Evaluation of Ki-67 as prognostic factor for pediatric neuroblastoma and the possibility of molecular-targeted drugs with VEGF and PDGFR

BACKGROUND

Neuroblastoma (NB) is a pediatric malignant solid tumor characterized as refractory cancer with poor prognosis. The Mitosis-Karyorrhexis Index (MKI) is a prognostic factor but is prone to observer bias. The usefulness of MKI with Ki-67, as a marker of malignancy, was investigated. The efficacy of molecular-targeted therapeutic agents with fewer side effects in tumors has been studied. Molecular-targeted therapy targets include vascular endothelial growth factor (VEGF), involved in tumor angiogenesis; c-Kit, receptor of Kit/stem cells involved in tumor growth, vasculature, and lymphangiogenesis; platelet-derived growth factor receptor (PDGFR); and B-Raf proto-oncogene, serine/threonine kinase (BRAF), involved in the RAS protein-mediated mitogen-activated protein kinase pathway. Therefore, expression profiles of these factors and growth inhibitory effects of molecular-targeted drugs against NB were investigated.

METHODS

Ten frozen NB tissue samples collected from January 1993 to December 2017 were evaluated immunohistochemically for Ki-67 and VEGF. c-Kit, PDGFR, and BRAF expression levels were evaluated using enzyme-linked immunosorbent assays; relationships between these factors and clinicopathological parameters of NB were analyzed.

RESULTS

Eight patients with NB showed no amplification of MYCN (MYCN proto-oncogene, bHLH transcription factor). There were two cases of ganglioneuroblastoma (GNB). More NB cells were positive for Ki-67 than for GNB cells. VEGF expression was observed in all NB specimens and was stronger in stage IIB and higher. No BRAF or c-Kit activity was observed; PDGFR activity was greater in NB than in GNB (P=0.02).

CONCLUSIONS

Thus, Ki-67 may help evaluate NB malignancy. As the first therapy for NB prevents amplification of MYCN, agents targeting PDGFR as well as VGFG can inhibit NB cell proliferation.

Subtype of Neuroblastoma Cells with High KIT Expression Are Dependent on KIT and Its Knockdown Induces Compensatory Activation of Pro-Survival Signaling

Neuroblastoma (NB) is a pediatric cancer with high clinical and molecular heterogeneity, and patients with high-risk tumors have limited treatment options. Receptor tyrosine kinase KIT has been identified as a potential marker of high-risk NB and a promising target for NB treatment. We investigated 19,145 tumor RNA expression and molecular pathway activation profiles for 20 cancer types and detected relatively high levels of KIT expression in NB. Increased KIT expression was associated with activation of cell survival pathways, downregulated apoptosis induction, and cell cycle checkpoint control pathways. KIT knockdown with shRNA encoded by lentiviral vectors in SH-SY5Y cells led to reduced cell proliferation and apoptosis induction up to 50%. Our data suggest that apoptosis induction was caused by mitotic catastrophe, and there was a 2-fold decrease in percentage of G2-M cell cycle phase after KIT knockdown. We found that KIT knockdown in NB cells leads to strong upregulation of other pro-survival growth factor signaling cascades such as EPO, NGF, IL-6, and IGF-1 pathways. NGF, IGF-1 and EPO were able to increase cell proliferation in KIT-depleted cells in an ERK1/2-dependent manner. Overall, we show that KIT is a promising therapeutic target in NB, although such therapy efficiency could be impeded by growth factor signaling activation.

Two Receptors, Two Isoforms, Two Cancers: Comprehensive Analysis of KIT and TrkA Expression in Neuroblastoma and Acute Myeloid Leukemia

Pediatric cancers represent a wide variety of different tumors, though they have unique features that distinguish them from adult cancers. Receptor tyrosine kinases KIT and TrkA functions in AML and NB, respectively, are well-characterized. Though expression of these receptors is found in both tumors, little is known about KIT function in NB and TrkA in AML. By combining gene enrichment analysis with multidimensional scaling we showed that pediatric AMLs with t(8;21) or inv16 and high KIT expression levels stand out from other AML subtypes as they share prominent transcriptomic features exclusively with KIT-overexpressing NBs. We showed that AML cell lines had a predominant expression of an alternative TrkAIII isoform, which reportedly has oncogenic features, while NB cell lines had dominating TrkAI-II isoforms. NB cells, on the other hand, had an abnormal ratio of KIT isoforms as opposed to AML cells. Both SCF and NGF exerted protective action against doxorubicin and cytarabine for t(8;21) AML and NB cells. We identified several gene sets both unique and common for pediatric AML and NB, and this expression is associated with KIT or TrkA levels. NMU, DUSP4, RET, SUSD5, NOS1, and GABRA5 genes are differentially expressed in NBs with high KIT expression and are associated with poor survival in NB. We identified HOXA10, BAG3, and MARCKS genes that are connected with TrkA expression and are marker genes of poor outcome in AML. We also report that SLC18A2, PLXNC1, and MRPL33 gene expression is associated with TrkA or KIT expression levels in both AML and NB, and these genes have a prognostic value for both cancers. Thus, we have provided a comprehensive characterization of TrkA and KIT expression along with the oncogenic signatures of these genes across two pediatric tumors.

Neuroblastoma Origin and Therapeutic Targets for Immunotherapy

Neuroblastoma is a pediatric solid cancer of heterogeneous clinical behavior. The unique features of this type of cancer frequently hamper the process of determining clinical presentation and predicting therapy effectiveness. The tumor can spontaneously regress without treatment or actively develop and give rise to metastases despite aggressive multimodal therapy. In recent years, immunotherapy has become one of the most promising approaches to the treatment of neuroblastoma. Still, only one drug for targeted immunotherapy of neuroblastoma, chimeric monoclonal GD2-specific antibodies, is used in the clinic today, and its application has significant limitations. In this regard, the development of effective and safe GD2-targeted immunotherapies and analysis of other potential molecular targets for the treatment of neuroblastoma represents an important and topical task. The review summarizes biological characteristics of the origin and development of neuroblastoma and outlines molecular markers of neuroblastoma and modern immunotherapy approaches directed towards these markers.