Chapter 9, Problem 4DAA

RIPs as Cancer Drugs Researchers are taking a page from the structure-function relationship of RIPs in their quest for cancer treatments. The most toxic RIPs, remember, have one domain that interferes with ribosomes, and another that carries them into cells. Melissa Cheung and her colleagues incorporated a peptide that binds to skin cancer cells into the enzymatic part of an RIP, the E. coli Shiga-like toxin. The researchers created a new RIP that specifically kills skin cancer cells, which are notoriously resistant to established therapies. Some of their results are shown in FIGURE 9.17.

FIGURE 9.17 Effect of an engineered RIP on cancer cells. The model on the left shows the enzyme portion of E. coli Shiga-like toxin engineered to carry a small sequence of amino acids (in blue) that targets skin cancer cells. (Red indicates the active site.) The graph on the right shows the effect of this engineered RIP on human cancer cells of the skin (); breast () liver (); and prostate ().

Why are some of the data points linked by curved lines?