Loss of phosphodiesterase 4D mediates acquired triapine resistance via Epac-Rap1-Integrin signaling

Abstract

Triapine, an anticancer thiosemicarbazone, is currently under clinical investigation. Whereas promising results were obtained in hematological diseases, trials in solid tumors widely failed. To understand mechanisms causing triapine insensitivity, we have analysed genomic alterations in a triapine-resistant SW480 subline (SW480/tria). Only one distinct genomic loss was observed specifically in SW480/tria cells affecting the phosphodiesterase 4D (PDE4D) gene locus. Accordingly, pharmacological inhibition of PDE4D resulted in significant triapine resistance in SW480 cells. Hence, we concluded that enhanced cyclic AMP levels might confer protection against triapine. Indeed, hyperactivation of both major downstream pathways, namely the protein kinase A (PKA)-cAMP response element-binding protein (Creb) and the exchange protein activated by cAMP (Epac)-Ras-related protein 1 (Rap1) signaling axes, was observed in SW480/tria cells. Unexpectedly, inhibition of PKA did not re-sensitize SW480/tria cells against triapine. In contrast, Epac activation resulted in distinct triapine resistance in SW480 cells. Conversely, knock-down of Epac expression and pharmacological inhibition of Rap1 re-sensitized SW480/tria cells against triapine. Rap1 is a well-known regulator of integrins. Accordingly, SW480/tria cells displayed enhanced plasma membrane expression of several integrin subunits, enhanced adhesion especially to RGD-containing matrix components, and bolstered activation/expression of the integrin downstream effectors Src and RhoA/Rac. Accordingly, integrin and Src inhibition resulted in potent triapine re-sensitization especially of SW480/tria cells. In summary, we describe for the first time integrin activation based on cAMP-Epac-Rap1 signaling as acquired drug resistance mechanism. combinations of triapine with inhibitors of several steps in this resistance cascade might be feasible strategies to overcome triapine insensitivity of solid tumors.

Inhibition of phosphodiesterase 4D decreases the malignant properties of DLD‑1 colorectal cancer cells by repressing the AKT/mTOR/Myc signaling pathway

“…Notably, the cytotoxic effects of cAMP in normal and malignant B cells are independent of PKA and EPAC (21). Additionally, activation of cAMP signaling by loss of PDE4D mediates resistance to the chemotherapeutic drug Triapine via EPAC in the SW480 human colon adenocarcinoma cell line (51). These data indicate that cAMP signaling is performed in a cell type-and context-dependent manner.…”

Understanding the metabolism of the anticancer drug Triapine: electrochemical oxidation, microsomal incubation and in vivo analysis using LC-HRMS

“…In these investigations, Triapine showed promising results against hematological diseases, but was widely ineffective against solid tumors. The underlying reasons are currently vague and might be based, besides rapid resistance development, 13,14 at least partially, on short plasma half-life time and fast metabolism. 15 .…”

“…ESI-HRMS: [C 7 H 7 N 5 S + H] + calculated m/z 194.0495, found m/z 194.0495. The 1 H, 13 C and 15 N one-and two-dimensional NMR spectra were recorded on an Avance III HD 700 MHz NMR spectrometer (Bruker BioSpin, Germany). 1 5-(3-Aminopyridin-2-yl)-1,3,4-thiadiazol-2-amine (4).…”

“…4,[9][10][11][12] The reasons are currently widely unknown and might be due to inappropriate drug delivery, fast excretion/ metabolism and/or drug resistance. [13][14][15] Furthermore, drug resistance can be directly related to the systemic and, often even faster, intratumoral pharmacokinetics, due to the overexpression of the metabolising enzymes. 16,17 Interestingly, the amount of ADME (absorption, distribution, metabolism and excretion) data for Triapine available in the literature is very limited.…”

Anticancer Thiosemicarbazones: Chemical Properties, Interaction with Iron Metabolism, and Resistance Development

“…Triapine proved to be only a weak ABCB1 substrate in two human MDR models and ABCB1 inhibition did not resensitize the Triapine-resistant SW480 cells to thiosemicarbazone treatment(127). In contrast, as already described above, the resistance in Triapine-resistant SW480 cells was based on the hyper-activation of the cAMP-signaling pathway(126). Interestingly, some reports suggest that common ABCB1 (and ABCC1) haplotypes may influence sensitivity of patients to Triapine treatment(26,179).…”