Final answer:
Cancer cells typically respond to growth factors, allowing unchecked proliferation, and often ignore signals for contact inhibition and apoptosis that would normally halt their growth or lead to cell death. They manage to survive by becoming insensitive to various mechanisms that would normally stop cell division or trigger cell death.
Step-by-step explanation:
Cancer cells often respond to cues that favor their growth and proliferation while ignoring signals that would normally inhibit their growth or lead to their death. Specifically, cancer cells typically respond to growth factors and may ignore contact inhibition, which is a mechanism that stops cells from dividing when they come into contact with each other. This lack of contact inhibition allows cancer cells to grow and multiply even when there's no space for them to do so.
Apoptosis, or programmed cell death, is a natural defense mechanism that removes damaged or dangerous cells. However, cancer cells often gain the ability to ignore apoptosis signals, which would normally instruct them to self-destruct when they are abnormal or no longer needed. Moreover, cancer cells may fail to respond to DNA repair signals, allowing them to continue dividing despite the presence of genetic damage. They can also become insensitive to signals that regulate cell cycle checkpoints, allowing them to bypass normal protective mechanisms that prevent cell division when conditions are not ideal.
Given these characteristics, cancer cells might have mutations that prevent the initiation of apoptosis signaling, lose expression of receptors for apoptosis-inducing ligands, or overexpress pathways that inhibit apoptosis. All of these factors contribute to the unchecked growth and survival of cancer cells.