Activation of p53 with Ilimaquinone and Ethylsmenoquinone, Marine Sponge Metabolites, Induces Apoptosis and Autophagy in Colon Cancer Cells

Abstract

The tumor suppressor, p53, plays an essential role in the cellular response to stress through regulating the expression of genes involved in cell cycle arrest, apoptosis and autophagy. Here, we used a cell-based reporter system for the detection of p53 response transcription to identify the marine sponge metabolites, ilimaquinone and ethylsmenoquinone, as activators of the p53 pathway. We demonstrated that ilimaquinone and ethylsmenoquinone efficiently stabilize the p53 protein through promotion of p53 phosphorylation at Ser15 in both HCT116 and RKO colon cancer cells. Moreover, both compounds upregulate the expression of p21WAF1/CIP1, a p53-dependent gene, and suppress proliferation of colon cancer cells. In addition, ilimaquinone and ethylsmenoquinone induced G2/M cell cycle arrest and increased caspase-3 cleavage and the population of cells that positively stained with Annexin V-FITC, both of which are typical biochemical markers of apoptosis. Furthermore, autophagy was elicited by both compounds, as indicated by microtubule-associated protein 1 light chain 3 (LC3) puncta formations and LC3-II turnover in HCT116 cells. Our findings suggest that ilimaquinone and ethylsmenoquinone exert their anti-cancer activity by activation of the p53 pathway and may have significant potential as chemo-preventive and therapeutic agents for human colon cancer.

The update on transcriptional regulation of autophagy in normal and pathologic cells: A novel therapeutic target

“…In contrast, P53 loss induces autophagy in the absence of stress signals, suggesting that basal levels of P53 activity inhibit autophagy [152][153][154]. The reason for the above phenomenon is that P53 controls the expression of many autophagy-related proteins, which show the opposite function in regulating autophagy [154,155]. Certain proteins that are under the control of P53 (such as DNA damage regulated autophagy modulator 1, DRAM1) stimulate autophagy flux, whereas others (such as AMPK) inhibit mTOR pointing to P53 as a positive regulator of autophagy [156,157].…”

“…Under normal physiological conditions, proteins that stimulate autophagy flux are in a dominant position. In contrast, proteins that inhibit autophagy play the main function in various extreme situations [155][156][157]. The autophagy-related target genes of P53 include ATG2, ATG4, ATG7, ATG10, BCL2, ULK1, DRAM1, AMPK, and so on [152][153][154][155][156][157] (Table 1).…”

“…P53 operates within a broader regulatory network to define autophagic control [152][153][154][155][156][157]. When cells are subjected to oncogenic activation or genotoxic stress and P53 is activated, P53 is shown to induce autophagy [152,153].…”

Inducible Inhibition of Gβγ Reveals Localization-dependent Functions at the Plasma Membrane and Golgi

“…One hypothesis is that ilimaquinone is functioning, directly or indirectly, through a GPCR located at the PM, whereas another possibility is that ␤␥ translocates from the PM to the Golgi to induce Golgi fragmentation after ilimaquinone treatment. Ilimaquinone promotes several cellular activities, in addition to Golgi fragmentation, but the cellular targets of ilimaquinone that mediate its effects on cells remain to be definitively identified (20,40).…”

Anticancer Effects of the Marine Sponge Lipastrotethya sp. Extract on Wild‐Type and p53 Knockout HCT116 Cells

“…Generally, agents that induce apoptosis or autophagy are of interest as potential cancer therapies [3, 4]. Apoptosis is called programmed cell death [5], is a critical developmental process, and is essential for tissue remodeling.…”