Cancer Chemoprevention by Phytochemicals: Nature's Healing Touch

Abstract

Phytochemicals are an important part of traditional medicine and have been investigated in detail for possible inclusion in modern medicine as well. These compounds often serve as the backbone for the synthesis of novel therapeutic agents. For many years, phytochemicals have demonstrated encouraging activity against various human cancer models in pre-clinical assays. Here, we discuss select phytochemicals-curcumin, epigallocatechin-3-gallate (EGCG), resveratrol, plumbagin and honokiol-in the context of their reported effects on the processes of inflammation and oxidative stress, which play a key role in tumorigenesis. We also discuss the emerging evidence on modulation of tumor microenvironment by these phytochemicals which can possibly define their cancer-specific action. Finally, we provide recent updates on how low bioavailability, a major concern with phytochemicals, is being circumvented and the general efficacy being improved, by synthesis of novel chemical analogs and nanoformulations.

Keywords: cancer chemoprevention; inflammation; nanotechnology; phytochemicals; pro-oxidant; tumor microenvironment.

Figure 1

Phytochemicals and their sources. EGCG: Epigallocatechin gallate.

Figure 2

Role of phytochemicals in human malignancies. Phytochemicals potentially scavenge reactive oxygen species (ROS) or upregulate anti-oxidant signalling to combat ROS generation in cancer cells to inhibit growth. There are also context dependent evidences which advocate the prooxidant cell death inducing behaviour of phytochemicals. Phytochemicals have also been shown to inhibit inflammation via targeting NF-κB pathway. Tumor micro environment (TME) plays a vital role in many solid tumors pathogenesis, and phytochemicals have been shown to target both tumor and stromal compartments.