Advantages of polyphenols as anticancer agents are their high accessibility, low toxicity, specificity
of the response and various biological effects. A combination of cytoprotective effects toward normal cells and cytotoxic effects toward cancerous cells thus represents the main advantage of polyphenols as anticarcinogenic agents [12]. Their role in carcinogenesis lies in the regulation of growth factor-receptor neteractions and cell signaling cascades that can induce cell cycle arrest and impact on cell survival and apoptosis of cancerous cells [13]. Polyphenols mainly induce apoptosis through pro-oxidative action that is exerted instead of their anti-oxidative action depending on their concentration, target molecule/s and environmental conditions [2,14,15]. For that reason, they may interact differently depending on the cell type: healthy versus cancerous one. Additionally, polyphenols help to establish the body’s immune system by inhibiting angiogenesis necessary for tumor growth and act as anti-inflammatory agents [13].
In the final stages of cancer, polyphenols attenuate the adhesiveness and invasiveness of cells therefore reducing their metastatic potential [13]. However, the bioavailability of polyphenols represents a big hurdle as they only reach the target organs in very low concentrations. One auspicious solution for this problem represents nanoformulation of polyphenols that has brought some promising results [13].
On the other hand, it may lead to a problem of toxicity of specific agents when administered in
high doses [2]. It was for example shown that some extracted polyphenols in high concentrations
act even in the opposite way: instead of preventing cancer they can contribute to its formation and
progression [4,16,17]. In contrast, some studies have shown that when in combination with other
polyphenols an individual polyphenol can exert significantly enhanced chemoprotective and other
favorable properties at considerably lower concentrations [18,19]. Synergistic action of polyphenolic
mixtures additionally results in the concurrent impact on different disease pathways consequentially contributing to a faster and more effective healing [19]. Polyphenols can also suppress the side effects of certain therapies already used in the cancer treatment like chemotherapy and radiotherapy and enhance their action [18].

https://www.mdpi.com/1420-3049/21/7/901/pdf

The Role of Polyphenols in Human Health and Food System