Module 3 - Chapter 10 Flashcards
How is tumour classified?
- tissue and organ of origin
- extent of distribution to other sites
- microscopic appearance of the lesion
- May include critical description of its genetic changes
Describe Benign tumours
- usually encapsulated with connective tissue, fairly differentiated, well organized stroma
- retain recognizable normal tissue
- do not invade beyond their capsule
- do not spread to regional lymph nodes or distant locations
- mitotic cells rarely present
How are benign tumours named
According to tissues from which they arise with suffix - oma
Describe malignant tumours
- rapid growth rate
- specific microscopic alterations (loss of differentiation, absence of normal tissue organization)
- large darkly stained nuclei
- mitotic cells are common
- disorganized substantial amount of stroma
- loss of normal tissue structure.
- lack capsule
- invade nearby vessels, lymphatics and surrounding structure.
- metastasis
What is the hallmark of cancer cells?
anaplasia - loss of cells differentiation
Pleomorphic
- marked variability of size and shape
- characteristic of malignant cell
Metastasis
ability to spread far beyond tissue of origin
how does cancer cells take their name
from their original cell type
Carcinoma in Situ (CIS)
preinvasive tumors, glandular in origin or squamous cell in origin
Where does CIS occur?
cervix, skin, oral cavity, esophagus, and bronchus
in glandural epithelium, in situ lesions occur in what places?
stomach, endometrium, breast, and large bowel
Where is DCIS in the breast located?
It fills the mammary ducts but not progressed to local tissue invation.
List the 3 fates of CIS?
- can remain stable for a long time
- progress to invasive metastatic cancer
- can regress and disappear
High grade lesion CIS
highest likelihood to become invasive Ca
What are the 2 fundamental concepts for understanding biology of cancer?
- Cancer - complex genetic disease with multiple mutations in genetic material
- microenvironment of a tumour is a heterogenous mixture of cells (both cancerous and benign)
Tumour initiation
- Process that produces initial cancer cells
- 1st stage of cancer development
- depends on specific mutations and characteristics of the microenvironment to influence transformation of these cells
Tumour Promotion
- 2nd stage
- population of cancer cells expands with diversity of cancer cell phenotypes
- gain in function
What enables the process of tumour promotion?
- additional mutations and changing tumour microenvironment
Tumour progression
- spread to tumour to adjacent distal sites
- governed by more mutations and more changes in microenvironment
Mutation
alteration in the DNA sequence affecting expression or function of a gene
Point mutations
-small-scale changes in the DNA
-alteration of one or a few nucleotide base pairs
- profound effect on the activity of resultant protein
Chromosomal translocation
- large changes in chromosome structures
- piece of one chromosome translocate to another
Gene amplification
- repeated duplication of a region of a chromosome (known as a promoter sequence)
- tens or hundreds of copies present instead of 2 copies of genes
What mechanisms are involved in genetic changes?
- Mutational
- Epigenetics
Give examples of mutational mechanism
- Point mutation
- Chromosomal translocation
- Gene Amplification
Give examples of epigenetic effects
- DNA methylation
- histone acetylation
- altered expression of non-coding RNA
Driver mutation
- drive the progression of cancer
- 140 different driver
Passenger mutations
- random events, just along for the ride
selective advantage
- clonal proliferation or clonal expansion
- progeny can accumulate faster than its non-mutant neighbours
Transformation
Process where normal cells become a cancer cell
what directs transformation
directed by progressive accumulation of genetic changes that alters the basic nature of the cell which drives it to malignancy
Stroma
Tumour microenvironment that surrounds and infiltrate the tumour
What cells forms the stroma?
Inflammatory or immune cells such as T lymphocytes, macrophages, b lymphocytes and neutrophils. also cells associated with tissue repair (fibroblasts, adipocytes, mesenchymal stem cells, endothelial cells and pericytes)
What is cancer development analogous to:
Wound healing
Whey is cancer development analogous to healing?
initial proliferation of cancer cells and enlargement of tumor elicit the synthesis of proinflammatory mediators by the cancer cells and adjacent non malignant cells
What does proliferation of cancer cells and enlargement of tumor cells elicit
Synthesis of proinflammatory mediators by the cancer cells and adjacent non malignant cells
How much stromal cells make up the tumour mass?
90%
Cancer heterogeneity arises form what factors?
Ongoing proliferation and mutation
consequences of Cancer-stromal interactions
hallmarks of cancer
What are some of the hallmarks and enablers
- Primarily genomic alterations that initiate and maintain development of cancer
- secondary genomic change
- Tumour resistance to destruction
- activating invasion and metastasis
What are included in genomic alterations?
- Sustained proliferative signalling
2.evading growth suppressors - genomic instability
- enabling replicative immortality
What are included in secondary genomic change?
1.angiogenesis
2. reprogramming energy metabolism
What are included in the tumour resistance to destruction?
- resistance to apoptotic cell death
- tumor-promoting inflammation
- evading immune destruction
What is the first and foremost hallmark of cancer
Uncontrolled cellular proliferation
How can proliferation can be discontinued?
By decreased level of growth factors in the environment or inactivation of signalling pathway components.
Cyclins
- effectively turn cell division - promising area for development of monoclonal antibodies in novel research of the treatment of cancer
proto oncogenes
Genes that encode components of receptor-mediated pathways designed to regulate normal cellular proliferation
oncogenes
- mutated or overexpressed proto-oncogenes
- independent of normal regulatory mechanism
- undergo uncontrolled cell growth
- can affect growth factor pathways
Autocrine stimulation
ability of cancer cells to secrete growth factors that stimulate their own growth
Oncogenes can also lead to what?
constant activation of the signal cascade from the cell surface receptor to the nucleus
Up to 1/3 of cancer have this?
activating mutation in the RAS gene resulting in a continous cell growth signal - even when growth factors are missing
What mutation is commonly observed in lung cancer
point mutation
What can point mutation results in ?
Continuous activation of EGF receptor tyrosine kinase
What changes the regulated proto-oncogene to an unregulated oncogene
A point mutation in RAS gene coverts it
What can activate oncogenes
Point mutations, translocations, gene amplifications
How can translocation activate oncogene?
- it can cause excess and inappropriate production of a proliferation factor
- chromosome translocation can lead to the production of novel proteins with growth promoting properties
BCR-ABL
unregulated protein tyrosine kinase that promotes growth of myeloid cells
Gene amplification can lead to what?
increased expression of an oncogene - in some cases, medication-resistance genes
Tumour-suppressor genes or antioncogenes
- regulate cell cycle
- inhibit proliferation from growth signals
- stop cell division with damage cells
- prevent mutations
What needs to happen in tumour suppressor gene for cancer to occur?
both copies of tumour suppressor genes must undergo mutations
What is the normal function of caretaker genes:
Maintain DNA and chromosome stability
What is the mutation effect with caretaker genes?
Chromosomes instability leads to increased rates of mutation
What is the normal function of dominant oncogenes?
Encode proteins that promote growth