Which of the following is a characteristic of cancer cells?

Cancer cells exhibit loss of contact inhibition, which is a key characteristic that distinguishes them from normal cells. In normal cells, contact inhibition is a regulatory mechanism that stops cell growth when cells come into contact with one another. This ensures that tissues maintain proper structure and organization.

In contrast, cancer cells ignore these signals and continue to proliferate even when they are in close contact with neighboring cells. This uncontrolled growth can lead to the formation of tumors as cancer cells replicate in an unregulated fashion. This characteristic contributes to the aggressive nature of cancer and is one of the reasons why it can spread to nearby tissues and organs.

The other characteristics mentioned do not align with the behavior of cancer cells. For instance, cancer cells do not undergo normal apoptosis, which is the programmed cell death that removes damaged or redundant cells. Rather, many cancer cells have developed mechanisms to evade this process. Similarly, cancer cells often have an extended lifespan compared to normal cells, often leading to persistent growth. Lastly, while cancer cells do proliferate, their cell division is not 'normal' as it is characterized by unregulated and excessive growth, diverging from the controlled proliferation seen in healthy tissues.