ROR1- A biomarker for chemoresistance in ovarian cancer.


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Eamaan Syed1,Frank Hills1,Britta Stordal1
1Middlesex University

Abstract

Background

Ovarian cancer has one of the highest mortality rates among female reproductive system related cancers. The standard treatment involves cytoreductive surgery followed by chemotherapy. Carboplatin, a platinum-based DNA damaging agent, is the chemotherapeutic drug of choice for treatment. However, most patients relapse with a more chemo-resistant form of the disease. Platinum resistance is both multifactorial and complicated. A novel biomarker; ROR1 was identified which can potentially predict platinum resistance or sensitivity

Method

Four cell lines; HEY, SKOV-3, OAW42 and OVCAR-3 were selected and their resistance profiles to cisplatin was determined. A gene expression assay (qPCR) and sandwich ELISA were carried out to investigate expression levels of the ROR1 in response to platinum-based drug treatments for each cell line. Immunocytochemistry was carried out to determine the localization of ROR1. Knockdown experiments were then carried out to study its effects on chemo-resistance.

Results

The HEY cell line was the most resistant to cisplatin (p<0.05) and OVCAR-3 cell line was the most sensitive (p<0.005). A strong correlation between chemo-resistance and ROR1 expression was also established (r= 0.99, p= 0.0051) .The cisplatin resistant (HEY) cell line displayed the highest ROR1 protein expression while the sensitive (OVCAR-3) cell line had the lowest. Immunocytochemistry also revealed similar patterns with HEY cells showing the highest ROR1 expression.  Gene expression assays of drug-treated cells showed decreasing mRNA levels of ROR1. However, in untreated cells OVCAR-3 cells showed a 2.3 fold change increase in mRNA levels of ROR1.  Mesenchymal marker (Vimentin) was also expressed in the HEY cells while there was no expression of the epithelial markers.  Knockdown effects of ROR1 and ROR2 in resistant (HEY) and sensitive (OVCAR-3) cell lines will be presented

Conclusion

ROR1 is a promising chemo-resistant biomarker and will be further validated in tissue microarrays.