Teresa Moliné

Oxidative stress and cancer: an overview.

Reactive species, which mainly include reactive oxygen species (ROS), are products generated as a consequence of metabolic reactions in the mitochondria of eukaryotic cells. In normal cells, low-level concentrations of these compounds are required for signal transduction before their elimination. However, cancer cells, which exhibit an accelerated metabolism, demand high ROS concentrations to maintain their high proliferation rate. Different ways of developing ROS resistance include the execution of alternative pathways, which can avoid large amounts of ROS accumulation without compromising the energy demand required by cancer cells. Examples of these processes include the guidance of the glycolytic pathway into the pentose phosphate pathway (PPP) and/or the generation of lactate instead of employing aerobic respiration in the mitochondria. Importantly, ROS levels can be used as a thermostat to monitor the damage that cells can bear. The implications for ROS regulation are highly significant for cancer therapy because commonly used radio- and chemotherapeutic drugs influence tumor outcome through ROS modulation. Moreover, the discovery of novel biomarkers that are able to predict the clinical response to pro-oxidant therapies is a crucial challenge to overcome to allow for the personalization of cancer therapies.

The dual PI3K/mTOR inhibitor PI‐103 promotes immunosuppression, in vivo tumor growth and increases survival of sorafenib‐treated melanoma cells

Melanoma is the most lethal human skin cancer. If metastatic, it becomes very aggressive and resistant to standard modalities of anticancer treatment. During the last 10 years, several therapeutic strategies have been tested including the use of single and combined small drugs. Experimental results indicate that RAS and PI3K pathways are important for the development and maintenance of melanoma. In this study, we assessed the in vitro and in vivo inhibition potential of PI‐103, a PI3K (p110α)/mTOR inhibitor and sorafenib, a BRAF inhibitor, as single agents and in combination in primary melanoma cell lines. Although PI‐103 and sorafenib inhibited melanoma in vitro cell proliferation and viability, the inhibition of RAS pathway appeared to be more effective. The combination of the two agents in in vitro showed a synergistic effect inhibiting RAS and PI3K pathways in a cell line dependent manner. However, no cooperative effect was observed in blocking in vivo tumor growth in immunocompetent mice. In contrary to the expected, the data indicate that PI‐103 induced immunosuppression promoting in vivo tumor growth and inhibiting apoptosis. Furthermore, in vitro studies examining the effects of the PI3K/mTOR inhibitor in tumor derived cell lines indicated that PI‐103 induced the anti‐apoptotic BH3 family proteins Mcl1, Bcl2 and BclxL favoring, the in vitro survival of sorafenib treated melanoma cells. These data certainly makes an argument for investigating unexpected effects of rational drug combinations on immunocompetent animal models prior to conducting clinical studies.

Methylthioadenosine (MTA) inhibits melanoma cell proliferation and in vivo tumor growth

BackgroundMelanoma is the most deadly form of skin cancer without effective treatment. Methylthioadenosine (MTA) is a naturally occurring nucleoside with differential effects on normal and transformed cells. MTA has been widely demonstrated to promote anti-proliferative and pro-apoptotic responses in different cell types. In this study we have assessed the therapeutic potential of MTA in melanoma treatment.MethodsTo investigate the therapeutic potential of MTA we performed in vitro proliferation and viability assays using six different mouse and human melanoma cell lines wild type for RAS and BRAF or harboring different mutations in RAS pathway. We also have tested its therapeutic capabilities in vivo in a xenograft mouse melanoma model and using variety of molecular techniques and tissue culture we investigated its anti-proliferative and pro-apoptotic properties.ResultsIn vitro experiments showed that MTA treatment inhibited melanoma cell proliferation and viability in a dose dependent manner, where BRAF mutant melanoma cell lines appear to be more sensitive. Importantly, MTA was effective inhibiting in vivo tumor growth. The molecular analysis of tumor samples and in vitro experiments indicated that MTA induces cytostatic rather than pro-apoptotic effects inhibiting the phosphorylation of Akt and S6 ribosomal protein and inducing the down-regulation of cyclin D1.ConclusionsMTA inhibits melanoma cell proliferation and in vivo tumor growth particularly in BRAF mutant melanoma cells. These data reveal a naturally occurring drug potentially useful for melanoma treatment.

Voltage-dependent Potassium Channels Kv1.3 and Kv1.5 in Human Fetus

Voltage-dependent K+ channels (Kv) control repolarization and membrane potential in electrically excitable cells. In addition, Kv channels are involved in the maintenance of vascular smooth muscle tone, insulin release, epithelial K+ transport, cell proliferation and leukocyte activation. Kv1.3 and Kv1.5 are widely distributed throughout the body and are involved in a variety of physiological processes taking place in the immune system, brain and muscle. Since the developmental pattern of Kv channels has an essential role in the maturing human, we aimed to study Kv1.3 and Kv1.5 channels in 8-10 week human fetal tissues. We chose that gestational age because all organs are in place and the nervous system, although not fully developed. However, the human embryo is undergoing major changes, which will lead to a defined adult pattern. Our results indicated that numerous tissues expressed Kv1.3 and Kv1.5. While Kv1.3 overlapped with the central and peripheral nervous systems, Kv1.5 was mostly localized in the central nervous system. In addition, both channels were abundantly expressed in the hematopoietic fetal liver. Finally, Kv1.5 heavily stained skeletal muscle and heart, whereas Kv1.3 was slightly present. This is the first study to analyze Kv1.3 and Kv1.5 in human during the beginning of fetal development.

Differential Expression of Kv1.3 and Kv1.5 Voltage-Dependent K+ Channels in Human Skeletal Muscle Sarcomas

Because Kv1.3 and Kv1.5 K+ channels are remodeled during tumorigenesis and participate in skeletal muscle proliferation, we analyzed their expression in human skeletal muscle sarcomas. Aggressive alveolar rhabdomyosarcoma (ARMS) and embryonal rhabdomyosarcoma (ERMS) were studied. Kv1.5 expression was moderate in adult muscle and low in ERMS, whereas it was notable in ARMS and embryonic samples. Kv1.3 expression showed no major differences between RMS and healthy samples. We found a correlation of Kv1.3 and Kv1.5 expression with the tumor malignancy.

A Mouse Model Uncovers LKB1 as an UVB-Induced DNA Damage Sensor Mediating CDKN1A (p21WAF1/CIP1) Degradation

Exposure to ultraviolet (UV) radiation from sunlight accounts for 90% of the symptoms of premature skin aging and skin cancer. The tumor suppressor serine-threonine kinase LKB1 is mutated in Peutz-Jeghers syndrome and in a spectrum of epithelial cancers whose etiology suggests a cooperation with environmental insults. Here we analyzed the role of LKB1 in a UV-dependent mouse skin cancer model and show that LKB1 haploinsufficiency is enough to impede UVB-induced DNA damage repair, contributing to tumor development driven by aberrant growth factor signaling. We demonstrate that LKB1 and its downstream kinase NUAK1 bind to CDKN1A. In response to UVB irradiation, LKB1 together with NUAK1 phosphorylates CDKN1A regulating the DNA damage response. Upon UVB treatment, LKB1 or NUAK1 deficiency results in CDKN1A accumulation, impaired DNA repair and resistance to apoptosis. Importantly, analysis of human tumor samples suggests that LKB1 mutational status could be a prognostic risk factor for UV-induced skin cancer. Altogether, our results identify LKB1 as a DNA damage sensor protein regulating skin UV-induced DNA damage response.

MicroRNA expression profiling identifies miR-31 and miR-485-3p as regulators in the pathogenesis of Discoid Cutaneous Lupus

Cutaneous lupus erythematosus is a common and disfiguring manifestation in systemic lupus erythematosus. Subacute cutaneous lupus erythematosus and discoid lupus erythematosus (DLE) are the most prevalent forms. Despite sharing histological similarities, clinically they differ in their course and prognosis, suggesting different pathogenesis. Here, we show that DLE-affected skin has a specific microRNA expression profile when compared with subacute cutaneous lupus erythematosus. Among the DLE-specific microRNAs, we identified one keratinocyte-derived microRNA, miR-31, and one leukocyte-derived microRNA, miR-485-3p. We show that UV and transforming growth factor-β1 stimulation up-regulates miR31 expression in DLE. Specific miR-31 overexpression induces keratinocyte apoptosis and NF-κB pathway activation with the production of related inflammatory cytokines and contributes to the recruitment of neutrophils and intermediate monocytes at the inflammation site. IL-1α and TGF-β1 stimulation increased the expression of miR-485-3p in peripheral mononuclear blood cells from DLE patients and induced T-cell activation, mainly of CD8 lymphocytes. In addition, miR-485-3p overexpression in dermal fibroblasts contributes to fibrosis by targeting peroxisome PGC-1α. Collectively, our findings suggest that overexpression of miR-31 and miR-485-p contribute to skin inflammation in DLE lesions by regulating the production of inflammatory mediators and attracting neutrophils and intermediate monocytes to the skin.