An Introduction to Human Cancers

Abstract

This introductory chapter delineates first the scope of the cancer problem, providing an overview on the incidence and mortality caused by cancers worldwide. Cancers are caused by many types of exogenous carcinogens, comprising physical, chemical, and biological agents (including viruses, bacteria, and parasites), and by endogenous processes that cause damage to the genome or facilitate the expansion of cell clones with altered genomes. Usually, several factors interact. Cancers display characteristic properties, prominently uncontrolled cell proliferation that is not balanced by cell death, suppression of replicative senescence, disturbed differentiation, genomic instability, as well as various metabolic changes, which are detailed in a special section. The defining properties of cancers—as opposed to benign tumors—are invasion and metastasis. Rational treatment of cancer requires classification by staging, grading, and histology and is increasingly supported by molecular diagnostics. Current cancer treatment relies primarily on surgery, radiotherapy, and chemotherapy. Cytotoxic chemotherapy is more and more supplemented and—in some cases—replaced by molecularly targeted chemotherapies employing small molecule drugs or antibodies. Their development—in particular—is based on insights from molecular cancer research. Immunotherapies have become more efficient and more widely used. New “genetic therapies” employing nucleic acids or therapeutic viruses add to the options for efficient cancer treatment.