Induction of caspase-independent apoptotic-like cell death of mouse mammary tumor TA3Ha cells in vitro and reduction of their lethality in vivo by the novel chemotherapeutic agent GIT-27NO

The Double-Faced Role of Nitric Oxide and Reactive Oxygen Species in Solid Tumors

Disturbed redox homeostasis represents a hallmark of cancer phenotypes, affecting cellular metabolism and redox signaling. Since reactive oxygen and nitrogen species (ROS/RNS) are involved in regulation of proliferation and apoptosis, they may play a double-faced role in cancer, entailing protumorigenic and tumor-suppressing effects in early and later stages, respectively. In addition, ROS and RNS impact the activity and communication of all tumor constituents, mediating their reprogramming from anti- to protumorigenic phenotypes, and vice versa. An important role in this dichotomic action is played by the variable amounts of O₂ in the tumor microenvironment, which dictates the ultimate outcome of the influence of ROS/RNS on carcinogenesis. Moreover, ROS/RNS levels remarkably influence the cancer response to therapy. The relevance of ROS/RNS signaling in solid tumors is witnessed by the emergence of novel targeted treatments of solid tumors with compounds that target ROS/RNS action and production, such as tyrosine kinase inhibitors and monoclonal antibodies, which might contribute to the complexity of redox regulation in cancer. Prospectively, the dual role of ROS/RNS in the different stages of tumorigenesis through different impact on oxidation and nitrosylation may also allow development of tailored diagnostic and therapeutic approaches.

Effects of GIT-27NO, a NO-donating compound, on hepatic ischemia/reperfusion injury

Hepatic ischemia/reperfusion injury (IRI) is a clinical condition that may lead to cellular injury and organ dysfunction that can be observed in different conditions, such as trauma, shock, liver resection, and transplantation. Moderate levels of nitric oxide (NO) produced by the endothelial isoform of the NO synthase protect against liver IRI. GIT-27NO is a NO-derivative of the toll-like receptor 4 antagonist VGX-1027 that has been shown to possess both antineoplastic and immunomodulatory properties in vitro and in vivo. In this study, we have investigated the effects of this compound in vitro, in a model of oxidative stress induced in HepG2 cells by hydrogen peroxide (H₂O₂), and in vivo, in a rat model of IRI of the liver. GIT-27NO significantly counteracted the toxic effects induced by the H₂O₂ on the HepG2 cells and in vivo, GIT-27NO reduced the transaminase levels and the histological liver injury by reducing necrotic areas with preservation of viable tissue. These effects were almost similar to that of the positive control drug dimethyl fumarate. These data suggest that the beneficial effect of GIT-27NO in the hepatic IRI can be secondary to anti-oxidative effects and hepatocyte necrosis reduction probably mediated by NO release.

Gasotransmitters and the immune system: Mode of action and novel therapeutic targets

Gasotransmitters are a group of gaseous molecules, with pleiotropic biological functions. These molecules include nitric oxide (NO), hydrogen sulfide (H₂S), and carbon monoxide (CO). Abnormal production and metabolism of these molecules have been observed in several pathological conditions. The understanding of the role of gasotransmitters in the immune system has grown significantly in the past years, and independent studies have shed light on the effect of exogenous and endogenous gasotransmitters on immune responses. Moreover, encouraging results come from the efficacy of NO-, CO- and H₂S -donors in preclinical animal models of autoimmune, acute and chronic inflammatory diseases. To date, data on the influence of gasotransmitters in immunity and immunopathology are often scattered and partial, and the scarcity of clinical trials using NO-, CO- and H₂S -donors, reveals that more effort is warranted. This review focuses on the role of gasotransmitters in the immune system and covers the evidences on the possible use of gasotransmitters for the treatment of inflammatory conditions.

Mechanism of the Antitumor and Radiosensitizing Effects of a Manganese Porphyrin, MnHex-2-PyP

AIMS

Cationic manganese (Mn)-substituted N-pyridylporphyrin-based potent mimics of the family of superoxide dismutases (SODs) protect normal tissues from injury related to ionizing radiation (IR) by reducing levels of reactive oxygen and nitrogen species (ROS/RNS). Furthermore, Mn-porphyrins have demonstrated antitumor and radiosensitizing effects on cancer cells by promoting IR-induced tumor vasculature damage and apoptotic processes. In this study, we explored the underlying mechanisms of Mn-porphyrin-mediated tumor radiosensitization using murine mammary carcinoma 4T1 and melanoma B16 cells in vitro and in vivo.

RESULTS

Combination treatment with MnTnHex-2-PyP and IR substantially reduced cell viability, clonogenic cell survival, and DNA damage repair and synergistically increased IR-induced apoptosis of 4T1 and B16 cells. MnTnHex-2-PyP in combination with IR caused a significant delay in growth of 4T1 and B16 xenograft tumors. MnTnHex-2-PyP dose-dependently enhanced IR-mediated production of H₂O₂-derived species, but not superoxide. Catalase overexpression reversed MnTnHex-2-PyP-enhanced ROS production and apoptosis. Demonstrated suppression of phosphorylation of several mitogen-activated protein (MAP) kinases and activation of NF-κB by MnTnHex-2-PyP/IR, which presumably inhibited activation of the antiapoptotic pathway, are in agreement with our other data on the apoptosis of cancer cells. Innovation and Conclusions: MnTnHex-2-PyP exerted a radiosensitizing effect on 4T1 and B16 tumor models in vitro and in vivo via pro-oxidative actions and therefore bears a large therapeutic potential. When combined with IR, it attenuated DNA damage repair and triggered a shift from prosurvival pathways to apoptotic cell death, likely due to increased ROS production and disturbed cellular redox balance, acting at the level of nuclear factor κB (NF-κB). Antioxid. Redox Signal. 27, 1067-1082.

Gasotransmitters in cancer: from pathophysiology to experimental therapy

The three endogenous gaseous transmitters - nitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H2S) - regulate a number of key biological functions. Emerging data have revealed several new mechanisms for each of these three gasotransmitters in tumour biology. It is now appreciated that they show bimodal pharmacological character in cancer, in that not only the inhibition of their biosynthesis but also elevation of their concentration beyond a certain threshold can exert anticancer effects. This Review discusses the role of each gasotransmitter in cancer and the effects of pharmacological agents - some of which are in early-stage clinical studies - that modulate the levels of each gasotransmitter. A clearer understanding of the pharmacological character of these three gases and the mechanisms underlying their biological effects is expected to guide further clinical translation.

Advances in targeting signal transduction pathways

Over the past few years, significant advances have occurred in both our understanding of the complexity of signal transduction pathways as well as the isolation of specific inhibitors which target key components in those pathways. Furthermore critical information is being accrued regarding how genetic mutations can affect the sensitivity of various types of patients to targeted therapy. Finally, genetic mechanisms responsible for the development of resistance after targeted therapy are being discovered which may allow the creation of alternative therapies to overcome resistance. This review will discuss some of the highlights over the past few years on the roles of key signaling pathways in various diseases, the targeting of signal transduction pathways and the genetic mechanisms governing sensitivity and resistance to targeted therapies.

Comparative study of rapamycin and temsirolimus demonstrates superimposable anti-tumour potency on prostate cancer cells

Rapamycin is a macrocyclic lactone currently used for the treatment of cancer and for the prevention of transplant rejection. The primary pharmacological mode of action of rapamycin occurs through the inhibition (blocking) of the mammalian target of rapamycin (mTOR). By doing so, rapamycin interferes with the phosphoinositide 3-kinase (PI3K)-Akt-mTOR axis that controls several cellular functions involving cell growth, proliferation and angiogenesis. The frequent activation of the phosphoinositide 3-kinase (PI3K)/AKT pathway in advanced prostate cancer has provided a rationale for the use of mTOR inhibitors in this setting. We carried out a comparative study on the effects of rapamycin and temsirolimus on the in vitro and in vivo growth of the prostate cancer cell lines, LnCap and PC3. Our results demonstrate that rapamycin and temsirolimus exert similar in vitro and in vivo anti-proliferative effects against prostate cancer cells.

Therapeutic potential of nitric oxide-modified drugs in colon cancer cells

We have examined the influence of the nitric oxide (NO)-modified anti-inflammatory drug (S,R)-3-phenyl-4,5-dihydro-5-isoxasole acetic acid (VGX-1027) named GIT-27NO or the NO-modified antiviral drug saquinavir (Saq) named Saq-NO on two colon cancer cell lines, mouse CT26CL25 and human HCT116. The effects of the drugs on cell viability, apoptosis, proliferation, and metastatic potential were analyzed. The release of NO and oxygen and nitrogen species was also determined. The efficacy of the drugs was evaluated in vivo in BALB/c mice injected with CT26CL25 cells. Both agents suppressed the growth of colon cancer cells in vitro and reduced tumor volume in syngeneic BALB/c mice. However, their mechanisms of action were different because GIT-27NO released larger amounts of nitrite than Saq-NO in cell cultures and its antitumor action depended on the intracellular NO release inside the cells. On the contrary, Saq-NO released barely detectable amounts of NO and its antitumor action was NO-independent. In fact, cotreatment with an NO-peroxynitrite scavenger revealed that GIT-27NO but not Saq-NO acts through peroxynitrite-mediated cell destruction. At the cellular level, GIT-27NO prevalently induced proapoptotic signals followed by caspase-dependent apoptosis. In contrast, Saq-NO blocked cell proliferation, changed the adhesive, migratory, and invasive properties of the cells, and decreased metastatic potential in vivo. In conclusion, differences in NO release and oxidative stress generation between GIT-27NO and Saq-NO resulted in different mechanisms that caused cell death.