N-acetyl-l-cysteine sensitizes pancreatic cancers to gemcitabine by targeting the NFκB pathway

Abstract

First-line therapy for pancreatic cancer is gemcitabine. Although tumors may initially respond to the gemcitabine treatment, soon tumor resistance develops leading to treatment failure. Previously, we demonstrated in human MIA PaCa-2 pancreatic cancer cells that N-acetyl-l-cysteine (NAC), a glutathione (GSH) precursor, prevents NFκB activation via S-glutathionylation of p65-NFκB, thereby blunting expression of survival genes. In this study, we documented the molecular sites of S-glutathionylation of p65, and we investigated whether NAC can suppress NFκB signaling and augment a therapeutic response to gemcitabine in vivo. Mass spectrometric analysis of S-glutathionylated p65-NFκB protein in vitro showed post-translational modifications of cysteines 38, 105, 120, 160 and 216 following oxidative and nitrosative stress. Circular dichroism revealed that S-glutathionylation of p65-NFκB did not change secondary structure of the protein, but increased tryptophan fluorescence revealed altered tertiary structure. Gemcitabine and NAC individually were not effective in decreasing MIA PaCa-2 tumor growth in vivo. However, combination treatment with NAC and gemcitabine decreased tumor growth by approximately 50%. NAC treatment also markedly enhanced tumor apoptosis in gemcitabine-treated mice. Compared to untreated tumors, gemcitabine treatment alone increased p65-NFκB nuclear translocation (3.7-fold) and DNA binding (2.5-fold), and these effects were blunted by NAC. In addition, NAC plus gemcitabine treatment decreased anti-apoptotic XIAP protein expression compared to gemcitabine alone. None of the treatments, however, affected extent of tumor hypoxia, as assessed by EF5 staining. Together, these results indicate that adjunct therapy with NAC prevents NFκB activation and improves gemcitabine chemotherapeutic efficacy.

Targeting reactive oxygen species in development and progression of pancreatic cancer

“…While single dose administration of NAC or gemcitabine failed to inhibit the growth of MiaPaca2 xenograft tumors in male athymic mice, combination of both agents reduced tumor growth by about 50%. Again, in this setting, activation of NF-κB was attenuated [130]. Finally, both vitamin E and resveratrol have been shown to amplify the anti-tumorigenic effects of gemcitabine in pancreatic cancer cells and in both xenograft and orthotopic MiaPaca2 mouse models of PDA in a manner that was dependent on the inhibition of NF-κB activity [131,132].…”

Coix seed emulsion synergistically enhances the antitumor activity of gemcitabine in pancreatic cancer through abrogation of NF-κB signaling

“…Nuclear factor-κB (NF-κB) plays a critical role in the development and progression of various human cancers that exhibit constitutive and continuous NF-κB activity (17,18). However, the induction of this signaling pathway is also associated with gemcitabine chemoresistance in PC cells (19)(20)(21). We thus reasoned that agents that block NF-κB activation may reduce chemoresistance to gemcitabine, and may be effective when used in combination with gemcitabine as a novel therapeutic regimen for treating PC.…”

Depletion of mucin in mucin-producing human gastrointestinal carcinoma: Results fromin vitroandin vivostudies with bromelain and N-acetylcysteine

“…In a similar attempt towards the management of oral cancer, Lee et al demonstrated that intraperitoneal treatment of human tongue squamous carcinoma xenografts with NAC significantly reduced mean tumor volume by 33% [ 36 ]. In a recent study by Qanungo et al, while single agent chemotherapy with the first-line agent gemcitabine failed to inhibit pancreatic cancer growth, adjunct treatment with intraperitoneal NAC reduced tumor growth [ 37 ]. Sayin et al, however, reported that supplementing the diet with NAC and vitamin E increased tumor progression in mouse models of B-RAF- and K-RAS-induced lung cancer [ 38 ].…”