New Pharmacological Strategies against Pancreatic Adenocarcinoma: The Multifunctional Thiosemicarbazone FA4

A new sigma-2 (σ2) receptor ligand (FA4) was efficiently synthesized and evaluated for cytotoxic, proapoptotic, and antimigratory activity on pancreatic ductal adenocarcinoma (PDAC) primary cell cultures, which restrained the aggressive and chemoresistant behavior of PDAC. This compound showed relevant antiproliferative activity with half maximal inhibitory concentration (IC50) values ranging from 0.701 to 0.825 μM. The cytotoxic activity was associated with induction of apoptosis, resulting in apoptotic indexes higher than those observed after exposure to a clinically relevant concentration of the gemcitabine, the first-line drug used against PDAC. Interestingly, FA4 was also able to significantly inhibit the migration rate of both PDAC-1 and PDAC-2 cells in the scratch wound-healing assay. In conclusion, our results support further studies to improve the library of thiosemicarbazones targeting the σ-2 receptor for a deeper understanding of the relationship between the biological activity of these compounds and the development of more efficient anticancer compounds against PDAC

DEVELOPMENT OF PHENOXYALKYLPIPERIDINES AS HIGH-AFFINITY SIGMA-1 (s1) RECEPTOR LIGANDS WITH POTENT ANTI-AMNESIC ACTIVITY

The sigma-1 (σ1) receptor plays a significant role in many physiological functions and pathological disease states, and, as such, it represents an attractive therapeutic target for both agonists and antagonists. Here, we describe a novel series of phenoxyalkylpiperidines (Figure 1) that were prepared and tested at σ1, σ2, and sterol Δ8- Δ7 isomerase (SI) sites by in vitro radioligand binding assays. These new compounds are derivatives of the σ ligand 1-[3-(4-chlorophenoxy)propyl]-4-methylpiperidine (L1), which has been claimed as a therapeutic agent for CNS disorders and neuropathies. In order to explore the structure-affinity relationships (SAFIRs) of this class of compounds, we modified the aryloxyl and piperidine moieties and the linker that connects them. In particular, we evaluated the influence of the stereochemistry on σ receptors affinity and selectivity through the introduction of methyl groups either on the chain or on the piperidine ring. The affinity at σ1 and σ2 receptors and at Δ8-Δ7 sterol isomerase (SI) ranged from subnanomolar to micromolar Ki values. While the highest affinity was displayed at the σ1 receptor (Ki = 0.34 nM), the chirality introduced by a methyl substitution in the linker resulted only in slight differences. The higher was the degree of methylation on the piperidine ring the lower was the ligand affinity, in agreement with other classes of σ1 receptor ligands. Nevertheless, the shorter oxyethylenic chain was beneficial for the σ1 selectivity. Importantly, these shorter-chain compounds displayed potent antiamnesic effects associated with σ1 receptor agonism, in two different memory tests. Overall, phenoxyalkylpiperidines hold potential for the development of high affinity σ1 receptor agonists

Sigma-2 Receptor Ligand Binding Modulates Association between TSPO and TMEM97

Sigma-2 receptor (S2R) is a S2R ligand-binding site historically associated with reportedly 21.5 kDa proteins that have been linked to several diseases, such as cancer, Alzheimer’s disease, and schizophrenia. The S2R is highly expressed in various tumors, where it correlates with the proliferative status of the malignant cells. Recently, S2R was reported to be the transmembrane protein TMEM97. Prior to that, we had been investigating the translocator protein (TSPO) as a potential 21.5 kDa S2R candidate protein with reported heme and sterol associations. Here, we investigate the contributions of TMEM97 and TSPO to S2R activity in MCF7 breast adenocarcinoma and MIA PaCa-2 (MP) pancreatic carcinoma cells. Additionally, the role of the reported S2R-interacting partner PGRMC1 was also elucidated. Proximity ligation assays and co-immunoprecipitation show a functional association between S2R and TSPO. Moreover, a close physical colocalization of TMEM97 and TSPO was found in MP cells. In MCF7 cells, co-immunoprecipitation only occurred with TMEM97 but not with PGRMC1, which was further confirmed by confocal microscopy experiments. Treatment with the TMEM97 ligand 20-(S)-hydroxycholesterol reduced co-immunoprecipitation of both TMEM97 and PGRMC1 in immune pellets of immunoprecipitated TSPO in MP cells. To the best of our knowledge, this is the first suggestion of a (functional) interaction between TSPO and TMEM97 that can be affected by S2R ligands