Lecture 2- Etiology and Epidemiology of Cancer Flashcards
What are the two underlying causes of cancer?
-DNA damage
-Genomic instability
What are the two types of cancer?
-Sporadic/spontaneous cancer: occurs randomly
-Inherited genetic mutations/familial cancers: genetic mutations inherited from parents, that eventually lead to cancer
Are cancers contagious among humans?
No, generally non-contagious; there are some very rare forms of cancers that are contagious
Discuss this genetic mutation and how it can cause cancer.
This is a reciprocal translocation of the Q arms of chromosomes 9 and 22. The Q arm of chromosome 9 breaks just above the ABL gene. The Q arm of chromosome 22 breaks just below BCR gene. The two genes fuse, creating a fused active BCR-ABL protein. The protein interacts with Interleukin 3beta(c) receptor subunit, triggering a downstream pathway. This mutated chromosome is much more active than the wild type. This results in cell cycle control loss, causing cells to replicate at a rapid pace, leading to cancer, particularly leukemia.
Discuss an example of how cancer can be transmitted through organ transplantation
A 53-year-old woman was an organ donor when she died. She had no relevant medical history, and no sign of metastasis in any tissues. She donated her kidneys, lungs, liver, and heart. The lung recipient died of metastatic adenocarcinoma. The left kidney recipient died of metastatic adenocarcinoma of the breast. The liver recipient died of metastatic adenocarcinoma of the breast. The right kidney recipient survived but ended up getting metastatic adenocarcinoma of the breast. Shows that micrometastasis can stay undetected.
Define transmissible cancer
a cancer cell or cluster of cancer cells that can be transferred between individuals without the involvement of an infectious agent
Discuss devil facial tumor disease (DFTD)
It is an aggressive non-viral clonal transmissible cancer that affects Tasmanian devils; develops in the face, and when they bite others, they can transmit the cancer cells.
What is the most significant risk factor of cancer?
Age
Is cancer preventable?
Over one-third of cancer deaths can be prevented; In the US, 75-80% of cancer associated deaths are preventable
Discuss hereditary cancers
They consist of 3-10% of all cancer cases, although there are 50 identified hereditary cancers, less than 0.3% of population are carriers of cancer-related genetic mutations
Define cancer syndrome
Aka inherited genetic defects; genetic disorder in which inherited genetic mutation in 1+ gene predisposes the affected individual to cancer development; the risk varies, however
What are some mutations that cause cancer syndrome cases
Tumor suppressor genes (TSGs)
DNA repair genes
oncogenes
genes involved in the production of blood vessels
What mutations increase risk of breast/ovarian cancer
in the BRCA1 and BRCA2 genes
What are the two types of colorectal cancer; What are they caused by
familial adenomatous polyposis
hereditary non-polyposis colon cancer
inherited genetic disorders
What can genetic testing do in diagnosing cancer?
can be used to identify mutated genes or chromosomes that are passed through generations
What are the two classes of gene mutations
-germline or somatic
-they depend on the cell type that they appear on
-germline mutations are carried through generations and increase the risk of cancer
Discuss Ataxia telangiectasia
Involves mutated ATM gene (repairs DNA damage); leads to a higher risk of blood cancer
Discuss Bloom syndrome
-characterized by short stature
-involves mutation of the BLM gene (which controls RecQ DNA helicase)
-increases risk of blood cancer and carcinoma
Discuss Fancoci anemia
-involves mutation in DNA damage repair genes
-increases risk of blood cancer
Discuss Li-Fraumeni syndrome
-involves mutation in the p53 germline
-increases risk of breast cancer; sarcoma
Discuss Nevoid basal cell carcinoma syndrome
-involves mutation in PTCH1 gene
-increases risk of skin cancer
Discuss Von Hippel-Lindau syndrome
-involves mutation in VHL gene
-increases risk of renal carcinoma and other carcinomas
Discuss Werner syndrome
-characterized by premature aging
-involves mutation of WRN gene (accelerates DNA methylation)
-increases risk of a variety of cancers
Discuss Xeroderma pigmentosum
-characterized by skin pigment
-involves mutation of DNA damage repair gene caused by UV lights
-increases risk of skin cancer
Approximately 20,000 cancer deaths and 40,000 new cases of cancer are attributed to what?
occupation; exposure to physical and chemical agents in the workplace
What cancers is smoking tobacco linked to
-lung (80% of cases)
-larynx
-stomach
-bladder
-esophagus
-pancreas
-blood
What are the carcinogenic properties of tobacco?
produce nitrosamines and polycyclic aromatic hydrocarbons
How many deaths does second-hand smoke cause
58,000
How much death is tobacco responsible for
1/3 of all cancer deaths in developed world
1/5 worldwide
Discuss E-cigs and cancer
-daily/long-term/high-voltage smoking produces formaldehyde forming chemicals (at a higher level than plain smoking)
-lifetime cancer risk is 5x-15x more than smoking
What are some fibrous particulates that cause cancer
-asbestos
-wollastonite
-attapulgite
-glass wool
-rock wool
cause mesothelioma
What are some non-fibrous particulates that cause cancer
-powdered metallic cobalt and Nickel
-crystalline silica (quartz, cristobalite, tridymite)
What are some other occupational carcinogens
-arsenic
-benzene
-beryllium
-cadmium
-chromium
-ethylene oxide
-plutonium
What level carcinogen is alcohol
Group 1 carcinogen
What cancers does alcohol increase the risk of
-mouth
-esophagus
-larynx
-pharynx
-stomach
-liver
-colon
-ovaries
How does alcohol cause cancer
-alcohol converts to acetaldehyde (a carcinogen) and increased exposure to this causes cancer
-causes nutritional deficiencies by messing with metabolism
-causes changes in DNA methylation
-induces oxidative stress in tissues
What cancers does red/processed meat increase the risk of
breast cancer, prostate cancer, pancreatic cancer
What cancer does a high-salt died increase the risk of
gastric cancer
What cancer does aflatoxin b1 increase the risk of
liver cancer
What cancer does chewing betel nut increase the risk of
oral cancer
What is Aflatoxin B1?
-a poisonous and cancer-causing cancer
-produced by certain molds: aspergillus flavus and aspergillus parasiticus
-lives in soil, decaying vegetation, hay, and grains
-binds guanine in DNA and forms AFB1-guanine adducts
-causes G to T transversion at codon 249 of the p53 gene (tumor suppressing gene)
-causes hepatocellular carcinoma
Discuss how obesity is related to cancer
-in the US, excess body weight showed association with the development of cancers
-excess body weight attributed to 14-20% of all cancer deaths
-bariatric surgery reduced cancer incidence and mortality
How does obesity cause liver cancer?
Increased adipose tissue increases inflammatory environment, particularly in the liver; this increases risk of developing liver cancer
How does physical inactivity affect cancer risk
Inactivity weakens the immune system and endocrine system, which helps cancer cells grow and migrate throughout body
How do hormones affect cancer risk?
-hormonal fluctuation increases the risk of cancer
-increased estrogen and progesterone increases risk of breast cancer
-a mother with breast cancer leads to daughters with higher level of estrogen and progesterone, increasing risk of breast cancer in the daughter
-increased level of testosterone in men increases risk of prostate cancer in men of African, asian or European ancestry
18% of cancer cases are related to..?
infectious diseases
What cancer does HPV lead to
Cervical carcinoma in females
What cancer does Epstein-Barr virus lead to
B-cell lymphoproliferative disease and nasopharyngeal carcinoma
What cancer does Kaposi’s sarcoma herpesvirus lead to
Kaposi’s sarcoma and primary effusion lymphomas
What cancer does Hep B and C lead to
Hepatocellular carcinoma
What cancer does human t-cell leukemia virus-1 lead to
t-cell leukemias
What are some bacterias that cause cancer
-Helicobacter pylori can cause gastric carcinoma
-mycobacterium tuberculosis can cause lung cancer
What are some parasites that cause cancer
-Schistosoma haematobium can cause squamous cell carcinoma of the bladder
-Liver flukes, opisthorchis viverrini, and clonorchis sinensis can cause cholangiocarcinoma (bile duct cancer)
Discuss the radium girls
Radium was used to paint watch dials bc of its glowing property. The workers were told it’s a harmless dye, and they used their lips to help make the tips of the brushes fine, so they were ingesting the dye. Many died from oral/other cancers
How does ionizing radiation increase risk of cancer
-It randomly hits molecules in the cell, destroying organelles in its path
-breaks up chromosome
-causes abnormal number of chromosomes
-inactivates one/more genes
-deletes parts of the DNA sequence
What are the stages for ionizing radiation induced cancer
starts with morphological changes to cell
acquires cell immortality, causing cell to lose normal, life-limited cell regulatory processes, then there are adaptations
What kind of cells does radiation affect the most
hematopoietic stem cells (produce blood cells)
What are the main sources of exposure to ionizing radiation
medical imaging and radon gas
How long does one need to be exposed to radiation to cause solid tumors?
10-15 years
How long does one need to be exposed to radiation to cause leukemia?
2-10 years
2x the risk for children and adolescents
10x the risk for babies in the womb
How does radiotherapy cause cancer
It is used for cancer itself, but it can induce cancer because it comes in direct contact with normal cells, and many become cancerous
How does radon gas increase cancer risk
It is similar to passive smoking in increasing risk
What are some examples of non-ionizing radiation?
UV radiation
x-rays
gamma radiation
How does non-ionizing radiation increase cancer risk
more exposure increases risk
What are some rare causes of cancer?
-maternal-fetal transmission through transplacental transmission
-organ transplantation
What cancers can be caused through transplacental transmission
-acute leukemia
-lymphoma
-melanoma
-carcinoma
Define epidemiology
Distribution and determinants of disease frequency in human populations
Define prevalence
existence of current disease in specified population
Define incidence
new cases of disease that develop in a population at risk over specified time period
Define the epidemiology of cancer
the study of the factors affecting cancer, as a way to infer possible trends and causes; uses epidemiological methods to find the cause of cancer and to identify and develop improved treatments
How many new cancer cases and cancer deaths in 2020?
19.3 million new cancer cases
10.0 million cancer deaths
What is the most commonly diagnosed cancer in 2020
Female breast cancer
What is the leading cause of cancer death in 2020
lung cancer
Where was overall incidence rate higher? where?
2-3x higher; in developed countries over developing
Which continent had the highest incidence rate? Country?
asia; china
which continent had the highest mortality rate? Country?
asia; china
Which continent had the lowest incidence rate? country?
Oceania
Which continent had the lowest mortality rate? Country?
Oceania
Which cancer has highest incidence rate?
Female breast cancer
Which cancer has the highest mortality rate?
lung cancer
Which cancer has highest incidence rate in males
Lung
Which cancer has highest mortality rate in males
lung
Which cancer has highest mortality rate in females
breast
Which cancer has highest incidence rate in females
breast
Which cancer has the most probable risk in males?
prostate; 1 in 2
Which cancer has the least probable risk in males?
pancreas; 1 in 60
Which cancer has the most probable risk in females?
breast; 1 in 3
Which cancer has the least probable risk in females?
leukemia; 1 in 80
Why was there a sudden spike in diagnosing prostate cancers?
Because there was an introduction of a new diagnostic tool called PSA (Prostate specific antigen) test
