p>Methods</p> <p>Cytostatic/cytotoxic effects of Zn(II)PPIX were evaluated with crystal violet staining and clonogenic assay. Western blotting was used for the evaluation of protein expression. Flow cytometry was used to evaluate the influence of Zn(II)PPIX on the induction of apoptosis and generation of reactive oxygen species. Knock-down of HO-1 expression was achieved with siRNA. Antitumor effects of Zn(II)PPIX alone or in combination with chemotherapeutics were measured in transplantation tumor models.</p> <p>Results</p> <p>Zn(II)PPIX induced significant accumulation of reactive oxygen species in tumor cells. This effect was partly reversed by administration of exogenous bilirubin. Moreover, Zn(II)PPIX exerted potent cytostatic/cytotoxic effects against human and murine tumor cell lines. Despite a significant time and dose-dependent decrease in cyclin D expression in Zn(II)PPIX-treated cells no accumulation of tumor cells in G1 phase of the cell cycle was observed. However, incubation of C-26 cells with Zn(II)PPIX increased the percentage of cells in sub-G1 phase of the cells cycle. Flow cytometry studies with propidium iodide and annexin V staining as well as detection of cleaved caspase 3 by Western blotting revealed that Zn(II)PPIX can induce apoptosis of tumor cells. B16F10 melanoma cells overexpressing HO-1 and transplanted into syngeneic mice were resistant to either Zn(II)PPIX or antitumor effects of cisplatin. Zn(II)PPIX was unable to potentiate antitumor effects of 5-fluorouracil, cisplatin or doxorubicin in three different tumor models, but significantly potentiated toxicity of 5-FU and cisplatin.</p> <p>Conclusion</p> <p>Inhibition of HO-1 exerts antitumor effects but should not be used to potentiate antitumor effects of cancer chemotherapeutics unless procedures of selective tumor targeting of HO-1 inhibitors are developed.</p

Photodynamic Therapy of Tumors Can Lead to Development of Systemic Antigen-Specific Immune Response

Background: The mechanism by which the immune system can effectively recognize and destroy tumors is dependent on recognition of tumor antigens. The molecular identity of a number of these antigens has recently been identified and several immunotherapies have explored them as targets. Photodynamic therapy (PDT) is an anti-cancer modality that uses a non-toxic photosensitizer and visible light to produce cytotoxic reactive oxygen species that destroy tumors. PDT has been shown to lead to local destruction of tumors as well as to induction of anti-tumor immune response. Methodology/Principal Findings: We used a pair of equally lethal BALB/c colon adenocarcinomas, CT26 wild-type (CT26WT) and CT26.CL25 that expressed a tumor antigen, β-galactosidase (β-gal), and we treated them with vascular PDT. All mice bearing antigen-positive, but not antigen-negative tumors were cured and resistant to rechallenge. T lymphocytes isolated from cured mice were able to specifically lyse antigen positive cells and recognize the epitope derived from beta-galactosidase antigen. PDT was capable of destroying distant, untreated, established, antigen-expressing tumors in 70% of the mice. The remaining 30% escaped destruction due to loss of expression of tumor antigen. The PDT anti-tumor effects were completely abrogated in the absence of the adaptive immune response. Conclusion: Understanding the role of antigen-expression in PDT immune response may allow application of PDT in metastatic as well as localized disease. To the best of our knowledge, this is the first time that PDT has been shown to lead to systemic, antigen- specific anti-tumor immunity.United States. National Cancer Institute (grant RO1CA/AI838801)United States. National Cancer Institute (grant R01AI050875

Zinc protoporphyrin IX, a heme oxygenase-1 inhibitor, demonstrates potent antitumor effects but is unable to potentiate antitumor effects of chemotherapeutics in mice-4

Cisplatin at a dose of 2.5, 5.0 or 7.5 mg/kg administered i.p. [A and B] or with cisplatin (5 mg/kg in a single i.p. injection) and 50 mg/kg of Zn(II)PPIX administered i.p. for 7 consecutive days [C and D]. Graphs show the influence of the treatment on the growth of melanoma in mice. *< 0.05 (two way Student's -test) in comparison with controls.<p><b>Copyright information:</b></p><p>Taken from "Zinc protoporphyrin IX, a heme oxygenase-1 inhibitor, demonstrates potent antitumor effects but is unable to potentiate antitumor effects of chemotherapeutics in mice"</p><p>http://www.biomedcentral.com/1471-2407/8/197</p><p>BMC Cancer 2008;8():197-197.</p><p>Published online 11 Jul 2008</p><p>PMCID:PMC2478682.</p><p></p

Zinc protoporphyrin IX, a heme oxygenase-1 inhibitor, demonstrates potent antitumor effects but is unable to potentiate antitumor effects of chemotherapeutics in mice-0

Rystal violet staining assay. Bars represent means ± SD. *< 0.05 (two way Student's -test) in comparison with controls.<p><b>Copyright information:</b></p><p>Taken from "Zinc protoporphyrin IX, a heme oxygenase-1 inhibitor, demonstrates potent antitumor effects but is unable to potentiate antitumor effects of chemotherapeutics in mice"</p><p>http://www.biomedcentral.com/1471-2407/8/197</p><p>BMC Cancer 2008;8():197-197.</p><p>Published online 11 Jul 2008</p><p>PMCID:PMC2478682.</p><p></p

Zinc protoporphyrin IX, a heme oxygenase-1 inhibitor, demonstrates potent antitumor effects but is unable to potentiate antitumor effects of chemotherapeutics in mice-6

Rystal violet staining assay. Bars represent means ± SD. *< 0.05 (two way Student's -test) in comparison with controls.<p><b>Copyright information:</b></p><p>Taken from "Zinc protoporphyrin IX, a heme oxygenase-1 inhibitor, demonstrates potent antitumor effects but is unable to potentiate antitumor effects of chemotherapeutics in mice"</p><p>http://www.biomedcentral.com/1471-2407/8/197</p><p>BMC Cancer 2008;8():197-197.</p><p>Published online 11 Jul 2008</p><p>PMCID:PMC2478682.</p><p></p

Zinc protoporphyrin IX, a heme oxygenase-1 inhibitor, demonstrates potent antitumor effects but is unable to potentiate antitumor effects of chemotherapeutics in mice-7

Nsecutive days. On day 14 after PDT, the plates were fixed with methanol and stained with crystal violet.<p><b>Copyright information:</b></p><p>Taken from "Zinc protoporphyrin IX, a heme oxygenase-1 inhibitor, demonstrates potent antitumor effects but is unable to potentiate antitumor effects of chemotherapeutics in mice"</p><p>http://www.biomedcentral.com/1471-2407/8/197</p><p>BMC Cancer 2008;8():197-197.</p><p>Published online 11 Jul 2008</p><p>PMCID:PMC2478682.</p><p></p

Zinc protoporphyrin IX, a heme oxygenase-1 inhibitor, demonstrates potent antitumor effects but is unable to potentiate antitumor effects of chemotherapeutics in mice-8

Is using ethanol-fixed, propidium iodide-stained cells. [B and D] Western blotting for expression of cyclin D1, cleaved caspase 3 or tubulin as a loading control was performed. [C] Induction of apoptosis was evaluated by staining of cells with propidium iodide and annexin V. [E] HO-1 silencing was evaluated with Western blotting. Controls represent expression of HO-1 in hemin-treated C-26 cells. HuHO-1 siRNA is a negative control targeting xenogeneic (human) HO-1 gene, muHO-1 siRNA is a murine sequence that knocks-down HO-1 expression in C-26 cells. [F and G] production of reactive oxygen species was evaluated with flow cytometry by measuring CM-HDCFDA fluorescence in comparison with controls.<p><b>Copyright information:</b></p><p>Taken from "Zinc protoporphyrin IX, a heme oxygenase-1 inhibitor, demonstrates potent antitumor effects but is unable to potentiate antitumor effects of chemotherapeutics in mice"</p><p>http://www.biomedcentral.com/1471-2407/8/197</p><p>BMC Cancer 2008;8():197-197.</p><p>Published online 11 Jul 2008</p><p>PMCID:PMC2478682.</p><p></p

Stable synthetic bacteriochlorins overcome the resistance of melanoma to photodynamic therapy.

Cutaneous malignant melanoma remains a therapeutic challenge, and patients with advanced disease have limited survival. Photodynamic therapy (PDT) has been successfully used to treat many malignancies, and it may show promise as an antimelanoma modality. However, high melanin levels in melanomas can adversely affect PDT effectiveness. Herein the extent of melanin contribution to melanoma resistance to PDT was investigated in a set of melanoma cell lines that markedly differ in the levels of pigmentation; 3 new bacteriochlorins successfully overcame the resistance. Cell killing studies determined that bacteriochlorins are superior at (LD(50) approximately 0.1 microM) when compared with controls such as the FDA-approved Photofrin (LD(50) approximately 10 microM) and clinically tested LuTex (LD(50) approximately 1 microM). The melanin content affects PDT effectiveness, but the degree of reduction is significantly lower for bacteriochlorins than for Photofrin. Microscopy reveals that the least effective bacteriochlorin localizes predominantly in lysosomes, while the most effective one preferentially accumulates in mitochondria. Interestingly all bacteriochlorins accumulate in melanosomes, and subsequent illumination leads to melanosomal damage shown by electron microscopy. Fluorescent probes show that the most effective bacteriochlorin produces significantly higher levels of hydroxyl radicals, and this is consistent with the redox properties suggested by molecular-orbital calculations. The best in vitro performing bacteriochlorin was tested in vivo in a mouse melanoma model using spectrally resolved fluorescence imaging and provided significant survival advantage with 20% of cures (P<0.01).Journal ArticleResearch Support, N.I.H. ExtramuralResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe