Transcriptional co-activator with PDZ-binding motif overexpression promotes cell proliferation and transcriptional co-activator with PDZ-binding motif deficiency induces cell cycle arrest in neuroblastoma

The Hippo Signaling Pathway in Cancer: A Cell Cycle Perspective

Simple Summary

Cancer is increasingly viewed as a cell cycle disease in that the dysregulation of the cell cycle machinery is a common feature in cancer. The Hippo signaling pathway consists of a core kinase cascade as well as extended regulators, which together control organ size and tissue homeostasis. The aberrant expression of cell cycle regulators and/or Hippo pathway components contributes to cancer development, and for this reason, we specifically focus on delineating the roles of the Hippo pathway in the cell cycle. Improving our understanding of the Hippo pathway from a cell cycle perspective could be used as a powerful weapon in the cancer battlefield.

Abstract

Cell cycle progression is an elaborate process that requires stringent control for normal cellular function. Defects in cell cycle control, however, contribute to genomic instability and have become a characteristic phenomenon in cancers. Over the years, advancement in the understanding of disrupted cell cycle regulation in tumors has led to the development of powerful anti-cancer drugs. Therefore, an in-depth exploration of cell cycle dysregulation in cancers could provide therapeutic avenues for cancer treatment. The Hippo pathway is an evolutionarily conserved regulator network that controls organ size, and its dysregulation is implicated in various types of cancers. Although the role of the Hippo pathway in oncogenesis has been widely investigated, its role in cell cycle regulation has not been comprehensively scrutinized. Here, we specifically focus on delineating the involvement of the Hippo pathway in cell cycle regulation. To that end, we first compare the structural as well as functional conservation of the core Hippo pathway in yeasts, flies, and mammals. Then, we detail the multi-faceted aspects in which the core components of the mammalian Hippo pathway and their regulators affect the cell cycle, particularly with regard to the regulation of E2F activity, the G1 tetraploidy checkpoint, DNA synthesis, DNA damage checkpoint, centrosome dynamics, and mitosis. Finally, we briefly discuss how a collective understanding of cell cycle regulation and the Hippo pathway could be weaponized in combating cancer.

A New Player in Neuroblastoma: YAP and Its Role in the Neuroblastoma Microenvironment

Neuroblastoma is the most common extra-cranial pediatric solid tumor that accounts for more than 15% of childhood cancer-related deaths. High risk neuroblastomas that recur during or after intense multimodal therapy have a <5% chance at a second sustained remission or cure. The solid tumor microenvironment (TME) has been increasingly recognized to play a critical role in cancer progression and resistance to therapy, including in neuroblastoma. The Yes-Associated Protein (YAP) in the Hippo pathway can regulate cancer proliferation, tumor initiation, and therapy response in many cancer types and as such, its role in the TME has gained interest. In this review, we focus on YAP and its role in neuroblastoma and further describe its demonstrated and potential effects on the neuroblastoma TME. We also discuss the therapeutic strategies for inhibiting YAP in neuroblastoma.

TP53BP2 decreases cell proliferation and induces autophagy in neuroblastoma cell lines

Tumor protein p53-binding protein 2 (TP53BP2), a member of the apoptosis-stimulating protein of p53 (ASPP) family, has previously been reported to be associated with tumor development. However, to the best of our knowledge, the role of TP53BP2 in neuroblastoma has not been elucidated. The aim of the present study was to investigate the function of TP53BP2 in the proliferation and autophagy of neuroblastoma. An expression vector that expresses TP53BP2-specific short hairpin RNA (shTP53BP2) was used for the experimental group and green fluorescent protein short hairpin RNA was used as a control. Cell proliferation was measured using MTT assays, self-renewal was evaluated using soft agar assays, light chain 3 (LC3) II expression level was examined by western blot and immunofluorescence analysis, and the autophagy-related 3 homolog (ATG3), autophagy-related 5 homolog (ATG5) and autophagy-related 9 homolog (ATG7) expression levels were examined using the reverse transcription-quantitative polymerase chain reaction (RT-qPCR). A genomics analysis revealed that TP53BP2 expression was associated with the survival of patients with neuroblastoma. Western blot and RT-qPCR assays indicated that TP53BP2 could be implicated in neuroblastoma, as the proliferative ability of the experimental group decreased compared with that of the control group (P<0.001) and the expression levels of genes associated with autophagy, including LC3 II. ATG3, ATG5 and ATG7, increased in the experimental group. In conclusion, an increased expression of TP53BP2 in patients with neuroblastoma may be associated with poor survival and shTP53BP2 may decrease the proliferative abilities of neuroblastoma cells, including BE(2)C and SK-N-DZ cell lines. In addition, the LC3 II, ATG3, ATG5 and ATG7 expression levels increased and were associated with increased rates of autophagy following upregulation of TP53BP2.