July 13, 2010

Q&A: Mode of Action of Antitumor Agents

Antitumor agents prevent or inhibit the formation or growth of tumors and are known as antitumor, anticancer, chemotherapeutic, or antimetastatic agents.

In this article:
Antitumor agents and cell division
MCQ clinical scenario
MCQ answer
MCQ explanation

Antitumor agents and cell division

Antitumor agents kill those cells that divide rapidly, which is one of the main property in most types of cancer cells.

Cellular growth, development, and differentiation are tightly controlled by a conserved biological mechanism: the cell cycle. This cycle is primarily regulated by cyclin-dependent kinase (CDK)-cyclin complexes, checkpoint kinases, and CDK inhibitors. Deregulation of the cell cycle is a hallmark of the transformation of normal cells into tumor cells. Given its importance in tumorigenesis, several cell cycle inhibitors have emerged as potential therapeutic drugs for the treatment of cancers-both as single-agent therapy and in combination with traditional cytotoxic or molecular targeting agents.

MCQ clinical scenario

Currently it is known that antitumor agents can arrest cell division by one or several mechanisms.

What mode of action is implicated in the use of vinblastine as an antitumor agent?

a) Microtubule Interference
b) Topoisomerase Catalytic Inhibition
c) DNA Alkylation
d) DNA Inhibition
e) Protein Synthesis Inhibition

MCQ questions & answers on medicalnotes.info

MCQ answer

The correct answer is A.
Vinblastine is a microtubule-disruptive drug.

MCQ explanation

Microtubules are dynamic, polymeric structures, which (besides other biological functions) are major constituents of the mitotic spindle, the latter being essential for the separation of chromosomes during mitosis. Chemically, they are polymers of certain heterodimers of alpha- and beta-tubuline.

A range of secondary metabolites of plants interfere with the process of assembling and disassembling of microtubules, resulting in the arrest of cells in mitosis and apoptosis. The most significant are the Vinca alkaloids, colchicine, maytansine, and paclitaxel.

Both Vinca alkaloids (vincristine, vinblastine, and especially the second generation vinorelbine) and Taxanes (paclitaxel, and especially docetaxel), largely used as antitumor agents in the conventional treatment of lung cancer, are derived by semisynthesis of natural plant compounds.

1). U.S. National Library of Medicine: Cell cycle regulation and anticancer drug discovery. Available online: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5785171/

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