1. Describe the advantages and limitations of xenografts and genetically engineered mouse model (GEMMs)
xenograft:
injection/ transplantation of tumor cells or tumor tissue into a host animal
—> within the same species: immunocompetent animals can be used
—> allogenic: immunocompromised e.g. Scid
—> patient-derived xenografts: transplantation of patient-derived primary isolates
advantages + limitations:
study using human or patient-derived materials, no interaction with immune system when allogenic, drug screenings as peronalized therapy, patient avatars
genetically engineered mouse model:
alteration in genotype that causes animal to develop tumor or recapitulate diesease phenotypes
study of immune system interaction/ invasion, study of tumor formation, no patient/ human material, study of tumor development in “native environemnt”
2. What are patient-derived xenografts? What is their advantage over established cancer cell lines?
patient-derived xenografts:
transplantation of patient-derived primary isolates in host animal, personalized drug screening, patient avatars, no immortalized cell lines
3. Sequencing of a clinical tumour cohort identifies a high frequency of a certain mutation in a proto-oncogene in melanoma. How would you design a GEMM?
melanoma —> skin cancer
conditional alleles:
Cre under control of tissue-specific promoter (fibrobalst-specific or whatever)
Knock in of modified locus of gene of interest after stop codon, wildtype gene + stop codon is floxed
or transgene in Rosa26 locus: floxed stop cassette in front of goi coding region with desired mutation
4. The KPC model for pancreatic cancer is based on the simultaneous induction of mutant KRAS and p53 during embryogenesis. The KPC model faithfully recapitulates the human disease in many aspect, but is does not reflect the natural progression form still benign pancreatic intraepithelial neoplasia (PanIN) stages to full-blown human pancreatic adenocarcinoma ,usually occurring over decades by step-wise acquisition of mutations in proto-oncogenes and tumour suppressor genes. Which of the methods discussed by Annette Neubüser could you apply to improve the modeling of multi-step carcinogenesis?
usage of nonconditional alleles to create early onset mutations —> preferably Flp recombinase
usage of additional conditional alleles and CreER or TetON/ TetOFF to model mutations that arise later in tumor progression
two transgenes: one CreER under control of pancreas-specific promoter e.g Pdx1, and one transgene with floxed stop cassette in front of coding region of mutated gene of interest
5. Where do you see the limitations of in vitro and in vivo experiments? What data can tissue culture experiments provide and which not?
in vivo:
mostly no human cells, more expensive
interaction with immune system
impact on whole organism
study in native environment
tumor onset
in vitro:
no interaction with immune system
no native environment
patient-derived tissues and tissue cultures
—> drug screenings, sequencing, tumor development (but not in native environment and no interactions with native environment)
6. How easy is it to transfer data from animal tumor models to the clinical situation? What do you think? Which factors could impair the success of translation?
depends on which animal models are used
can work really well but not necessarily has to
LOL
Species-specific differences
Genetic background variations
Different microenvironment
Immune system differences
Different drug metabolism
Pharmacokinetic variations
Genetic heterogeneity
Phenotypic variability
Controlled environment differences
Study design differences
Xenograft model limitations
GEMM limitations
Limited predictive power
High failure rates in clinical trials
Ethical concerns
Resource-intensive translation
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