Targeting the "undruggable": RNA-binding proteins in the spotlight in cancer therapy.

Tumors refractory to conventional therapy belong to specific subpopulations of cancer cells, which have acquired a higher number of mutations/epigenetic changes than the majority of cancer cells. This property provides them the ability to become resistant to therapy. Aberrant expression of certain RNA-binding proteins (RBPs) can regulate the sensitivity of tumor cells to chemotherapeutic drugs by binding to specific regions present in the 3´-UTR of certain mRNAs to promote or repress mRNA translation or by interacting with other proteins (including RBPs) and non-coding RNAs that are part of ribonucleoprotein complexes. In particular, an increasing interest in the RBPs involved in chemoresistance has recently emerged. In this review, we discuss how RBPs are not only affected by chemotherapeutic treatments, but also play an active role in therapeutic responses via the direct modulation of crucial cancer-related proteins. A special focus is being placed on the development of therapeutic strategies targeting these RBPs.

RNA-binding proteins: Underestimated contributors in tumorigenesis.

mRNA export, translation, splicing, cleavage or capping determine mRNA stability, which represents one of the primary aspects regulating gene expression and function. RNA-binding proteins (RBPs) bind to their target mRNAs to regulate multiple cell functions by increasing or reducing their stability. In recent decades, studies of the role of RBPs in tumorigenesis have revealed an increasing number of proteins impacting the prognosis, diagnosis and cancer treatment. Several RBPs have been identified based on their interactions with oncogenes or tumor suppressor genes in human cancers, which are involved in apoptosis, the epithelial-mesenchymal transition (EMT), DNA repair, autophagy, cell proliferation, immune response, metabolism, and the regulation of noncoding RNAs. In this review, we propose a model showing how RBP mutations influence tumorigenesis, and we update the current knowledge regarding the molecular mechanism by which RBPs regulate cancer. Special attention is being devoted to RBPs that represent prognostic and diagnostic factors in cancer patients.

Insights into new mechanisms and models of cancer stem cell multidrug resistance.

The acquisition of genetic alterations, clonal evolution, and the tumor microenvironment promote cancer progression, metastasis and therapy resistance. These events correspond to the establishment of the great phenotypic heterogeneity and plasticity of cancer cells that contribute to tumor progression and resistant disease. Targeting resistant cancers is a major challenge in oncology; however, the underlying processes are not yet fully understood. Even though current treatments can reduce tumor size and increase life expectancy, relapse and multidrug resistance (MDR) ultimately remain the second cause of death in developed countries. Recent evidence points toward stem-like phenotypes in cancer cells, promoted by cancer stem cells (CSCs), as the main culprit of cancer relapse, resistance (radiotherapy, hormone therapy, and/or chemotherapy) and metastasis. Many mechanisms have been proposed for CSC resistance, such as drug efflux through ABC transporters, overactivation of the DNA damage response (DDR), apoptosis evasion, prosurvival pathways activation, cell cycle promotion and/or cell metabolic alterations. Nonetheless, targeted therapy toward these specific CSC mechanisms is only partially effective to prevent or abolish resistance, suggesting underlying additional causes for CSC resilience. This article aims to provide an integrated picture of the MDR mechanisms that operate in CSCs' behavior and to propose a novel model of tumor evolution during chemotherapy. Targeting the pathways mentioned here might hold promise and reveal new strategies for future clinical therapeutic approaches.

Absence of Relationship between Mitochondrial DNA Haplogroups and Cisplatin-Induced Hearing Loss.

BACKGROUND: Many drugs used for cancer chemotherapy produce reactive oxygen species, thus leading to various complications including nephrotoxicity, cardiotoxicity, and ototoxicity. OBJECTIVE: We have provided a haplogroup analysis of a cohort of cancer patients treated with chemotherapy and compared factors associated with associated hearing loss. STUDY DESIGN AND METHODS: This observational cohort study includes a pure-tone audiometry of the patients who underwent chemotherapeutic treatment. Medical history, presence of risk factors for hearing loss, toxic habits, and association with haplogroups have been determined. RESULTS: 40% of patients developed hearing loss after administration of cisplatin, which was bilateral and symmetrical and of high frequencies. The most frequent haplogroup was H with a slight overexpression of groups V and K and a low frequency of groups J and T. No association of the haplogroup types with the hearing loss has been found; however age was revealed as an important determining factor. CONCLUSIONS: Ototoxicity caused by cisplatin is manifested as bilateral, symmetrical, and predominantly high frequency hearing loss. Although we did not find a strong correlation of haplogroups with ototoxicity, our results revealed the existence of a risk group of elderly patients over 60, which are more susceptible to hearing loss induced by cisplatin, than young adults, regardless of preexisting hearing loss.

The cancer stem-cell signaling network and resistance to therapy.

The study of cancer stem cells (CSCs) has shown that tumors are driven by a subpopulation of self-renewing CSCs that retain the capacity to engender the various differentiated cell populations that form tumors. The characterization of CSCs has indicated that CSCs are remarkably resistant to conventional radio- and chemo-therapy. Clinically, the remaining populations of CSC are responsible for metastasis and recurrence in patients with cancer, which can lead to the disease becoming chronic and incurable. Therefore, the elimination of CSCs is an important goal of cancer treatments. Furthermore, CSCs are subject to strong regulation by the surrounding microenvironment, which also impacts tumor responses. In this review, we discuss the mechanisms by which pathways that are defective in CSCs influence ultimately therapeutic and clinical outcomes.

Ribosomal proteins as novel players in tumorigenesis.

Ribosome biogenesis is the most demanding energetic and metabolic expenditure of the cell. The nucleolus, a nuclear compartment, coordinates rRNA transcription, maturation, and assembly into ribosome subunits. The transcription process is highly coordinated with ribosome biogenesis. In this context, ribosomal proteins (RPs) play a crucial role. In the last decade, an increasing number of studies have associated RPs with extraribosomal functions related to proliferation. Importantly, the expression of RPs appears to be deregulated in several human disorders due, at least in part, to genetic mutations. Although the deregulation of RPs in human malignancies is commonly observed, a more complex mechanism is believed to be involved, favoring the tumorigenic process, its progression and metastasis. This review explores the roles of the most frequently mutated oncogenes and tumor suppressor genes in human cancer that modulate ribosome biogenesis, including their interaction with RPs. In this regard, we propose a new focus for novel therapies.

Schwannomas, benign tumors with a senescent phenotype.

BACKGROUND: Schwannomas are benign nerve sheath tumors that only very rarely undergo malignant changes. Oncogenic-induced senescence is a defense mechanism against such malignant transformation. Different molecular pathways are involved in this process, such as RAS-RAF-MAPK. Based on the fact that the RAS-RAF-MAPK pathway is known to be activated in peripheral nerve sheath tumors, this study analyzes senescence markers in Schwannomas to demonstrate the possible role of senescence in their genesis. METHODS: A retrospective immunohistochemical study was done in 39 schwannoma and 18 malignant peripheral nerve sheath tumors (MPNST). Staining for p16INK4a, Ki67, p53 and CyclinD1 was performed in all the cases. Additionally, ß-galactosidase staining was done in those cases in which frozen tissue was available (n=8). RESULTS: Higher levels of p16INK4a (p=0.0001) and lower levels of Ki67 (p=0.0001) were found in Schwannomas. Beta-galactosidase activity was positive in 5/5 Schwannomas and negative in 3/3 MPNST. CONCLUSIONS: Our results support the senescence nature of Schwannomas and the absence of a senescence phenotype in MPNST.

MicroRNAs and cancer stem cells: therapeutic approaches and future perspectives.

Cancer stem cells (CSCs) are a sub-population of cancer cells that possess characteristics associated with normal stem cells but with the peculiarity that they are tumourigenic. This property allows them to persist in the tumour population, causing relapse and metastasis by giving rise to new tumours. Accordingly, if the CSCs were eliminated, then the tumour would simply regress due to differentiation and cell death. By selectively targeting CSCs, it may be possible to treat patients with aggressive, non-resectable tumours and prevent the tumour from metastasising. MicroRNAs are involved in all biological processes, and several studies have demonstrated their function in human tumourigenesis. Importantly, microRNAs have been implicated in the regulation of stem cells and CSCs. The most important concept to emerge with regard to CSC therapy is still controversial because a number of signalling pathways unique to normal stem cells may also be operating in CSCs, and these offer new targets for therapy. This article reviews how the modulation of microRNAs may revert tumour proliferation in vivo and in vitro and how this approach could be transferred to the clinic. Although the delivery of therapeutic microRNAs to target cells is a challenge that still needs to be overcome, microRNAs offer the advantage that they are small molecules that can be easily transported by body fluids, which makes them good candidates for cancer therapy.

p16(Ink4a) overexpression in cancer: a tumor suppressor gene associated with senescence and high-grade tumors.

p16(Ink4a) is a protein involved in regulation of the cell cycle. Currently, p16(Ink4a) is considered a tumor suppressor protein because of its physiological role and downregulated expression in a large number of tumors. Intriguingly, overexpression of p16(Ink4a) has also been described in several tumors. This review attempts to elucidate when and why p16(Ink4a) overexpression occurs, and to suggest possible implications of p16(Ink4a) in the diagnosis, prognosis and treatment of cancer.

[Attitude of the adult patient with atopic dermatitis to the disease and its treatment: the ACTIDA Study]. / Actitud del paciente adulto con dermatitis atópica frente a su patología y tratamiento. Estudio ACTIDA.

OBJECTIVE: To determine the attitude of adult patients with atopic dermatitis (AD) to their disease and its treatment. MATERIAL AND METHODS: A multicenter, cross-sectional study was performed in patients with at least 2 outbreaks of AD in the previous year. RESULTS: Two hundred twenty-seven dermatologists recruited 1441 analyzable patients, the majority women, with a mean of 3.6 outbreaks per year. Most of the patients (97.2%) indicated that they always or sometimes requested medical evaluation of a new outbreak. In the most recent outbreak, 72.2% had used combined therapy, regardless of the severity of the episode; 2-drug combinations were the most common. The majority of dermatologists prescribed combined therapy, most commonly a 2-drug combination for mild or minimal disease, and 3 or more drugs for moderate to very severe outbreaks. CONCLUSIONS: Treatments used by patients for an outbreak of AD are similar to those prescribed by dermatologists in recent outbreaks.

Multiple microRNAs rescue from Ras-induced senescence by inhibiting p21(Waf1/Cip1).

Overexpression of Ras(G12V) in primary cells induces a permanent growth arrest called oncogene-induced senescence (OIS) that serves as a fail-safe mechanism against malignant transformation. We have performed a genome-wide small interfering RNA (siRNA) screen and a microRNA (miRNA) screen to identify mediators of OIS and show that siRNA-mediated knockdown of p21(Waf1/Cip1) rescues from Ras(G12V)-induced senescence in human mammary epithelial cells (HMECs). Moreover, we isolated a total of 28 miRNAs that prevented Ras(G12V)-induced growth arrest, among which all of the miR-106b family members were present. In addition, we obtained a number of hits, miR-130b, miR-302a, miR-302b, miR302c, miR-302d, miR-512-3p and miR-515-3p with seed sequences very similar to miR-106b family members. We show that overexpression of all these miRNAs rescues HMECs from Ras(G12V)-induced senescence by prevention of Ras(G12V)-induced upregulation of p21(Waf1/Cip1). Our results establish an important role for the cell cycle inhibitor p21(Waf1/Cip1) in growth control of HMECs and extend the repertoire of miRNAs that modulate the activity of this tumour suppressor.

A new generation of proto-oncogenes: cold-inducible RNA binding proteins.

This review focuses on the roles of two major cold-inducible RNA binding proteins known in human cells: CIRP and RBM3. Both proteins were discovered when they were shown to be induced after exposure to a moderate cold-shock and other cellular stresses such as UV radiation and hypoxia. Initially, it was suggested that these proteins have a suppressive rather stimulatory effect on proliferation; however, proliferative and/or proto-oncogenic functions have recently been assigned to CIRP and RBM3. In a high throughput genetic screen, we recently identified CIRP as an immortalized gene in murine primary cells. On the other hand, the role of RBM3 in transformation has already been demonstrated. Interestingly, both CIRP and RBM3 have been found to be up-regulated in human tumors. This article highlights the roles of CIRP and RBM3 in tumorigenesis, and proposes a model by which CIRP might contribute to senescence bypass by counteracting the deleterious effects of oxidative damage.

Rplp1 bypasses replicative senescence and contributes to transformation.

To determine whether genes expressed by embryonic stem cells have a proliferative effect in primary cells, primary mouse embryonic fibroblasts were infected with an ES cell cDNA library. This led to identification of the ribosomal protein, Rplp1, a member of the P group of ribosomal proteins, whose putative role for bypassing replicative senescence in MEFs was investigated. Our results show that Rplp1 produces a two-fold increase in the expression of an E2F1 promoter and upregulation of cyclin E in MEFs. Therefore, this study is the first to show that overexpression of a single ribosomal protein, Rplp1, is a cause and not a consequence of cell proliferation. In addition, co-expression of Rplp1 with mutant rasVal12 contributed to transformation in NIH3T3 cells, as was evidenced by colony production in soft-agar assays. Moreover, the Rplp1 protein was upregulated in MEFs and NIH3T3 cells upon expression of a p53 dominant negative mutant gene designated p53R175H. Hence, mutation of p53 may facilitate immortalization in vitro by upregulating Rplp1. Lastly, Rplp1 mRNA was found to be upregulated in 16 of 26 human colon cancer biopsy specimens, a finding that may be of relevance to cancer research.

S-adenosylhomocysteine hydrolase downregulation contributes to tumorigenesis.

With the idea to discover novel genes involved in proliferation, we have performed a genome-wide loss-of-function genetic screen to identify additional putative tumor suppressor genes. We have previously identified five genes belonging to different biochemical families. In this report, we focused on the study of one of these genes designated S-adenosylhomocysteine hydrolase (SAHH), which has also been previously identified in an independent short hairpin RNA screening. SAHH inactivation confers resistance to both p53 and p16(INK4)-induced proliferation arrest. Interestingly, SAHH inactivation inhibits p53 transcriptional activity and impairs DNA damage-induced transcription of p21(Cip1). Given that SAHH downregulation modulates senescence in primary cells, we also studied SAHH expression in human tumors at the messenger RNA (mRNA) and protein levels. SAHH mRNA was lost in 50% of tumor tissues from 206 patients with different kinds of tumors in comparison with normal tissue counterparts. Moreover, SAHH protein was also affected in some colon cancers. Such findings may be of relevance to cancer research, suggesting that SAHH might be a largely unexplored tumor suppressor.

Cellular senescence bypass screen identifies new putative tumor suppressor genes.

Senescence is a mechanism that limits cellular lifespan and constitutes a barrier against cellular immortalization. To identify new senescence regulatory genes that might play a role in tumorigenesis, we have designed and performed a large-scale antisense-based genetic screen in primary mouse embryo fibroblasts (MEFs). Out of this screen, we have identified five different genes through which loss of function partially bypasses senescence. These genes belong to very different biochemical families: csn2 (component of the Cop9 signalosome), aldose reductase (a metabolic enzyme) and brf1 (subunit of the RNA polymerase II complex), S-adenosyl homocysteine hydrolase and Bub1. Inactivation, at least partial, of these genes confers resistance to both p53- and p16INK4a-induced proliferation arrest. Furthermore, such inactivation inhibits p53 but not E2F1 transcriptional activity and impairs DNA-damage-induced transcription of p21. Since the aim of the screen was to identify new regulators of tumorigenesis, we have tested their inactivation in human tumors. We have found, either by northern blot or quantitative reverse transcriptase-PCR analysis, that the expression of three genes, Csn2, Aldose reductase and Brf1, is lost at different ratios in tumors of different origins. These genes are located at common positions of loss of heterogeneity (15q21.2, 7q35 and 14q32.33); therefore,we have measured genomic losses of these specific genes in different tumors. We have found that Csn2 and Brf1 also show genomic losses of one allele in different tumors. Our data suggest that the three genes identified in the genome-wide loss-of-function genetic screen are putative tumor suppressors located at 15q21.2; 7q35 and 14q32.33.

[Clinical and therapeutic profile and quality of life of patients with seborrheic dermatitis]. / Perfil clínico, terapéutico y calidad de vida de los pacientes con dermatitis seborreica.

INTRODUCTION: The clinical characteristics of seborrheic dermatitis (SD), therapeutic strategies employed in current clinical practice and impact on the quality of life in the Spanish population are described. METHODS: An epidemiological, multicenter, transversal study in patients older than 16 years with seborrheic dermatitis. We evaluated the intensity of symptoms (scale 0-4), and impact on the quality of life by the Skindex-29 questionnaire (scale 0-100). RESULTS: Two thousand one hundred and fifty nine patients participated, the mean age was 43,6 years, 55 % were men and 42 % had a family history of seborrheic dermatitis. Diagnosis is usually carried out at a mean age of 33,7 years. The median number of outbreaks in the last year is three. The median duration of each outbreak is 14 days. The most involved areas are the face (88 %) and scalp (70 %). The mean intensities are as follows: scaling 1.9, erythema 1.89, pruritus 1.73, oily skin 1.52, and induration 0.87. Ninety-eight percent of patients report a trigger factor for outbreaks, namely stress/depression/fatigue (76 %) and seasonal variation (44 %). Acne is the most common concomitant disease (35 %). The most common treatments are topical steroids (60 %), imidazole antifungals (35 %) and hydratating/nutritive products (31 %). The mean Skindex-29 global score is 20.5. CONCLUSIONS: The most common clinical profile of seborrheic dermatitis is a 40-year-old patient with facial/scalp involvement of mild to moderate intensity with a history of stress/depression/fatigue prior to the outbreak. The most common treatments in the daily clinical practice are topical steroids and imidazole antifungals. The impact of seborrheic dermatitis in the quality of life is low.

[Observational study to evaluate the impact of an educational/informative intervention in the emotional status (anxiety) of patients with atopic dermatitis (CUIDA-DEL)]. / Estudio observacional para evaluar la repercusión de una intervención educativa-informativa en el estado emocional (ansiedad) de los pacientes con dermatitis atópica (CUIDA-DEL).

INTRODUCTION: One of the first therapeutic measures in atopic dermatitis should be the educational and informative approach about prophylactic aspects and evolution of the disease. This type of proceedings has been shown to be beneficial for the anxious type of emotional status in patients with atopic dermatitis. We evaluated the impact of an educational/informative intervention in the emotional status (anxiety) of patients with atopic dermatitis in Spain. MATERIAL AND METHODS: Investigators were randomized into two study groups: the control group (CG) that followed current clinical practice and the intervention group (IG) that handed patients, in each visit, a booklet of information about different prophylactic aspects and care of atopic dermatitis. The duration of the study was 6 months with quarterly visits. All included patients had a diagnosis of atopic dermatitis. Anxiety was evaluated with the STAI anxiety questionnaire and clinical data regarding dermatological aspects (IGA, pruritus scale, location of the lesions) were also recorded. RESULTS: A total of 1,247 patients were recruited thanks to the collaboration of 158 investigators. Patients were distributed as follows: 683 (54.7 %) in the CG and 564 (45.2 %) in the IG. Both group were homogeneous with respect to basal characteristics, and were constituted by 54 % of women with a mean age of 19 years. Eighty-six percent of atopic dermatitis lesions were preferentially located in extremities. Patients of both study groups showed improvement in their emotional status (trait and state anxiety) throughout the study with significant decreases in the STAI scores compared to basal ones. Regarding improvement in the questionnaire scores, no significant differences were observed between groups except in children aged 9 to 15 years, in the pediatric version of the STAI trait where the percentage of score decrease at 6 months adjusted to the basal score was 5.5 (19.0) for the CG and 10.6 (18.9) for the IG, (p < 0.05). A higher percentage of patients finished the study in the IG compared to the CG (83.1 % vs. 76.1 % p < 0.005). DISCUSSION AND CONCLUSIONS: Although patients in the IG showed greater compliance with the follow-up of the study, the informative intervention about prophylactic aspects of atopic dermatitis designed in this study does not appear to have had an impact in improving the emotional status of adult patients.

Protection from oxidative stress by enhanced glycolysis; a possible mechanism of cellular immortalization.

Reactive oxygen species (ROS) play a crucial role not only in the physiological signal transduction but also in the pathogenesis of several human diseases such as atherosclerosis, neuro-degenerative diseases, metabolic disorders, aging or cancer amongst others. Oxidative stress is also responsible for cellular and organism senescence, in accordance with what Harman initially proposed in the free radical theory of aging. Recent findings support the notion that protection from oxidative stress can increase life span significantly. We reported that enhanced glycolysis could modulate cellular life span with reduction of oxidative stress. Moreover, the tumor suppressor gene p53 controls post-transcriptionally the level of the glycolytic enzyme, phosphoglycerate mutase (PGM). As enhanced glycolysis is a distinctive and prominent feature of cancer cells (termed the Warburg effect), our findings disclosed a novel aspect of the Warburg effect: the connection between senescence and oxidative stress.

New p53 related genes in human tumors: significant downregulation in colon and lung carcinomas.

Human epithelial tumors need to accumulate multiple genetic alterations to form invasive carcinomas. These genetic alterations are related with growth factor receptors, cell signalling, the cell cycle and cell invasiveness. Importantly, cells need to avoid senescence and become immortalized for this process. Recently, five genes: RPS6KA6, HDAC4, KIAA0828, TCP1 and Tip60, which modulate p53-dependent function and avoid senescence were identified in a large-scale RNA interference screen. Twenty colon, 20 prostate and 20 lung carcinomas were studied to investigate whether these genes might be related with human tumors. RNA was extracted from both normal and tumor tissue from each patient. Real-time RT-PCR was performed using TaqMan probes corresponding to the RPS6KA6, HDAC4, KIAA0828, TCP1, Tip60 and p53 genes. In colon carcinomas, the RPS6KA6, HDAC4, KIAA0828 and Tip60 genes were downregulated in tumor tissue as compared with normal tissue (P < 0.001 for all genes). In lung carcinomas, HDAC4, KIAA0820 and Tip60 were downregulated (P < 0.01, P < 0.001 and P < 0.001 respectively). Whereas no significant differences were observed in prostate carcinomas, striking downregulation of the RPS6KA6 and KIAA0828 genes was observed in colon carcinomas and KIAA0828 in a subset of lung carcinomas. mRNA expression of these genes may control p53 function as well as the ras-MAPK pathway, methylation and transcriptional cellular programs. These results could unravel a novel set of regulatory suppressor genes involved in human colon and lung tumors.

Adenovirus E1A orchestrates the urokinase-plasminogen activator system and upregulates PAI-2 expression, supporting a tumor suppressor effect.

Invasiveness and metastatic potential are the two most important properties defining malignancy. The adeno-virus E1A (Ad-E1A) gene has a dual effect as a proliferative gene and as a tumor-suppressor gene, decreasing tumor growth and the metastatic potential of malignant cells. In order to study genes related with the antimetastatic effect of Ad-E1A in human cells, we performed a microarray analysis using OncoChiptrade mark. In three independent experiments, NIH3T3, IMR90 and MDA MB 435 cells were infected with pLPC retroviruses carrying the adenovirus 12S E1A gene or the GFP gene. We analyzed cDNA expression by using the CNIO OncoChipTM, a cDNA microarray containing a total of 6386 genes represented by 7237 clones. uPA, uPAr, tPA, PAI-1 and PAI-2 were also studied at RNA and protein levels. Microarrays of cDNA expression, RT-PCR and Western blot performed in IMR90 E1A-expressing cells showed downregulation of uPA, uPAr, tPA, PAI-1 and upregulation of PAI-2. These results were confirmed in NIH3T3 and MDA MB 435 breast carcinoma cells, with PAI-2 upregulation by RT-PCR and Western blot. In addition, zymographic analysis demonstrated that E1A expression greatly reduced the gelatinase activity of the pro-MMP2 and -MMP9 proteins. We propose that adenovirus E1A may orchestrate the expression of most members of the urokinase-plasminogen activation system, downregulating potentially invasive genes and upregulating PAI-2, which is associated with a better prognosis in human tumors.