Which metal compound is used for treatment of carcinoma?

Question

UnlockIAS · Accepted Answer

Correct — A, Platinum. The Commission, disposing of objections on 31 October 2025, gave its own reasoning: platinum-based compounds such as cisplatin, carboplatin and oxaliplatin are widely used against various carcinomas because they bind to the DNA of cancer cells, interfere with replication and lead to cell death — and it added that iron, by contrast, tends to promote cancerous growth. The founding drug is cisplatin, cis-diamminedichloroplatinum(II), cis-[Pt(NH₃)₂Cl₂], a square-planar platinum(II) coordination complex given as a short intravenous infusion in normal saline. Its mechanism is worth knowing precisely, because the chemistry is elegant. Outside the cell, where chloride sits near 100 mM, the two chloride ligands stay put. Inside the cell, where chloride is only about 3–20% of that concentration, one chloride is displaced by water — aquation — producing a reactive aqua complex. That species attacks the N7 nitrogen of guanine on DNA; displacement of the second chloride then locks the platinum to a neighbouring guanine. Roughly 90% of the resulting damage takes the form of 1,2-intrastrand cross-links between adjacent guanines, which kink the double helix, stall replication and mitosis, and when repair fails, trigger apoptosis. The drug has a datable history: first described by Michele Peyrone in 1845 as Peyrone's salt, with its structure deduced by Alfred Werner in 1893, then rediscovered biologically in 1965 when Barnett Rosenberg's group at Michigan State University found that platinum electrodes in a bacterial culture stopped E. coli dividing, leaving filaments up to 300 times normal length. It was approved by the US FDA on 19 December 1978 for testicular and ovarian cancer, and it is on the WHO Model List of Essential Medicines. Its clinical impact is the strongest evidence for the key: remission in testicular cancer rose from 5–10% before 1974 to 75–85% by 1984.

Why the other options are wrong — (b) Chromium is on the wrong side of the ledger entirely. Hexavalent chromium compounds are classified by the International Agency for Research on Cancer in Group 1 — carcinogenic to humans — on the evidence of lung cancer among chromate production, plating and pigment workers. Trivalent chromium is a trace element in the diet, but no chromium compound is an established anticancer therapy. The option tests whether you can tell a cause of cancer from a treatment for it.  (c) The most tempting wrong answer, because school biology installs 'iron is good for you' very early — it is the metal at the centre of haemoglobin, myoglobin and the cytochromes, and its deficiency causes anaemia. But essential is not the same as therapeutic. Free iron drives Fenton chemistry, generating hydroxyl radicals that damage DNA, and iron overload is linked to raised cancer risk; the Commission made exactly this point in its published remark, that iron further induces cancerous growth.  (d) Eliminated by the stem itself, which asks for a metal compound: chlorine is a halogen, a non-metal, a greenish-yellow gas used to disinfect water. The irony is what makes the option catch the eye of anyone who half-remembers the answer — chlorine really is inside cisplatin, as the two chloride ligands that are displaced when the drug activates. It is a genuine part of the right molecule, but it is not the metal that does the work.

Concept: Two ideas sit underneath this question. The first is what a carcinoma is. Cancers are named for the tissue they arise from: a carcinoma begins in epithelial tissue — skin, and the linings of the lung, breast, stomach, colon, cervix and other organs — while a sarcoma begins in connective tissue such as bone, muscle or cartilage, and leukaemias and lymphomas begin in blood-forming and lymphatic tissue. Carcinomas are by far the commonest group in adults, which is why a drug effective against them matters so much. The second idea is medicinal inorganic chemistry: the deliberate use of metal complexes as drugs. Cisplatin founded that field, and it remains its clearest demonstration that geometry, not merely composition, carries biological activity — transplatin, the trans isomer with the very same atoms, is essentially inactive, because its shape cannot form the characteristic cross-link between two adjacent guanines and it is deactivated before it reaches DNA. Cisplatin is also the standard illustration of a drug limited by its side effects: kidney damage is the dose-limiting toxicity, with nerve damage, hearing loss and severe nausea alongside it, which is why carboplatin and oxaliplatin were developed as better-tolerated successors. Metals appear elsewhere in the pharmacy too — lithium carbonate in bipolar disorder, gold compounds in rheumatoid arthritis, silver sulfadiazine on burns, gadolinium as an MRI contrast agent, technetium-99m in nuclear imaging, arsenic trioxide in one form of leukaemia — but platinum is the only metal at the centre of mainstream cytotoxic chemotherapy.

State PCS 2025 Q134 — Science & Technology PYQ with Answer

State PCS 2025 Q134 — Science & Technology PYQ with Answer