Lecture 40 – More on Cancer December 2, 2013
• Cigarette Smoke, Coal tars, Asbestos, etc. were all found to cause cancer.
• This led to the discovery of Carcinogens.
• Atype of mutagens- that is substances that cause genetic mutations.
• The mutations are highly varied from carcinogen to carcinogen.
• Developed theAmes Test, which tests for mutagenesis, while not all mutagens are carcinogens,
many are, so this test was a good check for possible carcinogens.
• The test was composed of a culture of bacteria highly susceptible to mutation, and when the
substance of interest had been added to the culture, bacterial mutation was measured.
• He selected bacteria on the verge of death that would die if a single pathway was knocked out.
• Showed that cancer types are very different from each other, and that there can be different
forms of the same type of cancer.
• Breast cancer, at least two major types:
◦ Hereditary – occurs early
◦ Late emergence – random in the population
• There are not many instances of inherited cancer tendency.
◦ Retinoblastoma, occurs in children:
▪ It was proposed that Retinoblastoma was a recessive trait cancer, so it does not show up
in all offspring. The gene is called RB.
• Peter Nowell
◦ Acytologist who looked for chromosomal defects
◦ He found that in some leukemia patients there was a distortion in a pair of chromosomes,
with one being longer than normal and the other shorter by the same length, as if the longer
one had somehow taken the DNA from the shorter chromosome.
◦ This was discovered in Philly, and was called the Philadelphia Chromosome, and was
clearly associated with a type of leukemia. • The breast cancer mentioned above:
◦ Agene was identified, HER, that codes for a growth factor receptor.
◦ Patients with this cancer had an overabundance of these receptors, and thus had excessive
amounts of cell growth.
Viral Transmission of Cancer
• Cancer was observed in mice using viral vectors to infect the rodents
• Some strains developed tumors, some did not.
• The agent of the tumors was found to be transferrable, it could be filtered out of the
• 1936 – Bittner did an experiment with lactating mice.
◦ Mice with tumors were allowed to give birth, and their young were moved to a non-tumor
mother to be nursed, these infants did not develop tumors.
◦ Non-tumor mothers were allowed to give