Final answer:
Normal cells grow as a monolayer due to contact inhibition and cease dividing when they reach confluence. In contrast, cancer cells lack this regulatory mechanism and grow uncontrollably, often forming multilayered masses. Normal primary cell cultures have a limited life span, while transformed cells can give rise to immortal cell lines without contact inhibition.
Step-by-step explanation:
Normal cells grow only as a monolayer and stop when no more room is available (contact inhibition), while cancer cells do not stop growing and can form multi-layers.
Normal cells demonstrate a behavior known as contact inhibition, where they grow and divide until reaching confluence, forming a monolayer wherein cells cease to divide. This is a key characteristic of how cells manage growth, acting similarly to how tissues form in the body. In contrast, cancer cells lack this regulatory mechanism, allowing them to grow uncontrollably, often leading to the formation of multilayered cell masses. These differences are not merely observable in culture but also play a significant role in the understanding of oncogenic processes, such as the lack of adhesion to the extracellular matrix and the potential for metastasis.
Furthermore, normal primary cell cultures have a finite growth capacity, usually ceasing to divide after a limited number of cell divisions due to senescence or insufficient culture conditions. However, some cells can become immortal through transformation, resulting in a cell line that can grow indefinitely under the right culture conditions. These immortalized cells typically exhibit aberrant growth behaviors, such as the loss of contact inhibition and the ability to grow without solid support.