WHAT IS ANTICANCER AGENT?

An anticancer agent is a substance that prevents, inhibits, or treats cancer by targeting cancerous cells. These agents work through various mechanisms, including disrupting DNA replication, blocking cell division, or enhancing the immune system's ability to destroy cancer cells. They encompass a wide range of drugs such as alkylating agents, antimetabolites, natural products (e.g., taxanes, vinca alkaloids), hormonal agents, targeted therapies, and immunotherapies. Each type targets specific aspects of cancer cell growth and proliferation, aiming to reduce tumor size, prevent metastasis, and improve survival rates for cancer patients.

What is the classification of anticancer agents?

Anticancer agents are classified based on their mechanism of action and chemical structure:

1. Alkylating Agents: Disrupt DNA replication (e.g., cyclophosphamide).

2. Antimetabolites: Mimic DNA/RNA building blocks, disrupting cell metabolism (e.g., methotrexate).

3. Natural Products: Derived from natural sources (e.g., vincristine, paclitaxel).

4. Hormonal Agents: Target hormone-dependent cancers (e.g., tamoxifen).

5. Targeted Therapy: Target specific molecules involved in cancer growth (e.g., trastuzumab).

6. Immunotherapy: Boost the immune system to fight cancer (e.g., pembrolizumab).

7. Monoclonal Antibodies: Bind to specific proteins on cancer cells (e.g., rituximab).

8. Radiation Therapy: Although not a drug, radiation is often used to kill or damage cancer cells.

Classification of Anticancer Agents

What is Alkylating Agents?

Alkylating agents are a class of anticancer drugs that work by adding alkyl groups to DNA, leading to DNA cross-linking and strand breakage [1]. This process disrupts DNA replication and transcription, ultimately causing cell death. They are effective against rapidly dividing cancer cells and treat various cancers, including lymphomas, leukemias, and solid tumors [2]. Common examples include cyclophosphamide, chlorambucil, and melphalan. Despite their effectiveness, they can also damage normal cells and cause side effects such as bone marrow suppression, nausea, and increased risk of secondary cancers. Examples of Alkylating agents are Cyclophosphamide, (used for various cancers including lymphomas and breast cancer), Chlorambucil (primarily used for chronic lymphocytic leukemia), Melphalan (Often used for multiple myeloma), Cisplatin (Commonly used for testicular, ovarian, and bladder cancers).

What are Antimetabolites?

Antimetabolites are a class of anticancer drugs that resemble natural substances within the cell, thereby interfering with cellular metabolism and replication [3]. They mimic the building blocks of DNA and RNA, substituting themselves during DNA synthesis or inhibiting enzymes involved in nucleotide production. This disruption prevents cancer cells from growing and dividing. Common examples include Methotrexate (Inhibits folic acid metabolism, used in leukemia, breast cancer, and osteosarcoma), 5-Fluorouracil (5-FU) (Inhibits thymidylate synthase, used in colorectal, breast, and head and neck cancers), Gemcitabine (Incorporated into DNA, causing chain termination, used in pancreatic, lung, and bladder cancers). These agents are particularly effective against rapidly dividing cancer cells.

Natural Products as an anticancer agent

Natural products are vital in anticancer therapy, offering unique mechanisms of action. Key examples include paclitaxel from the Pacific yew tree, which stabilizes microtubules, and vincristine from the Madagascar periwinkle, which inhibits microtubule formation. Camptothecins from Camptotheca acuminata target topoisomerase I, while anthracyclines from Streptomyces peucetius intercalate DNA. Other notable compounds include curcumin from turmeric, which modulates cell signaling, and artemisinin from sweet wormwood, generating reactive oxygen species. These natural compounds provide a rich source of anticancer agents, often leading to apoptosis and inhibiting cancer cell proliferation.

Rich source of therapeutic agents, including anticancer compounds, for centuries. Their diversity and complexity often provide unique mechanisms of action that are difficult to replicate synthetically. We have to work on some noble natural products that have shown anticancer properties. Where Taxanes wokring mechanism is Stabilizes microtubules and prevents their disassembly, disrupting cell division and leading to cell death. A major natural source of Taxanes is the Pacific yew tree (Taxus brevifolia). Two common examples of this anticancer agent are Paclitaxel (Taxol) and docetaxel.

Another natural product Vinca Alkaloids here a working mechanism is Inhibits microtubule formation, preventing cell division and leading to cell death. The major natural major source of Taxanes is  Madagascar periwinkle (Catharanthus roseus). We have to discuss two common Vinca Alkaloids, such as Vincristine, and Vinblastine.

Reference

1. Singh, A., Singh, B., Navneet. Bioactive compounds in cancer care and prevention. Role of Nutrigenomics in Modern-day Healthcare and Drug Discovery. 15, 439-468 (2023)
2. Alhmoud, J.F., Woolley, J.F., Moustafa, A-E.A., Malki, M.I. DNA Damage/Repair Management in Cancers. Cancers (Basel) 12(4) 1050 (2020)
3. Korenaga, MD.T.R., Crosland MD, B., Tewari, K.S. Cancer in pregnancy. DiSaia and Creasman Clinical Gynecologic Oncology (Tenth Edition) 12, 345-414.e10 (2023)
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