p.3
Cell Cycle Regulation and Cancer
What is apoptosis?
Apoptosis is the normal, programmed death of cells.
How do tumor cells migrate to other sites in the body?
By penetrating blood or lymphatic vessels and circulating through the circulatory system.
p.10
Cell Cycle Regulation and Cancer
How does p53 contribute to cell cycle regulation?
By halting the cell cycle in response to DNA damage.
p.6
Mutations in Cancer Cells
What is the effect of mutations in the regulatory region, such as the promoter?
They may lead to overexpression of the gene, causing overproduction of the normal functional protein.
p.1
Genetic and Environmental Risk Factors
What are the internal factors that can contribute to cancer?
Loss of immunity, genetic predisposition, and hormones.
p.13
Multi-Step Process of Cancer
What is the initial characteristic of benign tumors?
They lack the ability to invade or spread to other tissues.
p.10
Mechanisms of Cancer Development
What is the effect of accumulated DNA damage in a cell?
It increases the risk for cancer formation.
p.6
Mutations in Cancer Cells
How can point mutations in the coding region affect proteins?
They may change the 3D conformation of the protein, causing it to become hyperactive.
p.1
Mechanisms of Cancer Development
What is the role of mutations in cancer development?
Mutations accumulate over time, leading to changes in cancer cells and the development of malignant tumors.
p.10
Tumor Suppressor Genes
What happens when mutations occur in the p53 gene?
Non-functional p53 proteins are synthesized.
p.14
Causative Factors of Cancer
How does loss of immunity contribute to cancer risk?
It reduces the body's ability to eliminate infected or transformed cells.
p.11
Multi-Step Process of Cancer
What is the nature of cancer development?
Cancer development is a multi-step process involving the accumulation of mutations.
p.13
Angiogenesis and Metastasis
What role do new blood vessels play in tumor development?
They supply nutrients and oxygen to the growing tumor at the new site.
p.8
Mutations in Cancer Cells
What can errors in DNA replication lead to in cancer cells?
Extra gene copies through gene amplification.
p.8
Mutations in Cancer Cells
What is a key characteristic of gene amplification?
Selective replication of a region of a chromosome, leading to many copies.
p.6
Mechanisms of Cancer Development
What triggers the activation of the Ras protein?
The binding of an appropriate growth factor to a receptor.
p.12
Multi-Step Process of Cancer
What is the first step in cancer development?
A single cell in a tissue suffers a mutation in a gene involved in the cell cycle.
p.5
Genetic and Environmental Risk Factors
What is the significance of an oncogene in germ line cells?
It results in an inherited predisposition for tumors in the offspring.
p.11
Multi-Step Process of Cancer
What age group is most affected by cancer and why?
Most cancers occur in people over 40 years of age due to the need to inactivate several regulatory genes over decades.
p.14
Causative Factors of Cancer
What is the main cause of cervical cancer?
Human papillomavirus (HPV) infection.
p.12
Mechanisms of Cancer Development
How does the rate of mitosis affect DNA damage?
As the rate of mitosis increases, the chances of further DNA damage increases.
p.3
Genetic and Environmental Risk Factors
How many genes are thought to exist in the human genome?
Approximately 30,000 genes.
p.13
Angiogenesis and Metastasis
What is angiogenesis?
The formation of new blood vessels.
p.1
Multi-Step Process of Cancer
How is cancer development described in terms of process?
As a multi-step process that includes accumulation of mutations, angiogenesis, and metastasis.
p.8
Mutations in Cancer Cells
What happens to genes within the amplified portion of a chromosome?
They can be transcribed to produce normal proteins, leading to overproduction.
p.5
Mutations in Cancer Cells
What is a gain-of-function mutation?
A mutation where cells with the mutant form of the protein gain a new function not present in cells with the normal gene.
p.11
Multi-Step Process of Cancer
How many independent mutations are typically required for cancer development?
Approximately 4 to 6 independent mutations.
p.3
Cell Cycle Regulation and Cancer
What happens when telomeres reach a critical length?
The cell undergoes apoptosis once a critical length of the telomere is reached.
p.5
Mechanisms of Cancer Development
What genetic changes are associated with the conversion of a proto-oncogene into an oncogene?
A number of genetic changes lead toward cancer.
p.3
Genetic and Environmental Risk Factors
What causes cancer at the genetic level?
Cancer is caused by mutations in genes regulating the cell division cycle, leading to unrestrained cell proliferation.
p.12
Multi-Step Process of Cancer
What occurs when many mutations accumulate in a cell line?
The growth of the line of clones becomes completely unregulated.
p.9
Mutations in Cancer Cells
What is the consequence of mutations in tumor suppressor genes?
They result in a loss of function, preventing the inhibition of cell growth.
p.7
Mechanisms of Cancer Development
What does the abnormal Bcr-Abl protein do?
It is a constitutively active tyrosine kinase that causes myelocytes to grow and multiply uncontrollably.
p.2
Proto-Oncogenes and Oncogenes
What is the effect of gain of function mutations in proto-oncogenes like ras?
Gain of function mutations in proto-oncogenes like ras result in uncontrolled cell division.
p.1
Tumor Suppressor Genes
What type of mutation in tumor suppressor genes, such as p53, leads to uncontrolled cell division?
Loss of function mutation.
p.5
Proto-Oncogenes and Oncogenes
What happens when the Myc gene is over-expressed?
It leads to overproduction of the Myc transcription factor, causing enhanced cell proliferation.
p.6
Mechanisms of Cancer Development
What happens when GTP displaces GDP in the Ras protein?
The Ras protein becomes active and passes on the signal to cytoplasmic kinases.
p.6
Mechanisms of Cancer Development
What is the role of active Ras protein in cell signaling?
It activates transcription factors that turn on genes for proteins that stimulate the cell cycle.
p.14
Causative Factors of Cancer
What role does estrogen play in cancer?
It is needed for breast tumors to grow in females.
p.6
Proto-Oncogenes and Oncogenes
What is the consequence of a mutated Ras protein?
It remains constitutively active even in the absence of growth factor.
p.12
Multi-Step Process of Cancer
What can happen over time to descendant cells of a mutated cell?
They may suffer another mutation in another cell cycle regulatory gene.
p.11
Mutations in Cancer Cells
What are the consequences of accumulated mutations in cancer cells?
Overstimulation of cell growth and division, inability to halt the cell cycle, carry out DNA repair, and initiate apoptosis.
p.14
Causative Factors of Cancer
What is the impact of chronic hepatitis B viral infection on cancer risk?
It leads to a 100-fold increase in liver cancer risk.
p.4
Proto-Oncogenes and Oncogenes
What are proto-oncogenes?
Genes that normally trigger cell division when appropriate.
p.4
Proto-Oncogenes and Oncogenes
What is an example of a growth factor coded by proto-oncogenes?
Platelet-derived growth factor (PDGF).
p.3
Cell Cycle Regulation and Cancer
How do normal cells respond to DNA damage?
Normal cells cease to divide and undergo apoptosis when there is DNA damage.
p.14
Causative Factors of Cancer
How is HIV associated with cancer risk?
It increases the risk of cancers like lymphoma and Kaposi's sarcoma.
p.7
Mutations in Cancer Cells
What ability does the altered Ras protein lose due to mutation?
The ability to hydrolyze GTP to GDP.
p.7
Mechanisms of Cancer Development
What can chromosomal rearrangement result in?
A hyperactive fusion protein or over-production of a normal protein.
p.2
Cell Cycle Regulation and Cancer
What is contact inhibition?
Contact inhibition is the process where normal cells cease division upon contact with other cells.
p.2
Mechanisms of Cancer Development
How many times can a normal cell divide in culture?
A normal cell can divide only 20 to 50 times.
p.6
Mutations in Cancer Cells
What is a point mutation?
A small change in the base sequence, such as substitution or deletion, in the coding region.
p.3
Cell Cycle Regulation and Cancer
What is the limit on the number of cell divisions for normal cells?
Normal cells have a limit on the number of divisions and undergo apoptosis when they reach that limit.
p.1
Causative Factors of Cancer
What external factors are associated with an increased risk of cancer?
Chemical carcinogens, UV radiation, and ionizing radiation.
p.6
Mechanisms of Cancer Development
How does the Ras protein turn off the signaling pathway?
By hydrolyzing its bound GTP to GDP, becoming inactive again.
p.12
Multi-Step Process of Cancer
What happens to DNA damage in mutated cells?
It is passed on to all daughter cells produced from these mutated cells.
p.3
Mutations in Cancer Cells
How do cancer cells behave in response to DNA damage?
Cancer cells continue to divide even when there is significant DNA damage.
p.14
Causative Factors of Cancer
What effect does chronic tissue injury have on cancer risk?
It stimulates the rate of mitosis, increasing the chance of mutations.
p.9
Tumor Suppressor Genes
What actions can tumor suppressor proteins carry out if growth conditions are not met?
Halt the cell cycle, carry out DNA repair, and induce cell death (apoptosis).
p.9
Genetic and Environmental Risk Factors
How are mutations in tumor suppressor genes typically inherited?
They are usually recessive, requiring both copies of the normal alleles to be mutated for expression.
p.9
Tumor Suppressor Genes
What role does the p53 tumor suppressor gene play in cancer prevention?
It activates DNA repair proteins, holds the cell cycle at the G1 checkpoint, and can initiate apoptosis if DNA damage is irreparable.
p.9
Tumor Suppressor Genes
What is the role of p53 in maintaining genetic stability?
It activates DNA repair proteins when DNA has sustained damage.
p.4
Proto-Oncogenes and Oncogenes
What is the function of the receptor for epidermal growth factor?
It is a receptor tyrosine kinase that can become constitutively active when mutated.
p.4
Proto-Oncogenes and Oncogenes
What happens to the Ras protein when it is mutated?
It remains active and continues to send stimulatory signals, leading to more cell division.
p.2
Mechanisms of Cancer Development
How do cancer cells behave in relation to contact inhibition?
Cancer cells lose contact inhibition and continue to grow even after touching other cells.
p.13
Multi-Step Process of Cancer
When is a tumor regarded as malignant?
When it gains the ability to invade normal tissues and spread, thus being referred to as cancer.
p.1
Causative Factors of Cancer
What are some causative factors that may increase the chances of cancerous growth?
Genetic factors, chemical carcinogens, ionizing radiation, and loss of immunity.
p.6
Proto-Oncogenes and Oncogenes
What does the Ras gene code for?
A G-protein found on cell membranes.
p.14
Causative Factors of Cancer
What is a genetic predisposition to cancer?
Having a defective copy of a tumor suppressor gene inherited from parents.
p.3
Mutations in Cancer Cells
What role does telomerase play in cancer cells?
Telomerase is activated in cancer cells, allowing them to undergo unlimited cell divisions without triggering apoptosis.
p.8
Mutations in Cancer Cells
What is insertional mutagenesis?
Insertion of a retrovirus into DNA causing overexpression of a proto-oncogene.
p.9
Tumor Suppressor Genes
What is the primary function of tumor suppressor genes in normal cells?
They code for proteins that prevent cell division or lead to cell death (apoptosis).
p.2
Mechanisms of Cancer Development
What happens to cancer cells in terms of nutrient supply?
Cancer cells are considered 'immortal' if they have a continued supply of nutrients.
p.10
Tumor Suppressor Genes
What are the consequences of non-functional p53 proteins?
They cannot carry out DNA repair, halt the cell cycle, or induce apoptosis.
p.1
Proto-Oncogenes and Oncogenes
What type of mutation in proto-oncogenes, such as ras, contributes to uncontrolled cell division?
Gain of function mutation.
p.5
Proto-Oncogenes and Oncogenes
What is the role of the Myc transcription factor?
It stimulates the transcription of other genes required for cell proliferation.
p.14
Causative Factors of Cancer
What is the significance of the BRCA1 gene?
Its mutation increases the lifetime risk of breast cancer by 70%.
p.12
Mechanisms of Cancer Development
What advantage does a mutated cell have over other cells?
A slight growth advantage.
p.14
Causative Factors of Cancer
How does UV and ionizing radiation affect DNA?
It causes DNA bases to become more reactive and can lead to mutations.
p.12
Mechanisms of Cancer Development
What is the consequence of further mutations in descendant cells?
It further deregulates the cell cycle of that cell and its descendants.
p.3
Tumor Suppressor Genes
What are the two broad categories of genes involved in cancer?
Proto-oncogenes and tumor suppressor genes.
p.7
Mechanisms of Cancer Development
What does chromosomal rearrangement involve?
The breakage and re-joining of DNA (translocation).
p.9
Mutations in Cancer Cells
What is loss of heterozygosity in the context of tumor suppressor genes?
It refers to the disruption of the remaining normal allele after one allele has undergone mutation.
p.4
Proto-Oncogenes and Oncogenes
What do oncogenes code for?
Proteins that lead to overstimulation of cell growth and division.
p.4
Proto-Oncogenes and Oncogenes
What is the role of the Ras protein?
It is associated with the cytoplasmic surface of a membrane receptor and regulates cell signaling.
p.4
Proto-Oncogenes and Oncogenes
What is the function of Src protein?
It catalyzes the addition of phosphate groups onto other proteins, promoting cell survival and proliferation.
p.2
Mechanisms of Cancer Development
What is a key characteristic of cancer cells compared to normal cells?
Cancer cells divide excessively without control and have escaped from cell cycle control.
p.5
Proto-Oncogenes and Oncogenes
How do most oncogenes arise?
From dominant mutations, where a single copy of the oncogene is sufficient for expression of the trait.
p.14
Causative Factors of Cancer
What are chemical carcinogens?
Substances that damage or alter DNA, such as tobacco smoke and benzene.
p.11
Mutations in Cancer Cells
What are the genetic changes required for a cell to become cancerous?
Gain of function mutation in at least one proto-oncogene and loss of function mutations in several tumor suppressor genes.
p.2
Cell Cycle Regulation and Cancer
What happens to normal cells when growth factor synthesis is inhibited?
Normal cells stop dividing.
p.2
Tumor Suppressor Genes
What is the role of tumor suppressor genes like p53 in cancer development?
Loss of function mutations in tumor suppressor genes like p53 lead to uncontrolled cell division.
p.12
Mutations in Cancer Cells
What types of mutations can occur in the first step of cancer development?
Gain of function mutation in a proto-oncogene or loss of function mutation in a tumor suppressor gene.
p.11
Multi-Step Process of Cancer
Why is mutation in one proto-oncogene or tumor suppressor gene usually insufficient to cause cancer?
Because all controls at several checkpoints must be inactivated for cancer to be initiated.
p.8
Proto-Oncogenes and Oncogenes
How does a retrovirus affect a proto-oncogene during infection?
It integrates into the host DNA near the proto-oncogene, leading to overexpression.
p.11
Multi-Step Process of Cancer
What happens to mutations in a cancer-promoting cell?
They are passed to all its descendants.
p.11
Multi-Step Process of Cancer
What evidence supports the multi-step process of cancer development?
Analysis of tumors reveals different degrees of malignancy and accumulation of genetic alterations as tumors progress.
p.7
Mechanisms of Cancer Development
What is the result of the altered Ras protein being constitutively active?
It continuously delivers signals for cell growth and division, leading to uncontrolled cell division.
p.4
Proto-Oncogenes and Oncogenes
What happens when proto-oncogenes are activated at the wrong time or place?
They function as oncogenes, which can lead to cancer.
p.3
Mutations in Cancer Cells
What are telomeres?
Telomeres are non-coding, repetitive sequences at the end of chromosomes that act as buffers for coding sequences.
p.5
Multi-Step Process of Cancer
Is a single oncogene usually sufficient to cause cancer?
No, a single oncogene is usually not sufficient to cause cancer.
p.8
Proto-Oncogenes and Oncogenes
Why do retroviral sequences lead to overexpression of proto-oncogenes?
They do not respond to environmental signals that normally regulate expression.
p.7
Mutations in Cancer Cells
What is the effect of a point mutation in the ras oncogene?
It may cause a change in the 3D conformation of the Ras protein.
p.14
Causative Factors of Cancer
How does chronic inflammation contribute to cancer?
It generates DNA-damaging oxidizing agents in the cell.
p.7
Causative Factors of Cancer
In which cancers has the mutant ras oncogene been identified?
Pancreas (90%), colon (50%), lung (30%), thyroid (50%), bladder (6%), ovarian (15%), breast, skin, liver, kidney, and some leukemias.
p.4
Proto-Oncogenes and Oncogenes
What is the role of PDGF?
Stimulates proliferation of connective tissue cells at the site of injury for wound healing.
p.7
Mechanisms of Cancer Development
What causes chronic myeloid leukemia (CML)?
An exchange in a small section between chromosomes 9 and 22, resulting in a mutant Bcr-Abl gene.
p.9
Multi-Step Process of Cancer
What happens to cells with one normal and one mutated allele of a tumor suppressor gene?
They behave normally until other mechanisms cause the loss of the normal allele.
p.4
Proto-Oncogenes and Oncogenes
What is a characteristic of gliomas?
They have an over-expression of growth factors and receptors in undifferentiated cells.
p.2
Mechanisms of Cancer Development
Do cancer cells require growth factors to divide?
No, cancer cells have lost the need for growth factors and divide regardless of their presence.
