VR23

VR23 is an effective proteasome inhibitor, with IC50 values of 3 μmol/L, 1 nmol/L, and 50-100 nmol/L to inhibit activities of caspase-like proteasomes, trypsin-like proteasomes, and chymotrypsin-like proteasomes, respectively [1].

As a regulator, the ubiquitin-proteasome system is important for cell growth and apoptosis [2]. The ubiquitin-proteasome pathway is critical in the regulated degradation of proteins involved in tumor growth and cell cycle control [3].

Treatment with VR23 made cancer cells undergo an abnormal centrosome amplification cycle. This cycle was caused by the accumulation of ubiquitinated cyclin E. Bortezomib is clinically approved as a chymotrypsin-like proteasome inhibitor. VR23 in combinations with bortezomib, caused a synergistic effect in killing multiple myeloma cells. This synergistic effect was also effective to myeloma cells resistant to bortezomib [1].

In vivo, VR23 was effective in controlling metastatic breast cancer cells and multiple myelomas [1]. In engrafted animals, the treatment with VR23 at 30 mg/kg twice per week for three weeks inhibited tumor growth effectively. Following 24 hours pre-treatment with paclitaxel at 20mg/kg/week, the administration of VR23 enhanced the anti-tumor activity of paclitaxel by 70%. Histological data showed that VR23 substantially decreased mitotic index, inhibited tumor infiltration into surrounding tissues and remarkably reduced tumor cell proliferation and angiogenesis [4].

References:
[1].  Pundir S, Vu HY, Solomon VR, et al. VR23: A Quinoline-Sulfonyl Hybrid Proteasome Inhibitor That Selectively Kills Cancer via Cyclin E-Mediated Centrosome Amplification. Cancer research, 2015, 75(19): 4164-4175.
[2].  Almond JB, Cohen GM. The proteasome: a novel target for cancer chemotherapy. Leukemia, 2002, 16(4): 433-443.
[3].  Adams J, Palombella VJ, Sausville EA, et al. Proteasome inhibitors: a novel class of potent and effective antitumor agents. Cancer research, 1999, 59(11): 2615-2622.
[4].  Vu HYT, Pundir S, Solomon RV, et al. Anticancer effects and mechanism of VR23, a novel chloroquine derivative. Cancer Research, 2014, 74(19 Supplement): 4545-4545.

VR23: A Quinoline-Sulfonyl Hybrid Proteasome Inhibitor That Selectively Kills Cancer via Cyclin E-Mediated Centrosome Amplification.[Pubmed:26238784]

Cancer Res. 2015 Oct 1;75(19):4164-75.

The proteasome is clinically validated as a target for cancer therapeutics. However, proteasome-inhibitory agents that are cancer selective have yet to be developed. In this study, we report the identification of a safe and effective proteasome inhibitor with selective anticancer properties. We screened a chemical library constructed using a hybrid approach that incorporated a 4-piperazinylquinoline scaffold and a sulfonyl phamarcophore. From this library, we identified 7-chloro-4-(4-(2,4-dinitrophenylsulfonyl)piperazin-1-yl)quinoline (VR23) as a small molecule that potently inhibited the activities of trypsin-like proteasomes (IC50 = 1 nmol/L), chymotrypsin-like proteasomes (IC50 = 50-100 nmol/L), and caspase-like proteasomes (IC50 = 3 mumol/L). Data from molecular docking and substrate competition assays established that the primary molecular target of VR23 was beta2 of the 20S proteasome catalytic subunit. Notably, VR23 was structurally distinct from other known proteasome inhibitors and selectively killed cancer cells by apoptosis, with little effect on noncancerous cells. Mechanistic investigations showed that cancer cells exposed to VR23 underwent an abnormal centrosome amplification cycle caused by the accumulation of ubiquitinated cyclin E. In combinations with the clinically approved chymotrypsin-like proteasome inhibitor bortezomib, VR23 produced a synergistic effect in killing multiple myeloma cells, including those that were resistant to bortezomib. VR23 was effective in vivo in controlling multiple myelomas and metastatic breast cancer cells, in the latter case also enhancing the antitumor activity of paclitaxel while reducing its side effects. Overall, our results identify VR23 as a structurally novel proteasome inhibitor with desirable properties as an anticancer agent.

VR23 is a small molecule that potently inhibits the activities of trypsin-like proteasomes (IC50=1 nM), chymotrypsin-like proteasomes (IC50=50-100 nM), and caspase-like proteasomes (IC50=3 μM).

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