Master the cell cycle phases (G1, S, G2, M, G0) and how chemotherapy drugs target them. Differentiate Cell Cycle Specific (CCS) & Non-CCS agents for cancer trea
WEEK 3 The Cell Cycle (Understand This Well)Cancer drugs work by disrupting the cell cycle. So you MUST understand each phase: Phase What Happens Drugs that target it --- --- --- G1 Cell grows, synthesizes proteins, prepares for DNA copying L-Asparaginase S DNA is copied (replicated) Methotrexate, 5-FU, Cytarabine G2 Cell checks DNA, prepares for division Bleomycin M Cell physically splits into 2 daughter cells Vincristine, Paclitaxel G0 Resting — not dividing Alkylating agents still work here --- Cell Cycle Specific (CCS)- Only kill cells actively going through a specific phase - Useless against G0 (resting) cells - Need prolonged exposure — that's why they're given as continuous infusions or frequent doses - More effective against fast-growing tumors - Examples by phase: - S phase → Methotrexate, 5-Fluorouracil, Gemcitabine, Cytarabine - M phase → Vincristine, Vinblastine, Paclitaxel, Docetaxel - G2 phase → Bleomycin - G1 phase → L-Asparaginase - --- Non-Cell Cycle Specific (NCCS)- Kill cells at any phase including G0 - One large dose can be effective - More toxic to normal tissue because they don't discriminate - Better for slow-growing or bulky tumors - Examples: - Alkylating agents — Cyclophosphamide, Cisplatin, Carmustine - Antitumor antibiotics — Dactinomycin, Mitomycin C - Nitrosoureas — Carmustine (BCNU) - --- Why This Matters Clinically- Fast growing cancer (leukemia, lymphoma) → use CCS drugs - Slow growing/bulky tumor (colon, lung) → NCCS works better - Combination regimens mix both → hit cells at multiple phases + catch resting cells - --- How Classification Works — The LogicDrugs are classified by what they attack: Target Class Simple way to remember --- --- --- DNA itself (cross-linking) Alkylating agents "Glue the DNA strands together" DNA building blocks Antimetabolites "Fake ingredients — DNA can't be built" DNA uncoiling enzyme Topoisomerase inhibitors "Lock the zipper — DNA can't open" DNA intercalation Antitumor antibiotics "Wedge between DNA strands" Microtubules Mitotic inhibitors "Destroy the rope that pulls chromosomes apart" Specific proteins/receptors Targeted therapy "Sniper — one specific target" ---