Evaluation of Cytotoxic Properties of a Cyclopamine Glucuronide Prodrug in Rat Glioblastoma Cells and Tumors

Abstract

Glioblastoma multiforme (GBM) is the most common and aggressive primary brain tumor. Activation of the developmental hedgehog (Hh) pathway is observed in GBM, particularly in the so-called glioma stem cells (GSCs). An inhibitor of this pathway is the steroidal alkaloid cyclopamine, an antagonist of the Hh coreceptor Smoothened (SMO). To limit the toxicity of cyclopamine toward Hh-dependent non-tumor cells, our group previously reported the synthesis of a prodrug (called 1b), designed to deliver cyclopamine in the presence of β-glucuronidase, an enzyme found in the necrotic area of GBM. Here, we aimed to analyze the in vitro, ex vivo, and in vivo cytotoxic properties of this prodrug in the C6 rat GBM cells. In the presence of β-glucuronidase, the activated prodrug 1b was toxic and downregulated expression of Gli1, a Hh target gene, in C6 cells and C6-GSCs, but not in normal rat astrocytes in which the Hh pathway is weakly activated. In the absence of β-glucuronidase, prodrug 1b displayed no obvious toxicity toward rat brain tissue explants while cyclopamine clearly affected brain tissue viability. When administered to rats bearing fluorescent C6-derived GBM, the prodrug 1b reduced the tumor density more efficiently than cyclopamine. Prodrug 1b thus appears as a promising concept to optimize confinement of cyclopamine cytotoxicity within the tumors, with more limited effects in the surrounding normal brain tissue.

Developmental pathways associated with cancer metastasis: Notch, Wnt, and Hedgehog

“…The pivotal roles of this signaling pathway in maintaining the stemness of tissue stem cells and in regulating the tissue homeostasis and cell fate along the lifespan raise concerns for safety of Wnt-based anticancer strategies despite the potential of Wnt signaling targeting for cancer stem cell elimination 90,91 and metastasis suppression, discouraging their development. Preclinical studies 91 and phase 1 clinical trials 92 suggested that PRI-724 is relatively well-tolerated, and the drug is currently in phase 2 trials combined with chemotherapy drugs and the angiogenesis inhibitor bevacizumab (NIH trial IDs 3C-13-3, NCI-2015-00436, and NCT02413853).…”

VIP and PACAP analogs regulate therapeutic targets in high-risk neuroblastoma cells

“…The protocol of RT-qPCR was carried out with the LightCycler System (Roche Molecular Biochemicals) by using the « SYBR Premix Ex Taq kit» (Takara) as previously described [36]. GAPDH mRNA levels were used to normalize the mRNA levels between samples.…”

In situ targeted activation of an anticancer agent using ultrasound-triggered release of composite droplets

“…A glucuronide prodrug of monomethylauristatin E (MMAE-glu) [25][26][27][28][29][30][31][32] was chosen to perform this study [33,34]. Indeed, MMAE is a potent antimitotic agent currently employed in human for the treatment of lymphomas under the form of the brentuximab vedotin, an antibody-drug conjugate that reached the market in 2011 [35].…”