Abstract
BackgroundLate stage Ovarian Cancer is essentially incurable primarily due to late diagnosis and its inherent heterogeneity. Single agent treatments are inadequate and generally lead to severe side effects at therapeutic doses. It is crucial to develop clinically relevant novel combination regimens involving synergistic modalities that target a wider repertoire of cells and lead to lowered individual doses. Stemming from this premise, this is the first report of two- and three-way synergies between Adenovirus-mediated Purine Nucleoside Phosphorylase based gene directed enzyme prodrug therapy (PNP-GDEPT), docetaxel and/or carboplatin in multidrug-resistant ovarian cancer cells.MethodsThe effects of PNP-GDEPT on different cellular processes were determined using Shotgun Proteomics analyses. The in vitro cell growth inhibition in differentially treated drug resistant human ovarian cancer cell lines was established using a cell-viability assay. The extent of synergy, additivity, or antagonism between treatments was evaluated using CalcuSyn statistical analyses. The involvement of apoptosis and implicated proteins in effects of different treatments was established using flow cytometry based detection of M30 (an early marker of apoptosis), cell cycle analyses and finally western blot based analyses.ResultsEfficacy of the trimodal treatment was significantly greater than that achieved with bimodal- or individual treatments with potential for 10-50 fold dose reduction compared to that required for individual treatments. Of note was the marked enhancement in apoptosis that specifically accompanied the combinations that included PNP-GDEPT and accordingly correlated with a shift in the expression of anti- and pro-apoptotic proteins. PNP-GDEPT mediated enhancement of apoptosis was reinforced by cell cycle analyses. Proteomic analyses of PNP-GDEPT treated cells indicated a dowregulation of proteins involved in oncogenesis or cancer drug resistance in treated cells with accompanying upregulation of apoptotic- and tumour- suppressor proteins.ConclusionInclusion of PNP-GDEPT in regular chemotherapy regimens can lead to significant enhancement of the cancer cell susceptibility to the combined treatment. Overall, these data will underpin the development of regimens that can benefit patients with late stage ovarian cancer leading to significantly improved efficacy and increased quality of life.
Highlights
Late stage Ovarian Cancer is essentially incurable primarily due to late diagnosis and its inherent heterogeneity
To explore the potential synergies between Purine nucleoside phosphorylase (PNP)-Gene directed enzyme prodrug therapy (GDEPT), docetaxel and carboplatin, ovarian cancer cell lines representing the most common, adenocarcinoma of epithelial OC, with variable levels of sensitivity to platinum drug treatment were selected (Additional file 3 (Table S2) Based on preliminary evaluations, plating densities that resulted in logarithmic growth at day 7 were used
3.1 Efficiency of Ad-transduction in different ovarian cancer cell lines Before evaluating the AdPNP-GDEPT, the permissivity of ovarian cancer cell lines to Ad transductions was evaluated by assessing the efficiency of Ad/CMV/GFP transductions in different cell types at 48 h post infection
Summary
Late stage Ovarian Cancer is essentially incurable primarily due to late diagnosis and its inherent heterogeneity. It is crucial to develop clinically relevant novel combination regimens involving synergistic modalities that target a wider repertoire of cells and lead to lowered individual doses Stemming from this premise, this is the first report of two- and three-way synergies between Adenovirus-mediated Purine Nucleoside Phosphorylase based gene directed enzyme prodrug therapy (PNP-GDEPT), docetaxel and/or carboplatin in multidrug-resistant ovarian cancer cells. Cancer targeted molecular chemotherapy, engendered by locally administered Gene Directed Enzyme Prodrug Therapy (GDEPT) provides a potent strategy for treating both local and metastatic disease [1,2]., Combining GDEPT with conventional chemotherapy has the potential to increase treatment efficacy and is highly relevant clinically, given that the patients being enrolled in new trials often present with late stage cancer having failed previous chemotherapy [3]. The potential application of PNP-GDEPT for treating ovarian cancer remains relatively unexplored, with only one preclinical study being described [10]
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