Lecture 1 Flashcards
A tumor or Neoplasm is
a group of cells which display unregulated proliferation
Benign
Clustered in a single mass , not capable of indefinite growth and not able to invade healthy
surrounding tissue
CANCER refers specifically to
MALIGNANT tumour
Metastasis is the
ability of a malignant tumor to form 2o
tumors (metastases) at other sites in
the body. Small clusters of cancerous cells dislodge from the primary tumour to invade the
blood or lymphatic vessels and are carried to distant sites, take up residence and continue to
proliferate
Majority of human tumours arise from
Epithelial tissue
Carcinomas (80-90% cancers)
are of epithelial origin
eg skin, gut or epithelial lining of internal organs and glands)
Cancers of Breast, colon, prostate, lung, stomach, skin, oesophagus, liver, ovary, gallbladder and urinary bladder are
carcinomas.
Non-epithelial cancers
Leukemia, Lymphoma and multiple
myeloma (9% of all cancers) are
malignant tumours of hematopoietic
cells derived from bone marrow (cells
of the immune system, including T and
B cells.
Sarcoma (1% cancers)
arise from a variety
of mesenchymal cell types including
osteoblasts (bone-forming
cell)[Osteosarcoma], adipocyte (fat
cell)[Liposarcoma] and fibroblast
(connective tissue cell)[Fibrosarcoma].
The 3rd group of nonepithelial
tumours arise from cells that
form
part of the central and peripheral
nervous systems. Includes gliomas,
glioblastomas, neuroblastomas,
medulloblastomas. Makes up 1.3%
of all diagnosed cancers, but 2.5%
of cancer deaths.
Oncogenes are involved in
cell growth promoting
processes.
- Tumor-suppressor genes allow
cancer cell survival when
they fail
- Apoptosis
when faults-leads to abnormal cell survival
Oncogenes are usually
“gain of function mutations”
generally dominant eg cMYC
Tumor suppressor genes (TSGs) are usually
“loss of function mutations”
generally recessive eg Rb
Mutation of both copies of a tumor suppressor gene
allows
dysregulated division/ excess proliferation.
Is an activating mutation in a single oncogene sufficient to cause cancer
An activating mutation in a single oncogene is not sufficient
to cause cancer
Oncogenes must collaborate with one another and with what to generate cancers?
Oncogenes must collaborate with one another and with
inactivation of Tumour Suppressors in order to generate
cancers
In their normal state, TSGs prevents
cells from progressing
through the cell cycle inapproprately, functioning like
Brakes eg RB
In precancerous and cancerous cells many what are seen?
- In precancerous and cancerous cells many chromosomal
alterations are seen
Functions of Proto-oncogenes
In general they encode elements of the cell’s signal
transduction network and parts of the cell cycle control
system
>100 proto-oncogenes known.
Highly conserved through evolution
* Growth Factors
* Growth Factor Receptors
* Signal Transduction Molecules
* Nuclear Proteins
Proto oncogenes encode
Growth factors, growth factor receptors, signal transduction molecules and nuclear proteins
Signal transduction molecules
A. Cytoplasmic membrane associates proteins - src (tyrosine kinase); ras (GTP- binding protein)
B. Soluble signal transduction proetins - raf (serine/threonine kinase)