DDT 2 - Intro to Cancer Flashcards
What is cancer?
- A disease of unregulated growth of cells from genetic mutation
- Generic term for a large group of diseases that can affect any part of the body.
Definition: Malignant, ill-regulated proliferation of cells causing either a solid tumour or other abnormal conditions.
Usually fatal if untreated
Limit cells ability to replicate, in some cases goes into overdrive, produces tumors
Exception - children get leukemia, cancer of blood, does not form tumors
Does not respond to normal chemical cues, become very “selfish”, all they want is to grow, divide, consume
CAR T-cells recognize and attack cancer cells
Cancer cells are abnormal in many ways
- in the way they multiply indefinitely
- how they invade underlying tissue
- migrate to other sites of the body and multiply there
Cancer stats
-Cancer causes death because the cells don’t die instead they populate continuously crowding out healthy cells
- every year 6 million people die from cancer globally
-Half of all men and a third of all women will get cancer at some stage of there life.
Types of Cancers
Carcinomas - cells that cover internal and external body surfaces e.g. lung, breast, colon, bladder, prostate
Leukemia - blood cells
Lymphomas - lymph nodes and tissues
Sarcomas - cells in supportive tissues (bone/muscle)
Top 3 Cancers
Breast, Lung, Colon/Rectum
Neoplastic diseases:
Neoplasm = overgrowth of cells that serve no useful purpose (e.g. tumor)
(On the other hand, normal life processes are characterized by continuous growth and maturation of cells, all cells subject to control mechanisms that regulate their growth rate)
e.g. human papilloma virus (HPV) small benign growths
Classes of Tumors
Benign
- slow growth rate
- expansion
- remains localized
- well differentiated
Malignant
- rapid growth rate
- infiltration
- metastasis in bloodstream and lymphatics
- poorly differentiated
Types of Malignant Tumors
Carcinomas
= Malignant tumor from epithelial cells e.g. lung carcinoma, hepatic carcinoma, melanoma
Sarcomas
= Malignant tumour from connective tissue (osteosarcoma, fibrosarcoma, myosarcoma)
Lymphoma/Leukemia’s
= Neoplasm of blood cells leukemia, lymphomas, myeloma
Naming Tumors - Polyp/Papilloma
Any benign tumor projecting from surface epithelium
Naming tumors - Adenoma
Benign tumor of epithelial tissue with glandular origin
Often from glandular organs including adrenal glands, pituitary, thyroid, prostate
Naming Tumors - Carcinoma
Malignant tumor arising from surface, glandular/parenchymal epithelium (not endothelium or mesothelium)
approx 90% of human cancers
Naming Tumors - Sarcoma
Malignant tumor of any primary tissue other than surface, glandular, and parenchymal epithelium
Naming Tumors - Leukemia
Neoplasm of blood cells
Teratoma
Tumor of mixed cell components
Often arise in reproductive tract
May consist of fat, muscle, bone, hair, oil
e.g. dermoid cyct, common benign cystic teratoma in the ovary, contains hair and sometimes fully grown teeth
Oncogenesis
Transformation of normal cells into cancer cells entails concerted changes in gene expression
Acquire mutations in 2 different categories of genes: tumor suppressor genes and proto-oncogenes
Single oncogene is insufficient to make normal cells cancerous, whereas cooperation between 2 distinct oncogenic mutations can work
In many cases “normalizing” expression of even one of these genes is sufficient to attenuate tumor growth
Cancer Cell Division
Normally, cell divisions are controlled strictly
Cancer cells have lost the capacity to recognise signals from there surroundings
The cell number grows out of control;
- They may not detect neighbouring cells
- They may produce their own growth hormones to stimulate cell division
- They may not produce tumour suppressor proteins
- They ignore normal apoptotic processes
Angiogenesis supplies blood into tumors, become vascular, can continue to grow
Conventional Oncogenesis Model
With aging, higher chance of mutation occurring.
Aging primarily contributes to increased cancers by facilitating the accumulation of oncogenic mutations (red cells), including activating mutations in oncogenes or genetic/epigenetic inactivation of tumor suppressor genes.
More than 80% of human cancers diagnosed after 50, aging represents single most important prognostic factor for many cancers (lung, breast, colon, prostate, certain leukemias).
Therefore, as we age the risk of cancer increases. (model doesn’t account for all types of cancers)
Adaptive Oncogenesis Model
Ability of an oncogene to induce cancer is context specific.
Healthy population - ability of cells to effectively compete for niche space is high due to optimal progenitor cell fitness.
Competition is inherently tumor suppressive.
However, if cellular fitness decreases as a result of aging or environmental insults, the acquisition of an oncogenic mutation could beadaptivedue to its ability to correct or circumvent defective cellular function. In this context, these cells would be selected for, leading to carcinogenesis.
Cancer cells reproduce every…
2-6 weeks
Size of cancer cells :
- 1 million = head of pin
- 1 billion = small grape
If cancer cells divide every month, it would be 2.5 years before one cancer cell grows into a small grape-sized tumor.
A person has usually had cancer for several years before it is detected and/or causes side effects.
Novel markers for Cancer detection is being continuously researched.
Cancer growth
Invasion, metastasis, angiogenesis, necrosis
Invasion
When cancer cells spread (no longer benign) from the primary site to another part of the body
Metastasis
Tumor cells are transported through the circulatory system
Transport typically to the bone liver and lungs where they may form secondary/tertiary tumors
Most people who die of cancer die of metastatic disease
Tumor Angiogenesis
As a tumor develops it requires oxygen and nutrients for survival
Cancers secrete blood vessel stimulators (VEGF)
Blood vessels grow towards and into tumorgenic masses (angiogenesis)
Tumor Necrosis
As a tumor enlarges the center of the tumor may not receive enough nutrients, forming a necrotic core
Skin Cancer
Usually keratinocyte or melanocyte based tumours
- Nevus = a benign tumour of melanocytes
- Melanoma = malignant tumour of melanocytes
Clinicians must diagnose between a benign nevus (common mole) and amelanoma
Mole irregularities - skin cancer indicators
Asymmetry
Border - irregular/ragged indicates cancer
Color - same color mole, tends to be benign, not a melanoma (coloration changes, genetic mutations, some more melanin than they should)
Diameter changes - if mole’s diameter is larger than pencil’s ear
Other indicators - itchy, bleed, cluster, pus
Basal cell carcinoma
- 75% of all skin cancers
- highly treatable cancer
- starts in basal cell layer of epidermis (top layer of skin)
- grows very slowly
- appears as small, shiny bump/nodule on skin in areas exposed to sun (head, neck, arms, hands, face)
- common among people with light colored eyes, hair, complexion
Squamous cell carcinoma
- 20% of all skin cancer cases
- more aggressive than basal cell carcinoma, but highly treatable
- may appear as nodules or red,scaly patches of skin
- may be found on face, ears, lips, mouth, but can spread to other parts of the body
- usually in fair-skinned people
Malignant melanoma
- less common
- most deadly (79% of all skin cancer deaths)
- starts in cells producing pigment in the skin
- usually begins as a mole that turns cancerous, spreads quickly
- most often appears on fair-skinned men and women, but all skin types can be affected
Lung Cancer
- 1st cause of cancer deaths in the world
- Smoking is the leading risk factor
- Can arise in any part of the lung but 90-95% thought to arise from epithelial
cells lining the bronchi/bronchioles = “bronchogenic carcinomas” - Can arise from the pleura (mesotheliomas) or rarely from supporting tissue within the lungs such as blood vessels
- Two types of lung cancer (small cell lung cancer SCLC / non-small cell lung cancer NSCLC)
3 types of Blood Cancer
Leukemia, Lymphoma, Myeloma
Leukemia
- blood and bone marrow
- caused by rapid production of abnormal WBCs
- not able to fight infection, impair ability of bone marrow to produce RBCs and platelets
Lymphoma
- affects lymphatic system, which removes excess fluids from your body and produces immune cells
- abnormal lymphocytes (WBCs) become lymphoma cells, multiply and collect in lymph nodes and other tissues, over time impair immune system
Myeloma
- specifically targets plasma cells (WBCs producing disease/infection-fighting antibodies)
- myeloma cells prevent normal production of antibodies, leaving body’s immune system weakened and susceptible to infection
Breast Cancer
- A disease in which malignant cells form in breast tissues
- Most common = Ductal carcinoma
- 12% of women will develop breast cancer sometime
- Increased risk in females with tumour suppressor proteins BRCA1 and BRCA2 mutations (25% of hereditary breast cancers, 5-10% of all breast cancers)
- Mutation can be inherited from the mother or father
Tests to Diagnose Breast Cancer
- Physical exam and history
- Clinical breast exam (doctor feels breasts and under arms for lumps)
- Biopsy (removal of cells/tissues to be viewed under a microscope for signs of cancer)
- Ultrasound
- MRI
- Mammogram (breast x-ray)
- Blood chemistry studies
Prostate Cancer
Prostate = organ posterior to male genitalia, below bladder
- Commonest malignant tumour in men over 65 years
- At age 50 to 65, 15-20% have histological evidence rising to 50% at age 80
- Often metastasises to pelvic bone via lymphatics and blood supply - dangerous – can become osteosarcoma in pelvic bone
Can do digital rectal exam
Treated quite well if done early
Longer you live, all men will get some form of prostate cancer
Risk factors (prostate cancer) :
- Age: rare <40, 29% 6th decade, 67% 9th decade
- Hereditary: Risk doubled with 1st degree relative and x4 if 2 FDR
- Race: lower incidence of clinically evident disease in Japan and China
- Black > white, Jamaica highest mortality rate
- Diet: High saturated fat increased risk
