N. Kashyap, P.P. Kushwaha, A.K. Singh, S. Maurya, A.K. Sahoo, and S. Kumar () Department of Biochemistry and Microbial Sciences, Central University of Punjab, Punjab, India e-mail: shashankbiochemau@gmail.com Phytochemicals, cancer and miRNAs: An In silico approach Neha Kashyap, Prem P. Kushwaha, Atul K. Singh, Santosh Maurya, Ashish K. Sahoo, and Shashank Kumar Abstract Computer based drug design is an important tool nowadays save time and money in the research. Various online and offline computer based tools are available to predict the disease mitigating potential of phytochemicals as well as the role of miRNAs in various disease through signaling pathways. Cancer, a deadliest disease kills major population of humans. The processes involved in cancer development include metastasis, invasion, angiogenesis, and inflammation. These processes are regulated by microRNAs and different signaling pathways (Wnt/β-catenin, Notch, Sonic hedgehog, COX-2, EGFR, MAPK-ERK, JAK-STAT, Akt/PI3K/mTOR, NF-κB, AP-1, etc.). Phytochemicals such as dietary polyphenols play an efficient role in reducing the pace of cancer metastasis and other hallmarks of cancer as it modulates miRNAs associated with various signaling pathways involved in cancer. Phytochemicals controls epigenetic events (non- coding miRNAs, histone modification, DNA methylation) and indirectly affect multiple signaling pathways. Phytochemicals exert inhibitory effect on each step of metastasis and has anticancer potential by inducing apoptosis and by inhibiting cell growth, migration, invasion and apoptosis. The present chapter highlights the cancer signaling pathways and their mitigation by phytochemicals. Role of miRNAs in various signaling pathways and hall marks of cancer is also discussed. The most interesting part of the chapter include step by step tutorial to study the association of phytochemical modulated miRNAs in various signaling pathways related to cancer. Keywords Dietary phytochemicals, Micro-RNAs, Epigenetic modifications, Signaling pathways, Cancer, Metastasis 23.1 Introduction Cancer involves the process of carcinogenesis which turns normal cells into cancerous cells. The process includes three major steps of initiation, promotion and progression. In order to design therapeutics and drugs against cancer development one need to understand these major steps.