1. Introduction
Depending on the type and condition of cancer, conventional treatments may involve chemotherapy in combination with surgery, radiation therapy, hormone therapy, and/or highly targeted therapies such as immunotherapy and monoclonal antibody therapy. Chemotherapeutic drugs (synthetic, semi-synthetic, and naturally occurring compounds) are cytotoxic and often kill both cancerous and healthy cells, which are dividing rapidly. Their main mode of action involves signaling through both death receptors (extrinsic pathways) and mitochondrial pathways (intrinsic pathways) and by inducing one or more apoptotic pathways. Chemotherapeutic drugs can be classified by their mode of action into alkylating antineoplastic agents, kinase inhibitors, aromatase inhibitors, and topoisomerase inhibitors. Nature is an excellent and useful source of anticancer agents, about 60% of which are extracted from microorganisms, marine organisms, or plants (Iqbal et al., 2017). Important anti-cancer phytochemicals include vinca alkaloids, podophyllotoxin (PPT), taxol, camptothecin, and their derivatives.
These phyto-compounds are being used in various fields due to their active role against different types of cancers and are preferred over conventional chemotherapy due to their lesser. It is reported that 80% of the population worldwide traditionally uses natural compounds contained in medicinal plants, and more than 1800 experimentally authenticated anti-cancer compounds-target interactions have been documented at Naturally occurring Plant-based Anti-cancer Compound-Activity-Target Database (NPACT) (Aung et al., 2017).
There is a need for the continuous production of these compounds, which may be achieved using a range of biotechnological approaches involving the use of axenic plant cell and organ cultures. Moreover, bioengineering and metabolic engineering approaches can be used to study their biosynthetic pathways (Nobili et al., 2009). This review focuses on state-of-the-art biotechnological approaches for the production of effective anticancer compounds with a short description of their chemical structure, mode of action, and biological activities.