Targeted polytherapy in small cell sarcoma and its association with doxorubicin

Abstract

A paradigm shift has occurred in the last decade from chemotherapy to targeted therapy for the management of many patients with advanced sarcoma. This work identifies a combination of targeted agents and doxorubicin that are effective against small cell sarcoma cell lines. Three small cell sarcoma cell lines were studied: RD18 (rhabdomyosarcoma), A204 (undifferentiated sarcoma) and TC 71 (Ewing's sarcoma). Each cell line was exposed to increasing concentrations of vorinostat (HDAC inhibitor), 17-DMAG (HSP90 inhibitor), abacavir (anti-telomerase) or sorafenib (tyrosine kinase inhibitor) alone, combined with one another, or combined with doxorubicin. Cell viability, cell cycle analysis and apoptosis were assessed by MTS assay, propidium iodide-Annexin V staining, and caspase 3/7 activity, respectively. The Chou and Talalay combination index (CI) was used to determine whether the effects were additive (CI = 1), synergistic (CI < 1) or antagonistic (CI > 1). In monotherapy, targeted agents achieved 30-90% reductions in viability, with the exception of abacavir. Dual-targeted combination therapies with vorinostat, sorafenib and 17-DMAG demonstrated synergy. Abacavir was antagonistic with every other drug and was not further studied. Both vorinostat and 17-DMAG synergized with doxorubicin, achieving 60% cell killing compared to 12% with doxorubicin alone. No synergy was observed for sorafenib with doxorubicin. The triple therapy vorinostat, 17-DMAG and doxorubicin did not show synergy, but increased the subG1 population at 24H, from 30% to 70% compared to monotherapies with an increase in apoptosis. This work provides evidence of synergy of combinations of vorinostat, 17-DMAG and sorafenib in small cell sarcoma. In addition to doxorubicin, these combinations enhance doxorubicin cytotoxicity at therapeutically relevant concentrations.

Multiple Mechanisms Mediate Resistance to Sorafenib in Urothelial Cancer

“…We have made analogous observations in our previous analysis of vorinostat action in UC, where apoptosis was induced, but only at relatively high concentrations and in a delayed manner [ 39 ]. The combination of both compounds has been reported to act synergistically on various cancer cell lines, e.g., hepatocellular, renal, sarcoma and pancreatic cancer, albeit by often complex mechanisms [ 39 , 44 , 45 , 46 , 47 ]. Importantly, in these cell lines, the compounds induce and/or activate the death receptor CD95 (Fas) with subsequent caspase 8 cleavage and down-regulate the anti-apoptotic proteins Mcl-1 and c-FLIP as well as other proteins of the Bcl-2 family.…”

Elevated expression of HSP90 and the antitumor effect of an HSP90 inhibitor via inactivation of the Akt/mTOR pathway in undifferentiated pleomorphic sarcoma

“…Radiation-induced tumor genesis has also been identified. Heat shock proteins (HSPs) are chaperones responsible for protein folding in normal cells [ 2 ], and HSP90, a member of the HSP family, refolds certain denatured proteins under stress conditions and activates these proteins, which are called “client proteins” [ 3 ]. The proteins include the growth-stimulating proteins and kinases that support malignant transformation [ 4 ].…”

Dasatinib and Doxorubicin Treatment of Sarcoma Initiating Cells: A Possible New Treatment Strategy

“…Combining chemotherapy with RTK-targeted treatment presents an advantage for targeting cellular resistance against doxorubicin. This approach has been successful in overcoming tumour cell resistance to doxorubicin in small cell sarcoma cell lines [ 6 ]. In spite of this initial success, it is still unclear which RTKs to target and if a combined treatment modality is effective.…”