Abstract 2159: Expression of Sp1 and survivin in ovarian cancer specimens: potential novel therapeutic targets in disease treatment

Ovarian cancer (OC) is one of the most common female cancers and is the leading cause of death from gynecologic malignancies. Although, cisplatin is the front-line chemotherapeutic option for OC, its success is compromised due to dose-limiting toxicity and acquired resistance by tumor cells. Specificity protein 1 (Sp1) is a transcription factor that is over-expressed in several cancers and is inversely associated with survival. Survivin, a member of IAP family, is known to cause resistance to chemo- and radiation therapy. Studies from our laboratories have shown that the NSAID, tolfenamic acid (TA), targets Sp1 protein and inhibits expression of survivin in various cancer models. Our primary objective was to evaluate the expression of Sp1 and survivin in OC patients’ specimens and target these candidates using TA for enhancing the cisplatin response. Expression of Sp1 and survivin in clinical specimens was determined by qPCR and Western blots. qPCR showed increased expression of survivin (∼5-fold) and Sp1 (∼2-fold) in tumor samples. Western blot also revealed over-expression of both Sp1 (>2.6-fold) and survivin (>100-fold). OC cell lines (ES2, OVCAR-3) were used to determine the anti-proliferative response to cisplatin and TA. TA and cisplatin showed a dose- and time-dependent inhibition of cell viability in OC cell lines [TA (50 ÂμM) caused 50% (ES2) and 40% (OVCAR-3) growth inhibition and cisplatin (5 ÂμM) caused 60% and 40% inhibition at 48 h post-treatment]. Combination treatment using optimized doses of TA (50 ÂμM) and cisplatin (5 ÂμM) resulted in a synergistic response and caused stronger inhibition (ES2: ∼80%, OVCAR-3: >60) compared to single-agent. Increased inhibition of proliferation by the combination of TA and cisplatin was accompanied by cell-cycle arrest, predominantly in the G2/M phase. A significant increase in apoptosis, as determined by Caspase 3/7 activity, annexin-V staining, and PARP cleavage, was also observed in the combination treatment. Cell invasion and migration was assessed using matrigel coated transwell chambers. Compared to TA or cisplatin treatment alone, their combination significantly inhibited ES2 cell invasion. Analysis of ES2 cells by global proteomic profiling indicated that the combination treatment upregulated proteins associated with oxidative phosphorylation, apoptosis, and electron transport chain; and down-regulated cytoplasmic ribosomal proteins, translational factors, and proteins involved in DNA damage re