A novel orally active water-soluble inhibitor of human glutathione transferase exerts a potent and selective antitumor activity against human melanoma xenografts

Abstract

We designed and synthesized two novel nitrobenzoxadiazole (NBD) analogues of the anticancer agent 6-((7-nitrobenzo[c][1,2,5]oxadiazol-4-yl)thio)hexan-1-ol (NBDHEX). The new compounds, namely MC3165 and MC3181, bear one and two oxygen atoms within the hydroxy-containing alkyl chain at the C4 position of the NBD scaffold, respectively. This insertion did not alter the chemical reactivity with reduced glutathione, while it conferred a remarkable increase in water solubility. MC3181 was more selective than NBDHEX towards the target protein, glutathione transferase P1-1, and highly effective in vitro against a panel of human melanoma cell lines, with IC50 in the submicromolar-low micromolar range. Interestingly, the cellular response to MC3181 was cell-type-specific; the compound triggered a JNK-dependent apoptosis in the BRAF-V600E-mutated A375 cells, while it induced morphological changes together with an increase in melanogenesis in BRAF wild-type SK23-MEL cells.MC3181 exhibited a remarkable therapeutic activity against BRAF-V600E-mutant xenografts, both after intravenous and oral administration. Outstandingly, no treatment-related signs of toxicity were observed both in healthy and tumor-bearing mice after single and repeated administrations.Taken together, these results indicate that MC3181 may represent a potential novel therapeutic opportunity for BRAF-mutated human melanoma, while being safe and water-soluble and thus overcoming all the critical aspects of NBDHEX in vivo.

A new water soluble MAPK activator exerts antitumor activity in melanoma cells resistant to the BRAF inhibitor vemurafenib

“…These results confirm our previous evidence showing that MC3181 treatment exhibited no related signs of toxicity both in healthy and tumor-bearing mice after single and repeated administrations [20].…”

“…These data are in agreement with the ability of these agents to disrupt the interaction between GSTP1-1 and the adaptor protein TRAF2, promoting the activation of the downstream protein kinases JNK and p38 in different human melanoma cell lines, including A375 [5,7,16,20]. In parallel, we observed a with the ability of the MAPK JNK and p38 to cause cell death through specific phosphorylation of downstream mediators of apoptosis, including ATF2 and p53 [27,28].…”

“…We have analyzed their solubility in aqueous solutions and selectivity towards GSTP1-1 by determining the ability to inhibit GSTP1-1 and GSTM2-2 and by calculating the selectivity index (SI), i.e. the IC 50GSTP1-1 / IC 50GSTM2-2 ratio [19,20]. Among them, the compound MC3181 showed both higher water solubility (5 mM) and selectivity towards the target protein GSTP1-1 (SI = 32), compared to the parent compound NBDHEX (solubility limit = 0.1 mM and SI ≥ 80) [20].…”

“…the IC 50GSTP1-1 / IC 50GSTM2-2 ratio [19,20]. Among them, the compound MC3181 showed both higher water solubility (5 mM) and selectivity towards the target protein GSTP1-1 (SI = 32), compared to the parent compound NBDHEX (solubility limit = 0.1 mM and SI ≥ 80) [20]. MC3181 was highly effective against several human melanoma cell lines and was safely and effectively administered, in vivo, by both oral and intravenous routes [20].…”

“…Therefore, this new NBD compound overcomes all the critical aspects of testing NBDHEX in vivo. Moreover, we have recently shown that MC3181 is effective in vivo against the A375 human melanoma cell line, characterized by the BRAF V600E mutation [20], which leads to RAS-independent constitutive activation of BRAF causing over- M a n u s c r i p t 7…”