Why does a mutated epidermal growth factor receptor (EGFR) in lung cancer cells increase the likelihood of uncontrolled proliferation, even with functional cell cycle checkpoints?

💡 Explanation

The mutated EGFR signals continuously regardless of external growth factors, leading to constant activation of downstream pathways that promote cell cycle progression; because this constitutive signaling overwhelms the normal inhibitory signals from cell cycle checkpoints, uncontrolled proliferation occurs. Therefore, the cells divide rapidly rather than responding to normal regulatory signals or inducing apoptosis.

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