Prediction of neuroblastoma cell response to treatment with natural or synthetic retinoids using selected protein biomarkers

PBX1 as a novel master regulator in cancer: Its regulation, molecular biology, and therapeutic applications

PBX1 is a critical transcription factor at the top of various cell fate-determining pathways. In cancer, PBX1 stands at the crossroads of multiple oncogenic signaling pathways and mediates responses by recruiting a broad repertoire of downstream targets. Research thus far has corroborated the involvement of PBX1 in cancer proliferation, resisting apoptosis, tumor-associated neoangiogenesis, epithelial-mesenchymal transition (EMT) and metastasis, immune evasion, genome instability, and dysregulating cellular metabolism. Recently, our understanding of the functional regulation of the PBX1 protein has advanced, as increasing evidence has depicted a regulatory network consisting of transcriptional, post-transcriptional, and post-translational levels of control mechanisms. Furthermore, accumulating studies have supported the clinical utilization of PBX1 as a prognostic or therapeutic target in cancer. Preliminary results showed that PBX1 entails vast potential as a targetable master regulator in the treatment of cancer, particularly in those with high-risk features and resistance to other therapeutic strategies. In this review, we will explore the regulation, protein-protein interactions, molecular pathways, clinical application, and future challenges of PBX1.

HOXA9 Overexpression Contributes to Stem Cell Overpopulation That Drives Development and Growth of Colorectal Cancer

HOX proteins are transcription factors that regulate stem cell (SC) function, but their role in the SC origin of cancer is under-studied. Aberrant expression of HOX genes occurs in many cancer types. Our goal is to ascertain how retinoic acid (RA) signaling and the regulation of HOXA9 expression might play a role in the SC origin of human colorectal cancer (CRC). Previously, we reported that aldehyde dehydrogenase (ALDH) and other RA pathway components are co-expressed in colonic cancer SCs (CSCs) and that overpopulation of ALDH-positive CSCs occurs during colon tumorigenesis. Our hypothesis is RA signaling regulates HOXA9 expression, and dysregulated RA signaling results in HOXA9 overexpression, which contributes to CSC overpopulation in CRC. Immunostaining showed that HOXA9 was selectively expressed in ALDH-positive SCs, and HOXA9 expression was increased in CRCs compared to normal epithelium. Modulating RA signaling in CRC cells (HT29 and SW480) with ATRA and DEAB decreased cell proliferation and reduced HOXA9 expression. Bioinformatics analyses identified a network of proteins that functionally interact with HOXA9, and the genes that encode these proteins, as well as HOXA9, contain RA receptor binding sites. These findings indicate that the expression of HOXA9 and its functional network is regulated by RA signaling in normal colonic SCs, and, when dysregulated, HOXA9 may contribute to CSC overpopulation that drives CRC development and growth. Our study provides a regulatory mechanism that might be useful in developing treatments against CSC overpopulation in CRC.

Serotonin limits generation of chromaffin cells during adrenal organ development

Adrenal glands are the major organs releasing catecholamines and regulating our stress response. The mechanisms balancing generation of adrenergic chromaffin cells and protecting against neuroblastoma tumors are still enigmatic. Here we revealed that serotonin (5HT) controls the numbers of chromaffin cells by acting upon their immediate progenitor "bridge" cells via 5-hydroxytryptamine receptor 3A (HTR3A), and the aggressive HTR3Ahigh human neuroblastoma cell lines reduce proliferation in response to HTR3A-specific agonists. In embryos (in vivo), the physiological increase of 5HT caused a prolongation of the cell cycle in "bridge" progenitors leading to a smaller chromaffin population and changing the balance of hormones and behavioral patterns in adulthood. These behavioral effects and smaller adrenals were mirrored in the progeny of pregnant female mice subjected to experimental stress, suggesting a maternal-fetal link that controls developmental adaptations. Finally, these results corresponded to a size-distribution of adrenals found in wild rodents with different coping strategies.

The regulation of PBXs and their emerging role in cancer

Pre‐B‐cell leukaemia transcription factor (PBX) proteins are a subfamily of evolutionarily conserved, atypical homeodomain transcription factors that belong to the superfamily of three amino acid loop extension (TALE) homeodomain proteins. Members of the PBX family play crucial roles in regulating multiple pathophysiological processes, such as the development of organs, congenital cardiac defects and carcinogenesis. The dysregulation of PBXs has been shown to be closely associated with many diseases, particularly cancer. However, the detailed mechanisms of PBX dysregulation in cancer progression are still inconclusive. In this review, we summarize the recent advances in the structures, functions and regulatory mechanisms of PBXs, and discuss their underlying mechanisms in cancer progression. We also highlight the great potential of PBXs as biomarkers for the early diagnosis and prognostic evaluation of cancer as well as their therapeutic applications. The information reviewed here may expand researchers’ understanding of PBXs and could strengthen the clinical implication of PBXs in cancer treatment.

Biomarkers in Neuroblastoma: An Insight into Their Potential Diagnostic and Prognostic Utilities

OPINION STATEMENT

Neuroblastoma (NB) is a heterogeneous solid tumor of the pediatric population that originates from neural crest cells and affects the developing sympathetic nervous system. It is the most common neuroblastic tumor accounting for approximately 10% of all childhood cancers and 10-15% of pediatric tumor mortalities. The outcomes range from spontaneous tumor regression in low-risk groups to metastasis and death even after multimodal therapy in high-risk groups. Hence, the detection of NB at an early stage improves outcomes and provides a better prognosis for patients. Early detection and prognosis of NB depend on specific molecules termed biomarkers which can be tissue-specific or circulating. Certain biomarkers are employed in the classification of NB into different groups to improve the treatment and prognosis, and others can be used as therapeutic targets. Therefore, novel biomarker discovery is essential for the early detection of NB, predicting the course of the disease, and developing new targeted treatment strategies. In this review, we aim to summarize the literature pertinent to some important biomarkers of NB and discuss the prognostic role of these biomarkers as well as their potential role in targeted therapy.

The Role of Neurodevelopmental Pathways in Brain Tumors

Disruptions to developmental cell signaling pathways and transcriptional cascades have been implicated in tumor initiation, maintenance and progression. Resurgence of aberrant neurodevelopmental programs in the context of brain tumors highlights the numerous parallels that exist between developmental and oncologic mechanisms. A deeper understanding of how dysregulated developmental factors contribute to brain tumor oncogenesis and disease progression will help to identify potential therapeutic targets for these malignancies. In this review, we summarize the current literature concerning developmental signaling cascades and neurodevelopmentally-regulated transcriptional programs. We also examine their respective contributions towards tumor initiation, maintenance, and progression in both pediatric and adult brain tumors and highlight relevant differentiation therapies and putative candidates for prospective treatments.

Differentiating Neuroblastoma: A Systematic Review of the Retinoic Acid, Its Derivatives, and Synergistic Interactions

A neuroblastoma (NB) is a solid paediatric tumour arising from undifferentiated neuronal cells. Despite the recent advances in disease management and treatment, it remains one of the leading causes of childhood cancer deaths, thereby necessitating the development of new therapeutic agents and regimens. Retinoic acid (RA), a vitamin A derivative, is a promising agent that can induce differentiation in NB cells. Its isoform, 13-cis RA or isotretinoin, is used in NB therapy; however, its effectiveness is limited to treating a minimal residual disease as maintenance therapy. As such, research focuses on RA derivatives that might increase the anti-NB action or explores the potential synergy between RA and other classes of drugs, such as cellular processes mediators, epigenetic modifiers, and immune modulators. This review summarises the in vitro, in vivo, and clinical data of RA, its derivatives, and synergising compounds, thereby establishing the most promising RA derivatives and combinations of RA for further investigation.

MYCN Drives a Tumor Immunosuppressive Environment Which Impacts Survival in Neuroblastoma

A wide range of malignancies presents MYCN amplification (MNA) or dysregulation. MYCN is associated with poor prognosis and its over-expression leads to several dysregulations including metabolic reprogramming, mitochondria alteration, and cancer stem cell phenotype. Some hints suggest that MYCN overexpression leads to cancer immune-escape. However, this relationship presents various open questions. Our work investigated in details the relationship of MYCN with the immune system, finding a correlated immune-suppressive phenotype in neuroblastoma (NB) and different cancers where MYCN is up-regulated. We found a downregulated Th1-lymphocytes/M1-Macrophages axis and upregulated Th2-lymphocytes/M2-macrophages in MNA NB patients. Moreover, we unveiled a complex immune network orchestrated by N-Myc and we identified 16 genes modules associated to MNA NB. We also identified a MYCN-associated immune signature that has a prognostic value in NB and recapitulates clinical features. Our signature also discriminates patients with poor survival in non-MNA NB patients where MYCN expression is not discriminative. Finally, we showed that targeted inhibition of MYCN by BGA002 (anti-MYCN antigene PNA) is able to restore NK sensibility in MYCN-expressing NB cells. Overall, our study unveils a MYCN-driven immune network in NB and shows a therapeutic option to restore sensibility to immune cells.

URH49 exports mRNA by remodeling complex formation and mediating the NXF1-dependent pathway

The TREX complex integrates information from nuclear mRNA processing events to ensure the timely export of mRNA to the cytoplasm. In humans, UAP56 and its paralog URH49 form distinct complexes, the TREX complex and the AREX complex, respectively, which cooperatively regulate the expression of a specific set of mRNA species on a genome wide scale. The difference in the complex formation between UAP56 and URH49 are thought to play a critical role in the regulation of target mRNAs. To date, the underlying mechanism remains poorly understood. Here we characterize the formation of the TREX complex and the AREX complex. In the ATP depleted condition, UAP56 formed an Apo-TREX complex containing the THO subcomplex but not ALYREF and CIP29. URH49 formed an Apo-AREX complex containing CIP29 but not ALYREF and the THO subcomplex. However, with the addition of ATP, both the Apo-TREX complex and the Apo-AREX complex were remodeled to highly similar ATP-TREX complex containing the THO subcomplex, ALYREF and CIP29. The knockdown of URH49 caused a reduction in its target mRNAs and a cytokinesis failure. Similarly, cytokinesis abnormality was observed in CIP29 knockdown cells, suggesting that CIP29 belongs to the URH49 regulated mRNA export pathway. Lastly, we confirmed that the export of mRNA in URH49-dependent pathway is achieved by NXF1, which is also observed in UAP56-dependent pathway. Our studies propose an mRNA export model that the mRNA selectivity depends on the Apo-form TREX/AREX complex, which is remodeled to the highly similar ATP-form complex upon ATP loading, and integrated to NXF1.

Comparative Analysis of Putative Prognostic and Predictive Markers in Neuroblastomas: High Expression of PBX1 Is Associated With a Poor Response to Induction Therapy

The survival rate for patients with high-risk neuroblastomas remains poor despite new improvements in available therapeutic modalities. A detailed understanding of the mechanisms underlying clinical responses to multimodal treatment is one of the important aspects that may provide precision in the prediction of a patient's clinical outcome. Our study was designed as a detailed comparative analysis of five selected proteins (DDX39A, HMGA1, HOXC9, NF1, and PBX1) in one cohort of patients using the same methodical approaches. These proteins were already reported separately as related to the resistance or sensitivity to retinoids and as useful prognostic markers of survival probability. In the cohort of 19 patients suffering from high-risk neuroblastomas, we analyzed initial immunohistochemistry samples obtained by diagnostic biopsy and post-induction samples taken after the end of induction therapy. The expression of DDX39A, HMGA1, HOXC9, and NF1 showed varied patterns with almost no differences between responders and non-responders. Nevertheless, we found very interesting results for PBX1: non-responders had significantly higher expression levels of this protein in the initial tumor samples when compared with responders; this expression pattern changed inversely in the post-induction samples, and this change was also statistically significant. Moreover, our results from survival analyses reveal the prognostic value of PBX1, NF1, and HOXC9 expression in neuroblastoma tissue. In addition to the prognostic importance of PBX1, NF1, and HOXC9 proteins, our results demonstrated that PBX1 could be used for the prediction of the clinical response to induction chemotherapy in patients suffering from high-risk neuroblastoma.