Multiple mechanisms contribute to acquired TRAIL resistance in multiple myeloma.

Multiple Myeloma (MM) prognosis has recently improved thanks to the incorporation of new therapies to the clinic. Nonetheless, it is still a non-curable malignancy. Targeting cancer cells with agents inducing cell death has been an appealing alternative investigated over the years, as is the case of TRAIL, an agonist of DR4 and DR5 death receptors. This pathway, involved in apoptosis triggering, has demonstrated efficacy on MM cells. In this research, we have investigated the sensitivity of a panel of MM cells to this agent and generated TRAIL-resistant models by continuous culture of sensitive cells with this peptide. Using genomic and biochemical approaches, the mechanisms underlying resistance were investigated. In TRAIL-resistant cells, a strong reduction in cell-surface receptor levels was detected and impaired the apoptotic machinery to respond to the treatment, enabling cells to efficiently form the Death Inducing Signalling Complex. In addition, an upregulation of the inhibitory protein c-FLIP was detected. Even though the manipulation of these proteins was able to modify cellular responses to TRAIL, it was not complete, pointing to other mechanisms involved in TRAIL resistance.

Continuous endoglin (CD105) overexpression disrupts angiogenesis and facilitates tumor cell metastasis.

Endoglin (CD105) is an auxiliary receptor for members of the TFG-ß superfamily. Whereas it has been demonstrated that the deficiency of endoglin leads to minor and defective angiogenesis, little is known about the effect of its increased expression, characteristic of several types of cancer. Angiogenesis is essential for tumor growth, so high levels of proangiogenic molecules, such as endoglin, are supposed to be related to greater tumor growth leading to a poor cancer prognosis. However, we demonstrate here that endoglin overexpression do not stimulate sprouting or vascularization in several in vitro and in vivo models. Instead, steady endoglin overexpression keep endothelial cells in an active phenotype that results in an impairment of the correct stabilization of the endothelium and the recruitment of mural cells. In a context of continuous enhanced angiogenesis, such as in tumors, endoglin overexpression gives rise to altered vessels with an incomplete mural coverage that permit the extravasation of blood. Moreover, these alterations allow the intravasation of tumor cells, the subsequent development of metastases and, thus, a worse cancer prognosis.

The kinesin spindle protein inhibitor filanesib enhances the activity of pomalidomide and dexamethasone in multiple myeloma.

Kinesin spindle protein inhibition is known to be an effective therapeutic approach in several malignancies. Filanesib (ARRY-520), an inhibitor of this protein, has demonstrated activity in heavily pre-treated multiple myeloma patients. The aim of the work herein was to investigate the activity of filanesib in combination with pomalidomide plus dexamethasone backbone, and the mechanisms underlying the potential synergistic effect. The ability of filanesib to enhance the activity of pomalidomide plus dexamethasone was studied in several in vitro and in vivo models. Mechanisms of this synergistic combination were dissected by gene expression profiling, immunostaining, cell cycle and short interfering ribonucleic acid studies. Filanesib showed in vitro, ex vivo, and in vivo synergy with pomalidomide plus dexamethasone treatment. Importantly, the in vivo synergy observed in this combination was more evident in large, highly proliferative tumors, and was shown to be mediated by the impairment of mitosis transcriptional control, an increase in monopolar spindles, cell cycle arrest and the induction of apoptosis in cells in proliferative phases. In addition, the triple combination increased the activation of the proapoptotic protein BAX, which has previously been associated with sensitivity to filanesib, and could potentially be used as a predictive biomarker of response to this combination. Our results provide preclinical evidence for the potential benefit of the combination of filanesib with pomalidomide and dexamethasone, and supported the initiation of a recently activated trial being conducted by the Spanish Myeloma group which is investigating this combination in relapsed myeloma patients.

Mad2 overexpression promotes aneuploidy and tumorigenesis in mice.

Mad2 is an essential component of the spindle checkpoint that blocks activation of Separase and dissolution of sister chromatids until microtubule attachment to kinetochores is complete. We show here that overexpression of Mad2 in transgenic mice leads to a wide variety of neoplasias, appearance of broken chromosomes, anaphase bridges, and whole-chromosome gains and losses, as well as acceleration of myc-induced lymphomagenesis. Moreover, continued overexpression of Mad2 is not required for tumor maintenance, unlike the majority of oncogenes studied to date. These results demonstrate that transient Mad2 overexpression and chromosome instability can be an important stimulus in the initiation and progression of different cancer subtypes.

Ocoxin Oral Solution Triggers DNA Damage and Cell Death in Ovarian Cancer.

Ovarian cancer is the most fatal of all the reproductive cancers within the female population, mainly due to its late diagnosis that limits surgery and medical treatment. Classically, ovarian cancer therapy has included conventional chemotherapy, and other therapeutic approaches are now being used to treat these patients, but the outcomes of the disease are still poor. Therefore, new strategies are needed to improve life expectancy and life quality of ovarian cancer patients. Considering that, we investigated the effect of the nutritional supplement Ocoxin Oral Solution (OOS) in ovarian cancer models. OOS contains several nutritional supplements, some of them with demonstrated antitumoral action. In vitro studies showed that OOS inhibited the proliferation of several ovarian cancer cell lines, especially of those representative of the endometrioid subtype, in a time- and dose-dependent manner. A fast cell death induction after OOS treatment was observed, and when the molecular mechanisms leading to this effect were investigated, an activation of the DNA damage checkpoint was detected, as shown by activation (phosphorylation) of CHK1 and CHK2 kinases that was followed by the phosphorylation of the target protein histone H2AX. When tested in animal models of ovarian cancer, OOS reduced tumor growth without any observed secondary effects. Moreover, such reduction in tumor proliferation was caused by the induction of DNA damage as corroborated by the in vivo phosphorylation of CHK2 and Histone H2AX. Finally, OOS potentiated the action of carboplatin or olaparib, the standard of care treatments used in ovarian clinics, opening the possibility of including OOS in combination with those standard of care agents in patients with ovarian cancer.

Peptidylarginine deiminase 3 modulates response to neratinib in HER2 positive breast cancer.

Neratinib is a tyrosine kinase inhibitor that is used for the therapy of patients with HER2+ breast tumors. However, despite its clinical benefit, resistance to the drug may arise. Here we have created cellular models of neratinib resistance to investigate the mechanisms underlying such resistance. Chronic neratinib exposure of BT474 human HER2+ breast cancer cells resulted in the selection of several clones resistant to the antiproliferative action of the drug. The clones were characterized biochemically and biologically using a variety of techniques. These clones retained HER2 levels similar to parental cells. Knockdown experiments showed that the neratinib-resistant clones retained oncogenic dependence on HER2. Moreover, the tyrosine phosphorylation status of BT474 and the resistant clones was equally sensitive to neratinib. Transcriptomic and Western analyses showed that peptidylarginine deiminase 3 was overexpressed in the three neratinib-resistant clones studied but was undetectable in BT474 cells. Experiments performed in the neratinib-resistant clones showed that reduction of PADI3 or inhibition of its function restored sensitivity to the antiproliferative action of neratinib. Moreover, overexpression of FLAG-tagged PADI3 in BT474 cells provoked resistance to the antiproliferative action of neratinib. Together, these results uncover a role of PADI3 in the regulation of sensitivity to neratinib in breast cancer cells overexpressing HER2 and open the possibility of using PADI3 inhibitors to fight resistance to neratinib.

Trastuzumab deruxtecan in breast cancer.

Trastuzumab deruxtecan (T-DXd) is an antibody-drug conjugate (ADC) consisting of a humanised, anti-human epidermal growth factor receptor 2 (HER2) monoclonal antibody covalently linked to a topoisomerase I inhibitor cytotoxic payload (DXd). The high drug-to-antibody ratio (8:1) ensures a high DXd concentration is delivered to target tumour cells, following internalisation of T-DXd and subsequent cleavage of its tetrapeptide-based linker. DXd's membrane-permeable nature enables it to cross cell membranes and potentially exert antitumour activity on surrounding tumour cells regardless of HER2 expression. T-DXd's unique mechanism of action is reflected in its efficacy in clinical trials in patients with HER2-positive advanced breast cancer (in heavily pretreated populations and in those previously treated with a taxane and trastuzumab), as well as HER2-low metastatic breast cancer. Thus, ADCs such as T-DXd have the potential to change the treatment paradigm of targeting HER2 in metastatic breast cancer, including eventually within the adjuvant/neoadjuvant setting.

Multisite phosphorylation of Erk5 in mitosis.

The MAP kinase Erk5 plays important roles in cellular proliferation, and has recently been implicated in the regulation of mitosis. The classic pathway of Erk5 activation involves dual phosphorylation at its TEY microdomain by the upstream regulating kinase MEK5. Here we describe a second pathway that controls Erk5 phosphorylation. This pathway is activated in mitotic cells and involves kinase activities distinct from MEK5. Studies aimed at identifying these kinases suggested that CDK1 activity is required to sustain Erk5 phosphorylation in mitosis, as treatment with RO3306, a CDK1 inhibitor, reversed mitotic phosphorylation of Erk5. Moreover, CDK1 co-precipitated with Erk5 in mitotic cells. The mitotic phosphorylation of Erk5 occurs at multiple sites located at its unique C-terminal region, within an Erk5 subdomain that has formerly been implicated in the control of the subcellular location of Erk5. Furthermore, molecular studies indicated that phosphorylation at these sites may participate in the control of the transit of Erk5 between the cytosol and the nucleus, in addition to regulating its transcriptional activity. Together, our results demonstrate the existence of a second Erk5 phosphorylation pathway, that is activated in mitosis, and that may participate in the regulation of Erk5 functions.

A modular approach to trim cellular targets in anticancer drug discovery.

A Phenotypic Drug Discovery strategy was applied to study a set of pyrimidine analogs prepared by means of intramolecular oxidation-reduction reactions of N-substituted-N-(2,6-disubstituted-5-nitro-4-pyrimidinyl)aminoacetic acid methyl esters in basic media. The combined and rational use of specific assays allowed in short time reducing from all possible cellular targets to those involved in metaphase to anaphase transition.

Hec1 overexpression hyperactivates the mitotic checkpoint and induces tumor formation in vivo.

Hec1 (Highly Expressed in Cancer 1) is one of four proteins of the outer kinetochore Ndc80 complex involved in the dynamic interface between centromeres and spindle microtubules. Its overexpression is seen in a variety of human tumors and correlates with tumor grade and prognosis. We show here that the overexpression of Hec1 in an inducible mouse model results in mitotic checkpoint hyperactivation. As previously observed with overexpression of the Mad2 gene, hyperactivation of the mitotic checkpoint leads to aneuploidy in vitro and is sufficient to generate tumors in vivo that harbor significant levels of aneuploidy. These results underscore the role of chromosomal instability as a result of mitotic checkpoint hyperactivation in the initiation of tumorigenesis.

Ocoxin oral solution demonstrates antiviral properties in cellular models.

Ocoxin Oral Solution (OOS) and Viusid (VS) are nutritional supplements that include several natural products which affect different cellular functions, such as proliferation or the redox status. In addition, some of their constituent components have been described to exert an antiviral effect. Considering this, it was hypothesized that treatment with OOS and VS could protect from viral infections. In order to evaluate the impact of OOS and VS on viral infection, lentivirus and retrovirus whose genomes coded for green fluorescent protein were used. In addition, and as a second approach to measure viral infection, a hemagglutinin-tagged form of the mitogen-activated protein kinase ERK5 was also inserted in the retroviral vector. Viral particles produced in 293T cells were used to infect HeLa cells in the presence or absence of OOS or VS. It was observed that VS had a minimal effect on the capacity of either lentivirus or retrovirus to infect HeLa cells. However, OOS significantly reduced the infection of HeLa cells with both of these viruses. The effect was dose-dependent, reaching a maximum at a 1:100 dilution of OOS. These results suggested that, in addition to its well-known antitumoral properties, OOS may also inhibit infection with viruses. This effect is relevant since patients receiving oncological therapies are more susceptible to viral infections, and nutritional supplements such as OOS may help in reducing the severity of these potential pathogenic infections.

Novel ADCs and Strategies to Overcome Resistance to Anti-HER2 ADCs.

During recent years, a number of new compounds against HER2 have reached clinics, improving the prognosis and quality of life of HER2-positive breast cancer patients. Nonetheless, resistance to standard-of-care drugs has motivated the development of novel agents, such as new antibody-drug conjugates (ADCs). The latter are a group of drugs that benefit from the potency of cytotoxic agents whose action is specifically guided to the tumor by the target-specific antibody. Two anti-HER2 ADCs have reached the clinic: trastuzumab-emtansine and, more recently, trastuzumab-deruxtecan. In addition, several other HER2-targeted ADCs are in preclinical or clinical development, some of them with promising signs of activity. In the present review, the structure, mechanism of action, and potential resistance to all these ADCs will be described. Specific attention will be given to discussing novel strategies to circumvent resistance to ADCs.

Rb inactivation promotes genomic instability by uncoupling cell cycle progression from mitotic control.

Advanced human cancers are invariably aneuploid, in that they harbour cells with abnormal chromosome numbers. However, the molecular defects underlying this trait, and whether they are a cause or a consequence of the malignant phenotype, are not clear. Mutations that disable the retinoblastoma (Rb) pathway are also common in human cancers. These mutations promote tumour development by deregulating the E2F family of transcription factors leading to uncontrolled cell cycle progression. We show that the mitotic checkpoint protein Mad2 is a direct E2F target and, as a consequence, is aberrantly expressed in cells with Rb pathway defects. Concordantly, Mad2 is overexpressed in several tumour types, where it correlates with high E2F activity and poor patient prognosis. Generation of Rb pathway lesions in normal and transformed cells produces aberrant Mad2 expression and mitotic defects leading to aneuploidy, such that elevated Mad2 contributes directly to these defects. These results demonstrate how chromosome instability can arise as a by-product of defects in cell cycle control that compromise the accuracy of mitosis, and suggest a new model to explain the frequent appearance of aneuploidy in human cancer.

Antitumoral Properties of the Nutritional Supplement Ocoxin Oral Solution: A Comprehensive Review.

Ocoxin Oral Solution (OOS) is a nutritional supplement whose formulation includes several plant extracts and natural products with demonstrated antitumoral properties. This review summarizes the antitumoral action of the different constituents of OOS. The action of this formulation on different preclinical models as well as clinical trials is reviewed, paying special attention to the mechanism of action and quality of life improvement properties of this nutritional supplement. Molecularly, its mode of action includes a double edge role on tumor biology, that involves a slowdown in cell proliferation accompanied by cell death induction. Given the safety and good tolerability of OOS, and its potentiation of the antitumoral effect of other standard of care drugs, OOS may be used in the oncology clinic in combination with conventional therapies.

Adaptive resistance to trastuzumab impairs response to neratinib and lapatinib through deregulation of cell death mechanisms.

Small molecule inhibitors (TKIs) of HER2 have demonstrated clinical benefit in HER2-positive breast tumors. One of them, lapatinib, is used once advanced tumors become refractory to the HER2 antibody trastuzumab. Another one, neratinib, has shown benefit in high-risk early-stage breast cancer after trastuzumab-based therapies. A common characteristic is that patients are formerly treated with trastuzumab. We have explored whether trastuzumab previous therapy affects its antitumoral action. Long time exposure of the HER2+ cell line BT474 to trastuzumab resulted in trastuzumab-insensitive cells (BTRH cells). While treatment of wild type BT474 cells with lapatinib or neratinib resulted in decreased viability, BTRH cells were resistant to the action of these TKIs. Analogous results were obtained using trastuzumab-resistant cells derived from a PDX. Functional transcriptomic analyses and biochemical studies demonstrated that the TKIs caused DNA damage and apoptosis in wild type cells, but not in BTRH. Moreover, previous treatment with trastuzumab impairs response to small TKIs, by eliminating their proapoptotic action. Moreover, actioning on the apoptotic machinery using a chemical library of proapoptotic compounds led to the identification of clinical-stage drugs that may be used to fight trastuzumab-TKI resistance.

Neuregulins and cancer.

The neuregulins represent the largest subclass of polypeptide factors of the epidermal growth factor family of ligands. These molecules are synthesized as membrane-bound, biologically active growth factors that act by binding to the HER/ErbB receptor tyrosine kinases. Preclinical data have indicated that increased expression and function of neuregulins may provoke cancer. Furthermore, neuregulin expression has been detected in several neoplasias, and their presence may correlate with response to treatments that target the HER receptors such as trastuzumab. In addition, the neuregulins have also been implicated in resistance to anti-HER therapies. Therefore, targeting of the neuregulins may be helpful in neoplastic diseases in which these polypeptide factors contribute to tumor generation and/or maintenance.

Central Role of Cell Cycle Regulation in the Antitumoral Action of Ocoxin.

Nutritional supplements which include natural antitumoral compounds could represent safe and efficient additives for cancer patients. One such nutritional supplement, Ocoxin Oral solution (OOS), is a composite formulation that contains several antioxidants and exhibits antitumoral properties in several in vitro and in vivo tumor conditions. Here, we performed a functional genomic analysis to uncover the mechanism of the antitumoral action of OOS. Using in vivo models of acute myelogenous leukemia (AML, HEL cells, representative of a liquid tumor) and small-cell lung cancer (GLC-8, representative of a solid tumor), we showed that OOS treatment altered the transcriptome of xenografted tumors created by subcutaneously implanting these cells. Functional transcriptomic studies pointed to a cell cycle deregulation after OOS treatment. The main pathway responsible for this deregulation was the E2F-TFDP route, which was affected at different points. The alterations ultimately led to a decrease in pathway activation. Moreover, when OOS-deregulated genes in the AML context were analyzed in patient samples, a clear correlation with their levels and prognosis was observed. Together, these data led us to suggest that the antitumoral effect of OOS is due to blockade of cell cycle progression mainly caused by the action of OOS on the E2F-TFDP pathway.

TRAIL receptor activation overcomes resistance to trastuzumab in HER2 positive breast cancer cells.

The appearance of resistance to the anti-HER2 targeted drug trastuzumab constitutes, nowadays, an important challenge in the oncology clinic. To fight such resistance, we searched for potential vulnerabilities in cells resistant to that drug. To that end, we used cell lines primary resistant to trastuzumab, as well as cells made secondarily resistant to the drug upon continuous exposure. Using genomic and proteomic approaches, a deregulation in cell death pathways was identified in trastuzumab-resistant cells. More precisely, an increased response to the death factor TRAIL, caused by an increase in the cellular receptors for this factor, was observed. In parallel, a decrease in inhibitory components of the pathway was detected. This combination produces a more efficient assembly of the functional complex in the trastuzumab-resistant cells that translates in the observed increased response to TRAIL. Analysis of HER2 positive patient samples confirmed deregulation of this pathway in trastuzumab-resistant patients. Taken together our data identify a vulnerability of trastuzumab-resistant cells that could be used to design new targeted therapies in that context.

Antitumoral effect of Ocoxin, a natural compound-containing nutritional supplement, in small cell lung cancer.

Lung cancer is the most frequently diagnosed neoplasia and represents the leading cause of cancer-related deaths worldwide. Due to this fact, efforts to improve patient survival through the introduction of novel therapies, as well as preventive actions, are urgently required. Considering this scenario, the antitumoral action of the composite formulation Ocoxin® oral solution (OOS), that contains several antitumoral compounds including antioxidants, was tested in small cell lung cancer (SCLC) in vitro and in vivo preclinical models. OOS exhibited anti-SCLC action that was both time and dose dependent. In vivo OOS decreased the growth of tumors implanted in mice without showing signs of toxicity. The antitumoral effect was due to inhibition of cell proliferation and increased cell death. Genomic and biochemical analyses indicated that OOS augmented p27 and decreased the functioning of several routes involved in cell proliferation. In addition, OOS caused cell death by activation of caspases. Importantly, OOS favored the action of several standard of care drugs used in the SCLC clinic. Our results suggest that OOS has antitumoral action on SCLC, and could be used to supplement the action of drugs commonly used to treat this type of tumor.

Erk5 participates in neuregulin signal transduction and is constitutively active in breast cancer cells overexpressing ErbB2.

The four receptor tyrosine kinases of the ErbB family play essential roles in several physiological processes and have also been implicated in tumor generation and/or progression. Activation of ErbB1/EGFR is mainly triggered by epidermal growth factor (EGF) and other related ligands, while activation of ErbB2, ErbB3, and ErbB4 receptors occurs by binding to another set of EGF-like ligands termed neuregulins (NRGs). Here we show that the Erk5 mitogen-activated protein kinase (MAPK) pathway participates in NRG signal transduction. In MCF7 cells, NRG activated Erk5 in a time- and dose-dependent fashion. The action of NRG on Erk5 was dependent on the kinase activity of ErbB receptors but was independent of Ras. Expression in MCF7 cells of a dominant negative form of Erk5 resulted in a significant decrease in NRG-induced proliferation of MCF7 cells. Analysis of Erk5 in several human tumor cell lines indicated that a constitutively active form of this kinase was present in the BT474 and SKBR3 cell lines, which also expressed activated forms of ErbB2, ErbB3, and ErbB4. Treatments aimed at decreasing the activity of these receptors caused Erk5 inactivation, indicating that the active form of Erk5 present in BT474 and SKBR3 cells was due to a persistent positive stimulus originating at the ErbB receptors. In BT474 cells expression of the dominant negative form of Erk5 resulted in reduced proliferation, indicating that in these cells Erk5 was also involved in the control of proliferation. Taken together, these results suggest that Erk5 may play a role in the regulation of cell proliferation by NRG receptors and indicate that constitutively active NRG receptors may induce proliferative responses in cancer cells through this MAPK pathway.