Abstract 3554: A short ASPM splicing variant but not the full length variant as a molecular target in hepatocellular carcinoma
Authors: Pan Hung-Wei , Chen Yu-Chia 
Published: August 2015

Most solid tumor cells are aneuploidy and various cancer cell lines show “chromosomal instability” (CIN), meaning that they frequently lose and gain whole chromosomes during divisions. The cause of these observed chromosome imbalances is unknown, but will probably be found in defects in the processes that control chromosome segregation during mitosis. The clinical importance of CIN is underscored by its association with poor patient outcome in multiple cancer types. However, despite the prevalence and the clinical relevance of CIN, a consistent basis for how it is generated at the molecular level is poorly understood.

ASPM gene is the human orthologue of the Drosophila abnormal spindle (asp) protein associates with centrosomes and the most commonly mutated gene of autosomal recessive primary microcephaly. The homozygous semi-lethal mutation of Drosophila asp causes abnormal spindles, frequent polyploid cells and cytokinesis failure, leading to arrest of neuroblasts in metaphase and larval-pupal lethality. Centrosome defects cause chromosome misaggregation and aneuploidy, leading to genetic instability, a major driving force for malignant transformation and tumor progression. In our previous work, ASPM was shown often overexpressed in human HCC and associated with high serum AFP, bigger tumor, high-grade, higher- vascular invasion stage, and lower 5-year survival, early tumor recurrence and poor prognosis. We assessed the role of ASPM in ensuring the balance of genomic instability and cancer invasion in liver cancer.

Using the in vitro invasion-selection cell model, increased ASPM mRNA was corresponded to the invasive potential. Moreover, knock down of ASPM, using RNAi oligos, caused in tested cell lines a rising impaired chromosomal instability resulting in multi-nucleation, bi-nucleus and micronucleus formation of liver cancer cells. After ASPM RNAi treatment, an image-cytometry analysis revealed a correlation between the expression of genes related to chromosomal segregation such as CEP55 in mRNA, TPX2, Aurora A, and cyclin B1 in protein level and increasing 4N DNA content fraction of testing cells, indicating mitotic phase progression failure and loss the balance of genomic instability. In addition, Knock down of ASPM resulted in reduction of tumor cell growth, cell cycle progression and invasion in HCC cell lines. Surprisingly, theses cell functions inhibition were only come with downregulation of ASPM short splicing variant (variant #1) after a particular ASPM RNAi oligos transfection.

In conclusion, downregulation of ASPM short splicing variant suppressed tumor cell growth, delayed cell cycle progression and the formation of tumors in vitro, and led to chromosomal instability in liver cancer cells. Mechanistic analysis showed that the knockdown of ASPM short splicing variant reduced the expression of genes related to chromosomal segregation.

Citation Format: Hung-Wei Pan, Yu-Chia Chen. A short ASPM splicing variant but not the full length variant as a molecular target in hepatocellular carcinoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3554. doi:10.1158/1538-7445.AM2015-3554