The Camargo group at Children Hospital, Boston, and the B&Gu at MBC have recently published on Molecular Cell, that Hippo/YAP signaling pathway is a crucial regulator of tissue growth, stem cell activity, and tumorigenesis.
YAP interacts and recruits the Mediator complex to enhancers, allowing the recruitment of the CDK9 elongating kinase. Genetic and chemical perturbation experiments demonstrate the requirement for Mediator and CDK9 in YAP-driven phenotypes of overgrowth and tumorigenesis. Robust YAP binding is restricted to a relatively small number of distal regulatory elements in the genome and YAP occupancy defines a subset of enhancers and superenhancers with the highest transcriptional outputs. Notably, YAP/TAZ binding is predominantly restricted to few hundred genes that are critical for growth, making YAP/TAZ ideal targets for cancer therapeutics.
YAP Drives Growth by Controlling Transcriptional Pause Release from Dynamic Enhancers.
Galli GG, Carrara M, Yuan WC, Valdes-Quezada C, Gurung B, Pepe-Mooney B, Zhang T, Geeven G, Gray NS, de Laat W, Calogero RA, Camargo FD.
Mol Cell. 2015 Oct 15;60(2):328-37. doi: 10.1016/j.molcel.2015.09.001. Epub 2015 Oct 1.
Medulloblastoma is the most common malignant childhood brain tumor with the propensity to disseminate at an early stage, and is associated with high morbidity. New treatment strategies are needed to improve cure rates and to reduce life-long cognitive and functional deficits associated with current therapies. Extracellular Vesicles are important players in cell-to-cell communication in health and diseases. A clearer understanding of cell-to-cell communication in tumors can be achieved by studying EV secretion in medullospheres. This can reveal subtle modifications induced by the passage from adherent to non-adherent growth, as spheres may account for the adaptation of tumor cells to the mutated environment.
Formation of medullospheres from MB cell lines stabilized in adherent conditions was obtained through culture conditioning based on low attachment flasks and specialized medium. Evs collected by ultracentrifugation, in adherent conditions and as spheres, were subjected to electron microscopy, NanoSight measurements and proteomics. Interestingly, iron carrier proteins were only found in EVs shed by CSC-enriched tumor cell population of spheres. We used iron chelators when culturing MB cell lines as spheres. Iron chelators induced a decrease in number/size of spheres and in stem cell populations able to initiate in vitro spheres formation.
In conclusion this work suggests a not yet identified role of iron metabolism in MB progression and invasion and opens the possibility to use chelators as adjuvants in anti-tumoral chemotherapy.
A paper from Federica Cavallo's group shows that immunotargeting of breast cancer stem-like cells can sensitize them to chemotherapy, offering an effective strategy to overcome drug resistance and limit metastatic progression.
Resistance to therapy and lack of curative treatments for metastatic breast cancer suggest that current therapies may be missing the subpopulation of chemo- and radio-resistant cancer stem cells (CSC). The ultimate success of any treatment may well rest on CSC eradication, but specific anti-CSC therapies are still limited. In this study, published on Cancer Research (http://cancerres.aacrjournals.org/content/early/2015/11/13/0008-5472.CAN-15-1208.abstract), Stefania Lanzardo, Laura Conti and coworkers, through a comparison of the transcriptional profiles of murine Her2+ breast tumor TUBO cells and their derived CSC-enriched tumorspheres, have identified xCT, the functional subunit of the cystine/glutamate antiporter system xc-, as a surface protein that is upregulated specifically in tumorspheres. This finding was validated by cytofluorimetric analysis and immunofluorescence in TUBO-derived tumorspheres and in a panel of mouse and human triple negative breast cancer (TNBC) cell-derived tumorspheres. The authors further show that downregulation of xCT impaired tumorsphere generation and altered CSC intracellular redox balance in vitro, suggesting that xCT plays a functional role in CSC biology. DNA vaccination-based immunotargeting of xCT in mice challenged with syngeneic tumorsphere-derived cells delayed established subcutaneous tumor growth and strongly impaired pulmonary metastasis formation by generating anti-xCT antibodies able to alter CSC self-renewal and redox balance. Finally, anti-xCT vaccination increased CSC chemosensitivity to doxorubicin in vivo, indicating that xCT immunotargeting may be an effective adjuvant to chemotherapy.
Feline Leukemia Virus subgroup C Receptor 1 (Flvcr1) gene encodes for two heme exporters, FLVCR1a and FLVCR1b localized at the plasma and mitochondrial membrane, respectively. In a recent paper published on Haematologica, Sonia Mercurio and collegues addressed the specific functions of Flvcr1a and Flvcr1b in erythropoiesis, the process that produces the highest amount of heme. They showed that, in mice and zebrafish, Flvcr1a is required for the expansion of committed erythroid progenitors but cannot drive their terminal differentiation, while Flvcr1b contributes to the expansion phase and it is required for differentiation. Moreover, by using FLVCR1a- or FLVCR1a/1b-down-regulated K562 cells, they established a link, on one hand, between FLVCR1a deficiency, cytosolic heme accumulation and defective proliferation, and, on the other, between FLVCR1a/1b-down-regulation, mitochondrial heme accumulation and impairment of both proliferation and differentiation. These data support a model in which the coordinated expression of Flvcr1a and Flvcr1b contributes to control the size of the cytosolic heme pool required to sustain metabolic activity during the expansion of erythroid progenitors and to allow hemoglobin production during their terminal maturation. The studies on Flvcr1a and Flvcr1b, not only in erythroid cells but also in other cell types like hepatocytes and intestinal cells, reveal the exquisite mechanisms in controlling heme balance within the cell. Future work is needed to elucidate how intracellular heme transport coordinates with heme synthesis and degradation to achieve optimal intracellular heme balance.
Anaplastic Large Cell Lymphoma (ALCL) is a clinical and biological heterogeneous disease including systemic ALK positive and ALK negative entities.
To discover genes potentially related to the pathogenesis of ALK negative ALCL patients, Scarfo’, Pellegrino, Mereu et al. applied the Cancer Outlier Profile Analysis algorithm to a gene expression profiling data set including 300 cases of T-cell non-Hodgkin lymphoma and normal T-cells. The authors detected ectopic co-expression of ERBB4 and COL29A1 genes in 25% of ALK negative ALCL patients. RNA sequencing and 5’RNA Ligase-Mediated Rapid Amplification of cDNA Ends (RLM-RACE) identified two novel ERBB4 truncated transcripts, displaying intronic Transcription Start Sites. The study defined that the expression of ERBB4 aberrant transcripts is promoted by endogenous intronic Long Terminal Repeats (LTRs).
Importantly, the authors demonstrated that ERBB4 truncated forms show oncogenic potentials in vitro and in vivo and that ERBB4 inhibition partially controls ALCL cell growth and disease progression in a primary ERBB4 positive patient-derived tumorgraft model.
In conclusion, the study by Scarfo’, Pellegrino, Mereu et al. identified a new subclass of ALK negative ALCL characterized by aberrant expression of ERBB4 truncated transcripts carrying intronic 5’UTRs. These findings are clinically relevant since they provide new therapeutic opportunities for a specific subset of lymphoma patients.
A paper in collaboration between the group of Federica Cavallo and the group of Emanuela Noris (Institute for Sustainable Plant Protection, CNR, Torino, Italy) show that the rat ErbB2 tyrosine kinase receptor produced in plants is immunogenic in mice and confers protective immunity against ErbB2+ mammary cancer.
Overexpression and mutations of ErbB proteins lead to several malignancies including breast, lung, pancreatic, bladder and ovary carcinomas. ErbB2 is immunogenic and is an ideal candidate for cancer immunotherapy. In this paper (http://onlinelibrary.wiley.com/doi/10.1111/pbi.12367/epdf), we investigated the possibility of expressing the extracellular (EC) domain of rErbB2 in Nicotiana benthamiana plants. Synthetic variants of the rErbB2 gene portion encoding the EC domain, optimized with a human codon usage and either linked to the full TM domain, to a portion of it, or deprived of it were cloned in the pEAQ-HT expression vector as 6X His tag fusions and used to infiltrate Nicotiana benthamiana leaves. All rErbB2 variants were transiently expressed, but that expressing the EC domain without TM was the most expressed protein. When crude soluble extracts expressing this rErbB2 variant were administered to BALB/c mice, specific rErbB2 immune responses were triggered. Moreover, a potent antitumour activity was induced when vaccinated mice were challenged with syngeneic transplantable rErbB2+ mammary carcinoma cells.
The maintenance of heme homeostasis, mucosa cell renewal and redox environment in the intestine is essential to permit digestion, absorption, cell proliferation, cell apoptosis, immune response and to avoid the development of gut disorders. The Feline Leukemia Virus, subgroup C, Receptor 1a (FLVCR1a) is a heme exporter with an established role in erythroid cells, macrophages and hepatocytes. Flvcr1a is expressed in almost all cell types including intestinal cells, suggesting a role for this protein also in this tissue. In a recent paper published on Antioxidants and Redox Signaling, Fiorito et al. describe the role of FLVCR1a in the intestine taking advantage of intestine specific conditional Flvcr1a−knockout mice and of Flvcr1a−depleted colon adenocarcinoma Caco2 cells. The authors show that FLVCR1a−mediated heme export does not contribute to dietary heme absorption processes and that FLVCR1a is involved in the export of the excess of de novo synthesized heme from intestinal cells. In addition, they show that FLVCR1a participates in intestinal cell proliferation and in the maintenance of the peculiar homeostasis of proliferating cells, including their redox status and metabolic activity. Thanks to these functions, FLVCR1a is crucial for the survival of mice in a model of ulcerative colitis. The present work represents the first description of the function of the heme exporter FLVCR1a in the intestine and an advance in the understanding of heme metabolism in this tissue. The findings shed light on the role of heme export in heme absorption processes and unravel a new role for heme export in the control of mucosal renewal and in proliferating cell redox status and metabolic activity, demonstrating for the first time a crucial role for FLVCR1a in maintaining intestinal homeostasis in both physiologic and pathologic conditions.
Neonatal cancer is an issue of real urgency in oncology. Of the various therapeutic strategies used against this category of malignancy, immune-based therapies are the most promising, however the prevention of pediatric cancer has not yet become a reality. In this study, published on OncoImmunology, Giuseppina Barutello and coworkers applied a DNA vaccination strategy against Her2/neu (neu) in the framework of the pre-birth immunization in order to gauge whether maternal immunization can be used in neonatal cancer immune-prevention. Exploiting the BALB-neuT mouse model of autochthonous mammary carcinogenesis, the authors observed a significantly extended tumor-free and overall survival in BALB-neuT offspring born and fed by mothers vaccinated against neu, as compared to controls. Maternally derived anti-neu IgG were successfully transferred from mothers to newborns and were responsible for the protective effect. The vaccinated-mother’s offspring also developed an active immunity against neu as revealed by the presence of T-cell-mediated cytotoxicity against the neu immunodominant peptide. This active response was due to the milk transfer of immune-complexes formed between the neu extracellular domain, shed from vaccine-transfected muscle cells, and the anti-neu IgG induced by the vaccine. These findings show that maternal immunization has the potential to hamper mammary carcinogenesis in genetically predestinated offspring and to develop into applications against lethal neonatal cancer diseases for which powerful therapeutic options are currently unavailable.