What is the Difference Between Cell Cycle Specific and Cell Cycle Nonspecific

The main difference between cell cycle specific and cell cycle nonspecific is that cell cycle specific chemotherapy drugs kill cancer cells when they are dividing, whereas cell cycle nonspecific chemotherapy drugs kill cancer cells at rest. 

Cell cycle specific and cell cycle nonspecific are two chemotherapy drug types. Chemotherapy drugs kill cancer cells by halting cell division.  

Key Areas Covered

1. What is Cell Cycle Specific
– Definition, Types, Importance
2. What is Cell Cycle Nonspecific
– Definition, Types, Importance
3. Similarities Between Cell Cycle Specific and Cell Cycle Nonspecific
– Outline of Common Features
4. Difference Between Cell Cycle Specific and Cell Cycle Nonspecific
– Comparison of Key Differences

Key Terms 

Cell Cycle Nonspecific, Cell Cycle Specific

What is Cell Cycle Specific

Cell cycle-specific chemotherapy drugs are a type of chemotherapy drugs that kill cancer cells during their proliferation. There are two types of cell cycle-specific chemotherapy drugs. They are antimetabolites and plant alkaloids. 

Antimetabolites

Antimetabolites replace the natural substances used by the cancer cells to divide. For example, antimetabolites replace DNA’s building blocks. Also, they alter the function of the enzymes. Enzymes are important for cell metabolism and protein synthesis. Therefore, they mimic nutrients the cell needs for metabolism and protein synthesis. It leads to the eventual death of the cancer cells. Importantly, antimetabolites are cell-cycle specific. Also, they are most effective at the S phase of cell division, acting as metabolites for DNA synthesis. They act on the actively dividing cells, such as cancer cells. Examples of antimetabolites include purine antagonists, pyrimidine antagonists, and folate antagonists.

Figure 1: Actinomycin D

Plant Alkaloids

Plant alkaloids are a type of cell cycle-specific chemotherapy drugs that have a plant origin. They block the division of cancer cells. Importantly, plant alkaloids act upon all phases of cell division. But they are effective at the S and M phases of the cell cycle. Actinomycin D, doxorubicin, and mitomycin are examples of plant alkaloids. 

What is Cell Cycle Nonspecific

Cell cycle-nonspecific chemotherapy drugs are another type of anticancer drug that kills cancer cells in both proliferative and non-proliferative stages. The two types of cell cycle-nonspecific chemotherapy drugs include alkaloids and antitumor antibiotics. 

Alkylating Agents

Alkylating agents are the first used chemotherapy drugs. Also, they are the most commonly used type of chemotherapy drugs. They directly act on DNA, leading to the cross-linking of DNA, DNA strand breaks, and abnormal base pairing, preventing the cell from dividing. Importantly, they are cell cycle-nonspecific. It means they kill cancer cells in multiple stages of the cell cycle. Therefore, alkylating agents are important for treating the slow-growing cancer cells. Also, they are not effective on fast-growing cells. Chlorambucil, cyclophosphamide, thiotepa, and busulfan are examples of alkylating agents.

Figure 2: Cyclophosphamide

Antitumor Antibiotics

Antitumor antibiotics are another type of anticancer drugs that are cell cycle-nonspecific. They bind to DNA and prevent RNA synthesis. However, RNA synthesis is important for the survival of the cell. Further, they uncoil DNA strands, preventing cell division. Doxorubicin, mitoxantrone, and bleomycin are examples of antitumor antibiotics.  

Similarities Between Cell Cycle Specific and Cell Cycle Nonspecific

• Cell cycle-specific and cell cycle-nonspecific are two chemotherapy drugs that act against cancer cells.
• Chemotherapy drugs kill cancer cells by halting cell division. 

Difference Between Cell Cycle Specific and Cell Cycle Nonspecific

Definition

Cell cycle-specific refers to the chemotherapy drugs that kill cancer cells only when they are dividing, while cell cycle nonspecific refers to the chemotherapy drugs that kill the cell in various and multiple phases of the cell cycle.

Types

Cell cycle-specific chemotherapy drugs include plant alkaloids and antimetabolites, while cell cycle-nonspecific chemotherapy drugs include alkylating agents and some natural products.

Function

Plant alkaloids inhibit the G2 phase, and DNA synthesis inhibitors inhibit the S phase in cell cycle-specific chemotherapy drugs, while cell cycle-nonspecific chemotherapy drugs kill any phase of the cell cycle.

Importance

Cell cycle-specific chemotherapy drugs kill only proliferating cells, while cell cycle-nonspecific chemotherapy drugs kill both proliferating and non-proliferating cells. 

Dependency

Cell cycle-specific chemotherapy drugs are schedule-dependent, while cell cycle-nonspecific chemotherapy drugs are dose-dependent. 

Conclusion

In brief, cell cycle-specific and cell cycle-nonspecific drugs are two chemotherapy drugs that kill cancer cells. Cell cycle-specific chemotherapy drugs include plant alkaloids and antimetabolites. Plant alkaloids inhibit the G2 phase, and DNA synthesis inhibitors inhibit the S phase of the cell cycle. They kill only proliferating cells. Also, they are schedule-dependent. In comparison, cell cycle-nonspecific drugs include alkylating agents and some natural products. They kill cells in any phase of the cell cycle. Therefore, they kill cancer cells at any phase. Also, they are dose-dependent. Thus, cell cycle-specific and cell cycle-nonspecific drugs are their method of cancer cell killing. 

References:

1. Types of chemotherapy drugs. Types of Chemotherapy Drugs | SEER Training. (n.d.). https://training.seer.cancer.gov/treatment/chemotherapy/types.html

Image Courtesy:

1. “Actinomycin” By YourEyesOnly – Own work (CC-BY SA 3.0) via Commons Wikimedia
2. “Cyclophosphamide ” By Vaccinationist – Own Work (Public Domain) via Commons Wikimedia