The anticancer effects of daily consumption of polyphenols. These dietary polyphenols include chlorogenic acid, curcumin, epigallocatechin-3-O-gallate, genistein, quercetin, and resveratrol. These polyphenols have similar chemical and biological properties in that they can act as antioxidants and exert the anticancer effects via cell signaling pathways involving their reactive oxygen species (ROS)-scavenging activity. These polyphenols may also act as pro-oxidants under certain conditions, especially at high concentrations. Epigenetic modifications, including dysregulation of noncoding RNAs (ncRNAs) such as microRNAs, long noncoding RNAs, and circular RNAs are now known to be involved in the anticancer effects of polyphenols. These polyphenols can modulate the expression/activity of the component molecules in ROS-scavenger-triggered anticancer pathways (RSTAPs) by increasing the expression of tumor-suppressive ncRNAs and decreasing the expression of oncogenic ncRNAs in general. Multiple ncRNAs are similarly modulated by multiple polyphenols. Many of the targets of ncRNAs affected by these polyphenols are components of RSTAPs. Therefore, ncRNA modulation may enhance the anticancer effects of polyphenols via RSTAPs in an additive or synergistic manner, although other mechanisms may be operating as well.

| miRs | miR-16 | miR-22 | miR-34a | miR-141 | miR-145 | CUR | EGCG | GEN | QUEmiR-146a | miR-200c | |
|---|---|---|---|---|---|---|---|---|---|---|---|
| RES | |||||||||||
| Polyphenols |
| CGA | CUR | EGCG | GEN | QUE | RES | ||
|---|---|---|---|---|---|---|---|
| miR-7 SET8↓, Bcl-2↓, p53↑ [80]; Skp2↓, p57↑, p21↑ [81] miR-9 AKT↓, FOXO1↓ [82]; GSK-3β↑, β-catenin↑, Cyclin D1↓ [83] miR-15a Bcl-2↓ [9]; WT1↓ [84] miR-16-1 WT1↓ [84] miR-28-5p BECN1↓ [85] miR-29a DNMT1↓, 3A↓, 3B↓ [86] miR-30c-5p MTA1↓ [87] miR-33b HMGA2↓ [88]; XIAP↓ [89] miR-98 LIN28A↓, MMP2↓, MMP9↓ [90] miR-99a JAK1↓, STAT1↓, STAT3↓ [91] miR-101 | CUR | ||||||
| Cancer stemness↓ | RES | : Hagiwara et al. | [ | 13 | ] EMT↓ via vimentin, ZEB1↑, E-cadherin↓ RES: Dermani et al. [45] |
| miRs | miR-20a | miR-21 | miR-25 | miR-27a | miR-93 | miR-106b | miR-155 | miR-221 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| EZH2↓, EpCAM↓ [92 | Yang et al. [9 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Polyphenols | ]; Notch1↓ [93]; EZH2↓ [94] miR-124 Midkine↓ [95]CGA]
* Upregulation (↑) and downregulation (↓) of miR targets by polyphenols are indicated. ** Downregulation by RES is reported [130]. SET8; SET domain-containing lysine methyltransferase 8, Bcl-2; B-cell lymphoma 2, Skp2; S-phase kinase-associated protein 2, AKT; AKT serine/threonine kinase 1, FOXO1; forkhead Box O1, GSK-3β; glycogen synthase kinase-3 beta, WT1; Wilms’ tumor-1, BECN1; beclin 1, DNMT; DNA methyltransferase, MTA1; metastasis-associated 1, HMGA2; high mobility group A2, XIAP; X-linked inhibitor of apoptosis, LIN28A; Lin-28 homolog A, MMP; matrix metalloproteinase, JAK1; Janus kinase 1; STAT; signal transducer and activator of transcription, EZH2; enhancer of zeste homolog 2, EpCAM; epithelial cell adhesion molecule, Notch1; neurogenic locus notch homolog protein 1, ERRα; estrogen-related receptor alpha, PGK1; phosphoglycerate kinase 1, ATG2B; autophagy-related 2B, CXCL1; chemokine (C-X-C motif) ligand 1, PI3K; phosphoinositide-3 kinase, Wnt; wingless and int-1, BCR-ABL; BCR-ABL fusion gene, mTOR; mammalian target of rapamycin, circ-PRKCA; circ_0007580, PEG10; paternally expressed gene 10, MDR1; multidrug resistance mutation1, STIM2; Stromal interaction molecule 2, Orai1; ORAI calcium release-activated calcium modulator 1, KDM2A; lysine demethylase 2A, RXRα; retinoid X receptor alpha, RAC1; ras-related C3 botulinum toxin substrate 1, EGFR; epidermal growth factor receptor, EP300; E1A-associated protein P300, THBS1; thrombospondin 1, TAGLN2; transgelin 2, WEE1; WEE1 G2 checkpoint kinase, SNHG7; small nucleolar RNA host gene 7, HSP; heat shock protein, IGFBP; insulin-like growth factor binding protein, KRAS; KRAS proto-oncogene, GTPase, Numbl; NUMB like endocytic adaptor protein, Mcl1; myeloid cell leukemia 1, IGF2BP; insulin-like growth factor 2 mRNA binding protein.
* Targets upregulated and downregulated by polyphenols through downregulation of miRs are indicated by ↑ and ↓, respectively. ** EGCG-rich Polyphenon-E. PTEN; phosphatase and tensin homolog deleted on chromosome 10, Smad; Small mother against decapentaplegic, PDCD; programmed cell death, Bcl-2; B-cell lymphoma 2, NF-κB; nuclear factor-κB, AKT; AKT serine/threonine kinase 1, PARP; poly(ADP-ribose) polymerase 1, FBXW7; F-Box And WD Repeat Domain Containing 7, ZBTB10; Zinc finger and BTB domain containing 10, Sp1; specificity protein 1, EGFR; epidermal growth factor receptor, Spry2; Sprouty RTK signaling antagonist 2, tBid; truncated BH3 interacting domain death agonist, NLRP3; NLR family, pyrin domain containing 3, SOCS1; suppressor of cytokine signal 1, IL-6; interleukin-6, FOXO3a; forkhead Box O3, AP-1; Activator protein 1, PUMA; p53-upregulated modulator of apoptosis, ARHI; age-related hearing impairment, FGF2; fibroblast growth factor 2, MMP; matrix metalloproteinase, VEGF; vascular endothelial growth factor, HGF; hepatocyte growth factor.
Researchers further discuss the miR-modulating effects of polyphenols, which have been reported in studies using one or two of the six dietary polyphenols (Table 3 and Table 4). Furthermore, based on recent evidence on involvement of lncRs and circRs in anticancer mechanisms of these polyphenols, researchers summarize the modulatory effects of six dietary polyphenols on lncRs and circRs in relation to their anticancer effects.
Table 3. miRs upregulated by one of five dietary polyphenols and their proposed targets *.
* Upregulation (↑) and downregulation (↓) of miR targets by polyphenols are indicated. ** Upregulation by CUR is also reported [55]. PTEN; phosphatase and tensin homolog deleted on chromosome 10, Nkd2; naked cuticle homolog 2, CTR1; copper transporter 1, CASZ1; castor zinc finger 1, IL1RAPL1; interleukin 1 receptor accessory protein like 1, SOX17; SRY-box transcription factor 17, N4BP1; NEDD4-binding protein 1, ARHGDIA; rho-GDP dissociation inhibitor-alpha, ARHI; age-related hearing impairment, Fbw7; F-Box and WD repeat domain-containing 7, FOXM1; forkhead box M1, sFRP1; secreted frizzled-related protein 1, Smad; small mother against decapentaplegic, Dkk2; Dickkopf-related protein 2, Wnt; wingless and int-1, IGFBP; insulin-like growth factor binding protein.
2. Involvements of miRs in Polyphenol-Mediated Anticancer MechanismsmiRs are defined as small single-stranded molecules (approximately 20 to 25 nucleotides) and can regulate gene expression at the transcriptional and post-transcriptional levels, leading to modulation of beneficial health effects exerted by these polyphenols in diseases including cancer [7][8].
Table 1 and Table 2 summarize miRs modulated by at least three of six dietary polyphenols. Four of six dietary polyphenols upregulate miR-16, 34a and 141, and downregulate miR-20a and 221; five of six dietary polyphenols upregulate miR-145 and downregulate miR-21 and 155. Table 1 and Table 2 also list the molecular targets of miRs that are modulated by these polyphenols; targets associated with RSTAPs (Figure 1) are also shown in these tables. Thus, it appears that six dietary polyphenols can exert their anticancer effects not only by directly involving RSTAPs, but also by miR-mediated regulation of the molecular targets associated with RSTAPs.
One or two of the miRs up- and down-regulated by six polyphenols for which studies have been reported are listed in Table 3 and Table 4, respectively, together with determined or proposed targets of these miRs. Many miRs can target components of RSTAPs, but some contribute to other mechanisms that are not depicted in these pathways (Figure 1). Based on previous findings on positive crosstalk between NF-κB and Wnt/β-catenin signaling [144][145], the Wnt/β-catenin signaling is connected in Figure 1. Furthermore, previous findings are incorporated to show that TNF-α activates Wnt/β-catenin pathway, leading to increases in cancer stemness and epithelial-to-mesenchymal transition (EMT) which are involved in cancer cell renewals and tumorigenesis [146][147][148]. |