Abstract
Background
Mutations in the Kras proto-oncogene are found in 40%-45% of colorectal cancer (CRC) patients and occur mainly in codon 12 and 13. Kras mutant (MT) CRC tumours are resistant to EGFR mAb therapies. The aim of this study was to identify novel targets whose knock-down is synthetically lethal with Kras mutation in CRC models.
Method
Transcriptional profiling (Almac Diagnostics CRC DSA) of primary KrasMT and WT CRC tissues and paired KrasMT and WT CRC xenografts models was performed and Metacore pathway analysis was used to identify individual genes from novel Kras-dependent pathways for incorporation into a primary RNAi screen. Receptor tyrosine kinase array analysis of invasive cell line models was validated by Western blotting. EpHA2 expression in CRC FFPE sections was measured using IHC
Results
Using clinical and in vivo KrasMT/WT CRC samples and public available Kras signatures, we identified 30 signaling pathways and 160 genes associated with KrasMT CRC cancer. An siRNA screen identified a number of novel Kras synthetic lethal target genes with a critical role in EMT and cell adhesion/migration. In particular, down-regulation of members of the EpH/Ephrin family was found to be lethal in KrasMT but not KrasWT cells. In addition EpHA2 silencing resulted in strong increase in apoptosis in KrasMT cells and this was further synergistically enhanced in the presence of chemotherapy treatment. Overexpression of EpHA2 was also identified in our invasive isogenic cell line models and EpHA2 silencing inhibited migration and invasion in a panel of KrasMT cells. Importantly, high EpHA2 mRNA and protein expression were found to be associated with poor overall survival in early stage CRC tissues.
Conclusion
This study demonstrates the utility of microarray expression data and siRNA screens to identify novel Kras synthetic lethal targets and pathways. In addition, we found that EpHA2 is a poor prognostic marker and an important novel target for KrasMT CRC tumours in both the adjuvant and advanced disease setting.
Mutations in the Kras proto-oncogene are found in 40%-45% of colorectal cancer (CRC) patients and occur mainly in codon 12 and 13. Kras mutant (MT) CRC tumours are resistant to EGFR mAb therapies. The aim of this study was to identify novel targets whose knock-down is synthetically lethal with Kras mutation in CRC models.
Method
Transcriptional profiling (Almac Diagnostics CRC DSA) of primary KrasMT and WT CRC tissues and paired KrasMT and WT CRC xenografts models was performed and Metacore pathway analysis was used to identify individual genes from novel Kras-dependent pathways for incorporation into a primary RNAi screen. Receptor tyrosine kinase array analysis of invasive cell line models was validated by Western blotting. EpHA2 expression in CRC FFPE sections was measured using IHC
Results
Using clinical and in vivo KrasMT/WT CRC samples and public available Kras signatures, we identified 30 signaling pathways and 160 genes associated with KrasMT CRC cancer. An siRNA screen identified a number of novel Kras synthetic lethal target genes with a critical role in EMT and cell adhesion/migration. In particular, down-regulation of members of the EpH/Ephrin family was found to be lethal in KrasMT but not KrasWT cells. In addition EpHA2 silencing resulted in strong increase in apoptosis in KrasMT cells and this was further synergistically enhanced in the presence of chemotherapy treatment. Overexpression of EpHA2 was also identified in our invasive isogenic cell line models and EpHA2 silencing inhibited migration and invasion in a panel of KrasMT cells. Importantly, high EpHA2 mRNA and protein expression were found to be associated with poor overall survival in early stage CRC tissues.
Conclusion
This study demonstrates the utility of microarray expression data and siRNA screens to identify novel Kras synthetic lethal targets and pathways. In addition, we found that EpHA2 is a poor prognostic marker and an important novel target for KrasMT CRC tumours in both the adjuvant and advanced disease setting.
| Original language | English |
|---|---|
| Title of host publication | The receptor tyrosine kinase EpHA2 is a poor prognostic marker and a novel target in Kras mutant colorectal cancer |
| Place of Publication | Proffered paper sessions |
| Publisher | National Cancer Research Institute |
| Publication status | Published - Nov 2012 |
