Exploring the Role of the Inhibitor of Apoptosis BIRC6 in Breast Cancer: A Database Analysis.

PURPOSE: The aim of the present work was to investigate the role of apoptosis inhibitor BIRC6 (baculoviral IAP repeat-containing protein 6) in breast cancer (BC), focusing particularly on its involvement in the metastatic cascade. METHODS: We analyzed BIRC6 mRNA expression levels and copy number variations in three BC databases from The Cancer Genome Atlas comparing clinical and molecular attributes. Genomic analysis was performed using the cBioPortal platform, whereas transcriptomic studies (mRNA expression levels, correlation heatmaps, survival plots, and gene ontology) were performed using USC Xena and R. Statistical significance was set at P < .05. RESULTS: Our bioinformatic analyses showed that there was a differential expression of BIRC6 in cancer samples when compared with normal samples. Copy number variations that involve amplification and gain of BIRC6 gene were correlated with negative hormone receptor tumors, higher prognostic indexes, younger age at diagnosis, and both chemotherapy and radiotherapy administration. Transcriptomic and gene ontology analyses showed that, under conditions of high BIRC6 mRNA levels, there are differential expression patterns in apoptotic, proliferation, and metastatic pathways. CONCLUSION: In summary, our in silico data suggest that BIRC6 plays an antiapoptotic, pro-proliferative, and apparent prometastatic role and could be a relevant molecular target for treatment of BC tumors.

Preclinical efficacy of CIGB-300, an anti-CK2 peptide, on breast cancer metastasic colonization.

CK2 is a serine/threonine kinase that is overexpressed in breast cancer and its inhibition is associated to reduced tumor growth and disease progression. CIGB-300 is an antitumor peptide with a novel mechanism of action, since it binds to protein kinase CK2 catalytic subunit alpha and to CK2 substrates thus preventing the enzyme activity. Our aim was to evaluate the potential therapeutic benefits of CIGB-300 on breast cancer disease using experimental models with translational relevance. We demonstrated that CIGB-300 reduces breast cancer cell growth in MDA-MB-231, MCF-7 and F3II cells, exerting a pro-apoptotic action and cell cycle arrest. We also found that CIGB-300 decreased cell adhesion, migration and clonogenic capacity of malignant cells. Effect on experimental breast cancer lung metastasis was evaluated after surgical removal of primary F3II tumors or after tail vein injection of tumor cells, also we evaluated CIGB-300 effect on spontaneous lung metastasis in an orthotopic model. Systemic CIGB-300 treatment inhibited breast cancer colonization of the lung, reducing the size and number of metastatic lesions. The present preclinical study establishes for the first time the efficacy of CIGB-300 on breast cancer. These encouraging results suggest that CIGB-300 could be used for the management of breast cancer as an adjuvant therapy after surgery, limiting tumor metastatic spread and thus protecting the patient from distant recurrence.

In vitro and in vivo antitumor activity of Yerba Mate extract in colon cancer models.

Yerba Mate (Ilex paraguariensis St. Hill. Aquifoliaceae) is a native South American tree and has a large amount of bioactive compounds. Colorectal cancer (CRC) is one of the so-called westernized diseases and is the third most common cancer in both men and women. Efficient strategies for the treatment of CRC are extensively being explored including dietary intervention. The objective of our research was to evaluate the effects of Yerba Mate extract on cell proliferation, invasive capacity of tumor cells, and angiogenesis. For this, in vitro and in vivo experimentation was carried out using CRC models. The extract was generated by aqueous extraction and prepared according to traditional American procedure of preparing mate infusion. In vitro results showed that the Yerba Mate extract inhibits CT26 and COLO 205 cell proliferation with IC50 values of 0.25 and 0.46 mg/mL, respectively. We demonstrated by TUNEL assay that one of the mechanisms by which Yerba Mate extract decreases cell proliferation is by induction of apoptosis. In a murine syngeneic tumor model, oral administration of Yerba Mate extract in a dose of 1.6 g/kg/day significantly inhibited angiogenesis and tumor growth without affecting biological parameters or body weight. Our findings suggest that Yerba Mate may be a promising agent for the treatment of colon cancer and could be used as an herbal medicine or functional food ingredient. PRACTICAL APPLICATION: Considering the chemical composition and presence of phenolic compounds with their free-radical scavenging activities and bioactivities against colon cancer cells, Yerba Mate can be a promising candidate as healthy food sources in human nutrition, and also be considered a natural source of potential antitumor agents. Taking into account the economic importance of Yerba Mate in Argentina, this vegetable would have a greater commercial value as a functional food.

CIGB-300 anticancer peptide regulates the protein kinase CK2-dependent phosphoproteome.

Casein-kinase CK2 is a Ser/Thr protein kinase that fosters cell survival and proliferation of malignant cells. The CK2 holoenzyme, formed by the association of two catalytic alpha/alpha' (CK2α/CK2α') and two regulatory beta subunits (CK2ß), phosphorylates diverse intracellular proteins partaking in key cellular processes. A handful of such CK2 substrates have been identified as targets for the substrate-binding anticancer peptide CIGB-300. However, since CK2ß also contains a CK2 phosphorylation consensus motif, this peptide may also directly impinge on CK2 enzymatic activity, thus globally modifying the CK2-dependent phosphoproteome. To address such a possibility, firstly, we evaluated the potential interaction of CIGB-300 with CK2 subunits, both in cell-free assays and cellular lysates, as well as its effect on CK2 enzymatic activity. Then, we performed a phosphoproteomic survey focusing on early inhibitory events triggered by CIGB-300 and identified those CK2 substrates significantly inhibited along with disturbed cellular processes. Altogether, we provided here the first evidence for a direct impairment of CK2 enzymatic activity by CIGB-300. Of note, both CK2-mediated inhibitory mechanisms of this anticancer peptide (i.e., substrate- and enzyme-binding mechanism) may run in parallel in tumor cells and help to explain the different anti-neoplastic effects exerted by CIGB-300 in preclinical cancer models.

In vitro and in vivo evaluation of desmopressin-loaded poly(D,L-lactic-co-glycolic acid) nanoparticles for its potential use in cancer treatment.

AIM: To develop and characterize the antitumor activity of poly(D,L-lactic-co-glycolic acid) nanoparticles loaded with hemostatic and anticancer drug desmopressin (dDAVP). MATERIALS & METHODS: After full physicochemical characterization, anticancer activity of dDAVP-loaded poly(D,L-lactic-co-glycolic acid) nanoparticles (NPdDAVP) was evaluated in vitro and in vivo on a highly aggressive breast cancer model. RESULTS: After efficiently loading desmopressin in poly(D,L-lactic-co-glycolic acid) matrix, NPdDAVP exhibited suitable physicochemical characteristics for biomedical applications. NPdDAVP displayed a potent cytostatic effect in vitro, inhibiting tumor cell proliferation and colony forming ability. Moreover, intravenous treatment using nanoparticulated-dDAVP inhibited tumor progression and prolonged survival in animals bearing rapidly-growing mammary tumors. CONCLUSION: Within the framework of promising dDAVP repurposing studies, these findings support further preclinical development of the NPdDAVP for the management of highly aggressive cancer.

The synthetic peptide CIGB-300 modulates CK2-dependent signaling pathways affecting the survival and chemoresistance of non-small cell lung cancer cell lines.

BACKGROUND: Lung cancer is the most frequently diagnosed cancer and the leading cause of cancer-related deaths worldwide. Up to 80% of cancer patients are classified as non-small-cell lung cancer (NSCLC) and cisplatin remains as the gold standard chemotherapy treatment, despite its limited efficacy due to both intrinsic and acquired resistance. The CK2 is a Ser/Thr kinase overexpressed in various types of cancer, including lung cancer. CIGB-300 is an antitumor peptide with a novel mechanism of action, since it binds to CK2 substrates thus preventing the enzyme activity. The aim of this work was to analyze the effects of CIGB-300 treatment targeting CK2-dependent signaling pathways in NSCLC cell lines and whether it may help improve current chemotherapy treatment. METHODS: The human NSCLC cell lines NCI-H125 and NIH-A549 were used. Tumor spheroids were obtained through the hanging-drop method. A cisplatin resistant A549 cell line was obtained by chronic administration of cisplatin. Cell viability, apoptosis, immunoblotting, immunofluorescence and luciferase reporter assays were used to assess CIGB-300 effects. A luminescent assay was used to monitor proteasome activity. RESULTS: We demonstrated that CIGB-300 induces an anti-proliferative response both in monolayer- and three-dimensional NSCLC models, presenting rapid and complete peptide uptake. This effect was accompanied by the inhibition of the CK2-dependent canonical NF-κB pathway, evidenced by reduced RelA/p65 nuclear levels and NF-κB protein targets modulation in both lung cancer cell lines, as well as conditionally reduced NF-κB transcriptional activity. In addition, NF-κB modulation was associated with enhanced proteasome activity, possibly through its α7/C8 subunit. Neither the peptide nor a classical CK2 inhibitor affected cytoplasmic ß-CATENIN basal levels. Given that NF-κB activation has been linked to cisplatin-induced resistance, we explored whether CIGB-300 could bring additional therapeutic benefits to the standard cisplatin treatment. We established a resistant cell line that showed higher p65 nuclear levels after cisplatin treatment as compared with the parental cell line. Remarkably, the cisplatin-resistant cell line became more sensitive to CIGB-300 treatment. CONCLUSIONS: Our data provide new insights into CIGB-300 mechanism of action and suggest clinical potential on current NSCLC therapy.

CIGB-300, an anti-CK2 peptide, inhibits angiogenesis, tumor cell invasion and metastasis in lung cancer models.

OBJECTIVES: Casein kinase 2 (CK2) is overexpressed in several types of cancer. It has more than 300 substrates mainly involved in DNA reparation and replication, chromatin remodeling and cellular growth. In recent years CK2 became an interesting target for anticancer drug development. CIGB-300 is a peptidic inhibitor of CK2 activity, designed to bind to the phospho-acceptor domain of CK2 substrates, impairing the correct phosphorylation by the enzyme. The aim of this work was to explore the antitumor effects of this inhibitor in preclinical lung cancer models. MATERIALS AND METHODS: Human H125 and murine 3LL Lewis lung carcinoma cell lines were used to evaluate the effect of CIGB-300 treatment in vitro. For this purpose, adhesion, migration and invasion capabilities of cancer cells were tested. Proteolytic activity of tumor cell-secreted uPA and MMP after CIGB-300 incubation was also analyzed. In vivo anticancer efficacy of the peptide was evaluated using experimental and spontaneous lung colonization assays in C57BL/6 mice. Finally, in order to test the effect of CIGB-300 on tumor cell-induced angiogenesis, a modified Matrigel plug assay was conducted. RESULTS AND CONCLUSION: We demonstrate that treatment with low micromolar concentrations of CIGB-300 caused a drastic reduction of adhesion, migration and invasion of lung cancer cells. Reduced invasiveness after CIGB-300 incubation was associated with decreased proteolytic activity of tumor cell-conditioned medium. In vivo, intravenous administration of CIGB-300 (10mg/kg) markly decreased lung colonization and metastasis development of 3LL cells. Interestingly, after 5days of systemic treatment with CIGB-300, tumor cell-driven neovascularization was significantly reduced in comparison to control group. Altogether our data suggest an important role of CK2 in lung tumor development, suggesting a potential use of CIGB-300 as a novel therapeutic agent against lung cancer.

Synergistic interactions of the anti-casein kinase 2 CIGB-300 peptide and chemotherapeutic agents in lung and cervical preclinical cancer models.

CIGB-300 is a novel clinical-stage synthetic peptide that impairs the casein kinase 2 (CK2)-mediated phosphorylation of B23/nucleophosmin in different experimental settings and cancer models. As a single agent, CIGB-300 induces apoptosis in vitro and in vivo and modulates an array of proteins that are mainly involved in drug resistance, cell proliferation and apoptosis, as determined by proteomic analysis. However, the clinical oncology practice and cumulative knowledge on tumor biology suggest that drug combinations are more likely to cope with tumor complexity compared to single agents. In this study, we investigated the antiproliferative effect of CIGB-300 when combined with different anticancer drugs, such as cisplatin (alkylating), paclitaxel (antimitotic), doxorubicin (antitopoisomerase II) or 5-fluorouracil (DNA/RNA antimetabolite) in cell lines derived from lung and cervical cancer. Of note, using a Latin square design and subsequent analysis by CalcuSyn software, we observed that paclitaxel and cisplatin exhibited the best synergistic/additive profile when combined with CIGB-300, according to the combination and dose reduction indices. Such therapeutically favorable profiles may be explained by a direct cytotoxic effect and also by the observed cell cycle impairment following incubation of tumor cells with selected drug combinations. Importantly, on in vivo dose-finding schedules in human cervical tumors xenografted in nude mice, we observed that concomitant administration of CIGB-300 and cisplatin increased mice survival compared to single-agent treatment. Collectively, these findings provide a rationale for combining the anti-CK2 CIGB-300 peptide with currently available anticancer agents in the clinical setting and indicate platins and taxanes as compounds with major perspectives.

Mechanisms of cellular uptake, intracellular transportation, and degradation of CIGB-300, a Tat-conjugated peptide, in tumor cell lines.

CIGB-300 is a cyclic synthetic peptide that induces apoptosis in malignant cells, elicits antitumor activity in cancer animal models, and shows tumor reduction signs when assayed in first-in-human phase I trial in patients with cervical tumors. CIGB-300 impairs phosphorylation by casein kinase 2 through targeting the substrate's phosphoacceptor domain. CIGB-300 was linked to the cell penetrating peptide Tat to facilitate the delivery into cells. Previously, we showed that CIGB-300 had a differential antiproliferative behavior in different tumor cell lines. In this work, we studied differential antiproliferative behavior in terms of cellular uptake, intracellular transportation, and degradation in tumor cell lines with dissimilar sensitivity to CIGB-300. The internalization of CIGB-300 was studied in different malignant cell lines. We found that the cell membrane heparan sulfate proteoglycans act as main receptors for extracellular CIGB-300 uptake. The most sensitive tumor cell lines showed higher intracellular incorporation of CIGB-300 in comparison to less sensitive cell lines. Furthermore, CIGB-300 uptake is time- and concentration-dependent in all studied cell lines. It was shown that CIGB-300 has the ability to penetrate cells mainly by direct membrane translocation. However, a minor proportion of the peptide uses an energy-dependent endocytic pathway mechanism to gain access into cells. CIGB-300 is internalized and transported into cells preferentially by caveolae-mediated endocytosis. Lysosomes are involved in CIGB-300 degradation; highly sensitive cell lines showed degradation at earlier times compared to low sensitive cells. Altogether, our data suggests a mechanism of internalization, vesicular transportation, and degradation for CIGB-300 in tumor cells.

[Telomerase and telomere: their structure and dynamics in health and disease]. / Telomerasa y telómero: su estructura y dinámica en salud y enfermedad.

Telomerase is the enzyme responsible for the maintenance of telomere length by adding guanine-rich repetitive sequences. Its activity can be seen in gametes, stem cells and tumor cells. In human somatic cells the proliferative potential is limited, reaching senescence after 50-70 cell divisions, because the DNA polymerase is not able to copy the DNA at the ends of chromosomes. By contrast, in most tumor cells the replicative potential is unlimited due to the maintenance of the telomeric length given by telomerase. Telomeres have additional proteins that regulate the binding of telomerase, likewise telomerase associates, with a protein complex that regulates its activity. This work focuses on the structure and function of the telomere/telomerase complex and how changes in its behavior lead to the development of different diseases, mainly cancer. Development of inhibitors of the telomere/telomerase complex could be a target with promising possibilities.

Telomerasa y telómero: su estructura y dinámica en salud y enfermedad / Telomerase and telomere: their structure and dynamics in health and disease

La telomerasa es la enzima responsable del mantenimiento de la longitud de los telómeros mediante la adición de secuencias repetitivas ricas en guanina, y su actividad se observa principalmente en gametos, células madre y células tumorales. En las células somáticas humanas el potencial de proliferación es limitado, alcanzando la senescencia luego de 50-70 divisiones celulares, debido a que la ADN polimerasa no es capaz de copiar el ADN en los extremos de los cromosomas. Por el contrario, en la mayoría de las células tumorales el potencial de replicación es ilimitado debido al mantenimiento de la longitud telomérica dado por la telomerasa. Los telómeros tienen proteínas adicionales que regulan la unión de la telomerasa. De la misma manera la telomerasa también se asocia con un complejo de proteínas que regulan su actividad. Este trabajo se centra en la estructura y función del complejo telómero/telomerasa y a cómo las alteraciones en su comportamiento conducen al desarrollo de diversas enfermedades, principalmente cáncer. El desarrollo de inhibidores del sistema telómero / telomerasa podría ser un blanco con posibilidades prometedoras.

Telomerase is the enzyme responsible for the maintenance of telomere length by adding guanine-rich repetitive sequences. Its activity can be seen in gametes, stem cells and tumor cells. In human somatic cells the proliferative potential is limited, reaching senescence after 50-70 cell divisions, because the DNA polymerase is not able to copy the DNA at the ends of chromosomes. By contrast, in most tumor cells the replicative potential is unlimited due to the maintenance of the telomeric length given by telomerase. Telomeres have additional proteins that regulate the binding of telomerase, likewise telomerase associates, with a protein complex that regulates its activity. This work focuses on the structure and function of the telomere/telomerase complex and how changes in its behavior lead to the development of different diseases, mainly cancer. Development of inhibitors of the telomere/telomerase complex could be a target with promising possibilities.

Telomerasa y telómero: su estructura y dinámica en salud y enfermedad / Telomerase and telomere: their structure and dynamics in health and disease

La telomerasa es la enzima responsable del mantenimiento de la longitud de los telómeros mediante la adición de secuencias repetitivas ricas en guanina, y su actividad se observa principalmente en gametos, células madre y células tumorales. En las células somáticas humanas el potencial de proliferación es limitado, alcanzando la senescencia luego de 50-70 divisiones celulares, debido a que la ADN polimerasa no es capaz de copiar el ADN en los extremos de los cromosomas. Por el contrario, en la mayoría de las células tumorales el potencial de replicación es ilimitado debido al mantenimiento de la longitud telomérica dado por la telomerasa. Los telómeros tienen proteínas adicionales que regulan la unión de la telomerasa. De la misma manera la telomerasa también se asocia con un complejo de proteínas que regulan su actividad. Este trabajo se centra en la estructura y función del complejo telómero/telomerasa y a cómo las alteraciones en su comportamiento conducen al desarrollo de diversas enfermedades, principalmente cáncer. El desarrollo de inhibidores del sistema telómero / telomerasa podría ser un blanco con posibilidades prometedoras.(AU)

Telomerase is the enzyme responsible for the maintenance of telomere length by adding guanine-rich repetitive sequences. Its activity can be seen in gametes, stem cells and tumor cells. In human somatic cells the proliferative potential is limited, reaching senescence after 50-70 cell divisions, because the DNA polymerase is not able to copy the DNA at the ends of chromosomes. By contrast, in most tumor cells the replicative potential is unlimited due to the maintenance of the telomeric length given by telomerase. Telomeres have additional proteins that regulate the binding of telomerase, likewise telomerase associates, with a protein complex that regulates its activity. This work focuses on the structure and function of the telomere/telomerase complex and how changes in its behavior lead to the development of different diseases, mainly cancer. Development of inhibitors of the telomere/telomerase complex could be a target with promising possibilities.(AU)

Telomerasa y telómero: su estructura y dinámica en salud y enfermedad. / [Telomerase and telomere: their structure and dynamics in health and disease].

Telomerase is the enzyme responsible for the maintenance of telomere length by adding guanine-rich repetitive sequences. Its activity can be seen in gametes, stem cells and tumor cells. In human somatic cells the proliferative potential is limited, reaching senescence after 50-70 cell divisions, because the DNA polymerase is not able to copy the DNA at the ends of chromosomes. By contrast, in most tumor cells the replicative potential is unlimited due to the maintenance of the telomeric length given by telomerase. Telomeres have additional proteins that regulate the binding of telomerase, likewise telomerase associates, with a protein complex that regulates its activity. This work focuses on the structure and function of the telomere/telomerase complex and how changes in its behavior lead to the development of different diseases, mainly cancer. Development of inhibitors of the telomere/telomerase complex could be a target with promising possibilities.

Reduction of tumor angiogenesis induced by desmopressin in a breast cancer model.

Desmopressin (DDAVP), a synthetic peptide analog of vasopressin, is a safe antidiuretic and hemostatic compound that acts as a selective agonist for the vasopressin V2 membrane receptor. It is known that DDAVP can inhibit progression of residual metastatic cells and also improves chemotherapy effects in preclinical breast cancer models. Here, we explored the effects of DDAVP on tumor angiogenesis using the aggressive F3II mammary carcinoma in syngeneic Balb/c mice. Intravenous administration of the compound (2 µg/kg) markedly decreased vascularization of growing subcutaneous tumors, as well as inhibited the early angiogenic response around intradermal inoculation sites. In vitro studies confirmed the presence of vasopressin V2 receptors on F3II cells and a modest antiproliferative activity of DDAVP. Interestingly, conditioned media from F3II monolayers exposed to low doses of DDAVP (100 nM) significantly increased angiostatin formation in the presence of purified plasminogen. Such increase was associated with an enhancement of tumor-secreted urokinase-type plasminogen activator, suggesting the proteolytic conversion of plasminogen to angiostatin in vitro. Similar results were observed with the MCF-7 human breast carcinoma, a cell line known to express the vasopressin V2 receptor. No direct effects of DDAVP (100 nM­1 µM) were found on capillary-like tube formation by human microvascular cells HMVEC. Our studies showed that DDAVP induces anti-angiogenic effects that may be associated with the generation of angiostatin by tumor cells. Further preclinical studies with DDAVP and other vasopressin analogs are warranted to determine their potential in cancer management.

TGF-ß2 dictates disseminated tumour cell fate in target organs through TGF-ß-RIII and p38α/ß signalling.

In patients, non-proliferative disseminated tumour cells (DTCs) can persist in the bone marrow (BM) while other organs (such as lung) present growing metastasis. This suggested that the BM might be a metastasis 'restrictive soil' by encoding dormancy-inducing cues in DTCs. Here we show in a head and neck squamous cell carcinoma (HNSCC) model that strong and specific transforming growth factor-ß2 (TGF-ß2) signalling in the BM activates the MAPK p38α/ß, inducing an (ERK/p38)(low) signalling ratio. This results in induction of DEC2/SHARP1 and p27, downregulation of cyclin-dependent kinase 4 (CDK4) and dormancy of malignant DTCs. TGF-ß2-induced dormancy required TGF-ß receptor-I (TGF-ß-RI), TGF-ß-RIII and SMAD1/5 activation to induce p27. In lungs, a metastasis 'permissive soil' with low TGF-ß2 levels, DTC dormancy was short-lived and followed by metastatic growth. Importantly, systemic inhibition of TGF-ß-RI or p38α/ß activities awakened dormant DTCs, fuelling multi-organ metastasis. Our work reveals a 'seed and soil' mechanism where TGF-ß2 and TGF-ß-RIII signalling through p38α/ß regulates DTC dormancy and defines restrictive (BM) and permissive (lung) microenvironments for HNSCC metastasis.

Telomerase regulation: a key to inhibition? (Review).

Telomerase has been recognized as a common factor in most tumor cells, and in turn a distinctive feature with respect to non-malignant cells. This feature has made telomerase a promising target for cancer therapy. Telomerase studies revealed that it is a multi-subunit complex possessing different levels of regulation, including control of expression, phosphorylation state, assembly and transportation to sites of activity. Thus, we emphasize that targeting telomerase expression or activity is not the only way to shorten telomeres, induce cell senescence and apoptosis. Therefore, there are multiple sites capable of allowing the modulation of its enzymatic activity. In the development of strategies based on the regulation of telomerase activity the understanding of the mechanisms regulating their subunits is essential. Based on this, in this review we summarize the current state of knowledge of some regulatory mechanisms of the components of the telomerase complex, and hypothetize their potential therapeutic application against cancer.

Telomere structure and telomerase in health and disease (review).

Telomerase is the enzyme responsible for maintenance of the length of telomeres by addition of guanine-rich repetitive sequences. Telomerase activity is exhibited in gametes and stem and tumor cells. In human somatic cells, proliferation potential is strictly limited and senescence follows approximately 50-70 cell divisions. In most tumor cells, on the contrary, replication potential is unlimited. The key role in this process of the system of the telomere length maintenance with involvement of telomerase is still poorly studied. Undoubtedly, DNA polymerase is not capable of completely copying DNA at the very ends of chromosomes; therefore, approximately 50 nucleotides are lost during each cell cycle, which results in gradual telomere length shortening. Critically short telomeres cause senescence, following crisis and cell death. However, in tumor cells the system of telomere length maintenance is activated. Much work has been done regarding the complex telomere/telomerase as a unique target, highly specific in cancer cells. Telomeres have additional proteins that regulate the binding of telomerase. Telomerase, also associates with a number of proteins forming the sheltering complex having a central role in telomerase activity. This review focuses on the structure and function of the telomere/telomerase complex and its altered behavior leading to disease, mainly cancer. Although telomerase therapeutics are not approved yet for clinical use, we can assume that based on the promising in vitro and in vivo results and successful clinical trials, it can be predicted that telomerase therapeutics will be utilized soon in the combat against malignancies and degenerative diseases. The active search for modulators is justified, because the telomere/telomerase system is an extremely promising target offering possibilities to decrease or increase the viability of the cell for therapeutic purposes.

Sensitivity of tumor cells towards CIGB-300 anticancer peptide relies on its nucleolar localization.

CIGB-300 is a novel anticancer peptide that impairs the casein kinase 2-mediated phosphorylation by direct binding to the conserved phosphoacceptor site on their substrates. Previous findings indicated that CIGB-300 inhibits tumor cell proliferation in vitro and induces tumor growth delay in vivo in cancer animal models. Interestingly, we had previously demonstrated that the putative oncogene B23/nucleophosmin (NPM) is the major intracellular target for CIGB-300 in a sensitive human lung cancer cell line. However, the ability of this peptide to target B23/NPM in cancer cells with differential CIGB-300 response phenotype remained to be determined. Interestingly, in this work, we evidenced that CIGB-300's antiproliferative activity on tumor cells strongly correlates with its nucleolar localization, the main subcellular localization of the previously identified B23/NPM target. Likewise, using CIGB-300 equipotent doses (concentration that inhibits 50% of proliferation), we demonstrated that this peptide interacts and inhibits B23/NPM phosphorylation in different cancer cell lines as evidenced by in vivo pull-down and metabolic labeling experiments. Moreover, such inhibition was followed by a fast apoptosis on CIGB-300-treated cells and also an impairment of cell cycle progression mainly after 5 h of treatment. Altogether, our data not only validates B23/NPM as a main target for CIGB-300 in cancer cells but also provides the first experimental clues to explain their differential antiproliferative response. Importantly, our findings suggest that further improvements to this cell penetrating peptide-based drug should entail its more efficient intracellular delivery at such subcellular localization.

CIGB-300, a proapoptotic peptide, inhibits angiogenesis in vitro and in vivo.

We have previously demonstrated that a proapoptotic cyclic peptide CIGB-300, formerly known as P15-Tat delivered into the cells by the cell-penetrating peptide Tat, was able to abrogate the CK2-mediated phosphorylation and induce tumor regression when injected directly into solid tumors in mice or by systemic administration. In this work, we studied the role of CIGB-300 on the main events that take place in angiogenesis. At non-cytotoxic doses, CIGB-300 was able to inhibit adhesion, migration, and tubular network formation induced by human umbilical vein endothelial cells (HUVEC) growing upon Matrigel in vitro. Likewise, we evaluated the cellular penetration and localization into the HUVEC cells of CIGB-300. Our results confirmed a quick cellular penetration and a cytoplasmic accumulation in the early minutes of incubation and a translocation into the nuclei beginning at 12h of treatment, with a strong presence in the perinuclear area. A microarray analysis was used to determine the genes affected by the treatment. We observed that CIGB-300 significantly decreased four genes strongly associated with tubulogenesis, growth, and differentiation of endothelial cells. The CIGB-300 was tested in vivo on chicken embryo chorioallantoic membranes (CAM), and a large number of newly formed blood vessels were significantly regressed. The results suggested that CIGB-300 has a potential as an antiangiogenic treatment. The mechanism of action may be associated with partial inhibition of VEGF and Notch pathways.