Question

With regard to cancer cells, which of the following statements are true? A. Cancer cells are clonal, which means they are derived from a single mutant cell. B. To become cancerous, cells usually accumulate multiple genetic changes that eventually result in uncontrolled growth. C. Most cancers are caused by oncogenic viruses. D. Cancer cells have lost the ability to properly regulate cell division.

Short answer

Statements A, B, and D are true, while statement C is false.

Step-by-step solution

Evaluation of statement A

Cancer cells are indeed clonal, meaning they originate from a single mutant cell. This is due to a mutation within one cell that causes it to begin uncontrolled replication. Therefore, statement A is true.

Evaluation of statement B

Cancer cells usually undergo a number of genetic mutations that cause uncontrolled growth. These genetic changes prevent the cells from undergoing normal cell cycle control mechanisms which could lead to subsequent apoptotic cell death. Hence, statement B is also true.

Evaluation of statement C

Most cancers are not caused by oncogenic (cancer-causing) viruses. While certain viruses are known to increase the risk of cancer, such as HPV or Hepatitis C, it is not accurate to say that 'most' cancers are caused by them. Therefore, statement C is false.

Evaluation of statement D

Cancer cells are known to have lost the ability to properly regulate cell division. This loss often occurs as a result of mutations in genes that regulate cell cycle progression. Therefore, statement D is true.

Key concepts

Clonal Origin

Cancer cells exhibit what is known as a clonal origin. This means they are initiated from a single cell that has undergone mutation. In regular circumstances, cells follow an orderly pattern of growth and division. However, if a mutation occurs within a cell's DNA, this can lead to uncontrolled replication. This mutated cell then becomes the ancestor of a tumor, replicating its mutated characteristics to its cell offspring.

• All cancer cells in one tumor can be traced back to a single mutated cell.
• The mutation provides advantages for survival and replication.
• Over time, more mutations accumulate in the clonal descendants.

Recognizing the clonal origin of cancer helps us understand how tumors grow and spread, and directs the focus towards targeting these initial mutations for treatment.

Genetic Mutations

Cancerous cells are often characterized by several accumulating genetic mutations. These mutations alter normal cellular processes and lead to the development of cancer. Each mutation acquired can provide cells with different traits that may aid in survival or enhance their capacity for growth.

• Mutations may deactivate tumor-suppressor genes, negating their protective roles.
• Proto-oncogenes can be turned into oncogenes, promoting excessive cell division.
• Further mutations can impair apoptosis, allowing cells to evade programmed death.

Collectively, these genetic changes disrupt regular cell functions, leading to uncontrolled proliferation, a hallmark of cancer.

Oncogenic Viruses

While some viruses are associated with an increased risk of cancer, it is not accurate to claim that most cancers arise from viral infections. Oncogenic viruses like Human Papillomavirus (HPV) or Hepatitis B and C viruses can contribute to cancer development by integrating into the host genome, disrupting normal cellular control.

• HPV is linked to cervical and other types of cancers.
• Hepatitis B and C can lead to liver cancer.
• Viruses can introduce oncogenes or affect tumor suppressor genes.

Even though specific viruses significantly contribute to particular cancers, they account only for a subset of cancer cases when considering the broad spectrum of the disease.

Cell Division Regulation

Proper regulation of cell division is crucial for maintaining normal cellular function. In cancer cells, however, this regulatory mechanism is compromised, leading to uncontrolled growth. This failure often occurs due to mutations that affect genes involved in the cell cycle regulation.

• Key checkpoints during the cell cycle ensure correct DNA replication and division.
• Mutations can bypass these checkpoints, leading to rapid accumulation of cells.
• Defective cell cycle control ultimately contributes to tumor growth and potential metastasis.

Understanding cell division regulation sheds light on how cancer progresses and highlights potential pathways for therapeutic intervention to stop or slow down the disease.