Question

Multidrug resistance to chemotherapeutic drugs occurs because a. cancer cells can use plasma membrane carriers to pump drugs out of the cell. b. one drug may interfere with the activity of another drug. c. using several drugs at once will overtax the patient's immune system. d. using several drugs at once decreases the effectiveness of radiation therapy.

Short answer

Multidrug resistance to chemotherapeutic drugs occurs mainly because cancer cells can use plasma membrane carriers, such as ATP-binding cassette (ABC) transporters, to pump drugs out of the cell, leading to a decreased accumulation of the drugs inside cancer cells and making them less effective. The correct answer is option a.

Step-by-step solution

Option a: Cancer cells can use plasma membrane carriers to pump drugs out of the cell.

Option a is the correct answer. Cancer cells can develop multidrug resistance by using specific transport proteins in their plasma membrane, such as ATP-binding cassette (ABC) transporters, to pump chemotherapeutic drugs out of the cell. This process ultimately leads to the decreased accumulation of the drugs inside cancer cells, making the drugs less effective.

Option b: One drug may interfere with the activity of another drug.

Option b is incorrect. Although drug interactions can sometimes affect the effectiveness of individual drugs, the phenomenon of multidrug resistance in cancer cells is not primarily due to drug interactions. Instead, it is a result of cellular mechanisms like the increased expression of drug efflux transporters which decrease the intracellular drug concentrations.

Option c: Using several drugs at once will overtax the patient's immune system.

Option c is incorrect. The use of multiple drugs can sometimes place a considerable burden on the patient's body, but it is not the main reason for multidrug resistance in cancer cells. In fact, combination chemotherapy can often lead to better outcomes, as different drugs can target various aspects of cancer cell growth and survival, lowering the risk of developing resistance to one specific drug.

Option d: Using several drugs at once decreases the effectiveness of radiation therapy.

Option d is incorrect. The simultaneous use of several drugs does not necessarily decrease the effectiveness of radiation therapy. Rather, some chemotherapeutic drugs can actually enhance the effects of radiation therapy by making cancer cells more sensitive to radiation-induced damage.

Key concepts

Cancer Cells

Cancer cells are abnormal cells that divide uncontrollably, leading to the growth of tumors and the spread of cancer throughout the body. Unlike normal cells, cancer cells avoid the usual signals to stop growing, allowing them to proliferate without restrictions.
One of the challenges with cancer cells is their ability to develop resistance to treatments like chemotherapy. This resistance can hinder the effectiveness of treatment and make the cancer more difficult to manage. Understanding how cancer cells work is vital for developing better treatment strategies and improving patient outcomes.

Chemotherapeutic Drugs

Chemotherapeutic drugs are specialized medications used to treat cancer by targeting and killing rapidly dividing cells. These drugs aim to stop or slow down the growth of cancer cells.
There are various types of chemotherapeutic drugs, each designed to target specific pathways or cellular processes in cancer cells. Some common types include:

• Alkylating agents: which damage DNA and prevent cell division.
• Antimetabolites: which interfere with DNA and RNA growth.
• Mitotic inhibitors: which disrupt cell division.

Despite their potential effectiveness, chemotherapeutic drugs can face challenges, such as multidrug resistance, making treatment less effective over time.

Plasma Membrane Carriers

Plasma membrane carriers are proteins located on the cell membrane that play a crucial role in transporting substances into and out of cells. These carriers can move nutrients, ions, and other vital molecules necessary for cellular function.
In cancer cells, specific plasma membrane carriers are involved in the development of multidrug resistance. Their role involves actively transporting chemotherapeutic drugs out of the cells, reducing the drugs' effectiveness by lowering their intracellular concentrations. By expelling these drugs, the cancer cells can survive and continue proliferating despite the presence of chemotherapy treatments.

ATP-binding Cassette Transporters

ATP-binding cassette (ABC) transporters are a family of transport proteins that utilize energy from ATP to move a variety of substances across cell membranes. This family is one of the largest and most diverse group of membrane transporters found in many living organisms.
In the context of cancer cells, ABC transporters are often associated with multidrug resistance. They can pump out chemotherapeutic drugs, diminishing their concentration within the cancer cells and rendering treatment less effective. This process involves using the energy from ATP hydrolysis to actively transport drugs out of the cell. Understanding these transporters is critical for developing strategies to counteract drug resistance and improve treatment responses.