A Deadly Liaison between Oxidative Injury and p53 Drives Methyl-Gallate-Induced Autophagy and Apoptosis in HCT116 Colon Cancer Cells

Abstract

Methyl gallate (MG), which is a gallotannin widely found in plants, is a polyphenol used in traditional Chinese phytotherapy to alleviate several cancer symptoms. Our studies provided evidence that MG is capable of reducing the viability of HCT116 colon cancer cells, while it was found to be ineffective on differentiated Caco-2 cells, which is a model of polarized colon cells. In the first phase of treatment, MG promoted both early ROS generation and endoplasmic reticulum (ER) stress, sustained by elevated PERK, Grp78 and CHOP expression levels, as well as an upregulation in intracellular calcium content. Such events were accompanied by an autophagic process (16–24 h), where prolonging the time (48 h) of MG exposure led to cellular homeostasis collapse and apoptotic cell death with DNA fragmentation and p53 and γH2Ax activation. Our data demonstrated that a crucial role in the MG-induced mechanism is played by p53. Its level, which increased precociously (4 h) in MG-treated cells, was tightly intertwined with oxidative injury. Indeed, the addition of N-acetylcysteine (NAC), which is a ROS scavenger, counteracted the p53 increase, as well as the MG effect on cell viability. Moreover, MG promoted p53 accumulation into the nucleus and its inhibition by pifithrin-α (PFT-α), which is a negative modulator of p53 transcriptional activity, enhanced autophagy, increased the LC3-II level and inhibited apoptotic cell death. These findings provide new clues to the potential action of MG as a possible anti-tumor phytomolecule for colon cancer treatment.

Synthetic Derivatives of Natural ent-Kaurane Atractyligenin Disclose Anticancer Properties in Colon Cancer Cells, Triggering Apoptotic Cell Demise

“…However, in light of the impact of p53 status on cytotoxicity and anticancer activity, since p53 is frequently dysregulated in colon cancer [57,58], our future investigations will be focused on the role of p53 of colon cancer cells treated with di-oxidated derivatives of diterpene atractyligenin amides. For these studies, the two colon cancer cell lines used in this research represent ideal models that fit the scope well, since HCT116 cells possess wild-type p53 [52], while Caco-2 cells are p53-null.…”

“…Colon cancer cells (HCT116 and Caco-2) were purchased from the Interlab Cell Line Collection (ICLC, Genoa, Italy) and cultured as monolayers in DMEM supplemented with 10% (v/v) heat-inactivated FCS and 2 mM glutamine in the presence of a 1% penicillin/streptomycin solution [52]. Differentiated Caco-2 cells, used as an enterocyte-like model [53,54], were prepared as previously reported following the Natoli procedure [46].…”

Advances in the Astonishing World of Phytochemicals: State-of-the-Art for Antioxidants

“…The identification of phytomolecules with potential tailored applications represents a significant goal in the phytochemistry field. Particularly significant is the research discussed by Notaro et al exploring the biochemical action of methyl gallate (MG), a gallotannin widely used in traditional Chinese phytotherapy to alleviate several cancer symptoms [ 29 ]. The findings reported by the authors shed light on the antitumor potential of MG.…”