25 Onco Flashcards
general concept of how normal cells become tumor cells
transformation through genetic alterations1. activation of tumor promoting factors–oncogenes2. loss of tumor inhibitory effects–loss of tumor suppressor gene fxinitiation, promotion and progression
most familiar tumor suppressor gene
p53guardian of the genomecrucial to normal cell cycle regulation and entry into apoptosiscancer cells find a way to mutate this gene (mammary tumors, lymphoma, OSA)
genotypic changes that result in phenotypic characteristics of tumor cells
- self sufficiency in growth signals2. insensitivity to antigrowth signals3. tissue invasiveness/metastatic potential4. limitless replicative potential5. sustained angiogenesis6. evasion of apoptosis
recent advances in veterinary oncology
- PCR assay to detect ckit mutations (found in mast cell tumors)2. Metronomic therapies to prevent tumor angiogenesis and minimize toxicity3. tyrosine kinase inhibitors, toceranib (palladia) or mastinib (kinavet)
cell biology: cell cycle and division
DIVISION OF SOMATIC CELLS1. interphase: doubling of genetic material occurs—G1, S, G2 phases2. mitosis: division of genetic materials into 2 daughter cells
What phases make up interphase during the cell cycle
INTERPHASE–G1: growth factors signal cell division, restriction point–S: synthesis/doubling of new DNA occurs–G2: growth
regulation of the entry and progression of the cell cycle occurs through what
cyclin dependent kinases (important growth signals in the progression of both normal and neoplastic cells)
define initiation, promotion, progression as it is applied to cancer formation
- initiation–IRREVERSIBLE; heritable mutation 2. promotion–must come after initiator; a second mutation that promotes the growth advantage of a mutated cell over surrounding cells3. progression–invasion into surrounding tissues, establishing a new blood supply and potential for metastatic disease
T/Finitiation of cells is an irreversible process and all cells will go on to develop clinical neoplasia
FALSEinitiation is irreversibleBUT not all initiated cells will develop into clinically detectable neoplasia (needs a promoting agent)
T/F Golden retrievers have a heritable risk for lymph proliferative disease
TRUEsome good data supports
True genetic heritability has been established in what breeds with what tumors?
Scottish Deerhounds—OSAGSD–renal cystadenocarcinoma and nodular dermatofibrosis (autosomal dominant)
well established neoplasia and biological viral link in veterinary medicine
–retroviral FeLV and lymphoproliferative dz–feline retroviral sarcoma virus and FSA (co-infection with FeLV required)–papilloma virus–papillomas and SCC
well established neoplasia and biological parasite link in vet med
–spirocerca lupi (esophageal parasite) and esophageal sarcomas in dogs
how is transmissible veneral tumor transmitted
contagious veneral tumorDIRECT cell contact (tumor cell itself is the causative agent of disease)
types of physical carcinogenesis
–Asbestos–canine mesothelioma–Aluminum based adjuvant in vaccines–injection site sarcomas (cats)–trauma–ocular sarcoma–microchip implantation–FSA–metallurgy (slocum TPLO plates)–canine OSA
UV light carcinogenesis
UV B light 290-320 nm wavelengthdamage to basal cells of skin via dimerization of the pyrimidine bases (T, C) of DNASCC white catscutaneous hemangiomas in whippetsmay also suppress cutaneous T cell mediated immunity
mechanisms in which a protooncogene (normal gene) becomes and oncogene
- retroviral mediated2. translocation mutation3. amplification4. proviral insertiononcogenes become dominant form and drive formation of cancer thru cell signaling, differentiation, ECM production, and control of apoptosis
key transcription proteins made in response to oncogene translation
- growth factors2. growth factor receptors3. cytoplasmic kinases/Ras4. transcription factors* 5. anti-apoptotic proteins** difficult targets for drug therapy given sub cellular location
Ckit and mast cell tumors
ckit receptor = tyrosine kinase receptor made my tumor cells; binding with ligand leads to cell proliferationimportant for tyrosine kinase inhibitors (palladia–toceranib) for treatment of high stage or grade III MCT)
met and OSA
met = hepatocyte growth factor receptorplays a role in malignant nature of canine OSA
mutations in which oncogene family are the most common found in human and canine neoplasia
Ras oncogenes–> lead to the production of membrane bound proteins with key roles in relaying signals from cell surface/growth receptors to their down stream targets
enzymes responsible for intracellular signaling for oncogenes
cytoplasmic kinasesusually work by phosphorylating various proteins and signaling for transcription factors
most notable oncogene for production of anti-apoptotic proteins
Bcl-2overexpressed in tumors leading to continual growth and proliferation
difference btwn oncogenes and tumor suppressive genes
Oncogenes–DOMINANT, gain of function mutationtumor suppressive genes–recessive/loss of function mutations, BOTH alleles must be damaged (loss of heterozygosity)
Knudson’s two hit hypothesis
first mutation in tumor suppressor gene occurs in germline (heritable)second mutation in tumor suppressor gene occurs later on
two types of tumor suppressor genes
- gate keeper: function to inhibit growth while promoting cell death (p53 gene aka guardian of the genome)2. caretakers: ensure that SNA repair occurs while maintaining genomic stability
Vet sx 2008 Kirpenstein et al p53 gene and canine OSA survival times
dogs WITH p53 mutations had survival time 81 daysdogs WITHOUT p53 mutations had survival time 256 daysmutations in p53 seem to be a negative prognostic factor
in veterinary medicine, best examples of tumors resulting from an orderly progression (normal, dysplasia, cancer)
SCCTCCmay start normal–>dysplastic–>carcinoma in situ–> cancerous, local–> disseminated
characteristics of dysplasia
anisocytosisanisokaryosismitotic figureschromatin changes
define carcinoma in situ
dysplastic or now transformed cells exhibit a greater number of criteria of malignancy and occupy the entire thickness of the epithelium but have NOT invaded the basement membrane(once past basement membrane–> invasive)
T/Ftelomerase expression has been shown in 92-95% of canine maligancies
TRUEboth human and canine neoplastic tissues have been shown to exhibit HIGH levels of telomerase activity
which cells/tissues do NOT express telomerase activity
stem cellslens tissuemale germ line cellsactivated lymphocytessomatic tissues
T/Flack of apoptosis is a hallmark of carcinogenesis
TRUEapoptosis is an ACTIVE processnecrosis is a PASSIVE process
morphologic changes associated with apoptosis
- membrane blebbing2. contraction of cytoplasm3. nuclear condensation(different from necrotic cells—cell swelling, rupture of cell membranes)
what does entry into apoptosis depend on
balance btwn1. proapoptotic genes (p53), caspases2. antiapoptosis genes (Bcl-2)
3 major routes for metastasis to occur
- hematogenous2. lymphatic3. direct seedinginvolves detachment, migration thru tissue, intravasation, survival in vasculature, attachment to endothelial cell, extravasation, prolix/angiogenesis in new site
difference btwn carcinomas, round cells and sarcomas in terms of routes that they metastasize
carcinomas–lymphaticsround cell tumors (LSA)–lymphaticssarcomas–hematogenous
crucial factor for metastasis to occur as tumor cells leave primary bed and travel through tissue
MMP matrix metalloproteinases
what is anoikis
apoptotic signal that occurs when a group of cells lose contact with each other and surrounding matrix