Analysis of stromal cell secretome reveals the mechanism underlying acquired doxorubicin resistance: a systems pharmacology approach
Creators: name: Barneh, Farnaz
name: Salimi, Mona
name: Mohieddin Jafari
Publisher: name: F1000Research
Year: 2017

description: Aggressive tumors train their surrounding stromal cells consisting of fibroblasts, endothelial cells and leukocytes to provide them with survival benefits and protect them against environmental stressors such as chemotherapy-induced cytotoxicity (1). Given that myriads of cytokines and growth factors are secreted from surrounding stroma affecting chemoresistance-associated pathways, it is essential to integrate these effects into combination of druggable targets which can be manipulated to inhibit emergence of chemotherapy resistance. To reach this aim, we used proteomics-based data obtained from stromal cell secretome analysis in tumor microenvironment (2) and took a systems pharmacology approach to integrate the global effect of multiple cytokines and growth factors into underlying signaling pathways which lead to resistance following chemotherapy.<br><br>We found that the secretome derived from bone-marrow mesenchymal stem cells and cancer-associated fibroblasts (CAFs) imposed the highest protection on breast cancer cells. Classification of secreted factors based on their quantified amount showed three main clusters associated with IL-6, TNF -alpha and TGF-beta respectively which activated JAK/STAT, PI3K/AKT and KF-kB pathways. We then extracted the gene sets within these pathways from KEGG database and mapped them onto expression signature of Food and Drug Administration (FDA)-approved drugs from database of integrated Library of Integrated Network-based Cellular Signatures (iLINCS). Compared to targeted drugs such as Ruxolitinib (anti-IL6), Gefitinib (anti-EGFR), Pirfenidone (TGF-beta inhibitor pathway), Thalidomide and Aspirin (NF-kB pathway inhibitors), Sodium Valproate which inhibits Histone Deacetyleases (HDACs) was most effective in manipulating multiple targets in the underlying pathways leading to secretome- induced protection against chemotherapy (33-targets). To experimentally validate these in-silico results, we treated breast cancer cells with the secretome obtained from co-culture of MDA-MB-231 and bone-marrow mesenchymal stem cell (BM-MSC) plus 1uM Doxorubicin and 250uM Sodium Valproate and measured cell viability with tetrazolium salt assay (MTT). We observed that Sodium Valproate significantly (t-test, P &lt;0.05) inhibited the protective effects of BM-MSC on doxorubicin-induced cancer cell cytotoxicity. Primarily unknown to us, we found that a similar compound, Magnesium Valproate has been effective in increasing the cytotoxic effects of Doxorubicin in a phase-II clinical trial (3) which may in part be due to inhibiting stromal protective effects and further confirms the relevance of our approach in identifying proper drug combination to inhibit drug resistance. It is interesting to note that the authors of this study chose Magnesium Valproate solely based on the importance of epigenetic modulating drugs in cancer with no previous data-driven assumption. Thus our study provides a clinically relevant methodology to translate highthrouput data-driven hypotheses into set of drug combination with clinical application. <br> <br>References:

	1.Farmer P, Bonnefoi H, Anderle P et al. A stroma-related gene signature predicts resistance to neoadjuvant chemotherapy in breast cancer, Nat. Med. 2009;15:68-74.
	2. Straussman R, Morikawa T, Shee K et al. Tumour micro-environment elicits innate resistance to RAF inhibitors through HGF secretion, Nature 2012;487:500-504.
	3. Candelaria M, Gallardo-Rincón D, Arce C et al. A phase II study of epigenetic therapy with hydralazine and magnesium valproate to overcome chemotherapy resistance in refractory solid tumors, Annals of Oncology 2007;18:1529-1538.