Chemotherapy and Cancer Characteristics Quiz

Anticancer Agents

Cancer is a collection of diseases characterized by abnormal cell growth and uncontrolled division.
Neoplasms (tumors) can invade adjacent tissues (metastasis) making control difficult and potentially leading to patient death.
Tumors can be named after the discoverer (Hodgkin's disease) or by the tissue of origin (sarcoma, carcinoma, fibroma, leukemia).
Cancer etiology has several contributing factors but no single exact cause.
Genetic factors (mutations and altered gene expression) are a contributing factor.
Viruses such as HTLV-I are proven to cause certain types of leukemia.
Exposure to chemicals and/or radiation are physical contributing factors.
Hormonal factors can also contribute.
The primary cause of cancer is believed to be incorrect proto-oncogene expression, leading to oncogene formation and unchecked cell growth.
Tumor suppressor genes, like p53, help to regulate cell growth and prevent cancer formation. Their weakening or inactivation can promote cancer.
Two fundamental genetic mechanisms for cancer include: either enhanced oncogene expression or decreased activity of tumour suppressor genes.
Hallmarks of cancer represent six biological capabilities acquired during tumor development.
They include: sustaining proliferative signaling, evading growth suppressors, resisting cell death, enabling replicative immortality, inducing angiogenesis, and activating invasion and metastasis.
Cancer treatment options include surgery (if not metastasized), radiation therapy (effective at targeting tumors and minimizing surrounding damage), and chemotherapy (antineoplastic, cytotoxic, anticancer, and antitumor drugs).
Chemotherapy is mainly limited by the size of the tumor.
Common side effects of chemotherapy include nausea, hair loss, increased susceptibility to infection and others.
Agents that inhibit or interfere with DNA synthesis or cell division are cytotoxic agents.
Hormonal therapy is used for hormone-related cancers.
Targeted anticancer therapeutics include signal transduction inhibitors (e.g., kinase inhibitors), immunomodulators, and epigenetic therapies.
Cancer chemotherapeutics are categorized based on their chemical, pharmacological, and mechanistic profiles. These include DNA cross-linking agents (alkylating agents and organometallics), topoisomerase poisons, antibiotics, antimetabolites, hormone-based agents, signal transduction inhibitors, immunomodulators, and epigenetic therapies.

DNA Cross-linking Agents

Alkylating agents are important early cancer treatments such as nitrogen mustards.
These agents were first used after World War I when victims of sulfur mustard gas showed severe lymphoid aplasia and pulmonary irritation.
Modern use is more limited, primarily for lymphomas and Hodgkin's disease.
The nitrogen mustards, like Mechlorethamine, are bifunctional alkylating agents, reacting with guanine in DNA to cause cross-linking, halting mitosis and tumor cell division.
Alkylating agents like Nitrosoureas and Treazines have high lipid solubility and a greater ability to cross the blood-brain barrier, making them useful for brain tumors.
Further chemical modifications to nitrogen mustards allow them a broader application.
Mechanisms of action include chemical decomposition yielding intermediates that alkylate DNA.

Topoisomerase Poisons

Topoisomerases are enzymes controlling DNA supercoiling and play in DNA replication.
Topoisomerase II poisons disrupt DNA, causing irreparable damage.
Topoisomerase II poisons include Camptothecins, Epipodophyllotoxins, and Anthracyclines.
Camptothecins, Epipodophyllotoxins, and Anthracyclines block or disrupt topoisomerases, halting DNA replication and promoting cell death.

Antibiotics (Anthracyclines)

Anthracyclines are antibiotics extracted from Streptomyces bacteria.
Doxorubicin and daunorubicin are critical anthracycline anticancer drugs with a planar anthraquinone core molecule attached to an amino sugar.
They have a mechanism action involving binding to DNA and halting DNA replication, or interfering with topoisomerase processes.

Antimetabolites

Antimetabolites stop de novo DNA synthesis by inhibiting the formation of essential nucleotides for DNA creation processes.
Agents include pyrimidine (5-FU) and purine (6-Mercaptopurine, 6-Thioguanine) antagonists, DNA polymerase inhibitors, and DNA methyltransferase inhibitors.
Pyrimidine antagonists obstruct dTMP synthesis, interfering with DNA synthesis.
Purine antagonists block purine synthesis, curtailing the production of key nucleotides.
Methotrexate acts as an antifolate, thus preventing the synthesis of tetrahydrofolic acid for thymidylate synthetase essential for DNA production in cells.

Mitosis Inhibitors

Mitosis Inhibitors include Vinca alkaloids, which interrupt microtubule formation within cells preventing mitosis.
Taxanes, like Paclitaxel, also disrupt mitosis but by acting on the spindle assembly part of the process.