L12 Flashcards
What are the four main characteristics of cancer cells?
Uncontrolled proliferation, loss of differentiation, invasiveness, and the ability to metastasize.
What are the two main genetic changes that lead to cancer?
Inactivation of tumor suppressor genes (e.g., p53) and activation of oncogenes.
How do alkylating agents work in cancer chemotherapy?
They form covalent bonds with DNA, causing cross-linking and preventing DNA replication, leading to apoptosis (e.g., cyclophosphamide).
What is the mechanism of action of methotrexate?
Methotrexate inhibits dihydrofolate reductase, blocking the synthesis of tetrahydrofolate needed for DNA synthesis.
How do plant derivatives like vincristine work in chemotherapy?
Vincristine inhibits microtubule polymerization, blocking mitosis and stopping cell division.
What role does trastuzumab (Herceptin) play in cancer therapy?
Trastuzumab is a monoclonal antibody that inhibits the Her2/neu receptor, which is overexpressed in some breast cancers.
What are the main drawbacks of current cancer chemotherapy?
Non-specific targeting, resistance development, inability to eliminate all malignant cells, and limited effects on invasiveness and metastasis.
How does fluorouracil (5-FU) inhibit cancer cell growth?
Fluorouracil inhibits thymidylate synthetase, blocking DNA synthesis without affecting RNA or protein synthesis.
What are the therapeutic applications of glucocorticoids in cancer treatment?
Glucocorticoids inhibit lymphocyte proliferation, useful in leukemias and lymphomas.
What are future directions in cancer chemotherapy?
Inhibiting oncogene signaling, restoring tumor suppressor genes, targeting angiogenesis, and enhancing the immune response.
Explain the role of tumor suppressor genes and oncogenes in cancer development, with examples.
Tumor suppressor genes (e.g., p53) prevent uncontrolled cell division by regulating the cell cycle. Mutations in these genes disable their protective function, allowing cancer growth. Oncogenes are mutated proto-oncogenes that promote excessive cell division (e.g., mutations in growth factor receptors). Together, these genetic changes drive tumor development.
Discuss the mechanisms of action of cytotoxic drugs used in cancer chemotherapy.
Cytotoxic drugs include:
- Alkylating agents: Cross-link DNA to prevent replication (e.g., cyclophosphamide).
- Antimetabolites: Inhibit enzymes in DNA synthesis (e.g., methotrexate inhibits dihydrofolate reductase; fluorouracil inhibits thymidylate synthetase).
- Cytotoxic antibiotics: Inhibit topoisomerase II, blocking DNA unwinding (e.g., doxorubicin).
- Plant derivatives: Disrupt microtubule function, blocking mitosis (e.g., vincristine, paclitaxel).
What are the challenges and future prospects of cancer chemotherapy?
Challenges include:
- Non-specific toxicity to normal cells.
- Drug resistance development.
- Limited ability to target metastasis and invasiveness.
- Incomplete tumor eradication. Future approaches aim to:
- Target oncogenic pathways.
- Use gene therapy to restore tumor suppressor function.
- Develop angiogenesis inhibitors and immune-based therapies.
How do hormone therapies work in cancer treatment, and what are some examples?
Hormone therapies target hormone-dependent cancers:
- Tamoxifen: Competes with estrogen for its receptor, used in hormone-dependent breast cancer.
- Flutamide: An anti-androgen used for prostate cancer. These therapies inhibit the growth signals driven by hormones in cancer cells.
Describe the mechanism of action and therapeutic use of monoclonal antibodies like trastuzumab in cancer therapy.
Trastuzumab targets the Her2/neu receptor, a tyrosine kinase receptor overexpressed in some breast cancers. It inhibits receptor signaling, reducing cell proliferation, and may induce tumor-suppressor pathways (e.g., p53). It is effective in Her2-positive breast cancer patients.
