Pathology week 11

Tumour growth

-1st pillar of cancer formation -Tilt balance towards more proliferation and less controlled death -Growth inhibitors and factors cause balance in cell cycle -Several checkpoint proteins (Cyclin D/CDK4, Cycline E/CDK2) maintain balance between growth and death -Growth inhibitors: P53 and RB regulate this process -Growth factors: EGF, TGF-a, HGF and PDGF **Growth factors activate cyclines for growth where as growth inhibitors stimulate cycline inhibitors to stop growth

Characteristics of inherited cancer syndromes

-A large number are autosomal dominant -Often a point mutation of one allele -Tumours usually show tissue specificity -E.g colon caner--> Adenomatous polyposis coli gene (APC) causes pre-disposition to colon cancer -Multiple Endocrine Neoplasia (MEN) genes predispose to tumour development in multiple endocrine organs -May be syndromic (produce particular phenotype)- associated with other "markers" which are non-cancerous

How primary tumours behave in terms of metastatic potential

-A) some metastatic variants appear-->metastasis -B) All tumour cells acquire ability to metastasise (metastasis signature) in which there will be far greater capacity (than A) to metastasise -C) a mixture of A and B pathways can occur leading to metastasis -D) Tumour cells may utilise stromal response in terms of interaction with surface molecules which either promote or stop metastatic pathway which results in ultimate outcome on whether or not patient will develop metastasis

Genetic basis of cancer (genes regulating DNA repair)

-Also called mismatch repair genes -inactive mismatch repair genes e.g in hereditory non-polyposis coli (HNPCC) where accumulation of DNA defects leads to higher risk of colon cancer -Also higher risk of carcinoma of endometrium and ovary

Alterations of mismatch repair

-Alterations of mismatch repair genes prevent repair of damaged DNA -Biopsies from colon used to visualised mismatch repair via immunohistochemistry -Mistmatch repair gene expression stains brown in nuclei of crypts (normal) -In patient with absent mismatch repair gene expression in which won't have colour, treatment will likely be less effective than in patients who express mismatch repair gene as cell's own attempt to take care of repeated DNA damage will be compromised, mutations in mismatch repair genes play a role in development of cancer or its progression **brown=normal, no colour=abnormal (abscent)

Tumour angiogenesis

-Angiogenic factors (favour tumour growth as more vessels supply tumour): -vasuclar endothelial growth factor VEGF -basic fibroblast growth factor (bFGF) -Anti-angiogenic factors (cause ischemia) (doesn't favour tumour growth as less vessels if any, supply tumour growth) -Angiostatin -Endostatin -Vasculostatin Tumours that proliferate so rapidly would proliferate quicker than vessels hence tumour cells farther away from vessels will get ischemic and die

Genetic basis of cancer (genes controlling apoptosis)

-Apoptosis is programmed cell death -Imbalance of agonists (proaptotic) and agonists (antiapoptotic) leads to uncontrolled cell proliferation (due to P53 and c-myc mutations) -Pro-apoptotic genes: bax, bclxS, bad, bid -Anti-apoptotic genes: bcl2, bclxL

Acquired conditions risk factors for cancer: chronic irritation and scars

-Burns scar (marjolin ulcer): extensive and deep burns result in healing process producing excess scar tissue (fibrosis); triggers of damaged tissue due to thermal injury results in awakening of stem cells that can proliferate leading to cancer -Scars of varicose ulcers (if varicose veins persist, then can develop changes in surrounding tissue, especially overlying skin in which ulcer formation may occur, if untreated can get cancer in the healing scars) -Healed tubercular scars (in TB) -Liver cirrhosis (diffuse fibrosis)

p53 pathway immunophenotypes in bladder cancer

-Case 1: bladder tumour tissue with no brown colour hence normal p53 (acts via intermediary proteins to cause cell cycle arrest or apoptosis) -Brown colour in p21=normal -No colour in mdm2= normal **so overall p53,p21 and mdm2 all normal= ideal situation for bladder tumour as function will be maintained and proliferation + growth will be slow as well as accumulation of mutated DNA will be insignifcant as gene function is maintained -Case 2: bladder tumour tissue -Brown colour in p53=mutated -no colour in p21= abnormal (should be brown for normal) -brown colour in mdm2= abnormal **all abnormal= will behave more biologiclally aggressive as lost breaks to cell cycle= worse prognosis Same bladder tumour but different gene environment

Oncogenes

-Cause abnormal proliferation of cells and transform normal cells to cancer cells -Promote autonomous cell proliferation in the absence of normal growth promoting signals (can respond to selective signals if there is advantage for them in it) -Their gene products (oncoproteins) are not dependent on growth factors or other external signals

Control of normal cell growth and behaviour

-Cell growth: -regulated by growth promoting and inhibitory signals -Cell survival: -conditioned by genes that promote or inhibit apoptosis **localised growths will be pathalogical in which cell growth and survival controls are lost

Levels of activation of oncogene products in the cell

-Cell response to growth factor binding to growth factor receptor which triggers a cascade of signal transduction proteins that interact with nuclear regulatory proteins and cell cycle regulators

The cell cycle

-Cells wanting to multiply must leave resting G0 stage and enter cycle -Labile cells= can multiply (e.g lining epithelium cells) -Quiescent cells= can multiply if needed only (e.g hepatocytes) -Non-dividing permanent cells= can't divide so if lost they are lost (e.g neruons, cardiac monocytes)

Dysplasia example

-Cervix: -Cytology(PAP smear): notice in the top right that many cells have enlarged and dark staining nuclei of varrying size= High grade squamous intraepithelial lesion (HSIL) -If low grade it will be less invasive (LSIL) -Biopsy: -more invasive but gives more info -surface squamous lining is dark due to enlargement of disordered cells and nuclei of various shapes and sizes (pleomorphism) -CIN3 in biopsy corresponds to HSIL in cytology

Metaplasia

-Change of one type of epithelium to another -Important because it can become dysplasia -Specialised epithelium-->Squamous epithelium -Uterine cervix: Columnar to squamous (chronic inflammation, HPV) -Respiratory tract: -Pseudostratified ciliated columnar to squamous (smoking, pollution, pneumoconiosis) -Urinary trat: -Transitional to squamous (calculi, parasitic infection) -Gallbladder (cholelithiasis)

Chronic inflammation + viral infection

-Chronic inflammation + viral infection---> Dysplasia/cancer of liver (chronic hepatitis HBV) -Blue= dysplatic milieu of hepatocytes due to chronic inflammation **notice immune cells destroying liver tissue **Liver becomes regenerative which may be excess hence pre-disposing to tumorigenesis etc...

Inflammatory states and cancer

-Chronic inflammatory response can predispose to cancer, when immune response persists chronically, then inflammatory milieu containing immunological cells which are strained from normal path causes alteration in cell signals in which won't remain physiologic -Maladapted immune response -Cell survival and proliferation -Tissue remodelling (repair comp of chronic inflammation) -Angiogenesis -All result in expansion of stem cells (consistent stimulation of stem cells may go out of control hence potential carcinogenesis) -Mutagenic environment (cells multiplying and being replaced in compensatory sense but repeated DNA damage can produce an unstable environment, predisposing mutated cell to become cancerous

Scars and cancer visualised

-Chronic sun exposure can lead to squamous cell carcinoma especially in fair-skinned individuals

Squamous metaplasia in respiratory epithelium

-Ciliated pseudo-stratified squamous--> squamous -although squamous is stronger it is functionless in resp tract, it can also become dysplastic and turn to cancer

Endometrial hyperplasia

-Endometrial hyperplasia is a thickened endometrium due to increased number of proliferative glands with increased layers of lining cells -Usually occurs in response to hormones -Macroscopically: markedly red and thick endometrium (hyperplasia) -Microscopically: hyperplasia-->more cells and glands-->lining cells show abnormal changes in terms of nuclear crowding and enlargement -Clinically: endometrium is shed off (during menstruation), but because too thick will have abnormal bleeding -Hyperplasia on it's own isn't cancer but it can become dysplasia which can potentially become malignant

Genetic basis of cancer

-Every tissue as it grows is subject to external influences (in utero it will be mothers influence, after birth it will be exposures) -Potential DNA damage can occur due to injuries -If DNA repair (e.g mismatch repair) isn't carried out or not fully carried out and cell doesn't undergo apoptosis then DNA damage will persist and cell can divide passing damaged DNA and further DNA damage will accumulate and lead to (activation of protooncogenes, alteration of genes governing apoptosis, inactivation of tumour suppressor genes)--> leading to loss of of regulatory gene products-->cancer cell -Once cancer cell develops--> colonal expansion, additional mutations and heterogenecity -If cancer cell survives after treatment, it becomes worse as developed resistance and make more copies

Gene Signaling

-Genes send signals to cell surface through signalling molecules which transcribe to substances which are secreted or are receptors and vice versa to which cell responds -this is a 2 way link in which cells in a tissue that are determined to become cancerous communicate to gradually develop a tumour

Genetic basis of cancer (tumour growth promoting genes (oncogenes))

-Genes which drive the production of growth factors or growth factor receptors may drive proliferation -Tumours associated with overexpresion of platelet derived growth factors (PDGF) due to sis protoncogene are often tumours of the brain (astrocytoma) and bone (osteosarcoma) -The epidermal growth factor receptor erb-B2 is related to breast, ovary, lung and stomach cancers -Abl gene is translocated to fuse with BCR gene resulting in continuous activation contributing to chronic meyloid leukemia and acute lymphoblastic leukemia -Myc translocation is associated with burkitt lymphoma -n-myc amplification associated with neuroblastomas -Cyclins allow for cell cycle progression, hence if have translocation in genes encoding for cyclin D then will have mantle cell lymphoma

Genetics and environment

-Genetics and environmental factors cause changes on a cellular level hence can lead to cancer

Over-expression of oncogene erb-B2 (receptor)

-If erb-B2 gene and its protein prod are over-expressed in tissue biopsy sample from breast cancer patient then will drive more proliferation compared to patient that has breast cancer with no over-expression of erb-B2 -Brown colour shows that there is over-expression of erb-B2 -On the left images we can see immunohistochemical staining and fluoresence of ERB-B2 show weak expression thus patient is with overall better prognosis. The ones on the right show overexpression of erb-B2 -Theraputic options can be available for patients with such overexpression of erb-b2: ab-against ERB-B2 protein (Herceptin)

Cellular adaptions

-Increased endocrine stimulus causes hyperplasia -Response to chronic injury (protective mechanism)--> one cell type can change into another cell type when chronically damaged/injured

Multi-step carcinogenesis theory

-Initially, the tissue from which tumour develops is structurally normal and slowly acquires a series of genetic mutations (shown) at each step in which will accumulate mutations and gradually undergo morphological changes through sequence (dysplasia followed by cancer) to develop cancer -Thus may have time to detect at an early stage or pre-neoplastic stage... secreenings for some cancers in which will identify genetics and/or morphological changes before carcinogenesis

Biology of tumour invasion and metastases

-Invasion of surrounding extra cellular matrix: -loosening of cells from each other (loss of adhesion molecules like cadherins in squamous cells) -attachement to matrix components (fibronectin and laminin hold components together) -degradation of extra-cellular matrix by enzymes (metalloproteinases) (allows tumour cells to travel through) -Entry into the circulation (lymphatics + blood vessels) -migration of tumour cells to enter the circulation (locomotion) (reach best place for them where they can survive and grow using new vessels and nutritional supply) -Dissemination and homing of tumour cells: -adhesion to endothelial cells by adhesion molecule CD44 -chemoattractants recruit tumour cells to metastatic sites

Metaplasia to dysplasia visualised

-Left image: can see light pink appearing metaplastic squamous epithelium on the left but then an abrupt change occurs changing it to dysplastic which appears dark blue/ purple-->due to the fact that there will be crowding of cells and nuclei would be enlarged as they have dense chromatin -Right image: normal squamous epithelium (even tho metaplastic) with basal layer maturing into superficial squamous cells until change occurs where nuclei are much larger and at different angles showing dysplasia -If this detected in biopsy can take measures before cancer develops

Factors that further enhance tumour-genesis

-Limitless replication -Sustained angiogenesis -Ability to invade and metastasise - Tumour microenvironment

Burden of caner

-Major public health and economic issue and its burden is set to spiral with ageing populations and increase in risk factor -1 in 5 people develop cancer in life

Chronic inflammation of stomach

-Metaplasia (regenerated cells will have adapted hence different) in stomach lining due to chronic inflammation (most often due to chronic infection by helicobacter pylori, can be noninfectious) -H and E section shows chronic inflammation due to infiltration by immune cells -Alcian blue periodic acid schif stain helps identify goblet cells hence will better identify intestinal epithelia (in this metaplasia its glandular to intestinal epithelium) -Giesma stain showing h pylori bacteria occupying gastric glands

Genetic control of metastases

-Metastases suppressor genes: nm23, KAI-I and KiSS-I (if we determine involvement of these genes or their products then can predict good prognosis as tumour will be less likely to metastasize compared to tumours where these genes aren't active)

Hyperplasia to dysplasia

-Most often in endometrium and breast -Hyperplasia= increased thickening of epithelium with increased number of layers -Dysplasia= disordered orientation of cells within epithelium with nuclear pleomorphism -Hyperplasia (most in hormone responsive cells) may develop into dysplasia

Risk factors for cancer

-Multifactorial -Inherited/familial (not avoidable as such) -Environmental: -Toboacco use, alcohol use, unhealthy lifestyle, air pollution -Chronic infections: helicobacter pylori, human papilomavirus (HPV), hepatitis B virus, hepatitis C virus, Epstien barr, HIV **higher risk of developing cancer in chronic infections determined by severity of exposure and its long duration if allowed to persist (controllable and preventable)

Barrett's esophagus

-Natural oesophagal epithelium (squamous, white) change to intestinal (more red) at lower end of oesophagus (the more red seen the higher chance of developing cancer) -If allowed to persist then will development of tumours which will be adenocarcinoma

Normal cell growth and differentiation

-Normal cell proliferation is required in utero and growing individuals as well as in adults in certain physiological areas and in response to pathological damage in attempt to repair -Cells come from baseline undifferentiated cells which will proliferate and differentiate until their lifespan comes to and end and they die by apoptosis

Genetic basis of cancer (tumour suppressor genes)

-Normally stop cell cycle , if mutated will lose this control -Mutations in neurofibromatosis 1 and 2 genes: -Tumours due to somatic mutation: schwannoma(nf1 and 2) and meningioma->(only nf2) -Tumours due to inherited mutations: -Nf1: neurofibromatosis 1 and sarcomas -Nf2: neurofibromatosis 2 and acoustic schwannomas + meningiomas -Mutations in APC (adenomatous polyposis coli) gene results in colon, stomach and other types of cancers

Normal vs mutated p53

-Normally, p53 is active in which perceives damage and then activates other genes to produce proteins which arrest cell cycle and either repair DNA or trigger apoptosis -If p53 not functioning then DNA-damaged cell won't be controlled in which cell cycle won't be inhibited and DNA damage is passed on and further mutations occur

Metaplasia to dysplasia

-One epithelium to another (non-squamous) -Barret's oesophagus: squamous to intestinal (cause:reflux) -Intestinal metaplasia in stomach: -Columnar to intestinal (chronic inflammation, H.pylori)(columnar is rich in mucos cells which protects against acid, mucin prodcution) **chronic reflux of gastric acid contents pushed from stomach to lower end of oesophagus resulting in acid digestion of oesophagul lining which will adapt by initially inflammation and if persist then by changing from squamous to intestinal lining which may become dysplastic

The metastatic cascade

-Orange= tumour as cluster of cells developing in surface epithelium (blue) (notice orderliness of normal tissue compared to tumour) -Pink=basement membrane -Metastatic clone= cell that has ability of invading and moving on to new location -If tumour invasion were to occur (from primary site) then tumour cells will break through basement membrane to invade and travel through ECM (which holds epithelium in place) to reach nearest vessel (will penetrate directly or via metalloproteinase enzymes) -Once tumour cells are in circulation they may encounter immune cells which can attack the tumour, or the tumour cells can interact with platelets which coat and protect the tumour cells in which they will be able to move through circulation -At targeted destination tumour cells will move out of vessel to reach metastatic site

Genetic basis of cancer (tumour suppressor genes) 2

-P53 is most important in inhibiting cell cycle, loss of it will lead to predisposition to many cancers e.g Li-fraumeni syndrome + multiple carcinomas and sarcomas -P16 also regulates cell cycle by inhibiting CDKs in pancreas and oesophagus. mutation in it will lead to malignant melanomas -BRCA 1 and BRCA2 are important for DNA repair, if mutated will be predisposed to carcinoma of breast and ovary (brca1) and breast carcinoma of female and male (brca2)

Oncogene theory

-Proto-oncogenes -found at specific sites in the genomes -produce protein products, which regulate cell proliferation and differentiation Proto-oncogenes (P-oncs) ---->activated change--->Activated cellular oncogenes (C-oncs)

Mutated Rb gene

-RB controls specific parts of the cell cycle not all like p53 -2 ways Rb gene mutation (must be in both alleles of Rb gene) leading to retionoblastoma -Autosomal dominant inheritance -Eventhough born with one mutated Rb allele, must acquire mutation to develop retinoblastoma -Retinoblastoma occurs early in individuals with inherited Rb mutation (all cells already expressing mutated Rb) -If sporadic then 2 Rb alleles must be mutated independently, can have multiple tumours in one eye, can occur in both eyes -Rb gene is a tumour suppressor gene hence 2 alleles must be mutated in which develop retinoblastoma **look at PathXL case for further detail

Examples of predisposition to cancer

-RB-->retinoblastoma -P53--> Li-fraumeni syndrome -APC--> colon cancer -NF1, NF2--> neurofibromatosis 1 and 2 -BRCA1, BRCA2--> breast and ovarian tumours -MSH2, MLH1, MSH6-->Hereditary nonpolyposis colon cancer -VHL-->Renal cell carcinomas **MSH and MLH are normally responsible for DNA repair, hence if mutated damaged DNA won't be repaired which predisposes to cancer **P53 is the guardian that stops cell cycle from continuing if there is irreparable mutation

Pre-cancerous conditions

-Rather say precancerous -Very few progress to cancer -However, they carry a relative risk higher than the normal tissues -Significant for early detection and prevention by: -Removal of causative factor/prevent contact/inhalation: ocupational exposure -Screening: PAP smear for HPV infection -Theraputic intervention: antibiotics for H.pylori gastritis -Closer follow-up: endoscopic follow-up for inflammatory bowel disease **many of the predisposing condtions along with tissue change (b4 cancer) can be hindered from further development preventing carcinogenesis

7 pillars of malignant transformation

-Self sufficiency in growth signals -Insensitivity to inhibitory signals -Evasion of apoptosis -Defects in DNA repair -Limitless replication -Sustained angiogenesis -Ability to invade and metastasise **these factors play role in tumourgenesis (benign or malignant). In benign they are still controlled to certain extent

Chronic inflammatory states and cancer

-Some bacteria infect gallbladder contents as part gallbladder stones which evokes inflammation which may lead to gallbladder cancer -H.pylori causes chronic gastritis which predisposes to cancer -Epstein-Barr virus (often acquired through resp tract) may survive in immunocompromised individuals where it circulates in body predispossing lymph nodes to lymphoma -Herpves virus 8 in immunocompromised patients triggers epithelial proliferation (e.g HIV patients more prone to herpes and thus kaposi sarcoma) -Schistoma may indirectly cause cancer in urinary bladder as it settles in the lining of the urinary bladder where it provokes chronic inflammatory response **Remember chronic inflammation with cytokines + growth factors and perhaps fibrosis contribute to carcinogenesis, hence these inflammatory conditions are dangerous

Barrett's esophagus microscopically

-Squamous changes to intestinal

Cell proliferation

-Stimulators: -Growth factors -Cell injury -Cell death -Mechanical deformation of tissues -Inhibitors: -Biochemical mediators -Mechanical deformation of tissues **A balance must be kept between both

Stromal Microenvironment and Carcinogenesis

-Stromal microenvironment: - Tumour cell surrounded by immune cells, fibroblasts (produce collagen and provide structure), vessels, matrix (holds everything together) (all form comps of stromal microenv) -Non cellular constituents (promote or suppress metastasis): growth factors, proteases (MMP) and cytokines -Stromal components determine: growth, proliferation and differentiation **tumours can be controlled as long as in original location, once spread becomes very hard

Limitless replicative potential

-Telomeres (repeat sequences that cap the end of DNA strands) located at the ends of chromosomes progressively shorten with each division ultimately leading to cell death -Telomerase maintains the telomeres (prevents shortening) and is found switched on in majority of cancer cells (maintains short telomeres)

Occupational cancer

-There are many elements which are either toxic or accumulate in body chronically (typically in occupational exposure) in which will have heavy and chronic dose that predisposes cancer development -Lung is most predisposed to cancer -No need to memorise table just look

Chronic inflammation to dysplasia (ulcerative colitis)

-Ulcerative colitis is a type of inflammatory bowel disease -Normal: mucosa has parallely arranged crypts (e.g. crypt blue) with respective goblet cells -Dysplasia: mucosa crypts are disorded and of various shapes and sizes + globlet cells (functional component of colonic crypts) are lost, notice intense inflammation in lamina propria (e.g orange) where immune cells are -dysplasia is one step short from adeno carcinoma of colon in this case

Use of expression of apoptotic proteins

-Use expression of apoptotic proteins to help diagnose/distinguish caner e.g lymphoma from just reactive LN -Reactive node will be reacting against foreign ag etc... in which B and T cells proliferate (normal) -follicles mostly made up of B cell type -cells surrounding= mantle follicle (in blue brakcet) have antiapoptotic activity as they naturally react to ag and musn't die -In germinal centre of LN (yellow arrow), proapoptotic activity is present as once mantle follicles have done their job of combating injurious agents then must come to gernimnal centre and die -Follicular lymphoma: -If we perform stain for antiapoptotic marker (bcl2) and find in wrong site then indicates cancer. This is because antiapoptotic acvtivity must be shut of in germinal centre but in this case it won't be so proliferating cells wont die **So basically if find bcl2 in germinal centre rather than just surrounding it this indicates no apoptosis occurring= proliferation in excess= cancer

Normal cell vs cancer cell

Normal cell: -normal growth + differentiation--> controlled/pre-determined survival--> death/division Cancer Cells: -Disordered growth (different sizes, uncontrolled division) less differentiation--> proliferation keeps occurring with no death unless blood/nutrient supply cut off **Malignant tumour will grow rapidly as compared to benign -some cancer cells maintain some differentiation while some lose all differentiation