Search

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Hepatocellular carcinoma (HCC) is becoming one of the most prevalent types of cancer worldwide. The most efficient types of treatment at present include surgical resection and liver transplantation, but these treatments may only be used in a small percentage of patients. In order to identify novel therapeutic strategies for this disease, the present study explored the potential antitumoral effect of Ocoxin® oral solution (OOS) in HCC. OOS inhibited the proliferation of HCC cell lines in a time- and dose-dependent manner, being more efficient when used in combination with sorafenib, a standard of care treatment for patients diagnosed with advanced-stage disease. Mechanistic studies indicated that the effect of OOS was due to the induction of cell cycle arrest rather than the stimulation of apoptotic cell death. The cell cycle was slowed down in all phases in the HCC cell lines treated with OOS. Finally, when tested in animal models of HCC, OOS reduced tumor progression through the induction of necrosis in xenograft tumor models. Considering the poor prognosis and high resistance to antitumor treatments of HCC, the antiproliferative action of OOS, particularly in combination with sorafenib, provides the opportunity to investigate the effect of combined therapy in a clinical setting. [ABSTRACT FROM AUTHOR]

The use of thalidomide derivatives (IMIDs) has improved multiple myeloma prognosis, through an unknown mechanism of action. Recently one molecular target, the cereblon (CRBN) protein, has been identified. CRBN acts by binding to DDB1-CUL4-ROC1 forming a ubiquitin ligase multiprotein complex. We have generated antibodies to different regions of CRBN protein, and analyzed the biological consequences of augmenting or decreasing CRBN levels. CRBN was expressed in all the myeloma cell lines tested, independently of their sensitivity to IMIDs, and the CRBN-DDB1-CUL4 complex was efficiently formed. At the molecular level, long-term treatment with IMIDs induced a slight decrease in CRBN levels and a reduction in the CRBN-DDB1-CUL4 complex. Interestingly, treatment with other anti-myeloma drugs downregulated cellular contents of CRBN, and in a much faster fashion. These results suggest that CRBN is an important mediator of the cellular response to IMIDs, but also critical in the maintenance of cell viability and/or proliferation. [ABSTRACT FROM AUTHOR]

Simple Summary: A proportion of breast tumors bear the oncogenic transmembrane tyrosine kinase protein HER2. Even though therapies that target HER2 have changed the prognosis and quality of life of patients with HER2+ breast tumors, resistance to those therapies is still an important clinical problem. To improve the management of those tumors, a new category of antitumor agents, antibody-drug conjugates (ADCs), has emerged. These agents are created by linking a potent cytotoxic to an antibody that recognizes a membrane protein. Two anti-HER2 ADCs have been approved by the FDA for clinical use and several others are under development. The structure, mechanism of action, and resistance mechanisms to ADCs are reviewed in the present work, as well as potential strategies to overcome resistance to clinically approved anti-HER2 ADCs, including novel 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. [ABSTRACT FROM AUTHOR]

Multiple myeloma (MM) is a hematological disease characterized by an abnormal accumulation of plasma cells in the bone marrow. These cells have frequent cytogenetic abnormalities including translocations of the immunoglobulin heavy chain gene and chromosomal gains and losses. In fact, a singular characteristic differentiating MM from other hematological malignancies is the presence of a high degree of aneuploidies. As chromosomal abnormalities can be generated by alterations in the spindle assembly checkpoint (SAC), the functionality of such checkpoint was tested in MM. When SAC components were analyzed in MM cell lines, the RNA levels of most of them were conserved. Nevertheless, the protein content of some key constituents was very low in several cell lines, as was the case of MAD2 or CDC20 in RPMI-8226 or RPMI-LR5 cells. The recovery of their cellular content did not substantially affect cell growth, but improved their ability to segregate chromosomes. Finally, SAC functionality was tested by challenging cells with agents disrupting microtubule dynamics. Most of the cell lines analyzed exhibited functional defects in this checkpoint. Based on the data obtained, alterations both in SAC components and their functionality have been detected in MM, pointing to this pathway as a potential target in MM treatment. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract The ectodomain of the neurotrophin receptor TrkA has been recovered as a soluble fragment from the culture media of cells by a process that involves endoproteolytic cleavage. This cleavage may be upregulated by several treatments, including NGF treatment or protein kinase C activation. In this report we have investigated the cellular site and proteolytic activities involved in TrkA cleavage, and the effects of ectodomain truncation on signalling. Cleavage occurs when the receptor is at, or near, the cell surface, and it can be prevented by agents that affect protein sorting. Cleavage generates several cell-bound fragments, and their generation can be differentially blocked by inhibitors, documenting the involvement of multiple plasma membrane metalloendoproteases. The major cell-bound receptor fragment (i) is tyrosine-phosphorylated in vivo; (ii) does autophosphorylate in vitro; and (iii) is able to associate with intracellular signalling substrates. Artificial deletion of the TrkA ectodomain results in an active receptor that induced neurite outgrowth in pheochromocytoma cells. Cleavage by this natural cellular mechanism appears thus to serve not only as an outlet of receptor binding fragments, but also to generate signalling-competent cell-bound receptor fragments. In the nervous system this ligand-independent receptor activation could play important roles in the development and survival of neurons. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • Antibody-drug conjugates have significantly improved breast cancer (BC) treatment. • Trastuzumab deruxtecan's (T-DXd) structure allows large payload delivery to targets. • T-DXd has demonstrated unprecedented efficacy in patients with HER2+ advanced BC. • T-DXd has significantly improved survival rates in heavily pretreated BC patients. • T-DXd may change the treatment paradigm of targeting HER2 in metastatic BC. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Summary: 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. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]