Aurora Kinase B Expression, Its Regulation and Therapeutic Targeting in Human Retinoblastoma

Abstract

Aurora kinase B (AURKB) plays a pivotal role in the regulation of mitosis and is gaining prominence as a therapeutic target in cancers; however, the role of AURKB in retinoblastoma (RB) has not been studied. The purpose of this study was to determine if AURKB plays a role in RB, how its expression is regulated, and whether it could be specifically targeted. METHODS. The protein expression of AURKB was determined using immunohistochemistry in human RB patient specimens and immunoblotting in cell lines. Pharmacological inhibition and shRNA-mediated knockdown were used to understand the role of AURKB in cell viability, apoptosis, and cell cycle distribution. Cell viability in response to AURKB inhibition was also assessed in enucleated RB specimens. Immunoblotting was employed to determine the protein levels of phospho-histone H3, p53, p21, and MYCN. Chromatin immunoprecipitation-qPCR was performed to verify the binding of MYCN on the promoter region of AURKB. RESULTS. The expression of AURKB was found to be markedly elevated in human RB tissues, and the overexpression significantly correlated with optic nerve and anterior chamber invasion. Targeting AURKB with small-molecule inhibitors and shRNAs resulted in reduced cell survival and increased apoptosis and cell cycle arrest at the G2/M phase. More importantly, primary RB specimens showed decreased cell viability in response to pharmacological AURKB inhibition. Additional studies have demonstrated that the MYCN oncogene regulates the expression of AURKB in RB. CONCLUSIONS. AURKB is overexpressed in RB, and targeting it could serve as a novel therapeutic strategy to restrict tumor cell growth.

The Oncogene MYCN Modulates Glycolytic and Invasive Genes to Enhance Cell Viability and Migration in Human Retinoblastoma

“…In agreement with the existing literature, our data suggest that MYCN promotes RB cell growth and metastasis possibly via regulating the genes involved in the ECM modification. MYCN in addition to the regulation of genes involved in glucose metabolism and migration, has been shown to positively modulate the expression of mitotic protein kinase, aurora kinase B in RB [30] and other tumors [61]. Overall, our data along with the published literature show that MYCN may regulate a plethora of cellular functions in RB and other tumors [62].…”

“…Immunoreactivity score was assigned to the tissue specimens showing MYCN expression based on the intensity and extent of expression as described previously [30]. Intensity of MYCN expression was scored as follows; 0 = negative, 1 = low, 2 = medium and 3 = high.…”

“…Next, the expression level of MYCN protein was evaluated in archived RB tissue specimens (n = 58) by immunohistochemical staining and positive staining for MYCN was observed in 36 samples (62.06%). The scoring of IHC slides based on the intensity and extent of positive expression was carried out as described previously [30]. Among the 36 positively stained samples, weak, moderate and strong expression of MYCN was observed in 14 (38.88%), 13 (36.11%) and 9 (25%) specimens, respectively.…”

Integrated analysis of multiple bioinformatics studies to identify microRNA-target gene-transcription factor regulatory networks in retinoblastoma

“…Wu et al showed that AURKB silencing promotes apoptosis of osteosarcoma 143B cells through unc-51 like autophagy activating kinase 1 (ULK1) phosphorylation-induced autophagy (25). Recently, it was revealed that AURKB plays an important role in the regulation of mitosis and is gaining prominence as a therapeutic target in RB (26). A previous study overexpressed TOP2A in bladder urothelial carcinoma (BLCA) and concluded that TOP2A represents a diagnostic marker of BLCA (27).…”

Genome maintenance in retinoblastoma: Implications for therapeutic vulnerabilities (Review)

“…Since AURKA and AURKB contribute to correct mitotic spindle assembly and chromosome segregation (88), these kinases serve critical roles in ensuring mitotic fidelity and their inhibition is lethal for RB1-deficient cancer cells, which upregulate a number of mitotic genes as a result of E2F deregulation (50,51,82). As is the case with other RB1-deficient cancer cells, primary RB tumors display high expression levels of several mitotic genes, including AURKB, polo-like kinase 1 (PLK1), mitotic arrest deficient 2 like 1 and BUB1 mitotic checkpoint serine/threonine kinase (43,44,89,90). Two recent studies have demonstrated that pharmacological inhibition of AURKB and PLK1 in RB cells resulted in cell cycle arrest and increased apoptosis, whereas the effects of the inhibitors on a nontumoral retinal pigment epithelial cell line (ARPE-19) were negligible under identical conditions, which was indicative of a higher sensitivity of RB cells to these inhibitors (89,91).…”