Final answer:
Cancer cells can proliferate in the absence of serum due to the loss of contact inhibition, defective cell adhesion molecules, and altered telomere dynamics.
Step-by-step explanation:
Cancer cells can proliferate in the absence of serum due to several underlying reasons. One key factor is the loss of contact inhibition, a phenomenon where normal cells stop dividing when they reach confluence. In contrast, cancer cells continue to divide and pile up in multiple layers.
Additionally, cancer cells may have defective or fewer integrins and cadherens on their membranes, which affects their ability to form adherens junctions, attach firmly to the extracellular matrix, and respond to signals that regulate cell growth and division.
Moreover, cancer cells are often characterized by shortened telomeres and increased telomerase activity, which contribute to their limitless replicative potential.