Figure 19: Cancer Occurs and Can Be Treated at Every Scale. DNA, which resides in the nucleus (N) of every cell, is a long chemical chain of building
blocks called bases made of two kinds of chemicals, purines and pyrimidines (A). Many cytotoxic chemotherapies (purple dots and Table 2) work by
attacking the bases of DNA (A and B) or the cancer cell cytoskeleton (Csk), which is required for cell division. The DNA is organized into genes and
chromosomes and its activity is controlled in part by chemical modifications that make up what is known as epigenetics (B). Four different drugs
treat cancer by altering these DNA modifications. Activity of the genes within the nucleus (N) of each cell is controlled in part by various signaling
pathways (C). Many molecularly-targeted chemotherapies (yellow dots and Tables 1 and 2) work by blocking this signaling. Different types of cells
function together with their vasculature, nerves, extracellular matrices, and immune system to form the tissues of the body (D); several molecularly-targeted therapeutics (yellow and blue dots and Tables 1 and 2) function at the tissue level. Finally, various tissues function together to form organs,
like the lung (F), tumors at these levels (E and F) are treated best by radiation and/or surgical removal when possible.