Final answer:
Normal mammalian cells stop dividing when in contact with neighboring cells due to contact inhibition, a form of cell communication crucial for tissue formation. Cancer cells, in contrast, do not exhibit contact inhibition, leading to unchecked growth and potential metastasis.
Step-by-step explanation:
When normal mammalian cells come into contact with neighboring cells, they exhibit a phenomenon known as contact inhibition. This process inhibits the cells from further division once they form a confluent monolayer, simulating the completion of tissue formation. During culture, normal cells spread out and grow until this state of confluence is reached, at which point they 'know' to halt cell cycle progression. This contrasts with cancer cells, which lack contact inhibition and continue to divide beyond confluence, leading to the formation of multilayered clusters. Cancer cells often lack important cellular components such as gap junctions, cadherins, and integrins that are crucial for cell communication and proper attachment to the extracellular matrix. This deficiency can result in poor cell adhesion and can be a factor in cancer metastasis.
The capability of normal cells to cease division upon forming a tissue-like layer is tied to their ability to communicate through direct cell-to-cell contact, a key aspect of proper cellular function as outlined by the standard 3.D.2 which states that cells communicate with each other through direct contact or chemical signaling.