Anti-tumor Efficacy Assessment of the Sigma Receptor Pan Modulator RC-106. A Promising Therapeutic Tool for Pancreatic Cancer

Abstract

Introduction: Pancreatic cancer (PC) is one of the most lethal tumor worldwide, with no prognosis improvement over the past 20-years. The silent progressive nature of this neoplasia hampers the early diagnosis, and the surgical resection of the tumor, thus chemotherapy remains the only available therapeutic option. Sigma receptors (SRs) are a class of receptors proposed as new cancer therapeutic targets due to their over-expression in tumor cells and their involvement in cancer biology. The main localization of these receptors strongly suggests their potential role in ER unfolded protein response (ER-UPR), a condition frequently occurring in several pathological settings, including cancer. Our group has recently identified RC-106 , a novel pan-SR modulator with good in vitro antiproliferative activities toward a panel of different cancer cell lines. In the present study, we investigated the in vitro properties and pharmacological profile of RC-106 in PC cell lines with the aim to identify a potential lead candidate for the treatment of this tumor. Methods: Pancreatic cancer cell lines Panc-1, Capan-1, and Capan-2 have been used in all experiments. S1R and TMEM97/S2R expression in PC cell lines was quantified by Real-Time qRT-PCR and Western Blot experiments. MTS assay was used to assess the antiproliferative effect of RC-106 . The apoptotic properties of RC-106 was evaluated by TUNEL and caspase activation assays. GRP78/BiP, ATF4, and CHOP was quantified to evaluate ER-UPR. Proteasome activity was investigated by a specific fluorescent-based assay. Scratch wound healing assay was used to asses RC-106 effect on cell migration. In addition, we delineated the in vivo pharmacokinetic profile and pancreas distribution of RC-106 in male CD-1 mice. Results: Panc-1, Capan-1, and Capan-2 express both SRs. RC-106 exerts an antiproliferative and pro-apoptotic effect in all examined cell lines. Cells exposure to RC-106 induces the increase of the expression of ER-UPR related proteins, and the inhibition of proteasome activity. Moreover, RC-106 is able to decrease PC cell lines motility. The in vivo results show that RC-106 is more concentrated in pancreas than plasma. Conclusion: Overall, our data evidenced that the pan-SR modulator RC-106 is an optimal candidate for in vivo studies in animal models of PC.

Exploring the RC-106 Chemical Space: Design and Synthesis of Novel (E)-1-(3-Arylbut-2-en-1-yl)-4-(Substituted) Piperazine Derivatives as Potential Anticancer Agents

“…Such effect was mirrored by the impairment of proteasome activity (Figure 6), an enzyme involved in the protein homeostasis. This activity was also documented in our previous work focused on the antitumor activity of the hit RC-106 and where we showed its capability to trigger the UPR response machinery (Tesei et al, 2019). Accordingly, the compounds also hamper tumor cell growth starting from the lowest concentrations tested, as evidenced by the proliferation test (Figure 7) showing also a significant induction of cell death (∼50%) at the highest concentration tested (Figure 5).…”

“…Our medicinal chemistry campaign recently led to the identification of ( E )-4-benzyl-1-[3-(naphthalen-2-yl)but-2-en-1-yl]piperidine (henceforth RC-106 ) ( Figure 1 ). This compound is able to activate terminal unfolded protein response (UPR) and to inhibit proteasome complex activity, through the induction of endoplasmic reticulum stress (ER) (Tesei et al, 2019 ). Moreover, RC-106 possesses a pan-SRs profile—ability to bind both S1R and S2R—and shows a cytotoxic effect against a wide panel of cancer cell lines, all expressing SRs, acting as a proapoptotic drug, which induces a fast triggering of cell death program (Rui et al, 2016b ).…”

Pan-Sigma Receptor Modulator RC-106 Induces Terminal Unfolded Protein Response In In Vitro Pancreatic Cancer Model

“…To further our understanding of the relationship between SRs and the terminal UPR pathway, we first compared the activity of our compound with that of two well-known ER stress inducers: thapsigargin (TG) a SERCA inhibitor, and bortezomib (BTZ), a known proteasome inhibitor [ 46 ]. The choice of concentrations and exposure time used was based on literature data and on previous results obtained by Real-Time qRT-PCR [ 45 ]. To this purpose, cells were treated with the three molecules and the effect on the expression of ER-stress/terminal UPR markers compared.…”

“…Moreover, given that tissue distribution in target organs is at the core of the development process because of its direct impact on drug activity, we studied the pharmacokinetic profile of the modulator and evaluated its distribution in the pancreas. Our results showed that RC-106 was 25-fold more concentrated in the pancreas than in plasma, reaching a concentration higher than that required to be effective in all the in vitro experiments [ 45 ]. In light of the above considerations, we used RC-106 as a drug model to investigate the therapeutic role of SRs in activating the terminal UPR, mediated by ER stress induction.…”

Bi-phasic dose response in the preclinical and clinical developments of sigma-1 receptor ligands for the treatment of neurodegenerative disorders

“…Several S2R antagonists are shown to have beneficial effects in neurodegenerative diseases such as AD and are currently evaluated in clinical trials [150][151][152]. However, S2R agonists also induce neurodegeneration [151] and apoptosis, which makes them attractive as anti-cancer drugs [153]. Therefore, a relatively nonselective S1R agonist, with lower affinity, agonistic activity at S2R may activate the S2R at high doses.…”