Exploring Molecular Targeted Therapy for Hepatoceccular Carcinoma: Focus on Aurora Kinases
Date Issued
2010
Date
2010
Author(s)
Lin, Zhong-Zhe
Abstract
論文英文簡述 (Abstract in English)
Molecular therapeutics is the most promising field of contemporary cancer treatment modalities. Several molecule-targeted drugs have been used clinically in the treatment of lymphoma, and cancer of the lung, breast, colon, head and neck . Nevertheless, the molecular therapy of hepatocellular carcinoma (HCC), one of the most common fatal cancers in Taiwan, has not yet achieved any significant progress. Previous study indicated that molecular targets of HCC may be specific and different from other epithelial malignancies. Thus, searching for more effectivetherapeutic modalities such as modulating cellular signaling is mandatory for the exploration of molecular therapy in HCC.
One set of mitotic kinases called Aurora kinases, which are thought to be key regulators of chromosome duplication, segregation, and cytokinesis. Are known to play critical roles in the development of a variety of human cancer, including HCC (clarify).There are three members of human Aurora kinase family, including Aurora A, B, and C. Many studies have shown amplification and overexpression of Aurora kinases in various human cancers in vitro and in vivo . The roles of overexpression of these kinases in oncogenesis have also been demonstrated.
Frequent overexpression of Aurora A has been demonstrated in HCC, which plays important role in the tumor progression of HCC. Recent studies have shown that the inhibition of Aurora kinases can block cell proliferation and induce cell death via apoptosis in multiple types of human tumors. Profound repression of tumor growth was also achieved by inhibition of Aurora kinases in vivo. More importantly, clinically applicable inhibitors of Aurora kinases, such as VX-680, are quickly surfacing on the pipelines of key manufacturers. Thus, exploring the potential roles of these agents in the molecular therapy of HCC is both, is both academically and clinically imperative.
Aurora A and Aurora B kinases share a high degree of sequence homology in their catalytic domains, and the overexpression has been identified in many human cancers. Despite their sequence similarity, Aurora A and Aurora B differ in chromosomal gene loci, subcellular localization, cellular functions, and signaling substrates. The enthusiasm of exploring Aurora kinases as anticancer therapeutic targets initially centered on Aurora A. However, recent studies have demonstrated that several Aurora kinase inhibitors exhibit anticancer activity resembling that of Aurora B disruption induced by genetic methods. Therefore, determination of the distinctive roles of Aurora A and Aurora B in carcinogenesis and their individual clinical significance is mandatory.
Part I Preclinical studies of Aurora kinase inhibitor in the treatment
of advanced hepatocellular carcinoma
In mammals, there are three highly related Aurora kinases: Aurora A, B, and C. Overexpressions of Aurora A and Aurora B have been identified in many human cancers. Because of their roles in mitotic control, genomic instability and tumorigenesis, Aurora kinases have attracted much attention as potential cancer therapeutic targets. The inhibition of Aurora A by antisense oligonucleotides was first shown to effectively repress the tumor growth of lymphoma and pancreatic cancer cells. Later on, several Aurora kinase inhibitors were discovered, including VX-680 (MK-0457), ZM447439 , Hesperadin, PHA-680632, AZD1152, and MLN8054. VX-680 was the first Aurora kinase inhibitor showing broad antitumor activity in vitro and in vivo, and the foremost Aurora kinase inhibitor to be studied in clinical trials. Although clinical studies of Aurora kinase inhibitors have already reached phase II trials, their potential application in the treatment of HCC remains to be explored.
We previously demonstrated frequent overexpression of Aurora A kinase, and its correlation with higher tumor grade and more advanced tumor stage in HCC. The unmet medical need for effective HCC treatment prompted us to investigate the therapeutic potential of Aurora kinase inhibitors. In this study, we tested VE-465, an analog of VX-680 with comparable potency in Aurora kinase inhibition, in both in vitro and in vivo HCC models. The results showed that VE-465 effectively inhibited Aurora kinase activity and induced mitotic disturbance, endoreduplication, apoptosis, and growth suppression of HCC. Our observations suggest that VE-465 is a promising therapeutic agent in HCC and deserves further investigation.
The overexpression of Aurora A was associated with high-grade and high-stage tumors, and p53 mutation. These aggressive tumor phenotypes are characteristics of HCC with chromosome instability and imply that overexpression of Aurora kinases contributes to progression in human HCC. Furthermore, we found that overexpression of Aurora A contributed to worse patient survival. Consistently, Sistayanarain et al. reported that Aurora B transcripts were detectable in 12 (71%) out of 17 HCC cases. Okada et al.reported that a novel anticancer substance, MK-615, inhibited growth of HCC cells by suppressing Aurora A kinase activity. These findings indicate that Aurora kinases are potential therapeutic targets in HCC.
In this study, we have demonstrated that VE-465, a novel Aurora kinase inhibitor, is a promising therapeutic agent in HCC. Firstly, we found that VE-465 suppressed tumor cell viability in the tested liver cancer cell lines in a concentration- and time-dependent manner. The IC50 values of VE-465 for Huh-7 and HepG2 were far below the plasma concentrations of VE-465 achievable in mouse models. Secondly, we showed that VE-465repressed the Aurora signaling evidenced by the steady downregulation of histone H3 (Ser10) phosphorylation in Huh-7 and HepG2 cells. Thirdly , VE-465 administration led to the inhibition of Aurora signaling, tumor growth suppression, and apoptosis in animal studies Taken together,these results suggest that Aurora kinases represent potential novel therapeutic targets in HCC.
To better understand the anticancer effects of VE-465, we examined the morphologic changes in mitosis, cell cycle progression, and cell death in VE-465 treated liver cancer cells. VE-465 treatment led to the formation of monopolar spindles and the failure of centrosome maturation in Huh-7 and HepG2, which are remiscent of the functional deficiency of Aurora A. We also observed the detachment of chromosomes from the spindle structures in VE-465 treated HepG2 cells, implying dysregulation of Aurora B function. These mitotic disturbances induced by the inhibition of Aurora kinases may underlie the cytotoxic effects of VE-465 in HCC cells.
Following aberrant mitosis induced by Aurora kinases inhibition, cancer cells may be arrested in a pseudo G1 state controlled by a p53-dependent postmitotic checkpoint. Consistent with this suggestion, we demonstrated that endoreduplication was more readily elicited in the p53-mutated Huh-7 cells (codon 220 mutation) compared with the wild-type p53 HepG2 cells. The p53 function is also regarded as a major determinant of apoptosis induced by Aurora kinase inhibitors, but the regulatory mechanisms remain elusive. We showed that sub-G1 peaks induced by VE-465 in Huh-7 were greater than those in HepG2 cells, which may be at least in part attributed to the loss of p53 checkpoints in Huh-7 cells.
In summary, we demonstrated that VE-465 treatment resulted in profound inhibition of Aurora signaling in liver cancer cells, which led to defective mitosis, cell cycle arrest, endoreduplication, apoptosis, and eventually suppression of cancer cell growth. Our results suggest that VE-465 and probably other small-molecule inhibitors of Aurora kinases are promising in the treatment of HCC. Further clinical studies are needed to validate the therapeutic potential of Aurora kinase inhibitors in HCC patients.
Part II Exploring the clinicopathologic significances of Aurora kinases
overexpression in hepatocellular carcinoma
We previously showed that Aurora A was overexpressed in 137 (61%) of 224 human HCCs and that the overexpression of Aurora A was associated with aggressive tumor characteristics and poor prognosis of patients. Furthermore, we demonstrated that VE-465, a novel pan-Aurora kinase inhibitor, had anticancer effects in preclinical experimental models of human HCC. These findings indicated that Aurora kinases may be important biomarkers and potential therapeutic targets in HCC.
There are three highly related Aurora kinases in mammals, Aurora A, B, and C. Aurora A and Aurora B share a high degree of sequence homology in their catalytic domains, and their overexpressions have been identified in many human cancers. Despite their sequence similarity, Aurora A and Aurora B differ in chromosomal gene loci, subcellular localization, cellular functions, and signaling substrates. The Aurora A kinase gene is localized to chromosome 20q13.2, and Aurora B kinase to chromosome 17p13.1. (Repeatitive)Aurora A kinase protein is localized in the centrosome and spindle poles and plays important roles in centrosome maturation and spindle assembly. Aurora B kinase, which is a chromosome passenger protein localized in the centromeres during early mitosis and then at the spindle midzone after anaphase, is essential for chromosome biorientation, function of the spindle assembly checkpoint, and cytokinesis. The enthusiasm of exploring Aurora kinases as anticancer therapeutic targets initially centered on Aurora A, but recent studies have demonstrated that several Aurora kinase inhibitors exhibit anticancer activity resembling that of Aurora B disruption induced by genetic methods. Therefore, determination of the distinctive roles in carcinogenesis and individual clinical significance of Aurora A and Aurora B is mandatory. The aims of this study were to elucidate the clinicopathologic significance of Aurora B expression and Aurora A expression in HCC and to correlate their expression with p53 and β-catenin mutations, the two most frequently mutated genes in HCC.
Despite the sequence homology and common association with mitotic regulatory events, Aurora A and Aurora B differ in the subcellular localization and signaling substrates , and hence possess essentially distinctthe functions. We have reported that Aurora A is highly expressed in HCC and that the overexpression is closely associated with aggressive tumor phenotypes and worse patient prognosis. But the clinicopathologic significance of Aurora B in HCC progression remains to be clarified. In this study, we demonstrated that overexpressions of Aurora A and Aurora B were detected in 63% and 61% of 160 surgically resected, primary unifocal HCCs, respectively. By multivariate analyses, we showed that Aurora B overexpression was associated with high-stage (stages IIIA, IIIB, and IV) HCCs, which exhibit vascular invasion and various extents of intrahepatic spread (OR, 7.439; P = 0.0003). These findings suggest that overexpression of Aurora B is associated with tumor invasion and intrahepatic metastasis of HCC, as having been shown in Aurora A.Our findings suggest that Aurora B overexpression serves as a useful marker predicting ETR and hence poor prognosis.
In the present study, we showed AZD1152-HQPA, an Aurora B selective inhibitor, exerted anticancer effects in HCC cells. AZD1152-HQPA treatment resulted in profound inhibition of Aurora B signaling, which in turn led to cell cycle disturbance, apoptosis, and growth suppression in HCC cells. Our results suggest that Aurora B selective inhibitors are potential drugs for HCC treatment, confirming the observation that AZD1152 is a novel promising therapeutic approach for HCC.
We previously demonstrated that Aurora B overexpression correlated well with higher histology grade and more advanced stage of hepatocellular carcinoma (HCC). In this part of study, we sought to analyze the association between Aurora B overexpression and vascular invasion/metastasis of HCC, as well as the potential of AZD1152, a novel and selective Aurora B kinase inhibitor in preventing vascular invasion and metastasis of HCC. Univariate analysis showed that vascular invasion and metastasis were both associated with younger age (
Subjects
hepatocellular carcinoma
molecular targeted therapy
Aurora kinase
SDGs
Type
thesis
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