Biology Forums - Study Force

While studying to become chemo-certified, the nurse reviews some basic concepts about cancer cells. When a client asks about why the tumor grows so fast, the nurse will respond based on which of the following physiological principles?
 
  Select all that apply.
  A) Cancer cells have shorter cell cycle times than normal cells.
  B) Cancer cells do not die when they are programmed to die.
  C) Growth factors prevents cancer cells from entering resting (G0) cell cycle phase.
  D) Cancer cells will reach a balance between cell birth and cell death rate.
  E) Cancer cells never reach a flattened growth rate.

Ans: B, C
Feedback:
One of the reasons cancerous tumors often seem to grow so rapidly relates to the size of the cell pool that is actively engaged in cycling. It has been shown that the cell cycle time of cancerous tissue cells is not necessarily shorter than that of normal cells. Rather, cancer cells do not die on schedule, and growth factors prevent cells from exiting the cell cycle and entering the G0 or noncycling phase. The ratio of dividing cells to resting cells in a tissue mass is called the growth fraction. The doubling time is the length of time it takes for the total mass of cells in a tumor to double. As the growth fraction increases, the doubling time decreases. When normal tissues reach their adult size, an equilibrium between cell birth and cell death is reached. Cancer cells, however, continue to divide until limitations in blood supply and nutrients inhibit their growth. When this occurs, the doubling time for cancer cells decreases. The initial growth rate is exponential and then tends to decrease or flatten out over time.