The role of DNA damage and repair pathways in the efficacy of oncolytic adenoviruses in ovarian cancer
Lead Research Organisation:
Queen Mary University of London
Department Name: Barts Cancer Institute
Abstract
I am trying to develop new treatments for ovarian cancer using oncolytic viruses. These are common viruses that are altered so that they destroy cancer cells by multiplying within them, but cannot multiply within normal human tissues. The virus I am studying, dl922-947, is derived from an adenovirus, which is very common in the UK population and, under most circumstances, causes only a flu-like illness, even in its natural, active state.
Previous research has shown that dl922-947 has considerable potential as a treatment for ovarian cancer. We hope to commence a trial in women with recurrent ovarian cancer soon. We also wish to improve the anti-cancer effect of dl922-947.
Some cancer cells do not respond well to dl922-947. Recent results suggest that dl922-947 damages the DNA within cancer cells that it infects. Cells that are able to repair the damage efficiently are resistant to the effects of dl922-947, whilst those that cannot repair the damage are rapidly killed. I now wish to understand how the damage occurs and which mechanisms within cells determine whether the damage can be repaired. If we can prevent cancer cells from repairing the DNA, this will improve the effectiveness of viruses. Ultimately, this research could lead to better treatments for women with ovarian cancer.
Previous research has shown that dl922-947 has considerable potential as a treatment for ovarian cancer. We hope to commence a trial in women with recurrent ovarian cancer soon. We also wish to improve the anti-cancer effect of dl922-947.
Some cancer cells do not respond well to dl922-947. Recent results suggest that dl922-947 damages the DNA within cancer cells that it infects. Cells that are able to repair the damage efficiently are resistant to the effects of dl922-947, whilst those that cannot repair the damage are rapidly killed. I now wish to understand how the damage occurs and which mechanisms within cells determine whether the damage can be repaired. If we can prevent cancer cells from repairing the DNA, this will improve the effectiveness of viruses. Ultimately, this research could lead to better treatments for women with ovarian cancer.
Technical Summary
Background
Oncolytic adenoviruses are promising new treatments for ovarian cancer. The E1A-CR2 deleted vector dl922-947 replicates selectively in tumour cells with abnormal Rb pathway function, a finding seen in 90% of human cancers. Results have shown that dl922-947 has considerable activity in ovarian cancer. However, ovarian cancer cell sensitivity varies greatly, even in cells with similar infectivity. Further development of oncolytic adenoviruses depends upon identification of points in the virus life cycle that can be manipulated for therapeutic benefit. Sensitive, but not resistant, ovarian cancer cells activate cdc25A and over-replicate genomic DNA following infection, creating extensive double-strand breaks (DSBs). Knockdown of ATR and inhibition of Chk1 increase genomic DNA damage, inhibit Homologous Recombination (HR) repair and improve adenovirus efficacy both in vitro and in vivo.
Preliminary data
My preliminary data from a panel of ovarian cancer cell lines indicate that cell sensitivity to both dl922-947 and wild-type adenovirus correlates closely with the competence of Homologous Recombination pathways. This suggests that cancer cells that generate a large number of unrepaired DSBs upon infection will be more sensitive to adenovirus-induced death.
Aims and objectives:
1. To investigate the role of DNA damage repair mechanisms, specifically Homologous Recombination, in the efficacy of oncolytic adenovirus in ovarian cancer.
2. To investigate how DNA damage repair responses can be manipulated to improve viral efficacy in ovarian cancer.
Methodology
I will explore the role of HR in the biology of oncolytic adenoviruses using matched BRCA2 mutant and wild-type cancer cell pairs. Virus replication, protein expression and cell killing will also be assessed in a panel of established ovarian cancer cell lines, primary ascitic cells from patients and immortalised ovarian surface epithelial cells following siRNA-mediated knockdown of Rad51 and BRCA1 and BRCA2. The role of other DNA repair pathways in the efficacy of dl922-947 will be investigated using a high throughput siRNA screen using an siRNA library targeting 230 known and putative DNA repair proteins.
Clinical applications
This project will aid patient selection for clinical trials of oncolytic adenoviruses. Furthermore, greater understanding of cellular responses to virus infection and the role of these responses in viral efficacy will improve clinical responses, for example by combining adenoviruses with inhibitors of DNA damage repair, which are already entering clinical trials.
Oncolytic adenoviruses are promising new treatments for ovarian cancer. The E1A-CR2 deleted vector dl922-947 replicates selectively in tumour cells with abnormal Rb pathway function, a finding seen in 90% of human cancers. Results have shown that dl922-947 has considerable activity in ovarian cancer. However, ovarian cancer cell sensitivity varies greatly, even in cells with similar infectivity. Further development of oncolytic adenoviruses depends upon identification of points in the virus life cycle that can be manipulated for therapeutic benefit. Sensitive, but not resistant, ovarian cancer cells activate cdc25A and over-replicate genomic DNA following infection, creating extensive double-strand breaks (DSBs). Knockdown of ATR and inhibition of Chk1 increase genomic DNA damage, inhibit Homologous Recombination (HR) repair and improve adenovirus efficacy both in vitro and in vivo.
Preliminary data
My preliminary data from a panel of ovarian cancer cell lines indicate that cell sensitivity to both dl922-947 and wild-type adenovirus correlates closely with the competence of Homologous Recombination pathways. This suggests that cancer cells that generate a large number of unrepaired DSBs upon infection will be more sensitive to adenovirus-induced death.
Aims and objectives:
1. To investigate the role of DNA damage repair mechanisms, specifically Homologous Recombination, in the efficacy of oncolytic adenovirus in ovarian cancer.
2. To investigate how DNA damage repair responses can be manipulated to improve viral efficacy in ovarian cancer.
Methodology
I will explore the role of HR in the biology of oncolytic adenoviruses using matched BRCA2 mutant and wild-type cancer cell pairs. Virus replication, protein expression and cell killing will also be assessed in a panel of established ovarian cancer cell lines, primary ascitic cells from patients and immortalised ovarian surface epithelial cells following siRNA-mediated knockdown of Rad51 and BRCA1 and BRCA2. The role of other DNA repair pathways in the efficacy of dl922-947 will be investigated using a high throughput siRNA screen using an siRNA library targeting 230 known and putative DNA repair proteins.
Clinical applications
This project will aid patient selection for clinical trials of oncolytic adenoviruses. Furthermore, greater understanding of cellular responses to virus infection and the role of these responses in viral efficacy will improve clinical responses, for example by combining adenoviruses with inhibitors of DNA damage repair, which are already entering clinical trials.