Kuo-Ting Chang

Interrelationships between Cellular Nucleotide Excision Repair, Cisplatin Cytotoxicity, HER-2/neu Gene Expression, and Epidermal Growth Factor Receptor Level in Non-small Cell Lung Cancer Cells

Nucleotide excision repair (NER) is a major repair mechanism for DNA lesions induced by cisplatin. Overexpressions of epidermal growth factor receptor (EGFR) and HER‐2/neu have been reported to affect the sensitivity of certain human cancer cells to cisplatin, presumably by modification of DNA repair activity through interference with NER. Using an in vitro repair assay, we investigated NER activity of cisplatin‐induced DNA lesions in a panel of 16 non‐small cell lung cancer (NSCLC) cell lines. The interrelationships between NER activity, cisplatin sensitivity, HER‐2/neu expression and EGFR level, were also analyzed. The results showed that high NER activity was closely correlated with cisplatin resistance and high levels of HER‐2/neu expression (P < 0.05). Analysis of the relationships between EGFR level and each of the other three parameters revealed no statistically significant correlations (all P values were > 0.05 by Spearman rank correlation), but a trend of association (all the values of proportion of accordance were ≥62.5% by using a 2x2 contingency table). These results suggest that NER activity may play an important role in the cisplatin resistance of NSCLC cells and there may be an association between enhanced NER activity and high levels of p185neu and probably EGFR in NSCLC cells. The finding that high levels of EGFR showed very little influence on the relationship between p185neu and cisplatin resistance suggests that EGFR may be a less crucial factor in modulating the chemoresistance of NSCLC cells when compared with HER‐2/neu.

Aurora kinase inhibitors reveal mechanisms of HURP in nucleation of centrosomal and kinetochore microtubules

Significance In mitosis, microtubules extend and shrink before the bilateral attachment is established. However, which molecules regulate this activity for spindle formation is not fully elucidated. Using two in-house developed small molecules that target the Aurora kinases, we show that hepatoma up-regulated protein (HURP) is highly dynamic, trafficking between centrosome and kinetochore driven by Aurora A-dependent phosphorylation and protein phosphatase 1/2A-associated dephosphorylation. These compounds demonstrate a spatial hierarchical preference of HURP in the attachment of microtubules extending from the mother to the daughter centrosome. These findings help explain the biology of mitosis and may lead to the development of anticancer compounds. The overexpression of Aurora kinases in multiple tumors makes these kinases appealing targets for the development of anticancer therapies. This study identified two small molecules with a furanopyrimidine core, IBPR001 and IBPR002, that target Aurora kinases and induce a DFG conformation change at the ATP site of Aurora A. Our results demonstrate the high potency of the IBPR compounds in reducing tumorigenesis in a colorectal cancer xenograft model in athymic nude mice. Human hepatoma up-regulated protein (HURP) is a substrate of Aurora kinase A, which plays a crucial role in the stabilization of kinetochore fibers. This study used the IBPR compounds as well as MLN8237, a proven Aurora A inhibitor, as chemical probes to investigate the molecular role of HURP in mitotic spindle formation. These compounds effectively eliminated HURP phosphorylation, thereby revealing the coexistence and continuous cycling of HURP between unphosphorylated and phosphorylated forms that are associated, respectively, with microtubules emanating from centrosomes and kinetochores. Furthermore, these compounds demonstrate a spatial hierarchical preference for HURP in the attachment of microtubules extending from the mother to the daughter centrosome. The finding of inequality in the centrosomal microtubules revealed by these small molecules provides a versatile tool for the discovery of new cell-division molecules for the development of antitumor drugs.