There are several depths at which this question can be answered. See page 700. The simplest answer is aerobic respiration. Answers will vary. Genetics will dictate the specifics.
Environment plays a role in determining which developmental adaptations can survive and where.
Genetically, if the information for building the collagen isn't there, it won't be built. If the collagen is missing, the bone will be brittle. Any logical answer could be a method of getting the chemical to the tumor. Sharks are cartilaginous fish. Rats have relatively small amounts of cartilage.