230113 Flashcards
What is a Vogelstein model? Namely, what kind of knowledge can you learn from this model?
The vogelstein model shows the accumilation of mutations that is necessary to drive colerectal canciorogenesis forward.
It shows how normal epithelium develop an APC mutation and get genomic instability from this that causes early adenoma and then K-ras driving it into intermediate adenoma, p53 leading it to late adenoma to carcinoma etc.
What are the main roles of cancer stem cells in cancer development? Please list at least 4 cancer
stem cell markers.
Cancer stem cells (CSCs) are a subpopulation of cells within tumors that possess self-renewal properties and the ability to give rise to differentiated tumor cells. They are often considered responsible for the initiation, progression, and relapse of cancer. Here are the main roles of CSCs in cancer development:
Tumor Initiation:
CSCs are believed to be the cells that initiate the formation of the tumor. Due to their ability to self-renew and proliferate, CSCs are capable of regenerating the tumor even after treatment or therapy, leading to the development of new tumors.
Tumor Propagation:
CSCs are capable of sustaining the tumor by continuously producing differentiated progeny cells. This allows the tumor to grow and expand over time.
Therapy Resistance:
CSCs exhibit resistance to conventional therapies such as chemotherapy and radiation. They are more resistant to treatments that target rapidly dividing cells because they tend to be in a quiescent or slow-dividing state. This contributes to relapse after treatment, as CSCs can survive and repopulate the tumor.
Metastasis:
CSCs play a crucial role in the metastasis of cancer. They have the ability to migrate from the primary tumor site, invade surrounding tissues, and establish secondary tumors in distant organs. CSCs are believed to have enhanced migratory and invasive abilities, contributing to cancer spread.
Common Cancer Stem Cell Markers:
Cancer stem cells can be identified and isolated using specific markers. Below are four widely recognized markers associated with CSCs:
CD44:
CD44 is a cell surface glycoprotein involved in cell-cell interactions, cell adhesion, and migration. It is commonly expressed on CSCs and is linked to cancer progression and metastasis.
CD133 (Prominin-1):
CD133 is a membrane protein expressed on a variety of stem cells, including CSCs. It has been used as a marker to isolate and identify CSCs, particularly in brain tumors, colorectal cancer, and liver cancer.
ALDH (Aldehyde Dehydrogenase):
ALDH is an enzyme that detoxifies aldehydes and is highly expressed in stem-like cells, including CSCs. ALDH^high populations are often enriched in CSCs and correlate with increased tumorigenic potential and resistance to chemotherapy.
Oct4 (Octamer-binding Transcription Factor 4):
Oct4 is a transcription factor that plays a key role in maintaining pluripotency and self-renewal in stem cells. It is often overexpressed in CSCs and is involved in maintaining the undifferentiated state of these cells.
What are associations of cancer cells with their microenvironment? Please explain the interactions
between the cancer cells and their microenvironment by giving at least 2 examples to state how they
work together in cancer development, progression and/or metastasis.
The tumor microenvironment (TME) consists of various cellular and non-cellular components that interact with cancer cells. This dynamic environment includes stromal cells, immune cells, blood vessels, extracellular matrix (ECM) components, and soluble factors such as cytokines and growth factors. Cancer cells actively interact with and manipulate their microenvironment to promote their own survival, growth, and metastasis. Below are two key examples of how cancer cells and their microenvironment work together in cancer development, progression, and metastasis:
- Cancer-Associated Fibroblasts (CAFs) and ECM Remodeling
Interaction: Cancer-associated fibroblasts (CAFs) are one of the most abundant stromal cell types in the TME. They are activated by signals from tumor cells, such as growth factors (e.g., TGF-β, VEGF) and cytokines. CAFs secrete a variety of extracellular matrix (ECM) components, including collagen, fibronectin, and glycoproteins, and remodel the ECM through the activation of matrix metalloproteinases (MMPs).
Role in Cancer:
Tumor Growth and Invasion: The ECM not only provides structural support but also influences tumor cell behavior by modulating signaling pathways involved in cell proliferation, survival, and migration. ECM remodeling by CAFs facilitates tumor cell invasion and migration, allowing cancer cells to invade surrounding tissues.
Metastasis: The altered ECM in the tumor stroma creates physical and chemical cues that enable cancer cells to detach from the primary tumor, invade blood vessels (intravasation), and eventually colonize distant organs (extravasation). Additionally, the remodeled ECM can create a niche that supports the survival of circulating tumor cells (CTCs), promoting metastatic spread.
2. Tumor-Associated Macrophages (TAMs) and Immune Evasion
Interaction: Tumor-associated macrophages (TAMs) are immune cells that infiltrate tumors, often in large numbers. In the presence of tumor-secreted cytokines and growth factors (e.g., CSF-1, IL-4, and IL-10), TAMs can differentiate into an M2-like phenotype, which is immunosuppressive and promotes tumor progression.
Role in Cancer:
Immunosuppression: TAMs can suppress the anti-tumor immune response by secreting immunosuppressive factors such as TGF-β, IL-10, and VEGF, which inhibit the activity of cytotoxic T cells and natural killer (NK) cells. This creates an immunosuppressive microenvironment that allows cancer cells to evade detection and destruction by the immune system.
Tumor Progression: TAMs also promote tumor progression by secreting pro-tumorigenic factors like growth factors (e.g., EGF), cytokines, and proteases. These factors can induce angiogenesis (formation of new blood vessels), support tumor cell proliferation, and enhance tissue invasion and metastasis. TAMs help tumors grow by sustaining the nutrient and oxygen supply through blood vessel formation and by modifying the tumor’s extracellular matrix, making it more conducive to cancer cell survival and movement.
Please state the roles of autophagy in cancer development and/or treatment.
- Tumor Suppression in Early Stages
Role: Autophagy has a tumor-suppressive role, particularly in the early stages of cancer development. By removing damaged organelles, misfolded proteins, and other dysfunctional cellular components, autophagy prevents the accumulation of harmful mutations and DNA damage, which could otherwise lead to malignant transformation.
Mechanism: In normal cells, autophagy prevents the accumulation of reactive oxygen species (ROS), which can damage DNA, proteins, and lipids, contributing to cancer initiation. By maintaining cellular quality control, autophagy reduces the likelihood of mutations that could promote tumorigenesis.
- Support of Tumor Growth and Survival in Established Cancers
Role: Once a tumor has formed, autophagy can be hijacked by cancer cells to promote their survival, especially under nutrient deprivation, hypoxia, or other stress conditions within the tumor microenvironment.
Mechanism: In established tumors, autophagy helps cancer cells survive by providing an alternative source of nutrients through the degradation of intracellular components. This allows cancer cells to adapt to metabolic stress, such as low oxygen (hypoxia) or limited availability of glucose and amino acids, which are common in solid tumors.
Example: In tumors with limited blood supply, autophagy helps provide energy by degrading lipids, proteins, and other cellular components, thus allowing cancer cells to thrive in an otherwise harsh environment.
- Resistance to Chemotherapy and Radiation
Role: Autophagy can contribute to resistance to cancer therapies, such as chemotherapy and radiation, by promoting the survival of cancer cells exposed to these treatments.
Mechanism: Chemotherapy and radiation induce cellular stress, which can activate autophagy as a survival mechanism. In some cases, autophagy helps cancer cells survive and recover after treatment, leading to therapeutic resistance and relapse.
Example: Some cancer cells use autophagy to mitigate the damage caused by chemotherapy drugs like cisplatin or by radiation. Autophagy removes damaged organelles and proteins, thereby preventing cell death and promoting cell survival after therapy.
- Tumor Progression and Metastasis
Role: Autophagy also contributes to tumor progression and metastasis by facilitating the survival of circulating tumor cells (CTCs) and promoting cell migration and invasion.
Mechanism: Autophagy can support the migration of cancer cells by degrading cytoskeletal components and remodeling cellular structures. Additionally, autophagy may enable the survival of CTCs during their circulation through the bloodstream, which is a key step in metastasis.
- Autophagy as a Therapeutic Target
Role: Because of its dual roles in cancer, autophagy has become a potential target for cancer therapy. Inhibiting or enhancing autophagy in different cancer types could be used to either suppress tumor initiation or to overcome resistance to therapies.
Mechanism:
Autophagy Inhibition: Inhibition of autophagy in established tumors, particularly in combination with chemotherapy or radiation, may increase the effectiveness of treatment by preventing cancer cells from using autophagy as a survival mechanism.
Autophagy Induction: On the other hand, in certain contexts, autophagy can be induced to promote cancer cell death, especially in cancers with a high level of autophagic dependency.
Example: Drugs such as chloroquine and hydroxychloroquine, which inhibit autophagy, are being tested in clinical trials to enhance the effectiveness of chemotherapy and radiation therapy. Conversely, rapamycin, an autophagy inducer, has shown potential in certain cancers by promoting autophagic cell death.
Please make a signaling pathway involved in cancer development, in which you should include at
least 2 oncogenes, 2 anti-oncogenes (tumor suppressor genes), 2 apoptosis-related genes and 2
miRNAs.
PIK3CA (oncogene) activates the PI3K pathway, leading to increased production of PIP3, which activates AKT1 (oncogene).
AKT1 promotes cell survival and growth by inhibiting apoptotic signaling through proteins like BAX (pro-apoptotic) and by activating mTOR, which stimulates protein synthesis.
Loss of the tumor suppressor PTEN enhances the PI3K/AKT pathway, contributing to uncontrolled cell growth.
TP53 (tumor suppressor gene) normally induces apoptosis in response to DNA damage, but mutations in TP53 allow cancer cells to evade cell death.
Oncogenic miR-21 upregulates the PI3K/AKT pathway by targeting PTEN, promoting cell survival.
Tumor-suppressive miR-34a, activated by TP53, inhibits oncogenes and enhances apoptosis, counteracting the effects of miR-21.
What are the main differences between germ-line and sporadic mutations? Explain how germ-line
mutations are involved in hereditary cancer.
The Knudson’s Two-Hit Model: states that a person born with a herediatary mutation one has one healthy allele that can compensate and if they then aquire a second mutation they develop tumorigenesis while non hereditary cancers needs to develop to somatic mutations for this to develop which makes it less likely to occur.
How can we improve cancer diagnosis by, for example, advanced techniques, biomarker
analyses, etc?
- Liquid Biopsy for Early Detection
Technique: Liquid biopsy involves analyzing a blood sample to detect biomarkers released into the bloodstream by tumors, such as circulating tumor DNA (ctDNA), circulating tumor cells (CTCs), and exosomes.
Improvement in Diagnosis: Liquid biopsy is a non-invasive method that allows for early detection of cancer and monitoring of treatment efficacy. It can detect genetic mutations, methylation patterns, and other molecular markers associated with cancer, enabling early diagnosis even before clinical symptoms appear.
Example: The detection of KRAS mutations in blood for pancreatic cancer, or EGFR mutations in lung cancer, can help identify patients early in the disease course. - Next-Generation Sequencing (NGS)
Technique: NGS allows for the comprehensive sequencing of tumor genomes, identifying mutations, copy number variations, and other genomic alterations. It can be applied to biopsy samples or liquid biopsy samples.
Improvement in Diagnosis: NGS enables the identification of genetic mutations that may not be detectable with traditional methods. This leads to a more accurate and personalized diagnosis, allowing oncologists to tailor treatment based on the specific genetic profile of the tumor.
Example: NGS can detect mutations in genes like BRCA1/2 for breast cancer or EGFR for lung cancer, which can inform targeted therapies. - Immunohistochemistry (IHC)
Technique: IHC involves staining tissue samples with specific antibodies to detect the presence of cancer-related proteins. It is widely used in diagnosing various cancer types and understanding their molecular characteristics.
Improvement in Diagnosis: IHC helps in the identification of tumor markers, providing information about tumor type, grade, and prognosis. It also helps in detecting the expression of targetable proteins, guiding therapeutic decisions.
Example: Overexpression of the HER2 protein in breast cancer can be detected by IHC, and patients with HER2-positive cancer may benefit from therapies like trastuzumab. - Biomarker Analysis
Technique: Biomarkers, such as proteins, RNA, and metabolites, are analyzed to identify cancer and assess its progression. Biomarkers can be identified in blood, urine, tissues, or even breath.
Improvement in Diagnosis: Biomarker profiling helps identify early-stage cancer and predict patient outcomes. This can lead to earlier intervention and more accurate treatment decisions.
Example: PSA levels (Prostate-Specific Antigen) are used for the early detection and monitoring of prostate cancer. Similarly, AFP (Alpha-fetoprotein) is used for liver cancer diagnosis.
Please explain how chemotherapy and immunotherapy can induce cancer cell death by using 2
drugs for chemotherapy and 2 antibodies for the immunotherapy.
- Chemotherapy-Induced Cancer Cell Death
Chemotherapy drugs typically work by targeting rapidly dividing cells, which includes cancer cells. These drugs can induce cancer cell death by damaging DNA, inhibiting cell division, or inducing apoptosis.
a) Cisplatin (Chemotherapy Drug)
Mechanism: Cisplatin is a platinum-based chemotherapy drug that forms DNA adducts by binding to the DNA strand. This cross-linking interferes with DNA replication and transcription, causing DNA damage.
Induced Cell Death: The DNA damage induced by cisplatin activates DNA repair mechanisms, but if the damage is too severe, it triggers apoptosis (programmed cell death). This is mediated by the activation of proteins like p53, which induces the expression of pro-apoptotic proteins (e.g., Bax) and leads to mitochondrial dysfunction and cell death.
Effect on Cancer: Cisplatin is commonly used in the treatment of various cancers, including ovarian, lung, and testicular cancer.
b) Doxorubicin (Chemotherapy Drug)
Mechanism: Doxorubicin is an anthracycline drug that works by intercalating into DNA, inhibiting the enzyme topoisomerase II, and causing double-strand breaks in the DNA.
Induced Cell Death: Doxorubicin-induced DNA damage activates the p53 pathway, leading to the expression of genes involved in apoptosis. It also generates reactive oxygen species (ROS), which can damage cellular components, including lipids, proteins, and nucleic acids, triggering cell death via necrosis or apoptosis.
Effect on Cancer: Doxorubicin is used to treat cancers such as breast cancer, leukemia, and lymphoma.
2. Immunotherapy-Induced Cancer Cell Death
Immunotherapy uses the body’s immune system to recognize and destroy cancer cells. Antibodies used in immunotherapy can target specific antigens on the surface of cancer cells or immune checkpoints to enhance the immune response.
a) Pembrolizumab (Anti-PD-1 Antibody)
Mechanism: Pembrolizumab is a monoclonal antibody that targets the PD-1 receptor on T cells. PD-1 is an immune checkpoint receptor that, when activated by its ligands (PD-L1/PD-L2), suppresses T cell activity and allows cancer cells to evade immune surveillance.
Induced Cell Death: By blocking PD-1, pembrolizumab prevents the inhibitory signal from cancer cells, reactivating T cells and enhancing their ability to recognize and kill cancer cells. This leads to the destruction of tumor cells through immune-mediated cytotoxicity.
Effect on Cancer: Pembrolizumab is used to treat cancers like non-small cell lung cancer, melanoma, and head and neck cancer.
b) Trastuzumab (Anti-HER2 Antibody)
Mechanism: Trastuzumab is a monoclonal antibody that binds to the HER2 receptor, a protein that is overexpressed in some breast cancer cells. By binding to HER2, trastuzumab prevents the receptor from dimerizing and activating downstream signaling pathways that promote cell survival and proliferation.
Induced Cell Death: The binding of trastuzumab to HER2 leads to several effects, including inhibition of HER2-mediated signaling (which reduces cell growth), immune-mediated destruction of cancer cells through antibody-dependent cellular cytotoxicity (ADCC), and the induction of apoptosis through the activation of intracellular signaling pathways.
Effect on Cancer: Trastuzumab is used primarily for HER2-positive breast cancer, as well as for gastric cancer.
Please explain how radiotherapy can induce cancer cell death and explain the corresponding
mechanisms
DNA Damage: Radiation directly and indirectly induces DNA damage (e.g., DSBs, ROS generation).
DNA Repair Pathways: Cells attempt to repair the damage using repair mechanisms like NHEJ and HR.
Cell Cycle Arrest and p53 Activation: Cells arrest at checkpoints to repair damage; p53 can trigger apoptosis if repair is unsuccessful.
Apoptosis: Radiation-induced DNA damage leads to cell death via intrinsic or extrinsic apoptotic pathways.
Senescence and Autophagy: Cells may enter senescence or activate autophagy in response to radiation-induced damage.
Tumor Recurrence: Surviving cells can repopulate, leading to tumor recurrence, which is why fractionated radiation is used.
According to your experience from the lab practice of this course, please raise some comments
and suggestions that may improve further practice, including materials and methods and why?
