Bromelain and N-acetylcysteine inhibit proliferation and survival of gastrointestinal cancer cells in vitro : significance of combination therapy

Abstract

BackgroundBromelain and N-acetylcysteine are two natural, sulfhydryl-containing compounds with good safety profiles which have been investigated for their benefits and application in health and disease for more than fifty years. As such, the potential values of these agents in cancer therapy have been variably reported in the literature. In the present study, the efficacy of bromelain and N-acetylcysteine in single agent and combination treatment of human gastrointestinal carcinoma cells was evaluated in vitro and the underlying mechanisms of effect were explored.MethodsThe growth-inhibitory effects of bromelain and N-acetylcysteine, on their own and in combination, on a panel of human gastrointestinal carcinoma cell lines, including MKN45, KATO-III, HT29-5F12, HT29-5M21 and LS174T, were assessed by sulforhodamine B assay. Moreover, the influence of the treatment on the expression of a range of proteins involved in the regulation of cell cycle and survival was investigated by Western blot. The presence of apoptosis was also examined by TUNEL assay.ResultsBromelain and N-acetylcysteine significantly inhibited cell proliferation, more potently in combination therapy. Drug-drug interaction in combination therapy was found to be predominantly synergistic or additive. Mechanistically, apoptotic bodies were detected in treated cells by TUNEL assay. Furthermore, Western blot analysis revealed diminution of cyclins A, B and D, the emergence of immunoreactive subunits of caspase-3, caspase-7, caspase-8 and cleaved PARP, withering or cleavage of procaspase-9, overexpression of cytochrome c, reduced expression of anti-apoptotic Bcl-2 and pro-survival phospho-Akt, the emergence of the autophagosomal marker LC3-II and deregulation of other autophagy-related proteins, including Atg3, Atg5, Atg7, Atg12 and Beclin 1. These results were more prominent in combination therapy.ConclusionWe report for the first time to our knowledge the growth-inhibitory and cytotoxic effects of bromelain and N-acetylcysteine, in particular in combination, on a panel of gastrointestinal cancer cell lines with different phenotypes and characteristics. These effects apparently resulted from cell cycle arrest, apoptosis and autophagy. Towards the development of novel strategies for the enhancement of microscopic cytoreduction, our results lay the basis for further evaluation of this formulation in locoregional approaches to peritoneal surface malignancies and carcinomatosis.

Reactive oxygen species (ROS) are a key determinant of cancer's metabolic phenotype

“…Recent studies suggest that antioxidants accelerate tumor migration and metastasis . In direct contrast, other work has found that antioxidant administration prevents cancer proliferation, invasion, migration and metastasis …”

“…64,[82][83][84] In direct contrast, other work has found that antioxidant administration prevents cancer proliferation, invasion, migration and metastasis. 36,37,[85][86][87][88][89][90] The differing effects of ROS modulation are context dependent. Cells with low oxidation status may seek to enhance their ROS signaling for a survival and motility advantage.…”

N-acetyl-cysteine exhibits potent anti-mycobacterial activity in addition to its known anti-oxidative functions

“…In addition to the above clinical applications, NAC has been employed as a potent anti-oxidant in several experimental models of infection and cancer in vitro and in vivo [15–20]. In these settings, NAC serves as a pro-drug to L-cysteine, which is a precursor to the biologic antioxidant glutathione.…”

Bromelain: Methods of Extraction, Purification and Therapeutic Applications

“…These include P-388 leukemia, sarcoma (S-37), A-431 epidermoid carcinoma, A-375 melanoma, lewis lung cancer and ADC-755 breast cancer (Bhui et al 2011;Pavan et al 2012). Furthermore, the use of bromelain in conjugation with chemotherapeutic medicine improves the efficiency of these drugs to certain extent (Pillai et al 2013;Amini et al 2014). …”