DISCOVERY OF NORMAL CELL BIOLOGY

SLIDE 1. TITLE.

Cancer is always topical in the 21st century-particularly in the demographic that takes

Senior College courses. There is fascinating science and fierce human drama associated with the disease.

SLIDE 2. OUTLINE OF THE COURSE

We will lecture on six topics in this course. Today we lecture on normal cell biology and cancer biology, so you can better understand the how and why of cancer’s effects on patients. The first lecture may be the most challenging as it reviews basic science. In the 2nd lecture we discuss the causes of cancer, prevention of cancer, and screening tests for cancer. In the 3rd lecture we will discuss the evaluation of the cancer patient. In the 4th lecture we will discuss the treatment of cancer. In the 5th lecture we present seven cases that illustrate how the knowledge gleaned in the first four lectures was employed to help actual patients. In the sixth and final lecture we will discuss what is required of the patient; oncologist and care team; and the health care system to best help cancer patients. I hope to be permitted some philosophical reflections on patient care reflecting almost half a century of clinical training and practice. A heavy dose of medical history will be supplied in each lecture because medical history is interesting and will help you understand how it is we came to do what we do.

SLIDE 3. DILBERT STRIP ON ZOOM TECHNOLOGY

I’m not a fan of this new-fangled ZOOM technology and worry it will poleax me any minute. I will soldier on with information technology support.

SLIDE 4. DILBERT WITH A COMPLICATED PRESENTATION

The lectures are pitched to the intelligent layman. We’ve all felt like Alice after listening to Dilbert’s lecture. The lingua franca of oncology can be hard to follow. I’ll try my best to define the terms and simplify the concepts. I’ll periodically take any questions you relay to Dr. Scott both during the lectures,

and at the end of the lectures. We can provide transcripts of the lectures if you so desire. If I were you

I’d relax, listen to the lecture and view the slides. I’d raise any questions I had at the time I thought of it.

I’d get the transcripts of the lectures and review the transcripts after the lectures.

SLIDE 5. BURDEN OF CANCER IN THE USA.

I would hazard the guess everyone auditing this course has had someone near and dear who has had to cope with cancer. The statistics are sobering. One out of 225 American were diagnosed with cancer in 2020. 1 out of 630 Americans died of cancer in 2020-1 out of every 530 men and 1 out of every 740 women. African-American men were the most affected demographic: 1 out of 439 died of cancer..

Asian-American women were relatively least afflicted: 1 out of 1, 1168. There are 17 million cancer survivors in the USA. 40% of Americans will receive a cancer diagnosis in their lifetime.

SLIDE 6. DEFINITION OF CANCER.

We lecture today on normal cell biology. In order to appreciate what causes cancer, it is important to understand normal cell biology. With this understanding we then lecture on cancer biology. Cancer is basically altered cells caused by mutations in the genome.

SLIDE 7. SCHOOL OF ATHENS

The Greeks, as was their wont, got the ball rolling on characterizing normal cell biology with speculative natural philosophy. Pythagoras hypothesized, around 530 BC, that “likeness” was carried in the male semen, after coursing through a man’s body and absorbing vapors from each part. Aeschylus’s

Eumenides was performed in 458 BC. In the play Orestes was on trial for matricide. Apollo, called to judge, reasoned a father’s sperm carries “likeness”, while the mother just drips nutrients through the umbilical cord into the child. Apollo judged Orestes innocent since he was avenging a more serious crime-his father’s murder. Aristotle dismantled the Pythagorean theory of spermism by noting children also inherit features from their mother and other ancestors. He noted “In Sicily a woman committed adultery with an Ethiopian; the daughter did not become an Ethiopian, but the granddaughter did.”

SLIDE 8. GREGOR MENDEL

Father Gregor Mendel, was an Augustinian monk at St. Thomas’s Abbey in Brno, Moravia. Father

Mendel distilled a decades worth of scientific work breeding peas into a paper published in the 1866

Proceedings of the Brno Natural Science Society. Father Mendel had documented the laws of inheritance. Father Mendel was well aware of the relevance of his research to Darwin’s theory of natural selection. But Father Mendel’s attempts to interest professional scientists in his work failed. Father

Mendel’s epochal research languished in obscurity for 40 years. In 1905 William Bateson, “Mendel’s bulldog”, finally recognized the importance of Father Mendel’s research. Bateson publicized Mendel’s conclusions. Bateson also coined the word genetics from the Greek word “genno”-to give birth. In 1909 the word gene was first used for Mendel’s unit of heredity. The sum total of all our genes is the genome.

SLIDE 9. ALLELES Alleles are one of two or more alternative forms of a gene that are found at the same place on a chromosome. Another way to remember what alleles are is to think of them as allies: the gene on the chromosome from the father and the gene on the “homologue” chromosome of the mother ally to assign characteristics to the baby. The male and female alleles combine to assign hair color, eye color, etc. On the slide capital A is the dominant gene, coding for yellow peas. Small a is the recessive gene coding for green peas. In the Punnett square the peas are yellow when there are two dominant Capital A genes paired, yellow when a dominant capital A and recessive small a are paired, and only green when two recessive “green genes” are paired. 75% of the peas are yellow and 25% green over time. However, what happens to any individual pea is akin to a roll of the dice.

SLIDE 10. CHROMOSOMES ARE THE CELLULAR BASIS OF HEREDITY

In the 1890’s Theodore Boveri, a German embryologist working with sea urchins in Naples, proposed that genes resided in chromosomes, which resided in the nucleus of cells. Walter Sutton, a farm boy from Russell, KS who attended the University of Kansas, was later a graduate student at Columbia.

Sutton’s research at Columbia with grasshopper sperm and egg cells confirmed Boveri’s findings that genes resided in chromosomes in the nucleus of cells. In 1905 Nettie Stevens of Bryn Mawr College documented “maleness” in worms was determined by the Y chromosome. Thomas Morgan then documented genes for certain characteristics were physically linked on the chromosomes of fruit flies in

1912.

SLIDE 11. CHROMOSOME PAIRS

As pictured in the slide, we have 23 pairs of genes in the nucleus of each cell in our body. In each chromosome one of the strands comes from the father and one comes from the mother. The father’s strand is paired with its counterpart, called a homologue, from the mother. The two homologues are joined at the center by a centromere. In the lower right corner of the slide the sex chromosomes are pictured. Women inherit two X sex chromosomes. Men inherit an X and Y sex chromosome. Note how small the Y chromosome is. The genes on the Y chromosome instruct the embryo to turn into a male at age 6-7 weeks. Instructing the embryo to turn into a male is the only job a Y chromosome is asked to do. One of the X chromosomes also becomes inactive after conception. The inactivated X chromosome turns into something called a Barr body. The inactivated X chromosome (Barr body) is inactivated by a process called epigenetics which we will soon discuss. After the chromosomes were proven to be the locus of genes and heredity the search was then on for the molecular structure of chromosomes. The molecular structure of chromosomes needed to be characterized before we could fully understand the mechanisms of heredity and cancer.

SLIDE 12. STRUCTURE OF THE HUMAN CELL

As early as 1869 a Swiss biochemist, Friedrich Miescher, documented the dense, swirling strands of chemicals he found in salmon sperm and human white blood cells were acidic and located in the nucleus of those cells. By the early 1920’s biochemists documented nucleic acid came in two forms: DNA

(deoxyribonucleic acid) and RNA (ribonucleic acid). The cytoplasm is the area in the cell outside the nucleus. It is important to remember the mitochondrion has its own separate DNA. The mitochondrion is where respiration takes place and energy is produced. The ribosomes are sites where proteins are manufactured through assembly of amino acids.

In 1944 Oswald Avery documented DNA was the carrier of genetic information. Maurice Wilkins and

Rosalind Franklin produced clear X-ray crystallography images of DNA at King’s College London in 1952.

SLIDE 13. WATSON AND CRICK WITH THE DOUBLE HELIX

On February 28, 1953, Francis Crick and an American graduate student James Watson deduced the double helical structure of DNA at Cambridge University. They deduced the double helical structure of

DNA by building on the experimental data collected by Wilkins and Franklin and tinkering with the toy model pictured in the slide. Watson and Crick won the competition to determine the structure of DNA, lasting fame and the 1962 Nobel Prize in Medicine for their discovery.

SLIDE 14. DOUBLE HELIX STRUCTURE OF DNA

Pictured is a DNA molecule, shaped in the double helix. The DNA molecule has a sugar-phosphate double helix backbone. Base pairs are formed from A-T (adenosine-thymine) and C-G (cytosine- guanine) pairings. The sum total of the base pair combinations produces our genotype-our genetic code.

The genotype, in combination with the environment, triggers, and chance produces the phenotype. The phenotype is the expression of the genotype in the body. The distance across a DNA molecule is only 23 angstroms. By comparison a chloride atom is 1 angstrom in diameter. In every cell of our body we have

2 meters (over 6 feet) of DNA. There is enough DNA in the 37 trillion cells in your body to stretch 10 billion miles - to Pluto and back. There are 20,687 genes in the human genome. The genes code for everything from hair color, the cells lining the lungs, and structure of the red corpuscle. There are 3.2 billion bases in a molecule of DNA. If published as a book, with just the letters A-T-C-G it would be 66 times the length of the Encyclopedia Britannica. Only 1-2% of the DNA in our genome codes for proteins. Mutations in the non-coding portions of the genome cause no problems.

SLIDE 15. HOW DNA WORKS.

This slide illustrates the circular flow of biologic information. RNAs are copied, in a process called transcription, from portions of the DNA molecule. Messenger RNA carries the RNA out of the nucleus of the cell into the surrounding cytoplasm where the proteins that compose the body and make it work are formed. Ribosomal RNA forms the structure of the ribosome, the organelle in which protein synthesis takes place. Transfer RNA carries amino acids, which are combined to form proteins, to the ribosome.

Lipids and steroids are formed in the endoplasmic reticulum of the cell. Once a human being is formed from proteins, lipids and steroids, that human being can sense their environment. The environment provides feedback to RNA and proteins. The RNAs and proteins then regulate the DNA. RNA and protein can instruct the DNA to stop manufacturing RNA.

SLIDE 16. MEIOSIS-THE PROCESS BY WHICH WE GET OUR GENOMES FROM OUR PARENTS

This slide illustrates meiosis. Meiosis is the process by which we inherit our genomes from our parents and produce germ cells for our offspring. Meiosis is Greek for lessening. In the testes in men, and ovaries in women, our germ cells (sperm and egg) are formed. The genetic material first doubles.

The cell that now has double the genetic material undergoes the first stage of meiosis, where homologous chromosomes recombine and exchange genetic material, enhancing genetic variability. In the slide the recombination of homologous chromosomes with exchange of genetic material is labeled as Meiosis I. In Meiosis I some of the genetic material on the red chromosome is transferred to the grey chromosome, and a matching amount of the grey chromosome is transferred in exchange to the red chromosome. In the second stage of meiosis the cells divide again, leaving four gametes with a half (also called haploid) share of genetic material. Because the gametes produced have half the genetic material of normal cells the process that produced them was called meiosis, Greek for “lessening”. These gametes, with their haploid share of DNA, are ready to combine with their homologues from the gametes of their sexual partner. The ultimate goal of meiosis is for each parent to provide a half share of

DNA to their gamete (sperm or egg) to combine with the gamete of their sexual partner to form a zygote

(better known as a baby). SLIDE 17. SPERMATOZOA MEETING EGG

The sperm cell is the smallest human cell. By contrast the human egg is the largest cell in the human body. The egg is visible to the naked eye at 0.2 mm. Roughly 250 million sperm cells are in the typical male ejaculate, but only one sperm cell makes it past the velvet rope into an egg. Those are roughly the odds of winning the powerball lottery. The sperm’s sole task is delivery of male DNA. The egg supplies all the other components of the embryo. One curiosity arises from the fact that the only material supplied by the sperm to the embryo is male DNA. The mitochondria is an organelle in the cell which breathes oxygen and produces energy. The mitochondria has DNA separate from the DNA in the nucleus of the cell. So-if a woman has all male children her mitochondrial DNA is lost to posterity, because her son’s sperm has no mitochondria.

SLIDE 18. MITOCHONDRIAL EVE

Since women frequently bore only sons over the millennia, female mitochondrial DNA was weeded out. Through this process of selection, every human being on Earth ultimately inherited their mitochondrial DNA from one woman: the so-called mitochondrial Eve-likely a member of the San tribe in Botswana or Namibia.

SLIDE 19. BLASTOCYST

The zygote (embryo) at five days is called a blastocyst. A blastocyst is pictured on this slide. The blue internal cell mass in this slide is the start of the embryo. These are the famous pluripotent embryonic stem cells.

SLIDE 20. STEM CELL

This slide illustrates pluripotent embryonic stem cells in the blastocyst. Pluripotent embryonic stem cells in the blastocyst have the potential to develop into any cell line (which is why they are called pluripotent stem cells). Pluripotent stem cells only exist for about fourteen days at the beginning of embryo formation, during the blastocyst phase. By contrast, the “committed” stem cells, which develop from the early pluripotent stem cells, form later. The committed stem cells form after the early blastocyst phase. Committed stem cells must develop into one cell line, as pictured in the slide.

Committed stem cells may develop into any one of the cell lines pictured: from cardiac, to fat, to neuron, or to red blood cells. Stem cells are the only cells in the body that renew themselves and provide a long term solution to gene deficiency. Stem cells are a small percentage of the cells in our body: very approximately 2 X 10 to the –5th.

SLIDE 21. EARLY EMBRYO

Pictured is an embryo at a very early stage of development. It is attached to the uterine wall, but the placenta is still developing. Even at this early stage the committed stem cells have assembled in three different embryonic layers as pictured-the inner level known as the endoderm, from which the internal organs arise; the middle layer or mesoderm, from which the musculoskeletal and circulatory system arise; and the outer layer, or ectoderm, from which the hair, nails, skin and nervous system arise.

Tumors that arise from the outer layer of the lung-the pleural lining-ultimately are derived from the mesodermal tissue-hence they are called mesotheliomas.

SLIDE 22. MITOSIS.

Through mitosis, our stem cells (which divide roughly 40-50 times in a lifetime) replace senescent, dying cells and replenish the body. The slide shows how the committed stem cell first doubles the genetic material in mitosis into two new sets of DNA. The two new complete sets of DNA then migrate to opposite poles of the cell. The old cell then divides into two daughter cells. One of every 600 cells dies daily. It should be noted there are important exceptions to the rule that all cells die and turn over. Nerve cells-which we call neurons, and cardiac muscle cells do not die and turn over. This is why we can heal a cut, but can’t readily recover from a spinal cord injury, stroke or large heart attack. Because neurons and cardiac muscle cells don’t have stem cells that divide by mitosis, virtually no tumors ever form from neurons or cardiac muscle cells. Except for our neurons and cardiac muscle cells, by the end of a normal life span all the original cells in our body have died and been replaced by mitosis in stem cells. Normal committed stem cells that turn over frequently are more prone to mutation and development of cancer.

SLIDE 23. SHIP OF THESEUS

The ship of Theseus has been compared to the human body in this respect. Theseus, the legendary founding hero of Athens, made his mark by slaying the Minotaur. Theseus returned to Athens in his ship, bearing the flower of Greek youth whom he had rescued from sacrifice to the Minotaur. The grateful

Athenians pledged to maintain the ship in seaworthy condition, replacing any wood that rotted. Ancient philosophers were vexed by the question at what point the ship was no longer the ship of Theseus.

Enlightenment philosophers such as John Locke, who I’m proud to say was a physician as well as a British empiricist, took up the question as it applied to aging human beings. Locke concluded our personal identity was just our experiences, held together by associations that are constantly conjoined. This prompted ridicule from Alexander Pope and Johnathan Swift. In the 17th century science was also called natural philosophy. Many natural philosophy problems are no longer philosophical problems due to the advance of science. We still dispute how to characterize consciousness, the so-called mind- body problem. But in 2021 we cite the lifelong persistence of our neurons and our DNA’s genetic code as proof of our persistent identity despite ongoing cell turnover.

SLIDE 24. TYPES OF MUTATIONS

Once again-the germ cells are the egg and sperm which arise, respectively, in the ovary and testes.

Somatic cells are all the other cells in the body. Germ cells only have half as much DNA as is present in somatic cells. Germ cells have what we call a haploid (half) amount of DNA due to meiosis. When somatic cells divide by mitosis, two normal cells are produced with a normal amount (so-called diploid amount) of DNA. Mutation comes from the Latin word for change. Mutation is defined as change in structure of a gene. Mutations are classified as germ cell mutations, or somatic mutations. Mutations in germ cells (the sperm cells in the testes or the eggs in the ovary) lead to genetic abnormalities in all the cells of the body. Mutations in the somatic cells (all the other cells in the body) lead to changes only in those organs in which the mutation takes place. For example, a mutation in a colon stem cell, will only lead to colon cancer. Normal somatic stem cells only divide 40-50 times in a lifetime, so cancer may take a long time to develop, even in cells which divide rapidly, such as white blood cells that become leukemia cells. There are genetic changes in the DNA when mutations occur in both germ and somatic cells. However, only mutations in the DNA of germ cells are inherited. Congenital changes in DNA are changes in DNA present at birth. Congenital just means present at birth. Congenital changes in DNA in

Down’s syndrome are inherited changes in the genome. In contrast, the congenital changes in DNA structure from fetal alcohol syndrome result from changes in the DNA from environmental effects.

SLIDE 25. THE HUMAN GENOME PROJECT

In 2003 an international effort to map the entire normal human genome was completed. Needless to say, this was an epic human and scientific achievement built on the conceptual breakthroughs provided by creative scientists, starting with Mendel, and technical advances in gene splicing. Now that we have reviewed normal cell biology we are prepared to learn about cancer biology.

SLIDE 26. CANCER DEFINITION-DR. MUKHERJEE Dr. Siddhartha Mukharjee reflected: “Cancer is an ultimate perversion of genetics-a genome pathologically obsessed with replicating itself. The genome as self-replicating machine co-opts the cell, resulting in a shape-shifting illness.”

SLIDE 27. CHARACTERIZATION OF CANCER BIOLOGY-HISTORY