[1097] Hypoxia Potentiates the Inverse Relationship between Resistance to Cisplatin and Paclitaxel in Ovarian Cancer Cell Lines.

Lynda M McEvoy, Sharon A O'Toole, Cathy D Spillane, Cara M Martin, Orla Sheils, John J O'Leary. Trinity College Dublin, Ireland

Background: Long term survival for ovarian cancer is poor (<30%). Patients undergo debulking surgery followed by platinum-taxane based chemotherapy. Most patients respond well initially, however relapse with chemoresistance is frequent. Tumour hypoxia is a factor in chemoresistance via HIF-1 (hypoxia inducible factor-1) pathway activation. Recent reports indicate an inverse relationship between resistance to cisplatin and paclitaxel across a variety of tumour cell lines. This study aimed to examine whether hypoxia could play a role in this inverse relationship in two ovarian cancer cell lines, A2780 and its cisplatin-resistant derivative, A2780cis.
Design: Cell lines were grown in RPMI 1640 media (10% FBS, 1mM glutamax and 1% penicillin/streptomycin) at 37°C, 5% CO₂. Hypoxic exposure was carried out in an Invivo hypoxic chamber at 0.5% O₂. Drug resistance following hypoxic exposure was determined using MTT assays. Dose response curves, IC₅₀ values and Student t-test values were determined by GraphPad software. Experiments were performed in triplicate with significance at p<0.05.
Results: A2780cis were 5-fold more resistant to cisplatin than A2780s (IC₅₀ 10μM vs. 2µM, p<0.001). Conversely A2780cis were more than 10-fold more sensitive to paclitaxel than A2780s (IC₅₀ 250pM vs. 3.4nM, p<0.01). Exposure to acute hypoxia (4 h) prior to drug treatment significantly increased resistance to cisplatin in both cell lines. However, acute hypoxia before paclitaxel treatment increased sensitivity to the drug in A2780s, while increasing resistance in A2780cis. Chronic hypoxia (5 days) before treatment increased sensitivity to both cisplatin and paclitaxel in A2780s.

Table 1: IC₅₀ values and fold-changes relative to normoxia for cisplatin and paclitaxel when A2780 and A2780cis cells were exposed to hypoxia prior to drug treatment.

Cell Line	Acute Hypoxia Before Drug Treatment	Chronic Hypoxia Before Drug Treamtent	Cisplatin IC50 (fold change)	Paclitaxel IC50 (fold change)
A2780	+	-	2.9μM (1.6)**	1nM (0.3)*
A2780	-	+	1.2μM (0.6)*	765pM (0.2)**
A2780cis	+	-	14μM (1.35)**	1.9nM (7.6)**
A2780cis	-	+	10.9μM (1.04)	600pM (2.4)

*p<0.05 **p<0.01


Conclusions: A2780 and A2780cis have an inverse relationship between resistance to cisplatin and paclitaxel. This relationship can be further potentiated by exposing the cells to hypoxia prior to drug treatment. Genes involved in this process may include HIF-1, p53 and BRCA; known to play a role in cisplatin and paclitaxel resistance whilst also regulated by hypoxia.
Category: Gynecologic & Obstetrics

Tuesday, March 1, 2011 1:00 PM

Poster Session IV # 107, Tuesday Afternoon